Design of Steel Lighting System Support Pole Structures [1 ed.] 9780784483015

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ASCE STANDARD ASCE/SEI

72-21 Design of Steel Lighting System Support Pole Structures

ASCE STANDARD

ASCE/SEI

72-21

Design of Steel Lighting System Support Pole Structures

PUBLISHED BY THE AMERICAN SOCIETY OF CIVIL ENGINEERS

Library of Congress Cataloging-in-Publication Data Names: American Society of Civil Engineers, author. Title: Design of steel lighting system support pole structures. Description: Reston : American Society of Civil Engineers, 2021. | “ASCE/SEI 72-XX.” | Includes bibliographical references and index. | Summary: “Design of Steel Lighting System Support Pole Structures, ASCE/SEI 72-21, provides design parameters applicable to self-supporting structures, with base plates for installation on a concrete pier foundation, or as direct embedded, backfilled poles with the base section being either steel or concrete”– Provided by publisher. Identifiers: LCCN 2021022255 | ISBN 9780784415597 (soft cover) | ISBN 9780784483015 (pdf) Subjects: LCSH: Roads–Lighting–Supports–Design and construction–Standards. | Tubular steel structures–Design and construction–Standards. Classification: LCC TE228 .A523 2021 | DDC 625.7/9–dc23 LC record available at https://lccn.loc.gov/2021022255 Published by American Society of Civil Engineers 1801 Alexander Bell Drive Reston, Virginia, 20191-4382 www.asce.org/bookstore | ascelibrary.org This standard was developed by a consensus standards development process that has been accredited by the American National Standards Institute (ANSI). Accreditation by ANSI, a voluntary accreditation body representing public and private sector standards development organizations in the United States and abroad, signifies that the standards development process used by ASCE has met the ANSI requirements for openness, balance, consensus, and due process. While ASCE’s process is designed to promote standards that reflect a fair and reasoned consensus among all interested participants, while preserving the public health, safety, and welfare that is paramount to its mission, it has not made an independent assessment of and does not warrant the accuracy, completeness, suitability, or utility of any information, apparatus, product, or process discussed herein. ASCE does not intend, nor should anyone interpret, ASCE’s standards to replace the sound judgment of a competent professional, having knowledge and experience in the appropriate field(s) of practice, nor to substitute for the standard of care required of such professionals in interpreting and applying the contents of this standard. ASCE has no authority to enforce compliance with its standards and does not undertake to certify products for compliance or to render any professional services to any person or entity. ASCE disclaims any and all liability for any personal injury, property damage, financial loss, or other damages of any nature whatsoever, including without limitation any direct, indirect, special, exemplary, or consequential damages, resulting from any person’s use of, or reliance on, this standard. Any individual who relies on this standard assumes full responsibility for such use. ASCE and American Society of Civil Engineers—Registered in US Patent and Trademark Office. Photocopies and permissions. Permission to photocopy or reproduce material from ASCE publications can be requested by sending an email to [email protected] or by locating a title in ASCE’s Civil Engineering Database (http://cedb.asce.org) or ASCE Library (http://ascelibrary.org) and using the “Permissions” link. Errata: Errata, if any, can be found at http://dx.doi.org/10.1061/9780784415597. Copyright © 2021 by the American Society of Civil Engineers. All Rights Reserved. ISBN 978-0-7844-1559-7 (soft cover) ISBN 978-0-7844-8301-5 (PDF) Manufactured in the United States of America. 27 26

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ASCE STANDARDS

In 2016, the Board of Direction approved revisions to the ASCE Rules for Standards Committees to govern the writing and maintenance of standards developed by ASCE. All such standards are developed by a consensus standards process managed by the ASCE Codes and Standards Committee (CSC). The consensus process includes balloting by a balanced standards committee and reviewing during a public comment period. All standards are updated or reaffirmed by the same process every five to ten years. Requests for formal interpretations shall be processed in accordance with Section 7 of ASCE Rules for Standards Committees, which are available at www.asce.org. Errata, addenda, supplements, and interpretations, if any, for this standard can also be found at www.asce.org.

This standard has been prepared in accordance with recognized engineering principles and should not be used without the user’s competent knowledge for a given application. The publication of this standard by ASCE is not intended to warrant that the information contained therein is suitable for any general or specific use, and ASCE takes no position respecting the validity of patent rights. The user is advised that the determination of patent rights or risk of infringement is entirely their own responsibility. A complete list of currently available standards is available in the ASCE Library (http://ascelibrary.org/page/books/ s-standards)

Design of Steel Lighting System Support Pole Structures

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CONTENTS

PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ix

ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xi

1

GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 1 1

2

LOADS . 2.1 2.2 2.3 2.4 2.5 2.6 2.7

2.8

2.9 2.10

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STEEL DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Symbols . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Analysis . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Design Strength . . . . . . . . . . . . . . . . . . . . 3.5 Materials . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 Prequalified Structural Steel Material . . . 3.5.1.1 Supplementary Requirements 3.5.2 Other Structural Steel Material . . . . . . 3.5.3 Fasteners . . . . . . . . . . . . . . . . . . 3.5.4 Anchor Rods . . . . . . . . . . . . . . . . 3.5.5 Test Reports . . . . . . . . . . . . . . . .

Design of Steel Lighting System Support Pole Structures

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3.7 3.8 3.9

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3.11 3.12 4

FATIGUE 4.1 4.2 4.3 4.4

4.5

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vi

Corrosion Control . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.1 Members and Components. . . . . . . . . . . . . . . 3.6.2 Fasteners . . . . . . . . . . . . . . . . . . . . . . . . 3.6.3 Anchor Rods . . . . . . . . . . . . . . . . . . . . . . 3.6.4 Direct Embed Foundations. . . . . . . . . . . . . . . Member Properties . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.1 Round Members . . . . . . . . . . . . . . . . . . . . 3.7.2 Multisided Members . . . . . . . . . . . . . . . . . . Effective Yield Strengths . . . . . . . . . . . . . . . . . . . . . 3.8.1 Tubular Round Members . . . . . . . . . . . . . . . 3.8.2 Multisided Members . . . . . . . . . . . . . . . . . . Tubular Pole Design Strength . . . . . . . . . . . . . . . . . . . 3.9.1 Combined Axial Force, Shear, and Moments . . . . . 3.9.1.1 Nominal Axial Compressive Strength . . 3.9.1.2 Nominal Flexural Strength . . . . . . . . 3.9.1.3 Nominal Shear and Torsional Strengths . Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.10.1 Pole Slip Splices . . . . . . . . . . . . . . . . . . . . 3.10.2 Flange Plates . . . . . . . . . . . . . . . . . . . . . . 3.10.2.1 Socketed Connections . . . . . . . . . . 3.10.2.2 Butt-Welded Connections . . . . . . . . Components and Attachments . . . . . . . . . . . . . . . . . . . Anchor Rod Strength. . . . . . . . . . . . . . . . . . . . . . . .

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DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fatigue Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . Fatigue Thresholds . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 Pole Sections . . . . . . . . . . . . . . . . . . . . . . 4.4.2 Slip Splices. . . . . . . . . . . . . . . . . . . . . . . 4.4.3 Circumferential Welds . . . . . . . . . . . . . . . . . 4.4.4 Welded Attachments . . . . . . . . . . . . . . . . . . 4.4.5 Reinforced Holes and Cutouts . . . . . . . . . . . . . 4.4.6 Unreinforced Holes and Cutouts. . . . . . . . . . . . 4.4.7 Pole-to-Flange Plate Connections . . . . . . . . . . . 4.4.7.1 Effective Center Opening Diameter . . . 4.4.7.2 Stiffener Connection with Flange Plates. 4.4.8 Anchor Rods . . . . . . . . . . . . . . . . . . . . . . 4.4.9 Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . Miscellaneous Fatigue Strength Requirements . . . . . . . . . . 4.5.1 Pole Cross Sections . . . . . . . . . . . . . . . . . . 4.5.2 Holes and Cutouts . . . . . . . . . . . . . . . . . . . 4.5.3 Flange Plates . . . . . . . . . . . . . . . . . . . . . . 4.5.4 Butt-Welded Pole-to-Flange Plate Connections . . . . 4.5.5 Socketed Pole-to-Flange Plate Connections . . . . . . 4.5.6 Stiffened Pole-to-Flange Plate Connections . . . . . . 4.5.7 Foundations . . . . . . . . . . . . . . . . . . . . . .

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FOUNDATION DESIGN . . . . . . . . . . . . . . . . . . . . . . 5.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Symbols . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 General . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.1 Foundation Analysis . . . . . . . . . . . . . 5.3.2 Longitudinal Reinforcement . . . . . . . . . 5.3.3 Transverse Reinforcement . . . . . . . . . . 5.3.4 Shrinkage and Temperature Reinforcement . 5.4 Site Investigation . . . . . . . . . . . . . . . . . . . . . 5.4.1 Concrete Mix Design . . . . . . . . . . . . 5.4.2 Frost Depth. . . . . . . . . . . . . . . . . . 5.4.3 Expansive Soil . . . . . . . . . . . . . . . . 5.4.4 High Water Table . . . . . . . . . . . . . .

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STANDARD ASCE/SEI 72-21

5.5 5.6 5.7

5.8 5.9 5.10

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Drilled Shaft and Direct Embed Foundations . . . . . . . 5.5.1 Direct Embed Effective Foundation Diameter Mat Foundations . . . . . . . . . . . . . . . . . . . . . . Corrosion Control . . . . . . . . . . . . . . . . . . . . . 5.7.1 Direct Embed Steel Sections. . . . . . . . . . 5.7.1.1 Ground Sleeves. . . . . . . . . . 5.7.2 Direct Embed Precast Concrete Sections . . . Design Strength of Soil or Rock . . . . . . . . . . . . . Development of Anchor Rods . . . . . . . . . . . . . . . 5.9.1 Deformed Anchor Rods . . . . . . . . . . . . 5.9.2 Headed Anchor Rods . . . . . . . . . . . . . Seismic Considerations. . . . . . . . . . . . . . . . . . . 5.10.1 Longitudinal Reinforcement . . . . . . . . . . 5.10.2 Transverse Reinforcement . . . . . . . . . . . 5.10.3 Batter Piles . . . . . . . . . . . . . . . . . . .

FABRICATION . . 6.1 Scope . . 6.2 General . 6.3 Materials 6.4 Welding. 6.4.1 6.4.2 6.4.3 6.4.4 6.4.5 6.4.6 6.5 6.6 6.7 6.8 6.9 6.10 6.11

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7

INSTALLATION. . . . . . . . . . . . . . . . 7.1 Scope . . . . . . . . . . . . . . . . 7.2 General . . . . . . . . . . . . . . . 7.3 Direct Embed Foundations. . . . . 7.4 Drilled Shaft Foundations . . . . . 7.5 Anchor Rods . . . . . . . . . . . . 7.5.1 Anchor Rod Tightening 7.6 Pole Slip Splices . . . . . . . . . . 7.7 Pole Flange Plate Splices . . . . . 7.8 Miscellaneous Bolted Connections 7.9 Installation Tolerances . . . . . . .

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8

INSPECTIONS, ASSESSMENTS, AND MAINTENANCE 8.1 Scope . . . . . . . . . . . . . . . . . . . . . . . 8.2 Initial Construction Inspections . . . . . . . . . 8.3 Periodic Condition Assessments . . . . . . . . . 8.3.1 Evaluation of Dents in Steel Poles . 8.4 Damage Assessments . . . . . . . . . . . . . . 8.5 Additional Examination Requirements . . . . . 8.6 Maintenance . . . . . . . . . . . . . . . . . . . 8.6.1 Grouted Base Flange Plates . . . . .

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Design of Steel Lighting System Support Pole Structures

vii

APPENDIX A GEOTECHNICAL INVESTIGATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

43

APPENDIX B DAMAGE AND CONDITION ASSESSMENT EXAMPLES . . . . . . . . . . . . . . . . . . . . . . .

45

COMMENTARY TO STANDARD ASCE/SEI 72-21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C2 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C2.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C2.3 Classification of Structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C2.4 Combinations of Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C2.7.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C2.7.3 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . C2.7.5 Strength Design of Supporting Structures . . . . . . . . . . . . . . . C2.7.5.2.1 Effective Projected Area of Fixtures. C2.7.5.3 Design Wind Force Applied to Mounting Systems . C2.9.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C2.9.2 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . C3 Steel Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C3.3 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C3.4 Design Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C3.5 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C3.6.3 Anchor Rods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C3.12 Anchor Rod Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C4 Fatigue Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C4.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C4.3 Fatigue Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C4.4.7.2 Stiffener Connection with Flange Plates . . . . . . . C4.4.8 Anchor Rods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C4.4.9 Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C4.5.6 Stiffened Pole-to-Flange-Plate Connections . . . . . . . . . . . . . . C5 Foundation Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C5.3 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C5.4 Site Investigation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C5.10 Seismic Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C6 Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C6.3 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C6.4.6 Weld Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . C6.7 Punching Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C6.8 Forming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C6.9 Galvanizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C6.10 Additional Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C7 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C7.2 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C7.3 Direct Embed Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C7.5 Anchor Rods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C7.5.1 Anchor Rod Tightening . . . . . . . . . . . . . . . . . . . . . . . . C7.9 Installation Tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C8 Inspections, Assessments, and Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . C8.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C8.3 Periodic Condition Assessments . . . . . . . . . . . . . . . . . . . . . . . . . . . C8.3.1 Evaluation of Dents in Steel Poles . . . . . . . . . . . . . . . . . . C8.5 Additional Examination Requirements . . . . . . . . . . . . . . . . . . . . . . . C8.6 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C8.6.1 Grouted Base Flange Plates . . . . . . . . . . . . . . . . . . . . . .

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49 49 49 51 51 51 51 51 51 51 51 51 51 51 53 53 53 53 53 53 55 55 55 55 55 55 55 57 57 57 57 59 59 59 59 59 59 60 61 61 61 61 61 61 63 63 63 63 63 64 64

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

65

INDEX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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STANDARD ASCE/SEI 72-21

PREFACE

Lighting system support structures (primarily cold-formed singleand multi-pole tubular steel structures) differ from buildings in many performance-related characteristics. But, like buildings, lighting systems support structures are a critical public safety issue if they are not properly specified, designed, fabricated, installed, and actively inspected and routinely maintained by competent professionals. Current practices related to support structures of this type have been inconsistently developed and even more inconsistently applied, rendering many of those practices confusing—and even worse—ill-advised. The catastrophic failure of dozens of lighting system support structures around the country and the removal from service of hundreds more as a precaution in view of faulty or incomplete specifications for design, fabrication, installation, or ongoing maintenance prompted several members of ASCE’s Structural Engineering Institute to begin development of this document in the interest of improving public safety related to these structures. This consensus standard has been specifically written to unify the

core body of best practice knowledge available in the structural engineering community and to provide public and private agencies, practicing engineers, installers, and facility owners a consistent roadmap for the safe specification, design, fabrication, installation, and ongoing maintenance of structural supports of this type. The standard includes design parameters applicable to selfsupporting structures, with base plates for installation on a concrete pier foundation, or as direct embedded, backfilled poles with the base section being either steel or concrete. The standard provides for the proper specification and/or development of the various loads and load combinations to be applied to support structures of this type, as well as safe load resistance requirements. Special design issues for these structures include structure deflection, vibration, and fatigue. Issues related to fabrication and installation, as well as critical ongoing inspection and maintenance best practices, are also addressed.

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ACKNOWLEDGMENTS

The Structural Engineering Institute of ASCE acknowledges the devoted efforts of the Design of Steel Lighting System Support Structures Committee of the Codes and Activities Division. This group was composed of individuals with a variety of backgrounds and interests, including structure supply, consulting engineering, construction, and academic and education, who have contributed many hundreds of volunteer hours to develop this important standard. These committee members participated in developing this standard: Brian R. Reese, Chair Carl J. Macchietto, Vice-Chair Beth L. McCoy, Secretary George H. Brammer David G. Brinker Mark Dejong Martin L. De la Rosa John R. Erichsen Jerrod K. Franklin Travis Haskin David W. Hawkins Patrick Joyce Carl Kempkes

Design of Steel Lighting System Support Pole Structures

Simon W. Leland Corey Lines Ajay Kumar Mallik E. Mark Malouf Dylan Menes Michael R. Morel Vichien Nopratvarakorn Wesley J. Oliphant Aaron C. Poot Sougata Roy Tom Schepke James R. Sutphen Zach Thiemann

xi

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CHAPTER 1

GENERAL

1.1 SCOPE

Azimuth of Lighting Fixture: Direction in a horizontal plane that a lighting fixture is pointed to result in the desired lighting intensity. Ballast: Electrical device used for starting and regulating lighting fixtures, either integral to a lighting fixture or mounted remotely. Corrosive Soil: Soil identified in a geotechnical report as being corrosive to concrete or steel. Design Strength: Product of nominal strength and a resistance factor. Direct Embed Foundation: Steel pole or precast concrete section extending below grade and acting as the foundation. Discrete Appurtenance: Remote ballasts, speakers, signs, anticlimbing devices, or other similar attached items that may be modeled as a concentrated load. Effective Projected Area: Projected area of an object multiplied by a drag coefficient. Elastic Structural Analysis: Structural analysis based on the members of the structural model not exceeding their yield strength, resulting in the structure returning to its original geometry after the removal of loading. Equivalent Constant-Amplitude Stress Range: Constantamplitude nominal stress range that is theoretically equivalent, with respect to fatigue damage, to a lifetime of variable cyclic stress ranges from wind loading. Fatigue Failure: Visible crack growth from cyclic loading to an extent that the structure cannot be safely used in service.

Fatigue Limit State Static Pressure Range: Damageequivalent wind pressure for determining nominal stresses in structural members and components for the investigation of fatigue strength. Fatigue Threshold: Stress range below which a particular detail can withstand an infinite number of stress cycles without fatigue failure. Fixture Projected Area: Maximum fixture area projected onto a vertical plane within the range of working tilt angles prescribed by the fixture manufacturer. Flange Plate: Base or intermediate exterior flange welded to a tubular pole structure. Foundation: Substructure or extension of the superstructure designed to transmit reactions to the underlying soil or rock. Headed Anchor Rod: Deformed or a smooth bar with an attached end plate or nut. High-Risk Seismic Location: Location where the spectral response acceleration parameter at short periods defined by ASCE 7-16 exceeds 1.0. Lens: Surface from which light is emitted from a lighting fixture. Lighting Fixture: Enclosure with a lens to focus light in a specific direction. Lighting Fixture Mounting Plane: Vertical plane generally containing a group of lighting fixtures, or, for a single lighting fixture, the vertical plane normal to the azimuth of the lighting fixture. Lighting System: Combination of lighting fixtures and support members. Linear Appurtenance: Coax, conduit, lines, ladders, safety climb devices, step bolts, brackets, or other continuous or regularly spaced attachments that may be modeled as a distributed load. Mounting Components: Components used to mount a lighting fixture to a mounting pipe, frame, or other mounting system. Mounting System: Structural members used to support lighting fixtures on a supporting structure. Nominal Strength: Capacity of a structure or member to resist the effect of loads without a resistance factor applied. Nominal Stress: Stress in a member or component based on its cross-sectional properties without the use of magnification or stress concentration factors. Resistance Factor: Factor applied to the nominal strength to obtain the design strength that accounts for the unavoidable deviations of the nominal strength from the actual strength and for the manner and consequence of failure. Also referred to as a strength reduction factor. Service Basket: Mounting system that accommodates service personnel. Tilt Angle: Acute angle in a vertical plane between a line normal to a lens of a mounted lighting fixture and the horizon. Visor: Component used to minimize light scatter and/or to improve the aerodynamic profile of a lighting fixture.

Design of Steel Lighting System Support Pole Structures

1

Lighting system support structures have unique design and performance-related characteristics. This standard provides recognized literature for the structural design, fabrication, installation, inspection, and maintenance of cold-formed single and multiple-section tubular steel lighting system support pole structures. The standard is applicable to self-supporting poles with base plates supported on foundations with anchor rods, and to poles without a base plate supported on direct embedded, backfilled steel or concrete sections. This standard applies to round and symmetrical multisided cross section galvanized steel poles. Minimum design criteria are specified, including combinations of loadings, strength requirements, deflection limitations, and fatigue strength considerations. Guidelines for fabrication, installation, inspection, and maintenance are also provided. The design, fabrication, and installation provisions of this standard are intended for new structures. Means and methods for construction are not within the scope of this standard. 1.2 DEFINITIONS

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CHAPTER 2

LOADS

2.1 SCOPE This section provides minimum load requirements for the design of ground-supported steel lighting system support pole structures. Loads and appropriate load combinations, which have been developed to be used together, are set forth for strength design in accordance with the design specifications in Chapter 3. The design of lighting system support pole structures mounted on buildings or other structures is beyond the scope of this standard. The minimum load requirements of this standard are based on Minimum Design Loads and Associated Criteria for Buildings and Other Structures, ASCE 7-16 (ASCE 2017), LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, AASHTO LRFDLTS-1 (AASHTO 2015), and Structural Standard for Antenna Supporting Structures, Antennas and Small Wind Turbine Support Structures, ANSI/ TIA-222-H-1 (TIA 2019). When the requirements of this standard differ from the reference standards, this standard shall govern. Loads imposed during construction are not included in the scope of this standard. Construction loads are a function of the means and methods chosen by the erector. 2.2 SYMBOLS FOR CONSTRUCTION LOAD

other appurtenances shall be included in the determination of dead load. Dead loads of the structure shall be applied to the structural model either as uniform loads or as concentrated loads distributed to the nodes on the structural model. 2.6 LIVE LOAD Climbing facilities, including rung and rail climbing facilities, fall protection anchorages, step bolts, platforms, support rails, and service baskets, or other components, shall meet the requirements of TIA-222-H-1, Section 12.0. Live loads need not be considered in conjunction with the combination of loads specified in Section 2.4. 2.7 WIND LOAD 2.7.1 Scope The provisions of this section take into consideration the load magnification effects caused by wind gusts for extreme wind loading conditions. Section 2.9 provides design criteria for fatigue loading from natural wind gusts and vortex shedding. 2.7.2 Symbols for Wind Load

The weight of the structure, lighting fixtures, mounting components, mounting systems, climbing/working facilities, and all

Aa = Projected area of an appurtenance As = Projected area of a segment of the supporting structure C = Velocity coefficient Ca = Drag coefficient for an appurtenance Cd = Drag coefficient for a segment of the supporting structure Cdm = Drag coefficient for a multisided section Cdr = Drag coefficient for a round cross section d = Outside diameter for round cross sections and the outside corner-to-corner width for multisided sections EPA = Effective projected area (EPA)F = Effective projected area of a lighting fixture (EPA)N = Normal effective projected area of mounting system members (EPA)T = Transverse effective projected area of mounting system members Fa = Design wind force on appurtenances Fm = Design wind force on mounting systems Fs = Design wind force on a supporting structure Ft = Design wind force on lighting fixtures Fw = Total design wind force G = Gust effect factor HSS = Hollow structural sections Kd = Wind directionality factor Kz = Velocity pressure exposure coefficient Kzt = Topographic factor

Design of Steel Lighting System Support Pole Structures

3

D = Dead load Eh = Earthquake horizontal load Ev = Earthquake vertical load F = Fatigue load W = Wind load 2.3 CLASSIFICATION OF STRUCTURES Lighting system support structures shall be classified as Risk Category II structures as defined by ASCE 7-16, Section 1.5. 2.4 COMBINATIONS OF LOADS Structures, components, and foundations shall be designed such that their design strength equals or exceeds the effects of the factored loads in the following combinations: • • • • •

1.2D 0.9D 1.2D 0.9D 1.0F

+ 1.0W + 1.0W + 1.0Ev + 1.0Eh – 1.0Ev + 1.0Eh

2.5 DEAD LOAD

PFLS = Fatigue limit state static pressure range qz = Velocity pressure rc = Ratio of outside corner radius to half outside flat-to-flat width of a multisided section rm = Value of rc below which no reduction in drag coefficient from corner radius may be considered for a multisided section rr = Value of rc above which a multisided section may be considered as round for determining drag coefficients rs = Ratio of outside corner radius to outside flat-to-flat depth normal to the wind direction of a square or rectangular HSS member V = Basic wind speed, equal to a 3 s gust wind speed at 33 ft (10 m) above grade for ASCE 7-16, Exposure Category C 2.7.3 General Requirements The steps required for the determination of design wind forces are as follows: Step 1. Determine the basic wind speed, V, from ASCE 7-16, Section 26.5, or from the ASCE 7 Online Hazard Tool. For special wind regions, the basic wind speed shall be determined by the owner, the owner’s representative, or the authority having jurisdiction for a site-specific location, but shall not be less than 90 mi/h (40 m/s). Step 2. Determine the wind directionality factor, Kd, from Table 2-1. Step 3. Determine the exposure category from ASCE 7-16, Section 26.7, based on the surface roughness surrounding the structure. Exposure Category B shall not be considered. Step 4. Determine the topographic factor, Kzt, from ASCE 7-16, Section 26.8, at sites with abrupt changes in general topography such as isolated hills, escarpments, or ridges. For lighting system support structures on relatively level terrain, it shall be permissible to set Kzt to 1. Step 5. Determine the velocity pressure exposure coefficient, Kz, from ASCE 7-16, Section 26.10.1, based on the exposure category and the height above ground level. Step 6. Determine the velocity pressure, qz,: qz = 0.00256K z K zt K d V 2 ðpsfÞ qz = 0.613K z K zt K d V 2 ðN∕m2 Þ

(2-1) (2-1.SI)

where Kz = Velocity pressure exposure coefficient, Kzt = Topographic factor, Kd = Wind directionality factor, and V = Basic wind speed (mi/h, m/s). A reduction in air density caused by elevation above sea level shall not be considered.

