Proceedings of the 2nd International Civil Engineering and Architecture Conference: CEAC 2022, 11-14 March 2022, Singapore 9811942927, 9789811942921

Table of contents :
Preface
Organization
Conference Chairs
Program Chairs
Program Chairs
Steering Committee Chair
Publicity Committees
International Technical Committees
Contents
Building Materials and Technology
Possibility to Optimize Hydrothermal Conditions for the Production of Autoclaved Aerated Concrete Using Rice Husk Ash as the Silica Raw Material
1 Introduction
2 Materials and Methods
3 Results and Discussion
3.1 X-ray Diffraction Analysis (XRD)
3.2 Mechanical Properties
4 Conclusion
References
Innovative Research on the Mechanical Experiment of Steel Fiber Modified Waste Material Recycled Concrete
1 Significance of the Study
2 Construction Waste Material Utilization Status
3 Regenerated Aggregate Analysis
3.1 The Main Treatment Methods of Construction Waste Materials in China
3.2 Regenerative Aggregate Properties of Construction Waste Materials
4 Performance Analysis of Recycled Concrete
4.1 Compressive Strength
4.2 Durability Analysis
5 Steel Fiber Modified Recycled Concrete
5.1 Compressive Strength
5.2 Tensile Strength
5.3 Flexural Strength
5.4 Tensile Strength of Cleavage
5.5 Modulus of Elasticity of Recycled Concrete
5.6 Xu Variable Model Prediction
6 Conclusions and Prospects
References
Calculation Method of Asphalt Concrete Thermal Stress Based on Interface Mechanics
1 Introduction
2 Methods
2.1 Thermal Stress Calculation Model Based on Interface Mechanics
2.2 Asphalt Mixture Thermal Stress Considering Relaxation Effect
3 Verification of the Method
3.1 Calculation Parameter
3.2 Verification of Thermal Stress Calculation Method
4 Conclusion
References
Aging Performance of Base and Modified Bitumen
1 Introduction
2 Raw Materials and Experiments
2.1 Raw Material
2.2 Aging Test
2.3 Test Methods
3 Test Results and Discussion
4 Conclusion
References
An Approach to Reduce Strength Loss of Rubber Concrete
1 Introduction
2 Materials and Experiment
3 Results and Discussion
4 Conclusions
References
Carbon Efficiency-Oriented Design Optimization of Bamboo Construction: A Case Study in Guangzhou, China
1 Introduction
2 Method
2.1 Settings of the Standard Building Unit
2.2 Carbon Emission of Building Materials
2.3 Carbon Emission During Building Operation
2.4 Definition and Calculation of “Carbon Efficiency”
3 Result
3.1 Construction Type
3.2 Construction Framework
3.3 Core Cavity Arrangement
4 Discussion
4.1 Contribution of Building Materials and Building Operation to the Total Carbon Emission
4.2 Key Points for Improving the Carbon Efficiency
5 Conclusion
References
Study on the Performance of Eggshells as a Humidity Control Building Material
1 Introduction
2 Materials and Methods
3 Detection and Result
3.1 Control Group Experimental Materials A-CO
3.2 Control Group Experimental Materials B-SI
3.3 Test Group Experimental Materials C-ES
4 Discussion and Conclusions
4.1 Humidity Control Ability
4.2 Moisture Absorption Grade
4.3 Conclusions
References
The Mechanical Properties for Using Banana’s Peel Ash as Aggregate in Geopolymer Mortar
1 Introduction
2 Materials and Methods
3 Results and Discussion
4 Conclusions
References
Facile Fabrication of Superhydrophobic Robust Coatings with Solar Reflective Capability by One Step Spraying Method
1 Introduction
2 Materials and Methods
2.1 Materials
2.2 Preparation
3 Characterizations
4 Results and Discussion
5 Conclusion
References
Study on Carbon Emission of Laminated Bamboo Based on Life Cycle Assessment Method
1 Introduction
2 Material
3 Method
3.1 Mass Flow During the Manufacturing Process
3.2 Carbon Emission of the Production Energy Consumption (C1)
3.3 Carbon Emission of the Transport (C2)
3.4 Carbon Emission of the Addendum (C3)
4 Result and Analysis
4.1 Composition of the Carbon Emission
4.2 Major Carbon Emission Steps
5 Discussion
5.1 Comparison with Two Previous Case Studies on LB
5.2 Suggestion on Reducing Carbon Emission of LB
6 Conclusion
Annex Table
References
Study on the Mechanical Strength of Fiber-Reinforced Geopolymer Porous Materials
1 Introduction
2 Materials and Experiments
2.1 Materials
2.2 Experimental Program
3 Results and Discussion
3.1 Influence of Water Glass Content on Flexural Strength and Compressive Strength
3.2 The Influence of H2O2Content on Flexural Strength and Compressive Strength
3.3 The Influence of Different Fiber Content on the Flexural Strength and Compressive Strength
4 Conclusions
References
Bridge and Tunnel Engineering
Use of Non-destructive Tests to Evaluate the Concrete and Steel Bars of Vehicular Bridges Structural Elements
1 Introduction
2 Case of Study
2.1 Vehicular Bridge 1
2.2 Vehicular Bridge 2
3 Non-destructive Testing Method
3.1 Electromagnetic Concrete Coverage Meter
3.2 Original Schmidt Rebound Hammer Equipment
3.3 Pundit PL-200 Equipment
4 Results
4.1 Steel Bars
4.2 Concrete
5 Conclusions
References
Study on Laying Method of Trenchless Channel for Power Cables in Tianjin
1 Introduction
1.1 Research on the Suitable Laying Scale of Cable Lines
2 Material and Methods
3 Results and Discussion
3.1 Pipe Pulling Design
3.2 Pipe Jacking Design
4 Conclusion
4.1 Benefit Analysis
4.2 Research on the Suitable Laying Scale of Cable Lines
References
Analysis and Design of Pipe Gallery Bridge with Large Cross-Section and High Loading
1 Project Overview
2 Spatial Beam Finite Element Model Analysis of Pipe Gallery Bridge
3 Spatial Solid Finite Element Model Analysis of Pipe Gallery Bridge
4 Summary
References
Research on the Application of Computer Vision in Bridge Health Monitoring
1 Introduction
1.1 The Purpose and Significance of the Paper
2 The Status of Computer Vision in Bridges
2.1 Current Status of Research
2.2 The Problems Faced and the Future Development
3 Conclusion
3.1 Conclusion
References
Failure Analysis of High Strength Cables from Collapsed Myaungmya Suspension Bridge
1 Introduction
2 Review on Past Studies
3 Laboratory Experiments
3.1 Hardness Test
3.2 Tensile Test
3.3 Fatigue Test
3.4 Spectroscopic Test
3.5 Determining Bridge Cables’ Corrosion Products
3.6 Study on Surface Morphologies of Bridge Cables
4 Conclusion
References
Application of Anti-slide Pile-Plank Wall Combined with Backfilling in Treatment of Tunnel Portal Crack and Slope Collapse
1 Introduction
2 Project Overview
2.1 Geologic Conditions
2.2 Failure Characteristics
3 Cause Analysis of Slide
3.1 Bias Effect
3.2 Rainfall Effect
3.3 Impact of Construction Excavation
4 Treatment Measures
4.1 Treatment Ideas and Scheme Selection
4.2 Arrangement of Anti-slide Pile
4.3 Calculation of Anti-slide Pile
5 Treatment Effect
6 Conclusions and Recommendations
References
An Integrated Erection Method for Segmental Assembled Bridge in Urban District
1 Introduction
2 Multi-functional Bridge Erection Machine—TP120
2.1 General Structure Concept
2.2 Brief Description of Main Structure Components
3 Integrated Erection Flow Per Standard Bridge Span
3.1 Typical Installation of Multi-functional Erection Machine
3.2 Erection Procedures
3.3 Retreat Procedures
4 Engineering Application Case
4.1 Scheme of Implementation
4.2 Efficiency of Implementation
5 Summary
References
Study on Effective Temperature Extreme Isotherm Map of Steel-Concrete Composite Girder Bridge
1 Introduction
2 Numerical Simulation
2.1 Heat Conduction Theory
2.2 Finite Element Simulation
3 Effective Temperature Extremum Calculation
3.1 Historical Meteorological Data Investigation
3.2 Extreme Meteorological Conditions
3.3 Calculation Result of Effective Temperature Extreme Value
4 Effective Temperature Isothermal Map
5 Conclusions
References
Geotechnical Engineering and Engineering Geology
Dynamic Response Analysis of Rock Slope with Weak Layer Based on DOE Method
1 Introduction
2 Geological Background
3 Model Establishment and Preliminary Analysis
4 Design of Experiment
4.1 Introduction to DOE Method
4.2 Design Experiment
5 Analysis of Variance (ANOVA)
6 Conclusion
References
The Influence of Soil Parameters on the Bearing Performance of Super-Long Bored Pile Foundation
1 Introduction
2 Simulation of Soil Parameters
3 The Influence of Soil Cohesion C
4 Influence of the Stiffness of the Pile Side Soil
5 Influence of Pile Tip Soil Stiffness
6 Conclusion
References
Based on Immersion Study on Bearing Characteristics of Roadway Pillar Under Softening
1 Introduction
2 Engineering Background
3 Soaking Influence Analysis of the Entry Protection Coal Pillar in the Working Face
4 Evolution Law on the Excavation Stress of the Soaked Wide Coal Pillars
4.1 Numerical Modelling
4.2 Simulated Result Analysis
5 Microseismic Evolution Characteristics During the Working Face Mining in Large Soaked Coal Pillars
6 Conclusions
References
Numerical Study on Spudcan Penetration-Consolidation-Uplift in Soft Soil Using Large Deformation Simulation
1 Introduction
2 Numerical Mode
2.1 RITSS
2.2 Finite Element Mesh
2.3 Soil Parameters
3 Validation of the Program
4 Results and Discussion
4.1 Spudcan Penetration Force, Uplift Force and Excess Pore Pressure
4.2 Uplift Failure Modes
5 Conclusion
References
Effects of Rock Mass Deterioration Induced by Wetting-Drying Cycles on Slope Stability of Reservoir Banks
1 Introduction
2 Experimental
2.1 Experimental Materials
2.2 Experimental Methodology
3 Results and Analyses
3.1 Experiment Results
3.2 Experiment Analyses
4 Numerical Simulation
4.1 Simulation Model
4.2 Generalized Hoek-Brown Criterion-Based Bank Slope Parameters
4.3 Simulation Result Analyses
5 Conclusions
References
Research on Fine Management of Expressway Survey
1 Introduction
2 Project Overview
3 Fine Management of Geological Survey
3.1 Strictly Implement the Survey Specifications to Ensure the Quality
3.2 The Depth of Geological Survey Meets the Design Requirements
3.3 Topography and Geomorphology
3.4 Fine Control of the Whole Survey Process
4 Conclusion
References
Research Progress on the Formation Mechanism of Intraplate Volcanoes
1 Introduction
2 Plate Subduction
2.1 Mantle Convection in Mantle Wedge Caused by Shallow Plate Dehydration
2.2 Subducted Plate Retention and Plate Dehydration in Depth
2.3 Plate Fracture and Plate Collapse
2.4 Influence of Plate Subduction on Magma
2.5 Breif Summary
3 Lithosphere-Asthenosphere Interaction Mechanism
4 Hot Spot Volcano Formation Mechanism
5 Conclusion
References
Finite Element Analysis of Lateral Bearing Capacity for Pile in Spatially Variable Clay
1 Introduction
2 Methodological Aspects
3 Numerical Simulation
3.1 Finite Element Model
3.2 Model Verification
4 Random Data Analysis
5 Conclusion
References
Application of Numerical Simulation in Teeth Propotion Design of Diamond Bit
1 Introduction
2 Test Method
2.1 Technical Ideas
2.2 Modeling Process
3 Discussion of Results
3.1 Equivalent Stress
3.2 Maximum Shear Stress
3.3 Strain Energy
4 Conclusion and Prospect
References
Structural Engineering and Structural Mechanics
Bayesian Networks and Their Application to the Reliability of FRP Strengthened Beams
1 Introduction
2 Bayesian Networks
2.1 Concept
2.2 Construction
3 Application to the Reliability of FRP Strengthened Beams
4 Application to Beam Failure Mode Prediction
5 Summary
References
Static Loading Test of Soil-RC Pile System Using a Centrifuge Model
1 Introduction
2 RC Pile Model for Centrifuge Test
2.1 Design of Reduced RC Pile Model
2.2 Bending and Compression Loading Test
2.3 FEM Analysis Model of RC Pile
2.4 Comparison of Test and FEM Analysis Result
3 Static Loading Test of Soil-RC Pile System
3.1 Specimen of the Static Loading Test
3.2 Ultimate Strength of the Soil-Pile System
3.3 FEM Analysis Model of the Dry Soil-RC Pile System
3.4 Test Result
4 Conclusion
References
Evaluate Effect of Various Parameters on the Shear Strength of FRP-Reinforced Concrete Beams with or Without Stirrups
1 Introduction
2 Experimental Database Profile
3 Selected Previous Shear Strength Models for FRP-Reinforced Concrete Beams
4 Comparison Between the ED-Model and Other Models
4.1 Scattering of Predictions
5 Effect of Various Parameters
5.1 Effect of the Ratio Between Shear Span and Depth (a/d)
5.2 Effect of Concrete Compressive Strength (Fc’)
5.3 Effect of the Ratio Between the Transversal and Longitudinal FRP Reinforcements Axial Rigidity ( EFw/EFvv)
5.4 Effect of FRP Axial Rigidity (EFw)
5.5 Effect of Aspect Ratio (b/d)
6 Conclusions
References
Statistics and Probabilistic Modeling of Construction Materials Used in the UAE
1 Introduction
2 Research Objectives
3 Review of Related Studies
4 Statistics of Construction Materials in the UAE
4.1 Concrete
4.2 Reinforcing Steel Bars
4.3 Prestressing Steel Strands
5 Summary
References
Collapse Strength of Conical Wall Failure in Steel Cone-to-Cylinder Socket Connections Under Axial Compression
1 Introduction
2 Experimental Results
3 FE Analysis
3.1 General
3.2 FE Analysis Results
4 Prediction of Collapse Strength
5 Conclusions
References
Effectiveness of Laser Treatment on Carbon Steel with Various Forms of Corrosion Pits
1 Introduction
2 Experimental
3 Test Result
3.1 Surface Morphology of Laser-Treated Specimens
3.2 Scanning Electron Microscope (SEM-EDX)
4 Conclusions
References
Experimental Investigation of the Axial Load Capacity for DSTCs Manufactured with High Strength Concrete
1 Introduction
2 Specimen and Material Description
3 Specimen Preparation
4 Test Results
4.1 Effect of FRP Layers
4.2 Effect of the Cross-Sectional Shape of the Inner Steel Tube
5 Conclusion
References
Earthquake-Induced Vibration Measurement and Inverse Analysis of Bell-Shaped Pagoda
1 Introduction
2 Equation of Motion and Inverse Analysis
2.1 Inverse Analysis
2.2 Newmark’s Time Stepping Method
2.3 Gauss-Newton Scheme
3 Pagoda and Method of Measurement
3.1 Pagoda
3.2 Sensor
3.3 Earthquake Data
4 Results
5 Conclusions
References
Extended Critical Shear Crack Theory for Punching Shear of Lightweight, FRP-Reinforced, or Prestressed Concrete
1 Introduction
2 General Overview of the Critical Shear Crack Theory (CSCT)
3 ECSCT for Punching Shear of Lightweight Concrete [17]
4 ECSCT for Punching Shear of FRP Reinforced Concrete [18]
5 Failure Criteria for Punching Shear of Prestressed Concrete [19]
6 Punching Shear of Elements with Membrane Tensile Forces [20]
7 Model Validation
8 Concluding Remarks
References
Evaluation on Deterioration and Blister Progression of Duplex Layers Between Al-5 Mg Thermal Sprayed Coating and Heavy-Duty Paint Coating
1 Introduction
2 Experimental Procedure
2.1 Test Specimen
2.2 Atmospheric Exposure Test
2.3 Deterioration Evaluation Method
3 Test Result
3.1 Surface Observation
3.2 Blister Condition of Duplex Layers
4 Conclusions
References
Architectural Design and Theory
From the Intervalin Architecture: (In)visibilities – The Case of Smithsons’ “Project-Theory”
1 Introduction – Essay of an Interval Theory
1.1 Traces of an (In)visible Depth – an Aesthetics Beyond Western Dialectical Abstraction
1.2 (Re)Defining the Void: The Interval– A Key Element in Space Design and Organization
2 From the Intervalin Architecture – The Case of Smithsons’ “Project-Theory”
2.1 The Smithsons’ Trip(s) to Japan (1960–1975)
2.2 The Smithsons’ Personal Library
2.3 From Smithsons’ Theoretical Approach – From “The Charged Void”to “The Space Between”
2.4 From Smithsons’ Practical (Architectural) Approach – Objects in a Void
3 Brief Research Methodology
References
Spatial Design Strategies for Lightweight Roofing Buildings Driven by Rain Noise Reduction
1 Introduction
2 Methods
2.1 From Indoor Sound Pressure Levels to Sound Power Levels
2.2 Parametric Spatial Prototypes and Multi-case Comparative Study
3 Results
3.1 Noise Power Levels of Lightweight Roofing
3.2 LIACalculation for Parametric Spatial Prototypes
4 Discussion
5 Conclusions
References
Application of Lingnan Ventilation Skills in Contemporary Architecture – Lift Shaft Design of Pedestrian Footbridge in Macau
1 Introduction
2 Relevant Concepts
2.1 Wind and Thermal Pressure Ventilation
2.2 Chimney Effect
2.3 Piston Effect
3 Case Application
3.1 Design Brief
3.2 Marco Ventilation Skills
3.3 Micro Ventilation Skills
4 Conclusion
References
The Opportunities and Challenges of Using LCA-Based BIM Plugins in Early-Stage Building Design: An Industry Expert Perspective
1 Introduction
2 Methods
2.1 Data Analysis Method: Thematic Analysis
3 Analysis Results
3.1 Theme 1: Integrating LCA in Building Design Practice
3.2 Theme 2: LCA-Based BIM Plugins
3.3 Theme 3: Circularity in Building Context
4 Discussion and Conclusion
4.1 The Enablers and Constraints Relating to the Implementation of LCA in Design Practice
4.2 The Parameters Relating to Effective Use of the LCA Plugins
4.3 The Main Barriers in the Transition to the Circularity in Building Practice
5 Conclusion
References
The Factors of Environmental Living Design for Elderly Well-Being in Thai Spiritual Environments
1 Introduction
2 Research Background
3 Research Method
3.1 Factor Identification and Questionnaire Design
3.2 Research Hypotheses
3.3 Data Collection
4 Results
4.1 Descriptive Results
4.2 Structural Equation Modeling
5 Summary
References
Prototype Design of Smart Building Control System Based on Human Demand Information
1 Introduction
1.1 Application of Existing Intelligent Environmental Control Panel
1.2 Motivation
2 Methodology
2.1 Basic Information About the Site and Participants
2.2 Implement
3 Analysis and Discussion
3.1 Sensitivity Analysis
3.2 Interactive Interface Design
3.3 Feedback Analysis
4 Conclusion
4.1 Limitation
References
Urban Engineering and Spatial Planning
Exploring the Renewal and Practice Path of Old Neighborhoods with Multi-module Integration
1 The Old Neighborhoods have been Updated and Transformed Practices and Effectiveness in Putian City
1.1 Summary of Main Practices
1.2 Analysis of the Shortage of Effectiveness
2 The Current Situation of Old Neighborhoods in Putian City
2.1 Analysis of Sample Basic Data of Old Neighborhoods
2.2 The Main Problems of the Current Situation of the Old Neighborhood
2.3 This Research Conducted a Survey on the Participation and Willingness of Residents in Old Communities to Transform
3 Multi-module Integration Practice of Old Neighborhood Renewal and Transformation
3.1 Overall Planning Module to Promote Integrated Management
3.2 In Terms of Policy Guarantees, Modules are Built Through Diversified Channels
3.3 Furthermore, the Infrastructure and Public Service Modules Improve the Quality of Experience
3.4 Standardize the Long-Term Operation of the Community Through the Normal Management Module
4 Summary
References
Exploratory Planning of Urban Livelihood Group – Taking District L of Wuhan, China as an Example
1 Introduction
2 Concept and Connotation
3 Analysis of Current Situation
3.1 Emphasis on Big Facilities Land Problem, Ignoring Micro Facilities Space Problem
3.2 Emphasis on Special Design, Neglect Systematic Integration, Lack of Coordination Among Multi-majors
3.3 Emphasis on the Number of Facilities and Projects, Ignoring the Creation of Space Quality
3.4 Emphasis on Long-Term Virtual Control, Ignoring Actual Implementation Guarantees
4 Overall Planning of the People’s Livelihood Group
4.1 The Planning Method has Changed from Incremental Planning to Stock Planning, Focusing on an Equalized Layout
4.2 The Construction Mode is Shifted from Decentralized to Centralized, Focusing on Integrated Construction
4.3 The Space Creation is Shifted from Focusing on Facilities to Improving Quality, Focusing on Characteristic Creation
5 An Empirical Study on the Planning of the People’s Livelihood Group in District L of Wuhan
5.1 Current Situation of Construction
5.2 Planning the Layout
5.3 Division and Construction Guidance of People’s Livelihood Groups Based on Dynamic and Static Zoning
5.4 Implementation Effect
6 Summary
References
Technical Feasibility and Application of Rural Self-sufficiency Community in Cold Region: A Case Study of Beijing
1 Introduction
2 Autonomous Community for Self-sufficiency
3 Energy Consumption of Villages and Towns in Beijing
4 Main Technologies and Applications of Autonomous Community
4.1 Self-sufficiency Technology at Neighborhood Level
4.2 Self-sufficiency Technology at Group Level
4.3 Self-sufficiency Technology at Community Level
5 Conclusion
6 Notes
References
Healing Methods for the Loneliness of the Empty-Nest Elderly in Rural Areas Under the Background of Rural Revitalization: A Case Study of H Town in Hubei Province
1 Research Background
2 Causes of Loneliness
3 Investigation of the Current Situation in H Town
3.1 Policy Investigation
3.2 Resource Investigation
3.3 Residents Investigation
4 Healing Methods
5 Research Conclusions
References
Strategies of Water Management in Outdoor Space of Sustainable Housing-Water Material Heritage of Historic City of Nineveh
1 Introduction
2 The Material Water Heritage of Mesopotamia Civilization
2.1 Water Management in the Mesopotamia Civilization
3 Modern Principles and Strategies of Water Management
3.1 The Principles and Mechanism of Sustainability According to (Highlights of LEED V4.1 Residential Multifamily) Blog
3.2 “Siti Jamaludin” Study: Designing Conducive Residential Outdoor Environment for Community: Klang Valley, Malaysia
3.3 “Residential Landscape Sustainability, Smith, 2008” Study
3.4 Sustainable Landscape Construction a Guide to Green Building Outdoors, 2008 by William Thompson
3.5 Mumin Bani Mustafa’s Study: Rainwater Harvesting Techniques
4 Stratiges of Water Management
4.1 Control and Domination Strategy
4.2 Conservation Strategy
4.3 Environmental Sustainability Strategy
5 Conclusions
References
Reconstruction and Invigoration of Rural Housing Space from the Perspective of Sustainable Renewal
1 Introduction
2 Construct the Goal of Continuous Rural Renewal
3 Establish Continuously Updated Target
4 Planning the Sustainable Renewal Path of the Village
4.1 Overview of Zhuma Town
4.2 Industry-Oriented Renewal Path
4.3 Exemplary Rural Housing Reconstruction
5 Conclusions
References
Sustainable Urbanism Through City Information Modeling
1 Introduction
1.1 Paper Objectives
1.2 Problem Definition
1.3 Methodology
2 Building Information Modelling
3 Urban Planning Enhancement Through BIM
4 A New Era of Digital Transformation
4.1 From BIM to PIM for Enhancement of Urbanism
5 City Information Modeling (CIM)
5.1 The Relationship Between BIM and CIM
5.2 Smart Cities International Demand
5.3 Innovative Application of CIM in Urbanism
6 Standards for Sustainable Urbanism
6.1 Sustainable Urbanism Elements
6.2 LEED-ND
7 Green Sustainable Urbanism with City Information Modelling (CIM)
8 Final Thoughts/Conclusion
References
Landscape Planning and Design: Vernacular and Religious Architecture in Wood as Facilitators of Heritage Conservation. Chiloe’s School of Architecture, Chile
1 Introduction
2 Theoretical Framework
3 Methodology
4 Results
5 Conclusions
References
Exploration of Regional Characteristics of Steel Residential Structure in Rural China
1 Introduction
2 Overview of the Development of Steel Structure Residence
2.1 Type of Steel Residential Structure in Rural China
2.2 Practice of Steel Residential Structure in Rural China
3 Exploration of Regional Characteristics in Spatial Composition
4 Exploration of Regional Characteristics in Facade Characteristics
4.1 Proportional Scale
4.2 Characteristic Shape
4.3 Material and Color
5 Exploration of Regional Characteristics in Detail Components
5.1 Detail Decoration
5.2 Characteristic Components
6 Summary
References
Application of Clay Shock Method to Restrain Settlement in Tunnel Foundation Under Canal
1 Introduction
2 Project Overview
3 Construction Risk Analysis
3.1 Shield Risk
3.2 Surface Subsidence Risk
4 Clay Shock Method
5 Conclusion
References
Effects of Age on Urban Road Traffic Accident Using GIS: A Case Study of Bangkok Metropolitan Area, Thailand
1 Introduction
2 Material and Methodology
3 Result of Analysis
4 Conclusion
References
Sustainable Building and Energy Conservation in Building
Vernacular Architecture and Wood Construction. The Case of the Stilt House of Chiloé, Chile
1 Introduction
2 Theoretical Framework
3 Methodology
4 Results
5 Conclusion
References
Traditional Ventilation Skills of Lingnan Chinese Architecture – a Case Study of Macau Mandarin’s House
1 Introduction
2 Basic Ventilation Concept
2.1 Wind Pressure Ventilation
2.2 Thermal Pressure Ventilation
2.3 Synergy and Alternate Use of Thermal and Wind Pressure Ventilation
3 Case Study
3.1 Brief of Mandarin’s House
3.2 Marco Ventilation Skills
3.3 Medium-Scope Ventilation Skills
3.4 Micro Ventilation Skills
4 Conclusion
References
Wood Construction as a Facilitating Mechanism for Environmental Protection, Sustainability and Development. The Case of the Construction and Vernacular Architecture of the Palafitos of Chiloé
1 Introduction
2 Theoretical Framework
3 Methodology
4 Results
5 Conclusion
References
Heat Transfer Analysis of Double and Triple Glazed Glass Windows
1 Introduction
1.1 Heat Transfer Through Window
1.2 Double Glazed Windows
1.3 Triple Glazed Windows
2 Technical Approach
2.1 Methodology
2.2 Modelling
2.3 Numerical Solution Using MATLAB
3 Comparing Between Double and Triple Glass Window
3.1 Double Glass Window
3.2 Triple Glass Window
3.3 Comparing the Results of Double and Triple Glazed Window
4 Conclusion
References
Analysis on Energy Saving Design of Ancillary Buildings of Hydraulic Engineering
1 Introduction
2 Development Trend
3 Energy Saving Design
3.1 Building Energy Efficiency Design
3.2 Energy Saving Design of Water Supply and Drainage
3.3 Electrical Energy Saving Design
3.4 Energy Saving Design of HVAC
4 Summary
References
Experimental Study on Miniature Photovoltaic Roof Tile
1 Introduction
2 Structural Design of Small Photovoltaic Roof Tiles
2.1 Photovoltaic Cell
2.2 Basal Part
3 Process of the Small Photovoltaic Roof Tiles
3.1 Selecting and Molding of Materials
3.2 The Sintering Process of Tile Base
3.3 The Process of Combination of Tile Base and Solar Panel
4 Performance Test of Small Photovoltaic Roof Tiles
4.1 Appearance Detection
4.2 Density Determination
4.3 Impermeability Test Method
4.4 Test and Analysis of I-V Characteristics
5 Conclusion
References
Protection and Restoration of Architectural Heritage
Research on Conservation Techniques of Brick-Timber Building in the Republic of China—A Case Study of Dewey House
1 Introduction
2 Basic Information Research
2.1 Investigation of Current Situation
2.2 Investigation of Historical Information
3 Structural Reinforcement Method
3.1 Structural Inspection and Identification
3.2 Reinforcement of Brick Masonry
3.3 Reinforcement of Woodwork
4 Building Repair Method
4.1 External Wall Conservation
4.2 Door and Window Openings Conservation
4.3 Roof Conservation
4.4 Interior Conservation
5 Conclusion
References
Research on Construction Methods and Restoration Techniques of the Exterior Wall Surfaces of Nanjing’s Modern Buildings
1 Introduction
2 Research on Conservation of the Exterior Wall Surfaces
3 General Situation of Exterior Wall Surfaces of Nanjing’s Modern Buildings
3.1 Main Types of Exterior Wall Surfaces
3.2 Construction Processes of Exterior Wall Surfaces
4 Research on Conservation and Restoration Techniques
4.1 Analysis on Common Typical Diseases and Causes of Exterior Wall Surfaces
4.2 Research on Restoration Techniques
5 Conclusion
References
Study on Conservation Techniques of Traditional Timber Buildings in Jiangnan Area—A Case Study of Xiangdian of Xiaoling Mausoleum of Ming Dynasty
1 Introduction
2 The Features of Xiangdian
3 The Investigation of Present Situation
3.1 Current Situation of the Roof
3.2 Current Situation of the Timber Frame and Decorations
3.3 Current Situation of the Walls, the Ground and the Foundation
4 The Identification of Present Situation
4.1 Identification of the Foundation
4.2 Calculation of the Upper Bearing Structure
4.3 Test and Identification Results
5 Structural Reinforcement Techniques
5.1 Reinforcement Techniques of the Timber Frame
5.2 Reinforcement Techniques of the Walls
6 Architectural Repair Techniques
6.1 Repair Techniques of Roof Tiles and Timber Base
6.2 Repair Techniques of Timber Decorations
6.3 Repair Techniques of Outdoor Foundation
6.4 Repair Techniques of Outdoor Corridor and Indoor Floor
7 Conclusions
References
The Cultural Integration Phenomenon of Shenyang Architectural Heritage
1 Introduction
2 Representative of Cultural Integration – Xiaoqing Building
3 Conclusion
References
Research on Macau’sHistoric Buildings Blending Chinese and Western Cultures
1 Introduction
2 Diversity of Macau’s Architectural Styles
3 Civil Architecture in Macau Combining Chinese and Western Architectures
3.1 Chinese-Style Dwellings
3.2 Western-Style Dwelling
4 Study Value of Historical Buildings in Macau
References
Construction Project and Engineering Management
Modeling of Causal Factors of Conflicts in Thai SME Construction Projects
1 Introduction
2 Research Background
3 Research Method
3.1 Factor Identification
3.2 Questionnaire Design
3.3 Data Collection
4 Results
4.1 Descriptive Results
4.2 Exploratory Factor Analysis
4.3 Confirmatory Factor Analysis
5 Conclusions
References
Improvement of Quality Control in Retail-Type Works Through the Application of the BIM-LC Work Model
1 Introduction
2 Study Cases
2.1 Study Case 1
2.2 Study Case 2
3 Methodology
3.1 Inicial of Previous Stage
3.2 Aplication of Lean Construction and BIM Tools
3.3 Tracing and Control
3.4 Weekly Meetings
4 Validation Through Expert Judgment
4.1 Contributions
4.2 Regarding to Projects
5 Conclusions
References
The Role of Public-Private Partnerships of Project Construction – Shopping Mall as an Example
1 Introduction
2 Methodology
3 Case Study
3.1 Rongchuang Mall
3.2 Aqua Mall (Shuiyou Mall)
4 Discussion
5 Conclusion
References
Activity Time Variations and Its Influence on Realization of Different Critical Paths in a PERT Network: An Empirical Study Using Simulations
1 Introduction
2 Modifications to PERT
3 Research Methodology
4 Result and Discussion
5 Conclusion
References
Implementation of a Public Works Communication Management Model
1 Introduction
2 Methods and Tools
2.1 Method
2.2 Tools
2.3 Methodology
2.4 Results
2.5 Validation
3 Conclusions
References
A Study on the Impact of COVID-19 Epidemic on Civil Engineering System
1 Introduction
2 Increasing Need of Temporary Civil Systems
2.1 The Origin of the Need
2.2 Urgency of Building Such Temporary Civil System
2.3 Ways to Optimize the Efficiency of Building Temporary Civil System
3 Lack of Work Force
3.1 Reasons for Lacking Workforce
3.2 Impact of Lacking Workforce
3.3 Solutions
4 Uncertainty on the Need Assessment
4.1 Influence on the Need Assessment Phase
4.2 The Way to Minimize the Negative Influence
5 Great Changes to System Design
5.1 How COVID-19 Epidemic Change the Way of System Design
5.2 How to Deal with the Impact of This Change
6 Increased Difficulty the Cost Management
6.1 Impact on Different Kinds of Cost
6.2 Solutions
7 Difficulty in Construction and Preservation
7.1 Difficult to Construct and Preserve Buildings
7.2 Improve the Construction and Preservation Phases
8 Monitoring of the Users in Civil System
8.1 Impact on Monitoring
8.2 Better Way to Collect Users’ Information
9 Conclusion
References
Author Index

Citation preview

Lecture Notes in Civil Engineering

Marco Casini   Editor

Proceedings of the 2nd International Civil Engineering and Architecture Conference CEAC 2022, 11–14 March 2022, Singapore

Lecture Notes in Civil Engineering Volume 279

Series Editors Marco di Prisco, Politecnico di Milano, Milano, Italy Sheng-Hong Chen, School of Water Resources and Hydropower Engineering, Wuhan University, Wuhan, China Ioannis Vayas, Institute of Steel Structures, National Technical University of Athens, Athens, Greece Sanjay Kumar Shukla, School of Engineering, Edith Cowan University, Joondalup, WA, Australia Anuj Sharma, Iowa State University, Ames, IA, USA Nagesh Kumar, Department of Civil Engineering, Indian Institute of Science Bangalore, Bengaluru, Karnataka, India Chien Ming Wang, School of Civil Engineering, The University of Queensland, Brisbane, QLD, Australia

Lecture Notes in Civil Engineering (LNCE) publishes the latest developments in Civil Engineering - quickly, informally and in top quality. Though original research reported in proceedings and post-proceedings represents the core of LNCE, edited volumes of exceptionally high quality and interest may also be considered for publication. Volumes published in LNCE embrace all aspects and subfields of, as well as new challenges in, Civil Engineering. Topics in the series include: • • • • • • • • • • • • • • •

Construction and Structural Mechanics Building Materials Concrete, Steel and Timber Structures Geotechnical Engineering Earthquake Engineering Coastal Engineering Ocean and Offshore Engineering; Ships and Floating Structures Hydraulics, Hydrology and Water Resources Engineering Environmental Engineering and Sustainability Structural Health and Monitoring Surveying and Geographical Information Systems Indoor Environments Transportation and Traffic Risk Analysis Safety and Security

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More information about this series at https://link.springer.com/bookseries/15087

Marco Casini Editor

Proceedings of the 2nd International Civil Engineering and Architecture Conference CEAC 2022, 11–14 March 2022, Singapore

123

Editor Marco Casini Department of Urban Planning, Design and Technology of Architecture (DPTA) Sapienza University of Rome Rome, Italy

ISSN 2366-2557 ISSN 2366-2565 (electronic) Lecture Notes in Civil Engineering ISBN 978-981-19-4292-1 ISBN 978-981-19-4293-8 (eBook) https://doi.org/10.1007/978-981-19-4293-8 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

2022 2nd International Civil Engineering and Architecture Conference (CEAC 2022) was held online during March 11–14, 2022. Due to the evolving public health concerns and travel advisories issued for the avoidance of non-essential travel in view of COVID-19, the conference CEAC 2022 has been held virtually with about 90 guests hosted on Zoom video conference platform. It was a fully synchronized online conference that had live presentations, participants with Q&A sessions and other live events associated with the conference. The Lecture Notes in Civil Engineering (ISSN: 2366-2557) was selected for publishing the conference proceedings. The conference was organized in 13 sessions, with 4 plenary, 15 invited and 72 specialized papers presented. Scientists, researchers and engineers from China, Indonesia, Thailand, Germany, Japan and many other countries took part in the scientific forum. Each plenary speech lasted for 40 minutes, including 5 minutes for Q&A, invited speech lasted for 25 minutes, including 5 minutes for Q&A, while for other sessions, each of the presentations lasted 15 minutes, including 2 minutes for Q&A. The interaction session was real experience to the participants, and they had good exposure with foreign researchers, students and other delegates. The objective of CEAC was to provide a platform for engineers, scientists and industrial partners to discuss and disseminate and share their recent research findings in wide aspects of theoretical, experimental and practical civil engineering and architecture fields. Professionals, experts and scholars from various engineering disciplines were invited to share experiences, innovations, achievements and knowledge. The conference brought together academics, researchers and practitioners with the aim of bridging the gap between theory and practice in all civil engineering aspects. All papers in this proceeding were subject to peer-review by the conference committee members and international reviewers. The papers were selected for the proceedings based on quality and relevance to the conference. We would like to record our great appreciation and acknowledgement to all parties who supported CEAC 2022. The individual and institutional help was pivotal for the success of the conference. In particular, the organizing committee to thank those who offered their valuable advice and in the peer review of papers. We v

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Preface

sincerely hope that CEAC 2022 has been an outstanding discussion forum and a space for new ideas and the promotion of collaborative research. We are confident that the proceedings will serve as an essential reference source for scientific, engineering progress, and future products and processes. C. W. Lim Conference Chair

Organization

Conference Chairs Tan Kiang Hwee C. W. Lim

National University of Singapore, Singapore City University of Hong Kong, Hong Kong

Program Chairs Kyoung Sun Moon Minehiro Nishiyama Ippei Maruyama Marco Casini

Yale University, USA Kyoto University, Japan Nagoya University & The University of Tokyo, Japan Sapienza University of Rome, Italy

Program Chairs Mingfeng Huang Han Lin

Zhejiang University, China Nanjing Audit University, China

Steering Committee Chair Nuno Dinis Cortiços

University of Lisbon, Portugal

Publicity Committees Grit Ngowtanasuwan Duy Nguyen Phan Yi Shen Koorosh Gharehbaghi Zujian Huang

Mahasarakham University, Thailand Mientrung University of Civil Engineering, Vietnam Tongji University, China RMIT University, Australia Tsinghua University, China

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Organization

International Technical Committees Ludovic Jason Luigi Coppola Zbyšek Pavlík Liang Xu Mitsuyoshi Akiyama Wei Gao Sang Whan Han Yanjun Xu Leonardo Castillo Tianyun Li Sissi Santos Congqi Fang Shaoyao He Yibo Liu Abeer Samy Yousef Mohamed Ke Yin Jamal A. Abdalla Linchang Miao Benchen Fu Radhi Alzubaidi Wen Cheng Ahmed Farouk Deifalla Jian Wang S. J. Pawar Xiang Zhu Wenxue Gao J. Jeyanthi Shanshan Zhang Jinhua Sun Hage Chehade Fadi Jiangtao Yi Lingling Zhuang Daniel Macek Tong Yang

Université Paris Saclay, France University of Bergamo, Italy Czech Technical University, Czech Republic Beijing Gang Yan Diamond Products Company, China Waseda University, Japan Beijing Jiaotong University, China Hanyang University, South Korea Advanced Technology & Materials Co., China Peruvian University of Applied Sciences, Perú Huazhong University of Science and Technology, China Peruvian University of Applied Sciences, Perú Shanghai Normal University, China & Shanghai Jiaotong University, China Hunan University, Changsha, China Beijing Gang Yan Diamond Products Company, China Effat University, Saudi Arabia & Tanta University, Egypt Chongqing University, China University of Sharjah, United Arab Emirates Southeast University, China Shenzhen University, China University of Sharjah, United Arab Emirates Harbin Institute of Technology, China Future University in Egypt, Egypt University of Science and Technology of China, China Motilal Nehru National Institute of Technology Allahabad, India Huazhong University of Science and Technology, China Beijing University of Technology, China Government College of Technology, India Harbin Institute of Technology, China University of Science and Technology of China, China Lebanese University, Lebanon Chongqing University, China Shenyang Jianzhu University, China CTU in Prague, Czech Republic Xi’an Polytechnic University, China

Organization

Toshiaki Sato Yanfen Zhang Karina Vilela Di Wang Rini Kusumawardani Yong Jiang Sarunya Promkotra Guozhu Zhang Yaik Wah Lim Waleed Zeiada Mei Zhao Ghanshyam Pal Mohammad Arif Kamal Ying Xu Zihni Turkan Mohammad Arif Rohman Anizahyati Alisibramulisi Xin Sun Tamilsalvi Mari Try Ramadhan Edoghogho Ogbeifun Kornkamon Tantiwanit Boya Jiang Pimonmart Wankanapon Anjali Pathak Wei Jia Shadi Shaikh Yasin Pratch Piyawongwisal Yanxuan Ma Satawat Doungpan Sopokhem Lim Guo Yacheng Taki Eddine Seghier Peng Tu Christian Paglia Fernando Pachego Torgal Francesca Scalisi

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Kyushu University, Japan Guangdong Polytechnic of Science and Technology, China Universidad Peruana de Ciencias Aplicadas, Perú Taihu University of Wuxi, China Universitas Negeri Semarang, Indonesia Tsinghua University, China Khon Kaen University, Thailand Southeast University, China Universiti Teknologi Malaysia, Malaysia University of Sharjah, United Arab Emirates Beijing Institute of Technology, China Shiv Nadar University, India Aligarh Muslim University, India Harbin Institute of Technology Shenzhen Graduate School, China Near East University, Cyprus ITS, Indonesia Universiti Teknologi MARA, Malaysia Xi’an University of Technology, China Taylor’s University Lakeside Campus, Malaysia Universitas Pendidikan Indonesia, Indonesia University of Johannesburg, South Africa Thammasat University, Thailand Nanjing Tech University, China Thammasat University, Thailand Birla Institute of Technology Mesra Ranchi, India Tsinghua University, China American University of the Middle East, Kuwait Rajamangala University of Technology Lanna, Thailand Qingdao University of Technology, China Sukhothai Thammathirat Open University, Thailand Waseda University, Japan Qingdao University of Technology, China UCSI University, Malaysia Southwest Jiaotong University, China University of Applied Sciences of Southern Switzerland, Switzerland University of Minho, Portugal DEMETRA Ce.Ri.Med. (Euro-Mediterranean Documentation and Research Center, Italy

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Cuong Nguyen Kim Doo-Yeol Yoo Kedsarin Pimraksa Mohammed N. Abdulrazaq Alshekhly Trong-Phuoc Huynh Koorosh Gharehbaghi Omid Reza Baghchesaraei B. Kondraivendhan

Organization

Mien Trung University of Civil Engineering, Vietnam Hanyang University, South Korea Chiang Mai University, Thailand Management & Science University, Malaysia Can Tho University, Vietnam RMIT university, Australia Western Sydney University, Australia S. V., National Institute of Technology, India

Contents

Building Materials and Technology Possibility to Optimize Hydrothermal Conditions for the Production of Autoclaved Aerated Concrete Using Rice Husk Ash as the Silica Raw Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Taban Shams, Georg Schober, Detlef Heinz, and Severin Seifert

3

Innovative Research on the Mechanical Experiment of Steel Fiber Modified Waste Material Recycled Concrete . . . . . . . . . . . . . . . . . . . . . Cheng-yuan Wang and Zhang Xu

12

Calculation Method of Asphalt Concrete Thermal Stress Based on Interface Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wenhao Ke, Yu Lei, and Mingming Xu

23

Aging Performance of Base and Modified Bitumen . . . . . . . . . . . . . . . . Ma Li and Pan Yurong

33

An Approach to Reduce Strength Loss of Rubber Concrete . . . . . . . . . Haolin Su

39

Carbon Efficiency-Oriented Design Optimization of Bamboo Construction: A Case Study in Guangzhou, China . . . . . . . . . . . . . . . . Zujian Huang Study on the Performance of Eggshells as a Humidity Control Building Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wen-Cheng Shao, Yu-Wei Dong, Guan-Wei Fan, Jia-Wei Chen, and Chao-Ling Lu The Mechanical Properties for Using Banana’s Peel Ash as Aggregate in Geopolymer Mortar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trithos Kamsuwan

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Facile Fabrication of Superhydrophobic Robust Coatings with Solar Reflective Capability by One Step Spraying Method . . . . . . . . . . . . . . . Xingjie Tang, Yanyan Wang, Shu Liu, Zhiyong Xu, and Changsi Peng

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Study on Carbon Emission of Laminated Bamboo Based on Life Cycle Assessment Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zujian Huang and Wenyu Zhang

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Study on the Mechanical Strength of Fiber-Reinforced Geopolymer Porous Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Xiaoling Qu, Jun Pang, Zhiguang Zhao, and Chaocheng Yu

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Bridge and Tunnel Engineering Use of Non-destructive Tests to Evaluate the Concrete and Steel Bars of Vehicular Bridges Structural Elements . . . . . . . . . . . . . . . . . . . . . . . 107 Milady Inga Silva, Gianluca Josehf Olano Gálvez, and Cristian Daniel Sotomayor Cruz Study on Laying Method of Trenchless Channel for Power Cables in Tianjin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Tao Qin, Fang Geng, Suna Bai, Bingran Shao, Ran Lu, and Zhaohui Yang Analysis and Design of Pipe Gallery Bridge with Large CrossSection and High Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Lijun Chen, Fuwei Sun, and Lu Liu Research on the Application of Computer Vision in Bridge Health Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 Yimin Cao, Mingzheng Huang, Yixin Sun, and Cheng Li Failure Analysis of High Strength Cables from Collapsed Myaungmya Suspension Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Phyoe Wae Hein, Thinzar Khaing, Khin Maung Zaw, and Kunitomo Sugiura Application of Anti-slide Pile-Plank Wall Combined with Backfilling in Treatment of Tunnel Portal Crack and Slope Collapse . . . . . . . . . . . 146 Juzhi Zhang, Jingxuan Liang, and Hongqiang Zhang An Integrated Erection Method for Segmental Assembled Bridge in Urban District . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 Hong Zhang, Maolin Cheng, Hao Xia, Chenyang Fan, Hao Xiao, and Xiaoping Zhang Study on Effective Temperature Extreme Isotherm Map of SteelConcrete Composite Girder Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 Yun Zhang

Contents

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Geotechnical Engineering and Engineering Geology Dynamic Response Analysis of Rock Slope with Weak Layer Based on DOE Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 Ke Yang and Ke Yin The Influence of Soil Parameters on the Bearing Performance of Super-Long Bored Pile Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 Xuefeng Zhang Based on Immersion Study on Bearing Characteristics of Roadway Pillar Under Softening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 Yugeng Zhang, Yawei Zhu, Heng Zhang, and Wenhao Cao Numerical Study on Spudcan Penetration-Consolidation-Uplift in Soft Soil Using Large Deformation Simulation . . . . . . . . . . . . . . . . . . . . . . . 214 Taibin Zhang, Jiangtao Yi, Zhen Wang, and Fei Liu Effects of Rock Mass Deterioration Induced by Wetting-Drying Cycles on Slope Stability of Reservoir Banks . . . . . . . . . . . . . . . . . . . . . . . . . . 221 Zijuan Wang and Xinrong Liu Research on Fine Management of Expressway Survey . . . . . . . . . . . . . . 241 Hong Qiang Zhang, Ju Zhi Zhang, and Wei Li Research Progress on the Formation Mechanism of Intraplate Volcanoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 Hongyu Wang, Zeyu Zhang, and Xiaozhuo Luo Finite Element Analysis of Lateral Bearing Capacity for Pile in Spatially Variable Clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 Junjie Dong, Jiangtao Yi, Fei Liu, Po Cheng, and Zhen Wang Application of Numerical Simulation in Teeth Propotion Design of Diamond Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 Yanjun Xu, Liang Xu, Yibo Liu, and Qiang Xu Structural Engineering and Structural Mechanics Bayesian Networks and Their Application to the Reliability of FRP Strengthened Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 Osama Obaid and Moussa Leblouba Static Loading Test of Soil-RC Pile System Using a Centrifuge Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 Shuhei Takahashi, Tomoki Nakamura, Kazuhiro Hayashi, and Taiki Saito Evaluate Effect of Various Parameters on the Shear Strength of FRPReinforced Concrete Beams with or Without Stirrups . . . . . . . . . . . . . . 293 A. Deifalla

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Statistics and Probabilistic Modeling of Construction Materials Used in the UAE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 Omar Nofal, Moussa Leblouba, and Sami Tabsh Collapse Strength of Conical Wall Failure in Steel Cone-to-Cylinder Socket Connections Under Axial Compression . . . . . . . . . . . . . . . . . . . . 315 Tian Qixiang and Kuwamura Hitoshi Effectiveness of Laser Treatment on Carbon Steel with Various Forms of Corrosion Pits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 S. Park, S. Kainuma, M. Yang, H. Miki, and T. Asano Experimental Investigation of the Axial Load Capacity for DSTCs Manufactured with High Strength Concrete . . . . . . . . . . . . . . . . . . . . . 334 Zakir Ikhlasi and Thomas Vincent Earthquake-Induced Vibration Measurement and Inverse Analysis of Bell-Shaped Pagoda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Naremet Tantisukhuman, Chayanon Hansapinyo, Chinnapat Buachart, Mitsuhiro Miyamoto, and Manabu Matsushima Extended Critical Shear Crack Theory for Punching Shear of Lightweight, FRP-Reinforced, or Prestressed Concrete . . . . . . . . . . . . . 353 A. Deifalla Evaluation on Deterioration and Blister Progression of Duplex Layers Between Al-5 Mg Thermal Sprayed Coating and Heavy-Duty Paint Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 H. Yang, S. Kainuma, M. Yang, and T. Asano Architectural Design and Theory From the Interval in Architecture: (In)visibilities – The Case of Smithsons’ “Project-Theory” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371 João Cepeda Spatial Design Strategies for Lightweight Roofing Buildings Driven by Rain Noise Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 Shaohang Shi, Xiang Yan, and Yehao Song Application of Lingnan Ventilation Skills in Contemporary Architecture – Lift Shaft Design of Pedestrian Footbridge in Macau . . . 393 Johnny Kong Pang Ng The Opportunities and Challenges of Using LCA-Based BIM Plugins in Early-Stage Building Design: An Industry Expert Perspective . . . . . . 401 Seyma Atik, Teresa Domenech Aparisi, and Rokia Raslan

Contents

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The Factors of Environmental Living Design for Elderly Well-Being in Thai Spiritual Environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 Porntip Ruengtam Prototype Design of Smart Building Control System Based on Human Demand Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 Ziqi Lian Urban Engineering and Spatial Planning Exploring the Renewal and Practice Path of Old Neighborhoods with Multi-module Integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 Linsheng Huang Exploratory Planning of Urban Livelihood Group – Taking District L of Wuhan, China as an Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442 Shi Yuan, Yuan Jianfeng, and Huang Xiaofang Technical Feasibility and Application of Rural Self-sufficiency Community in Cold Region: A Case Study of Beijing . . . . . . . . . . . . . . 452 Wei Gao, Jiachen Hou, Qinghua Zhou, and Mei Zhao Healing Methods for the Loneliness of the Empty-Nest Elderly in Rural Areas Under the Background of Rural Revitalization: A Case Study of H Town in Hubei Province . . . . . . . . . . . . . . . . . . . . . 463 Haoru Shen Strategies of Water Management in Outdoor Space of Sustainable Housing-Water Material Heritage of Historic City of Nineveh . . . . . . . . 470 Shalwa Falih Al-Saffar and Ghada M. Younis Reconstruction and Invigoration of Rural Housing Space from the Perspective of Sustainable Renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491 Senyu Lou Sustainable Urbanism Through City Information Modeling . . . . . . . . . 500 D. Abeer S. Y. Mohamed Landscape Planning and Design: Vernacular and Religious Architecture in Wood as Facilitators of Heritage Conservation. Chiloe’s School of Architecture, Chile . . . . . . . . . . . . . . . . . . . . . . . . . . 515 Stefania Pareti, David Flores, Loreto Rudolph, and Martina Pareti Exploration of Regional Characteristics of Steel Residential Structure in Rural China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526 Mei Zhao, Yongmei Yang, Lu Zhu, and Wei Gao

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Application of Clay Shock Method to Restrain Settlement in Tunnel Foundation Under Canal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 536 Zhanming Guan, Zhiyong Hou, Jingchao Liang, Haibin Liu, Xiaoyi Qin, Weilong Zhao, and Jianfei Liu Effects of Age on Urban Road Traffic Accident Using GIS: A Case Study of Bangkok Metropolitan Area, Thailand . . . . . . . . . . . . . . . . . . 542 S. Chayphong and P. Iamtrakul Sustainable Building and Energy Conservation in Building Vernacular Architecture and Wood Construction. The Case of the Stilt House of Chiloé, Chile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 Stefania Pareti, David Flores, Loreto Rudolph, and Martina Pareti Traditional Ventilation Skills of Lingnan Chinese Architecture – a Case Study of Macau Mandarin’s House . . . . . . . . . . . . . . . . . . . . . . 556 Johnny Kong Pang Ng Wood Construction as a Facilitating Mechanism for Environmental Protection, Sustainability and Development. The Case of the Construction and Vernacular Architecture of the Palafitos of Chiloé . . . 564 Stefania Pareti, Loreto Rudolph, Vicente Valdebenito, and David Flores Heat Transfer Analysis of Double and Triple Glazed Glass Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571 Fahad Alosaimi and Abdulaziz Almutairi Analysis on Energy Saving Design of Ancillary Buildings of Hydraulic Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583 Zhen Yang, Mei hong Li, Hong Jie Xin, and Shi Cong Cheng Experimental Study on Miniature Photovoltaic Roof Tile . . . . . . . . . . . 588 Pengyuan Qi, Sumei Wu, Yuzhi Xue, Longxue Ji, and Jingbo Wang Protection and Restoration of Architectural Heritage Research on Conservation Techniques of Brick-Timber Building in the Republic of China—A Case Study of Dewey House . . . . . . . . . . . . . 597 Yang Ling and Chun Qing Research on Construction Methods and Restoration Techniques of the Exterior Wall Surfaces of Nanjing’s Modern Buildings . . . . . . . . . . . . . 607 Lang Wu and Qing Chun Study on Conservation Techniques of Traditional Timber Buildings in Jiangnan Area—A Case Study of Xiangdian of Xiaoling Mausoleum of Ming Dynasty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 618 Bei Peng and Qing Chun

Contents

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The Cultural Integration Phenomenon of Shenyang Architectural Heritage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 631 Lina Tang, Jian Tang, and Fei Guo Research on Macau’s Historic Buildings Blending Chinese and Western Cultures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 636 Yanfen Zhang and Haijun Mo Construction Project and Engineering Management Modeling of Causal Factors of Conflicts in Thai SME Construction Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647 Grit Ngowtanasuwan Improvement of Quality Control in Retail-Type Works Through the Application of the BIM-LC Work Model . . . . . . . . . . . . . . . . . . . . . . . . 658 Jesús Robles Ana Victoria Fiorella and Farje Mallqui Julio Enrique The Role of Public-Private Partnerships of Project Construction – Shopping Mall as an Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666 Ting Zhang, Fangqian He, and Di Wang Activity Time Variations and Its Influence on Realization of Different Critical Paths in a PERT Network: An Empirical Study Using Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 674 Saurabh Gupta, Riya Catherine George, Deepu Philip, and Syam Nair Implementation of a Public Works Communication Management Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 681 Estefani R. Miranda, Yong S. Ko, and Katia J. Melendez A Study on the Impact of COVID-19 Epidemic on Civil Engineering System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 691 Zhuogeng Xie Author Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701

Building Materials and Technology

Possibility to Optimize Hydrothermal Conditions for the Production of Autoclaved Aerated Concrete Using Rice Husk Ash as the Silica Raw Material Taban Shams1,2(B) , Georg Schober3 , Detlef Heinz2 , and Severin Seifert1 1 Fraunhofer Institute for Building Physics IBP, Inorganic Materials and Recycling Department,

Building Materials Technology Group, Fraunhoferstr. 10, 83626 Valley, Germany [email protected], [email protected] 2 Department of Civil, Geo and Environmental Engineering, Centre for Building Materials cbm, Technical University of Munich, Franz-Langinger-Str. 7, 81245 Munich, Germany [email protected] 3 Engineering Office for Materials Development and Process Technology, Marbstraße 6, 94405 Landau a.d. Isar, Germany [email protected]

Abstract. Rice husk ash (RHA) was utilized as a substitute for quartz sand to produce autoclaved aerated concrete (AAC). Different autoclaving temperatures in the range of 152 °C to 192 °C with an autoclaving duration of 6 h were applied. The compressive strength and phase formation were studied. Ordinary AAC samples which contained quartz sand exhibited their most favorable properties at the autoclaving temperature of T = 192 °C. However, this temperature was 165 °C when RHA was used as the silica raw material in AAC. Keywords: Autoclaved aerated concrete · Mechanical properties · XRD analysis · Rice husk ash

1 Introduction In the AAC factories, the common silica raw material used for manufacturing products is quartz sand. The results of the earlier studies [1, 2] published by authors revealed that the utilization of other silica materials which exhibit higher solubility than quartz sand in AAC mixture could lead to lower consumption of energy during hydrothermal treatment of AAC products through reduction of the required autoclaving temperature. However, in the aforementioned studies [1, 2], the raw material used as the silica material of a higher solubility was not economical. Therefore, in the current study, the feasibility of improving the autoclaving conditions using an economical as well as environmentallyfriendly material is assessed.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 3–11, 2023. https://doi.org/10.1007/978-981-19-4293-8_1

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Rice husk ash (RHA) is a waste produced in the course of agricultural procedures. Currently, disposal of these materials is a serious challenge for rice producers [3]. Highly pozzolanic RHA, obtained by controlling the combustion condition considering burning temperature and time, can react with calcium hydroxide and water to form C-S-H having strong cementitious properties [3]. Moreover, the main phase that is present in RHA can be cristobalite which is more soluble than quartz [4]. Therefore, RHA can be used as a material which exhibits higher solubility than quartz sand for the production of AAC. The properties of AAC containing quartz sand are comprehensively examined [5–7]. Moreover, the utilization of several kinds of by-products, secondary and waste materials such as air-cooled slag, silica fume, fly ash, bottom ash, zeolite, iron ore tailings, and waste glass in the AAC mixture has been studied [8–11]. Whilst carrying out research works related to the use of quartz sand and by-products materials in AAC, the optimization of the autoclaving condition in order to reduce energy consumption in AAC production has only been studied by Kunkarchiyan et al. [12] who did not report a possibility for reducing the autoclaving temperature and/or time. Subsequently, the object of this study is to examine the possibility of reducing energy consumption during the autoclaving process using RHA which is an economical and environmentally friendly material.

2 Materials and Methods The materials and methods used in this study are mainly the same as the previous studies [1, 2]. To avoid repetition, this section is explained briefly since a detailed explanation was already given in the previous studies. The AAC specimens were produced using quartz sand and RHA as silica sources. The chemical composition of quartz sand and RHA are provided in Table 1. The degree of crystallinity of these materials, which was obtained from DIFFRAC.EVA, is given in Table 2. Table 1. Chemical composition of quartz sand and RHA (wt %). Sample

SiO2

CaO

Al2 O3

Fe2 O3

MgO

TiO2

Na2 O

K2 O

L.O.I

Quartzsand

98.8

0.02

0.8

0.02

0.01

0.03

0.01

0.3

0.21

RHA

89.6

0.95

0.27

0.28

0.75

0.05

0.25

1.6

5.7

Table 2. The degree of crystallinity of quartz sand and RHA. Sample

Crystalline%

Amorphous%

Quartz sand

94

6

RHA

75

25

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Table 3. Results of particle size distribution measurement. Sample

D(10) μm

D(50) μm

D(90) μm

Quartz sand

3.69

20.4

65.6

RHA

6.52

25

56.2

The particle size distribution measurement was carried out using Malvern Mastersizer 3000. The percentile values, i.e. D (10), D (50), and D (90) are shown in Table 3. Table 4 shows the used in this study. In order to produce RHA-based AAC (RHA-AAC), RHA was substituted for quartz sand in the original recipe (quartz-AAC). Table 4. AAC mix ratios (wt %). Mixture

Quartz RHA Cement Lime Anhydrite GRA* C/S

Quartz-AAC 41 RHA-AAC

0

W/S Aluminum paste (g)

-

31

10

6

12

0.635 0.7

45.5

31

10

6

7.5

0.642 0.83 2.92

3.35

* ground recycled AAC

In most AAC factories, AAC demolition wastes are first ground and then reused into the ongoing production process. In this study, ground recycled AAC (GRA) was, therefore, used in the mixture to follow the industrial production process. The parameters of C/S of staring material and particle size distribution have a determining effect on the matrix structure and as a result the final properties of AAC. In order to examine the performance of RHA in the AAC, it is, therefore, necessary to use a close value of the starting C/S and the particle size distribution. As can be observed in Table 3, the particle size distribution of quartz sand and RHA are similar. Additionally, close values of starting C/S were used for both recipes (Table 4). A detailed explanation of the procedure of producing AAC samples, all experiments, and methods can be found in the previous study [1]. In this study, the autoclaving temperatures of 192 °C, 175 °C, 165 °C, and 152 °C were applied. The duration of the autoclaving process was fixed to 6 h.

3 Results and Discussion 3.1 X-ray Diffraction Analysis (XRD) Figure 1 shows the changes in the XRD pattern of RHA-AAC as a result of autoclaving at different temperatures. Figure 1 shows that autoclaving RHA-AAC at the temperature of 192 °C led to weak tobermorite peaks with low intensity. However, sharp tobermorite peaks with increased intensity were observed as a result of reducing the autoclaving temperature from 192 °C to 165 °C. The temperature of 192 °C is the common autoclaving temperature applied for manufacturing quartz- AAC in factories. Therefore, the results

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indicate that autoclaving RHA-AAC at lower temperatures, e.g. 165 °C was followed by an increase in tobermorite formation and its crystallinity. However, this increasing trend did not continue when temperatures below 165 °C were applied. By autoclaving RHA-AAC at the temperature of 152 °C, the tobermorite peaks almost disappeared.

Fig. 1. Diffractogram of the RHA-AAC.

Table 5. Amorphous and crystalline content of RHA-AAC. Autoclaving temperature

Crystalline%

Amorphous%

192 °C (12 bar)

65

35

175 °C (8 bar)

73

27

165 °C (6 bar)

75

25

152 °C (4 bar)

68

32

The percentages of amorphous and crystalline portions for RHA-AAC autoclaved at different temperatures are presented in Table 5. These values are calculated using DIFFRAC.EVA software. On the contrary to tobermorite peak intensity, amorphous content decreased with decreasing the autoclaving temperature. In another word, a decrease in the amorphous portion and an increase in the intensity of tobermorite peaks happened at the same time [2].

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Non-crystalline C-S-H, which is part of the amorphous portion, can transform to tobermorite through reaction with dissolved silica [13]. This could explain the possible reason for the above-mentioned changes. In fact, by autoclaving RHA-AAC at the temperature of 165 °C higher quantity of non-crystalline C-S-H likely transformed to tobermorite. The question is how applying lower autoclaving temperature could lead to the transition of a higher quantity of non-crystalline C-S-H to tobermorite. This could be attributed to the lower dissolution rate of RHA as a consequence of applying lower temperatures during the autoclaving process. This causes a decrease in the degree of supersaturation as a result of supplying dissolved silica with a gradual rat to the solution. This would yield to generating C-S-H with increased C/S and short silicate chains. According to the literature, the transition of C-S-H to tobermorite occurs more easily when silicate chains have a short length [14, 15]. However, it appears that the autoclaving temperature of 152 °C was not high enough to dissolve RHA. Therefore, diffusion of SiO4 4− can hardly be occurred and the solution would largely be dominated with Ca 2+ . This would generate non-crystalline C-S-H with a too high C/S which can not transform to tobermorite [16, 17]. The changes in diffractogram of quartz-AAC as a result of applying different autoclaving temperature is displayed in Fig. 2. The Diffragtogram of quartz-AAC exhibited sharp peaks of tobermorite with high intensity as a result of applying a temperature of 192 °C for autoclaving. However, the intensity of tobermorite peaks diminished as the temperature was reduced. This reduction lasted until tobermorite peaks became nearly invisible at the temperature of 152 °C. The percentages of amorphous and crystalline portions for quartz-AAC autoclaved at different temperatures are given in Table 6. According to Table 6, amorphous content showed a rising trend as the temperature was reduced.

Fig. 2. Diffractogram of the quartz-AAC.

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The above results suggest that autoclaving quartz-AAC at temperatures below 192 °C could suppress the formation of tobermorite as a result of a reduction in the dissolution rate of quartz which produces C-S–H with too high C/S. A similar temperature range (T > 180 °C) was reported in the literature for autoclaving quartz- AAC [18–20]. 3.2 Mechanical Properties The results of compressive strength and bulk density measurements are provided in Fig. 3 and Fig. 4, respectively. RHA-AAC exhibited higher compressive strength by autoclaving at lower temperatures, i.e. 165 °C and 175 °C. Unlike the RHA-AAC, the compressive strength of quartz-AAC decreased with lowering the temperature. For, RHA-AAC, an increase of 22% in compressive strength was observed by changing the temperature from 192 °C to 165 °C. This was in contrast to quartz-AAC which exhibited a reduction of 21% by applying the same change in the autoclaving temperature. For both quartz-AAC and RHA-AAC, the compressive strength decreased when the temperature of 152 °C was applied. For both RHA-AAC and quartz-AAC, applying different autoclaving temperatures did not cause a considerable change in the bulk density. The bulk density changed only by 1.3% and 1% for the RHA-AAC and quartz-AAC, respectively. This indicates that the variations in compressive strength do not stem from the changes in bulk density rather caused by the differences in the microstructure of samples which confirms the results of XRD analysis. Different tobermorite formation and amorphous content would produce different microstructures which result in different compressive strengths. In general, it appears that the ideal temperature for autoclaving RHA-AAC is T = 165 °C while for quartz-AAC, this temperature is T = 192 °C. Therefore, the opportunity exists to lessen the required energy for the autoclaving process through the utilization of RHA in the AAC mixture. Table 6. Amorphous and crystalline content of quartz-AAC. Autoclaving temperature

Crystalline%

Amorphous%

192 °C (12 bar)

80

20

175 °C (8 bar)

78

22

165 °C (6 bar)

76

24

152 °C (4 bar)

74

26

Possibility to Optimize Hydrothermal Conditions for the Production

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Fig. 3. Compressive strength of RHA-AAC and quartz-AAC.

Fig. 4. Bulk density of RHA-AAC and quartz-AAC.

4 Conclusion This study demonstrates that the utilization of RHA as a substitute for quartz sand in AAC could probably provide the benefits of reducing the temperature required for autoclaving AAC. Additionally, using RHA as one of the main constituents in the mixture could make AAC a more environmentally friendly product. In this study, autoclaving RHA-AAC at a temperature that was 27 °C lower than the common temperature (192 °C) increased the compressive strength by 22%. This implies that in addition to C-DE, other silica materials which are economical and show a relatively high dissolution rate can likely lead to a reduction in energy consumption during hydrothermal treatment. However, using all of those silica materials, e.g. RHA, in the AAC mixture might not lead to the simultaneous occurrence of reducing autoclaving temperature and reducing binder content which was obtained by using C-DE.

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Moreover, it is expected that more soluble silica-based AAC would probably exhibit a high drying shrinkage due to a high portion of non-crystalline C-S-H which was discovered in the RHA-AAC and C-DE-AAC. Accordingly, it is necessary to study the drying shrinkage of AAC containing more soluble forms of silica and if required improve it to an acceptable level.

References 1. Shams, T., Schober, G., Heinz, D., Seifert, S.: Production of autoclaved aerated concrete with silica raw materials of a higher solubility than quartz part I: Influence of calcined diatomaceous earth Constr. Build. Mater. 272, 1–11 (2021) 2. Shams, T., Schober, G., Heinz, D., Seifert, S.: Production of autoclaved aerated concrete with silica raw materials of a higher solubility than quartz Part II: Influence of autoclaving temperature Constr. Build. Mater. 287, 1–9 (2021) 3. Givi, A.N., Rashid, S.A., Aziz, F.N.A., Salleh, M.A.M.: Assessment of the effects of rice husk ash particle size on strength, water permeability and workability of binary blended concrete Constr. Build. Mater. 24, 2145–50 (2010) 4. Iler, R.K.: The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface Properties and Biochemistry of Silica. Wiley, London (1979) 5. Mitsuda, T., Sasaki, K., Ishida, H.: Phase evolution during autoclaving process of aerated concrete. J. Am. Ceram. Soc. 75(7), 1858–1863 (1992) 6. Chen, Y., Chang, J., Lai, Y., Chou, M.: A comprehensive study on the production of autoclaved aerated concrete: Effects of silica-lime-cement composition and autoclaving conditions Constr. Build. Mater. 153, 622–629 (2017) 7. Isu, N., Ishida, H., Mitsuda, T.: Influence of quartz particle size on the chemical and mechanical properties of autoclaved aerated concrete (I) tobermorite formation Cem. Concr. Res. 25, 243–248 (1995) 8. Mostafa, N.Y.: Influence of air-cooled slag on physicochemical properties of autoclaved aerated concrete. Cement and Concrete Research 35(7), 1349–1357 (2005). https://doi.org/10. 1016/j.cemconres.2004.10.011 9. Kurama, H., Topcu, I.B., Karakurt, C.: Properties of the autoclaved aerated concrete produced from coal bottom ash. Journal of Materials Processing Technology 209(2), 767–773 (2009). https://doi.org/10.1016/j.jmatprotec.2008.02.044 10. Hauser, A., Eggenberger, U., Mumenthaler, T.: Fly ash from cellulose industry as secondary raw material in autoclaved aerated concrete. Cement and Concrete Research 29(3), 297–302 (1999). https://doi.org/10.1016/S0008-8846(98)00207-5 11. Wang, C., et al.: Preparation and properties of autoclaved aerated concrete using coal gangue and iron ore tailings. Construction and Building Materials 104, 109–115 (2016) 12. Kunchariyakun, K., Asavapisit, S., Sombatsompop, K.: Influence of partial sand replacement by black rice husk ash and bagasse ash on properties of autoclaved aerated concrete under different temperatures and times Constr. Build. Mater. 173, 220–227 (2018) 13. Schober, G.: Chemical transformations during the manufacturing of autoclaved aerated concrete (ACC): Cement, lime, gypsum and quartz sand become cellular concrete. ZKG international 58, 63–70 (2005) 14. Sato, H., Grutzeck, M.: Effect of starting materials on the synthesis of tobermorite | MRS online proceedings library (OPL). Cambridge core material research society 245, 235–40 (1992). 15. Chen, J.J., Thomas, J.J., Taylor, H.W.F., Jennings, H.M.: Solubility and structure of calcium silicate hydrate Cem. Concr. Res. 34, 1499–519 (2004)

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16. Chan, C., Sakiyama, M., Mitsuda, T.: Kinetics of the CaO.quartz.H2O reaction at 120° to 180°C in suspensions. Cement and Concrete Research 8(1), 1–5 (1978) 17. Richardson, I.: Tobermorite/jennite- and tobermorite/calcium hydroxide-based models for the structure of C-S-H: applicability to hardened pastes of tricalcium silicate, β-dicalcium silicate, Portland cement, and blends of Portland cement with blast-furnace slag, metakaolin, or silica fume. Cement and Concrete Research 34, 1733–1777 (2004) 18. Matsui, K., Kikuma, J., Tsunashima, M., Ishikawa, T., Matsuno, S., Ogawa, A., Sato, M.: In situ time-resolved X-ray diffraction of tobermorite formation in autoclaved aerated concrete: Influence of silica source reactivity and Al addition. Cement and Concrete Research 41(5), 510–519 (2011) 19. Isu, N., Teramura, S., Ishida, H., Mitsuda, T.: Influence of quartz particle size on the chemical and mechanical properties of autoclaved aerated concrete (II) fracture toughness, strength and micropore. Cement and Concrete Research 25(2), 249–254 (1995) 20. Isu, N., Ishida, H., Mitsuda, T.: Influence of quartz particle size on the chemical and mechanical properties of autoclaved aerated concrete (I) tobermorite formation. Cem. Concr. Res. 25(2), 243–248 (1995)

Innovative Research on the Mechanical Experiment of Steel Fiber Modified Waste Material Recycled Concrete Cheng-yuan Wang(B) and Zhang Xu College of Architectural Engineering, Xinyu University, Xinyu 338000, Jiangxi, China [email protected]

Abstract. The recycling of building waste materials is a key issue for promoting urban reform and realizing sustainable development in China. Outward transportation and landfill method and open-air stacking method are the main treatment methods of building waste materials at present. This paper analyzes the particle size, surface structure, apparent density, bulk density, porosity, water absorption, strength the properties of recycled aggregate are analyzed from the aspects of durability, and the properties of recycled concrete are analyzed from the aspects of compressive strength and durability. After adding a certain amount of steel fiber into recycled concrete, the optimization of its properties is analyzed from the aspects of compressive strength, tensile strength, flexural strength, splitting tensile strength and elastic modulus, by constructing the creep prediction model of recycled concrete, the performance improvement and optimization of steel fiber modified waste recycled concrete are studied. Keywords: Construction waste · Sustainability · Recycled aggregates · Recycled concrete · Steel fiber

China is a country with a large amount of natural resources and a small amount of per capita resources, how to solve the low amount of per capita resources, it is one of the current development problems in China, so the efficient recycling of natural resources has become a key problem to be solved in China at present,The total amount of development of China’s real estate industry has increased year by year, and the accumulation of many construction waste materials not only pollutes the environment to occupy land resources, but also reduces the utilization rate of resources, and the recycling of resources can be realized through scientific means of processing construction waste materials. The Nineteenth National Congress of the Communist Party of China formulated the scientific policy that green mountains and green waters are golden mountains and silver mountains, pointing out the direction for achieving sustainable development, and the exploitation of some natural resources has been restricted, which has caused a considerable impact on the resource market, and there is a shortage of construction raw materials such as sand and gravel. Through the scientific and rational recycling of construction waste is an effective way to solve China’s environment and resources, is the key to achieving sustainable development in China, the recycling of waste, saving the manufacturing energy © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 12–22, 2023. https://doi.org/10.1007/978-981-19-4293-8_2

Innovative Research on the Mechanical Experiment

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consumption of building materials, reducing energy loss, reducing building energy consumption, promoting energy conservation and emission reduction, and improving the living environment.

1 Significance of the Study With the continuous advancement of urbanization in China, the number of construction waste materials has increased year by year, and the resources that can be recycled and reused have been increasing. At the same time, due to the huge population of our country and the influence of traditional ideas, the huge demand for housing has increased the pressure on sand and gravel resources. Since China’s reform and opening up, sand and gravel resources have been accompanied by the development of the construction industry has been exploited without restriction, resulting in a sharp reduction in my sand and gravel resources, and at the same time due to a large number of sand and gravel mining caused by serious damage to the environment, at this time the recycling of construction waste materials for saving resources, protecting the environment and realizing sustainable development has an irreplaceable role. Since the implementation of building energy conservation in China, certain achievements have been made in building energy conservation, but there is still room for improvement and development, building energy conservation is an important way to achieve sustainable development, how to better promote building energy conservation, is the problem we need to deal with at present. The regeneration of building waste can save the manufacturing energy consumption of building materials, reduce energy loss, and improve the utilization rate of resources; at the same time, improve economic benefits, reduce environmental pollution, and improve the environment in which people live. If the construction waste materials can be well utilized, it will effectively solve the problems of efficient use of resources and harmonious coexistence between man and nature, and promote the process of sustainable development. The recycling of construction waste materials is a key issue that must be solved in China to achieve the long-term goals of developed countries.

2 Construction Waste Material Utilization Status It can be seen from the report of the national energy information platform that in recent years, large-scale infrastructure transformation and urban reconstruction projects have been carried out in various parts of China, and the total amount of construction waste materials has been growing, and the treatment of construction waste materials has not been scientific, which not only greatly reduces the utilization rate of resources, wastes a lot of land resources, and the harmful substances in construction waste materials also cause damage to water, soil and air environment. On May 31, 2021, the National Development and Reform Commission issued the “14th Five-Year Plan for the Development of circular economy”, proposing that by 2025, the treatment capacity of municipal waste will be further improved, the utilization rate of renewable resources will be improved, the circular production mode will be implemented, and the circular economy will be developed to take the road of sustainable development. The plan also makes established requirements for the comprehensive utilization rate of construction waste, requiring that

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C. Wang and Z. Xu

the comprehensive utilization rate of construction waste reach 60% in 2025.At present, because the growth rate of construction waste recycling is smaller than the growth rate of construction waste, many construction waste materials cannot be recycled, which causes waste of resources and reduces the utilization rate of resources. At the same time, some cities have carried out large-scale infrastructure renovations, and the number of construction waste materials has increased rapidly, and cities are facing the problem of “building waste materials besieging the city.” The problem of resource utilization of construction waste materials is a key issue for China to promote urban reform and achieve sustainable development in China, and the problem of reuse of construction waste materials resources in China is a problem that needs to be solved urgently. The study of construction waste materials abroad started much earlier than China, and the first time it was proposed that the recycling of construction waste materials be profitable after World War II was the Federal Republic of Germany, and after nearly fifty years of development, the United States, Japan, the West, and other developed countries and regions have basically solved the problem. The problem of recycling and reusing construction waste materials has reduced, harmless, recycled, and industrialized construction waste materials, and the recycling of construction waste materials has exceeded 90%, and even reached 100%. At present, some countries have reached 100% of the resource treatment rate of construction waste materials, realizing the recycling and reuse of construction waste materials. First of all, they have a relatively mature recycling technology for building waste, which can deal with construction waste into renewable resources, and secondly, Japan’s treatment of construction waste is diverse, and construction waste can be put into the industry, so that the value of construction waste can be maximized. The efficient use of resources depends not only on recycling but also on a series of relevant policy support such as resource exploitation and resource use restrictions. It can be seen that the recycling of construction waste materials in the use of longterm, China still has a long way to go, there are more unknowns waiting for us to explore, to achieve the long-term goal of sustainable development in our country, it is necessary to make more efforts to study the recycling and reuse of construction waste materials, and at the same time to supplement the corresponding policy support for construction waste materials according to China’s national conditions, only two aspects can go hand in hand to maximize resources in our country, achieve harmony between people and the natural environment, and sit on the train of sustainable development.

3 Regenerated Aggregate Analysis 3.1 The Main Treatment Methods of Construction Waste Materials in China (1) Shipping landfill method. Transporting construction waste to hilly areas far from the city and filling up ravines in hilly areas, although this practice solves the problem of urban construction waste for a period of time, it seems to be both. Does not affect the urban environment and does not occupy land resources, but in fact, in the process of stacking construction waste, due to external environmental factors, construction waste materials will produce harmful substances due to complex environmental conditions. A large number of chemicals in building waste materials, a series of chemical reactions

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occur in a complex environment, resulting in substances that pollute the environment, such as organic substances such as wood planks will produce acidic substances in such an environment, when acidic substances volatilize into the air to pollute the atmosphere; at the same time, a large number of bacteria, particles, etc. contained in building waste will drift with the wind to endanger biological health. (2) Open stacking method. The open-air stacking method, as the name suggests, is to pile construction waste directly in the open, which is a method of directly stacking construction waste in the open air, although it is very low-cost, but it runs counter to the approach of sustainable development strategy. First, it occupies land resources, secondly, whether it is landfilled or open stacked, it directly or indirectly pollutes the environment. These simple construction waste treatment methods will be polluted to water, land, air, which will cause serious pollution to water resources, when the construction waste materials are washed by rainwater or soaked in groundwater, a large amount of sewage containing harmful substances will be generated, and sewage will cause serious pollution to water resources. At the same time, it will cause damage to the soil of the place where the construction waste is landfilled or stacked, and the heavy metal material in the construction waste will be absorbed and retained by the roots of the plant, which breaks the original material content of the soil and hinders the subsequent use of the soil. 3.2 Regenerative Aggregate Properties of Construction Waste Materials The research of Liu Shuhua and Sun Yongbo made a relatively complete induction on the properties of regenerated aggregates, and summarized the properties of regenerated aggregates from five aspects: particle size, surface structure, apparent density, bulk density and void rate, water absorption, strength and durability [1]. Aggregate crushing index: (δa) = (m0 − m1)/m0 × 100%

(1)

m0—Quality of the specimen, — Mass m1 of the specimen remaining after crushing test. The crushing indicator indicates the stone’s ability to resist crushing, in order to indirectly speculate on its corresponding strength. Apparent density: ρ = m/v

(2)

m Refers to the mass of the object, v refers to the apparent volume, the apparent volume is equal to the closed pore plus the solid volume. Porosity: β = (1 − ρ/ρa) × 100%

(3)

ρ Represents bulk density, ρa represents apparent density. The granular shape of the recycled aggregate is almost no different from that of natural aggregates, and even slightly better than that of natural aggregates; the surface structure is different from that of natural aggregates because of its surface adhesion Cement mortar, compared with natural aggregates, its roughness is greater, and because

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it has a higher area-to-volume ratio, its adhesion ability and hydrophilicity are better than natural aggregates when mixing with new cement mortar. Although the bulk density and apparent density of recycled aggregate are slightly lower than that of natural aggregates, the porosity is similar to that of natural aggregates; and the water absorption of aggregates is much greater than that of natural aggregates, one of the reasons is that its apparent density is smaller, and the material characteristics of regenerated aggregates and aggregate grains are also Determines its large water absorption. Whether it is natural aggregate or recycled aggregate, its strength and robustness play a decisive role in whether it can be used in building construction, aggregate strength includes crushing index, compressive strength, shear strength and elastic modulus of aggregate. Numerous studies have shown that the crushing index value of regenerated aggregate is higher than that of natural aggregate and the coefficient of variation is large, because the regenerated aggregate itself has large water absorption, large porosity, and cement mortar attached to the surface, which will also cause damage to the aggregate in the process of processing and crushing, so it is lower than the natural aggregate in both compressive strength and elastic modulus. The solidity of the recycled aggregate determines the service life of the building, but because it is attached to a layer of cement mortar on the surface, the porosity of the cement mortar is large and the hardness is low, so the frost resistance of the recycled aggregate is low. The treatment of recycled aggregate is an important step in the recycling and reuse of building waste materials, the basic properties of recycled aggregates are not the same as natural aggregates, how to improve the basic characteristics of recycled aggregates through scientific treatment, and use them better in production and life will be the direction we want to explore.

4 Performance Analysis of Recycled Concrete 4.1 Compressive Strength Regenerated aggregate substitution rate, porosity, size and permeability coefficient have a very important impact on the compressive strength of recycled concrete [2]. In the compressive test of the regenerated concrete test block, when the replacement rate of the regenerated coarse aggregate is 0%, 30%, 60% and 100%, respectively, the compressive strength of each concrete test block at the age of 3d, 7d and 28d, and the reinforced concrete increases with the proportion of aggregate substitution [3]. Its compressive strength decreases overall with the increase of the substitution rate, but the strength of the regenerated concrete is the largest when the substitution rate is 60%, which is because the aggregate ratio reaches the appropriate proportion when the regenerated aggregate substitution rate is 60%, and the combination of various materials in the concrete is enhanced, and the strength of the concrete can be improved to a certain extent. According to relevant experimental studies, when recycled concrete uses small-grain regenerated aggregate, the bonding area with the cement slurry will become larger, and the compressive strength of the recycled concrete is higher than when adding large-grain aggregate. At the same time, porosity and permeability coefficient will also affect the compressive strength of regenerated concrete, and the size of the porosity of regenerated aggregate also affects the permeability coefficient of regenerated concrete, the porosity of

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regenerated aggregate is large mainly because the surface adheres to this layer of cement mortar, coupled with the low strength of the cement mortar itself, at the same time, the greater the porosity The greater the permeability coefficient of regenerated concrete, the greater the permeability coefficient of regenerated concrete, the permeability coefficient increases the amount of water permeability at the same time, and the water absorption of concrete will reduce the strength of concrete. Therefore, the higher the porosity of the recycled concrete, the lower its strength. The strength of recycled concrete can also be strengthened to a certain extent by adding admixtures, such as fly ash and polypropylene fiber, and the current experimental studies have shown that the incorporation of a certain amount of fly ash or polypropylene fiber in the case of a reasonable water-to-glue ratio can improve the compressive strength of regenerated concrete [4]. 4.2 Durability Analysis Whether recycled concrete can be used for recycled concrete technical engineering its durability is a key indicator, the current regenerated concrete anti-chloride permeability, anti-carbonization ability, shrinkage performance, crack resistance, etc. are lower than ordinary concrete [5]. At present, the durability of recycled concrete is mainly improved by treating the recycled aggregate and adding suitable admixtures to the recycled concrete. Regenerated aggregate treatment is mainly for the regenerated aggregate internal cracks, gaps and surface of the cement mortar treatment, through the treatment to improve the strength of the regenerated aggregate, so that the quality of the regenerated aggregate is improved, the use of strength increased regeneration aggregate made of recycled concrete chlorine coefficient diffusion is minimal, crack resistance is significantly increased, shrinkage performance becomes better, anti-carbonization resistance Energy is also enhanced, and experimental studies have shown that the durability of concrete can be improved by using high-quality recycled aggregates. At the same time, when the recycled concrete is mixed with volcanic ash, fly ash, silicon ash and other additional substances, the durability of the recycled concrete can be improved to a certain extent.

5 Steel Fiber Modified Recycled Concrete Recycled concrete made of recycled aggregate, because the regenerated aggregate will produce cracks and cracks in the production process, and the aggregate surface is also attached to a certain cement mortar, the physical properties of the aggregate itself will affect the physical properties of the concrete when processed into recycled concrete [6]. The crushing index of recycled aggregate is high, the apparent density is large, the porosity is large, compared with natural aggregate, its dispersion of cement mortar is higher, in order to reduce the many adverse effects of the regenerated aggregate’s own characteristics on regenerative concrete, the mechanical properties of recycled concrete can be improved by adding an admixture in the regenerative concrete. Studies have shown that adding a certain amount of fiber to recycled concrete can improve many properties of recycled concrete, and different types of fibers have different effects on the performance of recycled concrete. At present, there are many types of fibers that can be

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added to the experimental study, and the effect of different fibers added to the recycled concrete is also different, and the fibers that can be incorporated are carbon fiber, steel fiber, polypropylene fiber and so on. Steel fiber is one of the fibers that can be added, steel fiber refers to the cutting of fine steel wire, cold-rolled strip shear, ingot milling or molten steel rapid condensation method to make fiber length and diameter ratio of 40–80 fibers [7]. When an appropriate amount of steel fibers is added to the recycled concrete, the mechanical properties of the steel fiber recycled concrete and the prediction of the actual production and use of the recycled concrete can be obtained through the corresponding calculation formula and simulation model. 5.1 Compressive Strength fc =

F A

(4)

In the above equation fc- compressive strength (MP).a. F- Average load (KN) of specimen failure. A- The pressure area of the specimen (mm). 5.2 Tensile Strength σ =

Fb So

(5)

In the above equation σ - tensile strength (N/mm2 ). Fb- Maximum force (KN) when pulling off. So——Specimen cross-sectional area (mm). 5.3 Flexural Strength fcf = 1.5

FL bhh

(6)

In the above equation f - flexural strength (MP).a. F- The specimen is subjected to a destructive load (KN) when it is resistant to bending. L- The distance between the two fulcrums (mm). b- Width of the cross-section of the specimen (mm). h- Specimen cross-sectional height (mm). 5.4 Tensile Strength of Cleavage ft =

2p πA

In the above equation ft- split tensile strength (MP).a p- Average load (KN) of specimen failure. A- The pressure area of the specimen (mm).

(7)

Innovative Research on the Mechanical Experiment

5.5 Modulus of Elasticity of Recycled Concrete σ E= ε

19

(8)

In the above equation E- modulus of elasticity. σ - Stress. ε- Strain. 5.6 Xu Variable Model Prediction The deformation of concrete that increases over time under load is called a thixo change, and the ACI-209 model can make a prediction of the thixo change of concrete, which was proposed by the American Concrete Society in 1982 and modified after 10 years, and is a commonly used concrete creep prediction model. The formula is as follows: ϕ(t, t0) = 2.35γ laγ RH γ hγ sγ φγ a

(t − t0)0.6 10 + (t − t0)0.6

(9)

In the formula: γ la—Influence coefficient of concrete loading age; γh —Influence coefficient of concrete Specimen Size; γ RH —Environmental relative humidity impact coefficient; γ s—Adjustment coefficient of concrete collapse; γφ —Adjustment coefficient of fine aggregate content; γ a—Concrete air content adjustment coefficient; t—Loading Age after Loading; t0—Conservation age at the time of age. The values of each coefficient of influence are as follows: γ la Indicates the impact coefficient of concrete loading age when loading moisture curing 7d or steam curing 3d, the formula is as follows: γ la = 1.25 ∗ (t0)−0.118 (wet curing); γ a = 1.13 ∗ (t0)−0.094 (steam curing). γ h Represents the dimensional influence coefficient of concrete, γ h which can be calculated by the body surface v/s method, and the calculation formula is as follows: When v/s = 38 mm, γ h = 1;  v 2 (10) v/s not 1, γ h = 1 + 1.13e−0.0213 s 3 γ RH Indicates the relative environmental influence coefficient when the ambient humidity is greater than 40%, and the formula is as follows: γ RH = 1.27 − 0.67RH (RH > 40%)

(11)

γ s The coefficient of influence of concrete slump is expressed, and the calculation formula is as follows: When S is 70 mm,γ h = 1; γ s = 0.82 + 0.0024S S - the collapse height of the freshly mixed concrete;

(12)

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γ a Represents the adjustment factor of coarse aggregate in concrete γφ = 0.88 + 0.0024Sa

(13)

Sa- Indicates that the mass of fine aggregates accounts for the total mass of all aggregates, when Sa = 50%,γ h = 1; γ a Represents the adjustment coefficient of the air content in the concrete, calculated as follows: When the air content is greater than 6%, γ a = 0.46 + 0.09ac

(14)

ac- Indicates the amount of air in the concrete When the air content is less than 6%, γ h = 1. Through the above formula calculation analysis and comparison of different recycled concrete of steel fiber recycled concrete, and ACI-209 of xu variable model analysis, it is obtained that the deformation of steel fiber recycled concrete increases with time under the action of load, when steel fiber is added to recycled concrete, the bending resistance, tensile resistance, and xu variable model prediction of recycled concrete will be improved to a certain extent, and the performance deficiencies of regenerated concrete are analyzed. Combined with the performance improvement brought by the incorporation of steel fibers into ordinary recycled concrete to ordinary recycled concrete, it can be found that steel fibers are high-quality addistribuses that reduce the impact of regenerated aggregate characteristics on recycled concrete. Studies have shown that the regenerative concrete itself has a large discrete property, when the size of the regenerated aggregate is larger, the more obvious the discrete nature of the regenerated concrete will be, the discrete nature of the regenerated concrete is mainly affected by the nature of the regenerated aggregate. When the surface of the regenerated aggregate is attached to a certain amount of cement mortar when making concrete, due to the large discreteness of the regenerated aggregate itself, and the regenerated aggregate will produce fine cracks inside when it is produced and processed, when the concrete is more likely to produce stress concentration phenomenon when it is stressed, the natural ability of the regenerated concrete to resist bending, tensile resistance and toughness will be weaker than that of ordinary concrete. The addition of steel fibers to the recycled concrete destroys the original knot structure, produces a new knot surface, reduces the dispersion of the regenerated concrete, improves the tensile mildness, toughness and bending strength of the recycled concrete, and improves the mechanical properties of the recycled concrete. The advantage of steel fiber recycled concrete is that it can improve the performance problems brought by recycled concrete to regenerated concrete due to the lack of aggregate properties, when the steel fiber recycled concrete is compared with ordinary regenerated concrete when the xu variable model test is carried out, it can be concluded that the addition of steel fiber in the recycled concrete can improve the tensile strength, toughness and bending strength of the recycled concrete. The addition of steel fibers in recycled concrete can effectively change the performance of recycled concrete, you can use more building waste materials, and improve the performance of recycled concrete at the same time, but also expand the scope of application of recycled concrete, so that recycled concrete can be used in other product forms for engineering construction, so

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that the corresponding consumption of recycled concrete can be increased, can improve the utilization rate of building waste materials, in response to the era theme of energy conservation and emission reduction, green development.

6 Conclusions and Prospects Although the research of recycled concrete in China has made certain achievements, there is still room for growth compared with developed countries, and more of our scholars need to devote themselves to it and overcome the technical difficulties. The compressive, bending, durability and other properties of recycled concrete are directly and importantly related to the properties of aggregates and admixtures, so how to better handle aggregates and find more suitable admixtures is one of our research directions to improve the performance of recycled concrete. The amount of steel fiber added and the proportion of other adjuvants still need to be explored and experimented, the excessive incorporation of steel fibers will reduce the fire resistance of concrete, and the amount of steel fiber incorporation is not enough to improve the mechanical properties of recycled concrete. In order to meet the improvement of the mechanical properties of steel fiber recycled concrete and to ensure that its fire resistance is basically unaffected, then the amount of steel fiber incorporated into steel fiber recycled concrete, and how much other incorporated material, is extremely important. Steel fiber thermal conductivity is good, excessive will affect the fire resistance of concrete, a small amount of regenerated concrete to improve the optimal, choose some other admixtures and the appropriate proportion of the steel fiber deficiencies to improve, you can maximize the steel fiber to the steel fiber recycled concrete. Recycled concrete is ultimately to face the market, applied to the project, to meet the requirements of the project is not limited to a certain nature, we can combine all the individual influencing factors together to explore, so as to produce recycled concrete that meets the standard and eventually apply it to the actual production and life. At the same time, in order to achieve the original intention of maximizing the utilization of renewable concrete resources, it is not only necessary to recycle resources, but also the relevant departments need to impose appropriate restrictions on related natural resources, so as to improve the recycling rate of construction waste materials and achieve the common development of technology and practical applications. Sustainable development is the country’s great plan, the recycling of construction waste resources still need more researchers to pay efforts, I believe that under the guidance of China’s policies and guidelines and the exploration of many professional scholars, we can maximize the use of resources. Acknowledgement. 1.2020 Jiangxi Provincial Department of Education Science and Technology Research Project “Steel Fiber Modified Waste Material Recycled Concrete Mechanical Experimental Research and Innovative Application” (Project No. GJJ202308); 2.2019 Jiangxi Provincial Department of Education Science and Technology Research Project “Innovative Application of Recycled Concrete in Prefabricated Buildings” (Project No. GJJ191062); 3. Jiangxi Provincial Education Science 13th Five-Year Plan Planning 2019 annual topic “Research and Practice on the Applied Talent Training Model of Local Undergraduate Colleges and Universities under the Background of Deep Integration of Schools and Enterprises - Taking the Civil Engineering Major

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of Our University as an Example” (Project No.19YB257); 4.2019 Jiangxi Provincial Department of Education Science and Technology Research Project “Research on The Innovation of New Horizontal Connection Nodes of Assembled Shear Walls” (Project No. GJJ191055); 5. Jiangxi Provincial College Students Innovation and Entrepreneurship Training Program 2021 Project “Innovative Research on New Horizontal Connection Nodes of Prefabricated Shear Wall” (Project No. DC202101001); 6.2021 Annual Project of Innovation and Entrepreneurship Training Program for College Students in Jiangxi Province “Mechanical Experimental Innovation Research on Modified Recycled Concrete of Waste Materials” (Project No. S202111508004).

