Innovative Design and Construction 9783955531713, 9783920034331

Table of contents :
Introduction
Foreword
Innovative Architecture – Research and Development
Cooperation between Producers and Designers
Portrait
Part 1. Steel and Glass Constructions
European Investment Bank, Luxembourg
Design and Implementation
Energy Concept and Facade Design
Fire Protection Planning
Structure and Teamwork
Westfield London
Digital Process Chain from Design to Execution
The Westfield Roof – from Concept to Fitting
The Role of the Facade Consultant
Minimised Shell Structures – Challenges and Prospects
Part 2. Foils and Membranes
Allianz Arena, Munich
From the Idea to the Detail
Roof Structure and Vertical Facade
Design Aspects of ETFE Foil Cushions
Development of Lightweight Building Shells
Part 3. Element Facades
The Future of the Element Facade
7 More London
Developing the Production of the Aluminium Element Facade
Construction Management
Tender Process and Design
Facades of High-Rise Buildings – Trends and Tendencies
Part 4. Structural use of Glass
Innovative Processes in the All-Glass Sector
Possible Applications of Cold-Bending
Fascinated by Glass
Glass Bridge and Glass Staircase
Applied Research Projects
Developing the Details
The Floating Seat
TriPyramid Structures
Challenges and Potential of Structural Glass
Testing and Inspection Procedures
Appendix
List of seele projects
Testing standards
Bibliography
Illustration Credits

Citation preview

INNOVATIVE

∂ development

seele

MANUFACTURING AND DESIGN SYNERGIES IN THE BUILDING PROCESS

DESIGN + CONSTRUCTION

INNOVATIVE

∂ development

seele

MANUFACTURING AND DESIGN SYNERGIES IN THE BUILDING PROCESS

DESIGN + CONSTRUCTION

Imprint

Imprint with contributions by: Herwig Barf, Dipl.-Ing. architect, senior consultant, Head of Façade Technology, DS-Plan, Stuttgart Stefan Behling, Prof. Dipl.-Ing. architect, Universität Stuttgart Christian Brensing, M.A. (RCA) London, freelance author and consultant, Berlin Ömer Bucak, Prof. Dr.-Ing., Laboratory for Steel and Lightweight Metal Construction, Munich University of Applied Sciences Tim Eliassen, CEO TriPyramid Structures, Boston, MA Andreas Fauland, Dipl.-Ing. mechanical engineering, CEO seele, Gersthofen Rudolf Findeiß, Dr.-Ing., SSP Sailer Stepan Partner, Munich Andreas Fuchs, Prof. architect, Hochschule Rhein-Main, Wiesbaden Günter Hartl, CEO seele pilsen, Pilsen Thorsten Helbig, Dipl.-Ing., Knippers Helbig Advanced Engineering, Stuttgart Christoph Ingenhoven, Dipl.-Ing. architect, CEO ingenhoven architects, Düsseldorf Michael Jurenka, Dipl.-Ing. mechanical engineering, Consultant Energy Design, DS-Plan, Stuttgart Bruno Kassnel-Henneberg, Dipl.-Ing. civil engineering, Product Development and Marketing, seele sedak, Gersthofen

Editorial services: Steffi Lenzen, Dipl.-Ing. architect; Katja Pfeiffer, Dipl.-Ing.; Roland Pawlitschko, Dipl.-Ing. architect; Sandra Reinalter, Dipl.-Ing. Barbro Repp, M.A.; Antje Schütze, M.A. Drawings: Daniel Hajduk, Dipl.-Ing.; Martin Hemmel, Dipl.-Ing.

Wolfram Klingsch, Prof. Dr.-Ing., CEO BPK Brandschutz Planung Klingsch GmbH, Düsseldorf Jan Knippers, Prof. Dr.-Ing., Knippers Helbig Advanced Engineering, Stuttgart Josef Ludwig, Dipl.-Ing. civil engineering, CEO seele austria, Schörfling Karsten Moritz, Dr.-Ing., Head of Research and Development, seele cover, Obing Laura Passam, Westfield Shoppingtowns, London Roland Pawlitschko, Dipl.-Ing. architect, architecture journalist, Munich Katja Pfeiffer, Dipl.-Ing., architecture journalist, Munich Johann Pravida, Prof. Dr.-Ing., SSP Sailer Stepan Partner, Munich Rebecca Rettner, Dipl.-Ing. civil engineering, BPK Brandschutz Planung Klingsch GmbH, Düsseldorf Emil Rohrer, Dipl.-Ing. mechanical engineering, Head of Research and Development, seele, Gersthofen Christian Schittich, Dipl.-Ing. architect, Editor-in-chief DETAIL, Zeitschrift für Architektur und Baudetail Kurt Stepan, Dr.-Ing. architect, CEO SSP Sailer Stepan Partner, Munich Ross Wimer, AIA Design Partner, Skidmore, Owings & Merrill, Chicago

This work is protected by copyright. All rights are reserved, specifically the right of translation, reprinting, citation, re-use of illustrations and tables, broadcasting, reproduction on microfilm or in other ways, and storage in databases of the material, in whole or in part. For any kind of use, permission of the copyright owner must be obtained..

Graphic Design Concept and Cover Design: Cornelia Hellstern, Dipl.-Ing.

Typesetting & production: Simone Soesters

Translator (German/English): Roderick O’Donovan, Vienna

Printed by: Kösel GmbH & Co. KG, Altusried-Krugzell 1st edition, 2009

© 2010 Institut für internationale Architektur-Dokumentation GmbH & Co. KG, München A special theme publication from DETAIL editorial office

This book is also available in a German language edition (ISBN: 978-3-920034-31-7).

ISBN: 978-3-920034-33-1

Printed on acid-free paper made from cellulose bleached without the use of chlorine.

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Contents

Contents Introduction Foreword Innovative Architecture – Research and Development Cooperation between Producers and Designers Portrait

Part 3 – Element Facades 7

The Future of the Element Facade

59

8

7 More London Developing the Production of the Aluminium Element Facade Construction Management Tender Process and Design

60

11 13

Part 1 – Steel and Glass Constructions

Facades of High-Rise Buildings – Trends and Tendencies

European Investment Bank, Luxembourg Design and Implementation Energy Concept and Facade Design Fire Protection Planning Structure and Teamwork

17 18 20 22 23

Westfield London Digital Process Chain from Design to Execution The Westfield Roof – from Concept to Fitting The Role of the Facade Consultant

28 30 34 37

Minimised Shell Structures – Challenges and Prospects

60 64 66

70

Part 4 – Structural use of Glass Innovative Processes in the All-Glass Sector Possible Applications of Cold-Bending Fascinated by Glass

75 80 81

Glass Bridge and Glass Staircase Applied Research Projects Developing the Details

82 82 86

39

The Floating Seat TriPyramid Structures Challenges and Potential of Structural Glass

90 91 92

Allianz Arena, Munich From the Idea to the Detail Roof Structure and Vertical Facade Design Aspects of ETFE Foil Cushions

41 44 46 48

Testing and Inspection Procedures

94

Development of Lightweight Building Shells

53

List of seele projects Testing standards Bibliography Illustration Credits

Part 2 – Foils and Membranes

Appendix 103 110 111 112

INTRODUCTION

Foreword

Foreword

In the public eye, as well as in specialist publications, it is above all the architects involved, possibly also the engineers, who are perceived to be the authors of a design or the creators of a spectacular building. But what use are the boldest ideas if no one can be found to translate them into reality? Precisely on account of the increasing complexity of construction it is the building firms and industries, with their specialized knowledge and abilities, that are often the key to enabling a vision to become reality. This applies to structural glass building as well as to foil and membrane constructions, to innovative timber building, slender steel structures and to modern facade construction. But in achieving their aims, how can designers profitably use the entire potential offered by such businesses? How can synergies between all those working in the design and building processes be most efficiently created? To achieve first class results it is of significant benefit to architects and engineers to have a precise knowledge of the processes and procedures used by the other side: what processes does a manufacturing and construction business use from the awarding of the contract to the completion of the project, what are the special areas of competence, what particular kind of know-how exists in such a firm? What possibilities exist for carrying out tests and checks, what is being currently researched, or are there perhaps already innovations that are simply waiting to be used in a suitable commission? The new DETAIL development series aims to provide answers to these and similar questions.

This book, the first volume in the series, is the outcome of close collaboration with seele, a highlyqualified specialist company based in Gersthofen that regularly explores and extends the boundaries of what is technically feasible. seele is in demand worldwide wherever bespoke solutions are required – in the area of all-glass, or steel and glass constructions, element facades and, since completing a successful acquisition, in the area of membrane structures. The design and construction processes involved in one or two representative buildings from each of the categories mentioned, along with more general articles on construction themes, form the focus of this book. Major protagonists describe the approaches and circumstances from their respective viewpoints: architects and structural designers, clients’ representatives, project managers, facade designers as well as other specialist engineers. At regular intervals, construction firm managers examine concrete questions and the solutions to them from a number of different angles – the dialogue between the various participants is therefore continued in this publication. Christian Schittich

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Introduction

Innovative Architecture – Research and Development

Innovative Architecture – Research and Development Stefan Behling, Andreas Fuchs, Stuttgart University 1 Prof. Stefan Behling, senior partner in the office of Foster and Partners, is director of the Institute for Building Construction and Design, L2 and head of the IBK Research + Development at Stuttgart University. The focal themes of research at this faculty are: solar building, building envelopes, building with glass, and bionics.

Prof. Andreas Fuchs, architect, a member of the scientific staff at IBK2 at Stuttgart University from 2001 to 2009, is a co-founder of the IBK Research + Development and since 2009 professor at the Hochschule Rhein-Main. Focal themes of his research are: transparent adhesive technologies, light-weight glass building elements, structural glass building and integrated high-performance facades.

1 Design perspective of the glass bridge for glasstec 2008 2 Assembling the glass bridge 3 Glass saucer dome, glasstec 1998

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Almost no other area of architecture has experienced such dramatic developments in the last few decades as the building envelope. The innovations have resulted from a number of different motivations. The desire for transparency seems to be a constant; at the same time the ecological and economic demands made on the building – and consequently on its envelope – are continuously increasing. These represent immense challenges for both the designers and the construction firms. In this area seele, as one of the leading manufacturers of glass, steel, aluminium and membrane constructions, regularly sets new standards. Most publications tend to concentrate on architectural striving for visual effects and on new kinds of surfaces and functions, whereas technical implementation or execution, which, if the building is constructed, affect the designer directly, are very rarely dealt with in any real depth. This book concentrates on precisely these aspects. Research and development For over a decade the Institut für Baukonstruktion und Entwerfen, Lehrstuhl 2 (Institute for Building Construction and Design, Chair 1) and the IBK Forschung+ Entwicklung (IBK research + development) have worked closely with seele to develop innovative solutions. The constant flow of new themes, many of which are often first defined in the course of joint discussions, demands new and innovative approaches from teams that are put together individually to deal with specific areas. Shielded from the deadline pressure of daily project work, we can venture together along new paths. Ideas are discussed on various levels, from the detail solution to strategic measures that open up entirely new possibilities for the use of glass. But ultimately the emphasis is always on the feasibility of the concepts, in the form of large, accessible and therefore understandable prototypes for glasstechnology live, the innovations section of the glasstec trade fair in Düsseldorf, culminating in joint research work. Every concept however innovative it may be, must prove its worth in the implementation phase, as this is the only way to achieve results that are both reliable and useful for large-scale applications. For example: the spherical glass saucer dome for

glasstec 1998 has a diameter of 13 m and exploits the considerable ability of glass to provide a loaddistributing, structurally effective building element. Glass is ideally suited for taking controlled compression forces. After all, its compressive strength of 700N/mm2 is 20 times greater than that of concrete. The structural system of this glass saucer dome is like that of an igloo, which, in the ideal case, is subject only to compression forces. The cable system with stainless steel joints is pre-tensioned to ensure that compression forces are dominant at all times. A passion for research Every innovation requires motivation. The wish or intention to rethink approaches to solutions or even to formulate them in an entirely new way is certainly one of the basic prerequisites for innovations. Another is the level or simply the amount of knowledge of those involved in the process. Together with an interest in experimenting, these are the most important characteristics of successful collaboration in research and development. Our experience has shown that innovations very rarely occur arbitrarily or by chance. Precisely in the area of the building envelope, an awareness of state-ofthe-art technology and the possibilities it offers form the basis of every further development. At the same time this knowledge should not in any way hinder the delight in experimenting. Every research project is the result of experiments, both successful and unsuccessful. The experience and awareness gained from these form a foundation that enables the performance level to be raised in each new research project. In addition new approaches to construction, new production technologies, materials and inspiration from other sciences, as well as the experience gained from research and implementation projects all make a contribution. For this reason the Institut für Baukonstruktion und Entwerfen, Lehrstuhl 2 has been involved for many years in research and development within the framework of the technology transfer initiative at Stuttgart University. The experience acquired in a development project for a new kind of glass sandwich element that can be used structurally could be employed in work on cold-formed glass elements for a bridge

Innovative Architecture – Research and Development

2

made entirely out of glass to be presented at glasstech 2008. Float glass is essentially flexible in the direction of the thickness of the sheet. In the sandwich building elements we experimented with float glasses 3 to 4 mm thick. In the form of elements measuring 4 ≈ 1 m these are extremely flexible and could be curved along one axis by using a simple mould, while still remaining within the permissible stress limits. Gluing to the flexible core and to a second outside layer in a way that is effective structurally (and therefore also in terms of construction) produces an extremely high-performance glass composite element that is not curved thermally. New methods of curving glass At around the same time seele built the new glass front building to Strasbourg railway station on the basis of French architect Jean-Marie Duthilleul’s design and in collaboration with the engineering office RFR. Cold-bent laminated toughened glass panes were used here for the first time in a primary structure consisting of 16 steel arches. Instead of the sandwich core that we had envisaged, a PVB foil took on the function of both spacer and structural connection of the two covering panes. The main advantage lies beyond doubt in the visual brilliance of the cold curved panes and the simplicity with which they can be made.

certainly not to develop a prototype for a glass bridge, but rather to prove the potential and performance offered by the new technology of »layered glass panes«. In addition to planar surfaces that can far exceed the standard dimensions of float glass (6 ≈ 3.21 m), the combination of building elements curved along one axis, and in the future possibly along two, allows completely new design approaches for large areas of glazing such as atriums. Collaboration between universities and firms Ideally, collaboration between industry and university takes the form of a continuous dialogue. This dialogue must be cultivated and nurtured: it is not the institutions but individual persons in them who communicate and cooperate with each other. Respect for the achievements of others is an important basis for continuing collaboration over a period of years. The goals certainly include achieving a balance between the constant stream of new technical possibilities and the demands of architec-

IBK2 Stuttgart University The Institut für Baukonstruktion und Entwerfen, Lehrstuhl 2 at Stuttgart University is headed by Prof. Stefan Behling and Dipl.-Ing. Peter Seger, Akad. Oberrat, who works in the areas of teaching and research. The teaching of building construction deals with the integration of the subsystems structure, envelope, and technical fitting-out in the overall system of the building from the viewpoints of function, aesthetics, economy and sustainability. The research department of the IBK2 concentrates on research into new materials and the development of new building technologies.

Development potential On the basis of this experience, the first sketches were made at Stuttgart University for the construction of an all-glass bridge made up of three glass elements, curved along a single axis, that can be walked across, without any supporting steel elements. The walkway consists of eight 4-mm-thick glass panes, and each of the parapets is made of six 4-mm-thick glass planes. Both the walkway of the bridge and one parapet were made of abutting and overlapping laminated glass panes in the core of the element. Consequently, in terms of the philosophy behind their production, they are closer to the principle of laminated veneer timber than to familiar structural glass construction elements. The transparent butt joints are so discrete that they are not noticed by observers. The goal here was 3

9

Introduction

4 Fitting the steps of the research project »all-glass stairs« for glasstec 2006: thanks to new, highly transparent gluing and laminating techniques the glass panes appear to hover on their supports, whereas in fact they form a structurally effective unit. The connection technique joins the individual elements to form an overall load-bearing construction while at the same time allowing easy assembly and demounting 5 An important branch of research in industry and universities deals with new applications and uses for membranes and foils

Literature • Sophia and Stefan Behling: Sol Power. Munich 1996 • Sophia and Stefan Behling: GLASS. Munich 1999 • Andreas Achilles, Jürgen Braun, Peter Seger, Thomas Stark, Tina Volz: glasklar. Munich 2003

Innovative Architecture – Research and Development

4

5

ture, and ensuring mutual inspiration and motivation. Industry can find competent and independent partners in the universities. Nowhere else are current trends in architecture with regard to both design and technology so intensively discussed as at the university. For years we have analysed and examined examples of excellent architecture irrespective of what particular design direction they followed. These analyses can be incorporated directly in research work and they help to broaden the basis for discussion from the very start. The work in recent years has dealt with a variety of different themes such as the integration of solaractive components in the building envelope, the development of the adaptable building envelope, transparent glued connections in structural glass building, production technologies for free-form facades made of metal or glass composite elements with integrated light-directing technology.

nologies are presented providing both an incomparable overview and source of inspiration. The intensive work on the exhibition and the dialogue conducted with the firms is evident in the books (e.g. Sol Power, GLASS, glasklar) that have been produced in the course of this cooperation. This exhibition has also enabled pioneering constructions to be built in collaboration with the firms and engineers involved and to present these to international visitors. Last but not least three projects, the all-glass bridge, the all-glass stairs and two2one, a glass partition wall system made by König+Neurath, were awarded the innovation prize Glas + Architektur by a jury made up of engineers and architects.

Membrane and foil architecture It is impossible to ignore the trend in the building envelope towards light-weight and efficient constructions with multi-functional characteristics. Here the use of membranes and foils plays a pioneering role. These form another important focal point of research and development work in industry and universities. In addition to transferring loads, the high-performance building material ETFE offers economic advantages and, where used sensibly in conjunction with professional planning, contributes to an economic use of resources. These positive qualities mean that we can expect the use of foils to become increasingly important in architecture. Developments such as LCD layers laminated with foils that change their transparency when current is applied, foil coatings that light up when radiated, or the introduction of light at the cut edges of foils suggest new innovative applications and offer architects and clients interesting perspectives. glasstechnology live Since 1996 the Institute has taken part in the glasstechnology live exhibition which forms part of glasstec in Düsseldorf. On an area of over 3000 m2 current trends in glass, glass refining, coating, architectural applications, solar design and facade tech-

10

Conclusion From the viewpoint of companies, one important advantage of collaboration with research institutes is the independent energy that it introduces to the discussion. Rather than seeing themselves as service providers, the research institutes regard themselves as partners of equal standing in a dialogue and coordinators of the joint research work. Innovation cannot be constrained by timetables. Otherwise, we could simply outline questions about the future supply of energy or mobility in working papers and then work through them. The future and the challenges it will present cannot be predicted, but we can work intensively on this area and, ideally, gain an intimation of the solutions that would provide all involved with a head start over the current state of technology. We hope that this book will offer the interested reader an insight into the exciting processes of construction, development and realisation of pioneering projects. The serious minded search for innovative solutions and strategies forms the common denominator for those involved in projects. We look forward to the challenges that the future will bring for all of us.

Cooperation between Producers and Designers

Cooperation between Producers and Designers Christian Brensing (CB) in conversation with Wolf Mangelsdorf (WM), Buro Happold

CB: How is the work divided up between Buro Happold and the firms that produce the facades? WM: Normally Buro Happold undertakes the structural and conceptual planning of the facade. Once the work has been handed over to construction firms, they take on responsibility for the details of the joints and for the execution of the steelwork. We engineers, on the other hand, deal with the specific load requirements, which we continue to determine on the basis of existing assumptions. A good design can really profit from involving the construction firms at an early stage. During this stage we determine the construction schedule, the method and manner of construction, and the materials. All of this contributes to the success of the project. We engineers can certainly come up with a lot of ideas but we cannot easily build all of it – or at least not within the constraints of a reasonable time and budget framework. CB: What does a working day in the project team look like? WM: The real value lies in the way we get on with each other and tackle the problems that emerge. I know of no single project that runs without any mishaps from beginning to end. There are always inconsistencies, the unforeseeable crops up regularly. The decisive thing is how we approach such uncertainties. At the beginning of each project we attempt to anticipate the future in some way or other; initially with the help of our ideas and calculations and later with the help of drawings. The important step here is the transition from the computer drawing to the actual building. And this step can never be planned 100 per cent. But inconsistencies can also emerge as the result of differences of opinion or through the way in which somebody wishes to implement their concept of something. This makes it essential from the very start to communicate and cooperate with each other. Only in this way can everybody be involved in the design process from the very start. This prevents us from designing something that cannot actually be carried out. This is a complex coordination process that extends through all the planning and construction phases. When something unforeseen

happens, for example when someone overlooks or forgets something important in his design, the important thing is that we deal with this situation together. A straight-forward, constructive and productive approach is the only sensible solution and ensures the success of the project. CB: Buro Happold is known for its collaboration with architects. How does the construction firm fit into this constellation? WM: We engineers ensure that the design is physically feasible. The process is based on a series of steps. First of all we work out technical engineering solutions and make our calculations. These often influence the aesthetics of the architect’s design. Take, for example, the roof over the courtyard of the British Museum in London. While not by seele this project is still a very useful example for studying the history of the development of the node. I can see an analogy in its design and geometry to the structure of Westfield Shopping Centre. In principle it is the same kind of construction, a lattice shell broken up into triangular areas. From the ground the human eye cannot register any major differences. After the architect had examined the engineer’s work from aesthetic points of view, the construction firms were called in. The exchange of ideas between architect and engineer improves the feasibility of the design. We should attach considerable importance to continuing this dialogue with the firms as well. It develops from the first idea through the entire design and construction process to the completed building. In this way we draw closer, step by step, to the final artwork.

Since 2002 architect and civil engineer Wolf Mangelsdorf has been a partner in Buro Happold – an international and multi-disciplinary engineering office with more than 30 years’ experience and over 1600 employees throughout the world – and he heads the structural design group in the London office. Wolf Mangelsdorf on the cooperation between Buro Happold and seele: “I believe that seele and Buro Happold have a number of things in common. Our design approaches, for instance, are very similar. In detail this means: exchanging ideas and opinions about the project from a very early stage, the joint selection of the right materials and structural systems, putting together the right team. When we cooperate with a firm of this kind, then this is something special: it is more fun and it is enjoyable to see how one’s own ideas are developed further. One joint project is Terminal 3 at Heathrow Airport in London. It shows that seele works very well with design teams and achieves solutions of true aesthetic quality.”

CB: For how long and up to which point do you follow the design process? WM: From design to the preparation of the tender documentation the engineer is responsible for designing the load-bearing elements. After this the construction firms take on responsibility for the execution and for calculating the connections. They develop the design further on the basis of our concept, make their specific calculations and detail our plans according to their technical standards. Naturally, we accompany the project beyond this point to the end. Either we appoint a project man11

Introduction

Cooperation between Producers and Designers

6 6 Protective roof in Pouilly-en-Auxois, architect: Shigeru Ban, structural designer: Buro Happold, Bath (2007) 7 Terminal 3, Heathrow Airport, architect: Foster + Partners (2007)

ager or we make regular site visits. In the production phase we also work very closely together with the construction firms. In the case of all the recent projects with their strongly shaped facades and steel details we continued to follow their progress in all areas as far as was possible.Today geometries of this kind are often highly complex and demand a different way of working from the structural engineer, for example as regards how he conveys information to the construction firms. CB: What design methods do you use at Buro Happold?

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WM: Increasingly we are moving away from the standard drawing and in the direction of threedimensional geometries. Our 3D models are then imported straight into the manufacturers’ 3D models. In preparing the information we are in constant contact with the architects and the construction company. Then we write the specifications and tender documentation for the project and decide upon a firm to carry out the job. We work together until we have acquired clear information about the production process. Complex geometries often have equally complex definitions of their interfaces. Here the important thing is the transfer of coordinates and conveying the three-dimensional forms. Very often this depends on the software used for the production. We adapt our entire information system accordingly so that the firm can take up the information quickly and easily. As a rule we develop the first details at the design phase. The idea behind this is that our concepts can then be pursued further and do not get lost along the way. Outline details can be developed very quickly. But elegant and sophisticated solutions require a first-class company. In my opinion in such cases seele works with a very special finesse that is suited to the individual situation. Everything is ultimately a question of the approach. We need the right people who understand that early involvement in the design process will result in a better end product.

Portrait

Portrait Christian Schittich (CS) in discussion with Gerhard Seele (GS) and Siegfried Goßner (SG)

CS: The seele company is now 25 years old. How was the business set up originally and how was the partnership between Gerhard Seele and Siegfried Goßner formed? GS: Towards the end of the 1970s, when I was the managing director of a glazing business with a staff of six, I received a commission from a steel construction firm in Augsburg. This was to glaze steel constructions without the use of putty. Mr. Goßner was the technical project manager in the client company. Thus for years we had dealt with much the same themes. However it became clear relatively soon that a steel construction company is focused more on tonnages than on the long-term development of well-functioning facade constructions. Moving from this realisation to the subsequent founding of an independent business did not take long. CS: In 1983 you set up your joint firm. How were the responsibilities divided between the two of you? GS: Mr Goßner was responsible for the engineering, in particular for the steelwork; I took over the commercial and glass technology aspects. I have retained this area within the management structure of seele holding up to the present day. As far as technology is concerned our coming together represented a symbiosis that could hardly have been any better. Knowledge of structural steel construction encountered experience with glass and metal building. Our philosophy was to provide the customers with a complete package of services in the areas of steel, aluminium and glass construction and thus to offer an alternative to the splitting up into individual trades that was still common in many places in the mid 1980s by providing an inclusive tender from just a single business. It soon became clear that our original intention to build up a larger metal working business to offer the complete package referred to above was not at the right scale, as, thanks to the technical office headed by Siegfried Goßner, entirely different possibilities arose. From the very beginning we were commissioned to carry out projects involving six and seven figure sums. Naturally, the structure of the firm lagged behind its sales and marketing success.

CS: What was the relationship between the commissions and the development of production capacity? GS: After only a few months a workshop with a floor area of 500 m2 that had been rented in 1984 had become too small. The discrepancy between the external appearance of the firm and the still non-existent »internal dimension« increasingly grew into a kind of all or nothing gamble. We had to prevent visits from architects and clients by using all imaginable kinds of tricks, so as to avoid them seeing the team, which was still small. For further expansion we urgently needed a new workshop specially adapted to our requirements. Increasing the number of staff, advance financing of projects that were not exactly small-scale, and the new building that was needed represented challenges that were almost impossible to manage in financial terms, as the banks were very cautious. Their involvement went little further than small private credits and building society loans. And so the acquisition of capital, and in particular short-term liquidity turned out to be an enormous obstacle to expansion. In 1984 a storm known as »The Munich Hailstorm« destroyed thousands of square metres of glazing. We saw our chance and immediately we sent anyone who had ever held a glass cutter in their hand or was able to use a putty knife to Munich, even though the issue here was not a commission to build a facade but merely conventional re-glazing work. I also exchanged my managing director’s coat for overalls and for weeks I worked at building up »short-term liquidity«. As the large projects from this time also produced positive figures, we were able to construct the new building in 1987. We had hardly moved in when the workshop, which was more than 1000 m2 in area, and the technical office attached to it again proved too small so that in 1989/90 we had to add a further 10 000 m2 of production area. The development of the heated facade made larger production areas necessary, in particular for varnishing and painting.

Company history In 1983 master glazier Gerhard Seele and steel construction expert Siegfried Goßner combined their knowhow in a joint firm in Gersthofen. From the outset seele used the latest developments in its projects and in the first year of business already developed a number of its own patents. Regional buildings were followed rapidly by large projects in Germany such as the Leipzig Trade Fair. Ten years after its founding seele registered a ten-fold increase in turnover and the number of staff. With the goal of becoming international, in 1994 a company was set up in Austria as well as sales branches in France and the UK. In 1996 there followed the establishment of additional production facilities in the USA. The headquarters in Gersthofen have also grown continuously. In the course of intensive research and development work in the field of building with glass, this area was given its own production building in 2004. 2007 saw the founding of seele sedak, a business that concentrates on all-glass constructions and highquality glass products. By acquiring covertex GmbH in August 2007 seele expanded its range of products to include membrane and textile constructions; in addition to the headquarters in Obing an important production facility in Shanghai forms part of this area of business. In 2008 a new administrative building was erected in Gersthofen, and at the same time a factory for producing aluminium element facades was erected. In 2009 seele expanded its production capacity in its home base by erecting a large hall for innovative glass building. In the same year covertex was integrated in the group of companies under the name seele cover.

CS: And expansion abroad then followed immediately? SG: Yes, back in 1993 we entered the markets in Hong Kong and the UK and subsequently in America and France. In these markets, too, the share13

Introduction

Portrait

holders’ positive attitude to making investments was the main source of support and has remained so to the present day. This approach is not confined to buildings and machines but also encourages the development of innovative ideas in particular. Staying abreast of the latest developments was the motto and has remained so. CS: What are your most important innovations? GS: Well, the heated facade already mentioned is certainly exceptional, as are the self-supporting glass roof constructions without a steel structure, but equally the serial production of element facades for high-rise buildings in the form of a precisely planned and prepared production line. Another extremely interesting area of innovation is the production of self-supporting glass elements with a length of up to 15 metres and the possibility of glass-to-glass connections using laminated connecting elements. Prefabricated cold-curved panes, which within certain limits even allow spherical curves, represent our current daily challenge. CS: How does architecture profit from these innovations? GS: It would be somewhat presumptuous on our part to speak of a direct influence on architecture. However we can demonstrate unimagined possibilities in steel or glass facade constructions in terms of structural design and building physics. For this reason it is necessary to make our know-how applicable by means of targeted investments in new production technology. I am thinking here in particular of the outsize toughened and laminated insulation glass panes, which, as either flat or curved units, allow new kinds of architecture. In this context it will be important to develop a connection system that allows glass structures without oversized substructures. I am thinking also of highly functional element facades for high-rise buildings. In this area, too, we are working on reducing the load-bearing structure without limiting performance. The gain in usable floor area would be a fine contribution in both technical and economic terms. CS: What role does the computer play in your creative work? 14

SG: These innovative designs would not be nearly as sophisticated without the use of 3D computeraided drawings linked directly to the machines. The shift from drawing towards modelling marks the start of a new era of possibilities that we cannot yet predict down to the last detail. The often elaborate geometries of modern buildings can only be translated into reality if we develop the architectural models in our computers further. We work the existing 3D models in terms of structural design and facade technology to such a stage that at the end of the process the architect is given back his own model along with a three-dimensional drawing of the facade. CS: That sounds like extremely close cooperation with the designers. SG: Clearly this integrated approach demands a special kind of collaboration between architect or engineer and the firm that carries out the work. One could even talk of the need for collaboration as partners, so that the architectural vision remains within the area of economic and structural feasibility. My personal vision is the creation of a specially trained task force in the company that works permanently on the development of the themes referred to and, as a result, within a short space of time works out technical solutions that are not only innovative but also economically realistic. After all, what is the point of technical feasibility if it is economically unaffordable? I therefore work with a team of 10 CAD technicians and mathematicians to research and develop solutions that make complex geometries economically viable. CS: Have there been encounters with engineers and architects that particularly impressed you and influenced your work? SG: I don’t want to mention any individuals or offices here, as in the course of the years we have cultivated close links with dozens of engineers and architects. However, I have been impressed by the fact that often architects and engineers brought visions to us that, at first glance, I assessed as too far removed from reality, but that, when looked at more closely, turned out to be feasible. I’m thinking here in particular of the beginnings of the cable

Portrait

and shell structures but also about self-supporting glass structures and constructions. Much of this was defined in the 1990s as revolutionary and consequently impossible to carry out. And nevertheless we meticulously conceived detail after detail and by means of calculations and tests we provided the proofs required in terms of structural stability and building physics. Today what was worked out back then with such effort has become the current “state-of-the-art”. CS: What value do you place on the theme of sustainability? GS: Sustainability plays a major role for us in three different areas. In the area of technology it can only be achieved through constant research and development. To do this we must adapt the budget for non-commission-related research to respond to the demands of the international markets. This requires investment in suitable staff and also investment in plant and buildings, so that a healthy mix produces a dynamism that I would almost call “natural”. A further important component in implementing sustainability is increasing the economic strength and profitability of the individual businesses in the concern. This ensures high credit-worthiness for the group as a whole. An important role here is strengthening our own capital. This ensures the availability of the necessary financial facilities at all times and in sufficient amounts. And finally, we implement structural sustainability on the management and social level. The founders and shareholders, Siegfried Goßner and I, resigned from the operative management two years ago. The entire seele group consists of locations in Gersthofen (D), Schörfling (A), Obing (D), London (UK), New York (USA), Strasbourg (F), Pilsen (CZ), Shanghai (VRC) and Dubai (UAE) each run by independent management that is responsible to the holding. The holding has mostly a controlling function, sets the goals of the concern and decides on the management staff. In my view this controlling but also visionary unit is an important structural contribution to achieving sustainability.

important goal, sustainability. All our other aims can be summarized under this heading. In my view a visionary goal is to be able to conserve special achievements and successes so as to be able to call again on the creative strength inherent in them at the right time. But probably a less philosophical vision is sufficient: the glass roof as a membrane-like construction without a separate substructure. GS: To expand our portfolio of products in the area of steel and glass facades and roof constructions, large element facades as well as glass-on-glass constructions we have expanded the product area to include membrane constructions. The development of transparent ETFE membranes is currently experiencing a boom, and the Allianz Arena project has certainly made this material known worldwide. A look into the future shows a corporate group that is well positioned in all areas and that in the decades to come will certainly remain a successful partner for both architects and building clients.

Gerhard Seele Gerhard Seele was born in 1955 in Augsburg. During his childhood his father, Wilhelm Seele sen., set up the glaziers Seele in Augsburg. At the age of 16 Gerhard Seele began an apprenticeship as glazier in his parents’ business, which he took over 20 years later, following the death of his father. After qualifying as a master craftsman glazier he built new business premises, and received his first small commissions in the field of metal and glass construction between 1981 and 1983. At the end of 1983 together with Siegfried Goßner Gerhard Seele set up the firm seele in Gersthofen. Siegfried Goßner Siegfried Goßner was born in Emersacker in 1954. From 1968 to 1972 he was apprenticed as a technical draughtsman in the steel construction at Stahlbau Beck in Augsburg where, after completing his apprenticeship, he was later employed. In 1982 he opened his own design office for structural steelwork and in the same year received the first commission from the company Glas Seele. Siegfried Goßner and Gerhard Seele have been business partners since 1983.

CS: And what are your visions for the future? SG: Gerhard Seele has already referred to our most 15

STEEL AND GLASS CONSTRUCTIONS

European Investment Bank, Luxembourg

European Investment Bank, Luxembourg Detail in conversation with Enzo Unfer (EU), EIB

Detail: Mr Unfer, in your role as the client’s representative you have accompanied this new building project from the preparation of the competition documentation onwards. What was called for in the architectural concept? EU: The design and the architect were chosen unanimously in October 2002 by means of an anonymous competition. The competition, chaired by the Spanish architect Ricardo Bofill, consisted of a pre-selection phase and two competition stages. Of primary importance in making a decision were, on the one hand, the experience and qualification of the office, on the other hand the planned budget and the environmental criteria. What we required of the architect was to design a building that would be “unostentatious, functional, transparent and environmentally friendly.” Detail: What were the main reasons for choosing Ingenhoven’s design? EU: ingenhoven architects were chosen because of their merits as an office and their architecturally innovative design in an urban context that harmonises with the surroundings on the Kirchberg. Of course, the fact that the design placed great emphasis on sustainability and saving energy was also much in its favour. The proposal is in accordance with current European environmental guidelines and surpasses them in certain areas. Detail: The building was inaugurated in June 2008 and was fully occupied the following winter. Does it live up to your expectations? EU: You can measure the success of this building on the one hand by the satisfaction of its users, and on the other by how efficient and economical it is. The new building boasts lavish amounts of daylight and natural ventilation; each office has a control panel that allows the user to adjust the temperature, the sun blinds and the lighting as required. The innovative energy concept guarantees regulated temperatures in the building. It helps lower the temperature on hot days and raise it on cold ones. In addition measures were introduced in all offices to improve sound insulation such as soundabsorbent carpeting instead of wooden floors. The building’s transparency and the feeling of open-

ness reflect the transparency of the EIB as an institution. All the efforts made by the designers and firms involved were directed at creating a building that reflects the highest standards in terms of environmental compatibility. The general response of the staff has been positive. We assume that the total energy consumption will be substantially less than in standard buildings of a similar size. Nevertheless, the actual energy consumption of the building depends on it being operated in an optimised, well-regulated way. This must be confirmed over time and adapted accordingly. In practice only time and performance will show how energy-efficient this building really is. Detail: How did the idea of a sustainable building arise? EU: The building reflects the goals of the EIB which makes a substantial part of its financial resources available for projects that protect the environment and combat the effects of climate change. By investing in “green architecture” we have demonstrated this commitment in our own building project. Detail: Are investments made in sustainable architecture “secure”? EU: The advantage of investing in sustainable architecture lies in the fact that this produces a building with a longer lifecycle. In this sense investments in sustainable architecture are certainly secure. In the particular case of the new EIB building the large glass dome has high maintenance costs, but this additional expenditure is partly offset by the gains generated by the glass roof in terms of reducing energy consumption and providing a maximum amount of daylight. In my opinion it is essential today to invest in sustainable architecture – irrespective of the kind of construction one is talking about. We can in this way contribute to creating a planet worth living on for future generations.