Step 7: Calculate the design wind force, Fw, from Section 2.7.5. The design wind force applied to a section of a structure shall be permitted to be based on the velocity pressure at the midheight of the section. The section length considered to have uniform velocity pressure shall not exceed 6 ft (1.8 m). 2.7.4 Shielding No reductions in wind loading caused by shielding by buildings, other structures, or terrain features shall be considered. 2.7.5 Strength Design of Supporting Structures The total design wind force for the strength design of supporting structures shall include the sum of the horizontal design wind forces applied to the structure, lighting fixtures, mounting systems, and appurtenances. All lighting fixtures, mounting systems, and appurtenances shall be assumed to remain intact and attached to the supporting structure. Strength design shall be based on the wind directions resulting in the maximum responses. The total design wind force for the strength design of supporting structures, Fw, shall be determined from the following equation: Fw = Fs þ Ft þ Fm þ Fa where Fs = Design wind force applied to the supporting structure (from Section 2.7.5.1), Ft = Design wind force applied to lighting fixtures (from Section 2.7.5.2), Fm = Design wind force applied to mounting systems (from Section 2.7.5.3), and Fa = Design wind force applied to appurtenances (from Section 2.7.5.4). Lighting fixtures, mounting systems, and appurtenances projecting above the top of the supporting structure shall be modeled such that the proper overturning moment is applied to the supporting structure. Wind forces shall be applied either as uniform loads or as concentrated loads distributed to the nodes on the structural model in the direction of the wind under consideration. Wind forces shall be determined for the directions which produce the most critical load effects in accordance with Section 3.3. 2.7.5.1 Design Wind Force Applied to Supporting Structures The design wind force shall be applied in the direction of the wind under consideration. No shielding or reduction in wind forces shall be considered. The design wind force, Fs, applied to each segment shall be determined from the following equation: F s = qz GC d As

Table 2-1. Wind Directionality Factor, Kd. Structure type

Lighting system support pole structures with multiple lighting fixtures mounted in the same general vertical plane Lighting system support pole structures with a single lighting fixture or with multiple lighting fixtures lighting adjacent areas

4

Kd

0.85

0.95

(2-2)

(2-3)

where qz = Velocity pressure at the midheight of the segment under consideration, G = 1.14, Cd = Drag coefficient for the segment under consideration (from Table 2-2), and As = Projected area of segment under consideration, based on the outside diameter for round cross sections and the outside corner-to-corner width for multisided sections. STANDARD ASCE/SEI 72-21

Table 2-2. Drag Coefficients, Cd, for Pole Structures. Pole shape

Round 16-sided 0 ≤ rc < 0.26* 16-sided rc ≥ 0.26* 12-sided 8-sided 6-sided 4-sided

C ≤ 39 (5.3) mi/h-ft (m/s-m) (subcritical)

39 (5.3) < C < 78 (10.6) mi/h-ft (m/s-m) (transitional)

C ≥ 78 (10.6) mi/h-ft (m/s-m) (supercritical)

1.10 1.10

129/C1.30 1.37 + 1.08rc – C/145 – Crc/36*

0.45 0.83 – 1.08rc*

1.10

0.55 + (78.2 – C) / 71

0.55

1.20 1.20 1.90 1.90

10.8/C0.60 1.20 1.90 1.90

0.79 1.20 1.90 1.90

C = (KztKz)0.5 Vd (mi/h-ft, m/s-m) Kzt = Topographic factor Kz = Velocity pressure exposure coefficient V = 3 s gust basic wind speed d = Outside diameter for round cross sections and the outside corner-to-corner width for multisided sections *rc = Ratio of outside corner radius to half outside flat-to-flat width of the multisided section. *When the corner radius is unknown, rc shall be taken as no greater than 0.20. Notes: 1. For multisided pole sections with eight or more sides with a known corner radius, a reduced drag coefficient may be considered in accordance with the following (refer to the values of rm and rr in Table 2-3): rm = value of rc below which no reduction in drag coefficient may be considered for the multisided section, and rr = value of rc above which the multisided section may be considered as round for determining drag coefficients. When rc ≤ rm, no reduction is allowed. When rm < rc < rr, the drag coefficient may be determined by interpolation: Cd = Cdr + (Cdm – Cdr) [(rr – rc) / (rr – rm)] where Cdr is the drag coefficient tabulated for a round cross section, and Cdm is the drag coefficient tabulated above for the multisided section.

When rc ≥ rr, the cross section may be considered as round.

2. Linear interpolation, based on the inscribed angle of each side, between the drag coefficients determined for the pole shapes shown, may be used for other cross sections with more than 16 sides with the same rc values. The inscribed angle for a round cross section shall be considered to be 0°. 3. When linear appurtenances such as rung and rail climbing facilities, step bolts, safety climb systems, brackets, or other similar regularly spaced appurtenances are attached on the outside of a pole shaft, the drag coefficients calculated in accordance with this table shall be multiplied by 1.10. The effective projected area of attached appurtenances shall be included in the determination of the total design wind force in accordance with Section 2.7.5.4.

Table 2-3. Corner Radius Ratios for Reduced Drag Coefficients. Pole shape

16-sided 12-sided 8-sided 6-sided 4-sided

rm

rr

0.260 0.500 0.750 n/a n/a

0.625 0.750 1.00 n/a n/a

with respect to wind direction, except that the total effective projected area of all fixtures need not exceed the projected area of a solid polygon bounding the group of fixtures multiplied by a drag coefficient of 1.5. The design wind force, Ft, applied to each lighting fixture shall be determined from F t = qz GðEPAÞF

(2-4)

where qz = Velocity pressure at the centroid of the projected area of the lighting fixture under consideration, G = 1.14, and (EPA)F = Effective projected area of the fixture (from Section 2.7.5.2.1).

2.7.5.2 Design Wind Force Applied to Lighting Fixtures For the purposes of determining design wind forces, each lighting fixture shall be considered individually. Design wind forces shall be applied in the direction of the wind under consideration at the centroid of the projected area of the lighting fixture. No shielding or reduction in wind forces shall be considered from adjacent fixtures or from the orientation or tilt angle of a lighting fixture

2.7.5.2.1 Effective Projected Area of Fixtures Determination of the effective projected area, (EPA)F, of an individual fixture shall consider the geometry of the fixture with attachments (e.g., a visor and/or a ballast) and the fixture mounting components.

Design of Steel Lighting System Support Pole Structures

5

Wind tunnel tests are the preferred method to determine the effective projected area of fixtures. Wind tunnel tests shall be conducted in accordance with the appropriate provisions of ASCE 7-16, Chapter 31, and shall be certified by a qualified professional engineer. Wind tunnel tests shall also be conducted in accordance with the following requirements:

The design wind force, Fm, applied to each mounting system shall be determined from the following equation:

• Wind speed shall be between 90 and 100 mi/h, 40 and 45 m/s. • Wind tunnel tests shall be conducted with the tilt angle within the working range of the fixture that produces the maximum (EPA)F. • Wind direction shall vary in 10 degrees maximum increments to determine the maximum effective projected area of the lighting fixture and mounting components for a given tilt angle. • Effective projected area, (EPA)F, for the lighting fixture and mounting components shall be based on dividing the maximum vector resultant of the drag and side wind forces by the test velocity pressure. • Calculated effective projected area, (EPA)F, shall be used to determine wind forces in accordance with this standard without reduction as a result of the orientation or tilt angle of the lighting fixture with respect to wind direction.

qz = Velocity pressure at the centroid of the projected area of the mounting system, G = 1.14, (EPA)N = Effective projected area of all members projected onto the lighting fixture mounting plane, and (EPA)T = Effective projected area of all members projected onto a plane normal to the lighting fixture mounting plane.

In the absence of wind tunnel tests, the effective projected area, (EPA)F, of a lighting fixture shall be determined by applying a drag coefficient of 1.2 to the maximum fixture projected area, with attachments and mounting components, from any direction onto a vertical plane, considering the full range of working tilt angles of the lighting fixture. The value of Kd from Table 2-1 shall apply to the determination of wind forces, regardless of the method used to determine the effective projected area, (EPA)F, of a lighting fixture. 2.7.5.3 Design Wind Force Applied to Mounting Systems In determining design wind forces, each member of a mounting system shall be considered individually. Design wind forces shall be applied in the direction of the wind under consideration at the centroid of the projected area of the mounting system. No shielding or reduction in wind forces shall be considered, regardless of member location or spacing, except at the intersections of members or components, where only one surface at the intersection need be included in the calculation of wind forces. The intersection shall be considered as a flat member unless both intersecting members are round. It shall be permissible to consider a platform surface as a flat member with a height equal to the thickness of the platform. Each member supporting a platform surface must be considered individually as a mounting system member.

F m = qz G ½0.75ðEPAÞN þ 0.25ðEPAÞT 

(2-5)

where

The term [0.75(EPA)N + 0.25(EPA)T] shall not be less than (EPA)N or (EPA)T. The effective projected area of all mounting system members shall be determined using the drag coefficients for appurtenances specified in Section 2.7.5.4. 2.7.5.4 Design Wind Force Applied to Appurtenances In determining design wind forces, each appurtenance shall be considered individually. Linear appurtenances shall be considered with each segment of the supporting structure with the design wind force applied in the direction of the wind under consideration. The design wind force on discrete appurtenances shall be applied in the direction of the wind under consideration at the centroid of the projected area of the appurtenance. The design wind forces may vary with the wind direction under consideration. Shielding shall only be considered for the portion of an appurtenance that is mounted directly behind the pole or another member for a given wind direction. The design wind force, Fa, applied to each appurtenance shall be determined from the following equation: F a = qz GC a Aa

(2-6)

where qz = Velocity pressure at the centroid of the projected area of the appurtenance under consideration, G = 1.14, Ca = Drag coefficient (from Table 2-4) for the wind direction under consideration, and Aa = Projected area of appurtenance onto a plane normal to the direction of the wind. Ballasts mounted on the structure or mounting systems that are not considered integral to a lighting fixture shall be considered as appurtenances.

Table 2-4. Drag Coefficients, Ca, for General Appurtenances. Member type

Aspect ratio ≤ 2.5

Aspect ratio = 7

Aspect ratio ≥ 25

Flat Round Square or rectangular HSS

1.2 0.70 1.2 – 2.8rs ≥ 0.85

1.4 0.80 1.4 – 4.0rs ≥ 0.90

2.0 1.2 2.0 – 6.0rs ≥ 1.25

Notes: Aspect ratio is the overall length/width ratio in the plane normal to the wind direction. (It is independent of the spacing between support points of a linear appurtenance, and the pole segment length considered to have uniform wind load.) rs = Ratio of outside corner radius to outside flat-to-flat depth normal to the wind direction of a square or rectangular HSS member. The outside corner radius of an HSS square or rectangular member shall be assumed to be 2.25 times the nominal wall thickness of the HSS member unless actual corner radius measurements are available for the member. Linear interpolation may be used for aspect ratios other than those shown.

6

STANDARD ASCE/SEI 72-21

2.7.6 Strength Design of Attachments The design wind force for the strength design of individual mounting systems and appurtenances and their connections to the supporting structure shall be determined using a gust effect factor G of 1.0 and a directionality factor Kd of 0.95. No shielding or reduction in wind forces shall be considered. This section does not apply to the determination of wind forces for the strength design of a supporting structure. 2.8 EARTHQUAKE LOAD 2.8.1 Scope The provisions of this section are intended to ensure sufficient strength, ductility, stability, and postelastic energy dissipation for steel lighting system support pole structures to resist the effects of seismic ground motions defined by ASCE 7-16. The design criteria are based on the response characteristics of cantilevered steel lighting system support pole structures and a minimal level of ductility and postelastic energy dissipation in the structure; therefore, special detailing requirements are not required for steel lighting system support pole structures designed in accordance with this standard. All foundation and anchorage requirements applicable to steel lighting system support pole structures to ensure that the level of ductility and postelastic energy dissipation assumed for earthquake design are realized are specified in Section 2.8.5. Earthquake loads shall be applied to the structural model as concentrated loads distributed to the nodes on the model based on the location of the masses generating the earthquake loads. 2.8.2 Symbols for Earthquake Load

Vsms = Scaled portion of the base shear contributed by the mth mode wi = Portion of total gravity load assigned to level i WL = Weight of structure, excluding attachments Wm = Combined effective modal gravity load WS = Weight of structure above ground, including attachments WU = Weight of discrete attachments in the top third of the structure wz = Portion of total gravity load assigned to level under consideration z = Number designating the level under consideration ρ = ASCE 7-16 redundancy factor ϕim = Displacement amplitude at level i when vibrating in the mth mode ϕzm = Displacement amplitude at level z when vibrating in the mth mode Ω = ASCE 7-16 overstrength factor 2.8.3 General Requirements The steps required for the determination of earthquake loads are as follows: Step 1. Determine the values of SS and S1 from ASCE 7-16, Figures 22-1 to 22-8, and TL from ASCE 7-16, Figures 22-14 to 22-17. Alternatively, the values of SS, S1, and TL shall be permitted to be obtained from the ASCE 7 Online Hazard Tool or from a site response analysis in accordance with ASCE 7-16, Chapter 21. Step 2. Determine the appropriate Site Class from ASCE 7-16, Section 11.4.3. A site response analysis shall be performed for structures on Site Class F sites in accordance with ASCE 7-16, Section 21.1. Step 3. Determine the values of SDS and SD1 from ASCE 7-16, Section 11.4.5. When Site Class D is selected as the default site class and no site information is available, SDS shall not be less than 0.80SS. Step 4. Perform a structural analysis in accordance with either Section 2.8.4.2 (equivalent lateral force procedure) or Section 2.8.4.3 (modal response spectrum analysis) to determine the horizontal earthquake load, Eh. Step 5. Determine the vertical earthquake load, Ev, from ASCE 7-16, Equation (12.4-4a).

Cs = Seismic response coefficient Czm = Seismic force distribution factor for the mth mode E = Modulus of elasticity of steel, 29,000 ksi (200,000 MPa) Eh = Earthquake horizontal load Ev = Earthquake vertical load Fzm = Seismic forces at level z for the mth mode Fy = Specified minimum yield strength of steel pole material g = Acceleration by gravity, 386 in./s2 (9,810 mm/s2) H = Height of pole structure i = Number designating the level of the structure IA = Average moment of inertia of structure IB = Moment of inertia at base of structure Ie = Importance factor for earthquake loads IT = Moment of inertia at top of structure m = Subscript denoting quantities in the mth mode n = Number designating the uppermost level of the structure R = Response modification coefficient Ry = Ratio of expected yield strength to the minimum specified yield strength Sam = Spectral response acceleration for the period of the mth mode SDS = Design spectral response acceleration parameter at short periods SD1 = Design spectral response acceleration parameter at a period of 1 s SRSS = Square root of the sum of squares SS = 5% damped, spectral response acceleration parameter at short periods S1 = 5% damped, spectral response acceleration parameter at a period of 1 s T = Fundamental period of the structure TL = Long-period transition period Vsm = Portion of the base shear contributed by the mth mode

2.8.4.1 Structural Analysis Considerations Structural modeling shall be in accordance with Chapter 3. The base of the structure shall be considered as nonelastic (fixed). The weight considered for analysis shall include the unfactored weight of the structure above grade and all attachments, including lighting fixtures, mounting components, mounting systems, ballasts, lines, and appurtenances. The determination of an ASCE 7-16 seismic design category is not required for lighting system support structures. A horizontal distribution of seismic forces is not required. Consideration of interaction effects from multiple directions is not required. R shall be 1.5. Ie shall be 1.0 for Risk Category II structures. Foundation reactions caused by seismic load effects shall not be reduced for foundation design. ρ shall be 1.0. Ω shall be 1.5 (refer to Section 2.8.5).

Design of Steel Lighting System Support Pole Structures

7

2.8.4 Analysis Considerations The considerations outlined in Sections 2.8.4.1, 2.8.4.2, and 2.8.4.3 shall apply to the structural analysis.

Drift limitations do not apply to lighting system support structures. 2.8.4.2 Equivalent Lateral Force Procedure The horizontal earthquake load, Eh, shall be determined in accordance with this section. The seismic base shear shall be determined from ASCE 7-16, Equation (12.8-1). The effective seismic weight shall be equal to WS. T shall be determined from ASCE 7-16, Section 15.4.4, or this standard, Section 2.8.4.2.1. Cs shall be determined from ASCE 7-16, Equations (12.8-2), (12.8-3), and (12.8-4), and shall not be less than 0.03 or the value from ASCE 7-16, Equations (15.4-1) and (15.4-2). The vertical distribution of forces shall be determined from ASCE 7-16, Section 12.8.3. A static analysis shall be performed without dead loads. The maximum load effects shall be considered as Eh and shall be applied with factored dead loads to the structural model for an elastic static analysis in accordance with Section 3.3. 2.8.4.2.1 Fundamental Period Calculation The fundamental period, T, of a lighting system support pole structure shall be determined using the structural properties and deformation characteristics of the structure. Alternatively, the fundamental period is permitted to be computed as sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi H 3 ðW U þ 0.236W L Þ seconds (2-7) T = 6.28 3gEI A where H = Height of pole structure above grade (in, mm), WL = WS – WU (kips, N), WS = Total weight of the structure above grade, including all attachments (kips, N), WU = Weight of discrete attachments in the top third of structure (kips, N), g = Acceleration by gravity (in/s2, mm/s2), E = Modulus of elasticity of structure material (ksi, MPa), IA = (IT + IB)/2 (in4, mm4), IT = Moment of inertia of pole cross section at top of structure (in4, mm4), and IB = Moment of inertia of pole cross section at base of structure (in4, mm4). 2.8.4.3 Modal Response Spectrum Analysis The horizontal earthquake load, Eh, shall be determined in accordance with this section. The natural modes of vibration for the structure, including the period of each mode, the modal shape vectors, and the effective modal gravity load, shall be determined from an analysis based on a structural model representing the spatial distribution of mass and stiffness throughout the structure. The design response spectrum shall be determined from ASCE 7-16, Section 11.4.6. The base shear contributed by each mode shall be determined from Section 2.8.4.3.1. The analysis shall include a sufficient number of modes to obtain a combined effective modal gravity load of at least 90% of the total gravity load (refer to Section 2.8.4.3.1). The combined base shear from all modes considered shall be determined by the SRSS method. The base shear contributed for each mode shall be scaled, when required herein, by comparing the combined base shear from all modes to the seismic base shear from the equivalent 8

lateral force method of Section 2.8.4.2. When the combined base shear is less than 85% of the total seismic force from the equivalent lateral force method, the base shear contributed by each mode shall be multiplied by 0.85 times the ratio of the seismic base shear from the equivalent lateral force method to the combined base shear from all modes. The seismic forces for each mode to be applied at each level of the structure as external forces shall be determined from Section 2.8.4.3.2 using the scaled modal base shear for each mode. A static analysis in accordance with Section 3.3 shall be performed for each mode without dead loads. The load effects determined from each mode shall be combined using the SRSS method. The maximum resulting load effects shall be considered as Eh and shall be added to the load effects from factored dead loads determined from an elastic static analysis in accordance with Section 3.3. Eh shall be considered additive to dead load effects regardless of the sign of the dead load effects. 2.8.4.3.1 Base Shear and Modal Mass Contributed by Each Mode The base shear, Vsm, contributed by each mode shall be determined from the following equations: Vsm =

Sam Wm I e R

 Pn Wm =

2 w ϕ i = 1 i im Pn 2 i = 1 wi ϕim

(2-8)

(2-9)

where Sam = Spectral response acceleration from the design response spectrum for the period of the mth mode, Wm = Combined effective modal gravity load, Ie = Importance factor, R = Response modification coefficient, equal to 1.5, n = Number of levels comprising the structural model, i = Number designating the level of the structure, starting from the base, to the uppermost level, m = Subscript denoting quantities in the mth mode, wi = Portion of total gravity load assigned to level i, and ϕim = Displacement amplitude (+ or –) at the ith level of the structure when vibrating in its mth mode. 2.8.4.3.2 Seismic Forces Contributed by Each Mode The seismic forces, Fzm, at each level z of the structure, for each mode m, shall be determined from the following equation: F zm = C zm V sms

(2-10)

where C zm = Pwn z φwzmφ , i=1

i im

Vsms = Scaled portion of the base shear contributed by the mth mode, z = Number designating the level under consideration, n = Number representing the uppermost level of the structure, i = Number designating the level of the structure, starting from the base, to the uppermost level, wz = Portion of total gravity load assigned to level z, wi = Portion of total gravity load assigned to level i, ϕzm = Displacement amplitude (+ or –) at level z when vibrating in the mth mode, and ϕim = Displacement amplitude (+ or –) at level i when vibrating in the mth mode. 2.8.5 Overstrength Factor An overstrength factor, Ω, of 1.5 shall be applied to the reactions from the earthquake loading STANDARD ASCE/SEI 72-21

distance that lighting fixtures or other appurtenances may extend above the pole tip.

Table 2-5. Ry Values for Steel Materials. Minimum design yield strength, Fy (ksi, Mpa)

Fy < 36 (248) 36 (248) ≤ Fy ≤ 42 (290) Fy > 42 (290)

HSS shapes

Plates/coils

1.5 1.4 1.3

1.3 1.3 1.1

Note: Ry is the ratio of expected yield strength to the minimum specified yield strength.

combinations from Section 2.4 in determining the required design strength of anchorages in accordance with Section 3.12, the strength of precast concrete direct embed slip splices in accordance with Section 5.5, and the development of anchorages in accordance with Section 5.9. When the actual material specification used to fabricate the base pole section is known, the overstrength factor need not exceed the ratio of the expected moment capacity of the base pole section at grade to the governing overturning moment reaction from the earthquake loading combinations. The expected moment capacity shall be determined by multiplying the nominal flexural strength (i.e., without a resistance factor) of the base pole section at grade by Ry from Table 2-5. Ry from Table 2-5 represents the ratio of the expected yield strength of a steel section to the minimum yield strength specified for the section. 2.9 FATIGUE LOAD 2.9.1 Scope The provisions of this standard are intended to consider fatigue loading from natural wind gusts and vortex shedding. The fatigue loads specified are based on a damage-equivalent static pressure range to simulate fatigue loading from variable wind conditions over the life of a structure. The nominal stresses from the fatigue loads specified represent an equivalent constantamplitude stress range and shall not exceed the fatigue thresholds specified in Chapter 4. The provisions for fatigue design are required for pole structures 55 ft (16.8 m) or greater in height. The height of a pole shall be defined as the pole tip elevation above grade, not including the

Design of Steel Lighting System Support Pole Structures

2.9.2 General Requirements The fatigue limit state static pressure range, PFLS, shall be 7.2 psf (0.35 kPa) unless otherwise specified by the owner or the owner’s representative. The steps for the investigation for fatigue strength are as follows. Step 1. Determine the wind directionality factor, Kd, from Table 2-1. Step 2. Determine the fatigue load from Section 2.7, with the following modifications: (1) Substituting the term KdPFLS for the term qzG in Sections 2.7.5.1, 2.7.5.2, 2.7.5.3, and 2.7.5.4 (i.e., for calculating all design wind forces applied to the supporting structure, lighting fixtures, mounting systems, and appurtenances). (2) Determining the drag coefficient, Cd, from Table 2-2 (for calculating the effective projected areas of the supporting structure) based on subcritical flow conditions (i.e., C ≤ 39). Step 3. Perform an elastic structural analysis in accordance with Section 3.3, using the fatigue loads with a load factor of 1.0 to determine nominal stresses. The nominal stresses shall be considered as equivalent constant-amplitude stress ranges. Step 4. Compare the absolute values of the nominal stresses from the analysis to the constant-amplitude fatigue threshold values in accordance with Chapter 4. 2.10 STIFFNESS REQUIREMENT 2.10.1 Scope This section provides a minimum stiffness requirement for steel lighting system support pole structures under wind loading. 2.10.2 General Requirements The steps for the determination of stiffness requirements are as follows. Step 1. Determine wind load from Section 2.7 using a 60 mi/h (97 km/h) basic wind speed, V, in place of the basic wind speed determined from Step 1 in Section 2.7.3. Step 2. Perform an elastic structural analysis in accordance with Section 3.3, using a load factor of 1.0 for dead and wind loads. The maximum horizontal displacement of the structure shall not exceed 4% of the structure height.