References 1. Xiao, L.G., Lin, X.: Application of recycled aggregate permeable concrete in sponge city. J. Jilin Jianzhu Univ. 34(04), 9–12 (2017) 2. Jiang, H.K., Li, Y., Wei, D.Y., Zhao, H.R., Wang, Z.C.: Research on compressive strength and water permeability of permeable concrete of recycled ceramic aggregate. Liaoning Chemical Industry 49(03), 227–232 (2020) 3. Deng, X.W.: Compressive strength test results and analysis of regenerated coarse aggregate concrete. Sci. Technol. Info. 13(16), 59–60 (2015) 4. Sha, D., Sun, J.G., Hao, J.F., Wang, Z., Cui, L.F.: Study on the properties of regenerated concrete for the walls of Manchu houses in northern China. Contemporary Chemical Industry 46(01), 42–46 and 50 (2017) 5. Xu, Y.M.: Study on the effect of recycled aggregates of different processes on the durability of concrete. Comprehensive utilization of fly ash 2019(05), 33–36 and 97 (2019) 6. Dou, J.C., Wang, Q., Fan, W., Wang, R., Leng, Z.Y.: Orthogonal experimental study on pressure resistance of recycled concrete. Sichuan Building Materials 43(09), 19–20 (2017) 7. Wang, Q.: The application of modern steel fiber concrete technology in road and bridge construction. Shandong Industrial Technology 2019(05), 116 (2019)

Calculation Method of Asphalt Concrete Thermal Stress Based on Interface Mechanics Wenhao Ke1(B) , Yu Lei1 , and Mingming Xu2 1 CCCC First Highway Consultants Co., LTD., Xi’an 710065, Shaanxi, China

[email protected] 2 Ningbo Municipal Transportation Comprehensive Administrative Law Enforcement Agency,

Ningbo 315040, Zhejiang, China

Abstract. The simplified physical model of asphalt mortar and aggregate was established, and the interfacial mechanical theory was used to calculate the thermal stress between asphalt mortar and aggregate. It could be seen from the calculation Equation of thermal stress that the maximum stress of asphalt mortar and aggregate occurs on the interface. The circumferential tensile stress on the interface between asphalt mortar and aggregate when cooling was taken as initial thermal stress calculation model. Considering the relaxation effect of asphalt concrete, the integral method and the discrete method were used to calculate the thermal stress of asphalt concrete, and the thermal stress calculation model was verified by TSRST. The results show that the calculated results agree with the results of TSRST before the breaking point. The maximum deviation rate from −5 °C to the temperature of breaking point was 18.18%, and the average deviation rate was 12.93%. Keywords: Thermal stress · Asphalt concrete · Asphalt mortar · Relaxation modulus · TSRST

1 Introduction Asphalt pavement cracks are caused by the combined effect of vehicle load and temperature changes, especially for the adverse weather areas, the changing temperature play an important role on the pavement performance. Many scholars carried out a lot of research for the thermal stress of asphalt concrete from different aspects. But the thermal stress was researched mainly from the view of homogeneous asphalt concrete, using finite element method, theoretical and experimental method [1–10]. However, asphalt mortar and aggregate are different material. When asphalt concrete subject to external loads, the destruction is always inclined to occur on the interface. Through establishing the simplified physical model of asphalt mortar and aggregate, the thermal stress was calculated using interface mechanics theory. Considering the relaxation effect of asphalt concrete, the integral method and the discrete method were used to calculate the thermal stress of asphalt concrete, which is verified by Thermal Stress Restrained Specimen Test (TSRST). © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 23–32, 2023. https://doi.org/10.1007/978-981-19-4293-8_3

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2 Methods 2.1 Thermal Stress Calculation Model Based on Interface Mechanics Model hypothesis. Asphalt mixture can be seen as composed of asphalt mortar and aggregate. As the asphalt mortar and aggregate have a different coefficient of thermal expansion, so when the temperature changes, the heat incompatible stress will occur on the interface between the asphalt mortar and aggregate. The model thermal stress calculation is simplified to the plane stress and the following assumptions are made: • The aggregate is round and the radius is R; • Aggregate is linear elasticity, and the elastic modulus Eg does not change with time and temperature; • Asphalt mortar is visco-elasticity, and relaxation modulus G(Ti , ti ) change with time and temperature; • The aggregate surrounded by Asphalt mortar; • The asphalt mortar thermal expansion coefficient α(T ) change with temperature, and the aggregate thermal expansion coefficient αg does not change with temperature (Fig. 1);

Fig. 1. The physical model of asphalt mortar and aggregate.

Thermal Stress Calculation Model. According to the only radial deformation coordination conditions of the aggregate and asphalt mortar interface, there are: uaT + uaσ = ugT + ugσ

(1)

where, uaT is asphalt mortar radial displacement due to temperature change. uaσ is the radial displacement caused by thermal stress of asphalt mortar and aggregate interface. ugT is the radial displacement of the aggregate due to temperature change; ugσ is the radial displacement caused by thermal stress of aggregate and asphalt mortar interface.

Calculation Method of Asphalt Concrete Thermal Stress

25

According to the elastic theory, the thermal stress of the model is an axisymmetric plane stress problem. The circumferential displacement v = 0, and the radial displacement u = u(r). r is the distance from the calculation point to the center of the circle, and there are the strain componen: εr =

du u , εθ = , γrθ = 0 dr r

(2)

where, εr is the radial strain. εθ is the circumferential strain. γrθ is the tangential strain. The physical equation can be expressed as follows: εr =

1 (σr − μσθ ) + αT E

εθ =

1 (σθ − μσr ) + αT E

(3)

where, E is the modulus. σr is the radial stress. σθ is the circumferential stress; μ is Poisson ratio. α is the thermal expansion coefficient. T is the temperature change. σr =

E [εr + μεθ − (1 + μ)αT ] 1 − μ2

σθ =

E [εθ + μεr − (1 + μ)αT ] 1 − μ2

(4)

The equilibrium equation combined with Eq. 4, there are: d 1 d dT ( (ru)) = (1 + μ)α dr r dr dr

(5)

After integration, there are: α u = (1 + μ) r



r

Trdr +

R

C2 C1 r+ 2 r

(6)

In a subdivision period, the temperature of the asphalt mortar can be considered to be evenly distributed and the interaction between the aggregate and the asphalt mortar is neglected, and the temperature-induced displacement component is:     r α (1 − μ)r 2 + (1 + μ)R2 R0 u= Trdr + Trdr (7) (1 + μ) r R20 − R2 R R According to the Eq. 7, the vertical displacement due to the temperature change of the asphalt mortar and aggregate interface can be obtained as follows: uaT = α(T )RT ugT = αg RT

(8)

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where, T is the temperature change within asphalt mixture. As the asphalt mortar and aggregate with different thermal expansion coefficient, under the action of temperature, the interface will generate force. Assuming that the force is uniform, the radial displacement due to the thermal stress of the asphalt mortar and aggregate interface can be obtained by the elastic theory as follows: σ (1 − μ)R Eg σ (1 + μa )R =− G(T , t)

ugσ = uaσ

(9)

where, σ is the normal stress caused by the temperature change on the interface. μg is the poisson’s ratio of the aggregate. μa is the poisson’s ratio of the asphalt mortar. When Eq. 1 was combined with Eq. 8 and Eq. 9, there are:   α(T ) − αg Eg G(T , t) T (10) σ = G(T , t)(1 − μg ) + Eg (1 + μa ) According to the elastic theory of thick ring solution, the stress of aggregate and asphalt mortar can be obtained as follows: Aggregate:   α(T ) − αg Eg G(T , t) σgr = σgθ = σ = T (11) G(T , t)(1 − μg ) + Eg (1 + μa ) Asphalt mortar:   α(T ) − αg Eg G(T , t) R2 σ R2 σar = 2 = T 2 (r ≥ R) r G(T , t)(1 − μg ) + Eg (1 + μa ) r   α(T ) − αg Eg G(T , t) R2 σ R2 σaθ = − 2 = − T 2 (r ≥ R) r G(T , t)(1 − μg ) + Eg (1 + μa ) r

(12) (13)

According to the above Equations, When temperature rising, the circumferential and radial tensile stress occur in the aggregate, and the circumferential compressive stress and radial tensile stress occur in the asphalt mortar. When temperature rising, the relaxation modulus decreases. The incremental tensile stress which occurred in the asphalt mortar is small, and the radial tensile stress has limited effect on the asphalt mortar, so that the asphalt mixture is less prone to crack during the heating process. As the relaxation modulus increase during the cooling process, a large circumferential tensile stress occurred in the asphalt mortar. When r = R, which means the interface between the asphalt mortar and the aggregate, it will occur maximum circumferential tensile stress. Therefore, the circumferential tensile stress which occurred on the asphalt mortar and aggregate interface is researched in the following.

Calculation Method of Asphalt Concrete Thermal Stress

27

2.2 Asphalt Mixture Thermal Stress Considering Relaxation Effect Calculate the Thermal Stress by the Integral Method. It is considered that the asphalt mixture thermal stress will occur stress relaxation effect in the subsequent time dt. Assuming in the continuous cooling process, the temperature is Ti when the relaxation time is dt. According to time-temperature equivalence principle, the relaxation time dt corresponding to the temperature Ti can be equivalent to the relaxation time t  corresponding to the temperature T0 . t =

dt β(Ti )

(14)

where, β(Ti ) is the shift factor of the temperature Ti relative to the temperature T0 . Therefore, the relaxation time t when time change from t0 to t and the temperature change from T0 to T can be equivalent to the relaxation time t  corresponding to the temperature T0 .  t dt  (15) t = t0 β(t) There is the relaxation stress of the thermal stress which generated during the minute period when the temperature is T0 in the subsequent continuous temperature change process:   α(Ti ) − αg Eg G(T0 , t  ) R2 d σ R2 dT (16) d σaθ = − 2 = − r G(T0 , t  )(1 − μg ) + Eg (1 + μa ) r2 The largest thermal stress occur in the asphalt mortar and aggregate interface, namely:   α(Ti ) − αg Eg G(T0 , t  ) dT (17) d σaθ = −d σ = − G(T0 , t  )(1 − μg ) + Eg (1 + μa ) Therefore, there is the thermal stress when the temperature changes from T0 to T and the time changes from t0 to t:     T α(Ti ) − αg Eg G(T0 , t  ) dT σaθ = − d σ = −  T0 G(T0 , t )(1 − μg ) + Eg (1 + μa )   (18)  t α(Ti ) − αg Eg G(T0 , t  ) =− dt  t0 G(T0 , t )(1 − μg ) + Eg (1 + μa ) The Thermal Stress Calculated by Discrete Method. The cooling process can be divided into n period of times, and The beginning and ending times of each period are t0 , t1 , t2 ……tn which corresponding to the temperature T0 , T1 , T2 ……Tn . The thermal stress generated in the time period of ti ~ ti+1 relaxing to the time tn in the temperature continuous change process should be considered firstly. There is the instantaneous thermal stress generated in the time period of ti ~ ti+1 :   α(Ti ) − αg Eg G(Ti+1 , 0) (Ti+1 − Ti ) (19) σaθ = − G(Ti+1 , 0)(1 − μg ) + Eg (1 + μa )

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The stress relaxation will occur in the subsequent time. As the temperature changing continuously, it’s necessary to convert the relaxation time of different temperatures to the relaxation time of temperature Ti+1 according to the time-temperature conversion principle. According to the above Equation, the stress when the instantaneous thermal stress generated in the time period of ti ~ ti+1 relax to the time tn can be obtained as follows: σaθ = −

  t −t t −t t −t α(Ti ) − αg Eg G(Ti+1 , 0 + βi+2 i+1 + βi+3 i+2 + . . . + βn n−1 ) (i+2,i+1) (i+3,i+1) (n,i+1) t

−t

t

−t

t −t

G(Ti+1 , 0 + βi+2 i+1 + βi+3 i+2 + . . . + βn n−1 )(1 − μg ) + Eg (1 + μa ) (i+2,i+1) (i+3,i+1) (n,i+1)    t −t α(Ti ) − αg Eg G(Ti+1 , nj=i βj i+1 ) (j,i+1) (Ti+1 − Ti ) =− n tj −ti+1 G(Ti+1 , j=i β )(1 − μg ) + Eg (1 + μa )

(Ti+1 − Ti )

(20)

(j,i+1)

where, β(j,i+1) is the shift factor of the temperature Tj corresponding to the time tj relative to the temperature Ti+1 . The shift factor is calculated using the Arrhenius Equation:  1 H 1 β = exp  ( − ) (21) R T T0 where, T is the Kelvin temperature. H is the material activation energy. R is the molar gas constant which is assigned to the value of 8.314. According to the above Equation, the thermal stress when time changes from t0 to tn in the temperature continuous change process can be obtained as follows: σaθ =

n

σi

i=1

   t −ti+1 ) α(Ti ) − αg Eg G(Ti+1 , nj=i βj (j,i+1) = − (Ti+1 − Ti ) n tj −ti+1 G(Ti+1 , j=i β(j,i+1) )(1 − μg ) + Eg (1 + μa ) i=1 n

(22)

3 Verification of the Method 3.1 Calculation Parameter Before calculating the asphalt concrete thermal stress from the t0 to tn , the asphalt mortar thermal expansion coefficient α(Ti ), the aggregate thermal expansion coefficient αg , the aggregate modulus Eg and the relaxation modulus main curve equation of asphalt mortar at different temperatures should be determined firstly. The thermal expansion coefficient of asphalt mortar varies with temperature and cooling rate, and is closely related to the properties of asphalt. The change trend is complicated. The asphalt mortar thermal expansion coefficient is assigned the value of 7.81 × 10–4 . The aggregate thermal expansion coefficient is assigned the value of 8 × 10–6 . The Aggregate elasticity modulus is assigned the value of 55.5 Gpa [12].

Calculation Method of Asphalt Concrete Thermal Stress

29

The asphalt creep stiffness modulus was measured by the test of bending beam rheometer(BBR). And the numerical iterative expression of relaxation modulus and creep compliance was established according to the constitutive relation between creep and relaxation. Then the asphalt mortar relaxation module can be calculated [11]. The technical indexes of modified asphalt selected for the test of BBR is shown in the following table (Table 1). Table 1. Asphalt technical parameters. Indexes

Unit

Technical parameters

Penetration (25 °C, 100 g, 5 s)

0.1 mm

74.3

Penetration index

–

−0.2

Ductility (5 °C, 5 cm/min)

cm

36.5

Softening point

°C

68

Density

g/cm3

1.012

Elastic recovery (25 °C)

%

78

Quality change

%

0.7

Penetration ratio (25 °C)

%

69

Ductility (5 °C, 5 cm/min)

cm

31

Residues after RTFOT

The creep stiffness modulus of modified asphalt at −12 °C, −18 °C and −24 °C through the test of BBR, are shown in the Fig. 2.

Fig. 2. Creep stiffness modulus at different test temperatures.

According to the principle of time-temperature equivalence, the creep stiffness modulus curve at −18 °C, −24 °C, −12 °C were translated to 0 °C, and the master curve of stiffness modulus is obtained as shown in the Fig. 3.

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W. Ke et al.

Fig. 3. Creep stiffness modulus master curve.

The above figure can be fitted to obtain material activation energy, H = 253300 J · mole−1 . The creep stiffness modulus was converted into relaxation modulus [11], as shown in the Fig. 4.

Fig. 4. Asphalt mortar relaxation modulus and relaxation time of 0 °C.

The data were fitted by the programming method to obtain the relationship between asphalt mortar relaxation modulus and relaxation time of 0 °C. G(0, t) =

7276 1 + (t/0.35)0.72

(23)

3.2 Verification of Thermal Stress Calculation Method The thermal stress restrained specimen test is used to verify the accuracy of the temperature stress calculation method. The cooling rate is assigned the value of −5 °C/h. The

Calculation Method of Asphalt Concrete Thermal Stress

31

initial temperature is assigned the value of 0 °C. The cooling time is discrete for 10s of each time period. The thermal stress was calculated using the above method. And the calculated values are compared with the TSRST values. The comparing result is shown in the Fig. 5. It can be seen that the thermal stress growth rate of the TSRST slows down before the breaking point, mainly due to the gradual decrease of the asphalt mortar thermal expansion coefficient with temperature decreasing. The calculated values agree with the value of TSRST before the breaking point, and the deviation increases after the breaking point. The deviation between the calculated value and the TSRST value gradually increases as the temperature decreases. The deviation rate showed a trend of first decreasing and then increasing. The maximum deviation rate from −5 °C to the temperature of breaking point was 18.18%, and the average deviation rate was 12.93%. After breaking point, the deviation value increases sharply which is mainly due to that the TSRST could simulate the damage of the asphalt concrete under the action of thermal stress, and the numerical calculation could not simulate the phenomenon.

Fig. 5. TSRST values and calculated value.

4 Conclusion According to the interface mechanics theory, the thermal stress between asphalt mortar and aggregate is calculated. It can be seen from the calculation equation of thermal stress that the maximum stress of asphalt mortar and aggregate occurs on the interface. Considering the relaxation effect of asphalt concrete, the integral method and the discrete method are used to calculate the asphalt concrete thermal stress. Through the test of TSRST, it’s shown that the calculated results agree with the results of TSRST before the breaking point.

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References 1. Klimova, B., et al.: Comparison of calculated and measured thermal stresses in asphalt concrete. Baltic J. Road & Bridge Eng. 10(1), 39–45 (2015) 2. SMZ Alavi: Comprehensive methodologies for analysis of thermal cracking in asphalt concrete pavements. Dissertations & Theses – Gradworks 64(3), 209–17 (2014) 3. Akentuna, M., et al.: Study of the thermal stress development of asphalt mixtures using the asphalt concrete cracking device (ACCD). Transportation Research Board 114, 416–422 (2016) 4. Islam, M.R., Tarefder, R.A.: Determining thermal properties of asphalt concrete using field data and laboratory testing. Constr. Build. Mater. 67, 297–306 (2014) 5. Hossain, M., et al.: Determining and validating thermal strain in asphalt concrete. Procedia Engineering 145, 1036–1043 (2016) 6. Hejazi, S.M., Abtahi, S.M., Safaie, F.: Investigation of thermal stress distribution in fiberreinforced roller compacted concrete pavements. J. Ind. Text. 45(5), 171–175 (2014) 7. Gao, D., Huang, C.: Low temperature performance test and thermal stress calculation model of fiber reinforced asphalt concrete. China J. Highw. Trans. 29(2), 8–15 (2016) 8. Guan, H., et al.: Intermediate principal stress effect on asp- halt mixture at low temperature. China J. Highw. Transp. 27(11), 11–16 (2014) 9. Guo, F., Fu, H., Shao, L.: Fatigue damage analysis of composite base asphalt pavement structure based on change of ambient temperature. J. Central South Univ. (Science and Technology) 5, 1869–1875 (2015) 10. Yi, F., Zhu, F., Yang, Y.: Action of stress and deformation analysis of asphalt pavement under temperature-stress coupling. Bulletin of the Chinese Ceramic Society 35(1), 316–321 (2016) 11. Xue, Z., et al.: Calculation of low-temperature relaxed modulus of elasticity for bitumen via creep test. J. South China Univ. Technol. (Natural Science Edition) 35(2), 64–68 (2007) 12. You, Z.P., Buttlar, W.G.: Discrete element modeling to predict the modulus of asphalt concrete mixtures. J. Mater. Civ. Eng. 16(2), 140–146 (2004)

Aging Performance of Base and Modified Bitumen Ma Li(B) and Pan Yurong Hubei University of Technology Engineering and Technology College, Wuhan 430068, Hubei, China [email protected]

Abstract. The influence of aging on the chemical structure of base bitumen and SBS modified binders was investigated by Nuclear Magnetic Resonance (NMR). The rolling thin film oven (RTFO), termed as short-term aging, and pressurized aging vessel (PAV), termed as long-term aging, tests were used to simulate the laboratory aging of this bitumen. In the process of aging, it was found that several chemical reactions were occurred including isomerization, dealkylation and dissociation. Due to ageing, asphaltene aggregates in base asphalt become larger, and network structure in SBS modified asphalt was disappeared. Keywords: Bitumen · SBS modified bitumen · Chemical structure

1 Introduction Compared with matrix asphalt, SBS modified asphalt is the most widely used polymer modified asphalt at home and abroad [1, 2] because of the non-softening at high temperature, non-brittleness at low temperature, wide application temperature range and good mechanical properties. Asphalt materials have aging in the process of mixing, paving, rolling and asphalt pavement use, which can result in different changes in rheological properties, pavement performance and chemical structure of pavement asphalt [3]. Therefore, it is particularly important to study the aging mechanism of matrix and SBS modified asphalt and establish the relationship between microscopic composition structure and macroscopic pavement performance of asphalt. Researchers used different chemical analysis techniques to characterize the composition, structure and rheological properties of matrix and SBS modified asphalt during aging. Siddiqui et al. analyzed the chemical reaction types and molecular weight changes of asphalt during aging by combining high pressure gel chromatography (HP-GPC) with nuclear magnetic resonance (NMR) spectroscopy [4]; It was found that asphaltene existed in the form of network structure in gel structure asphalt [5]. However, the current research on asphalt aging often focuses on one aspect of microstructure or road performance, and seldom studies the aging performance of matrix and modified asphalt comprehensively, and establishes the relationship between microstructure and macro road performance in the process of asphalt aging. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 33–38, 2023. https://doi.org/10.1007/978-981-19-4293-8_4

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Because the aging mechanism of asphalt is very complex, the research methods are different, and the composition and structure of asphalt are different, there is no unified view on the aging mechanism of asphalt. It is considered that the aging process of asphalt is related to the composition of asphalt [6–8]. Based on the laboratory simulation of short-term and long-term aging of asphalt, the aging mechanism of asphalt is studied by investigating the aging performance of matrix and SBS modified asphalt, which provides a theoretical basis for further establishing the intuitive relationship between microscopic composition and macroscopic performance of asphalt.

2 Raw Materials and Experiments 2.1 Raw Material The base asphalt AH-70 and SBS modified asphalt PG76 used in this experiment are produced by Hubei Ezhou Koch Asphalt Products Co., Ltd., and their basic performance indexes are shown in Table 1. Table 1. Technology properties of AH70 and PG76 Properties

AH-70

PG76

Penetration, 25 °C, 100 g, 5 s (0.1 mm)

73

52

Softening point (°C)

48

86

Viscostity, 135 °C (Pa •s)

0.4

2.9

2.2 Aging Test The short-term aging of asphalt was simulated by RTFOT (75 min, 163°C, air flow velocity 4 L/min), and the long-term aging was simulated by PAV (20°C, pressure 2.1 MPa) after RTFOT. The detailed sample preparation and aging method refer to “Test Specification for Asphalt and Asphalt Mixture in Highway Engineering” (JTJ 052–2000). 2.3 Test Methods The 1H NMR test analysis of asphalt before and after aging was carried out by ZNOVA 600 NMR spectrometer produced by Varian Company of USA. 0.1 g sample was dissolved in 0.5 ml deuterated chloroform to make solution sample. The spectrometer was operated at 600 MHz, the diameter of test tube was 5 mm, and TMS was used as internal standard. The test conditions were as follows: Spectrum width 10598.8 Hz, data point 40090, pulse width 6.025 ms (45°), pulse cycle time 1 s and instantaneous number 8.

Aging Performance of Base and Modified Bitumen

35

3 Test Results and Discussion Chemical composition analysis. Through the analysis of 1H NMR, the relative proton number of different composition structures of asphalt was calculated, and the composition structure changes of asphalt before and after aging were analyzed and identified. The 1H NMR maps of AH-70 and PG-76 under different aging modes are shown in Fig. 1, and the related hydrogen percentage distribution of various structures is shown in Table 2. It can be seen from Table 2 that the content of aromatic hydrogen (Har) of AH-70 shows a decreasing trend during the aging process. After RTFOT and PAV, the decrease of Har indicates that the aromatic structure condenses continuously during the aging process, and more substitution reactions occur on the aromatic ring during the aging process. Among the three assignments of Hα, Hβ and Hγ hydrogen atoms, Hβ accounts for most of the Hsat (Hsat = Hα +Hβ +Hγ ) content of saturated hydrogen atoms. Before and after aging, its content remained almost unchanged. The content of Hβ represents the structure of asphalt in a stable state during aging. The Hγ value represents a short paraffin chain, and the original Hγ value is relatively high. After RTFOT and PAV, the molecular structure of asphalt changed and the content of Hγ decreased, which indicated that short aliphatic straight chain appeared and aliphatic structure increased during the aging process. Obviously, this was due to the increase of paraffin chain and hydrocarbon group length attached to aromatic ring with the deepening of aging.

Fig. 1. 1H NMR spectra of AH70 and PG76 before and after ageing

36

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Table 2. The hydrogen distributing percent of AH70 and PG76 before and after ageing (%) AH70

PG76

Based

RTFOT

PAV

Based

RTFOT

PAV

H sat

79.1

79.5

83.1

91.9

92.1

92.4

Hα

22.1

23.6

27.9

12.0

12.5

12.8

Hβ

44.0

44.7

44.5

60.8

61.2

61.6

Hr

13.0

11.2

10.7

19.1

18.4

18.0

H ar

20.9

20.5

16.9

6.8

6.7

6.6

(H b1 + H b2 )

__

__

__

1.3

1.2

1.0

In the hydrogen distribution percentage of modified asphalt PG76, the H ar content of aged asphalt is lower than that of the original asphalt, which indicates that the aromatic structure condenses continuously during the aging process. The content of H α increased from 12.0% to 12.8% and H β increased from 60.8% to 61.6% after long-term aging, indicating that isomerization occurred during aging. After aging, the content of H γ decreased from 19.1% to 18.0%, and the length of straight chain of fat increased by isomerization during aging. Comparing the 1 H NMR spectra of PG76 and AH70, new hydrogen proton resonance absorption peaks appeared at the chemical shifts of 4.98 and 5.40. The absorption peak at 4.98 represents the proton on 1.2 addition unsaturated olefins, and the absorption peak at 5.40 represents the proton on 1.4 addition unsaturated olefins. This shows that compared with AH70, PG76 contains SBS modifier represented by butadiene. It can be seen from Table 2 that the proton H b of unsaturated olefins decreased from 1.3% in the original sample to 1.2% after short-term aging and 1.1% after long-term aging, which indicates that SBS cracked during aging and the content of SBS modifier in asphalt decreased. Compared with the modified asphalt and the base asphalt under the same aging mode, the changes of saturated hydrogen H sat and aromatic hydrogen H ar of PG76 are smaller than those of AH70. For example, the H sat content of AH70 increased from 79.1% to 83.1% of the long-term aged bitumen with an increase of 4.0%, while the H sat content of PG76 increased from 91.9% to 92.4% of the long-term aged bitumen with an increase of 0.5%; The H α content of AH70 increased from 22.1% to 27.9% of the aging sample, with an increase of 5.8%, while that of PG76 increased from 12.0% to 12.8% of the aging sample, with an increase of 0.8%; The H γ content of AH70 decreased from 13.0% to 10.7% of the aged sample, with a decrease of 2.3%, while the H γ content of PG76 decreased from 19.1% to 18.0% of the aged sample, with a decrease of 1.1%. This indicates that the existence of SBS modifier hinders the chemical reaction of the matrix asphalt in the aging process to some extent, which reduces the variation range of the hydrogen proton resonance absorption peak of the matrix asphalt during the aging process, that is, reduces the oxidation rate of the matrix asphalt. The change of proton content of unsaturated olefins indicates that the aging of SBS modified asphalt and the aging of SBS modified asphalt take place simultaneously and parallel during the

Aging Performance of Base and Modified Bitumen

37

aging process, and their joint action determines the chemical composition and pavement performance of SBS modified asphalt after aging. In the aging process, the change of asphalt chemical composition would cause the change of its microstructure and morphology. In this experiment, AFM was used to observe the microstructure and morphology of asphalt before and after aging directly.

Fig. 2. AFM three-dimensional –images of (a) AH70, (b) aged AH70

Fig. 3. AFM three-dimensional –images of (a) PG76, (b) aged PG

Figures 2 and 3 are three-dimensional atomic force microscope diagrams of original matrix asphalt and modified asphalt and PAV aged samples, respectively. As can be seen from Fig. 2(a), the original surface morphology of AH70 is relatively flat, with a small number of dentate bulges distributed in it, which are periodically overlapping, and each one looks like a bee. Therefore, this form is called ‘bee’ structure. However, in Fig. 4 (a), the surface morphology of PG76 is different from that of AH70. The original surface of PG76 is rough, but there is no dentate protrusion, but a network structure with uneven distribution. Some parts of the network structure distribution is dense, some parts of the network structure distribution is relatively sparse. The appearance of network structure may be due to the connection of SBS introduced into PG76 after a certain amount of SBS is introduced into PG76. The three-dimensional network structure formed by the

38

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presence of SBS modifiers hindered the aggregation and association of asphaltenes [9]. It can be seen from Fig. 2 (b) that after long-term aging, the surface morphology of AH70 asphalt becomes rough, the number of ‘bee’ structures increases, and it becomes longer, wider and higher. According to Rozeveld’s research, the bee structure is determined by the distribution of asphaltenes in asphalt. During the aging process, the dispersion of asphaltene in asphalt becomes worse, and more asphaltene molecules gather and associate together, which makes the surface morphology of aging asphalt rough. The increase of asphaltene content with high molecular weight in asphalt after aging is the reason for the formation of large bee structure. Figure 3 (b) shows that the network structure of PG76 asphalt disappears after long-term aging. On the surface of aging asphalt, there are a certain number of tooth-like protrusions, and each bee-like surface appears similar to the surface morphology of aging matrix asphalt AH70.

4 Conclusion The changes of chemical composition, surface morphology and rheological parameters of matrix and modified asphalt after short-term and long-term aging were studied. 1 H NMR analysis shows that the aromatic structure of asphalt condenses continuously after aging, and SBS modifier cracks. The existence of SBS modifier hinders the chemical reaction of asphalt during aging.

References 1. Yen, T.F., Chilingarian, G.V.: Asphaltenes and asphalts. Elsevier Science, pp. 381–387 (1994) 2. Siddiqui, M.N., Ali, M.F.: Investigation of chemical transformations by NMR and GPC during the laboratory aging of Arabian asphalt. Fuel 78, 1407–1416 (1999) 3. Loeber, L., et al.: New direct observations of asphalts and asphalt binder by scanning electron microscopy and atomic force microscopy. Journal of Microscopy 182, 32–39 (1996) 4. Petersen, J.C.: Asphalt oxidation-Anoverview including a new model for oxidation proposing that physic chemical factors dominate the oxidation kinetics. Fuel Sci Techno l Int’l 11(1), 57–58 (1993) 5. Herrington, P.R., Ball, G.F.A.: Temperature dependence of asphalt oxidation mechanism. Fuel 75(9), 1 and 129–1131 (1996) 6. Rozeveld, S.J., et al.: Network morphology of straight and polymer modified asphalt cements. Microsc Res Tech 38(5), 529–43 (1997) 7. Ruanl, Y., Davison, R.R., Glover, C.: The effect of long-term oxidation on the rheological properties of polymer modified bitumens. Fuel 82, 1763–1773 (2003) 8. Goodrich, J.L.: Asphalt and polymer modified asphalt properties related to the performance of asphalt concrete mixes. Asphalt Paving Technologists 57, 116–175 (1988)

An Approach to Reduce Strength Loss of Rubber Concrete Haolin Su(B) Elite Knowit Education Technology Co., Ltd., Shenzhen, China [email protected]

Abstract. This study explored the use of silane coupling agent (SCA) to modify surface of rubber for reducing strength loss of rubber concrete. According to the experimental results, SCA plays a significant role in reducing the strength loss, especially when concrete is at early age. The approach is even more effective as the concentration of SCA solution increases. Scanning optical microscope tests and analyses show that the adhesion between inorganic mixture and organic rubber material was enhanced. The improved interfacial transition zone leads to a decrease of compressive strength loss for rubber concrete. Keywords: Silane coupling agent · Strength loss · Interfacial transition zone · Rubber concrete

1 Introduction Rubber concrete has been studied for almost three decades. Numerous studies have been carried out and one of the agreements states that impact resistance, ductility and capacity of dynamic energy dissipation enhance as the increase of rubber material in the mixture [1–3]. Another consensus is the strength reduction which is consistently reported [3– 5]. However, how to diminish the strength reduction is still being investigated. Several ways have been suggested to pretreat rubber aggregate, including water rinse (rubber was washed by water before using) [6, 7], anchorage (rubber chips were drilled to form holes for anchoring with concrete matrix) [8], sodium hydroxide (crumb rubber was immersed in sodium hydroxide solution for certain time before using) [6, 9–12], organic sulfur compounds (wasted organic sulfur compounds generated in some petroleum refining plant were used to modify surface properties of crumb rubber) [13], partial oxidation (crumb rubber was partially oxidized in a container under certain circumstances) [14], pre-coating by limestone powder [15], by mortar [6] and by cement paste [6]. This study was initiated to explore the effect of silane coupling agent (SCA) on diminishing strength loss of rubber concrete.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 39–46, 2023. https://doi.org/10.1007/978-981-19-4293-8_5

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2 Materials and Experiment Raw materials of concrete in this study comprised cement containing fly ash (30 wt%) with 32.5 MPa characteristic strength, tap water, crushed gravels and recycled concrete aggregate as coarse aggregate, natural river sand and combination-sized rubber particles by blending rubber samples A, B, C as fine aggregate. Results of sieve analysis in accordance with BS EN 933-1 are plotted in Fig. 1. Test results of coarse aggregate crushing value according to BS 812-110 are listed in Table 1, coupled with water absorption and density of both types of aggregates in saturated surface-dried (abbreviated as SSD) state. Table 1. Properties of aggregates. Item

Crushed gravels

Recycled aggregate

River sand

Tyre rubber

Nominal maximum particle size (mm)

10

10

5

5

Aggregate crushing value

20

23

N/A

N/A

SSD water absorption (%)

1.26

7.09

1.37

8.46

SSD density (kg/m3 ) 2581

2539

2512

973

100

Percentage of passing (%)

80

60

rubber sample A rubber sample B rubber sample C combination-sized rubber sand crushed gravels recycled aggregate

40

20

0 0.01

0.1

1

10

Particle size (mm)

Fig. 1. Grading curves of aggregates.

Chemically pure SCA was diluted to 0, 5, 10, 15 and 20% of mass fraction, respectively. These SCA solutions entrapped five batches of rubber particles till all their surfaces were covered before taking them out. The target mean strength of concrete in this paper was to reach 43 MPa at age of 28 days with 60–180 mm slump. Fifty percent of crushed

An Approach to Reduce Strength Loss of Rubber Concrete

41

gravel was replaced with recycled aggregate by weight while 20% of sand was substituted with combination-sized rubber by volume. The contents of each component are tabulated in Table 2. Table 2. Contents of each component. Component

Content (kg/m3 )

Water

232

Cement

627

Gravel

501

Recycled aggregate

501

Sand

414

Rubber

40

Five sets of mixture with rubber aggregate were prepared according to the following procedure: Mixing – All aggregates in SSD state were measured properly and put in a mechanical mixer, the inner surface of which had been wetted. Then the mixer was started to blend the materials for 300 s, followed by pouring half amount of the desired water. After another 300 s, the other half was added for thorough mixing. Stopped mechanical mixer till the mixture appeared to be consistent. Sampling – Ahead of casting, the inner surfaces of 100 mm cube moulds were oiled to avoid adhering from concrete specimen. Two even layers of fresh concrete were poured in, each of which was mechanically vibrated for 30 s to compact. Then the naked surface was trowelled to a smooth and clean finish. Curing – The samples were kept at a fixed temperature of 20 ºC for 24 h in the moulds which were covered by a polythene sheeting to avoid moisture loss. After demoulding and labelling with their identities, the specimens were moved and stored in a water tank with a constant 20 ºC up to the required age. Testing – Compressive strength tests were conducted at ages of 1, 7 and 28 days in accordance with BS EN 12390-3. Three parallel tests of duplicates were carried out and the average was recorded.

3 Results and Discussion Compressive strength result is shown in Fig. 2. It can be seen that all of them were below 43 MPa at 28 days because of the incorporated rubber. However, concrete with surface-pretreated rubber aggregate was stronger than that containing as-received rubber aggregate. At age of 1 day, compressive strength of specimens with as-received rubber aggregate were below 10 MPa, which was lower than that of samples with SCA-treated rubber particles. At age of 7 days, compressive strength of SCA-0 was below 20 MPa while the others were about 22 MPa. Testing results became 37 MPa versus around

42

H. Su

41 MPa, with a difference of 4 MPa roughly which was even more significant at age of 28 day. Another finding is that compressive strength rose as concentration of SCA solution increased. The increment was 32.5% at age of 1 day, which was nearly double and triple of those at ages of 7 and 28 days. 45

target mean strength of 43 MPa at 28 days

35

SCA-0 SCA-5% SCA-10% SCA-15% SCA-20% increment

35 30 25

30 25 20

20 15

15

10

10

5

5 0

Percentage of increase (%)

Compressive strength (MPa)

40

40

1

7

28

0

Age (Days) Fig. 2. Compressive strength of the specimens at 1, 7 and 28 days.

Such phenomenon is basically due to cohesion nature of SCA which is a kind of organosilicon compound. There are two reactive groups in total, and one of which easily reacts and polymerises with inorganic material while the other is organophilic. YSi(OR)3 is usually used as the formula of SCA, where Y represents a non-hydrolytic group, Si is short for silicon and OR stands for a hydrolysable group. Non-hydrolytic group bonds rubber, resin etc. properly whilst hydrolysable group is liable to hydrolyse so as to produce a silanol group which reacts with silicate and generates hydrogen bond. Then condensation reaction proceeds to synthetic an oxygen covalent bond, followed by gradually coating inorganic material’s surface by reaction product, which is accounted for strengthening the cohesiveness [16]. The reaction process is demonstrated in Fig. 3. To sum up, the improved adhesion mechanism is that inorganic concrete mixture and organic rubber materials tends to properly connected on the surfaces due to the molecular structure of SCA, thereby increasing the bond strength of interface. Analyses of X-ray diffraction (XRD) were carried out towards concrete with SCAtreated and as-received rubber particles. From the diffraction peaks shown in Fig. 4, it can be identified that the main crystalline phases were quartz and calcite. The scales of peak intensity and diffraction angle of the both patterns are quite alike, indicating that both compositions are almost same. It means using SCA to pretreated rubber particles does

An Approach to Reduce Strength Loss of Rubber Concrete Y Y RO

Si

hydrolysis ⎯→ HO OR ⎯⎯⎯⎯⎯ reaction

HO

Y

polycondensation ⎯→ OH ⎯ reaction

Si

⎯

Si

O

Y

Si

⋅ ⋅ Si ⋅

Y O

OH

OH ⎯

OH ⎯

OH

OH

OH

⎯

OH

OR

Y

43

Si

OH

⎯ OH ⎯ OH

inorganic material

Y HO

formation of ⎯⎯⎯⎯⎯⎯→ hydrogen bond

Si

O

O H

Y

Y

Si

⋅ ⋅ Si ⋅

O

O

Si

H H

HH O

Y

OH

formation of ⎯⎯⎯⎯⎯⎯→ oxygen bond

O

O

H H O

Y

H O

O

HO

Si O

O

Y

Y

Si

⋅ ⋅ Si ⋅

O

O

Y O

Si

OH

O

inorganic material inorganic material

Fig. 3. Reaction process between inorganic material and SCA.

not significantly alter the phase composition of rubber concrete. Thus it can be further concluded that SCA plays an important role in strengthening the interface bonding due to its cohesion nature. ∗

∗ Quartz (46-1045, SiO2) • Calcite (05-0586, CaCO3) •

∗

Intensity

•

∗

# Germanium iron (25-0358, Fe3Ge)

∗

∗

∗

#

SCA-modified

∗

∗ • ∗

10

20

30

∗ ∗ ∗

40

∗ ∗

#

As-received

50

60

70

2-Theta (°) Fig. 4. XRD patterns of the specimens.

Scanning optical microscopic inspection of interfacial transition zone between rubber particle and concrete mixture from the crushed specimens at age of 28 days was

44

H. Su

conducted. Figure 5 shows micrographs of fracture surface and the corresponding threedimensional (3D) images. Distinct cracking in zones I and II can be clearly seen from Fig. 5(a). Its 3D image also shows the obvious discontinuity in Fig. 5(b). The observed cracking and fault along the boundaries indicate a poor adhesion, resulting in an increase of amount of weak phase [17]. In contrast, a well developed interface between concrete mixture and SCA-treated rubber particle can be found in Fig. 5(c), supported by its 3D image shown in Fig. 5(d) that the interfacial transition zone is smooth compared with the counterpart displayed in Fig. 5(b). These observations suggest that the micro interface has been strengthened, resulting in the improvement of macro property, i.e. compressive strength.

Fig. 5. (a) Micrograph of interface between as-received rubber and mixture; (b) 3D image of (a); (c) Micrograph of interface between SCA-treated rubber and mixture; (d) 3D image of (c).

A brief cost analysis was conducted. Pure SCA powder costs ¥180 per kilogram and it is prepared to certain concentration before using. From the cost listed in Table 3, it can be seen that the price of SCA solution is no more than ¥36 each kilogram in this study. Practically, SCA solution is able to be used for a large amount of rubber particles, which makes the application economically viable. This approach is potential for realistic engineering where both normal compressive strength and energy absorption are needed such as highway crash barrier, bridge damping support.

An Approach to Reduce Strength Loss of Rubber Concrete

45

Table 3. Cost of SCA solution. Material

Price (¥/kg)

Chemically pure SCA

180

5 wt% SCA solution

9

10 wt% SCA solution

18

15 wt% SCA solution

27

20 wt% SCA solution

36

4 Conclusions It experimentally indicates that there is a positive effect of SCA on strengthening rubber concrete, especially when concrete is at early age. This approach of using SCA-treated rubber particles is even more effective as the concentration of the SCA solution increases. Cohesion nature of SCA is demonstrated to play a part in enhancing interface adhesion, resulting in an improvement of bonding strength between concrete mixture and rubber particles. This offers one approach of reducing strength loss for rubber concrete, which is potential for practical application.

References 1. Guo, Y.C., Zhang, J.H., Chen, G., Chen, G.M., Xie, Z.H.: Properties and applications of foamed concrete; a review. Constr. Build. Mater. 53, 32–39 (2014) 2. Al-Tayeb, M.M., Abu Bakar, B.H., Ismail, H., Akil, H.M.: Effect of partial replacement of sand by recycled fine crumb rubber on the performance of hybrid rubberized-normal concrete under impact load: experiment and simulation. J. Clean. Prod. 59, 284–289 (2013) 3. Atahan, A.O., Sevim, U.K.: Testing and comparison of concrete barriers containing shredded waste tire chips. Mater. Lett. 62, 3754–3757 (2008) 4. Su, H., Yang, J., Ling, T., Ghataora, G.S., Dirar, S.: Properties of concrete prepared with waste tyre rubber particles of uniform and varying sizes. J. Clean. Prod. 91, 288–296 (2015) 5. Thomas, B.S., Gupta, R.C., Kalla, P., Cseteneyi, L.: Strength, abrasion and permeation characteristics of cement concrete containing discarded rubber fine aggregates. Constr. Build. Mater. 59, 204–212 (2014) 6. Najim, K.B., Hall, M.R.: Crumb rubber aggregate coatings/pre-treatments and their effects on interfacial bonding, air entrapment and fracture toughness in self-compacting rubberised concrete (SCRC). Mater. Struct. 46, 2029–2043 (2013) 7. Richardson, A.E., Coventry, K.A., Ward, G.: Freeze/thaw protection of concrete with optimum rubber crumb content. J. Clean. Prod. 23, 96–103 (2012) 8. Li, G., Stubblefield, M.A., Garrick, G., Eggers, J., Abadie, C., Huang, B.: Some mechanical and physical properties of cement mortar reinforced by steel wires of scrap tires. Cem. Concr. Res. 35, 305–312 (2004) 9. Meddah, A., Beddar, M., Bali, A.: Use of shredded rubber tire aggregates for roller compacted concrete pavement. J. Clean. Prod. 72, 187–192 (2014) 10. Youssf, O., ElGawady, M.A., Mills, J.E., Ma, X.: An experimental investigation of crumb rubber concrete confined by fibre reinforced polymer tubes. Constr. Build. Mater. 53, 522–532 (2014)

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11. Pelisser, F., Zavarise, N., Longo, T.A., Bernardin, A.M.: Concrete made with recycled tire rubber: effect of alkaline activation and silica fume addition. J. Clean. Prod. 19, 757–763 (2011) 12. Segre, N., Joekes, I.: Use of tire rubber particles as addition to concrete paste. Cem. Concr. Res 30, 1421–1425 (2000) 13. Chou, L.H., Lin, C.N., Lu, C.K., Lee, C.H., Lee, M.T.: Improving rubber concrete by waste organic sulphur compounds. Waste Manag. Res. 28, 29–35 (2010) 14. Chou, L.H., Yang, C.K., Lee, M.T., Shu, C.C.: Effects of partial oxidation of crumb rubber on properties of rubberized mortar. J. Compos. B Eng. 41, 613–616 (2010) 15. Onuaguluchi, O., Panesar, D.K.: Hardened properties of concrete mixtures containing precoated crumb rubber and silica fume. J. Clean. Prod. 82, 125–131 (2014) 16. Xanthos, M.: Functional fillers for plastics, 2nd edn. Wiley-VCH, Weinheim (2010) 17. Poon, C.S., Shui, Z.H., Lam, L.: Effect of microstructure of ITZ on compressive strength of concrete prepared with recycled aggregates. Constr. Build. Mater. 18, 461–468 (2004)

Carbon Efficiency-Oriented Design Optimization of Bamboo Construction: A Case Study in Guangzhou, China Zujian Huang(B) School of Architecture, Tsinghua University, Beijing 100084, China [email protected]

Abstract. Bamboo is a material with great potential in the design and application of low-carbon building, but the current discussion mostly focuses on the material level rather than the life cycle. In this study, a bamboo building unit in Guangzhou, China is studied for the carbon emission of building materials and building operation. On this basis, the design of bamboo construction is optimized with the aim of improving the life cycle “carbon efficiency”. Among the 60 construction schemes, the carbon emission proportion of building materials accounts for 5.0%–13.1% of the total, and building operation is the key stage to improve the carbon efficiency. For construction optimization, the 3-layer construction type has better carbon efficiency than the 2-layer type. As for the framework, the difference between BPB and BMB as interlayer board can be ignored, and the combination of BPB/BMB and indoor plaster shows better carbon efficiency than the BSB/BFB as inner board. As for the core cavity, the arrangement of infill and air layer can effectively improve the carbon efficiency, and the use of non-hygroscopic inorganic materials is more advantageous than the hygroscopic organic materials under the local climate conditions. Keywords: Carbon emission · Carbon efficiency · Bamboo construction · Life cycle · Design optimization

1 Introduction Bamboo is a fast-growing plant, and can efficiently absorb a large amount of carbon dioxide from the air during its growth. Through photosynthesis, this carbon dioxide is transformed and stored in the bamboo plant as biomass. When a bamboo plant, mainly the culm, is processed into durable building material products and applied in building sector, the carbon can be isolated from environment for a long period. If these bamboobased products can be used to replace some carbon-intensive building materials, such as aluminum, the embodied carbon emission of the building can be reduced [1]. So far, existing studies on the above effects mainly stay at the material level. Some scholars have measured the carbon footprint of bamboo products caused by industrial processing, including the round bamboo, laminated bamboo, bamboo scrimber [2, 3], bamboo mat board [4], etc., which show that the carbon footprint of bamboos is close © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 47–60, 2023. https://doi.org/10.1007/978-981-19-4293-8_6

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to or even lower than timber. At the building level, the carbon emission during the building operation stage is calculated through the conversion of energy consumption. Researches on bamboo construction from the perspectives of energy performance show that in hot climate areas, bamboo is conducive to playing its own heat storage advantages, making itself more energy-efficient than timber units of the same construction size [5]. The author also carried out simulations in the Asia-Pacific bamboo area, showing that after construction and material optimization, bamboo units can save the annual energy consumption by up to 14% compared to the timber units [6]. However, there is still a lack of research that can integrate the two levels. The aim of this study is to combine the carbon emission of bamboo construction during the stages of both material production and building operation, and propose a concept of “carbon efficiency” and its calculation method. On this basis, the design of bamboo construction for a standard building unit is optimized with the orientation of improving the life cycle “carbon efficiency”.

2 Method 2.1 Settings of the Standard Building Unit Framework of the Building Unit. A typical building unit is set up for case study in Guangzhou, China, as Fig. 1 shows. In order to be representative, it is based on the validated benchmark model given in the ASHRAE 140 [7] and adjusted according to the local conditions of Guangzhou. As a result, the building unit is given a size of width × depth × floor height = 6.0 m × 6.0 m × 3.0 m. There is no internal partition wall, and among the four exterior walls, only the south and the north ones are opened with two windows. The size of the four windows is same as width × height = 1.2 m × 1.5 m.

Fig. 1. Schematic diagram of the building unit.

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Setting of the Building Envelope. Considering that the four exterior walls are the objects investigated in this study, and in order to avoid unnecessary interference, here the ceiling and floor are defined as “partition between two spaces with the same internal conditions”. Figure 2 and Table 1 shows the setting of the bamboo exterior walls. As for the setting of the exterior walls, the lightweight layered construction is considered, including a 2-layer group (with single cavity) and a 3-layer group (with double cavities). The 3-layer construction group is derived from the 2-layer construction group by adding outwards a 12 mm interlayer board and a 40 mm air layer. As for the material selection of the construction framework, the 18 mm outdoor BFB (bamboo scrimber) is used as the outer board for all the construction groups. The 12 mm BMB (bamboo mat board) and 12 mm BPB (bamboo particleboard) are used as interlayer boards, while the 12 mm indoor BFB, 12 mm BSB (laminated bamboo), 12 mm BMB + 10 mm IP (indoor plaster) and 12 mm BPB + 10 mm IP are used as the inner boards. As for the arrangement of the core cavity, five conditions are considered, including arrangement from outside to inside the 0.2 mm PE (PE foil) + 40 mm air, 0.2 mm PE + 20 mm CF (cellulose fiber), 0.2 mm PE + 20 mm EPS (expanded polystyrene), 0.2 mm PE + 20 mm CF + 40 mm air, and 0.2 mm PE + 20 mm EPS + 40 mm air.

Fig. 2. Construction framework and material arrangement of the exterior walls.

2.2 Carbon Emission of Building Materials Calculation Method. The carbon emission of building materials is calculated based on the following function: n (Mi × CFi ) (1) Cbm = i=1 A where, C bm —carbon emission of building materials per unit building area, kgCO2 e/m2 ; M i —mass of the i-th building materials consumed, kg; CF i —carbon emission factor of the i-th building materials, kgCO2 e/kg; A—building area, m2 .

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Z. Huang Table 1. Setting of the bamboo exterior walls.

Type Partition Groups boards

Exterior PE board

Interlayer Interior board board

L

2

F-F F-S F-Mp F-Pp

BFB PE (18 mm) (0.2 mm)

L

3

F-M-F BFB PE BMB F-M-S (18 mm) (0.2 mm) (12 mm) F-P-F BPB F-P-S (12 mm) F-M-Mp F-M-Pp F-P-Mp F-P-Pp

BFB (12 mm) BSB (12 mm) BMB + plaster (12 + 10 mm) BPB + plaster (12 mm + 10 mm)

Cavity Outside

Inside

Air (40 mm) BF (org./inorg.) (20 mm) BF (org./inorg.) + air (20 mm + 40 mm)

BFB Air Air (12 mm) (40 mm) (40 mm) BSB BF (12 mm) (org./inorg.) BMB + (20 mm) plaster BF (12 mm (org./inorg.) + + air 10 mm) (20 mm + BPB + 40 mm) plaster (12 mm + 10 mm)

The area of south and north exterior walls (excluding the windows) is 14.4 m2 , while it is 18 m2 of the east and west walls. This area is multiplied by the thickness of each material layer shown in Table 1 to obtain the consumed volume value, which is then converted into mass value by bulk density. Carbon Emission Factor of the Building Materials. The carbon emission factor (CF) of different bamboo products is calculated based on the author’s previous investigation [1]. In that study, the calculation of CF value for bamboo products is divided into four stages, including the raw material stage, production of building material stage, material transportation stage, and the end-of-life stage. The end-of-life treatment are considered as combustion to generate electricity. The material transport distance can be flexible. In this study, the transport of raw material, hemi-products are calculated according to actual investigation, while the transport of building materials is assumed to be 300 km. The CF values of bamboo are shown in Table 2.

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Table 2. Carbon emission factor (CF) parameters of the bamboo products in this study. Items

Unit

BMB

BPB

BSB

BFB-o

BFB-i

Bulk density* ρ

[kg/m3 ]

853.83

685.65

620.19

1219.65

1219.65

Carbon emission factor** CF

[kgCO2 e/m3 ]

416.87

460.50

361.48

1434.55

1255.70

Note: *Bulk density corresponds to a state with moisture content MC = 10%; **The data is taken from a previous investigation by the author [1].

2.3 Carbon Emission During Building Operation Calculation Method. The carbon emission during building operation is calculated according to the following function: n (Ei × CFi × y) (2) Cbo = i=1 A where, C bo —carbon emission during building operation per unit building area, kgCO2 e/m2 ; E i —annual consumption of the i-th energy, kWh/a, or GJ/a; CF i —carbon emission factor of the i-th energy, kgCO2 e/kWh, or kgCO2 e/GJ; y—building service life (durability), a; A—building area, m2 . In this case, only electricity is consumed during building operation, and the amount is calculated according to the following energy consumption simulation. Energy Consumption Simulation External Climate Conditions. The case study is carried out under the local conditions of Guangzhou, China. It is a typical sub-tropical city located in Lat. 23.13°N and Lon. 113.32°E. Guangzhou belongs to the climate zone of “Hot summer and Warm winter”. The annual mean air temperature and relative humidity is, respectively, about 23.0 °C and 68%, and the annual total solar radiation and precipitation is, respectively, about 1142 kWh/m2 and 1818 mm. The meteorological data of Guangzhou, including annual hourly air temperature, relative humidity, solar total radiation and diffusion radiation, normal rain, wind and direction, cloud cover index and dew point temperature are input as the external climate conditions into the energy consumption simulation model. Internal Climate Conditions. The room occupancy period is set as from 8:00 to 18:00 in working days (from Monday to Friday). Inside the building unit, the heat and moisture loads, including the convective heat, radiant heat, moisture, CO2 , and personnel activities of a standard office room are given during the occupancy period, as shown in Table 3. For the rest periods, all the loads are set as 0. Ideal HVAC devices are given to this model, which maintains the indoor comfort during the room occupancy period. According to a local investigation [8], the indoor air temperature and relative humidity are maintained as Table 3 shows.

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Z. Huang Table 3. Setting of the indoor heat and moisture load and the HVAC conditions

Room occupancy period (h)

Convective heat (W)

Radiant heat (W)

Moisture (g/h)

CO2 (g/h)

Personnel activities (met)

Ideal HVAC condition

0:00–7:59

0

0

0

0

0

Off

8:00–17:59

94.68

31.68

72

61.2

1.2

On

18:00–23:59

0

0

0

0

0

Off

T i (°C)

RH i (–)

18–28

40%–70%

Building Durability Prediction. The building service life (durability) is predicted according to the method recommended by ref [1], where the biological damage to bamboo inner board is regarded as the main reason for the construction damage. The exposure time beyond critical relative humidity RH ref of mould growth or the surface temperature is lower than the indoor condensation temperature is accumulated as a dose value D. After Y crit year when D is higher than the critical value of bamboo Dcrit , the construction is considered to be damaged, and the Y crit is considered to be the surface life of corresponding construction. Considering the real durability of bamboo, if Y crit is larger than 30 years, the surface life should be determined as 30 years. Computer Tool and Input Data. The simulation of annual energy consumption of the building unit, as well as the surface temperature and relative humidity of the bamboo exterior walls is carried out with WUFI Plus, a software developed and validated by the Fraunhofer IBP of Germany. It can support coupled heat and moisture simulation for whole building system, which is beneficial for the studies on hygroscopic materials-based construction, such as the bamboo construction in this case. The physical properties of the bamboo products are tested by the author in previous studies [5]. The items include properties to characterize the basic properties, the heat storage and transport capacities, as well as the moisture storage and transport capacities. These physical parameters are necessary for the performance simulation of a building system. The physical properties parameters of the rest materials are sourced from the Fraunhofer IBP. 2.4 Definition and Calculation of “Carbon Efficiency” The “carbon efficiency” is defined as a ratio between the indoor comfort and the total carbon emission, which is calculated according to the following function: Ce =

IC × y IC × y = C Cbm + Cbo

where, C e —carbon efficiency of building, m2 ·a/kgCO2 e; IC—indoor comfort level, %; y—building service life (durability), a; C—total carbon emission of building per unit building area, kgCO2 e/m2 .

(3)

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The indoor comfort level is characterized by the time proportion that the indoor T i and RH i maintains within a comfort range (18 °C ≤ T i ≤28 °C , 40% ≤ RH i ≤70%). The C value is the sum of the carbon emission of building materials (C bm ) and the carbon emission building operation (C bo ).

3 Result The combinations of the materials and construction arrangement in this study have a total of 60 groups, including 40 groups of 3-layer construction and 20 groups of 2-layer construction. Based on the calculation results, the impact of construction types, construction framework material selection, core cavity arrangement on the C e are discussed hereinafter. For each comparison between two construction conditions, a group is set as reference model (RM), while the other one as the assessment model (AM). The ratio of AM to RM is used to characterize the difference between the two groups, and show the impact of changing one single construction factor. 3.1 Construction Type Compared with the 2-layer construction, the 3-layer construction is derived by adding a 12 mm interlayer board and a 40 mm air layer. It is certain that the C bm of the 3-layer construction is larger but at the same time the thermal performance is improved. As s result, the ratio of C e values between the 3-layer construction groups to the corresponding 2-layer groups is in the range 113.86%–133.42% (mean 119.83%), showing significant better carbon efficiency of the 3-layer construction type, and this is because its better performance brings energy-saving benefits to the building operation stages (Fig. 3).

Fig. 3. Carbon efficiency (C e ) comparison: 3-layer (AM) and 2-layer (RM) construction types.

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3.2 Construction Framework Inner Board. At present, BSB and BFB are mostly used as decorative panels since they have satisfying appearance. On the contrary, BPB and BMB have rough appearance so that they are not suitable to be exposed to indoor environment directly. In this study, indoor plaster (IP) is added to the inner side of BPB and BMB. Therefore, four groups of inner board are formed, namely the BSB, BFB, BPB+IP and BMB+IP. The comparison between BSB and BFB shows that the construction groups with BSB as inner board have slight advantage over the groups with BFB. Setting BFB groups as 100%, the C e values of BSB groups are in the range 102.04%–103.82% (mean: 103.11%) (Fig. 4).

Fig. 4. Carbon efficiency (C e ) comparison: BSB (AM) and BFB (RM) as inner board.

The comparison between the construction groups with BPB+IP and the groups with BMB+IP as inner boards shows that, generally, the BPB+IP has slightly better performance than the BMB+IP. Setting BMB+IP groups as 100%, the corresponding C e values of BPB+IP groups are in the range 101.13%–103.51% (mean: 101.65%) (Fig. 5). Meanwhile, the construction groups with BPB+IP as inner board also show better performance than the BSB groups above. The C e values of BPB+IP groups is 103.52%–111.48% (mean: 105.65%) of the corresponding values of the BSB groups (Fig. 6). Interlayer Board. The BPB and BMB are used as interlayer boards in the L3 construction groups to separate the inner core cavity and the outer air layer. The comparison shows that the C e values ratio of BPB groups to the corresponding BMB groups is in the range 99.09%–100.75%. This difference is quite narrow, and the reason is that the performance contribution of the interlayer boards to the entire constructions is quite small (Fig. 7).

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Fig. 5. Carbon efficiency (C e ) comparison: BPB+IP (AM) and BMB+IP (RM) as inner layer.

Fig. 6. Carbon efficiency (C e ) comparison: BPB+IP (AM) and BSB (RM) as inner layer.

Fig. 7. Carbon efficiency (C e ) comparison: BPB (AM) and BMB (RM) as interlayer board.

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3.3 Core Cavity Arrangement Infill Layer. For each of the L2 and L3 construction groups, five arrangement schemes are set for the core cavity, as explained in Sect. 2.1. The comparison of the groups “BF (org./inorg.) + air (20+40)” and “BF (org./inorg.) (20)” to the group “Air (40)” shows the impact of the construction infill layer. Setting group “Air (40)” as 100%, the C e values of the other four groups are in the range 111.72%–144.93% (mean: 123.37%), showing obvious benefits from the infill layer (Fig. 8).

Fig. 8. Carbon efficiency (C e ) comparison: core cavity with (AM) and without (RM) infill layer.

Material of the Infill Layer. In terms of the construction infill layer, two types of materials are used, including the CF and EPS. The former one is organic and hygroscopic while the latter one is inorganic and non-hygroscopic. The dry thermal conductivity values of CF and EPS are the same, but CF is would absorb moisture from the environment, which influences its thermal performance. The comparison shows that the C e values of the EPS groups is 102.34%–103.59% (mean: 102.95%) of the corresponding values of the CF groups. Although CF, as a plant-based material, has much lower carbon footprint than EPS at the material level. The poorer thermal performance during building operation makes it disadvantageous from a long-term perspective (Fig. 9).

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Fig. 9. Carbon efficiency (C e ) comparison: inorganic (AM) and organic (RM) materials as infill.

Air Layer. In terms of the air layer, the comparison of groups “BF (org./inorg.) + air (20+40)” to the groups “BF (org./inorg.) (20)” shows the impact of the 40 mm air layer. Results show that the C e values of the groups with air layer is 105.94%–111.31% (mean: 107.81%) compared with the corresponding values of the groups without air layer. It means that the air layer can improve the overall C e value by about 7.8% on average (Fig. 10).

Fig. 10. Carbon efficiency (C e ) comparison: core cavity with (AM) and without (RM) air layer.

4 Discussion 4.1 Contribution of Building Materials and Building Operation to the Total Carbon Emission In this study, the construction and demolition of the building unit is ignored, and the total carbon emission (C) is composed of two stages, namely the building materials (C bm )

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and the building operation (C bo ). Among the 60 construction groups in this case study, the C of 3-layer construction are in the range 20.62–27.87 (mean: 23.13) kgCO2 e/m2 ·a, including 2.11–2.92 (mean: 2.38) kgCO2 e/m2 ·a of C bm and 18.30–25.12 (mean: 20.75) kgCO2 e/m2 ·a of C bo . Generally, the C of 2-layer construction is higher, which is in the range 23.54–36.68 (mean: 27.82) kgCO2 e/m2 ·a, including 1.81–2.58 (mean: 2.07) kgCO2 e/m2 ·a of C bm and 21.52–34.23 (mean: 25.76) kgCO2 e/m2 ·a of C bo . As for the 3-layer construction, the proportion of C bm and C bo to C is, respectively, 7.78%–13.13% (mean: 10.36%) and 86.87%–92.22% (mean: 89.64%). As for the 2-layer construction, this proportion is 5.04%–10.11% (mean: 7.54%) and 89.89%–94.96% (mean: 92.46%), respectively. Compared with the 2-layer construction type, the C bm of the 3-layer type have higher proportion due to the use of more materials and the reduce of carbon emission during the building operation stage (Fig. 11). The above discussion shows that a building of low carbon at the material level does not guarantee a low-carbon performance at life cycle. For example, if more materials are used properly, it may promote the reduction of carbon emission during the building operation stage, although it increases the carbon emission at the building material stage.

Fig. 11. Contribution and proportion of building materials and building operation to the total carbon emission.

4.2 Key Points for Improving the Carbon Efficiency As explained in Sect. 3.1, even in the 3-layer construction groups, the average contribution of carbon emission of building materials is about 10%. The key stage to improve the carbon efficiency is to improve the construction performance during the building operation stage. Based on this, it can be understood why some construction groups have higher carbon emission at building material stage, but ultimately help reduce the total carbon emission. Generally, the 3-layer construction type owns better performance over the 2-layer type. In terms of the framework of the 3-layer construction groups, there is almost no difference between BPB and BMB as interlayer board. As inner board, the combination of

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BPB/BMB and indoor plaster shows obvious better carbon efficiency than the BSB/BFB, and there are slight advantages of the BSB and BPB+IP, respectively, over the BFB and BMB+IP. In terms of the core cavity arrangement, the comparison among relevant construction groups shows that, the arrangement of 20 mm infill and 40 mm air layer to the core cavity can, respectively, improve the average carbon efficiency to about 23.4% and 7.8%. As for the material of the infill layer, the inorganic infill shows generally better than the organic one, by improving the thermal performance during the building operation stage, although it has higher embodied carbon footprint at the building material stage.

5 Conclusion In this study, a bamboo building unit in Guangzhou, China is studied for the carbon emission of building materials and building operation, the “carbon efficiency” and its impact by construction factors. Among the 60 construction schemes, the proportion of carbon emission of building materials accounts for about 5.0%–13.1% to the total, and the building operation is the key stage to improve the carbon efficiency. For the construction design optimization, the 3-layer construction type has better carbon efficiency than the 2-layer type. As for the framework, the difference between BPB and BMB as interlayer board can be ignored, and the combination of BPB/BMB and indoor plaster shows obvious better carbon efficiency than the BSB/BFB as inner board. As for the core cavity, the arrangement of infill and air layer can effectively improve the carbon efficiency, and the use of non-hygroscopic inorganic materials is advantageous than the hygroscopic organic materials, under the local climate conditions in this study. It can be further concluded from this study that, the design of bamboo construction should be based on overall optimization in life cycle, rather than a single static aspect at building material or construction level. Acknowledgement. The study is funded by Science and Technology Projects in Guangzhou (202201010295), and National Natural Science Foundation of China (51908219).

References 1. Huang, Z.: Resource Driven Sustainable Bamboo Construction in Asia Pacific Bamboo Areas. Springer, Cham (2021) 2. Van der Lugt, P., Vogtländer, J.G.: INBAR Technical Report no. 35—the Environmental Impact of Industrial Bamboo Products. Life cycle Assessment and Carbon Sequestration. International Network for Bamboo and Rattan (INBAR), Beijing (2015) 3. Phuong, V.T., Xuan, N.V.: Life Cycle Assessment for Key Bamboo Products in Viet Nam. International Network for Bamboo and Rattan (INBAR), Beijing (2020) 4. Xiao, Y., Yang, R.Z., Shan, B.: Production, environmental impact and mechanical properties of glubam. Constr. Build. Mater. 44, 765–773 (2013) 5. Huang, Z., Sun, Y., Musso, F.: Assessment of bamboo application in building envelope by comparison with reference timber. Constr. Build. Mater. 156, 844–860 (2017)

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6. Huang, Z., Sun, Y.: Hygrothermal performance comparison study on bamboo and timber construction in Asia-Pacific bamboo areas. Constr. Build. Mater. 271, 121602 (2021) 7. ASHRAE 140: Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs (2011) 8. Zhang, Y.: Design criteria of built thermal environment for Hot Summer & Warm Winter zone of China. Build. Environ. 88, 97–105 (2015)

Study on the Performance of Eggshells as a Humidity Control Building Material Wen-Cheng Shao1 , Yu-Wei Dong2(B) , Guan-Wei Fan3 , Jia-Wei Chen2 , and Chao-Ling Lu2 1 Department of Architecture, National Taipei University of Technology, Taipei, Taiwan

[email protected]

2 College of Design, National Taipei University of Technology, Taipei, Taiwan

[email protected] 3 Department of Architecture, National Taipei University of Technology, 1, Sec. 3, Zhongxiao

E. Road, Taipei 10608, Taiwan

Abstract. With the sustainable development of global environmental protection, waste recycling has become an important policy for establishing a friendly environment. Humidity in the indoor environment can cause the growth of mold and the spread of bacteria, when in turn lead to health problems, such as respiratory diseases, asthma, allergies, fatigue, and headaches. Therefore, waste is effectively used as a building material for indoor humidity control. This will benefit the health of indoor occupants. In this study, discarded eggshells were selected as the research and development of indoor humidity control building materials, and were analyzed and compared with two natural humidity control coatings on the market. They were classified into three types as A-CO, B-SI and C-ES, and their humidity control capabilities are: (A) The moisture absorption capacity of A-CO is 74.77 g/m2 , and the moisture release capacity is 72.48 g/m2 . (B) The moisture absorption capacity of B-SI is 61.47 g/m2 , and the moisture release capacity is 51.92 g/m2 . (C) The moisture absorption capacity of C-ES is 100 g/m2 , and the moisture release capacity is 91.8 g/m2 . According to this result, the order of moisture absorption and dehumidification performance is C-ES > A-CO > B-SI; the overall performance ranking is C-ES > A-CO > B-SI. Through the equilibrium moisture content experiment of the developed building material (C-ES), we know that, on average, each 20 cm * 20 cm sample can absorb 4.05 g of water and release 3.66 g of water. This result can prove that discarded eggshells can be used as building materials for indoor humidity control, help reduce the amount of waste on the planet, and are environmentally friendly to the planet. Keywords: Eggshells · Humidity control building materials · Balanced moisture content · Indoor environmental humidity

1 Introduction In order to make the earth sustainable and environmentally friendly, the theory of circular economy is a recycling system that can restore and regenerate resources. In an effort to © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 61–69, 2023. https://doi.org/10.1007/978-981-19-4293-8_7

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utilize resources more efficiently the biological cycle is redesigned and reproduced from natural materials or agricultural waste to eliminate waste, and ultimately waste can be biodegraded back to the nutrients in the biological cycle. Taiwan has an island climate with high temperature and high humidity. According to statistics, the annual average relative humidity in Taiwan exceeds 75%, sometimes as high as 85% [1]. Living environments with high temperature and high humidity can lead to the growth of biological contaminants such as microorganisms and dust mites. According to research, if the indoor relative humidity exceeds 70%, it will make the occupants sick [2]. When the humidity exceeds 80%, the contamination of microorganisms will increase in multiples [3], but if the humidity is lower than 40%, it will increase the survival rate of infectious viruses and bacteria in the air [4]. Therefore, environmental humidity can cause biological contamination. Excessive humidity will not only affect the comfort and health of users [5, 6], but also indirectly cause health problems such as respiratory diseases, asthma, allergies, fatigue and headaches for the occupants [7]. Therefore, in view of the indoor humidity control problem, the use of humidity control building materials is an effective way to passively control humidity. The principle is to use porous building materials to absorb and release moisture to alleviate changes in indoor humidity. The use of humidity control building materials can effectively suppress the frequency of high indoor humidity, improve indoor air quality and the health of occupants [8]. This research object is a building material that can control humidity. In addition to the research and development of discarded eggshells as humidity control building materials, the efficacy of two natural humidity control building coatings on the market was also compared.

2 Materials and Methods The use of humidity control building materials to control indoor environmental humidity is to use the characteristics of building materials to absorb and release moisture to alleviate changes in indoor humidity. The ability to control humidity can be divided into “water capacity” and “Moisture absorption and desorption rate”. In order to maintain a certain indoor humidity, water capacity is a more important performance. The larger the water capacity and the larger the pore volume, the slower the absorption and desorption reaction rate. Conversely, the smaller the pore volume, the larger the relative surface area, and the faster the absorption and desorption reaction rate. Therefore, when choosing humidity control building materials, it is necessary to strike the best balance between the two according to the requirements of usage [9]. Currently commercially available natural humidity control building materials use materials with natural pores to adjust the humidity of the space, such as wood, soil, charcoal, and so on. This time, we selected discarded eggshells to develop humidity control building materials for research on indoor environmental humidity control. The reasons are as follows: (a) Eggshell is a natural high-biocalcium component, with 7000 to 17,000 small holes, which meets the basic requirements of humidity control building materials. (b) The annual output of Taiwan’s eggs is as high as 7.6 billion. Except for a small amount that can be used as organic fertilizers, adsorbents or feed additives, most

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of them are treated as garbage. If it can be effectively developed and used as a humidity control building material, it can effectively reduce the amount of waste and realize the benefits of circular economy. In this study, the humidity control building materials were made into test specimens and placed in a simulated indoor environment box with constant temperature and humidity to study the changes in the water content of the building materials themselves. In addition to referring to the moisture response method of JIS A1470-1:2014, and taking into account the increase in global average temperature, the experimental temperature was adjusted from 23 °C to 25 °C. When it absorbs moisture, its relative background humidity is set to 95%. When dehumidifying, the relative background humidity is set to 50%. In this simulated indoor environment system, a 24-h moisture absorption cycle (12 h for moisture absorption and 12 h for moisture release) is used to detect the amount of water absorbed and released by the test body. In addition, in order to avoid iterative switching of the simulated box in the experiment, affecting the stability of the value, the weight and moisture content are measured every 2 h. In this study, a moisture analyzer was used to determine the moisture content (%) of building materials and weighed with a precise balance. The content of the experiment is to measure the moisture absorption and desorption capacity of various materials by gravimetric method; the control group has two kinds of experimental materials: (a) The paint produced in Gifu Prefecture, Japan on the market, whose main raw material is cypress powder, named A-CO. (b) It is a ceramic mineral paint produced by Shirasutu, Japan, which is available on the market. The main raw material is silicic acid Si(OH)4 , named B-Si. (c) The experimental group is a self-developed paint, using membrane less eggshell (ES) as the main raw material, and the content and ratio of other materials are calculated as, eggshell powder: diatomaceous earth: cassava flour: hemp fiber: slaked lime = 6:2: 3:3: 3. named C-ES. All materials are used to make three test bodies. For each test body, apply the test material on a 20 cm * 20 cm aluminum plate and coat it with a thickness of 1.5 mm.

3 Detection and Result 3.1 Control Group Experimental Materials A-CO Before the experiment, all samples were balanced for 24 h according to the JIS A 1470-1-2014 standard test method, and the following results were obtained through the experiment: (a) Sample A-CO-1: original weight 182.270 g. After 12 h of moisture absorption test, it measured 185.768 g, the total moisture absorption was 3.498 g. After another 12 h of moisture release test, it measured 182.386 g, the total moisture release was 3.382 g. After calculation, the moisture absorption per unit is 87.45 g/m2 , and the moisture release per unit is 84.55 g/m2 . (b) Sample A-CO-2: Original weight 182.710 g. After 12 h of moisture absorption test, it measured 185.718 g, the total moisture absorption was 3.017 g. After another 12 h of moisture release test, it measured 182.792 g, the total moisture release was 2.926 g. After calculation, the moisture absorption per unit is 75.45 g/m2 , and the amount of moisture released per unit is 73.15 g/m2 . (c) Sample A-CO-3: Original weight 183.382 g. After 12 h of moisture absorption test, it measured 185.838 g, the total moisture absorption was 2.456 g. After another 12 h of moisture

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release test, it measured 183.449 g, the total moisture release was 2.389 g. After calculation, the moisture absorption per unit is 61.40 g/m2 , and the moisture release per unit is 59.73 g/m2 (Figs. 1 and 2) (Table 1).

Fig. 1. Sample A-CO moisture absorption and release weight change (g).

Fig. 2. Sample A-CO moisture absorption and release water content change. (%).

Table 1. Sample A-CO moisture absorption and release unite quantity Sample

A-CO-1

A-CO-2

A-CO-3

Average

Moisture absorption/per unit

87.45 g/m2

75.45 g/m2

61.40 g/m2

74.77 g/m2

Moisture release/per unit

84.55 g/m2

73.15 g/m2

59.73 g/m2

72.48 g/m2

3.2 Control Group Experimental Materials B-SI Before the experiment, all samples were balanced for 24 h according to the JIS A 1470-1-2014 standard test method, and the following results were obtained through the experiment: (a) Sample B-SI-1: original weight 229.883 g. After 12 h of moisture absorption test, it measured 233.495 g, the total moisture absorption was 3.662 g. After another 12 h of moisture release test, it measured 231.900 g, the total moisture release was 1.595 g. After calculation, the moisture absorption per unit is 91.55 g/m2 , and the moisture release per unit is 39.88 g/m2 . (b) Sample B-SI-2: Original weight 223.546 g.

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After 12 h of moisture absorption test, it measured 225.903 g, the total moisture absorption was 2.357 g. After another 12 h of moisture release test, it measured 223.577 g, the total moisture release was 2.326 g. After calculation, the moisture absorption per unit is 58.93 g/m2 , and the amount of moisture released per unit is 58.15 g/m2 . (c) Sample B-SI-3: Original weight 227.264 g. After 12 h of moisture absorption test, it measured 228.621 g, the total moisture absorption was 1.357 g. After another 12 h of moisture release test, it measured 226.312 g, the total moisture release was 2.309 g. After calculation, the moisture absorption per unit is 33.93 g/m2 , and the moisture release per unit is 57.73 g/m2 (Figs. 3 and 4) (Table 2).

Fig. 3. Sample B-SI moisture absorption and release weight change (g).

Fig. 4. Sample B-SI moisture absorption and release water content change. (%).

Table 2. Sample B-SI moisture absorption and release unite quantity. Sample

B-SI-1

B-SI-2

B-SI-3

Average

Moisture absorption/per unit

91.55 g/m2

58.93 g/m2

33.93 g/m2

61.47 g/m2

Moisture release/per unit

39.88 g/m2

58.15 g/m2

57.73 g/m2

51.92 g/m2

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3.3 Test Group Experimental Materials C-ES Before the experiment, all samples were balanced for 24 h according to the JIS A 1470-1-2014 standard test method, and the following results were obtained through the experiment: (a) Sample C-ES-1: original weight 310.384 g. After 12 h of moisture absorption test, it measured 314.413 g, the total moisture absorption was 4.029 g. After another 12 h of moisture release test, it measured 310.857 g, the total moisture release was 3.556 g. After calculation, the moisture absorption per unit is 100.73 g/m2 , and the moisture release per unit is 88.90 g/m2 . (b) Sample C-ES-2: Original weight 308.413 g. After 12 h of moisture absorption test, it measured 311.899 g, the total moisture absorption was 3.486 g. After another 12 h of moisture release test, it measured 308.783 g, the total moisture release was 3.116 g, after calculation, the moisture absorption per unit is 87.15 g/m2 , and the amount of moisture released per unit is 77.90 g/m2 . (c) Sample C-ES-3: Original weight 309.841 g. After 12 h of moisture absorption test, it measured 314.248 g, the total moisture absorption was 4.407 g. After another 12 h of moisture release test, it measured 309.928 g, the total moisture release was 4.320 g. After calculation, the moisture absorption per unit is 110.18 g/m2 , and the moisture release per unit is 108.00 g/m2 (Figs. 5 and 6) (Table 3).

Fig. 5. Sample C-ES moisture absorption and release weight change (g).

Fig. 6. Sample C-ES moisture absorption and release water content change. (%).

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Table 3. Sample C-ES moisture absorption and release unite quantity. Sample

C-ES -1

C-ES-2

C-ES-3

Average

Moisture absorption/per unit

100.73 g/m2

87.15 g/m2

110.18 g/m2

99.35 g/m2

Moisture release/per unit

88.90 g/m2

77.90 g/m2

108.00 g/m2

91.60 g/m2

4 Discussion and Conclusions 4.1 Humidity Control Ability According to the experimental results, their humidity control ability are: (a) A-CO has a moisture absorption capacity of 74.77 g/m2 and a dehumidification capacity of 72.48 g/m2 . (b) The moisture absorption capacity of B-SI is 61.47 g/m2 , and the dehumidification capacity is 51.92 g/m2 . (c)The moisture absorption capacity of C-ES is 99.35 g/m2 , and the dehumidification capacity is 91.60 g/m2 . According to this result (Fig. 7), the order of moisture absorption and dehumidification performance is C-ES > A-CO > B-SI; the overall performance ranking is C-ES > A-CO > B-SI.

Fig. 7. Moisture absorption and release performance.

4.2 Moisture Absorption Grade The test result is judged according to the Japanese building material moisture absorption standard. After comparing with the table (Table 4), it can be seen that the moisture absorption of the material is: (a) A-CO material has a moisture absorption of 72.48 g/m2 , which is the third-level material. (b) B-SI material absorbs moisture 61.47 g/m2 , which is the second-level material. (c) C-ES material has a moisture absorption of 99.35 g/m2 , which is the third-level material.

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Level

3h

6h

12 h

Third-level

36 g/m2

50 g/m2

71 g/m2

Second-level

25 g/m2

35 g/m2

50 g/m2

First-level

15 g/m2

20 g/m2

29 g/m2

4.3 Conclusions From the results of this experiment, it can be found that the humidity control ability of the building material with eggshell powder as the main raw material is better than that of the other two tested materials. In addition to providing a basis for follow-up research, further analysis and comparison of the proportion of research and development materials can be carried out. Furthermore, according to Rhodes et al., 2005. [12] The “Exploration of Humidity Control Design” is divided into three levels (Fig. 8). At the material level, discuss the “Moisture Effusivity” and “Ideal Moisture Buffer Value”. At the system level, discuss the “Moisture Buffer Capacity” (practical moisture buffer value). At the room level, discuss the “Moisture Buffer” (moisture buffering in the entire room related to, among other things, exposure areas of the surface materials present, moisture load, ventilation rate and indoor climate.), which can be used for further research in the future.

Fig. 8. Moisture absorption and release performance. (Rhodes et al. 2005)

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Patents. “Bio-calcium filter material and its manufacturing method” research obtained “Patent Certificate from Intellectual Property Office of the Ministry of Economic Affairs of Taiwan”. Republic of China Taiwan Invention Patent No. I715980. Author Contribution. Conceptualization, Resources, Review and supervision, by W.C. Shao; Experiment, by G.W. Fan; Methods, by C.L. Lu; Formal analysis, by J.W. Chen; Data planning, Writing and Editing, by Y.W. Dong.

References 1. Meteorological data of Taiwan Central Meteorological Bureau: https://www.cwb.gov.tw/ V8/C/ (1981–2020) 2. Meyer, B.: Indoor Air Quality. Reading, Mass.: Addison-Wesley Pub. Co., MA, USA, (1983) 3. Vereecken, E., Roels, S.: Review of mould prediction models and their influence on mould risk evaluation. Build. Environ. 51, 296–310 (2012) 4. Fanger, P.O.: Thermal comfort. Analysis and applications in environmental engineering. Copenhagen, Danish Technical Press Co., Record number: 19722700268 (1961) 5. Fang, L., Clausen, G., Fanger, P.O.: Impact of temperature and humidity on perception of indoor air quality during immediate and longer whole-body exposures. Indoor Air 8(4), 276 (1998) 6. Naydenov, K., Melikov, A., Markov, D., Stankov, P., Bornehag, C.-G., Sundell, J.: A comparison between occupants’ and inspectors’ reports on home dampness and their association with the health of children: the ALLHOME study. Build. Environ. 43(11), 1840–1849 (2008) 7. Mendell, M.J., Mirer, A.G., Cheung, K., Tong, M., Douwes, J.: Respiratory and allergic health effects of dampness, mold, and dampness-related agents: a review of the epidemiologic evidence. Environ. Health Perspect. 119(6), 748–756 (2011) 8. Yeh, Y.-C.: Prognosis and Assessment of Moisture Buffering Materials Applied in Residential Building. National Cheng Kung University, PhD dissertation, Institute of Architecture (2014) 9. Shun, O.Y.: The Research for Sintering Porous Wastes into Humidity Adjusting Construction Materials. Master’s Thesis. Master’s Program of the Institute of Environmental Engineering, National Central University (2008) 10. Shao, W.C., Dong, Y.W.: Study on the feasibility of improving the indoor air quality from the perspective of circular economy by activation of biological calcium. In: IEEE International Conference on Architecture, Construction, Environment and Hydraulics (ICACEH), Xiamen, China, 2019, pp.133–136 (2019). https://doi.org/10.1109/ICACEH48424,2019.041846 11. Shao, W.-C., Dong, Y.-W.: A study on physicochemical properties and formaldehyde adsorption and degradation of purifying air quality by modified biocalcium. Int. J. Environ. Sci. Dev. 11(7), 327–335 (2020) 12. Rhodes, C., et al.: Moisture buffering of building materials. Report of the Nordisk Innovations Center (Rep. No. BYG-DTU R-126). Copenhagen, Denmark: Department of Civil Engineering, Technical University of Denmark (2005)

The Mechanical Properties for Using Banana’s Peel Ash as Aggregate in Geopolymer Mortar Trithos Kamsuwan(B) Civil Engineering Department, Faculty of Engineering, Siam University, Bangkok 10163, Thailand [email protected]

Abstract. Geopolymer is a new alternative material for construction that does not contain cement and produces very little CO2 . Geopolymer was caused by the reaction of geopolymerization of high concentrations of alkali substances and oxides of silicon and aluminum that can transformed into a strong structural material. Therefore, it is an alternative material that can be used to replace cement. When mixed with charcoal powder of banana peel which is waste in agricultural products form banana plants. This study is mixing with geopolymer with charcoal powder banana peel at 0, 5, 10, and 15% by weight for testing a mechanical property. We used a ratio for fly ash 50% and the mixed with solution 1 part sodium silicate and 1 part of 12 molar sodium hydroxide into 50% by total weight. Last process, we mixed geopolymer part with river sand that passing through sieve no.16 in ratio of geopolymer 1 part per river sand 2 part by weight. Also, we were tested the mechanical properties and testing both powder with scanning electron microscope (SEM) and Energy Dispersive X-Ray Analysis (EDS). We found that charcoal powder banana peel mixed with geopolymer can improved the efficiency of compression and flexural strength and water absorption in an appropriate ratio. Keywords: Geopolymer · Cement · Banana peel · Fly ash · Construction

1 Introduction Banana are the popular fruit in international trade and one of the most common crops grown in the world, especially in Thailand. Today, banana production is an important source of income an employment for the major banana export countries. In Thailand, the great availability of bananas flesh in producing regions throughout the year makes their transformation into banana chip and banana Fig. 1, besides being an important alternative to avoid possible waste of the production. As industrial byproducts, peels represent about 30–40 g/100 g of fruit weight. This resulted in 200 tons of waste from banana peels in Thailand generated each day and this amount tend to increase annually (Pangnakorn, 2006) [1]. The banana peels waste is generally displace in municipal landfills, which contribute to the existing environmental problems.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 70–76, 2023. https://doi.org/10.1007/978-981-19-4293-8_8

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Fly ash is one of the by-products produced from the process of coal burning. In Thailand, fly ash is one of the most popular pozzolans [2]. Among the various types of construction waste that can employ highlights are the pozzolanic materials, fly ash concrete has become practically common [3]. The possibility of developing a new material with raw materials reused were studied and add improvements in the technical aspects for the mortar and concrete. In this context the need for the use of banana peel ash as aggregates in the production of mortar in term of Geopolymer is seen that the Geopolymer is the innovative material in the world. In this study, banana peel was mixed in Geopolymer as aggregate to investigate the mechanical properties. Geopolymer is the term used to represent the binders produced by polymeric reaction of alkaline liquid with silicon and aluminum as source materials [4]. The mixing with Geopolymer with waste from banana peel in term of powder for testing mechanical strength of mortar and water absorption properties. The experimental program involves casting of geopolymer mortar cubes testing them at 28 days for compressive strength, Flexural strength and water absorption. Different parameter for percentage of peel banana 0, 5, 10, and 15% by weight are investigated at the ratio of sodium hydroxide 12 Molarity and the ratio of sodium hydroxide to sodium silicate as constant (1:1). The results were showed that Banana peel ash have affected to the properties of geopolymer mortar.

2 Materials and Methods Materials: Fly Ash from the Mae Moh Power Plant in Northern Thailand, Banana’s peel powder, Fine aggregate (graded river sand passing sieve No. 16 and retaining on sieve No. 100), Standard Specification for Sampling and Testing Fly Ash or Natural Pozzolans use in Portland-Cement Concrete according to ASTM C 311/C 311M-13 [5]. The physical and chemical properties of materials were shown in Table 1. Table 1. The physical and chemical properties of materials Fly ash

Sand

2.77

2.56

0.06

0.47

Physical properties Specific gravity Absorption (%) Moisture content (%)

1.21

Voids (%)

34.6

Fineness modulus Blaine fineness (cm2 /g) Median particle size (micron)

2.76 2,580

– – (continued)

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T. Kamsuwan Table 1. (continued) Fly ash

Retained on sieve number 325 (%)

Sand –

Chemical composition (%) Silicon dioxide (SiO2 )

26.96

92.86

Aluminum oxide (Al2 O3 )

11.84

3.17

Iron oxide (Fe2 O3 )

10.36

0.27

Calcium oxide (CaO)

39.40

0.55

Magnesium oxide (MgO)

2.88

0.49

Potassium oxide (K2 O)

1.30

0.32

Sodium oxide (Na2 O)

1.30

0.42

Sulfur oxide (SO3 )

4.09

0.55

Loss on Ignition (LOI)

0.86

0.67

Methods: Microstructure of Banana’s peel ashes were studied by using scanning electron microscope (SEM) and EDS. In addition, chemical composition, specific gravity, median particle size and fineness of banana’s peel were investigated. Banana’s peel ashes were used to add on fly ash at dosage levels of 0%, 5%, 10% and 15% by mass of binder. A constant water to binder ratio (w/b) of 0.5 was used throughout the investigation. The pastes were mixed in a mechanical mixer and the specimens were cast in 50 × 50 × 50 mm cube moulds for compression samples and 50 × 50 × 150 mm moulds for flexural samples. The fresh samples were dried in the temperature room. After 24 h, the samples were removed from the moulds and cured in room temperature (35–37 °C). Mixing: All samples were separated testing according to ASTM standard, ASTM C 109 and ASTM C 1609. Each compressive strength and flexural strength values were the average of five samples. The experimental study was investigated with the mechanical properties of geopolymer mortar mixing with banana peel ash. The ratio of mixing geopolymer mortar were shown in Table 2.

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Fig. 1. Show physical of fly ash powder, Mae Moh, Lampang Province and banana peel charcoal powder

Table 2. The proportion of geopolymer mortar mixing with banana peel ash Sample

Fly ash (g.) NaOH (g.) Na2 SiO3 (g.) Sand (g.) Banana peel ash (g.)

0% banana peel ash

1500

375

375

3000

0

5% banana peel ash

1425

375

375

3000

75

10% banana peel 1350 ash

375

375

3000

150

15% banana peel 1275 ash

375

375

3000

225

3 Results and Discussion The process to produce banana’s peel ash is by burning the banana’s peel with 100 °C for 24 h in oven. Then, the material was crush to powder and was sent to laboratory to investigate the physical and chemical properties of banana’s peel ash by a Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Analysis (EDX) testing. Table 2 show the chemical compositions found in banana’s peel ash. In Fig. 2 and Fig. 3 show the fly ash results from Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Analysis (EDX) testing. Fly ash consists of siltsized particles which are generally spherical, typically ranging in size between 10 and 100 micron. In this study, fly ash is produced from the Mae Moh generating plant of the Electricity Generating Authority of Thailand in Lampang province, in the north of Thailand. In Fig. 4 show the banana’s peel ash results from Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Analysis (EDX) testing. Banana’s peel ash consists of silt-sized particles which are generally wavy cube typically ranging in size between 30 and 150 microns.

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Fig. 2. Show scanning electron microscope (SEM) of fly ash

Fig. 3. Show energy dispersive X-Ray analysis (EDX) of fly ash

Fig. 4. Show scanning electron microscope (SEM) of banana’s peel ash

Fig. 5. Show eZAF smart quant results of banana’s peel ash

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Both of particle shape between fly ash and banana peel ash are different in structure. Strength Results The mechanical properties of geopolymer mortar were shown in Table 3. Table 3. The mechanical properties of geopolymer mortar mixing with banana peel ash Samples

Compressive strength (MPa)

Flexural strength (MPa)

Absorption (%)

0%

30.48

3.31

7.83

5% with banana peel

40.94

4.17

2.81

10% with banana peel

42.32

2.78

4.46

15% with banana peel

41.80

2.62

5.13

From the test results, it was observed that the compressive strength is the highest at the ratio of 10% of banana peel charcoal powder, the compressive strength is 42.32 MPa. While the flexural strength of the test sample at the powder mixture ratio is 42.32 MPa. Banana peel charcoal at 5% was able to improve the flexural strength of 4.17 MPa. As for the absorption percentage of the test sample, it increases with the addition ratio of banana peel charcoal powder at 5%, 10% and 15%, respectively, with the greatest value being the mixing ratio at 0%. Absorption is 7.83%. It can be observed that the mixing ratio of banana peel charcoal powder in the geopolymer material increases. It will help to increase the compressive strength and flexural strength at the right mix ratio. which is likely to be caused by the calcium content in the chemical composition of banana peel powder. The water-absorbing properties of the geopolymer material mixed with banana peel charcoal will provide an effective protection against the accumulation of moisture in the geopolymer material. which in the ratio not mixed with banana peel charcoal powder It was found that the percentage of water absorption was higher than that of the samples mixed with charcoal powder. This is probably a result of the structure of the geopolymer material having a crystalline physical structure with a spherical shape. There is a gap in the crystallization. Therefore, when combining banana peel charcoal powder with a geopolymer material with a rather slender, wavy crystal structure as shown in the above Fig. 5, the crystal structure Therefore, there are few gaps in alignment with the geopolymer structure. Thus, reducing the water absorption ratio in an appropriate proportion.

4 Conclusions The research finding of the mechanical properties for using cement mixed with banana peel charcoal in geopolymer in three different percentages (5%, 10%, and 15%) are presented in this paper. These mechanical properties were used to investigate the effect of banana peel charcoal in the properties of geopolymer mortar at Alkaline Solution/Fly ash ratio 0.5 and ratio NaOH/Na2 SiO3 of 1:1 and ratio sand/Fly ash of 2:1 respectively

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at the sodium hydroxide concentration was 12 M. Based on the test results obtained, the following conclusion were drawn. 1. The water absorption rate of the test showed that the mixing of banana peel charcoal powder It can help to reduce the water absorption rate of the geopolymer material at an appropriate ratio of 5%. 2. Testing for compressive strength values showed that the mixing of banana peel charcoal powder The compressive strength can be increased at the 10% mixing ratio of banana peel charcoal powder at 10% 3. Testing the flexural strength values showed that the mixing of banana peel charcoal powder The flexural strength can be increased at the mixing ratio of banana peel charcoal powder at 5%. 4. Crystal structure of banana peel charcoal powder has a crystal structure with a wavy shape. There is a squareness on the surface which is different from the crystal structure of fly ash powder from Mae Moh, Lampang Province, which has a spherical shape, smooth surface and different chemical composition. 5. Banana Peel Powder Can Used in Geopolymer Material for Improving the Properties of Strength.