As the client’s representative, Enzo Unfer (MBA) headed the project for the new building between 2001 and 2008. Since its inception he has been responsible for the facility management of all EIB facilities.

Goals of the European Investment Bank The EIB was founded in 1958 under the Treaty of Rome as the long-term lending bank of what was later to become the European Union. Its mission is to strengthen EU policies through financing. Since its founding the EIB has provided around 600 billion euro for projects in the EU member countries, EU partners and candidate countries. Outside the EU the EIB is active in more than 150 countries. It provides financial support for projects in the private sector, in infra-structure development, securing energy supplies and in the field of sustainability.

History of the EIB buildings The first seat of the Bank in Luxembourg in 1968 was a building on Place de Metz. In 1980 the Bank moved into a new headquarters on the Kirchberg designed by the architects Denys Lasdun Partnership for 800 staff. Lasdun also carried out the extension for 300 employees built in 1994. The competition for the new building was set up in 2002. The official inauguration of the new EIB headquarters took place on June 2, 2008.

Specification documents for the new building After the pre-selection phase in summer 2004 the competition specifications were drawn up in September 2004. The submissions were made in November of the same year. The general contractor was commissioned in March 2005, seele just two months later.

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Steel and Glass Constructions

European Investment Bank, Luxembourg: Design and Implementation

Design and Implementation Christian Ingenhoven, ingenhoven architects Christoph Ingenhoven founded ingenhoven architects in1985. This Düsseldorf practice has won numerous prizes, including 30 first prizes, in both national and international competitions, as well as more than 60 awards for built projects.

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A tube-shaped glass roof spans the entire administration building of the European Investment Bank (EIB) in Luxembourg. The new building extends the existing facilities on the Kirchberg plateau. Located between Boulevard Konrad Adenauer and Val des Bons Malades, the extension provides 72 500 m2 of office space for up to 900 staff, as well as central facilities that serve the entire campus. The large glass roof, which has a surface area of 13 000 m2, guarantees maximum amounts of daylight and transparency. The zigzag floor plan of the office building under the 170-metre-long and 50-metre-wide roof allows the offices to be laid out so that they are equally advantaged, and positively supports interactive and communicative processes. Increasing the well-being of the users – for instance with windows that open onto the garden or atrium, and creating communicative spaces and a flexible, transparent working environment – are aspects that we always take into

account in our design work. An important basis for and an integral part of our designs are the micro-climates in “buffer zones”, various kinds of warm and cool atria, double facades, predominantly natural ventilation and the activation of the thermal mass of the concrete floor slabs. BREEAM certification The recognition of the new building’s ecological credentials represented by the BREEAM certificate rating “excellent” is an award not just for us but also for the client and for our design partners who supported this work-intensive approach. The glass roof and the V-shaped atria are the key to the ecological concept. The winter gardens facing towards the valley are not heated and serve as climatic buffers. In contrast the halls facing the Boulevard are used for circulation purposes and are temperature controlled. Both the winter gardens and the “warm” atria are naturally ventilated by flaps in the facade.

European Investment Bank, Luxembourg: Design and Implementation

Carrying out the project The EIB was the first project that we worked on together with seele. This firm was involved as a sub-contractor to Vinci CFE who was appointed main contractor. In the construction of the facade the services provided by seele comprised primarily the curved roof structure and the cable facades, including the fish-belly beams used for these facades. In the case of the steel construction components the designs supplied within the context of the specification by the design consortium headed by Ingenhoven were produced by Werner Sobek, the designs for the envelope by DS-Plan. The specifications were drawn up on the basis of the design, using guideline details. The main contractor and his sub-contractors (and therefore seele) assumed responsibility for the detail design and the further refinement of details. Within the framework of the tender the Gersthofen-based firm presented a special proposal to make the joints in the roof con-

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struction as bolted connections rather than welding them. This helped optimise the assembly process. This proposal was based on seele’s specific expertise know-how. To further ensure quality and work out the fine details, a model of a pre-defined important part of the facade was produced in Gersthofen. Working models of all further components produced especially for the project, such as the cast aluminium joints and the stainless steel point fixings augmented the technical supervision before the start of production. Design and construction were based on the joint goal of the designer and the construction firms: to produce an exceptional, technically flawless and attractive result. This goal was achieved.

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Building data Architects: ingenhoven architects, Düsseldorf; Christoph Ingenhoven Client: European Investment Bank Luxembourg Structural design, Roof and cable facade: Werner Sobek, Stuttgart Facade design and building physics: DS Plan, Stuttgart Technical equipment in the building: HL-Technik, Munich (design); IC-Consult, Frankfurt a. M.; pbe-Beljuli, Pulheim; S & E Consult, Luxembourg Gross Floor Area: 69 996 m2

Floor plans Scale 1:1500 1 Main entrance 2 Secondary entrance 3 Foyer 4 Conference area 5 “Cold” winter garden 6 “Warm” atrium 7 Office wing 8 Communication area 9 Existing building

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Steel and Glass Constructions

European Investment Bank, Luxembourg: Energy Concept and Facade Design

Energy Concept and Facade Design Herwig Barf, Michael Jurenka, DS-Plan 1 The engineering office DS-Plan was responsible for the facade technology, energy management and building physics. Herwig Barf heads the team in the facade technology department. Michael Jurenka is the EIB's project manager with responsibility for energy design and management.

Energy supply concept An urban combined heat and power plant supplies the building with heat. In summer the waste heat is used to cool the ambient air for the air conditioning system by means of a dessicant cooling system (DEC). A DEC system is a thermal cooling process for air conditioning spaces in which a combination of evaporation cooling and air dehumidification directly produces cool air. The potential for providing cooling offered by outdoor space at night is exploited by free cooling from the cooling towers to directly cool the thermal storage mass. Refrigeration machines provide the computer centre, IT rooms, other technical services rooms and the air conditioning plant for the conference area and kitchen with cooling energy. When the external temperature is suitable, cool outside air is used to indirectly cool the technical services spaces. This further reduces the amount of electrical energy required for mechanical cooling. (Source: Thilo Ebert, HL Technik)

Among the most important facade constructions of the European Investment Bank in Luxembourg are the timber facades facing onto the atria, the arched glass roof and the three cable facades. The winter gardens positioned on the north side are beneath the glass envelope and were conceived as unheated cold atria, in which the temperature in winter does not fall below 5 °C. In contrast the southern atria have temperature controlled areas where permanent workplaces can be located. Concept The starting point in designing the atria roofs and facades was to implement a heating and cooling concept that would use energy as economically as possible. Buffer areas in front of the working zones in the interior of the meandering office block not only improve the relationship between the surface area of the envelope and the volume of the space, they also allow individual window ventilation throughout the year and prevent users using the system incorrectly. In winter the flow of heated air from the offices has the side effect of gently warming the atria. If the user does not ventilate through the atrium facade, a highly efficient heat recovery system ensures that the heat energy of the waste air from the offices can be used by the basic mechanical ventilation system of the office spaces.

Zoning of the atria The high level of thermal protection enjoyed by the office spaces thanks to the atria in front of them allows the building to be temperature controlled by thermally activating building elements. The moderate temperatures involved ensure efficient use of energy. The north-facing winter gardens have no active heating or cooling system. In contrast in the south atria, where people spend longer periods of time, underfloor heating and cooling was provided. This guarantees pleasant working spaces on the floor levels where the reception and waiting areas are located, for example. The vaulted glass roof is an important part of the climatic building envelope and was therefore designed as a highly thermally insulated, prefabricated aluminium construction with two-pane heat absorbing thermal glazing. In the horizontal areas of the roof of the southern atria the triangular glazing has a highly selective, almost neutrally coloured sun protection coating. In a third of the roof or facade area there are electrically operated flaps. These function as inflow openings for the smoke extraction system in the atria, but also allow both the unheated northern winter gardens and the temperature controlled southern atria to be naturally ventilated throughout the year. During the cold season ventilation is carried out by means of a series of brief ventilation periods that exchange the air volume within a few minutes. During the warm part of the year the flaps are permanently opened, so as to expel excessive radiation loads and to avoid overheating. Integrated simulations The geometry of the roof surfaces helps to meet the thermal requirements. It allows the cushion of heat that builds up in summer to be extracted before overheating can occur in the working areas closer to the roof. To prevent discomfort the ventilation flaps in the facade are distributed in a manner that avoids excessively high wind speeds in circulation or working areas. We developed the surfaces and performance data required to implement the conditioning measures using integrated flow simulation in a virtual 3D model. Consequently we could be certain at an early design stage that

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European Investment Bank, Luxembourg: Energy Concept and Facade Design

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the heating concept would function properly and that the comfort criteria would be met. This allowed us to demonstrate the impacts of different construction options on the indoor climate in the atria or on the amounts of energy required – for instance when deciding between the use of single or double glazing, or the use of low-E glazing as against internal textile blinds. Ultimately the thermally optimized glass envelope turned out to be the best solution for the atria roofs and facades. One result of the simulations is the high degree of transparency and exploitation of daylight that guarantees good daylight levels in the offices, even on

the lower floors. As a result the expectations that visitors intuitively have of a generously glazed building are met without any reduction in terms of energy efficiency or in the quality of the spaces as a place to spend time.

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Environmental concept • Atria as climate buffers • Heat recovery • Thermal activation of the structure • Reduction of the general office lighting level to 300 lux • Energy requirements for offices and atria : electricity 21 kWh/am2, heating 29 kWh/am2, cooling 21 kWh/am2 1 Stale warm air escapes through vertical louver windows. Smoke ventilators are located in external spaces below the roof surface. 2 Lighting and temperature can be adjusted individually. A central control and monitoring plant checks these data several times daily and, where necessary, resets the controls to the most efficient level. 3 Air temperatures in summer with natural ventilation in the north atrium 4 Maximum air temperatures in summer in the south atrium 5 – 6 Central circulation in the main entrance area with a view of the staff canteen 7 Schematic section of the energy concept, not to scale

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Steel and Glass Constructions

European Investment Bank, Luxembourg: Fire Protection Planning

Fire Protection Planning Wolfram Klingsch, Rebecca Rettner, BPK Brandschutz 8 Prof. Dr.-Ing. Wolfram Klingsch has headed BPK Brandschutz Planung Klingsch Ingenieurgesellschaft in Düsseldorf and Frankfurt since 1997. He holds the Chair of Building Materials Technology and Fire Safety, Institute for Constructional Engineering at the Bergische Universität Wuppertal. From 2006 to hand-over of the building, civil engineer Dipl.-Ing. Rebecca Rettner who works for BPK, supervised the fire prevention concept.

8 The high degree of transparency of the V-shaped atria demanded a carefully conceived fire protection system.

Fire protection components The numerous technical fire protection components are linked to each other by means of a control matrix. This includes the components fire detection, further communication of the alarm, alarming persons with a call for evacuation, activating the safety lighting, activating natural or mechanical smoke extract systems, evacuation travel of the lifts, activating the air cleansing system in the stairwells.

A number of special design aspects related to the function of the ambitious new EIB building in Luxembourg meant that special proof of fire safety was required to obtain the building permit and special measures were introduced in constructing the building. Computer simulations and experiments were used here alongside a special interactive fire protection concept that integrates constructionrelated, technical and organisational measures. This made it possible, despite this building’s many special features, to fully meet the goals in terms of protecting both persons and objects. Ensuring transparency The facade geometry means that the staircases necessary to evacuate the building lie in the interior which called for special measures to safely exit the building via these staircases. The secure exit was achieved by rescue routes that are glazed so as to preserve the transparency of the building, and in particular of the entrance level, which is a main characteristic of the architecture. On the three lower levels the corridors required in front of the stairwells are glazed with EI 30 fire prevention glass. This preserves the visual connections desired in the atria and allows the meeting zones to be naturally lit. On the exit levels glazed horizontal extensions to the stairwells with EI 30 glazing and a sprinkler system adapted to the particular risks connect the staircases to the outdoors. Tests confirmed the high level fire safety offered by this special solution. The fire separation required between the two-storey restaurant and the adjoining level 3 was made using EI 30 rating glass. This does not obstruct the visual connections between the restaurant and level 3 and the outdoors. The optimal combination of sprinkler systems and fire safety glazing adapted to deal with the specific risks obviated the need for the solid separation walls normally required and achieves a high degree of visual transparency. Early fire detection and smoke venting The building has a comprehensive early fire and smoke detection system. Combined with an equally comprehensive alarm system, in the case of fire this ensures early warning of persons and

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the safe evacuation of endangered areas. The comprehensive sprinkler system helps to reduce and confine any fires that might occur. This means that the outbreak of fire can be restricted to a specific location. It is intended to use Atrium 2 as an assembly place for up to 1500 people. To deal with this situation we made a special study of the smoke venting. Smoke ventilators fitted in the roof area are automatically activated when smoke is detected, as are fresh air intake openings at floor level that provide the necessary inflow of fresh air. To minimize any possible disturbances due to wind, the activation of the intake openings is related to the prevailing wind direction. This allows a low-smoke zone of considerable height that ensures unhindered evacuation of the assembly area. We calculated the expected evacuation times using computerassisted dynamic evacuation simulations for a variety of different possible fire scenarios with regard to localization and intensity. This guarantees that no risks to persons result, even with maximum occupancy and critical scenarios. To ensure the correct implementation of the fire safety concept we closely coordinated our work with all the specialist designers and planners involved in the project, and the construction of the building was closely monitored. The final checking of the system to ensure that it functioned correctly confirmed to all involved in the design and construction of the building and to the authorities that a high standard of fire protection had been achieved.

European Investment Bank, Luxembourg: Structure and Teamwork

Structure and Teamwork Katja Pfeiffer (KP) in conversation with Werner Sobek (WS)

KP: Mr Sobek, the EIB is one of your many joint projects with the seele company. How did these long years of working together start in the first place? WS: I have been working with Gerhard Seele, Siegfried Goßner, the managing directors Thomas Geissler and Andreas Fauland and their staff for 14 years and I have greatly admired seele for a long time. As designers we know that this firm can meet our demands in terms of quality and can implement our design ideas. Technical developments frequently occur during the design stage as a result of discussions with the firm and innovations result from advance testing. In this manner constructive solutions have repeatedly been found that go beyond what we as designers initially had in mind. KP: Can you give us an example of this? WS: One joint project is the cable facade for the central area of Bremen University. The overall form of this building is cubic with a completely transparent, slightly dematerialised facade. It was

there that we first implemented the concept of a cable facade in the form of a construction made exclusively of vertically pre-tensioned cables to which the glass panes are fixed with clip connectors or pads. KP: From what stage onwards was the Gerstofen firm involved in the design? WS: We had worked out the concept for the facade but immediately after the awarding of the contract we collaborated with seele on the construction. Our aim was to minimise the clip connections and, in terms of construction, to design them in such a way that the glass would remain undamaged, despite the considerable deformation that occurs in the cable facades. There was also an entire series of problematic details, for example where the deforming cable facade meets rigid, non-deforming building elements. seele constructed 1:1 scale models to test the bearing capacity of the glass holders and examined alternatives for the seals that are subject to movement at the points of transition from the flexible cable facade to the fixed facade.

Architect and engineer Prof. Werner Sobek heads the engineering office Werner Sobek which operates globally. Since 2000 he has been head of the Institute for Lightweight Structures and Conceptual Design (ILEK) at Stuttgart University and since 2008 has been president of the German Sustainable Building Council (DGNB).

9 The atria facade is based on the principle of vertically pre-tensioned cables.

Fitting The primary construction (tube Ø 610 mm) was erected by the main contractor. Along with a 40-person team from seele we were responsible for supervising the fitting of the secondary structure and the glass skin. The Gersthofen-based firm had already worked out the fitting concept at the tender stage. The team of fitters for the secondary structure and the glass skin at peak times consisted of up to 90 fitters from a number of installation companies with whom seele had worked previously. Werner Sobek: "With constructions on the boundaries of what is feasible you have to start working out the installation during the design of the construction. This is the only way to be sure that an idea can be implemented."

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Steel and Glass Constructions

European Investment Bank, Luxembourg: Structure and Teamwork

Vertical section through beam and cable facade Scale 1:50

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The company tested brush seals, silicone seals and EDPM, among others. Designers often arrive at their limits in the area of seals and sealants.

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1 flat steel section 60 mm 2 top chord steel RHS Ø 323.9/60 mm 3 top chord steel RHS 2≈ Ø 244.5/50 mm 4 connection steel fin /beam flat steel ¡ 140/40 mm, bolts Ø 30 mm 5 lattice shell beam element steel RHS Ø 139.7 mm with steel fin 6 double glazing 2≈ 12 mm, 20 mm cavity 7 laminated safety glazing 2≈ 10 mm pre-stressed glass 8 gutter with grating that can be walked across 9 double glazing 2≈ 12 mm toughened glass with 20 mm cavity 10 steel cable Ø 30 mm 11 wind pin 30/20 mm 12 boss ¡ 35 mm 13 fixing piece with welded reinforcement (l = 600 mm) and sheer connector HEA 100

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KP: Would you describe the cable facade of the EIB as a further development of facades at Bremen University? WS: In the final analysis one could say that we did develop them further in that we increased the sizes of the glass panes and of the facade as whole. The movements that resulted from this also increased somewhat, but the metal elements of the structural construction including the entire detailing became smaller. Therefore on the one hand things become larger and more complex, while on the other there is a gradual reduction in the use of resources. The large trussed beam is a building element that meets the new demands made by the facade. It holds the cable facades that could not have been anchored at the top to the thin roof shell. We had envisaged classic cables for the beams in the first design. To place a post on a cable you need a cable clamp consisting of two parts. These two halves of the clamp must be pre-tensioned in relation to each other with a number of high strength bolts. In addition a transitional element is needed to provide the connection to the post that sits on the cable. In the course of the detail planning we replaced the lower chord by one with a solid cross section welded out of horizontal metal sections. As the uprights are, for the most part, subject to com-

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European Investment Bank, Luxembourg: Structure and Teamwork

Elevation and section beam head scale 1:20

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pression forces they consist of slender flat steel sections. With a circular-section tube as upright a deviation saddle would be required to fix the upright to the under-slung cable. This would have been far more complex than the solution as built. During the workshop planning phase, for reasons to do with welding and fitting, seele suggested, instead of a solid lower chord, to use one with an open cross-section made of vertical high-strength metal sections. This was the ideal solution – with a comparable aesthetic quality but simpler in terms of installation and joining. KP: Who else was in the design team? WS: We had worked together with Christoph

Ingenhoven’s team since the competition phase. The engineering office DS that was responsible for the facade technology in the traditional sense as well as the experts for building services, fire safety and others involved in the project also sat at the same table. We were involved in the design work for a period of two years. After seele had been commissioned for the roof shell and the special facades we immediately began intensive collaboration. Together we worked out the details and the workshop design of this ambitious project. The size, the precision with which the individual building parts had to be made, and that was required for the fitting and pre-tensioning processes (especially of the cable facade) did not allow any delay.

10 The beam head – what is shown here is the model produced by the foundry for approval – is a building element made of high strength cast steel with higher tolerance requirements. The cast part and the upper chord were welded together in the works. The anti-corrosion painting of the element was also carried out in the works. The painting of the welded connections to other building elements required additional finishing on site. 11 The various elements of the beam that were welded, trued and positioned in different works – the upper and lower chords, beam head and fins – were delivered to the building site by ship and truck. The individual parts were then put together using bolted connections, and, with the help of several mobile cranes, were fitted in place as single pieces. Once the roof was installed, the beams, which had been given a camber, took up their final shape as a result of the load placed on them. 12 The lower chord was originally designed as a solid element; seele suggested making it out of four vertical high strength flat steel sections. This solution obviated welded connections that are expensive and difficult to check. The connection of the roof with the cable beams was highly complex. The beams were connected to the lattice shell of the roof by fitted bolts. This approach was based on a sophisticated system of movability that had been worked out at the design stage. The facade cables were pre-tensioned before connecting the beams with the roof shell. An auxiliary strut stabilised the upper chord during this process. The roof could be moved into place with chain hoists so that the cable facade, beams and the steel roof fitted together without tolerances

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European Investment Bank, Luxembourg: Structure and Teamwork

Elevation and top view connections to secondary construction scale 1:50 1 steel RHS Ø 139,7 mm 2 cast steel connecting element 3 insulated glazing 8 mm toughened glass, cavity, laminated safety glass 2≈ 6 mm 4 extruded aluminium section 5 lift tower

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KP: Do you believe that the future of engineering lies in collaboration with construction firms? WS: Most definitely. In the EIB project seele won the competition and was awarded the contract. In the case of firms that we regularly work with we attempt to develop technical solutions further and to optimize them at as early a stage as possible. However, as designers we cannot discuss solutions before the tender stage with partners from the construction industry who will later apply for the contract. This will remain one of the great obstacles to innovation as long as the design processes and tender procedures are not changed. In the motor car industry or in airplane construction the approach is very different. There the designers find a number of partners and clearly outline the nature of the particular task. KP: So that benefits all those involved. How can this approach be implemented in practice? WS: In the case of our private clients we suggest two firms with which we develop the design, say for a facade, within the given cost framework and integrating the aims in terms of design, construction and building physics. The firms have a fair chance and if they offer good work I see no reason to go to the market just to save 10 % that would be lost again as a result of changes that must be made while carrying out the work.

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KP: In your view what was the greatest challenge presented by the EIB? WS: The sheer size, the precision required, the difficult geometry of the barrel vault shell, the large trussed beams and the situation regarding deformation, i.e. the fact that a large steel construction must be able to slide in relation to the massive solid structure on which it partly rests. KP: What other projects are you working on? WS: One of our joint research projects at present is the development of implants, very small securing systems within glass panes with which the glass panel can be fixed to other building elements. The implants are inserted directly into the pane. This will lead to an entirely new generation of glass retainers.

European Investment Bank, Luxembourg: Structure and Teamwork

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KP: In this context how do you evaluate the development work of a business? WS: seele can be described as an innovative force in that it continually drives forward technical innovations and grapples with a problem until it comes up with a solution. When a suitable project appears on the horizon, seele has the decisive competitive advantage. We, too, as a small to medium sized business, are very dependent on our innovative strengths on the world market. Consequently as designers we ensure that research work and joint product development with the construction firms are given adequate place. In this way we can profit from each other. In the building industry just copying the developments of others can result in a

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delay of two to three years – and this is something we cannot afford. And a firm like seele cannot afford it either, because it is called for precisely where and when top performance is required.

13 The steel lattice structure consists of what we call "rakes". They were lifted into position by crane and were then fixed temporarily to the scaffold. After measuring and checking they were bolted or welded together in their position on the roof in accordance with the structural requirements. Three expansion joints in the cross-section of the building resulted in eleven fitting stages. 14 The roof skin is made of standard insulation glass elements. They were fitted by crane, with the help of scaffolds that were erected inside the building and in the lower overhanging area. 15 The joint is fixed to the steel tubes of the "rake" by a high strength cast bolt connector. Where possible welding on site was avoided. The aluminium tertiary construction comprises a total of 2200 standard joints. There are a further 1100 non-standard joints. The latter are subdivided into 50 different sub-groups. They are located at the geometrically complex positions, for example at the expansion joints, at the edge of the roof, at the gutters or the exits from the roof. 16 The seele works in Pilsen (CZ) developed and built the secondary construction. It is made up of steel tubes with a diameter of Ø 139.7 mm and walls of different thicknesses. According to structural requirements they are fitted with one or two fins. By optimising the structural system in this way the same diameter tube could be used in all parts of the structure.

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Steel and Glass Constructions

Westfield London

Westfield London Laura Passam, Westfield Shoppingtowns 17 Laura Passam is press officer for Westfield Shoppingtowns Limited, London. With a total of 119 shopping centres in Australia, New Zealand, Great Britain and the USA the Westfield Group is among the world’s largest retail property companies. This business with headquarters in Sydney is engaged in the marketing and management of shopping centres and also undertakes responsibility for their development, design and the realisation of the built form. In the case of Westfield London, too, the Westfield Group was responsible for design, realisation and operation. In this particular case the Buchan Group was commissioned to provide support for the company’s own design team. In addition to providing the working drawings, this ondon-based office was also the principle point of contact for all those involved in the project.

After a construction period of three years Westfield London Shopping Centre was opened west London in October 2008. With an investment amounting to more than one billion pounds sterling, 270 shops, 40 restaurants, 14 large cinemas as well as sport and fitness facilities on a total floor area of 350,000 m2, this is currently Europe’s largest inner-city shopping mall. The design concept by the architects from the London-based Buchan group is based essentially on clearly structured shopping malls in the form of a giant figure-of-eight incorporating two main floors and a mezzanine level, the entire length of which is covered by an undulating glass roof. Arcades and central atrium The generous dimensions of the shopping streets are designed to allow an unobstructed view of the shop fronts, most of which have full-height glazing. The retail spaces themselves have ceiling heights of between 4.5 and 8.5 metres and offer a wealth of opportunities for the creative and contemporary

presentation of products for both small individual retailers as well as the big “anchor stores”. Oval or rectangular voids cut out of the upper floors allow vertical visual contact and connections between the individual levels, while also introducing daylight to the ground floor. Its size and position makes the atrium located at the heart of this complex a central meeting point but it also functions as a location for different kinds of events. Glass roof Perhaps the most striking thing about the appearance of Westfield London is the curving glass roof that was inspired by the movement of waves in water. The starting point for this idea was a digital model of a water basin in the area of the central atrium. The designers had two virtual pebbles thrown into this basin. The waves that gradually spread in different directions from these points were then overlaid on the floor plan of the shopping centre and were manipulated and processed until they matched the designers’ concept, while at

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Westfield London

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the same time remaining technically feasible. All the shopping streets are roofed by this steel and glass structure – its highest point is in the atrium. In contrast to the side arcades that are spanned without the need for columns, in the atrium a tree-like structure supports the roof. The slender cross-sections of its parts allowed an interior to be created that is awash with light and permeable on all sides. The distribution of the closed and transparent triangular panels only appears to be random; in fact it is the result of precise observation of the daily path of the sun. The aim here was to create a pleasant ambiance for visitors in the arcades with as much daylight as possible and, at the same time, to achieve solar energy gains. Over-heating in summer is avoided by the carefully worked out distribution of transparent and closed panels. Additionally, during the course of the day the glass roof, reminiscent of a sparkling baldachin, creates constantly changing effects of light and shade on the floor of the shopping malls. Those areas not roofed with glass have green roofs

that offer an inner city habitat for plants and animals and at the same time provide natural insulation. The utilization of rainwater, high energy efficiency standards and reduced CO2 emissions aims to create a sustainable building in the long term. Implementation Due to the immense time pressure Westfield commissioned two highly specialised firms to carry out the roof construction: seele, and Waagner Biro from Vienna. Waagner Biro took on the roofing of the central atrium, while seele assumed responsibility for the two outer arcades leading to the atrium as well as the entrance roofs. The load-bearing structure is made of bars, rectangular hollow sections and nodes connected to form a fine-meshed net of equilateral triangles. seele submitted its first tender for Westfield London a number of years before being awarded this commission. Preliminary discussions with the Westfield Group and the architects from the Buchan Group took place from this point onwards. Luxury Village Away from the glass-roofed arcades, in the southeastern part of Westfield London is “The Village”, an exclusive shopping precinct with a consistently restrained design where international luxury labels such as Prada, Gucci, Dior, Versace, Tiffany & Co., Miu Miu and Louis Vuitton are located. This enclave is characterized by opulent staircases, tall glass shop fronts and classic chandeliers but above all by gently curving forms as well as a sensual lighting and colour concept.

Building data Architects: Buchan Group International, London/Benoy, London Interior designers: Gabellini Sheppard Associates, New York Client: Westfield Shoppingtowns Limited, London Quality monitoring on behalf of the client: Arup London Retail area: ca. 150 000 m2 Construction period: 2006 – 2008

17 Layout plan: seele was responsible for the roofing of the eastern and western arcades as well as the entrance roofs, Waagner Biro took on the roof to the central atrium. 18 Westfield shopping centre is in Shepherd’s Bush in west London. It is presently Europe’s largest inner city shopping centre. 19 Energy gains were taken into account in determining the layout of opaque and transparent triangular elements. Most of the transparent triangular elements are in shade when the sun is low in the sky. 20 Alternating transparent and closed panels lead to a permanently changing play of light and shade on the floor.

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Westfield London: Digital Process Chain from Design to Execution

Digital Process Chain from Design to Execution Jan Knippers, Thorsten Helbig, Knippers Helbig Advanced Engineering In 2001 Jan Knippers and Thorsten Helbig founded the engineering office Knippers Helbig Advanced Engineering in Stuttgart. Jan Knippers is professor at Stuttgart University where he heads the Institute of Building Structures and Structural Design(itke).

21 The two seamless arcade roofs designed by seele have a total area of around 18,000 m2. 22 Form optimization processes applied to a wave originally planned by the architects: if the wave does not follow the orientation of the members this results in awkward faceting of the triangular elements along with difficulties in draining rainwater from the roof 23 The angle of 60° ultimately used best combines the requirements of structural design and aesthetics. 24 To give the roof a uniform appearance, all members have the same external cross section but their wall thicknesses are varied in accordance with the particular structural demands made on them. 25 Eastern area of the roof, state of progress in February 2008

From the 1970s onwards the structural calculation of grid shells with complex shapes became possible, but for reasons to do with fabrication such shells were generally restricted to just a few regular geometries. Economic construction remained inseparably linked with the industrial fabrication of large series of identical building elements until the end of the 20th century. For Max Mengeringhausen and Konrad Wachsmann, using as many identical building parts as possible was one of the important parameters in designing their space frames. And even when, at the start of the 1990s, Jörg Schlaich and Hans Schober introduced Frei Otto’s principles for lattice shells to steel and glass architecture with their dome in Neckarsulm, the use of uniform member lengths with a node connection that, despite a variable angle cleat, was made up of identical parts remained of central importance. Towards the end of the 20th century this situation changed radically within the space of just a few years due to the introduction of computer-aided production processes. Although certain decisions about construction, for example as regards the connection technology, still have to be made, a modular geometric order of the kind that had previously formed the basis for all building construction has greatly diminished in importance. Since the 1990s numerous free-form steel and glass shells have been constructed. It must be said, however, that alongside truly impressive constructions there are also

examples that are less than convincing in terms of both design and engineering. Not infrequently there is a yawning gap between the architectural intentions and its implementation. The reason for this is generally the strict separation common in the building industry between architectural design and the workshop planning of the construction firms. But complex structures demand a continuous process chain from design to execution. Westfield grid shell The successful roofing of the Westfield shopping centre in London is based on particularly close links between the workshop planning, production and fitting by seele and the detailing of the design and structural calculations carried out by our office, which will be described in greater detail below. The East and West Mall of the shopping centre are each roofed by a free-form grid shell with a triangular mesh and a standard span of 24 metres. Together the roofs have a total area of around 18,000 m2. The longest “arm” of the roof measures 124 metres in plan. Both roofs are made seamlessly and rest on edge brackets at 12 metre intervals. To reduce the stresses caused by thermal expansion the bearing points can slide parallel to the edge. There are fixed points roughly at the middle of the central “arm” of both roofs. Insulated glass and insulated metal panels were used as the roofing material.

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Westfield London: Digital Process Chain from Design to Execution

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Development of shell structures Among the most impressive achievements of the 19th century art of engineering are the elegant roofs of shopping arcades and glasshouses with their slender structural members. The design of these early glazed frame structures was determined largely by the methods of calculation and production available. The number of different members and nodes was reduced to a minimum to prevent the cost of production exploding. In addition the methods of structural design were restricted to just a few standard geometries. This led to the repetition of standard solutions for domes and vaults. Examples include the roofs for gasometers developed by Johann Schwedler in 1863, or, later, the shell made of members for the Zeiss planetarium designed in 1922 by Walter Bauersfeld which has a mesh pattern that Buckminster Fuller also used for his geodesic domes.

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Westfield London: Digital Process Chain from Design to Execution

26 All the nodes are geometrically adapted to take the members, each of which comes from a different three-dimensional direction. 27 The nodes and members are bolted together by means of a vertical contact surface. The holes are not visible from the ground. 28 + 29 With this modular system the individual parts are first placed in their respective positions and then bolted together. 30 Each of a total of 3000 nodes consists of 20 individual parts put together by hand and welded 31 The individual parts were delivered once the scaffolding that follows the undulating line of the roof shell had been completed. Thanks to just-in-time deliveries only a few elements needed to be kept in stock on site.

Form optimisation process Our first contribution consisted of optimising the shape designed by the architects. They had taken a free-form undulating roof as their starting point. But the geometry must be related to the subdivisions of the mesh. One side of the triangulated system should run parallel to the edge so as to support the longitudinal orientation of the mall, the two other sides cross the mall at an angle of 30°. From a structural viewpoint the waves are most effective, if, like in corrugated iron, they are laid out at right angles to the arcade. But this would have created faceting that would not only be visually unpleasant but could also cause problems in draining rainwater from the roof. Therefore in geometric terms a wave line parallel to the orientation of the members would be ideal, but this would conflict with the goal of an optimised structure. In this case we chose an angle of 60° which – just like the width of the waves – was then varied to achieve the impression of a free-form geometry. The net was projected from the plane onto the 3D surface and by means of uniform member and node identification system was used as the basis for the structural calculations, the workshop planning and fabrication.

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Construction seele suggested making the connection in the hollow section using pre-stressed class 12.9 bolts that would connect the node and the members by means of a vertical surface. Around 3000 nodes were defined within the overall system. Each node has a different geometry and consists of 20 different elements. All metal thickness as well as the number and diameter of the bolts were optimized to meet the structural demands made on the particular node. The final precision of the node was achieved by mechanically milling the end plates after welding, and measuring them electronically. The coated nodes were then packed in cases of six elements, delivered “just-in-time” to the position where they were to be used – which meant that only a very small number had to be stored on site – and were bolted together with the members. The roof consists of a total of around 10,000 members which are welded hollow section

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tubes measuring 160 ≈ 65 mm with an average length of about 2.30 metres. Digital chain One of the most significant achievements in the design and execution of this construction was the development of a completely automated planning process that coordinated fabrication, workshop planning and structural design. Our structural line model for the net structure served initially as a data base for the workshop planning. From this seele derived the geometric data for the detailed structural calculations required for the nodes and connections. We then passed the results for plate thicknesses and bolt number and diameter on to the firm’s workshop planning department which passed them directly on to the fabrication. Trusting in the very high degree of precision in the

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Westfield London: Digital Process Chain from Design to Execution

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prefabrication, the engineers envisaged no possibility of compensatory tolerances. And in fact, after a fitting length of 164 metres the measured horizontal difference to the planned geometry was only 15 millimetres. Moreover the high degree of prefabrication allowed rapid fitting independent of weather conditions and meant that corrosion protection could be carried out almost entirely in the works and was therefore of a very high quality. Aesthetic advantages The production technology chosen for Westfield shopping centre not only offered clear advantages in terms of construction but also significantly determined the appearance of the construction. In contrast to many other grid shells, in this case the grid or net has no visible node detail, despite the fact it was made entirely with bolted connections – apart from a few edge nodes subject to heavy loadings.

The nodes and members consist of very many geometrically different metal pieces invisibly connected to each other. As a result, when looking up at it from inside, you have the impression of a net that is as homogeneous as it is precise.

Further development In term of both the smooth functioning of the design and fabrication processes and the quality of the built structure, the methods used in Westfield London proved most successful. Consequently they have in the meantime been further developed for use in other buildings – such as the roof of the Institute of Peace in Washington D.C. designed by Moshe Safdie and the Echelon Hotel in Las Vegas.

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Steel and Glass Constructions

Westfield London: The Westfield Roof – from Concept to Fitting

The Westfield Roof – from Concept to Fitting Author: Günter Hartl, seele GmbH 32 Günter Hartl has run the seele works in Plzeň (CZ) since it was set up in 1996. During this period the steel construction firm has developed into a specialist for architecturally ambitious constructions. It constantly endeavours to find new ideas that in terms of construction, production and fitting processes can adequately translate architects’ highly complex designs into built reality.