9

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CHAPTER 3

STEEL DESIGN

3.1 SCOPE This chapter provides the minimum strength requirements for steel lighting system support pole structures. The minimum strength requirements of this standard are based on ANSI/AISC 360-16, Specification for Structural Steel Buildings (AISC 2016), AASHTO LRFDLTS-1, LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals (AASHTO 2015), and TIA-222-H-1, Structural Standard for Antenna Supporting Structures, Antennas and Small Wind Turbine Support Structures (TIA 2019). When the requirements of this standard differ from the reference standards, this standard shall govern. Fatigue design requirements are addressed in Chapter 4. Foundation design requirements are addressed in Chapter 5. 3.2 SYMBOLS Ag = Gross area of an anchor rod An = Tensile stress area of an anchor rod Ct = Torsional constant D = Outer diameter of a round member or outside flat-to-flat width of a multisided member d = Nominal diameter of an anchor rod dn = Tensile root diameter of an anchor rod E = Modulus of elasticity of steel, 29,000 ksi (200 GPa) Fnt = Critical shear stress for torsion Fnv = Critical shear stress for direct shear Fu = Specified minimum tensile strength Fy = Specified minimum yield strength F′y = Effective yield strength Iar = Clear distance from top of concrete to the bottom of an anchor rod leveling nut Lp = Height of a tubular pole structure Mn = Nominal flexural strength Mu = Flexural moment from factored loads n = Number of threads per inch Pn = Nominal axial strength Pu = Axial force from factored loads Puc = Anchor rod axial compression force from factored loads Put = Anchor rod axial tension force from factored loads Rnc = Nominal compression yield strength of an anchor rod Rnt = Nominal tensile strength of an anchor rod Rnv = Nominal shear rupture strength of an anchor rod Rnvc = Nominal shear yield strength of an anchor rod S = Minimum elastic section modulus t = Design wall thickness Tn = Nominal torsional strength Tu = Torsional moment from factored loads Vn = Nominal shear strength Vu = Transverse shear force from factored loads Design of Steel Lighting System Support Pole Structures

w = Flat width of a multisided member Z = Plastic section modulus ϕc = Resistance factor for compression or for shear occurring with compression ϕf = Resistance factor for flexure ϕr = Resistance factor for torsion ϕt = Resistance factor for tension ϕv = Resistance factor for shear occurring with tension 3.3 ANALYSIS Load effects on the structural system shall be determined by methods of structural analysis that take into account equilibrium, general stability, geometric compatibility, and material properties. The supporting structure shall be analyzed using geometrically nonlinear elastic stress analysis methods. The analysis shall take into account the effects of displacements on member forces (P-delta effects). The minimum acceptable analysis model for a tubular pole structure is an elastic three-dimensional beam-column model producing displacements, moments, shears, and axial forces in the structure. Unless the model considers second-order effects within each element, the minimum number of beam-column elements shall be equal to five per pole section, and the maximum beam-column element length shall not exceed 6 ft (1.8 m). Foundation displacements shall be permitted to be ignored for the strength and stiffness analysis of pole structures when the lateral displacement of drilled shafts or direct embed foundations at grade level is less than or equal to 0.75 in. (19 mm) for the stiffness requirement loading condition specified in Section 2.10 and for mat foundations that limit the maximum eccentricity of loading in accordance with Section 5.6. It shall be permissible to model flange plates as nodes on the beam-column model without additional flexibility when the plates are designed based on rigid plate behavior. Given the modeling complexity (e.g., meshing, element interconnection, and boundary conditions) of plate, shell, and solid element models, the stresses obtained from such models shall not be less than the stresses obtained from a beam-column model. 3.4 DESIGN STRENGTH The supporting structure and all structural components shall have sufficient design strength and stability to support the load effects from the combination of loads defined in Chapter 2. The design strength of tubular pole members shall be determined in accordance with Section 3.9. The design strength of other structural members, components, and connections shall be determined from the AISC, AASHTO, or TIA reference standards. 11

Design strength shall be based on the minimum nominal values for yield strength, Fy, and ultimate tensile strength, Fu, according to the appropriate ASTM specification for the type and grade of steel specified. The design strength of flange plates shall be determined in accordance with recognized criteria, accounting for the elastic or plastic distribution of normal and transverse bending stresses and the reduction in stiffness and strength from flange plate center openings. Design strengths based on testing shall also be permitted. 3.5 MATERIALS The minimum thickness for all members and components shall be 0.11 in. (2.8 mm), [i.e., the minimum measured thickness for nominal 11 gauge (0.125 in.) material]. 3.5.1 Prequalified Structural Steel Material The steel material standards listed in the AISC, AASHTO, and TIA reference standards, with the supplementary requirements of Section 3.5.1.1, shall be considered prequalified for use with this standard. 3.5.1.1 Supplementary Requirements Steel material conform to the following supplementary requirements:

shall

1. Structural steel for round pole sections with wall thicknesses greater than 0.5 in. (13 mm) and multisided pole sections of any wall thickness shall have a minimum Charpy V-notch impact strength in the longitudinal direction of 15 ft-lb (20 J) of absorbed energy at a test temperature of –20 °F determined in accordance with ASTM A370-19. The same supplementary requirements shall apply to flange plates welded to the pole sections specified earlier. 2. Tensile strength for round or multisided pole material shall not exceed 100 ksi (690 MPa). 3. Silicon content of round or multisided pole material shall not exceed 0.06%.

3.5.4 Anchor Rods Anchor rods shall conform to ASTM F1554-18 (smooth bars), A615-20 (deformed bars), or A70616 (deformed bars) or other anchor rod material recognized by the AISC, AASHTO, or TIA reference standards. Anchor rod material with specified minimum yield strengths greater than 55 ksi (380 MPa) shall have a minimum Charpy V-notch impact strength in the longitudinal direction of 15 ft-lb (20 J) of absorbed energy at a test temperature of –20 °F in accordance with ASTM A370-19. Testing frequency shall be in accordance with ASTM A673-17. When heat treatment is performed after threading or bending, impact tests shall be performed at Test Frequency P (Piece Testing) on the finished anchor rods. For other anchor rods, impact tests shall be performed either at Test Frequency H (Heat Lot Testing) on the bar stock used for the anchor rods or at Test Frequency P (Piece Testing) on the finished anchor rods. 3.5.5 Test Reports Certified mill test reports or certified reports of tests by the fabricator or a testing laboratory in accordance with ASTM A6-19 or A568-19, as applicable, shall constitute sufficient evidence of conformity to the requirements of this standard. 3.6 CORROSION CONTROL 3.6.1 Members and Components Steel members and components shall be hot-dip galvanized in accordance with ASTM A123-17. Tubular steel poles shall be considered as a structural shape for determining the required minimum coating thickness. Other corrosion control methods suitable for the application and site conditions shall be permitted when equivalent to the corrosion control methods specified in this standard. 3.6.2 Fasteners High-strength structural bolts [minimum specified tensile strengths between 120 ksi and 150 ksi (830 MPa and 1,040 MPa)] shall be coated in accordance with ASTM F3125-19. Other fasteners with lower tensile strengths shall be coated in accordance with ASTM B695-16 Class 55 (mechanically deposited zinc coating) or F2329-15 (hotdip zinc coating).

3.5.2 Other Structural Steel Material Steel material suitable for the application and site conditions shall be permitted when the following criteria are satisfied in addition to the supplementary requirements from Section 3.5.1.1:

3.6.3 Anchor Rods Anchor rods shall be coated in accordance with ASTM F2329-15. The minimum length of galvanizing on the exposed ends of anchor rods shall be

1. Conformance to the applicable requirements of ASTM A6-19 or A568-19. 2. Elongation shall not be less than 14%. 3. Carbon equivalent shall not exceed 0.45 for welded applications and 0.65 for other applications, as calculated by

• Upper 12 in. (300 mm) for nominal diameters ≤1.25 in. (32 mm), • Upper 16 in. (410 mm) for nominal diameters >1.25 in. (32 mm) but ≤1.5 in. (38 mm), and • Upper 20 in. (510 mm) for nominal diameters >1.50 in. (38 mm).

C þ ðMn þ SiÞ∕6 þ ðCr þ Mo þ VÞ∕5 þ ðNi þ CuÞ∕15: 4. For welded applications, appropriate welding procedures based on the material properties and the welding process are followed in accordance with AWS D1.1-15, Structural Welding Code–Steel, including but not limited to minimum preheat temperatures. 3.5.3 Fasteners High-strength structural bolts [minimum specified tensile strengths between 120 ksi and 150 ksi (830 MPa and 1,040 MPa)] shall conform to ASTM F3125-19. Lower-strength fasteners shall conform to fasteners recognized by AISC, AASHTO, or TIA. 12

Alternatively, it shall be permissible to galvanize the entire anchor rod length. 3.6.4 Direct Embed Foundations Corrosion control for direct embed poles is addressed in Section 5.7. 3.7 MEMBER PROPERTIES The design wall thickness shall be taken as equal to the nominal wall thickness for pole members fabricated from plate or coil. The design wall thickness of hollow structural sections shall be taken as 0.93 times the nominal wall thickness, except for sections produced according to ASTM A1065-18 or A1085-15, where the design wall thickness shall be permitted to equal the nominal wall thickness. STANDARD ASCE/SEI 72-21

qffiffiffiffiffiffiffiffiffiffiffi F y ∕E ðw∕tÞ ≤ 2.14; qffiffiffiffiffiffiffiffiffiffiffi F y0 = 1.578 F y ½1.0 − 0.233 F y ∕E ðw∕tÞ

The design strength of a pole member at holes and cutouts shall be determined considering the opening in the pole wall and the reinforcing around the opening, when provided. Refer to Chapter 4 for additional requirements for structures designed for fatigue. 3.7.1 Round Members The diameter-to-design wall thickness ratio, D/t, shall not exceed 300. 3.7.2 Multisided Members The flat width-to-design wall pffiffiffiffiffiffiffiffiffiffiffi thickness ratio, w/t, shall not exceed 2.14 E∕F y . The inside corner bend radius of a multisided pole member shall not be less than 3 times the nominal material thickness of the pole member. Refer to Chapter 4 for additional requirements for structures designed for fatigue. The inside corner bend radius for determining the flat width-to-design wall thickness ratio, w/t, of a multisided pole member for determining strength in accordance with this standard shall not exceed four times the nominal material thickness of the pole member. The inside corner bend radius for determining drag coefficients and strengths for multisided pole members shall be assumed to be 1.5t when the inside corner bend radius is not known. A minimum of eight sides shall be used for multisided pole members. Refer to Chapter 4 for additional requirements for structures designed for fatigue. 3.8 EFFECTIVE YIELD STRENGTHS The strength of a pole member shall be based on the effective yield strength determined in accordance with this section. 3.8.1 Tubular Round Members The effective yield strength, F′y, for a tubular round member shall be determined from the following equations: For D∕t ≤ 0.114E∕F y ;

F y0

= Fy

For 0.114E∕F y < D∕t ≤ 0.448E∕F y ; F y0 = ½ð0.0379E∕F y Þ∕ðD∕tÞ þ 2∕3F y For 0.448E∕F y < D∕t ≤ 300;

(3-1) (3-2)

F y0 = 0.337E∕ðD∕tÞ (3-3)

For 0.836 ≤

12-sided members: qffiffiffiffiffiffiffiffiffiffiffi For F y ∕E ðw∕tÞ < 0.992;

0

F y = 1.26F y

qffiffiffiffiffiffiffiffiffiffiffi F y ∕E ðw∕tÞ ≤ 2.14; qffiffiffiffiffiffiffiffiffiffiffi F y0 = 1.611F y ½1.0 – 0.220 F y ∕E ðw∕tÞ

(3-7)

(3-8)

For 0.992 ≤

8-sided members: qffiffiffiffiffiffiffiffiffiffiffi For F y ∕E ðw∕tÞ < 1.10;

F y0 = 1.24F y

qffiffiffiffiffiffiffiffiffiffiffi F y ∕E ðw∕tÞ ≤ 2.14; qffiffiffiffiffiffiffiffiffiffiffi F y0 = 1.578F y ½1.0 – 0.194 F y ∕E ðw∕tÞ

(3-9)

(3-10)

For 1.10 ≤

(3-11)

where Fy = Specified minimum yield strength, E = Modulus of elasticity, and w/t = Flat width-to-design wall thickness ratio. Members with more than 18 sides shall be considered as round, using an outside diameter equal to the outside flat-to-flat width of the member. 3.9 TUBULAR POLE DESIGN STRENGTH 3.9.1 Combined Axial Force, Shear, and Moments The design strength of a tubular pole member shall satisfy the following interaction equation:          Pu   M u       þ  þ  V u þ T u  ≤ 1.0 (3-12) ϕ P  ϕ M  ϕ V  ϕ T  c n f n v n r n

where

where

D/t = Diameter-to-design wall thickness ratio, E = Modulus of elasticity, and Fy = Specified minimum yield strength.

Pu = Axial compressive force from factored loads, Pn = Nominal axial compressive strength (from Section 3.9.1.1), Mu = Flexural moment from factored loads, Mn = Nominal flexural strength (from Section 3.9.1.2), Vu = Transverse shear force from factored loads, Vn = Nominal shear strength (from Section 3.9.1.3), Tu = Torsional moment from factored loads, Tn = Nominal torsional strength (from Section 3.9.1.3), ϕc = 0.90 = Resistance factor for axial compression, ϕf = 0.90 = Resistance factor for flexure, ϕv = 0.90 = Resistance factor for shear, and ϕr = 0.95 = Resistance factor for torsion.

3.8.2 Multisided Members The effective yield strength, F y0 , for a multisided member shall be determined from the following equations: 18-sided members: qffiffiffiffiffiffiffiffiffiffiffi For F y ∕E ðw∕tÞ < 0.759; Fy0 = 1.27 F y (3-4) qffiffiffiffiffiffiffiffiffiffiffi F y ∕E ðw∕tÞ ≤ 2.14; qffiffiffiffiffiffiffiffiffiffiffi Fy0 = 1.56 F y ½1.0 − 0.245 F y ∕E ðw∕tÞ

For 0.759 ≤

(3-5)

16-sided members: qffiffiffiffiffiffiffiffiffiffiffi For F y ∕E ðw∕tÞ < 0.836;

3.9.1.1 Nominal Axial Compressive Strength The nominal axial compressive strength, Pn, of tubular round and multisided members shall be determined from the following equation: Pn = F y0 Ag but not greater than F y Ag

F y0

= 1.27 F y

(3-6)

Design of Steel Lighting System Support Pole Structures

(3-13)

where

13

Table 3-1. Coefficient m for Tubular Pole Members.

F′y = Effective yield strength (from Section 3.8), Fy = Specified minimum yield strength, and Ag = Gross area of cross section.

Shape

m

3.9.1.2 Nominal Flexural Strength

For

D E ≤ 0.0714 ; t Fy

M n = Fy Z

E D E < ≤ 0.309 ; Fy t Fy   0.0207E Mn = þ 1 Fy S ðD∕tÞF y   E D 0.330E S For 0.309 < ≤ 300; M n = Fy t D∕t For 0.0714

(3-14) D = Outer diameter, t = Design wall thickness, and m = coefficient defined in Table 3-1. (3-15)

where D/t = Diameter-to-design wall thickness ratio, E = Modulus of elasticity, Fy = Specified minimum yield strength, Z = Plastic section modulus, and S = Elastic section modulus.

(3-16)

where F y0 is the effective yield strength as determined from Section 3.8, and S is the minimum elastic section modulus. 3.9.1.3 Nominal Shear and Torsional Strengths 3.9.1.3.1 Tubular Round Members The nominal shear strength, Vn, and nominal torsional strength, Tn, for tubular round members shall be determined from the following equations: V n = 0.5 F nv Ag

(3-17)

T n = F nt C t

(3-18)

where C t = mtðD − tÞ2 Fnv = greater of following but shall not exceed 0.6Fy: qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ð1.60EÞ∕ð ðLp ∕DÞðD∕tÞ5∕4 Þ and ð0.78EÞ∕ððD∕tÞ3∕2 Þ Fnt = greater of following but shall not exceed 0.6Fy: qffiffiffiffiffiffiffiffiffiffiffiffiffi ð1.23EÞ∕ð ðLp ∕DðD∕tÞ5∕4 Þ and ð0.60EÞ∕ððD∕tÞ3∕2 Þ Ag = Gross area of cross section, Fy = Specified minimum yield strength, E = Modulus of elasticity, Lp = Height of structure,

14

3.9.1.3.2 Multisided Members The nominal shear strength, Vn, and nominal torsional strength, Tn, for multisided members shall be determined from the following equations: V n = 0.6F y Ag ∕2

(3-19)

T n = 0.6F y C t

(3-20)

where

3.9.1.2.2 Multisided Members The nominal flexural strength for multisided members, Mn, shall be determined from the following equation: M n = F y0 S

1.57 1.58 1.59 1.61 1.66

Round 18-sided 16-sided 12-sided 8-sided

3.9.1.2.1 Tubular Round Members The nominal flexural strength for tubular round members, Mn, shall be determined from the following equations:

Ct = mt(D – t)2 Fy = Specified minimum yield strength, Ag = Gross area of cross section, and t = Design wall thickness, and m = Coefficient defined in Table 3-1. 3.10 CONNECTIONS Bolted connections shall be provided with a nut-locking device, except for high-strength bolted connections tightened to at least 70% of their ultimate tensile strength. Flange bolts and anchor rod nuts tightened in accordance with Chapter 7 do not require a nut-locking device. 3.10.1 Pole Slip Splices The nominal design length of a slip splice shall be determined considering manufacturing tolerances to result in a minimum installed slip splice lap length equal to 1.5 times the inside width of the base of the upper section at the splice. The inside width shall be measured between flats for multisided cross sections. Longitudinal seam welds for tubular pole sections shall have a 60% minimum penetration, except in the following areas, where the seam welds shall be complete joint penetration welds: longitudinal seam welds within 6 in. (150 mm) of circumferential welds or flange plate welds, and longitudinal seam welds for the outer section at a slip splice over the maximum slip splice lap length plus 6 in. (150 mm). Provisions for applying jacking forces to a slip splice shall be provided on the pole sections at each slip splice. Refer to Chapter 7 for installation requirements. 3.10.2 Flange Plates Flange plates used for connecting pole sections or for base flange plates used to connect to foundations shall satisfy the thickness requirement for plate bending and shear. The thickness of flange plates without stiffeners shall not be less than the connection bolt or anchor rod diameter, except that for anchor rods with specified minimum

STANDARD ASCE/SEI 72-21

yield strength not exceeding 75 ksi (520 MPa), the thickness shall not be less than the anchor rod diameter minus 0.25 in. (6 mm). Refer to Chapter 4 for additional requirements for structures designed for fatigue. Flange plates designed with stiffeners shall be based on a rational method to limit both normal and parallel stresses applied to the pole wall by the stiffeners to prevent buckling or tear-out of the pole wall and to prevent local buckling or rupture of the stiffeners as a load-bearing element. The design strength of a flange plate connection shall not be less than 50% of the design flexural strength of the pole member. A minimum of four flange plate connection bolts or anchor rods shall be used and be equally spaced in a symmetrical pattern. Refer to Section 3.12 for spacing requirements for anchor rods and to Chapter 4 for additional requirements for structures designed for fatigue. Flange plate connections connecting two pole sections shall use pretensioned high-strength bolts tightened in accordance with Chapter 7. For anchor rods used with base flange plates, the top nuts and bottom leveling nuts shall be tightened in accordance with Chapter 7. The minimum diameter of a structural bolt used in a flange plate connection between two pole sections shall be 0.625 in. (16 mm). The minimum diameter of an anchor rod used in a base flange plate shall be 0.75 in. (19 mm). Refer to Chapter 4 for additional requirements for structures designed for fatigue. The flange plate edge distance and hole spacing shall satisfy bearing strength requirements to resist the shear and torsion reactions of the structure. Oversized holes with appropriate washers above and below the flange plate shall be permitted to facilitate construction. Minimum edge distance requirements for structural members based on the hole, bolt, or anchor rod diameter shall not apply. Flange plates shall be detailed to prevent any portion of the bearing surface of a bolt head, nut, or washer (when used) from extending past the outer edge of the flange plate. Refer to Section 6.9 for center opening requirements for proper galvanizing. 3.10.2.1 Socketed Connections Socketed connections shall be connected with inner and outer fillet welds. The minimum insertion into a flange plate shall be equal to half the nominal thickness of the flange plate. The inner fillet weld size shall not be less than the pole wall thickness minus 0.06 in. (2 mm). The combined strength per unit length of the inner and outer fillet welds shall not be less than 0.90 times the product of the specified minimum yield strength and the design wall thickness of the pole material. The strength of fillet welds less than 0.19 in. (5 mm) shall be ignored. No increase in weld strength for fillet welds loaded transverse to the longitudinal weld axis shall be considered unless the inner fillet weld strength is ignored. The design strength per unit length of the outer fillet weld shall not be less than the design strength per unit length of the inner fillet weld. Refer to Chapter 4 for additional requirements for structures designed for fatigue. 3.10.2.2 Butt-Welded Connections Butt-welded connections shall be complete joint penetration groove welds with reinforcing fillet welds. The size of the reinforcing fillet weld shall result in a through-thickness stress on the flange plate no greater than 36 ksi (250 MPa). The calculation of the throughthickness stress shall consider the condition when the pole wall Design of Steel Lighting System Support Pole Structures

has reached the specified minimum yield strength of the pole material. Refer to Chapter 4 for additional requirements for structures designed for fatigue. 3.11 COMPONENTS AND ATTACHMENTS Components and attachments such as cross arms and brackets shall be designed to resist applied forces and shall consider the load path of those forces to the supporting structure. 3.12 ANCHOR ROD STRENGTH Anchor rod forces shall be determined by elastic analysis. Alternatively, plastic analysis shall be permitted when a group of anchor rods are fully developed in tension and compression and their design strength is not governed by either concrete breakout strength or concrete side-face blowout strength. The factored reactions for the earthquake loading combinations defined in Chapter 2 shall be multiplied by the overstrength factor from Section 2.8.5 for the anchor rod force analysis. Anchor rod forces for the investigation of fatigue shall be based on an elastic analysis. Leveling nuts shall be provided with anchor rods unless otherwise specified for site-specific applications. Cementitious grout, if used below a base flange plate in combination with leveling nuts, shall not be considered as load bearing for determining anchor rod compression and tension axial forces. Refer to Chapter 7 for anchor rod leveling nut and top nut tightening requirements. The clear distance from the top of the concrete to the bottom of the leveling nuts shall not exceed 3 in. (76 mm). The center-to-center spacing of anchor rods shall not be less than four times the nominal diameter of the anchor rod for diameters up to 1.5 in. (38 mm), and 6 in. (150 mm) for larger diameters, and shall satisfy the requirements for minimum cover, spacing, and edge distance for proper placement in concrete foundations. Embedded plates connecting a group of anchor rods shall have a center opening to facilitate the placement of concrete. The following interaction equations shall be satisfied for anchor rod forces: For Iar ≤ d,     Put 2 Vu 2 þ ≤ 1.0 (3-21) ϕt Rnt ϕv Rnv      Puc  Vu 2  þ ≤ 1.0 (3-22) ϕ R  ϕc Rnvc c nc For Iar > d but ≤ 3 in. (76 mm),        Put   Mu  2 Vu 2  þ  þ ≤ 1.0 ϕ R  ϕ M  ϕv Rnv t nt f n        Puc   Mu  Vu 2 þ  þ  ≤ 1.0 ϕ R  ϕ M  ϕc Rnvc c nc f n

(3-23)

(3-24)

where Iar = Clear distance from top of concrete to the bottom of a leveling nut, d = Nominal anchor rod diameter, Put = Anchor rod axial tension force from the factored reactions of structure,

15

Puc = Anchor rod axial compression force from the factored reactions of structure, Vu = Anchor rod shear force occurring with axial force under consideration (from the factored shear and torsion reactions of structure), Mu = Moment applied to anchor rod from factored shear force on anchor rod = 0.65 Iar Vu, Rnt = Nominal tensile strength = Fu An, Rnc = Nominal compression yield strength = Fy Ag, Rnv = Nominal shear rupture strength = 0.5 Fu Ag, Rnvc = Nominal shear yield strength = 0.45 Fy Ag, Mn = Nominal flexural strength = Fy Z, Fu = Specified minimum tensile strength of anchor rod, Fy = Specified minimum yield strength of anchor rod, An = Tensile stress area of anchor rod = 0.7854dn2, dn = Tensile root diameter of anchor rod = d – 0.9743/n for ANSI inch series threads, and = d – 0.9832(p) for ISO metric series threads, n = Number of threads per inch for anchor rods with ANSI inch series threads,

16

p = Pitch of threads (mm) for anchor rods with ISO metric series threads, Ag = Gross area of anchor rod = 0.7854d2, Z = Plastic section modulus of anchor rod based on the nominal diameter of the anchor rod = d3/6, ϕt = 0.75, ϕv = 0.75, ϕc = 0.90, and ϕf = 0.90. When the anchor rod projection, Iar, for an installation exceeds d but is not more than 3 in. (76 mm), it shall be permitted to consider Iar as less than or equal to d when 5,000 psi (34 MPa) minimum 7-day strength nonshrink, nonmetallic grout is properly installed between the top of the concrete and the base flange plate with properly installed leveling nuts. Drainage is required for all grouted base flange plates. Refer to Chapter 4 for additional requirements for structures designed for fatigue.