References 1. Pangnakorn, U.: Valuable added the agricultural waste for farmers using in organic farming groups in Phitsanulok, Thailand. In: Proceeding of the prosperity and poverty in a globalized world - challenges for agricultural research, pp. 275–278. Bonn, Germany, 11–13 Oct 2006 2. Chindaprasirt, P., Chareerat, T., Sirivivatnanon, V.: Workability and strength of coarse high calcium fly ash geopolymer. Cement Concr. Compos. 29(3), 224–229 (2007) 3. Davidovits, J.: Geopolymers - Inorganic polymeric new materials. J. Therm. Anal. 37(8), 1633–1656 (1991) 4. Davidovits, J.: Chemistry of geopolymeric systems, terminology. In: Davidovits, J., Davidovits, R., James, C. (eds.) Géopolymère’99, Proceedings of Geopolymer (1999) 5. ASTM C311/C311M-13 Standard Test Methods For Sampling And Testing Fly Ash Or Natural Pozzolans For Use In Portland-Cement Concrete

Facile Fabrication of Superhydrophobic Robust Coatings with Solar Reflective Capability by One Step Spraying Method Xingjie Tang1,2 , Yanyan Wang1,2(B) , Shu Liu1,2 , Zhiyong Xu1,2 , and Changsi Peng1,2(B) 1 School of Optoelectronic Science and Engineering and Collaborative Innovation Center of

Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, People’s Republic of China [email protected], {yywang,changsipeng}@suda.edu.cn 2 Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006, People’s Republic of China

Abstract. Building exterior wall coating will inevitably experience (temperature change, ultraviolet radiation, dust pollution, mechanical contact and so on) when it is used outdoors, which will reduce the solar reflectivity. Therefore, improving the durability of the solar reflective coating is the premise to ensure the long-term stable use of the solar reflective coating. In this study, we developed low-cost and eco-friendly ground calcium carbonate (GCC)/TiO2 coatings on the cement substrate using a simple one-step spraying method. The as-sprayed GCC/TiO2 coating surface is superhydrophobic with a sliding angle of 5 ± 0.6° and a contact angle of 158 ± 1.1°. The coating remained excellent superhydrophobic even after a 2 m length of abrasion and 50 peelings. Surprisingly, the solar reflectance of the coating surface is up to 0.895, which can lower the cement surface by nearly 10 °C. Furthermore, the coating has corrosion resistance, anti-ultraviolet, and selfcleaning properties, suggesting that the coatings have great potential in building cooling applications. Keywords: Superhydrophobic coating · Nanoparticles · Composite materials · Solar reflectance

1 Introduction In recent years, superhydrophobic coatings have attracted the interest of researchers due to a variety of their unique characteristics such as anti-corrosion [1–4], self-cleaning [5, 6], anti-icing [7, 8], etc. It has been found that the key factor for a coating to have superhydrophobic properties are the micro-nano-scale rough structures and low surface energy materials. In light of these considerations, various methods to fabricate superhydrophobic coatings have been developed, which include the chemical vapor deposition [9, 10], stencil method [11, 12], dip coating [13], etc. However, most of the fabrication © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 77–83, 2023. https://doi.org/10.1007/978-981-19-4293-8_9

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methods rely on complex manufacturing processes, toxic reagents, expensive equipment, and poor reproducibility, which hinders the practical applications of superhydrophobic coatings. It is well known that the micro/nanostructure of the superhydrophobic coating is easily destroyed. The researchers have proposed several new solutions to improve the durability of the superhydrophobic coating. For instance, Wang et al. prepared superhydrophobic coating with excellent self-cleaning properties and mechanical stability by the combination of hierarchical structure method and “paint + adhesive” method. The microscale diatomaceous earth (DE) formed a grading structure together with the sand powder and further bonded through Portland cement to improve the robustness [14]. In this study, we present a low-cost and facile method to fabricate solar reflective coatings with superhydrophobic properties. TiO2 because of its high chemical stability and high reflectivity along with the ground calcium carbonate (GCC) were used. Hydrophilic TiO2 and GCC were converted into hydrophobic particles by using room temperature vulcanized silicone rubber (RTV). GCC microparticles and TiO2 nanoparticles were mixed in a certain percentage to form a rough micro-nano structure. The modified GCC/TiO2 mixed solution is then sprayed on the uncured cement substrates by a simple one-step spraying technology. After the coating is fully solidified, it exhibited excellent mechanical stability, superhydrophobicity, and solar reflectivity. The proposed superhydrophobic coating can be widely used in the construction industry due to its low-cost constituent materials and the simple manufacturing process.

2 Materials and Methods 2.1 Materials Room temperature vulcanized silicone rubber (RTV, GB-107, 1000 cs) was supplied by Jinan Xing Fei Long Chemical Co., Ltd. Ground calcium carbonate (GCC, 7–9 µm) powders were purchased from Henan Yixiang New Material Co., Ltd., China. Tetraethyl orthosilicate (TEOS) and ammonia were supplied by Sinopharm Chemical Reagent Co., Ltd., China. Cement was purchased from Jiangxi Yinshan White Cement Co., Ltd. TiO2 (rutile, ~20 nm) powders were supplied by Shanghai Macklin Biochemical Co., Ltd., China. 2.2 Preparation Two g of TiO2 powers were evenly dispersed in 15 mL deionized water, and the mixture was magnetically stirred for 10 min at 500 rpm. Next, 6 g of CaCO3 was slowly added with the same stirring rate for 10 min. Then, 2 mL TEOS was slowly added and stirred for 2 min at 600 rpm. Finally, 2 mL RTV and 0.5 mL ammonia were dropped into the mixture. The reaction mixture was magnetically stirred for 1 h at a stirring speed of 600 rpm at room temperature. Then, the reaction mixture was put into the spray gun (RG-3L, Anest Iwata Corporation, Shanghai, China), and sprayed uniformly on the uncured base material made of cement. After spraying, the coating was cured for 12 h at ambient conditions. The powder is dried to form a uniform coating and embedded into the hard cement substrate.

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3 Characterizations The surface groups and morphologies of the coating were characterized by Fourier transform infrared spectroscopy (FT-IR, HYPERION 2000, Bruker, Germany) and scanning electron microscopy (SEM, Sigma 300, Zeiss, Germany). The spectral reflectance of the surface was measured with the help of a Spectrophotometer (Lambda 750S, PerkinElmer, USA). The contact angle measuring instrument (JCY-4, China) was used to measure the sliding angles (SA) and contact angles (CA) of a 4 µL water droplet. The SA and CA values were averaged by measuring the same sample at five different locations. The surface temperature of the coating was measured by a non-contact infrared thermometer (DM 5002, DELIXI, China).

4 Results and Discussion The GCC/TiO2 surface demonstrated excellent superhydrophobicity with a CA of 158° and a SA of 5.3° (Fig. 1a). The FTIR spectra of the TiO2 , the GCC, and the RTVGCC/TiO2 are shown in Fig. 1b. In comparison with the TiO2 and the GCC, RTVGCC/TiO2 exhibits new absorption peaks at 1259 and 2964 cm−1 , which belong to the skeleton vibration of the -CH3 group. The peaks at 1020 and 798 cm−1 belong to the stretching vibrations of Si–O–Si bond in RTV. The FT-IR spectrum indicates that the RTV successfully modified the GCC/TiO2 coating. As presented in Fig. 1c, the coating surface contains a quantity of micron-sized irregular pores and particles. The combination of nanoscale TiO2 and microscale CaCO3 particles creates a rough structure on the coating surface (Fig. 1d). Therefore, the low surface energy substance combined with the rough surface structure of the coating endue the coating surface superhydrophobicity.

Fig. 1. (a) Wettability of the GCC/TiO2 coating; (b) The FTIR spectra of TiO2 , GCC, RTVGCC/TiO2 ; SEM images of the GCC/TiO2 coatings (c) and (d).

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Fig. 2. Schematic diagrams of (a) abrasion test and (b) peeling test; variations of CA and SA in (c) abrasion cycles and (d) peeling cycles on the coating surface; pictures of 10 abrasion cycles in inset of (c), and 10 peeling cycles in inset of (d); corrosion test of the GCC/TiO2 coating in (e).

The mechanical stability of the superhydrophobic coating determines whether it can be widely used in various applications. The cement improves the adhesion of coating with the substrate, and the cured cement protects it from damage. For the abrasion test, the sample was moved 20 cm on a 400 grit sandpaper under a weight of 500 g (pressure ≥ 2 kPa), which defines a single wear cycle (Fig. 2a). After 10 cycles of abrasion test in Fig. 2c and inset of Fig. 2c, the CA was always larger than 150° and the SA was smaller than 10°. When the 800 grit and 1200 grit sandpapers were used, the results were similar to Fig. 2c, indicating that the coating has outstanding wear resistance. Furthermore, the coating stability was assessed by the tape peeling test under a weight of 1 kg (pressure ≥ 5 kPa) load (Fig. 2b), and then the tape was slowly removed. After repeating this process five times, the CA and the SA of the coating were recorded, the above process defines one peeling cycle. Similarly, Fig. 2d and inset of Fig. 2d show the variation of CA and SA of the coating surface during the peeling test, which demonstrated excellent adhesion and superhydrophobic characteristics after 10 peeling cycles. Moreover, Fig. 2e shows the liquid droplets on the coating surface with different pH values from 2 to 12, indicating the superb stability of the coating surface to withstand corrosive solutions. Table 1. The ratio of cement, CaCO3 and TiO2 in different coatings. Sample number

Mass (g) Cement

CaCO3

TiO2

8

0

0

S2

7

1

S3

6

2

S4

5

3

S5

4

4

S1

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Fig. 3. (a) Curves of solar reflectance spectra for the coating S1 –S5 ; (b) the calculated solar reflectance for the coating S1 –S5 ; (c) Surface temperature changes of the coating S1 –S5 ; (d) variations of CA and SA of the coating in UV irradiation; self-cleaning test of the GCC/TiO2 coating in (e) and (f).

The solar reflectance spectra of the five different coatings (S1–S5) shown in Table 1 were analyzed in the wavelength range of 300–2500 nm. The reflectance spectra of these five coatings are given in Fig. 3a. The reflectivity of S2 , S3 , S4 and S5 coating, in the wavelength range of 400–2500 nm, is significantly high as compared to the S1 coating. The calculated solar reflectance of these five coatings in the wavelength range of 300–2500 nm is shown in Fig. 3b. When the mass ratio of GCC:TiO2 was 3:1, the solar reflectance of GCC/TiO2 coatings (S3 ) was highest (~0.895). To study the heat reflection effect of the coating in an actual environment, the change in surface temperature of the coating under solar radiation was monitored from 9 am to 5 pm. The maximum outdoor temperature was 35 degrees. The surface temperature of the S3 coating was nearly 10 degrees lower than that of the S1 coating during 11 am to 2 pm (Fig. 3c). Similar trends in the surface temperature variation of S2 , S4 , and S5 were noticed. These results demonstrate that the GCC/TiO2 coating has excellent solar reflection characteristics. Moreover, the anti-ultraviolet radiation resistance of the coating was investigated over a 12-h cycle. As it can be seen in Fig. 3d, it still has excellent superhydrophobicity after 14 cycles of ultraviolet radiation. In practical applications, the surface of the coatings is inevitably deposited by various contaminants, therefore, the self-cleaning ability of the solar reflective coatings is crucial for the building exteriors (roofs and walls). Figure 3e shows irregularly dispersed dust on the surface of the GCC/TiO2 coating, and the dust on the coating surface was completely washed away by water droplets. With the exception of dust, various liquids commonly used in our daily life can easily contaminate the surface of the coating and reduce its solar reflectance. However, the GCC/TiO2 coating displays outstanding anti-fouling ability for various liquids such as blue ink, honey, sewage, brine, coffee, and coca cola (Fig. 3f). These droplets have ball-like shapes on the surface of the GCC/TiO2 coating and easily rolling away from the coating surface, demonstrating the remarkable self-cleaning ability of the GCC/TiO2 coating.

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5 Conclusion In this paper, the GCC/TiO2 superhydrophobic coating with excellent solar reflective ability and robustness was facilely prepared on the cement surface by a one-step spraying. The GCC/TiO2 coating has extraordinary mechanical stability to withstand a 2 m length of abrasion and 50 peeling cycles, which are crucial for its practical applications. Notably, the coating has a solar reflectance of ~0.895, which is sufficient to lower the surface temperature of the cement by nearly 10 °C. Moreover, the coating displayed excellent corrosion resistance, anti-ultraviolet, and self-cleaning properties. The solar reflective coatings fabricated by the above-described low-cost one-step method will undoubtedly have applications in the construction of building exteriors. Acknowledgements. The authors gratefully acknowledge financial supports by the National Key R&D Program Project of MOST (2018YFE0125800) and the National Natural Science Foundation of China (No. 61871281 and 11504251), and the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions.

References 1. Shi, L., et al.: A robust superhydrophobic PPS-PTFE/SiO2 composite coating on AZ31 Mg alloy with excellent wear and corrosion resistance properties. J. Alloy. Compound. 721, 157– 163 (2017) 2. Zhao, Y., Zhao, S., Guo, H., You, B.: Facile synthesis of phytic acid@attapulgite nanospheres for enhanced anticorrosion performances of coatings. Prog. Org. Coat. 117, 47–55 (2018) 3. Zhang, S., et al.: Underwater drag-reducing effect of superhydrophobic submarine model. Langmuir 31, 587–593 (2015) 4. Cai, C., et al.: Superhydrophobic surface fabricated by spraying hydrophobic R974 nanoparticles and the drag reduction in water. Surf. Coat. Technol. 307, 366–373 (2016) 5. Guo, X.-J., Xue, C.-H., Jia, S.-T., Ma, J.-Z.: Mechanically durable superamphiphobic surfaces via synergistic hydrophobization and fluorination. Chem. Eng. J. 320, 330–341 (2017) 6. Zang, D., Xun, X., Gu, Z.: Fabrication of superhydrophobic self-cleaning manganese dioxide coatings on Mg alloys inspired by lotus flower. Ceram. Int. 46, 20328–20334 (2020) 7. Zhang, Q.H., Hou, B.S., Li, Y.Y.: Two novel chitosan derivatives as high efficient eco-friendly inhibitors for the corrosion of mild steel in acidic solution. Corros Sci. 164, 108346 (2020) 8. Shen, Y., et al.: Anti-icing performance of Superhydrophobic texture surfaces depending on reference environments. Adv. Mater. Interfaces 4(22), 1700836 (2017) 9. Kang, H., Zhao, B., Li, L., Zhang, J.: Durable superhydrophobic glass wool@polydopamine@PDMS for highly efficient oil/water separation. J. Colloid Interface Sci. 544, 257–265 (2019) 10. Rezayi, T., Entezari, M.H.: Toward a durable superhydrophobic aluminum surface by etching and ZnO nanoparticle deposition. J. Colloid Interface Sci. 463, 37–45 (2016) 11. Ellinas, K., Tserepi, A., Gogolides, E.: Superhydrophobic, passive microvalves with controllable opening threshold: exploiting plasma nanotextured microfluidics for a programmable flow switchboard. Microfluid. Nanofluid. 17(3), 489–498 (2014) 12. Liu, X., Yang, X., Chen, Z., Ben, K., Guan, Z.: Robust and antireflective superhydrophobic surfaces prepared by CVD of cured polydimethylsiloxane with candle soot as a template. RSC Adv. 5(2), 1315–1318 (2015)

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13. Chen, Z., Liu, X., Wang, Y., Li, J., Guan, Z.: Highly transparent, stable, and superhydrophobic coatings based on gradient structure design and fast regeneration from physical damage. Appl. Surf. Sci. 359, 826–833 (2015) 14. Wang, P., Yang, Y., Wang, H.B., Wang, H.Q.: Fabrication of super-robust and nonfluorinated superhydrophobic coating based on diatomaceous earth. J. Colloid Interface Sci. 362, 90–96 (2021)

Study on Carbon Emission of Laminated Bamboo Based on Life Cycle Assessment Method Zujian Huang1 and Wenyu Zhang2,3(B) 1 School of Architecture, Tsinghua University, Beijing 100084, China 2 School of Architecture, South China University of Technology, Guangzhou 510640, China

[email protected] 3 State Key Laboratory of Subtropical Building Science, South China University of Technology,

Guangzhou 510640, China

Abstract. Laminated bamboo (LB) is an industrial bamboo product that has been successfully promoted to building sector. In order to qualify the carbon emission during the production (C) of LB and clarify its characteristics. The study defines the production steps and carbon emission calculation boundary of LB, and investigates the carbon emission of a 3-layer plain-pressed LB board. Results show that the total C value is 30.67 kg CO2 e/FU, and the composition of production energy consumption, transport and addendum accounts for 86.81%, 2.88% and 10.30%, respectively. The steps of processing bamboo strips generate the most carbon emission, followed by the 1-layer boards and the 3-layer board. The steps of drying carbonized strips, fine planning and rough planning account for more than half of the total carbon emission. By comparison with two previous case studies, the study suggests that reducing the carbon emission factor of electricity used in production is the key to reduce the total C value of LB. Keywords: Laminated bamboo · Manufacturing process · Production energy consumption · Transport · Glue application · Carbon emission factor

1 Introduction Due to the fast growing speed, bamboo is inherently capable to capture CO2 during its growth. When the biomass is converted to durable building products, the carbon is sequestrated from the air. Previous research proved that through material and construction optimization, the hygrothermal performance of bamboo in local buildings can be close to or even better than timber [1]. If bamboo-based building products are used to replace those materials of high carbon footprint, such as the concrete or steel, the embodied carbon emission of building can be reduced. To this end, industrial bamboo products are developed, including various bamboo-based panels. The carbon emission during the manufacturing of “Glubam”, a kind of bamboo mat board, was calculated, and results showed that the carbon emission of “Glubam” is −261 kg/m3 , which was © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 84–96, 2023. https://doi.org/10.1007/978-981-19-4293-8_10

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negative and smaller than the −168 kg/m3 of glulam (Note that this result included the carbon stocks in the biomass of raw bamboo [2]. Laminated bamboo (LB) is a kind of bamboo-based panel developed in the 1990s. Compared with some other bamboo-based panels, such as bamboo particleboard, bamboo OSB, the features of raw bamboo is better remained during the production of LB. This makes LB own the advantage of surface appearance, and be widely accepted by the building industry as decorative products, such as wall cladding, flooring, etc. In 2012, China produced about 35 million m2 bamboo flooring panels, including about 20 million m2 made of LB, which was about 57% of the total [3]. In order to qualify the carbon emission during the production (C) of LB and clarify its characteristics. The study carries out an investigation on the carbon emission of a 3-layer plain-pressed LB board based on a Life Cycle Assessment method. It provides a reference for the carbon emission calculation method and a basis for carbon emission reduction in the future production of LB.

2 Material The material sample is produced by a bamboo company in Zhejiang Province, China. The raw bamboo is the Moso (Phyllostachys edulis), a dominant bamboo species in temperate regions. The LB board is 3-layer plain pressed, and has a size of length × width × thickness = 2050 mm × 1280 mm × 22 mm, a bulk density of 680 kg/m3 , and a moisture content of 9%–12%. In the following calculation, this is regarded as a function unit (FU). 1 FU has a total mass of 2050 × 1280 × 22 × 680 × 10−9 = 39.255 kg, including 37.292 kg bamboo and 1.963 kg UF (Urea formaldehyde). Here the mass ratio of UF is 5%. Figure 1 is the photo of the LB sample.

Fig. 1. Photo of the 3-layer plain-pressed laminated bamboo board

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3 Method The production of LB board starts with the raw bamboos, which are harvested from the bamboo plantation; Then the raw bamboos are delivered to the bamboo strip manufacturing factory; Qualified bamboo strips are latter transported to the LB board manufacturing factory, where the bamboo strips are glued together to 1-layer boards and finally the 3layer LB boards. After on-site investigation, the manufacturing process and the carbon emission calculation boundary is clarified in Fig. 2, and would be explained in detail in Sects. 3.2, 3.3 and 3.4. diesel fuel

Raw bamboos

transport

eletricity

Bamboo strips

diesel fuel

transport

diesel fuel

eletricity

eletricity

1-layer boards

3-layer board

LB product

transport glue

Fig. 2. Manufacturing process and carbon emission calculation boundary during the production of the 3-layer plain pressed laminated bamboo board

3.1 Mass Flow During the Manufacturing Process There is non-ignorable mass loss during the production. According to the source data recorded by the bamboo strip and the LB board manufacturing factories, the mass loss mainly happens in four steps: Step 2, strip making, 1.3 t raw bamboos can produce 1.0 t bamboo strips; Steps 3 and 7, rough planning and fine planning, both mass transfer ratio is 70%; Step 14, sawing and sanding 3-layer board, there is a loss of 0.68 kg for each board. Therefore, if calculated in reverse, the bamboo mass for producing 1 FU final 3-layer LB board should be: Step 14: 37.292 kg; Steps 9–13: 37.292 + 0.68 = 37.972 kg (1.018 FU); Steps 7–8: 37.972/0.7 = 54.246 kg (1.455 FU); Steps 3–6: 54.246/0.7 = 77.494 kg (2.078 FU); Step 2: 77.494 × 1.3 = 100.743 kg (2.701 FU). Here it can be figured out that the total raw material utilization rate is 37.292/100.743 = 37.0%. This is the basis for the following calculation of carbon emission values. 3.2 Carbon Emission of the Production Energy Consumption (C 1 ) The production of LB is relatively complicated compared with its timber peers, since the constituent unit is strip, and making such regular bamboo strips from the hollow bamboo culms is much more difficult than that from wood. The production of LB mainly includes 14 steps, as shown in Table 1. In this investigation, the harvesting of raw bamboos, the strip selection, and the glue application are carried with manpower, so that no energy

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consumption is calculated. The carbon emission of the manufacturing process (C 1 ) is calculated according to the following formula: C1 =

n 

Pi × Mi × EFi

1

where, C 1 , carbon emission of the production energy consumption, kg CO2 ; i, each emission source; n, number of items; Pi , power of energy consumed during production, kWh/kg or kWh/FU; M i , amount of the materials being processed by energy, kg or FU; EF i , carbon emission factor of energy, kg CO2 /kWh. In this investigation, the energy consumed for production is electricity. The EF i of electricity refers to the value given by the Department of Climate Change, Ministry of Ecology and Environment. The electricity of Zhejiang Province is provided by the “East China Regional Grid”, where the EF i value is 0.7921 kg CO2 /kWh in 2019. Table 1. Calculation of the carbon emission of the production energy consumption (C 1 ). No.

Process step

Consumption

Pi Amount

Unit

M i [kg or FU]

C 1 per FU [kg CO2 ]

1

Harvesting of raw bamboo

(Manpower)

2

Strip making

Electricity

30

kWh/t raw bamboo

100.743 kg (2.701 FU)

2.3940

3

Rough planning

Electricity

70

kWh/t strips

77.494 kg (2.078 FU)

4.2968

4

Strip selection (Manpower)

5

Carbonization

Electricity

50

kWh/t strips

77.494 kg (2.078 FU)

1.2891

6

Drying carbonized strips

Electricity

151

kWh/t strips

77.494 kg (2.078 FU)

6.4882

7

Fine planning

Electricity

130

kWh/t strips

54.246 kg (1.455 FU)

5.5859

8

Quality screening

Electricity

50

kWh/t strips

54.246 kg (1.455 FU)

1.5039

9

Glue application (1-layer boards)

(Manpower)

(continued)

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Z. Huang and W. Zhang Table 1. (continued)

No.

Process step

Consumption

Pi Amount

Unit

M i [kg or FU]

C 1 per FU [kg CO2 ]

10

Pressing strips Electricity to 1-layer board

1.1

kWh/1-layer board

3 FU

2.6139

11

Sanding 1-layer board

0.5

kWh/1-layer board

3 FU

1.1882

12

Glue (Manpower) application (3-layer board)

13

Pressing 3 layers to 1 board

Electricity

1.1

kWh/3-layer board

1 FU

0.8713

14

Sawing and sanding 3-layer board

Electricity

0.5

kWh/3-layer board

1 FU

0.3961

Electricity

Total

26.6273

Note: the EF i value of electricity is calculated as 0.7921 kg CO2 /kWh

3.3 Carbon Emission of the Transport (C 2 ) The transport carbon emission (C2) includes: the transport of raw bamboos from plantation to the strip manufacturing factory, the transport of bamboo strips to the LB board manufacturing factory, and the transport of glue to the LB board manufacturing factory, as shown in Table 2. The consumption is diesel fuel. C2 is calculated according to the following formula: C2 =

n 

Mi × Di × EFi

1

where, C 2 , carbon emission of the transport, kg CO2 e; M i , mass of the materials being transported, t; Di , transport distance, km; EF i , carbon emission factor of transport, kg CO2 e/(t·km). The EF i values of different transport modes refer to the “GBT 51366–2019” [4]. Due to the lack of EF i value of “diesel truck (3t)”, the value of “diesel truck (2 t)” is used here for approximate calculation. The EF i values of “diesel truck (10 t)” and “diesel truck (2 t)” are, respectively, 0.162 and 0.286 kg CO2 e/(t·km).

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Table 2. Calculation of the carbon emission of the transport (C 2 ). No.

Process step

M i [kg]

Di [km]

EF i [kgCO2 e/(t·km)]

C 2 perFU [kg CO2 e]

1

Transport of raw bamboos to strip manufacturing factory (diesel truck, 10 t)

100.743 (2.701 FU)

30

0.162

0.4896

2

Transport of bamboo strips to LB board manufacturing factory (diesel truck, 3 t)

54.246 (1.455 FU)

0.1

0.286*

0.0016

3

Transport of glue to LB board manufacturing factory (diesel truck, 3 t)

1.963

700

0.286*

0.3930

Total

0.8842

Note: * the EF i value used here responds to the value of “diesel truck (2t)” in “GBT 51366–2019” [3]

3.4 Carbon Emission of the Addendum (C 3 ) The carbon emission of the addendum (C 3 ) during the production of LB is mainly from the glue application. C 2 is calculated according to the following formula: C3 =

n 

Mi × EFi

1

where, C 3 , carbon emission of the addendum, kg CO2 e; M i , mass of the addendum being added to the final product, kg; EF i , carbon emission factor of addendum, kg CO2 e/kg. As shown in Table 3, during the manufacturing of the 1-layer boards and the 3-layer board, the Urea formaldehyde (UF) is added. Altogether, the mass ratio of UF to the total is 5%. The EF i value of UF is calculated as 1.61 kg CO2 e/kg.

4 Result and Analysis 4.1 Composition of the Carbon Emission The total carbon emission during the production of LB (C) is the sum of C 1 , C 2 and C 3. which are shown in Tables 1–3. As a result, the C value is 30.67 kg CO2 e/FU. Figure 3

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Z. Huang and W. Zhang Table 3. Calculation of the carbon emission of the addendum (C 3 )

No.

Process step

Addendum

Mi [kg]

EF i [kg CO2 e/kg]

C 3 per FU [kg CO2 e]

1

Glue application (1-layer boards)

Urea formaldehyde

1.963

1.61

3.1600

2

Glue application (3-layer board)

Urea formaldehyde

shows the composition of C value of LB. The C 1 , C 2 and C 3 accounts for 86.81%, 2.88% and 10.30%, respectively. As for the composition of C 1 value, the steps during the processing of bamboo strips generate the most carbon emission, which is 70.29%, and this is followed by the 12.40% of the 1-layer boards and the 4.13% of the 3-layer board. 4.2 Major Carbon Emission Steps The carbon emission by each item of the production, transport and the addendum is shown in Fig. 4. The step of drying carbonized bamboo strips generates the largest carbon emission, which accounts for as high as 21.15% of the total. This is followed by the 18.21% of the fine planning and then the 14.01% of the rough planning. These three steps generates together more than half of the total emission. The glue application for the 1-layer boards and the 3-layer board together accounts for 10.30% of the total carbon emission, and if the transport of the glue is added, this glue related proportion of carbon emission would be increased to 11.58%.

Fig. 3. Composition of the total carbon emission during the production of laminated bamboo and the carbon emission of the production energy consumption

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Fig. 4. Carbon emission proportion of each manufacturing step during the production of laminated bamboo

5 Discussion 5.1 Comparison with Two Previous Case Studies on LB The calculation result is compared with two previous case studies on LB sheet products. Considering that the FUs are different among this study and the two cases, the calculation results are converted as 1 m3 in the following analysis, as shown in Table 4 and 5 and Fig. 5. The Case 1 is carried out by Van der Lugt P. The product is produced in Zhejiang, China, using Moso bamboo as raw material. It is also 3-layer LB but is combined with 2 layers of 5 mm plain-pressed board and 1 layer of 10 mm side-pressed board in between. 1 FU has a size of length × width × thickness = 2440 mm × 1220 mm × 20 mm, a total volume of 0.0595 m3 , and a mass of 41.7 kg (bulk density 700 kg/m3 ). The total C value during production is 32.874 kgCO2 e/FU. When converted to unit volume, it is 552.17 kgCO2 e/m3 [5]. The Case 2 is carried out by Phuong Vu Tan. The product is named “kitchen countertop panels”, which is made of 3-layer LB. The raw material is Luong bamboo (Dendrocalamus barbatus). The bamboo strips in this case are side-pressed for all the 3 layers. 1 FU has a size of length × width × thickness = 1860.6 mm × 1000.1 mm × 38.1 mm, a total volume of 0.0595 m3 , and a mass of 53.2 kg (bulk density 750 kg/m3 ). Excluding the item of final transportation from the factory to the international market, the total C value during production is 21.763 kgCO2 e/FU. When converted to unit volume, it is 307.91 kgCO2 e/m3 [6].

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Z. Huang and W. Zhang Table 4. Comparison of this study with two previous cases: total value and composition.

Items

Total

This study

Case 1

Case 2

461.25

448.97

224.71

C1

Carbon emission of the manufacturing process

C2

Carbon emission of the transport

15.32

50.61

22.09

C3

Carbon emission of the addendum

54.74

52.62

82.26

C

Total carbon emission

531.31

552.20

329.06

Table 5. Energy consumption during manufacturing process. Consumption

This study

Case 1

Case 2

Gasoline

0

3.76 l/m3

0

Electricity

582.32 kWh/m3

758.70 kWh/m3

547.85 kWh/m3

Carbon emission factor of 0.7921 kg CO2 /kWh 0.5773 kg CO2 /kWh 0.4103 kg CO2 /kWh electricity used

Fig. 5. Comparison of this study with two previous cases

5.2 Suggestion on Reducing Carbon Emission of LB In general, the C value of LB calculated in this study falls between the Case 1 and Case 2. It is closer to the Case 1 and significantly higher than the Case 2. As for the sub-item values, the C 2 in this study is the smallest of the three and meanwhile the C 3 value is close to the minimum, while the C 1 in this study is the larger than the other two.

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However, further analysis shows that the electricity consumption in this study, the Case 1 and the Case 2 is, respectively, 582.32 kWh/m3 , 758.70 kWh/m3 and 547.85 kWh/m3 , showing that the electricity consumption in this study is closer to the Case 2 and obviously lower than the Case 1. Therefore, the reason for the higher C 1 value in this study is not the amount of production energy consumption. It is because the carbon emission factor (EF i ) of electricity is higher. The EF i in this study is 0.7921 kg CO2 /kWh, much higher than the 0.5773 kg CO2 /kWh of the Case 1 and the 0.4103 kg CO2 /kWh of the Case 2. The EF i in the Case 2 is particularly low, almost half of the value in this study. Regardless of the difference of methods for adopting corresponding EF i values among these studies, it can be enlightened that for the LB in this investigation, reducing the carbon emission factor of the electricity power is the key to reducing the carbon emission of LB.

6 Conclusion The study carries out carbon emission (C) record for the production of a 3-layer plainpressed laminated bamboo (LB) based on LCA method. Results show that the total C value is 30.67 kg CO2 e per function unit or 531.31 kgCO2 e per m3 . The C values of production energy consumption, transport and addendum accounts for 86.81%, 2.88% and 10.30%, respectively. The steps of processing bamboo strips generate the most carbon emission, followed by the 1-layer boards and the 3-layer board. The steps of drying carbonized strips, fine planning and rough planning account for more than half of the total emission. Compared with two previous case studies on the production carbon emission of LB, the carbon emission of production energy consumption in this study is significantly higher. The greatest potential for cutting the carbon emission for LB in this study lies in reducing the carbon emission factor of the electricity used in the manufacturing process. Acknowledgement. The study is funded by: the Opening Foundation of State Key Laboratory of Subtropical Building Science (2022ZB07); the National Natural Science Foundation of China (51908219); Strategic Development Department of China Association for Science and Technology (2021ZZZLFZB1207088) and the Science and Technology Projects in Guangzhou (202201010295).

Annex Table The following annex Table 6 and Table 7 are the carbon emission data of the Case 1 and the Case 2, which are taken from ref [4] and ref [5]. Note that the source data are re-classified as C 1 , C 2 and C 3 .

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Item

No

Process step

Consumption

Amount

Unit

kgCO2 e/FU

C1

1

Cultivation and harvesting

Gasoline

0.224

liter/FU

0.651

2

Strip making

Electricity

1.38

kWh/FU

0.797

3

Rough planning

Electricity

8.62

kWh/FU

4.977

4

Strip selection

(Manpower)

5

Carbonization

Electricity

4.73

kWh/FU

2.731

6

Drying carbonized strips

Electricity

9.66

kWh/FU

5.577

7

Fine planning

Electricity

5.8

kWh/FU

3.349

8

Pressing strips to 1-layer board

Electricity

1.89

kWh/FU

1.091

9

Sanding 1-layer board

Electricity

1.62

kWh/FU

0.935

10

Pressing 3 layers to Electricity 1 board

1.65

kWh/FU

0.953

11

Sawing

Electricity

0.29

kWh/FU

0.167

12

Sanding 3-layer board

Electricity

0.86

kWh/FU

0.497

13

Dust Absorption (during all steps)

Electricity

8.67

kWh/FU

5.005

1

Transport from plantation to strip manufacturing factory (30 km)

Diesel fuel

0.260

liter/FU

0.699

2

Transport from Diesel fuel strip manufacturing factory to factory (300 km)

1.082

liter/FU

2.314

1

Glue application (1-layer boards)

Melamine formaldehyde

0.483

kg/FU

1.657

2

Glue application (3-layer board)

Emulsion Poly Isocyanate

0.908

kg/FU

1.476

C2

C3

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Table 7. Carbon emission data of laminated bamboo of Case 2 Item

No.

Process step

Consumption

Amount

Unit

kgCO2 e/FU

C1

1

Cut into pieces

Electricity

1.15

kWh/FU

0.472

2

Strip making

Electricity

1.59

kWh/FU

0.652

3

Removing notch and Electricity skin

1.67

kWh/FU

0.685

4

Carbonisation

Electricity

7.30

kWh/FU

2.994

5

Drying carbonised strips

Electricity

7.85

kWh/FU

3.220

6

Strip selection

7

Pressing strips to one-layer board

Electricity

2.30

kWh/FU

0.943

8

Sanding one-layer board

Electricity

2.11

kWh/FU

0.865

9

Pressing strips to three-layer board

Electricity

2.15

kWh/FU

0.882

10

Crushing board

Electricity

1.92

kWh/FU

0.788

11

Cutting panels to desired form

Electricity

0.45

kWh/FU

0.185

12

Dust absorption (all steps)

Electricity

10.35

kWh/FU

4.245

1

Transportation from Gasoline forest to bamboo buyers, motorbikes used

0.45

l/FU

0.300

2

Transportation from – the buyers’ home to BWG Company (28 tons truck EURO3, 50 km, transport of 790 FUs)

1.77

ton.km/FU

1.266

1

Glue application (first layer)

1.70

kg/FU

5.832*

2

Second glue application (3-layer board)

C2

C3

Melamine formaldehyde

Note: * here the carbon emission factor is set as 3.431 kg/kg, according to van der Lugt P, 2015 [5].

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References 1. Huang, Z., Sun, Y.: Hygrothermal performance comparison study on bamboo and timber construction in Asia-Pacific bamboo areas. Constr. Build. Mater. 271, 121602 (2021) 2. Xiao, Y., Yang, R.Z., Shan, B.: Production, environmental impact and mechanical properties of glubam. Constr. Build. Mater. 44, 765–773 (2013) 3. Huang, Z.: Application of Bamboo in Building Envelope. Springer, Cham (2019) 4. GBT 51366–2019: Standard for building carbon emission calculation (2019) 5. Van der Lugt, P., Vogtländer, J.G.: INBAR technical report no. 35—the environmental impact of industrial bamboo products. Life cycle assessment and carbon sequestration. International Network for Bamboo and Rattan (INBAR), Beijing (2015) 6. Phuong, V.T., Xuan, N.V.: Life cycle assessment for key bamboo products in Viet Nam. International Network for Bamboo and Rattan (INBAR), Beijing (2020)

Study on the Mechanical Strength of Fiber-Reinforced Geopolymer Porous Materials Xiaoling Qu, Jun Pang, Zhiguang Zhao(B) , and Chaocheng Yu School of Chemistry and Civil Engineering, Shaoguan University, Shaoguan 512005, China [email protected]

Abstract. In this paper, fly ash and slag were used as the main raw materials, water glass was used as the activator, and hydrogen peroxide was used as the foaming agent, to prepare the geopolymer porous material, focusing on the analysis of the mechanical properties of the geopolymer porous material. Experiments shown that when the ratio of slag to fly ash was 3:7, the content of water glass was 40%, the content of hydrogen peroxide was 1.75%, the content of foam stabilizer was 0.5%, and the content of fiber was 0.6%, the mechanical properties of porous materials were the best: the density was 898 kg/m3 , the flexural strength and the compressive strength obtained under standard conditions for 60d were 3.3 MPa and 9.5 MPa, respectively. Keywords: Geopolymer · Fiber · Porous material · Compressive strength · Flexural strength

1 Introduction Foamed concrete is a new type of wall insulation material with excellent fire resistance and heat insulation. At present, the preparation of foamed concrete can be roughly divided into two methods: physical foaming and chemical foaming [1, 2]. However, the extensive use of Portland cement in the preparation of foamed concrete results in high energy consumption and high CO2 emissions. In view of this, in order to reduce the energy consumption and cost of foamed concrete preparation, geopolymers have attracted more and more attention as a substitute for cement in the process of foamed concrete preparation. Geopolymer uses fly ash, slag and other aluminosilicate wastes as main raw materials. It is a green and environmentally friendly cementitious material with good mechanical properties and durability [3]. Like ordinary lightweight concrete, the mechanical properties of geopolymer foam concrete are mainly determined by density and porosity. Many scholars have done detailed studies on the relationship between pore structure and mechanical strength, and obtained a foam geology with uniform pore size distribution. There is a linear relationship between the pore size of the polymer and the compressive strength [4, 5]. In addition, the strength of the geopolymer foam concrete matrix will also affect the mechanical strength of the final product. However, © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 97–103, 2023. https://doi.org/10.1007/978-981-19-4293-8_11

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due to the light weight and high porosity of geopolymer foamed concrete, its flexural strength is very low. According to research, its flexural strength is 4–10 times lower than the compressive strength, and the flexural strength is more sensitive to changes in density and porosity characteristics, which will undoubtedly affect the service life of the geopolymer foam concrete [6]. At present, fiber is considered to be one of the main means to increase the flexural strength of cement-based materials [7]. Therefore, this paper adds proper amount of fiber to the geopolymer foam concrete to increase its flexural strength. Fly ash-slag-water glass were used as the geopolymer matrix and H2 O2 as the chemical foaming agent to study the influence of water glass, H2 O2 content and polypropylene fiber content on the mechanical properties (flexural strength, compressive strength) of geopolymer porous materials.

2 Materials and Experiments 2.1 Materials Fly ash: Grade II ash of Guangzhou Huangpu Power Plant; slag: S95 grade slag of Shaogang Jiayang New Material Co., Ltd.; commercial water glass: modulus 2.5, solid content 43%; sodium hydroxide: analytically pure; foaming agent: hydrogen peroxide, analytically pure; foam stabilizer: calcium stearate, analytically pure; commercially available polypropylene fiber: 20 µm in diameter and 12 mm in length. 2.2 Experimental Program The water glass and NaOH were adjusted into an alkali stimulant with a modulus of 1.5 in a certain ratio, and then fly ash, slag, fiber, calcium stearate and water were stirred and mixed in different proportions to form a slurry (see Table 1 for the experimental mix ratio), then added H2 O2 and stirred for 10 s, poured it into a mold of 40 mm × 40 mm × 160 mm, the slurry was demolded after hardening, and the test block was cured in a standard curing box at a curing temperature of 80 °C and a relative humidity of 90%. After the curing reached the specified age, a universal testing machine was used to test the compressive strength and flexural strength, and the test block was dried to a constant weight at 105 °C to calculate the absolute dry bulk density.

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Table 1. Experimental mix ratio of geopolymer porous materials. Num

Slag (%)

Fly ash (%)

Foam stabilizer (%)

H2 O2 (%)

Water glass (%)

Water (%)

Fiber (%)

Dry bulk density (kg/m3 )

A1

30

70

0.5

1.75

35

20

0

601

A2

30

70

0.5

1.75

40

17

0

710

A3

30

70

0.5

1.75

45

14

0

689

A4

30

70

0.5

1.75

50

10

0

694

A5

30

70

0.5

1.75

55

7

0

695

B1

30

70

0.5

1.1

40

17

0

948

B2

30

70

0.5

1.5

40

17

0

796

B3

30

70

0.5

2

40

17

0

596

C1

30

70

0.5

1.75

40

17

0.2

773

C2

30

70

0.5

1.75

40

17

0.4

843

C3

30

70

0.5

1.75

40

17

0.6

898

Note: The content of water glass, water, foam stabilizer, hydrogen peroxide, and fiber is calculated as the percentage of the total mass of powder (fly ash + slag)

3 Results and Discussion 3.1 Influence of Water Glass Content on Flexural Strength and Compressive Strength It can be seen from Table 1 that when the water glass content is 35%, the density of the material is 601 kg/m3 , and when the water glass content is 40% to 55%, the density of the material does not change much. As shown in Fig. 1, when curing for 3 days, the flexural strength of the material is the largest when the water glass content is 40%, which is 0.49 MPa. The flexural strength decreases as the water glass content. This phenomenon is more obvious at 7 days, in this case, the flexural strength of material with 40% water glass content is 58% higher than that when the water glass content is 35%, but the flexural strength gradually decreases with the water glass content. For 60 days curing, the flexural strength does not change much when the water glass content is 40%–50%, but when the water glass content increases to 55%, the flexural strength decreases significantly. In addition, it can be seen from Fig. 1 that the 3d compressive strength is significantly reduced when the content of water glass is greater than 50%. In particular, the compressive strength at 3d is the largest when the content of water glass is 40%, which is 5.3 MPa. Similarly, when curing for 60 days, the compressive strength of the material gradually decreases as the water glass content. It can be concluded that the optimal dosage of water glass is 40%. The reason may be that the water glass solution improves the fluidity of the slurry [8, 9]. The foam in the slurry is easily dispersed uniformly, forming uniform ventilated pores, and the ability to resist external pressure is enhanced. However, when the content of water glass is too high, the consistency of the slurry will

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increase, which will inhibit the foaming of hydrogen peroxide, causing the material to loosen, the distance between the gaps will increase, and the inside of the material will appear cracks, thereby reducing the mechanical strength (Fig. 1).

Fig. 1. The influence of water glass content on flexural strength and compressive strength.

3.2 The Influence of H2 O2 Content on Flexural Strength and Compressive Strength

(a) 1.1% H2O2

(b) 1.5% H2O2

(c) 1.75% H2O2

(d) 2.0% H2O2

Fig. 2. Optical photos of materials with different contents of H2 O2 .

The main function of H2 O2 is to generate pores and reduce the density of the material. It can be seen from Fig. 2 that as the content of H2 O2 increases, the number of pores

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increases, and the size of the pores increases. Figure 3 shows the pore size distribution inside the geopolymer porous material when the content of H2 O2 is different. It can be seen that most of the pore sizes are concentrated within 200 µm. The greater the amount of hydrogen peroxide, the fewer the number of small pores within 200 µm, and the greater the number of large pores larger than 200 µm, which is consistent with the results shown in Fig. 2. The influence of H2 O2 content on the flexural strength and compressive strength is shown in Fig. 4. As the H2 O2 content increases, the flexural strength and compressive strength of the geopolymer porous material decrease. When the H2 O2 content is 2%, the 3d flexural strength of the material is 0.28 MPa; when the H2 O2 content is 1.1%, the 3d flexural strength of the material is 1.00 MPa. With the extension of the curing time, the flexural strength increases, and when it reaches 60d, the flexural strength more than doubles. The change of compressive strength is basically the same as the flexural strength. The reason is that the increase of H2 O2 will increase the gas released by the reaction, and the overall porosity of the material will increase [10]. This leads to larger pore diameter and thinner pore wall. On the other hand, it will also increase the probability of overlap between pores, which will result in uneven pore distribution within the material [11]. Therefore, the mechanical strength of geopolymer porous materials will decrease.

Fig. 3. Pore size distributions of materials with different contents of H2 O2 .

3.3 The Influence of Different Fiber Content on the Flexural Strength and Compressive Strength Figure 5 shows that as the fiber content increases, the flexural strength of the geopolymer porous material will gradually increase. When the fiber content is 0.2%, the increase rate is not obvious. While, the flexural strength is increased by 77%, 78%, and 155% for the fiber content is 0.6% at 3d, 7d, and 28d, respectively. At the same time, the compressive strength increases with the increase of fiber content, but the effect is not as obvious as the flexural strength. When the fiber content is 0.6%, the compressive strengths of 3d, 7d, and 28d increase by 20%, 37%, 44%, respectively. This is because the fiber has excellent tensile properties, which can significantly improve the flexural strength of the

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Fig. 4. The influence of H2 O2 content on flexural strength and compressive strength.

Fig. 5. The influence of fiber content on flexural strength and compressive strength.

material [12]. With the increase of the fiber content, the lap effect of the fiber becomes stronger and the effect is more obvious. It is worth noting that the fiber will affect the density of the geopolymer porous material (see Table 1), because the addition of fiber will reduce the fluidity of the geopolymer slurry and hinder the foaming expansion, so the dry density will decrease.

4 Conclusions In this paper, slag and fly ash were used as raw materials, water glass was used as activator, and H2 O2 was used as foaming agent to prepare geopolymer porous materials. The influence of water glass, H2 O2 and polypropylene fiber were studied. The results show that the flexural strength and compressive strength generally increase first and then decrease with the content of water glass. When the content is 55%, the mechanical strength decreases significantly. When the H2 O2 content is 1.1%, 1.5%, 1.75%, 2.0%, geopolymer porous materials with density grades of 900 kg/m3 , 800 kg/m3 , 700 kg/m3 , and 600 kg/m3 can be prepared. Fiber can increase the mechanical strength of the material, but too high content will hinder foaming and expansion and increase the density of the material.

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Acknowledgments. This work is financially supported by the National Natural Science Foundation of China (52002245), the Natural Science Foundation of Guangdong Province (2019A1515012172), Key Platform and Major Scientific Research Project of Guangdong Province (2018KQNCX232), Science and Technology Plan Project of Shaoguan City (No. 2019sn057, 210726194533404), Scientific Research Projects of Shaoguan University (SY2020KJ12, SY2020KJ02, 408–99000623), and Innovation and Entre-preneurship Program for College Students (S202210576052).

References 1. Raj, A., Sathyan, D., Mini, K.M.: Physical and functional characteristics of foam concrete: a review. Constr. Build. Mater. 221, 787–799 (2019) 2. Wu, H., Zhao, G., Wang, G., Zhang, W., Li, Y.: A new core-back foam injection molding method with chemical blowing agents. Mater. Des. 144, 331–342 (2018) 3. Zhang, P., Wang, K., Li, Q., Wang, J., Ling, Y.: Fabrication and engineering properties of concretes based on geopolymers/alkali-activated binders - a review. J. Clean. Prod. 258, 120896 (2020) 4. Xu, F., Gu, G., Zhang, W., Wang, H., Huang, X., Zhu, J.: Pore structure analysis and properties evaluations of fly ash-based geopolymer foams by chemical foaming method. Ceram. Int. 44(16), 19989–19997 (2018) 5. Nguyen, T.T., Bui, H.H., Ngo, T.D., Nguyen, G.D., Kreher, M.U., Darve, F.: A micromechanical investigation for the effects of pore size and its distribution on geopolymer foam concrete under uniaxial compression. Eng. Fract. Mech. 209, 228–244 (2019) 6. Dhasindrakrishna, K., Pasupathy, K., Ramakrishnan, S., Sanjayan, J.: Progress, current thinking and challenges in geopolymer foam concrete technology. Cement Concr. Compos. 116, 103886 (2021) 7. Bai, C., Colombo, P.: Processing, properties and applications of highly porous geopolymers: a review. Ceram. Int. 44(14), 16103–16118 (2018) 8. Hajimohammadi, A., Ngo, T., Mendis, P., Nguyen, T., Kashani, A., van Deventer, J.S.J.: Pore characteristics in one-part mix geopolymers foamed by H2 O2 : the impact of mix design. Mater. Des. 130, 381–391 (2017) 9. Hajimohammadi, A., Ngo, T., Mendis, P., Sanjayan, J.: Regulating the chemical foaming reaction to control the porosity of geopolymer foams. Mater. Des. 120, 255–265 (2017) 10. Zhang, X., Zhang, X., Li, X., Tian, D., Ma, M., Wang, T.: Optimized pore structure and high permeability of metakaolin/fly-ash-based geopolymer foams from Al– and H2 O2 –sodium oleate foaming systems. Ceram. Int. 48(13), 18348–18360 (2022) 11. Huang, Y., Gong, L., Shi, L., Cao, W., Pan, Y., Cheng, X.: Experimental investigation on the influencing factors of preparing porous fly ash-based geopolymer for insulation material. Energy Buildings 168, 9–18 (2018) 12. Zhang, X., et al.: Porous geopolymer composites: a review. Compos. A Appl. Sci. Manuf. 150, 106629 (2021)

Bridge and Tunnel Engineering

Use of Non-destructive Tests to Evaluate the Concrete and Steel Bars of Vehicular Bridges Structural Elements Milady Inga Silva , Gianluca Josehf Olano Gálvez(B) and Cristian Daniel Sotomayor Cruz

,

Peruvian University of Applied Sciences, Lima, Perú {U201612044,U201522798,pccicsot}@upc.edu.pe

Abstract. Non-Destructive Testing (NDT) were applied to evaluate the quality of concrete and steel bars in reinforced concrete bridges. Steel bars diameter, compressive strength and ultra-sonic wave speed were evaluated in structural elements such as columns, pillars, concrete walls and slabs, by using the Profometer A630, Original Schmidt Rebound Hammer and Pundit PL-200 equipment in two reinforced concrete bridges. The concrete had a targeted rebound number of 27.1 to 48.6, a predicted compressive strength of 11 MPa to 47 MPa, a concrete thickness of 15 mm to 62 mm, steel bars diameter of 12.5 mm to 38.1 mm, and ultrasonic wave velocity of 2064 m/s to 4266 m/s. Structural elements were evaluated according to the construction standard codes. Keywords: Non-destructive testing · Reinforced concrete quality · Vehicular bridge

1 Introduction Non-Destructive Testing (NDT) has been developed in the last 50 years in North America to evaluate the reinforced concrete elements conditions for building and infrastructures constructions in the 20th Century. Design (37%), construction (51%), faulty materials (4.5%) and faulty maintenance (7.5%) were associated with durability and collapse problems in structures, in the traffic disruption for the specific case of the reinforced concrete bridges [1]. Maintenance is when the NDT equipment are able to detect the anomalies, allowing appropriate decisions to be made for intervention. An example of this is the Nanfang’ao bridge, ultra-sonic wave velocity NDT method was used to identify internal fractures inside reinforced concrete elements, mainly in the central concrete slab section of the bridge, an error in the design of the expansion joints was reported to the authorities [2]. Non-Destructive Testing provided quantitative and qualitive data about reinforced concrete structural elements to understand the structural behaviour of the infrastructure [3] e.g., compressive strength, internal fractures, oxidation in steel bars, etc.

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 107–114, 2023. https://doi.org/10.1007/978-981-19-4293-8_12

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2 Case of Study The structures where NDT equipment were applied are two reinforced concrete vehicular bridges. 2.1 Vehicular Bridge 1 The first reinforced concrete bridge for vehicular and pedestrian circulation, having 50 m of length, 35 m of width, and a total of 7 lanes, was selected to evaluate the quality of concrete in pillars, slabs and steel bars for structural elements. The bridge structural system consists in a concrete deck simply supported on beams and pillars, with a total of 26 pillars and 36 columns connected by the beams over the right and left sections of the bridge. The structure counts with a pair of stairs that connects with the inferior zone of the bridge, allowing access to the structural elements such as columns, pillars and slabs. Figure 1 shows a front view of the structure.

Fig. 1. Front view of the vehicular bridge 1.

2.2 Vehicular Bridge 2 The second reinforced concrete bridge is also use for both vehicular and pedestrian use, with an approximately length of 35 m and 23 m of width and has a total of 6 vehicular lanes. This bridge was selected to evaluate the quality of the reinforced concrete in the pillars, walls and steel bars. The bridge structural system consists in a concrete deck simply supported over reinforced concrete walls and three rows of pillars connected with beams, having a total of 18 pillars in the center, right side and left side of the bridge. Figure 2 shows a front view of the bridge, with the three rows of pillars and the sidewalks at both sides.

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109

Fig. 2. Front view of the vehicular bridge 2 in reinforced concrete with the rows of pillars and the walls at the edges.

3 Non-destructive Testing Method 3.1 Electromagnetic Concrete Coverage Meter The test was applied to determine the thickness of concrete around the steel bars and their respective diameters, both data in millimeters (mm) inside structural elements using the PROFOMETER A610 equipment. This equipment created a magnetic field transmitting the results to the touch screen once it made contact with steel bars [4]. Used over surfaces of structural elements e.g., columns, pillars, slabs and concrete walls locating the steel bars and their cover following the standard code ASTM A615 [5]. Figure 3 represents the use of the equipment over a reinforced concrete wall located in the central edge of the vehicular bridge 2.

Fig. 3. Use of the Profometer equipment in a reinforced concrete wall located in the vehicular bridge 2.

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The results obtained were the concrete thickness (mm), steel bar diameter (mm) and areas where steel bars are not located, which benefits the use of the next equipment. 3.2 Original Schmidt Rebound Hammer Equipment The rebound hammer was used to estimate the surface compressive strength of the concrete [6]. Calculates the strength of the material when the equipment points perpendicularly, showing the result after releasing the force of the hammer over the surface. Ultra-sonic wave propagation was used to calculate the rebound number, value directly related to the flexible and compressive strength [7] and meets the ASTM C805 normative [8]. Every layer of paint and dust needed to be removed, since it can affect the result. With the use of an external application, the rebound hammer was operated on nine different points in the center of a steel bar free area, with a 50 mm distance between each. The average value of these results is calculated for every structural element analyzed. Figure 4 shows the equipment is used in field applied in a reinforced concrete wall located in the edge of the bridge.

Fig. 4. Use of the original schmidt rebound hammer over a reinforced concrete wall.

The results obtained show the rebound number value for every structural element, which, alongside the next equipment, is used to calculate the reinforced concrete compressive strength in MPa. 3.3 Pundit PL-200 Equipment Measures ultra-sound waves propagation time to identify internal consistence of the material. Ultra-sonic waves travel between the external transducers as voltage pulse, knowing the distance between both transducers the velocity of pulse is determined in meters per second (m/s). Ultra-sonic wave velocity and compressive strength are related to concrete’s quality and elastic properties [9]. Both external transducers are perpendicularly applied over surfaces of structural elements at the same time the equipment is being operated to send and receive information about velocity. With the average rebound number data previously introduced on the

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111

equipment, the Pundit PL-200 calculated the compressive strength of the reinforced concrete elements [10]. Figure 5 shows the use of the equipment with the requirement of three operators: two applies the transductors over the surfaces in which paint layers were removed previously, the third uses the touch screen to start the voltage transmission and visualizes the results.

Fig. 5. Use of the Pundit PL-200 in field over a reinforced concrete pillar in the vehicular bridge 2.

4 Results In all the Tables, names of the elements are given with a code to identify their location in the structure. The code puts as first the direction of the bridge, the second is the first letter of the element and finally the row number, e.g., LC-2 is “Left” “Column” in the second row of the bridge; RP-14 is “Right” “Pillar” in the fourteenth row and RS-8 is “Right” “Slab” in the section of the eight rows of the bridge. 4.1 Steel Bars In Tables 1 and 2, results of the Profometer equipment over steel bars in the vehicular bridges 1 and 2 are shown. The data obtained are the concrete thickness and the diameter of the steel bars, both in millimeters. In the first bridge, concrete thickness is found in the range between 20 mm to 56 mm and in the second bridge, the range is between 22.5 mm to 57 mm when the minimum concrete thickness is 50 mm according to standard code AASHTO 5.12.3. [11] increasing the possibility of having a structural defect in the steel bar as a risk of oxidation due to the humid climate in the area. 4.2 Concrete In the Table 3 and the Table 4, the results obtained were rebound hammer, ultra-sonic wave velocity, in meters per second, and compressive strength, in MPa, over the vehicular bridges 1 and 2 respectively.

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Table 1. Results of the Profometer equipment over the steel bars of the reinforced concrete vehicular bridge 1. Name of the structural element

Diameter of the steel bar (mm)

Concrete thickness (mm)

Horizontal

Vertical

LC-2

38.1

38.1

44

LC-8

38.1

38.1

52.5

LC-14

38.1

38.1

56

LP-2

38.1

38.1

20

LP-8

38.1

38.1

26

LP-14

38.1

38.1

24

LS-2

12.5

12.5

15

LS-8

12.5

12.5

45

LS-14

12.5

12.5

32

RC-2

38.1

38.1

60

RC-8

38.1

38.1

62

RC-14

38.1

38.1

61

RP-2

38.1

38.1

24

RP-8

38.1

38.1

32.5

RP-14

38.1

38.1

30

RS-2

12.5

12.5

32

RS-8

12.5

12.5

56

RS-14

12.5

12.5

45

Table 2. Results of the Profometer equipment over the steel bars of the reinforced concrete vehicular bridge 2. Name of the structural element

Diameter of the steel bar (mm)

Concrete thickness (mm)

Horizontal

Vertical

Left wall

38.1

19.1

22.5

PL-1

19.1

19.1

32.5

PL-3

19.1

19.1

41

PL-6

19.1

19.1

42.5

Right wall

38.1

19.1

37.5

CR-1

38.1

19.1

40

PR-1

38.1

19.1

55

PR-3

38.1

19.1

50

PR-6

38.1

19.1

57

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Table 3. Results of the original Schmidt and Pundit pl-200 equipment over the reinforced concrete vehicular bridge 1. Name of the structural element

Average rebound number

Ultra-sonic wave velocity [m/s]

Compressive strength of the concrete [MPa]

CL-2

35

2113

21

CL-8

34.1

2438

26

CL-14

31.6

2064

24

PL-2

45.7

4410

47

PL-8

48.6

3528

34

PL-14

44

4194

42

CR-2

37

2190

23

CR-8

36.3

2072

24

CR-14

38

2357

26

PR-2

41.8

4351

46

PR-8

47.7

4219

44

PR-14

46

4097

42

Table 4. Results of the original Schmidt and Pundit pl-200 equipment over the reinforced concrete vehicular bridge 2. Name of the structural element

Average rebound number

Ultra-sonic wave velocity [m/s]

Compressive strength of the concrete [MPa]

Left wall

37.3

2316

20

PL-1

36.1

3452

36

PL-3

35.4

3369

34

PL-6

36.3

3397

36

Right wall

27.1

1964

11

CR-1

34.3

1989

18

PR-1

34.9

3235

32

PR-3

35.8

3127

32

PR-6

41.9

4266

44

In the results, the average rebound number value for the vehicular bridge 1 is found between 35 to 48.6 and for the vehicular bridge 2 the results are between 27.1 to 41.9. The ultra-sonic wave velocity results were obtained for the vehicular bridge 1 in the range of 2064 m/s to 4097 m/s, and for the vehicular bridge 2 the results are in the range of 2316 m/s to 4266 m/s. Compressive strength of each structural element was in the range between 21 MPa to 47 MPa for vehicular bridge 1, and between 11 MPa to 44 MPa

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in the vehicular bridge 2 when the minimum value is 23.5 MPa approximately according to the normative ASSHTO C5.4.2.1-1 [12].

5 Conclusions Non-Destructive Testing were applied using three specialized equipment in an specific order: Profometer, for the analysis over the steel bars as the diameter and the concrete thickness in millimeters and locating the free steel bars areas on the structural elements; Original Schmidt, calculated the rebound number of the structural elements on the free steel bars area; Pundit PL-200, calculated the ultra-sonic wave velocity in meters per second, and with previous data of the rebound number, estimated the compressive strength of the reinforced concrete on MPa for both of the vehicular bridges. Some of the structural elements analyzed managed to meet with the normative ASSHTO 5.12.3 for steel bars with a minimum of 50 mm for concrete thickness and the ASSHTO C5.4.2.1-1 for reinforced concrete used on bridges with a minimum compressive strength of 23.5 MPa, resulting on some of the bridges.

References 1. Helene, P.D.: Manual of repair, reinforcement and protection of concrete structures. (1997) 2. Focus Taiwan: Maintenance report reveals problems on Yilan bridge 3 years ago. [Online]. Available: https://focustaiwan.tw/society/201910020016 (2019) 3. Tavukçuo˘glu, A.: Non-destructive testing for building diagnostics and monitoring: experience achieved with case studies. MATEC Web Conf. 149, 01015 (2018). https://doi.org/10.1051/ matecconf/201814901015 4. PROCEQ SA: PROFOMETER Operation manual (2017) 5. American Society for Testing and Materials ASTM A615 Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement 6. PROCEQ S.A.: SilverSchmidt y Hammerlink Operation manual (2016) 7. Helal, J., Sofi, M., Mendis, P.: Non- destructive testing of concrete: a review of methods. Electronic J. Struct. Eng. 14, 97–105 (2015) 8. American Society for Testing and Materials ASTM C805: Standard Test Method for Rebound Number of Hardened Concrete 9. Solis Carcaño, R.G., Iván, É., Castillo, W.R.: Concrete strength prediction based on ultrasonic pulse velocity and an aggregate quality index. Engineering 8(2), 41–52 (2004) 10. PROCEQ S.A. Operation manual Pundit ® PL-200 11. Ministry of Transport and Communications: Bridges Manual, pp. 377–78. Lima (2018) 12. Ministry of Transport and Communications: Bridges Manual, pp. 144–45. Lima (2018)

Study on Laying Method of Trenchless Channel for Power Cables in Tianjin Tao Qin(B) , Fang Geng, Suna Bai, Bingran Shao, Ran Lu, and Zhaohui Yang State Grid Tianjin Economic Research Institute, Tianijn 300171, China [email protected]

Abstract. Power cables are crucial to economic development. At present, the laying methods of power cables are basically based on excavation and laying. However, large-scale excavation and laying of polar regions have greatly affected the development of transportation and economy, and also affected the environment and appearance of the city. Therefore, combined with the above unfavorable factors, a research on trenchless channel laying method of power cable in Tianjin area is carried out. Firstly, the suitable scale of cable line laying in pipe pulling and pipe jacking trenchless channel is studied. Secondly, the selection of main construction tools, the suitable soil condition of pipe pulling trenchless method and the crossing facilities are studied. The plane layout scheme of typical construction site at the entrance and exit points is formed, and the plane layout of construction site is completed. To the greatest extent, it solves the inconvenience to social development caused by the excavation of power cables in Tianjin. Keywords: Power cable · Laying method · Pipe-jacking · Slide-trom-bone · Flute

1 Introduction Power cable is an important part of the power system, which also drives the progress of social science and technology and promotes the rapid development of the national economy. For a region, the size of the laying area of power cables also reflects the economic development of the region. However, in terms of the existing laying technology, it is still based on the traditional laying method, which consumes a lot of manpower, material resources and financial resources, but cannot meet the needs of economic development, and the efficiency is extremely low [1–3]. Therefore, it is necessary to study and analyze its laying methods, and then improve the existing laying methods, which plays an important role in the laying of power cables. Combined with the actual situation in Tianjin, the laying of power cables has been studied and some results have been achieved. 1.1 Research on the Suitable Laying Scale of Cable Lines Pulling Tube Sub-catheter. Since 2015, the power industry has vigorously promoted the use of MPP “modified polypropylene” pipe, which is used as the material of pipe © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 115–120, 2023. https://doi.org/10.1007/978-981-19-4293-8_13

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drawing pipe. According to “Technical conditions for conduits for power cables Part 7, Modified polypropylene plastic conduits for trenchless cables” [4] “DL/T 802.7 – 2010”, three ring stiffness levels are divided according to different nominal inner diameters and nominal wall thicknesses. The structural shape is shown in Fig. 1.

d-nominal diameter, t-nominal wall thickness, L-overall length Fig. 1. Shape map of duct structure

Layout Principle of Pulling Pipe Section. 35 kV Cable. Layout principle, cable section 3 × 300 mm2 . Outer diameter 115 mm. The inner diameter of cable conduit is 200 mm. The wall thickness is 18 mm. The inner diameter of communication sub-catheter is 100 mm. Wall thickness 10 mm. The wall thickness of the jacket is 10 mm. 110 kV Cable. Layout principle, cable section 1 × 800 mm2 , 1 × 1000 mm2 . Outer diameter 110 mm, 115 mm. The inner diameter of cable conduit is 200 mm. The wall thickness is 18 mm. The inner diameter of communication sub-catheter is 100 mm. Wall thickness 10 mm. The wall thickness of the jacket is 10 mm. 220 kV Cable. Layout principle, cable section 1 × 800 mm2 , 1 × 1200 mm2 , 1 × 1600 mm2 , 1 × 2000 mm2 and 1 × 2500 mm2 . Diameter 122 mm, 130 mm, 135 mm, 145 mm and 155 mm. The inner diameter of the cable conduit is 200 mm, 225 mm and 250 mm. The wall thickness is 18 mm, 20 mm and 22 mm. The inner diameter of the communication tube is 100 mm, the wall thickness is 10 mm, and the wall thickness of the outer sleeve is 10 mm. Top Tube Conduit. According to the requirements of using habits in Tianjin, PVC-C pipe and MPP pipe are used as pipe materials for pipe jacking. According to “Technical conditions for power cable conduits Part 3, chlorinated polyvinyl chloride and rigid polyvinyl chloride plastic cable conduits” “DL/T 802.3 – 2007”, PVC-C pipes are divided into two types, chlorinated polyvinyl chloride plastic cable pipe and rigid polyvinyl chloride plastic cable pipe [5–7]. The structural shape is shown in Fig. 2. 35 kV Cable. Layout principle, cable section 3 × 300 mm2 . Outer diameter 115 mm. The inner diameter of cable conduit is 175 mm. Wall thickness 11 mm. The inner diameter of communication sub-catheter is 100 mm. The wall thickness is 6 mm. The wall thickness of the jacket is 150 mm. 110 kV Cable. Layout principle, cable section 1 × 800 mm2 , 1 × 1000 mm2 . Outer diameter 110 mm, 115 mm. The inner diameter of cable conduit is 200 mm. The wall thickness is 13 mm. The inner diameter of communication sub-catheter is 100 mm. The wall thickness is 6 mm. The wall thickness of the jacket is 150 mm. 220 kV Cable. Layout principle, cable section 1 × 800 mm2 , 1 × 1200 mm2 , 1 × 1600 mm2 , 1 × 2000 mm2 and 1 × 2500 mm2 . Diameter 122 mm, 130 mm, 135 mm,

Study on Laying Method of Trenchless Channel

d-nominal diameter, -socket diameter, t-wall thickness, L-overall length,

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-the depth of the socket, -effective length

Fig. 2. Shape map of duct structure

145 mm and 155 mm. The inner diameter of cable conduit is 250 mm. The wall thickness is 15 mm. The inner diameter of the communication tube is 100 mm, the wall thickness is 6 mm, and the wall thickness of the outer sleeve is 160 mm.

2 Material and Methods Flow sand layer can be divided into sand and gravel soil in engineering geology. Sand has no plasticity, and it is loose during drying. Its permeability is better than that of clay, and the slightly wet sand has pseudo cohesion. The soil with particle size greater than 2 mm and particle mass greater than 0.5 of total weight is gravel soil. The permeability of this soil is the strongest, loose state when drying, and well-graded dense state of sand does not collapse [8]. In the clay stratum with high viscosity, it is not necessary to worry about hole collapse and excessive loss of drilling fluid by using horizontal directional drilling rig for trenchless pipe laying engineering construction. At the same time, the clay debris cut off during the hole expansion is stirred by the diffuser to form a slurry similar to colloid, which can suspend the cut block debris and take it out of the hole. Therefore, in terms of drilling fluid preparation, viscosity reduction should be focused on and other secondary factors should be ignored, so as to save raw materials and reduce costs. Long-distance crossing, drilling guide hole is the key. When drilling the guide hole, the drill string is very long, and its weight is very large. The friction between the drill pipe and the hole wall increases, and the thrust required for the drill pipe to advance is large [9–11]. The diameter of the drill pipe is generally small, and it is easy to lose stability under pressure, resulting in excessive bending of the drill pipe and damage to the drill pipe.

3 Results and Discussion Design measures, to ensure the safe distance from the entry and exit point to the foot of the levee, to increase the crossing angle, to select the suitable crossing strata, to change the radius of curvature, and to restore and deal with geological survey drilling holes in time. Construction measures, optimizing directional crossing slurry configuration technology, strictly controlling construction technology, and taking monitoring auxiliary measures.

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Design measures are as follows, optimizing the diameter of the last-stage expanding pipe, reducing the diameter of the crossing pipe, increasing the buried depth of the crossing pipe, selecting the location of the soil layer with larger deformation modulus to cross, and selecting the location of the soil layer with larger internal friction angle to cross. Construction measures, optimizing construction tunneling parameters, optimizing grouting scheme, implementing monitoring measures and selecting matching grouting pressure [12]. Taking measures to improve foundation settlement deformation and subgrade uplift deformation, at the same time, strengthening the deformation monitoring of viaduct pier, finding problems and solving them in time [13–15]. 3.1 Pipe Pulling Design Guidance trajectory design, curve guidance trajectory design, three-stage guidance trajectory design, five-stage guidance trajectory design. Calculation of maximum allowable tension of copper core cable, Tmax = kδqs

(1)

In the formula, T max , Maximum allowable tension of copper-core cable, N. k, Correction factor, power cable 1, control cable 0.6. δ, Conductor permitted tensile strength, copper core 68.6 × 106 N/mm2 . q, Number of cable cores. s, Cable conductor cross-sectional area, m2 . 3.2 Pipe Jacking Design According to the route layout of transmission lines, combined with the site environment of the drilling site, the positions of the working well and the receiving well are selected to determine the pipe jacking length. Determine the drilling depth of pipe jacking according to the specific requirements of pipe jacking facilities and pipelines. Plane and profile mapping data need to be obtained. According to the pipe jacking drilling depth to determine the inspection well and well depth. The form, layout and size of the inspection well are determined by the position relationship between the pipe jacking and the lines at both ends. Field investigation of survey major, and the support scheme of working well is designed according to the plane size and depth of the detection well. Review the relationship between the well and supporting structure and the surrounding environment and underground pipelines, and determine the relocation work. Preliminary design of pipe jacking general plan and profile.

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4 Conclusion 4.1 Benefit Analysis Economic Benefit. Although the investment of non-excavation construction method is higher than that of excavation method in the channel body, the investment gap will be reduced if the caused by traffic delay, pipeline migration and support are considered, which has advantages from the perspective of comprehensive economic cost. Environmental Benefits. Do not cause damage to the crossing facilities, during the construction of dust, noise and other adverse factors less, in line with the State Grid Co., Ltd. ‘environmentally friendly’ construction concept. Social Benefits. The trenchless construction method is easy to be approved by the property rights unit of the crossing facilities, which increases the feasibility of the project. It reduces the impact of social risks and has good social benefits.

4.2 Research on the Suitable Laying Scale of Cable Lines In view of the developed economy and the shortage of underground space resources in Tianjin, the non-excavation construction method has the application conditions. It is proposed to be popularized and applied in the 35 kV–220 kV cable line project, involving the following crossing facilities, High-speed railway ‘including electrified railway’. Highways ‘including grade highways’. Navigable rivers ‘including rivers of different grades’. Other facilities not suitable for excavation.

Acknowledgments. This work was supported by State Grid Tianjin Electric Power Company Science and Technology Project. “KJ21–1-31” Research on Capacity Improvement and Typical Design Scheme of Urban Power Cable Channel.

References 1. Ainhirn, F.: A comparison of machine learning algorithms for thermal rating calculations of power cable systems based on measurement data. In: The 2020 IEEE Power and Energy Student Summit, PESS, 5–7 Oct 2020 2. Cao, D., Liu, X., Deng, X.: The suitability analyses of sheath voltage limiters for HV power cable transmission lines. In: The 2nd International Conference on Electrical Materials and Power Equipment, ICEMPE, 7–10 April 2019 3. Chang, C.K., Lai, C.S., Wu, R.N.: Decision tree rules for insulation condition assessment of pre-molded power cable joints with artificial defects. IEEE Trans. Dielectr. Electr. Insul. 26(5), 1636–1644 (2019)

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4. Fu, C.Z., Si, W.R., Quan, L., Yang, J.: Numerical study of heat transfer in trefoil buried cable with fluidized thermal backfill and laying parameter optimization. Math. Probl. Eng. 2019, 1–13 (2019) 5. Han, J., Hao, Y., Deng, J., Zhang, G.: Analysis of current carrying capacity and temperature field of power cables under different laying modes. In: The 7th IEEE International Conference on High Voltage Engineering and Application, ICHVE 6–10 Sep 2020 6. He, G., Zhang, P.: Large-section cable laying method of high-drop and narrow environments. In: The 2018 3rd International Conference on Insulating Materials, Material Application and Electrical Engineering, IMMAEE 15–16 Sep 2018 7. He, G., Zhang, Z.: Research and engineering verification of high-voltage cable laying method under complicated working conditions. In: The 2018 3rd International Conference on Insulating Materials, Material Application and Electrical Engineering, IMMAEE 15–16 Sep 2018 8. Jiang, D., Bing, W., Yang, X., Van Gelder, P.H.A.J.M.: A fuzzy evidential reasoning based approach for submarine power cable routing selection for offshore wind farms. Ocean Eng. 193, 106616 (2019) 9. Ke, W., Gang, W., Haiyan, Z., Gang, X., Gang, Z., Chen, B.: Study of mechanical stress distribution in high-voltage cable laying on high-difference terrain. In: The 3rd IEEE International Conference of Safe Production and Informatization, IICSPI 28–30 Nov 2020 10. Pang, D., Wu, H., Dai, B., Zhao, C.: Research on optimum laying method for increasing underground power cable ampacity. In: the 2019 International Conference on Advanced Material Research and Processing Technology, AMRPT 19–21 July 2019 11. Ryzhiy, N.V., Karagodin, V.V., Smirnov, S.V.: Application of a mathematical model of thermal processes of a three-core power cable for calculating active power losses in its current-carrying cores. In: The 2020 International Conference on Industrial Engineering, Applications and Manufacturing, ICIEAM 18–22 May 2020 12. Wu, D., Kong, X., Liu, J., Ge, A.: Research on large-scale cable intelligent laying technology based on graph theory. In: The 2020 Asia Conference on Geological Research and Environmental Technology, GRET 10–11 Oct 2020 13. Xiong, L., Chen, Y., Jiao, Y., Wang, J., Xiao, H.: Study on the effect of cable group laying mode on temperature field distribution and cable ampacity. Energies 12(17), 3397 (2019) 14. Xing, X., Chen, X., Meng, F., Paramane, A.: Grounding system analysis of 220 kV power cable lines installed underneath a bridge. IEEE Tran. Power Delivery 37(2), 1130–1139 (2022) 15. Zhang, Z., et al.: Electrothermal finite element modeling and simulation of air laying single core high voltage cable. In: The 3rd IEEE Information Technology, Networking, Electronic and Automation Control Conference, ITNEC 15–17 March 2019

Analysis and Design of Pipe Gallery Bridge with Large Cross-Section and High Loading Lijun Chen(B) , Fuwei Sun, and Lu Liu Wuhan Municipal Engineering Design and Research Institute Co., Ltd., Wuhan 430023, China [email protected]

Abstract. The pipe gallery bridge is a unique project of a comprehensive pipe gallery at the overhead crossing. It is essential to ensure its quality and security due to its complex structure and stress state. Based on a pipe gallery bridge with a large cross-section and high loading, the beam and solid element models are established separately to research the stress of the bridge when it is under construction, completed and service stage. The results show that the stresses of the pipe gallery bridge are in good agreement with the current codes, and the results have been used for the design of the bridge. Keywords: Pipe gallery bridge · Large cross-section · High loading · Finite element method · Spatial analysis

1 Project Overview The Wuhan-Jiujiang Railway Utility Pipe Gallery Project runs through Luojiaxiang Open Channel near the Erqi Yangtze River Bridge, only about 300 m away from Yangtze River. Bordering the river, the project can only be constructed in a non-flood season. If an underground pipe gallery is built under-crossing Luojiaxiang Open Channel, the construction will inevitably interrupt the normal operation of the channel. Furthermore, large safety risks will occur if the project cannot be completed within a non-flood season. Besides, a green walkway is planned at the crossing over the open channel, equipped with a footbridge. The “gallery + bridge” scheme is proposed upon overall considerations, with the underground gallery replaced with an upper crossing one [1, 2]. Once completed, residents can walk on the footbridge, with vegetation and flowers on both sides of the gallery. This will become a highlight of the Wuhan-Jiujiang Gallery Green Walkway. With an overall length of 31 m, an overall width of 20.1 m, and a beam depth of 4.6 m, the pipe gallery bridge is a cast-in-place prestressed concrete box girder structure divided into three chambers: pipe chamber, integrated chamber, and HV power chamber. With a dead load of about 2,900 tons and a total weight of up to 4,700 tons after the pipelines are installed, the pipe gallery bridge boasts the largest cross-section and the highest single-unit loading in China. Its cross-sectional layout is as shown below (Fig. 1).

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 121–126, 2023. https://doi.org/10.1007/978-981-19-4293-8_14

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Fig. 1. Cross-section arrangement (unit: mm)

2 Spatial Beam Finite Element Model Analysis of Pipe Gallery Bridge As the pipe gallery bridge features a large cross-section and a high loading, to ensure structural safety, a spatial finite element model of the pipe gallery bridge was established firstly with structural analysis software for qualitative analysis of the overall safety. In the model, main beams of C55 concrete were simulated by beam elements, and loads were calculated regarding the dead load, pipelines, decks, and some other secondary dead loads, as well as other loads such as temperature and pedestrians. The finite element model was calculated as shown in the following Fig. 2.

Fig. 2. Spatial finite element model of the bridge

With the finite element model, the carrying capacities of the pipe gallery bridge were calculated under the ultimate state and serviceability limit state at construction and operation stages. From the calculated results of the overall space beam element model, the overall strength and stresses (at different stages) of the pipe gallery bridge were within the specified limits, indicating the whole structure is safe [3]. The following table shows the calculated results (Table 1):

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Table 1. Stress results of the pipe gallery bridge Name

Item

Symbol

Unit

Limit value

Calculated value

 0.7fck

MPa

20.72

7.71

 0.7fck

MPa

1.76

0.03

Ultimate 0.5 f ck compressive stress

MPa

17.75

10.56

Main ultimate 0.6 f ck compressive stress

MPa

21.30

11.37

Instant state Ultimate compressive stress Ultimate tensile stress Permanent state

Compressive stress limit

Tensile stress limit

Carrying capability

Ultimate tensile stress under short-term effect combination

σst − σpc ≤ 0.7 ftk

MPa

1.92

−3.45

Main ultimate tensile stress under short-term effect combination

0.5 f tk

MPa

1.37

0.45

Ultimate tensile stress under long-term effect combination

σlt − σpc

MPa

0

−3.41

Bending capacity in the normal section

γ0 S ≤ R

KN.m

294350

203760

Shear capacity in oblique section

γ0 S ≤ R

KN

307650

249380

3 Spatial Solid Finite Element Model Analysis of Pipe Gallery Bridge To study the stress condition of concrete box girders with large cross-sections under the action of high loading, and ensure the local structural safety of the pipe gallery bridge, a solid finite element model of the pipe gallery bridge was established by large space software. Concrete and prestressed steel tendons were stimulated by solid units and steel rebars. The dead load, prestressed load, secondary loads, alive loads, flower beds, pipelines, and some other loads were considered in the model [4, 5]. The finite element model and prestressed rebars are as shown in the following Fig. 3 and Fig. 4:

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Fig. 3. FEM model of the pipe gallery bridge

Fig. 4. Layout of three-dimension prestressing

Through finite element analysis, the distribution of longitudinal & transverse stresses and main tensile & compressive stresses of the pipe gallery bridge box could be calculated under long-term and short-term effect combinations, respectively. As seen from the stress distribution diagram of the solid model, as the prestressed pipes and anchor bearing plates have not been stimulated, some stress concentration areas scattered near prestressed anchor bearing plates and support bases, but they did not bring any substantial impact on the stress distribution in the proposed area, so they could be ignored. Limited by space, considering the similar stress distribution under both conditions, this paper only lists the stress contour maps under short-term effect combination, as shown in Figs. 5 and 6.

Transverse stress SYY

Longitudinal stress SYY

Main tensile stress P1

Main compressive stress P3

Fig. 5. Contour map of stress near the end of the beam (MPa)

According to the above solid model analysis results, the overall structure was under the compressed state near the end of the beam, with local tensile stresses scattered, where Sxx = −1.04–−7.09 MPa and Syy = 0.07–−3.4 MPa. The maximum tensile stress in the normal section was 1.04 MPa, meeting the requirements of the codes for Category A prestressed components regarding the crack-resistant normal tensile stress in the normal section σst − σpc ≤ 0.7 ftk (i.e., 1.92 MPa). The maximum main tensile stress was 1.19 MPa, satisfying the requirements of the codes regarding the crack-resistance main tensile stress in oblique section σtp ≤ 0.5 ftk (i.e., 1.37 MPa). Upon the above solid model analysis, the overall structure was under the compressed state at the middle span of the beam, with local tensile stresses scattered, where Sxx =

Analysis and Design of Pipe Gallery Bridge

Transverse stress SYY

Longitudinal stress SYY

Main tensile stress P1

Main compressive stress P3

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Fig. 6. Contour map of stress near the mid-span of the beam (MPa)

−0.64– −7.72 MPa; Syy = 0.59– −5.7 MPa. The maximum tensile stress in the normal section was 1.15 MPa, meeting the requirements of the codes for Category A prestressed components regarding the crack-resistant normal tensile stress in the normal section σst − σpc ≤ 0.7 ftk (i.e., 1.92 MPa). The maximum main tensile stress was 1.28 MPa, satisfying the requirements of the codes regarding the crack-resistance main tensile stress in oblique section σtp ≤ 0.5 ftk (i.e., 1.37 MPa).

4 Summary Considering the unique characteristics such as large cross-section and high loading of the pipe gallery bridge in the project, an overall beam element model and a solid finite element model were established, respectively. Upon the finite element analysis, the following conclusions were made: (1) The calculated results of the overall model revealed that the concrete strength and stresses of the main beams of the pipe gallery bridge were consistent with the codes, so the overall structure was safe. (2) Upon the solid model analysis, the stress distribution of the pipe gallery bridge was compliant with the codes. Moreover, from the stress distribution diagrams (Figs. 5 and 6), local tensile stresses occurred at the junctions between webs with roofs and bottom slabs. As the hydrochemical thermal effect during concrete placing may lead to large tensile stresses, local enhancements were recommended at corners. (3) When the utility pipe gallery crossed a river channel, if the upper crossing was proposed for the pipe gallery bridge, generally, the structural dimension of the pipe gallery bridge and the loads to be carried by the pipe gallery bridge had to exceed those of conventional concrete beam bridges. Special node design and studies must be conducted. The related analysis ideology and experience described in this paper can provide references for the practical design of concrete pipe gallery bridges. The research outcomes of the paper have been applied in guiding the design and

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construction of the pipe gallery bridge. At present, the project has been completed and put into operation, showing good conditions.

References 1. Zhang, Y., Yan, L.Z., Chen, B., Wang, Y.: Design and construction of formwork for cast-inplace dedicated utility tunnel bridge on upper crossing expressway. Constr. Technol. 21, 51–54 (2017) 2. Zhu, L.: Design and application of utility tunnel crossing river by bridge. Urban Roads Bridges Flood Control 07, 121–124 (2021) 3. Ministry of Transport of the People’s Republic of China: Specifications for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts. China Communications Press, Beijing (2018) 4. Chen, L.J., Hu, N., Li, Y., et al.: Local stress analysis of segment No. 0 of a continued right frame bridge. Highw. Eng. 05, 228–230 (2015) 5. Zhou, S.J., Wang, X., Wang, M.W., et al.: Fine analysis of concrete main girder of pipe gallery bridge. Highway 03, 107–111 (2022)

Research on the Application of Computer Vision in Bridge Health Monitoring Yimin Cao1 , Mingzheng Huang1 , Yixin Sun1 , and Cheng Li2(B) 1 Chang’an-Dublin International College of Transportation, Chang’an University,

Shaanxi 710021, China 2 School of Highway, Chang’an University, Shaanxi 710021, China

[email protected]

Abstract. This article starts from the theory of computer vision in bridge health monitoring summarizes how it has been used in bridges by applying data collection, data analysis, and data management of bridge health monitoring systems. All these technologies can be used adeptly in their aspects. In the past, China used manual detection of bridge cracks, relying on large mechanical devices such as bridge trucks to send people under the bridge to monitor the health of the bridge. This method was time-consuming and labor-intensive, and the safety of manual labor could not be guaranteed. It is easy to cause diagnostic errors [1]. This research introduces the general situation and summarizes the main problems in this field of computer vision. Keywords: Bridge health monitoring · Computer vision · Cracks

1 Introduction 1.1 The Purpose and Significance of the Paper The purpose of this paper is to summarize the current research status and the problems still faced in the field of applied research of computer vision in the field of bridge construction and health monitoring. The significance of the research in this paper is to provide a review report to scholars who are about to enter the field of computer vision in the field of bridge construction and health monitoring but do not have much knowledge in this field so that they can grasp the general situation in this field.

2 The Status of Computer Vision in Bridges 2.1 Current Status of Research As the throat of highway traffic, bridges need a long-term healthy operation, which cannot be separated from long-term monitoring and maintenance. In the past, traditional bridge monitoring was mostly manual or semi-automatic monitoring; workers used some hand tools or professional instruments to measure surface data and observe the external © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 127–136, 2023. https://doi.org/10.1007/978-981-19-4293-8_15

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shape. It is impossible to have a comprehensive grasp of the bridge’s internal structure, and it is only for regular monitoring, and the bridge cannot be monitored stably for a long time. With the development of civil technology in civil engineering, many bridges have been built, and traditional monitoring methods with low efficiency and low reliability can no longer meet the requirements of infrastructure monitoring. The rise of computer technology has proposed a new development path for the health monitoring of bridges. This part will analyze the current research status of computer vision in the direction of bridges from three aspects: data collection, data processing, and data management. Data Collection. Data collection is the prerequisite for bridge health monitoring. Due to various limiting factors, with the rapid development of modern transportation technology, manual traditional detection methods are gradually being replaced by new detection tools such as UAVs and sensors. These new detection tools have high detection efficiency, strong scientificity, high reliability, and comprehensive functions. Data collection mainly monitors the load and effect-related problems of the bridge structure and then outputs in the form of other physical quantities, such as electricity, light, sound, heat, etc. After these physical quantities are output, they are more conducive to information collection and processing. To become a convenient form of observation and analysis through computer processing. In bridge health monitoring, data collection mainly refers to real-time data collection on various bridge parts using hardware facilities such as sensors and UAVs. At this stage, UAVs have been widely used in various fields such as military, agriculture, electric power, and transportation. In the field of a bridge inspection, in the face of special structures such as bridges with large hips and high piers and suspension bridges, such as the underside of bridges, cable-stayed suspension cables, tower tops, etc., manual inspection operations are difficult, and UAVs can respond well to traditional inspections. Limitations, especially quadrotor UAVs, are highly flexible and can fully automate regular inspections of bridges, discover problems, and repair them in time. The regular inspection content of the bridge is shown in Table 1. The sensor system plays a significant role in data collection. Regarding sensor data collection, Jang Shinae (2010) [2] invented wireless smart sensor networks (WSSNs); this new distributed sensor network system achieves low consumption, easy installation, and can provide a large amount of useful data. It has also been applied to the Jindo Bridge and a cable-stayed bridge in South Korea. These examples prove that this technology can monitor large engineering buildings well. Table 1. Regular inspections of bridges [3] Parts of a bridge to check

Details to check

Guardrail (railing)

The joints fall off, the steel components are rusted, peeled off, the curb is broken, etc.

Expansion joint

Anchorage damage, structural damage, seam edge concrete cracking, damage and Waterproof material aging, shedding, water leakage, jumping, etc. (continued)

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Table 1. (continued) Parts of a bridge to check

Details to check

Bridge deck paving

Vertical and horizontal cracks, potholes, ruts, looseness, subsidence, bridgehead jumping, etc.

Sidewalk

Damage, peeling, cracks, defects, looseness, honeycomb, pitted surface, etc.

Bridgehead and embankment junction

Bridgehead jumping, sinking, cracking, etc.

Drainage facilities

There are inadequate design considerations, clogged drain holes, missing drain hole covers, damaged drain pipes, etc.

Superstructure

Forced structures such as beams, slabs, abnormals in arch ribs like deformation, vertical vibration, lateral swing, etc.

Cone slope, slope protection

Cone collapse, slip cracks, partial shedding, pavement defects, etc.

Pier and platform foundation

Erosion, weathering, displacement, concrete surface damage, cracks, exposed steel bars, garbage blockage, etc.

Support

Cleanliness, completeness, fracture condition, dislocation, aging, void, etc.

Structural health monitoring is a vital part of bridge inspection. Sun Zongjun et al. (2019) elaborated on the application of ground-penetrating radar technology (GPR) in the nondestructive inspection of bridge structures. Ground-penetrating radar can detect the internal structure of bridge piers and bridge spans, including the position and arrangement of steel bars and location of the cavity created during the concrete pouring process, the internal cracks and imperfect areas of the concrete, and the thickness of the protective layer of the concrete, etc. The technology was developed early and is relatively complete, with high accuracy and fast speed, and is not restricted by the testing site [4]. Zhou Ying et al. (2018) proposed a non-contact measurement method based on machine vision that does not require artificial targets. It uses consumer-grade cameras as the acquisition device and SIFT points as the recognition structure system for tracking objects. Compared with the previous traditional methods, It has higher measurement accuracy and can accurately identify the structure’s dynamic characteristics, such as natural frequency and mode shape [5]. In addition to this technology, in terms of internal and structural inspection, Medhi et al. (2019) developed a structural health monitoring system based on Real-Time Video Surveillance [6]. In monitoring the external deformation of the bridge for a long time, the bridge displacement parameter is the focus of monitoring. The conventional distributed displacement measurement technology of various civil structures currently used is limited by insufficient accuracy, excessive localization of measurement points, measurement drift, and stability problems. For bridge deformation monitoring, Dong Chuanzhi (2016) proposed hot spot monitoring technology and magnetic flux

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sensor device [7]. Through the application of GPS and GIS, this technology can measure various parameters such as structural strain, stress, and dynamic response and has high sensitivity and strong electromagnetic interference resistance. Qian Cheng (2016) explained the construction process of the OpenWrt system in the router and the migration process of MJPG-streamer using the camera as the monitoring device, providing a software platform for the realization of remote wireless acquisition; finally, according to the working principle of MJPG-streamer, it is realized through programming The control of image acquisition [3]. In terms of the external bending deformation of the bridge, Cai Bo (2016) proposed a relatively fixed multi-viewpoint sequence image detection method [8], which uses a relatively fixed point of view and collects the bridge image sequence through a telecentric lens. This method is relative to the three-dimensional acquisition Flexibility is reflected in the detection of bridges across rivers (sea). Shen Jian (2017) used the analysis to derive the inclination deflection conversion algorithm [9], the optical wavelength strain conversion algorithm, and the curve fitting algorithm when studying the Tianjin Haihe Bridge to collect relevant data. In terms of research outside of China, Santos et al. (2012) considered that the measurement of vertical and lateral displacement is limited by the shape of the basic structure, and proposed a solution based on a non-contact vision measurement system [10], and introduced a method to calibrate the vision system. The method can significantly improve measurement accuracy with limited information, even if it is severely affected by noise. Aliansyah et al. (2018) proposed using LED marking optical technology [11] as a dynamic distributed displacement measurement method, providing visual cues and easy-to-identify marking positions. This technology combines a high-speed camera system and a telephoto lens to capture the lateral and vertical displacement of the bridge and LED markings to cope with incident light at long distances and small camera apertures. Similar to this, Artese et al. (2018) used a laser pointer to analyze a single frame of a high-definition video projected on a flat target with a laser beam imprint to measure the inclination of the elastic line [12]. Yanwen et al. (2020) proposed a 3D laser scanning technology based on a three-dimensional laser scanner [13] to collect data for the deformation of the maglev train bridge, thus effectively ensuring the safety of the maglev train. The internal deformation of the bridge is mainly reflected in the deformation caused by bridge cracks and local extrusion. In terms of bridge crack recognition, Wang Lin (2015) introduced small quadrotor UAVs equipped with a binocular shooting system to collect images [1], focusing on the core of the collection system, which is a powerful arm platform: Radxa rock card computer. It can realize the drive of the camera, the collection, and the preservation of the image. The application of CCD technology in the collection of crack images is introduced, the relationship between collection speed and image resolution is compared, and a suitable light source and illumination system are selected for the system [14]. Like this technology, Ye Yan (2017) analyzed the causes of bridge defects and proposed a set of intelligent software systems to measure and identify cracks at the bottom of the bridge. The system compares the advantages and disadvantages of CCD cameras and CMOS cameras to capture images and confirms CMOS industrial camera tripod head and industrial lenses suitable for crack monitoring. In addition, the lighting system for the environment at the bottom of the bridge and the corresponding image capture card was also selected to complete the overall hardware image capture system [15].