In roofs like that of the Westfield shopping centre the structural bays are normally constructed in the workshop and delivered to the building site where they are then welded together. The main disadvantages of this method are that the welding and corrosion protection have to be carried out under particularly difficult building site conditions. The basic idea of seele for the Westfield shopping centre consisted of devising an automated method that allowed the roof construction to be delivered to the site ready to be assembled. We also aimed to develop a node and member system with a well designed node hub able to elegantly accommodate the members that connect to it from different directions and angles. In the solution that was eventually used, the fully automated method was applied to the entire chain of processes involved in the project – from the calculations to the construction and the execution. The opportunity to create a rational design in an engineering office and of serial production, the quick and precise assembly by means of bolted connections and the final visual appearance are all the results of a method of building based on the use of a continuous digital chain. Construction seele undertook the development of the node with the assistance of the structural designers Knippers Helbig. They optimised the geometry of the construction and its structural performance, made detailed structural calculations for each element and worked out the necessary wall thicknesses. The complete net geometry is based on these designers’ structural model, which was transferred, along with all the x-y-z coordinates, to the programme Pro Engineer. Using the node that had already been constructed in detail, the Bachschuster company programmed a macro that generated every single one of the geometrically different nodes as well as the members using the existing coordinates of the line model. The data in Pro Engineer − around 270 000 different workshop drawings − were transformed into NC data so that all the NC processes such as oxygen cutting, milling, boring or folding could be transmitted directly to the machines. This meant that the timeconsuming intermediate step of programming

the production machines directly could be eliminated. By means of this highly sophisticated technological approach, around 70,000 individual pieces for the nodes and the members were generated using computer programmes and produced by CNC machines (to be put together). This method ensured the maximum degree of precision and reduced errors to an absolute minimum. Fabrication The individual nodes and the members connecting them are put together by hand out of the parts already described with the aid of a template or assembly jig and then welded, the end plates are mechanically finished after welding and the heads of the nodes are weld-finished to achieve the geometry required. The decimal point precision with regard to angle and length resulted in precisely fabricated building components that were

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Westfield London: The Westfield Roof – from Concept to Fitting

Field

Node

Mock-up 1, 2, 3 5, 6, 7 8 9 10 4 Total

[Stck] 77 1014 1509 126 128 51 69 2897

Weigh [kg] 2464 31 423 46 763 4025 6549 1502 2208 92 470

Parts [Stck] 1579 20 787 30 935 2583 2624 1046 1415 59 389

Draw- Data ings [Stck] [Stck] 1617 3311 21 801 129 792 32 444 193 152 2709 16 128 2752 16 384 1097 6528 1484 8832 62 286 370 816

Rods [Stck] 182 3265 4600 532 513 210 268 9388

Weight [kg] 8542 159 832 219 199 28 740 40 846 8769 17 297 474 683

Parts [Stck] 1820 32 650 46 000 5320 5130 2100 2680 93 880

Drawings [Stck] 910 3610 4015 1460 1920 1050 1340 13 395

Data [Stck] 4732 21 315 24 675 7832 10 113 5460 6968 76 363 35

subsequently checked and documented at a digital measurement station. When bolted together the nodes and the members form a perfectly fitting shell construction. This roof shell is a flowing surface without any discernible central nodes. In earlier days it was practically impossible to achieve this kind of appearance using bolted constructions. An important point in this context is that the recessed plate at the centre of the node was filled with a special glass fibre material that was subsequently grinded down. Once assembled, the fact that the members meet the node from very different three-dimensional directions is completely invisible to the observer. Finally, the edge beams with small intermediate edge tubes welded to them and a node connection were produced in the works, precisely according to the coordinates. This defined the basic geometry and established the precision of the net.

Execution seele undertook the installation work with a team made up of fitting and construction management staff and head fitters – and with the assistance of a partner company of long-standing that put together a team of fitters consisting of up to 60 workers. This company had considerable experience in assembling and fitting seele projects. For maintenance and inspection purposes the entire roof can be walked across. Sixty per cent of the roof surface consists of opaque insulated panels; the remaining area is made of insulated glazing. The pattern of opaque and transparent triangular elements is anything but arbitrary and in fact results from careful consideration of the expected energy inputs. When the sun is low in the sky this layout ensures that most of the transparent elements are in shade. The triangular roof elements rest on sealing strips on the grid structure; on the longitudinal sides they are held by two point fixings

32 Milling the end plates on a CNC machine 33 + 34 Checking the node geometry by electronic or analogous measurements 35 Detailed overview of the workshop documentation 36 The record of the results of the electronic measurement reveal that at none of the points measured is the discrepancy greater than 0.03 mm.

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Steel and Glass Constructions

Westfield London: The Westfield Roof – from Concept to Fitting

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and wet-jointed. seele designed the roof slopes so that all low points drain externally.

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39 37 Result of the design analysis of the steel rodes which uses colour gradients to illustrate the utilisation and distribution of areas subject to tensile and compressive forces 38 + 39 The node components are generated using computer programs and individually numbered so that they can then be assembled with templates or assembly gigs and welded together. 40 Assembled and tack-welded nodes

Fitting and logistics Because of the considerable roof height and the undulating roof form it made sense to erect a two-part assembly scaffold, consisting of a scaffold platform and an elevated stepped scaffold that followed the line of the roof at a distance of 1.5 metres. Temporary auxiliary supports were used to take the weight of the shell at the node points in accordance with the structural requirements. These temporary supports were positioned precisely, according to the coordinates, before assembling the net structure, and were bolted to a steel grid that had been made in advance so that they could be placed exactly under the centre points of the nodes. The materials were delivered to and stored at the appropriate location on the site only after the assembly scaffold had been erected. The steel construction elements, ready for use, were brought by truck from the works in Pilsen (CZ), the glass and panels were bought readymade and cut to size from suppliers in Slovenia and Croatia. seele Pilsen delivered the edge ladders in the form of fixed building elements. The ladders, 118 in total,

are welded box sections complete with connection pieces for the roof shell. The problem was to achieve the same degree of precision in the connecting elements that we had with the roof (members and nodes): the edge beams were precisely adjusted to fit with the steel structure of the facade, measured and braced accordingly so that the shell could then be put together piece by piece, according to the modular principle. The position of each individual node was defined by means of 3D coordinates and the nodes and members welded to the edge beams: the individual parts were coded to ensure that they would be correctly positioned: each node had a number that indicated its direction as well as which members were to be connected to it. The glass panes and panels were grouped together and temporarily stored before being lifted into their correct position by crane immediately prior to fitting. This method enabled the fitters to carry out their work almost entirely without drawings.

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Westfield London: The Role of the Facade Consultant

The Role of the Facade Consultant Christian Brensing (CB) interviews Graham Dodd and Wieslaw Kaleta, Arup

CB: What is the difference between a facade consultant and a facade engineer? Arup: A facade consultant has a good overview of the entire facade industry and the systems available. He helps the architect in using these systems and checks their quality. We define what Arup offers as the work of a facade engineer, because we go beyond the existing facade systems and design new, custom-made solutions. This also includes the structural engineering in the design of new facades and roofs. We also develop new concepts for the application of new materials and structural systems – whether for glass, metal or stone facade. Additionally the concerns of structural design are linked to those of building physics, i.e. the control of the facade with regard to the passage through it of heat, light, moisture and air. As a result the engineer arrives at a new approach to the facade. A facade consultant is involved at the start of a project, whereas a facade engineer is involved throughout the project up to its completion. CB: Does Arup offer both these services? Arup: We offer the entire range – from the early design phase to consultancy about which facade types and materials are best suited to the particular project. This is not just about engineering but also other aspects such as costs, procurement and scheduling. CB: How did you come to be involved in the project and what were your responsibilities? Arup: We actually joined the project at a very late stage, when seele and all the other firms were already on board. Our client was Westfield Shoppingtowns and our job was to report on the design and on-site implemantation of the project. In view of the size of the entire project the client split the contract for the construction of the roof between two firms, seele und Waagner Biro, so as to be sure that the project would be completed within the tight budgetary and time framework. It was Arup’s responsibility to review the designs and to check the calculations with regard to building physics and the glass specifications. In this way we were able to validate all the calculations made by seele. We attended in tests, evaluated them and we

checked both factory production and assembly on site. CB: Was Arup involved in the conventional facades in Westfield? Arup: We were involved in all the facades of the Westfield Shopping Centre. Essentially Arup Facade Engineering is involved in every aspect of building that has to do with the building envelope. We are regularly consulted on all specialist questions with regard to materials, feasibility, research and testing, procurement, thermal insulation and sustainability. Naturally we also deal with roofs, in particularly with glazed roof areas. By the way: the Westfield client also consulted us about the stone facades and floors. CB: What role did automated procedures play during the design and construction phase? Arup: As this is an enormous project is was clear from the very start that the fabrication and fitting on site was impossible without the use of the latest CAD programmes, in particular because of the 3D form. Westfield is one of those projects that were digitally designed throughout. The definition of the roof form and the architectural 3D drawings during the design phase could only be planned and carried out by specialised steel and glass companies. These must be able to work from a 3D model through the working drawing stage to the definition of the individual components. The old methods simply couldn’t handle the amount of data or feed it into the production process. We had around 4000 different pieces of glass, every node was different. The same was true of the parts connected to the node. The supervision and logistics were also very difficult. Each individual component had to be given its own number. They had to be labelled, brought to the correct place on the building site and then assembled the right way around. Naturally it was the architects who designed the undulating roof, but it was the construction companies who optimized it and dealt with the alarming number of different components. CB: Was Arup able to influence the design? Arup: We weren’t involved in the design itself. Of course we made some comments but the major

To test the design developed for Westfield, seele built a 1:1 model. This stands in the headquarters of the group in Gersthofen, which houses the central research and development department and the large test facility in addition to project management, engineering and production,.

Arup’s designers, engineers, planners and consultants work all around the globe. The headquarters of this international business are in London and it employs 10,000 staff in 37 countries. Graham Dodd is project manager for building projects in Europe, Asia, and North America; Wieslaw Kaleta is a facade engineer and responsible for developing business in Poland.

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Westfield London: The Role of the Facade Consultant

41 Pouring synthetic fibre filler into the central node created a shell that has a smoothly flowing surface without visible node points. 42 + 43 Due to the sheer size of the project and the tight schedule Westfield divided the glass roofing between the two firms – seele and Waagner Biro. Working on the basis of the same design concept both firms designed shells but followed very different approaches. Whereas seele used bolts to connect the nodes with the elements in the roofs to the west and east arcades, in the central atrium (where due to the bigger spans “tree-columns” had to be used) Waagner Biro employed welding.

part of the work on the roof was carried out by seele and Waagner Biro themselves. The extremely undulating form of the roof was rationalised during the further development of the design. In the entire roof the concept of the triangular frame structure is based on machined stiff nodes and loose members. This kind of structure had proved itself in a number of other projects. Despite this the calculations for this structure were extremely demanding. It was Arup’s job to scrutinize all the assumptions regarding loads and the entire concept. We also examined the forces that occur, for example deflection – but without repeating the calculations, as this was not within the scope of what we were commissioned to do.

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CB: Arup also reviewed Waagner Biro. How did cooperation with them differ from that with seele? Arup: These two firms took a different approach, even though dealing with the same project. The two roof sections, one built by seele, the other by Waagner Biro have different forms and different structures. Both are a kind of shell, the roof by seele spans up to 25 metres. On account of the even larger spans in their roof Waagner Biro had to design tree-like columns. The second difference from the very start was that seele fixed the loose members to the nodes with bolts, whereas Waagner Biro used welding throughout. There are pros and cons to both approaches. But it was fascinating to observe how the same problem can be solved in two different ways. This example shows where the difference between a facade consultant and a facade engineer lies. If Arup had become part of the project at an earlier stage we would have been involved in deciding whether all connections on site should be made by welding or using bolts. We would also have worked out the advantages and disadvantages of these two engineering approaches. Perhaps we might have come to the same conclusion. In the area of the “trees” it makes more sense to weld on site; in other areas, where shorter spans are involved, using bolts makes more sense. I think that the beauty of engineering lies in the fact that one can carry something out in completely different ways. Arup did not want to hinder this. 43

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Westfield London: Minimised shell structures – Challenges and Prospects

Minimised shell structures – Challenges and Prospects

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Josef J. Ludwig, seele

The challenge of designing shell structures essentially lies in roofing as large a space as possible without columns and using a minimum amount of material, and combining this with ease of fixing and assembly. The shells currently found in the field of glass construction are mostly grid or lattice structures that are divided up into bar elements simply in order to withstand normal forces alone (i.e. compressive and tensile forces). The familiar triangular and orthogonal structures, generally with diagonal ties, allow a certain freedom in the choice of sections, form and geometry, but have clearly defined boundaries as regards aesthetics and transparency. Today technical developments provide opportunities to create more economical and better designed systems. In this context I should like to mention optimization with the help of userfriendly 3D form and geometry tools, and the associated net generation and optimization. Looking to the future The possibilities of our system are far from being exhausted. We deal both with new approaches to basic geometry determination and with detail optimization (improved fabrication and assembly possibilities). A series of highly promising approaches and ideas allows us to speculate that sophisticated and ambitious designs lie ahead. In the near future and following further research and exploitation of the structural possibilities of glass it seems possible that grid shells with glass as bracing will be used. This represents a further step towards to economic use of material and exploitation of the potential offered by different materials. Here one can imagine hybrid constructions with load-bearing and wide-spanning glass that, either through using a new kind of glass or through interlayers, are able to bridge large spans and thus to form larger areas; or constructions using curved or arched elements that, through exploiting their form, allow a bigger mesh size and therefore achieve better use of material and greater transparency. The use of optimised fabrication and production processes as well as innovative materials (for instance with greater structural strength) gives us reason to hope for optimal results with regard to

this kind of structure. In view of the fact that in such structures the dead load of the structure itself plays an important role, the use of materials that reduce weight is essential. A sideward glance at the automotive and aerospace travel industries gives us some idea of the diverse possibilities that composite fibre materials and gluing as a jointing method will offer in the future. It seems to me that the construction of all-glass shell structures is almost within our reach. Following the development of load-transferring all-glass shells in our firm, the next step is using curved elements, and thus utilizing the form, to make completely dematerialized, transparent shells. Expanding boundaries and creating new possibilities in construction remains a most exciting task.

After studying steel construction in the civil engineering faculty of the FH Munich, Josef J. Ludwig worked as a structural designer at seele, later becoming head of the structural design department. In 1996 he set up his own engineering office for structural design. Since 2006 Ludwig has been managing director of seele austria.

44 The Mansueto Library in Chicago is a reading room that extends the existing Regenstein Library. As well as the bridge connecting the buildings seele’s commission also includes the dome which consists of steel tubes and nodes with raised aluminium sections to carry the glass. 45 Locally and globally vaulted shell structure 46 Lattice shell with large curved glass sheet

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FOILS AND MEMBRANES

Allianz Arena, Munich

Allianz Arena, Munich Detail in conversation with Jacques Herzog and Robert Hösl, Herzog & de Meuron (H&deM)

Detail: How does a famous office like Herzog & de Meuron, which in recent years has carried out so many spectacular cultural buildings worldwide, come to take part in a building developers’ competition – and furthermore under such enormous pressure in terms of time and costs? H&deM: There were two reasons: firstly our close and intense relationship with football and the awareness that this stadium represented an exceptional commission in Germany, a stadium for two premier league soccer clubs that would also host the opening of the World Championships in 2006. Secondly, because of our special relationship with Munich over many years with such important projects as the Goetz Collection, an early international key project, and the Fünf Höfe, a large public project with relevance for urban design. When this competition was set up we had already had an office in Munich for several years. Detail: Jacques Herzog, can you describe your personal relationship with football more closely? H&deM: I love football. I grew up right beside a football pitch, so to speak in the backyard of FC Basel and I played myself for a long time. Today I still love watching matches in the stadium. This meant that I was very familiar with the subject from the spectator’s viewpoint, too. Detail: What kind of importance does football have in society today? H&deM: Football is no longer a purely working class sport, but one that attracts large sectors of the population. Football has successfully asserted its place in post-industrial society. It has become a kind of social opera on a grand scale, without replacing the classic opera. A number of players are treated like film stars and are unbelievably highly paid, like David Beckham for instance, who has become a kind of pop star. A few years earlier this kind of thing would have been completely unimaginable. Detail: Did this development have an effect on the architecture of stadiums? H&deM: Up to now this change in the importance of football has never played a role, as the stadiums were generally designed by engineers or special-

ised firms and only very rarely by architects. The Olympiastadion (Olympic Stadium) here in Munich is architect-designed but otherwise there was hardly a single stadium with any real architectural aspirations until our project in Basel. As far as I’m aware, it was the first stadium building of the new generation in which architecture was really at the forefront of the considerations, and not the greatest possible spans, a large sliding roof or other populist acts of daring.

This conversation is an excerpt from an interview that Frank Kaltenbach and Christian Schittich made in July 2005 with Jacques Herzog and Robert Hösl for DETAIL 09/2005.

Together with Pierre de Meuron, Jacques Herzog founded the Baselbased architects office Herzog & de Meuron in 1978. Robert Hösl has been a partner in this office since 2003.

Detail: You mentioned the Olympiastadion in Munich, which opens towards a landscaped park. Is the introverted Allianz Arena the antithesis to it? H&deM: The Olympiastadion is a magnificent building but has nothing to do with our project. Nor did we try to introduce analogies, as that rarely works. I think it’s great that Munich now has two very different architectures that start from completely different concepts. Because it is a light athletics stadium a greater openness and a certain calm are called for in the Olympia Stadium, the competitions are friendlier, there is more discipline on the sports field. Obviously that is expressed in the architecture. In contrast football always means a direct confrontation between one team and the other. The matches are rather like hostile encounters and the stadium almost resembles a castle, the pitch a battlefield – to exaggerate somewhat. Detail: Mr Herzog, do you not have any problems with this? In response to the club’s wishes you design a cauldron that heats up the mood further, could this not lead to outbreaks of violence? H&deM: I don’t refer to the interior of the stadium as a cauldron, but a “machine for perception”. The interaction, the total intensifying of the emotions is the most important aspect of all our projects. Hooliganism has nothing to do with architecture. Architecture can intensify emotions but hooliganism can neither be started nor curtailed by architecture. We can’t make boring architecture just because of radical, uncontrollable emotions – not for an opera house, nor a museum, nor a football stadium. 41

Foils and Membranes

Cross-section Scale 1:2500

Allianz Arena, Munich

Detail: Could you briefly describe the concept of the Allianz Arena? H&deM: It’s much like a child’s drawing: dot, dot, comma, line and the face is ready. There are three or four aspects that are radically and precisely addressed. One very specific aspect is the esplanade, this almost ceremonial route between the metro station and the stadium, where the stadium visitors meander on their way to the stadium that lies behind the gentle hill and only reveals itself as you walk down to it. The spectators move around the stadium in an embracing gesture. The cascade stairs continues this entrance ritual inside the building. The other aspect is, naturally, the building as a symbol that changes its colour from white to red and blue, like a membrane that transports the energy from inside to outside where it is perceived as a beacon of light. And, thirdly, the radicalization of the interior space which, as we said, is like an interactive perception machine, almost like a classical arena. Detail: A special aspect was designing a stadium for two football clubs. When you started designing, were there alternatives as regards how this requirement should be met? H&deM: No, we knew that the two clubs should be able to identify with the same stadium and that the national team also plays there. From the very start the lighting concept with the changing colours was an important part of the design. Detail: Is the lighting concept a further development of your St. Jakob Stadium, where the facade glows red when FC Basel scores a goal? H&deM: Yes, back-lighting in the club colours seemed to us a possibility in both these spatially different situations. In Munich, where the building stands alone on an open site, the effect is clearly more interesting, while the Basel Stadium is integrated in the development that surrounds it. From a technical viewpoint we are using the experience we gained in Munich in the addition of a further level to Basel Stadium for the European Championships in 2008 and we will use ETFE cushions rather than the polycarbonate light domes we employed originally.

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Detail: In your book “Naturgeschichte” you show the influence of nature and art as sources of inspiration for your designs. Were there any such models involved in arriving at the form for the stadium envelope? H&deM: No. We wanted different forms to individualize the surface. The alternative concept would have been a smooth envelope over the entire building, without any subdivisions. But this differentiated quality seemed important to us, to reflect the interior of the stadium outside, i.e. in concrete terms the scale of the individual spectator. Detail: The envelope is divided up into diamond or lozenge shapes. Was this geometry dictated by the technology or was it chosen to give the building a dynamic effect? H&deM: To a certain extent it has to do with folklore. When it is lit up in blue and white diamonds the pattern resembles the Bavarian flag. The diamond also has other advantages in terms of both construction and design. For instance it responds to the upward movement of the cascade stairs running around the building. A purely vertical facade would have looked banal, like a plastic version of neoclassical architecture. We always look at different structures that can connect constructional and iconographic elements. Detail: How should the Munich Stadium be classified in terms of your complete work? With its clear geometry and monochrome materiality it recalls your early minimalist projects more than the recent, often highly decorative designs. H&deM: We don’t allow ourselves to be pinned down here. We are interested in architecture as a way of expressing oneself today. Before we started with minimal architecture no other architect had done this kind of thing. We were the first because we were looking for a way to assert ourselves in a world where deconstructivism and postmodernism were emerging – and we succeeded in doing this. This total simplification was the sole effective weapon against the overabundance of forms that was common at the time. But now the world has changed once again and architecture has many dif-

Allianz Arena, Munich

ferent faces. With us, depending on the particular project, the result can turn out to be decorative or less decorative. Detail: Where is the link, the red thread running through your work? H&deM: A building is either better or less good, right or less right, appropriate or less appropriate – those are our criteria. Whether the formal idiom is minimal or maximal, mannered or less mannered we don’t find so important. We have no particular preferences in this regard; it depends on the individual building commission. Detail: Modern stadia are generally overloaded with additional functions like fan areas, business clubs, restaurants. There’s even an old people’s home integrated In the St. Jakob stadium. (...) H&deM: We have no problems with this. In earlier days stadia were integrated in districts much like churches, built directly against shops, they were real centres of urban neighbourhoods. Today it is the other way around, the city is growing outwards in the direction of the stadia, like in Basel. In Munich this is not yet the case. But there, too, in the foreseeable future– with or without a master plan – it

will be revealed that this urban development is inescapable because the stadium is a strong attractor and an urban symbol. What additional functions are located under the stands and under the pitch or whether they are built as separate buildings beside the stadium, doesn’t play such an important role. The decisive thing is the way it is done. Detail: What architectural approaches and elements create a good atmosphere in a stadium? H&deM: The transparent glass roofs used in recent years were a development in the wrong direction, as they do not allow a specific spatial quality to develop inside. The energy evaporates. The Allianz Arena also has a transparent roof to allow sunlight to reach the pitch but during the match a membrane is drawn across it. In Basel the roof is closed from the start. Compactness, a spatial definition at the top is extremely important for the atmosphere. (...)

Building data Client: Allianz Arena München Stadion GmbH Architects: Herzog & de Meuron, Basel General contractor: Alpine Bau Deutschland, Eching Structural design: Arup, Manchester; Sailer Stepan Partner, Munich; Kling Consult, Krumbach; Walter Mory Maier, Basel; IB Haringer, Munich Facade design: R & R Fuchs, Ingenieurbüro für Fassadentechnik, Munich Calculation for inflated shell: Engineering + Design, Linke und Moritz GbR, Rosenheim Building services: TGA Consulting, Munich Lighting design: Werner Tropp Schmidt, Munich ETFE envelope: Covertex, Obing Foil material ETFE foils: Asahi Glass Europe, Amsterdam Cutting of ETFE foils: KfM GmbH, Edersleben Assembly of ETFE cushions: Membranteam, Ravensburg Air supply ETFE cushions: Gustav Nolting, Detmold

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Foils and Membranes

Allianz Arena, Munich: From the Idea to the Detail

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From the Idea to the Detail Detail in conversation with Tim Hupe (TH), formerly with Herzog & de Meuron Between 1999 and 2004 Tim Hupe worked as an architect for Herzog & de Meuron. For the Allianz Arena project he headed a 30-person team and his area of responsibility extended from the first sketch to the completion of the planning process. He subsequently set up his own architecture practice, Tim Hupe Architekten, in Hamburg.

Detail: Mr Hupe, people in the media christened the Allianz Arena the “rubber ring” and the “inflatable dinghy”. How does that sound to you? TH: Allianz, the main sponsor, wanted to build a very safe stadium. Interestingly enough both these objects you mentioned are associated with fun and safety. And so these metaphors don’t seem absurd to me. Detail: How did you arrive at this striking form? TH: The basic idea is that the stadium stands by itself in the landscape and, together with the wind turbine, forms a kind of city gateway. In contrast to the Olympia Stadium, the Allianz Arena is a solitary building that functions only from within and from the inside out. This resulted in a very introverted figure with the stands as the front and the exterior as, in fact, the back of the building. With the competition team at Herzog & de Meuron our goal was to make a front side out of this “back” and that meant giving the building an image. In attempting this we examined different objects – cauldron, pots, vases, baskets ...What fascinated us about the latter was the proportionality that weaving produces. A sense of scale is created between the individual parts and the scale of the object. Applied to our building that meant a structure that connects roof and facade with each other. The diagonals in a woven pattern seemed a suitable way of doing this. A facade construction made of glass would have tied us to certain element sizes,

and there was the added danger of making the stadium look like an office building or a shopping centre. Detail: Does that mean that the foil facade was an important part of your design concept from the very start? TH: In the early stages we thought about a polycarbonate element facade, only the roof was to be made as a foil envelope. During the second competition phase the facade designer R & R Fuchs gave us the idea of using foil for the facade as well. At the beginning we weren’t so sure, but then we quickly decided in favour of this suggestion, even though we knew that this construction would raise a number of eyebrows among those involved. Detail: But you were able to persuade the sceptics with sound arguments TH: Yes, otherwise we would never have been able to implement this idea. The deadline for completion was already determined, the 2006 World Championships and, due to the negotiation process for appointing the general contractor, we had to show that our idea would work before the contract was awarded. When the construction principle for the envelope had been worked out, we had it checked from a number of different viewpoints, such as vandalism, fire protection and transparency. For fire protection, for instance, the ETFE foil, compared to polycarbonate, turned out to offer clear advantages. As the skin has a thickness of a mere 0.2 mm the fire loads are negligible. The foil immediately retracts from the source of the fire. Detail: You had already worked with the specialist planners in an earlier design phase? TH: Yes. For the competition phase Arup Berlin had worked out a structural concept for the stadium bowl. After the commission was awarded the engineering office of Sailer Stepan from Munich joined our team. This office knew the local authorities, which was naturally a great advantage for the further planning. Detail: What were your requirements from the structural engineers?

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Allianz Arena, Munich: From the Idea to the Detail

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TH: Well actually the support structure was secondary for us. The spectator is more interested in what’s happening on the pitch than in the beam he is sitting on. Moreover a “beautiful” structure is very expensive. The only requirement we made of the structural engineer was to design an economical construction. Detail: Did you already have a vision of the light animation during the design phase? TH: Yes, this was one of the first ideas. The printing played a major role here. On the one hand the cushions must be animated with light at night; on the other they must be transparent. At the same time the lights at the upper and lower edge of the cushion must be invisible to achieve the desired effect of depth for the viewer. Working from these requirements we decided on printing a pattern of points that reduces in intensity from the edge to the centre of the cushion, where only 20 % of the foil is printed. Working on up to 12 1:1 sample cushions at the same time, we examined different kinds of printing and lighting. This was a lengthy process. Detail: Did the building turn out the way you had imagined it? TH: Yes, absolutely. In fact even better. Because beforehand you couldn’t imagine it in this complexity. I would even maintain that the result is better than our original idea. It lay beyond our powers of imagination, so to speak. Detail: What was the greatest challenge for you? TH: One of the greatest challenges was certainly the time pressure. The date on which the competition was announced was the latest possible. At first it seemed to me impossible to carry out the project within such a limited period of time. But we were ensured that everyone would pull together. Detail: And so work was carried out on the building site 24 hours a day. TH: Work on the site was carried out according to a three-shift system. Very severe winters delayed the construction work to some extent. But the decisions by the client and the various approval proce-

dures took place extremely quickly. The procedures were shortened, and decisions were made directly and promptly. The first sketches were made in September 2001, we won the competition on 8 February 2002 and three months later we submitted the building application. The first concrete was poured in October 2002. Everyone pulled together, as FIFA wanted to hold the first test match a year before the championships. Therefore we had a time slot of a good two and a half years for the building. Our planning work was essentially complete by spring 2004. Detail: How and when did Covertex, today known as seele cover, appear on the scene? TH: Covertex had submitted a tender for the facade to Alpine Bau, the general contractor. We weren’t involved in the negotiations about awarding contracts. The engineering office R & R Fuchs was the technical consultant to Alpine Bau. It was they who recommended Covertex, who was ultimately awarded the contract for the envelope. Their tender convinced everyone above all because of the well thought-out, plausible details. One example of this was the point of intersection of the cushions. We, as the designers, first of all envisaged a metal cover piece over the gutter. On inspecting samples it became clear that we could do without it. Ultimately the input here also came from Covertex. By omitting this metal piece we saved time and money. There was also a design advantage. The open gutter functioned as a visual joint between the membranes. So essentially we made a virtue out of omitting and economising.

Section through roof of west stand Scale 1:50 1 Ventilation lifting element with ETFE cushion 2 Upper chord steel tube | 600/600 to 300/200 mm 3 Cushion ETFE foil transparent 0.2 mm 4 Eaves cushion ETFE foil white 0.2 mm 5 Drainage pipe in case of technical failure 6 Stainless steel safety rail 7 Gutter 8 Roof lining, extendable, PU/glass fibre fabric 9 Hinged column steel tube Ø variable 10 Spring bar Ø 140 mm

Detail: What was the most moving moment for you? TH: Certainly the start of the competition. But also something else: from our construction office we could follow the progress of the building in situ. It was fascinating to watch the fitting of the roof beams and foil cushions. What we drew was implemented almost immediately. For me these were two and a half thoroughly exciting years.

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Foils and Membranes

Allianz Arena, Munich: Roof Structure and Vertical Facade

diagonal member

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768 rhomboid-shaped membrane cushions

Roof Structure and Vertical Facade Rudolf Findeiß, Johann Pravida, Kurt Stepan, Sailer Stepan Partner Rudolf Findeiß und Johann Pravida are managers in the engineering office of Sailer Stepan und Partner (SSP), Munich, which was responsible for the structural design of the roof and the steel facade. Kurt Stepan is managing director of this office.

The externally uniform appearance of the stadium roof in fact conceals three different structural support systems. The Munich office of Sailer Stepan und Partner (SSP) was responsible for the structural design. Widely cantilevered steel trusses whose upper and lower chords describe parabolas form the main structure, known as the primary structure, of the stadium roof. A total of 48 trusses arranged in a radial pattern carry the loads from the roof of the secondary structure out to the edge of the stadium, where, by means of tension bearings, they are inserted into the columns of the solid structure. The skin of the roof and facade is made up of airfilled, diamond-shaped ETFE cushions whose substructure, both for the roof and the immediately adjoining but separate vertical facade, consists of diamond-shaped grillages. Roof with diaphragm action The 2016 ETFE membrane cushions that make up the roof skin are under constant internal pressure and cover an area of around 40,000 m2. They are fixed to the members of the secondary structure which is divided into circumferential and diagonal members. These members are hollow square sections with sides measuring 180 mm that are connected rigidly to each other at the nodes by bolted or welded joints. The loads of the secondary structure are transferred to the trusses via short columns with hinged joints. The primary construction cantilevers up to 62 metres, the distance between upper and lower chord at the bearing points is between 8 and 12 metres. This difference in height results from optimizing the visibility of the pitch in the corner areas and is related to the curved line followed by the upper tiers of the stadium. To direct the compression forces into the solid structure at the front bearing points, low friction cup-and-ball-bearings are used that transfer normal forces of up to 5000 kN. At the rear bearing point the tensile forces of maximum 3300 kN from the fixed end moment are directed by means of composite mounting components into the external columns. Bracing is provided by concentric ring purlins, horizontal wind braces and, finally, a continuous ring truss at the height of the compression bearing points.

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These are designed to distribute the deviation forces in the horizontal projection generated by the bending of the trusses within an expansion joint bay, and thus equalise the reaction forces. The individual parts, weighing up to 100 t, were fitted in place by a caterpillar crane operating from the pitch. Two preassembled trusses, connected to each other, were lifted into each of the eight bays separated by expansion joints and bolted to the bearing constructions to provide initial stability. After this the individual trusses could be connected by means of the ring purlins. The roof structure, like the solid base structure, was divided into eight expansion joint bays to keep stresses caused by temperature change to a minimum. To implement the architects’ concept of a seamless cushion plane, SSP suggested placing the spatially curved grillage (diamond-shaped in plan) on vertical columns that are completely hinged at the ends and connecting this structure to the primary structure at the zenith in the area of the straight lines and curves, by means of four tangential bracings. This holds the entire structure horizontal. The hinged-end columns mean that both parts of the construction can move with respect to each other without causing strain. Thermal expansion of the secondary or primary structures merely causes the tangential bracings to tilt, so that the strain imposed as the result of temperature change remains extremely slight for this kind of bearing. To obtain additional stiffness in the grillage in each of three circumferential rows,

Allianz Arena, Munich: Roof Structure and Vertical Facade

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96 diagonal spring elements were laid out in a radial arrangement between the primary and secondary structures. The stiffness of the spring elements is adjusted both to provide adequate support and to prevent the constraint forces generated from becoming excessive. Assembly SSP carried out its own calculations for the assembly period. The fitting of the diamond-shaped structure was carried out in 12 stages; the steel substructure was fitted in place only shortly before mounting the ETFE cushions. The individual steps in the assembly procedure had to be precisely planned in advance with the steel construction firm and the cushion manufacturer, as both temperature fluctuations as well as changing effects of snow and wind on the surface of the cushions had to be taken into account. The cushions in the roof area were installed from May 2004 to January 2005, so that seasonal temperature variations could be taken into account. The aid of the secondary structure as a continuous diaphragm could only be used at a very late stage. It was only by precisely planning the insertion and removal of assembly braces that it was possible to guarantee the stability of the building at all times. As an aid to calculations we used a monitoring program that included the inclination of the hinged columns as well as the forces actually present in the spring elements.

Vertical facade with hinged nodes The vertical facade is structurally separated from the roof construction. Analogous to the roof surface the cushion layer here is also made up of horizontal and diagonal members in the form of rectangular hollow sections measuring 120 ≈ 220 mm and with different wall thicknesses. It was connected to the solid substructure by inserting mounting parts and short cantilever arms into the points of intersection. At various points in the cascade stairs a load-distribution torsion-resistantring beam was positioned to bridge the openings in the solid substructure. With the vertical facade, too the architectural specifications required the construction joints in the solid substructure to be invisible. But the changes in length in the circumferential direction caused by temperature made a jointless construction impossible. Instead we adopted a solution that envisaged a normal force hinge in each horizontal plane of members between each cushion. In discussions with the manufactures of the ETFE membrane cushions we fixed the hinge’s ability to slide at ±13 mm. In this way thermal expansion could be compensated while also effectively preventing creasing of the cushions. Non-linear calculation were performed which took into account impact on the normal force hinge when subject to increasing load. We coordinated the structural calculations for the steel structure with the planned assembly process. The deflection of the cantilever arms and the torsion beams caused by the structure’s unloaded weight was compensated by precisely calculated cambers. This guarantees the proper functioning of the sliding joint in the building’s final state.

Schematic illustration of roof structure Scale 1:1000 Detail Scale 1:400 1 Primary structure 2 Secondary structure, square section steel tube | 180/180 mm 3 Spring bar 4 Tangential bracing secondary/ primary structure 5 Hinged column 6 Joint between roof and vertical facade 7 Cup and ball bearing (compression) 8 Tension bearing 9 Ring bracing steel truss

Edge tensile forces The internal pressure of the cushions in the roof construction and in the vertical facade is permanently controlled and adapted to deal with wind and snow pressure so as to prevent the cushions collapsing. The changing edge tensile forces that this causes exert an effect on the steel substructure and must be taken into account in the structural calculations, and, in particular, when considering deformation.

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Foils and Membranes

Allianz Arena, Munich: Design Aspects of ETFE Foil Cushions

Design Aspects of ETFE Foil Cushions Karsten Moritz, seele 1 Dr.Ing. Karsten Moritz has been head of the research and development department of seele cover GmbH since 2007. Before this, together with Dieter Linke, he managed the engineering office Engineering + Design GbR in Rosenheim, which carried out the structural dimensioning of the ETFE cushion envelopes of the Allianz Arena and the AWD Arena.

2 R & D laboratory The installation of tension test stand at the seele cover research and development laboratory represented an important step towards acquiring deeper knowledge about the mechanical material performance of lightweight construction materials. The universal test machine installed, which has a temperature chamber (40 °C to +100 °C) (fig. 2) and allows contact-free measurement of expansion, enables important specific values to be calculated under simulated environmental conditions over a wide area. Ultimately, knowledge of mechanical properties also provides the basis for the compatibility of composite, multiple layer building elements and can help open up new possibilities in terms of building physics.

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The architecture of the Allianz Arena is characterised in a particular way by the translucent envelope with its diamond-patterned surface structure that can glow in different colours. It is this envelope alone that makes the building unique. It consists of a foil made of the high performance plastic ETFE. A building envelope of this form could not have been made using any other material. Development of the ETFE foil cushions ETFE or, more accurately, E/TFE is the chemical abbreviation for the thermo-plastically workable material Ethylene/Tetrafluorethylene Copolymer. The film or foil produced from it was first brought onto the market in 1970 by DuPont, under the trade name Tefzel. After polymerization the powdery ETFE is made into a granulate and then extruded as a foil. After use ETFE foil can be returned almost completely to the cycle of materials. In the building industry it was initially used to roof greenhouses on account of its high light and UV transmission properties. At the beginning of the 1980s the first permanent large ETFE roof elements for botanical gardens were built, followed later by roofs for swimming pools, atria etc. The number of competent specialist firms working in this area is limited, the number of suitable foil producers equally so. The firm Covertex from Obing am Chiemsee, today known as seele cover, which specializes in the area of membrane and foil construction, carried out the ETFE envelope of the Allianz Arena and the transparent foil roof of the AWD Area in Hannover. In both these projects Fluon ETFE Film produced by Asahi was used. Covertex commissioned the engineering office Engineering + Design, Linke und Moritz GbR, Rosenheim to carry out the structural dimensioning of both foil systems. Construction method These stadia illustrate two fundamentally different approaches to building with membranes. The foil envelope of the Allianz Arena in Munich consists of air-supported cushions made up of several layers. The transparent roof over the stands in the AWD Arena Hannover demonstrates the principle of the single layer, mechanically pre-stressed membrane.