STANDARD ASCE/SEI 72-21

CHAPTER 4

FATIGUE DESIGN

4.1 SCOPE This chapter provides fatigue design procedures for groundsupported steel lighting system support pole structures with pole tip elevations 55 ft (16.6 m) or more above grade (not including the distance lighting fixtures or other appurtenances may extend above the pole tip). Fatigue thresholds based on a constantamplitude cyclic load are specified. The fatigue thresholds specified are based on AASHTO LRFDLTS-1, LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals. When the requirements of this standard differ from the referenced standard, this standard shall govern. Fatigue threshold values for lighting system support pole structures that do not conform to the dimensional limitations specified in this standard must be determined by a qualified professional engineer using recognized standards. The design procedures specified in this standard are intended to result in wind-induced fluctuating stresses that do not exceed the fatigue resistance of the details and connections typically used for steel lighting system support pole structures. The design procedures are intended to ensure that a structure performs satisfactorily for its design life to an acceptable level of reliability without significant fatigue damage. 4.2 SYMBOLS CBC = Ratio of bolt circle diameter to pole diameter for a flange plate connection COP = Ratio of effective center opening diameter pole diameter for a flange plate connection DBC = Bolt circle diameter for a flange plate connection DOP = Effective center opening diameter in a flange plate connection DT = Pole diameter at a flange plate connection Gr = Geometry coefficient for a flange plate connection H = Effective weld throat per unit length at a stiffener connection to a flange plate hST = Longitudinal stiffener height along the pole wall for a flange plate connection KF = Fatigue stress concentration factor for finite life for a flange plate connection KI = Fatigue stress concentration factor for infinite life for a flange plate connection L = Length of a welded attachment, measured along the longitudinal axis of a pole NS = Number of sides for a multisided cross section NST = Number of longitudinal stiffeners used for a flange plate connection rb = Inside corner bend radius of a multisided cross section

Design of Steel Lighting System Support Pole Structures

tA = Nominal thickness of an attachment welded to a pole tST = Longitudinal stiffener nominal thickness for a flange plate connection tT = Design wall thickness of a pole at a flange plate connection tTP = Nominal flange plate thickness ΔFTH = Fatigue threshold ϕ = Resistance factor for fatigue Pole diameter shall equal the external diameter for round sections or the external flat-to-flat width for multisided sections. 4.3 FATIGUE ANALYSIS An analysis of the support structure shall be performed using an elastic analysis with the fatigue loads from Section 2.9. The resulting nominal member stresses shall be considered as equivalent constant-amplitude stress ranges. Equivalent constant-amplitude stress ranges shall not exceed the fatigue thresholds specified in Section 4.4. 4.4 FATIGUE THRESHOLDS The stresses calculated from the fatigue analysis shall not exceed ϕΔFTH, where ϕ is 1.0 and ΔFTH is as specified in this section for any location on the structure. The stress to be calculated from the fatigue analysis, unless otherwise specified, is the nominal stress in the load-carrying member parallel to its longitudinal axis at the location of the detail or connection under investigation. Backer bars, when used, shall be ignored in the determination of nominal stresses. It shall be permissible to determine the nominal stress at the nominal centerline elevation of a detail under investigation, including the investigation at welded attachments, holes and cutouts, ground sleeves, doubler plates, and so on. The nominal stress for the investigation of a flange plate shall be permitted to be based on the nominal stress at the node on the structural model representing the nominal elevation of the flange plate, including the investigation at the termination of longitudinal stiffeners, backing rings, and so on. 4.4.1 Pole Sections The fatigue threshold at pole cross sections without a longitudinal seam weld shall be 24.0 ksi (165 MPa). The fatigue threshold at pole cross sections with a longitudinal seam weld designed in accordance with this standard shall be 12.0 ksi (83 MPa). 4.4.2 Slip Splices The fatigue threshold at pole cross sections directly above and below a slip splice designed in accordance with this standard shall be 16.0 ksi (110 MPa).

17

Table 4-1. Fatigue Details.

Description

Example 1 Complete joint penetration groovewelded splices (with or without backing ring removed)

Fatigue threshold, ΔFTH

7.0 ksi (48 MPa) 4.5 ksi (31 MPa)

Potential crack location

In pole wall along weld toe when weld reinforcement is ground smooth In pole wall along weld toe when weld reinforcement is not ground smooth

Example 2 All-around fillet welds at ends of ground sleeves and doubler plates

4.5 ksi (31 MPa)

In pole wall at the ends of ground sleeve or doubler plate

Example 3 Ends of longitudinal attachments.

Refer to Table 4-2

In pole wall at the terminations of attachment

Example 4 Reinforced openings

7.0 ksi (48 MPa)

In pole wall and hole reinforcement from the toe of reinforcement-to-pole weld

16.0 ksi (110 MPa)

Illustration

In pole wall and hole reinforcement from the toe of reinforcement-to-pole weld

Notes for Example 4: 1. Refer to Section 4.5.2 for opening limitations. 2. Refer to Section 4.4.5 for stress concentration factors to apply to calculated nominal stresses. Example 5 Unreinforced openings

24.0 ksi (165 MPa)

In pole wall at center elevation of opening

Notes for Example 5: 1. Refer to Section 4.5.2 for opening limitations. 2. Refer to Section 4.4.6 for stress concentration factors to apply to calculated nominal stresses. 18

continued STANDARD ASCE/SEI 72-21

Table 4-1. (Continued). Fatigue Details. Description

Fatigue threshold, ΔFTH

Example 6 Socketed joints

Refer to Section 4.4.7

In pole wall along fillet weld toe

Example 7 Complete joint penetration groove-welded butt joints welded from both sides with backgouging (without backing ring)

Refer to Section 4.4.7

In pole wall along groove weld

Example 8 Complete joint penetration groove-welded butt joints with backing ring attached at the top to the pole wall and at the bottom to the flange plate

Refer to Section 4.4.7

In pole wall along groove weld or along upper fillet weld toe

Example 9 Complete joint penetration groove-welded butt joints with backing ring only attached at the bottom to the flange plate

Refer to Section 4.4.7

In pole wall along groove weld

Example 10 Complete joint penetration groove-welded butt joints with backing ring only attached at the top to the pole wall

Refer to Section 4.4.7

In pole wall along groove weld or along upper fillet weld toe

Potential crack location

Illustration

continued

Design of Steel Lighting System Support Pole Structures

19

Table 4-1. (Continued). Fatigue Details. Description

Fatigue threshold, ΔFTH

Potential crack location

Example 11 Stiffened joints Refer to Section 4.5.6 for dimensional limitations.

7.0 ksi (48 MPa)

In pole wall at termination of stiffeners on the pole wall

Refer to Section 4.4.7

In pole wall along weld at flange plate

Example 12 Stiffened joints

Refer to Section 4.4.7

Through stiffener thickness at flange plate and through the effective weld throat

4.4.3 Circumferential Welds The fatigue threshold at circumferential complete joint penetration groove-welded pole butt splices shall be 7.0 ksi (48 MPa) when welds are ground to provide a smooth transition between the connected sections and 4.5 ksi (31 MPa) when weld reinforcement is not removed. Butt splices shall be limited to sections with equal nominal thicknesses. Refer to Example 1 in Table 4-1. The fatigue threshold at circumferential fillet welds at pole ground sleeves and doubler plates shall be 4.5 ksi (31 MPa). Refer to Example 2 in Table 4-1. 4.4.4 Welded Attachments The fatigue threshold at the ends of longitudinal pole attachments, excluding stiffeners at flange plate connections, shall be determined from Table 4-2. Refer to Example 3 in Table 4-1. 4.4.5 Reinforced Holes and Cutouts The fatigue threshold at the toe of the weld between the reinforcing rim and the pole shall be 7.0 ksi (48 MPa). It shall be permissible to calculate the nominal stress using the internal moment and the cross-sectional properties of the pole at the mid-height elevation of the opening without the cutout or reinforcing. Refer to Example 4 in Table 4-1. A stress concentration factor of 1.0 shall be applied to the nominal stress when the clear width between the rim reinforcing does not exceed 40% of the pole diameter at the mid-height elevation of the opening. For larger openings conforming to Section 4.5.2, a stress concentration factor of 1.5 shall be used. The fatigue threshold at the root of the weld between the pole and the reinforcing rim at the vertical transition of the rim shall be 16 ksi (110 MPa). It shall be permissible to calculate the nominal stress using the internal moment and the cross-sectional properties of the pole at the mid-height elevation of the opening, including the cutout and the reinforcing rim. A stress concentration factor of 4.0 shall be applied to the nominal stress when the 20

Illustration

Table 4-2. Fatigue Thresholds for Welded Longitudinal Pole Attachments, ΔFTH. Length of attachment along pole axis, L

Fatigue threshold, ΔFTH

L < 2 in. (50 mm) 10 ksi (69 MPa) 2 in. (50 mm) ≤ L ≤ 12tA 7.0 ksi (48 MPa) and 4 in. (100 mm) 4.5 ksi (31 MPa) L > 12tA or 4 in. (100 mm) when tA ≤ 1 in. (25 mm) 2.6 ksi (18 MPa) L > 12tA or 4 in. (100 mm) when tA > 1 in. (25 mm) L is the length of attachment, measured along longitudinal axis of pole, and tA is the attachment thickness. Refer to Example 3 in Table 4-1.

clear width between the rim reinforcing does not exceed 45% of the pole diameter at the mid-height elevation of the opening. For larger openings conforming to Section 4.5.2, a stress concentration factor of 5.7 shall be used. The section modulus for the cross section with the cutout and reinforcing rim shall be based on the distance in the direction under consideration from the centroid of the cross section with the cutout and reinforcing rim to the extreme fiber of the pole cross section at the interface with the reinforcing rim. 4.4.6 Unreinforced Holes and Cutouts The fatigue threshold at the mid-height elevation of the opening shall be 24 ksi (165 MPa). The nominal stress shall be calculated using the internal moment and the cross-sectional properties of the pole at STANDARD ASCE/SEI 72-21

Table 4-3. Flange Plate Fatigue Stress Concentration Parameters for Finite Life. Joint type/location

Round pole cross sections at flange plate Multisided pole cross sections at flange plate Socketed joints

Butt joints

Joints with stiffeners at stiffener termination Joints with stiffeners at stiffener base

Equations for determining parameters Gr and KF

G r = 1.00 G r = 1.00 þ ððD T − r b Þ∕ðN S 2 ÞÞ ðG r = 1.00 þ ððD T − r b Þ∕ð25.4N S 2 ÞÞÞ K F = G r ½2.20 þ 4.6ð15t T þ 2ÞðD T 1.2 − 10Þðt TP −2.5 ÞðC BC 0.03 − 1Þ ðK F = G r ½7154 þ 309ð0.59t T þ 2ÞðD T 1.2 − 485Þðt TP −2.5 ÞðC BC 0.03 − 1ÞÞ  i h K F = G r 1.35 þ 16ð15t T þ 1ÞðD T − 5Þðt TP −2 Þ ðC BC 0.02 − 1Þ∕ð4C OP −0.7 − 3Þ   i h K F = G r 871 þ 406ð0.59t T þ 1ÞðD T − 127Þðt TP −2 Þ ðC BC 0.02 − 1Þ∕ð4C OP −0.7 − 3Þ    K F = ðt ST 0.4 Þ∕ðt T 0.7 Þ þ 0.3 ð0.4D T 0.8 Þ∕ðN ST 1.2 Þ þ 0.9    K F = ð2.64t ST 0.4 Þ∕ðt T 0.7 Þ þ 0.3 ð0.03D T 0.8 Þ∕ðN ST 1.2 Þ þ 0.9     K F = 130ðD T 0.15 Þ∕ðN ST 1.5 Þ þ 1 0.13∕ðh ST þ 7Þ 6.5∕ðt ST 0.5 Þ − 1 ðK F for socketed jointsÞ       K F = 80ðD T 0.15 Þ∕ðN ST 1.5 Þ þ 1 3.3∕ðh ST þ 178Þ 32.8∕ðt ST 0.5 Þ − 1 ðK F for socketed jointsÞ

* For existing poles, when the inside corner bend radius is not known, it shall be permissible to assume an inside corner bend radius equal to 1.5 times the pole wall thickness. CBC = DBC/DT (when 12, use 12 to calculate KF) rb = Inside corner bend radius (in.,mm) (when >4 in. (100 mm), use 4 in. (100 mm) to calculate Gr)* tST = Longitudinal stiffener nominal thickness(in., mm) tT = Design wall thickness of pole at flange plate (in., mm) tTP = Nominal flange plate thickness (in., mm)

Note: Refer to Section 4.5 for limitations on joint geometry.

the mid-height elevation of the opening with the cutout. Refer to Example 5 in Table 4-1. A stress concentration factor of 4.0 shall be applied to the nominal stress when the clear width of the opening does not exceed 45% of the pole diameter at the mid-height elevation of the opening. For larger openings conforming to Section 4.5.2, a stress concentration factor of 5.7 shall be used. It shall be permissible to neglect the effects of fatigue at holes installed in accordance with Section 4.5.2 and with a diameter not exceeding the smaller of 2.5 in. (64 mm) and 5% of the diameter of the pole at the center elevation of the hole. 4.4.7 Pole-to-Flange Plate Connections The fatigue threshold at flange plate connections shall be determined in accordance with this section. Refer to Examples 6 through 12 in Table 4-1. The steps required for the determination of the fatigue threshold are as follows. Step 1. Determine the fatigue stress concentration factor for finite life, KF, from Table 4-3. Step 2. Determine the fatigue stress concentration factor infinite life, KI, from the following equation: h i K I = K F ð1.76 þ 1.83tT Þ − 4.76ð0.22ÞK F (4-1) Design of Steel Lighting System Support Pole Structures

KI = KF

h

 i 1.76 þ 0.072t T − 4.76ð0:22ÞK F

(4-1m)

where tT is the design wall thickness of pole at flange plate (in., mm). Step 3. Determine the fatigue threshold, ΔFTH, from Table 4-4. Step 4. In addition, for stiffened joints, determine the fatigue threshold, ΔFTH, at the connection of the stiffeners with the flange plate in accordance with Section 4.4.7.2. 4.4.7.1 Effective Center Opening Diameter Holes or radial slots for galvanizing drainage and venting shall be permitted to be neglected in the calculation of the effective center opening diameter when all of the following criteria are met: • Not more than four equally spaced holes or radial slots are used. • Hole diameter or radial slot width does not exceed 2 in. (50 mm). • Clear distance between each hole or radial slot and the center opening is not less than 2 in. (50 mm). When holes or slots not meeting these requirements are used, the effective center opening diameter shall be calculated as the greater of the following: 21

Table 4-4. Fatigue Threshold at Pole-to-Flange Plate Connection Details, ΔFTH. Joint type/location

Socketed joints1

Butt joints1,2

Joints with stiffeners at stiffener terminations3 Joints with stiffeners at stiffener bases2,4,5

KI

ΔFTH

KI ≤ 4.0 4.0 < KI ≤ 6.5 6.5 < KI ≤ 7.7 KI ≤ 3.0 3.0 < KI ≤ 4.0 4.0 < KI ≤ 6.5 KI ≤ 5.5 KI ≤ 4.0 4.0 < KI ≤ 7.7

7.0 ksi (48 MPa) 4.5 ksi (31 MPa) 2.6 ksi (18 MPa) 10.0 ksi (69 MPa) 7.0 ksi (40 MPa) 4.5 ksi (31 MPa) 7.0 ksi (48 MPa) 7.0 ksi (48 MPa) 4.5 ksi (31 MPa)

Notes: The provisions for pole-to-flange plate connections apply to flange plate splices between pole sections and to base flange plates supported on anchor rods. Refer to Section 4.4.7 to determine KI values based on the values of KF from Table 4-3. 1. Fatigue threshold applies to the nominal stress in the pole cross section at the toe of the fillet weld on the pole. 2. Backing bars shall be ignored for all nominal stress calculations. 3. ΔFTH value for the stiffener termination location applies to the nominal stress in the pole wall at the termination of the stiffeners on the pole wall based on the cross section of the pole without the stiffeners. 4. ΔFTH value for the stiffener base location applies to the nominal stress in the pole wall at the top of the flange plate based on the cross section of the pole without considering the stiffeners. 5. Refer to Section 4.4.7.2 for ΔFTH values for the stiffener and the stiffener weld to the flange plate.

• Diameter of the circular center opening, if present; • Diameter of the circle inscribed within the opening; and • Seventy-five percent of the diameter of the circle circumscribed around all openings, holes, and slots. 4.4.7.2 Stiffener Connection with Flange Plates The fatigue threshold through the stiffener base metal or the effective weld throat shall be determined from the following equations: For tST ≤ 0.50 in: ð13 mmÞ; ΔF TH = 10.0 ksi ð69 MPaÞ (4-2) For tST > 0.50 in ð13 mmÞ;    H ðtST −0.17 Þ ≤ 10.0 ksi ΔF TH = 10.0 0.0055 þ 0.72 t ST (4-3)    H ðt ST −0.17 Þ ΔF TH = 17.3 0.0055 þ 0.72 tST ≤ 69 MPa

(4-3m)

where tST is the longitudinal stiffener nominal thickness (in., mm), and H is the effective weld throat at the stiffener connection to the flange plate (in., mm), not greater than tST. The nominal stresses for investigating the stiffener connection to a flange plate shall be based on the gross cross section of the pole, including the stiffeners and excluding the weld. The nominal stress shall be calculated at the outermost tip of the stiffener, based on a linear stress distribution. Refer to Example 12 in Table 4-1. 4.4.8 Anchor Rods The fatigue threshold for anchor rods shall be 7.0 ksi (48 PMa). Anchor rod forces shall be determined based on an elastic analysis. Grout shall be ignored if used. Nominal stresses shall be calculated using the tensile stress area of the anchor rod. When the clear distance between the bottom of a leveling nut and the top of concrete does not exceed the nominal 22

anchor rod diameter, it shall be permissible to ignore the bending stress in the anchor rod. 4.4.9 Bolts The fatigue threshold for bolts shall be 7.0 ksi (48 MPa). The nominal stresses in bolted connections, such as bolted flange splices between pole sections, shall be calculated considering prying action and the tensile stress area of the bolt. 4.5 MISCELLANEOUS FATIGUE STRENGTH REQUIREMENTS 4.5.1 Pole Cross Sections Tubular pole structures shall be of round or multisided cross sections with diameters between 8 in. (200 mm) and 50 in. (1300 mm). The minimum number of sides for a multisided member shall be based on the outside, flat-to-flat width of the member, as follows: • 8 sides for diameters from 8 in. (200 mm) up to 13 in. (330 mm), • 12 sides for diameters greater than 13 in. (330 mm) and up to 28 in. (710 mm), and • 16 sides for diameters greater than 28 in. (710 mm) and up to 50 in. (1,300 mm). The inside corner bend radius for multisided cross sections shall not be less than five times the section wall thickness or 1.0 in. (25 mm), whichever is larger, and shall be uniform throughout the arc of the bend. 4.5.2 Holes and Cutouts Reinforcing rims around the perimeter of reinforced holes and cutouts in a pole wall shall not be less than 0.25 in. (6 mm) or greater than 1 in. (25 mm) nominal thickness welded to the pole wall to meet the strength requirements of Chapter 3. Starting and stopping of the rim-topole wall weld shall be limited to the top and bottom of the hole or cutout. When a fillet weld is used, a minimum 0.31 in. (8 mm) weld size is required. Reinforcing rim splices shall be made with complete joint penetration groove welds ground flush. STANDARD ASCE/SEI 72-21

Unreinforced holes and cutouts shall be limited to openings not exceeding 5 in. (130 mm) in diameter or width and outside length-to-width ratios not greater than 2.0. The pole wall surface around the perimeter of reinforced or unreinforced holes and cutouts shall have a surface roughness profile not exceeding 1,000 μin (25.4 μm). The surface roughness requirement shall be considered to be satisfied for all drilled holes and for thermally cut surfaces when ground smooth. The inside corner radius of a reinforcing rim or of an unreinforced opening shall not be less than 30% of the inside clear width. The inside clear width of a reinforcing rim or of an unreinforced opening shall not exceed 55% of the pole diameter at the midheight elevation of the opening for a pole diameter not exceeding 30 in. (760 mm). For pole diameters greater than this, the inside clear width of a reinforcing rim or of an unreinforced opening shall not exceed 40% of the pole diameter at the midheight elevation of the opening. The clear distance from a reinforcing rim or from an unreinforced opening to the surface of a flange plate shall not be less than the pole diameter at the midheight elevation of the opening. 4.5.3 Flange Plates Flange plate connection bolts and anchor rods shall be on a symmetrical circular pattern. A minimum of eight equally spaced connection bolts or anchor rods shall be used, with a minimum nominal diameter of 1.0 in. (25 mm). The bolt circle diameter shall not exceed 2.5 times the pole base diameter. The spacing between connection bolts or anchor rods measured circumferentially along the bolt circle shall not exceed 6 times the flange plate thickness, but in no case shall the spacing exceed 15 in. (380 mm). The flange plate thickness shall not be less than 1.5 in (38 mm) for pole diameters up to 8 in. (200 mm) and not less than 2 in. (50 mm) for larger diameters. Flange plate thickness shall not exceed 4 in. (100 mm). 4.5.4 Butt-Welded Pole-to-Flange Plate Connections The nominal pole wall thickness for butt-welded flange plate connections, with or without stiffeners, shall be between 0.18 in. (5 mm) and 0.63 in. (16 mm). Butt-welded connections shall be complete joint penetration groove welds with reinforcing fillets. The reinforcing fillet welds shall have unequal legs, with the long leg along the pole wall subtending an approximately 30-degree angle on the pole wall. The effective center opening diameter in the flange plate shall not be greater than 0.90 times the pole base external diameter.