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Large bridges’ cable vibration and wire rope safety face low wire rope safety and low monitoring efficiency. Chen Hui (2012) combined X-ray inspection technology, digital imaging system, and electromagnetic ultrasonic nondestructive testing technology to propose an effective method of testing steel wire rope safety [16]. Aiming at monitoring stay cables, Ji Yunfeng (2013) used plastic pipes to simulate stay cable vibration test and stay cable vibration test, which proved that the feasibility and accuracy of targetless computer vision technology are better than traditional stay cable vibration test methods. (Such as acceleration sensor) [17]. Wang Xiang (2014) tested cable amplitude and frequency spectrum and verified the machine vision system [18]. He Pei (2012) proposed computer vision three-dimensional reconstruction technology to reconstruct the analysis of cable defects [19]. The parameters of the known shape are directly placed in the 3D visualization software to generate the corresponding 3D image of the cable. Li Xinke (2014) uses a CCD image sensor array to obtain surface images around the surface of the cable in the distributed machine-based visual inspection technology for collecting cable surface defect data [20]. In terms of bridge vibration monitoring, Liu Jianqiao (2011) designed a track beam sway monitoring system based on machine vision, which can efficiently and accurately detect the sway amplitude value of the track beam. It has been successfully applied to the straddle monorail traffic track beam in the shaking detection item in Chongqing [21]. To overcome the limitations of the vibration measurement method based on contact sensors, Kuddus et al. (2019) proposed a method based on computer vision and digital image processing to measure the dynamic displacement of the structure and used traditional accelerometers and laser displacement sensors (LDS). The measured results are compared, verifying the method’s accuracy for vibration measurement [22]. In terms of bridge load, collecting traffic load information, especially heavy trucks, is essential for bridge statistical analysis, safety assessment, and maintenance strategies. Although traditional load sensors are accurate and reliable, they are usually too expensive to monitor continuously. Corsi et al. (2020) evaluated the capabilities of geophone sensors to provide continuous, accurate, and reliable data on the dynamic load of the bridge. Moreover, compared with the interferometric radar experiment, it verifies the feasibility of geophone sensors. The new sensor is low-cost, easy to install, and can continuously monitor operating status by transmitting data to a remote server [23]. Jian et al. (2019) proposed a traffic sensing method. This method is based on deep learning computer vision technology to obtain the accurate position of the vehicle on the bridge. The average weighing error for the BWIM system research is within 5%. It can identify the vehicle weight, speed, types, axle numbers, and temporal and spatial distribution, especially for bridges equipped with structural health monitoring systems and monitoring cameras [24]. Khuc et al. (2018) proposed a new structure identification (St-Id) framework and damage indicator, UIS [25]. UIS damage indicator can use computer vision to integrate vehicle load (input) modeling framework and use image-based structure recognition to diagnose load parameters of beam or slab structures (for example, single-span or multi-span bridges and their decks). Data Processing. Data processing is the most distinctive part of the new monitoring method based on computer vision that is different from the traditional monitoring method. A basic idea of data processing is to visually transform the collected data,

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program and design algorithms on a computer, apply the algorithms to image processing or data analysis, and finally use modeling software (such as AutoCAD) to form a relatively fixed Model. However, the treatment methods used for different bridge parts are different. In terms of bridge cracks, the collected crack images need to measure the size of the cracks through a suitable crack recognition algorithm. The crack image must be preprocessed first, including gray-scale and denoising processing. The appropriate averaging, weighting and maximization algorithms can enhance the picture’s contrast in gray-scale processing. Both median filter and mean filter can effectively reduce image noise. Li Haotian (2019) [26] proposed a crack detection algorithm based on a Bilateral-Frangi filter, which can better suppress noise interference, and the false detection rate is much lower than the conventional Frangi filter algorithm. Next is image segmentation processing. Ye Yan (2017) [15] compared the processing results of three binarization segmentation algorithms: Otsu Otsu method, optimal threshold iteration method, and local threshold adaptive method through experiments. The results show that the local threshold is The adaptive method that can better separate the complete crack and the background color. Cai Bo [8] proposed an algorithm for initial contour selection based on the uniformity of the region and the degree of boundary coincidence and proposed a new segmentation process and algorithm modification, which has good stability for image segmentation. There is also morphological processing [15], first expanding to automatically stitch the edge contour and then etching to compress the contour. To enhance the sensitivity of the edge contour, a suitable edge detection operator can be selected for edge extraction. Common algorithms include the Sobel operator, canny operator, and Laplace operator. In the face of curves with more complex shapes, Zhao Yafeng [27] improved the Hough algorithm to improve the efficiency and accuracy of extracting crack features. Li Xinke [20] based on non-negative support domain recursive inverse filtering (NAS-RIF) and total adaptive variation (Total Variation, T.V.) regularized blind image restoration method can solve the problem of image blur. In terms of bridge deformation, the accuracy of sequence image stitching dramatically influences the accuracy of deformation detection. Cai Bo [8] experimented on image stitching of different distributions; it is proved that the highly adaptable feature point extraction and secondary stitching algorithm can effectively improve the accuracy and stability of stitching. On this basis, the resulting bridge span sequence is subjected to bending detection. Yanwen et al. [13] applied the B.P. neural network to the highprecision 3D modeling of the point data obtained by the 3D laser scanner along the Shanghai maglev train. Based on the 3D laser scanner technology, the deformation of the maglev train bridge can be monitored, which has been further verified by the Shanghai maglev train bridge deformation monitoring experiment. In terms of bridge vibration and cable defects, Jianqiao Liu [21] uses appropriate edge detection algorithms and threshold segmentation to extract and analyze the swaying image features, and automatically self-made templates to match the images with the produced templates to quickly calculate The amplitude of the shaking of the track beam. (2018) [11] The FFT (Fast Fourier Transform) peak-picking method adopted by Aliansyah et al. (2018) played a significant role in the natural vibration frequency of the structure. He Pei [19] focused on the study of feature point extraction and matching,

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combining three-dimensional modeling and three-dimensional reconstruction to show cable defects in three-dimensional form. The novelty of this technology is that according to the motion trajectory of the snakehead joint of the snake-like robot in this experiment, the posture of the camera at any time can be obtained so that the combined algorithm can be used in the cable feature detection part to detect more feature points and optimize Three-dimensional information. Data Communication and Data Management. Data communication connects the data terminal and the computer through the transmission channel to realize the transmission and sharing of data. The sensor converts the monitored data into a physical form and then transmits the data through a transmission cable or optical cable, a digitalto-analog conversion card, etc., and also uses some software, such as VC++, CVI, or LabVIEW, etc. CVI and LabVIEW are computer programming languages, the former mainly focuses on text-based programming languages, and the latter is a programming language used for image processing. Wu Qisheng (2007) found shortcomings in traditional bridge monitoring research data communication and proposed a large-scale bridge wireless monitoring system based on GRPS (General packet radio service) network [28]. From the load environment, geometric monitoring, structural static, and dynamic monitoring. The monitoring software has been updated in 7 aspects, including real-time alarm, health status assessment, system management, and database server, which shows the characteristics of good real-time performance and high reliability. GRPS network can help engineers quickly find problems in the bridge by superior data processing and transmission. Data management also plays a significant role in the health monitoring of bridges. Putting the analyzed data into the database in the computer helps to deal with bridge defects and provides experience for subsequent data analysis. Generally speaking, data management software [14]consists of two parts: an image database system and an image recognition and evaluation system. Support Vector Machine (SVM) technology [27] is often used in the crack database to train and classify the crack samples, and through the adjustment and optimization of the training model, the cracks can be identified more accurately, and the stability is good. Neural networks can improve the efficiency of data management. Bao et al. (2019) [29] composed a training data set of randomly selected and manually labeled image vectors into deep neural networks or deep neural network clusters. These neural networks are trained by stacked autoencoders and layer-by-layer greedy training techniques. The trained deep neural network can detect potential anomalies in many unchecked structural health monitoring data. The structural damage detection method based on Faster R-CNN [30] can provide real-time simultaneous detection and location of multiple types of damage, effectively making up for the traditional convolutional neural network damage detection method that cannot provide Disadvantages of injury location. The original architecture of “Faster R-CNN” has been modified, trained, verified, and tested to show strong stability. In actual engineering, neural network technology develops rapidly. The artificial neural network system performs well in the application of Hangzhou Bay Bridge and 104 National Road, reflecting the extensiveness and stability of the neural network system [31].

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2.2 The Problems Faced and the Future Development Although previous generations of bridge engineers have spent much effort on the health monitoring of bridges, there are still some problems with the current bridges. Jian Ma (2014) [32] believes that many current studies are mainly focused on controlling the total life cycle of the project. Cost. However, this is not the only criterion. The aesthetics, structural performance, and environmental impact must also be considered. The second problem is that the current bridge design is developing to make the earth’s biodiversity. Now it still needs the simultaneous development of other disciplines to achieve the reliability of bridge design. The third is that the external factors of bridge health monitoring have been roughly studied, such as ship collisions, harsh environments, natural disasters, and other influencing factors. However, the research on the characteristics of the bridge itself is still relatively scarce. The bridge is in a complicated environment every day, which leads to measurement difficulty. For example, the change in the structure’s natural frequency caused by half of the damage is easily submerged in environmental factors. Support failure, loss of prestressing, etc., may harm the vibration mode. Yu Shuying (2015) [33] proposed that SHM (Structure health monitoring technology) can change the traditional method’s loopholes because the original method has inaccurate measurement and consumes a lot of workforces and material resources sensor system also has reliable. Durability has the corresponding problem of cost. Most of the health detection problems are solved by the remaining energy of the node. Although there are some solutions, such as duty-cycling, data compression, etc., there are some limitations, so energy is needed. Technologies such as collection and wireless charging to supplement energy are all problems that need to be solved. In addition, a large amount of data every day will cause significant problems for storage, so a suitable method is needed to analyze and process in time and to clean up redundant data. Inaccurate measurement data will cause great misunderstandings in identifying bridge structure damage. Therefore, it is necessary to adopt high-precision measuring instruments or new technologies to improve accuracy. In the existing acquisition equipment, in the future, the existing imaging system will be expanded, the source and expression of visual signals will be expanded, combined with advanced theories and technologies such as visual learning, pattern recognition, and mathematical statistics, to complement and improve existing technologies [7]. The current algorithm still has many defects. The disadvantage of the Sobel operator is that there will be an edge blur effect [1], resulting in low edge extraction efficiency, so more advanced algorithms are needed to process images more conveniently and quickly. Zhao Yafeng (2016) [27] analyzed the crack identification algorithm and mentioned a feasible algorithm-principal component analysis (PCA).

3 Conclusion 3.1 Conclusion This paper is based on academic research reports on bridges. It provides a detailed understanding of the current application of computer vision technology in this field and the problems it faces and summarizes the summed-up content through a review.

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However, some aspects still have deficiencies, and further in-depth understanding is needed. Regarding the future development direction of bridges, Wu Xiaoguang (2003) [34] mentioned the improvement of the intelligent control system, the optimization of sensors and the better arrangement of sensors, the use of network sharing, and the use of big data to realize real-time monitoring of information. Nowadays, we still use very traditional methods to monitor the cracks and destruction of bridges. Those methods are time-consuming, waste workforce, and waste money. In future research, we need to combine other disciplines such as computers or artificial intelligence to develop more convenient, fast, and cost-saving methods for bridge health monitoring.

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17. Ji, Y.: Research on the application of targetless computer vision technology in the vibration test of stay cables. Vibration and Shock 32(20), 184–188+202 (2013) 18. Xiang, W., Peng, W., Hui, C.: Research on online monitoring technology of bridge deformation based on machine vision. Highw. Eng. 39(01), 198–201 (2014) 19. He, P.: Research on 3D Reconstruction Method Based on Image Sequence and Its Application in Bridge Cable Inspection. South China University of Technology (2012) 20. Li, X.: Research on the Key Technology of Image Detection of Bridge Cable Surface Defects. Chongqing University (2014) 21. Liu, J.: Straddle Monorail Track Beam Sloshing Detection System Based on Machine Vision. Chongqing University (2011) 22. Kuddus, M.A., Li, J., Hao, H., Li, C., Bi, K.: Target-free vision-based technique for vibration measurements of structures subjected to out-of-plane movements. Eng. Struct. 190, 210–222 (2019) 23. Corsi, G., Frediani, F., Miccinesi, L., Micheloni, M., Pieraccini, M.: Bridge Monitoring Using Geophones: Test and Comparison with Interferometric Radar. In: Wahab, M.A. (ed.) Proceedings of the 13th International Conference on Damage Assessment of Structures. LNME, pp. 25–34. Springer, Singapore (2020). https://doi.org/10.1007/978-981-13-8331-1_2 24. Jian, X., Xia, Y., Lozano-Galant, J.A., Sun, L.: Traffic sensing methodology combining influence line theory and computer vision techniques for girder bridges. J. Sens. 2019, 1–15 (2019) 25. Khuc, T., Catbas, F.N.: Computer vision-based displacement and vibration monitoring without using physical target on structures. Struct. Infrastruct. Eng. 13(4), 505–516 (2017) 26. Haotian, L., et al.: Bridge crack detection algorithm based on Bilateral-Frangi filter. Prog. Laser Optoelectron. 56(18), 170–176 (2019) 27. Zhao, Y.: Research on Machine Vision Recognition Algorithm for Structural Cracks. Hunan University of Science and Technology (2016) 28. Qisheng, W., Dan, W., Qiucai, W.: Large-scale bridge health wireless monitoring system. J. Chang’an Univ. (Nat. Sc. Ed.) 05, 70–74 (2007) 29. Bao, Y.Q., et al.: Computer vision and deep learning-based data anomaly detection method for structural health monitoring. Struct. Health Monit. Int. J. 18(2), 401–421 (2019) 30. Suh, G., Cha, Y.J.: Deep faster R-CNN-based automated detection and localization of multiple types of damage. Sens. Smart Struct. Technol. Civ. Mech. Aerosp. Syst. 2018, 10598 (2018) 31. Xu, A.: Research on durability and health monitoring of 70-meter box girder structure of Hangzhou Bay Cross-sea Bridge. Zhejiang University (2008) 32. Ma, J.: Seismic Performance of Continuous Rigid Frame Bridge and Damage Analysis of its Main Pier. Changsha University of Science and Technology (2014) 33. Yu, S.-Y., Wu, X.-B., Chen, G.-H., Dai, H.-P., Hong, W.-X.: Wireless sensor network in bridge health (2016) 34. Wu, X., Xu, Z.: Health monitoring trends and development trends of large bridges. J. Chang’an Univ. (Nat. Sci. Ed.)

Failure Analysis of High Strength Cables from Collapsed Myaungmya Suspension Bridge Phyoe Wae Hein1(B) , Thinzar Khaing2 , Khin Maung Zaw2 , and Kunitomo Sugiura1 1 Department of Civil and Earth Resources Engineering, Graduate School of Engineering,

Kyoto University, Kyoto, Kyoto 615-8540, Japan [email protected] 2 Department of Civil Engineering, Yangon Technological University, East Gyogone, Insein, Yangon 11011, Myanmar

Abstract. The review on past bridge failures with detailed observations contributes to bridge engineers for applying the lessons learned in new projects and implementing effective failure prevention measures. This paper presents an experimental forensic investigation on high strength cables from Myaungmya Suspension Bridge in the delta region of Myanmar, which collapsed in 2018. It is reported that the failure of poorly-maintained, corroded bridge cables leads to its catastrophic collapse. Through the YTU-SATREPS project collaborating with the Ministry of Construction - Myanmar, sample collection is carried out from the anchorage, the critical part of bridge failure. Laboratory experiments are conducted according to the guidelines of the United States of America - NCHRP Report 534 and ASTM standards. Mechanical properties of cables at the time of bridge failure are evaluated by means of hardness test, tensile test, and fatigue test. The elemental composition of the bridge cable is determined by the spectroscopic test. Moreover, the nature of corrosion products and surface morphologies are examined by XRD and SEM methods. The results show that extremely-severe corrosion in bridge cables brings about a decrease in their ultimate tensile strength and finally causes brittle rupture of cables. Keywords: Failure analysis · Suspension bridge · Bridge cable strand · High strength steel · Corrosion · Mechanical properties · Surface morphology

1 Introduction Corrosion attack is one of the severe background problems related to the design, construction, and maintenance of Myanmar long-span bridges, mainly constructed within the limited resources and construction time around the 1990s to develop a better transportation network [1]. As shown in Fig. 1, the 1270 feet long Myaungmya suspension bridge, situated on the highway of Yangon and Pathein, collapsed on 1st April 2018 after 22 years of service. It consists of one main span of 600 ft constructed by a PC girder. A bridge deck width of 24 ft 7.3 in is used for two traffic lanes with a 5 ft width lane of sidewalk at both © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 137–145, 2023. https://doi.org/10.1007/978-981-19-4293-8_16

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sides. Reinforced concrete bored pile foundation is used due to soft alluvial ground. Permissible load is defined as 60 tons for the heavy trailer and 36 tons for passenger cars, while design loading is assigned as HS 20 of AASHTO highway loading and 41.77 psf of crowd loading. The bridge construction started on 1st March 1994, and the bridgeopening ceremony was held on 18th September 1996. Its general elevation is illustrated in Fig. 2. The steel strand of cables comprises seven 5-inch diameter wires with designed ultimate strength (1570 MPa). Rubber asphalt sealer and class-40 steel wire mesh cement are used for cable corrosion protection [2]. Since it is located in the delta region, the monsoonal climate is dominant. The effect of the tidal current is also observed in the river, especially during the rainy season. Many deteriorations have been detected during its service time, and several maintenance works have been done, such as repainting and re-wrapping of steel cables. However, the bridge unexpectedly fractured after three of its four suspension cables had been broken, and two brothers driving the eight-ton truck died. By the site investigation report, its failure was initiated by the rupture of the main cables due to corrosion induced by water accumulation at the anchorage. Therefore, this research paper aims to evaluate the strength of Myaungmya bridge cables at their failure, find out the influence of corrosion on bridge cables, and determine the root cause of bridge cable failure.

2 Review on Past Studies As mentioned in reports before bridge failure, many challenges related to the construction, operation, and maintenance were faced, such as the movement of abutment towards the river while erecting the main cable, the inclination of main towers, especially at Myaungmya side (MM side), which collapsed, and the corrosion problems at its main structural components, as described in Fig. 1 [3]. By the investigation report on bridge failure, it is observed that there was severe corrosion of bridge cables in the concrete anchorage, and the rupture of bridge cables seemed to be initiated from its anchorage. Water accumulation was found in the anchorage part of MM side, along with pits on cable surfaces. Corrosion can be neglected in main cables above the bridge decking due to the re-wrapping [4]. Possible scenarios of bridge cables’ failure include changes in internal cable forces due to tilting of the tower, lack in the structural integrity of cable, anchorage, and tower due to poor construction, an out-of-date corrosion protection system, and weakness in monitoring and maintenance.

3 Laboratory Experiments The experiments are conducted under the standards of the American Society for Testing and Materials (ASTM Standards). Moreover, some guidelines from the United States of America - Transportation Research Board’s National Cooperative Highway Research Program Report 534 (NCHRP Report 534) are followed. Through sample collection of the YTU project by Science and Technology Research Partnership for Sustainable Development (YTU-SATREPS Project) in April 2018 and the author’s site visit in May

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2019, most bridge cables used in the experiment are taken from the bridge’s anchorage part, which is the worst and critical point for the bridge failure.

(a) Location

(d) Collapse [4]

(b) Tower tilting [3]

(c) Corrosion of stiffening girder and main cables [3]

(e) Condition of anchorage cables at failure [4]

Fig. 1. Description of Myaungmya Suspension Bridge

Fig. 2. General elevation view of Myaungmya Suspension Bridge

The corrosion stage of all bridge cables is found to be “Stage-4 Corrosion”, the severest stage with existing cracks in some cables. They are further classified as “Good (G)”, “Moderate (M)”, and “Severe (S)” based on the integrity of wire strands in the cables. It is shown in Fig. 3. Mechanical properties such as hardness, tensile strength, and fatigue strength are evaluated. Chemical analysis for determining chemical composition is carried out by spectroscopic test. Moreover, corrosion products are observed, and corrosion morphologies are examined for corrosion analysis. 3.1 Hardness Test The macro-hardness test procedure is followed since the diameter of each wire is about 5 mm. The Rockwell hardness test is performed at (i) Physical Metallurgy Laboratory, Department of Metallurgical Engineering and Material Science, Yangon Technological University, and (ii) Hardness Test Laboratory, No. (3) Steel Mill - Ywarma, Myanmar Economic Corporation.

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(a) Corrosion condition

(b) Good, moderate and severe types (left to right)

Fig. 3. Corrosion condition and sample categorization of bridge cables

The hardness reading values for both core and outer wires of bridge cables are measured for eleven specimens. They are converted to approximate tensile strength values by ASTM A370-11, and uncertainty in Rockwell hardness measurement for central core wire is calculated by ASTM E18-15. It is observed that the actual hardness test values of core wires at bridge failure will be 44.80 ± 2.84 HRC which means the approximate tensile strength will be between 1338 MPa and 1618 MPa with an average value (1470 MPa) for 44.80 HRC. Therefore, it means that the tensile strength of bridge cable at the time of bridge failure may be lower than its specified ultimate tensile strength (1570 MPa). 3.2 Tensile Test The tensile test is conducted by using Shimadzu 100 kN Universal Testing Machine at the Structural Laboratory, Department of Civil Engineering, Yangon Technological University. By ASTM A416/A416M-12, the loading is applied to the cable with the 2 mm/min loading rate by ensuring secure grips. By NCHRP Report 534 guidelines, fracture types of bridge cable are examined as A for being ductile (cup and cone), B for being ductile (cup and cone) with shear lips alternating above and below fracture plane, B-C for being semi-ductile; Ragged with partial shear lips and reduction in area, C for being brittle (Ragged) with minimal or no reduction in area, and D for being brittle with cracks [5]. Calculated values of tensile strength and percentage of area reduction are described in Table 1, along with tensile test results and fracture types in compliance with NCHRP Guidelines. The mean ultimate tensile strength is found to be 1644.88 MPa which is greater than 1570 MPa. However, the cracks, perpendicular to the tensile axis of the cable, are observed on the fracture surfaces of the wire, which contribute to considering the strength models for strength estimation. According to NCHRP Report 534’s guidelines, the “Simplified Model” is beneficial for inspecting the most severely deteriorated parts, although there can be a strength underestimation of up to 20%. The primary assumption of the “Brittle-Wire Model” is that the same tensile stress is to be observed in all the wires subjected at any strain, and it is used in the case where more than 10% of the total cable wire population is

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composed of cables with cracks. Unusual variations in tensile strength, induced by the carbon content’s variation, are considered in the “Limited Ductility Model” [5]. Since the population of the cracked wires (two out of twelve test samples) is 16.67% which is more than 10% of the total tested wire population, the brittle-wire model should be used. Nevertheless, it is difficult to reflect the exact number of broken wires in the anchorage part, and thus “Simplified Model” is assumed for the simplicity of the worst-case anchorage. By the simplified model, the minimum tensile strength found for the cracked specimens should be used as an estimated ultimate tensile strength. Thus, the ultimate tensile strength of bridge cables at bridge failure is estimated as 1490.41 MPa. Moreover, it is observed that this tensile result is not significantly different from the result of the hardness test for the average value of core wire (1470 MPa). Table 1. Results of tensile test Cable Type

Max. Load (kN)

Tensile Str. (MPa)

G-1 G-2

248.77 245.79

1809.99 1788.27

G-3

214.41

1559.97

G-4 G-5 G-6 G-7 G-8

244.64 223.65 238.34 207.05 211.91

1779.92 1627.22 1734.09 1506.44 1541.81

M-1

204.85

1490.41

M-2 S-1 S-2 Mean Std. Dev. Max.

239.93 226.70 206.91 226.08

1745.65 1649.36 1505.43 1644.88

16.824

122.403

2487.77

1809.99

Mini.

204.85

1490.41

Elong. in 10-in gauge (%) 1.5 1.5

Reduction in Area (%) 43.75 43.75

Frac. Type

Remark

B B

Note 2, H Note 2, H Crack 1/4 D, 0.5 2 D Note 2, H 1.75 37.59 B Note 2, H 1.5 39.16 B Note 2, S 1.25 39.16 B Note 2, H 0.5 36 B-C Note 2, S 0.5 36 B-C Note 2, S Crack 1/6 D, 0.5 2 D Note 2, S 1.25 36 B-C Note 2, H 0.5 32.76 B-C Note 2, S 0.5 19 B-C Note 2, S 0.98 30.60 Remark: L = Local, O = Overall, M = Moderate, 0.516 14.783 H = Heavy, S = Severe Note 1 = Surface of wire covered with a gummy material, possibly rubber asphalt (as drawing), Note 2 = Surface corrosion is present at the fracture location, which is the probable initiation point of fracture.

3.3 Fatigue Test The fatigue test is carried out by the use of a rotating cantilever-beam-type testing machine of INDIA Scientific Goods (maximum bending moment up to 400 kg.cm) at Solid Mechanics Laboratory, Department of Mechanical Engineering, Mandalay Technological University. The constant amplitude test is carried out with a test speed of

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4200 rpm, and loads that can be applied in this test are 1.2 kg, 2.56 kg, and 4.98 kg due to the installation restriction of the specimen in the machine. By the procedures of ASTM E466-96 and ASTM E468-90 standards, twenty specimens (Ten for each corrosion condition) are tested, but only test results of eighteen specimens (Nine for each corrosion condition) are correlated for S-N curves since the failure of the rest two specimens is observed outside the gauge length of the specimens. The laboratory temperature range is 86 ± 4 °F, while the variation in laboratory relative humidity is 76 ± 3%. The following correlation equations are obtained from S-N Diagrams for both slightly-corroded and severely-corroded conditions of bridge cables. • For slightly-corroded condition, σmax = 991.93 N−0.0035 , R2 = 0.848 • For severely-corroded condition, σmax = 848.51 N−0.0024 , R2 = 0.748 According to the study by T. L. M. Morgado [6], the exponents of S-N curves, which are less than −0.1, ensure that a slight variation in the exponent n of the curves leads to a significant variation in fatigue stress or fatigue life. The steel strand is found to be sensitive to fatigue stress in a corrosive environment due to the range of observed exponents (n) of both S-N curves, which is −0.1 < n < 0. The lowest stress value is observed at the severe corrosion condition of bridge cables with longer fatigue life (2 × 106 cycles). There is a remarkable reduction in fatigue strength (over 120 MPa) based on corrosion conditions, and a slight significant reduction (13%) in fatigue life is observed. All fracture surfaces are cleavage fractures with nearly no reduction in cross-sectional area. 3.4 Spectroscopic Test By guidelines of NCHRP Report 534, spectroscopic tests are carried out by taking six cable samples at Material Characterization Laboratory of Yangon Technological University, Insein Locomotive Workshop’s Laboratory of Myanmar Railway, and Department of Research and Innovation (Aelar). The steel type used as bridge cables is determined as high strength hypereutectoid steel since carbon percentage observed is greater than 0.8%. Chemical composition in which the content of carbon and chromium is beyond the maximum limit (>0.84% for C, >0.10% for Cr) also adds the brittle behavior of bridge cable. By using the results of tensile test and spectroscopic test, only the China standard of steel wire strand with a nominal tensile strength of not less than 1570 MPa, such as GB/T 33026 and GB/T 5224, is found to be the best fitted in determining the type of high strength cables used. 3.5 Determining Bridge Cables’ Corrosion Products X-ray diffraction (XRD) method is applied to determine the nature of the corrosion product. Rust powder from slightly-corroded and severely-corroded parts of steel cable is collected according to ASTM G1 Standard and examined at Department of Research and Innovation and Universities’ Research Center.

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It is found that the corrosion products are mainly iron oxides (Fe3 O4 , FeOOH, Fe3 O(OH), Fe2 O3 , and FeO) and chloride salts (FeOCl). The abundant amount of iron oxide formation with different chemical compounds ensures severe corrosion conditions of bridge cable. In addition, magnetite (Fe3 O4 ) is also observed due to the limited oxygen supply within the concrete. An example of XRD result on severely-corroded bridge cable (S-1) is described in Fig. 4.

Fig. 4. XRD result of S-1 bridge cable

3.6 Study on Surface Morphologies of Bridge Cables The SEM Analysis is performed at the National Analytical Laboratory of the Department of Research and Innovation, Kabaraye. As illustrated in Fig. 5, the surface morphology related to corrosion behavior and the nature of corrosion products and the fracture surfaces are determined. In most areas, the pit openings connect each other, and uniform corrosion due to pit propagation and connection has been mostly found. Observation of all these four iron oxides such as γ-FeOOH, α-FeOOH, β-FeOOH, and Fe3 O4 confirms the severe corrosion condition of bridge cables and the presence of a corrosive environment near Myaungmya Suspension Bridge [7]. SEM results add the certainty of results by XRD examination and fractographic analysis on the fracture surfaces.

4 Conclusion In this study, the condition of severe corrosion on bridge cables, initiated from pits, is confirmed through tests on mechanical properties and results of SEM and XRD examinations. It is proved that the high strength steel is used as a bridge cable, and only the China Standard such as GB/T 33026 and GB/T 5224 is found to be the best fitted in determining the steel standard. The tensile strength of the bridge cable at its failure is observed to be less than the designed ultimate tensile strength. Moreover, bridge cables at failure are determined to be sensitive to fatigue stress because of the observed low exponents of S–N curves

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( 2.5, therefore, the internal force is calculated according to the elastic pile. Landslide thrust on single pile ET = En · L = 400 × 4 = 1600 (kN), the thrust distributes in trapezoid, and the distribution proportion q1/q2 = 0.5. Bending moment and shear force are calculated using the method of cantilever beam. The bending moment at the top of the lower section is 3200 (KN · m), while the shear force at the sliding surface is 1600 kN.

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The configuration quantity of longitudinal tensile reinforcement should be determined by sections according to the bending moment diagram, The cross-sectional area bh0 . should be calculated by As = K1 ξ ffcm y The stirrup configuration shall be checked according to the shear strength of inclined section, the formula is Vcs = 0.07fc bh0 + 1.5fyv Assv h0 . And it is required to meet the conditions: 0.25fc bh0 ≥ K2 V . 8 rebars made up of 3* 25 are selected for bending reinforcement, while stirrup used 14 with spacing of 10–20 cm (Figs. 7 and 8).

Fig. 7. Shows the structural reinforcement

Fig. 8. Shows the effect after treatment

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5 Treatment Effect Through the observation of surface settlement, it is found that the settlement is large in the early collapse. And the deformation tends to be stable, settlement tends to be convergent in some lateral parts because of the anti-slide pile backfilling pressure. The settlement changes slightly during the lower bench excavation in the tunnel, and then tends to be stable, which indicating that the anti-slide pile back pressure is effective.

6 Conclusions and Recommendations 1. The stability of tunnel portal slope is usually a problem in tunnel construction. When excessive deformation of surrounding rock affects slope stability, the cause of the problem should be correctly analyzed and targeted treatment measures should be taken [4]. 2. During route selection, the tunnel axis should be orthogonal or nearly orthogonal to the topographic contour as far as possible, in case of restriction, it should enter the tunnel at a large angle. When bad topographic conditions are unavoidable, geologic survey and bias analysis should be strengthened, and effective treatment should be carried out in advance based on geologic conditions to ensure construction safety [4]. 3. During construction, the management should be strengthened, the construction should be carried out strictly follow the drawings. The observation of vault subsidence, horizontal convergence and surface settlement in the tunnel should be strengthened, so as to provide a reliable basis for analyzing the causes of accidents. The designer should apply the dynamic design principle, follow up in time and adjust the design documents to ensure construction safety [4]. 4. The design and application of anti-slide pile should be flexible, the appropriate design parameters should be determined according to the scale and type of landslide, and the beam and prestressed anchor cable should be set based on needs. If necessary, it can be used as load-bearing anti-slide pile in combination with the characteristics of the building.

References 1. Liu, X., Zhang, Y., Gao, S., et al.: Mechanism analysis and treatment technique of surrounding rock instability for tunnel portal section in weak surrounding rock. Rock Soil Mech. 33(7), 2229–2234 (2012) 2. Specification of design and construction for landslide stabilization (DZ 0240-2004) 3. Specification for Design of Highway Landslide Stabilization (JTG/T 3334-2018) 4. Guidelines for Design of Highway Tunnel (JTG/T D70-2010) 5. Zhang, H., Fang, H.: Comprehensive study on landslide and initial crack management at North Chenting tunnel opening. J. China Foreign Highway

An Integrated Erection Method for Segmental Assembled Bridge in Urban District Hong Zhang1 , Maolin Cheng1,2,3,4 , Hao Xia1,2,3,4 , Chenyang Fan1,2,3,4 , Hao Xiao1,2,3,4 , and Xiaoping Zhang1,2,3,4(B) 1 CCCC Second Harbour Engineering Co. Ltd., Wuhan, People’s Republic of China

[email protected]

2 Key Laboratory of Large-Span Bridge Construction Technology, Wuhan,

People’s Republic of China 3 Research and Development Center of Transport Industry of Intelligent Manufacturing

Technologies of Transport Infrastructure, Wuhan, People’s Republic of China 4 CCCC Highway Bridge National Engineering Research Centre Co. Ltd., Wuhan,

People’s Republic of China

Abstract. Segmental assembled bridge erection has become the researching hotspot for constructors as demands of large interchange projects increase in recent years. In this paper, we mainly proposed an integrated bridge erection method and a newly designed multifunctional erection machine-TP120 that is capable of implementing super- and sub-structures construction simultaneously compares to traditional erection method, wherein, brief introductions of erector TP-120’s, bridge erection and retreat procedures, and a typical engineering practice are described. The implemental results show the proposed method is considerably competitive when facing strict environmental and technical requirements in urban area. Keywords: Integrated erection · Segmental assembled bridge · Super-structure · Sub-structure · Urban bridge construction

1 Introduction Urban traffic infrastructure constructions have been the foundation and the symbol of its economic prosperity, and in turn thrive of urban economy stimulates further investments of traffic infrastructure construction [1]. Over the past decade, urban interchange construction boom has been continuing in developing countries to fulfill their increasing logistics demands. For local government and contractors, an environmentally friendly construction scheme is very much in need that ecology development would not be disturbed in maximum during construction period [2]. Thanks to the advent of bridge erection machine, applications of prefabrication and on-site assembly technologies prevailed, efficiency, convenience and techniques of urban bridge erection were largely improved [3, 4]. For now, full-framing, crawler hoisting and on-site pouring methods only worked as assistant roles when engineering quantity is relatively small or construction condition permits, otherwise cost saving and efficiency improving would be considerably compromised, which were not in accordance with green and fast construction spirits [5]. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 154–165, 2023. https://doi.org/10.1007/978-981-19-4293-8_18

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Fig. 1. Typical Segment of bridge deck

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Fig. 2. Traditional erection machine in practice.

In the meantime, segmental assembled bridge has become one of the mainstream bridge types as prefabrication and on-site assembly spirits carrying out worldwide [6]. Segments divided as per Short-Line principle, shown in Fig. 1, can be well prefabricated in remote factory, easier transported by carriers to the engineering site, further hoisted, prestressed and assembled as deck by using cranes and erection machines, specially paired with external prestressing that minimize the concrete consumption. Moreover, this type of bridge deck has been fully welcomed by most contractors thanks to its better alignment adaptation and high-efficient production which enables fast and economic bridge constructions [7–10]. In terms of using erection machine [4, 11–13], shown in Fig. 2, assembly practices of various type of bridge have been further extended from sea, river, and lake crossings to urban interchanges and mountainous rail transport tunnels. Commonly, there were two main legs and an assisting leg for erection machine’s bearing capacity conversion. Supported by already assembled deck and front pier, the erector can repeatedly perform segments hoisting, beam prestressing, main legs transporting and its main framework’s forward moving. Apart from functions design, researches were focused on stability analysis and safety level predictions when erection exposed to salt corrosion, stormy weather, sea wave impaction, wherein FEA methods are used [14–24] for analysis. Yet, for evolution of bridge erection approach itself, little effort and few achievements have been made since this common erection method was proposed. Considering what will bring if full framing and on-site pouring method wouldn’t be replaced, traditional bridge erection method definitely has taken a solid step forward of converting extensive construction to green construction. But, problems and difficulties regarding occupation of public traffic areas, intervention of existing traffic operations, necessities of crane machineries for substructure erection, pre-establishment of special aisle for carriers and etc. remained. In view of the substantial existence of condition limitations of urban bridge construction and intense demands of integrated bridge construction, in the following parts of this paper, we propose a comprehensive urban segmental assembled bridge erection method and a newly designed machinery that will realize the integration erection for both super- and sub-structures components, which correspondingly offers a better solution for urban bridge erections.

2 Multi-functional Bridge Erection Machine—TP120 To match the demands of certain supporting project in urban district, a multi-functional erection machine TP-120 was specifically developed, see Fig. 3, and was supposed to

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realize the integrated erection of small-medium span bridge in urban area in terms of cantilevered assembly approach.

Overhead Travelling Crane

Rear Leg

Rear-middle Leg

Segments erection zone

Supporting Framework

Front-middle Leg

Pier erection zone

Front Leg and Toe

Fig. 3. Newly designed multi-functional erection machine TP-120.

2.1 General Structure Concept TP-120 specifications of which are described in Table 1, mainly includes supporting frameworks, four functional legs respectively located at front, middle and rear parts of the framework, two overhead travelling cranes, hoisting appliances, pier corbel, service platform, electro-hydraulic system and ancillaries. There are generally three spans for this machine framework along direction of erection, wherein the front span is mainly for assembly of pier and segment block positioning on pier top, the middle span is for segment block assembly and the rear span is for girder segments feeding and transporting. In addition, supporting framework is composed of two main trusses in terms of transversal connections, on top chord of which two overhead travelling cranes can move by. 2.2 Brief Description of Main Structure Components Supporting Framework. As shown in Fig. 4, TP-120 Framework is assembled together by two parallel truss frames and connection transoms at two ends. Framework has 9 sections and total length of 89.3 m, wherein, pin connections in between sections are used. Center to center spacing of two trusses is 6.5 m. In addition, framework reinforcements are adopted for more robust hoisting, more travelling abilities of some truss segments and simultaneously saving overall structure cost. Legs. As shown in Fig. 5, 6 and 7, Front leg, worked as the front supports of framework during assembly of pier and segment block locating on top, is located at the front end of framework and hinged to the support on top of cushion beam. Thanks to the telescoping mechanism, there are three working position of leg toes, which correspond to normal, under travelling and supporting status. The reach of adjustment is 2.5 m–16 m. Middle legs are the most important functional components. There are two sets of middle legs with identical design, which mainly worked as mobile load transferrers when machine proceeding forward erection or retreat. The movement mechanism consists of

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Table 1. Specifications of integrated erection machine TP-120 Items

Para.

Items

Para.

Eng. Approach

Full Span Suspension Assembly

Feeding Manner

Bottom and end feeding

Span

≤40 m

Payload Capacity

≤120 t/≤100 t

Longitudinal Gradient

≤4%

Lifting Weight per Span

≤800 t

Transversal Gradient

≤3%

Scope of Lifting

25 m (below appliance)

Curve Radius

≥500 m

Winch Speed

0–2.5 m/min (heavy duty)

Electric Station

Three-Phase Four-Wire AC 380 V at 50 Hz

Crane Travel Speed

0–15 m/min (heavy duty)

Installed Power

About 220 kw (not include pump motor)

Dead Weight

About 440 ton

Conditions of Carriage

Within Road limit

Hoisting Appliances

Rotatable with ±4% adjustment in plane

sliding support, rotational cushion, longitudinal and transversal movement driving systems, transom, anchoring and jacking devices. Rear leg, worked as temporary support as machine retreats or proceeds longitudinal erection, mainly consists of top and bottom transoms, suspending walking device, height adjustment device, anchoring and service platform.

Fig. 4. Supporting framework.

Fig. 5. Front leg structure.

Overhead Transporting Crane. As shown in Fig. 8, two units are set to hoist piers and segment blocks with capacity of 120 t (the front one) and 100 t (the rear one), respectively. It consists of moving mechanism, steel body, hoisting system, movable pulley sets and power supply system. In addition, for safety considerations, overload protection, stop block device are set to accommodate exceptional operating case as well. Hoisting Appliances. As shown in Fig. 9, consists jacking group in longitudinal and transversal direction, transom, jib and other components. Segments and pier can be lifted

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Fig. 6. Middle leg structure.

Fig. 8. Overhead transporting crane.

Fig. 7. Rear leg structure.

Fig. 9. Hoisting appliances.

in terms of 4 or 8 connections between their pre-assembled rings on it and shackles on appliance ends. The pose of segment is able to adjust within ±4% limit.

3 Integrated Erection Flow Per Standard Bridge Span 3.1 Typical Installation of Multi-functional Erection Machine Prior to erection, Multi-Functional Erection Machine shall be installed. As aforementioned, two identical middle legs are most important supporting components that will be firstly set up on ground, hoisted and anchored to pretreated foundation, wherein assembly distance and levels between each leg shall be precisely determined according to steel framework dimension of erection machine and longitudinal gradient of bridge. Whereafter, middle part of supporting frameworks shall be assembled on ground, hoisted in terms of using two lorry-mounted cranes on each side, bearing capacity of which depends on unit weight of framework to be lifting, and precisely rested and locked their longitudinal rail on two pre-installed middle legs. Likewise, front and rear parts of framework, front and rear legs, overhead travelling cranes are then sequentially hoisted and mechanically connected to their adjacent structure components. Moreover, miscellaneous devices such as slings, electric motors, cables shall be accordingly installed as well, wherein, checking and debugging of electrical and hydraulic system shall be taken with extreme care. 3.2 Erection Procedures Unlike traditional erection requiring caterpillar crane group or other supporting framework structures to erect substructure components like pier, pile cap, etc., the implementation of which needs clear transport corridor, this proposed method simply used

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the multifunctional erection machine to realize erection of super-components and pier component without complex local traffic management and a large amount of temporary works. The standard erection procedures include 8 steps per bridge span, details are described as follows and in Fig. 10: Step 1. For reiterative erection flow, the erection machine has just finalized the construction of the previous bridge span. To initiate the new span construction, rear-middle leg shall be firstly transported, by using the front overhead travelling crane, and rests on segment block previously located on front pier top. Step 2. For requirement of balancing weight during framework travelling, the rear overhead crane shall travel to position adjacent to the same of front through guide rail on framework top chord. Then, driven by pushing jacks at connections between framework and middle legs, framework performs travelling through its longitudinal direction till 10 m distance is reached. Front leg remains its connection to the framework while rear leg keeps still to the constructed girder during this step. To note that the design of travelling distance is changeable as per dimensions of the framework or the on-site bridge span to be constructing. Step 3. Anchoring of rear leg from lower chord of framework is released so as to continuously move framework for further 15 m. In the meantime, two overhead travelling cranes shall move to position where is on top of the middle pier for weight balancing. Then, on this basis, framework might finalize span travelling till front leg reaches front end of the pier to be assembling and anchors to the ground. Step 4: Two overhead travelling cranes move to rear end of framework to fetch the two ends of prefabricated pier to be assembling in terms of using wire ropes, shackle and lift slab, respectively. Step 5. Pier is transported to some clear space of front span and rest on ground by smoothly releasing wire ropes. Then, unlock the lifting hook of rear overhead travelling cranes to rear end of pier and individually lifting pier using front overhead travelling crane till it becomes upright. Step 6. Transport pier to assembly position and perform assembly. Then, perform transporting, lifting and localization of segmental block(s) on pier top after strength of pier meet the design requirements. To note that there are might be two consecutive segmental blocks to be assembling when one continuous girder unit construction is finished. Details of application depends on the actual situation.

3.3 Retreat Procedures As engineering demand that two bridges erection along same alignment might use only one set of erection machine due to budget control or complexity of synchronization process management considerations, formulation of retreat procedures is needed for the convenience of the consecutive bridge erection. The standard retreat procedures include 7 steps per bridge span, details are described as follows and in Fig. 11: Step 1. For reiterative retreat flow, erection machine has finished the last span of bridge erection in this step. Then, anchoring of rear leg to constructed girder is released.

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Step 1:

Step2:

Step3:

Step4:

Step5:

Step6:

Step7:

Step8: Fig. 10. Integrated erection flow chart.

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Step 2. Rear leg retreats back to the end of framework, In the meantime, the two overhead travelling cranes move to position on top of rear middle leg where they may perform weight balancing. Step 3. Framework, driven by two longitudinal pushing jacks at connection of middle legs and framework, travels back for 10 m, while the two overhead travelling cranes keep the same position to ground reference. Step 4. Two overhead travelling cranes move forward to position on top of front middle leg, after which framework may continue moving 15 m to finalize span travelling. Then, anchoring of rear leg to constructed girder is set. Step 5. Framework continue moves forward till front leg reaching position of abutment end, which is adjacent to front middle leg and locked to the rear middle leg.

Step1:

Step2:

Step3:

Step4:

Step5:

Step6:

Step7: Fig. 11. Retreat flow chart.

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Step 6. Front leg is transported, using front overhead crane, to rear end of framework adjacent to rear middle leg. Step 7. Repeat Step1 to Step 6 till erection machine retreats back to starting point of this alignment.

4 Engineering Application Case In this section, an engineering practice of segmental assembled bridge under construction in terms of using this integrated erection method and newly designed machine is shown to verify the feasibility and effectiveness. This application is based on a large interchange construction project located in Yantian district, the north part of city Shenzhen, China. The interchange will work as an important transportation hub for five-way connections of local areas. The straight section C1 and D2, shown in Fig. 12, are two parallel ramp bridges, with longitudinal gradient of 3.95% and lengths of 385 m (4 × 35 + 4 × 35 + 3 × 35) m and 315 m (3 × 35 + 3 × 35 + 3 × 35) m, to be respectively constructing. The main girder to be tensioning with 3 m long and around 80 t single box single-room reinforcing concrete segments, the deck with 9.3 m width and single column piers of vase type are integrated erected on-site in terms of aforementioned method, as shown in Fig. 13. The completion of those ramp sections will be regarded as the first exemplary application of prefabrication assembly engineering for transportation infrastructure constructions of local cities.

Fig. 12. Overview of engineering case.

Fig. 13. Segment blocks and pier erection in practice.

4.1 Scheme of Implementation As there might be intervene and multitap delay if simultaneously proceed two ramp erections, only one set of integrated erection machine is deployed for both lines. After completion of line D2, erection machine will draw back from the end point to its start point, then transversally move to alignment of ramp C1 and start erection till the end, wherein the construction details of the first span, the last span and the side span of every continuous bridge unit shall be further noted in addition to standard span as per characteristics of this project. For construction of the first and the last span, shown in Fig. 14, middle leg shall be moved back to subgrade area where it could be anchored to support to protect the abutment from being damaged. For construction of the side spans of each continuous girder unit, shown in Fig. 15, brackets around pier top and support on top of foundation shall be set to meet the segments locating and foundation bearing demands.

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Fig. 14. Scheme of the first and the last span erection.

Fig. 15. Scheme of side span erection. Table 2. Integrated erection flow rhythm No.

Procedures

Schedule

1

Installation of forefront span pier

1 day

2

Strengthening of forefront span pier

2 days

3

Suspension, gumming and temporary prestressing of rear span segment blocks

2 days

4

Installation of segment blocks on pier

1 day

5

Pouring of wet joints

1 day

6

Strengthening of wet joints

2 days

7

Prestressing of segmental girder

1 day

8

Span travelling of erector

1 day

1

2

3

4

5

6

7

4.2 Efficiency of Implementation As shown in Table 2, integrated erection method provides the same overall erection efficiency by using multi-functional erection machine, which is designed to have an additional span of steel structure beam, a front leg and accordingly be given pier assembly function. The erection period of single span for this project is controlled with 7 days.

5 Summary To conclude, the advantages compared to traditional erection include: 1) lifting and transporting efficiency are increased due to individually controlling of two overhead

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transporting cranes which provides synchronous construction capacity. 2) important prefabricated structure components like pier, segment blocks on it, girder segments can be simply assembled by using TP-120 in each construction cycle without any help of on-ground hoisting equipment like caterpillar crane groups. 3) super- and sub-structures can be simultaneously erected and to the extends of which 4) the dedicated transport corridor for caterpillar crane or transporting vehicle is not required any more so that there are less impacts to local traffic operation let along a large amount of temporary construction may be saved. However, there is no significant improvement when it comes to the overall erection efficiency of proposed method. Anyhow, the proposed method offers a greener solution, regarding less occupation of public areas and less intervention of existing traffic operations, for urban bridge erection when construction requirements are stricter. The future work may include more about the integrated erection researches such as pile construction and the corresponding erector, or even construction factory using the idea of the industrial assembly line for reference.

References 1. Zhou, X.H., Zhang, X.G.: Thoughts on the development of bridge technology in China. J. Eng. 5(6), 1120–1130 (2019) 2. Yan, B., Dai, G.L., Hu, N.: Recent development of design and construction of short span high-speed railway bridges in China. Eng. Struct. 100, 707–717 (2015) 3. Schueller, M., Singh, P.R.: Design and construction of the Deh Cho Bridge challenges, innovation, and opportunities. In: TAC Conference & Exhibition Transportation: Innovations and Opportunities (2012) 4. Rosignoli, M.: Self-launching erection machines for precast concrete bridges. PCI J. PC Inst. 55(1), 36–57 (2010) 5. Kindmann, R.: Fabrication and assembly trends in steel bridge construction. Stahlbau 55(11), 341–345 (1986) 6. Xu, G.X., Li, C.H., Liang, L., et al.: Construction techniques of segment assembling for erection of each two-span girders of Beidongkou waterway bridge of Pingtan straits railcum-road bridge in one time. J. Bridge Constr. 48(3), 105–110 (2018) 7. Sventek, M., Štens, L.: Fabrication and erection of the bridge steel structure for highway R1. Procedia Eng. 40, 428–433 (2013) 8. Linzell, D.G., Shura, J.F.: Erection behavior and grillage model accuracy for a large radius curved bridge. J. Constr. Steel Res. 66(3), 342–350 (2010) 9. Heggade, V.N., Bansal, S.: Construction of an iconic signature bridge in Delhi. J. Bridge Constr. 47(2), 1–6 (2017) 10. Shim, C., Lee, S.Y., Park, S., Koem, C.: Experiments on prefabricated segmental bridge piers with continuous longitudinal reinforcing bars. Eng. Struct. 132, 671–683 (2017) 11. Zhang, Y.H., Chen, S.T.: Original design of the SSJ900-type bridge girder erection machine. In: Proceedings of the 2nd International Conference on Transportation Engineering, ASCE 2009, pp. 1724–1729 (2009) 12. Chen, S.T., Sun, Z.X., Zhang, P., et al.: Design, selecting type and application of SLJ 900/32 mobile bridge erecting machine. CHN. J. Railway Eng. Soc. 32(1), 88–92, 114 (2015) 13. Jiang, D.Y., Long, H.: Design of 20 t girder erection machine for super large bridge over Yellow river at Sunkou. CHN. J. Hoist Convey Mach. 11, 11–14 (1995)

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14. Chen, Y.X., Lv, P.M.: Structural optimization design for high-speed railway bridge erecting machine. In: Proceedings of the International Conference on Advanced Technology of Design and Manufacture, vol. 2010, no. 576, pp. 176–180 (2010) 15. Wang, X.Y., Zhao, J.Y.: Synchronous drive control of the double bridge girder erection transporters combined operation. In: Proceedings of the International FIB Cong., pp. 220–224 (2018) 16. Cheng, Y., Xie, J.R., Zhang, L.Q.: Study on the buckling stability of TPZ/48 steel box girder type bridge erection machine under construction state. J. China Railway Sci. 33(1), 35–40 (2012) 17. Chen, S.T., Cheng, Y., Xu, H.W., Zhang, Y.H.: Damage identification for main girder of bridge erecting machine considering working conditions. ZhongGuo Tiedao Kexue/China Railway Sci. 40(3), 44–53 (2019) 18. Shang, G., Tong, Y., Yang, L., Wu, D.: The application of SolidWorks in bridge erecting machine’s structure design. In: Proceedings of the 3rd International Conference on Manufacturing Science and Engineering, Advanced Materials Research, vol. 472–475, pp. 678–682 (2012) 19. Ling, Z.Y., Cao, H., Wang, Y., et al.: Test of a simulation platform of multi-software for 900 ton bridge-erecting machine. CHN. J. Zhendong Ceshi Yu Zhenduan/J. Vib. Measur. Diagn. 29(3), 295–298 (2009) 20. Zhou, Y.T., Yan, K.: Safety evaluation of pier under impact of bridge girder erection machine. In: International Conference on Computer Mechanical and Materials & Engineering, Advanced Materials Research, vol. 147, pp. 86–91 (2011) 21. Yang, S., Fang, X., Zhang, J., Wang, D.: Dynamic behavior of bridge-erecting machine subjected to moving mass suspended by wire ropes. Appl. Math. Mech. 37(6), 741–748 (2016). https://doi.org/10.1007/s10483-016-2087-6 22. Liu, Y.B.: Erecting prefabricated beam bridges in a mountain area and the technology of launching machines. Struct. Eng. Int. 22(3), 401–407 (2012) 23. Yang, S.P., Wang, L.Y., Pan, C.Z.: Safety analysis of large construction machinery based on safety factor method. CHN. J. Vib. Shock 32(8), 55–57 (2013) 24. Pedro, R.L., Demarche, J., Miguel, L.F.F., Lopez, R.H.: An efficient approach for the optimization of simply supported steel-concrete composite I-girder bridges. Adv. Eng. Soft. 112, 31–45 (2017)

Study on Effective Temperature Extreme Isotherm Map of Steel-Concrete Composite Girder Bridge Yun Zhang(B) CCCC First Highway Consultants Co., Ltd., Xi’an 710075, Shaanxi, China [email protected]

Abstract. Aiming at the refined value of effective temperature of steel-concrete composite girder jointless bridge, the historical meteorological data of 38 national benchmark weather stations in Inner Mongolia, China for more than 40 years were investigated. The most unfavorable weather conditions of composite girder once in 100 year’s period were simulated according to the measured historical meteorological data. Based on the finite element model and section weighted average method, the extreme effective temperature of composite girders at various weather stations was calculated. Then the isothermal map of the extreme effective temperature of Steel-concrete composite girders is obtained by spatial interpolation, which is compared with the Chinese Specifications. The results show that the effective temperature of composite girders is significantly affected by climate and environment. The maximum effective temperature and the minimum effective temperature in Inner Mongolia, China range from 37.46 °C to 46.07 °C and −41.92 °C to −10.13 °C, respectively. The regional differences reach 8.61 °C and 31.79 °C, and the influence of low temperature is more obvious. The results of this paper show that the effective temperature in most areas is higher than specifications, which may lead to the serious underestimation of temperature effect in the design of jointless bridges in Inner Mongolia, China. Keywords: Bridge engineering · Steel-concrete composite girder · Effective temperature extreme value · Isotherm map · Seamless bridge

1 Introduction There are many reasons for setting expansion joints and expansion devices in bridges, one of which is that considering the temperature effect will cause expansion and contraction deformation of bridge structures, especially for statically indeterminate structures, the temperature effect will also generate temperature secondary stress inside the structures, thus affecting the bearing capacity of the structures [1–4]. Compared with the jointless bridge, the jointless bridge eliminates expansion joints and expansion devices, and the superstructure is continuous. The longitudinal direction of the superstructure can be regarded as a statically indeterminate structure, and the structural deformation is dominated by temperature deformation. Therefore, one of the key points in the structural © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 166–177, 2023. https://doi.org/10.1007/978-981-19-4293-8_19

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design of jointless bridge is to reasonably consider the temperature effect of the structure. Taking the integral bridge in jointless bridge as an example, the effect of temperature will not only cause the structural internal force change and structural deformation of the beam body in the longitudinal direction, but also change the stress state of the whole abutment and the fill behind abutment, and further affect the stress state of the whole structure due to the interaction between the fill behind abutment and the structure. In the design stage, it is necessary to accurately consider the temperature effect on the jointless bridge, so as to accurately calculate the specific deformation and determine the maximum allowable deformation, so as to scientifically guide the subsequent structural design and ensure the safety and reliability of the structural design of the jointless bridge [5–12]. In General Specifications for Design of Highway Bridges and Culverts (JTG D60— 2015) [13], the maximum and minimum effective temperature standard values of different bridge structures under uniform temperature are given according to the classification of severe cold region, cold region and warm region [7]. China has a vast territory, and the rough partition value method in General Code for Design of Highway Bridges and Culverts can’t reflect the difference of uniform temperature in each partition. Many scholars, such as Liu Jiang [7] and Xue Jun-qing [8], have shown that it is difficult to envelope the long-term temperature stress or deformation of the bridge structure under the temperature action of specifications, which leads to the risk of unsafe design and calculation. Regarding the value of temperature action of jointless bridges, Fujian local specification DBJ/T13 265–2017 for jointless bridges gives the sectional temperature difference values of hollow slab and small box girder suitable for Fujian province according to the classification of northeast coast, southeast coast, northern mountain area and southern mountain area, and gives the calculation formulas of the maximum and minimum effective temperatures based on the sectional temperature difference values. However, for steel-concrete composite girders, there is a difference between the temperature effect and the concrete bridge, because they are composed of two kinds of materials with completely inadequate thermal properties. American code AASHTO-LRFD [9] not only divides the United States into cold and mild regions, but also gives the effective temperature extremum of concrete bridges in each region and the design temperature extremum isotherm diagram of American concrete bridges. Compared with temperature action zoning area, the value of temperature action contour area is more accurate, which can better meet the design requirements of jointless bridge. In this paper, combined with the engineering example of a steel-concrete composite girder jointless bridge in Inner Mongolia, China, the finite element model was established by ABAQUS to simulate the temperature field, and the meteorological data of 38 national meteorological stations in Inner Mongolia, China for more than 50 years were collected. According to the historical long-term meteorological data of meteorological stations, the most unfavorable combination of meteorological parameters was simulated to calculate the effective temperature extreme value. Spatial interpolation analysis of the effective temperature extremum can obtain the effective temperature isotherm map, which improves the accuracy of Chinese Specifications and contributes to the fine design of steel-concrete composite girder jointless bridges.

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2 Numerical Simulation 2.1 Heat Conduction Theory The temperature field of the bridge belongs to the unsteady temperature field caused by the influence of meteorological conditions such as solar radiation and ambient temperature. The temperature action on the bridge has obvious characteristics of time and space. There are many and complex factors affecting the temperature field of bridges, and the finite element method is one of the most effective methods to solve the temperature field of bridges. Under sunshine, the temperature distribution of the bridge depends on the heat exchange with the outside world and the internal heat conduction. Because the temperature difference along the bridge direction is small and negligible, and the composite girder bridge in the operation stage does not need to consider the influence of hydration heat, the problem of solving the temperature field of the bridge under sunshine is changed from the problem of three-dimensional heat conduction to the problem of solving the two-dimensional unsteady heat conduction differential equation without internal heat source. The key problem to determine the accuracy of numerical simulation lies in the selection of sunshine boundary conditions. Under the action of sunshine, the heat exchange between the bridge and the surrounding environment mainly includes solar radiation, convection heat exchange and radiation heat exchange. Solar radiation can be divided into direct radiation, scattered radiation and ground reflected radiation. The heat exchange between the bridge and the surrounding environment is shown in Fig. 1.

Fig. 1. Schematic diagram of heat exchange of composite girders under sunshine.

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2.2 Finite Element Simulation Taking a steel-concrete composite girder jointless bridge project in Inner Mongolia, China as an example, the finite element model of composite girder section of jointless bridge is established by ABAQUS program, and the long-term two-dimensional temperature field numerical simulation is carried out. Among them, the concrete bridge deck, steel beam and asphalt pavement are all simulated by the four-node linear heat transfer quadrilateral element (DC2D4) provided by ABAQUS program, and the interface between the bridge deck, asphalt pavement and steel beam is simulated by “binding” constraint, which means that the temperature and heat flow on the interface are continuous and meet the requirements of the fourth boundary condition. The finite element model and mesh division are shown in Fig. 2. See Table 1 for thermal parameters of steel, concrete and asphalt in the model.

Fig. 2. Section size and finite element mesh division (unit: mm). Table 1. Thermal parameters of each material. Characteristics

Steel

Deck concrete

Asphalt pavement

Density ρ, kg/m3

7850

2300

2100

Specific heat capacity c, J/(kg · °C)

460

900

875

Thermal conductivity λ, W/(m · °C)

55

3

1.6

Solar radiation absorptivity α

0.5

0.4

0.88

Emissivity ε

0.8

0.85

0.88

3 Effective Temperature Extremum Calculation 3.1 Historical Meteorological Data Investigation Because the temperature of bridge structure is significantly affected by climatic and environmental factors, in order to explore the differences of temperature effects in different regions, various measured meteorological data from meteorological observation

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stations in Inner Mongolia, China Autonomous Region were investigated and collected, and the data source was “National Meteorological Science Data Center” (http://data. cma.cn/). A total of 38 weather stations were collected. See Fig. 3 for the distribution of weather stations. Data collected by meteorological stations include sunshine hours, daily maximum temperature, daily minimum temperature and daily average wind speed, etc. In addition, some radiation weather stations also provide solar radiation data such as total daily solar radiation, total direct radiation and total scattered radiation. The time span of meteorological data is from January 1, 1953 to December 31, 2011. The influence of solar radiation on the temperature of steel-concrete composite girder bridge is also very significant. For the missing solar radiation data, the theoretical value of solar radiation calculated by numerical method in reference [10] can be supplemented.

Fig. 3. Distribution of meteorological stations in Inner Mongolia, China.

3.2 Extreme Meteorological Conditions In order to get the extreme value of effective temperature in each weather station, it is necessary to determine the most unfavorable weather conditions of each weather station. The occurrence dates of the highest temperature and the lowest temperature observed by meteorological stations from January 1, 1953 to December 31, 2011 were selected as the conditions for the occurrence of the maximum effective temperature and the minimum effective temperature, respectively. At the same time, according to the long-term observation data, the highest temperature and the lowest temperature were revised to obtain the environmental temperature extreme value of every meteorological station once in 100 years according to the normal distribution (95% guarantee rate). For the maximum effective temperature, the maximum value of solar radiation during the observation period was also considered, while the minimum effective temperature was not considered. The wind speed is taken from the actual observation data synchronized with the air temperature.

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The observation data of meteorological stations are only the daily maximum and minimum values. In order to meet the needs of numerical simulation analysis, the following sine function [11] can be used to further obtain the hourly temperature.  Tmax − Tmin Tmax + Tmin π + sin (t − t0 ) (1) T (t) = 2 2 12 where, T a (t) is the daily temperature change function; T a,max and T a,min are the highest and lowest temperatures in a day; t is time; t 0 represents the time when the highest temperature and the lowest temperature occur. When t 0 = 9, the highest temperature is at 15: 00 p.m. and the lowest temperature is at 3: 00 a.m. Solar radiation can use Hottel model and Liu-jordan model to calculate hourly direct solar radiation curve and scattered solar radiation curve on summer solstice [10]. 3.3 Calculation Result of Effective Temperature Extreme Value Based on the above-mentioned extreme weather condition setting method, the most unfavorable weather boundary conditions of 38 weather stations in Inner Mongolia, China were obtained, and the calculation models of composite girder temperature field were established by ABAQUS software respectively. The unit type, mesh division, internal and external boundary condition setting method and material characteristics of the models were the same as those in Sect. 1.2. The ambient temperature at 0: 00 is taken as the initial temperature field of the section, and the boundary conditions of meteorological parameters of that day are repeatedly calculated for three days, and the calculation results of the last day are taken for analysis [12] to eliminate the influence of initial errors. The effective temperature T e can be calculated according to formula 2. Finally, the extreme values of the maximum effective temperature and the minimum efficiency temperature of each weather station are obtained, as shown in Table 2.  αi Ei Ai Ti (2) Te =  αi Ei Ai where: T i is the temperature value of each unit in the finite element model; Ai is the area of the unit; α i and E i are the thermal expansion coefficient and elastic modulus of the materials of each unit, respectively.

4 Effective Temperature Isothermal Map Based on the calculation of finite element method to obtain the representative values of temperature action of 38 stations, the ArcMap program in ArcGIS 10.8 software platform is used for spatial interpolation calculation, and the contour map of temperature action is further drawn. The spatial interpolation calculation process is shown in Fig. 4. In order to keep the data of sample points unchanged after spatial interpolation, and avoid extreme interpolation results on the basis of controlling the smoothness of interpolation curves, the REGULARIZED curve in the spline interpolation method built in the software is selected to produce smooth surface and smooth first derivative, with interpolation weight of 0.1 and interpolation points of 10.

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Y. Zhang Table 2. Extreme value of effective temperature in Inner Mongolia, China.

Meteorological station information Name of weather station Inner Manzhouli Mongolia Hailar autonomous Small two channel region Xin barag right banner

Geographic information

Effective temperature/°C

Station Latitude Longitude Altitude/m T e,max number

T e,min

50514

−40.21

49.35

117.19

661.8

43.95

50527

49.15

119.42

649.6

42.71

−40.79

50548

49.12

123.43

286.1

42.43

−38.50

50603

48.41

116.49

542.4

45.37

−37.06

Xin barag left banner

50618

48.13

118.16

642

43.50

−38.63

Boketu

50632

48.46

121.55

739.7

40.44

−34.17

Zhatun

50639

48

122.44

306.5

43.43

−30.53

Soren

50834

46.36

121.13

499.7

41.68

−34.47

Ulanhot

50838

46.05

122.03

274.7

43.66

−31.46

Dongwuzhumuqin 50915

45.31

116.58

838.9

41.36

−34.12

Holingola

50924

45.33

119.39

860

42.25

−30.01

Bayannuoergong

52495

40.1

104.48

1323.9

42.21

−29.74

Ayouqi

52576

39.13

101.41

1510.1

42.06

−26.51

Erenhot

53068

43.37

111.56

963.1

43.67

−31.16

Narenbaolige

53083

44.37

114.09

1181.6

40.59

−35.53

Mandula meteorological station

53149

42.32

110.08

1225.2

41.47

−28.34

Agaqi

53192

44.01

115

1147.7

40.57

−34.64

Sonid Zuoqi

53195

43.51

113.38

1036.7

42.62

−33.85

Urad Middle Banner

53336

41.34

108.31

1288

41.80

−29.31

Maoqi meteorological bureau

53352

41.42

110.26

1376.6

40.18

−25.97

Siziwang

53362

41.32

111.41

1490.1

40.46

−33.64

Huade

53391

41.54

114

1482.7

37.76

−31.98

(continued)

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Table 2. (continued) Meteorological station information

Geographic information

Effective temperature/°C

Name of weather station

Station Latitude Longitude Altitude/m T e,max number

T e,min

Baotou Meteorological Observatory

53446

40.32

109.53

1004.7

37.55

−30.39

Hohhot

53463

40.51

111.34

1153.5

41.29

−25.62

Jining

53480

41.02

113.04

1419.3

38.27

−33.03

Jilantai

53502

39.47

105.45

1031.8

40.35

−30.71

Linhe

53513

40.44

107.22

1041.1

43.27

−29.02

Otog banner

53529

39.05

107.58

1381.4

40.90

−24.39

Wu Zhao

53547

39.06

109.02

1312.2

39.09

−23.93

Alxa left banner

53602

38.5

105.4

1561.4

42.38

−22.68

Zarut

54026

44.34

120.54

265

39.93

−34.70

Balin eft banner

54027

43.59

119.24

486.2

44.16

−25.08

Xilin Hot

54102

43.57

116.07

1003

37.58

−28.30

Linxi county

54115

43.38

118.02

825

40.51

−32.35

Tongliao

54135

43.36

122.16

178.7

43.29

−29.47

Niute banner

54213

42.56

119.01

634.3

38.16

−33.28

Chifeng

54218

42.18

118.5

668.6

41.24

−23.84

Baotu

54226

42.2

120.42

400.5

42.22

−23.13

Fig. 4. The spatial interpolation calculation process.

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Make the contour map of the maximum effective temperature in Inner Mongolia, China, as shown in Fig. 5. For the effective temperature T e , the maximum effective temperature T e,max after interpolation ranges from 37.46 °C to 46.07 °C, among which the maximum T e,max occurs in the northwest of Inner Mongolia, China, which is also the area with high temperature all the year round. The minimum T e,max occur in the southeast of Inner Mongolia, China. Figure 6 is the map of the minimum effective temperature. It can be seen that the minimum effective temperature T e,min ranges from −41.92 °C to −10.13 °C, with a variation range of 31.79 °C, and T e,min shows an obvious trend of decreasing from north to south. The low temperature of T e,min mainly occurs at the junction of north and northeast Inner Mongolia, China, which is mainly caused by the sharp decrease of the minimum temperature with the increase of latitude.

Fig. 5. Maximum effective temperature extremum contour map.

Figure 7 shows the climatic zoning map of the effective temperature value in Chinese Specifications. Table 3 shows the comparison between the calculation results of this paper and Chinese Specifications. It can be seen that in the specification, Inner Mongolia is almost completely in the severe cold area, with the recommended maximum effective temperature is 39 °C. Compared with the results of this paper, more than half of the regions in the north and northwest of Inner Mongolia, China exceed the code value. The recommended value of the minimum effective temperature is −32 °C, but the calculation result in this paper is −41.92 °C–−10.13 °C. If the value is unified according to the specification, it is obviously too rough, and the design of composite girder jointless bridges in most areas of southern Inner Mongolia, China will be too conservative, while the temperature effect in the design of jointless bridges in northern Inner Mongolia, China will be seriously underestimated.

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Fig. 6. Minimum effective temperature extremum contour map.

Fig. 7. Climate Zoning Map in General Specifications for Design of Highway Bridges and Culverts.

Table 3. Comparison of effective temperature results. Effective temperature Chinese specifications Results of this paper Value range

Maximum difference 8.61 °C

T e,max

39 °C

37.46 °C–46.07 °C

T e,min

−32 °C

−41.92 °C–−10.13 °C 31.79 °C

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Y. Zhang

5 Conclusions In this paper, the regional difference of effective temperature of steel-concrete composite beam bridge is studied by using historical meteorological data. The following conclusions can be drawn: (1) The meteorological data was employed to calculate the bridge temperature field, and the extreme value of bridge temperature can be obtained through the most unfavorable value of long-term meteorological data, which is more reasonable. (2) The effective temperature of composite girders is significantly influenced by climate and environment. The maximum effective temperature and the minimum effective temperature in Inner Mongolia, China range from 37.46 °C to 46.07 °C and − 41.92 °C to −10.13 °C, respectively. The regional differences reach 8.61 °C and 31.79 °C, and the minimum effective temperature has greater regional difference. (3) According to Chinese highway specifications, it is unsafe to consider the temperature effect in most areas of Inner Mongolia, China. The isotherm diagram in this paper can directly show the regional distribution law of the effective temperature extremum of composite girder bridge. The effective temperature extremum in the region between different isotherms can be obtained by linear interpolation.

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12. Xue, J., Li, Z., Lin, J., et al.: Influence of initial temperature computing method on temperature distributions of concrete box girders. J. Guangxi Univ. (Nat. Sci. Ed.) 46(5) (2021) 13. JTG D60-2015, General Specifications for Design of Highway Bridges and Culverts. China Communications Press, Beijing (2015)

Geotechnical Engineering and Engineering Geology

Dynamic Response Analysis of Rock Slope with Weak Layer Based on DOE Method Ke Yang1,2(B) and Ke Yin1,2 1 College of Civil Engineering, Chongqing University, Chongqing 400045, China

[email protected], [email protected] 2 Key Laboratory of New Technology for Construction of Cities, Ministry of Education,

Chongqing University, Chongqing 400045, China

Abstract. The study of dynamic response of rock slope with soft layer is always an important subject in slope stability. In order to further explore the feature of weak layer to the influence of the dynamic response of rock slope in the engineering background of Daguangbao Slope, slope model is established by means of FLAC3D and design scheme using the DOE methods. The effects of Angle, Thickness, Elastic-Modulus, Tensile-Strength, and Poisson’s Ratio of the soft layer on the PGA amplification of slope top are investigated, as well as their relevance. ANOVA method is used to analyze the data, and it is concluded that the Angle, Thickness and Elastic-Modulus of soft layer have significant influence on the amplification effect of slope, and the significance degree is Angle > Thickness > Elastic-Modulus. In addition, within a certain range, the slope acceleration amplification coefficient increases as the inclination angle increases and reduces as the thickness and elastic modulus increase. Simultaneously, the interaction between dip Angle and Thickness, Elastic-Modulus, and Tensile-Strength influences the amplification impact of rock slope to a degree. When the inclination Angle is small, the PGA amplification coefficient decreases with the increase of Thickness, Elastic-Modulus and Tensile-Strength. When the Elastic-Modulus is large, the amplification coefficient decreases with the increase of Tensile-Strength. Keywords: Weak layer · Dynamic response · DOE · Analysis of variance · PGA amplification factor

1 Introduction Seismic activity occurs frequently and with great severity in China. Because China is located between the circum-Pacific seismic belt and the Eurasian seismic belt, which are the two largest seismic zones in the world, and is compressed by three major plates (the Pacific plate, the Indian plate and the Philippine Sea plate), seismic fault zones are developing rapidly. Therefore, China is one of the earthquake-prone countries in the world [1]. According to statistics, the Wenchuan earthquake in Sichuan produced K. Yang—Research Fund for Doctoral Programs of Higher Education Institutions of the Ministry of Education (20110191110027). © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 181–195, 2023. https://doi.org/10.1007/978-981-19-4293-8_20

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more than 20,000 to 30,000 landslides and collapses, affecting an area of more than 100,000 km2 and resulting in massive losses of life and property. Weak intercalation is a type of weak structural plane or weak zone that exists in the rock (soil) body and has weak physical qualities and a particular thickness. It has a negative impact on slope stability during earthquake conditions due to its weak elastic modulus and poor strength [2, 3]. Tang Yunbo et al. [4] investigated the slope response law by loading seismic waves under various working conditions and found that the weak layer increased slope response and the risk of slope failure during earthquake activity. For bedding rock slope, Feng Zhiren et al. [5] studied that the horizontal acceleration amplification coefficient of slope increases with the increase of elevation, seismic wave amplitude and frequency, while the impact of seismic duration can be ignored. Du Xiaoli et al. [6] used finite element analysis software to show that there is a direct relationship between structural plane inclination Angle and slope stability under earthquake action, it means that there is a critical Angle of 50° at which the slope enters a state of limit equilibrium. The dynamic response characteristics of the layered slope under seismic action were studied using FLAC3D software by Song Danqing et al. [7], who concluded that the weak interlayer caused local amplification in the propagation of seismic waves in the slope, and the topmost weak interlayer was a potential slip plane. Huang Runqiu et al. [8] simulated the impact of elastic-plastic parameters of concealed weak interlayer on seismic wave amplification, and concluded that interlayer amplification is mainly related to wave velocity. It can be seen that the soft layer has a great influence on the dynamic response of rock slope, and there are many factors. However, few scholars systematically analyze the characteristics of the soft layer on the dynamic response of rock slope. One of the main reasons is that the experimental design for studying multi-factor influence is complex and time-consuming. Design of Experiment (DOE) is a statistical technique used to quickly optimize the performance of a system with known input variables, which can be used to analyze the significance of the influence of multiple factors and the interaction between factors concisely and effectively [9, 10]. Therefore, the introduction of DOE experimental design method can not only simplify the test and reduce the time cost, but also evaluate the significance of each factor and the influence of the interaction between factors on the dynamic response of slope. In this paper, taking the Daguangbao slope in Wenchuan as the geological reference, using the DOE experimental design method and the FLAC3D numerical simulation software, the dynamic response of the consequent weak layer rock slope is simulated under the conditions of different dip angles, thicknesses, tensile strengths, elastic moduli and Poisson’s ratios of the weak layer. Analysis of variance (ANOVA) was used to evaluate the influence of different factors and their interactions on the amplification coefficient, and the influence weight of each factor was obtained. At the same time, regression analysis was used to obtain the fitting relationship between the factors and the output variables.

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2 Geological Background In the heart of the Longmenshan fault zone, the Daguangbao landslide is located in Gaochuan Township, Anxian County, Sichuan Province. Nearly two kilometers of bedding slip surface can be seen in the Daguangbao area after the earthquake, making it the greatest landslide in the Wenchuan earthquake. Huang Runqiu et al. [11] made a detailed study of the geological conditions of the Daguangbao slope and found that the position of the main sliding surface on the south side of the landslide was obviously layered and controlled by the interlayer fault zone with a dip Angle of about 30°, which nearly ran through the whole slide source area, as shown in Fig. 1. The direction indicated by the landslide scratches distributed on the upper part of the sliding surface is consistent with the direction indicated by the macroscopic characteristics of the landslide, which indicates that the landslide slides out along the strike direction of the dislocation zone. Hence, the existence of the interlayer dislocation zone is an important factor for the formation of the landslide.

Fig. 1. Daguangbao slope strata [12].

Stratum A and Stratum B in Fig. 1 are both dolomites. Stratum A is mainly massive algae-rich dolomite, while Stratum B is mainly massive microcrystalline dolomite. Stratum C is a weak layer with a thickness of about 5 m. The angle between the rock surface and the horizontal plane is nearly 30°. According to previous studies and in combination with the geological conditions of the Daguangbao slope, the main physical and mechanical parameters of the rock strata are shown in Table 1.

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K. Yang and K. Yin Table 1. Main physical and mechanical parameters of rock strata [4].

Category

Density/(kg · m−3 )

Elasticity modulus/Pa

Poisson’s ratio

Internal friction angle/ (°)

Cohesion/MPa

Tensile strength/MPa

Stratum A

2700

5e9

0.2

45

1.0

15.0

Stratum B

2500

2e9

0.2

34

0.5

3.0

Weak layer

1900

1e8

0.25

28

6.0

2.5

3 Model Establishment and Preliminary Analysis Due to the complex topography and geomorphology of Daguangbao, a generalized analysis model based on the geological parameters of the Daguangbao slope is established in order to focus on the study of the influence of weak layer characteristics on the dynamic response of rock slope, as shown in Fig. 2.

Fig. 2. Slope model and distribution of measuring points (unit: m).

The length of the model is 250 m, the height of the slope is H = 50 m, and the slope angle is 60°. The physical and mechanical parameters of stratum A and stratum B are based on Table 1. The weak layer is located between rock A and rock B. The thickness of the medium weak layer is 5 m, the angle with the horizontal plane is 30°. From the top of the slope to the bottom, 5 measuring points are arranged in the vertical direction, and the distance between the measuring points is 10 m. At the same time, the measuring point A0 is arranged at the bottom so as to record the horizontal acceleration and ensure that it is consistent with the input seismic wave.

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The model is established by FLAC3D, and the Mohr-Coulomb constitutive model is used for the elasto-plastic characteristics of rock mass. In the dynamic simulation, the static boundary and the free field boundary are used as the boundary conditions, it means that the static boundary is applied at the bottom of the model, and the free field boundary is applied around the model. Rayleigh damping with a critical damping ratio of 0.05 is applied at the same time. In order to truly simulate the seismic response of rock slope with weak layer under the action of earthquake, the EW-direction Wenchuan earthquake wave is selected to carry out horizontal loading, the duration of the earthquake wave is 20 s, and the acceleration amplitude is 2 m/s2 . After filtering and baseline correction, the earthquake time history is converted into stress time history and applied to the bottom of the model. By comparing the acceleration time history at the bottom of the model with the input seismic wave, as shown in Fig. 3. The obtained results are basically consistent, indicating that the model establishment and the application of ground motion load are correct.

Fig. 3. The acceleration time-history curves of Wenchuan seismic wave and A0 measuring point.

The amplification factor is the key metric for analyzing the slope’s dynamic amplification impact. Perform preliminary analysis on the original model to obtain the change relationship of the measuring point’s acceleration, velocity, and displacement amplification factor along the elevation, as shown in Fig. 4. As different working conditions are involved in the follow-up, the amplification factor is defined as the ratio of the peak value of each measuring point’s acceleration, velocity, and displacement time history curve to the peak value of the corresponding time history curve of the base, in order to ensure the accuracy and consistency of the output results.

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a. Acceleration

b. Speed

c. Displacement Fig. 4. The acceleration, velocity and displacement amplification coefficients of point A vary along the elevation.

It can be seen from Fig. 4 that under the action of seismic waves, with the increase of elevation, the acceleration, velocity and displacement amplification coefficient are all increasing, and they all reach the maximum at the top of the slope. The PGA, PGV and PGD coefficients increase rapidly from the measuring point 4 to the measuring point 3, that is, between the height of 70 m and 80 m, which indicates that the dynamic response of the soft layer and its upslope body is greatly increased because of the mechanical characteristics of the soft layer with small modulus and low strength and the position characteristic between two intact rock blocks. According to the elastic theory, the seismic wave will have a strong reflection and refraction in the slope body due to the shape of the slope and the presence of the weak layer, resulting in energy accumulation in the slope body, particularly in the rock mass above the weak layer, making the slope above the weak layer more vulnerable to damage. The landslide mechanism on the Daguangbao slope along the interlayer dislocation zone under seismic action is consistent with this phenomenon.

4 Design of Experiment 4.1 Introduction to DOE Method The Design of Experiment (DOE) method can provide an effective scheme and approach to explore the influence of weak layer characteristics on the amplification effect of rock slope, simplify the test and save time as much as possible. DOE is a powerful method for data collection and analysis, including not only orthogonal design, full factorial design,

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it also includes the scientific and effective processing of analyze data by using methods such as analysis of variance (ANOVA) after the test is completed. As a branch of applied statistics, it involves planning, running and controlling the test and using statistical tools to process the analysis results, so as to evaluate the impact of input (X) on result (Y) [13, 14]. Multiple input factors can be studied at the same time using the DOE approach, and the importance of their impacts on output variables can be assessed. In addition, by manipulating multiple inputs, potential interactions between input variables can also be evaluated, which are often easily overlooked in experiments conducted with only one factor at a time. Therefore, the DOE method is more effective than the traditional single factor analysis [15]. 4.2 Design Experiment Targeting. To begin, the issues that experimental design will be used to tackle are identified. The effect of weak layer characteristics on the dynamic response of a rock slope is investigated using an experimental design method in this research. Determine the Response and Select the Factor and Its Level. It can be seen from Fig. 4 that the response laws of slope acceleration, velocity and displacement are roughly the same, and they all reach the maximum at the top of the slope, so the amplification coefficient of rock slope top acceleration response can be selected as the response variable (output variable) to observe the amplification effect of slope. Five factors are selected as input variables: Dip Angle, Thickness, Poisson’s Ratio, Tensile Strength and Elastic Modulus. Each factor is based on geological data of Daguangbao slope, and two levels within the floating range are chosen, and the center point is taken to estimate the test error, so as to enhance the estimation ability of nonlinear response of input variables [16], as shown in Table 2.

Table 2. Factor level table. Level Thickness/m Dip angle/° Elastic modulus/Pa Tensile strength/Pa Poisson’s ratio −1

3

20

0.80E+08

1.00E+06

0.23

0

5

30

1.00E+08

2.50E+06

0.25

1

7

40

1.20E+08

4.00E+06

0.27

Select Experiment Plan. The most appropriate choice for a five-factor, two-level design, ignoring the impacts of cubic terms and above, is a full factorial experiment with 1/2 partial implementation [17]. The test arrangement after coding is shown as Table 3. The simulation test shall be carried out in strict accordance with the test sequence arranged in the table.

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K. Yang and K. Yin Table 3. 1/2 full factorial test table.

Running order

Input variable 1

2

3

4

5

1

−1

1

1

−1

1

2

1

1

1

1

1

3

0

0

0

0

0

4

−1

1

−1

−1

−1

5

1

−1

−1

1

1

6

1

−1

1

−1

1

7

1

−1

1

1

−1

8

1

1

1

−1

−1

9

−1

−1

1

−1

−1

10

−1

−1

−1

1

−1

11

0

0

0

0

0

12

1

1

−1

1

−1

13

1

1

−1

−1

1

14

−1

−1

−1

−1

1

15

0

0

0

0

0

16

−1

1

−1

1

1

17

−1

1

1

1

−1

18

1

−1

−1

−1

−1

19

−1

−1

1

1

1

Conduct Experiments and Collect Data. According to the test arrangement in, the corresponding slope model is constructed for simulation calculation, and the calculation results are presented in the last column of the factor design table, as shown in Table 4.

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Table 4. Factor design table. Running order

Dip angle θ (°)

Thickness H (m)

Poisson’s ratio ν

Tensile strength Rm (kPa)

Elastic modulus E (kPa)

PGA amplification factor β

1

20

7

0.27

1000

120000

3.764

2

40

7

0.27

4000

120000

6.627

3

30

5

0.25

2500

100000

5.500

4

20

7

0.23

1000

80000

2.063

5

40

3

0.23

4000

120000

5.235

6

40

3

0.27

1000

120000

5.210

7

40

3

0.27

4000

80000

7.497

8

40

7

0.27

1000

80000

8.851

9

20

3

0.27

1000

80000

5.666

10

20

3

0.23

4000

80000

5.635

11

30

5

0.25

2500

100000

5.500

12

40

7

0.23

4000

80000

9.957

13

40

7

0.23

1000

120000

6.697

14

20

3

0.23

1000

120000

6.728

15

30

5

0.25

2500

100000

5.500

16

20

7

0.23

4000

120000

2.288

17

20

7

0.27

4000

80000

1.813

18

40

3

0.23

1000

80000

6.320

19

20

3

0.27

4000

120000

5.931

Build Analysis Model and Analyze Data. The intuitive analysis method and the variance analysis method, for example, are two DOE data analysis methodologies. The intuitive analysis method is straightforward and simple to use. It assesses the impact of each element on the response by measuring the range, but it is unable to examine data fluctuations produced by changes in test settings (factor level) [18]. The use of variance analysis in this research allows for a more accurate assessment of the significance of changes in factor levels and interactions between factors on output variables.

5 Analysis of Variance (ANOVA) Analysis of Variance (ANOVA) is a standard statistical method widely used to assess the significance of one or more factors on a variable in a given response [19, 20]. When determining the variability of the data, the goal is to evaluate the contribution of each parameter as well as the two-factor interaction. Standard tables can be used to compute

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and organize the analysis of variance. The table includes the following critical metrics: Sum of Squares (SS), Degrees of Freedom (DOF), Mean Squares (MS) and correlation F-test [21]. Calculated in the following manner: K  A  A2i T2 − ssA = nAi N

(1)

i=1

In the Eq. (1), SS A is the sum of the squares of factor A, KA is the number of the level of factor A, nAi is the number of tests at factor A Level i, Ai is the sum of the results at factor A Level i, T is the sum of all test results. SS e = SS T − (SS A + SS B + . . . )

(2)

SS e is the squared error, and SS T , the sum of the squares of all the observations, is given by: SS T =

N 

yi2 −

i=1

T2 N

(3)

The formulas for calculating DOF and F-test value are: DOF A = KA − 1 FA = MS A =

MS A MS e

SS A SS A = DOF A KA − 1

(4) (5) (6)

When the significance hypothesis test of the factor is true, FA follows an F distribution, so that the P-value can be calculated. When the P value is less than 0.05, it is considered that the factor has a significant impact on the response, and the smaller the P value, the higher the significance, and vice versa. The necessary calculations for the analysis of variance are summarized in Table 5. The results show that the weak layer’s Dip Angle, Thickness, and Elastic Modulus have a significant impact on the PGA amplification factor, whereas the tensile strength and Poisson’s ratio have a smaller impact. Besides, there is a significant interaction between the Dip Angle of weak layer and other three factors: the Thickness, Tensile Strength and Elastic Modulus. The interaction between Elastic Modulus and Tensile Strength also has a significant effect on the PGA amplification factor at the top of the slope. In order to explore the significance of the impact factors more accurately, the known non-significant impact factors in the table were removed to avoid interference, and then the remaining factors were analyzed by ANOVA. The Pareto diagram of factor effect is obtained as shown in Fig. 5. It can be seen that the amplification effect of the slope top is strongly influenced by variations in Dip Angle, Thickness, and Elastic Modulus of the weak layer, with the influence degree being Dip Angle > Thickness > Elastic Modulus.

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Table 5. ANOVA analysis results. Source

Degree of freedom

Sum of squares

Mean square

F value

P value

θ

1

31.6576

31.6576

1848.89

0.000

H

1

2.3726

2.3726

138.57

0.001

ν

1

0.0119

0.0119

0.7

0.465

Rm

1

0.0063

0.0063

0.37

0.587

E

1

1.7705

1.7705

103.4

0.002

θ*H

1

29.9759

29.9759

1750.68

0.000

θ*ν

1

0.0147

0.0147

0.86

0.423

θ*Rm

1

1.4363

1.4363

83.89

0.003

θ*E

1

9.5945

9.5945

560.35

0.000

H*ν

1

0.0071

0.0071

0.41

0.566

H*Rm

1

0.0708

0.0708

4.13

0.135

H*E

1

0.1049

0.1049

6.13

0.090

ν*Rm

1

0.5364

0.5364

31.33

0.051

ν*E

1

0.0334

0.0334

1.95

0.257

Rm*E

1

1.1680

1.1680

68.22

0.004

3

0.0514

0.0171

18

78.8123

Error Totally

Fig. 5. Factor standard effect Pareto graph.

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The slope of the Angle, Thickness, and Elastic Modulus to the response mean value is larger in the main effect plot of the PGA amplification factor (Fig. 6), indicating that these three weak layer parameters have a greater impact on the amplification effect of the slope top. Furthermore, the amplification effect of the slop top increases with the increase of the angle of the weak layer and reduces with the increase of thickness and elastic modulus within the selected value interval. Factor interaction diagrams as shown in Fig. 7. From Fig. 7a to Fig. 7c, the interactions between the Angle and other three factors: Thickness, Tensile Strength and Elastic Modulus have a great influence on the amplification effect of slope top: when the angle is 20°, the amplification effect of slope top decreases rapidly with the increase of tensile strength and elastic modulus; when the angle is 40°, the effect of high tensile strength on reducing the amplification effect at the top of slope is not significant. It is noteworthy that, when the dip angle of the weak layer is 20°, the amplification factor decreases with the increase of the thickness, while when the dip angle is 40°, the amplification factor increases with the growth of the thickness. Furthermore, Fig. 7d shows that the interaction between the elastic modulus and the tensile strength is also sensitive. A lower amplification effect at the top of the slope can be obtained with a high tensile strength and a high elastic modulus, while an increase in the elastic modulus does not significantly reduce the amplification factor when the tensile strength is low.

Fig. 6. Main effect diagram of PGA amplification factor.

Regression analysis is a method of statistical inference to study the possible correlation between variables. In many cases, the input variables cannot be completely determined with the response variables, yet there is still a certain quantitative relationship in the sense of statistical average [22]. Therefore, after obtaining the experimental residual data, the relationship between the response and the input variables can be fitted

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193

Fig. 7. Factor interaction diagram.

linearly, and the link between the response and the factors can be determined using the regression model. Y = b0 +

k 

bi Xi +

k 

i=1

bij Xi Xj + εi

(7)

ij

where b0 is the intercept of the model and is the overall mean of all test results, bi and bij are the coefficient values of the linear and interactive terms, respectively, Xi is the input variables (θ, H, ν, Rm, and E), Y represents the response result (β). The fitting equation is shown in Eq. (8). The regression model is only an approximation of the response based on the input design parameters. β = − 2.43 + 1.736e−1 θ − 1.856H + 12.4ν + 1.925e−3 Rm + 1.04e−4 E + 6.844e−2 θ × H − 1.51e−1 θ × ν + 2e−5 θ × Rm − 4e−6 θ × E − 5.27e−1 H × ν − 2.2e−5 H × Rm − 2e−6 H × E − 6.1e−3 ν × Rm + 1.11e−4 ν × E − 1e−8 Rm × E

(8)

Curves of numerical and regression responses are shown in Fig. 8. The estimated value of the response is quite near to the numerical simulation value, demonstrating that the estimation model is essentially effective. This relationship can be used to estimate the amplification effect at the top of the slope for slopes with similar physical properties.

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Fig. 8. Simulated versus regression response plot.

6 Conclusion (1) The Daguangbao slope is used as the geological background in this research to investigate the impact of weak layer features on the dynamic response of a rock slope. It is discovered that due to the presence of the weak layer, the acceleration, velocity, and displacement amplification coefficients at the weak layer position increase dramatically, and continue to increase as the slope height increases, reaching a maximum at the top of the slope. (2) The dynamic response of rock slope with different Dip Angles, Thicknesses, Elastic Modulus, Tensile Strengths and Poisson’s Ratios was simulated by DOE method, and the experimental results were analyzed and evaluated by ANOVA method. The results show that the Dip Angles, Thicknesses and Elastic Modulus of the weak layer have a significant effect on the amplification of the slope. The importance degree is Dip Angle > Thickness > Elastic Modulus; In the range of the values taken in this paper, the amplification factor increases with the increase of the dip angle of the weak layer, but decreases with the increase of its thickness and elastic modulus. (3) The interaction between the Dip Angle and other three factors: Thickness, Elastic Modulus and Tensile Strength, and the interaction between elastic modulus and tensile strength have significant effects on the amplification effect of slope. When the dip angle is 20°, the amplification factor of PGA at the top of the slope decreases rapidly with the increase of thickness, elastic modulus and tensile strength. When the elastic modulus is 40°, the amplification factor decreases rapidly with the increase of tensile strength. (4) The relationship between the characteristic factors of the weak layer and the acceleration amplification factor of the slope top was determined using regression analysis; however, because the acceleration amplification factor is related to slope shape, slope height, and other factors, the relationship is not universal, and only applies to similar slopes.

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The Influence of Soil Parameters on the Bearing Performance of Super-Long Bored Pile Foundation Xuefeng Zhang(B) Research Institute of Highway Ministry of Transport, M.O.T, Beijing 100088, People’s Republic of China [email protected]

Abstract. With the rapid development of the transportation industry, the number of highway and bridge constructions is huge, and the super-long bored pile foundation is widely used. Because the super-long bored pile foundation is different from ordinary pile foundations, the loading conditions of the tested piles are limited. The ultimate bearing capacity of super-long bored pile foundations can be obtained through load test methods. Therefore, the bearing performance of super-long bored pile foundations has always been a difficult point in engineering construction, and the safety of bridge foundations is the foundation of the safe operation of highways and bridges. In this paper, the large-scale numerical analysis software ANSYS is used to calculate and analyze the stress of the super-long pile under the vertical load, and to study the influence of the soil parameters on the bearing performance of the super-long bored pile foundation. Keywords: Super long bored pile · Ultimate bearing capacity · Soil parameters · Numerical analysis

1 Introduction With the vigorous development of China’s road transportation, a large number of road bridges have been built across the country, some of which are large bridges across bays and rivers, which are essential to ensure the smooth flow of road transportation [1, 2]. More and more bored pile foundations with convenient construction and high bearing capacity are adopted for their foundations. Both pile length and pile diameter have made great breakthroughs [3]. Pile foundations with a diameter of more than 2 m and pile lengths of more than 60 m have been used in these foundations. It is widely used in large bridges. Due to the lack of research on the bearing performance of super-long piles, there are hidden safety hazards or cost waste in foundation projects [4–6]. This paper uses the finite element software ANSYS to study the influence of soil parameters on the bearing performance of super-long bored pile foundations, which provides an important reference for the design, detection and treatment of super-long pile foundations of highway bridges. The Special Fund of Chinese Central Government for Basic Scientific Research Operations in Commonweal Research Institutes (2021-9072a). © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 196–201, 2023. https://doi.org/10.1007/978-981-19-4293-8_21

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2 Simulation of Soil Parameters Rock, soil, concrete and other materials are all granular materials. The yield strength of such materials under compression is much greater than the yield strength under tension, and the particles will expand when the material is sheared [7–9]. The commonly used VonMises yield criterion is not suitable for this type of material. In soil mechanics, the commonly used yield criterion is Mahr-coulomb criterion [11]. Another strength criterion that can more accurately describe this type of material is the Drucker-Prager yield criterion [12, 13]. Materials using the Drucker-Prager yield criterion are referred to as DP materials. In the finite element analysis of rock and soil, the use of DP material can get more accurate results [14–16].

3 The Influence of Soil Cohesion C For the convenience of calculation and analysis, an ultra-long pile foundation with a pile length of 60 m, a pile diameter of 2 m, and the soil around the pile as the same soil is selected for spatial finite element simulation calculation and analysis, and the soil cohesion C is 0 kPa, 1 kPa, 3 kPa, 6 kPa, 60 kPa. The Q-S curves of pile foundations with different soil cohesion C values are shown in Fig. 1.