In terms of both appearance and structural performance there are clear differences between these methods: the cushions formed out of at least two layers are pre-stressed by overpressure of the enclosed air volume and stabilized. This creates a synclastic surface over wide areas – i.e. curved in the same direction in the two main directions of curvature. It is only at the corners that local anticlastic areas – i.e. curved in opposite directions – occur, much like with a cushion. In contrast mechanically pre-stressed membranes are anticlastic surfaces. By inserting them tightly in a fixed surround they are pre-stressed mechanically rather than pneumatically. The areas of foil of the AWD Arena Hannover, which are almost level, are a borderline example of the anticlastic building method due to their lack of curvature. Cushions, in contrast to mechanically pre-stressed membranes, have adjustable pre-tension, thanks to the internal pressure. To create the internal pressure there is a blower room (station) in each corner of the Allianz Arena with three blower boxes (units) to two blowers (fans). Each unit supplies one quarter of the facade or one eighth of the roof cushions by means of a branching system of air pipes with a nominal internal pressure of 300 Pa (roof) to 450 Pa (facade). When snow loads occur the pressure is increased to 800 Pa. The two fans in a unit alternate automatically with each on a weekly basis. The capacity of each fan is designed for the air requirement of one quarter of the stadium, so that if one unit fails the support pressure can be maintained by the supply pipes. If there is a power failure an emergency power supply keeps the system in operation. Important elements of the air supply are thus redundantly designed. The envelope of the Allianz Area measures around 66,500 m2 and is made up of 2784 diamond-shaped areas or bays, 2760 of these bays are filled with double layer ETFE foil cushions (secondary system membrane). The diamond-shaped cushions, which vary in size up to 4.6 ≈ 17 metres, produce a maximum bay size of about 40 m2 and an enclosed cushion volume of up to around 25 m3. If the spatially curved cushions were flattened out this would produce a total foil surface of around 147,000 m2. By changing the internal pressure the loads resulting from dead weight, wind and snow

Allianz Arena, Munich: Design Aspects of ETFE Foil Cushions

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are directed from the foil into the substructure (steel secondary system). This is what gives the cushion envelope its unique diamond-pattern structure. It consists of 96 spiral and 29 ring-shaped steel beams that direct the roof loads, generally by means of hinged posts, into the main structure (steel primary system). Drainage of the cushions An innovative design development was introduced in the Allianz Arena project in the form of a self-acting cushion drainage system. It is to be found in 1900 cushions in the flat area of the roof. When an unscheduled loss of air pressure occurs at the same time as rainfall, this drainage system automatically directs the water out of the cushions, thus preventing larger amounts of water gathering. As both the power supply and the blowers for the cushions are essentially redundantly designed, the likelihood of such a case occurring is slight, but nevertheless forms an important aspect of the safety concept (figs. 6 and 7, p. 50). Expansion joints The expansion joints in the substructure of the cushion envelope represent a second construction innovation. It was due solely to this innovation that areas of the steel substructure for the cushion envelope in the Allianz Arena could be made continuous. Otherwise the opening and closing of the expansion joints caused by variations in tempera-

ture could have possibly destroyed the thin foil of the cushion in the long term. This innovation consists of a spring steel plate at each expansion joint in the obtuse corners of the diamond which translates the change in the width of the joint into a change in the span of the cushion, so that the thin foil is not damaged. This solution called for a further innovation, namely a holding fixture made of the elastomer EPDM which, thanks to its flexibility, can easily cope with the change of radius of the spring steel plate. This development, too, was used for the first time in the Allianz Arena (Figs. 3 – 5). Approval of individual cases A general building regulation approval that could be interpreted as allowing the use of ETFE foil as envisaged in the Allianz Arena did not exist. The system consisting of foils, connections of edges and part areas could not be classified in terms of standardized building products or types of building. This meant that its suitability had to proven on an individual basis through the building regulations approval procedure. The supreme building authority in Munich specified requirements based in principle on the Bavarian building regulations in relation to this project and gave its approval, on the basis of the expert reports, calculations and material tests submitted. The focus of this procedure was on fire protection and structural safety.

1 Mono-axial tension test 2 Universal test machine with temperature chamber 3 Obtuse corners of diamond: edge section with spring steel plate to take up temperature expansion from the secondary structure 4 Cross-section through gutter and edge section 5 Junction of members in the facade

R Gutter section facade scale 1:5 1 ETFE cushion air-filled (membrane thickness 0.15 – 0.25 mm) 2 EPDM weather strip Ø 6 mm 3 EPDM seal strip, fitted in works 4 Sealing of gutter thermoplastic polyolefin 5 Aluminium fixing section, anodised 6 Steel bar 60/5 mm, in obtuse angle corners spring steel plate to take up movement at junction 7 Secondary structure Rectangular section tube 120/220 mm

Fire protection According to test certificates the ETFE foil used is a B1 building material with low flammability (DIN 41021). With direct flame impingement it begins to melt at a temperature of around 275 °C, which allows gas and heat to be extracted via the source of fire. The melted material quickly solidifies so that the foil is classified as “does not fall (drip) when burning” according to DIN 4102. Due to the low weight per unit area its fire load is extremely small. As the ETFE envelope of the Allianz Arena forms both the roof and the outer layer of the double facade for the eight-storey solid structure the requirements imposed by the fire protection plan agreed with the relevant authorities were relatively stringent. Fire tests on roof and facade 5

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Foils and Membranes

Allianz Arena, Munich: Design Aspects of ETFE Foil Cushions

6a

6b Water loads When the system is operating normally the curvature of the cushions ensures that meltwater and rainwater flow into the channels in the members and from there into the three main circumferential drainage gutters. With horizontal cushions the possibility of water pockets forming during a breakdown of the system is also examined in principle. In comparison to textiles, foils have a considerably lower breaking strength so that they frequently represent the “predetermined breaking point” of the entire system. Due to the extreme softness of foil material in the plastic area – the breaking elongation can, depending on the state of stress, amount to several hundred per cent – water loads could accumulate in a hollow that had once formed, without the water flowing over the edge. It is therefore difficult to calculate a mathematical maximum load that could be used as a basis for proving the tension performance of the foil. To exclude the possibility of water collecting in the flat area of the Allianz Arena roof during a breakdown in the operating system, 1900 cushion elements are equipped with a self-activating cushion drainage system: water can flow out of the hollow through a pipe that is fixed to the upper foil and runs through a sealing ring in the lower layer (figs. 6, 7). The cushion drainage system is used only where, despite the built-in redundancy, the air supply system fails and, at the same time, heavy, or long-lasting, precipitation occurs. As the sinking of the internal cushion pressure below a set minimum value sets off an automatic alarm in the services control centre, loss of pressure can quickly be recognized and corrected, so that the cushion drainage system is rarely used.

elements carried out at the MFPA in Leipzig showed fire performance suitable for this use (fig. 8). Structural security Up to recently very few accepted technical regulations in the form of special guidelines, dimensioning or test standards existed for membranes made of textiles or foils. Therefore a verification plan (effects, material qualities, mathematical model, safety etc.) was agreed upon at an early stage with the inspecting engineer, Professor Albrecht from Munich Unloaded weight The minimal thickness of the foils results in a low unloaded weight which as a rule can be neglected in calculations With a specific weight 1.75 kN/m3 the two layers of foil in a cushion (2≈ 250 μm) result in a mass per unit area of less than 1.0 kg/m2. In comparison 4-mm thick glazing has a mass per unit area of around 10 kg/m2, and 25-mm-thick twin wall polycarbonate panel around 3.5 kg/m2. This means a weight saving for the cushion of about 90 % compared with the glass pane and about 70 % compared with the twin wall panel – in just the covering alone. If one takes into account the spans of 4 to 5 metres that can be achieved with cushions (according to load, without cable support) this reveals a further potential saving in the substructure (note: on account of

8

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7

pre-stressing and external effects with membrane constructions, unlike in rigid coverings, loads also occur in the membrane plane that reduce these savings). As the unloaded weights of the covering and substructure are directed, together with the external loads from wind pressure and snow, to the foundations, the cross-sections and unloaded weights of the entire load-bearing construction are reduced. Pre-stressing The pre-stressing of the foil caused by the internal pressure in the cushions serves primarily to stabilise the cushions against wind. It prevents knocking of the foils during gusts of wind and reduces their deformation. The extent of the pre-stressing is dependent on the curvature and the internal pressure of the cushion. In the Allianz Arena the nominal internal pressure of 300 Pa results in an average pre-stressing of the foil of around 1.0 kN/m. Wind loads Wind tunnel tests on models of the stadium in built and fitted-out state as well as wind reports based on these from the office of Wacker Ingenieure, Birkenfeld provided the wind loads for dimensioning the cushion envelope (fig. 11, p. 52). These were overlaid with the other adverse loads Overlaying wind loads and internal cushion pressure The wind load on a cushion results from the difference between the air pressure occurring above and below it. Each of the foil layers is stressed by the pressure difference between the adjoining air pressure and the internal pressure in the cushion in response to the wind load. When wind suction occurs on the upper face the air pressure above the cushion – i.e. the supporting force of the air – is reduced. Consequently, the upper foil deforms upwards and is stretched. Its rise (maximum height) increases – in relation to its pre-stressed state with nominal internal pressure (fig. 9). Since the fan is not capable of supplying a larger volume of air through the small cross section of the air ducts (ca. 20 cm2) when brief gusts occur, the number of air molecules enclosed in the cush-

Allianz Arena, Munich: Design Aspects of ETFE Foil Cushions

Ws f OL under load

pi

VOL

FOL H OL

H

H

H IL

f IL under load

V IL

FIL

H = HOL + H IL V

|V| = |VOL | - |VIL | = |Ws,v | x L x 0,5

V

L 9

ion remains almost constant. Assuming a constant temperature during the gust, the enclosed air relaxes according to Boyle’s gas law (p ≈ v = constant), i.e. the volume of the cushion increases and internal pressure decreases. Thus the lower foil is relieved and its height reduces. If the wind suction loads on the upper face are so high that the lower foil is relaxed completely, the internal cushion pressure matches the air pressure below the cushion. In this case the internal cushion pressure should not be overlaid with the wind suction. When wind pres-

sure is on the upper face the system behaves according to the same law: the enclosed volume of air is compressed, the pressure in the cushion rises – in relation to the nominal internal pressure – and the lower foil is stretched and its strain increases. This is the load transfer principle of the cushion. To calculate the internal cushion pressure under wind loads, a calculation method was developed by Engineering + Design that takes into account both the gas law and the pre-stressing stored in the foil.

6 The function of cushion drainage a Cushion with regular internal pressure b Breakdown of operating system, the collected water is emptied through the drainage pipe 7 Drainage pipe 8 Fire test 9 Cushion section on steel, double layer, deformation and reactions at bearings under wind suction 10 Fitting the ETFE foil cushions in place

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Foils and Membranes

Allianz Arena, Munich: Design Aspects of ETFE Foil Cushions

11 11 Model in the wind tunnel

Snow loads Between 1952 and 2003 the German Weather Service measured the water equivalent of the snow cover on the ground at the location Munich-North three times weekly. Experience has shown that the amounts measured on the ground are greater than those on an elevated roof surface exposed to the wind. With the agreement of those involved in the project, the authorities and the inspecting engineer, the assumed snow loads were based on these measurements. In winter 2004/2005 there were heavy snow loads on the almost completed roof. It turned out that the snow is distributed unevenly, but favourably, on the cushions. It tends to be blown completely off the rounded top of the cushions and into part of the gutter. Contrary to what had been envisaged it was not necessary to increase the internal cushion pressure, as the major part of the load was led directly into the gutters. For dimensioning purposes, the snow and wind load assumptions were overlaid in accordance with the dimensioning concept. Dimensioning The vertical symmetry plane in the centre of the stadium creates 1392 different spatial geometries. Combined with the different load situations this means that each foil is differently stressed. In the circumferential direction, i.e. around the perimeter of the stadium, these differences are considerably less that across the section of the stadium, i.e. from eaves to the inner edge of the roof. Therefore it was possible to calculate the dimensions for the most heavily stressed cushion of a ring, without this resulting in serious economic losses. The foil thickness was increased in increments of 50 μm in accordance with the stress of each of the 29 cushions examined. The thickness of the outer foil varies between 200 and 250 μm, that of the inner foil between 150 and 250 μm. It was possible to influence the resulting membrane forces within certain boundaries by modifying the maximum height of the cushions. These limits were determined by the required appearance and the wish to avoid collisions with the steel building. The dimensioning of the foil was carried out on the basis of known material values. Long-term testing under simulated

52

weather conditions (influence of water and xenon arc radiation in accordance with DIN 53387) helped assess long-term performance. The structural stability of the cushions does not depend solely on the structural performance of the foil itself. The connections of different areas of foil and the edge connections must also be able to transfer the foil forces. Connecting areas of foil The broad slit extrusion production process at present allows a maximum foil width of 1.60 metres (Fluon ETFE Film). Therefore to produce the spatially curved surfaces the lengths of foil delivered in rolls to the works had to be welded together in accordance with the cutting pattern. The thermally produced welded connection in the form of a flat seam is about 10 mm wide and approximately as thick as the sum of the layers welded together. In contrast to textiles in which, normally speaking, only the coating but not the fabric is welded, with welded seams in foil a homogeneous connection of the two cross-sections that transfer the load is created. In the Allianz Arena project adequate load capacity of the welded seams was guaranteed by the self-monitoring and quality control exercised by the company responsible for the work. In addition, external monitoring of the manufacturing process was performed by Labor Blum, Stuttgart, a testing, monitoring and certification centre approved for membranes by the Deutsches Institut für Bautechnik (DIBt).

Development of Lightweight Building Shells

Development of Lightweight Building Shells Karsten Moritz, seele

The Allianz Arena in Fröttmaning near Munich was completed in 2005. Does it represent a milestone in the history of buildings in general and stadium buildings in particular – like the Olympiastadion in Munich for example – or is the construction method of the cushion envelope merely an architectural episode that follows a short-lived trend? How should this building envelope be evaluated in an architectural context? These questions offer plenty of material for discussion. One way of judging the quality of a building or part of a building is to view it in the architectural context, i.e. against the background of its specific purpose and function. Useful criteria in making such an evaluation include quality along with the well-considered and harmonious integration of the following individual aspects (fig. 13, p. 54): • Form • Function • Construction • Ecology • Economy These aspects overlap and are related to and affect each other. Their qualitative assessment is by no means constant but – like the design of buildings itself – is subject to cultural and social influences. The reasons for this could be, for example: cultural developments and an altered sense of tradition, change of values, increasing demands and an improved standard of life, trends and changes in taste, inventions, developments and the associated state of science and technology but also changes in laws, standards and guidelines.

the opposite is true. The “ecological” approach proves to be a source of and a challenge for creative work. Commitment to ecology should not merely take the form of lip service, it must become part of our thinking and action. We must learn to see this criterion as a characteristic that determines the design and quality of architecture. Ecology and economy are mutually dependent The criterion “ecology” includes a wealth of aspects e.g. long life-span, environmental compatibility, esource conservation, saving of energy, CO2 emissions, environmental performance assessment and recyclability. It is nowadays generally agreed that neglecting these ecological aspects inevitably has economic consequences which we will have to answer for and bear the cost of, perhaps not always immediately and directly, but certainly in the longterm and indirectly. Consequently, ecology and economy are not antitheses but are directly related to each other. The more our supply of non-renewable resources dwindles, the more cost-effective ecological products and actions become. Today already the ability to design, plan and build in an ecologically aware manner offers a decisive competitive edge. Franz Alt writes: “Never before has it been so easy to do what is ecologically reasonable.” [5] This development leads to Brian Cody’s hypothesis: “form follows energy”. [6] This principle can be interpreted in a number of ways, if one thinks for example of the energy efficiency of a building, its

Ecology However fundamental and powerful Louis Sullivan’s (1896) principle that “form follows function” [1] may be, it can be applied to building today only to a very limited extent. We are standing at a social turning point, at which ecology as a criterion will become the determining factor in our work. The challenge for architects and engineers today lies in achieving harmony between form, function, construction and economy, under ecological premises. The criterion of ecology is occasionally viewed as an irritating restriction to design freedom. However

Dr.Ing. Karsten Moritz has been head of the research and development department of seele cover GmbH since 2007. Before this, together with Dieter Linke, he managed the engineering office Engineering + Design GbR in Rosenheim, which carried out the structural dimensioning of the ETFE cushion envelopes of the Allianz Arena and the AWD Arena.

12 Insulated and translucent membrane envelope (carried out by Covertex GmbH) in the course of the refurbishment and renovation of the Olympia indoor swimming pool, Munich

Olympiahalle Munich In 2007 the membrane roof of the Olympia indoor swimming pool in Munich was renovated with particular emphasis placed on building physics. The roof consists of four layers of different translucent or transparent materials, which, combined, provide a thermally insulated translucent external envelope. The layers are built up as follows (from inside) [2]: • supporting membrane made of translucent, PVC-coated polyester textile • 70 mm translucent and impregnated polyester fleece insulation with active ventilation system that reacts adaptively to attack by water by means of moisture sensor (as a result vapour barrier can be omitted) • Sealing made of transparent ETFE foil • Back-ventilated acrylic glass elements on cable net This project documents the complexity of constructing double curved surfaces with built up layers of this kind. However it also shows the enormous potential that lies in the intelligent use of lightweight construction methods and in the combination of different membrane materials.

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Foils and Membranes

Development of Lightweight Building Shells

Form

Society • Culture, tradition • Values, demands, standard of living • Trends, tastes • Inventions, developments • Level of knowledge and technology • Laws, standards, guidelines

Construction

Function Building part Building

Ecnomy

Ecology 13

AWD Arena Hannover The AWD Arena Hannover was built at around the same time as the Allianz Arena. In this project an area of around 10,000 m2 was roofed with almost level, single-layer, mechanically pre-stressed ETFE foil panels. This building represents a combination of a slender primary structure, which minimizes the use of building parts exposed to deflection forces and connects flying masts to form a ring, and a secondary structure subject to tensile forces with cable-supported ETFE foil panels. This led to a very efficient lightweight construction and a load-bearing system used here for the first time. The AWD Arena Hannover was awarded the IngenieurbauPreis 2006. The jury was particularly impressed by “ ... the fact that here, despite the size of the building, a technically aesthetically, economically and ecologically balanced solution was found.” [3, 4]

(ecological) impact, of the flow of forces in a building or of the energy used in production, operation, recycling/downcycling and disposal i.e. on the entire cycle of materials in a construction. Certain qualities are not always obvious from the building’s form alone. For example, without further information an outsider can rarely recognise a building’s environmental footprint. Manifesto »Vernunft für die Welt« (Reason for the World) Awareness of the consequences of neglecting or ignoring ecology also forms the basis for the manifesto “Vernunft für die Welt” [7] formulated in March 2009. German architects, engineers and town planners here made a plea for a different, future-oriented kind of architecture and engineering. The authors and signatories of this document commit themselves to a way of designing and building that is both climate and environmentally friendly and therefore the manifesto represents a recognition of the particular responsibilities borne by those who make buildings. Sustainable architecture and engineering can and should form a decisive element in the urgently needed change to the way we use resources. The goal must remain unaltered: to achieve traditional architectural values, a high level of quality as well as harmony of form, function, design and economy – but using current technical possibilities and an understanding of environmental relationships and taking into

14

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account long-term consequences. Thus designing and building today has been enriched by an important criterion, and, as a consequence, more complex. Lightweight building Lightweight constructions offer ecological advantages and, where used sensibly and in the context of professional planning, they contribute to resource conservation. A lightweight plate or shell structure such as a membrane construction often weighs only 1/100th of a massive structure that could be used as an alternative. This advantage in terms of weight can be entered in the ecological balance sheet at various points, for example in production, transport, assembly, dismounting and disposal. Other factors include the use of nonrenewable energy in production, which is an aspect of every material and every construction method, the consumption of energy, energy gain during use, life span, the possibility of recycling or the expenditure involved in separating different materials for disposal, in particular with composite materials. Assessing a construction method solely in terms of its mass would therefore be one-sided. Despite this, thanks to their low weight alone, lightweight constructions do have an advantage when drawing up an energy balance sheet. Function Lightweight building constructions are principally used as load-bearing structures, i.e. to carry external loads (e.g. wind and snow). Extremely strong but light weight materials are ideal. Lightweight plate and shell structures subject to tensile forces are generally made of textile membranes or foils. [8] In addition to carrying a load, such structures must increasingly meet the demands imposed by fire protection as well as building physics and internal climate. Since light shell structures alone are not suitable for such applications due to their thinness, composite or multiple layer systems are often employed. In this context the umistakeable trend is towards light and efficient structures with multifunctional qualities. Consequently this area is an important focus of research and development at universities and in industry. The relationship

Development of Lightweight Building Shells

15

between lightweight building and resource conservation is also expressed in expanding public interest and increasing importance in teaching, as well as in the growing number of such structures being built. The relationship between form and the flow of forces, which can generally be understood by experts and laypersons alike, as well as the often extremely high degree of translucency or transparency, have certainly contributed to this development.

All three kinds of lightweight buildings aim to meet the demands made on a building or building part with minimal employment of our resources. This minimalistic approach applies to the entire material cycle, i.e. from the production of raw materials, their utilisation and the disposal of all building parts. Consequently, the goal of lightweight building is to reduce the use of resources in terms of the nature and function of the building, and not solely to reduce the weight of the building.

Types Werner Sobek identifies three kinds of lightweight construction: [9] • Material lightweight building • Structural lightweight building • System lightweight building Accordingly lightness is achieved by: • Light building materials (material lightweight building), which in the case of a load-bearing building element are high-strength in order to carry loads over large areas and without columns. • Structures that are particularly slender, with cross-sections that are adapted to the material, the construction method and the loading, (structural lightweight building) whether it be through avoiding bending loads and favouring tensile rather than compressive stress; through the short-circuiting of forces (e.g. tension and compression ring in a spoked wheel); or by employing load-bearing elements which are oriented towards the force path of the loading that determines the shape or have a density distribution that matches their stress distribution (as with a skeletal structure). • The use or combination of systems that can reduce construction elements or building parts (lightweight system building), for example controllable systems that can change to fulfil several functions (multi-functional elements) or that can adopt different states (e.g. phase change materials, electrochrome/photochrome or electrotrope/phototrope surfaces), or even elements that adapt to the demands made on them (adaptive systems).

Potential of foil cushions – the example of the Allianz Arena in Munich With its envelope of ETFE foil cushions the Allianz Arena qualifies as a material lightweight building. Air-filled cushions form a remarkably light construction in terms of both unloaded weight and structural weight of the primary load-bearing structure. First of all the primary structure only has to direct the low unloaded weight of the cushions, that is of the secondary structure, into the foundations. And secondly in comparison to that of other materials (for example glass) the span of these cushions is relatively large, which increases the intervals between the beams and columns of the primary structure and thus also reduces its structural weight. In the Allianz Arena the maximum dimensions of the ETFE cushions is no less than 4.5 ≈ 17 m measured along both axes of the diamond shapes. The foil cushions also meet the criterion for a structural lightweight building, as they are subject solely to tensile forces. In this construction bending or compressive forces are negligible, as the extremely thin foils avoid this stress by deforming. As tensile stress represents the ideal kind of stress for achieving minimal cross-sections, the cushions result in a minimal construction mass, positioned exactly where the tensile forces can ideally be transferred, i.e. in the outer boundary surfaces of the volume they enclose. Between the foil there is nothing but air that transfers external loads through compressing to the respective load-bearing foil. In the case of wind suction this is the outer foil, with wind pressure and snow the inner foil of the double layer cushion. From a structural point of view a lighter and more efficient system is scarcely imaginable.

13 Important aspects in evaluating a building element or building 14 AWD Arena Hannover, carried out by Covertex GmbH (2005) 15 Indoor swimming pool in Neydens, carried out by seele cover GmbH (2009) Indoor swimming pool and climbing facility Neydens The envelopes for the swimming pool and climbing facility building in Neydens consist of triple-layer ETFE foil cushions. Analogous to the German system of approval of individual cases, for the foil cushion construction system, which does not fall within normal categories, the French procedure Appréciation Technique d’Expérimentation (ATEx) was used here. The construction firm carried out comprehensive mechanical and physical tests on a 1:1 mock-up of a section of the climbing hall shell. The irregular geometries of the two buildings demonstrate that complex free-form areas are also possible with ETFE foil cushions. Each bay, each edge and each cushion has its own geometry.

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Foils and Membranes

Development of Lightweight Building Shells

16 16 Climbing hall in Neydens (2009) 17 Allianz Arena, Munich (2005), architects: Herzog & de Meuron 18 Opening onto the landscaped park; Olympiastadion Munich (1972), architects: Behnisch und Partner

Furthermore the cushions meet the requirements of system lightweight building, for instance through the fact that the internal pressure of a cushion adapts to the size of the external load. The inherent ability of ETFE foils to accomodate different loads creates an adaptive system. The TTV (time temperature shift) that occurs in visco-elastic thermoplastics ensures that rapid wind loads (gusts) during high summer temperatures encounter similar material strength and stiffness to slowly occurring snow loads at low temperatures. [10] Finally, cushions made of ETFE foil used to form a transparent shell allow different daylight effects in interiors as well as permitting the illumination of facades (e.g. printing, coating, colour-coating, integrated louvers or blinds, pneumatic regulation of light with alternate printing of middle and outer layer). As a result there is often no need for window elements or blind systems. Thus ETFE foil cushions realize the dream of “the transparent structure” with regulated entry of light, and thus represent a further form of lightweight system building. The potential and variety of uses of different membrane construction methods [11] and of building with polymer materials has certainly not yet been exhausted, one thinks here of combinations with flexible photovoltaic elements to harvest energy over large areas or with aerogel to form light, thermally insulated and yet translucent building envelopes. Further potential lies in the use of foils or films that absorb or reflect certain spectral components (IRcut, UVcut, low emissivity (lowE) films) and thus meet special building physics requirements. Adaptive and switchable films have already been produced as small samples, so that it is only a matter of time before electro- or photochromic or electro- or phototropic films become reality. Summary The example of foil cushions allows us to conclude that lightweight shell structures, in addition to transferring load, can harvest energy, provide daylight, illumination, projection surfaces or control the indoor climate. Structural engineers tend to be unfamiliar with this aspect as many of these functions fall within the brief of others involved in

56

the building project. Therefore structural engineers will increasingly have to abandon a view of the structure as a frame that stabilizes the building. Through new materials, production methods, jointing and connecting techniques and planning tools modular, homogeneous or heterogeneous, single or multiple layer plate and shell structures can now meet the demands of building physics and room climate, making them the central building element of complex external envelopes. The Allianz Arena demonstrates the enormous potential of foil envelopes particularly clearly. [12] However, this building only marks the start of a development that views transparent shell structures as modular and multi-functional envelopes. In the Allianz Arena the high quality and the harmony of form and function stand out in particular and have resulted in a building that has attracted much attention. Yet the primary structure concealed behind the cushion envelope does not seem unmistakably to belong to this envelope, in contrast to the structure and skin of the Olympiastadion in Munich. In the latter building form, function, structure and landscape unite to form an overall sculpture, which in the framework of this particular building commission, could not be more harmonious. This explains the Olympiastadion’s status as a milestone in the history of architecture. But in comparison to the Munich Olympic building the shell of the Allianz Arena consisting of primary load-bearing structure (steel structure) and the secondary structure (ETFE foil cushions) had to be suitable for the seven-to-eight storey building complex (which meets the criteria for a high-rise building) and for the widely cantilevered roof to the stands. This made it a very different commission to the Olympiastadion in terms of function and planning, which is why the two buildings can hardly be compared. Like almost no other building the Allianz Arena, described as a “witches’ cauldron”, embodies a football temple for a fan community in an event-oriented society at the start of the 21st century. In contrast the Olympiastadion, more than 30 years older, symbolizes a natural, transparent and open democracy in harmony with nature.

Development of Lightweight Building Shells

17 Sources [1] Sullivan, L. H.: The tall office building artistically considered. In: Lippincott’s Magazine, Nr. 03/1896 [2] Göppert, K. u.a.: Erneuerung der abgehängten Decke in der Olympiaschwimmhalle München. In: Detail, Nr. 05/2008 [3] Moritz, K.: Bauweisen der ETFE-Foliensysteme. In: Stahlbau, Nr. 05/2007 [4] Verlag Ernst & Sohn: IngenieurbauPreis, PresseInformation. Berlin 2006 [5] Alt, F.: Die Botschaft des Jahrhunderts:

Die Sonne schickt uns keine Rechnung. In: Detail Green, Nr. 01/2009 [6] Cody, B.: Form follows energy. Lecture at the Institut für Gebäude und Energie IGE. Technische Universität Graz 2007 [7] Vernunft für die Welt – Manifest der Architekten, Ingenieure und Stadtplaner für eine zukunftsfähige Architektur und Ingenieurbaukunst. Berlin 2009 [8] Moritz, K., Schiemann, S.: Structural Design Concepts, Manuskript,

[9] [10]

[11]

[12]

Masterstudy Membrane Structures. FH Anhalt, Dessau 2009 Sobek, W.: Bauen für das 21. Jahrhundert. Basel 2001 Moritz, K.: TimeTemperature Shift (TTS) of ETFE foils, Conference Structural Membranes. Stuttgart 2009 Moritz, K.: Bauweisen der ETFEFoliensysteme. In: Stahlbau, Nr. 05/2007 Moritz, K.: Die Stadionhülle der Allianz Arena. In: Detail, Nr. 09/2005

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ELEMENT FACADES

The Future of the Element Facade

The Future of the Element Facade Detail interviews Andreas Fauland, seele

Detail: What is special about your element facades? AF: Our solutions for facades are the outcome of an inclusive approach which recognizes that, alongside their primary functional qualities, facades also have to meet aesthetic demands as well as requirements in the areas of thermal insulation, day-lighting, comfort and ecology. Our particular strength, we believe, lies in the fact that we combine all these aspects in an overall concept and, as a consequence, are in a position to advise architects in this area. We do not restrict ourselves to flat elements and planar surfaces, we also carry out three-dimensional fadades with complex geometries as well as elements built up of several layers to meet the different demands made on the fadade. Detail: How do you manage to carry out such complex constructions within an economically realistic budget? AF: Here a number of components play a role: firstly in-house expertise that comes from including specialists in our project team, which means we can develop and construct the facade in a way that bridges the boundaries between different skilled trades. A second aspect is the efficiency gained by making use of technical aids such as CAM. We can directly import the data obtained from the 3D drawing to control the machines. This results in greater efficiency, low incidence of errors, improved logistics and, not least, higher product quality. Ultimately however economic viability and quality depend on sensible management, thorough and consistent work and good integrative processes. Detail: Do you have a vision for the field of element facades? AF: My vision is, to define and implement the challenges and requirements of a project together with the designers and the client at an even earlier stage than previously, and in this way to give the entire project an additional value. A further vision is to provide designers with freer geometries and a greater variety of types. This will lead to more flexible facade concepts, and to the development and use of new materials. The facade components used in the future will achieve an optimum performance

in their respective position in the building and be able to adapt flexibly to the demands made on them. As a rule the repetition of the same facade elements is a determining cost factor. In the future the flexibility offered by 3D development and construction processes will allow greater design and functional freedom. In the areas of fabrication and logistics project development will increasingly be influenced by 3D processes. Detail: A key term today is “flexible, smart materials”. What steps are you taking in this direction? AF: We are working on a number of research projects at the moment, but as I’m sure you’ll understand I can’t say anything about them at the moment. Glass remains for us a decisive element. The question is how intelligently and efficiently one employs it. A further aspect has to do with natural ventilation and a facade that individuals can open as they require. In this area, too, we are looking at new approaches, although it is not our intention to develop a uniform conceptual facade. For us our clients’ requirements and individual wishes will always take precedence, and we wish to remain faithful to our goal of developing solutions that are tailor-made to suit these demands and wishes. Detail: What know-how were you able to rely on when you applied for the major 7 More London contract? AF: We started the serial production of the element facades at a very high level. Here we profited from a wealth of experience in constructing facades, an awareness of the processes involved and of the background in terms of building physics and materials, as well as knowledge of how to implement facade solutions tailored to specific projects. Speaking the architects’ language and recognizing and understanding their ideas and visions was certainly also decisive. But essentially the theme is always the same: developing bespoke solutions in a highly efficient way and within the shortest possible time that offer maximum functionality combined with the highest possible quality.

Andreas Fauland (Dipl.-Ing. FH Mechanical Engineering) has been managing director of seele GmbH & Co. KG since 2007. Before this he was managing director of Bug-Alutecnic and of Josef Gartner. Combined with seele’s particular strength in the area of innovation, his many years of experience in the construction of element facades forms the basis for designing pioneering solutions for facades.

Tender procedure and design In 2007 the construction manager (Mace Ltd.) invited the Gersthofenbased firm and one other firm to submit tenders. First of all a prequalification stage was held in which both firms had to prove their ability to carry out the work. This required comprehensive presentations, detailed calculations and concepts for production and assembly, logistics and fitting. The proposals and calculations were then subjected to close scrutiny by the construction manager. After that a three-month PCSA phase (PCSA = Pre-Construction Services Agreement) began. This phase precedes the actual awarding of the contract. During this time the design is optimized, for example by integrating the aspects of production and assembly in the architects’ design. With the details from the contractors the client can then, where necessary, correct the available budget for the individual trades and make new calculations. At the end of the PCSA phase the firm submits a definitive price and detailed drawings.

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7 More London: Developing the Production of the Aluminium Element Facade

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7 More London: Developing the Production of the Aluminium Element Facade Andreas Fauland, seele 1a 1 a + b Axonometrics of 7 More London indicating the location of the different facade element types 2 + 3 Setting up the fabrication centre and a five-axis CNC machine for sawing, drilling and milling the sections 4 High-rise rack with 288 storage places, each with a maximum bearing load of 1.2 t 5 The sorted elements are put together on mobile tables that move along an assembly line.

On the role of the facade consultant A harmonious relationship between all design partners is of paramount importance for a project’s success. The facade consultant plays a particularly important role in cases where facades are individually developed. He carries out the technical examination, paying particular attention to points such as seals and compatibility of materials. The facade consultant is the expert assessor of the work of the construction firms and a consultant to the architect. His experience enables him to introduce other, different viewpoints. In his role as mediator he enjoys the trust of both client and architect and in addition liaises with the authorities.