Design of Steel Lighting System Support Pole Structures

4.5.5 Socketed Pole-to-Flange Plate Connections Socketed flange plate connections without stiffeners shall not be permitted for pole diameters larger than 24 in. (0.61 m). The nominal pole wall thickness shall be between 0.18 in. (5 mm) and 0.50 in. (13 mm). The outer fillet weld shall have unequal legs, with the long leg along the pole wall subtending an approximately 30 degree angle on the pole wall. 4.5.6 Stiffened Pole-to-Flange Plate Connections The use of stiffeners to increase the fatigue threshold for flange plate connections shall be permitted only for pole diameters of 24 in. (0.61 m) and greater and with nominal pole wall thicknesses between 0.25 in (6 mm) and 0.63 in. (16 mm). The ratio of stiffener nominal thickness to the nominal pole wall thickness shall not exceed 1.25. The stiffener thickness shall not be less than 0.25 in. (6 mm) or greater than 0.75 in. (19 mm). A minimum of eight stiffeners shall be provided. The stiffeners shall be equally spaced around the pole base, with a maximum 16 in. (0.41 m) center-to-center spacing between the stiffener connections to the pole wall at the flange plate. Stiffeners shall meet the requirements of Chapter 3 and shall be detailed to result in a nominal 15 degree termination angle to the pole wall. The stiffener height shall not be less than 12 in. (300 mm) or greater than 42 in. (1,100 mm). The stiffener connection to the pole wall and to the flange plate shall be permitted to be a complete joint penetration weld, a partial joint penetration weld, or an all-around fillet weld. The effective throats shall meet the strength requirements of Chapter 3. When a fillet weld is used for the connection to the pole wall, the top of the stiffeners shall be detailed without a transition radius, and the wrap-around fillet weld shall not be ground. Stiffeners shall be detailed with a 1 in. (25 mm) minimum corner cope or as required to provide a 0.38 in. (10 mm) minimum clearance from the stiffener weld toes to the unequal fillet weld toes connecting the pole wall to the flange plate. 4.5.7 Foundations Mat foundations shall be sized such that a compressive soil bearing stress from the stiffness requirement loading condition specified in Section 2.10 exists over the entire base of the foundation. The minimum depth of direct embed foundations, pile foundations, piers, and caissons shall be determined considering repetitive lateral loading soil conditions.

23

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CHAPTER 5

FOUNDATION DESIGN

5.1 SCOPE This chapter provides design procedures and criteria for commonly used foundations for ground-supported steel lighting system support pole structures designed in accordance with this standard. It is not the intent of this standard to exclude other foundation types when approved by a qualified professional engineer for a specific application. Supplementary requirements for high-risk seismic areas are defined in Section 5.10. The reinforced concrete design criteria in this section are based on ACI 318-19, Building Code Requirements for Structural Concrete (ACI 2019). 5.2 SYMBOLS Ag = Gross area of an anchor rod c = Soil cohesion d = Nominal anchor rod diameter Fy = Specified minimum yield strength of an anchor rod f'c = Specified compressive strength of concrete Id = Basic development length of a deformed anchor rod k = Lateral modulus of soil reaction Ld = Minimum embedment depth of an anchor rod N = Standard penetration value of soil Sf = Soil nominal ultimate skin friction α = Development length modification factor based on specified minimum yield strength of an anchor rod β = Development factor modification factor based on anchor rod spacing γ = Effective unit weight of soil ε50 = Soil strain at 50% of ultimate compression ϕ = Soil angle of internal friction

foundations (e.g., grillages, H-piles, and pipe-piles) shall be determined in accordance with AISC 360-16. The design strength of direct embed foundations shall be determined in accordance with Chapter 3. The projection above grade of a foundation shall be based on the specified height of the lighting fixtures and the specified length of the assembled pole. 5.3.1 Foundation Analysis The design of drilled shafts and direct embed foundations based on rigid foundation analysis methods shall be limited to foundations with aspect ratios (depth/ diameter) not exceeding 6. Flexible foundation analysis methods shall be used for foundations with aspect ratios greater than 6. For drilled shaft or direct embed foundation lateral load analysis models that model the lateral stiffness of the soil, factored reactions for the analysis shall be divided by 0.75. The soil parameters related to the lateral stiffness of the soil shall not be reduced using a resistance factor. The foundation internal forces and moments from the lateral load foundation analysis shall be multiplied by 0.75 for the strength design of the foundation. Reactions shall not be modified when investigating foundation displacements for the stiffness requirement loading condition specified in Section 2.10. For structures designed for fatigue, refer to Chapter 4 for additional foundation design requirements.

Foundations shall be designed by a qualified professional engineer based on the reactions from an analysis of the pole structure certified by a qualified professional engineer for the combination of loads defined in Chapter 2. Reactions shall be designated as factored reactions on design documents provided to the foundation engineer for foundation design. The foundation engineer shall be responsible for the proper development of anchor rods in accordance with Section 5.9. The design strength of a foundation and the design strength of the supporting soil or rock shall be equal to or greater than the factored reactions from the combination of loads defined in Chapter 2. Unless otherwise specified in this standard, the design strength of concrete foundations (e.g., drilled shafts, mat foundations, and precast pole foundation sections) shall be determined in accordance with ACI 318-19, and the design strength of steel

5.3.2 Longitudinal Reinforcement The minimum longitudinal reinforcement ratio shall be 0.005 for drilled shafts and piers supported on mat foundations. Longitudinal reinforcement in a drilled shaft or a pier supported on a mat foundation used to develop a group of anchor rods shall be fully developed in tension in accordance with ACI 318-19, Chapter 25, on both sides of an assumed potential concrete breakout surface originating at the embedded end of a group of deformed anchor rods or at the bearing surface (head of nut or surface of embedded plate) of a group of headed anchor rods and projecting outward and upward from the anchor rod bolt circle at a 35 degree angle with the horizontal. The center-to-center diameter of the foundation longitudinal reinforcement arrangement (cage diameter) shall not exceed the anchor rod bolt circle by more than the embedment depth of the anchor rods. Longitudinal pier reinforcement in a pier supported on a mat foundation shall be fully developed in tension above and below the slab interface. In addition, when compression in the longitudinal pier reinforcement is considered in the determination of nominal strength, the longitudinal reinforcement shall also be developed in compression for the maximum longitudinal reinforcement compressive force. Hooks shall be ignored in the development of longitudinal reinforcement for compression. The embedment depth for a hooked bar in compression shall be

Design of Steel Lighting System Support Pole Structures

25

5.3 GENERAL

considered equal to the depth from the top surface of the mat to the bottom outer surface of the hook. Refer to Section 5.10 for additional requirements for sites in high-risk seismic areas. 5.3.3 Transverse Reinforcement Closed stirrups that provide shear strength or lateral support to longitudinal reinforcement under compression in drilled shafts or piers supported on a mat foundation shall be developed in accordance with ACI 318-19, Chapter 25, using staggered laps or staggered hooks. Lap lengths shall not be less than 1.3 times the development length based on the nominal stirrup diameter. Anchor rods in drilled shafts or piers supported on mat foundations shall be enclosed within the top 5 in. (130 mm) of the foundation with a minimum of two No. 3 (10M) or larger closed stirrups enclosing the longitudinal pier reinforcement, anchored at each end with staggered hooks, in accordance with ACI 318-19, Chapter 25. Refer to Section 5.10 for additional requirements for sites in high-risk seismic areas. 5.3.4 Shrinkage and Temperature Reinforcement For drilled shafts and piers supported on mat foundations, horizontal reinforcement for shrinkage and temperature stresses shall be provided within the top 6 in. (150 mm) when the distance between the anchor rod bolt circle and the perimeter of the foundation exceeds 30 in. (760 mm). The reinforcement provided shall not be less than 0.125 in.2/ft (265 mm2/m) in each direction, with a center-to-center spacing not to exceed 9 in. (230 mm).

When concrete backfill for a direct embed foundation is extended above grade, shrinkage and temperature steel shall be provided. The minimum reinforcement shall be equivalent to No. 3 closed stirrups at 3 in. (76 mm) spacing extending to a 12 in. (300 mm) minimum depth below grade. 5.4 SITE INVESTIGATION In the absence of a geotechnical report, the presumptive soil parameters provided in Table 5-1 shall be permitted to be used for foundation design. Presumptive soil parameters and other assumptions required for foundation design shall be validated for a specific site prior to installation. 5.4.1 Concrete Mix Design Concrete foundations shall meet the durability requirements of ACI 318-19, Chapter 19, including high-sulfate conditions and other soil and groundwater conditions known to be corrosive to concrete as indicated in a geotechnical report. 5.4.2 Frost Depth For sites where the soil may display significant ice lens development during freezing, the foundation depth shall be at or below the 100-year frost depth or the depth specified in a geotechnical report. 5.4.3 Expansive Soil Foundations shall extend below the depth of seasonal moisture variation in expansive soils as indicated in a geotechnical report. The depth of the foundation shall be adequate to prevent uplift of the foundation. The tension capacity of the foundation must be adequate to resist the net

Table 5-1. Presumptive Soil Parameters. Nominal ultimate net bearing strength (lb/ft2) [kPa]

Soil type

Clay Sand

N (blows/ft) [blows/m]

ϕ (°)

γ (lb/ft3) [kN/m3]

c (lb/ft2) [kPa]

Mat Deep foundations foundations

Sf (lb/ft2) [kPa]

k (lb/in.3) [kN/m3]

ε50

8 [26] 10 [33]

0 30

110 [17] 110 [17]

1,000 [48] 0 [0]

5,000 [240] 9,000 [430] 4,000 [190] 9,000 [430]

500 [24] 500 [24]

150 [41,000] 35 [9,500]

0.01 n/a

N = Standard penetration value ϕ = Angle of internal friction γ = Effective unit weight of soil c = Soil cohesion Sf = Nominal ultimate skin friction k = Lateral modulus of soil reaction ε50 = Strain at 50% of ultimate compression Notes: 1. 2. 3. 4. 5. 6. 7.

26

Actual soil design parameters based on a geotechnical report with similar standard penetration values may vary from the tabulated values. Nonexpansive soil assumed. Dry soil conditions (nonbuoyant) assumed. Noncorrosive soil conditions assumed. Site Class D assumed for earthquake design. When the site location is unknown, the frost depth shall be assumed to be 3.5 ft (1.1 m). Presumptive soil parameters and other assumptions required for foundation design shall be validated for a specific site prior to installation.

STANDARD ASCE/SEI 72-21

uplift tension forces from the expansive soil as specified in the geotechnical report. Net uplift design tension forces from expansive soil shall be based on a load factor of 1.2 applied to the expansive soil tension force and a load factor of 0.9 applied to dead loads. The tension forces from expansive soil need not be considered to occur simultaneously with the combination of loads defined in Chapter 2. 5.4.4 High Water Table Reduction in the weight of material by buoyancy and the effect on soil properties and strength shall be considered when submerged conditions are indicated in a geotechnical report. Direct embed pole sections shall be designed to prevent upheaving under the high-water-table condition. 5.5 DRILLED SHAFT AND DIRECT EMBED FOUNDATIONS The strength of drilled shafts and direct embed foundations shall be investigated for the forces and moments in the foundation based on the soil strength distribution along the length of the foundation required to resist the factored reactions from the combination of loads defined in Chapter 2. Alternatively, it shall be permissible for the foundation engineer to specify a point of fixity distance below grade for the purpose of investigating strength requirements. A direct embed foundation shall not be considered to act compositely with backfill (e.g., concrete, specialty backfill materials, soil, or gravel) when determining the strength of the foundation. A bearing plate or similar device shall be provided at the base of direct embed steel pole sections. Precast concrete direct embed foundations with a slip splice connection with the pole, in addition to the foregoing, shall be designed for the shear forces from the internal couple resisting the factored shear and overturning moment reactions from the combination of loads defined in Chapter 2. The factored reactions for the earthquake loading combinations shall be multiplied by the overstrength factor from Section 2.8.5. The slip splice lap length shall be designed to prevent a crushing failure at the surface of the concrete at the top of the foundation and at the termination of the steel pole section below the top of the foundation. Longitudinal reinforcement shall be fully developed in tension within the minimum slip splice lap length. The default minimum slip splice lap length specified in Section 3.10.1 shall not be considered to satisfy this condition unless otherwise supported by tests or calculations. 5.5.1. Direct Embed Effective Foundation Diameter The effective foundation diameter shall be based on the type of backfill used for the foundation. For concrete backfill, it shall be permissible to consider a constant effective foundation diameter over the embedment depth equal to the outer diameter of the concrete annulus surrounding the embedded section. For gravel backfill, it shall be permissible to consider a constant effective foundation diameter over the embedment depth equal to the average of the mid-depth width of the embedded section and the mid-depth outer diameter of the gravel annulus, not to exceed the embedded section base width plus 9 in. (230 mm). For soil or other backfill materials, it shall be permissible to consider a constant effective foundation diameter over the embedment depth equal to the mid-depth width of the embedded section. Pole width shall equal the external diameter for round sections or the external flat-to-flat width for multisided sections. Design of Steel Lighting System Support Pole Structures

5.6 MAT FOUNDATIONS The weight of a mat foundation and the weight of soil or other material directly above a mat foundation shall be considered as dead load for the combination of loads defined in Chapter 2 and shall be factored by the appropriate dead load factor, with no resistance factor applied. The weight of soil or other material outside the perimeter of a mat foundation, if considered to resist overturning reactions, shall be considered as a nominal soil strength and shall be multiplied by a 0.75 resistance factor. It shall be permissible to consider the distribution of soilbearing stress on the base of a mat foundation as either triangular or rectangular. The maximum eccentricity of loading (i.e., gross overturning moment divided by gross axial load) shall not exceed 45% of the minimum foundation base dimension. Overturning shall be considered to occur from both the parallel and the diagonal axes of the foundation. Factored overturning moments in piers supported on a mat foundation shall be transferred to the mat by a combination of flexure and eccentricity of shear (punching shear). Sixty percent of the factored overturning moment shall be considered to be transferred by flexure, and 40% shall be considered to be transferred by punching shear. The effective mat width for resisting overturning moment transferred by flexure shall not exceed the width of the pier plus 1.5 times the thickness of the mat on each side of the pier. The factored shear stress resulting from the overturning moment transferred by punching shear shall be considered to vary linearly about the centroid of the critical section and shall be combined with the factored shear stress from axial loads transferred from the pier. 5.7 CORROSION CONTROL A protective coating shall be provided around the perimeter of direct embed foundations when required in accordance with this section. Unless otherwise specified, the protective coating shall extend 12 in. (300 mm) minimum above grade. Protective coatings shall not terminate at the top of a ground sleeve and shall have a feathered edge at the termination of the coating. A surface coating providing UV protection shall be applied over the coated area extending above grade under either of these conditions: (1) The protective coating is not intended for exposure to UV where the physical properties of the coating required for corrosion protection may significantly degrade under UV exposure, or (2) when the color of the protective coating is selected for landscaping or other aesthetic purposes and the base protective coating color is not intended to be stable under UV exposure. 5.7.1 Direct Embed Steel Sections A protective coating over galvanized direct embed steel sections shall be provided around the perimeter of the embedded sections under the following conditions: • Soil backfill is used. • Gravel or concrete backfill is used with less than 6 in. (150 mm) of cover. • Gravel backfill is used in corrosive soil conditions indicated in a geotechnical report. • Concrete backfill does not meet the durability requirements of ACI 318-19, Chapter 19. When concrete or gravel backfill is not extended to grade and soil is used for the upper portion of the embedment (e.g., for landscaping purposes), a protective coating is required for the 27

embedment depth exposed to soil plus a minimum additional depth of 18 in. (460 mm). It shall be permissible to eliminate protective coatings for direct embed steel sections when cathodic corrosion protection methods are installed using sacrificial anodes or impressed currents. 5.7.1.1 Ground Sleeves Ground sleeves shall be considered as supplementary corrosion control for direct embed steel sections and shall not eliminate the requirements for protective coatings specified in Section 5.7.1. Ground sleeves shall be continuously welded to the embedded section at the top and bottom of the ground sleeve. Seam welds for ground sleeves shall meet the requirements for the embedded pole section. Provision shall be made for venting of the air gap between the pole section and the ground sleeve during the galvanizing operation.

Ld = I d · α · β

where Ld is the minimum embedment depth of anchor rod, and Id is the basic development length of anchor rod. Threaded portions of deformed anchor rods shall not be considered as contributing to the embedment depth. The basic development length of a deformed straight anchor rod under tension shall be determined from the following equations: I d = larger of

I d = larger of

Anchor rods shall be developed into a foundation to support the anchor rod forces from the factored reactions from the combination of loads defined in Chapter 2. The factored reactions for the earthquake loading combinations shall be multiplied by the overstrength factor from Section 2.8.5. Deformed anchor rods shall be developed in accordance with Section 5.9.1 or 5.9.2. Smooth anchor rods shall be developed in accordance with Section 5.9.2. 5.9.1 Deformed Anchor Rods Deformations of deformed anchor rods shall meet or exceed the deformation requirements of ASTM A615. The minimum specified yield strength of deformed anchor rods shall not exceed 75 ksi (520 MPa). The minimum embedment depth for deformed anchor rods under tension or compression shall be determined from ACI 31819, Chapter 25, except for deformed straight anchor rods under tension, which shall be determined from the following equation:

28

(5-2)

0.0191Ag F y pffiffiffiffi and 0.057 d F y f c0

(5-2M)

for bars up to and including #11ð36MÞ 2.69F y I d = pffiffiffiffi0 for #14ð43MÞ and #14J bars fc 26.0F y I d = pffiffiffiffi0 for #14ð43MÞ and #14J bars fc

5.8 DESIGN STRENGTH OF SOIL OR ROCK

5.9 DEVELOPMENT OF ANCHOR RODS

1.27Ag F y pffiffiffiffi and 0.400 d Fy f c0

for bars up to and including #11ð36MÞ

5.7.2 Direct Embed Precast Concrete Sections Concrete shall meet the durability requirements of ACI 318-19, Chapter 19, including high-sulfate conditions and other soil and groundwater conditions known to be corrosive to concrete as indicated in a geotechnical report, unless a protective coating is provided in accordance with Section 5.7.

The nominal strength of soil or rock shall be based on the principles of soil or rock mechanics. The design strength of soil or rock shall be determined by multiplying the nominal strength by a 0.75 resistance factor. The nominal strength of soil or rock determined from geotechnical recommendations that are based on allowable strengths shall be determined by multiplying the allowable strength by the corresponding safety factor reported in the geotechnical recommendations. When specific geotechnical parameters or the factor of safety used to determine allowable strengths are not reported in the geotechnical recommendations, a safety factor equal to 2.0 shall be used to determine nominal strengths. For soil strengths that are a function of the soil overburden weight (e.g., gross soil bearing resistance, skin friction, or lateral soil resistance), the unfactored in-place overburden weight of the soil shall be used to determine nominal soil strengths. The design strength shall be determined by multiplying the nominal strength by a 0.75 resistance factor.

(5-1)

3.52F y I d = pffiffiffiffi0 for #18ð57MÞ and #18J bars fc 34.0F y I d = pffiffiffiffi0 for #18ð57MÞ and #18J bars fc

(5-3)

(5-3m)

(5-4)

(5-4m)

where Ag = Gross area of the anchor rod (in.2, mm2), Fy = Specified minimum yield strength of anchor rod (ksi, MPa), f′c = Specified compressive strength of concrete (ksi, MPa), d = Nominal anchor rod diameter (in., mm), a = 1.0 for Fy ≤ 60 ksi (415 Mpa) and 1.2 for Fy > 60 ksi (415 Mpa), and β = 1.0 for center-to-center spacing less than 6 in. (150 mm) and 0.8 for greater spacing. 5.9.2 Headed Anchor Rods The development of headed anchor rods shall satisfy the provisions of ACI 318-19, Chapter 17, for concrete strength. For groups of headed anchor rods connected to an embedded plate developed with drilled shaft or pier longitudinal reinforcement in accordance with Section 5.3.2, only the provisions for side-face blowout and pullout strength (i.e., bearing on anchor rod head) shall apply, unless as specified in this section for smooth-headed anchor rods. It shall be permissible to satisfy concrete breakout requirements for a group of headed anchor rods that are not developed with drilled shaft or pier longitudinal reinforcement by providing adequate punching shear strength (two-way shear) in accordance with ACI 318-19, Chapter 22, assuming that all anchor rod axial forces are equal to the maximum anchor rod axial force in the group, considering the combination of loads defined in Chapter 2. The factored reactions for the earthquake loading combinations shall be multiplied by the overstrength factor from Section 2.8.5. The embedment depth considered for punching shear for the tension and compression force conditions shall be the depth from the potential breakout surface to the bearing area of the anchor rod nut or embedded plate.

STANDARD ASCE/SEI 72-21

For smooth-headed anchor rods with the headed end near the bottom surface of a foundation, additional nuts at the upper ends of the anchor rods shall be provided when required to transfer anchor rod compression forces from the download and overturning reactions of the structure, considering the limited punching shear capacity of the anchor rod group near the bottom breakout surface of the foundation. When deformed anchor rods are used as headed anchor rods, the contribution from bar deformations shall be ignored, except it shall be permitted to develop deformed anchor rods in compression in accordance with the provisions of ACI 31819, Chapter 25, for compression reinforcement. Concrete pryout shall be considered as a potential failure mode for anchor rods with an embedment depth less than 25 times the nominal anchor rod diameter. Concrete shear breakout strength shall be considered as a potential failure mode, except for anchor rod groups in drilled shafts or piers supported on mat foundations when the anchor rod group is enclosed within spirals or closed stirrups on a maximum 6 in. (150 mm) center-to-center spacing around the longitudinal foundation reinforcement over the embedment depth of the anchor rods. Closed stirrups shall have staggered lap lengths equal to 1.3 times the development length based on the nominal stirrup diameter or shall be anchored at each end in accordance with ACI 318-19, Chapter 25.

earthquake spectral response acceleration parameter at short periods from Chapter 2 is greater than 1.0. 5.10.1 Longitudinal Reinforcement Longitudinal reinforcement in piers supported on a mat foundation or in piles, piers, or drilled shafts supporting a cap or mat shall be continuous and extend into the mat and be fully developed in tension at the interface. When hooks are used for the development of longitudinal reinforcement in piers, it shall be permissible for the free ends of the hooks to be oriented inward toward the center of the longitudinal reinforcement arrangement or outward away from the center of the longitudinal reinforcement arrangement. When grouted longitudinal reinforcing is used at the interface with a mat, the grouting system shall be demonstrated by testing to develop at least 125% of the minimum specified yield strength of the longitudinal reinforcing. 5.10.2 Transverse Reinforcement Transverse reinforcement in concrete piles, piers, or drilled shafts supporting a cap or mat shall be in accordance with ACI318-19, Sections 18.13.5.3, 18.13.5.4, 18.13.5.5 and 18.13.5.7, and shall be anchored in accordance with ACI318-19, Sections 25.7.2, 25.7.3, or 25.7.4. 5.10.3 Batter Piles Pile caps supported on batter piles shall be designed to resist the full compressive strength of the batter piles acting as short columns.