Fig. 1. Q-S curve of pile foundation (C = 60 kPa)

It can be seen from Fig. 1 that the soil cohesive force C value increases from 0 to 1 kPa, and the ultimate bearing capacity of the pile foundation increases rapidly; the soil cohesive force C value increases from 1 kPa to 3 kPa and the ultimate bearing capacity of the pile foundation increases slightly.; The soil cohesion C value increases from 3 kPa to 60 kPa, the ultimate bearing capacity of pile foundation increases slightly. Figure 2 and Fig. 3 show the pile foundation settlement diagrams corresponding to the ultimate bearing capacity of the pile foundation with different soil cohesion C values:

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Fig. 2. Settlement diagram of pile foundation (C = 0)

Fig. 3. Settlement diagram of pile foundation (C = 60 kPa)

4 Influence of the Stiffness of the Pile Side Soil In this paper, a three-dimensional finite element simulation of a pile with a soil depth of 60 m and a pile diameter of 1.0 m is carried out. The shear modulus of the soil on the side of the pile is taken as: 1 MPa, 10 MPa, 50 MPa, and 100 MPa. Figure 4 shows the PS curves corresponding to different pile side shear moduli.

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Fig. 4. Q-S curve of pile foundation of different pile side soil (L = 60 m)

It can be seen from the Fig. 4 that changing the shear stiffness of the pile side soil has a significant impact on the bearing capacity of the pile foundation and the settlement of the pile foundation: with the increase of the pile side soil shear stiffness, the bearing capacity of the pile foundation also increases Especially when the pile-side soil shear modulus increases from 1 MPa to 10 MPa, the ultimate bearing capacity of the pile foundation increases more; the pile-side soil shear stiffness increases and the pile foundation settlement value decreases.

5 Influence of Pile Tip Soil Stiffness In order to analyze the influence of the stiffness of the pile tip on the bearing performance of the pile foundation, this paper carries out the spatial finite element simulation analysis on the 20 m pile foundation and the 60 m pile foundation with a pile diameter of 2 m. The calculation results are as follows:

Fig. 5. Q-S curve of pile foundation with different pile tip soil stiffness (L = 20 m)

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Fig. 6. Q-S curve of pile foundation with different pile tip soil stiffness (L = 60 m)

From the calculation results in Fig. 5 and Fig. 6, it can be seen that the bearing capacity of the 20 m pile foundation is more sensitive to the stiffness of the pile tip soil, while the 60 m pile foundation bearing capacity increases slightly with the increase of the pile tip soil stiffness. This is because the 20 m pile foundation The supporting force of the soil at the pile tip contributes a lot to the bearing capacity of the pile foundation, while the force of the 60 m pile-length pile foundation is represented by friction piles, and the supporting force of the soil at the pile tip has little effect on the bearing capacity of the pile foundation.

6 Conclusion Through the above calculation and simulation analysis, the following conclusions can be drawn: (1) The influence of soil cohesion on the bearing performance of the pile foundation: the influence of the soil cohesion C value on the vertical bearing performance of the pile is mainly manifested as the shear strength of the shallow foundation soil varies with the cohesive force C of the soil. The value increases and increases, but it has little effect on the vertical bearing performance of super-long bored piles. (2) The influence of the pile side soil stiffness on the bearing performance of the pile foundation: the pile side soil stiffness has a greater impact on the pile foundation settlement. When the pile side soil shear stiffness increases, the pile foundation settlement will decrease. (3) The influence of the stiffness of the pile tip on the bearing performance of the pile foundation: the vertical bearing capacity of the short pile increases faster with the increase of the stiffness of the pile tip; Increase, the vertical bearing capacity of the pile does not increase significantly.

Acknowledgments. This study was funded by Chinese Central Government for Basic Scientific Research Operations in Commonweal Research Institutes (2021-9072a). The author thank the

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anonymous reviewers and the Editor for their constructive comments and advice, which greatly improved the quality of this paper.

References 1. Lin, K., et al.: Experimental study on long-term performance of monopile-supported wind turbines (MWTs) in sand by using wind tunnel. Renew. Energy 159, 1199–1214 (2020) 2. Yukawa, H., et al.: Mathematical model of long pile synthetic turf for calculating shock attenuation properties in various conditions. Procedia Eng. 112, 16–21 (2015) 3. Arshad, M., O’Kelly, B.C.: Model studies on monopile behavior under long-term repeated lateral loading. Int. J. Geomech. 17(1), 04016040.1–04016040.12 (2017) 4. Shen, Y., Yu, Y., Ma, F., Mi, F., Xiang, Z.: Earth pressure evolution of the double-row longshort stabilizing pile system. Environ. Earth Sci. 76(16), 1–11 (2017). https://doi.org/10.1007/ s12665-017-6907-z 5. Lü, X.-L., Ma, Q., Fang, H.: Model tests on the long-term settlement of pile-net composite structure subgrade for high-speed railways. Yantu Gongcheng Xuebao/Chin. J. Geotech. Eng. 39, 140–144 (2017) 6. Dirkx, R., Dimitrakopoulos, R.: Optimizing infill drilling decisions using multi-armed bandits: application in a long-term, multi-element stockpile. Math. Geosci. 50(1), 35–52 (2018) 7. Ottolini, M., Dijkstra, J., Tol, F.V.: Immediate and long-term installation effects adjacent to an open-ended pile in a layered clay. Can. Geotech. J. 52, 982–991 (2015) 8. Cao, Z., Liu, H.-L., Kong, G.-Q., Zhou, H.: Physical modelling of pipe piles under oblique pullout loads using transparent soil and particle image velocimetry. J. Central South Univ. 22(11), 4329–4336 (2015). https://doi.org/10.1007/s11771-015-2981-0 9. Wang, L.Z., et al.: Effect of consolidation on responses of a single pile subjected to lateral soil movement. Can. Geotech. J. 52(6), 150113073645001 (2015) 10. Long, X.U., Feng, Y., Yao, Y.: Cooling and annealing effect on indentation response of lead-free solder. Int. J. Appl. Mech. 09(4) (2017) 11. Nicolas-Boluda, A., et al.: Intracellular fate of hydrophobic nanocrystal Self-assemblies in tumor cells. Adv. Funct. Mater. (2020) 12. Kogut, J.P., Pilecka, E.: Application of the terrestrial laser scanner in the monitoring of earth structures. Open Geosci. 12(1), 503–517 (2020) 13. Ronduda, H., et al.: A high performance barium-promoted cobalt catalyst supported on magnesium-lanthanum mixed oxide for ammonia synthesis. RSC Adv. 11(23), 14218–14228 (2021) 14. Roland, S., Xiang, L., Pileni, M.P.: N-heterocyclic carbene ligands for au nanocrystal stabilization and three-dimensional self-assembly. Langmuir 32, 7683–7693 (2016) 15. Fourmentel, D., et al.: In-pile qualification of a fast-neutron-detection-system. IEEE Trans. Nucl. Sci. 65, 2443–2447 (2018) 16. Mishra, et al.: Time-dependent settlement of pile foundations using five-parameter viscoelastic soil models. Int. J. Geomech. (2018)

Based on Immersion Study on Bearing Characteristics of Roadway Pillar Under Softening Yugeng Zhang1 , Yawei Zhu2(B) , Heng Zhang2 , and Wenhao Cao2 1 School of Mines Engineering, China University of Mining and Technology, Xuzhou, China 2 School of Civil Engineering, Nanyang Institute of Technology, Nanyang, China

[email protected]

Abstract. In order to study the influence of coal softening on the retention of coal pillar in the working face, taking the mining of 1314 working face in Xiaoyun coal mine as the engineering background, the variation law of coal pillar lateral bearing pressure before and after water softening is analyzed by FLAC3D numerical simulation, and it is determined that platform wide coal pillar should be selected for water soaking coal pillar. Then the excavation of coal pillar roadway with different width is simulated, and the stable coal pillar range of roadway is obtained. Further simulating the mining of the working face, it is obtained that the stress change in the elastic core area in the coal pillar with different widths basically reaches a stable state at 28 M. Combined with the internal stress change of coal pillar in the mining process, the reasonable reserved width of water immersed wide coal pillar is determined to be 28 M. Through the analysis of microseismic evolution characteristics in the mining process of 1314 working face, the stability of water-soaked wide coal pillar in the mining process is verified. This paper provides a reference for the rational design of roadway pillar under the condition of water immersion and softening. Keywords: Water immersion softening · Wide coal pillar design · Roadway pillar · Stress distribution · Microseismic

1 Introduction The research on the bearing characteristics of coal pillar has always been an important research direction in mining science [1–7]. Zhang Jie et al. studied the stability of shallow burial-depth coal pillars and obtained the migration law of overlying stratum in the process of mining under such conditions [8]. Xu Qingyun et al. obtained the initial spatial position of coal pillar instable failure by studying the narrow coal pillar of the entry protection [9]. Zhu Weibing et al. studied the stability of room-type coal pillars and quantitatively presented the relationship between the elastic core zone and the stability of coal pillars [10]. Wu Yongping et al. studied the instable failure characteristics of the long-arm working face (large dip angles) and obtained two types of instable failure for coal pillars on the working face of large dip angles [11]. Zhang Ming et al. studied © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 202–213, 2023. https://doi.org/10.1007/978-981-19-4293-8_22

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the stability of both the shallowly-buried thick and hard rock stratum and the coal pillar structure mode [12], providing guidance for the prevention and control of mine disasters under such conditions. Zhu Defu et al. calculated the instability probability of coal pillars based on the calculation of the plastic zone in the room-type coal pillar, and tested its reliability on the spot [13]. Zhang Xinguo et al. studied the stability of the strip coal pillar on the backfill working face through a filling body monitoring system [14]. It can be seen from the above that the research on the bearing characteristics of coal pillar has become mature at the present stage. However, very few researches focus on the bearing characteristics of the soaked coal pillar. Therefore, this paper takes the unique site conditions as the starting point, and studies the bearing characteristics of the soaked coal pillar through the numerical simulation and the field observation to ensure the safe production of the working face. Meanwhile, it also provides reference for the reasonable design of the entry protection coal pillar in the rock softening conditions after the production of water-inrush mine is resumed.

2 Engineering Background In Xiaoyun Coal Mine, the ground elevation of the 1314 working face is +37.7–+37.9 m, and the working face elevation is −555.9–−665.5 m. Strike length is 955 m, dip length is 219 m, the area is 209,145 m2 , the average coal thickness is 3.2 m, and the average dip angle is 15. The developed igneous rock wall intrudes the dike in the working face, and two scouring and thinning areas of the coal seam are developed in the working face. A water inrush accident broke out in the mine on September 10, 2018, with the maximum water inflow of 1500 m3 /h. The underground coal body is obviously softened by water immersion and the 1314 working face layout is shown in Fig. 1.

1312 Goaf

1314 Worki ng Face

1314 Heade ntry

1314 Tailg

ate

Fig. 1. Working face layout

3 Soaking Influence Analysis of the Entry Protection Coal Pillar in the Working Face In the original design of Xiaoyun coal mine, the 6 m small coal pillar was kept for roadway excavation and the mining of 1314 working face. According to the field measurement, the water content of the coal body in the soaking side of 1314 working nquaface reached

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up to 11%. Based on this, it is considered that the coal body has lost its basic bearing capacity in this area. Therefore, according to the original design, the 6 m small coal pillar was kept for roadway excavation and the roadway cannot bear the pressure of the overlying stratum. Moreover, the coal pillar cannot support the working face in the process of mining. After the coal pillar is crushed, the working face is likely to be affected by unsafe factors such as residual water in the goaf. To ensure the safety, the wide coal pillar must be set up to solve the problem that the 1314 working face cannot produce. The wide coal pillar of the working face should be designed according to site conditions. Because wide pillars waste coal resources and the mining of the working face will form a new bearing pressure zone inside the coal pillar. If the pillar is not wide enough, the bearing pressure peaks on both sides are overlaid. As a result, it will cause the high bearing pressure distribution zone of coal pillars, and the pressure in the middle of the coal pillar is always greater than the original rock stress. Because of the mining disturbance and the stress wave disturbance caused by the rotation fracture of the high stratum over the roof, rock burst accidents are easy to occur in the coal pillar. For this reason, the following section will simulate the evolution law of the coal pillar’s bearing characteristics in order to determine the reasonable reserved width of coal pillars.

4 Evolution Law on the Excavation Stress of the Soaked Wide Coal Pillars 4.1 Numerical Modelling To study the stress response of coal pillars with different widths in the mining, FLAC3D numerical simulation was used, and a similar numerical model was established based on the actual geological conditions of 1314 working face in Xiaoyun coal mine. In the model, the strike-length was 1,080 m, the tendency width was 570 m and the height was 70 m. The thickness of 3 coal is 3.8 m. Physical and mechanical parameters of the rock strata were taken from the rock mechanics test report of the geological borehole in working face 1314, as shown in Table 1. Table 1. M-C criterion mechanical parameters Lithology

Shear modulus /(GPa)

Bulk modulus /(GPa)

Cohesion /(MPa)

Internal friction angle/(°)

Fine sandstone

17.61

8.22

16.9

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0.70

0.7

24

Siltstone

11.80

6.50

5.7

30

Mudstone

7.60

4.70

3.8

35

Tensile strength /(MPa) 6.34 0.53 12.6 2.60

Density /(kg.m−3 ) 2810 1400 2689 1560

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4.2 Simulated Result Analysis Before simulating the excavation, the supporting pressure distribution characteristics of coal pillars on soaked sides should be determined. The simulated lateral stress distribution is shown in Fig. 2. 60 No water effect Underwater influence 50

6.1 m,47 Mpa

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Fig. 2. Lateral stress distribution of the 1312 goaf

It can be known from Fig. 2 that the lateral stress peak before soaking was 47 MPa and the distance from the coal wall was 6.1 m. After soaking, the stress peak of the coal pillar decreased slightly to 45 MPa, about 14.1 m away from the coal wall. It shows that: the stress peak shifted to the deep after the coal strength decreased. In both cases, the influence ranges of the bearing pressure are both 80 m. According to the distribution characteristics of the lateral stress in 1312 goaf, the coal pillar width should be greater than 14 m, but the greater width of coal pillars would cause a waste of resources. Therefore, the wide coal pillar of 1314 working face was set up as the platform-type coal pillar. Therefore, when the coal pillar width was 20, 22, 24, 26, 28 and 30 m, respectively, this paper discussed in detail the distribution characteristics of both internal stress and the plastic zone inside the coal pillar after roadway excavation and the 1314 working face mining. • Roadway excavation stability of coal pillars at different widths With different coal pillar widths, Fig. 3 shows the internal stress distribution curve of the coal pillar after the roadway excavation.

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Fig. 3. Internal stress distribution of the coal pillar at different widths after roadway excavation

It could be known from Fig. 3 that: as the coal pillar width gradually increased from 20 m to 30 m, the stress peak of the coal pillar increased first and then decreased. When the coal pillar was 20 m, the minimum stress peak was 47 MPa. The stress peak reached the maximum 72 MPa when the coal pillar was 24 m. As the coal pillar width continued to increase, the stress peak began to decrease, that is, when the width was 26 m, 28 m and 30 m, the stress peak was 62 MPa, 58 MPa and 55 MPa respectively. Meanwhile, the stress peak value in the coal pillar in the figure was magnified to compare the variation trend of each curve. It could be known from the comparison that: when the coal pillar width was 20 m, 22 m, 24 m and 26 m, the stress curve presented a single peak state, indicating that the bearing pressure of the 1312 goaf side and the roadway side was overlaid to form a high stress area. When the coal pillar width was 28 m and 30 m, the internal stress curve of the coal pillar presented a double peak state, indicating that the lateral stress superposition of both the 1312 goaf and the roadway was relatively small. Therefore, the width of 20 m, 28 m and 30 m were suitable given that the relatively low value of the internal coal pillar stress were selected after roadway formation. Besides avoiding the accumulated high stress in the coal pillar, the stability of roadways and coal pillars should be combined with the plastic zone for comprehensive analysis. In the FLAC3D numerical model, the coal body in the plastic zone can be considered to have been destroyed and the cracks are relatively developed. Therefore, the overall plastic state of the coal pillar should be avoided and the middle should retain a certain elastic core. The internal plastic zone distribution of coal pillars with different widths was shown in Fig. 4.

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(a) coal pillar width 20m

(b) coal pillar width 28m

(c) coal pillar width 30m Fig. 4. Plastic zone distribution of the coal pillar at different widths

It can be seen from Fig. 4 that: when the width was 20 m, plastic failure happened to the whole coal pillar. Considering that the coal body had been soaked in water, the whole plastic coal pillar was likely to cause deformation and the overall instability. When the coal pillar width was greater than 28 m, the elastic zone appeared inside the coal pillar. Therefore, considering the stability of the coal pillar, the coal pillar width should be greater than 28 m. The comprehensive stress analysis results showed that: the pillar width of 28 m and 30 m were more suitable. • Internal stress distribution of coal pillars at different widths during mining The monitoring line layout is shown in Fig. 5. Figure 6 shows the internal stress variation curves of coal pillars at different widths after the mining of the 1314 working face is finished.

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Fig. 5. Monitoring line layout of coal pillar stress during mining 100

90

Peak value in coal pillar

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Vertical Stress/MPa

e Enlarg

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Distance From 1312 Goaf Lateral Coal Wall/m

1314 Goaf 40

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Fig. 6. Internal stress distribution of coal pillars at different widths after the mining of the 1314 working face is finished

It can be seen from Fig. 6 that: as the reserved width increased, the stress distribution in the coal pillar gradually changed from the single peak state to the double peak distribution. Meanwhile, the stress peak value in the coal pillar gradually decreased, but this decrease was not infinite and a stable value existed. Namely, when the pillar width was 28 m, the stress peak was about 60.95 MPa. When the width continued to increase to 30 m, the stress peak was about 60.76 MPa. The results showed that: when the pillar width exceeded 28 m, the increase of the pillar width had no obvious effect on reducing the internal stress concentration of the pillar. Therefore, the reserved width of coal pillar should be 28 m when considering the mining of the 1314 working face. • Coal pillar stability in the whole process of the working face mining During the mining of the working face, when the coal pillar width is 28 m, rock burst accidents are likely to happen under the cumulated influence from the lateral supporting pressure of the elastic core zone in the coal pillar. In order to study in detail the variation trend of coal pillars’ internal stress in different mining stages and test the safety of coal pillars, the monitoring line is set along the coal pillar length, where the starting point of the monitoring is A (the coal pillar length is 0) and the finishing point is B, as shown in Fig. 7. When the extracted distance of the working face is different, the stress distribution law of coal pillars along the length direction is also obtained. Moreover, the stress peak change law of both coal pillars at different distances and the working face at different distances is also obtained, as shown in Fig. 8 and 9.

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Fig. 7. 1314 working face mining and the monitoring line layout of the coal pillar 90

No Mining Mining 200m Mining 400m

Vretical Stress/Mpa

80

Mining 600m Mining 800m

70 60 50 40 30 20 0

200

400

600

800

1000

Coal Pillar Length

Fig. 8. Stress distribution law of coal pillar along the length at different mining lengths

It can be seen from Fig. 8 that: the peak value of internal stress in the coal pillar can reach 37 MPa before mining. The peak value of the coal pillar’s internal stress changed slightly and was basically 67–70 MPa when different distances were extracted on the working face. However, the stress varied greatly in different positions of the coal pillar. The coal pillar with high stress was located on the 1314 goaf side mainly due to the rock caving in the goaf of the 1314 working face. Another reason was that the lateral bearing pressure caused the stress to increase in the coal pillar. For the non-extracted part of the working face, the stress of the adjacent coal pillar section was relatively small.

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Vertical Stress/MPa

70 First

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Weighting

60

Periodic Pressure

55 50 45 40 0

200

400

600

800

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Mining Distance Of 1314 Working Face/m

Fig. 9. Peak value change law of the working face stress and the coal pillars at different mining lengths

It can be seen from Fig. 9 that: when the working face advanced to 0–120 m, the stress peaks in the working face and the coal pillar increased significantly, and then began to decrease. This indicated that: the initial pressure obviously influenced the working face and the coal pillar stress. When the working face continued to advance 140–880 m, the peak values of the coal pillar and the working face showed a periodic fluctuation, which is caused by the periodical pressure of the working face, but the stress didn’t fluctuate greatly. Namely, the influence of the incoming pressure is not obvious. It can be known from the above simulation analysis that: when the coal pillar width is 28 m, the vertical stress of the coal pillar is always at a low level, and no stress concentration is shown in the coal pillar, which can realize the safe mining in the working face and save coal resources.

5 Microseismic Evolution Characteristics During the Working Face Mining in Large Soaked Coal Pillars According to the production experience, the internal stress of the coal pillar is prone to present the high value instability of the stage and it is risky during the initial square and the second square. Therefore, the microseismic data were analyzed by taking the square as the research node. Figure 10 is the microseismic location plan in the dangerous stage of the working face mining.

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(a) microseismic location plan near the initial square of the mining (1.9-2.27)

(b) microseismic location plan near the second square of the mining (5.13-4.13) Fig. 10. Microseismic location plan of the dangerous stage during the working face mining

Around 40 m was selected from the square dangerous zone. Figure 10(a) shows that: microseismic events are mainly minimal energy events in the microseismic location of the initial square stage. Microseismic events are distributed and concentrated near geological structures. It can be seen that the coal pillar is in a stable state in the initial square stage. It could be known from Fig. 10(b) that: microseismic events further decreased in the second square stage of the working face. The roadway on both sides of the coal pillar was excluded, and no cubic events occurred inside the coal pillar. It can be seen that there is no instability failure of the coal pillar in this dangerous stage. It could be known from Fig. 10 that: in the two possible dangerous stages of the coal pillar, the number of events didn’t accumulate inside the coal pillar in the microseismic event plan. It shows that the stability of coal pillar is in good condition and the designed width of the coal pillar is reasonable.

6 Conclusions • According to the actual situation, it is concluded that: in order to ensure the coal pillar stability during the working face mining, the reserved wide coal pillar design should be selected. By studying the lateral bearing pressure distribution of the coal pillar, the selected platform shape of the wide coal pillar was initially determined based on the comprehensive analysis of the soaking influence and the economic benefits in the coal pillar. • By comparing the lateral stress distribution law of the goaf before and after soaking, it can be seen that: the peak value of the lateral stress decreased from 47 MPa to 45 MPa

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after soaking, and the distance from coal wall shifted from 6.1 m to 14.1 m. Therefore, the reserved coal pillar width should be ensured to be greater than 14 m at least. • By comparing the stress peak values and the plastic zone evolution of coal pillars at different widths throughout the 1314 transportation tunneling, it can be seen that: the inner stress of 20-m-wide coal pillars was relatively low, but the overall plastic state may destroy the instability. When the width was 28 m and 30 m, it could ensure the low stress of the coal pillar. Meanwhile, a certain elastic zone existed inside the coal pillar. It is conducive to the coal pillar stability as a whole. • By simulating the 1314 working face mining and reserving coal pillars at different widths, it could be known from the stress changes of the coal pillars that: The peak value of stress in coal pillars decreased gradually with the increase of the width. However, when the width was greater than 28 m, the stress value became stable along with the increase of the coal pillar width. Therefore, the reasonable reserved width of coal pillars should be 28 m, and the coal pillar stability got verified again by simulating different mining stages. • By analyzing the microseismic evolution characteristics of the working face when mining to the initial square and the second square, it could be known that: there were relatively few cubic events in the coal pillar during the working face mining. No abnormality was found during the working face mining, and no instability sign was found in the coal pillar. The designed width of the coal pillar was reasonable.

Acknowledgments. Henan projects of tackling key problems in science and technology & Henan key R&D and promotion projects (tackle key problems in science and technology), Nanyang, 710054.

References 1. Gu, H.L., Tao, M., Cao, W.Z., Zhou, J., Li, X.B.: Dynamic fracture behaviour and evolution mechanism of soft coal with diferent porosities and water contents. Theor. Appl. Fract. Mech. 103, 102265 (2019) 2. Guo, J., et al.: Dynamic mechanical behavior of dry and water saturated igneous rock with acoustic emission monitoring. Shock Vib. 2348394 (2018) 3. Qian, R.P., Feng, G.R., Guo, J., Wang, P.F., Jiang, H.N.: Efects of watersoaking height on the deformation and failure of coal in uniaxial compression. Appl. Sci. 9(20), 4370 (2019) 4. Wang, F.T., Liang, N.N., Li, G.: Damage and failure evolution mechanism for coal pillar dams affected by water soaking in groundwater reservoirs. Geofuids 2985691 (2019) 5. Yin, et al.: Wall rock instability mechanism study of working face across empty roadways. J. Min. Saf. Eng. 35(03), 457–464 (2018) 6. Zhu, et al.: Instable rock burst mechanism study related to the bottom coal’s overall slip in the slicing of the super high seam. J. Min. Saf. Eng. 38(01), 31–40 (2021) 7. Tu, et al.: Study on the overlying stratum structure evolution of the large space islet stope and the reasonable coal pillar width between sections. J. Min. Saf. Eng. 38(05), 857–865 (2021) 8. Zhang, Wang: Study on the isolated coal pillar stability of the shallowly buried interval goaf and the overlying stratum characteristics. J. Min. Saf. Eng. 37(05), 936–942 (2020)

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9. Xu, et al.: Study on the influence of fully intensive mechanized mining on the fracture instability mechanism and control technology of narrow coal pillars. J. Min. Saf. Eng. 36(05), 941–948 (2019) 10. Zhu, et al.: Dynamic instability and disaster mechanism of shallowly buried close-distance coal seam mining and room-type coal pillar groups. J. Coal 44(02), 358–366 (2019) 11. Wu, et al.: Coal pillar instability mechanism in the coal seams with large dip angles based on large range rock strata control technology. J. Coal 43(11), 3062–3071 (2018) 12. Zhang, et al.: Study on the structural model and stability of hard-and-thick strata and coal pillar in shallowly buried mining face. J. Rock Mech. Eng. 38(01), 87–100 (2019) 13. Zhu, et al.: Stability evaluation of coal pillar groups in shallowly buried room-type goaf. J. Coal 43(02), 390–397 (2018) 14. Zhang, et al.: Monitoring study on the stability of the strip coal pillar’s backfilling in the paste backfill mining. J. Coal Sci. Technol. 41(02), 13–15 (2013)

Numerical Study on Spudcan Penetration-Consolidation-Uplift in Soft Soil Using Large Deformation Simulation Taibin Zhang(B) , Jiangtao Yi, Zhen Wang, and Fei Liu School of Civil Engineering, Chongqing University, Chongqing 400045, China [email protected]

Abstract. This paper presents a numerical approach to perform large deformation simulation of spudcan penetration-consolidation-uplift process in soft soil. The coupled pore fluid flow and stress are simulated with large deformation finite element analysis, by using the remeshing and interpolation technology using small strand (RITSS) method in ABAQUS v2016. The surrounding soil is simulated by using modified Cam clay model. The simulation is validated by comparting with centrifuge test results. The calculation results show that the maximum uplift force of spudcan has a linear relationship with the penetration depth, and the negative excess pore pressure at the spudcan invert is almost equal to the hydrostatic pressure. By analyzing the soil velocity vector diagram at the corresponding position of the maximum uplift force at different penetration depths, three failure mechanisms of the soil at the position corresponding to the maximum uplift force are summarized. Keywords: Spudcan · Uplift · RITSS · Excess pore pressure

1 Introduction Jack-up rigs are mostly used for offshore drilling/production activities in shallow water areas down to 120 m depth. Modern jack-up rigs are generally supported by three to four independent truss-type rigs. Below these rigs are independent foundations called ‘spudcan’ [1]. In order to withstand the self-weight and operating load of the jack-up rigs, the spudcan needs to be penetrated to different depths, according to the soil conditions. The penetration depth is usually between 1.0–3.0 times of the spudcan diameter (D). The maximum penetration depth is reported in the Gulf of Mexico, reaching 5.6D, which is 56 m embedment [2]. When the jack-up rigs are moved from the site and redeployed, the spudcan must be uplifted out of the soil. It may take very long time to uplift the deep-penetrated spudcan in soft soil, which will cost lot to the jack-up rig. The uplift of spudcan was widely studied by using experiments and numerical simulations in the past few decades. Craig & Chua [3] conducted a centrifugal model study and believed that the compressive bearing stress prior to uplift exceeded four times the undrained shear strength of the soil will produce suction at the invert. Purwanna [1] simulates the penetration of the spudcan at 1.5D through a centrifuge experiment. During © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 214–220, 2023. https://doi.org/10.1007/978-981-19-4293-8_23

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different operation periods, it proves that there is a suction between the spudcan invert and the soil. The suction under the spudcan increases with the operation time. According to the results of the Particle Image Velocimetry (PIV) technique, the failure mechanism of the uplift of the spudcan is proposed. Zhou [4] developed a finite element model based on Purwana’s centrifuge experiment results to simulate the uplift process of spudcan in soft clay. The spudcan are assumed to be ‘wished in place’, focusing on the invert force, top force and maximum penetration force of the spudcan. Relationship, the maximum uplift force can be calculated through this ratio. Through the centrifuge experiment, Kohan et al. [5] supplemented the simulation of the embedment depth of 1.5-3D and the operation time of 2 years. The conclusion is that the suction at the spudcan invert is increases linearly with the burying depth for the same operation time. To date, the research on spudcan uplift is mainly at a depth of 1.5D, and numerical simulations use ‘wished in place’, in which the installation effect was not considered well. Therefore, this research mainly uses the RITSS method to simulate the penetration of spudcan in soft clay at different depths, and the following operation-uplift process. The relationship between penetration depth and the maximum uplift force of spudcan, and the corresponding velocity vector diagram is analysed to find the failure mechanisms during the spudcan uplift at different penetration depths.

2 Numerical Mode 2.1 RITSS The implementation of RITSS involves five steps [6], show in Fig. 1: (1) generate the initial model, (2) conduct a small Lagrangian incremental step analysis, (3) extract the deformed mesh, node variables (pore pressure, pore ratio, etc.), integral point variables (stress, etc.), (4) generate new soil part based on the old mesh, reposition the boundary conditions and generate a new mesh. (5) The stress and material properties extracted in (3) are mapped from the old mesh to the new mesh. In any subsequent analysis, repeat steps (2)–(5) until the analysis of the whole large deformation is completed. Step (2) use the commercial finite element software ABAQUS v2016. Step (3) step (4) is mainly automated by using python script, and step (5) is conducted by using ABAQUS script command ‘map solution’. 2.2 Finite Element Mesh Because the spudcan is circular in plan and only considers the vertical load, it can be modeled as an axisymmetric, as shown in Fig. 2. By using 0.1D, 0.05D, 0.025D, 0.02D, 0.01D meshes for the soil around the spudcan, it is finally proved that the meshes converge with 0.02D. Using the method of constant displacement uplift, spudcan penetration and uplift at a rate v of 0.3 mm/s. Each cycle step in the RITSS process is uplifted by 0.05 m.

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Fig. 1. RITSS procedure

Fig. 2. Finite element model and boundary conditions.

2.3 Soil Parameters The soft soil is simulated as modified Cam-clay constitutive model, and the parameters presented in the paper by Kohan et al. [5] is adopted here, as listed in Table 1. Table 1. Properties of kaolin clay. Liquid limit (LL)

61%

Plastic limit (PL)

27%

Specific gravity (Gs)

2.6

Effective unit weight (γ )

6.0 kN/m3

Angle of friction (φ )

23°

Effective Poisson’s ratio, υ

0.33

Slope of isotropic virgin compression line, λ

0.205

Slope of swelling/recompression line, κ

0.044

Consolidation coefficient, cv

3.99 m2 /year

Void ratio at p = 1 kPa on VCL, eN

2.14

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3 Validation of the Program The uplift of the spudcan with penetration depths of 1.5D and 2.5D and operation time of 2 years is simulated, and the calculation results of the uplift pressure resistance (q) and the invert excess pore pressure (ui) are shown in Fig. 3. The comparation of the calculation results and the values measured in the centrifuge tests by Kohan, shows good consistency. Table 2 shows the spudcan penetration bearing capacity coefficient Nc defined by Hossain [7], being approximately 12.0. These values are found to agree closely with the current experimental and numerical results, which proves that it is feasible to change the numerical simulation method.

0

50

100

q(kPa)

150

200

0

H(m)

3 6

kohan-1.5D

kohan-2.5D

RITSS-1.5D

RITSS-2.5D

9

12 15

(a)

18 -150

-100

Δui (kPa)

-50

0 0

kohan-2.5D

RITSS-1.5D

RITSS-2.5D

3 6 9

H(m)

kohan-1.5D

12 15

(b)

18

Fig. 3. Comparison results from finite element model and centrifuge tests, (a) q, (b) ui .

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T. Zhang et al. Table 2. Summary of simulations results.

H [m]

uiu [kPa]

utu [kPa]

H/D [-]

Qp.max [MN]

Nc [-]

Qu.max [MN]

4.50

0.75

1.99

11.57

1.52

−53.14

12.87

6.00

1.00

2.55

11.62

2.23

−69.22

19.89

7.50

1.25

3.13

11.62

2.92

−82.17

27.44

9.00

1.50

3.72

11.78

3.70

−98.03

40.58

10.50

1.75

4.33

11.91

4.43

−110.99

52.60

12.00

2.00

4.92

12.03

5.16

−123.52

66.20

15.00

2.50

6.13

12.25

6.47

−143.30

95.31

18.00

3.00

7.29

12.26

7.67

−163.27

119.08

21.00

3.50

8.46

12.29

8.82

−183.42

140.71

24.00

4.00

9.62

12.29

9.90

−220.93

165.72

4 Results and Discussion 4.1 Spudcan Penetration Force, Uplift Force and Excess Pore Pressure The RITSS method is used to simulate the penetration of the spudcan into different depths-after the complete consolidation-uplifting. The results are shown in Table 2. The embedment ratio is the penetration depth (H) divided by the diameter (D) of the spudcan, the penetration force is Qp , the uplift force is Qu , and the maximum uplift force corresponds to the excess pore pressure (relative to the hydrostatic pressure) at the spudcan invert and top is uiu and utu . It can be observed that Qu.max , uiu and utu increases linearly with penetration depth. And the decrease in excess pore pressure at the invert is close to the hydrostatic pressure during the uplift process. 4.2 Uplift Failure Modes The diagrams of the soil velocity vector at the position of the maximum uplift force show there are three different uplift failure modes, corresponding to the penetration depths, as shown in Fig. 4. When spudcan penetrates shallow (≤1.5D), the failure of the surrounding soil is mainly above the spudcan to form a slip, as shown in Fig. 4(a) by taking the penetration depth 0.5D as example. Oppositely, when the spudcan penetrates deep (≥3.5D), the failure of the surrounding soil is only around the spudcan to form a local flow, as shown in Fig. 4(c) by taking the penetration depth of 4D as example. When the penetration depth is between 1.5D and 3.5D, the failure of the soil is at the side and above spudcan to form a sliding surface, as shown in Fig. 4(b) by taking the penetration depth of 2D as example.

Numerical Study on Spudcan Penetration-Consolidation-Uplift in Soft Soil

(a)

219

-18 -19 -20 -21

y(m)

-22 -23 -24 -25 -26 -27

0

1

2

3

4

5

6

x(m)

(b)

(c)

Fig. 4. Three uplift failure mechanisms, (a) shallow embedment, (b) intermediate embedment, (c) deep embedment.

5 Conclusion In this paper, the RITSS method is used to simulate the spudcan penetration-operationuplifting process. It is found that the maximum uplift force and the penetration depth have a linear relationship after the spudcan penetration and fully consolidation. The simulation also illustrates the three uplift failure modes at the position of the maximum uplift force corresponding to different penetration depths.

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References 1. Purwana, O.A., Leung, C.F., Chow, Y.K., Foo, K.S.: Influence of base suction on extraction of jack-up spudcans. Geótechnique 55(10), 741–753 (2005) 2. Menzies, D., Lopez, C.R.: Four atypical jack-up rig foundation case histories. In: 13th International Conference, The Jack Up Platform (2011) 3. Craig, W.H., Chua, K.: Extraction forces for offshore foundations under undrained loading. J. Geotech. Eng. 116(5), 868–884 (1990) 4. Zhou, X.X., Chow, Y.K., Leung, C.F.: Numerical modelling of extraction of spudcans. Geótechnique 59(1), 29–39 (2009) 5. Kohan, O., Gaudin, C., Cassidy, M.J., Bienen, B.: Spudcan extraction from deep embedment in soft clay. Appl. Ocean Res. 48, 126–136 (2014). https://doi.org/10.1016/j.apor.2014.08.001 6. Tian, Y.H., Cassidy, M.J., Randolph, M.F., Wang, D.: A simple implementation of RITSS and its application in large deformation analysis. Comput. Geotech. 56, 160–167 (2014) 7. Hossain, M.S., Randolph, M.F., Hu, Y., White, D.J.: Cavity stability and bearing capacity of spudcan foundations on clay. In: Proceedings of the Offshore Technology Conference (2006)

Effects of Rock Mass Deterioration Induced by Wetting-Drying Cycles on Slope Stability of Reservoir Banks Zijuan Wang1(B) and Xinrong Liu2 1 School of Management Science and Engineering, Chongqing Technology and Business

University, Chongqing 400067, China [email protected] 2 College of Civil Engineering, Chongqing University, Chongqing 400045, China

Abstract. In view of the degradation of the rock mass mechanical parameters of the reservoir bank slope fluctuation zone caused by rainfall and the rise and fall of the reservoir water level, the moderately weathered sandstone of a slope in the Three Gorges reservoir area was selected as the research object. The “saturated” sandstone was subjected to Brazilian split test, uniaxial and triaxial compression tests. The test results show that the mechanical parameters of sandstone in the “dry” state are greater than those in the “saturated” state under the same number of dry-wet cycles (n); The uniaxial compressive strength, elastic modulus, tensile strength, cohesion, and internal friction angle of sandstone decrease logarithmically with the increase of n, and the Poisson’s ratio increases with the increase of n. The effects of dry-wet cycles have different degrees of degradation of different mechanical parameters of sandstone. As the number of cycles (n) increases, the envelope of the M-C rule in the π plane gradually moves to the center of the circle. In this paper, the M-C yield criterion of sandstone in two water-bearing states under different dry-wet cycles is revised. Sandstone is used as the representative rock mass, and the water-rock interaction of the reservoir bank slope rock mass under the condition of reservoir water fluctuation is simulated through experiments. During the process, FLAC3D was used to carry out a numerical simulation of bank slope stability under the action of water-rock circulation, which provided a useful basis for the stability analysis of reservoir bank slopes. Keywords: Wetting-drying cycle · Modified Mohr-Coulomb criterion · Water level fluctuation in reservoir regions · Safety factor

1 Introduction Among previous commonly reported geological disasters, landslides account for the largest proportion (over 50%) and also impose the severest damages upon life and property. Rainstorms, reservoir filling, volcanic activities, earthquakes, etc. can all induce landslips, whereas more than 80% of them are related to the influence of water. Effects of water stored in reservoirs, rainfall and groundwater infiltration are the primary reasons for slope failure of reservoir banks, which has direct impacts on life and property, © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 221–240, 2023. https://doi.org/10.1007/978-981-19-4293-8_24

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landscapes and cultural relics, shipping, and railways and roads [1–4]. The deterioration grows with the increase in dry-wet cycles in a cumulative manner, which is characterized by the minor variation in each cycle and yet non-linear accumulated growth after repeated cycles. As it evolves gradually, the slope stability reaches the critical state and the geological disaster follows [5–9]. Rock is a heterogeneous, porous and defect-rich material formed by a variety of minerals after a long period of geochemical action. The heterogeneity of the rock makes the overall strength of the rock much lower than the strength of its constituent mineral materials, and its porous and multi-defect characteristics further reduce the strength of the rock greatly. The mechanism of rock deterioration under the action of aqueous solution is extremely complicated. Many scholars have done meticulous work in this field. Through the efforts of experts from all over the world, we have gained a certain understanding of the effects of dry and wet cycles on the micro-structure and deterioration of soil and concrete. However, the influence of dry-wet cycles on the change law of rock mechanical parameters and damage characteristics is mainly analyzed by fitting experimental data, leaving room for further research on the mechanism of rock degradation [10–12]. With regard to the study of the dry-wet cycle of rocks, Deng et al. [13, 14] conducted a more in-depth study on the macroscopic degradation law and the secondary porosity change law of the reservoir bank slope rock mass under the action of long-term immersion-air-drying cycle. Liu et al. [15, 16] systematically studied the macro-physical and mechanical parameters and meso-parameter degradation laws of sandstone under the action of neutral and acidic dry-wet cycles. Xiong et al. [17] conducted Brazilian splitting, uniaxial compression and conventional triaxial compression tests on sandstone, sandy mudstone and mudstone under free and saturated conditions, and found that saturation has the strength and deformation characteristics of the three types of rocks. Mudstone has the most obvious effect of varying degrees, followed by sandy mudstone and sandstone. Ding et al. [18] analyzed the test results of rock specimens corroded by different chemical solutions and showed that under the action of chemical solution corrosion, the connection between mineral particles was disturbed, and the particles were corroded at the same time, which significantly reduced the strength of the rock and caused damage to the rock structure. Li et al. [19] studied the main cement components of calcareous cemented sandstone under different pH environments, and proposed a rock chemical damage strength model that can be applied to acid solutions. The results show that the tensile strength of sandstone decreases logarithmically as the number of cycle increases, and the strength decreases after water saturation, and the strength recovers after drying. It also shows that under the influence of wet and dry cycles, the tensile strength of saturated samples decreases faster than that of samples immersed in water for a long time. Roetting et al. [20] studied the changes of porosity, permeability, water retention curve, and reaction surface during the dissolution of carbonate. Critelli et al. [21] studied the dissolution rate of the mineral actinolite and chlorite in metabasalt at a temperature of 25 °C and a pH of 2–12, and found that the dissolution rate of the main constituent minerals in multiphase rocks Not affected by other existing minerals. In nature, in addition to continuous aqueous solution soaking, part of the rock mass is still under continuous dry-wet cycles, and this part of the rock mass area happens to be

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the most prone to engineering failure, so we study the dry-wet cycle The mechanism of later rock deterioration is particularly important. At present, the research on the macro- and meso-mechanical test methods and cumulative damage and degradation mechanisms of rocks under the action of dry-wet cycles is still very weak, and many factors need to be considered (rocks with different mineral compositions, different pH aqueous solutions, different sizes, and different dry and wet Cycle process, different loading methods, etc.). Most of the researches are based on the appearance analysis of the results of the macro and meso-scale test data. It is concluded that the mechanical parameters of the rock sample change with the number of cycles. There is little analysis of the macro- and microscopic damage mechanism of the slope rock mass under the action of the dry-wet cycle [22, 23]. In this paper, on the basis of indoor test physical and mechanical performance measurement of sandstone samples, by fitting the test data, the degradation mode of rock mass properties under the influence of dry-wet cycle is obtained. In addition, the rock mass strength under the prescribed Geological Strength Index (GSI) is calculated according to the generalized Hoek-Brown theory, and the reservoir bank slope is numerically simulated for the water level fluctuation zone, and the measures to prevent and control the slope will be analyzed.

2 Experimental 2.1 Experimental Materials The sandstone sample was taken from a rock slope in the fluctuation zone of the Three Gorges Reservoir. The thin layer inspection results show that the sample is mediumfine-grained feldspar sandstone without obvious bedding. Most of the mineral clastic particles are 0.05 mm–0.4 mm in size, with 0.05–0.25 mm clastic grains accounting for about 71% and 0.25 mm–0.4 mm ones, 29%. Particles present sub-angular-sub-rounded shapes, with medium roundness, and are grain-supported and pore-cemented. Contents of minerals of the sample are shown in Table 1. Table 1. Mineral content (Percentage) Quartz

Feldspar

Rock fragment

Calcite

Interstitial material

Heavy mineral

Opaque material

40%

31%

15%

6%

5%

2%

2%

2.2 Experimental Methodology The ZS-100 vertical coring machine in the Geotechnical Laboratory of Chongqing University was used for sample preparation. 50–70 specimens were retrieved from each rock sample. As required by the ISRM-suggested methods for corresponding rock mechanical tests, the specimen was φ50 mm × 25 mm (for the Brazilian disk split test) or

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φ50 mm × 100 mm (for the compression test), with the diameter error less than 0.1 mm and the non-parallelism between the top surface and the bottom surface is less than 0.02 mm (see in Figs. 2a and 2b). Ultrasonic testing and Schmidt hammer measurements were conducted prior to the mechanical test, in order to identify and remove specimens with extreme longitudinal wave velocity and Schmidt hammer-based strength. All specimens were divided into two cases: one is the saturated case under effects of dry-wet cycles; the other is the dry case under effects of wetting-drying cycles. Each group was then divided into six groups, with each having eight specimens (three for 50 × 25; five for 50 × 100). One group in each case was used as the backup and the other seven groups were respectively used in cyclic wetting-drying tests with numbers of cycles n = 0, 1, 3, 6, and 10 using distilled water. In this paper, with regard to the laboratory mechanical testing method of ISRM, the specimen was first kept in a heating oven at 105 °C for 24 h and then kept in an intelligent concrete vacuum-based water saturation instrument for another 24 h, which was also defined as a wetting-drying cycle. Three of 50 × 25 specimens and three of 50 × 100 ones in each group were respectively used for the disk split test and uniaxial compression test. The average value of the three measurements was noted as the uniaxial compressive strength or tensile strength of the corresponding sample. Then, the other two specimens were subjected to pseudotriaxial compression tests with confining pressures of 1 MPa and 6 MPa, respectively, and the peak strengths under different confining pressures were obtained. The split test instrument is AGI-250-kN servo tensile testing machine manufactured by SHIMAZU, a Japanese company (see in Fig. 1c). The loading was controlled using the displacement feedback, the speed was 0.1 mm/min. The instrument for the pseudo-triaxial compression test is a multi-funtional triaxial rock creep testing machine manufactured by the

(a)50*25 mm

(c)AGI-250

(b)50*100mm

(d)TOP INDUSTRIE

Fig. 1. Some samples

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TOP INDUSTRIE, a French company (see in Fig. 1d). The loading was also controlled via the displacement feedback, the speed was 0.01 mm/min.

3 Results and Analyses 3.1 Experiment Results The mechanical parameters of saturated and dry sandstone samples measured under different dry- wet cycles in uniaxial compression test, pseudo triaxial compression test and split test are shown in Table 2. The elastic model adopts the near-straight section of the front peak of the stress-strain curve in the uniaxial compression test of sandstone (between about 30% and 50% of the peak strength), in which the average elastic modulus is based on the measured elastic modulus of the selected section and the corresponding average Poisson’s ratio as the measured Poisson’s ratio. The uniaxial compressive strength (namely the peak strength σ ; abbr. UCS) of dry and saturated specimens versus the number of wetting-drying cycles (n) is plotted in Fig. 2a. It is shown that the UCS of sandstone presents non-linear reduction as n grows. Moreover, the UCS of sandstone in the saturated state decreases faster with n than that of sandstone in the dry state. Also, the UCS falls relatively fast during the early stage of the increase of n, while the reduction slows down in the late stage. The UCS declines from 66.78 MPa in terms of n = 0 (the dry state) to 44.68 MPa in terms of n = 1 (the saturated state), with reduction by 33.09%. However, the UCS grows by 11.21 MPa from 44.68 MPa in cases of n = 1 (the saturated state) to 55.89 MPa in cases of n = 1 (the dry state), with recovery of 33.09%, compared with the initial UCS. This indicates that during a wetting-drying cycle, the strength of the rock sample restores to some extent, as the saturated specimen turns into the dry state, whereas the damage is unrecoverable. Hence, the mechanical parameter of the specimen in the dry state is defined as the base of the damage variable. Similar correlations can be found between the elastic modulus, tensile strength, cohesion and internal friction angle and the number of wetting-drying cycles. The Poisson’s ratio of sandstone specimens in dry and saturated states that have been through varied wetting-drying cycles versus the number of cycles is shown in Fig. 2b. It is illustrated that the Poisson’s ratio is in direction proportion to the number of dry-wet cycles. As the wetting-drying process continuously repeats, the Poisson’s ratio grows constantly, which means the circumferential strain induced by the same axial strain increases and the dilation of the rock sample intensifies. The Poisson’s ratio of saturated sandstone samples climbs up faster with n than that of dry samples, and the growth is relatively fast in the early stage of the wetting-drying-cycling process and gradually slows down. From the variation regularities of a series of physical and mechanical parameters with n, a dimensionless normalized function was obtained using the least square method and is shown below: yn = 1 − j ln(nk + 1) (1) R= y0 where yn represents the mechanical parameter of sandstone in the nth wetting-drying cycle; yn is the mechanical parameter of the initial dry state of sandstone (n = 0); j and k are fitting coefficients, seen in Table 3.

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n

Status

σc /MPa

σt /MPa

E/GPa

c/MPa

ϕ/MPa

μ

0

Drying

66.78

5.99

9.195

11.49

48.80

0.226

1

Wetting

44.68

3.36

6.719

7.22

47.93

0.288

Drying

55.89

5.35

8.540

9.87

46.97

0.246

3

Wetting

35.57

2.81

5.096

5.72

44.61

0.272

Drying

51.89

4.81

7.621

9.04

46.81

0.277

6

Wetting

28.07

2.31

4.096

4.58

41.69

0.302

Drying

45.60

4.47

6.351

8.20

45.57

0.265

Wetting

21.17

1.59

3.068

3.60

40.80

0.320

Drying

35.41

3.89

5.142

6.59

42.13

0.289

10

70 65

drying

60

wetting

UCS (σc)/MPa

55

Drying（Fitting）

50

Wetting（Fitting）

45 40 35 30 25 20 15 0

1

2

3

4

5

6

7

8

9

10

n

(a) UCS

Poisson’s ratio (μ)

0.35

drying wetting Drying（Fitting） Wetting（Fitting）

0.30

0.25

0.20 0

2

4

6

8

10

n

(b) Poisson’s ratio Fig. 2. Relationship between the mechanical parameters of sandstone and “n” under dry and saturated condition.

3.2 Experiment Analyses In the Haigh-Westergaard stress space, the Mohr-Coulomb (M-C) criterion of sandstone tensile shear considering the effects of dry-wet cycles can be expressed as:  σ3 = σt(n) (2) σ1 = b(n) σ3 + d(n)

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Table 3. Fitting coefficients between the mechanical parameters of sandstone and n under dry and saturated condition. Status

Fitting coefficient

σc

E

σt

c

ϕ

μ

Drying

j

0.1917

0.0822

0.146

0.1725

0.0329

−0.1576

k

0.9291

2.1897

0.953

0.9446

1.4686

0.6303

R2

0.9496

0.9768

0.9881

0.9602

0.7861

0.8396

j

0.4690

0.3939

0.609

0.5326

0.0272

−0.3177

k

0.5091

0.6437

0.344

0.4165

2.7668

0.3611

R2

0.9990

0.9992

0.9927

0.9998

0.9873

0.8439

Wetting

where σ1 refers to the maximum principal stress, MPa; σ3 refers to the minimum principal stress, MPa; σt(n) is the tensile strength of sandstone when the number of wet and dry φ(n) cycles is n, MPa; b(n) and d(n) are the M-C criterion coefficients, b(n) is equal to 1+sin 1−sin φ(n) ,

cos φ(n) d(n) is equal to 2c(n) 1−sin φ(n) , with c(n) and ϕ(n) are the cohesion and internal friction angle of sandstone when the number of dry and wet cycles is n. b(n) and d(n) of the sandstone yield surface were calculated on the basis of the experimental data. A logarithmic correlation between the M-C criterion coefficients and n was found, which can be expressed as Eq. 3. The fitting coefficients j and k were determined using the least square method, and are shown in Table 4. It is shown that the M-C coefficients b(n) and d(n) both decline gradually with the increasing n, and moreover the reduction tendency of d(n) surpasses that of the b(n) , due to the fact that d(n) is under the combined effects of c and ϕ, while b(n) is only concerned with ϕ. The above analysis demonstrates that the deterioration factor of c with regard to n exceeds that of ϕ. Therefore, as the intergrade reflection of c and ϕ, the deterioration factor of d(n) in terms of n prevails over that solely based on ϕ. The reduction of M-C criterion coefficients of saturated sandstone outruns that of dry sandstone. ⎧   ⎪ ⎨ b(n) = b(0) 1 − jb ln(nkb + 1)   (3) ⎪ ⎩ d(n) = d(0) 1 − jd ln(nkd + 1)

Combine Eq. 2 and Eq. 3, M-C yield criterion under dry-wet cycles can be described as:





σ3 = σt(0) 1 − jσt ln(nkσt + 1)



σ1 = b(0) 1 − jb ln(nkb + 1) σ3 + d(0) 1 − jd ln(nkd + 1)

(4)

The stress envelope curves in the π -plane of dry and saturated sandstone samples in the wetting-drying-alternating process with n and principal stresses are plotted in Fig. 3. It is shown the yield surface is an inequilateral hexagon in the stress space. As the number n increases, the envelope curves of the M-C criterion in the π -plane gradually move towards the center. For dry sandstone samples, the yield strength changes rapidly with the number of cycles in the early stage, while the gap between lines narrows gradually.

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Table 4. Fitting coefficients of M-C coefficient and n of sandstone under two kinds of States Status

Fitting coefficient

bp (n)

dp (n)

0-Dry

y0

7.078

61.137

Drying

j

0.0858

0.2142

k

1.2114

0.9149

R2

0.9987

0.9995

j

0.0776

0.5642

k

1.9559

0.4440

R2

0.9944

0.9992

Wetting

When the number of dry-wet cycles is the same, the envelope of the saturated sample is within the envelope of the dry. The outside envelope curve expands with the increase in the first stress invariant I1 .

(a) I1 (0) = 66.78MPa

(b) I1 (0) = 73.89MPa

(c) I1 (0) =107.45MPa

Fig. 3. The form of π plane of failure and residual strength criterion under dry-wet cycles

4 Numerical Simulation 4.1 Simulation Model In order to shed light under the action of dry-wet cycles on the slope stability, it was assumed that a certain bank slope in a reservoir region should be affected by a 30 m-wide water level fluctuation (WLF) belt. The phreatic line of the underground water was calculated on the basis of Reference 23. In view of effects of the WLF belt of the reservoir region, the rock mass materials of the bank slope in FLAC3D were divided into three groups: the overlying rock mass above the WLF belt (Group I), the rock mass in the WLF belt (Group II) and the rock mass below the WLF belt (Group III). Among the three groups of materials, only the rock mass in the WLF belt was subjected In order to shed light under the action of dry and wet cycles on the slope stability, and correspondingly

Effects of Rock Mass Deterioration Induced by Wetting-Drying Cycles

229

suffers from mechanical property variations. For simplicity in modelling, the calculated phreatic line was approximately regarded as polygonal line. Eight displacement observation spots (P1–P8) were set within and on the outside of the bank slope; five stress observation spots (Su1–Su5), along the upper phreatic line of the WLF belt; also five stress observation spots (Sd1–Sd5), along the lower phreatic line of the WLF belt. The geometric model and the underground water level are shown in Fig. 4.

Fig. 4. Slope model

4.2 Generalized Hoek-Brown Criterion-Based Bank Slope Parameters Based on the generalized Hoek-Brown criterion, this paper derives the measured mechanical parameters of the complete rock sample to determine the rock mechanical properties of the bank slope rock mass. It was assumed that the Geological Strength Index (GSI) of the WLF belt would be 50; the GSI of the overlying rock mass, 45 (due to the severe surface weathering, assumption was made that the GSI would be 5 points less than that of the jointed rock mass in the initial dry state); the GSI of the underlying rock mass, 70 (due to low degrees of weathering of the intact saturated rock mass). In terms of the disturbance factor, D = 0. The generalized Hoek-Brown criterion based on GSI is shown in Eq. 5.  a σ (5) σ1 = σci mb 3 + s + σ3 σci  GSI − 100 (6) mb = mi exp 28 − 14D where σ1 and σ3 are respectively the maximum and minimum effective stresses durrock ing failure; mi and mb respectively refer to the material constants of the intact

 −100 1 1 −GSI /15 −20/3 are releand a = e + − e and rock mass; s = exp GSI 9−3D 2 6 vant parameters of rock mass; σ is the UCS of the intact rock; σcm = σci sa and ci

 1−D/2 are the UCS and elastic modulus of the rock mass. Em = Ei 0.02 + 1+e[(60+15D−GSI )/11]

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Equation 7 is obtained from the Mohr Coulomb criterion of rock mass: σ1 = qm σ3 + σcm cm =

(7)

σcm (1 − sin θm ) 2 cos θm

(8)

1+sin θm θ Let qm = q = 1+sin 1−sin θ = 1−sin θm , then θm ≈ θ , Substitute θm into Eq. 8 to get cm . Since the standard laboratory rock mechanics test method stipulates the extreme conditions of dryness (105 °C) and vacuum water saturation (−80 kPa), the degradation effect of each dry and wet cycle greatly exceeds that of the reservoir area where the water level is on the bank slope. However, it can be said with certainty that there are similarities in the subsequent change patterns of mechanical parameters with n. The maximum number of n is 10, assuming that dry-wet cycles of the jointed rock mass on the simulated site has the same order of magnitude (20 cycles).The rock mass parameter in the WLF belt changed with the given number of dry and wet cycles, and such parameters were calculated via deduction based on the generalized Hoek-Brown criterion with the prescribed GSI using Eqs. 5–8. Equivalent M-C criterion parameters were then obtained using the previously calculated mechanical parameters of jointed rock, namely mb , s, a and Em . The calculation results of the parameters are shown in Table 5.

Table 5. Parameters of jointed rock mass under n = 0–20 Rock Density/kg/m3 State

H-B criterion parameters

σm /MPa mb

Equivalent M-C parameters

E m /GPa s/ 10–3 a

c/MPa ϕ/°

I

2200

Drying

2.99

1.504 2.056

2.218

0.508 0.84

42.41

II

2400

Drying

4.02

1.799 2.825

3.866

0.506 0.94

43.07

1-drying

3.48

1.654 2.664

3.866

0.506 0.87

42.14

3-drying

2.99

1.686 2.246

3.866

0.506 0.82

41.62

6-drying

2.60

1.596 1.909

3.866

0.506 0.76

40.75

10-drying

2.28

1.354 1.652

3.866

0.506 0.65

38.77

20-drying

1.83

1.479 1.301

3.866

0.506 0.65

38.55

1-wetting

2.71

2.010 2.053

3.866

0.506 0.81

42.05

3-wetting

2.11

1.743 1.592

3.866

0.506 0.71

40.29

6-wetting

1.66

1.567 1.236

3.866

0.506 0.50

38.63

10-wetting 1.30

1.712 0.948

3.866

0.506 0.53

36.57

III

2500

20-wetting 0.77

1.928 0.528

3.866

0.506 0.50

35.94

Wetting

2.339 5.550

35.67

0.501 1.06

44.97

5.226

Effects of Rock Mass Deterioration Induced by Wetting-Drying Cycles

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4.3 Simulation Result Analyses Displacement Nephogram. Numerical calculations are carried out on the slope based on the rock mass mechanical parameters of the drawdown zone under different dry-wet cycles, and the influence of the dry-wet cycles on the slope displacement is comparatively analyzed. It can be seen from Table 6 by comparing the simulation results of Cases 20Dry, 20-Wet and 0-Dry (Due to limits of the paper length, only the shear strain and displacement contour maps of the bank slope in the initial state and with the maximum number n are presented here in this paper) that the area with shear strains over 3.5‰ originates from the upper section of the WLF belt and gradually develops to cover the middle-upper section. The contour of the total displacement (the vertical displacement) presents a concave shape, and variations of displacement mainly concentrate at the top of the bank slope, where the maximum displacement exists. The area on the slope crest with the total displacement (vertical displacement) over 0.3 m gradually expands. In cases of n = 20, it almost penetrates through the whole slope crest. The horizontal displacements are also great. As n increases, the area with the horizontal displacement exceeding 0.045 m expands from the middle-lower section of the WLF belt to the lower rock mass. The vertical and horizontal displacement measured by the 8 displacement observation spots of the bank slope (P1–P8) versus the number n is shown in Fig. 5. Under the same working conditions, the longitudinal and lateral displacements of the outer parts of the slope are different. The closer to the top of the slope, the greater the vertical displacement, and the vertical displacement of the same observation point is greater than the horizontal displacement. The vertical displacement of the WLF belt in the saturated state slightly exceeds that of the WLF belt in the dry state, while the vertical displacement measured by the observation spot on water side of the bank slope encounters only a slight growth with the number n increases. In terms of the horizontal displacement, it is relatively large in the WLF belt and reduces as the location approaches the slope crest. It also tends to grow with the repeating dry-wet cycle, and the growth is faster in locations closer to the WLF belt. Given n ≤ 6, the growth magnitude is relatively large; it slows down and gradually converges when n ≥ 10. For Observation Spot P6, in the 20-S case, its vertical displacement grows by 14.027 mm, with an increase of 5.47% from the initial state; the horizontal displacement grows by 10.442 mm, with an increase of 27.95% from the initial state. This indicates that the horizontal displacement is much more sensitive to wetting-drying cycles.

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Z. Wang and X. Liu Table 6. Slope displacement contours using model of this paper

Name

Shear strain

Total displacement

Vertical displacement

Horizontal displacement

Scale of division

(0-Dry)

(20-Dry)-

(20-Wet)

Effects of Rock Mass Deterioration Induced by Wetting-Drying Cycles 300 250

250

Vertical displacemen/mm

Vertical displacement/mm

300

200

200

150

150

100

100 50 0 0

2

4

6

P1-Dry P4-Dry P7-Dry

8 10 12 14 16 18 20 n P2-Dry P3-Dry P5-Dry P6-Dry P8-Dry

50 0 0

2

P1-Dry P4-Dry P7-Dry

4

6

8 10 12 14 16 18 20 n P2-Dry P3-Dry P5-Dry P6-Dry P8-Dry

(c)Horizontal displacement-n (Dry)

4

6

8 10 12 14 16 18 20 n P2-Wet P3-Wet P5-Wet P6-Wet P8-Wet

(b)Vertical displacement -n (Wet) Horizontal displacement/mm

Horizontal displacement/mm

55 50 45 40 35 30 25 20 15 10

2

P1-Wet P4-Wet P7-Wet

(a)Vertical displacement -n (Dry)

0

233

55 50 45 40 35 30 25 20 15 10 0

2

P1-Wet P4-Wet P7-Wet

4

6

8 10 12 14 16 18 20 n P2-Wet P3-Wet P5-Wet P6-Wet P8-Wet

(d)Horizontal displacement-n (Wet)

Fig. 5. Relationship between vertical displacement, horizontal displacement and n of different observation points on the surface of the slope

Stress Nephogram. Table 7 shows that no notable variation has been found in the maximum principal stress contour map, while relatively great changes in the minimum principal stress distribution are seen in the slope crest, according to the comparison between calculation results of Case 20-Dry, 20-Wet and the initial state (Case 0-Dry). Due to space limitations, only the slope displacement cloud diagram and shear strain cloud diagram under the initial state and the maximum number of dry-wet cycles are displayed. With the accumulation of dry-wet cycle, the slope crest zone with the minimum principal stress lower than 0.1 MPa gradually expands to the whole slope crest. Moreover, from the shear stress contour map, the shear zone basically develops along the direction with a specific intersection angle with the WLF belt. The shear stress in the slope crest is relatively small, whereas it reaches its maximum value in the slope base.

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Z. Wang and X. Liu Table 7. Stress contours using model of this paper Name

Scale of division

(0-Dry)

(20-Dry)-

(20-Wet)

Maximu m principal stress

Minimum principal stress

Maximu m shear stress

The variations of maximum and minimum principal stresses and the octahedral shear stress of the observation spots in the upper and lower phreatic lines of the WLF belt with the number n are shown in Figs. 6, 7 and 8. The maximum and minimum principal stresses, octahedral shear stress of each observation spot in the upper phreatic line are below those of each corresponding observation spot in the lower phreatic line. It is shown that on the boundary of the WLF belt, the maximum principal stress is under the slight influence of dry-wet cycle and basically rises and falls mildly from the average value. The maximum principal stress gradually rises, as the location moves downward along the phreatic line. The lower section of the WLF belt has a relatively large maximum principal stress, while the upper section has a small one. The effects of dry-wet cycle on minimum principal stress and octahedral shear stress in each observation spot are relatively considerable. The variations of the two stresses with increasing number n are relatively great in the early stage, and gradually approaches the equilibrium with n ≥ 10. The observation spots in the lower section of the WLF belt suffer from relatively significant impacts of wetting-drying cycles.

2500

235

2500

2000 1500 1000 500 0 0

2

4

6

Su1-Wet Su4-Wet

8 10 12 14 16 18 20 n Su2-Wet Su3-Wet

Maximum principal stress/kpa

Maximum principal stress/kpa

Effects of Rock Mass Deterioration Induced by Wetting-Drying Cycles

2000 1500 1000 500 0 0

Su5-Wet

Sd1-Wet

2

4

6

8 10 12 14 16 18 20 n Sd2-Wet Sd3-Wet

Sd4-Wet

Sd5-Wet

2500

M aximum principal stress/kpa

M aximum principal stress/kpa

(a) Wetting

2000 1500 1000 500 0 0

2

4

2500 2000 1500 1000 500 0 0

8 10 12 14 16 18 20 n Su2-Dry Su3-Dry

6

Su1-Dry Su4-Dry

Su5-Dry

2

4

6

Sd1-Dry

8 10 12 14 16 18 20 n Sd2-Dry Sd3-Dry

Sd4-Dry

Sd5-Dry

(b) Drying

1000

Mi ni mum principal s tress/kpa

Minimum principal stress/kpa

Fig. 6. Relationship between maximum principal stress and n of different observation points in the slope zone

800 600 400 200 0 0

2

4

6

1000 800 600 400 200 0 0

8 10 12 14 16 18 20 n Su3-Wet Su2-Wet

Su1-Wet Su4-Wet

Su5-Wet

Sd1-Wet

2

4

6

8 10 12 14 16 18 20 n Sd2-Wet Sd3-Wet

Sd4-Wet

Sd5-Wet

(a) Wetting Mi ni mum principal s tress/kpa

Mi ni mum principal s tress/kpa

1000 800 600 400 200 0 0

2

4

Su1-Dry Su4-Dry

6

1000 800 600 400 200

8 10 12 14 16 18 20 n Su2-Dry Su3-Dry Su5-Dry

0 Sd1-Dry

0

2

4

6

8 10 12 14 16 18 20 n Sd2-Dry Sd3-Dry

Sd4-Dry

Sd5-Dry

(b) Drying

Fig. 7. Relationship between minimum principal stress and n of different observation points

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Z. Wang and X. Liu 1000 M aximum shear stress/kpa

M aximum shear stress/kpa

1000 800 600 400 200 0 0

2

4

6

Su1-Wet Su4-Wet

800 600 400 200 0

8 10 12 14 16 18 20 n Su2-Wet Su3-Wet

0

Su5-Wet

2

4

6

8 10 12 14 16 18 20 n Sd3-Wet

Sd1-Wet

Sd2-Wet

Sd4-Wet

Sd5-Wet

(a) Wetting 1000 M aximum shear stress/kpa

1000

M aximum shear stress/kpa

800 600 400 200 0 0

2

4

Su1-Dry Su4-Dry

6

800 600 400 200

8 10 12 14 16 18 20 n Su2-Dry Su3-Dry Su5-Dry

0 0

2

4

6

Sd1-Dry

8 10 12 14 16 18 20 n Sd2-Dry Sd3-Dry

Sd4-Dry

Sd5-Dry

(b) Drying

Fig. 8. Relationship between shear stress and n of different observation points in the slope zone

Plastic Zone of Bank Slope. The schematic plastic zone development of the rock bank slope under dry-wet cycles is shown in Table 8. It shows that no plastic zone exists in the bank slope in the initial dry state. The plastic zone occurs and expands in the upper section of the WLF belt, which can be attributed to the effects of wet and dry cycles. It gradually grows until it passes throughout the whole WLF belt, as the number n increases. it is also demonstrated that the bank slope plastic zone with the dry WLF belt (the water level in the reservoir region equals to 145.00 m) is smaller than that with the WLF belt in the saturated state (the water level reaches 175.00 m). This means that with lower water levels in the reservoir region, the plastic zone of the bank slope shrinks and the slope stability recovers. As wetting-drying cycles repeat, the difference between plastic zones in dry and saturated states gradually narrows, which indicates that wetting-drying cycles have caused unrecoverable damages to the bank slope and such damages accumulates in a non-linear manner with the increasing number n. Safety Factor of Bank Slope. Since the slope safety factor of FLAC3D is only applicable to Mohr-Coulomb model, a calculation program was coded in the FISH language on the basis of the strength reduction method. Trials have shown that the calculation can converge after about 3200 calculation steps, with an unbalance factor lower than 1 × 10−5 . Therefore, in this paper, the convergence capability after 10000 calculation steps was used as the criterion. In cases that the calculation converges, the reduction factor is regarded as too small and upward difference will be implemented. On the contrary, if the calculate fails to converge, the reduction factor is regarded as too large, and downward

Effects of Rock Mass Deterioration Induced by Wetting-Drying Cycles Table 8. Plastic zone of slope under different dry-wet cycles n

0

1

3

6

10

20

drying

wetting

No wetting state

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difference will be practiced in this case. The strength reduction stops as the difference between reduction factors of two successive calculations is within the prescribed error range, and the corresponding reduction factor is regarded as the final result. The MohrCoulomb model-based slope safety factor calculation indicates a safety factor of 2.43. The calculated safety factors with varied mechanical parameters in the WLF belt owing to the different number n are shown in Fig. 9. Results show that wetting-drying cycles cut down the slope safety factor, which declines relatively fast in the early stage of the wetting-drying-alternating process and tends to reaches the equilibrium state with n ≥ 10. The slope safety factor with the water level of 145.00 m exceeds that with the water level of 175.00 m. With the accumulation of wet and dry cycles, the difference of the safety factor between the two extreme cases of water levels gradually becomes stable. With n = 20, the safety factor with the water level of 145.00 m reduces by 20.96%, and that of the water level of 175.00 m falls by 33.24%.

3

Dry Wet

Safety factor

2.5

2

1.5

1 0

2

4

6

8 10 12 14 16 18 20 n

Fig. 9. Safety factor of slope

5 Conclusions (1) In order to simulate the impact of water level rise and fall on the rock mass mechanical parameters of the slope water level in the Three Gorges reservoir area, the designed dry-wet cycle test was carried out on the sandstone under the “dry” and “saturated” states, split test, uniaxial compression test, three The axial compression test shows that the various mechanical parameters of sandstone vary with n. The mechanical parameters of the rock decrease during the “saturation” process, and the mechanical parameters increase during the “loss of water” process, but it cannot be completely restored to the initial state. In this way, irreversible damage is produced under the repeated alternating action of “saturation-loss of water”. (2) Through drawing, tabulation, calculation, inductive analysis, etc., the macromechanical parameters of sandstone under the action of dry-wet cycles obtained by different test methods were compared and analyzed, and a series of relationship curves were obtained, for the two states of “saturated” and “dry” The following

Effects of Rock Mass Deterioration Induced by Wetting-Drying Cycles

239

rock samples can be fitted with the function y(n) = y0 [1 − j ln(nk + 1)], which can provide a basis for the parameter selection of the later numerical simulation. (3) Through the establishment of a simple slope model for numerical calculation, Results show that with the action of the dry-wet cycle, the upper area of the decay zone gradually appears plastic area, and with the increase of n, the plastic area gradually develops and penetrates; the dry-wet cycle The effect causes the slope safety factor to decrease, and the initial descent speed is faster. When n ≥ 10, it tends to be stable. The slope safety factor at the water level of 145.00 m is greater than 175.00 m. With the accumulation of the number of cycles, the safety of the slope at the two extreme water levels the coefficient difference tends to be stable. When n = 20, the safety factor when the slope is at the water level of 145.00 m drops by 20.96%, and the safety factor when the water level is at 175.00 m drops by 33.24%. (4) In the follow-up study, the model test (structural plane and weak interlayer can be considered) will be further carried out on dry-wet cycle of the on-site rock mass. The parameters obtained from the model test will be numerically simulated in combination with the specific engineering background, the stability coefficient of the reservoir bank slope will be calculated, and the measures to prevent and control the slope will be analyzed.

Acknowledgement. This work was supported by Basic Research and Frontier Exploration project of Chongqing in 2018, (Grant No. cstc2018jcyjAX0453), and High Level Talent Introduction of Scientific Research Start Fund Project of Chongqing Technology and Business University (Grant No. 1855002).

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Research on Fine Management of Expressway Survey Hong Qiang Zhang(B) , Ju Zhi Zhang, and Wei Li Hebei Provincial Communications Planning, Design and Research Institute Co., Ltd., Shijiazhuang 050011, China [email protected]

Abstract. Expressway requires relatively strict geological conditions. And geological survey is particularly important especially in complex mountainous areas. The single methods and lack of meticulousness in the geological survey may bring many changes to the construction process, and even induce landslides or other geological disasters, which effects the driving safety after the road is open to traffic. With the project construction and the accumulation of engineering experience, more and more engineers agree that refined pre-investigation could not only improve the survey accuracy, but also reduce the costs, shorten the time, reduce the geological disasters and increasing traffic safety. The geological survey of Yanchong Expressway is refined and strictly conducted according to the “Implementation Regulations”. Through geological mapping, investigation, geophysical exploration, exploration, digging, wave velocity testing and other methods, the geological survey can provide accurate, optimal and satisfactory geological data for the design. It can provide a reference for similar projects. Keywords: Highway · Geological survey · Refinement · Geological hazard

1 Introduction Although China has accumulated some technology and experience in the survey technology of complex mountainous areas, it is not very perfect. In the past, due to the influence of construction period and cost, many projects adopted too single geological survey means, and even some mountainous geological survey adopted the survey means of plain area, which will bring many problems in later design and even construction. It causes a lot of unnecessary waste, and even causes geological disasters such as slope collapse, tunnel collapse, water gushing and so on, affecting the traffic safety. Therefore, the introduction of fine management of geological survey in complex mountainous areas is particularly important. Taking Yanchong expressway as the research background, this paper ensures the safe implementation of the project through a large number of fine survey means [1–6].

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 241–247, 2023. https://doi.org/10.1007/978-981-19-4293-8_25

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2 Project Overview In order to implement the important directive spirit of general secretary Xi Jinping’s preparations for the twenty-fourth Winter Olympic Games, the Ministry of transport has carried out key deployment of major traffic guarantee projects for the Winter Olympic Games. It also formulated the promotion plan for major transportation support projects for the Winter Olympic Games, and put forward three categories of tasks, namely, the main Olympic transportation channel, relevant road network construction and industry guidance and coordination. Yanqing Chongli expressway is a major traffic guarantee project for the 2022 Beijing Zhangjiakou Winter Olympic Games. At that time, contestants, staff and spectators from all countries will be able to realize the rapid transition between Zhangjiakou and Yanqing competition areas through the expressway. Meanwhile, Yanchong expressway is also a key project of transportation integration in Beijing, Tianjin and Hebei. The construction of the expressway will shorten the traffic distance between Beijing urban area, Yanqing new town and Zhangjiakou, Hebei Province. It is of great significance to promote tourism development and economic development along the line, improve the expressway network of Hebei Province, and promote the coordinated development of Beijing, Tianjin and Hebei. Yanqing–Chongli Expressway (hereinafter referred to as Yanqing Chongli Expressway) starts from xiyangfang, Yanqing and ends at Prince Chongli city. It directly connects Yanqing and Zhangjiakou. It is the main channel of Olympic transportation and the key project of Winter Olympic transportation. The total length of the project is about 144 km. The section from xiyangfang to Chongli taizicheng in Yanqing is about 98 km long (including 17 km in Beijing section and 81 km in Hebei Section), the South extension project of Beijing section (Xiyu Road) is about 15 km long, the north extension project of Hebei Section (taizicheng Zhangcheng Expressway) is about 16 km long, and the Chicheng branch line is about 15 km long. On May 10, 2016, Minister Yang Chuantang of the Ministry of transport chaired a special meeting to study and deploy the promotion of major transportation support projects for the Winter Olympic Games. The meeting called for taking the construction of Yanqing Chongli expressway as the top priority of the work, aiming at realizing the transfer within one hour, innovating ideas, improving quality, strengthening supervision, and building the transportation guarantee project of the Winter Olympic Games into a quality project and demonstration project.

3 Fine Management of Geological Survey 3.1 Strictly Implement the Survey Specifications to Ensure the Quality The geological survey of the project strictly implements the current specifications for highway engineering geological survey, and refers to other industrial specifications and standards. In the same survey content, the specifications and standards with high quality and accuracy are implemented to carry out specific and fine survey of the project. The geological survey of the project is divided into two stages: preliminary survey and detailed survey. Firstly, the technical guidance and survey outline of each stage are prepared in combination with the actual characteristics of the project, which clearly

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stipulates the purpose, quantity and results of the preliminary survey and detailed survey. Combined with the survey purpose and tasks of each stage, the number, depth, location, sampling and in-situ test of exploration points on the route, subgrade and structures are carried out, In terms of geophysical exploration, specific survey requirements are put forward, especially for high fill, deep cutting, unfavorable geology and special rock and soil; Secondly, from the organizational structure of the geological exploration project department, to the input of personnel and equipment, from the on-site coordination and management, operation process control, to the laboratory test, from the on-site data entry, to the geological analysis report, we have made fine planning and strictly implemented according to the specifications; Finally, the survey results report submitted provides accurate geological parameters for preliminary design and construction drawing design. 3.2 The Depth of Geological Survey Meets the Design Requirements Due to the existence of tunnels, high embankments, deep cuttings and steep slope embankments in previous mountain projects, the investigation workload is less. Moreover, the survey means are mainly drilling and few other means, and the refinement degree of the overall results is not high. The geological survey integrates the survey specifications of local mountainous areas in Zhejiang and Guizhou, and adopts comprehensive survey means such as engineering geological mapping, survey visit, drilling, excavation exploration, geophysical exploration, in-situ test, geotechnical test and water quality analysis. Through systematic analysis of various geological factors in the area, the focus is on adverse geology, special geotechnical and potential dangerous engineering geological problems. Scientifically formulate the survey plan and reasonably determine the survey workload. Ensure the depth and quality of survey work. The details are as follows: The route is mainly based on engineering geological mapping, supplemented by exploration and testing. Especially strengthen the mapping of unfavorable geological sections. Representative samples are selected to test the engineering geological properties of special rock and soil sections in combination with excavation and exploration. The general subgrade is carried out by surface mapping, excavation and exploration and drilling. One exploration point every 300–500 m, with a depth of 3–15 m. The spacing of exploration points in loess section is less than 300 m. One transverse exploration section is completed for each section of high embankment and steep slope embankment. And there are no less than 2 exploration points in the exploration section. The exploration depth is 3–5 m below the bearing stratum or bedrock surface. For each section of deep cutting, 1 vertical section and 1–2 cross sections shall be completed. And the number of boreholes or test pits in each cross section is 2–3. The drilling depth is 3–5 m below the design elevation. The number of transverse exploration sections completed in each section of the support works is 1, and there are 2 exploration holes in each section of transverse exploration section. The exploration depth is 3–5 m below the bearing stratum. One exploration point has been completed for small bridges, channels and culverts. Drilling, excavation exploration or engineering geophysical exploration shall be adopted,

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and the exploration depth shall be 3–5 m to the bearing layer. The exploration depth in loess area shall reach the top surface of non collapsible loess below the basement. The survey of large and medium-sized bridges is mainly based on drilling and in-situ testing, supplemented by geophysical prospecting and mapping. Generally, the bridge with span greater than 40 m shall be drilled pier by pier; When the span is no more than 40 m and the geological conditions are complex, it is advisable to drill pier by pier; When the geological conditions are simple, the drilling can be carried out at intervals. For bridge sites with large changes in horizontal geological conditions, complete horizontal survey points or geophysical survey lines. The drilling depth of natural foundation or shallow foundation under the bearing stratum shall not be less than 3 m; The depth of pile foundation drilling below the bearing stratum shall not be less than 5 m. The tunnel exploration adopts a comprehensive exploration method based on drilling and in-situ testing, supplemented by geophysical exploration, excavation exploration and mapping. Firstly, the detailed engineering geological mapping of the tunnel is carried out; Secondly, geophysical prospecting shall be carried out, focusing on the results of survey and mapping, and the workload of geophysical prospecting shall be increased for the structural parts. The shallow burial adopts high-density electrical method, and the deep burial exceeds 80 m adopts magnetotelluric EH4; Thirdly, combined with surveying and mapping and geophysical exploration, drilling shall be comprehensively considered for shallow burial, fault fracture zone, fracture development zone and geophysical anomaly zone. The exploration depth is 5–10 m below the tunnel design elevation. Based on the specific requirements and depth of the above survey, strengthen the dynamic and effective communication with the design and supervision, and conduct supplementary survey for those that do not meet the design requirements. 3.3 Topography and Geomorphology The landform of the project is mainly the mountainous area in Northwest Hebei and the transitional mountainous area under the dam and on the dam, with local areas of river valley plain and alluvial proluvial slope. The engineering geological problems in this area mainly include collapse, debris flow, iron ore roadway and goaf, tailings pile, wind snow, collapsible loess, seasonal frozen soil, etc. For the above unfavorable geology and special rock and soil, formulate survey technical requirements and implement special survey, as follows: Collapse: Some mountains in the transition zone above and below the dam are steep. During the excavation of high slope, the joints and fissures of rock mass are developed in an open shape, and colluvial deposits are accumulated at the foot of the slope. On the basis of strengthening geological mapping, vertical and horizontal longitudinal faults are arranged in the deep cutting area. The weak structural planes such as rock joints and faults are found out by excavation and drilling. Concrete frame beam reinforcement or active falling object prevention net protection shall be adopted for unstable sections, and monitoring shall be strengthened at the same time. Debris flow: mapping and exploration are adopted. The mapping scope includes the formation area, circulation area, accumulation area and stable section of debris flow; Explore and test to find out the composition, thickness and properties of deposits. On the right side of K34 + 680–K34 + 770 section of the project is a narrow and long valley,

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about 50 m wide and 1.46 km long. The average gradient of the longitudinal slope of the main ditch is about 7.5°, the catchment area on the right is 1.4 km2 , the surface runoff is concentrated, and the thickness of gravel layer in the valley is 10.2–15.0 m. After the line adjustment, toupao No. 2 bridge is set to cross the gully mouth, and the pier column has strengthened the debris flow protection design. Roadway and goaf: The mapping shall be combined with the setting of the route and structures along the line. Fully collect regional seismic, geological and mining data. Find out the formation lithology, geological structure, hydrogeological conditions, ground motion parameters, goaf, surface subsidence and the relationship between routes and structures. The mapping scale is 1:2000, and the mapping range is not less than 200 m on both sides of the central line of the route; The number and location of exploration and testing shall be determined according to the topographical and geological conditions, the type and scale of goaf, surface deformation and the type and scale of structures; Magnetotelluric method and high-density electrical method should be combined with drilling for comprehensive exploration, and the exploration lines should be arranged in a grid shape. Tailings dump: Strengthen geological mapping, exploration and sampling, and find out the scope, thickness and nature of tailings pile. Iron ore waste residue accumulation can be seen in K18 + 210–K18 + 300 section of Chicheng branch pipeline. Distributed on both sides of the route. It is mainly ore waste slag, mostly in the shape of gravel and block stone, with general block diameter of 3–10 cm, maximum block diameter of 30 cm and local powder. The thickness within the subgrade range is 1.0–4.0 m. The route passes through this section in the form of filling. The maximum filling height of the route center is 3.5 m. Dynamic compaction is recommended. Wind blowing snow: Mainly for data collection and investigation. Focus on finding out the landform, air flow activity law and vegetation growth of snow covered sections; Collect the causes of wind blown snow and local meteorological data; Find out the type, distribution range, thickness and causes of snow affecting and controlling subgrade design; Find out the geomorphic position, topographic characteristics and slope direction of the snow section; Investigate local engineering measures and experience in snow prevention and control. Loess: Engineering geological mapping focuses on finding out the boundary of geomorphic units, collapsible depressions, depressions, sinkholes, loess landslides, scattered, man-made pits, etc.; The comprehensive exploration shall be carried out by excavation and drilling for exploration and testing. The number and location of exploration and test points shall be determined according to topographical and geological conditions, collapsibility of loess, type and scale of structures, etc.; The average spacing of exploration holes shall not be greater than 300 m; Horizontal exploration layout shall be carried out in Loess development section, and the number of exploration points in each cross section shall not be less than 2; According to the laboratory test data and the collapsibility coefficient, the collapsibility degree of loess must be divided. Seasonal frozen soil: Strengthen mapping, exploration and sampling. Find out the scope, thickness and nature of frozen soil in low fill and shallow excavation sections.

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In K45 + 380–K54 + 000 and K72 + 280–k78 + 920 sections, river valleys and first and second terraces, quaternary silty clay and silt are discontinuously distributed, with a total length of 20.1 km. The local water content of the soil layer is high, with weak frost heaving–frost heaving. Anti freezing and thermal insulation measures shall be taken for low filling and shallow excavation sections, and waterproof and drainage design shall be done at the same time. 3.4 Fine Control of the Whole Survey Process The technical quality management of engineering geological survey shall be uniformly coordinated and managed by the quality survey project team. The survey technical requirements will be formulated according to relevant highway engineering geological survey regulations, specifications and technical standards, and implemented in strict accordance with the required contents. During the field survey, the survey project team shall conduct self inspection in time. And strengthen communication and negotiation with the owner, the designer and the supervisor. Strengthen advance guidance. The rationalization suggestions put forward shall be actively implemented to ensure the survey quality of this survey. Key and difficult projects shall be submitted to the supervision unit and expert group in time. Adjust the scheme in time in combination with the guiding opinions put forward by experts. To ensure that the survey quality meets the requirements; For the survey results, the “second verification and second review” shall be strictly implemented. The details of survey quality shall be properly controlled to avoid “mistakes, omissions, collisions and deficiencies”, so that the intermediate results of survey output and the final engineering geological survey report meet the requirements. According to the requirements of ISO9000 three system documents of our institute, standardized and standardized monitoring management shall be implemented for the whole survey process.

4 Conclusion Yanchong expressway project is an important supporting project for the Winter Olympic Games. Our province focuses on the four directions of “green construction and maintenance, intelligent construction, intelligent security and intelligent operation”. Build Yanchong Expressway into a science and technology demonstration project integrating “green·intelligence” and “construction operation”. Implement the national regional development strategy of “coordinated development of Beijing, Tianjin and Hebei” to serve the 2022 Winter Olympic Games and meet the economic and social development after the Olympic Games. However, the geological conditions are not clear, and the above objectives can only be said to be castles in the air. Therefore, the concept of fine management is introduced into the geological survey of the project to provide accurate geological data for design and construction through comprehensive survey means, so as to escort the smooth implementation of the project.

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References 1. Zhai, S., An, Y., Zhai, Z.: Discussion on engineering geological problems of Yakang expressway tunnel. Disaster Sci. 33(S1), 138–142 (2018) 2. Zhang, S., Jiang, J., Han, X.: Comprehensive investigation and evaluation of subgrade in goaf of Xiaomiyao expressway. Disaster Sci. 21(4), 66–70 (2006) 3. Tuojundi, Wu, S., Fei, Y., et al.: Study on comprehensive survey method of karst disaster in Wujiang Bridge site. Disaster Sci. 27(1), 73–77 (2012) 4. Lei, J.: Research on key issues of fine management of expressway reconstruction and expansion project. Chang’an University (2011) 5. JTG C20-2011, Code for highway engineering geological survey 6. GB50021-2001, Code for geotechnical

Research Progress on the Formation Mechanism of Intraplate Volcanoes Hongyu Wang(B) , Zeyu Zhang, and Xiaozhuo Luo School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei, China [email protected]

Abstract. Research now suggests that most volcanoes occur at plate boundaries. The occurrence of boundary volcanoes is related to the relative movement of plates, the formation of weak zones, and the upwelling of magma. However, volcanism also occurs in plates far away from the boundary, and volcanism in plates is pointed out to be caused by various local actions. For example, small-scale mantle convection, mantle melting caused by interaction between lithosphere and asthenosphere, etc. At present, great achievements have been made in the study of the formation mechanism of boundary volcanoes, but obviously these mechanisms are not well used to explain the formation mechanism of intraplate volcanoes, so it is particularly important to study and summarize the mechanism of intraplate volcanoes. This paper systematically analyzes and summarizes the causes of the existing intraplate volcanic mechanism, integrates many scholars’ understanding and opinions on the causes of the formation of intraplate volcanoes, and summarizes their conclusions. At present, the formation mechanism of intraplate volcanoes mainly includes plate subduction, lithosphere asthenosphere interaction, hot spot volcanism, and other small-scale old mantle migration, etc. Keywords: Intraplate volcanoes · Formation mechanism · Plate subduction · Lithosphere & Asthenosphere Interaction

1 Introduction Volcano refers to a kind of landform formed by the earth, moon and earth like planets’ crust breaking and opening, through which hot materials (magma, ash, gas, etc.) flow out. According to the statistical data, Most of the active volcanoes are located in the Pacific ring subduction zone, partly along the collision boundary between the Indian plate and the Eurasian plate, and sporadically in hot spots and in plate environment [1]. For volcanoes distributed in the subduction zone around the Pacific Ocean, their genesis can be attributed to the formation mechanism of island-arc volcanoes [2]. When the oceanic plate meets the continental plate, the oceanic plate will fall below the continental plate because of its density. The water released from the subduction of the oceanic plate reduces the melting temperature of the overlying mantle wedge, which is easy to form magma [3]. At the same time, the heat generated by friction between plates will also promote the © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 248–258, 2023. https://doi.org/10.1007/978-981-19-4293-8_26

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generation of magma, which rises slowly by buoyancy and finally gathers into a magma reservoir. Magma erupts in weak areas of the lithosphere, forming volcanoes. However, the formation mechanism of intraplate volcanoes cannot be explained by the formation mechanism of boundary volcanoes [4]. So it is very important to find out the mechanism of the formation of intraplate volcanic. At present, the main models of intraplate volcanism are plate subduction, lithosphereasthenosphere interaction and hot spot volcanism. The first is caused by plate subduction. The second caused by slow melting of lithosphere which caused by upwelling of asthenosphere under the condition of lithosphere extension. The origin of hot volcano is the action of constant mantle plume. In addition, there are also small-scale migration of the old mantle, which is mainly through the activation of old mantle residues.

2 Plate Subduction At present, a large number of scholars have found that the Mariana Islands on the edge of the Western Pacific [5, 6], the Andes on the edge of the eastern Pacific [8], the volcanoes near the Qinghai Tibet Plateau in the west of China [8] and the Changbai Mountain volcanoes in the northeast of China [4, 10] are related to the subduction of the plate. Plate subduction can be divided into three steps according to time: 1. Shallow dehydration during subduction resulted in island arc volcanoes. 2. Deep dehydration of subducted plates [10]. 3. Subduction plate tears and mantle plume upwelling [5]. For example, regarding the genesis of Changbai Mountain volcano, Tang et al. [11] believed that it was caused by the gap in the remaining plate, while Wei et al. [12] and Lei et al. [13] believed that it was caused by the deep dehydration of the remaining plate.In addition to the above three ways, Ma F F [14] believes that in the process of plate subduction, with the increase of temperature and pressure, the subduction plate will partially melt to form subduction mantle plume, which will form upwelling, but at present, the origin and process of mantle plume are not familiar. There are two types of plate subduction: 1. Subduction of oceanic plate, which can be divided into two kinds. The ocean plate meets the ocean plate, one subduction to the bottom of the other; the ocean plate meets the continental plate, and The former dive to the bottom of the latter [15–17]. 2. Subduction of continental plate. When the continent meets the another, the front edge of one continental plate subducts under another plate. Among them, oceanic plate subduction is the main form of plate subduction. When the ocean plate moves relative to the continental plate, because the asthenosphere under the continental plate has a small viscosity [18], so the motion resistance is small, which leads to the ocean plate is easy to dive under the continental plate. Li Haijiang et al. [19] believe that all oceanic plates will dive to the bottom of the upper mantle. When the plate subduction started successfully, the oceanic plate began to move downward until the 660 km, and the plate suffered strong resistance [20]. A lot of people think that the ocean plate will deflect at this time [3]. However, some people think that the oceanic plate will directly pass through the 660 km discontinuity and enter the lower mantle [21]. With the continuous movement of plates, the subducted plates tend to be horizontal and thickened [15, 22]. The deep dehydration of the lying plate further causes mantle convection to form volcanoes or plate tearing, and the plume upwelling from the gap causes volcanism.

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2.1 Mantle Convection in Mantle Wedge Caused by Shallow Plate Dehydration The subducted oceanic plate is mainly composed of hydrated oceanic crust, marine sediments and part of upper mantle. In the early stage of plate movement, the oceanic plate will be affected by bending stress when it starts to subduct under the continental plate. The existence of bending stress will make the oceanic plate form cracks or faults. Under the action of gravity, water can enter the ocean plate through these cracks, so that the subduction plate contains large quantities of water. located above the subducted plate, the mantle wedge is the lithospheric mantle sandwiched between the subducted plate and the continental crust. With the plate continuously downward, water migration will occur due to the temperature difference between the plate and the mantle wedge. Continental lithosphere results in lower plate temperature in subduction zone [22], which indicates that the mantle wedge of continental plate is cold and has no mobility [23]. On the contrary, the temperature of continental mantle wedge is higher than that of subduction plate, as shown in Fig. 1. With the increase of environmental pressure and temperature gradient between the mantle and plate, most of the free water will break away at 10–20 km [17, 23]. However, with the addition of a large amount of cold subduction materials, the temperature drop at the bottom of the mantle wedge overlying the subduction plate decreases gradually, and the temperature gradient of between the mantle and plate decreases gradually [15]. At the same time, a series of solid-solid transformations of the dense hydrous magnesia silicate in the relatively cold environment [5]. This will prevent the further separation of water. And most of the free water has been removed at this time, with the increase of the depth, the shallow dehydration gradually weakened. In the process of plate shallow dehydration, water separated from plate enters mantle wedge, weakening mantle wedge peridotite and reducing viscosity coefficient [16]. At the same time, due to the downward movement of the plate, the mantle wedge is affected by the shear force. Because of the shear force, the barrier curve of the liquid molecules becomes asymmetric, and the barrier decreases in the flow direction. The increase of flow velocity leads to the strengthening of small - scale convection (Fig. 2). With the gradual increase of water, the melting point of material near the mantle will decrease and the melting of mantle material will be generated. The melting mantle material rises gradually under the action of thermal convection and buoyancy. With the continuous accumulation of molten material at the bottom of the lithosphere, the lithosphere is continuously thinned, and finally a gap is formed, from which the molten mantle material erupts, forming an island arc volcano.