The 7 More London project offered seele a unique chance: With a facade area of 20 000 m2 this project represented our firm’s first major commission for a purely aluminium element facade. Up to this we had been involved mostly in the areas of steel and glass or glass and glass, but for some time we had been thinking about a large-scale expansion of our aluminium facade production, partly because clients and architects had repeatedly asked us about all-inclusive packages. Thus a demand already existed, as did the idea of widening our scope of activity. The London project by Foster + Partners offered us the opportunity to link the two. However it also meant a new beginning in a certain sense. We had already carried out a number of aluminium facades, such as for the Museum of Arts and Design in New York or John Lewis Department Store in Leicester but the scale of 7 More London was something entirely different. Here the major challenge was internally reorganising this sector of our business, which involved far-reaching changes such as investments and restructurings. On the basis of my previous experience in the area of aluminium facades, in collaboration with experienced colleagues I put together a list of the measures required. Among the first of these was to build up a new team that we were able to integrate in the existing structures quickly and within the envisaged time frame. Construction of a new production building In addition we decided to erect a new production building. Start of construction was summer 2007 at the beginning of the PCSA phase. As at that time we did not yet have a fixed contract, this step was taken at our own risk. But in the three-month period that followed, the first intensive meetings with the architects, the construction manager Mace Ltd and the facade consultant Emmer Pfenninger took place. On the basis of sketch details provided by the architect (computer drawings with approximately dimensioned sections) we developed the basic details of the sections, supplied budget prices and built the first 1:1 facade elevations. Finally, in December 2007, the contract to carry this work out was signed. This was then followed by the development phase and the construction of a performance mock-up that

we used to test the facade. By May 2008 our production building was completed, the machines were set-up, the development of the sections had been agreed upon and a new team formed. Production for 7 More London could then start. Production circumstances Aluminium facades involve different forms of production and a different fabrication process than steel and glass facades. As a rule the steel and glass facade is a made-to-order production, whereas the aluminium element facade is based on serial production. Special facades derive their character from a wealth of individual details that are difficult and technically demanding but are not serial in charac-

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7 More London: Developing the Production of the Aluminium Element Facade

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ter. Generally speaking, aluminium element facades are technically less demanding, but the high amount of repetition requires solutions that are optimized in terms of fabrication and the use of material. The amount of material flow is greater, the lead times are longer and greater storage capacities are required. Advance planning in the steel and glass area is faster paced and if changes have to be made at short notice there are more alternative options available. With the high tonnages involved in aluminium facades this is not the case. This means that the delivery, receiving, checking and storage of material are significant factors for success in the aluminium facade sector. Recognising this fact we invested in an automated section stor-

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age area where the material can be directly put in storage and taken out again. We had the sections, which were specially designed for the London project, extruded by a supplier. The Gersthofen site In 2006, for economic reasons, serious consideration was given to expanding our aluminium fabrication at a different location. Ultimately however the company decided to remain in Gersthofen. We are convinced that direct contact with production is an additional value for the construction side. What does a section look like when it is processed, when it is joined? The background and technical aspects of skilled production can be adequately

Facade types • EWS 1: Element facade with recessed metal panel and louver construction hung in front, “zigzag” facade • EWS 1C: Element facade, straight, with louver construction hung in front • EWS 2: Smooth element facade with glass panel, without louver construction • EWS 3: Element facade to courtyard, with glass panel, without louver construction • EWS 4: “Backpack” element facade with glass panel and vertical sun protection louvers

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7 More London: Developing the Production of the Aluminium Element Facade

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6a 6 Exploded drawing of junctions between sections a Junction of top transom b Junction of middle transom c Junction of bottom transom 1 Sealant 2 Polyamide moulded component 3 Vapour pressure compensation opening /drainage opening 4 Glazing support bracket 5 SG sealing strip

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understood only by seeing the material in reality and by direct contact with the colleagues responsible. With us the end project, even in the case of serial production, remains hand-made and of a unique quality. Backed by established principles for the construction and manufacture of aluminium element facades, we can bring a noticeable energy to this sector by continuously developing new approaches. The growing importance of the element facade in terms of design, economics and ecology demands innovative and cost-effective solutions. Our entry into the area of high quality element facades indicates that we have recognized this sign of the times, to the benefit of investors, architects, clients and users

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Developing the sections For 7 More London we developed a total of 52 aluminium sections and 45 sealing profiles and had the requisite tools made. From the very start we were closely involved in the detail planning of the facade. This was to some extent a result of the immense time pressure. The geometric complexity of 7 More London meant that only four months were available for this stage. In addition to 3D visualisations and drawings we used 1:1 elevation models and performance mock-ups. The first elevation model, a wooden mock-up, allowed us to modify and modulate the design rapidly. We later constructed a 6 ≈ 9 m 1:1 performance mock-up for each of two facade types using original materials and sections. Before arriving at its final form the facade went through a number of development stages. Often it was design or economic reasons that spoke in favour of specific solutions. The g-value – derived from the different coatings and the shape of the louvers – also played an important role. Here, too, several versions were designed and rejected before the final solution emerged. At the beginning of the PCSA phase the architect envisaged a system for the zigzag facade consisting of two large angles with an all-glass corner. This version would have required us to make a rigid corner. But given the circumstances under which the assembly work had to be done – the facade had to be fitted in place without the use of a crane – this would have been technically extremely

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complex. The version of the zigzag facade finally carried out consists of three elements, whose corner posts are mitred together. Generally speaking we develop the sections for our aluminium element facades ourselves. We agree upon certain basic principles with the architects: the visual appearance, the dimensions, and the function of the facade, which naturally includes requirements regarding noise protection and the g-value, to mention just two. Then we carry out a comprehensive series of tests (earthquake safety, movement of the building, settlement, expansion, joint sealing etc). We consult the firms that produce the sections on various technical questions, such as cutting sections or the kind of insulation bar to be used. Our development department designs the specifications for the sealing systems. Although the demands made on sections are always quite similar, we develop them from scratch for each new project. Production To optimise the production processes we combined our sections warehouse and the processing centres. The warehouse has 15 different stations for delivering or collecting material. First of all the sections are delivered. They arrive in our building already coated. After examining them on arrival we wrap them in protective sheeting and put them into storage until required using computer operated machines. The high-rack warehouse is specially designed for bar stock up to 6 metres in length. There are 288 storage areas in all, each capable of taking a maximum weight of 1.2 t. Directly in front of the warehouse there are six CNC fabrication machines and processing centres, three of these are five-axis machines with a length of 15 metres. While a section is being processed on one side of a machine a worker can feed the machine on the other. When only saw cuts are required, we work on several double mitre saws. After being machined the sections are sorted according to when they will be required and put into interim storage until called for. In addition to sections, other materials such as insulation and sealing strips are also stored in this building.

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Fabrication and assembly We created a new assembly line to optimise the assembly process. Here the sections are put together, brackets to hold the sun protection system are fixed in place, insulation panels are inserted and the glass panes are fixed in place with adhesive. At the start of the assembly line each element is given its own mobile assembly table on which it travels through the various assembly stations. We tested the concept of the assembly line for several weeks from the start of the series using the prototypes for the mock-up. Particular attention was paid to quality control: the aim was to achieve a maximum of consistent product quality by combining in-house quality control with external monitoring by an independent institute. At peak times the assembly line building was completely taken up with work for the 7 More London project. Initially fitting work on the building site went through a short optimization phase, after this we fitted up to 30 facade elements per day. Then followed smaller works such as fitting the connecting flashings. On site a core team of twelve seele staff consisting of construction management and head fitters was responsible for supervision and coordination of the fitting work; they were assisted by a sub-contractor team of up to 80 fitters. We had already collaborated successfully in the past with this subcontractor – which meant that on 7 More London we could work as a well-rehearsed team.

7 CNC laser working on metal sheets 8 Sheet metal being taken from the high-rack warehouse 9 Exploded drawing Composition of an element 1 Extruded aluminium section 2 SG-seal 3 Glazing gasket 4 Insulated glazing 5 Silicone seal / weather joint 6 Sun protection louvers

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7 More London: Construction Management

Construction Management Christian Brensing (CB) interviews Gordon Barnes (GB), Mace, May 2009 10 Gordon Barnes is 7 More London project manager for Mace Group Ltd. The Mace Group Ltd., a construction and consultancy firm with headquarters in London, employs more than 2000 staff in eleven branches throughout the world

Building data Architect: Foster + Partners Client: More London/Mace Completion: August 2009 Facade designer: RPP

CB: What is the role of the construction manger in the project 7 More London? GB: The Mace Group was commissioned by the client as the construction manager. In the form of construction management used here contracts are placed between the client and the particular contractor. The Mace Group manages the project on behalf of the client – incidentally, we have worked for More London for approximately ten years. The architects are Foster + Partners, who also drew up the master plan. Over the past few years we have supervised a number of other projects on the same site, such as Plots 3 & 4 as well as the City Hall building (Greater London Authority). In the case of Plot 7 we manage the construction process on and off site. That is to say we operate there like a main building contractor.

CB: How would you define the project in terms of architectural quality? GB: It’s my belief that the client sees 7 More London as something special, as it is the last major building project on this site. The client had a vision that this building should be somewhat different to the others, and consequently allowed the architect a greater degree of artistic license here. With regard to the exterior this led to a kind of zigzag facade aimed at giving as many people working in the building as possible a direct view of the river. The site is narrow but it offers a direct view of the Thames and in particular of Tower Bridge and the Tower of London. The zigzag shape and the bris soleil (sun protection louvers) in front of the facade also contribute to comfortable temperatures in the building. CB: As regards the facade what do you see as the advantages and disadvantages of the British system of tendering, and how did this influence you in awarding the contract? GB: With the client’s agreement we did not invite tenders for 7 More London in the traditional way. The client already had close contacts with a number of construction firms from earlier projects, and was thus able to put together a selection of firms. Together we chose Permasteelisa, which is involved in a whole series of other projects at More London, and seele because of its involvement in City Hall. We were convinced that the Gersthofenbased firm would be able to prove its ability as a new player in this sector of the market Previously seele had specialised in innovative steel and glass constructions where a high level of engineering skill is called for, but they had little experience with standard curtain walls. Their main reference project was their work at City Hall. They did not make the entire facade there, just a particularly difficult part of it. This part is known as the “lens” and is located at the front of the building, facing the Thames. The steel construction of City Hall functions like a large radiator: the steel frame is filled with water to prevent the glass panes from misting over and to ensure agreeable ambient temperatures. Additionally seele had carried out a series of other

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large projects for the Mace Group, for example the Royal Bank of Scotland in Edinburgh and the GlaxoSmithKline headquarters in London. The principle followed in securing tenders for 7 More London was that we invited a limited number of our preferred firms to make presentations, rather than issuing a general invitation to tender. Both Foster’s office and Mace wanted to commission a firm that would be able to help with the design of the curtain wall facade. The reason for this approach was the extremely quick project start. In a normal tendering process you prepare detailed drawings, send these as a package to the individual firms which then send back their price for the work – but this procedure would have taken far too long. We wanted to involve just two firms in a competitive tender process and we provided them both with information. We asked them to come back to us with their own ideas on the design as well as with a cost. And so only seele and Permasteelisa submitted tenders, along with their interpretations of how to build Foster’s design. CB: Were there any other restrictions with regard to design and construction? GB: As I mentioned already the project had started very quickly. Construction on site started in August 2007 and we began work as construction manager in February 2007. We had about five months for the scheme design phase. After that we had to work out a plan for completion of the building by August 2009. The reason for this relatively short period of time was that More London did not want to commit to the project until they had a tenant. We had a time window of two years construction with 45 months preconstruction. Therefore we decided not to use the standard tender procedure. We had to commission the facade firm at an early stage so as to work out the design together with the mechanical engineers Roger Preston and with Foster’s. Arup were the structural engineers. We wanted to have all these firms in our planning team.

were very similar but we all felt that seele would be better for this project. CB: What demands were made on the construction forms and what were the development steps? GB: We had envisaged a two-stage contract. The first stage was a design phase restricted to about 16 weeks. We then had the costs from seele for the preliminary design – not the detail design. We employed a two-fold principle: the firm had to design the project within a certain budget, as well as within a certain time frame. This gave us an idea how much time would be available to develop the facade system so as to arrive at a final price. We developed the facade system together with seele and Foster’s office. We attempted at all times to stay within the budget. At the end of this process we asked the firm to commit to a fixed price, which they did. Working out the contract was similar: we set a time frame within which the facade had to be completed.

10 Site plan scale 1:7500 11 The new building is formed around a courtyard that opens towards the nearby Thames. The building envelope is formed by an aluminium element facade. The facade in the courtyard is faceted. Glazed bridges connect opposite ends of the inner facade on the 2nd, 5th and 8th floors 12 This office building is part of More London Riverside urban development area. Directly beside it is the GLA headquarters whose unusual form makes it the symbol of the ensemble

CB: Can you quantify seele’s contribution to the success of the project? GB: Here I’m going to risk a look into the future. Among all those involved I can see a strong interest in finishing the project successfully and on time. seele invested a lot of money in its production facilities in order to be able to take on 7 More London. Their factory in Germany has doubled in size in the past two years. This firm had made other facade types, perhaps of a comparable value, but the contract for 7 More London is certainly the first of its kind. It is now May, we still have two months in front of us, but there’s no indication that it is not going to be ready on time.

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7 More London: Tender Process and Design

Tender Process and Design Katja Pfeiffer (KP) interviews Mike Jelliffe (MJ), Foster + Partners Mike Jelliffe has worked for the London office of Foster + Partners since 1989. He is project manager for 7 More London. With a staff of 900 Foster + Partners is one of the best-known and busiest architecture offices in the world.

Cooperation with the architects With the fabrication of elements it is generally the contractor who is responsible for developing the facade sections. Preserving the architect’s visual concept has top priority. In 7 More London this was also the case. Thanks to years of experience in working together with architects the contractor was able to understand and adapt to the architect’s specific requirements and wishes. The contractor attempted to integrate the ideas in the construction in advance. The architect on the other hand also demonstrated great understanding for the problems posed by fabrication or other technical difficulties. The contractor describes the collaboration with Foster + Partners and with Mace in positive terms. There were never any real problems with obtaining approval of drawings. The drawings were returned to the contractor, at the very least, status B (approved, with some minor comments to be taken into account).

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The 7 More London Riverside office building, located close to the Thames and Tower Bridge, is the last element in the More London urban expansion area. Laid out around an almost circular courtyard, the new building is externally a polygon out of which a wedge is sliced, thus opening the courtyard towards the river. On the ground floor and a number of upper levels, bridges connect the ends of the building separated by the incision. At this point the building reveals its two “faces”: a rather technically restrained and smooth facade in the inner area, while the exterior has a zigzag facade, an aluminium element construction that was particularly tricky in terms of building physics. In the so-called “backpack building” the element facade is smooth and has red vertical louvers. On three sides of the main building an aluminium frame with vertical sun shade louvers is set in front of the facade.

KP: How was the tender procedure for 7 More London carried out? MJ: The tender procedure had to be modified somewhat to deal with the immense time pressure in the 7 More London project. We wanted to involve potential tenderers in the planning from the very start. This allowed us as designers to profit at a very early stage from the technical know-how of the specialist firms. The tender process was divided up into two stages. First of all the design team made up of Foster + Partners, Mace, RPP, Arup und Davis Langdon organized a briefing session for the contractors who were going to tender. To enable the firms to submit a proper tender we had to put together an adequate information package: Foster + Partners explained their facade concept with drawings, renderings, diagrams and models. Mace presented the programme, the construction timetable, as well as the building masses, explained the special logistical aspects of the site, the tender procedure and the sales strategy. Our consultants, building energy planner Roger Preston + Partners (RPP) and Arup as structural designers, worked out technical guidelines. After a very short calculation phase the firms submitted their prices, along with their ideas on the structure and organization of the planning and construction processes, together with details about the resources they had available. The offers which we received were initial ideas about how the design criteria could be met. This presentation involved some extremely lively discussions. Building on this procurement process and with the help of the concepts presented we as architects were able to design a facade system that we were sure was technically feasible and could be carried out within the time available and on budget. In the second phase of the tender procedure the client asked the planning team to give a concrete recommendation about the firm to carry out the work. On the basis of a list of criteria that included factors such as design, technology, costs and programme, each partner in the planning team gave the individual contractors a “score”. The contractor with the most points was then recommended for the job.

7 More London: Tender Process and Design

Element design The facade elements, consisting of up to eight areas per unit, form a modular concept in which, according to the particular function, glazing, metal panels or service modules are placed. All facade elements arrived in London pre-assembled and ready for fitting. The ground floor elements with dimensions of 3.4 ≈ 7 m high posed a serious challenge in terms of transport and fitting. Although based on an aluminium construction, they reach weights of up to 1.6 t.

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Fitting A total of twelve seele staff, made up of building managers and head fitters supervise and coordinate the fitting. They manage a fitting team of up to 80 workers provided by a sub-contractor.

Section and floor plan, level 1 Scale 1:1000

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Schematic illustration of zigzag element facade Scale 1:20 1 Insulated panel, profiled metal (outside), 900/1500 mm 2 Insulated glazing with solar insulation coating, Tempered glass 10 mm + 16 mm cavity + laminated safety glass 2≈ 5 mm float 3 Extruded aluminium section, powder-coated RAL 7021 4 Galvanised steel fixing bracket and hook; fixed to concrete with cast-in-place channels 5 Sun protection louvers, anodised extruded aluminium section with bonded stainless steel sheet in “linen finish” 6 Firestop, connection to primary structure made of insulation, steel frames and seal

7 More London: Tender Process and Design

KP: What was working with seele like? MJ: Foster + Partners have been working with this Gersthofen-based firm for some 15 years. We first met the team for the 7 More London project when we visited the company premises in Gersthofen. The meetings were then held every two weeks, initially in London and then alternately in London and Gersthofen, which meant we could visit the production facility every month. Initially we presented the development of the design to seele. This was combined with recommendations from Arup and RPP, for instance on tolerances and possible movement between elements of the facade. Further aspects included the proportion of opaque facade required and the positioning and dimensioning of the external shading system. In subsequent meetings seele presented their interpretation of our ideas. This system allowed them to develop the concept further, or, if necessary, to develop alternative solutions at an early stage, thus reducing the interval between the individual design phases and making best possible use of the limited time available. As all the teams worked in a very concentrated way on preserving the visual idea behind the design, we were able to develop a number of problem-solving strategies. The most

successful part of the meeting was what was called the mock-ups. One elevation model and one test model were made. KP: What was the design idea behind the zigzag facade? MJ: To obtain the “BREEAM Excellent” certificate, it was essential to minimize the amount of solar gain through the clear glass. To achieve this we required an active shading system. In view of budget and time pressure the zigzag facade offered the best solution here. The system of external sun protection louvers gives the building a lively appearance, it’s somewhat like a screen that captures light and colours and projects them inside. This creates a sparkling effect that fulfils one of the building’s further aims: to be the “jewel” in the setting of the More London development project. The design concept, in particular the design of the external louver system, was carried out in collaboration with American architect James Carpenter. The appearance of 7 More London could be compared to a chestnut, which has a rough exterior but a smooth interior – like the facade onto the cylindrical courtyard. The zigzag shell was also helpful in planning the interior layout, as each facade module corresponds with a standard cellular office unit. KP: Were there optimisation phases in developing the facade concept? MJ: We developed the technical aspects of the facade further with our facade consultant Emmer Pfenninger Partner AG (EPP). From an early stage we assisted seele with advice from EPP. The Gersthofen-based firm re-dimensioned the facade to suit their system, and also developed custommade elements themselves (vertical sun shade louvers, spandrel panels, and the metal sections), rather than outsourcing. In aesthetic terms the materials and finishes preserve our design intention – and they were checked along the way by means of work samples and mock-ups. In addition seele adapted the facade system to meet energy and noise protection requirements.

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Facades of High-Rise Buildings – Trends and Tendencies

Facades of High-Rise Buildings – Trends and Tendencies Ross Wimer, Design Partner, Skidmore Owings & Merrill (SOM), Chicago 13 Ross Wimer has worked as an architect for Skidmore, Owings & Merrill LLP (SOM) since 1995: He became a partner in the practice in 2003. His projects include the master plan for Marina Bay, the Changin Airport Terminal 3, the Zhengzhou Greenland Plaza as well as industrial design projects such as the standard street lighting for New York. His work has been exhibited worldwide, including at the Biennale in Venice, in the Art Institute of Chicago and the Museum of Modern Art in New York. He has been awarded numerous prizes including three P/A awards. Skidmore, Owings & Merrill LLP (SOM) is one of the world’s leading architecture offices with branches in Los Angeles, New York, San Francisco, Washington DC, London, Hong Kong, Shanghai and Brussels. Architecture, town planning, engineering and interior design are among the areas of activity. The office was founded in the 1930s by Louis Skidmore, Nathaniel Owings and John Merrill.

During the past 75 years SOM has been among the world’s most important pioneers in the development of building envelopes. Starting from the principle of an interdisciplinary design approach we make use of the particular skills and contributions of engineers, technicians and architects – from design to project completion. This integrated team structure allows us to create new solutions that represent fundamental improvements to building performance. The building facade has to respond efficiently to a number of influences. These range from form and structure to natural forces such as wind, sun, precipitation and seismic activity. Although buildings are frequently judged by their external appearance, our design work is always backed by veryfiable and measurable values such as user comfort and energy efficiency.

Energy efficiency and comfort Against a background of stricter requirements and higher standards for “green design”, architects and developers are searching for sustainable concepts that will allow them to reduce the carbon emissions and lower the costs of their projects. This makes energy efficiency one of the most important factors to be considered in designing the building envelope. For the Pearl River Tower – a 71-storey building with a height of 310 metres currently under construction in Guangzhou, China, our multidisciplinary team of architects and engineers aimed at creating an integrated glass facade that would offer exceptional thermal performance combined with high transparency to allow views outside and the natural daylighting of the building (fig. 13). These goals are achieved even when the position of the sun requires the blinds to be fully closed. We used a double skin to preserve the balance between high transparency and temperature regulation. The north and south facades consist of an internally ventilated double skin system of insulated, double glazed modular units measuring 3 ≈ 3.9 metres. Two single-glazed hinged inner

13 The Pearl River Tower in Guangzhou, China, has a glazed double skin facade. A photocell fixed on the roof controls the sunshades integrated in the facade. 14 A glazed cable net facade measuring 90 ≈ 60 m with a V-shaped internal cable encloses the triangular plan of the Peking Poly Plaza 15 a + b Horizontal metal louvers determine the external appearance of the 120 metre tall Arrowhead office building in London. The twin-skin facade allows the spaces to be naturally air conditioned.

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In recent years this planning approach has increasingly led us to rely on the aid of digital models in developing and testing building envelopes. Our research groups, for instance the BlackBox in Chicago, use parametric digital models to examine factors such as environmental protection, visual quality and structural efficiency of building envelopes. Looking back over the work of SOM of the past few years different focal points can be identified. The search for structurally improved solutions influences the way in which we integrate the facade in the “skeleton” of the building. For us, sustainable building design means we view the external skin as an indispensable element in saving and recovering energy and also as a means of regulating temperature and increasing user comfort. Our projects are characterised by the fact that they meet the requirements of both structural and environmental performance while never neglecting design aspects and visual expression. The following projects offer an idea of the latest developments from our practice.

Facades of High-Rise Buildings – Trends and Tendencies

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leaves measuring 1.5 ≈ 2.8 metres enclose a 200 mm cavity with a small air gap at the bottom. In the cavity a motorised, 50-mm-wide perforated silver blind minimizes solar gain as well as glare. This blind can be fixed in three positions: fully open (horizontal), at an angle of 45 degrees, and completely closed (vertical). The angle is determined by a photocell mounted on the roof of the building that tracks the movement of the sun and via the BMS (building management system) adjusts the position of the blind. The rays of the sun that meet the external skin warm the air in the cavity that functions as a natural chimney. Cooler air flows into the cavity through the gap at the bottom of the hinged inner leaves and acts as pressure relief allowing fresh air to enter the occupied spaces. The air in the cavity is then extracted through the ceiling void and, depending on the season and the outdoor air temperature, is used as pre-warmed or pre-cooled air. We employed a further innovative approach to energy efficiency in Arrowhead, a new office complex in London on the north side of the Millennium district, not far from Canary Wharf (figs. 15 a + b). This 26-storey tower with a height of 113.5 metres boasts an energy-optimised external envelope in which climate-controlled glass walls are combined with metal shading. The climate envelope consists of an external glass skin and an inner layer of insulated double glazing. The twin-skin facade reacts to weather conditions and temperatures in its surroundings to provide pleasant internal conditions throughout the year. It has a minimum light transmittance level of 65 per cent. A passive temperature control system prevents frost, condensation or moisture in the cavity. Glass with a low metal content and internally mounted window hardware ensures a transparent facade and marvellous views outside.

The design of the external envelope allows sun to enter in winter and transports heat outside during summer. To do this it exploits the natural stack effect which creates an air temperature in the inner cavity of less than 10° C above the ambient outdoor temperature. On each floor level heat build-up is led off through narrow ventilation slits at the top and the bottom. The system is modularized; the outer modules are coordinated with the 1.5 m inner modules to prevent air escaping or water entering. A metal catwalk integrated in the wall provides easy maintenance access to the cavity. Structural innovation The successful combination of architecture and engineering has long been a distinctive characteristic of high-rise buildings designed by SOM. One of the best recent examples of this is the new Peking Poly Plaza (fig. 14). This 24-storey, 110-meter multi-purpose building is located near the Forbidden City at a prominent intersection on the Second Ring Road. The high-rise building rises above a triangular footprint, with an enormous cable net facade enclosing the hypotenuse of the triangle. Almost four times the size of the cable net facade of the Time Warner Center in New York it is currently among the largest external envelopes of this kind in the world. The conventional approach would have been to use massive trusses to support the glass wall as a continuous plane, but this would have drastically reduced the transparent effect. Instead the shell is held by an enormous V-cable, which is counterweighted by a lantern-like structure hanging in the central void of the building. This V-cable is connected to the lantern structure by a specially developed pulley that allows the main cable to compensate movement that might occur during seismic activity by giving more or less slack to accommodate displacement. The external envelope is “folded” over the V-cable in a subtle triangular shape; this reduces the deflection caused by strong winds, allows the size of the supporting cable to be reduced, while giving the facade a facetted dimension. A team from SOS used a similarly unconventional

Double-skin facades The important characteristic of the double skin facade is a second layer placed in front of what is actually the exterior enclosure skin, without interrupting natural ventilation. The outer layer is generally hung as a non-loadbearing element. Compared with single layer facades, double-skin facades offer improved thermal insulation and noise insulation as well as allowing natural ventilation at locations with high wind speeds. The double skin facades include subcategories such as shaft, corridor and box windows facades as well as facades in which the outer layer is placed at a greater distance from the inner layer.

Element facade This term is used to describe facades made of individual prefabricated elements. An important characteristic is that the elements are assembled completely in the factory. With glass facades the individual prefabricated parts generally consist of glass set in frames, hence the term frame construction is also used. No scaffolding is required for installation. The elements can be unloaded – forinstance as a just-in-time delivery – directly from the truck using a mobile or revolving crane and then fitted in position. Another possibility is to mount them from the respective floor levels with the help of storey cranes or a track system.

Mullion-and-transom facade In contrast to element facades the mullion and transom facade is made up of individual parts: the vertical facade mullions and the horizontal facade transoms or rails, which are put together on site. Today mullion and transom facades are generally used for lower buildings.

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Element Facades

Facades of High-Rise Buildings – Trends and Tendencies

16 16 Prototype of the “kinetic curtain wall” 17 China World Trade Center: the pleated structure and the vertical glass sunshades at right angles to the plane of the facade lend it a visual depth. 18 Kinetic curtain wall: a closed b open 1 Hinge-fixed facade element equipped with photovoltaic cells 2 Insulated glazing 3 Back-lit spandrel panel 19 The facade of the 7 World Trade Center developed together with James Carpenter consists of a grid of alternating recessed, patterned and reflective stainless steel panels.

approach in a prototype for a kinetic curtain wall as a way of introducing flexibility and movement into the structure of high-rise buildings. Here the aim was to devise a system that adapts to changing environmental conditions and can vary the surface facade within a selected framework to maximize energy efficiency (figs. 16, 18 a + b). The prototype was a double-skin curtain wall with an exterior glass pane hinged to a spandrel panel. The hinge is fixed to a track that allows the external panel to slide or “bend” up to 6 degrees from its original position. The spandrel panel is equipped with photovoltaic cells that drive a small motor connected to a thermal sensor and a magnetic release switch. During the hottest part of the day the thermal sensor sends a signal to the motor to extend the panel by six degrees, the spandrel panels automatically reacts by leaning into the hinge at an angle of almost 45 degrees optimizing the absorption of solar energy, with an average energy yield of 175 watts per day. In the cold season or when there is little sunlight the external pane remains at zero degrees, hermetically sealing the void. This encloses the heat and insulates the building. The way the external envelope can adjust to reflect or absorb more or less energy and light, brings about a marked improvement in the efficiency and costs of the system. In addition the spandrel panels have a coating of photo-luminescent paint, so that at night, when the external panes are returned flush against the building, the spandrel panels trace glowing lines across the facade of the tower.

spandrel panels that interplay with the outer glass plane. A slender aluminium panel set behind the glass creates a unique visual depth along the entire facade. Modular curtain glass facades usually consist of storey-height elements that are anchored to the ends of the floor slabs and are connected by a stack joint at parapet height that accommodates construction tolerances and movements. Our goal here was to create a unique glass overlap at the parapets. By positioning the stack joint at the top of the glass pane we solved the problem of differential panel movements across the facade. In this way we also solved the problem of weatherproof jointing, as the stack joint provides a complete seal against the inner glass skin. Examinations and analyses showed that any loss of heat at the overlapping glass edges would be balanced by the insulation mass of the spandrel panel, allowing SOM to pre-

Design expression In the 7 World Trade Center – the first building to be erected in the World Trade Center reconstruction project – our SOM team aimed at creating a building that is simple and uniform in urban terms as well as on a human scale (fig. 19). The building is a parallelogram in shape and forms the northern access point to the World Trade Center complex. The facade was developed in collaboration with James Carpenter and is the central design element of the 52-storey, 218-meter tall tower. It is made up of a subtle grid of modular panels fitted with recessed, patterned and reflective stainless steel 17

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Facades of High-Rise Buildings – Trends and Tendencies

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serve the aesthetics of the facade without any loss of thermal performance. A similar process was employed in the design of the facade for the tower of the China World Trade Center (fig. 17). The external envelope is designed so that the pleated facade, in combination with vertical glass sunshades, captures and reflects daylight. For the clear height of 2.9 metres between floor and ceiling SOM team used glass panes that are longer than the ceiling height in the occupied area of the interior, allowing daylight to penetrate deeper into the occupied floor area. In addition we wanted to create visual unity between the vision glass areas and the floor/spandrel panels. Refining the language of the pleated facade led to the development of a pleated aluminium plate reflector to provide penetration and reflection of light. A series of 50 mm wide aluminium extrusions were placed 150 mm behind the vision

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glass in the spandrel, allowing light to penetrate deeper than with standard curtain walls. When caught by sunlight this pleated structure produces a visual depth that makes the alternating glass and extruded panels blend to form a cohesive entity. Summary From the design of Lever House in New York in 1952 – one of the first International Style office buildings in USA with a curtain wall – to the incorporation of modern, energy-efficient curtain wall facades SOM continuously searches for new ways to achieve a perfect balance between the structure, performance and form of a building. The short snapshot of trends presented and described here shows the depth and the range of our current research work from concept design to construction.

The work of James Carpenter James Carpenter studied architecture and sculpture at Rhode Island School of Design. A central aspect of his work is the relationship between glass and light, Carpenter’s architecture and art works are characterised by the different uses of these two complementary “building materials”. They deal with transmitting, reflecting and breaking light on glass. His office, James Carpenter Design Associates, is located in New York

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STRUCTURAL USE OF GLASS

Innovative Processes in the All-Glass Sector

Innovative Processes in the All-Glass Sector Bruno Kassnel-Henneberg, seele

Architects and designers all over the world constantly call for more transparency for facades and roofs. This leads to glass constructions in which the exterior enclosure is combined with a structural function. One of the ways to make all-glass constructions more transparent is to use larger glass elements. A further central challenge for us is jointing structural glass elements using the adhesive technique. Architectural goals demand innovations In recent years the design demands on glass structures made by modern architecture have grown enormously. The use of CAD and FEM in architects’ and engineers’ offices offers the opportunity to design increasingly sophisticated constructions. Although in structural glass design planar surfaces are still dominant, the unmistakeable trend is in the direction of more complex geometries in which curved panes are frequently used. Thanks to their geometry, such sheets can offer considerably better structural qualities. These must be used effectively to increase the structural performance of all-glass constructions. Against this background we believe our role is to further develop structural glazing technologies and products and redefine certain areas. Our special know-how and exceptional production facilities put us in a position to further develop the performance and service offered by the seele group. Close collaboration with universities in various research projects concentrates our efforts in working out the theoretical basis for laminated and bonded connections. In particular complex questions such as the “cold bending” of glass are an important research theme. With our very high level of commitment to realising ambitious architectural designs, we also strive to bring new impetus to structural glazing. The fact that our business combines development and production facilities has turned out to be a great advantage in developing innovative solutions. Out of abstract ideas real products are made that we know can be produced and whose performance we can test intensively in our own company laboratory.

Further refinement of glass opens up new paths Today seele sedak sees itself as a glass manufacture with CNC processing centres and autoclaves for the laminating process in which laminated glass can be produced in sheets up to 15 metres long and 3.21 metres wide. For the near future we are planning further developments that will enable the production of pre-stressed glass with lengths of up to 12 metres. The next important step will be the production of oversize insulated glazing with lengths of up to 12 metres and width of 3 metres. The lamination of extremely large panes means new approaches as regards the quality of laminating. Extreme sizes demand more robust laminates, a demand that can generally be met by using shear-rigid SG foil from DuPont. We have adapted our entire production process to suit high quality laminating with this type of foil. This means that we laminate every individual pane using the “vacuum bagging” process. The advantages of this process are the enormous adhesive strength of the connection between foil and glass. In addition this process results in extremely well-finished edges to laminated glasses, a decided advantage for free edges or those exposed to the weather. By exploiting the stiffness of the foil our laminating technology makes it possible for laminated glass panes to transfer significantly greater and permanent loads as well as allowing greater spans in glass used overhead. Our quality control supervises the structural function of laminations by checking reference elements to provide proof of laminate stiffness. In the context of the system of approvals for individual cases we have also been able to convince German building authorities of our new dimensioning concept for laminated glass in a number of instances. Cold bending with form shaping lamination We also use foil’s high shear strength to laminate glass in a way that determines its form. We are referring here to shaping the individual glass sheets in a stack before the laminating process, so that they can then be laminated in this geometry. After the autoclave process the laminated glass

Bruno Kassnel-Henneberg, Dipl.-Ing. civil engineering (specialising in structural engineering), worked for seele from 2001 to 2009 as a structural designer and head of structural planning in the area of structural glass construction. Since 2009 he has been responsible for product development and marketing in the daughter company sedak.

Location seele sedak The second site in Gersthofen, seele sedak, deals primarily with the area of structural glass. The foundation provided by intensive research and development enables high quality glass products and all-glass constructions to be created. Project management, engineering and production here work hand-inhand. At this site the various threads of the company’s worldwide marketing strategy come together. A vital role in research and development is played by collaboration with architects and engineers such as Dewhurst Macfarlane, Arup, Buro Happold or architect Professor Stefan Behling from IBK2 at Stuttgart University.

Machining centre A machining centre is a CNC-operated tool equipped with three or more axes and an automatic tool changer. With a five-axis machine all surfaces and edges that exist in space can be worked upon. The machine drills holes, makes cuts, flat and angled outer edges, and offers all machining processes such as drilling, milling, sanding, edging and polishing. A face wheel fitted to a 3D spindle-head that can move in space offers optimum results in sanding and polishing glass edges. With a machining length of 16 metres and width of 4 metres this machine is unsurpassed.

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Structural use of Glass

Innovative Processes in the All-Glass Sector

23.716 21.081 18.446 15.811 13.176 10.54 MN 7.905 5.27 MX 2.635 X Y

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2a 1 “Cold-bent glass” means that glass sheets are laminated in a predetermined curved geometry. seele carries out cold-bending: two or more flat glass sheets are put together to form a laminated glass sandwich, before laminating they are fixed on a frame that determines the form (cold-bent), subsequently they are laminated in the autoclave as a preformed glass and foil package to form a single unit. The use of a nonshear resistant foil is refered to as “form-supporting lamination”, since with this version the glass sheets are mechanically fixed to a substructure that gives them their form and enables their geometry to be permanently retained. When a shear-rigid foil is used (e.g. SG foil, DuPont) we speak of form-giving lamination. The geometry is guaranteed solely by the shear stiffness of the foil, making a form-shaping substructure unnecessary in this case. 2 Glass facade Strasbourg, Deformation a one entire sheet during the fitting process, clamped at points with provisional fixings under wind load b quarter sheet under load from cold-bending and snow 3 a + b the geometry of the new front building to Strasbourg railway station is formed by glass sheets measuring 4.5 ≈ 1.5 metres. A total of four different radii of curvature are used, depending on the height at which the element is fitted, in order to achieve an optimal geometry. To reduce the buildup of heat in the hall and to reduce the reflection effect of the glass from outside, the elements are printed inside with black dots and outside with white ones.

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sheet produced retains the geometric curvature permanently, without the need for a substructure of the same shape. The particular advantages of cold bending include the high visual quality of the glass due to fewer reflections and imperfections. The fact that standardized tempered or toughened glass, with its wide range of possibilities in terms of printed patterns and solar protection coatings, can be used represents a further decisive advantage. In addition laminated glass made with SG foil has an almost monolithic structural effect, suggesting further possibilities for its use. We see the technique of cold bending as an important innovation. In the area of new adhesive connections we are working intensively on making glass shell structures without visible metal connecting elements. Pilot project Strasbourg The first large scale use of the cold-bending technique was for the new facade to Strasbourg railway station. This project, designed jointly by French architect Jean-Marie Duthilleul and the engineering office RFR, has a continuous, 120-metre-long and 25-metre-high transparent facade made of steel and curved glass, 6000 m2 in area. This construction is a glazed hall placed in front of the historic railway station building. Transparency, minimization of reflections and a maximum view of the existing building were the architect’s requirements. The complex geometry describes

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a toroidal form. The curvature of this rotated figure results from a curve revolved around an inclined axis. This produced glass elements (4.5 ≈ 1.5 m) with four different radii of curvature. This project had to undergo a specific French approval process for individual cases, known as ATEX, involving extensive tests and structural proofs. Cold bending with form-supporting lamination Instead of using hot-bent panes we produced the curved glass elements by cold-bending with the aid of lamination that supports the form. We opted for this new method after the first laminating tests had proved very positive. In response to the special aspects of this project we used shearsoft PVB foil to connect the glass sheets. Laminating in a curved state assists the form. But to permanently preserve the curved geometry the sheet must be fixed in a way that holds its shape. The Strasbourg facade impressively documents the design advantages of cold bending: the surface has a planarity impossible to achieve with hotbent sheets. The sheets are, literally, under stress, a fact that the observer of the building notices and internalises. Build-up We carried out comprehensive quality and development tests on the facade for Strasbourg in our testing facility. The technical description of the sheets is “cold-bent laminated safety glass unit”.

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Innovative Processes in the All-Glass Sector

3b

We chose the laminated glass unit on the one hand to reduce the build-up of heat in the building, on the other to preserve an unobstructed view of the old building. The upper area of the laminated safety glass units is printed in two overlaid colours (white outside, black inside); a special sun protection foil in PVB laminate (XIR from Southwall, our firm is one of only five official licence holders worldwide), has a low-e coating on the inside.

with the original panes. Tests involving throwing sandbags combined with subsequent testing of residual bearing capacity confirmed very good bearing performance in exceptional load situations.