5.10 SEISMIC CONSIDERATIONS The requirements specified in this section shall apply to foundations in high-risk seismic areas, defined as locations where the

Design of Steel Lighting System Support Pole Structures

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CHAPTER 6

FABRICATION

6.1 SCOPE This section provides fabrication procedures and requirements for ground-supported steel lighting system support pole structures. 6.2 GENERAL Fabrication shall be in accordance with this standard and ANSI/ AISC 303-16, Code of Standard Practice for Steel Buildings and Bridges (AISC 2016b) or AASHTO LRFDLTS-1, LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals. Welding shall be in conformance with AWS D1.1:2020, Structural Welding Code–Steel. When the requirements of this standard differ from the reference standards, this standard shall govern. Fabrication shall be performed by a fabricator certified in accordance with AISC 207-16, Certification Standard for Steel Fabrication and Erection, and Manufacturing of Metal Components (AISC 2016a). Refer to Chapter 4 for additional fabrication requirements for structures designed for fatigue. 6.3 MATERIALS The fabricator shall maintain a system of record keeping, in accordance with AISC’s certified fabricator requirements as provided in AISC 207-16 (AISC 2016a), to allow verification that all materials furnished (e.g., plate steel, steel shapes, anchor rods, structural fasteners, and welding materials) meet the requirements of this standard. Structures shall be permanently marked with an identification that provides traceability to the raw materials used for the pole section and flange plates (when used) and the quality checks performed during fabrication. Pole sections fabricated from plate processed from coil (e.g., ASTM A1011-18) shall be tested, inspected, and so on, in conformance with the requirements of ASTM A6 and certified by the plate supplier to be in conformance with the appropriate ASTM plate specification (e.g., ASTM A572-18, Grade 65). The processing of coil includes decoiling, leveling, and cutting to length, among other steps. Fabrication processes for forged flange plates shall be established to account for the differences in material flatness and waviness tolerances compared to plate material specifications. 6.4 WELDING Welding procedure specifications, procedure qualification records, inspection procedures, and individual inspector, welder, welding operator, and tacker certifications and continuity logs shall conform to the requirements of AWS D1.1. Unless otherwise specified in Design of Steel Lighting System Support Pole Structures

this standard, the AWS D1.1 requirement for nontubular members shall apply to round and multisided steel poles. Welding materials shall be compatible with the parent materials being welded, in accordance with AWS D1.1 requirements. Weld materials shall be specified with Charpy V-notch impact strengths not less than the minimum requirements for the parent materials. Performance qualification testing of weld procedures shall include testing for required Charpy V-notch impact strengths, in accordance with AWS D1.1 requirements. 6.4.1 Tack Welds Tack welds shall be performed with the same AWS D1.1 requirements as for structural welds. Tack welds for backing shall not be placed in the corners of multisided pole sections. Tack welds shall be removed or incorporated into a final weld. 6.4.2 Seam Welds Reinforcing weld metal on seam welds shall be ground smooth within the maximum expected lap length of pole slip splices for the lower pole sections at slip splices. Reinforcing weld metal of seam welds shall not be considered as contributing to the minimum penetration requirement specified in Section 3.10.1. 6.4.3 Backing Backing for complete joint penetration flange plate welds shall not exceed a thickness of 0.25 in. (6.4 mm) and shall be continuous around the inside perimeter of pole sections. Backing splices shall be made with a complete joint penetration weld and shall not be located at pole section seam weld locations or at the corners of multisided sections. Backing shall be attached with a continuous weld to the pole wall at the top of the backing, or to the flange plate at the bottom of the backing, or at both locations. Backing welds shall be performed with the same AWS D1.1 requirements for structural welds. The connection shall be permitted to be a continuous fillet weld, a partial joint penetration weld, or a complete joint penetration weld. When backing is welded to the pole wall, the height of the backer shall not exceed 2 in. (50 mm). AWS D1.1 weld inspection acceptance criteria for structural welds shall apply to backing welds, including undercut in the base material of the pole section at the top of the backing. When the top of the backing is not welded to the pole wall, the gap between the backing and the pole wall shall be sealed with caulking after galvanizing to prevent ingress of moisture. 6.4.4 Fit-Up For socketed flange plates and for reinforcing rims around openings, when the width of the gap to the pole wall exceeds 0.06 in. (1.5 mm), fillet weld sizes required for strength shall be increased by the width of the gap. The width of the gap shall not exceed 0.19 in. (5 mm). 6.4.5 Anchor Rods Welding shall not be performed on smooth anchor rods. Welding on deformed anchor rods shall 31

be permitted at the embedded end for attaching a plate or ring to maintain the geometry of the anchor rod cage during handling and placement when the development length below the weld is ignored for determining the minimum required anchor rod embedment depth. 6.4.6 Weld Inspections Fillet and partial joint penetration groove welds (e.g., seam welds) shall be 100% visually inspected, in accordance with AWS D1.1 visual acceptance/ rejection criteria. Visual inspections shall be performed by or under the direction of an AWS Certified Weld Inspector. Complete joint penetration welds (e.g., flange plate welds and seam welds in locations required to be complete joint penetration welds per Chapter 3) shall be 100% examined with ultrasonic testing (UT), in accordance with AWS D1.1 acceptance/rejection criteria. Complete joint penetration flange plate welds and circumferential splices in pole sections shall be ultrasonically inspected after galvanizing. Personnel performing UT shall be qualified in accordance with AWS D1.1 requirements. For joints with backing, the UT procedures shall account for the geometry of the backing. Flange plate material thicker than 2 in. (50 mm) shall be ultrasonically inspected for laminar defects after weld-out of complete joint penetration joints using an AWS D1.1 qualified UT procedure. For structures designed for fatigue, inspection acceptance criteria shall be based on AWS D1.1 acceptance/rejection criteria for cyclically loaded nontubular connections in tension. 6.4.6.1 Ultrasonic Testing The AWS D1.1 UT procedures and standards apply only to material between the thicknesses of 5/16 in. (8 mm) and 8 in. (200 mm), inclusive. For other thicknesses, a qualified UT procedure is required, conforming to the requirements of AWS D1.1, Annex O. The UT procedure shall be prepared by a person familiar with the applicable joint configuration, including the type and size of backing (when used), and shall be qualified in accordance with AWS D1.1, Annex O, Section O2. The transducer size, shape, beam angle, and frequency shall be documented in the procedure, along with calibration and other requirements for the UT process outlined in AWS D1.1 Annex O, Section O3. 6.5 SHEARING Shearing shall be permitted for steel up to a maximum thickness of 0.50 in. (13 mm). Burrs from the shearing process shall be removed by grinding or other means. As a minimum, sheared edges shall be visually inspected for cracks, tears, and burrs. 6.6 BURNING It shall be permissible for straight or curved edges of parts to be burned with a mechanically guided torch using laser, plasma, or oxy-fuel. Procedures shall be established to prevent cracks or other notch-type defects from forming at the prepared edge. Slag from the burning process shall be removed along a prepared edge prior to welding and galvanizing. Reentrant locations shall be formed and rounded in accordance with AWS D1.1 requirements. 6.7 PUNCHING HOLES It shall be permissible to punch holes in material up to a maximum thickness of 0.75 in. (19 mm) when the material thickness of the steel does not exceed the diameter of the hole. Visual inspection is required for punched holes. 32

6.8 FORMING The minimum inside corner bend radius for forming shall be equal to 3 times the material thickness. For structures designed for fatigue, the inside corner bend radius shall not be less than 5 times the material thickness or 1 in. (25 mm), whichever is larger. 6.9 GALVANIZING Galvanizing shall be performed in accordance with ASTM A123. Sections with flange plates shall be immersed into molten zinc in a manner to minimize the formation of air pockets, the accumulation of excessive zinc, and the entrapment or inclusion of ash, dross, or zinc skimmings. Double dipping of sections shall not be allowed. All fabrication shall be performed prior to the hot-dip galvanizing process. Repairs to galvanizing surfaces shall conform to ASTM A780-15. A center opening or a combination of a center opening and vent holes or slots in a flange plate shall, as a minimum, provide an area equivalent to a circle with a diameter equal to 30% of the external diameter or flat-to-flat width of the pole section at the flange plate connection, to allow proper drainage and venting. When additional holes or slots are used in combination with a center opening, they shall be placed adjacent to the interior pole surface intersection with a flange plate and oriented to allow the escape of air and prevent the formation of an air pocket at the top of the section and the drainage of molten zinc and galvanizing impurities at the bottom of the section during immersion and withdrawal. Sections and components shall be processed after galvanizing to remove all zinc drips (icicles) and excessive galvanizing in holes and on slip splice or flange plate splice faying surfaces and other areas that would impact the installation or use of the pole sections. Threaded holes and welded nuts (e.g., used for jacking slip splices together, or grounding lugs) shall be coated with a compound to prevent the galvanizing coating from adhering to the internal threads or shall be tapped after galvanizing to allow the insertion of the proper threaded fastener. Other methods of protecting threads shall be permitted when approved by a qualified professional engineer. Inspection of galvanizing shall be in accordance with ASTM A123, including verification of the required coating thickness from Section 3.6.1. The galvanizer shall maintain a quality assurance program which documents the inspection program and the record-keeping process for inspections. 6.10 ADDITIONAL COATINGS Below-grade coatings and coating systems applied above grade shall be applied in accordance with the coating manufacturer’s specifications. The required surface preparation for the coating system (e.g., light sand blasting, cleaning, or chemical treatment) shall be inspected prior to the application of a coating over a galvanized surface. Additional coatings shall be applied over galvanizing and shall not be substituted for hot-dip galvanizing as a corrosion control coating. The coating facility shall maintain a quality assurance program which documents the inspection program and the record-keeping process for inspections. The inspection process shall address surface preparations, preparation of equipment, mixing of multiple-part coating systems, environmental controls, application of coating, color control, number of coats, thickness requirements for each coat, curing times, required adhesion tests, and other items critical to the selected coating system. Repairs to a coating shall be performed in accordance with the coating manufacturer’s specifications. STANDARD ASCE/SEI 72-21

6.11 FABRICATION TOLERANCES The following tolerances shall apply to the fabrication of pole sections, unless more stringent tolerances are specified related to the proper performance of a lighting system:

• Pole section length: ±0.50 in. (13 mm), • Pole section camber (straightness): 0.125 in. (3.2 mm) for each 5 ft (1.5 m) of length, and • Pole section twist: 1 degree for each 5 ft (1.5 m) of length.

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CHAPTER 7

INSTALLATION

7.1 SCOPE

7.3 DIRECT EMBED FOUNDATIONS

This section outlines installation provisions for ground-supported steel lighting system support pole structures, including the most commonly used foundation types. It is not the intent of this standard to exclude other foundation types when approved by a qualified professional engineer for a specific application. Installation provisions related to the lighting system, electrical power, grounding, lightning protection, and so on, are not within the scope of this standard. Installation shall be performed in conformance with applicable building codes and safety regulations. This standard does not address the safety and stability of the structure and lighting system during assembly and erection, which are the responsibility of the erector, based on the means and methods chosen by the erector.

Refer to Chapter 5 for protective coatings required for direct embed foundations. Damages to coatings shall be repaired in accordance with the coating manufacturer’s specifications. The base of the foundation excavation shall be prepared in accordance with the foundation design for proper support of the direct embedded section and for proper drainage for the pole interior. Direct embed sections shall be set to meet the plumbness tolerances of Section 7.9 for the installed pole. Backfill shall be installed and compacted in accordance with the foundation design. A means to maintain plumbness during backfill operations shall be provided. For sections with a belowgrade coating, care shall be taken during the backfilling process to prevent damage to the coating.

7.2 GENERAL Procedures for the protection of the excavation, existing construction, and utilities shall be established prior to a foundation installation. Material for the structure and lighting system shall be stored out of contact with the ground and dissimilar material, and in a manner to prevent excessive deflection, stresses, and buckling. Installation shall be in such a manner as to prevent damage to the structure and lighting system. Requirements for verification of soil conditions at a site shall be completed before the installation of a foundation. Concrete for foundations shall be placed in accordance with ACI 318-19, Building Code Requirements for Structural Concrete. Splices in reinforcing bars shall not be allowed unless otherwise specified or approved by a qualified professional engineer. Welding on reinforcing or anchor rods shall be prohibited unless approved by a qualified professional engineer. Proportions of concrete materials shall be suitable for the installation method and shall meet the durability requirements of ACI 318-19, Chapter 19, based on the site conditions. Exposed edges of concrete foundations shall have a minimum 0.75 in. (19 mm) chamfer. Drainage of the surrounding area shall be away from the base of a pole structure. For concrete foundations and for direct embed foundations with concrete backfill, the top of the concrete shall be sloped to drain away from embedded components. When a concrete drilled shaft or pier foundation does not extend above grade, landscaping or hardscaping shall be provided to keep soil and vegetation away from the base flange and anchor rods. Installing holes, enlarging holes, or welding on steel pole sections shall not be permitted unless otherwise specified or approved by a qualified professional engineer. Design of Steel Lighting System Support Pole Structures

7.4 DRILLED SHAFT FOUNDATIONS Loose material shall be removed from the base and sides of the foundation prior to the placement of concrete. Spacers shall be attached intermittently over the length of the vertical reinforcing cage to insure concentric placement of the cage in the excavation and to assure a minimum 3 in. (76 mm) clear cover to reinforcing. The reinforcing cage shall be braced to retain the proper dimensions during handling and placement of concrete. When casing is anticipated for the excavation, the bracing shall be adequate to resist the forces from flowing concrete during casing extraction. When the excavation depth exceeds the design depth of the foundation, the top of the reinforcing cage shall be supported to result in the top of the cage being no more than 2 in. (50 mm) from the top of the foundation, unless otherwise specified. Free fall concrete placement shall be permitted, provided the fall is vertical, without hitting the sides of the excavation, reinforcing bars, cage bracing, or other obstructions. Concrete shall not be allowed to fall through water. Construction joints shall not be permitted unless otherwise specified or approved by a qualified professional engineer. Casing, when used, shall not be left in place unless otherwise specified or approved by a qualified professional engineer. When high water is present or when drilling fluid is used, concrete shall be placed using a tremie pipe. Contaminated concrete shall be removed from the top of the foundation and replaced with fresh concrete. 7.5 ANCHOR RODS Anchor rods shall be set with templates to assure the proper spacing and projection above concrete and to assure the proper orientation for the supported lighting fixtures. Required washers 35

Table 7-1. Anchor Rod Top Nut Rotation. Top nut rotation beyond snug-tight Nominal anchor rod diameter

≤1.5 in. (38 mm) >1.5 in. (38 mm)

Fy ≤ 36 ksi (250 MPa)

Fy > 36 ksi (250 MPa)

1/6 turn (60 degrees) 1/12 turn (30 degrees)

1/3 turn (120 degrees) 1/6 turn (60 degrees)

Notes: Fy = specified minimum yield strength of anchor rod. The tolerance on rotation shall be +20 degrees, −0.

specified for use, with oversized holes, shall be provided on both sides of the base flange plate. Templates shall have center openings to facilitate the placement of concrete. Anchor rod base flange plate holes shall not be enlarged in the field unless approved by a qualified professional engineer. Additional washers required based on the hole diameter shall be provided on both sides of the base flange plate. Leveling nuts below the base flange plate shall be used to plumb the pole. The maximum gap between the top of the concrete and the bottom surface of the leveling nut shall not exceed the nominal diameter of the anchor rod, unless the strength requirements of Section 3.12 are satisfied and verified by a qualified professional engineer. Beveled washers shall be used above and below the base flange plate when the face of the base flange plate is sloped more than 1:40 (1.43 degrees) with respect to a plane normal to the axis of the anchor rods. Grout, when specified under a base flange plate, shall be nonshrink, nonmetallic grout with a 5,000 psi (34 MPa) minimum 7-day strength and without chlorides or other harmful additives that could cause anchor rod corrosion. Before grout is placed, anchor rods shall be fully tightened in accordance with Section 7.5.1. Grout shall completely fill the area beneath the base flange plate bearing surface. The thickness of grout shall not exceed 3 in. (76 mm). Provision for drainage shall be provided to drain the grout pad and the pole interior. 7.5.1 Anchor Rod Tightening Anchor rod top nuts and leveling nuts shall be tensioned in accordance with the following procedure, unless otherwise specified. Step 1. After anchor rod placement into concrete, clean and lubricate the exposed threads of all anchor rods and leveling nuts. Relubricate the exposed threads of the anchor rods and the threads of the leveling nuts if more than 24 h has elapsed since earlier lubrication, or if the anchor rods and leveling nuts have become wet since they were first lubricated. Step 2. Verify that the nuts can be turned onto and backed off the anchor rods past the elevation corresponding to the lowest anticipated location of the leveling nuts, by hand or using a 12 in. (300 mm) long wrench or equivalent (i.e., without a pipe extension on the wrench handle). Step 3. Turn the leveling nuts onto the anchor rods and align the nuts to the same elevation, with the gap between the bottom of the leveling nuts and the top of the concrete not greater than the nominal diameter of the anchor rods. Place the required washers on top of the leveling nuts. Step 4. Install the base flange plate on the anchor rods, with the required washers on the top of the base flange plate. Step 5. Install and tighten the top nuts to a snug-tight condition in an incremental star pattern. Snug-tight is defined as the 36

tightness obtained from a nut rotation resulting from a worker using a 12 in. (300 mm) long wrench or equivalent. An incremental star tightening pattern is one in which the nuts on opposite or near-opposite sides of the anchor rod circle are successively tightened in a pattern resembling a star (e.g., for an eight-anchor rod circle with anchor rods numbered 1 to 8, tighten nuts in the order 1, 5, 7, 3, 8, 4, 6, 2). Step 6. Tighten the leveling nuts to a snug-tight condition in a similar incremental star pattern as used for the top nuts. Step 7. After tightening all top and leveling nuts to a snug-tight condition, mark the reference position of each top nut with a suitable marking on one flat and a corresponding reference mark on the base flange plate at each anchor rod. Incrementally rotate the top nuts, using a star pattern, with the leveling nuts secured, until achieving the top nut rotation indicated in Table 7-1. Rotation shall be performed in at least two full cycles to achieve the required nut rotation. 7.6 POLE SLIP SPLICES Burrs and foreign material shall be removed from the faying surfaces of slip splices. Slip splices shall be jacked together to obtain a tight even joint. Jacking shall be performed, regardless of the specified minimum lap length for the slip splice and the lap length obtained during initial fit-up. The jacking forces shall be applied symmetrically, for equal pressure around the perimeter of the pole, to result in a straight and fully seated joint. The jacking forces shall be increased until no additional movement of the joint occurs. The lower pole section at a slip splice shall be marked to verify that the minimum lap length has been obtained. Alternatively, the distance from the base of the lower section to the base of the upper section at a slip splice shall be used for verification of the lap length obtained. The use of lubricants to facilitate obtaining the slip splice lap length shall not be allowed unless approved by the pole manufacturer or a qualified professional engineer. When multiple sections with a slip splice are lifted, temporary links across the slip splices shall be provided to prevent separation of the splice during lifting. Repairs to a coating at the termination of a slip splice shall be performed in accordance with the coating manufacturer’s specifications. 7.7 POLE FLANGE PLATE SPLICES Burrs and foreign material shall be removed from the bearing surfaces of flange plates prior to installation. Flange plate holes shall be aligned to permit the insertion of the flange bolts without damage to the threads. Flange bolt nuts STANDARD ASCE/SEI 72-21

Table 7-2. Flange Bolt or Nut Rotation. Combined thickness of flange plates, Lf

Lf ≤ 4d 4d < Lf ≤ 8d 8d < Lf ≤ 12d

Nut or bolt rotation beyond snug-tight

1/3 turn (120 degrees) 1/2 turn (180 degrees) 2/3 turn (240 degrees)

Notes: The tolerance on rotation shall be +60 degrees, −30 degrees. When the combined thickness of flange plates exceeds 12d, the required nut rotation shall be determined by actual testing in a suitable tension calibrator to result in a minimum bolt tension equal to 70% of the minimum specified tensile strength of the bolt. Lf is the combined thickness of flange plates, and d is the nominal flange bolt diameter.

shall be capable of being threaded onto the flange bolts by hand or using a 12 in. (300 mm) long wrench or equivalent (i.e., without a pipe extension on the wrench handle). Washers shall be installed with the bolt assemblies as specified for the flange plate splice. Hardened ASTM F436-19 beveled washers shall be used where a bearing surface for a nut or bolt head has a slope of more than 1:20 (2.86 degrees) with respect to a plane normal to the axis of the bolt. Flange bolts shall be initially tensioned to a snug-tight condition in an incremental star pattern, as defined in Section 7.5.1, to bring the flange plates into uniform firm contact for proper alignment of the two pole sections. More than one cycle through the initial bolt tightening process may be required. After tightening all bolt assemblies to a snug-tight condition, a reference position of each nut or bolt head in the snug-tight condition shall be marked, with a suitable marking on one flat and a corresponding reference mark on the flange plate at each flange bolt. The nut or bolt head shall be rotated using an

Design of Steel Lighting System Support Pole Structures

incremental star pattern, with the opposite end of the bolt assembly secured, until the top nut rotation indicated in Table 7-2 is achieved. Rotation shall be performed in at least two full cycles to achieve the required rotation. Because of distortions from cutting, welding, and galvanizing, continuous contact across the flange plate surfaces after final bolt tensioning shall not be required. When the flange plate contact surface and clamping force are continuous around the perimeter of the pole cross section, it shall be permissible for gaps up to 0.125 in. (3 mm) to occur around the edges of the flange plate connection. For larger gaps, galvanized or stainless steel shims or washers shall be installed at the flange bolt locations to completely fill the gap. 7.8 MISCELLANEOUS BOLTED CONNECTIONS Unless otherwise specified, bolted connections shall be installed with nut-locking devices. 7.9 INSTALLATION TOLERANCES The following tolerances shall apply unless otherwise specified: • Center of anchor rod group from center of foundation: 2 in. (50 mm). • Anchor rod spacing: ±0.125 in. (3 mm). • Anchor rod circle orientation: ±2°. • Anchor rod projection above concrete: +1 in. (25 mm), −0. • Anchor rod plumbness: 1:40 (1.43 degrees) from vertical. • Minimum nut engagement: flush with end of bolt or anchor rod. • Slip splice lap length: +10%, −0% of specified minimum lap length. • Pole height: ±2 in. (50 mm) +5% of each slip splice design lap length. • Pole plumbness: 0.5 degrees from vertical. • Pole camber: 0.125 in. (3 mm) for each 5 ft (1.5 m) of height. • Pole twist: 1 degree for each 5 ft (1.5 m) of height.