Fig. 1. Mantle convection caused by shallow plate dehydration [4]

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2.2 Subducted Plate Retention and Plate Dehydration in Depth The top of ocean lithosphere is relatively thin basalt. With the increase of depth, the basalt first transforms into gabbro and then into garnet [5]. The density of garnet is higher than the surrounding mantle, which will cause the plate to continuously subduct until 660 km. With the development of the study of the earth structure, the earth structure can be divided into core, upper mantle, lower mantle, outer crust and inner crust. There is a mantle transition zone between the upper mantle and the lower mantle. The mantle is divided into upper mantle and mantle transition zone by a global wave velocity discontinuity zone with a depth of about 410 km. The global wave velocity discontinuity at a depth of about 660 km divides the mantle into mantle transition zone and lower mantle. When the subduction plate reaches a depth of 660 km, it will be blocked. The thickness of 660 km discontinuity has global variability. Early scholars thought that it could reach 20–30 km [5]. Later, the 660 km discontinuity thickness of Fiji Tonga is considered to be within 5 m, with high sharpness, which may be caused by the phase transformation of Linwood stone into perovskite and siderite [5]. At the same time, Wang Xin [23] and Chen [15] et al. Found that the thickness of oceanic plate before subduction into mantle transition zone was about 90 km, and the thickness after subduction into mantle transition zone increased to 140 km. The larger the velocity of subduction plate, the greater the viscous resistance with mantle. And the thicker the overlying plate, the greater the blocking effect on the subduction plate. The 660 km interface has a negative Clapeyron slope, which is endothermic reaction. And the subduction plate delays phase transition and generates positive buoyancy [19]. In general, at the 660 km discontinuity, there is a continuous accumulation of mater at the front of the plate, which leads to an increase in the resistance of the plate and a decrease in the advance rate. Meanwhile, the transformation of linwoodite to perovskite and magnesite will cause the increase of viscosity and liquid volume to form positive buoyancy, which will hinder the further movement of the plate and stop at 660 km. This idea has been confirmed by plate holdup found under Changbai Mountain in eastern China and Tengchong volcano in Western China [25]. At this time, the plate motion rate is lower, and there is more time for heat exchange with mantle. The temperature of the plate increases gradually. Under the action of high temperature and pressure, the water that remains in the plate after initial dehydration will come out. For some plates with large age (thickness), fast speed and cold, the shallow dehydration is very small, and the plate will retain a large amount of water, at this time, severe dehydration will occur. The addition of a large amount of water will reduce the solid-liquid phase line of mantle material, make the mantle melt and generate local convection [4]. If the water separated from the plate melts the mantle around the plate completely, there is still surplus. Under the effect of negative buoyancy, the water will gradually rise and enter the mantle wedge, promoting the melting of mantle peridotite. The molten material will be added to the magma chamber and the magma content will increase continuously. So the deep dehydration of the subducted plate can cause volcanism hundreds of kilometers away from the plate boundary.

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2.3 Plate Fracture and Plate Collapse For intraplate volcanism related to plate subduction, the origin can generally be attributed to plate retention and dehydration. However, through global P-wave imaging, it is found that there is a gently inclined high-speed anomaly at 200 km below the eastern Indian plate. And the high-speed anomaly is considered as a subducted Indian plate, and the plate broke at 220 km [25]. The gap formed by plate fault provides a channel for the upwelling of mantle plume, which leads to the formation of Tengchong volcano. Tang et al. [11] interpreted the low velocity anomaly area under Changbai Mountain as a gap in the subduction plate of the detained Pacific Ocean in the mantle transition zone. The thermal material under the mantle transition zone upwelling through the vacancy of the recumbent plate. These materials are decompressed and melted in the upper mantle to form volcanoes. There are two reasons for plate faults. On the one hand, the subducted ridges and seamounts themselves are weak zones. On the other hand, seamounts are rich in carbonate sediments, which are easy to dehydrate and melt in the mantle. Both of them weaken the strength of the plate and break the plate [5]. Another theory holds that subduction plate retention is only a temporary geological phenomenon, and will eventually sink into the lower mantle in the form of plate collapse [19]. When the remaining plate breaks or collapses, the barrier between the lower mantle and the mantle transition zone disappears, and the mantle plume between the lower mantle can be successfully upwelling. These materials are decompressed and melted in the upper mantle to form volcanoes [19]. 2.4 Influence of Plate Subduction on Magma The ultimate expression of volcanism is the eruption of magma. Plate subduction affects the formation and eruption of magma. During the subduction of oceanic plate, during about 55–88.9ma, the sediments retained within 200 km due to plate subduction began to melt to form magma [19]. After the magma has formed, it needs channels up and windows for the eruption. Plate subduction affects the channel and window mainly in two ways. The first is the destruction of lithospheric structures by mantle convection induced by subduction [27]. In this way, the lithosphere needs to be weakened by adding water. The second is the destruction of the overlying lithospheric mantle by the subduction plume formed in the late stage of plate subduction. As the plate subducts to a depth of 500 km, rising temperatures and pressures cause the plate and sediment to melt, mixing to form a melting column with a density lower than that of the surrounding mantle. Driven by buoyancy, the molten column is continuously upwelling. After reaching the bottom of the upper lithosphere, decompression melting takes place, and mushroom like lateral erosion takes place at the top of the column as the center, which further leads to the heating and melting of the lithospheric mantle. The resulting molten material continues to rise along the original channel [14], making the channel larger and larger. Until the 55–88.9 Ma period, the magma formed retraced to the accretionary wedge along the subduction channel, forming a magma chamber. Magma erupts to form volcanoes in weak areas of the lithosphere.

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2.5 Breif Summary The influence of the subduction of intraplate volcanic mainly through three aspects: Plate shallow dehydration: the subduction plate of the ocean rich in a large amount of water dehydrates at a shallow depth of 10 –20 km, promoting mantle convection in the mantle wedge, with the increase of magma, volcanoes eventually form from the weak areas of the lithosphere. (1) Plate of deep dehydration: when dehydration effect is weak in shallow plate after 660 km a recumbent stagnation, due to changes in the environment of deep dehydration, leading to a deep mantle convection, the formation of the melt upward movement, eventually form volcanoes. (2) Plate faulting: subducting plate ruptures, causing upwelling of the underlying mantle plume, which decompresses and melts in the upper mantle, resulting in intraplate volcanism.

3 Lithosphere-Asthenosphere Interaction Mechanism First on the lithosphere stretching mode refers to the passive chasmic function formed by the lithosphere stretching modes, including simple pure shear deformation and shear deformation in two forms. Lithospheric stretching effect and interaction with the asthenosphere is the important content of deep mantle dynamics research. Asthenosphere is a relatively low velocity zone of seismic waves, below the lithosphere of the earth’s crust and in the upper mantle. Under the long-term action of pressure, it flows slowly in a semi-viscous state, so it is called asthenosphere. Mechanism of the interaction of lithosphere and asthenosphere mainly embody in magmatic melt need dynamics mechanism, it is differences in subduction leads to another dynamics mechanism of mantle melting. Mesozoic volcanic rocks are widely distributed in eastern China. For the whole eastern Mesozoic volcanic rocks, the spatial distribution along the Pacific coast is nnetrending and wide banded, and the lithology is similar to the calc-alkaline properties of island arc volcanic rocks, etc. Therefore, the formation of Mesozoic volcanic rocks in eastern China has been considered to be related to the subduction of the ancient Pacific plate (Kula or Izanagi) [27–31]. One of the important evidences is that the related volcanic rocks are calc-alkaline volcanic rock assemblage with island-arc volcanic rocks, such as enriched LILE and LREE, and depleted HFSE. However, more and more studies have shown that calc-alkaline volcanic rocks with similar characteristics can also form slowly in the intracontinental rock mass, and the dynamic melting process is mainly related to lithospheric extension-thinning [32–34], especially in numerous orogenic belts, such as the qinghai-tibet plateau [35, 36], the dabie-xulu orogeny [37–39], the xingmeng orogeny [38, 40] and the western basin province [34, 41, 42]. The main genesis of these calc-alkaline magmas is caused by plate subduction, and the main difference between calc-alkaline magmas produced in the same subduction island arc volcanic belt is the difference in melting dynamics: the calc-alkaline magmas produced in the same subduction island arc volcanic belt are water-bearing melting caused by the dewatering metasomatism of the subduction plate and the slow wedge overlying the subduction plate, resulting in the decline of its melting temperature [43–45]. And formed in the orogenic belt and

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intracontinental calcium alkaline magma is due to the collapse of the orogenic belt or thickening of the lithosphere removed or go to the root, can also be deep faulting caused by lithosphere stretching and soft flow enclosure slow upwelling, therefore caused by different partial melting of lithosphere and asthenosphere [34, 46]. By Jiang Shao fault zone area of jiangshan, pujiang, mafic volcanic rocks of the trace elements and isotopic geochemical studies of the results showed that overall, Jiang Shao fault zone late Mesozoic of three groups of mafic volcanic magma source and geochemical characteristics, is a good way to interact through a lithosphere asthenosphere and in different proportions of partial melting mechanism for better explanation. Therefore, based on the analysis of rock genesis, Qin shecai believed that the late Mesozoic mafic volcanic rocks in the jiangshao fault zone were the result of the interaction between asthenosphere and lithosphere in the case of lithospheric extension. Similarly, the cause of zhejiang pujiang Mr Tak qualitative volcanic rocks and no direct evidence that is related to plate subduction, but from lowe schiscosomiasis Mr Tak qualitative volcanic rocks and the region, regional high contrast of rock and combined with the research results in recent years, the rock formation and lithospheric stretching/thinning of the lithosphere dynamics environment - asthenosphere has larger contact interaction mechanism [47]. In addition, there are research scholars study a shear drive upwelling (SDU) mechanism, it is only through the asthenosphere of viscous shear flow heterogeneity caused upwelling. Using numerical flow model, studied the viscosity heterogeneity within the asthenosphere on the influence of viscous shear flow. Research shows that the mechanism is largely due to the interaction of asthenosphere and lithosphere and asthenosphere and shearing action will produce upwelling, hereinafter referred to as asthenosphere upwelling, leading to the mantle melting and intraplate volcano magma eruption.

Fig. 2. A schematic diagram of the formation of zuadakite volcanic rocks

In recent years, some scholars have found similar adakian andesite and inganite [48– 51] in the late Mesozoic volcanic rocks in eastern China. The genesis of these rocks is not directly related to subduction of oceanic plate. Has some evidence that the period of late Mesozoic in the lithospheric stretching along the southeast coast thinning, asthenosphere upwelling extensional environment, leading to a large magmatic activity area. In general, the genesis of mafic magma in the cretaceous of zhejiang-fujian province can be attributed to the interaction of lithosphere-asthenosphere and decompression melting products in the case of lithospheric extensional structure. The extensional thinning

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of the lithosphere is probably the result of extensional collapse after the indo-chinese orogeny and the action of multiple surrounding plates. Dupal anomaly also reflects asthenosphere distribution [52]. The existence of the phenomenon in the upper mantle of the western Pacific Ocean has not been clearly concluded. Some scholars believe that Dupal anomaly is caused by the northward shift of asthenosphere characteristics in the southern hemisphere, or the mixed asthenosphere in the lower part of the east Asian continent [53]. The location of the south China sea at the junction is of great significance to the distribution of Dupal anomaly. They found that Dupal anomalies of basalts in the south China sea were from different sources from other plates, indicating that Dupal anomalies of basalts in the south China sea reflected the asthenosphere characteristics of the southeast Asian continent. This research result is of great value for studying the origin of mantle endolith in the south China sea and the source of Dupal anomalies in the asthenosphere in the southern hemisphere. In other words, the phenomenon of Dupal anomaly is of great significance for studying the distribution of asthenosphere in the northern and southern hemispheres. The asthenosphere and lithosphere in intraplate volcanic formation mechanism are summary. (1) the genesis of some volcanoes (such as mafic magma in the cretaceous of zhejiang and fujian) is the result of the interaction between lithosphere-asthenosphere under the background of lithospheric extension, while the related lithospheric extension/thinning is the result of the action of surrounding plates. (2) the difference in the source of Dupal anomaly of basalt in the south China sea from other plates reflects the asthenosphere characteristics of the southeast Asian continent, which is of great significance to the study of asthenosphere distribution in the northern and southern hemispheres.

4 Hot Spot Volcano Formation Mechanism The above two cases are the main mechanism of intra-plate volcanic formation, which can explain the slow and stable volcanic activity. However, these two models cannot be used to explain the formation of the Hawaiian islands, Reunion, Yellowstone park and Galapagos islands [54]. So still need to other models to explain further. For piece of undersea volcanoes, or continuous emergence of volcanic islands, they are the cause of the great probability is the hot spot volcanism [54, 55], below the plate there is a constant source of heat, produces a constant heat source to the upper mantle or fluctuation of mantle plume mantle boundary, when moving plates, constant in the hot mantle plume will leave over the plate track, which is a series of consecutive volcano. Although derived from the same plume, the composition of volcanic magma varies with the thickness of the lithosphere. Based on plate reconstruction and geophysical data, the series of volcanoes (Central volcanoes and leucite series volcanoes)developed in the Cosgrove hot spot trajectory in eastern Australia were formed by the same mantle plume that broke through the lithosphere and ejected to the surface at different ages. However, Davies et al. [56] found the thickness of the lithosphere of magma composition has important influence.

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5 Conclusion The subduction of intraplate volcanic eruptions in mainly through deep shallow dehydration and dehydration of the plates, as well as the plate fracture occurred after stranding, causing the mantle convection. (1) the influence of lithosphere and asthenosphere on the formation of intraplate volcanoes is mainly due to the interaction between lithosphere-asthenosphere under the background of lithosphere extension, which causes asthenosphere upwelling and thus leads to the formation of magma. (2) formation mechanism of hot spot volcanoes: there is a constant heat source deep in the lower mantle. When the plates move, a series of volcanoes will be formed on the plates, and a series of seamounts will be formed on the seabed. (3) for seamounts that appear in patches, their characteristics are contrary to those of hot volcanoes, which may be caused by the activation of old mantle materials.

References 1. Zhao, B.: Recognizing volcanoes. City Disast. Reduct. (5) (2018) 2. Wang, J.L., Zou, Y., Sun, J.X., Zhang, W.J., Zhang, C.J.: A review of global volcanic activity in 2016. Recent Dev. World Seismol. (9) (2018) 3. Yu, H.M.: Volcano classification. City Disast. Reduct. (5) (2018) 4. Sheng, J., et al.: Influence of the Pacific plate subduction on the Tianchi volcano. City Disast. Reduct. 41(11) (2018) 5. Hu, J.F.: Detailed structures of the 660-km discontinuity and D” discontinuity in mantle. Dissertation for Master, Zhejiang University (2019) 6. Alt, J.C., Shanks, W.C., III., Jackson, M.C.: Cycling of sulfur in subduction zones: the geochemistry of sulfur in the Mariana Island Arc and back-arc trough. Earth Planet. Sci. Lett. 119(4), 477–494 (1993) 7. Yan, Q., Zhang, P., Metcalfe, I.: Geochemistry of axial lavas from the mid- and southern mariana trough, and implications for back-arc magmatic processes. Mineral. Petrol. 113, 803–820 (2019) 8. Xu, Z.Q., Zhao, Z.B., Ma, X.X., Chen, X.J., Ma, Y.: From Andes orogen to Gangdese orogeny: from ocean continent subduction to continent- continent collision. Acta Geol. Sinica 93(1), 1–11 (2019) 9. Yang, W.C., et al.: Asthenosphere of the Qinghai Tibet Plateau and subduction of the Tethys ocean plate. Geol. Rev. 65(3) (2019) 10. Tian, Y., et al.: Effects of subduction of the western Paffic plate on tectonic evolution of Northeast China and geodynamic implications. Chin. J. Geophys. 62(3), 1071–1082 (2019) 11. Tang, Y.C., et al.: Changbaishan volcanism in Northeast China linked to subduction-induced mantle upwelling. Nat. Geosci. 7(6), 470–475 (2014) 12. Wei, W., Zhao, D.P., Xu, J.D., Wei, F.X., Liu, G.M.: P and S wave tomography and anisotropy in Northwest Pacific and East Asia. J. Geophys. Res. 120(3), 1642–1666 (2014) 13. Lei, J.S., et al.: Is there a gap in the stagnant pacific slab in the mantle transition zone under the Changbaishan volcano. Acta Petrol. Sinica 34(01), 13–22 (2018) 14. Ma, F.F., Lou, D., Dai, L.M.: Numerical simulation of subduction-induced molten plume: destruction of overriding plate and its dynamic topographic responses? Marine Geol., Quarter. Geol. 39(5), 186–196 (2019)

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Finite Element Analysis of Lateral Bearing Capacity for Pile in Spatially Variable Clay Junjie Dong(B) , Jiangtao Yi, Fei Liu, Po Cheng, and Zhen Wang School of Civil Engineering, Chongqing University, Chongqing 400045, China [email protected]

Abstract. Pile foundations are widely used in high-rise buildings, bridges, transmission towers, offshore platforms, and offshore wind power structures. In addition to bearing vertical loads, these structures also bear relatively large horizontal loads. Therefore, many scholars have carried out studies on the lateral bearing capacity of pile foundations. In these studies, the undrained shear strength is a deterministic parameter, which increases uniformly or linearly in the entire soil. However, other studies have shown that the lateral bearing capacity of piles may be overestimated if the spatial variability of the soil is not considered. Therefore, this paper will use the three-dimensional random finite element analysis method to study the lateral ultimate bearing capacity of the pile foundation in the spatially variable clay. Through the analysis, it is found that the random lateral ultimate bearing capacity obeys the log-normal distribution, and the relationship between the safety factor and the failure probability is established. The research results of this paper provide a basis for the safe design of the lateral bearing capacity of the pile foundation. Keywords: Spatial variability · Random finite element analysis · Lateral bearing capacity of pile · Pile · Failure probability

1 Introduction At present, the research on the lateral bearing capacity of pile foundations is mainly carried out through theoretical analysis, model tests and numerical simulations. These studies are mainly carried out based on the pile-soil response of the pile foundation. In these studies, the P-y curve method is considered to be a more effective method to evaluate the lateral bearing capacity of piles, and many scholars have researched, discussed and improved the P-y curve, such as the P-y curve method recommended by API [1]. This method is mainly based on the field test conducted by Matlock [2]. Through this test, Eq. (1) defines ultimate soil resistance Pu .    su Z  Pu = Np su = min 3su + σv + J (1) ), 9su D where Np is the lateral pile capacity factor, Z is the depth below soil surface, σv  is the vertical effective stress, J is the dimensionless empirical constant, su is the undrained shear strength. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 259–265, 2023. https://doi.org/10.1007/978-981-19-4293-8_27

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Later, more and more scholars have carried out research on this formula, and revised this formula through numerical simulation and theoretical analysis. These studies found that the soil Np is not 9 at the deeper position of the soil layer. The theoretical analysis of Randolph & Houlsby [3], Murff & Hamilton [4] and Martin & Randolph [5] found that the value range of Np for smooth piles is 9–10, and for absolutely rough piles the value range is 10–12. Later, Templeton [6], and Tzivakos & Kavvadas [7] used 3D finite element simulation to find that this value ranges from 12 to 15. Truong & Lehane [8] In the centrifuge test, it was found that this value fluctuates around 12.5. However, these results given by these authors are restricted to a deterministic approach without considering the soil spatial variability. Thus, there is still a need to study develop a design approach for estimating the laterally load of pile considered soil spatial variability. In this paper, the probabilistic lateral load of pile in spatially variable soils with linearly increasing shear strength is investigated by three-dimensional random finite element analysis.

2 Methodological Aspects This paper will use Abaqus 6.14 to carry out three-dimensional random finite element simulation, use the modified linear estimation method Liu [9] to generate a threedimensional Gaussian random field, and transform it into a lognormal random field through exponential transformation. The selection of the lateral ultimate bearing capacity of a pile is generally based on the allowable displacement of the pile head in the design. In this paper, the ultimate lateral bearing capacity F of the pile will be determined based on the load-displacement curve of the pile head. The corresponding lateral load when the head lateral displacement y reaches half the diameter is regarded as the ultimate bearing capacity. Random parameter combinations used in this study are listed in the Table 1. Table 1. Parameter combinations for the undrained shear strength of soil. Serial number

COVsu

θh (m)

θv (m)

I

0.1

3.8

50

II

0.3

3.8

50

III

0.5

3.8

50

IV

0.3

3.8

20

V

0.3

3.8

90

VI

0.3

1.5

50

VII

0.3

10

50

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3 Numerical Simulation 3.1 Finite Element Model This three-dimensional finite element analysis will be performed using the commercial software Abaqus 6.14. In order to ensure the effectiveness of the simulation, the deterministic soil simulation results will be compared with the centrifuge test reported by Truong & Lehane [8]. The finite element model size is shown in Fig. 2. In this research, the soil was modeled by an elastoplastic model with a tresca yield criterion. The ratio of the elastic modulus to the undrained shear strength of the soil is E = 500su . Table 2. Parameters of spatially varying soil. Properties of soil

Denotation

Value

Value of su at mudline (kPa)

su0

0

Gradient of su (kPa/m)

k

1.4

Unit weight of soil (kPa/m3 )

γ

6

Poisson’s ratio

ν

0.49

Internal friction angle (°)

ϕ

0

Horizontal scales of fluctuation of su (m)

θh

20 –90

Vertical scales of fluctuation of su (m)

θv

1.5–10

Coefficient of variation of su

COVsu

1.0 –5.0

Pile body is made of linear elastic material, the cross section is a round solid element, Model parameters of the finite element analysis will be placed in the Table 2 and Table 3. Table 3. Parameters of pile. Properties of soil

Denotation

Value

Pile diameter (m)

D

0.88

Flexural rigidity of the pile (kNm2 )

EI

106

Pile embedment length (m)

L

6

load eccentricity from soil surface (m)

e

1.32

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3.2 Model Verification Compare the load-displacement curve obtained by the finite element simulation in the deterministic soil with the result of the centrifuge test as shown in the following Fig. 1. We can find that the results of the numerical simulation are consistent with the experimental results of the centrifuge test, which verifies the accuracy of this simulation.

250

/(k*D^3)

200 150 100

Finite-element result

50

Centrifuge test result

0 0

0.2

0.4 0.6 y/D

0.8

1

Fig. 1. Comparison of centrifuge test results and numerical simulation results.

Fig. 2. Finite element model.

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4 Random Data Analysis This section will combine the Monte Carlo simulation method to analyze the influence of the spatial variability of soil undrained shear strength on the lateral bearing capacity of piles. In this paper, the K-S test is used to analyze the goodness of fit for the lateral bearing capacity of the pile obtained by the simulation. In the process of sampling, the number of samples will determine the authenticity of our simulation. Therefore, the number of samples is analyzed and it is found that the simulation results have converged when a group of spatially variable soils are simulated for 200 times. In this paper, seven groups of spatially variable soils with different parameter combinations are selected, and each group of parameters is simulated 200 times. The K-S test results are shown in the following Table 4. Table 4. The result of K-S test. Serial number

I

II

III

IV

V

VI

VII

P

1

0.74675

0.86891

0.55472

1

0.64335

0.71758

It can be seen from the above Table 4 that the lateral bearing capacity of random soil simulation under each set of parameters conforms to the lognormal distribution. In order to facilitate the study of the relationship between failure probability and safety factor, this paper defines the ratio of random lateral bearing capacity Fran to deterministic lateral bearing capacity Fdet as the bearing capacity model factor λ. Equation (2) defines failure probability P where  is the CDF of normal distribution, μln(λ) and δln(λ) are the mean and standard deviation of the natural logarithm of λ, respectively.   ln(1/n) − μln(λ) (2) P(λ < 1/n) = φ δln(λ) The following Fig. 3 shows the relationship between failure probability and safety factor n.

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70% Probability of failure

60%

Parameter of combination Ⅰ Parameter of combination Ⅱ Parameter of combination Ⅲ Parameter of combination Ⅳ Parameter of combination Ⅴ Parameter of combination Ⅵ Parameter of combination Ⅶ

50% 40% 30% 20% 10% 0% 1

1.2

1.4 n

1.6

1.8

Fig. 3. Variation trend of probability of failure with n for each parameter combination.

The specific data of the simulation will be shown in Table 5. Table 5. n corresponding to different probabilities of failure under each parameter combination. Probability of failure (%)

Parameter combinations I

II

III

IV

V

VI

VII

1

1.09

1.31

1.49

1.33

1.25

1.195

1.46

0.1

1.125

1.42

1.67

1.43

1.335

1.265

1.65

0.01

1.145

1.51

1.83

1.54

1.41

1.41

1.8

5 Conclusion From this research, we can find that under the same failure probability: as the coefficient of variability COVsu increases, the safety factor also increases, the horizontal correlation length θh has little effect on the safety factor, and with the vertical correlation length θv Increasing the safety factor will also increase. When the failure probability is within the range of 1% to 0.1%, the safety factor of 1.6 can meet the requirements for the failure probability of the pile foundation.

References 1. API (American Petroleum Institute). ISO 19901-4: Geotechnical and foundation design considerations. API recommended practice 2GEO; 1st edn. Washington, DC (2011)

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2. Matlock, H.: Correlation for design of laterally loaded piles in soft clay. In: Proceedings of the Offshore Technology Conference, Houston, TX, USA, Paper OTC 1204 (1970) 3. Randolph, M.F., Houlsby, G.T.: The limiting pressure on a circular pile loaded laterally in cohesive soil. Géotechnique 34(4), 614–623 (1984) 4. Murff, J.D., Hamilton, J.M.: P-ultimate for undrained analysis of laterally loaded piles. J. Geotech. Eng. 119(1), 91–107 (1993) 5. Martin, C.M., Randolph, M.F.: Upper-bound analysis of lateral pile capacity in cohesive soil. Géotechnique 56(2), 141–145 (2006) 6. Templeton, J.: Finite element analysis of conductor/seafloor interaction. In: Proceedings of the Offshore Technology Conference, Houston, TX, USA, Paper OTC-20197 (2009) 7. Tzivakos, K.P., Kavvadas, M.J.: Numerical investigation of the ultimate lateral resistance of piles in soft clay. Front. Struct. Civ. Eng. 8(2), 194–200 (2014) 8. Truong, P., Lehane, B.M.: Effects of pile shape and pile end condition on the lateral response of displacement piles in soft clay. Géotechnique 68(9), 794–804 (2018) 9. Liu, Y., Lee, F.-H., Quek, S.-T., Beer, M.: Modified linear estimation method for generating multi-dimensional multi-variate Gaussian field in modelling material properties. Probabil. Eng. Mech. 38, 42–53 (2014)

Application of Numerical Simulation in Teeth Propotion Design of Diamond Bit Yanjun Xu1(B) , Liang Xu1 , Yibo Liu1 , and Qiang Xu2 1 Advanced Technology & Materials Co., Beijing 100095, China {xuyanjun,xuliang}@gangyan-diamond.com, [email protected] 2 Beijing Gang Yan Diamond Products Company, Beijing 102200, China [email protected]

Abstract. The teeth proportion of bit is one of the most important factors affecting the comprehensive performance of the bit. Through the comparison between the numerical simulation and the experimental data in this paper, it can be concluded that for the 102 mm diameter bit, when the number of bit teeth is 9 and the teeth proportion is 67%, the equivalent stress and the maximum shear stress are the highest under the load of 300N and rotating speed 1250 rpm, which reflects the high efficiency of the bit; When the number of teeth is 8 or 9, the strain energy is the smallest, which reflects the long life of the bit. In conclusion, when the teeth proportion is 67%, the comprehensive performance of the bit is the best. Through multiple modeling to verify the comprehensive performance of the whole series of bits, the guide book of bit teeth proportion can be obtained, which can be used for the specification design of the whole series of bits. Keywords: Finite element · Sliding wear · Diamond bit · Equivalent stress · Maximum shear stress

1 Introduction Diamond bit is generally composed of three parts: drill pipe, connection and diamond cutting teeth (Fig. 1). The comprehensive performance of drill bit is mainly reflected in drilling speed and bit life, as well as other subjective feelings such as cutting feel and jitter. Bit teeth propotion refers to the ratio of the projected area of cutting teeth to the total circumference area. The teeth propotion of a bit is the most important parameter other than the formula, so a reasonable design of the teeth propotion is very important for the overall performance of the bit. This paper focuses on the teeth propotion of diamond bit, and mainly studies the influence of different teeth propotion on the comprehensive performance when drilling concrete. The traditional method explores the optimal teeth propotion through a large number of tests [1, 2]. For a single diameter bit, it needs to be tested 3–5 times. The whole series of bits have dozens of specifications, which has a huge test workload and a serious waste of human resources and materials. Through numerical simulation, the optimal value of teeth propotion matching drilling performance is found, supplemented by a small amount of experimental data, and the database of bit service performance is obtained to guide production, which has practical significance. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 266–274, 2023. https://doi.org/10.1007/978-981-19-4293-8_28

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Fig. 1. Structure of diamond bit.

2 Test Method 2.1 Technical Ideas In this paper, the sliding wear process between drill bit and concrete is analyzed from equivalent stress, maximum shear stress and strain energy, in order to obtain the optimal teeth propotion, which maximize the equivalent stress of concrete and minimize the strain energy of drill bit. 2.2 Modeling Process This paper chooses the 102 mm diameter bit which the tooth length is 24 mm, and the number of teeth is 6, 7, 8, 9, 10 and 11 respectively. The teeth proportion is calculated as the basic data of modeling. The bit matrix is CoNiMnW [3], and the volume fraction of diamond is 40%. The density, Young’s modulus and Poisson’s ratio of the matrix at room temperature can be obtained through JMatPro, and test materials are established in the material library. Concrete parameters are directly selected in the material library. The contact type is surface to surface contact mode. The upper bit is the elastomer contact surface and the lower concrete is the elastoplastic target surface [4]. The contact type is frictional and the friction coefficient is 0.2. 300N pressure and 1250 rpm rotation rate are applied to the drill bit, which is 0.048 s for 102 mm drill bit rotating one turn. The end time step is set to 0.05 s, the initial time step is 0.01 s, the minimum time step is 0.001s and the maximum time step is 0.05 s. 22.8 N•m of bit torque can be calculated by the power of 3.0 kw and linear velocity of 6.7 m/s. [5, 6] Fixed restraint shall be applied to the lower surface of the concrete.

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3 Discussion of Results 3.1 Equivalent Stress The equivalent stress follows the fourth strength theory of material mechanics, which is a yield criterion. It is an equivalent stress based on shear strain energy, which can be used to evaluate fatigue and failure. Equivalent stress is the key factor to determine whether concrete is broken or not. The greater the equivalent stress of concrete, the easier it is to break. From the comparison cloud diagram of equivalent stress, it can be seen that the equivalent stress does not change in proportion to the pressure and contact area. There is an optimal teeth propotion to maximize the equivalent stress. When the number of bit teeth is 8 and 9, the equivalent stress of the concrete is relatively uniform. It can be seen from Fig. 2 that when the number of teeth is 9, the area value corresponding to the equivalent stress is the largest, which means that the crushing area is the largest. The equivalent stress increases first and then decreases, and it is highest when the number of teeth is 9. It can be inferred that the drilling efficiency increases first and then decreases when the number of bit teeth is from 6 to 11.

Fig. 2. Comparison of equivalent stress of bits with different tooth numbers.

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It can be seen from Fig. 3 that the equivalent stress on outside of bit tooth is small, the inner side is large. Different equivalent stress of bit teeth results in less wear on outside than innerside during drilling, and bit tooth has the phenomenon of low innerside and high outside, as shown in Fig. 4.

Fig. 3. Equivalent stress diagram of teeth.

Fig. 4. Outer wear of teeth is less than inner wear.

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3.2 Maximum Shear Stress The third strength theory is the maximum shear stress theory, assumes that the maximum shear stress is the cause of material yield, that is, under any stress state, as long as the maximum shear stress somewhere in the material reaches the limit value of shear stress at uniaxial tensile yield, the material will undergo significant plastic deformation or yield.

Fig. 5. Comparison of maximum shear stress.

It can be seen from Fig. 5 that the variation trend of the maximum shear stress is basically similar to equivalent stress, which is the inflection point when the number of bit teeth is 9. It can also be inferred that the drilling efficiency first increases and then decreases when the number of bit teeth is from 6 to 11.

Fig. 6. Maximum shear stress of bit.

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Fig. 7. Cracks in drill pipe.

It can be seen from Fig. 6 that the maximum shear stress is at the initial and end of the teeth, and the connection position between the teeth and drill pipe which is close to drill pipe. These positions are weak and if the strength is not enough, it is likely to cause drill pipe deformation and crack (Fig. 7) or weld fracture. Therefore, some drill pipe need to be thickened when they are designed close to the bit teeth. 3.3 Strain Energy The strain energy is directly proportional to the friction work, which reflects the deformation and wear caused by energy change. Friction power plays a decisive role in bit wear. The greater the friction work, the more serious the wear of the drill bit. The smaller the friction work, the longer the service life of the bit. From the comparison of strain energy shown in Fig. 8, it can be seen that when the number of teeth is 8 or 9, the strain energy is small, the friction work is small, the bit teeth are more wear-resistant, which reflecting the characteristics of long service life of the bit.

Fig. 8. Comparison of strain energy.

The performance of the bit is mainly reflected in the two aspects of drilling speed and bit life. Based on the above analysis, it can be concluded that the comprehensive

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performance is the best when the number of bit teeth is 9 and the teeth proportion is 67%. This is basically consistent with the test data, as shown in Table 1. Table 1. Drilling test data of diamond bit. Machine

weka32, 3.2 kw, 1250 rpm

Drilling material

C35 CONCRET

Samples No.

1#

2#

3#

Diameter (mm) Num of Segments

7

8

285

278

258

305

10# of cut Average Time/s

4#

102 9

10

Finishing time (Sec.)

Drilling rate comp.

90.5%

92.80%

100%

84.50%

Segment height wear/mm

4.8

3.0

2.4

2

Life rate comp.

50%

80%

100%

120%

Combining the equivalent stress, maximum shear stress, strain energy and drilling test data, the comparison can be obtained as shown in Table 2, and the goodness of fit is shown in Fig. 9. It can be seen from Fig. 9 that the calculated data of equivalent stress and maximum shear stress are highly consistent with the experimental data, Especially when the number of teeth is 9 which the teeth propotion is 67%, the fitting degree is the highest. The fitting degree between the calculated value of bit life and the experimental value is slightly lower, because the input parameters are different from the actual working conditions, such as material parameters and friction coefficient. Therefore, the more accurate the input parameters of numerical simulation are, the closer the calculated results are to the actual data. Table 2. Comparison of equivalent stress, maximum shear stress, strain energy and drilling test. No. of teeth

7

8

9

10

Teeth proportion

52%

60%

67%

75%

Equivalent stress

80%

87%

100%

83%

Maximum shear stress

89%

88%

100%

82%

Strain energy

101%

102%

100%

96%

Drilling speed efficiency

90.5%

92.8%

100%

84.5%

Bit life

50%

80%

100%

120%

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Fig. 9. Comparison of fitting degree of three results.

4 Conclusion and Prospect Through the comparison of numerical simulation and experimental data in this paper, it can be concluded that when the number of teeth is 9 and the teeth proportion is 67%, the equivalent stress and maximum shear stress are the highest under the conditions of 300 N load and 1250 rpm rotating speed, which reflects the high efficiency of the bit. When the number of teeth is 8 or 9, the strain energy is the smallest, which reflects the long life of bit; in conclusion, when the teeth proportion is 67%, the comprehensive performance of bit is the best. The teeth proportion is one of the most important factors affecting the comprehensive performance of bit. Therefore, through multiple modeling to verify the comprehensive performance of the full series of bits, the bit teeth proportion guide can be obtained for the specification design of the full series of bits. Numerical simulation plays a more and more important role in industrial production and manufacturing. It can greatly shorten the R & D cycle, reduce the test cost and improve the target rate of product R & D.

References 1. Lin, M., Li, W.J., Song, D.D.: Simulation and experimental research on cutting efficiency of the impregnated teeth. Chinese J. Undergr. Space and Eng. 6, 1558–1563 (2018) 2. Chen, M.T., Wang, W.J., Liu, Q.Y.: Study on the relationship between rail wear volume and friction work. J. Railway Eng. Soc. 146(11), 52–55 (2010) 3. Gao, C.Q.: Metal tribology. Press of Polytechnic University of Harbin, Harbin, p. 39−42 (1998)

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4. Sun, Y.H., Gao, K., Zhang, L.J.: High drilling efficiency and wear-resistant mechanism of coupling bionics impregnated diamond bit. J. Jilin Univ. (Earth Science Edition) 42(3), 220–225 (2012) 5. Wang, J.L., Zhang, S.H., Zhou, H.F.: Simulation analysis on the influence of cutting teeth structure on drilling efficieney of impregnated diamond bit. Explor. Eng. (Rock & soil drilling and tunneling) 42(3), 69–75 (2015) 6. Xu, L., Sun, Y.H.: Efficient rock fragmentation mechanism analysis of impregnated diamond bionics bit. J. Jinlin Univ. 38(6), 1015−1019 (2008)

Structural Engineering and Structural Mechanics

Bayesian Networks and Their Application to the Reliability of FRP Strengthened Beams Osama Obaid(B)

and Moussa Leblouba

Department of Civil and Environmental Engineering, University of Sharjah, P.O. Box 27272, Sharjah, UAE {u18200523,mleblouba}@sharjah.ac.ae

Abstract. Bayesian Network (BN) is one of the powerful computational methodologies for rare events prediction (i.e., failure probability). Its concept is based on identifying all the different parameters affecting any given problem’s expected output and formulating a network among these variables based on their probabilistic dependencies. Moreover, BNs are capable of handling newly available data and updating the existing model to deliver an updated prediction based on the added information. This study explores the suitability of BNs in predicting the structural reliability of fiber-reinforced polymers externally bonded reinforced concrete beams by estimating their probability of failure. The present article is a preliminary study of a more extensive program to apply the BN framework to assess the structural reliability of bridge systems. The BN will identify the bridge components and explore the probability of failure for each one of them separately. The directed acyclic graph will also illustrate the variables’ dependencies and their conditional probabilities. Finally, the study will evaluate the conditional probability of each specific event occurrence. The BN can also be used for bridge system probability of failure prediction, structural systems monitoring, and maintenance requirements. Keywords: Bayesian networks · Fiber-reinforced polymer · Reinforced concrete · Directed acyclic graph · Reliability

1 Introduction Bayesian networks are a type of graphical model that can be used to represent the relationships between variables in a problem. They are often used in artificial intelligence applications, as they can handle variable uncertainty better than other types of models. Bayesian networks are represented by a directed acyclic graph (DAG), which shows the nodes (variables) and the arrows between them representing the dependencies or cause-effect relationships. Each node is associated with a conditional probability that represents the variable’s probability of existence. The values of these probabilities are usually obtained through historical data or expert judgment. In what follows, we review some recent and relevant publications. Shahriari and Naderpour [1] performed a reliability and sensitivity analysis on an experimental data set of beams with different wrapping schemes. They found that the © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 277–284, 2023. https://doi.org/10.1007/978-981-19-4293-8_29

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fully wrapped configuration was the least reliable and that increasing the concrete grade or applied load led to an increase in reliability. Additionally, they found that the fiberreinforced polymers (FRP) modulus of elasticity was the most efficient parameter on the resulting probability of failure. Firouzi, Taki, and Mohammadzadeh [2] studied the chloride-induced corrosion effect on externally bonded carbon fiber reinforced polymer (CFRP) beams and found that in harsh environments, the existing probability of brittle shear failure may weaken the FRP strengthening. Zhou et al. [3] looked at the reliability-based design analysis of FRP shear strengthened reinforced concrete (RC) beams and found that while the reliability index target was increasing, the resistance factor required a higher FRP amount compared to the partial safety factor format. Tolentino and Carrillo-Bueno [4] developed a methodology to evaluate the structural reliability of a RC building at the end of the time interval subjected to different data sets of seismic ground motions. The confidence factor was used as a measure of reliability, and an enhanced closed-form mathematical expression was developed to consider the degradation of structural capacity caused by corrosion. The results showed that there is a difference of 3.5% in building construction when the magnitude of the seismic input increases to 6.5 or greater. A study by Vu and Stewart [5] investigated the effects of various durability design specifications on the long-term reliability of a RC bridge. The authors found that deicing salts are one of the most affecting causations of the structure’s long-term deterioration and that it leads to a reduction in the structural safety of the low durability design specification. Dueñas-Osorio and Padgett [6] proposed a closed-form combinatorial methodology that aims to assess all possible manners that bridge components may be subjected to failure under different limit states. In their study, the authors illustrated the proposed augmentation methodology by considering bridges as built-in addition to rehabilitated conditions under seismic loads and the application of the reliability analysis method. The results showed an increase of 4 to 20% in system fragility at moderate limit states when compared to methods that do not consider augmentation. The enhanced Bayesian network (eBN) computational framework developed by Straub and Der Kiureghian [7] combines normal Bayesian networks (BNs) with the methods of structural reliability (SRMs). This approach takes advantage of a node elimination algorithm that removes continuous nodes to produce reduced Bayesian networks (rBNs). These rBNs will only have discrete nodes that can be solved by current inference and algorithms. The resulting enhanced eBNs are capable of accurately evaluating the probabilities of complex structures’ rare events. Luo and Dong [8] proposed a new method for forecasting the bearing capacity of pile foundation on Jeffrey’s Noninformative Prior by utilizing the Bayesian theory Markov chain Monte Carlo (MCMC) method. This method was presented to estimate the normal distribution parameters. In addition to using numerical simulation to create pseudo samples, the study also found that the Bayesian theory was better than the maximum likelihood in forecasting the normal distribution model, and the accuracy was enhanced by increasing the pseudo sample number.

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Studies on BN applications have been studied extensively in recent years. For instance, Vereecken, et al. [9] utilized Bayesian Networks to update the evaluation of service life model parameters for concrete girders subjected to chloride-induced corrosion. The analysis found that the Bayesian Networks accurately represented the data and updated the service life model parameters. Mahadevan et al. [10] proposed a methodology to use Bayesian Networks in the reliability assessment of structural systems. The authors found that their proposed methodology proved its applicability to the reliability assessment of large and complex structures when new data is introduced. Liu et al. [11] developed a reliability and serviceability evaluation technique of a simply supported bridge using modal flexibility theory and enhanced Kriging approach enhanced by artificial bee colony algorithm. The authors found that the bridge deflection values indicated a high level of agreement between the empirical and the proposed methodology. Hackl and Kohler [12] proposed a stochastic modeling framework for RC corrosioncaused deterioration which uses Bayesian Networks. Hackl and Kohler found that their proposed framework provides a general overview of existing service life models and facilitates the estimation of unexpected and rare events for RC structures accurately in a consistent way. Abadi et al. [13] used Bayesian networks to perform reliability analysis of moored floating structures. The authors found that their methodology can be used to reduce the risk of marine structures. As a first part of the ongoing project, to present paper, we explore the application of BNs to predict and update the probability of failure of RC beams externally bonded with CFRP. An application is provided to showcase how to estimate different probabilities based on the developed network.

2 Bayesian Networks 2.1 Concept Bayesian networks follow the concept of Probabilistic Graphical Modeling. It aims to calculate the uncertainties by utilizing the concept of probabilities by using the Directed Acyclic Graphs. The probability of P (A, B, C, D, E) is called the joint probability, i.e., the probability of these variables happening at the same time. As shown in Fig. 1, the nodes (A, B, C, D, E) represent the variables, and the links represent how these variables are related. The relationship between variables is the conditional probability that connects the variable. In other words, P (E|D) means the conditional probability of the occurrence of an event (E) given that event (D) has already occurred. The Bayesian Network can be represented by the below equation: n P(Yi|parents(Yi)) (1) P(Y1 , Y2 , . . . . . . .Yn ) = i=1

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In the below example, the joint probability of the variables (A, B, C, D, E) equals to: P(A, B, C, D, E) = P(E|C, D) × P(C) × P(D|A, B) × P(A) × P(B)

(2)

Fig. 1. Directed acyclic graph hierarchy.

2.2 Construction Constructing a BN depends on assigning conditional probabilities for each variable. These probabilities can be acquired from two main sources: firstly, the experts’ opinion of the relative field, and secondly, the available statistical data. In order to build a BN, five main steps must be followed: 1. Identify the variables that will be included in the model and will highly affect the problem’s anticipated outcomes. 2. Variables Discretization: Specify the state of the variables; for example, if it is high and low, present or absent, difficult and easy, and so on. 3. The hierarchical structure of the problem-directed acyclic graph shall be identified, i.e., the network edges in addition to the dependencies\independencies that will formulate the shape of the BN. 4. Specify the conditional probability functions for all the variables. This will clear the dependencies among the BN variables. 5. Finally, results verification shall be executed through sensitivity analysis as well as validating the model by the analysis of similar scenarios with previously known results.

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3 Application to the Reliability of FRP Strengthened Beams The below graph demonstrated in Fig. 2 below represents the parameters that affect the reliability of FRP externally bonded concrete (EBFRP) strengthening with their assigned conditional probabilities. These different parameters are the Wrapping Scheme (W), the Shear Gain (SG), the FRP sheets center to center spacing (Sf ), the beam Shear Span to its effective depth (s/d), and the FRP mode of failure (M). The description denoted for each parameters’ categorization is as follows: • Wrapping Scheme is split into four categories, namely (1) Gr: Grooving, (2) S: Side Bonding, (3) U: Three Side Bonding, and (4) U+: Three Side Bonding with Anchoring, W: Full Wrapping. • Shear Gain is split into three categories, namely (1) L: Low, (2) M: Medium, and (3) H: High. • FRP sheets Spacing is split into two categories, namely (1) L: Low and (2) H: High. • Beam Shear Span to its effective depth (s/d) is split into two categories, namely (1) L: Low and (2) H: High. • Model of Failure is split into three categories, namely (1) RT: Rupture, (2) DB: Debonding, and (3) P: FRP Pass. • Probability of Failure is split into two categories, namely (1) F: Fail and (2) P: Pass. As an application, we consider computing the following probabilities. The probability of low shear gain value equals:      n (SG L × W GR × Sf L × s/d L + SG L Sf nL s/d nL = P SG L = P SG L |WGR GR H L L GR L H L GR H • × W × Sf × s/d + SG × W × Sf × s/d + SG × W × Sf . × s/d H + W S × Sf L × s/d L . . . ...) = (0.075 × 0.15 × 0.7 × 0.65

+ 0.125 × 0.15 × 0.3 × 0.65 + . . . .) = 0.1575 The probability of Rupture Mode of Failure value equals to:         P(MRT ) = p M RT |SG L × P SG L + p M RT |SG M × P SG M     • + P M RT |SG H × P SG H = 0.3 × 0.1575 + 0.2 × 0.3575 + 0.15 × 0.485 = 0.1915

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Fig. 2. Directed acyclic graph for example 1.

Based on the previous illustrative example, it can be inferred that the Bayesian network directed acyclic graph can be successfully deployed to obtain a precise estimation of the FRP externally bonded RC system’s overall probability of failure, in addition to the probability of each of the system’s components separately, such low or high levels or the probability associated with conditional statements.

4 Application to Beam Failure Mode Prediction Moving to the second illustrative example shown in Fig. 3, the parameters that affect the mode of failure of the reinforced concrete beam whether it is a brittle, ductile failure, or shear failure. • The probability of P (P, Fc, R, B, TH, W) = p (P | Fc, R, B) × p(R) × p(B) × P (Fc |TH, W) × p(TH) × p(W). The description denoted for each variable is as follows: • • • • • •

Water Cement Ratio (W): L: Low, H: High Temp and Humidity (TH): L: Low, H: High Beam Width (B): L: Low, H: High. Concrete Strength (Fc): L: Low, H: High. Reinforcement % (R): L: Low, H: High. Probability of Failure (P): F: Fail, P: Pass.

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Fig. 3. Directed acyclic graph for example 2.

5 Summary The article discusses the use of Bayesian networks to predict the probability of failure for beams externally bonded with CFRP and provides a detailed illustrative example. The network is constructed based on expert opinions and statistical data. The variables that affect the reliability of the beams are discretized, and the network is hierarchically structured. The conditional probabilities for all the variables are specified, and then the failure probabilities are computed. The limitations of this study include the lack of data on the behavior of beams externally bonded with CFRP in shear. This can be overcome by future studies that collect data on the behavior of beams externally bonded with CFRP in shear from different available published databases. Acknowledgments. This study is supported by the college of graduate studies of the University of Sharjah. The authors are grateful for this support.

References 1. Shahriari, S., Naderpour, H.: Reliability assessment of shear-deficient reinforced concrete beams externally bonded by FRP sheets having different configurations. Structures 25(March), 730–742 (2020) 2. Firouzi, A., Taki, A., Mohammadzadeh, S.: Time-dependent reliability analysis of RC beams shear and flexural strengthened with CFRP subjected to harsh environmental deteriorations. Eng. Struct. 196(June), 109326 (2019) 3. Zhou, Y., Zhang, J., Li, W., Hu, B., Huang, X.: Reliability-based design analysis of FRP shear strengthened reinforced concrete beams considering different FRP configurations. Compos. Struct. 237(January), 111957 (2020)

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4. Tolentino, D., Carrillo-Bueno, C.A.: Evaluation of structural reliability for reinforced concrete buildings considering the effect of corrosion. KSCE J. Civ. Eng. 22(4), 1344–1353 (2018). https://doi.org/10.1007/s12205-017-1650-2 5. Vu, K.A.T., Stewart, M.G.: Structural reliability of concrete bridges including improved chloride-induced corrosion models. Struct. Saf. 22(4), 313–333 (2000) 6. Dueñas-Osorio, L., Padgett, J.E.: Seismic reliability assessment of bridges with user-defined system failure events. J. Eng. Mech. 137(10), 680–690 (2011) 7. Straub, D., Der Kiureghian, A.: Bayesian network enhanced with structural reliability methods: methodology. J. Eng. Mech. 136(10), 1248–1258 (2010) 8. Luo, Z., Dong, F.: Statistical investigation of bearing capacity of pile foundation based on Bayesian reliability theory. Adv. Civ. Eng. 2019(1) (2019) 9. Vereecken, E., Botte, W., Lombaert, G., Caspeele, R.: A Bayesian inference approach for the updating of spatially distributed corrosion model parameters based on heterogeneous measurement data. Struct. Infrastruct. Eng. 18, 30–46 (2020) 10. Mahadevan, S., Zhang, R., Smith, N.: Bayesian networks for system reliability reassessment. Struct. Saf. 23(3), 231–251 (2001) 11. Liu, H., He, X., Jiao, Y., Wang, X.: Reliability assessment of deflection limit state of a simply supported bridge using vibration data and dynamic Bayesian network inference. Sens. (Switz.) 19(4), 837 (2019) 12. Hackl, J., Kohler, J.: Reliability assessment of deteriorating reinforced concrete structures by representing the coupled effect of corrosion initiation and progression by Bayesian networks. Struct. Saf. 62, 12–23 (2016) 13. Abaei, M.M., Abbassi, R., Garaniya, V., Chai, S., Khan, F.: Reliability assessment of marine floating structures using Bayesian network. Appl. Ocean Res. 76(March), 51–60 (2018)

Static Loading Test of Soil-RC Pile System Using a Centrifuge Model Shuhei Takahashi1(B) , Tomoki Nakamura1 , Kazuhiro Hayashi2 , and Taiki Saito1 1 Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi-shi, Aichi,

Japan [email protected] 2 Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba-shi, Chiba, Japan

Abstract. In the 2016 Kumamoto Earthquake, reported that the pile foundations of many buildings were damaged. Evaluating the elasto-plastic behaviour and ultimate strength of RC pile foundations is important to prevent from being damaged. In this paper, to investigate the elasto-plastic behaviour of soil-RC pile interaction, static loading test was performed under a 50G field to reduced RC pile model and soil-RC pile interaction. The diameter of the reduced pile model was 25 mm (Full scale: 1.25 m). The degradation behaviour of the reduced pile model was almost equivalent to that prototype, and the FEM analysis was corresponded to the test result. Soil-pile interaction, the strength evaluated by Broms’s equation almost corresponded to the maximum strength of the test result. In the FEM analysis, its behaviour corresponded to the test result with a small displacement range, but the maximum strength was underestimated. Keywords: Soil-RC pile interaction · Centrifuge test · FEM analysis · Ultimate strength evaluation

1 Introduction In the 2016 Kumamoto Earthquake (main shock of the earthquake measured moment magnitude 7.3), many pile foundations such the city hall supported by RC pile foundation were damaged [1]. Many researchers investigated the relationship in soil-pile interaction, but there are few studies considering non-linear soil and elasto-plastic pile behaviour. K. T. Chau conducted a shaking table test and 2D FEM analysis for a soil-RC pile-structure interaction. The superstructure and pile foundation were modelled by non-linear beam elements and the soil was modelled by four-node plane strain solid elements [2]. Kimura conducted static loading tests using an RC pile model under a centrifuge field [3]. Higuchi conducted a dynamic centrifuge test and 2D FEM analysis [4]. However, these studies were not discussed about ultimate strength. Evaluating the elasto-plastic behaviour and the ultimate strength of an RC pile and the interaction is important when estimating earthquake resistance. In this paper, conducted a static loading test for a soil-RC pile system under a 50G centrifuge field and simulate the behaviour using FEM analysis. Besides, the ultimate strength of the soil- pile interaction was evaluated. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 285–292, 2023. https://doi.org/10.1007/978-981-19-4293-8_30

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2 RC Pile Model for Centrifuge Test 2.1 Design of Reduced RC Pile Model The experiment was conducted under a 50G field. Figure 1 shows the details of the reduced RC pile model (hereinafter, pile model). The pile model was designed to reproduce the elasto-plastic behaviour of concrete piles. It consisted of mortar, 4-main reinforcement bars, and a spiral hoop reinforcement bar. The diameter of the pile model was 25 mm (full scale: 1.25 m), the main reinforcement bar 1.2 mm and the spiral hoop reinforcement bar was 0.8 mm, respectively. The spiral hoop was spaced at 5 mm. The compressive strength of the mortal was 13.33 N/mm2 . Table 1 shows a comparison of pile cross sections: the main and the hoop reinforcement ratio of the model almost corresponded to the example cross section suggested by design example of foundation structures in Japan [5]. 2.2 Bending and Compression Loading Test The bending and compression loading test was conducted to evaluate the performances of the pile model. Figure 2 shows the loading system of the pile model. Its bottom was rigidly jointed to a reaction force jig, and the top was connected to a horizontal loading device by a pin jig and a vertical roller jig. The deformation was measured by a laser displacement transducer. The horizontal cyclic loading was input to 56.25 mm (2.25D, full scale: 2.813 m) above the critical section, and the loading device was controlled according to rotation angles of 0.005, 0.01, 0.02, 0.03, 0.04, 0.06, 0.08, 0.1, and 0.12 rad. The rotation angle of the model was calculated by the distance between the laser displacement transducer and the critical Sect. (56.25 mm). All subsequent data are presented herein at full scale. Table 1. Comparison of pile cross sections. RC pile model Diameter (mm) Main reinforcement bar Hoop reinforcement bar

Example cross-section

25

1800

Rebar

4-φ1.2

45-D29

Ratio (%)

0.92%

1.13%

Rebar

φ 0.8@5

D13@150

Ratio (%)

0.27

0.26

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Fig. 1. Cross section of RC pile model.

Fig. 2. Bending and compression loading system.

2.3 FEM Analysis Model of RC Pile To simulate the bending and compression loading test, FEM analysis was carried out with TDAP III [6]. Table 2 shows the details of the analysis model. Its length was 2.813 m (2.25D). Bottom of the analysis model was rigidly fixed for all degrees of freedom. Others were allowed to deform in a horizontal direction. The Young’s modulus was 8500 N/mm2 , mass density was 2.3 g/cm3 . The stiffness reduction with loading progress was determined based on the skeleton curve of the experimental result. Figure 3 shows the moment-curvature relationship for the tri-linear element. A horizontal monotonic loading was input to the top of the analysis model until the displacement was reached 0.4m. This value was determined by the cyclic loading protocol (maximum deformation was 0.34 m). 2.4 Comparison of Test and FEM Analysis Result Figure 4 shows the moment-displacement relationship of test result and FEM analysis result for the pile model. A black line indicates the test result, and a red line indicates the FEM analysis result. The maximum bending moment of the test result was 4617 kNm. In the test result, the model performed degradation behaviour after reached maximum bending strength suggesting that the model reproduced to elasto-plastic behaviour of prototype. The FEM analysis result, the red line traces the skeleton curve of the test result, indicating that FEM analysis was corresponded to the loading test.

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S. Takahashi Table 2. Details of FEM analysis model.

Length (m)

2.831

Young’s modulus (N/mm2 )

Mass density (g/cm3 )

First yield point

Second yield point

Curvature (m−1 )

Moment (kNm)

Curvature (m−1 )

Moment (kNm)

8500

2.3

0.00147

1500

0.03

4617

Fig. 3. Moment-curvature relationship.

Fig. 4. Test and FEM analysis results.

3 Static Loading Test of Soil-RC Pile System 3.1 Specimen of the Static Loading Test To investigate the fracture behaviour of dry soil-RC pile interaction, the static loading test was performed under a 50G field. Table 3 and Fig. 5 show the dimension and the specimen of the static loading test. The length of the pile model was 340 mm (full scale: 17 m). The soil model was Toyoura dry sand (specific gravity Gs = 2.635, maximum void ratio emax = 0.966, minimum void ratio emin = 0.600, D50 = 0.18 mm with no fines content under 75tim [7]) with relative density 60%. The pile model was embedded 320 mm (Full scale: 16 m) into the dry soil model and the top was connected to a horizontal loading device by a pin jig and a vertical roller jig. The horizontal cyclic loading was input at the top of the model. The loading was controlled according to top displacement, at 0.313, 0.625, 0.05, 0.075, 0.1, 0.15, 0.2 and 0.25 mm. The deformation was measured by a laser displacement transducer.

Static Loading Test of Soil-RC Pile System

289

Table 3. Details of FEM analysis model.

Piles

Soil

Length

Scaling law

Unit

Full scale

Model scale

1/λ

m

17

0.34

Diameter

1/λ

mm

1250

25

Yield stress of mortar

1

N/mm2

13.33

13.33

Relative density

1

%

60

60

Fig. 5. Specimen of the static loading test.

3.2 Ultimate Strength of the Soil-Pile System Broms proposed an equation to evaluate the ultimate strength Qeva of a soil-pile system [8]. The equation assumes that lateral soil reactions are distributed in a triangle shape and calculated as Eq. (1).    h Qeva Qeva Mu + 0.544 (1) = Kp γ B3 B Kp γ B3 Kp γ B4 where M u is the full plastic moment of pile, K p is the coefficient of passive earth pressure, γ is the unit weight of soil, h is distance from ground surface to loading point and B is the diameter of the pile. 3.3 FEM Analysis Model of the Dry Soil-RC Pile System FEM analysis of the dry soil-RC pile interaction was performed to simulate a static loading test. Figure 6 shows the FEM analysis model. Details of the RC pile property was the same as for Sect. 2.3, and the length was 17 m. The soil springs were modelled with a tetra-linear spring element and connected with RC pile element except for the top 4 nodes. The setting of soil spring was varied depending on the depth. The soil spring

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constant K h1 was calculated by Eq. (2). Kh1 = α · ξ · E0 · B−3/4

(2)

where α is Viscous soil = 60, Dry soil = 80, ξ is Single pile = 1.0, E 0 is Deformation coefficient of soil, and B is Diameter of the pile. Deformation coefficient of soil E 0 was calculated by Eqs. (3), (4) and (5). E0 = 700N φ=



(3)

20N1 + 20

(4)

  N1 = N 98 σV 0

(5)

where N 1 is the N-value considering effective overburden pressure, σV 0 is effective overburden pressure, and φ is internal friction angle of soil (in this paper, φ = 39°). Horizontal plastic soil reaction Pu was calculated by Eq. (6). Pu = 3Kp γ z

(6)

where γ is the unit weight of soil, z is depth of soil springs, and K p is coefficient of passive earth pressure. In this paper, Coulomb’s earth pressure was applied to K p . It was calculated by Eq. (7).   −2 sin(θ + δ) sin(θ + β) sin2 (θ + φ) Kp = 1− sin(θ − δ) sin(θ − β) sin2 θ sin(θ − δ)

(7)

where θ is Angle of inclination of the pile = 90°, β is Slope of the ground surface = 0°, δ is friction angle between soil and pile surface (The internal friction angle of soil φ by referring to the paper [10]). Figure 7 shows the spring reaction force-displacement relationship for the tetralinear model. Initial stiffness of soil was 3.16K h1 by referring the Recommendations for Design of Building Foundations [9]. Settings of tetra-liner model were decided as total energy of the tetra-liner model until reaching Pu was same as total energy soil reaction-displacement relation curve suggesting in [9]. A horizontal monotonic loading was input to the top of the RC pile element until the displacement was 0.5 m. 3.4 Test Result Figure 8 shows the load-displacement relationship of the test result and the FEM analysis. A blue broken line is the ultimate strength Qeva . Results show the ultimate strength Qeva almost corresponds to the test result. The FEM analysis, the behaviour corresponded to the test result in a small displacement range. However, the FEM analysis result was underestimated too far in the large displacement range, indicating that the soil spring setting didn’t correspond to the real soil behaviour.

Static Loading Test of Soil-RC Pile System

Fig. 6. FEM analysis model.

Fig. 7. Spring reaction force-displacement relationship.

291

Fig. 8. The test and FEM analysis result.

4 Conclusion This paper conducted a static loading test on a soil-pile interaction and tried to simulate the behaviour of the test result using FEM analysis. The following results were obtained: 1) A reduced RC pile model was proposed for this study. According to the bending and compression loading test result, the pile model reproduced to elasto-plastic behaviour of prototype, and the FEM analysis of the RC pile corresponded to the test result. 2) The ultimate strength of the soil-pile interaction can be evaluated by Broms’s equation. Compared to the maximum strength of the static loading test result, the evaluated strength was a close match. 3) In the FEM analysis of soil-pile interaction, that behaviour matched the test result in a small displacement range, but that was underestimated by far in a large displacement range, indicating that the soil spring setting didn’t correspond to real soil behaviour.

Acknowledgments. This work was partially supported by the Japan Society for Promotion of Science under Grant Numbers 19K04709.

References 1. Architectural Institute of Japan 2018 Report on the Damage Investigation of the 2016 Kumamoto Earthquakes (In Japanese) 2. Chau, K.T., Shen, C.Y., Guo, X.: Nonlinear seismic soil–pile–structure interactions: shaking table tests and FEM analyses. Soil Dyn. Earthq. Eng. 29(2), 300–310 (2009) 3. Kimura, M., Adachi, T., Yamanaka, T., Fukubayashi, Y.: Failure mechanism of axially-loaded concrete piles under cyclic lateral loading. In: Centrifuge 98 (1998) 4. Higuchi, S., Tsutsumiuchi, T., Otsuka, R., Ito, K., Ejiri, J.: Centrifugal vibration test of RC pile foundation. Jpn Soc. Civ. Eng. 68(4), 642–651 (2012) 5. Architectural Institute of Japan 2004 Design problems in foundation engineering (in Japanese)

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6. TDAP III. https://www.ark-info-sys.co.jp/jp/product/tdap/english/. Accessed December 2021 7. Koseki, J., Yoshida, T., Sato, T.: Liquefaction properties of toyoura sand in cyclic torsional shear tests under low confining stress. JGS-Soils Found. 45(5), 103–113 (2005) 8. Broms, B.B.: Lateral resistance of piles in cohesion less soils. J. Soil Mech. Found. Divis. ASCE 90(3), 123–156 (1964) 9. Architectural Institute of Japan 2016 Recommendations for Design of Building Foundations (in Japanese) 10. Wada, S., Kouda, M., Enami, A.: Experimental study on passive earth pressure Part1: the experimental device and an example of the passive earth pressure tests by the device. Archit. Inst. Jpn. (503), pp. 69–76. (in Japanese)

Evaluate Effect of Various Parameters on the Shear Strength of FRP-Reinforced Concrete Beams with or Without Stirrups A. Deifalla(B) Department of Structural Engineering and Construction Management, Future University in Egypt, New Cairo City 11835, Egypt [email protected]

Abstract. Most of the available design codes and models are overly conservative or not comprehensive. The purpose of this study is to investigate the effect of various parameters, including (1) the ratio between shear span and depth, (2) concrete compressive strength, (3) FRP axial rigidity, (4) the ratio between the transversal and longitudinal FRP reinforcements axial rigidity, and (5) cross-section aspect ratio on the prediction of the shear strength of beams with and without FRP stirrups using an existing genetic programming model. Form 80 investigations, a total of about 552 beams tested under shear were gathered. In addition, a few available models in the literature were selected and used to calculate the shear strength of the tested beams. The proposed model represented the arch action mechanism, effect of concrete strength, transversal and longitudinal FRP reinforcement, stirrup effect on concrete contribution, and aspect ratio in a much better way than other methods concerning experimental results. Keywords: Shear · FRP · Arch action · Stirrups

1 Introduction Steel reinforcement corrosions in reinforced concrete (RC) structures lead to an expensive restoration and reduce the buildings’ life cycle. In contrast, FRP-reinforced concrete structures are corrosion free; thus, FRP reinforcements can be used instead of steel reinforcements [1]. This usage opens an area of research, which is FRP-RC beams’ design under shear [2–7]. Over the last four decades, the concrete shear capacity of FRP-RC beams has been investigated by many researchers. Razaqpur et al. investigated the concrete contribution to the shear strength of FRP-RC members, where they concluded that both the Canadian and Japanese recommendations have good correlation with respect to the experimental data [8]. Ashour proposed a simplified model for the shear resistance of concrete beams with GFRP bars, which had an agreement with the experimental results [9]. El-Sayed et al. conducted an experimental investigation for the shear strength of high strength concrete (HSC) beams reinforced with FRP bars, while it was found that the HSC FRP-RC beams have a slightly lower shear strength compared to normal FRPRC beams [10]. Razaqpur and Isgor proposed an improved method for evaluating the © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 293–303, 2023. https://doi.org/10.1007/978-981-19-4293-8_31

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shear strength of FRP-reinforced concrete members without stirrups, which accounts for the effect of longitudinal reinforcement, moment-shear interaction, concrete strength, and beam size [11]. The behavior and shear strength of FRP slender RC beams were investigated by El- Sayed et al. [12, 13]. Their test results indicated that the relatively low modulus of elasticity of FRP bars reduced the shear resistance compared to the RC beams; Thus, a modified design equation was proposed based on the experimental results. Kim and Jang proposed a new formula for calculating the shear contribution of concrete to FRP-RC beams without stirrups, which was found to be more accurate than the equations of an American Concrete Institute standard and like the equations of a Canadian Standards Association standard [14]. In contrast, a much smaller number of researchers investigated the concrete shear resistance of FRP reinforced beams with stirrups. Most of the investigations towards FRP-RC beams with shear stirrups was directed towards design code development. Bentz et al. concluded that, in fundamental, the shear behavior of FRP-RC beams is quite like that of RC beams [15]. Fico et al. evaluated the shear design of the FRP-RC beams using the Eurocode compared to various guidelines [16]. In 2012, the Canadian Standards Association issued a standard for designing and constructing building components with FRP, CAN/CSA-S806-12, (will be referred to as CSA). The shear and torsion design of the CSA is based on simplification for Vecchio and Collins’s modified compression field theory (MCFT) and later verified by Razaqpur and Spadea [17–19]. The CSA was found to be more accurate and consistent. Elmeligy et al. [20] examined the CSA for the case of FRP-reinforced beams with FRP stirrups. Further, they implemented a slight modification to calculate the strut angle of inclination, which was first proposed by Deifalla et al. [21] for torsion. The proposed modified CSA (MCSA) was better than the original CSA. With the availability of a larger database of experimental testing, the use of AI techniques yields better results. However, most of the current ones are complicated for design purposes [4, 5, 22–24]. Nehdi et al. [23] have shown that current guidelines for the shear design of FRP-reinforced concrete beams are either inadequate or very conservative. Thus, they proposed simple yet better equations, which can calculate the shear strength of FRP-reinforced concrete beams based on the genetic algorithms approach. However, the proposed equation is different from that used to design steel-reinforced concrete beams in shear. Kara [22] proposed a formula using Gene Expression Programming (GEP), which can be used to predict the shear strength of FRP-reinforced concrete beams without stirrups. The proposed GEP model was found to be more accurate and consistent compared to available shear design guidelines. Ebid and Deifalla [24] proposed an unfired formula for the shear strength of FRP reinforced concrete beams with or without stirrups using Genetic programming. Therefore, It is clear that: 1) No unified method for the case of FRP-RC beams under shear; 2) existing models are either complicated, not comprehensive, or overly conservative; 3) works focused on either FRP-RC beams with stirrups or that without stirrups; and 4) the Artificial intelligence models are more accurate and consistent with experimental testing results, however, need to be mor simpler and comprehensive. This paper is part of an extensive work on progress by Deifalla and co-workers in FRP-RC beams under shear, torsion, or combined loading [21, 24–28]. This study aims to investigate the effect of various parameters on the

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shear strength using artificial intelligence. The GP technique was selected to capture the experimentally observed behavior compared to selected models. Concluding remarks were discussed.

2 Experimental Database Profile From a total of tests 56 investigations, an experimental data set of 419 FRP-reinforced concrete beams without stirrups tested under shear was collected from 1993 till 2014. Type of longitudinal reinforcement includes bars and grids of Glass, Aramid, Carbon FRP with various ratios from 0.09% to 4.00%. The Beams cross-section depth varied from 73 to 938 mm and its width varied from 89 to 1830 mm. The shear span to depth ratio ranged between 1.50 and 16.22. From 25 studies, 133 tested FRP-reinforced concrete beams with stirrups were collected. The type of both longitudinal and stirrups includes bars and grids of AFRP, GFRP & CFRP with different ratios from 0.12% and up to 4.00% for longitudinal reinforcement and from 0.04% to 1.5% for stirrups. The Beams cross-section depth varied from 170 to 937 and its width varied 110 to 914 mm. The ratio between effective span and beam depth is ranged between 1.80 and 7.50. Further details of the database can be found elsewhere (Ebid and Deifalla, 2021; Ali et al., 2021).

3 Selected Previous Shear Strength Models for FRP-Reinforced Concrete Beams Four models were selected as follows: (1) Nehdi et al. (N-model), which was proposed based on genetic algorithm (GA) technique for FRP-RC beams with and without stirrups [23]; (2) Kara (K-model), which was developed using the Gene expression programming technique to predict the shear strength of FRP-RC beams without stirrups [22]; (3) CSA, which is shear design provisions developed based on the MCFT for FRP-RC beam with and without stirrups [17]; and (4) Ebid and Deifalla (ED-mode), which is a unified formula developed Using Genetic programming technique for FRP-RC beams without and with stirrups [24]. Further details of the database can be found elsewhere (Ebid and Deifalla, 2021; Ali et al., 2021).

4 Comparison Between the ED-Model and Other Models 4.1 Scattering of Predictions For Beams without stirrups, from Figs. 1(a-d), the correlation coefficient (R2 ) between experimental and predicted are 0.872, 0.85, 0.82, and 0.873 for N-model, K-model, CSA, and ED-model, respectively, which indicates that scattering of ED-model is slightly less than other selected models. For Beams with stirrups, from Figs. 2(a-c), it can be seen that the correlation coefficient (R2 ) between experimental and predicted are 0.8744, 0.7645, and 0.8854 for N-model, CSA, and ED-model, respectively, which indicates that scattering of ED-model is slightly less than other selected models. In addition, Table 1 shows the statistical measures for the ratio between the experimentally measured shear

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strength of all tested beams and that calculated using various models. The average value of the ratio for models N-model, K-model, CSA, and ED-model is 0.910, 1.456, 1.123, and 1.011, respectively. The coefficient of variation of the ratio for models N-model, K-model, CSA, and ED-model is 24%, 25%, 38%, and 23%, respectively. The maximum ratio value for models N-model, K-model, CSA, and ED-model is 1.932, 1.848, 3.537, and 1.902, respectively. The minimum value of the ratio for models N-model, K-model, CSA, and ED-model is 0.456, 0.308, 0.367, and 0.544, respectively. Therefore, it could be concluded that the ED-model performed slightly better overall than all other models. Table 1. Statistical measures for the ratio between measured and calculated strength using all models. Category

Method

Maximum

Minimum

Average

Coefficient of variation

All

N

1.93

0.46

0.91

24%

K

1.85

0.31

0.95

25%

CSA

3.54

0.37

1.12

42%

a/d < 2.5

fc’ > 40

With stirrups

ED

1.9

0.54

1.01

23%

N

1.582

0.48

0.79

24%

K

1.49

0.31

0.61

49%

CSA

3.41

0.72

1.46

45%

ED

1.55

0.63

0.92

19%

N

1.93

0.47

0.93

25%

K

1.85

0.49

1

22%

CSA

3.59

0.63

1.07

30%

ED

1.85

0.63

1.068

24%

N

1.91

0.48

0.89

29%

CSA

3.54

0.74

1.53

40%

ED

1.9

0.63

1.00

24%

5 Effect of Various Parameters 5.1 Effect of the Ratio Between Shear Span and Depth (a/d) Previous investigations showed that the effect of a/d is more pronounced when a/d is less than 2.5 for rectangular sections. Figure 3(a-d) shows the ratio between measured and calculated shear strength using models N-model, K-model, CSA, and ED-model, respectively, versus the a/d ratio. The scattering for a/d value less than 2.5 is more pronounced, while the ED-model shows less scattering than other models. Table 1 shows the statistical measures for the strength of beams with a/d less than 2.5, which is predicted

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using different methods. The average using models N-model, K-model, CSA, and EDmodel is 0.795, 0.603, 1.456, and 0.922, respectively. In addition, the coefficient of variation using models N-model, K-model, CSA, and ED-model is 24%, 49%, 45%, and 19%, respectively. Moreover, the minimum using models N-model, K-model, CSA, and ED-model is 0.478, 0.308, 0.721, and 0.625, respectively. Therefore, it is clear that the ED-model represented the arch action mechanism compared to experimental results much better than other methods.

Fig. 1. Predictions without stirrups a) N, b) CSA, c) K, and d) ED-model.

5.2 Effect of Concrete Compressive Strength (Fc’) Figures 4(a-d) show the shear strength predicted using models N-model, K-model, CSA, and ED-model, respectively, versus the fc’. It can be shown that the model predictions are not dependent on the fc’, except for using the CSA for beams with stirrups. In addition, the predictions of all models for beams with high-strength concrete (fc’ > 40 MPa) were analyzed separately. Table 1 shows the statistical measures for the strength of beams with a/d less than 2.5, which is predicted using different methods. The average using models N-model, K-model, CSA, and ED-model is 0.931, 1, 1.064, and 1.068, respectively. In

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Fig. 2. Scattering predictions with stirrups a) N-model, b) CSA, and c) ED-model.

addition, the coefficient of variation using models N-model, K-model, CSA, and EDmodel is 25%, 22%, 30%, and 24%, respectively. Moreover, the minimum using models N-model, K-model, CSA, and ED-model are 0.470, 0.491, 0.496, and 0.63, respectively. Therefore, the ED-model prediction for beams with the high strength concrete agrees better with the experimentally measured strength compared to other methods. 5.3 Effect of the Ratio Between the Transversal and Longitudinal FRP Reinforcements Axial Rigidity (EF ρw /EFv ρv ) Figures 6(a-c) show the shear strength predicted using models N-model, CSA, and EDmodel, respectively, versus the value of the ratio (EF ρw /EFv ρv ). It can be shown that the model predictions are scattered at a value of the ratio (EF ρw /EFv ρv ) less than one, while the scattering of the CSA predictions is wider and extend to ratio (EF ρw /EFv ρv ) value of two. In addition, the predictions of all models for beams with stirrups were analyzed separately. Table 1 shows the statistical measures for the strength predicted using different methods. The average using models N-model, CSA, and ED-model is 0.891, 1.525, and 0.999, respectively. In addition, the coefficient of variation using models N-model, CSA, and ED-model is 29%, 40%, and 24%, respectively. Moreover, the minimum using models N-model, CSA, and ED-model are 0.478, 0.741, and 0.630, respectively. Therefore, it is clear that the ED-model prediction for beams with stirrups

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yields much better results concerning the experimentally measured strength compared to other methods.

Fig. 3. The ratio between measured and calculated shear strength using models N-model, Kmodel, CSA, and ED-model versus a/d.

5.4 Effect of FRP Axial Rigidity (EF ρw ) Figures 5(a-d) show the shear strength predicted using models N-model, K-model, CSA, and ED-model, respectively, versus the EF ρw . It can be shown that the model predictions are not dependent on the EF ρw Except for that, using the CSA for beams with stirrups. It is clear that the CSA predictions are overly conservative for the case of EF ρw Less than 100 MPa.

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Fig. 4. The ratio between measured and calculated shear strength using models N-model, Kmodel, CSA, and ED-model versus fc’.

5.5 Effect of Aspect Ratio (b/d) Equation (9) shows that the effect of the stirrups on the concrete contribution is dependent on the b/d ratio, which ranges between 6 to 30%. This dependency could be because, except for the ED-model, design codes and methods have not quantified the effect of stirrup on the concrete shear contribution. Previous investigations have shown that the increase in the concrete shear contribution due to stirrup confinement is significant. However, this mechanism is associated with complexity, and it is not quantified in most available codes and models (Zhang et al., 2016). In addition, the strength of the stirrups was dependent on the b/d ratio. Previous investigations by Deifalla (2015) and the ACI-440 (2015) proposed that the stirrup strength is dependent on the ratio of the stirrup diameter to the beam depth and the ratio of the bent radius to stirrup diameter, respectively. Therefore, using the b/d ratio is easier and more practical.

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Fig. 5. The ratio between measured and calculated shear strength using models N-model, Kmodel, CSA, and ED-model versus FRP axial stiffness.

Fig. 6. The ratio between measured and calculated shear strength using models N-model, CSA, and ED-model versus ratio between transversal and longitudinal rfts.

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6 Conclusions A shear strength model based on Genetic programming was developed (Ebid and Deifalla, 2021), a unified model for shear resistance for both FRP beams with and without stirrups. The formula was implemented to investigate the effect of various parameters and the following was found: (1) ED-model represented the arch action, high strength concrete, transversal and longitudinal FRP reinforcements, and the effect of stirrup on the concrete shear contribution. mechanism compared to experimental results much better than other methods.

References 1. ACI-440.1R-15, Guide for the design and construction of concrete reinforced with FRP bars, A report by ACI committee 440 Farmington Hills, American Concrete Institute (2015) 2. Alam, M.S., Hussein, A.: Size effect on shear strength of FRP-reinforced concrete beams without stirrups. J. Compos. Constr. 17(4), 507–516 (2013) 3. Dhahir, M.K., Nadir, W.: A compression field-based model to assess the shear strength of concrete beams reinforced with longitudinal FRP bars. Constr. Build. Mater. 191, 736–751 (2018). https://doi.org/10.1016/j.conbuildmat.2018.10.036 4. Jumaa, G.B., Yousif, A.R.: Predicting shear capacity of FRP-reinforced concrete beams without stirrups by artificial neural networks, gene expression programming, and regression analysis. Hindawi, Adv. Civil Eng. 2018, Article ID 5157824, 16 (2018). https://doi.org/10.1155/ 2018/5157824 5. Naderpour, H., Poursaeidi, O., Ahmadi, M.: Shear resistance prediction of concrete beams reinforced by FRP bars using artificial neural networks. Measurement. (2018). https://doi. org/10.1016/j.measurement.2018.05.051 6. Nasrollahzadeh, K., Aghamohammad, R.: Reliability analysis of shear strength provisions for FRP-reinforced concrete beams. Eng. Struct. 176(2018), 785–800 (2018) 7. Cholostiakow, S., Di Benedetti, M., Pilakoutas, K., Guadagnini, M.: Effect of beam depth on shear behavior of FRP RC beams. J. Compos. Constr. 23(1), 04018075 (2019). https://doi. org/10.1061/(ASCE)cc.1943-5614.0000914 8. Razaqpur, A., Isgor, B., Greenaway, S., Selley, A.: Concrete contribution to the shear resistance of fiber-reinforced polymer reinforced concrete members. J. Compos. Constr. 8, 452–460 (2004). https://doi.org/10.1061/(ASCE)1090-02688:5(452) 9. Ashour, A.F.: Flexural and shear capacities of concrete beams reinforced with GFRP bars. Constr. Build. Mater. 20, 1005–1015 (2006) 10. El-Sayed, A., Soudki, K.: Evaluation of shear design equations of concrete beams with FRP reinforcement. J. Compos. Constr. 15(1), 9–20 (2011) 11. Razaqpur, A.G., Isgor, O.B.: Proposed shear design method for FRP-reinforced concrete members without stirrups. ACI Struct. J. 103, 93–102 (2006) 12. El-Sayed, A.K., El-Salakawy, E.F., Benmokrane, B.: Shear capacity of high-strength concrete beams reinforced with fiber-reinforced polymer bars. ACI Struct. J. 103(3), 383–389 (2006) 13. El-Sayed, A.K., El-Salakawy, E.F., Benmokrane, B.: Shear strength of FRP- reinforced concrete beams without transverse reinforcement. ACI Struct. J. 103(2), 235–243 (2006) 14. Kim, C.H., Jang, H.S.: Concrete shear strength of normal and lightweight concrete beams reinforced with FRP Bars, 04013038–1, J. Compos. Constr. (2014). https://doi.org/10.1061/ (ASCE)CC.1943-5614.0000440

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15. Bentz, E.C., Massam, L., Collins, M.P.: Shear strength of large concrete members with FRP Reinforcement, J. Compos. Constr., ASCE, 14(6), 637–646 J. Compos. Constr. (2010). https:// doi.org/10.1061/(ASCE)CC.1943-5614.0000108 16. Fico, R., Prota, A., Manfredi, G.: Assessment of Eurocode-like design equations for the shear capacity of FRP RC members. Compos. Part B Eng. 39, 792–806 (2008) 17. CSA S806–12, Design and construction of building components with fiber-reinforced polymers, Mississauga, Ontario, Canada, Canadian Standards Association, (2012) 18. Vecchio, F.J., Collins, M.P.: Modified compression-field theory for reinforced concrete elements subjected to shear. J. Am. Concr. Inst. 83(2), 219–231 (1986) 19. Razaqpur, A.G., Spadea, S.: Shear strength of FRP-reinforced concrete members with stirrups. J. Compos. Constr., ASCE 04014025–1, (2014). https://doi.org/10.1061/(ASCE)CC.19435614.0000483 20. ElMeligy, O., El-Nemr, A.M., Deifalla, A.: Reevaluating the modified shear provision of CAN/CSA S806–12 for concrete beams reinforced with FRP stirrups. AEI 2017, 324–335 (2017) 21. Deifalla, A., Khali, M.S., Abdelrahman, A.: Simplified model for the Torsional strength of concrete beams with GFRP stirrups. Compos. Constr., ASCE 04014032–1, (2014). https:// doi.org/10.1061/(ASCE)CC.1943-5614.0000498 22. Kara, I.F.: Prediction of shear strength of FRP-reinforced concrete beams without stirrups based on genetic programming. Adv. Eng. Softw. 42, 295–304 (2011). https://doi.org/10. 1016/j.advengsoft.2011.02.002 23. Nehdi, M., El Chabib, H., Saïd, A.A.: Proposed shear design equations for FRP-reinforced concrete beams based on genetic algorithms approach. J. Mater. Civ. Eng. 19(12), 1033–1042 (2007).https://doi.org/10.1061/(ASCE)0899-1561 24. Ebid, A., Deifalla, A.: Prediction of shear strength of FRP reinforced beams with and without stirrups using (GP) technique. Ain Shams Eng. J., Elsevier. 12(3), 2493–2510 (2021). https:// doi.org/10.1016/j.asej.2021.02.006 25. Deifalla, A.: Torsional behavior of rectangular and flanged concrete beams with FRP reinforcements. J. Struct. Eng. 10.1061/(ASCE)ST.1943-541X.0001322,04015068, 1–14 (2015) 26. Deifalla, A., Hamed, M., Saleh, A., Ali, T.: Exploring GFRP bars as reinforcement for rectangular and L-shaped beams subjected to significant torsion: An experimental study. Eng. Struct. 59, 776–786 (2014) 27. Hassan, M.M., Deifalla, A.: Evaluating the new CAN/CSA-S806-12 torsion provisions for concrete beams with FRP reinforcements. Mater. Struct. 49(7), 2715–2729 (2015). https:// doi.org/10.1617/s11527-015-0680-9 28. Ali, A., Hamady, M., Chalioris, C.E., Deifalla, A.: Evaluation of the shear design equations of FRP-reinforced concrete beams without shear reinforcement. Eng. Struct., Elsevier, 235 (2021)

Statistics and Probabilistic Modeling of Construction Materials Used in the UAE Omar Nofal1(B) , Moussa Leblouba1 , and Sami Tabsh2 1 University of Sharjah, Sharjah, United Arab Emirates

{U19104387,mleblouba}@sharjah.ac.ae

2 American University of Sharjah, Sharjah, United Arab Emirates

[email protected]

Abstract. Designing codes requires the application of reliability analysis on structural members considering probabilistic load and resistance models. Developing a probabilistic resistance model requires consideration of uncertain structural behavior, fabrication, and materials. Each of these factors is represented by its probability distribution, bias factor, and coefficient of variation. In an LRFD design framework, load factors are used to scale up the imposed loads and resistance factors to scale down the resistance to achieve a design that meets a target reliability index. In the UAE, the statistical properties of materials and fabrication processes differ from those used in other countries due to local practice and procedures. However, engineers are still using resistance factors developed for US codes to design structures built in the UAE. This needs to be rectified, and we propose to create our material and fabrication factors. The considered materials are concrete, different ranges of reinforcing steel bars and Prestressing steel strands. The collected data from different factories and plants as well as different testing laboratories. The compressive strengths of concrete data are collected based on different size projects, and various sites from Dubai and northern emirates. Reinforcing steel test data are collected from different sources available in the country (fabricated in the UAE and those imported and used in the UAE). It is understood that the concrete cube is the most commonly tested specimen in the UAE, therefore, a procedure will be developed based on current published literature that converts results from cube tests to cylinder tests. This is because the ACI code equations are based on cylinder tests. Keywords: Concrete · Steel · Prestressed concrete · Statistical parameters · Bias factor · Coefficient of variation · Probability distribution function

1 Introduction When designing limit states, the effect of the load is compared with the load-carrying capacity (resistance). There are limit state functions for each failure mode, representing a state of equilibrium where the load and resistance balance each other and a safety margin exists between load and resistance. Load and resistance parameters are subject to uncertainty and should be treated as random variables. Therefore, reliability can be © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 304–314, 2023. https://doi.org/10.1007/978-981-19-4293-8_32

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used as a measure of structural performance. A set of load and resistance factors must be considered in the design process known as limit state design for each limit state. The objective of the code calibration is to select these three main parameter factors (professional factor, fabrication factor, and material factor) to achieve the targeted level of reliability for the designed structures. Develop probabilistic resistance models for beams in flexure and shear as well as columns under pure axial compression. These include rectangular sections, T-sections, doubly reinforced sections, etc. Monte Carlo simulation will be used to estimate all probabilistic parameters. The obtained results are used to calculate the actual reliability indices of different buildings built in the UAE according to ACI.

2 Research Objectives The main objectives of this study are as follows: 1. Collect statistics on the mechanical properties of construction materials and fabrication for structures built in the UAE. 2. To develop probabilistic resistance models for structural concrete used in the UAE based on local materials and workmanship.

3 Review of Related Studies Sami W. Tabsh & A. Aswad [1]; obtained statistical analysis and revealed that steamcured plant-produced high-strength concrete in compression has a favorable strength ratio and coefficient of variation based on 2200 cylinders. The statistical properties of the concrete strength are also studied. The results indicate that the coefficient of variation and the mean nominal ratio are higher for normal concrete than for high-quality concrete. The mean-to–nominal ratio varied between 1.078 and 1.255, whereas the range of the coefficient of variation found was 0.06528–0.1353 based on the 28-day compressive strength. Additionally, this study showed that the coefficient of variation and meanto-nominal ratio of concrete produced during the cold season were lower than those of concrete produced during the warm season. The research will aid in probabilistic resistance models for concrete structures that can be used to develop load and resistance factor design codes. Sami W. Tabsh & A. Aswad [2], resistance reduction factors are used to determine the design of load and resistance factor codes for certain materials. This paper summarizes the statistical analysis of steam-cured plant-produced concrete based on 399 specimens obtained from Pennsylvania concrete producers. The seasonal effect and the coefficient of variation are also considered. The variability of in-situ concrete is predicted using statistics on cylinder strengths. The statistical properties of high strength concrete are also studied. The goal of this study is to help developers and engineers in the design and construction of high-strength concrete structures. Andrzej S. Nowak, Anna M. Rakoczy, and Ewa K. Szeliga [3] The objective of this study was to modify the resistance model of the ACI 318 Code by using material test data. The statistical parameters related to the load-bearing capacity of various reinforced

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concrete beams, columns, and slabs were analyzed, Concrete is classified into two types: ordinary concrete and high-strength concrete. Regular concrete test data were collected from ready mix suppliers and precasting plants. The ready mix concrete database has fc’ values ranging from 3000 to 6000 psi, whereas the plant-cast concrete database includes fc’ values ranging from 5000 to 6500 psi. The statistical parameters R, fc’, fy’, cross-section, and reinforcing steel area were also estimated. Monte Carlo simulations are performed to determine the statistical limits of the bearing strength of concrete. The resistance parameters are formulated as random variables. Andrzej S. Nowak, Anna M. Rakoczy, and Ewa K. Szeliga [3] The objective of this study was to modify the resistance model of the ACI 318 Code by using material test data. The statistical parameters related to the load-bearing capacity of various reinforced concrete beams, columns, and slabs were analyzed, as shown in Fig. 1 and Fig. 2. Concrete is classified into two types: ordinary concrete and high-strength concrete. Regular concrete test data were collected from ready mix suppliers and precasting plants. The ready mix concrete database has fc’ values ranging from 3000 to 6000 psi, whereas the plant-cast concrete database includes fc’ values ranging from 5000 to 6500 psi. The statistical parameters R, fc’, fy’, cross-section, and reinforcing steel area were also estimated. Monte Carlo simulations are performed to determine the statistical limits of the bearing strength of concrete. The resistance parameters are formulated as random variables. S. Nowak and M.M. Szerszen [4] This paper presents a two-part technical paper that explains the process used to validate the load combinations and reliability-based calibration of ACI 318. The ASCE 7 Standard on Minimum Design Loads for Buildings and Other Structures was adopted in 2002. This foundation explains the various components of the reliability-based test evaluation process for the design and construction of structures. Nowak and Latsko (2017) [5] examined the original calibration used to derive previous versions of LRFD standards and proposed new load and resistance factors. The optimum factors for the intended or goal reliability index are described as new sets of load and resistance factors for distinct bridges. The proposed load and resistance factor were tested on typical bridges given in NCHRP Study 368, the initial calibration report for the AASTHO LRFD specification. Even though the load resistance factors are approximately 10% lower than the current factors, reliability analysis revealed satisfactory agreement. According to the computations, the dead load factor and live load factor. However, the required moment capacity of the bridge girders was increased by 3% to 5%, and shear capacity was increased by 5%; the recommended resistance factors were smaller than the resistance factor given in the AASTHO LRFD. A new resistance factor for reinforced T beams has been developed.0.80 is recommended, approximately 11% less than the required resistance factor. Historical structures outperform existing and new structures in terms of the target reliability index; historical structures have superior economic, social, and political values. They have less maximum moment and shear effects but a more significant coefficient of variation of loads since they are assessed in a reference time period less than the design period (usually 50–75 years).

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4 Statistics of Construction Materials in the UAE The material factors are obtained as the actual to nominal material properties ratio. Each of these factors (professional factor, fabrication factor, and material factor) is represented by its type of probability distribution, bias factor, and the coefficient of variation. The considered materials are concrete, reinforcing steel bars and Prestressing steel strands. 4.1 Concrete The statistical parameters of material factors are determined from the data provided by the different ready-mix concrete industries. The data sources were collected from various supplies in the UAE, including Jamix, Commix, Tech remix, Safe mix, Tre mix, Reem mix, and Uni mix. The test data are obtained from the standard cube test mostly at 28-day compressive strength which converted the results from cube tests to cylinder tests. This is because the ACI code equations are based on cylinder tests. As shown in Fig. 1. The collected nominal compressive strengths of concrete are (30, 40, 57 63 and 82.5) MPa. The statistical parameters for a normal distribution will be plotted as a probability distribution.

Fig. 1. Compression test for cube concrete.

The data for compressive strengths are collected from different resources. Based on the data of the 100 tests, the statistical parameters for different compressive strengths are obtained. The compressive strength test data for concrete (30 MPa) is a lognormal distribution with a bias factor = 1.5 and a coefficient of variation = 0.09 and for (82.5 MPa) with a bias factor = 1.05 and a Coefficient of Variation = 0.025. Table 1 summarizes the statistical parameters of the material factors for concrete. The concrete compressive strength. Figure 2, Fig. 4, Fig. 6, Fig. 8, Fig. 10 show the density of the material factor bias λm for different compressive strengths for concrete. After obtaining the parameters, the bias values were plotted against the probability to evaluate the best fit, as shown in Fig. 3, Fig. 5, Fig. 7, Fig. 9, Fig. 11.

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O. Nofal et al. Table 1. Statistical parameters for concrete.

f’c (MPa)

Bias factor (λ)

Coefficient of Variation (COV)

Probability distribution type

30

1.5

0.09

Lognormal

40

1.3

0.051

Lognormal

57

1.2

0.041

Lognormal

63

1.14

0.032

Lognormal

82.5

1.05

0.025

Lognormal

Fig. 2. Density of the material bias factor for concrete (class C30).

Fig. 3. Probability plot of the material bias factor for concrete (class C30).

Fig. 4. Density of the material bias factor for concrete (class C40).

Fig. 5. Probability plot of the material bias factor for concrete (class C40).

Statistics and Probabilistic Modeling

Fig. 6. Density of the material bias factor for concrete (class C57).

Fig. 8. Density of the material bias factor for concrete (class C63).

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Fig. 7. Probability plot of the material bias factor concrete (class C57).

Fig. 9. Probability plot of the material bias factor for concrete (class C63).

Fig. 10. Density of the material bias factor for Fig. 11. Probability plot of the material bias concrete (class C82.5). factor for concrete (class C82.5).

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4.2 Reinforcing Steel Bars Reinforcing steel test data are collected from different sources available in the country (fabricated in the UAE and those imported and used in the UAE) as shown in Fig. 12. As a result, the nominal sizes of the bar vary from (#10 to #32) mm. The laboratories obtain data from Tarmac, Al Hai & Al Mukaddam, Falcon, and the National Lab. The laboratories have provided test data for the yield strength of various reinforcing steel bars.

Fig. 12. Steel bars.

The data for compressive strengths are collected from different resources. Based on the data of the 100 tests, the statistical parameters for different yield strengths of various reinforcing steel bars are obtained. The statistical parameters of the yield strength are presented in Table 2. Table 2. Statistical parameters of the yield strength for steel bars. Bar size

Bias Factor (λ)

Coefficient of Variation (COV)

Probability distribution type

#10

1.1

0.024

Lognormal

#12

1.12

0.018

Lognormal

#16

1.08

0.017

Lognormal

#20

1.12

0.013

Lognormal

#25

1.12

0.020

Lognormal

#32

1.1

0.033

Lognormal

Figure 13, Fig. 15, Fig. 17, Fig. 19, Fig. 21, Fig. 23 show the density of the material factor bias for different yield stresses for reinforcing steel bars. After obtaining the parameters, the bias values were plotted against the probability to evaluate the best fit, as shown in Fig. 14, Fig. 16, Fig. 18, Fig. 20, Fig. 22, Fig. 24.

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Fig. 13. Density of the material bias factor for steel bar #10.

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Fig. 14. Probability plot of the material bias factor for steel bar #10.

