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A methodology for detailing applied to point-supported-glass wall systems

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A methodology for detailing applied to point-supported-glass wall systems

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Content A METHODOLOGY FOR DETAILING APPLIED TO POINT-SUPPORTED-GLASS WALL SYSTEMS by Xiaojun Cheng A Thesis Presented to the FALCULTY OF THE SCHOOL OF ARCHITECTURE UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF BUILDING SCIENCE May 2007 Copyright 2007 Xiaojun Cheng ii Acknowledgments Firstly, the author would like to thank G.G. Schierle, the chair of the thesis committee, for his superior instructions throughout the thesis. From the selection of topics to grammar checks, he helped the thesis to be presented as a valuable product. The author would also like to thank the committee members Marc Schiler, Douglas Noble, and Tomas Spiegelhalter, for their inspiring suggestions regarding the research and methodology of the thesis. The thesis would not have been successful without their invaluable help. Secondly, the author wants to give special thanks to the ASI (Advanced Structures Incorporated) for providing important data (CAD files and photos) of the case studies presented in the thesis. Thank the ASI professionals, Sreemathi Iyer, Dr. T.J. Deganyar and Sanjeev Tankha, for answering many questions and organizing thesis presentations. In addition, Karen Kensek and Ralph Knowles provided useful comments during the thesis reviews. Besides, the author’s classmates participated in the experiment mentioned in the thesis conclusion. The author would like to thank all of them, as well as all other people whose names are not shown here, but who gave help and support to the thesis in different ways. iii Table of Contents Acknowledgments ii List of Tables viii List of Figures ix Abstract xvii Introduction 1 Chapter I Why choose detailing and PSG (Point-Support Glass) wall? 2 1.1 What is detailing? 2 1.1.1 Definition of detailing 2 1.1.2 The relationship of design and detailing employed in this thesis 2 1.2 Reasons for detailing methodology 3 1.2.1 Overview of existing detailing methods 4 Methods based on detail drawing collections 4 Methods based on pure theories 4 Methods based on case studies 7 1.2.2 Advantages of methods based on combined issues 7 Principles + methodology + worked examples + case studies 7 1.3 What is a PSG wall? 8 1.4 Why choose PSG wall systems for demonstration? 9 1.4.1 The wide use of point-support glass wall systems 9 1.4.2 PSG wall systems represent advanced technology in architecture 10 1.4.3 Point-support glass walls involve all aspects required for detailing 10 Chapter II Research method 11 2.1 Statement 11 2.2 Hypothesis 11 2.3 Thesis structure and research process 11 2.4 Product 13 Chapter III Eight general rules 14 3.1 In general 14 3.2 Learning the eight rules 14 3.2.1 Know basic knowledge of PSG wall systems 14 3.2.2 Know design concept 14 3.2.3 Know principles 15 3.2.4 Study from good designers and good detail examples 16 3.2.5 Consult with manufacturers as needed 17 3.2.6 Create detail designs (process) 19 3.2.7 Mock-up examples and test as needed 19 3.2.8 On-site supervision as needed 20 Chapter IV Exploring PSG wall systems 22 4.1 In general 22 4.2 Materials 22 4.2.1 Glass 23 What is glass? 　 23 iv Glass manufacturing processes 24 Glass type 25 Glass size 28 Glass strength 29 4.2.2 Steel, stainless steel and aluminum 31 4.2.3 Silicone 32 4.3 Components 34 4.3.1 Glazing panels 35 4.3.2 Glass fittings 39 PSG systems without perforation 40 PSG systems without perforation 41 4.3.3 Glazing support attachment 48 4.3.4 Glass support structure (back up structure) 51 Metal frame support 52 Truss support 54 Tension cable support 56 Glass fin support 58 Cable net support 60 4.3.5 Building infrastructure 63 Horizontal infrastructure 63 Vertical infrastructure 65 Grid infrastructure 67 Chapter V Detailing principles 69 5.1 Overview 69 5.2 General principles 69 5.2.1 What is expected? 70 Safe, durable, beautiful, sustainable, comfortable, within budget, smart, advanced, maintainable, constructible, legal 70 5.2.2 What should be considered? 