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CHAPTER 8

INSPECTIONS, ASSESSMENTS, AND MAINTENANCE

8.1 SCOPE This section provides initial construction inspection, periodic condition assessment, damage assessment, and maintenance procedures for ground-supported steel lighting system support pole structures required to assure their expected reliability and public safety. Procedures related to the lighting system, electrical power, grounding, lightning protection, and so on, are not within the scope of this standard and shall be performed in conformance with applicable building codes and safety regulations. The means and methods of performing the procedures outlined in this standard are not within the scope of this standard; they are the responsibility of the party performing the activity. 8.2 INITIAL CONSTRUCTION INSPECTIONS Construction inspections shall be performed during and immediately after an installation to confirm conformance to the design and project specifications. A construction inspection shall also be performed after structural repairs or modifications to a structure. Concrete foundations shall be inspected in accordance with ACI 318-14, Building Code Requirements for Structural Concrete. A written inspection report for construction, with photographic evidence, shall be provided to the owner, indicating conformance and items requiring remediation. The construction inspection report shall address the following, as appropriate for a specific site: • Geotechnical parameters that require verification in accordance with the foundation design or the geotechnical report for the site; • Condition of subgrade immediately prior to concrete placement; • Foundation dimensions; • Reinforcing steel grade, size, condition, support, placement, and cover; • Concrete mix design documentation, design strength, maximum aggregate size, durability requirements, and so on; • Concrete tests required prior to placement for water/cement ratio, slump, temperature, air content, test cylinders, and so on; • Anchor rod size, grade, spacing, embedment depth, orientation, and projection; • Concrete placement methods; • Finishing of top-of concrete; • Concrete curing; • Backfill material and placement requirements, lift thickness, moisture content, in-place density, and so on; • Pole orientation;

Design of Steel Lighting System Support Pole Structures

• Condition of top cap and access opening covers; • Condition of faying surfaces of slip splices and flange plate splices. • Slip splice fit-up, lap length, jacking forces applied, and condition of coatings; • Fit-up of flange plate splices; • Conformance to installation tolerances; • Height of base flange plate leveling nuts above top of concrete; • Grade of base flange plate top and leveling nuts, tightening procedures, and type of washers (e.g., standard, oversized, or thickened) installed; • Conditions at interior of pole; • Drainage of grout pad and pole interior and presence or absence of grout; • Lighting system component attachments and orientation; • Type of nut-locking devices installed on non-pretensioned bolt assemblies; • Type and presence of protective coating applied to steel pole sections in direct contact with soil; • Type and use of repair of galvanizing and other protective coatings; • Type of landscaping/hardscaping and drainage around pole base; • Condition of climbing facilities, if present; and • Visibility and condition of warning signs and labels. 8.3 PERIODIC CONDITION ASSESSMENTS After installation, periodic condition assessments shall be performed over the life of a pole structure. Assessments shall be performed by a qualified inspector with training and experience in the visual inspection of steel pole structures. Periodic condition assessments shall as a minimum include a thorough visual examination of the pole and lighting system from the ground. The visual examination shall include the use of binoculars or other means to review the full length of the pole and the lighting system. When required to gather additional information that cannot be obtained from the ground, a further examination shall be performed using a lift, a drone (unmanned aerial vehicle), or the climbing facility of the pole. A written condition assessment report shall be provided to the owner for each condition assessment. The report shall include a summary of the assessment, photographs, the results of specific testing performed, and indications discovered of damage, deterioration, or other conditions of concern. The condition assessment report shall address the following, as appropriate for a specific site:

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• Review of previous assessment and maintenance reports; • Field modification since the last assessment, including the addition of lighting fixtures or other attachments; • Presence of dents, scrapes, or other damage; • Signs of field welding, cutting, or the addition of holes in the pole wall; • Condition of galvanizing and the exposed portion of the below-grade coating; • Plumbness of pole; • Presence and condition of top cap or access opening covers; • Condition of welds around base pole section access openings based on visual inspection; • Condition of welds around base flange plate weld to the pole shaft based on visual inspection; • Condition of welds at the termination of stiffeners around the base pole section based on visual inspection; • Condition of anchor rods, removing covers from nuts or base, when present for assessment; • Presence of top and leveling anchor rod nuts and washers; • Tightness of top and leveling anchor rod nuts; • Height of base flange plate leveling nuts above top of concrete; • Presence and tightness of flange plate splice bolts or washers; • Condition of slip splices and seam weld; • Condition of lighting system component hardware and nutlocking devices; • Condition of direct embed poles at the ground line; • Means of drainage of pole interior; • Signs of corrosion; • Accumulated debris or trapped water inside the pole or around the base; • Condition of insect and rodent screens surrounding the base flange plate; • Condition of exposed portions of concrete foundation; • Condition of landscaping, hardscaping, or vegetation around pole base; • Drainage away from base of pole; • Settlement of backfill material; • Condition of climbing facility, including safety climb system; and • Condition and visibility of warning signs and labels. Refer to Appendix B for examples of issues discovered in condition assessments of steel pole structures. 8.3.1 Evaluation of Dents in Steel Poles Remediation of dents shall not be required in round or multisided pole sections when all of the following criteria are met: • No cracking in the pole section at or around the dent; • No sharply folded kinks in the dent; • Dent is located away from holes, welded plates, or other attachments; • Pole plumbness is within the installation tolerance of 0.5 degree from vertical; • Depth of dent does not exceed the thickness of the pole wall; • Maximum width of dent does not exceed 5% of the circumference of the pole; and • Maximum length of dent does not exceed 10% of the circumference of the pole. The evaluation of dents, including all measurements required for evaluation, shall be documented in the condition assessment report. On review by a qualified professional engineer, it shall be permissible to not require remediation of larger dents, depending 40

on the yield strength of the steel, the diameter-to-thickness or flat-width-to-thickness ratio of the pole cross section, and other structural considerations. Dents not meeting all of these criteria shall require a damage assessment in accordance with Section 8.4. 8.4 DAMAGE ASSESSMENTS A damage assessment shall be performed to collect additional data to determine the proper remediation for reported or suspected structural issues from storm damage, vehicular impact, excessive corrosion, deterioration, vandalism, , cracks, or other anomalous issues discovered during a periodic condition assessment. Damage assessments require an in-depth, close-up, hands-on examination by a qualified and experienced inspector familiar with steel pole structures. A written damage assessment report with photographs and the results of all examinations shall be provided to the owner. When remediation is required, the report shall be provided to a qualified professional engineer with experience in damaged steel pole structures for evaluation and creation of a plan for remediation. 8.5 ADDITIONAL EXAMINATION REQUIREMENTS Additional visual examinations and nondestructive evaluation performed in conjunction with a periodic condition assessment or required as the result of a periodic condition or damage assessment shall be performed by skilled and experienced technicians qualified for the examination methods in accordance with AWS standards, Chapter 6, unless otherwise specified. Nondestructive testing procedures shall be suitable for the application and qualified in accordance with AWS standards unless otherwise specified. 8.6 MAINTENANCE Maintenance activities shall be performed over the life of a pole structure as specified by the owner. The maintenance program shall address the following as appropriate for a specific site: • Tightening loose anchor rod top and leveling nuts; • Replacing missing anchor rod top nuts and washers; • Replacing missing flange plate splice bolts, nuts, and washers; • Ensuring that pole cap and pole access opening covers are installed; • Replacing missing hardware, including nut-locking devices for lighting system components; • Clearing base flange plate grout weep holes or other drainage means; • Removing vegetation and debris (e.g., grass, weeds, trash) in and around the base of the pole; • Tightening safety climb cable; • Touching up or repairing pole galvanizing or other coatings; and • Touching up or repairing exposed portion of below-grade coating. Missing nuts, washers, and other hardware shall be replaced with the type, size, grade, and finish specified for the installation of the pole. 8.6.1 Grouted Base Flange Plates The integrity of grout used below base flange plates shall be maintained unless otherwise STANDARD ASCE/SEI 72-21

removed on the recommendation of a qualified professional engineer based on the strength and development of the anchor rods and the base flange plate. Cracked or deteriorating grout shall be replaced with a nonshrink, nonmetallic grout suitable for

exterior exposure with a 7-day 5,000 psi (34 MPa) minimum compressive strength unless otherwise specified. The means used to drain the pole interior and the grout pad shall be kept clean and free to drain.

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APPENDIX A

GEOTECHNICAL INVESTIGATIONS

The following information should be addressed in a site-specific geotechnical investigation report: 1. Date, sampling methods, and number and type of samples. 2. Description of the soil strata according to the Unified Soil Classification System. 3. Site classification for earthquake design according to ASCE 7. 4. Depths at which strata changes occur, referenced to a site benchmark elevation. 5. Standard penetration test blow counts for each soil layer. 6. Soil unit weight for each soil layer. 7. Internal angle of friction for each soil layer. 8. Cohesion for each soil layer. 9. Ultimate bearing capacity for each soil layer or at the recommended bearing depth(s). 10. Ultimate skin friction for each soil layer. 11. Lateral modulus of soil reaction for each soil layer.

Design of Steel Lighting System Support Pole Structures

12. Soil strain at 50% of ultimate compression (ε50) for each soil layer. 13. For expansive soil conditions, the active zone of influence, and recommendations for design. 14. Elevation of free water encountered and the groundwater depth below grade to be considered for design. 15. Frost depth to be considered for design. 16. Soil electrical resistivity, pH, water-soluble sulfate concentration, and corrosive nature of soil. 17. ACI 318 Exposure Class appropriate for the foundation concrete mix design. 18. Other pertinent soil design data and recommendations. 19. Recommendations for alternate foundation types. 20. Topographic information for the site. 21. Facilities that may affect electrolytic corrosion [e.g., within a 1,000 ft (300 m) radius of the structure, the presence of underground pipelines, buried concentric neutral power wires or electrical substations].

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APPENDIX B

DAMAGE AND CONDITION ASSESSMENT EXAMPLES

Figure B-1. Severe corrosion caused by base covers and no drainage.

Figure B-3. Corrosion caused by grout trapping moisture around base plate.

Source: Courtesy of EXO Group.

Source: Courtesy of EXO Group.

Figure B-2. Corrosion and weld failure at base of pole. Source: Courtesy of EXO Group.

Design of Steel Lighting System Support Pole Structures

Figure B-4. Corrosion-reduced diameter of a 2.25 in. diameter anchor rod. Source: Courtesy of EXO Group.

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Figure B-5. Corrosion from moisture at interior base of pole.

Figure B-8. Improper field-modified anchor rod hole. Source: Courtesy of EXO Group.

Source: Courtesy of Wiss, Janney, Elstner Associates.

Figure B-6. Corrosion from moisture at interior base of pole.

Figure B-9. Pullout of anchor rod through base plate. Source: Courtesy of Wiss, Janney, Elstner Associates.

Source: Courtesy of Wiss, Janney, Elstner Associates.

Figure B-7. Adaptor plates due to improper anchor rod installation.

Figure B-10. Distressed anchor rods. Source: Courtesy of Wiss, Janney, Elstner Associates.

Source: Courtesy of EXO Group.

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STANDARD ASCE/SEI 72-21

Figure B-11. Slotted hole with no plate washer. Source: Courtesy of EXO Group.

Figure B-14. Loose slip splice. Source: Courtesy of EXO Group.

Figure B-12. Anchor rod failure caused by fatigue. Source: Courtesy of EXO Group.

Figure B-15. Fatigue failure at base of pole. Source: Courtesy of EXO Group.

Figure B-13. Failure caused by overloading with lighting fixtures. Source: Courtesy of EXO Group.

Design of Steel Lighting System Support Pole Structures

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Figure B-18. Dent on pole wall. Source: Courtesy of Wiss, Janney, Elstner Associates.

Figure B-16. Longitudinal crack in direct embed concrete section. Source: Courtesy of EXO Group.

Figure B-17. Weld defects identified by ultrasonic testing. Source: Courtesy of EXO Group.

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STANDARD ASCE/SEI 72-21

CHAPTER C1

GENERAL

C1.1 SCOPE Before the publication of this standard, current practices related to the design, installation, inspection, and maintenance of steel lighting system support pole structures for athletic fields and similar lighting system applications were not consistent and, in some cases, resulted in clear public safety issues. This standard has been developed to provide a consistent approach by providing minimum design criteria considered appropriate for lighting system support structures as well as guidelines for

Design of Steel Lighting System Support Pole Structures

their proper fabrication, installation, inspection, and maintenance. This standard applies to galvanized steel pole structures, but the provisions for strength may be applied to weathering steel poles. Special considerations apply for materials, welding procedures, detailing, fabrication, direct embed foundations, installation, inspections, and so on, that are not within the scope of this standard. The use of weathering steel for a specific application should be directed by a qualified professional engineer.

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CHAPTER C2

LOADS

C2.1 SCOPE Lighting system support pole structures are considered sensitive to wind and fatigue loading and, in high-risk seismic areas, earthquake loading. This standard provides design criteria for these loading conditions. These structures are not considered sensitive to ice loading or temperature effects; therefore, consideration of ice loading and temperature effects is not required by this standard. Lighting system support pole structures that also support cables (such as for supporting netting or powering speakers) may have strength requirements governed by ice loading and are beyond the scope of this standard. C2.3 CLASSIFICATION OF STRUCTURES For extreme wind loading events, a 7% probability of exceedance in 50 years is considered appropriate for lighting system support structures. For installations where lighting system support structures are desired to be classified higher than Risk Category II for determining wind and earthquake loads, the basic wind speed, V, for calculating wind loads defined in Section 2.7 may be obtained from ASCE 7 based on the desired mean recurrence interval. The importance factor for determining earthquake forces defined in Section 2.8 may be obtained from ASCE 7 for the desired risk category. C2.4 COMBINATIONS OF LOADS Wind and earthquake loads specified in the standard are factored; therefore, a load factor of 1.0 is used. C2.7.1 Scope The total effective projected area of a lighting system is a critical design consideration. The effective projected areas of lighting systems are highly dependent on wind direction. Lighting fixtures are typically pointed in multiple directions for lighting efficiency, which results in exposure of their front, back, top, bottom, and sides. The total effective projected area for a lighting system is complex, considering the interaction of lighting fixtures with mounting systems and other appurtenances. Very slight changes in wind direction expose multiple lighting fixtures and multiple members of mounting systems. For these reasons, this standard prescribes methods of determining design wind forces. C2.7.3 General Requirements Consideration of reduction in air density owing to elevation above sea level is disallowed in this standard as a result of the athletic field lighting industry’s standard practices of using a single design to manufacture poles for use at many facilities. In addition, for most lighting system support structures, the fatigue design requirements in Chapter 4 typically control the lateral force design, rather than wind Design of Steel Lighting System Support Pole Structures

requirements. As a result, neglecting the effects of reduced air density has no significant effect on the final support structure design. C2.7.5 Strength Design of Supporting Structures For discussion of the use of G = 1.14, refer to AASHTO LRFDLTS 3.8.6 and commentary. C2.7.5.2.1 Effective Projected Area of Fixtures Pre-engineered lighting system support structures based on maximum lighting system EPA values are often developed for use with a variety of lighting systems and locations. The documentation for pre-engineered structures should include the basic wind speed, exposure category, topographic considerations, earthquake criteria, fatigue limit state static pressure range, the maximum effective projected areas for the lighting system, and the appropriate mounting system configuration. The selection of the proper pre-engineered supporting structure for specific lighting fixtures and mounting systems should be the responsibility of the party integrating the lighting system with the supporting structure. Determination of (EPA)F values for lighting fixtures should be the responsibility of the fixture manufacturer. The lighting fixture manufacturer should state the method used to determine published (EPA)F values. Commercially-available lighting fixtures in current production use a variety of methods to determine published (EPA)F values. Those that use wind tunnel tests typically report that wind speeds 90 mi/h (144.8 km/h) or greater were used in the testing. It should be noted that wind tunnel testing of lighting fixtures is performed on full-sized fixtures and is distinct from the use of wind tunnel testing of scale-model buildings or other structures to determine design pressure coefficients. C2.7.5.3 Design Wind Force Applied to Mounting Systems The design wind force equation is based on considering a wind direction 30° from a direction normal to the lighting fixture mounting plane. Wind forces have been shown to vary based on the square of the wind incidence angle from the normal to a surface, resulting in cos2(30) = 0.75 for (EPA)N and cos2(60) = 0.25 for (EPA)T. C2.9.1 Scope The damage-equivalent wind pressure for investigating fatigue is intended to provide the minimum level of reliability considered appropriate for steel lighting system support pole structures governed by fatigue based on their typical use and the fact that they are exposed, allowing for routine examinations to detect fatigue damage (Chapter 8). C2.9.2 General Requirements The strength requirements of lighting system support pole structures are relatively low compared to poles used for other applications, resulting in structures with relatively low stiffness. Typical steel lighting 51

system support pole structures also have low levels of damping, subjecting them to potential fatigue damage. The stiffness and fatigue strength requirements specified in the standard provide a minimum level of protection from cyclic loads from vortex shedding and natural wind gusts. Vortex-shedding-induced oscillations are difficult to predict and may occur under unique circumstances even if the requirements of this standard are satisfied. Vibration mitigation devices may be required after installation. Often an iterative process is

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required for successful implementation. Maintenance and condition assessments are essential to identify and mitigate fatigue damage and other issues should they develop. Fatigue occurs as a result of fluctuating stresses; permanent loads or dead loads do not contribute to fatigue. Accordingly, fatigue loading in Section 2.4 is considered as a separate load combination without dead load. The nominal stresses from the specified fatigue loading provide the equivalent range of fluctuating stresses from wind.

STANDARD ASCE/SEI 72-21

CHAPTER C3

STEEL DESIGN

C3.3 ANALYSIS An example of a rigid plate behavior design procedure is presented in Annex Q of the TIA reference standard. Flange plates designed to reduce prying action to insignificance may also be considered as designs based on rigid plate behavior. C3.4 DESIGN STRENGTH An example of an acceptable flange plate design procedure is given in Annex Q of the TIA reference standard. Special attention is required for socketed connections to avoid excessive stresses being transferred to the pole wall as a result of the flexibility of the flange plate. In many cases, the fatigue strength requirements of Chapter 4 will govern the design of flange plates.

In recent years, a great deal of research related to failures of steel lighting system support pole structures has focused on fatigue failures resulting in fracture at the base of poles with base flange plates or at other stress concentration areas, such as openings. Fracture is normally associated with lowtemperature exposure, high cyclic stress levels, and material or welding discontinuities. The potential for fracture in fabricated steel products can be minimized by proper material selection that incorporates proper energy impact characteristics and by implementing proper design and manufacturing techniques that reduce stress risers and geometrical discontinuities. C3.6.3 Anchor Rods Zinc/aluminum coatings may react with concrete foundations and are therefore not listed as an acceptable corrosion control method for anchor rods.

C3.5 MATERIALS

C3.12 ANCHOR ROD STRENGTH

One of the most critical factors related to the ability of a fabricator to successfully manufacture a steel lighting system support pole structure is the proper specification of materials. Pole structures are typically exposed to a wide range of weather conditions, from extreme cold temperatures to hot and humid environments. In addition, pole structures can be exposed to highly corrosive conditions (either atmospheric or from the soil, irrigation, fertilizers for grass, chemicals for weed control, etc.).

The use of grout should be limited to mitigation of installation issues for existing structures. Relatively large-diameter base flange plates with center opening used for galvanized pole sections require special installation procedures. Inspection should be performed during and after the installation of grout. See Appendix B for examples of corrosion issues from entrapped moisture because of improperly installed grout.

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CHAPTER C4

FATIGUE DESIGN

C4.1 SCOPE Lighting system support pole structures conforming to this standard may develop fatigue cracking over their design life. Unpredictable wind conditions may produce stresses exceeding the fatigue thresholds, resulting in fatigue cracking during the design life. Other variables, such as installation of the structure and workmanship, can also affect fatigue life. The maintenance and condition assessment recommendations of this standard are intended to identify and mitigate fatigue-induced concerns in a structure prior to a catastrophic failure. C4.3 FATIGUE ANALYSIS The fatigue design procedures are based on limiting nominal member stress ranges to levels corresponding to the fatigue threshold of the respective details and connections to provide infinite life. Except as specified in Sections 4.4.5 and 4.4.6, nominal stresses need not be amplified by stress concentration factors because the fatigue thresholds specified in this standard correspond to defined details and connections categorized according to their level of stress concentration, inherent weld defects, and notch geometry. C4.4.7.2 Stiffener Connection with Flange Plates The fatigue threshold at the interface with the flange plate applies to both the nominal stress in the stiffener and the nominal stress on the effective throat of the weld connecting the stiffener to the flange plate. For example, for an all-around fillet weld with a combined (both sides of stiffener) effective throat equal to 50% of the stiffener thickness, a 5 ksi (34 MPa) calculated nominal stress for the stiffener would result in a 10 ksi (69 MPa) nominal stress for the effective weld throat.

A fatigue threshold is specified for anchor rods because the tightening of anchor rod nuts in a double nut base flange plate connection does not result in pretensioning of the anchor rods below the leveling nut. With each reversal in applied load, the anchor rods will experience a stress reversal just below the leveling nuts. Although tightening of a double nut anchor rod does not result in pretension in the anchor rod below the leveling nut, tightening to avoid loose nuts is required to prevent excessive stresses from developing in the base flange plate, anchor rods, and pole wall, which can significantly reduce the fatigue strength of the base flange plate connection. For example, when a leveling nut is not tight and the direction of overturning moment results in a downward force on the leveling nuts, the base flange plate must span between adjacent leveling nuts, essentially doubling the span for transferring reactions to the anchor rods. This greater span significantly increases the deformation and stresses in the base flange plate, which in turn introduces additional stresses in the anchor rods and the pole wall. A similar situation occurs when the direction of overturning moment results in an upward force on the top nuts and a top nut is not tight. The higher cyclic stresses from alternate downward and upward loading conditions can cause fatigue cracks to form in the pole wall or in the anchor rods. It is therefore important that both leveling and top nuts be tightened against the base flange plate. C4.4.9 Bolts Properly pretensioned high-strength flange plate connection bolts between pole sections (see Chapter 7) may experience a significant change in stresses with each reversal in applied load because of prying action.

C4.4.8 Anchor Rods The fatigue strength of the welded connection of the pole to the base flange plate is adversely affected by loose anchor rod top and bottom nuts. See Chapter 7 for installation requirements.

C4.5.6 Stiffened Pole-to-Flange Plate Connections Reducing the ratio of stiffener height to stiffener spacing may reduce the fatigue strength of a stiffened flange plate connection. A costeffective configuration occurs when the stiffener height is approximately 1.6 times the stiffener spacing.

Design of Steel Lighting System Support Pole Structures

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CHAPTER C5

FOUNDATION DESIGN

C5.3 GENERAL The foundation design criteria of this standard are based on limit state design criteria using factored reactions; therefore, factored reactions must be provided to the foundation engineer and designated as such on design documents to avoid possible confusion with nonfactored reactions. Use of nonfactored reactions based on an allowable stress design analysis would result in inappropriate foundation designs with inadequate strength to support the structure. In the event that reactions are not designated as factored reactions on design documents, the foundation engineer should request written documentation that the reactions are factored. A minimum height above grade for a concrete foundation may be desired to protect the pole from landscaping, vehicular impacts, and so on. The length of the assembled pole should be coordinated with the desired height above grade for the foundation. For direct embed foundations with a slip splice, the

Design of Steel Lighting System Support Pole Structures

projected height above grade of the slip splice should be adequate for proper installation considering the extension of below-grade coatings above grade. C5.4 SITE INVESTIGATION Recommendations for information to be addressed in a geotechnical investigation are provided in Appendix A. C5.10 SEISMIC CONSIDERATIONS The requirements of Section 5.10 are supplementary to the requirements for concrete foundations in low-risk seismic areas. The supplementary requirements provide for the desired ductility and energy-absorbing properties assumed for the earthquake loading design criteria of this standard, considering the unique characteristics and responses of steel lighting system support pole structures.

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CHAPTER C6

FABRICATION

C6.3 MATERIALS Fabrication processes for flat plates should not be assumed to be appropriate for forged plates, given the possible differences in flatness and waviness tolerances. Forged ring flange plates may require supplementary material requirements and unique qualified welding and inspection procedures (e.g., ultrasonic testing). C6.4.6 Weld Inspections The hot-dip galvanizing process introduces significant thermal stresses in a pole section, which may result in cracks in the weld medal or in the base metal adjacent to the weld. The formation of cracks has been difficult to predict and is influenced by several factors, such as the ratio of flange plate to pole wall thickness, material properties, joint geometry, degree of restraint, degree of strain hardening at pole bend lines, the welding process (including preheat and interpass temperatures), the galvanizing process, and kettle chemistry, among others. Undetected cracks may grow under service conditions, depending on the size and location of the crack and the magnitude and type of loading. UT inspection has proven to be the most effective method of detecting cracks and is required after hot-dip galvanizing for this purpose. Most cracks can be successfully repaired using qualified procedures. Caution should be used when repairing galvanized surfaces with zinc-based solders that contain high levels of lead or tin, because these elements may cause additional cracking after application. Laminar defects in plates from the plate manufacturing process or from through-thickness weld shrinkage stresses can significantly reduce the strength of a flange plate joint. The formation of laminar defects increases as the plate thickness increases.

of the free edges at the bend line, the temperature of the steel during bending, and whether the steel will be hot-dip galvanized. The most commonly used forming methods are press brake forming, roll forming, and stretch forming (e.g., hydroforming). Forming for pole sections generally involves cold bending parallel to the grain of the steel. Poles of various cross sections, round or multisided, can be produced by these methods. Each method has limitations as to the type of cross section that can be formed and its length, diameter, thickness, material strength, and so on. C6.9 GALVANIZING

There are limits on the tightness of the bend that can be made in a piece of steel. These limits are usually expressed in terms of a ratio of the inside radius of the bend to the material thickness. Some of the factors that affect the limits for a particular plate are the angle of the bend, the length of the bend, the mechanical properties of the plate, the direction of the bend in relation to the direction of the roll or grain in the steel, the preparation

Venting of the inside of a pole section is required to ensure the proper immersion rate into molten zinc, which is required for proper coating and to avoid trapping air at inside corners, which would prevent the coating of interior surfaces. Improper drainage can result in excessive buildup of zinc and other quality issues as a pole section is withdrawn from the kettle. Quenching in liquid following immersion into molten zinc is commonly performed to produce a desired coating appearance and to shorten the aircooling period required for handling. Double-dipping is a process used when the item to be galvanized is too large for total immersion into the molten zinc bath, given the length of the galvanizing kettle. Double-dipping involves immersing one end of the item into the zinc bath, removing it, and then immersing the other end. This process often results in an objectionable surface appearance and can also leave bare spots or trapped impurities on the interior of pole sections, which can cause premature corrosion. Zinc drips often form when a pole section is removed from the galvanizing kettle and can result in solid, extremely sharp, hazardous icicles. The method of their removal should be documented in the galvanizer’s quality manual. Filing is the preferred method, because power grinding can thin the coating on the pole section below the minimum coating thickness required. Hot-dip galvanizing is an excellent form of corrosion protection and has served many industries well for decades in numerous environmental conditions. Although it is a well-proven corrosion control method for steel structures, it should not be considered as a cosmetic coating. The following references provide valuable information on the process for owners, engineers, detailers, fabricators, and galvanizers: ASTM A143, Safeguarding against Embrittlement of Hot-Dip Galvanized Structural Steel Products and Procedure for Detecting Embrittlement. ASTM A384, Safeguarding against Warpage and Distortion during Hot-Dip Galvanizing of Steel Assemblies.