Fig. 15. Density of the material bias factor for Fig. 16. Probability plot of the material bias steel bar #12. factor for steel bar #12.

Fig. 17. Density of the material bias factor for steel bar #16.

Fig. 18. Probability plot of the material bias factor for steel bar #16.

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Fig. 19. Density of the material bias factor for Fig. 20. Probability plot of the material bias steel bar #20. factor for steel bar #20.

Fig. 21. Density of the material bias factor for Fig. 22. Probability plot of the material bias steel bar #25. factor for steel bar #25.

Fig. 23. Density of the material bias factor for Fig. 24. Probability plot of the material bias steel bar #32. factor for steel bar #32.

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4.3 Prestressing Steel Strands One grade of prestressing steel strands was obtained at 1860 MPa the nominal diameter was 12.7 mm with seven-wire strand steel bars as shown in Fig. 25.

Fig. 25. Steel strands.

The data for steel strand are collected from different laboratory. Based on the data of the 100 tests, the statistical parameters for breaking load are obtained. The statistical parameters are summarized in Table 3. Table 3. Statistical parameters for steel strand. Steel strand diameter (m)

Bias factor (λ)

Coefficient of Variation (COV)

Probability distribution type

12.70

1.1

0.011

Lognormal

Figure 26 show the density of the material factor bias for steel strand. After obtaining the parameters, the bias values were plotted against the probability to evaluate the best fit, as shown in Fig. 27.

Fig. 26. Density of the material bias factor for steel strand.

Fig. 27. Probability plot of the material bias factor for steel strand.

5 Summary The statistical analysis of the properties of construction materials used in the UAE has led to the following conclusion:

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1. The lognormal distribution best fit all the materials considered in the study. 2. As the concrete compressive strength increases, both the bias factor and coefficient of variation decrease. 3. The bias factor for the yield strength of rebars varies within a narrow range when considered with the rebar diameter. On the other hand, the coefficient of variation did not have a consistent trend with the rebar diameter as it was high for the small and large diameter rebars (#10 and #32), and small of the rebars that lie in between (#12 to #25). 4. The coefficient of variation for 12.7 mm 7-wire prestressing strands was very small, in the range of 1%, indicating high quality

References 1. Tabsh, S.W., Aswad, A.: Statistics of high-strength concrete cylinders. ACI Mater. J. September-October (1997) 2. Tabsh, S.W., Aswad, A.: Statistical proper-ties of plant-produced high strength concrete in compression, Precast/Prestressed Concrete Institute, July-August, (1995) 3. Nowak, A.S., Rakoczy, A.M., Szelig, E.K.: Revised statistical resistance models for R/C structural components, (2011) 4. Nowak, A.S., Szerszen, M.M.: Calibration of design code for buildings (ACI 318), Part 1: Statis-tical models for resistance. ACI Struct. J. (in press) 5. Nowak, A.S., Latsko, O.: proposed recalibration of AASHTO Specifications. University of Auburn, Department of Civil Engineering, United States (2017)

Collapse Strength of Conical Wall Failure in Steel Cone-to-Cylinder Socket Connections Under Axial Compression Tian Qixiang1(B)

and Kuwamura Hitoshi2

1 Planning and Design Research Center, China Construction Science and Technology Group

Co., Ltd., Shenzhen 518118, China [email protected] 2 School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan

Abstract. A new type of steel connection was proposed, which is named cone-tocylinder socket connection. A great advantage of this socket connection is that the connection can be assumed to be a pin-node or pin-support in all directions. Such a pin joint substantially reduces the stresses in the cylindrical piles and mitigates the damages by a severe earthquake. In this paper, with a focus of conical wall failure, experimental and analytic examinations are performed to inspect the detail of failure mechanism. Compressive loading tests are performed with parameters on vertex angle of cone, thickness of cone, and diameter of cylinder. The contact region of conical wall and cylinder edge contributes to generate the vertical resistance of conical wall failure. From the results of FE (Finite Element) analysis, the relationship of collapse strength and friction coefficient is found to linearly increase with a strong correlation. Plastic collapse mechanism governs the collapse strength of conical shell. Based on the principle of virtual work, formula of plastic collapse strength is derived. Collapse strength with actual mild steel material is finally predicted by considering strain hardening effect. Proposed formulae slightly overestimate the actual collapse strength of specimens. One way to improve the precision is to consider the interaction of meridional stress resultant with meridional bending moment and hoop stress resultant. Keywords: Collapse strength · Conical wall failure · Cone-to-cylinder socket connection · Axial compression · Principle of virtual work

1 Introduction A new type of steel connection, which is named cone-to-cylinder socket connection, was proposed by Kuwamura [1] in order to facilitate connecting a circular hollow section member to another cylindrical or different shaped section member. As shown in Fig. 1, this connection consists of four parts: a conical shell, a cylindrical shell, a tapered ring, and a lid plate. In general, the lid plate is welded in advance to the foot of conical shell in order to serve as a splice to fix the connected member. Then, the apex part of conical shell © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 315–327, 2023. https://doi.org/10.1007/978-981-19-4293-8_33

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is plugged into the upper end of cylindrical shell. A tapered ring is used to strengthen the cylinder edge. As a great advantage of this connection, it can be assumed as a pin support in all directions [2]. Such a pin support can substantially reduce the bending stress in pile heads and mitigate the damage by a severe earthquake, which was largely observed in 1995 Hyogoken-Nanbu Earthquake [3]. Besides pile head, this connection can be also applied to column base and support of truss, as illustrated in Fig. 2. Feasibility assessment tests on this socket connection were conducted by Steel Structural Laboratory of the University of Tokyo. It revealed that the connection is strong and rigid enough to be applied to construction practice of low to middle-rise buildings. For all the specimens under axial compression, failure modes were clarified into four cases according to failure positions: cylinder edge failure, tapered ring failure, conical wall failure, and welded joint failure. The first two modes have been analyzed in the previous research [4, 5]. Conical wall failure is focused in this paper. For the strength of conical wall failure, Kuwamura et al. [6] proposed a theoretical solution for elastic limit strength of conical wall according to bending theory of shells. The formula is a little complicated and not suitable in practice. Tomioka [7] proposed an empirical formula for yield strength based on the experimental results. Full plastic strength and collapse strength of connections were then predicted. The results were found to be more easy-to-use, but the friction coefficient between conical wall and cylinder edge was assumed to be 1.0. It is a little great and needs further investigation. In this paper, solid axisymmetric FE models are created and validated by comparing collapse strength with experimental results. Friction property in the contact region between conical wall and cylinder edge is discussed. Then, FE analysis is undertaken to investigate the distribution of stress resultants. Based on limit analysis, formula for collapse strength of specimens is derived and the precision is validated by comparing them with experimental results.

Conical shell

Lid-plate

Metal touch

Welding

Tapered ring

Cylindrical shell

a᧥Components

b) Connections

Fig. 1. Components of steel cone-to-cylinder socket connection

Collapse Strength of Conical Wall Failure

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Fig. 2. Application of steel cone-to-cylinder socket connection

2 Experimental Results Set up of experiments is shown in Fig. 3. Compressive loading P is transformed to the connections through a round loading plate. Axial deformation of the specimen in the loading direction is measured by four laser displacement sensors. For each specimen, the bottom edge of cylindrical shell is metal-touched to foundation and the top edge of conical shell is welded to lid plate. Selected positions for tensile coupons of conical wall are shown in Fig. 4. For each kind of conical wall, the average results of coupons are employed. Material properties of coupons are listed in Table 1. The actual measurement of specimens and experimental results of full plastic strength and collapse strength are summarized in Table 2. The 13 specimens with conical wall failure are picked up from the data of 104 specimens. Variations are designated by thickness tC and semi-vertex angle α of conical wall, and thickness tP and external diameter DP of cylindrical wall. Collapse strength Pu is defined as peak load. Full plastic strength Pp is defined as the load where the slope of load versus axial deformation curve reduces to 1/6 of initial stiffness K0 [8]. Ratios of collapse strength to full plastic strength is summarized. The average value is 1.21, with a coefficient of variation (C.V) of 0.15. Take specimen No.47 for example. The deformation of specimen at collapse load and that of conical wall post collapse is shown in Fig. 5. It can be seen that the out of plane deformation of conical wall is quite obvious. Plate for laser irradiation

Load cell Piston head

Round loading plate Laser displacement sensor

Foundation

Fig. 3. Set up of experiments

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Weld seam

Conical shell (SS400) Coupon

Fig. 4. A selected position for the coupons of conical wall

Table 1. Material properties of steel SS400 for conical shell Material (JIS grade)

Size (t C0 )

tC

σy

σu

mm

MPa

MPa

C-45-1

4.20

296

C-45-2

4.22

302

No.

mm SS400

4.50

9.00

εy

εu

437

0.0034

0.2156

439

0.0033

0.1891

Average

4.21

299

438

0.0034

0.2024

C-9-1

8.77

312

414

0.0037

0.2135

C-9-2

8.27

322

417

0.0035

0.2227

Average

8.52

317

416

0.0036

0.2181

Note: σ y yield stress, σ u tensile stress, εy strain at yield stress and εu strain at ultimate stress. Subscript “0 ” means nominal dimensions.

3 FE Analysis 3.1 General Because both the geometry of specimens and loading are axisymmetric, axisymmetric solid model in ABAQUS FE package [9] is employed, as shown in Fig. 6. Two coordinate systems, (r, θ, x) and (t, θ, s), are used for conical shells, in which the character t means normal direction and s means meridional direction. Static loading is controlled by displacement Δ. Mesh size of conical wall is 0.5 mm, and that of the contact region of cylindrical wall is 0.125 mm. The convergence of analysis results is verified. True stress s and equivalent plastic strain ep curves of conical wall (tC = 4.5 mm) is shown in Fig. 7. Amontons-Coulomb friction law with formulation of Penalty is adopted and friction coefficient μ1 is assumed to be a constant during the whole deformation process. Calibrate the value of μ1 to make the collapse strength of FE models Pu−FEA close to that of experimental specimens Pu−EXP . The upper limit value of μ is assumed as 0.50. The calibration values of μ1 for all the models are summarized in Table 3. The average is 0.43, with a high C.V of 0.27. Variation of the ratio of Pu−FEA to Pu−EXP along with

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Table 2. Main parameters and collapse strength of specimens Specimen no.

Main parameters Conical wall Semi-angle

Thickness

Cylindrical wall

Ring

Thickness

Thickness

External diameter

Full plastic strength

Collapse strength

α

tC

tP

DP

tR

Pp-EXP

Pu-EXP

deg.

mm

mm

mm

mm

kN

kN

Pu-EXP./Pp-EXP

9

60.0

8.6

6.0

140.0

–

561.5

601.2

1.07

34

46.1

8.6

6.0

139.9

12.0

620.0

872.8

1.41

36

62.4

8.6

4.1

139.9

9.1

527.3

625.7

1.19

43

33.3

3.1

4.2

139.9

12.1

153.6

234.9

1.53

44

33.5

4.2

4.2

140.0

12.0

294.7

389.9

1.32

46

46.0

3.1

4.2

139.9

12.0

158.7

178.4

1.12

47

46.7

4.3

4.2

139.9

12.0

218.5

274.2

1.25

48

48.0

5.7

4.2

140.0

12.0

400.0

510.0

1.27

49

61.4

3.1

4.2

139.8

12.1

123.5

125.2

1.01

50

60.6

4.3

4.2

139.9

12.0

190.0

194.9

1.03

51

59.6

5.6

4.2

139.9

12.0

336.5

352.8

1.05

52

44.8

4.3

4.3

114.5

12.0

208.5

251.8

1.21

53

46.2

4.2

5.6

165.8

12.0

254.3

309.3

1.22

–

Average

1.21

C.V

0.15

Note: specimens listed in Table 2 are picked up from the data of 104 specimens. 350

No.47

K

Load P (kN)

300

Pu

250

K

200

Pp

150 100 50 0 0

at collapse load post collapse

5 10 15 Axial deformation Δ (mm)

20

Fig. 5. Load versus axial deformation curve and deformation

the increase of μ1 is shown in Fig. 8. Their relationship is found to linearly increase with a strong correlation. While the slope of the line is relatively low. It means that the influence of friction coefficient μ1 upon collapse strength of conical wall failure mode is not significant. Friction coefficient μ2 between cylinder edge and tapered ring is set to be 0.2 for all the models.

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t

x

Δ

tC

Lid-plate Cone

r

Axis of symmetry

α tP

DP /2

Cylinder

Fig. 6. Details of axisymmetric solid FE models

Internal forces acting on an infinitesimal body cut out from conical wall are defined in Fig. 9. Hoop stress resultant Nθ , meridional stress resultant Ns , meridional bending moment Ms , and shear stress resultant Qts are defined as  Nθ =

t/2 −t/2

 sθ dz; Ns =

t/2 −t/2

 ss dz; Ms =

t/2 −t/2

 ss zdz; and Qts =

t/2 −t/2

sθ dz

(1)

Herein, s is normal stress, τ is shear stress, and z is the radially outward distance from its middle surface. The following dimensionless variables are introduced for stress resultant distributions: √ 3Qts Ns Nθ Ms Ns ; ms = ; and qts = ; (2) ; ns = ; and ns = ns = σyt σy t Msp0 σy t σy t where, Msp0 = σy t 2 /4. The σy is set to be positive for both tension and compression. In addition, the ratio of average equivalent stress seq in a section to yield stress σy is defined as  t/2 seq −t/2 seq dz (3) = r= σy σy t where, seq in each small mesh of FE model is obtained by  seq = ss2 − ss sθ + sθ2 + 3τts

(4)

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Table 3. Comparison of the collapse strength of models Model no.

Experiments

FE analysis

Comparison

Collapse strength

Friction coefficient

Collapse strength

Pu-EXP

μ1

Pu-FEA

μ2

(kN)

Pu-FEA /Pu-EXP

(kN)

9

601.2

0.18

614.2

1.02

34

872.8

0.50

0.20

873.6

1.00

36

625.7

0.50

581.8

0.93

43

234.9

0.50

206.3

0.88

44

389.9

0.50

358.1

0.92

46

178.4

0.50

161.9

0.91

47

274.2

0.40

265.2

0.97

48

510.0

0.50

435.7

0.85

49

125.2

0.50

122.9

0.98

50

194.9

0.21

190.6

0.98

51

352.8

0.50

337.2

0.96

52

251.8

0.31

246.9

0.98

53

309.3

0.50

287.3

0.93

Avg.

–

0.43

–

–

0.95

C.V

–

0.27

–

–

0.06

Note: The μ1 is friction coefficient in the contact region between conical wall and cylinder edge. Upper limit is set to be 0.50. The μ2 is friction coefficient in the contact region between cylinder edge and tapered ring.

600 500 Actual material

True 400 stress s 300 (MPa)

Perfectly-plastic material

sy=σy=299MPa

200 100 0

0

0.05 0.1 0.15 0.2 Equivalent plastic strain ep

Fig. 7. The s~ep curves for materials of conical walls (tC0 = 4.5 mm)

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Specimen No.47

1.5 1 0.5 μ1=0.40 0

0

0.1

0.2

0.3

μ1 0.4

0.5

Fig. 8. Variation of collapse strength along with the increase of friction coefficient

s t

θ dθ

Ns

z

x

r

Axis of revolution

o

Ms tC

Nθ

Qts

α

Fig. 9. Definition of stress resultants in conical wall

3.2 FE Analysis Results Specimen No. 47 is taken as a typical model to investigate the characteristics of stress distribution. Figure 10 shows the distribution of normal stress ss in meridional direction at collapse load. In contact region, the convex side is under compression and the concave side is under tension, while in upper and lower parts of conical wall, the convex side is under tension and the concave side is under compression. The greatest value of ss strongly exceeds yield stress σy .

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ss (MPa) 688 344 299 150 100 50 0 -50 -100 -150 -299 -344 -785

Fig. 10. Distribution of normal stress in meridional direction of conical wall (Specimen No. 47: at collapse load)

D si on le ss

0

s

0 1.

F

r

y tit

E

an

t.

m

qu

5 0.

t.

t.

5 1.

C on

ic al

w al l

G

0 −6

0 −4

c Se

Lo 20 −

c Se

n tio 0 a c

(m 0 2

.5 -0

c Se

s

en im

0 ) 0 6 m 4

.0 80 -1

Fig. 11. Distribution of meridional bending moment and equivalent stress of conical wall (Specimen No. 47: at collapse load)

Figure 11 shows the distribution of meridional bending moment ms and equivalent stress r in conical wall at collapse load. The ms reaches maximum at sections E and G and reaches minimum at section F, where equivalent stress r is all greater than yield stress σy .

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Pp

s

Lid-Plate

t

dE /2

x θ

r

Axis of revolution

O

E F

dF /2 w G

μR

ΦE

L FE

ΦG

L

FG

dG /2

R

(Plastic hinge)

tC Conical wall

α

Fig. 12. Proposed failure mechanism for models with conical wall failure 1000

Pp-PRE. (kN)

800 600

400 Average: 1.03 C.V: 0.12

200

0 0

200

400 600 Pp-EXP. (kN)

800

1000

Fig. 13. Comparison of predicted full plastic strength to the experimental results

4 Prediction of Collapse Strength Based on the FE analysis, plastic collapse mechanism is proposed to derive the full plastic strength of conical wall failure. As shown in Fig. 12, plastic hinges are assumed to form at sections E, F and G. Reaction force R and friction force μ1 R are both acted at section F. Radial displacement in t direction is defined as w. The equilibriums for full plastic strength in 360° in hoop direction are given by Pp = −R(μ1 cosα + sinα)

(5)

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325

1000

Pu-PRE. (kN)

800 600

400 Average: 1.06 C.V: 0.20

200

0 0

200

400 600 Pu-EXP. (kN)

800

1000

Fig. 14. Comparison of predicted collapse strength to the experimental results

Mises’ yield condition is obeyed and the interaction of stress resultants is neglected. Assuming tC  LFE and conical wall is very long (infinite) in hoop direction, stress resultants in plastic hinges are in plane strain state and those in segments FE and FG are in plane √ stress state. For plastic hinges E, F and G, meridional bending moment msp = 2/ 3 [10]. For segments FE and FG, hoop stress resultant nθp = 1.0. Based on the principle of virtual work, the equilibrium of external work and dissipation of internal energy for the whole mechanism in 360° in hoop direction during rotations ∅E and ∅G is given by   dF tC dF tC (6) Rw = π wσyc tC LFE cosα + √ + LFG cosα + √ 3LFE 3LFG According to upper bound theorem, the R can be obtained by  dF tC √ R = 4π σyc tC √ cosα 3

(7)

Herein, the length of segments √ LFE = LFG =

3d F tC 3cosα

(8)

Substituting Eq. (7) into Eq. (5), predicted full plastic strength Pp−PRE is calculated as

 Pp−PRE = 4π wσyc tc

dF tC √ cosα(μ1 cosα + sinα) √ 3

where, μ1 = 0.43, referred from Table 3.

(9)

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Comparison of Pp−PRE with experimental results Pp−EXP is shown in Fig. 13. It can be found that the average value is 1.03, with a C.V of 0.12. Enhancement factor ρ is employed to consider the influence of strain hardening effect of mild steel material on the collapse strength of specimens. It is assumed as the average of ratios of collapse strength to full plastic strength. The ρ is equal to 1.21, as shown in Table 2. Collapse strength Pu is predicted by Pu−PRE = ρ · Pp−PRE = 1.21Pp−PRE

(10)

Comparison of the predicted collapse strength with the experimental results is shown in Fig. 14. The average value is 1.06, with a C.V of 0.20. It can be found that the proposed formula in Eq. (10) slightly overestimates the collapse strength of specimens. One of the reasons is that the interaction of meridional stress resultant with meridional bending moment and hoop stress resultant is not considered.

5 Conclusions In this paper, with a focus of conical wall failure in steel cone-to-cylinder socket connections, stress distribution and failure mechanism are investigated based on the effective finite element analysis. Collapse strength is then derived by limit analysis. The influence of strain hardening effect of mild steel material on the strength of specimens is considered. The main conclusions are as follows: (1) Friction coefficient between conical wall and cylinder edge contributes to the collapse strength of specimens. Their relationship is found to linearly increase with a strong correlation. (2) Conical wall failure is found to be controlled by plastic collapse; and (3) Easy-to-use formula for collapse strength is derived by limit analysis. It slightly overestimates the actual strength of specimens. One way to improve the precision is to consider the interaction of meridional stress resultant with meridional bending moment and hoop stress resultant.

References 1. Kuwamura, H., Ito, T., Tomioka, Y.: Study on steel cone-to-cylinder socket connection. J. Struct. Constr. Eng. Arch. Ins. Jpn. 598, 155–162 (2005). (in Japanese) 2. Kuwamura, H., Ito, T.: Study on steel cone-to-cylinder socket connections part 2 Frictional rotation resistance of steel cone-to-cylinder socket connections. J. Struct. Constr. Eng. Arch. Ins. Jpn. 622, 169–176 (2007). (in Japanese) 3. Tanaka, R., Kobayashi, K., Sasaki, S.: Report on damage of cast-in-place concrete pile during the 1995 Hyogoken-Nanbu earthquake. Fujita Tech. Res. Rep. 51, 57–62 (2015). (in Japanese) 4. Tian, Q., Kuwamura, H.: Study on steel cone-to-cylinder socket connection, (Part 10 Stress distribution in cylinder edge failure mechanism investigated by FEA). In: 86th Architectural Research Meeting of Kanto Chapter. Architectural Institute of Japan (2015)

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5. Tian, Q.: Collapse strength of tapered ring failure in steel cone-to-cylinder socket connections under axial compression. In: 11th Pacific Structural Steel Conference, Shanghai, China (2016) 6. Kuwamura, H., Ito, T., Tomioka, Y.: Study on steel cone-to-cylinder socket connections part 3 strength of cones. Summaries of Technical Papers of Annual Meeting of Architectural Institute of Japan, pp. 887–892 (2005). (in Japanese) 7. Tomioka, Y.: Compressive strength of steel cone-to-cylinder socket connections. Master thesis, The University of Tokyo, Japan (2006). (in Japanese) 8. Tateyama, E., Inoue, K., Sugimoto, S., Matsumura, H.: Study on ultimate bending strength and deformation capacity of H-shaped beam connected to RHS column with through diaphragms. J. Struct. Constr. Eng. Arch. Inst. Jpn. 389, 109–121 (1988). (in Japanese) 9. ABAQUS Standard Manual (Version 6.14). Hibbitt, Karlsson & Sorensen, Inc., Pawtucket (2014) 10. Save, M.A., Massonnet, C.C.: Plastic Analysis and Design of Plates, Shells and Disks, pp. 12– 28. North Holland Publishing Co., Amsterdam (1997)

Effectiveness of Laser Treatment on Carbon Steel with Various Forms of Corrosion Pits S. Park1(B) , S. Kainuma1 , M. Yang1 , H. Miki2 , and T. Asano3 1 Department of Civil Engineering, Kyushu University, Fukuoka, Fukuoka 819-0395, Japan

[email protected]

2 Cool Laser Division, TOYOKOH Inc, Hamamatsu, Shizuoka 434-0004, Japan 3 Bridge and Structural Engineering Division, West Nippon Expressway Co., Ltd., Osaka, Japan

Abstract. A high-power continuous-wave laser is applied in this study as a replaceable surface treatment method for steel structures. Various forms of corrosion pits will affect the laser treatment efficiency for surface preparation of severely corroded steel structures. In order to evaluate the effect of laser treatment on the steel surface with corrosion pits, carbon steels with artificial pits of various depths and widths were performed and treated by laser irradiation. SEM-EDX analysis distinctly identified laser-treated areas under conditions by mapping elements. Results indicate the laser beam can reach the bottom of pits, promising cleaning efficiency of laser irradiation is still worth expecting. Keywords: Continuous-wave laser treatment · Artificial pits of various depths and widths

1 Introduction Surface preparation is an important procedure for the maintenance of steel structures. Insufficient surface treatment directly affects the stability of the structure by exacerbating the durability of the coating or welding. Currently, blast treatment is the conventional method for steel surface preparation, with advantages of high cleaning effect and low cost. However, emissions of dust and abrasive waste during blasting bring about serious ecological problems. Also, residual contaminators after blasting will affect the surface characteristic as well [1]. Laser is a new surface preparation method to overcome these problems. Laser has found successful applications in automotive, shipbuilding, and artwork conservation. Research by Chen et al. [2]. indicated laser can efficiently remove the surface contaminants, including rust, salt, grease, and paint by controlling the operating parameters. In this sense, improving cleanliness and the surface properties of steel can be achieved by repeating laser scanning pass, the laser would be a promising method for effective surface preparation for various industries. Advantages of laser include cost-effectiveness maintenance, flexibility, and high-power delivery. Albeit laser surface treatment had been attracting attention in recent years, a systemic research result has not been established currently regarding surface cleaning with continuous wave (CW) fiber laser. In this study, a high-power CW laser was adopted as a surface treatment method. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 328–333, 2023. https://doi.org/10.1007/978-981-19-4293-8_34

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In consideration of severely corroded steel plate, the corrosion pits on the steel surface may induce positive defocus of the laser beam, and affect laser treatment efficiency, as shown in Fig. 1. Laser defocus is a common problem during laser treatment [3], the deep corrosion pit that exists in severely corroded steel surfaces may induce power attenuation. To verify the laser treatment effects inside corrosion pits, steel plates with artificial corrosion pits are prepared for laser irradiation, and the surface morphology is observed under an optical microscope and SEM-EDX.

Fig. 1. Laser treatment for corroded steel surface.

Fig. 2. Specimens with artificial corrosion pits and laser irradiation path.

Fig. 3. Observation positions on specimen.

2 Experimental The laser surface treatment was executed with a 2 kW fiber laser running at fixed scanning speed and power. CW fiber laser was carried out in the following processes to improve the efficiency of treatment: After focusing on the sample surface through the lens, the laser spot was rotated to a fixed diameter laser ring by a motor-driven prism [4]. The whole area of the carbon steel plate was irradiated using a laser ring at a designed speed and direction. On the surface of severely corroded steel plates, various shapes of corrosion pits are included. The main control variables which affect laser surface treatment most are pitting depth and width [5]. The depth of the corrosion pit induces the laser to defocus at the bottom, which may weaken the laser output power density. On the other hand, a narrow corrosion pit only allows a short irradiation period inside the pinhole, thus limiting heat transfer from laser beam to the bottom of the corrosion pit. In consideration of irregular corrosion morphology on the steel plate, the corrosion depth and pinhole width are regarded as separate parameters for the evaluation of laser

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treatment effects. Carbon steel plate according to JIS G3106 SM490A with dimensions of 150 × 70 × 9 mm is prepared for artificial corrosion pit processing. A flat drill was used during drilling processing, in order to acquire smooth bottom for surface analysis. To compare the laser effects at the upper surface and inside the artificial pit, the milling process was adopted before drilling to remove the mill scale and provide similar surface conditions for both positions. For specimens with different corrosion depths, the same pitting diameter of 4 mm is chosen, and the pitting depths are range from 2 mm to 8 mm. The same pitting depth is manufactured in a line, and different depth of artificial pits was separated to avoid mutual interference when irradiating adjacent corrosion pits. During surface treatment, laser ring scanning across the line of corrosion pits at a given speed, then interval time was prepared between each irradiation, allowing steel plate cooling down to room temperature. The same laser treatment method was applied to the specimen with different pitting widths, in which the pitting depth maintain at 4 mm. Figure 2 shows the specimens with artificial corrosion pits and laser irradiation method.

3 Test Result 3.1 Surface Morphology of Laser-Treated Specimens Two positions as the upper surface near the edge of the corrosion pit and the bottom surface at the center of the corrosion pit were selected to observe the surface morphology, as shown in Fig. 3. The surface upon corrosion pit was used as a comparison to identify the effects of corrosion pits on laser treatment. The results of surface morphology are shown in Fig. 4. From Fig. 4a, the laser paths were observed in every depth of corrosion pits, demonstrating effective laser irradiation for all corrosion depths investigated in this study. The positive defocus of the laser beam on the corrosion pit bottom enlarges the size of the laser spot, thus laser defocus is likely to reduce power density in case of a larger spot size. The laser surface treatment is mainly depending on thermal effects induced by the laser beam, thus lower power density will limit the interaction between the laser beam and the target surface. However, on the basis of surface morphology observed inside corrosion pit up to 8 mm depth, an acceptable laser treatment effect was provided. Figure 4b shows the surface morphology inside corrosion pits with different pitting widths. Although the laser scanning paths were also presented at the bottom, a blurry image of the laser path is shown inside a corrosion pit with a 2 mm width. Among the corrosion pits with different width, identical laser defocus are ensured because of the same depths. On the other hand, the steep wall of the pinhole results in discontinuity in the upper surface and the corrosion bottom, thus reducing the thermal effects during laser irradiation. In addition, high-density fumes and particles are generated in narrow pit hold during laser irradiation, hence reducing the power of the laser beam reaching the bottom surface. However, the laser paths still confirmed the effectiveness of laser treatment inside corrosion pits with different widths. Taking the residual salts into account, the melting point and boiling point of NaCl are 1074 K and 1738 K respectively, much smaller than the steel material (melting point 1698 K, boiling point 3273 K) [6]. This level of laser power is still enough to remove residual salts inside the corrosion pits.

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(a)Surface morphology of laser-treated specimen with different artificial corrosion depth.

(b) Surface morphology of laser-treated specimen with different artificial corrosion width. Fig. 4. Surface morphology of laser-treated specimens.

3.2 Scanning Electron Microscope (SEM-EDX) SEM-EDX analysis was conducted to quantitatively analyze the effects after laser treatment. Oxygen is observed on the steel surface after laser treatment from the SEM-EDX results shown in Fig. 5. Oxygen mainly exists in the center of the laser scanning track. A quantitative analysis of EDX found that the oxygen content of the laser-treated surface was 22.5, 32, 28.8, and 35.2 wt% at 2, 4, 6, and 8 mm, respectively, based on different pitting depths. The high oxygen content at all treatment depth conditions showed that laser ablation was performed at all depth conditions. Pitting depth has no obvious effects on the laser treatment efficiency. In Fig. 5a, the mapping of oxygen elements showed the same positions as the SEM photograph of the laser track at a depth of 2 mm. Thus, it can be seen that the steel surface with different corrosion depths has a similar laser ablation effect. Figure 5b shows the results of laser treatment at different pitting widths at a depth of 4 mm. At pitting widths of 2, 4, 6, and 8 mm, the oxygen content was 14.8, 32, 31.9, and 37.3 wt%, respectively. As with the evaluation on a depth basis, the laser energy absorbed on the steel surface was compared with the shape of the laser track. Given that fewer oxygen elements were found at 2 mm width, it can be seen that laser energy is restricted by the narrow pitting width. The larger the treatment area, the more oxygen

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elements could be found in the same area as the laser track. Most of the surface at bottom of pitting presented laser scanning tracks except for 2 mm pitting width. Therefore, it proved that fumes and particles generated in narrow pit hold during laser irradiation, reduce the power of the laser beam reaching the bottom surface.

(a) SEM-EDX results of laser-treated specimen with different artificial corrosion depth.

(b) SEM-EDX results of laser-treated specimen with different artificial corrosion width.

Fig. 5. SEM-EDX results of laser-treated specimens.

4 Conclusions The effects of corrosion pits on laser surface treatment were investigated in this study. Steel plates with different depths and widths of artificial corrosion pits are manufactured and used as specimens. Test results indicate: 1) Laser ablation effects can be observed inside deep corrosion pit up to 8 mm. 2) Albeit small width of the corrosion pit limits the thermal effectiveness of laser irradiation, cleaning efficiency of laser irradiation can be expected. Further investigation of the laser thermal effects on steel plates with corrosion pits requires surface physics analysis and cross-section evaluation. In addition, the evaluation of coating quality for laser-treated steel plates is also important for actual structure application.

References 1. Kainuma, S., Yang, M., Ishihara, S., Kaneko, A., Yamauchi, T.: Corrosion protection of steel members using an Al-Zn base sacrificial anode and fiber sheet in an atmospheric environment. Constr. Build. Mater. 224, 880–893 (2019) 2. Chen, G.X., Kwee, T.J., Tan, K.P., Choo, Y.S., Hong, M.H.: High-power fibre laser cleaning for green shipbuilding. J. Laser Micro Nanoeng. 7, 249–253 (2012)

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3. Metelkova, J., Kinds, Y., Kempen, K., de Formanoir, C., Witvrouw, A., Van Hooreweder, B.: On the influence of laser defocusing in Selective Laser Melting of 316L. Addit. Manuf. 23, 161–169 (2018) 4. Zhuang, S., Kainuma, S., Yang, M., Haraguchi, M., Asano, T.: Characterizing corrosion properties of carbon steel affected by high-power laser cleaning. Constr. Build. Mater. 274, 122085 (2021) 5. Liu, A., Previtali, B.: Laser surface treatment of grey cast iron by high power diode laser. Phys. Procedia 5, 439–448 (2010) 6. Gandy, D.: Carbon steel Handbook. Carbon N. Y. 3, 172 (2007)

Experimental Investigation of the Axial Load Capacity for DSTCs Manufactured with High Strength Concrete Zakir Ikhlasi(B) and Thomas Vincent College of Science and Engineering, Flinders University, Adelaide, South Australia 5042, Australia [email protected]

Abstract. Fiber-reinforced polymer (FRP)-concrete-steel double skin tubular columns (DSTCs) also known as hybrid DSTCs are a composite column made of an outer FRP tube, an inner steel tube and concrete filled in between. Combining these three materials provides several advantages not found in the traditional columns due their unique properties, such as; high ductility, high strength to weight ratio and good corrosion resistance. In this study a total of 18 DSTCs were manufactured with high strength concrete and have been experimentally tested under axial compression. All specimens were cylindrical with a diameter of 152 mm and height of 305 mm. The test parameters examined by this research were FRP tube thickness and cross-sectional shape of the inner steel tube. The results show that an increase in the FRP tube thickness leads to an increase in the maximum load capacity of the DSTC where this effect is more noticeable as the diameter of the steel tube decreases. It was also observed that the effect of the cross-sectional shape of the inner steel tube on axial load capacity is dependent on the size of the steel tube. Keywords: Double skin tubular columns · Hybrid DSTCs · Composite columns · High-strength concrete · Fiber reinforced polymer · Steel · CFRP · Axial loading

1 Introduction In the past several decades fiber-reinforced polymer (FRP)-concrete-steel double skin tubular columns (DSTCs) or Hybrid DSTCs have gained a lot of research attention [1– 23]. DSTCs consist of three constituent materials, a FRP outer tube, an inner steel tube, and concrete sandwiched in between. Compared to traditional reinforced concrete (RC) columns [24–26] DSTCs offer the additional benefit of high strength-to-weight ratio and good corrosion resistance. The combination of these materials has demonstrated excellent structural performance due to their unique properties [1–16]. Numerous experimental and numerical studies have been conducted on the behavior of DSTCs, including investigating monotonic axial compression [4–8], cyclic axial compression [9, 10], flexure [11–13], and a combination of axial compression loading and © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 334–341, 2023. https://doi.org/10.1007/978-981-19-4293-8_35

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lateral load reversals [14–16]. However, as presented in a review paper by Ozbakkaloglu [26] the majority of these studies have used normal-strength concrete (NSC) with a limited number of studies conducted on DSTCs manufactured with concrete having a compressive strength above 50 MPa, referred to as high-strength concrete (HSC). To address this gap in the existing research, this paper presents results of an experimental study on the axial compressive behavior of DSTCs using HSC. The test parameters of this study were FRP tube thickness and cross-sectional shape of the inner steel tube.

2 Specimen and Material Description A total of 18 DSTCs were prepared for this experimental study, all the specimens were cylindrical and 152 mm in diameter and 305 mm in height. Using a manual wet lay-up technique, the outer FRP tube was formed from carbon fiber-reinforced polymer (CFRP). The CFRP used for the outer FRP tube had the following mechanical properties; thickness of 0.167 mm, tensile strength of 4000 MPa and elastic modulus of 230 GPa. Grade 250 steel was used for the inner steel tube of the DSTCs, Table 1 illustrates a summary of the inner and outer tube properties. Table 1. Summary of specimen details. Cross-sectional shape of Nominal bore/size (mm) Thickness (mm) Number of FRP layers steel tube Circular

40

2.3

1, 2, 3

Circular

50

2.3

1, 2, 3

Circular

65

2.3

1, 2, 3

Square

40 x 40

2.5

1, 2, 3

Square

50 x 50

2.5

1, 2, 3

Square

65 x 65

2.5

1, 2, 3

The specimens were poured with HSC that had a measured slump of 40 mm and compressive strength of 56.8 MPa. Table 2 illustrates the details of the concrete-mix design, where the water to cement ratio is 0.51. Table 2. Concrete mix design. Equivalent ratios

Material (kg/m3 )

Cement

1

330

Sand

2.3

750 (continued)

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Material (kg/m3 )

Coarse aggregate

3.5

1165

Water

0.51

168

3 Specimen Preparation To manufacture the DSTCs a base plate and clamp type device was designed for the moulds to ensure that the steel tube would remain central during the pouring and vibrating of the concrete. The concrete was then left to set for 24 h after being poured. After 24 h the specimens were demoulded and moved into the water tank to cure for 20 days at 20 °C. After 20 days of curing, the specimens were then wrapped with CFRP using the manual wet lay-up application process. After the specimens were wrapped, they were left to set for another 7 days to allow the epoxy to cure adequately. The specimens were experimentally tested under axial compression 28 days after the concrete was poured. To gain an understanding of the contribution the inner steel tube has on the DSTC system, steel tube samples were tested in isolation under axial compressive loading. Two sets of steel tube lengths were tested, one was at the full height of the DSTCs and the other was a 1:2 width to height ratio.

4 Test Results Table 3 illustrates the details of the specimens, the first letter in the name of the specimens refers to the cross-sectional shape of the inner tube where C indicates circular, and S indicates square inner tube. The double-digit number after the first letter is the nominal bore size of the inner tube. The letter T followed by a number refers to the thickness of the inner steel tube. The letter L followed by a number refers to the number of FRP layers applied. Although both circular and square steel tubes were manufactured from the same grade of steel, it can be seen in Table 3 that square cross-sections recorded slightly higher peak stresses compared to circular sections. It was also observed that failure of all steel tubes was due to localized buckling, as it can be seen in Fig. 1a) and b). Moreover, full height and 1:2 specimens record similar values, indicating that full height steel specimens are not experiencing premature failures due to global buckling. All DSTC specimens failed by FRP sheet rupture at approximately mid specimen height, as it can be seen in Fig. 1c) and d), followed by a rapid loss of axial load. Close inspection of the steel tubes showed that localized buckling occurred at mid-height of the specimen over a height of approximately 10–20 mm.

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Table 3. Test results. Specimen name

DSTCs maximum load capacity (kN)

Average steel compressive strength 305 mm full height (MPa)

1:2 Diameter to height (MPa)

C40T2.3L1

1176

405

442

C40T2.3L2

1416

C40T2.3L3

2001

C50T2.3L1

1124

367

388

C50T2.3L2

1353

C50T2.3L3

1868

C65T2.3L1

1065

345

368

C65T2.3L2

1305

C65T2.3L3

1639

S40T2.5L1

1252

487

516

S40T2.5L2

1594

S40T2.5L3

2000

S50T2.5L1

1243

494

501

S50T2.5L2

1500

S50T2.5L3

1822

S65T2.5L1

1094

413

418

S65T2.5L2

1246

S65T2.5L3

1426

a)

b)

c)

d)

Fig. 1. Specimen failure a) full height square steel tube b) 1:2 width to height ratio circular steel tube c) DSTC with 1 layer of FRP d) DSTC with 2 layers of FRP.

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4.1 Effect of FRP Layers To investigate the influence of FRP layers on the compressive strength of DSTCs manufactured with HSC, both circular and square specimens were examined within their comparable groups of specimens with varying layers of FRP. As shown in Fig. 2, there is a 20–30% increase in the maximum load capacity of the DSTCs with the circular inner steel tube, when the FRP layers are increased from 1 to 2 layers. However, when the FRP layers are increased from 1 to 3 layers the maximum load capacity of the DSTCs with circular inner steel tube increases by 33–40%. In the DSTCs with square inner steel tube the maximum load capacity is increased by 10–20% as the FRP layers are increased from 1 to 2 layers. Furthermore, as the FRP layers are increased from 1 to 3 layers the maximum load capacity of the DSTCs with square inner steel tube increase by 20–35%. Although the overall general trend appears similar, on closer inspection it can be seen that an increase in FRP layers has a larger effect for specimens prepared with a smaller diameter steel tube, with this effect applicable to both square and circular specimens.

Fig. 2. Maximum load capacity vs number of FRP layers.

4.2 Effect of the Cross-Sectional Shape of the Inner Steel Tube To investigate the influence of the cross-sectional shape of the inner steel tube on the compressive strength of the DSTCs manufactured with HSC, specimens with circular and square inner tubes were compared. In this comparison only the cross-sectional shape of the inner steel tube varied, all other key parameters of the steel tube such as width, thickness and strength remained comparable. Furthermore, the specimens were only compared for the same number of FRP layers. The effect of the cross-sectional shape of the inner steel tube is dependent on the number of FRP layers applied to the specimen. As it can be seen in Fig. 3, when there is 1 layer of FRP applied, the DSTCs with circular inner steel tube have a slightly lower maximum load capacity than the DSTCs with square inner steel tube. However, as the number of FRP layers increase to 3 layers, the DSTCs with circular inner steel tube begin to have a similar or higher maximum load capacity compared to DSTCs with square inner steel tube.

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Fig. 3. Maximum load capacity vs cross-sectional shape of inner tube.

5 Conclusion This paper presents the results of an experimental study on the behavior of fiberreinforced polymer (FRP)-HSC-steel double skin tubular columns (DSTCs). In this study 18 test specimens were manufactured and tested under axial compression. The test parameters were FRP tube thickness and cross-sectional shape of the inner steel tube. From the tests conducted the following conclusions are made: o An increase in the number of FRP layers for DSTCs manufactured with HSC results in a significant increase in load capacity. This increase is noticeably higher for DSTCs manufactured with circular inner steel tubes compared to square tubes. o The effect of the cross-sectional shape of the inner steel tube is relatively minor and dependent on the number of FRP layers applied. For low levels of confinement, the DSTCs with square inner steel tube has a higher maximum load capacity. However, when the number of FRP layer are increased the DSTCs with circular inner tube begin to have a higher maximum load capacity than the DSTCs with square inner tube.

References 1. Teng, J.G., Yu, T., Wong, Y.L., Dong, S.L.: Hybrid FRP–concrete–steel tubular columns: Concept and behavior. Constr. Build. Mater. 21, 846–854 (2007). https://doi.org/10.1016/j. conbuildmat.2006.06.017 2. Wong, Y.L., Yu, T., Teng, J.G., Dong, S.L.: Behavior of FRP-confined concrete in annular section columns. Compos. B Eng. 39, 451–466 (2008). https://doi.org/10.1016/j.compositesb. 2007.04.001 3. Yu, T., Wong, Y.L., Teng, J.G.: Behavior of hybrid FRP-concrete-steel double-skin tubular columns subjected to eccentric compression. Adv. Struct. Eng. 13, 961–974 (2010). https:// doi.org/10.1260/1369-4332.13.5.961

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4. Louk Fanggi, B.A., Ozbakkaloglu, T.: Square FRP–HSC–steel composite columns: Behavior under axial compression. Eng. Struct. 92, 156–171 (2015). https://doi.org/10.1016/j.engstr uct.2015.03.005 5. Louk Fanggi, B.A., Ozbakkaloglu, T.: Compressive behavior of aramid FRP–HSC–steel double-skin tubular columns. Constr. Build. Mater. 48, 554–565 (2013). https://doi.org/10. 1016/j.conbuildmat.2013.07.029 6. Yu, T., Teng, J.G.: Behavior of hybrid FRP-concrete-steel double-skin tubular columns with a square outer tube and a circular inner tube subjected to axial compression. J. Compos. Constr. 17, 271–279 (2013). https://doi.org/10.1061/(ASCE)CC.1943-5614.0000331 7. Albitar, M., Ozbakkaloglu, T., Louk Fanggi, B.A.: Behavior of FRP-HSC-steel double-skin tubular columns under cyclic axial compression. J. Compos. Constr. 19, 04014041 (2015). https://doi.org/10.1061/(ASCE)CC.1943-5614.0000510 8. Yu, T., Zhang, B., Cao, Y.B., Teng, J.G.: Behavior of hybrid FRP-concrete-steel double-skin tubular columns subjected to cyclic axial compression. Thin-walled structures, recent research advances on thin-walled structures 61, 196–203 (2012). https://doi.org/10.1016/j.tws.2012. 06.003 9. Idris, Y., Ozbakkaloglu, T.: Flexural behavior of FRP-HSC-steel double skin tubular beams under reversed-cyclic loading. Thin-walled Struct. 87, 89–101 (2015). https://doi.org/10. 1016/j.tws.2014.11.003 10. Idris, Y., Ozbakkaloglu, T.: Flexural behavior of FRP-HSC-steel composite beams. ThinWalled Struct. 80, 207–216 (2014). https://doi.org/10.1016/j.tws.2014.03.011 11. Yu, T., Wong, Y.L., Teng, J.G., Dong, S.L., Lam, E.S.: Flexural behavior of hybrid FRPconcrete-steel double-skin tubular members. J. Compos. Constr. 10, 443–452 (2006). https:// doi.org/10.1061/(ASCE)1090-0268(2006)10:5(443) 12. Han, L.H., Tao, Z., Liao, F.Y., Xu, Y.: Tests on cyclic performance of FRP–concrete–steel double-skin tubular columns. Thin-Walled Struct. 48, 430–439 (2010). https://doi.org/10. 1016/j.tws.2010.01.007 13. Ozbakkaloglu, T., Idris, Y.: Seismic behavior of FRP-high-strength concrete-steel double-skin tubular columns. J. Struct. Eng. 140, 04014019 (2014). https://doi.org/10.1061/(ASCE)ST. 1943-541X.0000981 14. Zhang, B., Teng, J.G., Yu, T.: Experimental behavior of hybrid FRP–concrete–steel doubleskin tubular columns under combined axial compression and cyclic lateral loading. Eng. Struct. 99, 214–231 (2015). https://doi.org/10.1016/j.engstruct.2015.05.002 15. Ali, H.A., Salman, W.D.: Effect of void ratio of inner steel tube on compression behavior of double skin tubular column. Presented at the IOP Conference Series: Materials Science and Engineering (2019). https://doi.org/10.1088/1757-899X/584/1/012027 16. Peng, K., Yu, T., Hadi, M.N.S., Huang, L.: Compressive behavior of hybrid double-skin tubular columns with a rib-stiffened steel inner tube. Compos. Struct. 204, 634–644 (2018). https://doi.org/10.1016/j.compstruct.2018.07.083 17. Wang, W., Wu, C., Liu, Z.: Compressive behavior of hybrid double-skin tubular columns with ultra-high performance fiber-reinforced concrete (UHPFRC). Eng. Struct. 180, 419–441 (2019). https://doi.org/10.1016/j.engstruct.2018.11.048 18. Yu, T., Zhang, S., Huang, L., Chan, C.: Compressive behavior of hybrid double-skin tubular columns with a large rupture strain FRP tube. Compos. Struct. 171, 10–18 (2017). https://doi. org/10.1016/j.compstruct.2017.03.013 19. Zeng, L., Li, L., Xiao, P., Zeng, J., Liu, F.: Experimental study of seismic performance of full-scale basalt FRP-recycled aggregate concrete-steel tubular columns. Thin-Walled Struct. 151, (2020). https://doi.org/10.1016/j.tws.2019.106185 20. Fam, A., Schnerch, D., Rizkalla, S.: Rectangular filament-wound glass fiber reinforced polymer tubes filled with concrete under flexural and axial loading: Experimental investigation. J. Compos. Constr. 9, 25–33 (2005). https://doi.org/10.1061/(ASCE)1090-0268(2005)9:1(25)

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Earthquake-Induced Vibration Measurement and Inverse Analysis of Bell-Shaped Pagoda Naremet Tantisukhuman1 , Chayanon Hansapinyo2 , Chinnapat Buachart2(B) Mitsuhiro Miyamoto3 , and Manabu Matsushima3

,

1 Department of Civil Engineering, Faculty of Engineering,

Chiang Mai University, Chiang Mai, Thailand 2 Center of Excellence in Natural Disaster Management, Department of Civil Engineering,

Faculty of Engineering, Chiang Mai University, Chiang Mai, Thailand [email protected] 3 Faculty of Engineering, Kagawa University, Takamatsu, Japan

Abstract. Ancient historic buildings are constructed with antiquated construction techniques. Hence, they are vulnerable to an earthquake and require appropriate seismic strengthening. To complete the task, dynamic parameters are needed. This study proposes an inverse analysis to identify the dynamic properties of the structure. The proposed algorithm uses Newmark’s time stepping method with the Gauss-Newton scheme. An earthquake-induced vibration of a selected pagoda was recorded by pre-installed two accelerometers, which were used to perform the inverse analysis. The average acceleration and linear acceleration of Newmark’s scheme were adopted, and the obtained dynamic properties were compared. The results show that the dynamic structural parameters from the two methods are comparable. The values of natural frequency are in the range obtained from the previous study. Keywords: Vibration time history · Inverse analysis · Structural dynamic parameters

1 Introduction Earthquakes induce a shock load that is powerful to cause massive destruction to cities [1–3]. As the occurrence of the earthquake cannot be avoided, many efforts have been paid to establish an effective preparedness plan [4, 5]. More critical buildings have been classified based on the impact of consequence loss. Historic buildings have been built for many years, and the construction technique used at that time is substandard without seismic consideration. In addition, the buildings are recognized as valuable beliefs of people. Hence, the buildings are classified and ranked as the most critical ones, and urgent seismic strengthening is required [6]. Many active faults have been found in the North of Thailand. There was a magnitude 6.3 earthquake in Chiang Rai Province on May 5, 2014. The strike caused damage to buildings in a large area [7]. There are many historic buildings in the North of Thailand that require seismic strengthening. To achieve © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 342–352, 2023. https://doi.org/10.1007/978-981-19-4293-8_36

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the task, information about the dynamic properties of the structure, e.g., the damping ratio and fundamental period of vibration, are indispensable. Modal analysis of a fully three-dimensional finite element model has been successfully adopted to estimate the dynamic properties. However, the method is limited to the building with an available as-built drawing. Lacking the data of the long time-built historical buildings, using the modal analysis requires unknown assumptions, which could lead to an unrealistic result. The ambient vibration test is a widely used technique to identify the dynamic properties of historical buildings. The ambient vibration test on the masonry roof of the Basilica of the Fourteen Holy Helpers was conducted in Bavaria, southern Germany [8]. These dynamic structural parameters, identified using the operational modal analysis method, allow the adjustment of numerical models to obtain a more accurate estimation of the actual behavior of the structure. The ambient vibration tests are also used in Lebanon and Turkey [9, 10]. The method provides the vibration properties from a global point of view. Unfortunately, as the vibration intensity is a very low signal, it is unable to identify the dynamic properties of specific elements with a local character. Another popular method to estimate the dynamic properties of buildings is inverse analysis. This method is driven based on the precise measurement of the deformation of the structure during a loading test, and the subsequent inverse mathematical analysis is then performed. The inverse analysis was applied to the diagnostics of a historical bridge in the Czech Republic [11]. In the present work, the inverse analysis method is used to identify the dynamic properties of a pagoda located in Chiang Mai province, in the North of Thailand. Two vibrational sensors were installed on the pagoda at the top and base levels to monitor the vibration responses when an earthquake occurs. The earthquake induced vibration provides a high signal. The measured ground and top acceleration from the sensors versus numerical analysis were used to compute the dynamic properties of the pagoda, which are the damping ratio and natural frequency. Then the results from using Newmark’s average acceleration method and the linear acceleration method were compared to verify the performance of the proposed inverse analysis procedure.

2 Equation of Motion and Inverse Analysis The vibration of the pagoda can be simplified using a single degree of freedom system, as shown in Fig. 1, which has an equation of motion as follows: m¨u + cu˙ + ku = −m¨ug

(1)

where u, u˙ , ü are relative lateral displacement, velocity, and acceleration between the top versus ground of the pagoda, respectively. In Fig. 1, the attached sensors at the top (Ch1) and ground (Ch2) are also shown. Structural mass is denoted by m. The damping coefficient and stiffness are represented by c and k, respectively. Ground acceleration, which is measured at Ch2, is denoted by üg . Equation (1) can be rewritten in terms of the damping ratio (ζ ) and natural angular velocity (ω) of the structure. Substituting relation between stiffness and natural angular

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Fig. 1. Simplified SDOF system of Pagoda and motion measurement.

frequency of structure k = mω2 , and damping ratio versus damping coefficient c = 2mωζ to Eq. (1) and divide by structural mass (m), yields u¨ + 2ωζ u˙ + ω2 u = −¨ug

(2)

Then, Eq. (2) is used to perform inverse analysis to identify the dynamic parameters, ζ and ω, of the pagoda. 2.1 Inverse Analysis To perform an inverse analysis, the dynamic parameters in Eq. (2) are redefined to new parameters, namely b1 = 2ωζ and b2 = ω2 . Hence, Eq. (2) is expressed in the form u¨ + b1 u˙ + b2 u = −¨ug

(3)

For the next step, the numerical solution of relative acceleration in Eq. (3) due to input ground accelerations is obtained [12]. In this work, two Newmark’s time stepping schemes, linear and average accelerations are performed with initial guests of dynamic parameters b1 and b2. Then the updated values of dynamic parameters b1 and b2 are estimated using the Gauss-Newton scheme [13]. The numerical solution of Eq. (3) and Gauss-Newton are iterated until the total sum-square-error of relative acceleration from numerical schemes versus measured acceleration is minimized. 2.2 Newmark’s Time Stepping Method The Newmark’s time stepping method is a single-step numerical time integration scheme used to evaluate the structural responses at the current time step ti + 1 from the response

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at the previous time step ti. The velocity and displacement at the current time step are approximated as follows: u˙ i+1 = u˙ i + (1 − γ )t u¨ i + γ t u¨ i+1 ui+1 = ui + t u˙ i +

1 2

 − β t 2 u¨ i + βt 2 u¨ i+1

(4) (5)

where γ and β are constant parameters. Setting γ = 0.5 and β = 0.25 obtains an average acceleration scheme. Also, the linear acceleration scheme is obtained using γ = 0.5 and β = 1/6. The time step size is denoted by t = t i+1 – t i . To determine acceleration at the current time step, substituting Eqs. (4) and (5) into Eq. (3) yields   1 + b1 γ t + b2 βt 2 u¨ i+1 = −¨ug − b1 u˙ p − b2 up (6)   where u˙ p = u˙ i + (1 − γ )t u¨ i and up = ui + t u˙ i + 21 − β t 2 u¨ i . Solving for an acceleration u¨ i+1 from Eq. (6), and then substitutes into Eqs. (4) and (5), obtain velocity and displacement at the current time step. 2.3 Gauss-Newton Scheme The Gauss-Newton scheme is used to compute an updated value of parameters b1 and b2 in Eq. (3). Minimize the total sum-square-error (SSE) between the relative acceleration obtained from Newmark’s scheme in the current iteration and the measured relative acceleration brought to the normal equation as following ⎞ ⎛   ∂ u¨ i 2 ∂ u¨ i ∂ u¨ i   ∂ u¨ i ¨i) i ∂b1 · ∂b2 ⎟ b1 ⎜ i ∂b1 i ∂b1 · (ai − u = ∂ u¨ i (7)  2 ⎠ ⎝ ∂ u¨ i ∂ u¨ i ∂ u¨ i b2 ¨i) i ∂b2 · (ai − u i ∂b1 · ∂b2 i ∂b2 where ai denotes relative acceleration between top and ground of pagoda at time ti measured from the sensor at Ch1 and Ch2 as shown in Fig. 1. The numerical solution of relative acceleration at time ti, computed from Newmark’s time stepping method, is denoted by ü. Then, the values of parameters b1 and b2 are updated using incremental values b1 and b2 obtained from Eq. (7), i.e., b1 ← b1 + αb1

(8)

b2 ← b2 + αb2

(9)

Based on a numerical experiment, the value of α is set to 0.05. Then the new values of parameters b1 and b2 are replaced in Eq. (3), and structural responses are re-evaluated using Newmark’s time stepping. Gauss-Newton and Newmark’s time stepping will be repeated until the changes in the dynamic parameters are very small, i.e.,  (10) (b1 )2 + (b2 )2 ≤ 10−4

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The value of the damping ratio and natural angular velocity are then evaluated via parameters b1 and b2 as follows: b1 ζ = √ 2 b2  ω = b2

(11) (12)

The natural angular velocity is also related to the natural frequency (f ) of the structure, i.e. f =

ω 2π

(13)

To perform the Gauss-Newton scheme, the partial derivatives of relative acceleration with respect to b1 and b2 have to be evaluated by solving Eqs. (14) and (15): ∂ u¨ ∂ u˙ ∂u + b1 + b2 = −˙u ∂b1 ∂b1 ∂b1

(14)

∂ u˙ ∂u ∂ u¨ + b1 + b2 = −u ∂b2 ∂b2 ∂b2

(15)

Note that Eqs. (14) and (15) are derived from taking the partial derivative of Eq. (3) with respect to b1 and b2 , respectively. The partial derivatives of acceleration in Eqs. (14) and (15) are also obtained numerically via Newmark’s time stepping method and used to compute matrix and vector elements in Eq. (7). In this work, Newmark’s time stepping and Gauss-Newton procedures are employed via MATLAB script [14].

3 Pagoda and Method of Measurement 3.1 Pagoda The pagoda in Umong temple (as shown in Fig. 2), which is located to the west of Chiang Mai city, is investigated. The pagoda was built in 1297 by King Mengrai. The height of the pagoda is 25.72 m, and the diameter at the base is 16.48 m. The pagoda was constructed using brick masonry without reinforcement in a bell-shape. The approximate volume of the pagoda is 1,655 m3 . The Young’s modulus and Poisson’s ratio of the brick are approximately equal to 1,000 MPa and 0.15, respectively. The density of brick is about 1,800 kg/m3 [15]. 3.2 Sensor Two accelerometer sensors from aLab Inc. were installed on the pagoda at the top and base. The sensor is illustrated in Fig. 3. The sensors are kept in a box that protects them from severe environment conditions such as temperature, humidity and rain. The list of specifications [16] is shown in Table 1. The two sensors measure seismic waves for 24 h. The measured accelerations were sent to a server through a local station PC online to store and analyse the data, as shown in Fig. 4.

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Fig. 2. Umong pagoda.

3.3 Earthquake Data The earthquake data on March 17, 2018 with the epicenter at WSW of Pyu, Myanmar (18.385°N 96.151°E), was recorded and used in the analysis. The hypocenter is 19.1 km depth underground with 5.1 mb magnitude. The distance between the location of the epicenter and the pagoda is about 300 km, as shown in Fig. 5 [17]. Table 1. Specification of sensor [16]. Specification

Value

Acceleration range

±2,450 cm/s2 (X, Y, Z axes)

Noise

0.1 cm/s2

Resolution

24 bits

Sampling

100 times/s

Power supply

PoE

Temporal precision

NTP dependence

Temperature

−10 to 40 °C

Water proof

IP67

Communication

Ethernet 100/10 Mbps

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Fig. 3. Installation of accelerometer.

Fig. 4. Diagram of process data [13].

Earthquake location Pagoda

Fig. 5. Locations of the earthquake source and the Pagoda.

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4 Results After performing the inverse analysis as described in Sect. 2 using the recorded earthquake in Sect. 3.3, the convergences of parameters b1 and b2 are observed. In Fig. 6, the results show that the b1 value in the North-South direction has converged to approximately 1.35 within 100 iterations. In the East-West direction, the value b1 has converged to approximately 0.65 within 100 iterations. However, due to the stopping criteria in Eq. (10), the Gauss-Newton will end in approximately 225 iterations. Figure 7 shows the convergence of the b2 parameter. Also, the value of b2 converges within 100 iterations, the same as in the case of the b1 parameter. However, the value of b2 obtained from the average acceleration method is slightly greater than the value obtained from the linear acceleration method in both the North-South and the East-West directions. The value of the sum-square-error of measured versus approximated relative acceleration is shown in Fig. 8. The curve also shows that the convergences are reached within 100 iterations. Table 2 concludes the number of iterations, the value of natural angular velocity, and the damping ratio obtained from converged values of parameters b1 and b2 . The sum-square-error of measured versus approximated relative accelerations of the Pagoda are also described in the table. The average values of the damping ratio are 0.030 and 0.015 in the North-South direction and in the East-West direction, respectively. The average values of natural frequency are approximately 3.58 Hz in the North-South direction and 3.63 Hz in the East-West direction. Note that these results are slightly lower than the modal analysis of the threedimensional finite element model from the previous study [15], which reported the fundamental frequency of Umong pagoda to be 4.45 Hz. However, the cost of finite element analysis is very expensive compared with the present simplified single-degree of freedom model. Also, the finite element model [15] may tend to be stiffer than the real structure due to the pagoda’s being assumed to be a fully solid shape, without holes inside. Therefore, the result of the present study implies an effect of non-homogenous properties. It is possible that there is a hole or a room inside the pagoda. Table 2. Dynamic properties of pagoda from the inverse analysis. Direction

Newmark’s method

Results Damping ratio (ζ)

Natural frequency [f , Hz]

No. of iteration

Sum of square error

Running time [sec]

(North-South)

Linear

0.030

3.58

224

125

2.31

Average

0.030

3.58

218

125

2.16

(East-West)

Linear

0.015

3.63

228

130

2.24

Average

0.015

3.63

218

130

2.15

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NS average NS linear

EW average EW linear

Fig. 6. Convergence of parameter b1.

EW average EW linear

NS average NS linear

Fig. 7. Convergence of parameter b2 .

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Fig. 8. Convergences of sum-square-error.

5 Conclusions In this study, an algorithm of inverse analysis to evaluate the dynamic properties of a historic building is proposed. The measured acceleration of the Umong pagoda is used to verify the performance of the proposed algorithm. The values of the dynamic parameters, e.g., the damping ratio and natural frequency, are estimated via the proposed algorithm. The convergence of parameters shows that the computed values converge within 100 iterations in both the North-South and the East-West directions. The converged values obtained from the Newmark’s average acceleration versus linear acceleration are slightly different. Also, the values of natural frequency are in the same range as obtained from the previous study. The results show that the adoption of the proposed scheme to investigate the dynamic parameters of other historic buildings is acceptable. The extension of the proposed scheme to different types of structures, such as office buildings, which need to be modeled in a multi-degree of freedom system, has to be further investigated.

References 1. Hansapinyo, C., Limkatanyu, S., Zhang, H., Imjai, T.: Residual strength of reinforced concrete beams under sequential small impact loads. Buildings 11(11), 518 (2021) 2. Hansapinyo, C., Wongmatar, P., Vimonsatit, V., Chen, W.: Pounding of seismically designed low-rise reinforced concrete frames. Proc. Inst. Civ. Eng.: Struct. Build. 172(11), 819–835 (2019)

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3. Tantrapongsaton, W., Hansapinyo, C., Wongmatar, P., Chaisomphob, T.: Flexural reinforced concrete members with minimum reinforcement under low-velocity impact load. Int. J. GEOMATE 14(46), 129–136 (2018) 4. Ketsap, A., Hansapinyo, C., Kronprasert, N., Limkatanyu, S.: Uncertainty and fuzzy decisions in earthquake risk evaluation of buildings. Eng. J. 23(5), 89–105 (2019) 5. Saicheur, K., Hansapinyo, C.: Seismic loss estimation and reduction after structural rehabilitation in Chiang Rai City. Walailak J. Sci. Technol. 14(6), 485–499 (2017) 6. Saicheur, K., Hansapinyo, C.: Structural repair prioritization of buildings damaged after earthquake using fuzzy logic model. J. Disaster Res. 11(3), 559–565 (2016) 7. Hansapinyo, C., Latcharote, P., Limkatanyu, S.: Seismic building damage prediction from GIS-based building data using artificial intelligence system. Front. Built. Environ. 6, Article no. 576919 (2020) 8. Compan, V., Pachón, P., Cámara, M.: Ambient vibration testing and dynamic identification of a historical building. Basilica of the Fourteen Holy Helpers (Germany). Proc. Eng. 199, 3392 –3397 (2017) 9. Salameh, C., et al.: Using ambient vibration measurements for risk assessment at an urban scale: from numerical proof of concept to Beirut case study (Lebanon). Earth Planets Space 69(1), 1–17 (2017). https://doi.org/10.1186/s40623-017-0641-3 10. Ahmet C.A., Karahasan, O.S., Okur, F.Y., Kalkan, E., Özgan, K.: Ambient vibration test and modelling of historical timber mosques after restoration. In: Proceedings of the Institution of Civil Engineers-Structures and Buildings, vol. 173, no. 12, pp. 956–968. ICE Virtual Library (2020) 11. Klusáˇcek, L., Neˇcas, R., Bures, J.: (2015). Diagnostics of a historical bridge using measuring methods and inverse analysis. Appl. Mech. Mater. 764–765, 1064–1069 (2015) 12. Chopra, A.K.: Dynamics of Structures. Prentice-Hall, Hoboken (2012) 13. Miyamoto, M., Hanazato, T.: Vibration characteristics of historical masonry buildings based on seismic observation. In: 2nd International Conference on Preservation Maintenance and Rehabilitation of Historic Buildings and Structures, Porto, Portugal, pp. 789–797 (2015) 14. MathWorks Homepage. https://www.mathworks.com/products/matlab.html. Accessed 16 Jan 2022 15. Yanathanom, K.: Static and dynamic behavior under seismic loading of pagodas in Chiang Mai city by finite element method. Master thesis, Chiang Mai University (2010) 16. aLab Homepage. http://www.alab.jp/product.html. Accessed 16 Jan 2022 17. USGS Homepage. https://earthquake.usgs.gov/earthquakes/search. Accessed 16 Jan 2022

Extended Critical Shear Crack Theory for Punching Shear of Lightweight, FRP-Reinforced, or Prestressed Concrete A. Deifalla(B) Future University in Egypt, New Cairo, Egypt [email protected], [email protected]

Abstract. The punching shear strength of conventional reinforced concrete elements has been a highly interesting topic for many reasons, including having a brittle and catastrophic failure, being influenced by many parameters and mechanisms, and lacking the physically based rigorous models. In addition, with the uprising evolution of concrete construction technology, more complexity was added to this already complex problem. Special cases included lightweight concrete and prestressed concrete [1–5]. Moreover, new advanced materials were implemented in the construction industry, including fiber-reinforced polymer (FRP) to replace conventional steel reinforcements [6–11]. Finally, in many cases, shear is combined with membrane forces, particularly tensile forces [12, 13]. Several strength models were developed for punching shear over the years [14–16]. A sequence of research studies is outlined briefly [17–20]. Those studies aimed to develop an extended critical shear crack theory (ECSCT) for various punching shear problems, including lightweight concrete, FRP-reinforced concrete, prestressed concrete, and punching shear combined with tensile forces. The ECSCT was validated using 585 slabs tested under punching load. The model strength predictions were compared with existing design codes [21–24]. The model is physically based and more accurate and consistent than other design codes. Keywords: Punching shear · FRP reinforced concrete · Lightweight concrete · Tensile force · FRP · Prestressed concrete

1 Introduction For punching shear, design codes require reasonable models for this complicated problem. Punching shear resistance of concrete slabs without shear reinforcements is composed of several mechanisms [14–20]. Failure of concrete slabs under punching shear is sudden and could be catastrophic. Several parameters affect the punching shear strength and deformation. Lightweight (LW) concrete is a good alternative for conventional normal weight (NW) concrete due to its economic advantage. Although many design codes permit LW concrete, there is no consensus on the method used to account for LW concrete [21–24]. However, very limited number of studies tackled LW concrete slabs under punching. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 353–361, 2023. https://doi.org/10.1007/978-981-19-4293-8_37

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For LW, existing design codes reduce the aggregate interlock or without decrease the concrete strength based on the concrete density regard to aggregate interlock. Fiber-reinforced polymers (FRP) reinforced concrete is becoming popular as an option for reinforcing concrete, which has the mechanical properties different from that of steel reinforcements. Thus, the shear strength of FRP reinforced concrete is an open area of research [18]. Prestressed concrete slabs are being used in various applications; however, its failure is quite sudden with very little warning. For punching shear of prestressed concrete slabs, design methods vary in the effective factors, which are different from one design code to another [19]. In-plane tension forces occur combined with punching shear in many situations, for example, 1) walls of nuclear containment vessels, 2) restrained large RC slabs, without construction joints, due to change in temperature, and 3) seismic and wind loading on the RC slabs [20]. Thus, there is a need for extending these mechanical models to the special problems, including, and not limited to: lightweight concrete (LW), FRP-reinforced concrete, prestressed concrete, and those subjected to combined punching and membrane tensile forces. The Critical shear crack theory (CSCT) was adapted and further extended to special problems in this current study. The extended CSCT (ECSCT) was validated using over 580 elements and compared with existing design codes.

2 General Overview of the Critical Shear Crack Theory (CSCT) For punching shear, mechanical models and design codes differ in the effective parameters used or how these parameters are accounted. The CSCT is a well-developed punching shear model, the base for the many design codes [14, 15], where the punching shear strength (v) is calculated such that:   ν  = f ω, ddg 2  fc

(1)

while ω is the crack width, f c is the cylinder compressive strength, and ddg is the aggregate factor. And the crack width is such that: ω ∝ ψd

(2)

where d is the effective depth, and ψ is the slab rotation. For the CSCT, a failure criterion was proposed to relate the punching shear resistance to the crack width, where the punching shear strength (V) and the rotation ( ψ) are calculated such that:  3/ 3  2 V V r s fy 4 2  = and ψ = 1.5 f c bo d d Es Vflex 1.0 + 15ψd ddg

(3)

 ddg is 16 mm and 16 + dg min 60 , 1 ≤ 40 mm for LW and NW concrete, respectively,  f c

d is the effective depth, bo is the perimeter of the punching shear critical section, fc is the concrete compressive stress, c is the loading area dimension. rs is the distance between the loading area centerline and the inflection point, fy is the flexure reinforcement yield

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stress, Es is the flexure reinforcement young’s modulus, V is the punching shear force acting on the area, and Vflex is the punching shear corresponding to the flexure capacity, s , mR is the two-way shear for flexure failure in N, which is which is taken as 2π mR rq r−r c ⎞ ⎛ ⎜ taken as d 2 ρfy ⎝1 −

ρfy 2fc



30 fc

1/

3

⎟ ⎠. ρ is the flexure reinforcement ratio, rq is the distance

between the centerline of the loading area and the loading point, and rc is the distance between the centerline and the edge of the loading area (Fig. 1).

Fig. 1. Schematic for CSCT.

Fig. 2. Failure criteria for different cases.

3 ECSCT for Punching Shear of Lightweight Concrete [17] The punching shear resistance across the diagonal crack for LW concrete is significantly different from NW ones. The crack propagates through LW, resulting in a smoother crack; thus, the aggregate size and the roughness of the contact surface have less effect on the shear resistance. Based on, a mechanical model was developed. In addition, the CSCT was modified using an experimental database of over 130 concrete LW slabs under punching shear. The aggregate was found to affect LW concrete slabs’ punching strength significantly. Figure 3 compares the CSCT, ACI, and ECSCT, respectively. The ACI is conservative for slabs experiencing small rotation while unconservative for slabs undergoing large rotation. The CSCT is slightly unconservative compared to the experimental results. Based on the ECSCT, (V ) is calculated such that: 3  V 4 2  = fc (4) 15ψd bo d 1.0 + ddg   γc 3 where ddg = 16 + λdg min 60 f  , 1 ≤ 40 mm, λ = 2400 , and γc is the concrete density c

in kg/m3 .

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4 ECSCT for Punching Shear of FRP Reinforced Concrete [18] FRP reinforced concrete undergoes considerable strain and consequently more significant deformations and wider cracks. The mechanisms of punching shear transfer depend on the slab level of cracking, slenderness ratio, and flexure reinforcements. The main differences between punching shear behavior of RC and FRP-reinforced concrete slabs include but are not limited to: (1) FRP being brittle with no yield plateau or post ultimate behavior; (2) FRP have many types, including and not limited to carbon, glass, aramid, and basalt, while each one has different material properties; (3) FRP have relatively lower stiffness compared to steel, which varies depending on the FRP type; (4) FRPreinforced slabs depends on the concrete for ductility which is due to the brittle nature of the FRP reinforcement; (5) FRP-reinforced concrete slabs dissipate less energy after maximum strength, providing a minor warning before failure in the structure compared to that provided by steel RC slabs; and (6) the failure is associated with wider cracks and larger cracks deformations. Based on experimental testing of 189 FRP-reinforced concrete slabs under punching shear, the following form, which involves the effect of FRP young’s modulus (E), is proposed:   α1 0.39 V V 2  2  = = f ⇒ fc   c bo d bo d 1.0 + α2 EEs ψddgd 1.0 + 15 EEs ψddgd

(5)

where E is young’s modulus of FRP longitudinal reinforcements. Figure 4 shows the experimental observed failure strength and rotation and the failure criteria using the original CSCT and the ECSCT. From Fig. 4, the ECSCT fits the data better than the original CSCT. In addition, inspired by the CSCT for steel-reinforced slabs, the following form for rotation is proposed:     V 0.4 V α4 r s ff rs fy  ⇒ ψ = 0.28 ψ = α3 d E Vflex d Es Vflex 

(6)

where rs is the distance between the loading area centerline and the inflection point, ff is the flexure reinforcement design stress, which is taken at concrete crushing (i.e., concrete compressive strain value of 0.0035 mm/mm), E is the flexure reinforcement young’s modulus, V is the punching shear force acting on the area in N, and Vflex is the s , mR punching shear corresponding to the flexure capacity, which is taken as 2π mR rq r−r c ⎞ ⎛ ⎜ is the two-way shear for flexure failure in N, which is taken asd 2 ρff ⎝1 −

ρff 2fc



30 fc

1/

3

⎟ ⎠.

rq The distance between the centerline of the loading area and the loading point, and rc is the distance between the centerline and the edge of the loading area.

5 Failure Criteria for Punching Shear of Prestressed Concrete [19] The prestressed concrete slab is the best structural system in many buildings; however, very limited models exist for the punching shear behavior of these slabs, especially one

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that accounts for all effective parameters and can predict both strength and deformation. Therefore, an experimental database of 213 slabs tested under punching shear was compiled from the literature, emphasizing lightweight concrete. The ECSCT included the effect of prestressing in terms of the following mechanisms: (1) the in-plane compression stress due to prestressing force; (2) the bending moment due to the eccentricity of prestressing force; and (3) the vertical shear component of the prestressing force. Based on the original CSCT and the physical observations, the following form was proposed, where the shear strength is such that: ⎞ ⎛  α 1 2  fc + α3 λσ ⎠bo d + α4 V p + α5 λπ mp V =⎝  1.0 + α2 ψddgd ⎛ ⎞  0.75 2  ⇒V=⎝ fc + 0.38λσ ⎠bo d + Vp + 2λπ mp (7)  1.0 + 15 ψddgd The failure criteria for the original CSCT were plotted as shown in Fig. 5a. It was clear that the prestressing compression stress does affect the rotation as derived within the CSCT by Clement et al. (2014). Thus, the ECSCT proposed that rotation was modified using linear regression to reflect the reduction due to prestressing axial compression stresses, as shown in Fig. 5b, such that: ψ  = 1.5

 3/ 2 V σ rs fy − 120 d Es Vflex λEc

(8)

where rs is the distance between the loading area centerline and the inflection point, fy is the flexure reinforcement yield stress, Es is the flexure reinforcement young’s modulus, V is the punching shear force acting on the area in N, and Vflex is the punching shear corresponding to the flexure capacity in N.

6 Punching Shear of Elements with Membrane Tensile Forces [20] The CSCT was adapted and modified to include the effect of the in-plane tensile forces, where modified equilibrium equations and the load-rotation relationship must account for the presence of in-plane tensile forces. Figure 2 shows the influence of in-plane forces on the punching shear strength of slabs and the moment-curvature relationship reported by Muttoni and coworkers [20–22]. Based on a detailed structural analysis and physical observation of the experimental testing results, using a modified yield strength for the ECSCT in the case of combined punching shear and axial tension is proposed such that:   fs (9) f y  = fy 1 − fy where fs is the stress in the flexure reinforcements due to in-plane tensile forces; thus, the load-rotation relation is such that:  3 rs fy  αs V /2  (10) ψ = 1.5 d Es Vflex

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where αs are 1.15, 1.4, and 1.5 for middle, edge, and corner slabs, respectively. rs is the distance between the loading area centerline and the inflection point, fy is the flexure reinforcement yield stress, Es is the flexure reinforcement young’s modulus, V is the punching shear force acting on the area in N, and Vflex is the punching shear corresponding to the flexure capacity in N. Figure 6(a–c) show a comparison of the experimentally observed failure load versus rotation of slabs under punching shear only or punching shear combined with axial tension as well as that using original CSCT, CSCT for prestressed slabs and ECSCT, respectively. It is proposed that punching shear strength be calculated such that:  0.75 V 2 fc =  (11)  bo d αs 1.0 + 15 ψddgd

ACI

Fig. 3. Failure criteria for lightweight concrete.

Fig. 4. Failure criteria for FRP-reinforced concrete.

7 Model Validation The punching shear strength was calculated using the ECSCT and compared with that computed using the original CSCT, ACI, EC2, JSCE, CSA, MC design codes [21–24].

Extended Critical Shear Crack Theory

Fig. 5. Failure criteria for prestressed concrete.

CSCT-I

Fig. 6. Failure criteria for punching with tension.

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Table 1 shows the average and coefficient of variation for the ECSCT compared to other design codes. The ECSCT predicted the strength in a much precise and consistent manner compered to other design codes. For further details, see research studies [17–20]. Table 1. The average and coefficient of variation of the safety factor using various methods. Type

Number Extended ACI CSCT

EC2

JSCE

CSA

MC

Lightweight concrete [17]

130

1.01 (36%)

1.58 1.46 (37%) (25%)

FRP-reinforced 190 concrete [18]

0.98 (39%)

2.20 (39)

Prestressed concrete [19]

213

1.01 (54%)

1.27 1.81 (53%) (41%)

Not Not 1.31 available available (65%)

With axial tension [20]

52

1.05 (29%)

1.25 1.47 (14%) (25%)

Not Not Not 0.85 available available available (27%)

Not Not 1.44 available available (46%)

Not 2.87 available (36%)

1.20 (37%)

Original CSCT 1.23 (39%)

Not Not available available 1.5 (56%)

8 Concluding Remarks A brief outline of the extension of and validation for the critical shear crack theory was presented, which included punching shear strength of lightweight concrete, FRPreinforced concrete, and prestressed concrete, as well as punching shear combined with tension.

References 1. ACI 213R-03: Guide for structural lightweight-aggregate concrete. ACI Committee 213 2014 American Concrete Institute Farmington Hills, Michigan, USA 2. Deifalla, A.: Torsion design of lightweight concrete beams without or with fibres: a comparative study and a refined cracking torque formula. Structures 28(2020), 786–802 (2020). https://doi.org/10.1016/j.istruc.2020.09.004 3. Deifalla, A., Awad, A., Seleem, H., AbdElrahman, A.: Investigating the behavior of lightweight foamed concrete T-beams under torsion, shear, and flexure. Eng. Struct. 219, 110741 (2020). https://doi.org/10.1016/j.engstruct.2020.110741 4. Deifalla, A., Awad, A., Seleem, H., AbdElrahman, A.: Experimental and numerical investigation of the behavior of LWFC L-girders under combined torsion. Structures 26, 362–377 (2020). https://doi.org/10.1016/j.istruc.2020.03.070 5. Deifalla, A.: Design of lightweight concrete slabs under two-way shear without shear reinforcements: a comparative study and a new model. Eng. Struct. 222(2020), 111076 (2020). https://doi.org/10.1016/j.engstruct.2020.111076 6. Deifalla A.: Torsional behavior of rectangular and flanged concrete beams with FRP. J. Struct. Eng. ASCE 141(12) (2015). https://doi.org/10.1061/(ASCE)ST.1943-541X.0001322. In this issue

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7. Deifalla, A., Hamed, M., Saleh, A., Ali, T.: Exploring GFRP bars as reinforcement for rectangular and L-shaped beams subjected to significant torsion: an experimental study. Eng. Struct. 59, 776–786 (2014) 8. Deifalla, A., Khali, M.S., Abdelrahman, A.: Simplified model for the torsional strength of concrete beams with GFRP stirrups. Compos. Construct. ACSE 19(1), 04014032 (2015). https://doi.org/10.1061/(ASCE)CC.1943-5614.0000498 9. Ebid, A., Deifalla, A.: Prediction of shear strength of FRP reinforced beams with and without stirrups using (GP) technique. Ain Shams Eng. J. (2021). https://doi.org/10.1016/j.asej.2021. 02.006 10. El-Meligy, O., El-Nemr, A.M., Deifalla, A.: Re-evaluating the modified shear provision of CAN/CSA S806-12 for concrete beams reinforced with FRP Stirrups. AEI (2017). https:// doi.org/10.1061/9780784480502.027 11. Hassan, M.M., Deifalla, A.: Evaluating the new CAN/CSA-S806-12 torsion provisions for concrete beams with FRP reinforcements. Mater. Struct. 49(7), 2715–2729 (2015). https:// doi.org/10.1617/s11527-015-0680-9 12. Deifalla, A.: Assessment of one-way shear design of RC elements subjected to axial tension. Case Stud. Constr. Mater. 2021 (2021). https://doi.org/10.1016/j.cscm.2021.e00620 13. Deifalla, A.: A comparative study and a simplified formula for punching shear design of concrete slabs with or without membrane tensile forces. Structures 33, 1936–1953 (2021) 14. Muttoni, A.: Punching shear strength of reinforced concrete slabs without shear reinforcement. ACI Struct. J. 105(4), 440–450 (2008). https://doi.org/10.14359/19858 15. Muttoni, A., Fernández Ruiz, M., Simões, J.T.: The theoretical principles of the critical shear crack theory for punching shear failures and derivation of consistent closed-form design expressions. Struct. Concr. 19(1), 174–190 (2018) 16. Matthews, S., Bigaj-van Vliet, A., Walraven, J., Mancini, G., Dieteren, G.: FIB model code 2020: towards a general code for both new and existing concrete structures. Struct. Concr. 2018(19), 969–979 (2020). https://doi.org/10.1002/suco.201700198 17. Deifalla, A.: Strength and ductility of lightweight reinforced concrete slabs under punching shear. Structures 27(2020), 2329–2345 (2020). https://doi.org/10.1016/j.istruc.2020.08.002 18. Deifalla, A.: Punching shear strength and deformation for FRP-reinforced concrete slabs without shear reinforcements. Case Stud. Constr. Mater. 16, e00925 (2022). https://doi.org/ 10.1016/j.cscm.2022.e00925 19. Deifalla, A.: A mechanical model for concrete slabs subjected to combined punching shear and in-plane tensile forces. Eng. Struct. 231, 111787 (2021) 20. Deifalla, A.: A strength and deformation model for prestressed lightweight concrete slabs under two-way shear. Adv. Struct. Eng. 24, 1–12 (2021). https://doi.org/10.1177/136943322 11020408 21. ACI-318-19: ACI Committee 318. Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary on Building Code Requirements (ACI 318-19). Farmington Hills (MI): American Concrete Institute (2019) 22. EC2: EN 1992-1-1:2004: Eurocode 2: Design of concrete structures – Part 1-1: General rules and rules for buildings. Incl. Corrigendum 1: EN 1992-1-1:2004/AC:2008, incl. Corrigendum 2: EN 1992-1-1:2004/AC:2010, incl. Amendment 1: EN 1992-1-1:2004/A1:2014 (2004) 23. Fib, M.C.: Fédération internationale du béton. Fib Model Code for Concrete Structures 2010. Lausanne; 2013 (2010) 24. JSCE: Standard Specifications for Concrete Structures-2007: Design. Japanese Society of Civil Engineering, No. 15 (2007). ISBN 978-4-8106-0752-0759

Evaluation on Deterioration and Blister Progression of Duplex Layers Between Al-5 Mg Thermal Sprayed Coating and Heavy-Duty Paint Coating H. Yang1(B) , S. Kainuma2 , M. Yang2 , and T. Asano3 1 Department of Civil Engineering, Kyushu University, Fukuoka, Fukuoka 819-0395, Japan

[email protected]

2 Department of Civil Engineering, Faculty of Engineering, Kyushu University, Fukuoka,

Fukuoka 819-0395, Japan 3 Bridge and Structural Engineering Division, West Nippon Expressway Co., Ltd., Osaka, Japan

Abstract. It is commonly duplex layers partially placed on a thermal sprayed coating when narrow parts are difficult to thermal spray. In a previous study, it was shown that when the duplex layer has a defect, thermal spray coating deteriorates faster than the single-layer coating. It is critical to evaluate and anticipate the occurrence and progression of duplex layer degradation and blistering in order to execute effective maintenance management for steel structures. In this investigation, specimens with duplex layers were exposed to the atmosphere and corrosion environment was monitored using ACM-type corrosion sensors and temperaturehumidity sensors. Based on these findings, we proposed a method to evaluate the deterioration and blister progression of duplex layer between Al-5Mg thermal sprayed coating and heavy-duty paint coating in an environment without rain-washing action of adhered sea salt. Keywords: Atmospheric exposure test · Al-5Mg thermal sprayed coating · Heavy-duty paint coating · Duplex layers · ACM-type corrosion sensors

1 Introduction Recently, in Japan, Al-5Mg alloy thermal sprayed coatings have been applied to improve the anti-corrosion performance and durability of highly corrosive areas such girder ends [1, 2]. And it was partly covered by heavy-duty paint coating when it is hard to apply the thermal spray coating on the bridge components. These thermal spray duplex coating systems are supposed to provide a long lifetime, and also will be both cost-effective and environment friendly. However, in the previous study [3], these duplex layers showed low durability than thermal sprayed coating and severe film blister has occurred when defects were introduced into specimens. This propensity was shown to be stronger in environments without rain-washing action of adhered sea salt than in environments with rain-washing action of adhered sea salt. Until now, the deterioration characteristics of © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 362–368, 2023. https://doi.org/10.1007/978-981-19-4293-8_38

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the duplex layers between Al-5Mg alloy thermal sprayed coating and heavy-duty paint coating have not been investigated in detail. In a previous study, the anti-corrosion characteristics of Al-5Mg alloy thermal sprayed coating have been investigated by an atmospheric exposure test [4]. In this study, to evaluate the deterioration and blister progression of duplex layer between Al5Mg thermal sprayed coating and heavy-duty paint coating in an environment without rain-washing action of adhered sea salt, ACM-type corrosion sensors and temperaturehumidity sensors were used to estimate the atmospheric environment using the wetting time, chloride content, and daily average electricity content. After the exposure test, the surface observation and coating deterioration of the tested specimens were evaluated. Herein, to determine the deterioration degree at various portions of specimens, the coating blister area was scanned using a 3D scanner.

2 Experimental Procedure 2.1 Test Specimen This test used a 150 × 70 × 6 mm carbon steel plate, per JIS G3106 SM490A. To prevent the film at the steel sheet‘s edge from degrading quicker than the film elsewhere in the test, a 2R chamfering method was employed to provide acceptable film thickness. The steel plate was blasted using a steel grid (#70) as the grinding media according to Sa3.0 in ISO 8501-1. On the specimen are three sections: thermal sprayed coating, duplex layer and paint coating. The two types of specimens are OVL (no sealing treatment) and OVL-S (sealing treatment). There are two types of coating defects: linear (LN) and ribbon (RB). The exposed steel substrate widths for LN and RB flaws are 0.2 mm and 12 mm, respectively, to compare the sacrificial anodic effect and thermal sprayed coating throwing power. The Rc-I series coating used for repainting was applied to specimens in accordance with the Japan Road Association’s specification for highway bridges (Fig. 1). Moreover, the Al-5Mg thermal sprayed coating was applied for all specimens, using a plasma arc spraying (air pressure: 0.40 N/mm2 , plasma gas pressure: 0.30 N/mm2 , current: 60 A), and the target thickness was set between 100–150 μm. The mean coat ing thickness of the duplex layer, and the single layer of Al-5Mg thermal sprayed coating and Rc-I coating were measured by an electromagnetic induction film thickness meter (measurement accuracy: 1 μm; resolution: 1 μm (0–999 μm), 10 μm (1–8 mm)). The mean value was calculated based on 11 measurements, where the mean thickness of duplex layer, Al-5Mg thermal sprayed coating and Rc-I coating were 584 μm, 170 μm and 417 μm, respectively. 2.2 Atmospheric Exposure Test The corrosion progress of the different structural details may differ significantly due to the effects of the localized environment, such as airborne salinity, rainfall, and dew. In this study, to compare the difference in the localized environment, the atmospheric exposure test was conducted at two field sites for three years. Information of two fields, as shown in the following: 1) Momochi, Fukuoka (hereafter called Momochi), the exposure

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field is set under the viaduct of Fukuoka Kitakyushu Highway No. 1, located about 70 m distance from the Hakata Bay coastline, (Lat.33°35 N, Long.130°21 E), 2016/09– 2019/08. 2) Kyoda, Okinawa (hereafter called Kyoda.), the exposure field is under the viaduct of Okinawa expressway, which is located about 30 m from the western coastline of Okinawa island, (Lat.33°35 N, Long. 130°12 E), 2016/10–2019/09. Table 1 shows the annual average values of the temperature T (°C), relative humidity RH (%), and the amount of airborne salt (JIS Z 2382 (dry gauze method)) ω (mdd) and the daily average electricity q (C/day) measured by ACM sensor in the previous study [5]. Rather than relying on simple measurements of T, RH, and ω, the corrosive environment in each specimen was monitored every 10 min using an ACM sensor (JIS Z 2384, output: 0.1 nA–1 mA) and a temperature-humidity sensor. The daily average electricity from the ACM sensor output can be used to quantify the association between air exposure and micro corrosion at the site level of the real structure. 2.3 Deterioration Evaluation Method After the exposure test, test specimens were recovered, and the surface of specimen is pre-washed with distilled water immediately to remove salt and dust adhering to the surface. Then, an ultrasonic cleaning (frequency: 43 kHz, water temperature: 60 °C) was performed on specimens for 30 s to remove residual salt, ensuring that salt and dust did not interfere with surface observation and measurement of the blistering area. The blistering properties of the specimen were determined by a 3D scanner (measuring pitch: 0.2 mm, resolution: 0.01 mm).

Fig. 1. Dimensions of specimens and coating film conditions

The oxidative blistering area was examined to quantify duplex layer deterioration. A plane representing the average value of the healthy film was first computed using the

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Table 1. The atmospheric environments of two exposure fields Atmospheric Exposure Field

Temperature T (°C)

Relative Humidity RH (%)

Airborne Salt ω (mdd)

Daily Average electricity q (C/day)

Momochi, Fukuoka, Japan

18.0

74.0

0.52

0.049

Kyoda, Okinawa, 23.0 Japan

83.0

0.46

0.193

measured values of the duplex layer section obtained before the test. Then the standard deviation of the measured data was calculated. The film’s blistering area was calculated using the standard deviation. The average surface was then computed using the duplex layer‘s un-blistering area after the test. The difference between this average surface and the complete area of the duplex layer film after the test identified the location of the blistering. The blistered area was defined as the circumference of the blistered area. This study assessed duplex layer deterioration. The exposed steel substrate was not included in the evaluation area since it was not evaluated for blistering.

3 Test Result 3.1 Surface Observation Figure 2 shows the appearance of specimens collected after exposure of three years. For the specimens with 0.2 mm defect in Fig. 2, white corrosion products were adhered to the exposed steel surface of the duplex layer coating on the skyward side for both OVL and OVL-S specimens in Momochi and Kyoda. In addition, white corrosion products were adhered and the blistering of thermal sprayed coating was observed around the defect area, which suggests that the oxides of thermal sprayed coating expanded in volume due to the deterioration of the thermal sprayed coating under the coating in the duplex layer area. For test specimens with a 12 mm defect, because there is no accumulation of sea salt, there are almost no white corrosion products on the groundward side. And because the electrolyte from the flying sea salt accumulates towards the edge of the defect area, the sacrificial anode activity of the thermal sprayed coating is more likely to occur on the skyward side than on the groundward side. As a result, it can be concluded that the thermal sprayed coating in the duplex layer area degrades and expands solely on the skyward side, where sea salt tends to concentrate.

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3.2 Blister Condition of Duplex Layers The blister conditions of each test specimen are shown in Fig. 3. Since the groundward side of the specimens in Momochi and Kyoda did not swell much even after three years of exposure, we mainly focus on the blistering of the skyward side of each specimen. Regardless of the exposure filed, the skyward side blistered due to the sacrificial anode action of the thermal sprayed coating.

M o m o c h i

K y o d a OVL OVL-S (a) 0.2 mm defect

OVL OVL-S (b) 12 mm defect

Fig. 2. Photos of OVL, OVL−S specimens tested after exposure of three years

■-2.1㹼-1.8 ■-1.8㹼–1.5 ■-1.5㹼–1.2 ■-1.2㹼–0.9 ■-0.9㹼-0.6 ■-0.6㹼-0.3 ■-0.3㹼 0.0 ■ 0.0㹼 (mm)

(a) Momochi

(b) Kyoda

Fig. 3. Blister conditions of OVL, OVL-S specimens on the skyward side

For 0.2 mm defects, Kyoda’s duplex layer coating blistered more than Momochi’s. Diverse exposure settings may be altering the duplex layer coating degrading mechanism. In Momochi, the duplex layer coating is higher than the bottom. Water and salt enter the thermal sprayed coating from the upper end, making deterioration simpler than in the bottom end. In Kyoda, all test specimens with a 12 mm defect had significant blistering on the other side, regardless of exposure field or sealing technique. Inferred sacrificial anode activity of thermal sprayed coating and duplex layer coating portions can be seen

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in the skyward side paint coating area. The thermal sprayed coating of the duplex layer coating component is susceptible to early disintegration when airborne sea salt attaches and accumulates, and the surface of the specimen is moist from rain or condensation. Figure 4 shows that the blistering of the duplex layer is more noticeable in Kyoda, where q is larger than in Momochi. The results suggest that Kyoda has larger blistering area than Momochi. The blistering course of the OVL and OVL-S specimens is nearly same regardless of the sealing treatment. In Momochi, some specimens have unequal blistering with 0.2 mm defects and a small blistering area, due to the close proximity to the shore and the sea breeze at Momochi, the sea salt did not stick evenly to the specimens. In both Momochi and Kyoda, the blistering progress is independent of the defect type, and the trend is practically the same for the 0.2 mm defect test specimen and the 12 mm defect test specimen. Thus, the blistering of duplex layer coating is no longer associated with the width of the defect, and is assumed to progress in the specimen’s width direction.

(a) Momochi

(b) Kyoda

Fig. 4. Variations in the blister area according to exposed period in the duplex layer region

4 Conclusions In this study, the main results obtained in this study are shown below. 1) In an environment where there is no rain-washing effect of flying sea salt, degradation of the thermal sprayed coating in the duplex layer region occurs only on the skyward side where sea salt tends to accumulate. 2) When the surface of the specimen gets wet during rainfall or condensation due to the accumulation of flying sea salt, the thermal sprayed coating of the duplex layer region tends to deteriorate at an early stage due to the sacrificial anode effect on the exposed steel substrate.