Structural calculations In performing the structural calculations we took into account the internal stress of the glass that results from the curvature of the glass during the laminating process. First we examined the mechanical performance of the laminated glass stack in the individual production and fitting stages, then, using the planned pre-shaping for the desired geometry, followed structural calculations on the performance of the glass for all important load situations (self-weight, wind, snow, load from people walking over it). This means that in the calculations we overlaid the internal stresses in the glass due to cold bending with the stress imposed by external loads. The production and fitting tolerances of the substructure are also included in the stress calculations for the glass. Following the mathematical proofs we examined the structural performance and resistance to wind loads and impact loads using a model of the facade

Pilot project West Village In the West Village project, the construction of the internal facades in London’s Westfield shopping centre, the use of structural laminated glass sheets posed a special challenge. Extremely slender glass fins with spans of up to 9 metres give the shop window fronts their stability. The fins in turn are stabilised by the facade glazing. Glued and laminated detail connecting elements join the facade glazing and the glass fins. To develop optimal adhesion we carried out extensive examinations of several adhesive systems that were monitored by an expert. The results speak for themselves: the adhesive connection is reduced to a visual minimum and is highly transparent. Despite this optimization, the design of the facade is characterized by a high degree of redundancy. This results from the special positioning and layout of the connecting elements which, even in the case of a pre-damaged structure, ensures the safe transfer of loads. Guaranteeing this residual bearing capacity is a central element in the design of all glass constructions and should be integrated in the facade as seamlessly as possible in detail construction terms. This is what we achieved in the facades for the West Village.

4 Production of a glass string with laminated stainless steel inserts at the NCA plant “Giant” in the “outer zone” of the glass processing centre. 5 Cleaning the glass sheets before laminating in the “inner zone” an absolutely dust-free room. 6 The glass sheets are vacuumbagged for laminating. 7 Laminating special glass elements and high-quality glass products: workers slide the large glass elements into the autoclave along a specially developed air-cushioned track.

Autoclave An autoclave is a high pressure chamber in which, under controlled temperature and pressure conditions, a pre-laminated glass “package” is laminated to form a permanent bond. In the initial vacuum bagging process gas is continually extracted, thus achieving a particularly high quality laminate. The Gersthofen-based firm has one of the largest autoclaves used for glass processing. With a total weight of 65 t and peak performance of 1000 KW, it can laminate glass sheets up to 3.2 ≈ 15 m. The maximum glass thickness is limited only by the materials used.

Strasbourg: construction of the glass element • 6 mm thermally pre-stressed glass (toughened glass) with low-E coating • Printing (screen print process) with two precisely congruent patterns, one black, one white • Composite plastic film with integrated sun protection film • 6 mm thermally pre-stressed glass with low-e coating (toughened glass)

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Structural use of Glass

Innovative Processes in the All-Glass Sector

8 Chemical hardening of glass During treatment in a special salt bath, ion exchange produces strong compressive stress in a thin surface layer which significantly improves the strength of the glass. This process is described as chemical hardening. The bending tensile strength of such glass exceeds the strength of thermally pre-stressed glass by a factor of 2. However, the extremely thin nature of the surface layer under pressure requires careful consideration of how the glass is to be employed, and especially where it is to be used as a structural element. Chemically pre-stressed glass also offers improved resistance to impact and scratching as well as to temperature change. Examples of all-glass staircases Examples of all-glass staircases include the stairs developed for glasstec 2006 (p. 82ff.), the Comcast glass staircase, Philadelphia (p. 108), the glass staircase in the new building for the seele group Gersthofen, as well as a series of spiral staircases, some of them extending through two storeys in Japan, the USA, France and Germany.

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All-glass bridge glasstec 2008 gave us an opportunity to present the new design opportunities offered by coldbending to a wider public. Together with Stefan Behling und Andreas Fuchs from IBK2 in Stuttgart University and the engineers Engelsmann Peters we developed an all-glass bridge that has a free span of 7 metres and weighs 1.7 t. By means of the new bending technique, the use of SG foil and the “smart” shapes of the individual elements we made a three-dimensional object with maximum transparency that could be walked across. In the glass bridge a total of eight 4-mm float glass panes form a friction grip connection. All-glass staircase Manufacturing staircases makes up a major part of our glass production. The special feature of the construction is that all the structural loads are transferred exclusively by the glass. The treads not only take the vertical live load but also determine the stability of the staircase strings. The structural connection between the treads and the string fixes the strings in a way that is essential for the successful transfer of a horizontal load in a widespanning staircase. The connection of the steps to the string is a central aspect in the design of the staircase. In adhesive technology we are constantly searching for new applications and developments. For instance we look at how to reduce the visual dominance of metal connecting pieces. Here there are essentially two methods: in the conventional solution the steps are connected through holes made in the strings. The connection is similar to the familiar point fixing method as used in standard facade constructions. In the second method of connecting tread and string, there is no need to make holes in the laminated sheet. Instead of the “point fixing solution” an adhesive technique is employed. The connection is provided by a laminated SG foil or adhesive. The advantages of this approach are obvious: it avoids the weakening of the glass caused by holes, and the outer face of the glass string is free of connecting elements.

Spiral staircases Spiral stairs occupy a special place in the field of all-glass staircases. This has to do with the use of curved sheets and the structural and construction demands they impose. In addition to requiring greater tolerances at connections, the glass used for curved strings presents us with an entire series of new challenges. Essentially for structural glass strings we use triple laminated glass so that, even if the structural glass string is damaged, adequate bearing capacity to allow use of the stairs is still guaranteed. The forces released by drilling holes in the glass (which can be sizable) make the use of toughened glass essential. The triple layer construction can only be made using chemically hardened sheets. In comparison to thermally pre-stressed glass there are important differences here as regards strength characteristics. Chemically hardened glass has an extremely thin pre-stressed layer, a fact that must be very carefully considered in the detailing. In addition the strength of such glass should be determined for each manufacturer, and should be checked by applying special quality control measures. Glass columns Employing the new laminating technology as used for the glass staircase in collaboration with IBK2, we made a laminated glass column. The new kind of technology allowed an entirely new interpretation of the structural glazing facade. With the help of SG foil, constructions spanning 6 to 9 metres, i.e. two to three storeys, are possible. The column functions as a structural hollow section that not only takes loads in a vertical direction but also functions as a bracing element. A laminated glass column consists of two curved halves made of 8 mm thick glass shells and two steel sections, which are connected by laminating with SG foil. A mechanical jointing technique is used to connect the two shells to form a column. This obviates the problems caused by drilling holes in the glass, and the loads can be transferred via the glued surfaces. As a result the individual building elements are stressed in an optimal way.

Innovative Processes in the All-Glass Sector

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Structural all-glass facades Glass fins are frequently used as stiffening or bracing elements in structural all-glass facades. The insertion of certain laminated foils can optimise the construction from the structural designer’s viewpoint. Examples of structural all-glass facades include the shop fronts in Westfield London (West Village), the glass facades of the Unilever headquarters in London (p. 92f), and the Lincoln Center in New York, as well as various retail outlets, where in some cases glass fins span as much as 13 metres. Structural insulated glass The insulated glass element with rigid edge bonding represents a further step in building widespanning glass facades divorced as far as possible from a structurally load-bearing substructure. It is in fact a transparent “box section” with an amazing structural capacity. The “flanges” formed by the inner and outer glass leaves of the unit, are connected by the “webs“, a newly developed shearrigid bonding technique, along the edges of the sheets. Heights of 6 to 8 metres with sheet widths of up to 3 metres using almost standard insulating glass thicknesses allow transparent walls to be made. The excellent heat transfer coefficient, Ucw ≈ 0.8 W/m2K, places this product close to the top in terms of current thermal standards for facade systems, as does its performance in the areas of sound insulation, providing a barrier against falling, and deterring burglary. The structural function of the insulated glass unit remains ensured, even when the panes of the unit are damaged.

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the building envelope (coloured glass elements, e.g. the Unilever headquarters). Cleaning the smooth surfaces presents no problems. This system allows materials to be employed outdoors that alone would not withstand the weather conditions. Printing on glass elements offers a further possibility in terms of both design and building physics (for instance as sun protection). Examples here include the Strasbourg project and the John Lewis Department Store in Leicester.

8 Shop facades in West Village, Westfield London with structural glass fins. The shop fronts are connected by laminated and glued point connections. 9 Metal fixing laminated in place, here in a glass staircase. The symmetrical introduction of tension and compression forces into the fixings ensure as even a distribution of stress in the glued area as possible. Generally speaking, glued connections that direct connection forces across a wider area result in a better distribution of stress than conventional solutions using point fixings. 10 Test rig for structural insulated glazing. Even when damaged, the bearing capacity of the insulated glass unit is ensured. 11 Sample of facade pattern for Strasbourg with congruent printing of white points outside and black ones inside (the latter are not visible) 12 Section of the facade, John Lewis Department Store, Leicester: The ornamental pattern consists of two layers of a double facade, 80 cm apart. Both are printed with the same motif applied using different techniques. The pattern applied by sputtering to the outer facade is highly reflective and provides protection against the sun and inquiring gazes. The congruent ornament on the inner face of the insulated glazing is made with enamel paint.

Foils/interlayers /printing Laminating using the vacuum bagging process permits a variety of materials to be employed. Layers that direct light or absorb sunlight (Bremen University, see p. 105) can be used as interlayers to meet specific functional requirements. Including foils and natural materials such as textiles, leaves, wood or paper in the laminating process offers opportunities both in the area of interior design (for example opaque partitions created with stainless steel gauze laminated with glass), as well as in 79

Structural use of Glass

Possible Applications of Cold-bending

Possible Applications of Cold-bending Roland Pawlitschko (RP) interviews Niccolò Baldassini (NB), RFR 13 In 1982 Peter Rice founded RFR, an international engineering office for structural design, with headquarters in Paris and branches in Stuttgart, Shanghai and Abu Dhabi. Among the projects by RFR are the pyramid and glass roofs of the Louvre, the 2F CDG air terminal, the Niedersachsen football stadium in Hannover, the entrance pavilion to the Irish parliament in Dublin and the sculptures by Frank Stella in London. Niccolò Baldassini is one of the directors of RFR. He is both an architect and engineer and has an M.Sc. in aerospace engineering (specialising in finite elements and composite materials). His work concentrates above all on the areas of lightweight building and unconventional structures, where he works together with various international architects. In addition Baldassini teaches at the Ecole Spéciale d‘architecture in Paris and writes articles on the relationship between engineering and technology for a number of international journals.

RP: Cold-bent glass was used in the extension to Strasbourg railway station, why wasn’t hot-bent glass used and what effects did this decision have on the design of the facade? NB: RFR has worked with cold-bent glass for many years now. Back in the late 1980s we built the glass roof of the railway station in Lille and ten years later the facade of the station in Avignon. Both these projects provided us with proof that this technology can offer simple answers to complex questions – both as regards geometry and costs. The toroidal shape of the Strasbourg station extension turned out to be ideal for using cold-bent glazing. The best visual results can be achieved in a very economical way as, unlike in the hot bending process, the surface of the glass does not show any marked unevenness. As the result of an optimization process in Strasbourg we were able to use elongated sheets of glass with low material thickness. Hot-bent glass would have led to different proportions and this would have produced an entirely different appearance. RP: What do you see as the principal differences between cold and hot-bent glass in terms of construction? NB: Specialists such as Dutch architect Mick Eekhout have carried out intensive research work in this area but mostly in the area of spiralling glass. The glass bridge exhibited at glasstech takes a very different approach. In that case very thin glass sheets were laminated together with an SG foil to create a stable “multi-layer composite material”. The PVB laminated glass used for the facade in Strasbourg exploits the structural effect of its curved surface, which is to say it uses the material in the most efficient way possible. RP: To what extent could this technology change architects’ work? NB: Cold-bent glass is the focus of our “IndustryAcademia Partnerships and Pathways” research work on free-form design. This is, at least in part, due to the fact that there is a trend towards complex geometries that are no longer facetted (as in the Musée de la Dentelle) but call for softer transi-

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tions. The Strasbourg project and also Frank Gehry’s “Fondation Louis Vuitton pour la Création” in Paris illustrate the possibilities of single-curved glass sheets. But now we can go a step further. Thanks to new algorithms it is possible to break any double curvature surface down into single curvature surfaces; here the technology of cold-bending plays a key role. RP: In the “Fondation Louis Vuitton pour la Création” cold-bent glass is also to be used. Given the highly complex nature of that glass facade what are the special aspects? NB: Well, first of all the “glass wings” are not conceived as double-curved but as developable surfaces. The fixed architectural form and the radii, some of them very tight, impose new constraints. The surface can be approximately represented by cylindrical hot-curved glass. These are then coldbent and in this way shaped into the desired geometry. RP: As regards cold-bent glass: what kind of progress do you expect in the next few years, and what developments would you hope for? NB: Architectural research into free forms in glass has produced a rich variety of forms and single curvature, non-cylindrical glass panes with increasingly small radii. In this case glass, which has already been hot-formed, is then cold-bent into different radii. The new materials for laminating glass sheets are equally promising. By virtue of their characteristics SG foils already offer an alternative to standard PVB foils. A new generation of high-strength foils originally developed for aerospace applications will soon be used in the building industry. From a scientific viewpoint visco-elastic qualities will be fundamental in extending and redefining the boundaries of glass technology.

Fascinated by Glass

Fascinated by Glass Christian Brensing (CB) interviews Wolf Mangelsdorf (WM) 14

CB: How do you assess glass as a construction material, compared, say, to concrete or steel? WM: As a building material glass has a major disadvantage: it is fragile. All the same it harbours an enormous potential and it is certainly a source of great fascination for me. Everyone knows that a glass tumbler breaks when you let it drop, and so everyone knows that this is a dangerous material. To put it briefly there is something daring about glass. At the same time it helps our fantasies take flight. And glass is also ideal for attracting attention. Naturally, choosing the right material is always important. As an abstract material glass is fascinating on account of its qualities such as transparency as well as its brittleness. And it has this “hey, take a look at me” kind of potential. I often think about this combination. CB: Are there any developments that you would like to pursue further? WM: I recently became involved in research work at Dresden TU. The Institute for Building Construction there headed by Professor Bernhard Weller is examining glass and steel composites as well as means of bonding the two materials together. The goal is to overcome one of the inherent problems of glass, the fact that it is brittle and has no expansion reserves. A discussion forum organized by seele during the glasstec in Düsseldorf offered me a further opportunity as I was able to obtain an insight into the research work carried out by this firm. We

spoke about the challenges in using glass in construction, among other themes. Personally I see a chance for great developments here. But when I compare what is being built on the European continent with what is built in Britain I recognize serious differences. I believe this has to do with the different approval procedures. In England, if the criteria of stability are met, we can more or less build as intended. In Germany in contrast for designs that are not standard the authorities require “approvals for individual cases” and all sorts of tests. CB: What do you think is the reason for this? WM: Perhaps it has something to do with the famed British engineering spirit? In Great Britain we are often obsessed with trying something out and researching things further. This tradition originated with Thomas Telford or the Iron Bridge. In England we tend to be more adventurous. seele is always prepared to carry out these developments with us. It’s interesting that all the important glass and facade firms working in the British market come from a region that I always define by drawing a large circle around the Alps: from northern Italy, Austria, southern Germany or Switzerland.

Since 2002 architect and civil engineer Wolf Mangelsdorf has been a partner in Buro Happold, an international and multi-disciplinary engineering office with more than 30 years experience and a staff of over 1600 throughout the world. Mangelsdorf heads the structural design group in the London office.

13 Breaking a free-form up into single-curved surfaces, research project of the “Industry-Academia Partnerships and Pathways” 14 Musée de la Dentelle, Calais (2009), architects Moatti & Rivière 15 Model for the “Fondation Louis Vuitton pour la Création”, Paris, architect Frank Gehry

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Glass Bridge and Glass Staircase: Applied Research Projects

Glass Bridge and Glass Staircase: Applied Research Projects Stefan Behling, Andreas Fuchs, University of Stuttgart Professor Stefan Behling, senior partner at Foster + Partners, is director of the Institut für Baukonstruktion und Entwerfen L2 (Institute for Building Construction and Design) and head of IBK Research & Development at the University of Stuttgart. Focal points of research in the faculty are solar building, building envelopes, building with glass and bionics. Professor Andreas Fuchs, architect, from 2001 to 2009 scientific assistant/lecturer at IBK2 of the University of Stuttgart, is a co-founder of IBK Research & Development and since 2009 Professor at Hochschule RheinMain. The focal points of his research work are transparent adhesive technologies, lightweight glass building elements, structural glass building and integrated high-performance facades. Responsible for research and development at IBK2: Dipl.-Ing. Peter Seger, Akad. Oberrat

Building data glass bridge Design + development: IBK Research + Development, University of Stuttgart; Stefan Behling, Andreas Fuchs, assistant: Michael Meyer Structural design: Engelsmann Peters GmbH; Stephan Engelsmann, Stefan Peters, assistant: Christoph Dengler Client, development, implementation: seele GmbH & Co. KG Completion: 2008 Material: 4 mm float glass, white glass, SG foil DuPont Parapets (2): 6≈ 4 mm float glass, 5≈ 1.5 mm SG foil; 540 kg Walkway: 8≈ 4 mm float glass, 7≈ 1.5 mm SG foil; 950 kg Self weight: 2030 kg Bearing capacity: 7280 kg Live load (500 kg/m2): 10.5 m2 surface area: 5250 kg

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In the previous century hardly any other material fascinated architects and engineers to the same extent as glass. And even today anyone looking at dematerialised glass constructions is still amazed by the performance of this transparent material. In addition to transparency its numerous positive qualities such as surface hardness, resistance to (vapour) diffusion and ability to block or withstand UV are important factors in using glass in a building envelope. Its brittleness and its ensuing sudden failure are this material’s most significant negative qualities. To prevent failure, laminated safety glass is used in all safety glazing and glass structures. A minimum of two glass sheets are laminated together with a PVB foil between the sheets and thus obtain a residual bearing strength should the glass fail. Additionally this system avoids the risk of injury caused by individual glass splinters whenever monolithic glass shatters. For years the performance of these PVB foils and the bonding effect with the glass sheets has been a topic of discussion in engineering circles. In mathematical and construction terms this bonding effect has not yet been exploited in Germany, due to its heavy dependence on the concept of duration of load effect and temperature. The two projects described below, which demonstrate the potential of the high-performance SentryGlas foil from DuPont (SG foil), represent the result of intensive collaboration in research and development between seele and the authors. This product is an alternative to the standard PVB foils used to produce very rigid glass to glass connections, and to conventional adhesives used in making high strength structural connections between glass and, for instance, metal hardware. Both projects were constructed for the Düsseldorf “glass technology live” trade fair where they were presented to the public. The all-glass staircase with its minimized stainless steel connectors laminated into the structure was awarded the Glass and Architecture 2006 innovation prize. A completely new approach was taken for the all-glass bridge in 2008. Planar standard float glass sheets were cold-bent and, thanks to the use of SentryGlas foil, could retain their shape after laminating. This process, comparable to curved gluelam panels, opens up an

entire new construction philosophy not achievable with PVB foils. The all-glass bridge (BRÜCKE 7) was also awarded the innovation prize Glass and Architecture, in this case in 2008. BRÜCKE 7 all-glass bridge, 2008 The all-glass bridge consists of a curved walkway with two curved glass parapets, all elements being made from cold-bend laminated safety glass measuring 2.0 ≈ 7.0 curved length for the walkway, and1.2 ≈ 7.0 metres (curved length) for the parapets. When fitted together the single curvature bent sheets produced a three-dimensional body made up of curved surfaces. The walkway is made of eight 4-mm float glass panes and seven sheets of highly transparent 1.5 mm SG foil. The parapets consist of six 4-mm float glass panes with five SG foils. This composition of comparatively thin glass panes and thick foils creates a new volume relationship between glass and laminating foil of around 3:1. Prior to this, standard practice was to bend flat panes of glass while hot, which involved heating them to over 640 °C, causing the glass to lose its stiffness and to settle plastically into the form required. The disadvantages of this method are the costs of the moulds, the limitations on size imposed by the ovens in which the sheets are heated, visual defects caused by the heating process and flaws that arise during the cooling of the glass. With the cold-bent structural glass elements used for the BRÜCKE 7 these difficulties do not arise. In cold-bending the glass panes are stacked in a form before laminating, that is before the bonding of the individual glass layers. This creates bending stress in the glasses. This can be calculated by an FE model or alternatively the moment-curvature relationship can be observed to arrive at the bending stress in the glass. This states that the curvature is the quotient of bend, bending moment and bending stiffness. The bending stress that results from the curvature is the quotient of moment and section modulus. Moment-curvature relationship, bending stress, section modulus Thin flexible panes are suitable for the cold-bend-

Glass Bridge and Glass Staircase: Applied Research Projects

ing process as they allow tight radii of curvature with relatively low flexural stresses. This also explains why a layered construction was chosen for the glass elements used in BRÜCKE 7, which is made of a number of thin glass sheets. In this case the 4 mm float glass panes were curved with a radius of 16 metres. This produced a flexural stress of around 9 N/ mm2, which in terms of the technical regulations could be regarded as permissible for the permanent loading of float glass, while at the same time offering sufficient stress reserves for the loads that would later be applied to the building element. Through the lamination process that followed the internal stresses were suspended. As a result of the high shear strength of the SG foil and the great flexural stiffness of the glass “package” the amount of movement back to the original position is negligible. The use of SG foils is an important material feature of this bridge. A further feature is the structural performance of the bridge as an arch. The glass arch is almost a parabola in

shape and can direct evenly distributed loads almost entirely as compression forces. Here creating sufficiently rigid abutments is of paramount importance. In the walkway the relationship between the rise (height of arch) and span is 1:18 and the relationship between cross-sectional height and the span is 1:162, making it an extremely shallow arch. For asymmetrically distributed live loads of 5.0 kN/m2 the walkway must be stabilised. This is done by means of the parapets that are joined to walkway along a length of 6 metres with an elastic adhesive joint made with two-component silicone. The same principle is applied to take the horizontal loads of 1.0 kN/m. These are transferred in both directions via the arch effect of the parapets; here the walkway takes on the job of stabilising the shape in the case of unevenly distributed loads. To take down the bridge the silicone joints between walkway and parapets can be separated using a cutter knife in much the same way as the fixed front window screen of a car

SG foils In terms of material technology the use of SG foils is an important characteristic of this bridge. In recent years this product by DuPont has been increasingly used in the area of structural glass. The strength and stiffness of these transparent thermoplastics is considerably greater than that of PVB foils. These qualities result in a bonded bearing behaviour approaching that of a monolithic construction element.

Construction The glass bridge consists of a curved glass walkway and two curved glass parapets, made out of cold-bent glass panes. The walkway measures 1.2 ≈ 7 m (curved length) and the parapets 1.2 ≈ 7 m. Fitting together these single curvature sheets produces a three-dimensional body.

Walkway The walkway of the bridge consists of eight 4 mm float glass panes and seven highly transparent 1.5 mm SG foils.

Parapets The parapets consist of six 4 mm float glass panes and five SG foils. This construction of relatively thin glass panes and thick foils creates a new ratio of glass to laminate foil of around 3:1. This reduces the self weight of these glass elements.

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Glass Bridge and Glass Staircase: Applied Research Projects

16 16 Isometric connection of glass step to parapet 17 + 18 All-glass bridge in the company headquarters in Gersthofen

Building data: glass staircase Design + Development: IBK Research + Development, University of Stuttgart, Stefan Behling, Andreas Fuchs Structural design: ITKE Forschung und Anwendung, Jan Knippers, Stefan Peters Client, development, implementation: seele GmbH & Co. KG Completion: October 2006 Length of glass staircase: 8000 mm Width of glass staircase: 1500 mm Pane size glass string: 8000/130 mm Number of glass steps: 21 Weight of glass step: 60 kg Weight of glass strings: 2≈ 1070 kg Weight of glass staircase: 3780 kg Construction of glass string: 3≈ 15 mm float glass, 2≈ 1.5 mm SG foil Construction of glass step: 3≈ 12 mm float glass, 1≈ 8 mm float glass, 3≈ 1.5 SG foil mm Length of glass box: 2760 mm Width of glass box: 1500 mm Height of glass box: 4150 mm Weight of glass box: 3250 kg Total weight of glass: 7030 kg

is removed. This procedure can be repeated several times if required, so that the entire construction can be assembled, taken down and re-erected successfully. All-glass staircase, 2006 The all-glass staircase that was exhibited at glasstec 2006 spans seven metres and consists essentially of just two elements, the vertical strings and the horizontal steps. The two strings are each made of three panes of 15 mm float glass without joints. Like the steps, which consist of three 12 mm and one 8 mm layers of float glass, they are laminated with SG foils to form laminated safety glass sheets. All the steel fittings at the connecting points of the stairs are laminated into position using SG foils. In addition to the considerable span of the strings the staircase is also an impressive demonstration of the potential that laminating offers for point load transfer in structural glass. The stresses on the strings are divided into two main components: firstly the

stress acting on a pin-ended simple beam with a span of 7 m under vertical load, and secondly the stresses in a fixed parapet with a horizontal load. The bending stress in the strings around the strong axis is very low thanks to the considerable structural height. Fixing the strings to the exclusively horizontal steps (treads, no risers) was considerably more demanding both structurally and in terms of construction. To avoid peak stresses from a fixed bearing the joint between steps and strings allows for movement. The entire horizontal bracing of the staircase is provided by the sheet action of the steps. This is achieved via two fixing points at each side of each step, which in this case counter the moment from the horizontal load with a lever arm of around 9 cm. In addition to the vertical bearing loads, the fixing points must also transfer, as the decisive load, the couple consisting of tension and compression forces. One of the decisive questions during the entire design phase was the problem that transverse vibration could pose. Horizontal res-

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Glass Bridge and Glass Staircase: Applied Research Projects

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onance frequencies of about 4 Hz under self weight and 3 Hz under full load were worked out. In general, where the horizontal resonance frequency lies above 3.5 Hz undesirable effects are not anticipated. When built the staircase confirmed the calculations, as even when in full use during the fair neither horizontal nor vertical vibrations could be felt. Details of the construction In assembling the stairs essentially three construction details had to be solved: the bearing point of the strings at the top and the bottom, and the connection of the steps to the strings. The latter was the central detail of this staircase. The stress on the joint between step and string is made up of the vertical bearing load and the tension and compression forces to stabilize the strings already described. The easy replacement of damaged steps was an important part of the concept and led to the solution eventually chosen: fittings are laminated to the inner face of the string and steel sheets are laminated into the steps. Structural calculations required the symmetrical direction of the tension and compression forces into the fittings to assure as even a distribution of stress as possible in the area of adhesion. In principle, by spreading the forces across the adhesive connections a far better distribution of stress was achieved than, for example, results from drilling point fixings that damage the glass as a result of the mechanical process involved. In the final version stainless steel fittings measuring 100 ≈ 39 mm made from 15 mm sheet steel were chosen, and a track-like groove was milled out of the side facing the step to take the connection. Each step is fixed by a total of four laminated fixings, two on each side, in such a way that, should any of these adhesive joints fail, the step will not collapse. Extensive FE calculations and trials were carried out parallel to the development of the details. Producing such large glass elements confronted the contractors with major challenges. In addition to putting the stairs together at the fair the greatest challenge was the lamination process in the autoclave and the precise positioning of 42 fittings on each string without the failure of a single adhesion point.

Summary It is our belief that the potential for innovation offered by glass combined with new processing techniques and finishing methods remains enormous. Naturally, reference should be made here to the great challenges that precision in planning, production and fitting present for architects, engineers and constructors. To master the complex geometry, the processing of steel and glass as well as laminating and assembly technology, a wealth of experience is required, along with state-of-the-art facilities. Both the bridge for glasstec 2008 as well as the staircase for glasstec 2006 should not be seen as products in the classical sense but as successful experiments and as a demonstration of a technology that can be used in the future in structural glass and facade construction.

Further reading • Behling, Sophia und Stefan: GLASS, Konstruktion und Technologie. Munich 1999 • Bucak, Ö.: Glas im Konstruktiven Ingenieurbau, Stahlbau Kalender. Berlin 1999 • Glass strength according to AS 1288-06, Australian Code • ASTM E 1300-2, Standard Practice for Determining Load Resistance of Glass in Buildings • Peters, S. u. a.: Ganzglastreppe mit transparenten SGP-Klebeverbindungen – Konstruktion und statische Berechnung. In: Stahlbau Heft, Nr. 03/2007 • Bennison, S.: Structural Properties of Laminated Glass: Werkstoffangaben zu SentryGlas (DuPont) • Fuchs, A. u. a.: Transparente Experimente – Innovationspreis Glas und Architektur. In: GLAS Architektur und Technik, Nr. 6/2009

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Glass Bridge and Glass Staircase: Developing the Details

Developing the Details Katja Pfeiffer (KP) interviews Stefan Peters (SP), Engelsmann Peters 19a From 2000 to 2006 Stefan Peters worked as an assistant to Professor Knippers at the Institut für Tragkonstruktion und Konstruktives Entwerfen (ITKE) in Stuttgart. Together with Stephan Engelsmann he has headed the engineering office of Engelsmann Peters Beratende Ingenieure in Stuttgart since 2007.

19 Detail of connection glass tread to string Scale 1:5 a Top view b Cross-section c Elevation 20 + 21 The metal fittings fixed to the treads and strings allow the steps to be easily fitted and removed again.

Assembly Four fitters worked for four days in putting together the stairs for the fair. First of all they erected the separate glass landing “box” and secured it to the ground with dowels. They then lifted the glass strings measuring 8.00 ≈ 1.30 m and weighing 1.3 t into the two bearing points and stabilized them in position. Then the fitters slid the steps into the metal connection pieces on the strings and secured them.

KP: Mr. Peters, what was your particular area of responsibility and how was the cooperation organized in terms of work process? SP: The glass staircase was developed through teamwork between the architect, engineer and the construction firm. Meetings were held regularly at the university institutes or in Gersthofen. The requirements of design, construction, and the production methods available were continuously weighed against each other. The engineer, that is to say I myself, was responsible for the structural design, including dimensioning the elements and for collaboration in developing the details, as well as for carrying out and evaluating the testing of building elements. At the time I was working as an assistant to Professor Knippers at the Institut für Tragkonstruktion und Konstruktives Entwerfen (ITKE) in Stuttgart. With the stairs the main focus was on developing a new kind of jointing technique for structural glass constructions by laminating steel fittings in place and using SG foil. We concentrated on the connection between the steps and the string. We started by having a track milled out of the innermost of the three sheets that made up the string and laminated a kind of inlay in place. The samples we made did not produce satisfactory results, so we had to start anew. The second detail design then led to a radically reduced solution with a steel fitting laminated flat against the string. We were able to prove its bearing capacity through tests accompanied by

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calculations. The precise placing and laminating of 22 of these steel fittings on a glass element 7 metres long demanded a great deal of experience as well as technical equipment of the highest standard. KP: Was this technique developed especially for the glass staircase or did it already exist? SP: It represents a new development in the area of fitting and adhesive technology. What was new about this project was the use of stainless steel fittings laminated in place to direct loads into large glass building elements. In a sense the laminated foil replaces a wet adhesive. Projects of this kind should always be understood as prototypes. The experience that the project team acquired in working on the stairs was extremely useful in constructing the glass bridge, particularly with regard to the bearing characteristics of laminated SG foils. KP: Were you also involved in the bridge? SP: Given our knowledge about the strength of laminated foils, it seemed a fairly obvious idea to cold bend glass panes, place them on top of each other interleaved with layers of foil and then to laminate the entire “package” in its curved form in the autoclave. The first sketches and models for a glass bridge made of three curved glass parts came in 2007 from Stefan Behling and Andreas Fuchs. In this case the faculty invited our engineering office,

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Glass Bridge and Glass Staircase: Developing the Details

19b

Engelsmann Peters, to undertake the structural design. In this case, too, the combination of object designer, structural designer and production firm built up a very effective team. KP: What did the structural design involve? SP: First of all we looked for a suitable structural concept for the design. In the case of the bridge after a few studies it became clear that we should use an arch structure. In the initial phase the most important thing was to determine a critical radius of curvature for the glass panes, so that we could work out the geometry of the bridge. For this project the development team could make use of 7 metre long glass sheets, the standard glass size from a float glass works is normally 6 ≈ 3.21 metres. In addition we had to calculate the necessary number of layers and the permissible curvature using a finite element programme. An arch can transfer symmetrical loads by means of its specific structural performance, but in this case unilateral loads had also to be taken into account. The more shallow the arch, the greater the danger of failure under asymmetrical loads. For this reason the parapets of the glass bridge provide reinforcement. These parapets are connected to the walkway by an elastic silicone joint and help to stabilize the form. At the same time this stabilization also functions the other way around: the parapets themselves also function as arches that transfer horizontal loads to the bearings. To deal with unevenly distributed horizontal loads the parapets are stabilized by the walkway. This complex symbiosis of two building parts is achieved with an almost non-existent detail: a black silicone joint. Arch structures require two rigid abutments. In the structural system of a two-hinged arch as used here, any yield in the abutments immediately leads to a change in the distribution of tension in the glass sheets. Consequently the system must be carefully dimensioned to establish the intended distribution of stress in the glass. The end bearings and the construction of the abutments were developed through working in close collaboration with seele. This is a highly complex geometry, a U-shaped steel element that was difficult to weld and to mill was produced in Gersthofen.

19c

KP: Can you describe the process of developing the detail for the joint between the walkway and the parapet? SP: For a long time we thought about using a steel angle laminated in place. But in the production process it turned out that this angle could not be laminated in position. We then decided to join the walkway and parapets with a butt adhesive joint and to look at how to deal with the biaxial stress in the joint by means of testing. The joint is about 10 mm thick and has a certain degree of elasticity. We employed a two-component silicone, a standard product used in structural glazing. The load was to be transferred for the most part by means of the arch to the abutments and should not wander directly into the parapets. An additional advantage is that a silicone adhesive joint can be cut open easily and then made again when re-erecting the structure.

Construction The construction was developed through close collaboration and continuous dialogue between IBK Research + Development, ITKE Research and Application and seele. The staircase is made up of just two elements: the strings and the horizontal steps. The stress on the strings is essentially broken up into two components: firstly the stress in a simple beam spanning 8 metres under a vertical load, and secondly the stress of an end-fixed parapet with a horizontal load. The connection between the steps (which consist only of treads, no risers) and the strings is flexible and thus accommodates both stresses. The entire staircase was developed using models and complex calculations with finite elements.

KP: Was a special structural design required for assembling the bridge, and were you involved in the discussions about production? SP: The concept for the assembly and the scaffolding required were developed by seele. To produce the elements a laminating frame had to be developed on which the float glass panes can be laid with the required curvature. A 4 mm thick pane with a length of 7 m is as soft as a cloth. If you lift it the wrong way it breaks. Here we had to make sure that the laminating frame was dimensioned so that no appreciable transverse bending occurred in the glass panes during the laminating process.

Adhesive connections There are essentially three construction details in the stairs: the upper and lower bearing points and the connection of the steps to the strings. Generally drilled point fixings or mechanical clamping plates are used to make connections in structural glass constructions. The advantage of the adhesive approach is that the forces acting on the connections are directed over an area and there is no need to drill holes in the glass strings which can be problematic in structural terms. The elements are connected only by means of the friction-grip of the laminated fittings. Unlike PVB foils, the SG foils used here can be used in transferring loads

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Structural design concept The preliminary structural studies quickly revealed that using the loadtransfer effect of the arch made considerable sense. The glass arch is almost a parabola and can transfer evenly distributed loads almost exclusively as compression forces. Here constructing sufficiently rigid abutments is of paramount importance. In this example the walkway is a two-hinged arch, a structurally indeterminate system that reacts sensitively to the development of tension stress due to movement in the bearings. Consequently the two stepped abutments are rigid steel constructions connected by ties and have additional ballast to prevent tilting. The relationship between the rise of the glass bridge walkway and its span is 1.18 and the relationship between its cross-sectional height and its span is 1:162, making it an extremely slender and shallow arch. To cope with asymmetrically distributed live loads of around 5.0 kN/m2 the walkway had to be stabilised so as to avoid undesirable bending and shear stress as well as stability problems.

22 FE model of the glass bridge: Steel substructure, glass walkway and glass parapets 23 Static load test of the cold-bent glass sheets 24 Cross-section: connection of walkway to parapet Scale 1:5 1 Parapet, 6≈ 4 mm float glass, 5≈ 1.5 mm SG foil 2 Walkway, 8≈ 4 mm float glass, 7≈ 1.5 mm SG foil 3 Joint, silicone 5 mm 25 Static load test silicone joint 26 Pattern of deformation under: a Full load b One-sided horizontal load 27 Glass parapet after the laminating process

Glass Bridge and Glass Staircase: Developing the Details

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KP: Did you run up against any major problems in the production? SP: The first walkway that was laminated cracked during the laminating process. High temperature loads build up in the autoclave. As soon as the SG foil cools off and solidifies and the glass also cools, temporary local stresses can occur. This meant that a second walkway had to be laminated. A special aspect here was that we made the second walkway out of what is called a “staggered” glass construction. The two outer faces are 7-metre-long cover sheets, between them are six inner leaves. Each inner leaf is made up of two sheets with lengths of 4 and 3 metres or alternately 3 and 4 metres. This staggers the position of the joints between the inner sheets, creating a glass element with a total length of 7 metres that is made up of much shorter sheets. We tested the construction principle on a 4 meter long test arch. This consisted of seven glass layers with a staggered joint construction. The test model was loaded with sandbags. We programmed a comparative mathematical model which we calibrated until the calculation matched the real load-bearing performance. In developing prototypes one regularly has to deal with new situations and unfamiliar processes. At the same time the question arises as to where else these innovations could be applied. In this case the development could also be used for instance in a glass roof, sooner or later.