Design of Steel Lighting System Support Pole Structures

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C6.7 PUNCHING HOLES Depending on material properties, equipment wear, material temperatures, edge distances, and so on, punching a hole may result in cracks or tears along the perimeter of the hole, excessive blowout on the bottom side of the hole, noncircular holes, and indentations in the steel. C6.8 FORMING

ASTM A385, Providing High-Quality Zinc Coatings (Hot Dip). ASTM A780, Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings. AGA (American Galvanizers Association), Design of Products to be Hot-Dip Galvanized after Fabrication. AGA, Estimating the Life of Hot-Dip Galvanized Coatings.

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C6.10 ADDITIONAL COATINGS Coatings over hot-dip galvanized surfaces, in general, require special procedures compared to conventional coating systems over nongalvanized surfaces. Coating systems applied over galvanizing should be carefully selected for poles with slip splices. Damage to the coating may occur during the process of jacking pole sections together.

STANDARD ASCE/SEI 72-21

CHAPTER C7

INSTALLATION

C7.2 GENERAL Foundation design modifications may be required in the event that the soil conditions assumed in foundation design are not consistent with the actual conditions at the site. Cut or fill operations at a site location may affect the depth below grade required for a foundation. C7.3 DIRECT EMBED FOUNDATIONS Local damage to a below-grade coating can result in accelerated corrosion at the damaged area; therefore, proper repair is essential. Adjustments to the embedment depth at the time of installation for unexpected subsurface conditions are limited for direct embed foundations; therefore, their use should be limited to sites where the subsurface conditions are known. Adjustment for plumbness is limited for direct embed foundations after backfilling; therefore, care must be taken to set and support the embedded portion during backfilling operations. Proper placement of backfill is essential for the performance of a direct embed foundation. Improper backfill material or placement can result in permanent tilt of the pole when subjected to lateral loading.

Because of the variable friction conditions between a galvanized anchor rod and nut, torque verification measurements should not be substituted for the specified top nut rotations from the snug-tight condition. The 0.13 friction coefficient used in Equation (C7-1) is based on a conservatively low estimate of the friction for galvanized fasteners, accounting for creep in the galvanizing within the threads. A conservatively low estimate is desired to prevent thread stripping during verification. Direct-tension-indicating washers (DTI washers) can provide a means of verifying that proper anchor rod tightening has been achieved when tightening is performed in an incremental star pattern. ASTM specification F2437 covers DTI washers for threaded fastener diameters up to 2.5 in. (64 mm). The desired installation anchor rod tension should be specified when purchasing DTI washers. DTI washers should be placed between the leveling nuts and the base flange plate to assure that both the top nut and the leveling nut are properly tightened. Hardened ASTM F436 washers should be placed under the top nut and between the DTI washer and the leveling nut. C7.9 INSTALLATION TOLERANCES

C7.5 ANCHOR RODS The use of grout should be limited to special applications approved by a qualified professional engineer. Improper installations have resulted in premature corrosion of anchor rods and pole sections; see Appendix B for examples. Grout also inhibits the inspection of leveling nuts and anchor rods. C7.5.1 Anchor Rod Tightening Verification of the tightness of the top anchor rod nuts 48 h or more after tightening is recommended to account for possible creep in the galvanizing within the threads. Verification can be performed using a torque wrench applied to the top nuts. The torque value for verification can be determined from the following equation: T v = 0:13 d Pb

Fy = Specified minimum yield strength of anchor rod (ksi, MPa), and Ag = Gross area of anchor rod based on nominal diameter (in.2, mm2).

(C7-1)

where Tv = Verification torque (in.-kips, Nm), d = Nominal anchor rod diameter (in., m), Pb = Desired installation anchor rod tension (kips, N), = 0.50 Fy Ag for Fy ≤ 36 ksi (250 MPa), = 0.60 Fy Ag for Fy > 36 ksi (250 MPa),

Design of Steel Lighting System Support Pole Structures

Many sports lighting systems are factory-aimed, requiring precise control of the installed anchor rod group orientation. Even for systems that are not factory-aimed, it is desirable to control the orientation for aesthetic reasons. The 0.5 degree plumbness tolerance is intended to satisfy aesthetic considerations, as opposed to preventing excessive stresses in the structure under wind or earthquake loading. Most casual observers will not detect a 0.5 degree deviation from vertical, especially when there are no other vertical visual references, such as tall buildings in the background or other poles installed in a straight line. Poles can be much farther from plumb before the additional stresses in the structure become significant. For typical steel lighting system support pole structures, tilts as large as 1.5 degrees have been shown by analysis to increase stresses by only 1.5% to 2.5%. When evaluating pole plumbness, the curvature caused by unequal thermal expansion from radiant heating of one side of the structure by the sun (often termed the sunflower effect) should be considered. Evaluation of plumbness or straightness should be made at dawn in calm conditions.

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CHAPTER C8

INSPECTIONS, ASSESSMENTS, AND MAINTENANCE

C8.1 SCOPE The inspections, assessments, and maintenance procedures for a specific site may vary; therefore, not all of the procedures outlined will be applicable to all sites. Similarly, the procedures in this standard are not intended to be comprehensive with regard to all possible site conditions and applications. C8.3 PERIODIC CONDITION ASSESSMENTS Periodic condition assessments are required for the early detection and mitigation of structural issues from inevitable deterioration, corrosion, vandalism, storm damage, unexpected fatigue damage, vehicular impacts, and so on. These assessments are required to be performed by qualified inspectors with training and experience in the visual inspection of steel pole structures, but are not required by this standard to be performed by a professional engineer or a certified welding inspector. It is recommended that a condition assessment program be initiated after 6 months but not more than 1 year after the initial installation and on a 1 year interval thereafter. Shorter intervals may be required based on previous condition assessment findings or in coastal regions, corrosive environments, or areas subject to frequent vandalism. A condition assessment should also be performed after severe wind, ice, earthquake, or other extreme conditions. Many slender steel pole structures, particularly those with base plates commonly used to support lighting systems, are susceptible to fatigue cracking. The most common fatigue cracking occurs at the base flange plate weld to the pole wall. All visual inspections of poles with base flange plates (i.e., supported on anchor rods) should include up-close observations of the welded connection between the pole and base plate, with the primary focus on the weld toe on the pole wall. If cracks are suspected, appropriate nondestructive testing (NDT) techniques should be used to determine the extent of the crack, if present (refer to Section 8.5). All similar poles at the site should also be evaluated. The fatigue design provisions of this standard are intended to minimize the potential for fatigue cracking; however, unique site conditions and other factors have been known to result in unexpected fatigue cracking. In addition, many existing steel lighting system support pole structures were not designed for fatigue. Many of the catastrophic failures of steel poles over the past 10 years were primarily related to fatigue failure. Although the fatigue design provisions of this standard are believed to be conservative, the recommended condition assessment interval is intended to identify and mitigate fatigue and other issues to avoid a catastrophic failure. Many fatigue-related cracks take a significant time to propagate to a length that would cause a collapse. Frequent condition assessments allow the repair of fatigue cracks and modifications to the structure, such as adding damping or other devices to prevent further damage. Design of Steel Lighting System Support Pole Structures

Whereas corrosion may be the result of protective coatings being damaged or simply deteriorated, corrosion can be an indication of more severe underlying conditions; therefore, signs of corrosion should be taken very seriously. In particular, localized corrosion products may become evident at fatigue cracks well before the cracks themselves can be visually identified. In some cases the evidence of corrosion may only be visible on the inside pole wall surface. Rust staining seeping out from a base flange plate could also indicate corrosion of the anchor rods, leveling nuts, or the bottom of the base plates. Often when a portion of grout is removed from a grouted base flange plate for examination, gross corrosion of the anchor rods is discovered. Condition assessment reports should be maintained by the owner and provided to the responsible party performing future condition assessments. C8.3.1 Evaluation of Dents in Steel Poles Section 17 of the reference standard in Chapter 2, LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, AASHTO LRFDLTS-1, provides information related to the evaluation of larger dents in steel poles. C8.5 ADDITIONAL EXAMINATION REQUIREMENTS Nondestructive evaluations use equipment, tools, and procedures to identify and evaluate defects or deficiencies in steel, welds, or protective coatings such as galvanizing. NDE methods are also available to measure the remaining wall thickness of corroded steel pole sections. NDE of steel structures is generally performed by one or more of the following: ultrasonic testing (UT), magnetic particle testing (MT), or dye-penetrant testing (PT). Each has its advantages and disadvantages. PT for example, will only identify weld or base metal cracks that are at the surface of the metal. MT has essentially the same limitation for surface defects, but some shallow subsurface indications may be identified. UT is the most comprehensive testing method, and can detect and identify cracks at and below the surface. It can also be used to detect severely cracked or deteriorated anchor rods. UT requires a technician with specialized skill and experience, particularly when examining galvanized base flange plate welds with backing bars or backing welds. Different UT procedures are required for detecting weld cracks, versus detecting fatigue cracks, in anchor rods. All NDE methods require qualified procedures performed by qualified, properly certified technicians. NDE is required to identify defects not readily detectable by a routine condition assessment or visual examination of welds. Visual inspection alone, even by the most experienced inspectors, may not detect cracks that have developed or are beginning to develop. For this reason, it is recommended that the following 63

types of NDE be performed as part of a condition assessment on a 3-year interval: • MT and/or UT of the base flange plate to pole shaft weld, focusing on the toe of the weld on the pole wall and at the termination of stiffeners on the pole wall; • MT of the bottom 5 ft (1.5 m) of longitudinal seam welds in the base pole section; • MT of rim reinforcement welds to the pole wall at the base of the pole; • MT of pole base metal around unreinforced openings at the base of the pole; • UT of anchor rods to detect fatigue cracking; and • UT thickness measurements of pole wall and base flange plate, when corrosion is detected. Annex P of the reference standard, Structural Standard for Antenna Supporting Structures, Antennas and Small Wind Turbine Support Structures, ANSI/TIA-222-H-2017, provides an approach for evaluating weld toe cracks for steel tubular pole flange plates. A crack classification system is presented, along with a recommended repair schedule based on the age of the structure and the length and depth of the crack. C8.6 MAINTENANCE Pole modifications, especially those requiring cutting, drilling, welding, or adding attachments that may increase wind area, add weight, or add any other type of static or dynamic loading, should

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be designed and detailed by a qualified professional engineer. Section 8.2 requires a construction inspection after structural repairs or modifications. C8.6.1 Grouted Base Flange Plates The use of grout has been determined to be undesirable based on the past performance of steel pole structures given the difficult installation circumstances and drainage associated with relatively large base plates with center openings. Improperly placed grout has been shown to trap moisture and prevent the drainage of the pole interior and grout pad, accelerating corrosion of the anchor rods and the pole interior. The proper installation of grout requires placement under the entire bearing surface of the base plate, with a reliable means to drain the grout pad and the pole interior. Grout may be needed when there is an excessive distance between the top of the concrete and the bottom of the leveling nuts, creating significant bending stresses in the anchor rods (refer to Section 3.12). In some existing installations, leveling nuts have not been provided, and the grout has been installed as a structural element to transfer compression to the concrete. In other cases, the grout may be considered to act together with the anchor rods under compression to provide the required strength. In these cases, grout cannot be removed or replaced without special precautions to support the pole. For all conditions where grout is used, it is essential that a proper placement procedure be used and that drainage of the pole interior and the grout pad be provided and maintained.

STANDARD ASCE/SEI 72-21

REFERENCES

AASHTO. 2015. LRFD specifications for structural supports for highway signs, luminaires, and traffic signals. 1st ed. Washington, DC: AASHTO. ACI (American Concrete Institute). 2014. Building code requirements for structural concrete. ACI 318-14. Farmington Hills, MI: ACI. AISC (American Institute of Steel Construction). 2006. Standard for steel building structures. 201-06. Chicago: AISC. AISC. 2016a. Certification of code of standard practice for steel buildings and bridges. 207-16. Chicago: AISC. AISC. 2016b. Code of standard practice for steel buildings and bridges. 303-16. Chicago: AISC. AISC. 2016c. Specification for structural steel buildings. ANSI/ AISC 360-16. Chicago: AISC. ASCE. 2017. Minimum design loads and associated criteria for buildings and other structures. ASCE/SEI 7-16. Reston, VA: ASCE. ASTM. 2015a. Standard practice for repair of damaged and uncoated areas of hot-dip galvanized coatings. A780-15. West Conshohocken, PA: ASTM. ASTM. 2015b. Standard specification for cold-formed welded carbon steel hollow structural sections (HSS). A1085-15. West Conshohocken, PA: ASTM. ASTM. 2015c. Standard specification for zinc coating, hot-dip, requirements for application to carbon and alloy steel bolts, screws, washers, nuts, and special threaded fasteners. F232915. West Conshohocken, PA: ASTM. ASTM. 2016a. Standard specification for coatings of zinc mechanically deposited on iron and steel. B695-04 (2016). West Conshohocken, PA: ASTM. ASTM. 2016b. Standard specification for deformed and plain low-alloy steel bars for concrete reinforcement. A706-16. West Conshohocken, PA: ASTM. ASTM. 2017a. Standard specification for sampling procedure for impact testing of structural steel. A673-17. West Conshohocken, PA: ASTM. ASTM. 2017b. Standard specification for zinc (hot-dip galvanized) coatings on iron and steel products. A123-17. West Conshohocken, PA: ASTM. ASTM. 2018a. Standard specification for anchor bolts, steel, 36, 55, and 105-ksi yield strength. F1554-18. West Conshohocken, PA: ASTM. ASTM. 2018b. Standard specification for cold-formed electricfusion (arc) welded high-strength low-alloy structural tubing

in shapes, with 50 ksi [345 mpa] minimum yield point. A106518. West Conshohocken, PA: ASTM. ASTM. 2018c. Standard specification for high-strength lowalloy columbium-vanadium structural steel. A572-18. West Conshohocken, PA: ASTM. ASTM. 2018d. Standard specification for steel, sheet and strip, hot-rolled, carbon, structural, high-strength low-alloy, highstrength low-alloy with improved formability, and ultra-high strength. A1011-18. West Conshohocken, PA: ASTM. ASTM. 2019a. Standard specification for general requirements for rolled structural steel bars, plates, shapes, and sheet piling. A6-19. West Conshohocken, PA: ASTM. ASTM. 2019b. Standard specification for hardened steel washers inch and metric dimensions. F436-19. West Conshohocken, PA: ASTM. ASTM. 2019c. Standard specification for high strength structural bolts and assemblies, steel and alloy steel, heat treated, inch dimensions 120 ksi and 150 ksi minimum tensile strength, and metric dimensions 830 mpa and 1040 mpa minimum tensile strength. F3125-19. West Conshohocken, PA: ASTM. ASTM. 2019d. Standard specification for steel, sheet, carbon, structural, and high-strength, low-alloy, hot-rolled and coldrolled, general requirements for. A568-19a. West Conshohocken, PA: ASTM. ASTM. 2019e. Standard test methods and definitions for mechanical testing of steel products. A370-19e1. West Conshohocken, PA: ASTM. ASTM. 2020. Standard specification for deformed and plain carbon-steel bars for concrete reinforcement. A615-20. West Conshohocken, PA: ASTM. AWS (American Welding Society). 2015. Structural welding code–steel. AWS D1.1/D1.1M. Doral, FL: AWS. TIA (Telecommunications Industry Association). 2017. Structural standard for antenna supporting structures, antennas, and small wind turbine support structures. ANSI/TIA-222-H2017. Arlington, VA: TIA.

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OTHER REFERENCES (NOT CITED) AGA (American Galvanizers Association). n.d. Technical publication. Centennial, CO: AGA. Accessed November 12, 2021. https://galvanizeit.org/education-and-resources/publications ASCE. 2011. Design of steel transmission pole structures. ASCE/SEI 48-11. Reston, VA: ASCE.

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INDEX Figures are indicated by f; tables are indicated by t. anchor rods: examples of damage to, 46f, 47f; fatigue design, 55; fatigue thresholds, 22; foundation design, 28–29, 28e; installation and tightening of, 35–36, 36t, 61; steel design, 12, 15–16, 15–16e, 53; welding and, 31–32 appurtenances: discrete appurtenances defined, 1; wind load and, 6, 6e, 6t ASCE Standard, generally: definitions, 1; scope, ix, 1, 49 assessments, of damage, 40; evaluation of dents in steel poles, 40; examples of, 45f, 46f, 47f, 48f; periodic, 39–40, 63. See also inspections attachments, wind load and, 6t azimuth of lighting fixture, defined, 1 ballast, defined, 1 batter piles, foundation design, 29 bolts: fatigue design, 55; fatigue thresholds, 22 burning, in fabrication, 32 butt-welded connections, flange plates, 15, 23 circumferential welds, fatigue thresholds, 20 coatings, in fabrication, 32, 60 concrete mix design, foundation design, 26 connections, steel design, 14–15 corrosion: examples of, 45f, 46f; foundation design, 27–28; steel design, 12 corrosive soil, defined, 1 dead loads, 3 design strength: defined, 1; steel design, 11–12, 53 direct embed foundations: defined, 1; example of longitudinal damage to, 48f; foundation design, 27; installation, 35, 61; steel design, 12 direct embed steel sections, foundation design, 27–28 discrete appurtenance, defined, 1 drilled shaft foundations: foundation design, 27; installation, 35 earthquake load, 7; general requirements, 7; modal response spectrum analysis, 8, 8e; overstrength factor, 8–9, 9t; structural analysis considerations, 7–8; symbols for, 7 effective opening diameter, fatigue thresholds, 21 effective projected area, defined, 1 elastic structural analysis, defined, 1 equivalent constant-amplitude stress range, defined, 1 expansive soil, foundation design, 26–27 fabrication: additional coatings, 32, 60; burning, 32; forming, 32, 59; galvanizing, 32, 59–60; general requirements, 31; materials, 31, 59; punching holes, 32, 59; scope, 31; shearing, 32; tolerances, 33; welding, 31–32 fasteners, steel design, 12 fatigue design: analysis, 17, 55; fatigue thresholds, 17, 18–20t, 20–22, 20t, 21t, 22t; scope, 17, 55; symbols for, 17 fatigue failure, defined, 1 fatigue limit state static pressure range, defined, 1 fatigue load, 9

Design of Steel Lighting System Support Pole Structures

fatigue thresholds: defined, 1; fatigue design, 17, 18–20t, 20–22, 20t, 21t, 22t fit-up, welding and, 31 fixture projected area, defined, 1 flange plates: defined, 1; fatigue analysis, 55; fatigue thresholds, 23; maintenance of grouted base plates, 40–41; steel design, 14–15 forming, in fabrication, 32, 59 foundation design, 25, 57; anchor rod development, 28–29, 28e; corrosion control, 27–28; design strength of soil or rock, 28; drilled shaft and direct embed foundations, 27; foundation analysis, 25; longitudinal reinforcement, 25–26; mat foundations, 27; scope, 25; seismic considerations, 29, 57; shrinkage and temperature reinforcement, 26; site investigation, 26–27, 26t, 57; symbols for, 25; transverse reinforcement, 26 foundations: defined, 1; fatigue thresholds, 23 frost depth, foundation design, 26 galvanizing, 32, 59–60 geotechnical investigations, 43 grouted base flange plates, maintenance of, 40–41, 64 headed anchor rods: defined, 1; foundation design, 28–29 high water table, foundation design, 27 high-risk seismic location, defined, 1 holes and cutouts: example of damage to slotted, 47f; fatigue thresholds, 20–21, 22–23; punching of, 32, 59 inspection: examination requirements, 63–64; of initial construction, 39; scope, 39; of welds, 32, 59. See also assessments installation: anchor rods, 35–36, 36t, 61; direct embed foundations, 35, 61; drilled shaft foundations, 35; general requirements, 35; miscellaneous bolted connections, 37; pole flange plate splices, 36–37, 37t; pole slip splices, 36; scope, 35; tolerances, 37, 61 lens, defined, 1 lighting fixture, defined, 1 lighting fixture mounting plane, defined, 1 lighting system: defined, 1; examples of damage to overloaded pole, 47f linear appurtenance, defined, 1 live load, 3 loads: classification of structures, 3, 51; combination of loads, 3, 51–52; dead load, 3; design wind force and mounting systems, 51–52; earthquake load, 7–9; fatigue load, 9; live load, 3; scope, 3, 51; stiffness requirement, 9; symbols for, 3; wind load, 3–7 longitudinal reinforcement, foundation design, 25–26, 29 maintenance, 40–41, 64 mat foundations: fatigue thresholds, 23; foundation design, 27

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materials: fabrication, 59; steel design, 12, 53 member properties, steel design, 12–13 modal response spectrum analysis, earthquake load, 8, 8e mounting components, defined, 1 mounting systems: defined, 1; design wind force and, 51–52; wind load and, 6, 6e multisided members, steel design, 13, 13e, 14e nominal strength, defined, 1 nominal stress, defined, 1 overstrength factor, earthquake load, 8–9, 9t periodic assessments, 39–40, 63 pole base, example of damage to, 47f pole cross sections, fatigue thresholds, 22 pole flange plate splices, installation, 36–37, 37t pole sections, fatigue thresholds, 17 pole slip splices: installation, 36; steel design, 14 pole wall, example of dent on, 48f pole-to-flange plate connections: fatigue design, 55; fatigue thresholds, 21, 21e prequalified structural steel material, 12 reinforced holes and cutouts, fatigue thresholds, 20 resistance factor, defined, 1 round members, steel design, 13 seam welds, 31 seismic considerations, foundation design, 57 service basket, defined, 1 shearing, in fabrication, 32 shrinkage and temperature reinforcement, foundation design, 26 site investigation, foundation design, 26–27, 26t, 57 slip splices: example of loose, 47f; fatigue thresholds, 17 socketed pole-to-flange plate connections, fatigue thresholds, 23

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soil or rock, foundation design, 28 steel design: analysis, 11, 53; anchor rod strength, 15–16, 15–16e, 53; components and attachments, 15; connections, 14–15; corrosion control, 12; design strength, 11–12, 53; effective yield strength, 13, 13e; materials, 12, 53; member properties, 12–13; scope, 11; symbols for, 11; tubular design strength, 13–14, 13e, 14e, 14t stiffened pole-to-flange connections, fatigue thresholds, 23 stiffener connection with flange plates, 55; fatigue thresholds, 22, 22e stiffness requirement, loads, 9 structural analysis, earthquake load, 7–8 supporting structures: structural design, 51; wind load and, 4–6, 4e, 5e, 5t, 6e, 6t symbols: construction load, 3; earthquake load, 7; fatigue design, 17; foundation design, 25; loads, 3; steel design, 11; wind load, 3–4 tack welds, 31 tilt angle, defined, 1 tolerances: in fabrication, 33; installation specification, 37, 61 transverse reinforcement, foundation design, 26, 29 tubular design strength, steel design, 13–14, 13e, 14e, 14t tubular round members, steel design, 13, 13e ultrasonic testing, of welds, 32; damage found by, 48f unreinforced holes and cutouts, fatigue thresholds, 20–21 visor, defined, 1 water table, foundation design, 27 welds: example of defective, 48f; in fabrication, 31–32; fatigue thresholds on attachments, 20; inspection, 59 wind load, 3–7; general requirements, 4, 4e, 4t; shielding, 4; strength design of attachments, 7; strength design of supporting structure, 4–6, 4e, 5e, 5t, 6e, 6t; symbols for, 3–4

STANDARD ASCE/SEI 72-21