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3) The progress of degradation and blistering of the duplex layer coating is highly correlated with the daily average electricity calculated from the ACM type corrosion sensor output, regardless of the presence or absence of sealing treatment and the width of the steel substrate’s defect.

References 1. Kainuma, S., Guo, X., Kobayashi, J., Muto, K., Miyata, H.: Fundamental study on anticorrosion characteristics of al-5mg alloy thermal spraying coatings in highly corrosive environment with NaCl. J. Jpn. Soc. Civ. Eng. Ser. A1 (SE/EE) 72(3), 440–452 (2016) 2. Muto, K., Kainuma, S., Du, J., Liu, S., Yang, M., Miyata, H.: Corrosion resistance and anticorrosion performance of overlapping layers between Al-5Mg thermal sprayed coating and heavy duty paint coating with a cross-cut defect. J. Jpn. Soc. Civ. Eng. Ser. A1 (SE/EE) 75(3), 280–292 (2019) 3. Kainuma, S., Fujimoto, H., Du, J., Yang, M., Muto, K., Miyata, H.: Fundamental study on corrosion resistance and anti-corrosion of interface between Al-5Mg thermal sprayed coating and heavy duty paint coating. J. Jpn. Soc. Civ. Eng. Ser. A1 (SE/EE) 73(2), 496–511 (2017) 4. Kainuma, S., Yang, H., Yang, M., Muto, K., Miyata, H.: Corrosion resistance and anti-corrosion characteristics of interface between Al-5Mg thermal sprayed coating and heavy duty paint coating in airborne sea salt environment. J. Jpn. Soc. Civ. Eng. Ser. A1 (SE/EE) 77(1), 180–198 (2021) 5. Kainuma, S., Yamamoto, Y.: Fe/Ag ACM practical method for estimating time-dependent corrosion depth of uncoated carbon steel plate under atmospheric environment using Fe/Ag galvanic couple ACM-type corrosion sensor. Zairyo-to-Kankyo 63(2), 50–57 (2014)

Architectural Design and Theory

From the Interval in Architecture: (In)visibilities – The Case of Smithsons’ “Project-Theory” João Cepeda(B) FAUP – Faculty of Architecture of the University of Porto, Porto, Portugal [email protected]

Abstract. The Japanese way of building and inhabiting – deeply rooted in a secular tradition, but manifesting innovative architectural and engineering solutions – has decisively influenced many Western authors. Regarding Western context, “Japan’ness” was appropriated through different manners – however, surprisingly, a subliminal (yet essential) Japanese cultural feature seems to have been overlooked – at least, as far as the analysis and research on its possible reverberations on Western design is concerned. As a Nipponese principle that only exists in Japan, its term is untranslatable. Here named (and interpreted) as interval, this notion embodies a concept that, although hidden or intuited, is transversal to all Japanese realm. Based on these indications, and grasping some traces that lie in some modern Western authors whose life and work, somehow, underlyingly reveal a true fascination with Japanese aesthetics, this paper focuses on this (little-known to the West) original conception, to finally rehearse an interpretation of the potentiating effects it may have had in Western building context – by driving attention to the example of one of the twentieth-century most prominent European architects – the Smithsons –, and taking on a critical and different review of their theoretical and practical work, and an in-depth examination of their personal archives. Keywords: Architectural theory · Architectural design · Interval · Japan · Smithsons

1 Introduction – Essay of an Interval Theory Japanese exotic ambiences and iconic scenarios summons Westerns to an intuitive recognition of a kind of pre-existing reality – like a culture that seems to exist before time itself. After all, as Bruno Taut brilliantly warned in 1958, in the traditional architecture of the land of the rising sun, “(…) our eyes think” [1]. 1.1 Traces of an (In)visible Depth – an Aesthetics Beyond Western Dialectical Abstraction The Western ontological “architecture” designed by Aristotle suggested only two hypotheses – to be or not to be. These, anchored in the foundations of ‘identity’ and © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 371–382, 2023. https://doi.org/10.1007/978-981-19-4293-8_39

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‘non-contradiction’, neglected the third alternative that, in-between the two, lies latent in the middle, ‘neither being, nor not being’ – and which the philosopher called ‘the third excluded’ [2]. Thus, Aristotelian logic entails in itself the impossibility of a theorem neither being true, nor false – no proposition could be situated in this intermediate space. As such, what could be ‘one and the other’, or ‘neither one, nor the other’, would be (forever) outside of the Western dualistic rational normative system established for the evolution of scientific knowledge. The Japanese ideogram ‘間’ represents an untranslatable conception, whose word and meaning only exist in Japan. In the Japan of traditions that coexist harmoniously, this is a concept that, like others, inhabits the very particular common sense of the Japanese: although everyone knows it and clearly senses it, they are still not capable to express it precisely through words. As a conceptual precept applied not only to architecture, but (apparently) transversal to all areas of Japanese culture, this notion contains this boundary space of in-between existence, this (im)precise intermediary universe, ignored – or forgotten – by the Western traditional approach, commonly based upon a (merely) oppositional dualistic abstraction. 1.2 (Re)Defining the Void: The Interval – A Key Element in Space Design and Organization Although some Western authors have already given some thought around this seemingly (un)defined principle – as the articles written by Nitschke (1966) [3] and Pilgrim (1995) [4] stand as the most notorious examples –, in reality, there are (still) no apparent Western in-depth scientifical studies that approach this Nipponese concept and way of thinking. As such, already in 1976, the well-known and awarded Japanese architect Arata Isozaki prepared and showcased an exhibition on the theme in Paris, aiming to enlighten this enigmatic theme to the Western understanding. However, records from the time unanimously highlighted an apparent “fiasco”, reporting the sensation of the visitors in “(…) venturing into an absolutely secret and impenetrable universe” [5], as Augustin Berque pointed out. From then on, several terms have been suggested as possible translations: ‘gap’, ‘distance’, ‘pause’, ‘intermediate space’, or even, simply, ‘space’ – among some other different vocables. From this vast “ensemble”, this investigation elected the word interval to, from here on, better name this concept – but, above all, to try to interpret and/or represent it. Exploring this (originally Japanese) principle of interval invites us then, precisely, to scrutinize that remaining in-between space, of the simultaneous and contradictory, occupied by what can simultaneously be ‘one and the other’, or ‘neither one, nor the other’. This (intangible?) character of possibility, potentiality and ambivalence latent in the interval, seems to give rise to a particular aesthetic that emphasizes the importance, for example, of the white spaces not drawn on a paper (see Fig. 1), the silences in a musical composition, the pauses in a theatrical piece – but also of spaces that are located in the interstice, in the intermediation of the full and the empty, the internal and the external, the inside and the outside, the open and the closed, or the natural and the built. It is

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in this universe that this interval invites us to embark. In the atmospheres that, as Taut previously suggested, the eyes look for, but (apparently) do not see. According to some Japanese main cultural and aesthetical compendiums [6], the interval may be apprehended through a keen awareness of both space and place. However, this perception should not result simply from their physical and three-dimensional dimension, but rather – and mainly – through a simultaneously empirical, intuitive, sensory, and temporal understanding of form (‘what exists’), and non-form (which should not be understood as ‘what does not exist’, but rather as ‘what exists beyond the form’). It is not something resulting from addition – the interest of its focus falls precisely on the reverse, on a kind of void or negative space. It is precisely that space that ‘is not there’ that, perceived as an interval, gives shape to ‘what is’ – the negative and intuitive space that ‘is not there’, ends up emerging as the main and principal actor. As such, the theoretical principle of the interval does not suggest a celebration of things, objects, or any architectural elements in themselves – but of the space between them. Thus, the spirit of this notion fundamentally represents a concept of ‘absence’ – contrary to the Western typical thinking, which privileges the physical and tangible. In the famous 1906’s classic “The Book of Tea”, Kakuzo Okakura declared that “(…) true beauty can only be discovered by one who mentally completes the incomplete, and the emptiness” [7]. Later, in the same century, and in the West, a European philosopher seems to have sensed a similar, or at least parallel, direction. In 1943’s “Being and Nothingness”, Sartre suggested that, if between ‘being’ and ‘non-being’ there is a space of nothingness, then, this nothingness does not represent total emptiness, or plain ‘nonexistence’ – but rather an eloquent and promising space, full of presence and possibility: “(…) That nothingness carries being in its heart” [8]. Therefore, as a possibility, the interval may be physically associated with this emptiness – however, its meaning diverges diametrically from the (more) common Western notion, whose connotation is simply nothingness. Conceptually, this emptiness may be seen rather as an absence of something that does not reveal itself, but whose “presence” is manifested by its potentiality. An empty space (physical, but mental and intuitive) which, in this way, can contain everything, and, thus, boosts, fosters and generates the possibility and availability for the new – and not the absolute ‘non-existence’.

Fig. 1. The interval in the six-fold screens painting “Pine Trees” (c. 1595), by Tohaku Hasegawa. © Japan’s National Treasure – Tokyo National Museum.

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2 From the Interval in Architecture – The Case of Smithsons’ “Project-Theory” Sharing the well-known fascination for Japanese architectural and artistic imaginary which influenced many of the Western architects of modernity (such as Wright, Raymond, Neutra, Schindler, Korsmo, Asplund, Sverre Fehn, Aalto or Corbusier, among many others), this paper’s objective is not – as referred before – to state or search for any more different cases of authors who were directly “influenced” by Nipponese architecture, or whose work may have been directly “influenced” by its aesthetics. The direct issue of this work is the interval – initially, searching to build a “theory” that rehearses and problematizes a thematization around and in search of the (in)definition of this original (and relatively unknown to the West) concept; and afterwards, from that theoretical framework, to inspect the potentiating effects that it can bring to Western reality, in architectural terms (as a practice). In order to do so, and for a number of different reasons, the decision to focus on the well-known English architects Alison and Peter Smithson arose as an (almost) obvious choice. If there were several criteria that, cumulatively, traced the choice of this couple, there was firstly one very specific primordial criterion: the hypothesis that these authors’ architectural approach seems to contain some design achievements that, in their own way, raise, translate or represent the interval theme. Secondly, there were other subsequent premises and parameters that seemed to further consolidate the adequacy and relevance of this pair to the researched theme: they both traveled to Japan; they both expressed a deep admiration and enchantment for the country, and specifically for its traditional culture and architecture, with which they had the important opportunity to confront and experience directly, “in loco”; they both registered – in some cases, with some abundance and detail – their impressions of these journeys together; and lastly, they both were examples of architects who wrote about their own work – a fact, also, of the upmost relevance, due to the obvious relationship between theory and practice, which is a key focal point of this paper’s investigation. 2.1 The Smithsons’ Trip(s) to Japan (1960–1975) Frequently, the Smithsons are directly associated with the creation of the so-called “New Brutalism”, a movement determined to theoretically revise the more international and dogmatic Modern Movement in architecture – one of the primary intentions of the wellknown “Team 10” group, of which they were also active and vigorous members. As a result of this, and of some of their projects and proposals, some influential authors (as Reyner Banham [9]) suggested a direct link between this movement and possible impacts from Japanese traditional architecture. In fact, although it is still to be proven in what ways exactly this inspiration could be fertile to the movement, the Smithsons occasionally stated, whether orally or in a written manner, their profound interest in Japan and its culture – “(…) We always had books and closely followed Japanese traditional architecture. Then we had the chance to visit (…)” [10].

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As CIAM (“Congrès Internationaux d’Architecture Moderne”) members, the Smithsons duo received an invitation to the international meeting “WoDeCo – World-DesignConference”, to be held in Tokyo in 1960. Consequently, as far as this research was able to grasp so far, this major global seminar that intended to focus on some of the highest cutting-edge design methodologies of that time, marked the very first journey of Alison and Peter Smithson to Japan – a destiny that, logically, was very dear to them, as they were aiming to visit the country for quite some time, planning and expecting for when the opportunity might arise, in order to pursue their Nipponese strong passion (see Fig. 2). In that first expedition, not only they had the chance to attend the conference being one of several relevant guests, as they also fulfilled their desire to directly explore the exotic Japanese culture. Apart from Tokyo, where they accommodated at Frank Lloyd Wright’s former Imperial Hotel, the Smithsons detoured through Osaka, Kyoto, Nikko and Nara, visiting several historic temples and palaces – like the Katsura Imperial Villa, Ryoan-ji, Tofukuji or Chion-in (among others), some of Maekawa’s and Tange’s brutalist works, but also many gardens and natural parks. The numerous photographs found in their personal archives clearly suggest the true enthusiasm of Smithsons’ approach to those places. Following a career cycle traced back to the beginning of the 1950’s, the Smithsons frequently travelled around the world, having then, in 1960, (finally) reached the distant – and beloved – Japan, country that, from then on, they continued to visit. Although it is still to be exactly determined how many times they visited, the fact is that the Smithsons had a great contact with Japan during the period ranging from 1960 until 1975, and it is known that they also visited, in addition to the already above-mentioned places, Hiroshima, Kanazawa, Kawagoe, and Kagawa’s prefecture. These trips allowed Alison and Peter Smithson the time and occasion to experiment the ancient Japanese culture and architecture, and to further deepen their indirect knowledge of Nipponese philosophy – constituting, thus, a unique landmark in their architectural thinking onwards.

Fig. 2. Alison Smithson in Kyoto, Japan, in 1960. © The Alison and Peter Smithson Archive – Harvard University Graduate School of Design

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2.2 The Smithsons’ Personal Library Even taking into account the apparent and deliberate Smithsons’ interest in Japan, their trips to the country, and some traces of their theoretical and architectural works, it’s still surprising to inspect their personal private collection and past architectural office’s possessions. Scrutinizing the Smithsons’ former office’s library, but also their private personal collection, they include several original editions of some of the most relevant theoretical compendiums of Japanese architectural culture. Including more than 30 authentic copies, apparently the Smithsons drew their interest not only for Japanese architecture presented by some Japanese referential authors, but also by Western ones. Among others, some Nipponese essential references presenting Japanese architectural foundations stand out: Hideto Kishida’s “Japanese Architecture” (1948) [11], Tetsuro Yoshida’s “Japanische Architektur” (1952) [12] and “Japanese House and Garden” (1955) [13], and Jiro Harada’s “Lesson of Japanese Architecture” (1954) [14] and “Japanese Gardens” (1956) [15] – having the Smithsons acquired some of these volumes even before visiting Japan. Moreover, it is also relevant to pinpoint Josiah Conder’s “Domestic Architecture in Japan” (1886) [16] and “Further Notes on Japanese Architecture” (1886) [17], Bruno Taut’s “Fundamentals of Japanese Architecture” (1936) [18] and “Houses and People of Japan” (1958) [1], Norman Carver Jr.’s “Form and Space of Japanese Architecture” (1955) [19], and Heinrich Engel’s “The Japanese House: a Tradition for Contemporary Architecture” (1964) [20] – all constituting cornerstone Occidental works disclosing Japan’s ancient architecture. Furthermore, the Smithsons’ library suggests an even more attentive regard, when we verify that, approximately between 1955 until 1975, the duo subscribed the Japanese architectural magazine “JA – The Japan Architect” [21] – the most important Japanese periodic about Japan’s architectural realm, founded in 1956. This magazine was organized emphasising the most relevant architectural developments originating in Japan, showcasing contemporary Japanese architecture from that period, but also taking on Japanese brutalism, the metabolists, and traditional Japanese architecture. Also collecting other special thematic editions, the Smithsons possessed an extraordinary collection of over 115 issues of this periodical, comprising projects of authors like Kenzo Tange, Kunio Maekawa, Junzo Sakakura and Kiyonori Kikutake, among many others. Receiving these issues directly from Japan on a constant monthly basis, shows Alison and Peter Smithsons’s real attentiveness in following the Japanese scene. Additionally, the couple also possessed other editions of some other (bygone) 1960’s Japanese architectural periodics, like “Kokusai-Kentiku” [22] or “Kenchiku-Bunka” [23]. Finally, apart from all of these 1930’s/1950’s/1960’s/1970’s keystone “oeuvres”, the Smithsons also collected other noteworthy Japanese publications, ranging from diverse cultural and societal books, to other artistic and aesthetics compilations – from which the (already mentioned) Okakura’s seminal “treatise” “The Book of Tea” (1906) [7] stands out.

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2.3 From Smithsons’ Theoretical Approach – From “The Charged Void” to “The Space Between” Before Alison and Peter Smithson’s death, they both prepared a series of last written works, which they thought of as being, rather than a monography of their work, a synthesis of the whole of their thinking and activity as architects. However, Alison and Peter Smithson died in 1993 and 2003, respectively, having left these last books compiled but unfinished – and, of course, unpublished. Nevertheless, it is particularly interesting to note the titles that they chose to name and designate their ultimate writings, which were then posthumously published – “The Charged Void” (2005) [24], and “The Space Between” (2017) [25]. In fact, in these last written works, the Smithsons state that, embedded in Vitruvius’s, Alberti’s and Palladio’s antique tradition, their writings are directed to future architects, and to their mental building design approach, asserting that “(…) the most mysterious, the most charged of architectural forms are those who capture the empty air” [25]. Moreover, they affirm that they observed their architectural thinking evolving throughout time, originally more concerned with themes like green spaces, mobility and connectiveness (among others), to end up approaching primarily other subjects they considered more complex, and ultimately, more accurately representative of their work – which they named, among others, ‘density’, ‘measure’ and ‘interval’. Furthermore, the way the Smithsons chose to take on so many different topics in these books – approaching, for example, matters like their own works, Mies van der Rohe, the Greeks, the Eames couple, the pavilion-scheme typology, the field barns’ structure, Sigurd Lewerentz, Le Corbusier, and several others –, is left without explanation. The reason(s) how and why all of these are put in relation – in a practically unmediated way, or not fully directly interrelated –, resulting in a kind of confrontation between apparently different (or even distant) ideas and concepts, ends up generating huge curiosity and, in certain cases, some enigma or mystery. Here, the “space between” the tackled themes seems to intentionally shape a sort of space which is left open to speculation and interpretation – like an interval with an apparent and illusory absent meaning, yet (and therefore) full of possibility. Finally, and however, Alison and Peter Smithson never come to fully or clearly express their own personal meaning of interval, or even of expressions like “charged void” and “space between” – prominent and standout terminologies that, after all, end up titling these books. Nevertheless, the fact is that, along all of these writings, often referring and alluding, in a way, to an intermediate space, and an emptiness or a vacuity which can be circumscribed, but which is difficult to define, seems to be particularly suggestive for this paper’s topic interpretation – and even more so, if we perceive the numerous references to Japan in diverse thematic texts, or the theoretic and conjectural philosophies behind some of their designs and projects’ descriptions (as we’ll see in the next final subchapter). “(…) The space between (…) is a quality (…) we can feel and act upon, but cannot necessarily describe (…)” [25]. “(…) The charged void has special presence, more awesome than object presence (…)” [26].

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“(…) In Japan, the (…) void seems (…) unique – (…) the buildings are deliberately arranged to modulate the spaces between – the outside space between becoming as recognizably spatially organized, and part of the space inside the buildings; (…) the space is always flowing, always in-between” [25]. 2.4 From Smithsons’ Practical (Architectural) Approach – Objects in a Void As mentioned before, Alison and Peter Smithsons’ architectural approach seems to comprise some works or projects that consubstantiate – in their practice – what they postulated throughout their career – in their theory. This premise gains consistency when a part of their architectural achievements (that is, project practices) is examined through the spectrum of the hypothesis that, in their own way, they appear to raise, interpret, represent, or even (intuitively) translate the interval theme and problematics – or in whose main characteristics or qualities this question emerges in a more evident way. Beholding, for instance, their project for the Wayland Young Pavilion in Bayswater (1959–1982), this is a perfect example of how the Smithsons reconceptualize a housing program with spaces completely uncluttered and empty, polyvalent and open to appropriation – almost asking the occupants how they would like to use the space (feature which is also legible in their first highly celebrated project, the Hunstanton Secondary Modern School [1949–1954]). Furthermore, the boundary between interior and exterior is intentionally blurred with long wide glass windows, producing an environment where one feels like in an intermediate “halfway” space, in-between inside and outside (see Fig. 3). Completing the building extension, and “mediating” these “available” spaces, connecting all the rooms, a rear corridor that is not completely sealed to the exterior, reinforces, thus, this blurred in-between structured ambiance.

Fig. 3. The Wayland Young Pavilion in Bayswater, by Alison and Peter Smithson, in 1962. © The Alison and Peter Smithson Archive – Harvard University Graduate School of Design

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Considering, in turn, their renowned project for the Upper Lawn ‘Solar’ Pavilion in Fonthill (1959–1982), it is especially striking to verify some excerpts of the Smithsons’ project description. In a kind of (genuine) written “declaration of interests”, the architects announce that “(…) the inhabitants are expected to move between inside and outside” [25], and that their design was intended to “(…) call for an emptiness” [25], as its spaces should “(…) be used in a number of different ways, and (…) accept a collection of different usages (…).” [25] “(…) We want its architecture to do this, that, and even more beyond – it has to have multiple uses” [25]. As a matter of fact, the pavilion’s design urges its occupants to constantly move – or live – in the in-between spaces – as if the (Japanese) impermanency and possibility of use of those empty areas would more greatly enhance its residents’ quality of life (see Fig. 4).

Fig. 4. The Upper Lawn ‘Solar’ Pavilion in Fonthill, by Alison and Peter Smithson, in 1978. © The Alison and Peter Smithson Archive – Harvard University Graduate School of Design

Bearing in mind the Economist building in London (1959–1964), another example of one of their most celebrated architectural works, one can additionally find the extreme importance trusted to one of the Smithsons’ special planning “tenets” – the design of intermediary spaces that, by separating the buildings, “(…) offers fundamental bridging elements, (…) intermediary spaces, necessary pause-spaces (…) that allows a person to sense where he is and what he is about” [24], as Peter Smithson himself accurately describes. The architect goes on declaring that “(…) the plateau of the plaza raised above the surrounding streets offers an (…) intermediary space in which there is time to rearrange sensibilities (…), (…) as places can only be comprehended by the nature of the spaces within them (…)” [24]. In fact, the designed podium – and “plaza” – that Peter Smithson is referring to, offers a transitional area in-between the buildings which is crucial for the urban arrangement of the complex (see Fig. 5).

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Fig. 5. The Economist building in London, by Alison and Peter Smithson, in 1964. © The Alison and Peter Smithson Archive – Harvard University Graduate School of Design

Even scrutinising their famous design of the Robin Hood Gardens in London (1966– 1972) (see Fig. 6), it is striking how the Smithsons spend much more time exploring and explaining their design of the immense gap between the buildings – a green artificial mound –, than the buildings itself. What seems relevant and of deep interest to them is that absence between the forms, and not the forms themselves, specifically – what is not built, what is absent from the construction emerges as the fundamental factor in the design process.

Fig. 6. The Robin Hood Gardens’ site plan, by Alison and Peter Smithson (1966–1972). © The Alison and Peter Smithson Archive – Harvard University Graduate School of Design

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This work and research ideology can be perceived in more of Smithsons’ projects – and interestingly enough, it may also be even further apprehended if an attentive look to the images and photographs that the Smithsons themselves have chosen, in order to publish their works, is done. Often, these are pictures that only show extracts from the entire work – like pieces or fragments of the whole –, which, not seldom, focus on displaying the relationship of the buildings with the void(s) beside them. Concluding – although not necessarily translating itself physically in form, and in the construction –, this apparent interval-like approach seems, in a way, to be always running through their entire thinking as architects, from beginning to end, permeating their entire theoretical and practical research work – even if it’s not directly obvious in some of their plans. The (apparent) concentration of their theoretical and practical efforts, not rarely, on certain themes – such as the absent space, the tension created between empty and intermediate spaces, and the apparent dissolution of the function (or the design of structures which, despite having specific and clear functional programs, are left open to interpretation) – seems, thus, to comprehend an (in)visible and transversal interval “project-theory”. “(…) Architecture and buildings are objects in a void. Is it a luxury to experiment an empty space? No. Life takes place in-between, in the void. So, we have to build that in-between” [10].

3 Brief Research Methodology In order to investigate on this (little-known to the West) original conception of the interval, and to finally interpret its possible potentiating effects in Western architectural context, the global strategy was to focus, firstly, in some of the most fundamental Japanese aesthetic and cultural compendiums cited in the text and in the References chapter, and secondly, in the example of the renowned architects Alexis and Peter Smithson, by taking on a critical review of their theoretical and practical work. The several reasons that defined the choice of this couple were guided by one primordial criterion: the hypothesis that their architectural approach seems to contain some design achievements that represent the interval theme. The subsequent premises that seemed to further strengthen the adequacy of this duo to the researched theme were the following: the fact that they both traveled to Japan; they both expressed a deep admiration and enchantment for the country, and specifically for its traditional culture and architecture, with which they had the important opportunity to experience directly; and the fact that they both registered their impressions of these journeys together. This specific inspection was undertaken by an in-depth observation of their architectural works, visiting and photographing on site all the buildings referred to in the text, and by collecting supplementary data from all the theoretical books of their authorship, also mentioned in this paper. Additionally, and finally, in order to uncover new information or create better understanding of the studied topic for analysis, a thorough (and, we believe, unprecedented) investigation of “The Alison and Peter Smithson Archive” – the Smithsons’ personal

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collection – was done, complementarily hosted by the Frances Loeb Library of Harvard’s University Graduate School of Design at Cambridge, and by the Netherlands Architecture Institute at Rotterdam. Acknowledgements. Firstly, the author would like to acknowledge his two Ph.D advisors from the Faculty of Architecture of the University of Oporto (FAUP), the architects and Professors Nuno Brandão Costa and João Pedro Serôdio; secondly, the director of both his field of studies (Architecture – Project Design Theory and Practices) and his research laboratory from the same faculty (CEAU – Centre for Studies in Architecture and Urbanism), the architect and Professor José Miguel Rodrigues; thirdly, the staff from Frances Loeb Library of Harvard’s University Graduate School of Design at Cambridge, and from Netherlands Architecture Institute at Rotterdam – both hosting different parts of “The Alison and Peter Smithson Archive”; fourthly, the Foundation for Science and Technology (FCT) for the financial support, granting the author with a fully funded Ph.D scholarship; and lastly, his Ph.D colleagues.

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.

Taut, B.: Houses and People of Japan. Sanseido, Tokyo (1958) Aristotle: The Organon. Franklin Classics Trade Press, London (2012) Nitschke, G.: The Japanese sense of ‘place’. Archit. Design 118–123 (1966) Pilgrim, R.: Space and time: foundations for a Religio-aesthetic paradigm in Japan. In: Japan in Traditional and Post-Modern Perspectives, pp. 255–275 (1995) Berque, A.: Vivre l’Espace au Japon (translation Miyahara M), p. 71. Vivre l’Espace au Japon (1982) Kâto, S.: Le Temps et L’Espace dans la Culture Japonaise. CNRS Éditions, Paris (2007) Okakura, K.: The Book of Tea. Penguin Little Black Classics, London (1906) Sartre, J.: Being and Nothingness. Washington Square Press, New York (1943) Banham, R.: The new Brutalism. Archit. Rev. 33–53 (1955) Smithson, P.: Conversations with Students. Princeton Architectural Press, New York (2005) Kishida, H.: Japanese architecture. Travel-Bureau, Tokyo (1948) Yoshida, T.: Japanische architektur. Wasmuth, Tubingen (1952) Yoshida, T.: Japanese House and Garden. Praeger, New York (1955) Harada, J.: Lesson of Japanese architecture. Studio-Limited, London (1954) Harada, J.: Japanese Gardens. Brandford, Boston (1956) Conder, J.: Domestic Architecture in Japan. London Transactions RIBA, London (1886) Conder, J.: Further Notes on Japanese Architecture. London Transactions RIBA, London (1886) Taut, B.: Fundamentals of Japanese Architecture. Kokusai Bunka Shikokai, Tokyo (1936) Carver Jr., N.: Form and Space of Japanese Architecture. Shokokusha, Tokyo (1955) Engel, H.: The Japanese House: A Tradition for Contemporary Architecture. Charles Tuttle, Tokyo (1964) JA – The Japan Architect. Shinkenchiku-sha, Tokyo Kokusai-Kentiku. Shokokusha, Tokyo Kenchiku-Bunka. Shokokusha, Tokyo Smithson, A., Smithson, P.: The Charged Void: Architecture. The Monacelli Press, New York (2005) Smithson, A., Smithson, P.: The Space Between. Walther Konig, Koln (2017) Smithson, A., Smithson, P.: The canon of conglomerate ordering. Ital. Thoughts 62 (1993)

Spatial Design Strategies for Lightweight Roofing Buildings Driven by Rain Noise Reduction Shaohang Shi1,2 , Xiang Yan1,2 , and Yehao Song1,2(B) 1 Tsinghua University, No. 30 Shuangqing Road, Haidian District, Beijing, China

[email protected] 2 Key Laboratory of Eco Planning and Green Building, Ministry of Education, Tsinghua

University, No. 30 Shuangqing Road, Haidian District, Beijing, China

Abstract. Lightweight building technologies have been widely used in recent years, but lightweight roofs generate high levels of rain noise. Architects and engineers usually reduce rain noise in buildings with lightweight roofing by optimizing roof construction layers’ design or by adding acoustic insulation. The study investigates the impact of three spatial design strategies on the optimization of the indoor acoustic environment, which are room floor area, room floor height and room plan form, by evaluating the rain noise levels in rooms with different spatial forms. A design approach is proposed, which can improve the indoor acoustic environment as well as rationalize the cost savings of building materials or manpower. 20 parametric models are generated as research objects and the results show that rain noise can be reduced by (1) increasing the room floor area (2) increasing the room floor height (3) increasing the room length/width ratio, with the priority of the three strategies being (1) = (2) > (3). This method can be employed to enhance the rain noise isolation potential of spatial prototypes such as atriums and shafts, or functional rooms such as wards and bedrooms. However, the schematic design needs to establish the priority of the design objectives at first, considering various aspects comprehensively. For rooms with special requirements for acoustic quality, room spatial design strategies alone may not be sufficient and a synergistic approach is required. The design approach and data presented in this paper can provide a framework or guidance for architectural design and practice. Keywords: Rain noise · Lightweight roofing · Spatial design strategy · Sound environment optimization

1 Introduction During the initial period of COVID-19, Huoshenshan (Fire God Mountain) hospital and Leishenshan (Thunder God Mountain) hospital adopted lightweight construction structures, which fully reflected the advantages of lightweight structures such as rapid construction [1]; In recent years, lightweight roofing has been widely used in buildings requiring a high quality of indoor environment, such as villas and gymnasiums, due to its © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 383–392, 2023. https://doi.org/10.1007/978-981-19-4293-8_40

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high economical performance, low self-weight, superior toughness and relatively short construction period, but a corresponding problem is that the rain noise of lightweight roofing degrades the quality of indoor acoustic environment [2]. Since people spend about 90% of their lives indoors, the quality of the indoor environment has a significant impact on human health [3, 4]; usually people pay careful attention to indoor air quality, but with the improvement of people’s living standards, the quality of the acoustic environment of indoor environments is also gaining more and more attention [5].The negative effects of rain noise are evidenced in numerous ways: excessive rain noise may interfere with people’s communication, such as in classrooms or learning spaces, which require a high level of acoustic environment [6]. Muhammad et al. [7] found that construction rain noise would increase people’s noise exposure, affecting their work and study efficiency and their indoor health. Architects who take into account performance requirements of a building during the programming phase can contribute to rational decision-making on the project and guarantee the technological performance of built buildings [8]. To cope with rain noise generated through lightweight roofing, it is common for architects and engineers to minimize negative effects of rain noise by locating rooms with high acoustic requirements at lower floors, or by adopting design of constructions with good sound insulation capacity Table 1. Traditional technical solutions to rain noise in buildings with lightweight roofs [9].

No 1

2

3

4 5 6 7 8

Applied phase

Technical solutions

Technical principles Heavy roofs with low inIncreasing the quality of the herent frequencies - the law roof of mass The reflection of sound Multi-layer construction strategy waves through the interface reduces the sound energy Initial design transmitted to the room phase, optimiImproving the acoustic zation of the Acoustic wool insulation performance of roof layer building constructions Reduces transmission of Insulation panels airborne sound between layers Reduction of the rigidity of the Reduces the transmission of sound bridge solid sound to interior Weakening the impact of Rainscreens rainwater After completion, Reducing the vibration additional Damping layers amplitude of the roof construction Acoustic suspended ceilings Same as No.3 filled with acoustic wool

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(Table 1). In this paper, a new design approach is proposed: How can rain noise be reduced through architectural spatial design strategies? This approach can improve the acoustic comfort of the building interior as well as rationalize on the consumption of construction materials and manpower according to different needs of projects. In addition, the study explores the applicable scenarios of spatial design strategies based on the sound pressure level requirements for different buildings and different rooms according to the GB 50118–2010 Code for design of sound insulation of civil buildings (Table 2). Table 2. Sound pressure level limits for buildings and corresponding rooms with the highest requirements for the sound environment in GB 50118-2010 [10].

Building type

Room function

Space typology

Sound pressure level [dB]

Residential

Bedroom (night) Language classroom, reading room Hearing test room Ward, staff lounge (night) Intensive care units (night) Guest rooms (night)

Small spaces

37

Large spaces

40

Small Spaces

25

Small / large space

35

Small / large space

35

Small spaces

40

Small spaces

40

Small / large space

40

Staff lounge

Small spaces

40

Atrium space

Tall spaces

-

Schools

Hospitals

Hotels Office buildings Commercial buildings -

Private office TV and telephone conference room

2 Methods The study tested the A-weighting sound pressure level (LIA , [dB] - reflecting the noise level in the built environment) of a lightweight roofing under laboratory rainfall conditions of 2 mm/min (extra heavy rain intensity) for different frequencies (f) by introducing a third party test. Further, by converting the sound power level of the lightweight roofing and the sound pressure level of the room, the values of LIA were calculated for the rooms with different parametric spatial prototypes. In the end, the optimization effect of different spatial design strategies for interior sound environment is evaluated based on the case set, which is developed by rooms of different forms and the corresponding interior LIA s (Fig. 1).

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Fig. 1. Research process.

2.1 From Indoor Sound Pressure Levels to Sound Power Levels The study takes a lightweight roof as an example and introduces a third party test to test the sound pressure levels at different frequencies of the lightweight roof by simulating rain noise conditions in the laboratory. In the next step, the A sound power level of the roof was calculated by using the conversion formula in 8.4.1 of GB/T 6881.1-2002 Acoustics - Determination of sound power levels of noise sources using sound pressure - Precision methods for reverberation rooms. From Eq. (1), it can be seen that when the room floor area (S0 , [m2 ]) and the room floor height (H, [m]) change, the volume of the room (V, [m3 ]) and the total surface area of the room (S, [m2 ]) will also change, which leads to the variation of LIA ; the value In Eq. (1), A0 and B0 are constants, usually taken as 1 m2 and 1.013·105 Pa respectively [11].  A Sc 427 B 273 A ) − 25lg[ · ] − 6} (1) Lw = Lp+{10lg +4.34 +10lg(1+ A0 S 8Vf 400 273 + θ B0 Where the speed of sound (c) at a defined temperature (θ) is calculated by Eq. (2): √ c = 20.05 273 + θ (2) For different frequencies of rain noise, the equivalent sound absorption area (A) of the room is calculated according to Eq. (3): A=S·α

(3)

In Eq. (1), the sound power level (Lw ) of the measured sound source is calculated from the sound pressure level in the room at different frequency (f) - while the room temperature (θ), sound velocity (c) and atmospheric pressure (B) are kept constant, and then the LIA can be calculated by Eq. (4) [12] and the A-weighting correction value. In Eq. (4), Lj refers to the sound intensity level in the jth 1/3rd octave band, Cj refers to the standard A-weighting factor, and jmax corresponds to the value of Cj in the 1/3rd octave band at different centre frequencies. In Eq. (4), Lj refers to the sound intensity level at the jth 1/3rd octave band, Cj refers to the standard A-weighting factor, and jmax corresponds to the Cj value at different central frequencies. is the average absorption coefficient of the room, which is the control variable to explore the optimal design strategy of the indoor acoustic environment under the same interior decoration conditions, so the absorption coefficients corresponding to different frequencies of rain noise are consistent in this study (Table 3). Within the given different parameterized spatial proformas, the total surface area S and room interior volume V of the room interior vary. By calculating the

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average sound pressure level corresponding to the same rainfall conditions in the room with the same lightweight roof cover for different rooms, it is then used to compare the change trend of the indoor sound environment quality under different design strategies and to judge the improvement benefit of different design strategies on the indoor sound environment. LIA = 10lg

jmax 

100.1(Lj + Cj)

(4)

j=1

Table 3. Indoor sound absorption coefficient of the sound receiving room (Data source: Acoustics Laboratory, Building Environment Testing Centre, Tsinghua University). f [Hz]

125

250

500

1000

2000

4000

Sound absorption factor

13.95

19.16

23.95

22.81

23.95

23.56

2.2 Parametric Spatial Prototypes and Multi-case Comparative Study The parametric spatial prototypes in this study are square, based on the basic spatial scale of architectural scheme design, and sort out different types of spatial prototypes, including large spaces, small spaces and tall spaces. And based on three design strategies of room floor area, room floor height and room plan shape, a case set of 20 parametric space protoforms is developed (Fig. 2).

Fig. 2. Parametric spatial prototypes for rooms based on area, floor height and shape design strategies.

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3 Results 3.1 Noise Power Levels of Lightweight Roofing The study simulates the sound insulation effect of a certain lightweight roof cover under rainfall conditions in the Acoustics Laboratory of Tsinghua University. The sound power levels of this lightweight roof cover are shown in Table 4, which demonstrates the noise sound power levels at different frequencies of this lightweight roof, as well as the A sound power level of the roof, a value that reflects the rain noise insulation capability of this roof. Table 4. Sound power level per unit area of a lightweight roof under laboratory simulated rainfall conditions at 2 mm/min (Data source: Acoustics Laboratory, Building Environment Testing Centre, Tsinghua University). f [Hz]

125

250

500

1000

2000

4000

Sound power level A

Sound power level [dB]

45.7

39.3

32.2

19.8

12.5

10.3

34.8

Table 5. Spatial form indicators and LIA for different rooms.

Case number

Room height [m]

Length/width

Room area [m2]

LIA [dB]

1

4

1.67

15

36.38

2

4

2.00

18

35.82

3

4

1.25

20

35.73

4

4

1.50

24

35.19

5

4

1.00

25

35.15

6

4

1.00

36

34.13

7

4

1.33

48

33.26

8

4

1.50

96

31.10

9

4

1.00

144

29.82

10

4

1.33

192

28.82

11

4

1.00

256

27.84

12

4.5

1.00

25

34.87

13

5

1.00

25

34.60

14

8

1.00

25

33.24

15

12

1.00

25

31.90

16

16

1.00

25

30.88

17

4

1.44

144

29.78

18

4

1.78

144

29.73

19

4

2.25

144

29.65

20

4

4.00

144

29.34

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3.2 LIA Calculation for Parametric Spatial Prototypes Based on the noise power level of this lightweight roof, the indoor LIA of this roof used in different spatial forms of rooms is investigated to determine the indoor sound environment quality during rainfall. The spatial form of the room and the indoor LIA are shown in Table 5 and Fig. 3, and a comparative case study based on three design strategies are shown in Table 6.

Fig. 3. Data distribution of spatial morphological indicators and LIA . Table 6. A comparative case study based on three design strategies.

Comparison items

Case number

Room area

1

2

3

4

5

6

Room height

5

12

13

14

15

16

Room flat shape

9

17

18

19

20

7

8

9

10

11

4 Discussion (1) Room floor area and rain noise: cases 1–11 show that the larger the room floor area is, the less rain noise indoors. Based on cases 4, 7 and 8, for every twice the floor

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area, the indoor rain noise is reduced by approximately 2 dB. To investigate this, as the room floor area increases, the increase in the rain receiving area leads to an increase in the sound energy of rain noise. However, the surface area of the room and the amount of sound absorption increase at the same time, and this trend is more significant than the increase in enhanced sound energy, so the indoor sound environment is optimized. Case 1 has the highest indoor LIA at 36.38 dB, with a room area of 15 m2 , a space scale suitable for small bedrooms and offices. Case 11 has the lowest indoor LIA at 27.84 dB, but the room has a relatively large area of 256 m2 , which is suitable for large spaces such as lecture halls, but not for rooms such as bedrooms and lounges - there is no need to expand the floor area to that scale in order to reduce rain noise. In addition, although 27.84 dB is the lowest LIA in all cases, it still does not meet the sound environment requirements for rooms with particular requirements, such as hearing test rooms in hospitals which require 25 dB. In the case of hospital wards, it is clear from this conclusion that large multi-person wards are more favourable than single-person wards in reducing rain noise. At the same time, although larger wards are preferred to reduce rain noise, the interaction noise [13] or privacy issues [14] may be detrimental to the patient’s sleep experience, stress recovery or satisfaction with care for most of the time. (2) Room floor height and rain noise: cases 5, 12–16 show that the higher the room height, the lower the indoor rain noise. In cases 5, 14 and 16, for every twice the room height, the indoor rain noise will be reduced by about 2 dB. To investigate this, the sound energy of rain noise unchanges under the condition that the rain receiving area keeps the same. As the room floor height increases, the surface area and sound absorption of the room increases, so the indoor sound environment is optimized. Based on this conclusion, it can be seen that for spatial design of tall spaces such as atriums or shafts, increasing the space net height will reduce rain noise indoors. (3) Room plan shape and rain noise: cases 9, 17–20 show that the larger the length/width ratio of the room, the lower the indoor rain noise. A room with a length/width ratio of 4 reduces rain noise by 0.48 dB compared to a room with a length/width ratio of 1, which is a comparatively minor improvement. Besides, changing the room plan shape may also result in losing well-balanced spatial scale as the room floor plan becomes excessively narrow.

5 Conclusions The study proposes a new design approach, based on an architects’ perspective, to enhance the rain noise insulation of lightweight roofing through spatial design strategies in the early stages of programming design. Based on the above analysis, conclusions are as followed: (1) In the initial stage of the architectural design, rain noise can be effectively reduced by increasing the room floor area or the room floor height. The larger the length/width ratio of the room plan, the lower the indoor rain noise - but the effectiveness of it is relatively insignificant. Therefore, three spatial design strategies are prioritized as: room floor area = room floor height > room plan shape. However, the

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combination of spatial scale and functional requirements of a room needs to be considered carefully in order to achieve multi-objective optimization and improve the comprehensive performance of the building rather than any single aspect. (2) In the case of small rooms with a specific requirement for sound quality (small room area, low room floor height), spatial design strategies to raise the potential for rain noise insulation are not applicable. Instead, a synergistic optimization can be achieved through avoiding locating the room on the top floor, modified roof layers and additional sound isolation. (3) The construction design of lightweight roofing determines its cost and acoustic insulation potential - Although three strategies discussed above can reduce the impact of rain noise on the indoor acoustic environment to varying degrees, the area of the building envelope (construction materials) and costs of labor may also subsequently rise. In future studies, a sensitivity analysis will be carried out to find the optimal solution, taking into account economic factors - the construction cost of additional roof isolation layer (more cost due to improved roof construction) and the cost of building envelopes (more cost due to increased area of building envelopes) in the game process. In summary, this study discusses the effectiveness of three spatial design strategies for reducing rain noise in buildings with lightweight roofing and explores scenarios applicability. Especially for buildings with lightweight roofing in districts with heavy annual rainfall, this design approach can provide data-based design guidance for architects. Acknowledgments. This work was funded by National Natural Science Foundation of China (Project No. 52078264).

References 1. Lin, Z., Song, Y.: DSF prototype design for lightweight prefabricated building oriented to the surface energy regulation and control based on a comparative experimental platform in cold zone of China. Build. Energy Efficiency 49, 10–20 (2021) 2. Yan, X., Qin, Y.: Research on rain noise. In: Building Physics Branch of the Chinese Institute of Architecture. Architecture and Urban Physical Environment in the Process of Urbanization: Proceedings of the 10th National Conference on Building Physics, pp. 209–213. South China University of Technology Press, Guangzhou (2008) 3. Woodcock, A., Custovic, A.: ABC of allergies: avoiding exposure to indoor allergens. BMJ 316, 1075 (1998) 4. Thompson, C.R., Hensel, E.G.: Gerrit Kats: outdoor-indoor levels of six air pollutants. J. Air Pollut. Control Assoc. 23, 881–886 (1973) 5. Kang, J.: Acoustic comfort in non-acoustic spaces: a review of recent work in Sheffield. Proc. Inst. Acoust. 25, 125–132 (2003) 6. New Zealand Ministry of Education: Designing Quality Learning Spaces (DQLS), Acoustics. New Zealand Ministry of Education, Education Infrastructure Service (2020) 7. Idris, M.F.M., Musa, M.M., Ayob, S.M.: Noise generated by raindrop on metal deck roof profiles: it’s effect towards people activities. Proc. Soc. Behav. Sci. 36, 485–492 (2012) 8. Nguyen, A.-T., Reiter, S., Rigo, P.: A review on simulation-based optimization methods applied to building performance analysis. Appl. Energy 113, 1043–1058 (2014)

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9. Yan, X.: Research on rain noise of lightweight roofing. Tsinghua University (2008) 10. China Academy of Building Research, Tongji University, China IPPR International Engineering Company Limited, Beijing Institute of Architectural Design, Southeast University, Taiyuan University of Technology, Tsinghua University, University of Hong Kong: GB 501182010, Code for design of sound insulation of civil buildings. General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China, Beijing, China (2010) 11. Nanjing University, The Institute of Acoustics of the Chinese Academy of Sciences: GB/T 6881.1-2002, Acoustics - Determination of sound power levels of noise sources using sound pressure - Precision methods for reverberation rooms. General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China, Beijing, China (2002) 12. Tsinghua University, China Academy of Building Research, The Institute of Acoustics of the Chinese Academy of Sciences: GB/T 19889.18-2017, Acoustics-Measurement of sound insulation in buildings and of building elements - Part 18: Laboratory measurement of sound generated by rainfall on building elements. General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China; Standardization Administration of the People’s Republic of China, Beijing, China (2017) 13. Alvarsson, J.J., Wiens, S., Nilsson, M.E.: Stress recovery during exposure to nature sound and environmental noise. Int. J. Environ. Res. Public Health 7, 1036–1046 (2010) 14. van de Glind, I., de Roode, S., Goossensen, A.: Do patients in hospitals benefit from single rooms? A literature review. Health Policy 84, 153–161 (2007)

Application of Lingnan Ventilation Skills in Contemporary Architecture – Lift Shaft Design of Pedestrian Footbridge in Macau Johnny Kong Pang Ng(B) Faculty of Humanities and Arts, The Macau University of Science and Technology, Macao, China [email protected]

Abstract. Extreme weather happens more often than any time before in recent years due to the global warming effect. In many regions, people spend more and more energy and cost to combat the change of the warming environment. It is unsustainable and very fragile in the long term. Therefore, this article takes lift shaft design in Macau as an example, to demonstrate how Lingnan local ventilation skills could be integrated into contemporary architectural design. The result tackles the overheat and energy consumption issues of the lift shafts at the end through different traditional methods, such as wind & thermal pressure ventilation, chimney effect, piston effect, etc. This research-based design acts as an example to encourage more people to reconsider the linkage between buildings and environment for future sustainable development. Keywords: Ventilation · Lingnan · Lift shaft

1 Introduction Macau, a city located in southern China, was still a colonized area of Portuguese 22 years ago. Now it is known for its gambling industry. Thousands of tourists from all over the world come for visiting this cultural-mixed old town every year. As the Portuguese had started settling in Macau since 16th century, Macau well preserve the mid-century European urban fabric and traditional Chinese architecture as well. These abundant historic elements make up Macau as a world cultural heritage on the one hand, they restrict the redevelopment of old town on the other hand. As the old district aging over the time, many infrastructures could not meet the basic need of contemporary requirement. For example, traffic jams, limited pedestrian areas, crossing risks are the most emerging issues in recent years due to the rapid growth of private vehicle. Though pedestrian overpass could mitigate the pressure from the urban traffic and improve the accessibility of pedestrian network, many existing footbridges in Macau are lack of disabled facilities due to limited budget, space, land right and technical issue in the past. It causes many inconveniences to the minorities. To build up a more inclusive, well-designed urban environment, Macau government decided to © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 393–400, 2023. https://doi.org/10.1007/978-981-19-4293-8_41

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install elevators on all existing footbridges and all proposed footbridges are required to consider disable design in the future [1]. The massive installation of elevators leads to another issue-energy consumption. Macau is a city located in Sub-tropical area. The weather is warm and mild in winter, but very hot and humid in summer. This has caused the energy consumption rocketing during July to September. One of the contributors is cooling machine, such as air conditioning, mechanical cooling, etc. The overheat problems of lift shaft is very common in the summer, which might cause the equipment malfunctioning. As a result, many artificial cooling methods were employed in the lift shaft. These methods are not sustainable and very costly for energy and money. Therefore, making use of traditional Lingnan ventilation skills into the lift shaft design might be one of the ways to cope with these energy and environmental issues. This article will take one footbridge transformation project in Macau as an example to investigate how traditional methods could help developing a more sustainable contemporary design. The result tackles the overheat and energy consumption issues of the lift shafts at the end through different traditional means, such as wind & thermal pressure ventilation, chimney effect, piston effect, etc. This research-based design acts as an example to encourage more people to reconsider the linkage between buildings and environment for future sustainable development.

2 Relevant Concepts The research and application of ventilation skill applied in lift shaft is a relative complex system. It is essential to go through the basic relevant concepts before digging into its mechanism. The whole final system would be a synthesis which is made up by those different basic concepts in a specific logic. 2.1 Wind and Thermal Pressure Ventilation There are two basic ventilation strategies: Wind pressure ventilation (WPV) and Thermal pressure ventilation (TPV). Even they are individual physical phenomena, they always co-exit side by side in different practical situations. Wind pressure ventilation is the most common ventilation skill people used in usual live. It is caused by the regional climate and weather, which influences the shape, opening and direction of the buildings. Though WPV is the prior strategy to ventilate our buildings, it is unstable and unpredictable due to the ever-changing weather. To deal with this problem, thermal pressure ventilation could be the substitute when wind pressure is low. Different from WPV, TPV is more stable and gentler. It happens because of the pressure difference, which is caused by different temperature and moisture density. As a result, the air from the high-dense area would spontaneously flow to low-dense area. This process could help achieving the air/heat exchange. These two phenomena always happen together, so called synergy effect. This synergy could either weaken each other on the one hand, while strengthen the effect on the other hand. Therefore, how to make use of synergy effect in order to enhance the ventilation efficiency in terms of lift shaft design is the main issue this essay going to explore.

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Fig. 1. The concept diagram of chimney effect and piston wind. (Picture source: “https:// www.dummies.com/home-garden/green-living/energy-sources/how-to-use-the-chimney-effectto-cool-your-home/” [2])

2.2 Chimney Effect The concept of chimney effect is developed based on thermal pressure ventilation. It also makes use of the air buoyancy which occurs due to different air density, so as to achieve the movement of fresh air into and out of buildings. Take housing ventilation as an example (Fig. 1), the hot air automatically goes up to ceiling as the result of the air buoyancy generated by its low density. At the same time, the installation of roof vent sucks the hot air out of the building, which enhance the effect of this process. The movement of hot air generates a negative pressure zone at its original area, then the new fresh cool air will fill out this negative pressure zone again. The whole dynamic process is constant and will become a cycle as long as the condition keeps stable. The control of neutral pressure plane (NPP) could be vital for the chimney effect as it determines the infiltration and exfiltration of air. NPP occurs where there is no pressure difference between up and down, inside and outside. The air flow is static near the NPP, and is pulled by negative pressure on the one side, while pushed by positive pressure on the other side. Its location depends on wind, opening, temperatures of the space. 2.3 Piston Effect There is always more than one ventilation strategy could be applied in practical situation since the real world is more complicated than theory. Even the strategies should be customized accordingly in some specific cases, such as lift shaft. In this case, piston effect is more like a mechanic strategy to ventilate the space rather than the other passive strategies like wind & thermal pressure ventilation. The formation mechanism of the piston effect is based on the formation of piston wind and the vertical airflow distribution when the object passes through a limited space [3, 4]. The mechanism of piston effect will be explained in more detail by the case study of lift shaft design latter in this article. Though it is a mechanical method rather than a passive method to solve the heat issue, this ventilation strategy suits for being applied in lift shaft as it could make use of the movement of passengers to generate piston wind. The more people use the elevator, the more efficient this ventilation strategy is.

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3 Case Application The following section is to take R.das Lorchas pedestrian footbridge’s lift shaft design as an example, so that the application of Lingnan ventilation skills could be explained by the detailed design analysis. It demonstrates how traditional ventilation skill could be applied in the contemporary architecture, and to minimize the carbon footprint generated in usual. 3.1 Design Brief As mentioned in the introduction, Macau government is trying to improve the accessibility for minorities such as disables, elderly people, kids, etc. Installation of lift shaft is the priority for the renovation strategy. Like many other existing footbridges in old district, R.das Lorchas footbridge is aging and lack of extra space to install lift facility (Fig. 2). Its existing escalators could not meet the needs of minorities. Furthermore, the maintenance cost is high because it locates in the low-lying area close to the inner harbour, which always make its components suffered the damages from flooding. After many revisions of the proposal, Macau government decided to demolish the existing escalators in order to leave sufficient space for lift shaft installation. As a result, it will be one lift shaft on both sides, each of them also meets the design requirements for disabilities. In addition, all elements and facilities will be renovated except its original main structure. A brand new and inclusive pedestrian footbridge will be presented to citizens after the renovation work (Fig. 2).

Before

After

Fig. 2. Footbridge model before and after the renovation. (Picture source: by author)

The design proposal for lift shaft installation is fully considered in regard of traditional ventilation strategies. Different scales of strategies are applied into the design based on different scenarios. These strategies could ensure the elevators working normally even in the hottest summer period on the one hand, while they also save a lot of energy from lift regular operation on the other hand. It might be an efficient way that could help developing a more sustainable environment.

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In the following parts, different scales of ventilation strategies will be illustrated and explained accordingly. This could help people understand how theories could be transferred into practices in terms of tradition ventilation. 3.2 Marco Ventilation Skills The Macro ventilation strategies mainly focus on the relationship between the lift shaft and its surrounding environment. The design proposal hopes to figure out the overheat issues by the means of layout arrangement. Wind and heat pressure ventilation skills are also applied in these situations. Strategies Based on Prevailing Wind and Typhoon. The summer prevailing wind of Macau is mainly from southwest direction. Though the inner harbor is reclaimed by artificial landfill, its main structure and existing old district’s fabric are parallel to the prevailing wind and inner river (Fig. 3). Therefore, it is advantageous to plan the lift shaft’s openings in correct direction, which makes use of the prevailing wind to ventilate the internal heat generated by its machines. In this case, the southwest openings are under positive pressure, while the northeast openings are under negative pressure. They create a suction between these openings. The southwest-northeast oriented openings are also beneficial for lift shaft to ventilate under the typhoon days as most of typhoons are generated in South China Sea and coming from the south. Besides ventilation strategies, there is also an emergency system to tackle the flooding caused by typhoons. The elevators will automatically go up to the first floor when the sea water has flooded into the lift shaft. After the sensors detect the flooding has slipped away, the water pump at the basement will start to extract the sea water out from the bottom of lift shaft. At the end, the lift shaft could work as normal without damages.

Fig. 3. Summer prevailing wind and sea wind near the footbridge. (Picture source: by author)

Strategies Based on Urban Fabric and Water Resource. The urban fabric near the R.das Lorchas pedestrian footbridge is well preserved for its typical southern Chinese waterfront village characteristics. Beside of the paralleled roads, many other roads are perpendicular to the waterfronts for the convenience of port goods loading. This urban characteristic is also good for the heat exchange between river and inner city (Fig. 3).

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As the heat storage coefficient of water is relatively high comparing to air, so water is the ideal materials to regulate the micro climate near the waterfront. Take the footbridge as an example, in the morning, the water in the river is cooler than the concrete in the city, the cool air will spontaneously flow to the inner city through the perpendicular road; When it is at night, the temperature of water is more stable due to its high heat storage coefficient, the cool air will flow back from the inner city to the waterfronts. Therefore, the urban fabric and waterfront environment is beneficial for lift shaft to ventilate itself. The direction of openings should also take into consideration in regards of this matter.

3.3 Micro Ventilation Skills Different from macro ventilation strategies, micro ventilation strategies mainly focus on how to optimize the internal ventilation efficiency through its own components, such as openings, details, depth-width ratio, equipment, etc. Opening Ratio and Distribution. According to research by different scholars [5], the ventilation efficiency is optimized when the opening area reaches 25% of cross-section area. Therefore, in this case, 2m2 louvers are used as the openings corresponding to 8m2 lift shaft cross-section. Furthermore, there are two louvers on the top while only one louver at the bottom. The distribution of the openings is decided based on synergy effect, which means wind pressure and thermal pressure are to the same direction. When the summer monsoon is prevailing, the top two louvers lead to a convection current near the top. The convection current does not only dispel the heat on the top (where the main machine locates), but also wind up the air from the bottom of the lift shaft. At the same time, once the new fresh air gets into the bottom opening, they would go up to the top since there is only one opening at the bottom facing the prevailing wind and it is under positive pressure (Fig. 4). On the other hand, the warm air is also going up due to the thermal pressure effect. As a result, the wind pressure generated by external resources synergizes with the effect of thermal pressure ventilation in the lift shaft, which maximizes the whole ventilation efficiency.

Fig. 4. Different ventilation scenarios are considered in the design process. (Picture source: by author)

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Chimney Effect. In order to accelerate the speed of air flow inside, the depth-width ratio (5:1) of the lift shaft is well considered so as to achieve chimney effect for internal ventilation [6]. Meanwhile, the proposed distribution of openings lifts up the original neutral pressure plane (NPP) to a higher position, which enhance the air buoyancy at the bottom, so more air would rise up. In addition, the concept of thermal storage roof is also applied in this matter. As the roof absorb the energy from sun radiation, the warm air near the heated roof is in low pressure, then it attracts the cool air below to supplement this balance. All these strategies above strengthen the chimney effect for the lift shaft. Piston Effect. The lift shaft has its mechanism to ventilate the internal heat. When people take the lift to upper floor, the elevator goes up through the lift shaft. The air near the elevator could not fully flow to the bottom through its sides. As a result, some of the air will be pushed and discharged to the top of the lift shaft opening. At the same time, the movement of the elevator generate a negative pressure vortex area behind, which will suck new fresh air into the lift shaft through the bottom opening. As a result, the piston wind is formed and the heat is expelled from the top (Fig. 5). As R.das Lorchas pedestrian footbridge is next to the border gate between Macau and Zhuhai, the volume of passenger is much higher than ordinary footbridges in other districts. The more people use the facilities, the higher efficiency it has in terms of piston effect. Therefore, piston effect works as another effective measure to solve the heat issue. Details and Equipment. The tailor-made louvers work as wind deflectors at the openings. Its extended louver blades are set to 35°, which could enhance the convection current on the one hand, the 35° wind direction also wind up the bottom air in the lift shaft on the other hand. The louvers also protect the lift shaft from entering water in rainy days. Furthermore, temperature-sensing fans are installed based on the direction of prevailing wind. The fans will start working once the temperature inside the lift shaft is over the setting limit. It provides a back-up protection to the equipment in case the weather is windless, such as the days before typhoon.

Fig. 5. Different ventilation strategies are applied in the lift shaft design. (Picture source: by author)

4 Conclusion According to the case study of R.das Lorchas pedestrian footbridge, it demonstrates how Lingnan traditional ventilation skills could be applied in contemporary architecture

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practices. Though the basic concepts are general in our live, the combination of these different methods solve the technical problems in a regional scale. Many buildings in the similar area could also apply these strategy sets to develop a more sustainable future. However, different regions and types of building might have different combinations of ventilation strategy. Therefore, investigation of external condition is necessary for setting up a suitable ventilation solution. Though this article highlights the significance of re-applying traditional ventilation strategies into contemporary design, the article is lack of data support to quantify and compare the improvement of environmental quality. Data collection like energy saving, temperature reduction, power efficiency will be analyzed to justify the issue in the future.

References 1. Information on. https://www.dssopt.gov.mo/zh_HANT/menu/latestNews/id/28 2. Information on. https://www.dummies.com/article/home-auto-hobbies/garden-green-living/ sustainability/green-building/how-to-use-the-chimney-effect-to-cool-your-home-188651/ 3. Pan, S., et al.: A review of the piston effect in subway stations. Adv. Mech. Eng. (2013) https:// doi.org/10.1155/2013/950205 4. Chiang, C.M.: Building Physics, 89–94 (1997) 5. Wang, G., et al.: Air pressure natural ventilation wind tunnel test with different barriers in the room. J. Sol. Energy 37(03), 666–672 (2016) 6. Guo, X.: Application of chimney effect in ecological architecture. J. Huazhong Archit. 29(06), 80–82 (2011)

The Opportunities and Challenges of Using LCA-Based BIM Plugins in Early-Stage Building Design: An Industry Expert Perspective Seyma Atik1(B)

, Teresa Domenech Aparisi2

, and Rokia Raslan1

1 Institute for Environmental Design and Engineering, University College London, 14 Upper

Woburn Place, London WC10NN, UK [email protected] 2 Institute for Sustainable Resources, University College London, 14 Upper Woburn Place, London WC10NN, UK

Abstract. The integration of Building Information Modelling (BIM) and Life Cycle Assessment (LCA) has gained importance in building design decisionmaking processes, where various approaches have been developed. Nevertheless, in moving towards a circular economy (CE), current integration approaches still face limitations regarding the integration of CE principles into building design. This paper focuses on LCA-based BIM plugins and investigates through a series of semi-structured interviews with expert practitioners in the field, the opportunities and challenges associated with the integration between BIM and LCA platforms as way by which to enhance the incorporation of CE principles. Findings reveal the considerable potential of using LCA-based BIM plugins at early design stages as a decision-making tool to enhance circularity. However, the results also highlight the importance of the data requirements and accuracy in both BIM and LCA modelling; and thus, the need for (i) effective management relating to both time and work, (ii) clear guidance for BIM modelling and use of LCA plug-ins, and (iii) increased knowledge regarding the proper implementation of LCA and the application of CE concepts. Keywords: Building information modelling · Life cycle assessment · Early-stage building design · Net-zero carbon · Circular economy

1 Introduction In response to the growing threat of global warming, there is an urgent need to significantly mitigate greenhouse gas emissions through ambitious reduction targets [1, 2]. In addition to this, there is also need for a fundamental shift towards a circular economy (CE), as a potent contributor to achieving zero-carbon prosperity across all sectors [3]. The architecture, engineering, and construction (AEC) sector accounts for 36% of global energy use and nearly 40% of total direct and indirect CO2 emissions [4]. It is therefore a major target of mitigation efforts [5] and an area where there has been the increased © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 401–408, 2023. https://doi.org/10.1007/978-981-19-4293-8_42

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attention directed towards exploring the way of incorporating the CE principles into the design practice [6]. In this context, Life Cycle Assessment (LCA) has allowed the holistic evaluation of environmental performance of buildings throughout their entire lifespan. However, it is a complex, data-intensive process due to the fact that buildings consist of various elements and components and have a long-life span [7]. As Building Information Modelling (BIM) tools offer the opportunity to overcome data management difficulties, recent work in academia and industry has focused on integrating BIM and LCA to reduce the time required for data input to support automatic implementation of multiple analyses in early design stages [8–10]. However, technical limitations, such as the complexity of data, interoperability, lack of data exchange standards and inadequate levels of knowledge and expertise in both areas still exist and have resulted in relatively limited use in the practice [11, 12]. In addition, from an architectural perspective, the outcomes of standalone LCA analyses may be disregarded in favour of more aesthetically appealing designs [7]. LCA-based BIM plugins may provide a solution to aforementioned issues since they offer a range of integration pathways (from fully to partially compatible) with a range of software tools that support the design, analysis and delivery of energy efficient buildings, such as IES VE and DesignBuilder. They also support automated data input, thus can minimise practitioner effort [9, 13]. To investigate current practices of implementing LCA-based BIM plugins, a series of in-depth industry interviews were undertaken to gauge the perspective of industry practitioners in regard to: • Identifying current opportunities and challenges associated with the process, • Highlighting solutions for achieving the practical application of the plugins, • Investigating opportunities for the inclusion of CE principles during early design stages.

2 Methods A qualitative research approach involving a series of semi-structured interviews with expert practitioners in the field was adopted. In the relevant literature, the number of participants in ‘expert voices’ studies is rarely defined, whereby the quality of the analysis is deemed more important than the quantity of interviews [14]. Saunders [15] proposes a range of 4 to 12 participants chosen from a homogeneous population to achieve data saturation. Given this, a study sample size of 4 was deemed as appropriate and in line with similar work in the field. A non-random purposive sampling approach supported by snowballing strategy was employed to select participants. The interviewees were selected based on the criteria which aimed to ensure relevant industry experience and expertise, where they were expected to be LCA practitioners with experience in the implementation of both LCA and BIM in sustainability practices across Europe. Potential interviewees were identified via their organisational LinkedIn profiles, then contacted via email. The main topics covered in the interview were: (i) actions in the design process at early design stages, (ii) influence of LCA tools on the decision-making process, (iii)

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issues in the application of the tools, (iv) analysis process of sensitivity and uncertainty in LCA results, (v) opinions about the efficiency of LCA tools in terms of the ability of the tools to provide accurate enough results, and (vi) future development in the tools considering the circularity context. 2.1 Data Analysis Method: Thematic Analysis A “thematic analysis” approach was used for data analysis where key information from interviews was identified and encoded; then sub-themes and main themes were derived and interpreted [16], using the systematic guideline proposed by Braun and Clarke [17, 18]. Theme generation was based on an inductive and a data-driven approach. The qualitative analysis software NVivo 20 was used to support the analysis and a participant coding system was used to enable cross-referencing (e.g., P1 denoting Participant 1).

3 Analysis Results The interviews provided feedback on how the LCA-based BIM tools are used within the design process and the way in which influence the decision-making process. In addition, more comprehensive information about the specific actions taken by practitioners in each life cycle stage to reduce overall environmental impacts of design alternatives within the consideration of circularity context was derived. The three themes discussed below were identified. 3.1 Theme 1: Integrating LCA in Building Design Practice This theme covers the barriers and enablers in the implementation of LCA in the design process as a part of the effective decision-making mechanism. Participants were asked to determine drivers and constraints to the influence of LCA in the design process and these were identified as: • The lack of regulatory enforcement to undertake LCA was indicated as the main constraint. As an example, one interviewee stated that “…the challenges that there is ‘no’ regulation that forces anyone to do it…as a less serious thing to solve…(P4)”. • Building certifications and planning applications were considered to be main drivers “…the driver is all the certifications; BREEAM, LEED, DGNB…those LCAs are …part of the planning application…(P2)”. • The time demanding LCA process and unrealised potential of LCA as an effective decision-making tool were also highlighted by interviewees, in statements such as “It is more like a just ‘do it’. Doing the assessments is not kind of used for any meaningful design tool…(P3)” “…Then, that is time-consuming…(P2)”. • The knowledge gaps within the design team, which were mostly attributed to a lack of familiarity with LCA were identified as the most common barriers in the implementation of LCA during the design process. Several statements supporting this included “…people could just use them in the design process, and not needing me to come at the end of the process and tell them what is good. This does not have so much sense…(P1)”

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“…the architects themselves should do the calculations early stages…(P3)” “…it takes time and time before my team to get involved and by that point maybe the point of influence has already been passed…it would be really helpful to allow them to do their own quick analysis…(P4)”. This was in part due to the unclear sequence of data transfer involved and subsequent resistance to implementing design changes in response to analysis outcomes. 3.2 Theme 2: LCA-Based BIM Plugins This theme aimed to explore the benefits and main difficulties in using LCA-based plugins in the decision-making process and requirements in achieving a robust integration between BIM and LCA plugins. The benefits of using LCA-based BIM plugins were identified as: • Provision of time-efficient assessment and the ability of the tools to conduct a quick analysis of the design alternatives e.g., “…it is reasonably fast to do different iterations and test different reduction opportunities…it is quick…(P4)”. • Supporting the decision-making process and the ability of the tools to conduct simultaneous calculations for various iterations to reduce building impacts. Examples given include “…you can get very good information…(P1)” and “…it allows you to again do a hotspot analysis of where the biggest chances of making the building more circular…(P4)”. • The suitability of using the tools in the certification process; the interviewees stated that “…It will work for BREEAM as well…(P4)” and “…it has all the tools you need in order to a BREEAM assessment…(P1)”. Difficulties in achieving a robust integration between BIM and LCA plugins were identified as: • The larger size of model data and the unsuitability of the early-stage BIM models to performing an LCA in most cases where “…larger projects might get a little bit hard to handle because of the size of data…early-stage models don’t have anything useful for LCA…they’re not really useful…(P3)”. Two similar and often compatible discourses emerged in relation to the lack of suitability of BIM models: • The lack of useful data at early-stage models and the inaccuracy stemming from the modelling simplifications. Examples of reported issues included “…the main constraint is getting good and accurate data on which to base the LCA…at the earlier stages of the projects…the BIM models and drawings just really were not accurate enough for us to rely on for any materials, quantities, all types…(P4)” and “…especially in the early design stages you don’t have much information…(P1)”.

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In regard to these statements, the main requirement in achieving a robust integration highlighted was having a “well-built” model to perform an LCA. This requirement was associated with two main factors: • Harmonisation: Standardising naming conventions across tools to enable the recognition of materials when assigning the relevant data to the building elements “…It was very difficult for me to understand which material they have corresponds to what material in Revit. Because they have different names…(P1)”, • Minimising user errors during modelling: Through training and provision of an LCA/BIM modelling, e.g., “…training…so, they can be overcome…and…a BIM guide on how to prepare BIM models for LCA that lists all the things should be integrated into the BIM process…(P2)”. 3.3 Theme 3: Circularity in Building Context Within this theme, the following issues were identified: (i) the barriers to transitioning to circularity in building design, and (ii) the difficulties in the use of LCA-based plugins to aid the selection of building materials with a focus on their reusability and recyclability. Similar constraints as those discussed in Theme 1 were highlighted, where the main barriers were: • The lack of regulatory enforcement, clear standards, and metrics to assess the circularity in building “…there is ‘no rules’…and… ‘no standards’ around…circularity score…all of these make it challenging to do circularity assessments as part of LCAs…there is no clear metrics around building circularity…(P2)” • The lack of proper understanding of the concept of circularity and a lack of motivation to assess circularity; “…in terms of assessing circularity or level of circular economy, the materials efficiency calculation…is ‘kind of’ doing that. It is rating proportion of the material is virgin against recycled or reusable…(P4)” and “…module D like we reported but then we don’t really measure it, we don’t really summarise all together. We just reported somewhere…(P1)”. Since findings illustrated that LCA was not properly adopted in the current building design practice, the difficulties in implementing CE principles via LCA-based BIM plugins were not particularly prominent in the interview data.

4 Discussion and Conclusion Based on the practical assessment of LCA-based BIM plugins by the practitioners, this study provides insights into the enablers and constraints relating to the implementation of LCA in building design, the parameters relating to effective use of LCA plugins and finally the main barriers in the transition to the circularity in building practice. The insights gained and discussed are as follows:

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4.1 The Enablers and Constraints Relating to the Implementation of LCA in Design Practice The analysis revealed four groups of insights. Firstly, regulations can play a vital role through the mechanisms of both enforcement and education. Given the increased policy attention in the disclosure of Environmental Product Declarations (EPDs) for construction materials [19] and the pursuit in the development of material passports to enable a systematic shift in the building sector [20], the legal requirement to undertake LCA as a part of the design process can create awareness, help building capacity and encourage wider implementation. Since LCA remains non-compulsory, this constrains the potential benefits achievable through widening its utilisation in the industry. Secondly, even though building certification requirements, such as BREEAM Mat 01 and LEED MR, have helped drive increased utilisation, the influence of LCA in design practice was limited to that particular process. As a result, LCA practice was in most cases not utilised as a decision-supporting tool during the design process. Likewise, it was found that the LCA ‘knowledge gap’ and absence of required skills to perform it have further constrained its potential as a powerful decision-making tool. Mechanisms to overcome barriers included increased engagement particularly between architects and other members of the design team with the LCA process and the incorporation of LCA tools and consultants as early as possible within the design process. Given the frequency of design changes and the laborious LCA process, this suggests the importance of organising the sequence of data transfer to improve clarity. Moreover, it is important to upskill the workforce with LCA training as well as provide clear guidance for the assessment process to further enable the implementation of LCA within design practice. 4.2 The Parameters Relating to Effective Use of the LCA Plugins Findings demonstrate that the use of LCA-based BIM plugins at early design stages as a decision-making tool can potentially help to assess the overall environmental impacts of the building and identify the reduction potential during the design process. The quality of LCA undertaken and the effectiveness and reliability of LCA plugins were closely associated with the accuracy of BIM models where the maturity of BIM models was identified as a key aspect for accuracy. The need for well-built models was one of the main priorities highlighted; therefore, modelling guidance that clearly specifies the requirements for well-built models is crucial. 4.3 The Main Barriers in the Transition to the Circularity in Building Practice As a highly novel topic in the AEC industry, the absence of regulations, standards, and clear metrics to guide the assessment process as well as inadequate motivation on both organisational and individual levels were the main barriers noted. Given the difficulties identified in current LCA practice and the limited capabilities of current tools in assessing the uncertainties associated with the impacts and benefits of reused building materials, the implementation of CE and circular design principles currently requires substantial effort.

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5 Conclusion These key messages which can be concluded from this study are: • The use of LCA-based BIM plugins can play a considerable role in aiding the transition towards a net-zero carbon built environment. • Due to the lack of regulatory enforcement and sectoral motivation, the use of LCA plugins is in most cases currently limited to supporting building certification rather than as part of a design process that aims to improve the environmental performance of buildings. • Therefore, the potential of LCA as a powerful decision-making tool is unrealised and considerable efforts are still required to make its use widespread. In considering the wider scope of the environmental impact agenda, the findings related to the circularity in building practice indicates that the important role of regulations, standards, and metrics to assist and encourage the practitioners to implement CE principles. Moreover, insufficient knowledge regarding the conceptual foundations of CE were identified as further barriers to the wider adoption of circular design principles in the sector. The interview findings suggest the following solutions which can be used to overcome these challenges and to facilitate the inclusion of CE principles to the building design process: (i) effective time and work management, (ii) clear guidance for BIM modelling, (iii) increasing knowledge levels regarding the proper implementation of LCA, and (iv) the improvement of workforce skills. It should be noted that the study findings provide a view of the “current use” of the LCA-based BIM plugins in the practice, which was limited to, and reflective of the European context and thus may vary from the more global view. Given this, an extended study with a more international scope might reflect on the varied role of the regulations may play within these different contexts. As such, further research intends include a wider group of practitioners and investigate extending the use of these plugins to support the implementation of circular design principles. Acknowledgements. The research has been funded by the Republic of Turkey Ministry of National Education. The authors would like to acknowledge the interview participants for generously giving their time and providing the most valuable information that was of vast benefit to the data collection.

References 1. Allen, M.R., et al.: Framing and context. In: Global Warming of 1.5°C. pp. 49–91 (2018) 2. Passer, A., et al.: Sustainable built environment: transition towards a net zero carbon built environment. Int. J. Life Cycle Assess. 25(6), 1160–1167 (2020). https://doi.org/10.1007/s11 367-020-01754-4 3. Ellen MacArthur Foundation: How the circular economy tackles climate change, pp. 1–71 (2021) 4. GlobalABC, IEA and UNEP: Global status report for buildings and construction (2019)

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5. Roberts, M., Allen, S., Coley, D.: Life cycle assessment in the building design process – a systematic literature review. Build. Environ. 185, 107274 (2020) 6. Mhatre, P., Gedam, V., Unnikrishnan, S., Verma, S.: Circular economy in built environment – literature review and theory development. J. Build. Eng. 35, 101995 (2021) 7. Hollberg, A., Ruth, J.: LCA in architectural design—a parametric approach. Int. J. Life Cycle Assess. 21(7), 943–960 (2016). https://doi.org/10.1007/s11367-016-1065-1 8. Hollberg, A., Genova, G., Habert, G.: Evaluation of BIM-based LCA results for building design. Autom. Constr. 109, 102972 (2020) 9. Santos, R., Costa, A.A., Silvestre, J.D., Pyl, L.: Integration of LCA and LCC analysis within a BIM-based environment. Autom. Constr. 103, 127–149 (2019) 10. Röck, M., Hollberg, A., Habert, G., Passer, A.: LCA and BIM: Visualization of environmental potentials in building construction at early design stages. Build. Environ. 140, 153–161 (2018) 11. Wastiels, L., Decuypere, R.: Identification and comparison of LCA-BIM integration strategies. IOP Conf. Ser.: Earth Environ. Sci. 323, 012101 (2019) 12. Safari, K., AzariJafari, H.: Challenges and opportunities for integrating BIM and LCA: methodological choices and framework development. Sustain. Cities Soc. 67, 102728 (2021) 13. Atik, S., Domenech Aparisi, T., Raslan, R.: Investigating the effectiveness and robustness of performing the BIM-based cradle-to-cradle LCA at early-design stages: a case study in the UK. In: Howard, B., Oraiopoulos, A., Brembilla, E. (eds.) Proceedings of the 5th IBPSA-England Conference on Building Simulation and Optimization (Virtual), International Building Performance Simulation Association, Loughborough, UK (2020) 14. Baker, S.E., Edwards, R.: How many qualitative interviews is enough? National Centre for Research Methods Review Paper (2012) 15. Saunders, M.N.K.: Choosing research participants. In: Symons, G., Cassell, C. (eds.) The Practice of Qualitative Organizational Research: Core Methods and Current Challenges, pp. 37–55. Sage, London (2012) 16. Boyatzis, R.E.: Transforming Qualitative Information: Thematic Analysis and Code Development. Sage, California (1998) 17. Braun, V., Clarke, V.: Using thematic analysis in psychology. Qual. Res. Psychol. 3(2), 77–101 (2006) 18. Braun, V., Clarke, V.: Teaching thematic analysis: overcoming challenges and developing strategies for effective learning. Psychologist 26(2), 120–123 (2013) 19. Resalati, S., Kendrick, C., Hill, C.: Embodied energy data implications for optimal specification of building envelopes. Build. Res. Inf. 48(4), 429–445 (2020) 20. Honic, M., Kovacic, I., Rechberger, H.: Improving the recycling potential of buildings through material passports (MP): an Austrian case study. J. Clean. Prod. 217, 787–797 (2019)

The Factors of Environmental Living Design for Elderly Well-Being in Thai Spiritual Environments Porntip Ruengtam(B) Interior Architecture Program, Faculty of Architecture, Urban Design, and Creative Arts, Mahasarakham University, Riang 44150, Thailand [email protected]

Abstract. This study reviews the design of the physical environment within a residence that is suitable for comfortable and safe elderly living. Various guidelines and knowledge are available, yet there remains a lack of knowledge that focuses on design that leads to mental happiness. This research studies and analyzes the spiritual factors affecting the living environment of elderly Thais. The study then proposes a guideline to design spiritual living environments for the Thai elderly. The population and target groups are elderly people in Roi Et, Khon Kaen, Maha Sarakham, and Kalasin provinces in Thailand. Data was collected from in-depth interviews and a questionnaire survey. The results reveal that lifestyle changes in the homes of Thai elderly people have led to them placing importance on spiritual spaces within their homes. Moreover, the design of a religious space or prayer room within a dwelling is influenced by social characteristics (income and education) as well as physical characteristics (walk-mobility and smell) affecting. Keywords: Environmental design · Spiritual environments · Elderly

1 Introduction Today, knowledge about the design of the physical environment in elderly people’s housing to make it comfortable and safe has been published by both the government and the private sector. However, good interior architectural design principles are not only suitable for a comfortable and safe living, but also create a sense of satisfaction and joy for working in the space. These principles of good interior architectural design are consistent with the great theory “Maslow’s hierarchy of needs” [1]. The first of these are the basic housing requirement (physiological needs), followed by personal security and safety, a space of love and belonging, being filled with spiritual values (esteem), and a complete response to self-replenishment (self-actualization) [1]. At present, the elderly in Thailand suffers from higher rates of depression than other age groups. Potential explanations for this include psychological and social changes such as loss of a partner and having to leave work due to retirement which both require elderly people to adjust to a new lifestyle. Guidelines to care for the mental health of the elderly include creating a feeling of positivity about oneself, recognizing the value of one’s own children © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. Casini (Ed.): CEAC 2022, LNCE 279, pp. 409–418, 2023. https://doi.org/10.1007/978-981-19-4293-8_43

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and others, living a simple life, seeking peace of mind, and being as close to nature as possible. From the self-care guidelines for the elderly, it is found that emotional and mental management is an important factor which makes the elderly happy at the end of life from depression. Elderly people spend most of their time within their own residence. The guidelines are consistent with the results of a study on the lifestyle and well-being of the elderly in the Eastern region of Thailand [2], which ranked the factors that affect the health of the elderly in the region as spiritual health followed by social, mental, physical, and finally environmental health. It shows that spiritual environment design [2, 3] refers to the design of environments based on one’s spiritual experiences and expressions. A unique and dynamic environment design that reflects a supernatural belief in connection with the self, others, nature, and multidimensional involves integration of the mind, body, and spirit. This is an environment design concept that positively correlates with the quality of life of the elderly [4]. In the Thai cultural context, the spiritual environment consists of the relationship between subject matter and invisible form [5]. This relationship between the subject matter and the invisible form determines a positive spiritual environment, personal happiness, sustainable behavior, and environmental quality determinants. Therefore, this study presents a guideline to design a spiritual environment within a residence for elderly people in Thailand. The study scope is focused on surveys related to perceptions of Thai elderly people and data was collected from Khon Kaen, Roi Et, Kalasin, and Maha Sarakham provinces in the central region of northeastern Thailand. The research results can help architects and designers understand how to design homes that meet the needs of the elderly in Thailand and promote good living within housing.

2 Research Background The National Committee on the Elderly, Ministry of Social Development and Human Security Thailand [6] stated that the elderly are not a social burden and that they can participate in social development. Thai elderly people therefore must be accepted and supported by their families, communities, and the government in order to live a life of worth, dignity, and maintain a healthy standard of living for as long as possible. Regarding the spiritual environment, the World Health Organization [7] describes the term “health” as referring to a state of living that includes the dimensions of physical, mental, social, and spiritual sensations. The term “spiritual” [3] refers to a person’s spiritual experiences and expressions that are unique and dynamic and reflect their beliefs and worship in a god or the supernatural that are linked to the individual, others, nature, or gods and the integration of multiple dimensions with the mind body and soul. This concept has been positively correlated with quality of life among the elderly [4]. This concept, partly abstract in nature and partly innate in the soul [8], deals with the spatial relationship of the spiritual environment with other environments. Whereas the spiritual environment is the natural environment created and sustained by a godly figure. This spiritual environment is unique in that it describes the achievements of individuals, communities, and nations on earth such as humanity, religion, and God. Thus, the spiritual environment is a space created to express the achievements of a person and the core values of life. Thus, the spiritual environment is related to environmental psychology

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which emphasizes studying the interactions between environment and behavior [9]. The spiritual environment is an environment of people that is both culturally constructed and meaningful. In the Thai cultural context, the spiritual well-being of the elderly refers to a society that coexists with respect for seniority, sacred things, and Buddhism. In addition, the spiritual well-being of older people is related to their faith in religious activities, such as watering the hands of respected elders, participation in religious ceremonies, meditation, pledge-holding, and beliefs in fate [10]. As Barrera-Hernandez et al. [5] concluded, the spiritual environment consists of the relationship between the substance and the invisible form, and the relationships between the subject and the invisible form that determines the environment, positive spirituality, personal happiness, sustainable behavior and environmental quality factors. Plunz [11] said environmental design is the process of defining surrounding variables when planning projects, plans, policies, buildings, or products.

3 Research Method The National Committee on the Elderly, Ministry of Social Development and Human Security Thailand [6] stated that the elderly are not a social burden and that they can participate in social development. Thai elderly people therefore must be accepted and supported by their families, communities, and the government in order to live a life of worth, dignity, and maintain a healthy standard of living for as long as possible. Regarding the spiritual environment, the World Health Organization [7] describes the term “health” as referring to a state of living that includes the dimensions of physical, mental, social, and spiritual sensations. The term “spiritual” [3] refers to a person’s spiritual experiences and expressions that are unique and dynamic and reflect their beliefs and worship in a god or the supernatural that are linked to the individual, others, nature, or gods and the integration of multiple dimensions with the mind body and soul. This concept has been positively correlated with quality of life among the elderly [4]. This concept, partly abstract in nature and partly innate in the soul [8], deals with the spatial relationship of the spiritual environment with other environments. Whereas the spiritual environment is the natural environment created and sustained by a godly figure. This spiritual environment is unique in that it describes the achievements of individuals, communities, and nations on earth such as humanity, religion, and God. Thus, the spiritual environment is a space created to express the achievements of a person and the core values of life. Thus, the spiritual environment is related to environmental psychology which emphasizes studying the interactions between environment and behavior [9]. The spiritual environment is an environment of people that is both culturally constructed and meaningful. In the Thai cultural context, the spiritual well-being of the elderly refers to a society that coexists with respect for seniority, sacred things, and Buddhism. In addition, the spiritual well-being of older people is related to their faith in religious activities, such as watering the hands of respected elders, participation in religious ceremonies, meditation, pledge-holding, and beliefs in fate [10]. As Barrera-Hernandez et al. [5] concluded, the spiritual environment consists of the relationship between the substance and the invisible form, and the relationships between the subject and the invisible form that determines the environment, positive spirituality, personal happiness, sustainable

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behavior and environmental quality factors. Plunz [11] said environmental design is the process of defining surrounding variables when planning projects, plans, policies, buildings, or products. 3.1 Factor Identification and Questionnaire Design After reviewing the literature, relevant theories, and research, factors and indicators were determined and data collection methods were selected that were suitable for the design of spiritual living environments for the elderly in Thailand. The factors consist of generalizations of the elderly, religious and spiritual beliefs, the design of spiritual spaces or monk rooms within a dwelling, the current physical characteristics of the spiritual space within that residence, and the housing and well-being of the elderly. The factors and items are summarized and listed for the next step. A questionnaire survey was designed for data collection to confirm the factors and item requirements in the residences of elderly people in the research area, with the research subjects consisting of a group of elderly Thai people in the aforementioned four provinces. The questionnaire was designed in two sections by referring to the listed factors. The first section collected general participant data, such as gender, marital status, age, education, and economic status (5 questions). The second section was concerned with their opinion items in the characteristics of the elderly (8 questions), religious and spiritual beliefs (6 questions), paying attention to the design of religious spaces (4 questions), and well-being of the elderly (3 questions). The first section was measured by frequency (percentage) of the respondents, while the second was assessed using a five-point Likert scale from ‘strongly disagree’ to ‘strongly agree’. The questionnaire items are listed in Table 1. Table 1. Questionnaire items. Factor

Item

Characteristics of the elderly (CE) Physical characteristics CE1: Age CE2: Current health (walking and mobility) CE3: Current health (vision) CE4: Current health (hearing) CE5: Current health (smelling) CE6: Overall current health Social characteristics

CE7: Education level CE8: Average current income per month

Religious and spiritual beliefs (RSB)

RSB1: Belief in Thai style of religious space (continued)

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Table 1. (continued) Factor

Item RSB2: Belief in the Chinese style (Feng-Shui) of religious space RSB3: Belief in the spirit of ancestors of religious space RSB4: Belief in Thai style of placement of an amulet shelf RSB5: Belief in the Chinese style (Feng-Shui) of placement of an amulet shelf RSB6: Belief in the spirit of ancestors of placement of an amulet shelf

Paying attention to the design of religious spaces (PA)

PA1: Space pattern PA2: Location of the area PA3: Position and direction inside the residence PA4: Functional placement within the spiritual space

Well-being of the elderly (WB)

WB1: Satisfaction WB2: Happiness WB3: Delight

Reliability and validity tests were performed against the questionnaire items to ensure that the items were appropriate for the data collection. For the validity test, the researcher interviewed three experts in related fields to identify factors in order to confirm the results. The experts reviewed and commented on whether the item lists were accurate representations and ready to measure the opinions of elderly Thais. Where necessary, they also made more appropriate recommendations for the research context. The technique was useful in term of content validity and item clarity. For the reliability test, Cronbach’s alpha was used to check the reliability of the questionnaire by conducting a pilot group study from four provinces with sample groups of 30 individuals per province for a total of 120 participants, against which 21 items within the four factors were tested (measured with a five-point Likert scale) by computer statistical software. The result shows that the Cronbach’s alpha coefficient of factor of characteristics of the elderly (CE) was 0.870, religious and spiritual beliefs (RSB) was .0.898, paying attention to the design of religious spaces (PA) was .767, and well-being of the elderly (WB) was 0.844. All the factors were higher than 0.7, indicating that the questionnaire is reliable [12].

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3.2 Research Hypotheses Summaries of the factors and variables were categorized according to theories and the experts’ recommendations. This concept was presented as the conceptual research model (Fig. 1). Five research hypotheses were developed as follows: H1: Characteristics of the elderly have an effect on religious and spiritual beliefs. H2: Characteristics of the elderly have an effect on paying attention to the design of religious spaces. H3: Religious and spiritual beliefs have an effect on well-being of the elderly. H4: Paying attention to the design of religious spaces has an effect on the well-being of the elderly. H5: Religious and spiritual beliefs have a correlation with paying attention to the design of religious spaces.

Fig. 1. Conceptual research model.

3.3 Data Collection After designing the questionnaire, the researcher selected a group of Thai elderly people using a technique of convenience non-probability sampling which targeted Thai elderly people who stayed in residential buildings in Roi Et, Khon Kaen, Maha Sarakham, and Kalasin provinces which are located in the central region of northeast Thailand. During the 3-month (May-July 2021) data collection period, the researcher conducted face-toface and online interviews to explain the details of the questionnaire and ensure that the target group understood the study aims and objectives. Of the 2,000 questionnaires that were completed, 464 were discarded due to incomplete and biased responses, leaving 1,536 recognized as valid for analysis. The researcher then developed a model using the statistical technique called structural equation modeling (SEM) to study the causal factors of the model including four factors of CE (CE1 to CE8), RBS (RBS1 to RBS6), and PA (PA1-PA4) and then subsequently formulated the effect factors to test that the model fit with the SEM by including WB (WB1 to WB3) in the model.

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4 Results 4.1 Descriptive Results Data profiles of the 1,536 Thai elderly respondents were analyzed in terms of demographics as shown below in Table 2. Table 2. Descriptive results. Description

Frequency

Percentage

Gender - Man

636

41.4%

-Woman

881

57.4%

- LGBT

19

1.2%

- 60–69 years

1209

78.7%

- 70–79 years

309

20.1%

- 80–89 years

12

0.8%

6

0.4%

- Single

146

9.5%

- Married

928

60.4%

- Widowed

329

21.4%

- Divorced

133

8.7%

Age

- More than 90 years Marital status

Education level - Primary school

249

16.2%

- Secondary school

446

29.0%

82

5.3%

663

43.2%

96

6.3%

- Less than 10,000 baht/month

299

19.5%

- 10,000–30,000 baht/month

723

47.1%

- 30,001–50,000 baht/month

383

24.9%

11

0.7%

120

7.8%

- High school - Bachelor degree - Postgraduate degree Economic status (final income before retirement)

- 50,001–70,000 baht/month - Over 70,000 baht/month

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4.2 Structural Equation Modeling In this research, the modeling is structural equation modeling (SEM) [13] which is used to describe the causal relationships between variables and factors in environmental design that affect the well-being of the elderly in the research area. The modeling process began with exploratory factor analysis (EFA). The characteristic factors of the elderly were analyzed at this stage. EFA was applied by varimax rotation using statistical software [14]. The outputs showed that Kaiser-Meyer-Olkin (KMO) measure of sampling adequacy = 0.95 (KMO > 0.7) [15]. Bartlett’s test of sphericity had a significant value = 0.001 (less than .05). The result found that the factor of characteristics of the elderly were divided into two groups, physical characteristics and social characteristics. The researcher then analyzed the measurement model, which confirmed the factor group. Confirmatory factor analysis (CFA) [13] was used at this stage. The output showed that the model perfectly fit and the results were in accordance with the previous analysis. Finally, the process is an analysis to formulate a structural equation model [15]. The researcher created a model based on the conceptual model and analyzed it using statistical software. The outputs were not fit in the first analysis. The software outputs suggested that some variables should be deleted from the study model, including CE1, CE3, CE4, CE6, RBS1, RBS3, RBS4, RBS5, RBS6, PA1, PA2, PA3, and WB2. The author acted according to the suggestions and analysis. A second analysis was undertaken, with the outputs showing that the model fit with Chi-square = 16.464, df = 14, p = .286 (>.05), CMIN/df = 1.176 (< 3),RMSEA = .011, GFI = .997 (>.90) [16]. The SEM results in Fig. 2 and Table 3 show path coefficients in the standardized estimate of regression weight. Research hypotheses H1, H2, and H5 were significantly supported and H3 and H4 were rejected at the .05 level.

Fig. 2. Structural equation model of environmental living design for elderly well-being in Thai spiritual environments.

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Table 3. Results of the tested hypotheses. Hypothesis

Relationship

Standardized path coefficient

Result

Significant (p)

H1

Characteristics of the elderly → Religious and spiritual beliefs

.258

Supported

***

H2

Characteristics of the elderly → Paying attention to the design of religious spaces

.889

Supported

***

H3

Religious and spiritual beliefs → Well-being of the elderly

.053

Rejected

.554

H4

Paying attention to the design of religious spaces → Well-being of the elderly

−.106

Rejected

.281

H5

Religious and spiritual beliefs ←→ Paying attention to the design of religious spaces

1.747

Supported

.***

*** P 0.7), p-value = 0.001 (Sig.)

Results of EFA (Table 3) categorized the 32 variables of conflicts into 5 factors comprising factor 1 (pre-construction phase 1) consisting of PRE2, PRE1 and PRE5, factor 2 (pre-construction phase 2) consisting of PRE4, PRE3, PRE10 and PRE9, factor 3 (construction phase 1) consisting of CON3, CON2, CON11, CON4, CON7, CON12 and CON1, factor 4 (construction phase 2) consisting of CON6, POS6, CON16, CON10, CON8 and CON15, and factor 5 (all phases) consisting of POS3, POS2, CON5, CON13, POS4, POS5, CON14, PRE7, PRE6, PRE8, POS1 and CON9. 4.3 Confirmatory Factor Analysis Confirmatory factor analysis (CFA) is a model that measures the statistical results and confirms whether the variables are grouped into factors that fit perfectly or not [13]. In this study, first-order CFA was used to confirm whether the grouping of variables, classified into five factors according to EFA, fitted or not using statistical software. Results showed

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that the first-order CFA model did not fully fit and the software suggested eliminating some variables and factors. After eliminating the variables and factors suggested by the software, the model of first-order CFA fitted perfectly, with Chi-square = 8.653, df = 6, p = .194 (>.05), CMIN/DF = 1.442, GFI = .987 (>.90) and RMSEA = .045 (.05), CMIN/DF = 1.442, GFI = .987 and RMSEA = .045 (