KP: Do you have any follow-up projects with seele? SP: At present we are working on the structural design for a large steel lattice shell with a glass envelope in Chicago. The architects Murphy/Jahn and Werner Sobek’s office as the client’s engineer are also involved. They are planning the project to a certain depth. It will then be handed over to a contractor, in this case seele. The Gersthofen-based firm put the engineering services involved in the detail planning out to tender and we were awarded the contract.

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KP: As a relatively young office how do you assess collaboration with industry? SP: Working together with industry and contractors means that we as engineers are more closely involved in carrying out the building or in product development than is normally the case. When we produce detail planning for a firm like as seele, we are automatically involved in matters to do with the assembly and production processes. The responsibility for structural design is in our hands. This kind of collaboration produces synergy effects that encourage the development of innovations and, as a further benefit, lead to particular quality.

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Glass Bridge and Glass Staircase: Developing the Details

Deformations IuI [mm]

4.5 4.1 3.7 3.3 2.9 2.5 2.1 1.7 1.3 0.9 0.5 0.1 Max. Min. 26a

4.5 0.1

26b Silicone adhesive joint The walkway of the glass bridge is stabilised by the parapets at both sides. They are connected to the walkway along a length of 6 metres by an elastic adhesive joint made with 2-component silicone. The same principle is used to take the horizontal loads of 1.0 kN/m. They are transferred in both directions by the arch effect of the parapet, with the walkway helping to stabilize the form in the case of unevenly distributed loads. The bearings for each of the parapets are provided by two vertical steel sections that take up tension and compression forces with little deformation.

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The Floating Seat

The Floating Seat Christian Brensing (CB) interviews Graham Dodd and Wieslaw Kaleta, Arup 28 Arup is a worldwide business employing designers, engineers, planners and consultants. The Arup headquarters are in London and the business has 10 000 staff in 37 countries. Graham Dodd is project head with Arup for construction projects in Europe, Asia and North America, Wieslaw Kaleta is a facade engineer and responsible for business development in Poland.

28 The Floating Seat was presented to the public for the first time at glasstec 2008.

The “zoomorphic” version of the Floating Seat A version of the Floating Seat that was not carried out was known as the “zoomorphic bench” on account of its flowing natural forms. The design also proposed glass panes stacked side by side but the stainless steel leg was dispensed with in the final version. Instead the glass panes continued to the ground and were held together with steel rods and plates at both ends. Another important difference was that the glass plates were hollowed out by machine.

As well as the glass bridge there was a smaller, but no less striking, exhibit at glasstec 2008, the so-called “Floating Seat”. This glass seat was originally planned for the Plantation Place development by British Land in Fenchurch Street in London, an office building by the London office of Arup Associates. CB: How did the “Floating Seat” come about? Arup: Mick Brundle was the architect in charge of the Plantation Place project and he came up with the idea of a floating glass bench as a piece of furniture for the reception area. But when seele had carried out the engineering calculations and produced the bench, the client, British Land, sold the project. The glass bench is both a piece of art and a functional item of furniture. It is a rectangular slab of glass that stands on a steel leg positioned about a third of the way along its length and, so to speak, floats above the ground. With its five shallow, seatshaped indentations it reminds me of an old tractor bench seat. It was produced by machine from a series of oblong glass panes stacked on end. They are held together by steel rods running through the glass panes and anchored to the stainless steel leg. The individual glass rectangles are profiled to create the “tractor seats”. The single leg is made from a stainless steel sheet that extends deep into the ground. CB: The glass rectangles are stacked side-by-side. Are they bonded together like in the glass bridge? Arup: One of the biggest challenges was how to deal with the load at the end of the cantilever. The stainless steel leg itself is under great tension, and there are huge compressive loads on the glass. In our opinion it wasn’t possible to use adhesives or interlayers between the glass plates, as the heavy loads would have just caused them to squish out. We suggested using clean glass plates stacked face to face. seele then carried out extensive tests. At first they examined the version with adhesive and interlayers of all kinds, but eventually they came to the same conclusion as Arup, i.e. that the construction loses strength when you put anything between the layers of glass. The company also tested whether there was anything to be gained by

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toughening the glass or whether it could be left in its annealed state. In the end the glass was toughened, which gives it greater strength. CB: What advantages does Arup see in the structural use of glass? Arup: Using glass as a compression element, like here as a stack with pressure applied externally, creates a unique structural element. It is very stiff, really rather strong and has an interesting lightness and transparency. The glass bench can be lit from below, for instance. We had small light fixtures inserted in the ground beneath the seat. A further idea would be to light the Floating Seat from inside. Glasstec 2008 indicated two important routes for development in structural glass: stacked glass without any adhesive with the load transferred externally, and the laminated version which allows increasingly larger constructions, often using toughened glass and high-strength interlayers. This results in extremely good shear coupling. A fine example here is offered by the shop fronts in the Village area of Westfield shopping centre in London. Arup was not involved in this part of the interior fitting out but it is all the same an impressive construction that goes far beyond the standard industrial solutions. The fronts, almost 9 metres tall, are based on laminated glass fins that are 250 mm wide. With a height of 8.50 metres this gives a length to width relationship of 1.34 which is far above the standard value of 1:10. The glass itself has a low iron content and is completely white. In addition the stainless steel hinges are bonded to the glass, not fixed by bolts and act as structural members. This kind of connection is a very intelligent solution and in my opinion this project is a truly successful piece of work.

TriPyramid Structures

TriPyramid Structures Tim Eliassen, TriPyramid Structures 29

TriPyramid Structures which is based in Boston, Massachusetts, designs and manufactures special architectural hardware for load-bearing constructions. These are generally custom-made pieces. The Tripyramid design team is made up of designers and engineers. In direct collaboration with architects, artists, and structural designers we develop components that enhance the aesthetic quality of a design while at the same time meeting the engineers’ structural requirements. In one of our most recent projects we supplied large scale steel construction elements as well as large vertical steel mullions to support glass facades. In addition we have what is perhaps the widest range of tension elements: stainless steel ties with diameters from 4 mm to 100 mm in three different strength grades, cables of stainless steel and galvanized steel in thicknesses ranging from 6 to 100 mm. In 1989 I set up the firm together with Michael Mulhern with the aim of transferring the high-level technology of stainless steel components used in building racing yachts, atomic submarines and racing bikes to the world of art and architecture. Our first architecture project was the development and manufacture of 3800 tension rods that support Ieoh Ming Pei’s glass pyramid for the Louvre in Paris. Other projects include the Tokyo International Forum by Rafael Viñoly, and the Rose Center Planetarium by Polshek Partnership Architects in New York, as well as the Apple flagship stores.

Previous projects For the Rose Center TriPyramid developed high strength stainless steel rods of small and elegant dimensions. This meant that the end fixings could be smaller and more minimalised than would have been the case if lower strength rods or cables had been used as tension members. In the pyramid in the Louvre TriPyramid joined the design phase at a relatively late point. Local firms initially suggested using stranded cables with standard end fixing points. The samples presented in no way met the architect’s expectations. While the cables and hardware proposed would have achieved the desired transparency of the building, the details that are visible throughout the structure and can even be touched with the hand at eye-level were so rough that they would have impaired the overall impression made by the pyramid. The designers then decided to use high strength slender stainless steel rods instead of cables. The rods have a smaller diameter which meant we could develop more architecturally appropriate end fixings. Focussing on these details created a clearly legible structure that enhances the experience for visitors inside the pyramid also. The Tokyo International Forum project followed a somewhat similar path. Here TriPyramid collaborated with architects, structural designers, clients and the Japanese steel suppliers. For the numerous tension rods in the roof structure we used high strength steel which allowed us to reduce the diameter of the rods from 100 to 75 mm, this in turn meant that smaller and perceptibly more elegant end fixings for the rods could be used.

The engineers Tim Eliassen and Michael Mulhern, who originally worked in the field of yacht building, founded TriPyramid Structures Inc. at the end of the 1980s, motivated by a commission they received from architect I. M. Pei to provide a stainless steel support system for the glass pyramid in the Louvre.

29 Glass pyramid in the Louvre 30 Tokyo International Forum

Titanium connections Many of the components produced by TriPyramid are made of high strength stainless steel. In special cases, however, other materials such as titanium are used, wherever special properties are required. The fixings for staircase treads are a good example of such a case. The thermal expansion coefficient of titanium is very close to that of the glass used for the treads. As both values are similar, the stress that can arise due to different thermal expansion during cooling down from the lamination temperature is reduced to a minimum. The use of titanium for fixings substantially reduces the problem of glass breakage during fabrication.

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Structural use of Glass

Challenges and Potential of Structural Glass

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Challenges and Potential of Structural Glass Christian Brensing (CB) interviews Tim Macfarlane (TM), Dewhurst Macfarlane

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Together with Laurence Dewhurst Tim Macfarlane has headed the engineering office of Dewhurst Macfarlane and Partners in London since 1985. Theirs is one of the leading offices worldwide in the development of structural glass constructions.

CB: You work regularly with seele, I believe, how did you first come across the firm? TM: The first contact was made through Marc Simmons, a facade consultant and designer, who started work in our engineering office in 1999. In May 2001 we were appointed facade specialists for the Burberry Flagship Store on 7 East 57th Street, New York, two years later for the Seattle Library. At Marc’s suggestion we recommended seele for both projects and in both cases they obtained the commission. Thanks to their performance – the technical and organizational abilities that they demonstrated – we put the company on the list of tenderers for the Apple Store in Prince Street, New York. CB: What is special about the Apple Stores? TM: Back then laminating steps with Sentry-Glas Plus as an interlayer was something entirely new. For the first time a laminated glass was used that had a stiffness comparable to that of a monolithic glass sheet of the same thickness. In addition, even if all the glass elements fracture the structural behaviour of the panel still provides sufficient strength to take the full design load. This development first made it possible to use 2.4 metre long free-spanning glass steps that could take a full live load while remaining within the required strength and deflection limits. In the same way we integrated stainless steel or titanium connections in the steps, which was also a first. Although these design concepts were already in existence by the time seele came along, carrying out this work without their technical and manufacturing knowledge would have been extremely difficult.

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CB: What experience did you gain from the project? TM: The Apple Stores were a fantastic opportunity for both sides to develop and implement new approaches to designing with glass. The inspiration for the project and its success are due to the client Apple Inc., and in particular to Steve Jobs’ personal commitment. The architect had the imagination to translate Jobs’ vision using the wealth of opportunities offered by structural glass. During this phase the engineer played an important role especially in terms of exploring the various construc-

tional possibilities of the materials and the expressive strength of the connections. Ultimately all of this was possible thanks the group of firms around Gerhard Seele and Siegfried Goßner that by this time was already well integrated in the project. In my experience such close integration of client, designers and fabricator is a rare thing. Everyone involved used the chance to push the boundaries in all directions. CB: How was it possible to bridge the differences in design cultures between countries, work groups and professions? TM: After seele had been awarded the contract for the Apple Store our design was subjected to rigorous scrutiny. This led to a series of tests and analyses that we agreed to, as we saw them as part of the famed “Teutonic thoroughness”. The advantage of such comprehensive testing was that in the end we understood our own design better. This process also confirmed our method of work, the search for and development of new ideas. Craftsmanship, structural integrity functionality and delight are the marks of a successful project. The appreciation of results like this overcomes all borders between different cultures, languages and disciplines. CB: You are regarded as one of the best glass engineers. Where do you think the potential of glass as a structural material lies? TM: Today we can construct every glass building element as a structural element. The requirements to make a column, a beam or a floor slab of glass are well-known. In my view the interest will now begin to focus on the environmental technology aspects of glass. Its transparency and inert quality make glass the first choice for transparent panels and facades. It seems highly unlikely that it will be replaced in this area by other materials in the foreseeable future. As regards the demands made on facades this building material certainly possesses qualities that are still under-developed. CB: What kind of developments are you thinking about? TM: At the “Glass Processing Days” in 2007 a

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German firm presented 12.9 mm glass panes with a U value of 0.4 W/m2/Celsius. This is achieved by welding, in a vacuum, two 6 mm panels a distance of 0.9 mm apart along the edges. The panes have distance pieces positioned on a 50 ≈ 50 mm grid. These pieces are so small that they cannot be seen by the human eye. I find this idea fascinating, as it means significant increase in efficiency in a simple, easily understandable way. There are also processes in which liquids are pumped through the cavity in insulated glazing and the warmth produced by solar radiation is then stored in special tanks. This is relatively complicated but it could be a useful technique for storing energy. In a similar way Southwall Technologies from California produce triple glazing using two glass panes and two layers of a coated film which together have a U value of 0.4 and reflect 82 % of incident solar radiation. Astonishingly this glass is still highly transparent. Another development involves bonding glass with other materials to form a composite material. I have long had in mind to bond two 4 mm panels of toughened glass with a rigid thermal insulation panel to create a hard, well insulated, storey-height wall ele-

ment. At certain points you could remove the insulation to make visibility openings. There is also the chance to experiment with coloured glasses or to place reflective metals or other materials directly behind the glass surface – inside or outside. Glass is like brick, it is completely universal. Louis Kahn used to say to his students: “Ask the brick what it wants to be.” We could ask glass what it would like to be – we could certainly learn a great deal.

31 a + b Vertical and horizontal sections through the Unilever glass facade. Scale 1:5 1 Compression /tension rod Ø 50 mm, steel S355 J2G3, wet painted RAL 9010 2 Steel shoe to take horizontal glass fins 3 Horizontal glass fin, 4 mm float glass + 1.14 mm 3M foil + 2≈ 12 mm heat strengthened glass + 1.52 mm PVB 4 Tension rod Ø 24 mm to transfer vertical loads, stainless steel 1.4571-K70, brushed 5 Insulated glazing, 8 mm toughened glass + 16 mm cavity, 2≈ 15 mm float glass + 1.52 mm PVB 6 Horizontal press strip with clip section 7 Vertical silicone joint 32 In the field of structural glass the transport of large glass elements represents a special challenge. For their work in a store for a leading computer firm seele had to charter a freight plane from Korean Airways. The tolerance between the containers and the interior lining of the aircraft was a mere 2 centimetres. 33 West facade of the Unilever headquarters (2008), architect Kohn Pedderson Fox: the glass functions as a structural element. The vertical transfer of loads by the panes takes place by means of tension rods placed behind the joints, friction-grip fixed to the facade by steel shoes. Horizontal fins of laminated glass brace the facade against wind loads. They consist of three-ply glass with a rainbow coloured foil interlayer, the glass alters its colour depending on the angle you are looking from.

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TESTING AND INSPECTION PROCEDURES

Testing and Inspection Procedures

Testing and Inspection Procedures Emil Rohrer, seele; Ömer Bucak, Munich University of Applied Sciences 1

Tested and approved building projects form a basis for all construction activity and provide a legal safeguard for production firms and contractors. Both designers and clients rely upon building legislation that demands that products should meet technical rules as listed in the building regulations. The technical norms, guidelines and regulations they contain provide a basis for construction and help to establish standards. A clear distinction should be drawn between product, application and test standards. Guidelines and standards that form part of building law must be observed. Departures from standards may be made where appropriate proof of fitness for use is supplied. In meeting standards by using different methods and materials, new paths are opened up for unusual constructions and innovations. Testing and inspection centres To ensure the proper manufacture and use of building products and constructions, the use of testing, inspection and certification centres (known in Germany as PÜZ centres) may be called for. Such centres must be recognised in accordance with the building regulations of the particular German state (Land) or the construction products law. As impartial third parties these centres carry out initial type-testing at national level within the conformity procedure, undertake external inspection and monitoring, and grant product certificates. At European level they can carry out, within the conformity procedure, sample testing, initial inspection of both the factory and of the factory’s own quality control methods, and can grant certificates. Recognition of the PÜZ centres is the area of competence of the individual German states (Länder). The Deutsche Institut für Bautechnik (DIBt) prepares the approval according to the criteria laid down in the approval ordinances of the federal and regional governments, or grants approval in cases where the Länder have transferred their competence to DIBt. However, the DIBt as a German approval centre can also grant national technical approvals for construction products and methods of construction, and European technical approvals (ETA) for construction products and kits.

Approval in individual cases Building regulation law distinguishes between regulated and non-regulated construction products or construction methods on which substantial demands are made. Construction products or construction methods are regarded as non-regulated when no technical construction regulations or generally accepted technical regulations, in particular DIN standards, exist for them, or when they depart from these technical regulations. The fitness for use of non-regulated construction products and construction methods must be proven through a national technical approval, a national test certificate or through an approval for an individual case. An approval for individual case is required for the use of non-regulated construction products when there exists no national technical approval or no national certificate or where such products differ substantially to an existing approval or certificate. Essentially the decisions on whether such a substantial difference exists is to be made by the producer, in certain cases together with bodies that operate in the proof of conformity procedure or that grant national technical certificates and approvals. The approval for an individual case – in contrast to the standard approval and certificate – always applies only to a specific building project.

Emil Rohrer studied mechanical engineering at the FH Augsburg. On graduating he worked for nine years in the development department of a supplier to the automotive industry, where he was engaged in the development of catalytic convertors and exhaust systems. He has been working for seele since 1992, and heads the department of development and application technology. Professor Ömer Bucak studied and took his doctorate in civil engineering at the University of Karlsruhe. Since 1995 he has been professor there for steel construction and welding technology, head of the laboratory for steel and lightweight metal building and, since 2009, head of the competence centre for adhesives at the Hochschule Munich (previously FH Munich).

1 The performance mock-up of the facade for 7 More London is exposed to wind loading generated by an aircraft propeller.

Comparable regulations in different countries The equivalent of the German approval for an individual case is known in France as the ATEx (Appréciations Techniques d’Expérimentation). In Great Britain there is no comparable form of approval, the technical inspection is generally the responsibility of the local inspecting engineer or inspection office. There is however a final control and acceptance. It is carried out by the building inspector at the time of the planning application, at the very latest during the construction phase. As the basis for evaluating the new building product or new method of building, he uses the building regulations that are valid for standard products and building projects, which he interprets according to his judgment and discretion. This kind of approval is thus subject to far less stringent criteria than comparable procedures in Germany and France. The BBA (British Board of Agrément) can issue BBA 95

Testing and Inspection Procedures

Construction products lists The building regulations of the respective German Länder (states) stipulate that the technical rules introduced by the supreme building authorities of the Länder by public proclamation are to be observed. These lists are revised annually and are issued by DIBt: Constructions products list A Construction products, for which technical rules are given in the Construction Products List A, Part 1, or construction products, which are named in the Construction Products List Part 2, require attestations of conformity. Distinctions are made between: • ÜH – declaration of conformity by the manufacturer • ÜHP – declaration of conformity by the manufacturer following testing of the construction product by a recognised testing centre. • ÜZ – certificate of conformity from a recognised certification centre

Principles and Practical Examples

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certificates. This approval certification is not obligatory, the average time required from application to issuing the certificate is about nine months.

approve tests there. We work together with a number of certified inspection institutes, allowing us to profit from their know-how. To ensure a regular feed-back of information and to minimize expensive testing outside our premises – in the past we shipped large test samples to England or America where they were erected by our own assembly team – we set up our own testing centre in Gersthofen in 2003 (see list p. 97).

Test and inspection procedures at seele Our business has to supply proof of the fitness for use of our construction products and systems according to the currently valid inspection norms. With innovative building projects that venture outside of the usual standards and norms the building authorities generally impose a system of approvals for individual cases. This often makes additional inspections necessary. To obtain approval from the building authorities, accredited inspection institutes must be used. Staff from such institutes regularly visit our headquarters in Gersthofen and

Test 1

Air permeability/infiltration

Test 2

Air permeability/exfiltration

Test 3

Water penetration resistance – static

Construction products list B The Construction Products List B, Part 1 is reserved for construction products that are placed on the market based on the Bauproduktengesetz (Construction Products Law) and for which there exist technical specifications and, depending on the intended use, classes and performance levels. The Construction Products List B, Part 2 includes those construction products that are placed on the market on the basis of directives other than the Construction Products Directive, which have the CE mark, and which do not meet all the essential requirements of the Bauproduktengesetz. On this account additional verifications of suitability are required.

Test 4

Test 4 Wind resistance – serviceability

Test 5

Repeat air permeability/infiltration

Test 6

Repeat air permeability/exfiltration

Test 7

Repeat water penetration resistance – static

Test 8

Water penetration resistance – dynamic

Test 9

Building movement regime

Test 10

Repeat air permeability/infiltration

Test 11

Repeat air permeability/exfiltration

Test 12

Repeat water penetration resistance – static

Test 13

Water penetration resistance – hose test

List C List C contains construction products for which there exist neither technical rules for works nor rules of technology and for which fulfilment of requirements in construction law plays only a secondary role.

Test 14

Wind resistance – safety

Test 15

Additional structural tests: • Impact test on internal face • Impact test louvers • Pull-out test of restraint point

Test 16

Dismantling and inspection

Load tests Static load tests belong to the second category of standard tests and examine the structural performance of a building or the behaviour of a material under different loads. We generally carry out these examinations as pendulum impact tests and bearing capacity tests. Samples or separate test rigs are required. We forward the results of the tests carried out (in accordance with the legal regulations or the requirements from the customer’s specifications) to the client’s respective specialist planners who can then check conformity with the requirements once again. Special tests Research and development are essential to our business in order to meet our own quality standards and to promote innovation. One example of the successful result of research is the development of the cold-bending technique for glass panes first used for the facade of the railway station in Strasbourg. In this case a kind of testing was required that differed from standard test procedures. Using a number of samples of the facade with cold-bent 2c

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Tightness tests Tightness tests form part of standard testing procedures and examine the effects of environmental influences according to the criteria of air, water, wind and atmosphere. Air- and rain-tightness testing is performed on original size test elements in static laboratory tests using a vacuum chamber. Wind deformation tests can be carried out statically using a vacuum or pressure chamber, or dynamically using an aircraft propeller. In the climate chamber we simulate different climatic influences on material samples in long-term tests.

Principles and Practical Examples

3a

original panes and different radii of curvature, in addition to standard tests we examined resistance to wind and impact loads (by sandbag tests, among other methods), bearing capacity in the case of snow loads and residual bearing capacity if the glass breaks (see chapter “Structural use of Glass”, p. 74ff.). Small-scale tests and feasibility studies These can take place from the development to the execution phase; they are an aid to internal quality control and reinforce the firm’s innovative strengths. One example is the project 7 More London: in addition to various tightness tests, using a 1:1 facade performance mock-up we simulated various scenarios for the different fitting procedures and optimized these for later use on the building site. Sound insulation In Germany requirements and verifications for sound insulation are laid down in DIN 4109. Accredited sound insulation laboratories carry out sound insulation testing for seele. In sound insulation cabins they test for flanking sound transmission, using completed and original size facade elements. Submitting just a single pane to this laboratory test would not provide a useful result, as this would not take into account the influence of the frame and fitting on the building site. Examples Facade testing procedure for 7 More London The 7 More London project called for extensive testing (see Chapter »Element facades« p. 58ff.). We made two 1:1 performance mock-ups for the 18 600 m2 aluminium element facade. We then carried out various tests on them, including air permeability and rain-penetration, as well as wind deformation. The shifting of floor levels above one another was also simulated. The tests proved that the facade can withstand real loads and deformation and will achieve the expected lifespan. The elaborate mock-ups were not the full height of the facade but all the important parts were made using the planned materials, so that the test results are fully applicable to the real facade.

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Load tests for Central Library Seattle The main focus in testing the facade of the Central Library in Seattle by OMA/Rem Koolhaas was on the stress caused by seismic loads. The building had to be able to move without incurring damage. To achieve this we developed special sliding bearings and seals with low friction sealing strips. The test construction, which can slide 5 mm, consisted of a sample panel in the original geometry which the inspectors fixed to a frame. The frame made of aluminium sections matched the original construction. The frame construction was deformed by means of a pneumatic drive and the deformation of the facade caused by seismic loads was simulated. A load cycle of 50 000 load changes tested whether the seal or the butyl tape would take up the movement. After an initial visual examination we decided on a special product, a butyl tape band that preserves the seal even if it creases. Using the mock-up the inspectors evaluated its workability at different temperatures. They heated the band in a heat chamber to about 70 °C and exposed it to slight deformation movement. After cooling the band had regained its original consistency. Load tests in structural glass For a suspended spiral all-glass staircase for a project in Osaka we created asymmetrical loads on half of the construction using sandbags, and carried out a pendulum impact test with a 55 kg car tyre. We noted that, despite damage in the form of cracks and fissures, thanks to the high bonding effect of the sheets the system remained intact. With the glass bridge for glasstec 2008 we examined a glued silicone joint that connects the parapet to the walkway and ensures that the arch does not deform using a test construction specially developed for this purpose. The structural designer involved in the project set up a comparative computer model which he calibrated until the calculation matched the real load-bearing behaviour (see Chapter “Structural use of Glass”, p. 88f.).

2 7 More London: a Air-permeability testing with foil to calibrate the test chamber b Testing water-penetration resistance using a hose c Air permeability and water penetration resistance tests 3 Central Library, Seattle a mock-up of the sample pane in the heat chamber b sample pane with aluminium frame and butyl tape for earthquake simulations

The testing and inspection facilities at seele: 1. Test site with facade testing centre (up to c. 120 m2) to carry out: • air permeability and water penetration resistance tests: This includes static tests with a vacuum chamber as well as dynamic tests with wind loads produced by an aircraft propeller • measurements of deformation after static and dynamic tests 2. Climate chamber for material samples to simulate changing effects of climate in long-term testing 3. Equipment to carry out various load tests such as pendulum impact tests and residual bearing capacity tests.

External facilities whose assistance is used when required (selection): • Labor für Stahl- und Leichtmetallbau, Hochschule München, Karlstraße 6, 80333 Munich, D • IFT Rosenheim, Institute for Window Technology, TheodorGietl-Straße 7– 9, Rosenheim, D • Taywood (Taylor Woodrow Engineering & Consultancy), 345 Ruislip Road, Southhall, GB

Kaufhof Chemnitz – fatigue strength testing of a glass fin support under dynamic stress The facade of the Chemnitz department store consists mainly of glass panels fixed by means of 97

Testing and Inspection Procedures

Principles and Practical Examples

Load level [%]

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Number of load cycles

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25 % load level 50 % load level

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Test rig for the department store facade in Chemnitz A test frame with a steel shoe support is equipped with a pneumatic drive to apply alternating loads (fig. 6). A Festo DNGU 100/500 pneumatic drive controls a reduction lever. This substantially increases the power of the pneumatic drive. Control is by means of the system’s adjustable operating pressure. An adjustable pulse generator controls the frequency of the load cycles. In addition the force at the fin can be adjusted over a wide range by means of different pivot positions or the reduction relationships of the lever. Calibrated gauges at the point of transition between the fin and the steel shoe (maximum displacement) record the measurements and the deformation.

clamp plates in the joints. Horizontal wind loads are transferred from the facade to the reinforced concrete floor slabs. However, in the area of the main entrance there are no floor slabs available for this purpose. Here the wind load is diverted by means of horizontally fixed glass fins that are connected by steel shoes made of milled steel. The side fixing is also made by means of the steel shoe system. At the edge these shoes are rigidly fixed by means of pockets, the glass fins are secured by pouring a special mortar system into the steel shoes (see »List of Buildings«, p. 105).

reduced the fixed-end moment from 84.0 KNm to 54.0 KNm. The stress profile for the varying load ran without interruption with a load change frequency of c. 3.7 per minute (222 load changes per hour). A total of 280,000 load changes were carried out.

“Lyon Confluences” Shopping Mall In 2010 another large project involving the use of ETFE foil cushions will be completed in France, the Pole de Loisirs et de Commerces “Lyon Confluences”. The slender, partly freestanding roof construction is particularly striking. In this case the long axis of the diamond-shaped cushions between the steel beams has a length of 24 metres. This is around 1.5 times as long as the cushions in the Allianz Arena. This is made possible by the 300-μm foil now available which can be used even where high wind loads must be expected. It is used in the edge areas of the upper layer which are subjected to sizable stress. The short axis measures 4.5 metres, and is thus approximately the same in both projects.

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Test rig As at the time our firm did not yet have its own laboratory we commissioned the Central Structural Engineering Laboratory of Stuttgart University (Professor Werner Sobek) to carry out the loading tests on the glass fins. The institute simulated deformations of the fin under various loads up to the theoretical breaking load. To carry out the test the team set up a test rig with a steel shoe support. This was equipped with a pneumatic drive to apply variable loads (fig. 6). Calibrated gauges at the point where the fin meets the steel shoe (movements directly in the support / in the mortar bed) and at the end of the fix (maximum amplitude) recorded the values and the deformations. As the clearance depends on the thickness of the mortar bed, in a second test the team used a thinner mortar bed (3 mm instead of the original 7 mm). In addition they

Results At the start of the first loading test there was a noticeable increase in the clearance. After relatively few load changes this began to flatten off asymptomatically. After 12,000 stress reversals with 100 % of the working load there was no recognisable damage to the mortar bed. The resulting play of the fin in its support and the reduced bearing areas did not give reason to fear any unacceptably high stress values in the glass fin. Therefore the glass fin fulfilled its requirements in terms of the structural calculations. However, the relatively large clearance of the glass fin support was not satisfactory. By reducing the thickness of the mortar bed it was possible to reduce the clearance that developed after a few load changes by about 50 % in comparison to the first series of measurements. Even after 280 000 stress cycles with the programme described and additional extreme loads the inspectors did not note any serious signs of wear in the glass fin bearing or fixing. The deformation of the steel cables has a far greater influence on the overall deformation behaviour of the construction than the mortar bed fixing of the glass fin. Thus the safe transfer of all wind loads occurring on the

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Laboratory for Steel and Lightweight Metal Construction of Munich University of Applied Sciences

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facade should be guaranteed for a building life of 50 years. Membranes and foils – light and climate tests The research and development laboratory of seele cover undertakes the material testing of membranes and foils. The universal testing machine stationed there with a temperature chamber (-40 °C to +100 °C) and contact-free measurement of expansion allows important values to be calculated for different simulated environments. As a rule large 1:1 foil cushion mock-ups are erected and tested at Gersthofen; examples include the rain penetration test on samples for the climbing hall in Neydens or the sample set up for the shopping mall in Lyons. In the latter case we tested the colour effects of differently printed opaque and transparent membranes. A crane hired especially for the purpose lifted the 20 t and 25 ≈ 10 ≈ 5 m sample to a height of 30 metres. This spectacular test took place at night in the presence of the architects and lighting designers (fig. 9). Laboratory for Steel and Lightweight Metal Construction of Munich University of Applied Sciences, Prof. Ö. Bucak Themes relating to structural glass and facade building such as laminated glass interlayers, the load-bearing behaviour of laminated glass, glued steel-glass constructions and the load-bearing behaviour of curved panes are among the focal points of research work carried out in the laboratory for steel and lightweight metal construction at Munich University of Applied Sciences. Trials and examinations of new constructions and products as well as the production of expert reports also form part of the work. Our laboratory is commissioned by industry, public authorities, and the courts, as well as by architects and engineers offices. We employ nine engineers, six of whom deal mostly with the area of glass building and glass constructions.

10

glass products used in construction. The most recent research programmes (for instance 3TVB, LAKKI, Back-Point) deal thematically with the research and development of adhesive technology as an alternative jointing method in structural glass building. Here we cooperate to a certain extent with other research centres, including the Steel Construction Faculty of the RWTH Aachen and the Workgroup Materials and Surface Technologies at the Technical University of Kaiserslautern (AWOK). In addition to our activities as a research centre and testing institute, every year we organize a two-day specialist meeting on “Glass in Structural Engineering”. This event is planned for between 300 and 350 participants and is directed primarily at those working in the field of structural glass building, architects and engineers.

4 – 6 department store facade Chemnitz: 4 close-up of the glass fin/steel shoe construction 5 test series 2: a load intervals b loading programme 6 test set-up/frame 7 + 8 staff test the material quality and structural behaviour of a glass stairs for a project in Osaka using pendulum impact tests and loading with sandbags. 9 1:1 mock-up for light, mechanical and physical tests for the “Lyon Confluences” events and shopping centre, Lyon 10 Rain penetration resistance test on a mock-up for Migros, Neydens 11 Long-term loading test on all glass stairs

Test set-ups There follows a description of a number of constructions and test set-ups from the research projects mentioned above. In the research programme “adhesive connections for structural glass” we dealt with new connecting elements developed especially for silicone adhesive connections. Here we examined different geometries of adhesion (fig. 12) as well as different types of new glued point fixings in terms of their load-bearing and deformation behaviour (fig. 13). For the 3TVB research project we loaded a glued laminated beam (span 6 metres) in a four-point bending test

The laboratory for steel and lightweight metal building has been certified as a testing centre by DIBt, both nationally (BAY27) and at a European level (NB1643), for a variety of products including 11

99

Testing and Inspection Procedures

DIBt The Deutsches Institut für Bautechnik (DIBt) is a joint institute of the Federal and Länder Governments whose purpose is to achieve the uniform fulfilment of technical tasks in the field of public law. These tasks include in particular: • Granting of European technical approvals for construction products and systems, • Granting of “national technical approvals” for construction products and types of construction, • Approval of testing laboratories, inspection bodies and certification bodies for tasks within the framework of the Ü-Zeichen (‚Ü mark‘) and the CE marking of construction products • Publication of Construction Products List A, B and C (see p. 96) DIBt (Deutsches Institut für Bautechnik) is a member of EOTA (European Organisation for Technical Approvals) and of UEAtc (The European Union of Agrément).

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Laboratory for Steel and Lightweight Metal Construction of Munich University of Applied Sciences

12

13

until failure (fig. 14 a + b). As well as glued beams this programme that deals with new components for structural glass building also examines glued steel-glass-columns and completely transparent glass-glass frame corners which make a particularly light impression. In addition to the examples mentioned for publicly funded research, many of our projects are commissions from industry. In particular, innovative companies in the field of structural glass and facade building come to us to get the load-bearing capacity of their newly designed elements confirmed by testing. These tests often deal with the individual building parts of particularly innovative constructions. For example for seele we tested the stairs and parapets intended for the store of a computer manufacturer. This was a new kinds of all-glass construction that had not been carried out in Germany before. For this reason extensive testing programmes, on the bearing capacity and residual capacity among others, were necessary (fig. 17). These showed that the construction reached the required safety level.

that enable us to carry out large building part tests. With the equipment mentioned above we can also, by means of experiments, produce verifications for bolted cable constructions (cables for seele, fig. 18). For a research programme into explosion stress we rebuilt a testing machine in the laboratory so that we were able to simulate explosion loads on materials in the area of high expansion rates. We also have testing machines to undertake fatigue tests on steel samples. These are a further focus of our work. In all the laboratory has more than 25 testing machines, several ovens, low temperature chambers and conditioning cabinets as a climate test chamber with internal dimensions of 2.80 ≈ 7.50 metres.

Testing facilities In addition to testing facilities specifically for glass and facade construction which include a vacuum testing centre measuring 2.60 ≈ 6.0 metres, the laboratory also has testing machines with a tensile force ranging from 10 kN (Kilonewton) to 12 MN (1200 t) and an 8 MN (800 t) compression press (fig. 15). Single-cylinder engines are also available

Some of our projects Our projects include: • Load-bearing capacity and residual strength tests for the staircase and parapets in the stores of a computer manufacturer in San Francisco, New York, Tokyo and Munich for seele (fig. 17; fig. 11, p. 99) • Load-bearing capacity and residual strength tests on the spherically curved insulated glazing panels of the Elbphilharmonie in Hamburg (Gartner, Interpane) • Petuelring Tunnel in Munich (Stadtwerke München) • Examination of the stability and loading capacity of glass beams and fins

14a

14b

Laboratory for Steel and Lightweight Metal Construction of Munich University of Applied Sciences

15

• Examination of the durability and residual strength of stone-glass laminates • Examination of the load bearing capacity and resistance of structural bonding with highstrength adhesives. • Tests for various zoos (glass-walled enclosures; calculation of impact loads for cattle, tigers, polar bears and gorillas, among other animals). For a cattle enclosure in a German zoo our laboratory was asked to comment in an expert report on the dimensioning of a planned glass protective screen. The force of the load that results from an attempt to escape depends primarily on the speed and weight of the animal. While the zoo experts had such data ,these were valid only for animals living in the wild. As a rule animals in captivity are larger and, generally speaking, are described as “lethargic”. On the basis of these data we devised an alternative with equivalent dynamic qualities and carried out a pendulum impact test on the planned glass pane. This then enabled us to determine the relevant loads and glass thicknesses (fig. 16).

17

16 12 Different kinds of adhesive geometries 13 Glued point fixings 14 a + b Hybrid bonded steel and glass beam before and after failure 15 Vierendeel girder with glass bracing under a bending load in an 800-tonne testing machine 16 Pendulum impact test for an animal enclosure 17 Loading capacity test on a glass step 18 Variable load testing of steel cable clamps for a steel and glass facade

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LIST OF SEELE PROJECTS • APPENDIX

Steel and Glass Constructions

Berlin Brandenburg International Airport, D From 2011 onwards all national and international air traffic in the Berlin-Brandenburg region will be concentrated at Schönefeld Airport, in the southeast of the city. The terminal building is the central element and the head of the complex. The concept is based on a “spine” formed by the central axis of the parallel take-off and landing runway systems. The main circulation elements are organized around this axis. The passenger terminal consists of main terminal with a pier in front of it. seele was commissioned to fabricate and fit the facades and roof surfaces for the passenger terminal construction phase 2, the terminal hall and the pier.

Architect pgbbi: gmp Architekten/ J.S.K Architekten/IGK-IGR Client Flughafen Berlin Schönefeld GmbH Structural design/facade design Schlaich Bergermann und Partner/ Schüßler-Plan Ingenieurgesellschaft/ Prof. Michael Lange Ingenieurgesellschaft mbH Completion 2011

Museum of Fine Arts, Boston, USA In addition to the redesign and renovation of the two historic entrances and the visitor centre this project also includes a new exhibition wing and a glazed roof to a courtyard at the centre of the complex. Reopening the two museum entrances creates a central north-south axis. The glass-roofed Ruth and Carl J. Shapiro Family Courtyard forms a connecting element between the existing buildings and the new American Wing. Centrally located and in close proximity to the visitor centre, it is a meeting point for visitors and a location for events held outside of normal museum opening times.

Architect Foster + Partners Client Museum of Fine Arts Structural design/facade design Buro Happold/Simpson Gumpertz & Heger Façade area 8000 m2 Completion 2011

Elm Park, Dublin, IRL Dublin 4 is one of Dublin’s most elegant residential districts, within easy reach of the city centre. Elm Park office, residential and leisure complex by architects Bucholz McEvoy stands on a green site about 6 hectares in area. The basic architectural concept of the elongated buildings includes natural ventilation which is achieved by means of a twin-skin facade. seele undertook the design and execution of the double facades, the free-spanning glass roofs and the winter gardens. The large double facade on the west side is a successful combination of wooden beams, steel construction, aluminium sections, coloured glass and timber claddings. It is continued above the height of the compact building behind it. Ventilation flaps at the back of this uppermost part of the facade enable the different storeys to be cross-ventilated. The prevailing west wind creates considerable negative pressure at ventilation flaps facing away from the wind that draws in cooler air in front of the east facade. When the air inside the double facade is warmed and begins to rise, it assists this air flow. In the winter gardens the double facade is continued as a roof plane. A horizontal, 30-meter long laminated timber beam with steel bracing transfers the loads from the roof construction.

Architect Bucholz McEvoy Architects Structural design/facade design RFR Paris Completion 2008

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List of seele projects

Steel and Glass Constructions

Architect Make Client Geoff Springer London & Regional Properties London Structural design/facade design Expedition Engineering Completion 2008

Baker Street London, UK The glazed roof structure in Baker Street in London was made in the course of refurbishing a commercial complex dating from the 1950s. It is made up of three roofs, the central element hovers at a height of 17 metres above a 400 m2 atrium. A diagonally spanned steel band connects the three elements to form a self-supporting construction that sits above the existing building, decoupled from it by hinged columns. In working out the geometry of the connections between the glass skin and the existing building, as well as the constructional and technical details, all parts and building element groups were designed in 3D.

Architect BPR Architects Client Middlesex University Structural design/facade design Dewhurst Macfarlane and Partners Completion 2005

Hendon Quadrangle, London, UK The courtyard of Hendon University in London which is covered by a steel and glass folded plate roof, functions as a forum and meeting place for students attending Middlesex University Business School and the School of Computing Sciences. The space is dominated by the glass roof resting on four symmetrically positioned “tree columns”. One of the major challenges presented by this construction was making a wind and weatherproof connection to the existing building. The folded plate roof placed on hinged columns on the roof cornice is connected by continuous 30 cm high bellow-type seals and can therefore move in all directions while still remaining weather-tight.

Architect Murphy/Jahn Client Bayer AG Structural design/facade design Werner Sobek Façade area 11,850 m2 Completion 2001

Headquarters Bayer AG, Leverkusen, D Under the leadership of architect Helmut Jahn a modern administration building was erected in the grounds of Bayer AG in Leverkusen that, thanks to its transparent aesthetics and ecologically sustainable approach, provides a contrast to the existing buildings in its surroundings. The wings of this semi-elliptical building are terminated by a twin-shell facade consisting of an aluminium construction as the inner shell and a suspended allglass facade as the outer layer. The double facade is a decisive component in the building’s energy concept. The facade glazing, both toughened glass and laminated safety glass, rests on vertical glass fins by means of cast stainless steel fittings. The facade cavity is ventilated by over 966 glass flaps that are opened by stainless steel fittings and centrally positioned motors. The highlight of the building is the glazed entrance hall at the centre that divides the building into two wings. The high degree of transparency and transmission of light achieved by the cable-spanned facade with an area of almost 1250 square metres is particularly impressive. To achieve this effect around 70 steel cables hanging from the roof structure were anchored to the ground by spring brackets. Their tension is set so that under wind pressure the all-glass facade can deflect by up to 90 cm.

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Steel and Glass Constructions

Galeria Kaufhof, company headquarters, Chemnitz, D The Galeria Kaufhof department store and multistorey car park building stands at a prominent location opposite Chemnitz Town Hall. For the facade glazing both suspended and standing constructions were used. Almost 1000 insulated glass panes measuring 2 ≈ 4 metres held together by clamp fixings form a dematerialized glass surface. The facades are suspended by tension rods running in the vertical joints from the 4th to the 1st floor. At the main entrance, where the facade spans 18 metres, it is braced in the longitudinal direction by horizontal fins of laminated safety glass.

Architect Murphy/Jahn Client MRE – Metro Real Estate Management GmbH Structural design/facade design Werner Sobek Facade area 7400 m2 Completion 2001

Airport Cologne/Bonn, D The important design elements of this terminal are the 12,000 m2 fully glazed, cable-spanned facade and a glass and steel roof measuring almost 23,000 m2 whose opened flaps and slender branching structure recall the lightweight construction methods used for aircraft. The individual segments of the roof, 40 metres long and 6.5 metres wide, hover apparently weightlessly above 22 steel “treecolumns”. The continuous system of ridges that run at 45° degrees to the facade and geometrically intersect presented a major technical challenge.

Architect Murphy/Jahn Client Flughafen Köln/Bonn GmbH Structural design/facade design IG Tragwerksplanung Facade area 35,000 m2 Completion 1999

Entrance hall Bremen University, D Together with the Fallturm, or drop tower, the glazed entrance hall to Bremen University is one of the symbols of the campus. It has a floor area of 22 ≈ 43.5 metres and is joined on two sides to the existing university building. A visually slender steel grillage hovers at a height of 15 metres, resting in the entrance area on six V-columns and braced at the rear against the university building by means of six hinged columns. The roof surface consists of an accessible triple glazing made of one 6 mm layer of printed toughened glass and 2 ≈ 8 mm layers of heat strengthened glass. Five hologram discs in the roof plane increase the amount of daylight in the hall.

Architect Störmer Murphy and Partners Client Bremer Hochbau management Structural design/facade design Werner Sobek Facade area 1100 m2 Completion 1999

Grand Theatre, Shanghai, VRC The Grand Theatre in the historic centre of the Chinese metropolis Shanghai is regarded as one of Asia’s most modern opera houses. For this building Jean-Marie Charpentier designed a curved roof. An important feature of the design is the foyer glazing that hangs like a matt veil in front of the sculpturally shaped internal structure. Inverting normal structural principles, the solid concrete half shell rests on the transparently glazed colonnaded plinth. Large sheets of 15 mm thick toughened white glass are joined to form a smooth facade extending from the widely cantilevering roof structure to the ground floor slab.

Architect Arte Charpentier Architectes Client Engineering Department of Shanghai Grand Theatre Facade area 3600 m2 Completion 1997

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List of seele projects

Foils and Membranes

Architect Herzog & de Meuron Design Consortium Herzog & de Meuron, Arup, China Architectural Design & Research Group Artistic Advisor Ai Weiwei, Peking Client National Stadium Co., Ltd., Peking/ VRC Material EFTE, PTFE Membrane area 46,000 m2 Completion 2008

“Bird‘s Nest”, National Stadium Peking, VRC Peking’s national stadium, popularly known as the “Bird’s Nest”, is regarded by experts as a masterpiece in terms of logistics, technology and craftsmanship. The stadium consists of a “woven” steel structure and an internal concrete “cauldron”. The primary structure is formed by 24 portal beams. A secondary structure of columns and struts supports this construction. A translucent membrane provides protection against the elements. This 250 μm thick ETFE foil is printed with pattern of silvery grey dots to modulate the amount of light entering. The 38,000 m2 membrane is made up of 880 bays, measuring up to 216 m2 in area, which are supported by 4690 stainless steel cables.

Architect HOK Asia Pacific Client Suzhou Harmony Group Material ETFE, PTFE Membrane area 9500 m2 + 800 m2 Completion 2008

Suzhou Industrial Park, Suzhou, VRC SIP, one of China’s most modern industrial parks, is under joint Singapore/Chinese management. The total floor area of the complex is 210,000 m2 and consists essentially of a business zone, a recreation zone and a shopping mall. The centre point of the shopping mall is one of the longest LED roofs in the world. With a length of 500 metres and a width of 32 metres, around 20 million LEDs are mounted on a PTFE mesh membrane. 292 air cushions make the roof watertight. The contractor devoted particular attention to inspecting the steel structure and fitting the cushions without creases.

Architect Grand Architects Client Fondation du Centre Mondial du Cyclisme Aigle Material PVC-PES Membrane area 10,000 m2 Completion 2001

Aigle Velodrome, CH The Grand Architects office from Lausanne roofed the elliptical velodrome in Aigle with a double-skin pneumatic membrane construction. With dimensions of 90 ≈ 70 m and a membrane area of 5000 m2 this membrane cushion is one of the largest constructions of its kind in the world. In plan the steel structure consists of three compression rings, one inside the other, and connected by “spokes” made of hollow tubular sections. The outer ring is made as a space frame. Between there are vertical “flying masts”, each of which is braced above and below by a pyramid formed by four tension rods.

Architect ABB Architekten Client BMW AG Material PVC-PES, ETFE Membrane area 6500/1500 m2 Completion 2001

BMW trade fair stand Frankfurt a.M., D For the presentation of the new BMW-7 series at the IAA 2001, ABB Architekten designed a futuristic pavilion, called the “Dynaform”. Laser-cut hollow steel box sections form the 130 m long load-bearing structure that weighs 700 t. The roof is formed by 6600 m2 of membrane made of PVC-coated polyester fabric. In contrast to standard practice the PVC PES textile membrane was spanned in one dimension only, in the long axis of the pavilion. The two short ends are closed with low pressure cushions made from 500 m2 of transparent ETFE foil and white PVC polyester fabric.

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Element Facades

Hotel Wagram, Paris, F Hotel Wagram is on the eponymous Avenue Wagram, one of the splendid Parisian streets that run towards the Arc de Triomphe. The hotel front is articulated into three glass facades that differ in design and construction: the restaurant, the “vitrine” and the undulating main facade to the hotel bedrooms. The first two facades describe straight lines and are made of glass panes measuring 2 ≈ 4.30 metres, the vertical joints between the panes are sealed with silicone. The wavy facade of the upper floors is made up of curved insulated glazing with eleven different geometries and radii ranging from 900 to 2300 mm.

Architect Atelier Christian de Portzamparc Client SAS Wagram Structural design/facade design Van Santen & Associés Facade area 1400 m2 Completion 2009

John Lewis Department Store Leicester, UK Foreign Office Architects (FOA), London won the competition for the design of the new John Lewis shop in Leicester with a radical proposal: a shimmering, net-like curtain – which in the dark is back-lit in 256 changing colours – encloses the 25,000 m2 of the new building. The ornamented all-glass facade makes a reference to the origins of the John Lewis Company in the world-wide textile trade. The motif is a historic pattern dating from the 18th century. The facade consists of two glass layers set a distance of 80 cm apart, they are congruently printed with the same motif, applied differently to each of the two layers.

Architect Foreign Office Architects Client Shires GP Ltd. Structural design/facade design Adams Kara Taylor Completion 2008

Seattle Public Library, USA The Central Library rises up in the centre of Seattle like an oversized stack of books. Rem Koolhaas put together five completely glazed building parts, each several storeys high and staggered in relation to each other to make an eleven storey library building with a footprint measuring 60 ≈ 65 metres. The result is a light-flooded, cubically folded building. Each element defines a library cluster for a particular function. The glass facade measures almost 12,000 m2 and gives the “crystal” its face. Vertical external surfaces are blended with parts of the facade that slope inwards and outwards, which represented an enormous challenge in terms of detailing and fitting the external skin. A total of 9994 panes were fitted, one third of these were special one-off sizes. A secondary structure of small-scale diamond-shaped steel mesh placed on the primary structure of large steel beams provides the necessary earthquake stiffness and shapes the building’s architecture. The glass panes are fixed using a cover strip that allows them to slide and in this way are decoupled from the movement of the building. This enables the construction to meet the stringent requirements of building in this earthquake zone. Differently treated types of glass ensure a pleasant atmosphere inside the building despite its great transparency.

Architect OMA/LMN Joint Venture Client Seattle Public Library Structural design/facade design Skilling Ward Magnusson Berkshire Facade area 11,900 m2 Completion 2004

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List of seele projects

Structural use of Glass

Architect Gabellini Sheppard Associates LLP Client Westfield Shoppingtowns Ltd. Structural design/facade design Eckersley O’Callaghan Facade area 4000 m2 Completion 2008

Westfield West Village London, UK In addition to the spectacular roof over the shopping arcades, a further eye-catcher in Westfield shopping mall is the glazing of the shop fronts. It is made up of panes up to 8.5 metres tall that create a “facetted” all-glass facade with an area of 4000 m2. The joints are open and the panes are connected at only a few points by clamps. The stiffening that is structurally necessary is provided by glass fins at right angles to the tall shop fronts. These fins are made of 3 ≈ 10 (12) mm sheets of float laminated safety glass which are bonded with SPG foils. The shop front glazing and the staggered fins describe a zigzag line in plan, the fins sitting against the glass surface of the shop windows.

Architect RMJM Client Abu Dhabi National Exhibitions Company Facade area 8000 m2 Completion 2007

Abu Dhabi National Exhibition Centre, UAE As they meander in a U-shape across the trade fair site, the eleven elongated halls form internal atria, halls or, somewhat further apart, large circulation areas for deliveries or for parking. Particularly striking features include the gently rounded corners and the roof structure that curves to form a soft transition to the continuous inclined glazing. Hinge-fixed 8.5 metre tall glass fins compensate the movement of the steel roof structure and support the glass facade with clamps at their short end. Almost 8000 m2 of insulated glazing – flat or, at the corners, curved and conically tapering, forms a transparent band.

Architect Gensler/ Daroff Design Client Comcast Philadelphia Structural design Thornton Tomasetti Completion 2007

Comcast glass staircase, Philadelphia, USA Comcast is a US telecommunications business based in Philadelphia, Pennsylvania. On the 51st floor of the new headquarters a free-standing allglass staircase connects the three levels occupied by the senior management. The construction rests on the floor plane while two 20 m tall steel columns rising between the flights of the staircase are fixed to the uppermost floor slab. The flights are connected to the floor slabs. In addition to the laminated glass fins, the handrail also functions as a structural element. The bearings are bolted to the strings; the fittings are directly laminated to the treads.

Architect Kohn Pedersen Fox Associates Client Unilever Plc Structural design/facade design Arup Facade area 6800 m2 Completion 2007

Unilever Headquarters, London, UK The headquarters of Unilever, the third largest producer of foodstuffs in the world, is located in the heart of the British capital. The complete gutting of the existing building was followed by a major redesign of the interior featuring a continuous atrium that is lit by a glazed roof and a completely glazed west facade. Thanks to almost invisible vertical joints the atrium glazing forms a seamless, meandering glass band. The horizontal emphasis is further strengthened by the glass fibre reinforced plastic cladding to the parapets that seem to connect with each other as if poured in one cast.

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Structural use of Glass

Maximilianmuseum Augsburg, D The Maximilianmuseum is the main building of Augsburg’s art collections and museums. An extensive renovation and modernisation of the existing building complex consisting of two historic burghers’ houses was carried out between 1999 und 2002. So that the courtyard could be used to exhibit sculpture it was given a delicate, barrel-vaulted glass roof. Together with structural designers Ludwig & Weiler, the seele engineers developed a slender lightweight construction – modern but at the same time respecting the historic building fabric. A total of 527 glass panes span the historic courtyard that measures 37 ≈ 14 m. The all-glass shell required a minimum of solid building elements. Only the tubular frame defines the outlines of the vaulted shape and rests on slender columns that adapt flexibly to the complex bearing situations on the right-hand and left-hand sides. The shell of the barrel vault with its twodimensional curvature allowed uniformly sized panes to be produced in advance, a solution with considerable economic benefits. The compressive stress in the structure is directed into nodes. The panels have stainless steel caps at the edges with which they rest on the node plate. The node is friction-grip fixed to the steel caps by means of a central pin with adjustable screws.

Architect Hochbauamt der Stadt Augsburg Head: Dipl.-Ing.(Univ.) Günter Billenstein Client Kulturreferat der Stadt Augsburg Structural design/facade design Ludwig & Weiler Ingenieurgesellschaft mbH, Augsburg Facade area 560 m2 Completion 2000 (1.BA)

Glass bricks The idea of shaping a brick and stacking it in courses to form a wall is almost as old as the history of mankind. The system “brick plus joint” has been varied and optimized over the course of the centuries, a development that still continues today. The new glass brick, made up of layers laminated to form a block, has a transparency that makes it seem almost weightless. Combined with traditional bricklaying skills, its crystalline appearance allows new design solutions for interiors and facades to be discovered. In re-examining the idea of the wall, designers can unlock the potential of the glass brick. Structural insulating glass element A further step in carrying out glass facades that are divorced as far as possible from a load-bearing substructure is the insulated glass element with rigid edge bonding. In fact it is a transparent “box section” with an astonishing load-bearing performance. The “flanges” formed by the outer and inner laminate leaf of the unit are connected by the “webs”, a newly developed shear-rigid bonding technique along the edges of the panes. Spans of 6 to 8 metres high, with pane widths of up to 3 m using insulating glass of almost standard thicknesses allow the construction of transparent walls.

Span 6–8 m Pane width Up to 3.0 m Thermal insulation UCw to 0.8 W/m2K Fall protection All categories Noise insulation Very good

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Appendix

Testing Standards

Testing Standards for Glass

Testing Standards for Films

(selection)

(selection) DIN 16906:2007-10

Testing of plastic sheeting and plastic films – Sample and specimen – Preparation and conditioning

DIN 18204-1:2007-05

Components for enclosures made of textile fabrics and plastic films (awnings) for structures and tents – Part 1: PVC coated polyester base fabric

DIN 53122-1:2001-08

Testing of plastics and elastomer films, paper, board and other sheet materials – Determination of water vapour transmission – Part 1: Gravimetric method

DIN 53351:2003-09

Testing of artificial leather and similar sheet materials – Behaviour under permanent folding (Flexometer-method)

DIN 53363:2003-10

Testing of plastic films – Tear test using trapezoidal test specimen with incision

DIN 53370: 2006-11

Testing of plastics films – Determination of the thickness by mechanical scanning

Glass in building – Insulating glass units – Part 6: Factory production control and periodic tests

DIN 53377: 2007-10

Testing of plastic films - Determination of dimensional stability

DIN EN 1288-3:2000-09

Glass in building – Determination of the bending strength of glass – Part 3: Test with specimen supported at two points (four point bending procedure)

DIN 53380-2: 2006-11

Testing of plastics – Determination of gas transmission rate – Part 2: Manometric method for testing of plastic films

DIN EN 1288-4:2000-09

Glass in building – Determination of the bending strength of glass – Part 4: Testing of channel shaped glass

DIN 53380-3:1998-07

Testing of plastics – Determination of gas transmission rate – Part 3: Oxygen-specific carrier gas method for testing of plastic films and plastics mouldings

DIN EN 12150-1:2000-11

Glass in building – Thermally toughened soda lime silicate safety glass – Part 1: Definition and description

DIN 53380-4:2006-11

DIN EN 12153:2000-09

Curtain walling – Air permeability – Test methods

DIN EN 12155:2000-10

Curtain walling – Watertightness – Laboratory test under static pressure

Testing of plastics – Determination of gas transmission rate – Part 4: Carbon dioxide specific infrared absorption method for testing of plastic films and plastic mouldings

DIN EN 495-5:2001-02

DIN EN 13830:2003-11

Curtain walling – Product standard

Flexible sheets for waterproofing – Determination of folding behaviour at low temperature – Part 5: Plastic and rubber sheets for roof waterproofing

DIN EN ISO 62: 2008-05

Plastics – Determination of water absorption (ISO 62:2008)

DIN EN ISO 291:2008-08

Plastics – Standard atmospheres for conditioning and testing (ISO 291:2008)

DIN EN ISO 527-1:1996-04

Plastics – Determination of tensile properties – Part 1: General principles (ISO 527-1:1993 including Corr 1:1994)

DIN EN ISO 527-3:2003-07

Plastics – Determination of tensile properties – Part 3: Test conditions for films and sheets (ISO 527-3:1995 + Corr 1:1998 + Corr 2:2001) (includes Corrigendum AC:1998 + AC:2002)

DIN EN ISO 2286-1:1998-07

Rubber- or plastics-coated fabrics – Determination of roll characteristics – Part 1: Method for determination of the length, width and net mass (ISO 2286-1:1998)

DIN EN ISO 6721-1:2003-01

Plastics – Determination of dynamic mechanical properties – Part 1: General principles (ISO 6721-1:2001)

DIN EN ISO 6721-2:2008-09

Plastics – Determination of dynamic mechanical properties – Part 2: Torsion-pendulum method (ISO 6721-2:2008)

DIN EN ISO 10350-1:2008-11

Plastics – Acquisition and presentation of comparable single-point data – Part 1: Moulding materials (ISO 10350-1:2007)

DIN EN ISO 11403-1:2003-09

Plastics – Acquisition and presentation of comparable multipoint data – Part 1: Mechanical properties (ISO 11403-1:2001)

Draft DIN EN 15977:2009-08

Rubber or plastic coated fabrics – Mechanical properties – Determination of the elongation under load and the residual deformation

DIN ISO 1817: 2008-08

Rubber, vulcanized – Determination of the effect of liquids (ISO 1817:2005)

DIN EN 356:2000-02

Glass in building – Security glazing – Testing and classification of resistance against manual attack

DIN EN 1279-1:2004-08

Glass in building – Insulating glass units – Part 1: Generalities, dimensional tolerances and rules for the system description

DIN EN 1279-2:2003-06

Glass in building – Insulating glass units – Part 2: Long term test method and requirements for moisture penetration

DIN EN 1279-3:2003-05

Glass in building – Insulating glass units – Part 3: Long term test method and requirements for gas leakage rate and for gas concentration tolerances

DIN EN 1279-4:2002-10

Glass in building – Insulating glass units – Part 4: Methods of test for the physical attributes of edge seals

DIN EN 1279-6:2002-10

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Testing Standards /Bibliography

Bibliography ISO 11502:1995-09

Plastics – Film and sheeting – Determination of blocking resistance

ISO 20753:2008-03

Plastics: Test specimens

Draft DIN 16726:2008-02

Plastic sheets – Testing

Draft DIN EN 15977: 2009-08

Rubber or plastic coated fabrics – Mechanical properties – Determination of the elongation under load and the residual deformation

Draft DIN EN ISO 4611:2008-05

Plastics – Determination of the effects of exposure to damp heat, water spray and salt mist (ISO 4611:2008)

Draft DIN EN ISO 6721-1/ A1:2008-05

Plastics – Determination of dynamic mechanical properties – Part 1: General principles – Amendment 1 (ISO 6721-1:2001/DAM 1:2008)

Draft DIN EN ISO 6721-2:2008-01

Plastics – Determination of dynamic mechanical properties – Part 2: Torsion-pendulum method (ISO/FDIS 6721-2:2008)

Draft Plastics – Differential scanning calorimetry (DSC) – DIN EN ISO 11357-1:2008-04 Part 1: General principles (ISO/DIS 11357-1:2008) Draft prEN ISO 1043-1: 2008-12

Plastics – Symbols and abbreviated terms – Part 1: Basic polymers and their special characteristics (ISO/DIS 1043-1:2008)

Draft prEN ISO10432:2008-12

Plastics – Symbols and abbreviated terms – Part 2: Fillers and reinforcing materials (ISO/DIS 1043-2:2008)

Draft DIN ISO 812: 2008-08

Rubber, vulcanized or thermoplastic – Determination of low-temperature brittleness (ISO 812:2006)

Statistical evaluation of test results DIN 53598-1: 1983-07

Statistical evaluation at off-hand samples with examples from testing of rubbers and plastics

DIN 53803-1: 1991-03

Sampling; statistical basis; one-way layout

DIN 55303-2: 1984-05

Statistical interpretation of data; tests and confidence intervals relating to expectations and variances

DIN 55303-2 Beiblatt 1: 1984-05

Statistical interpretation of data; operating characteristics of tests relating to expectations and variance

DIN ISO 3534-1: 2009-10

Statistics - Vocabulary and symbols – Part 1: General statistical terms and terms used in probability (ISO 3534-1:2006)

DIN ISO 10576-1: 2009-10

Statistical methods - Guidelines for the evaluation of conformity with specified requirements – Part 1: General principles (ISO 10576-1:2003)

Achilles, Andreas u. a.: Glasklar: Produkte und Technologien zum Einsatz von Glas in der Architektur. Munich 2003 Ambrose, James/Tripeny, Patrick: Simplified Design of Steel Structures. Hoboken 2007 Arbeitsgemeinschaft für Industriebau e. V.: Stahl, Glas und Membranen im Industriebau. Ein Leitfaden für Architekten, Ingenieure und Unternehmen. Munich 2003 Behfar, S. M. u. a: Stahl im Hochbau. Düsseldorf 1995 Behling, Stefan u. Sophia: Konstruktion und Technologie in der Architektur. Munich 2000 Behnisch, Günter/Hartung, Giselher: Glas- und Eisenkonstruktionen des 19. Jahrhunderts in Grossbritannien. Darmstadt 1984 Bell, Michael: Engineered Transparency – The Technical, Visual, and Spatial Effects of Glass. New York 2009 Bißbort, Sonja u. a.: DVG Hannover. Stuttgart 2003 Blanc, Alan/McEnvoy, Michael: Architecture and Construction in Steel. London 1993 Compagno, Andrea: Intelligente Glasfassaden: Material, Anwendung, Gestaltung. Basel 2002 Crafti, Stephen: Houses of steel. Mulgrave 2009 Crisinel, Michel u. a.: EU COST C13 Glass and Interactive Building Envelopes. Delft 2007 Crosbie, Michael J.: Curtain Walls. Recent Developments by Cesar Pelli and Associates. Basel 2006 Eggen, Arne P., Sandaker, Bjørn N.: Stahl in der Architektur. Konstruktive und gestalterische Verwendung. Stuttgart 1996 Elstner, Michael: Beschichtungen auf Glas für die architektonische Anwendung. In: Detail, Nr. 07+08/2009 Friemert, Chup: Die gläserne Arche. Kristallpalast London 1851 und 1854. Munich 1988 Fröhler, Alfons W.: Lexikon für Glas und Glasprodukte. Schorndorf 2005 Grimm, Friedrich: Energieeffizientes Bauen mit Glas. Grundlagen – Gestaltung – Beispiele – Details. Munich 2004 Grimm, Friedrich/Richarz, Clemens: Hinterlüftete Fassaden. Stuttgart 2000 Hank Haeusler, Matthias: Media Facades. History, Technology, Content. Ludwigsburg 2009 Hausladen Gerhard u. a.: Einführung in die Bauklimatik. Berlin 2003 Hausladen, Gerhard u. a.: ClimaSkin. Munich 2006 Heinz, Thomas A.: Frank Lloyd Wright’s Stained Glass & Lightscreens. Layton 2005 Herzog, Thomas u. a.: Fassaden Atlas. Basel 2004 Hess, Rudolf / Weller, Bernhard: Glasbau-Praxis in Beispielen. Berechnung und Konstruktion. Berlin 2005 Heusler, Winfried/Hindrichs, Dirk U.: Fassaden – Gebäudehüllen für das 21. Jahrhundert. Basel 2004 Hix, John: The Glasshouse. London 2005 Hochschule für Technik und Architektur (Hrsg.): Atrium. Glasüberdeckte Höfe und Hallen – ein interdisziplinäres Planungswerkzeug. Basel 2004 Holl, Christian/Siegele, Klaus: Metallfassaden. Munich 2007 Institution of Structural Engineers: Structural use of glass in buildings. London 1999 Kaltenbach, Frank: Transluzente Materialien. Munich 2003 Knaack, Ulrich u. a.: Fassaden. Basel 2007 Knaack, Ulrich u. a.: The Future Envelope 1. Amsterdam 2008 Kohlmaier, Georg/v. Sartory, Barna: Das Glashaus. Ein Bautypus des 19. Jahrhunderts. Munich 1988 Krampen, Martin: Glasarchitekten/Glass Architects – Konzepte, Bauten, Perspektiven. Ludwigsburg 1999 Kunz, Martin Nicholas u. a.: Glass Design. Cologne 2005 Leatherbarrow, David/Mostafavi, Mohsen: Surface Architecture. Cambridge 2005 LeCuyer, Annette: Stahl & Co. Neue Strategien für Metalle in der Architektur. Basel 2003 Lefteri, Chris: Glas – Material, Herstellung, Produkte. Ludwigsburg 2002 Loughran, Patrick: Falling Glass. Glasschäden in der neueren Architektur. Basel 2003 Lückmann, Rudolf: Baudetail-Atlas Fassaden. Kissing 2008 Marpillero, Sandro: James Carpenter. Environmental Refractions. Basel 2006 McGrath, Raymond: Glass in Architecture and Decoration. London 1961 Moor, Andrew: Architektur – Glas – Farbe: Zeitgenössische Beispiele. Munich 2006 Nijsse, Robert: Tragendes Glas. Elemente, Konzepte, Entwürfe. Basel 2003

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Appendix

Bibliography/Illustration Credits

Oberacker, Reiner: Glas- und Fenstertechnik 2008. Stuttgart 2008 Oesterle, Eberhard u. a.: Doppelschalige Fassaden. Munich 1999 Pottgiesser, Uta: Fassadenschichtungen – Glas: Mehrschichtige Glaskonstruktionen. Typologie, Energie, Konstruktionen, Projektbeispiele. Berlin 2004 Reichel, Alexander u. a.: Bauen mit Stahl. Munich 2006 Rice, Peter/Dutton, Hugh: Transparente Architektur. Glasfassaden mit Structural Glazing. Basel 2000 Richards, Brent, with photographs by Dennis Gilbert: New Glass Architecture. London 2006 Rothen, Beat u. a.: Wohnbau. Stuttgart 2005 Schulitz, Helmut C. u. a.: Stahlbau Atlas. Munich/Basel 2001 Sedlacek, Gerhard: Glas im Konstruktiven Ingenieurbau. Berlin 2009 Siebert, Geralt: Entwurf und Bemessung von tragenden Bauteilen aus Glas. Berlin 2001 Slessor, Catherine: See-Through Houses: Inspirational Homes and Features in Glass. London 2002 Stacherl, Rudolf: Das Glaserhandwerk. Renningen 2006 Staib, Gerald u. a.: Elemente und Systeme. Munich 2008 Thiekötter, Angelika u. a.: Kristallisationen, Splitterungen. Bruno Tauts Glashaus. Basel 1993 Uffelen, Chris van: Clear Glass: Creating New Perspectives. Berlin 2009 Voigt, Wolfgang: Felsen aus Beton und Glas. Die Architektur von Gottfried Böhm. Frankfurt am Main 2006 Wagner, Ekkehard: Glasschäden. Oberflächenbeschädigungen – Glasbrüche in Theorie und Praxis. Schorndorf 2008 Watts, Andrew: MBF Moderne Baukonstruktion Fassaden. Vienna 2005 Weitkamp, Mareike: Weitergedacht... Energetisches Optimierungspotential von Glasfassaden: Wärmebrückenanalysen, U-Werte, Oberflächentemperaturen. Saarbrücken 2008 Weller, Bernhard u. a.: Kleben im Bauwesen – Glasbau. In: Detail, Nr. 10/2004 Weller, Bernhard/Rexroth, Susanne: Material wirkt – Neue Entwicklungen an der Fassade. In: Detail, Nr. 11/2005 Weller, Bernhard u. a.: Konstruktiver Glasbau. Grundlagen, Anwendung, Beispiele. Munich 2008 Wigginton, Michael: Glas in der Architektur. Stuttgart 1997 Wörner, Johann-Dietrich: Glasbau. VDI-Buch. Berlin 2009 Woods, Mary/Warren, Arete: Glass Houses. A History of Greenhouses, Orangeries and Conservatories. London 1990 Wurm, Jan: Glas als Tragwerk: Entwurf und Konstruktion selbsttragender Hüllen. Basel 2007 Zahner, William L.: Architectural Metal Surfaces. Hoboken 2005

Membrane and foil architecture

Illustration credits The authors and publishers would like to express their sincere gratitude to all those who have assisted in the production of this book, be it through providing photos or artwork or granting permission to reproduce their documents or providing other information. All the drawings in this book were specially commissioned. Photographs not specifically credited were taken by the architects or are works photographs or were supplied from the archives of the magazine DETAIL. Despite intensive endeavours we were unable to establish copyright ownership in just a few cases; however, copyright is assured. Please notify us accordingly in such instances. The photographs kindly provided by seele came from the archives of the following photographers: • René Müller Photographie • Matthias Reithmeier, Diamond Graphics • Dominik Obertreis • Jochen Thieser • Weiss Werbefotografie P. 6, 10 right, 12 – 18, 24 – 27, 29 top, 31, 34 centre, 35 – 37, 38 top, 39, 48 – 49, 50 bottom, 54 – 56, 58, 60 – 69, 74, 76 – 79, 84, 86 bottom right, 90, 92 – 98, 99 top, 102 – 109: seele holding GmbH & Co. KG P. 8: IBK Forschung + Entwicklung/Michael Meyer, Stuttgart P. 9 top, 10 left, 83 bottom, 86 bottom left, 89 bottom: IBK Forschung + Entwicklung/Andreas Fuchs, Stuttgart P. 9 bottom: Jens Willebrandt, Cologne P. 19, 20 bottom, 21– 23: Hans Georg Esch, Hennef P. 20 top: Roland Pawlitschko, Munich P. 21 top, bottom: DS-Plan, Stuttgart P. 28, 38 bottom right: Westfield Shoppingtowns Limited, London P. 30, 31 top, 32 – 33, 34 top, 34 bottom: Knippers Helbig Ingenieure, Stuttgart P. 38 bottom left, 44, 46 bottom, 57 top, 85: Christian Schittich, Munich P. 40, 43 top, 47, 50 top, 51: Frank Kaltenbach, Munich

Barthel, Rainer u. a.: Frei Otto, das Gesamtwerk: Leicht bauen – natürlich gestalten. Basel 2005 Berger, Horst: Light Structures – Structures of Light: The Art and Engineering of Tensile Architecture. Bloomington 2005 Brinkmann, Günther: Leicht und Weit. Zur Konstruktion weitgespannter Flächentragwerke. Weinheim 1990 Boxer, Keith/Scheuermann, Rudi: Tensile Architecture in the Urban Context. New York 1996 Bubner, Ewald u. a.: Membrankonstruktionen. Essen 1999 Dalland, Todd/Goldsmith, Nicholas: FTL. Softness, Movement and Light: Innovations in Tensile Structures. London 1997 Höller, Ralf: FormFindung. Architektonische Grundlagen für den Entwurf von mechanisch vorgespannten Membranen und Seilnetzen. Mähringen 1999 Hoppe, Diether S.: Freigespannte Textile Membrankonstruktionen. Geschichtliche, materialtechnische, konstruktive und gegenwärtige Entwicklungen. Vienna 2007 Ishii, Kazuo: Membrane Designs and Structures in the World. Tokyo 1999 Koch, Klaus-Michael: Bauen mit Membranen. Munich 2004 LeCuyer, Annette: ETFE. Technologie und Entwurf. Basel 2008 Moritz, Karsten: Membranwerkstoffe im Hochbau. In: Detail, Nr. 06/2000 Moritz, Karsten/Barthel, Rainer: Transparente Architektur – Bauen mit ETFE-Folien. In: Detail, Nr. 12/2002 Moritz, Karsten: ETFE-Folie als Tragelement, Dissertation, Technische Universität Munich. Munich 2007 Schock, Hans-Joachim: Segel, Folien und Membranen – Innovative Konstruktionen in der textilen Architektur. Basel 1997 Seidel, Michael: Textile Hüllen – Bauen mit biegeweichen Tragelementen. Materialien, Konstruktion, Montage. Berlin 2008 Wagner, Rosemarie: Bauen mit Seilen und Membranen. Berlin 2009

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P. 43 bottom: Klaus Leidorf, Buch am Erlbach P. 46 top: Sailer Stepan Partner, Munich P. 52: Wacker Ingenieure, Birkenfeld P. 53: schlaich bergermann partner/Michael Zimmermann, Stuttgart P. 57: Max Prugger, Munich P. 70 bottom: SOM/ Tim Griffith, Chicago P. 70 top, 71 links, 72, 73 top: SOM, Chicago P. 71 right: Miller Hare Limited, London P. 73 bottom: SOM/Chuck Choi, Chicago P. 80 – 81: RFR, Paris P. 82 – 83 top: IBK Forschung + Entwicklung, Stuttgart P. 88, 89 top: Peters Engelsmann Ingenieure, Stuttgart P. 91 top: Pixelio/Chris P. 91 bottom: TriPyramid, Boston P. 99 bottom, 100 –101: Labor für Stahl- und Leichtmetallbau, Munich