72 Function, structure type, structural behavior, material property, life cycle analysis (LCA), maintenance, light control, thermal control, ventilation, cost control, sound control, aesthetics, integration, fire resistance, water proofing, synergy 72 5.2.3 Illustration of selected points 79 Light control 79 Structural behavior 85 Thermal control 88 Cost control 90 5.3 Important principles 94 5.3.1 Tolerance 94 Tolerance to allow components to be assembled together 95 Tolerance to allow thermal expansion and contraction 95 Tolerance to allow movement under different loads 96 Methods to deal with tolerance 96 5.3.2 Manufacture, assembly, installation 97 Manufacture process 98 Assembly process 98 Installation process 99 Innovative details combining design and industry understandings 101 v 5.3.3 Waterproof 　 102 Four ways in the waterproof design for joinery 103 The connection between the glass panes 105 The connection between the glass and glass fixings 107 The connections between the glass and infrastructures 107 5.3.4 Maintenance 107 How detailing affects maintainability 107 Integration of maintenance equipment 108 5.3.5 Aesthetics 109 How detailing affects aesthetics 109 Chapter VI Detailing process 110 6.1 In general 110 6.2 Learning the process in detail 111 6.2.1 Identify the building infrastructure 111 6.2.2 Determine modular size 111 6.2.3 Identify the back up structure 112 6.2.4 Make a checklist of all elements based on four categories 112 6.2.5 Define the position, shape and size of each element 113 6.2.6 Define all connections based on nine categories 113 6.2.7 Define the material and method for each connector 116 Connection in truss supported systems 116 Connection in tension cable systems 120 Cable and tube connection using clamping or gusset plate 123 6.2.8 Define any other requirements 124 6.2.9 Design each connection 124 Chapter VII Demonstrations overview 125 7.1 Introduction of the four case studies 125 7.1.1 Case study one for cable support structure 125 7.1.2 Case study two for truss support combined structure 126 7.1.3 Case study three for cable-net structure 126 7.1.4 Case study four for glass-fin support structure 126 7.2 Overview of the detailing process applied to each case study 126 7.3 Introduction of failure studies 133 7.3.1 Failure types 133 7.3.2 Projects with failures 134 Chapter VIII Case study one – University of Connecticut, Stamford, Connecticut 136 8.1 Introduction 136 8.1.1 Project information 136 8.1.2 Images 139 8.2 Detailing process for a typical section 144 8.2.1 Identify the building infrastructure 144 8.2.2 Determine modular size 144 8.2.3 Identify the back up structure 145 8.2.4 Make a checklist of all elements based on four categories 145 8.2.5 Define the position, shape and size of each element 146 Example of structural calculation 146 8.2.6 Define all connections based on nine categories 149 8.2.7 Define the material and method for each connector 149 vi 8.2.8 Define any other requirements 153 A gusset plate with an extra hole for pre-stressing 153 8.2.9 Design each connection 153 Detailing a typical joint type (rod + strut) – starting from a concentric connection 154 Detailing a typical joint type (rod + strut) – starting from an eccentric connection 159 Chapter IX Case study two – McCarren International Airport, Las Vegas 167 9.1 Introduction 167 9.1.1 Project information 167 9.1.2 Images 169 9.2 Detailing process for a typical section 172 9.2.1 Identify the building infrastructure 174 9.2.2 Determine modular size 174 9.2.3 Identify the back up structure 175 9.2.4 Make a checklist of all elements based on four categories 175 9.2.5 Define the position, shape and size of each element 176 9.2.6 Define all connections based on nine categories 178 9.2.7 Define the material and method for each connector 179 9.2.8 Define any other requirements 190 A splice plate is used to connect two pieces of steel tubes with the same outside diameters but different thickness 190 A safety anchor loop is designed on the truss tubes to allow additional structural loads applied onto the glass wall 190 Two bracing rods in truss structure are eccentrically designed in vertical direction to allow one crossing over the other one 190 9.2.9 Design each connection 193 Detailing a typical joint type Joint A (rod + strut) 193 Detailing a typical joint type Joint B (rod + strut) – starting from a concentric connection 199 Detailing a typical joint type Joint B (rod + strut) – starting from an eccentric connection 203 Chapter X Case study three – UBS Building, Chicago, Illinois 211 10.1 Introduction 211 10.1.1 Project information 211 10.1.2 Images 215 10.2 Detailing process for a typical section 216 10.2.1 Identify the building infrastructure 217 10.2.2 Determine modular size 217 10.2.3 Identify the back up structure 218 10.2.4 Make a checklist of all elements based on four categories 220 10.2.5 Define the position, shape and size of each element 220 10.2.6 Define all connections based on nine categories 222 10.2.7 Define the material and method for each connector 223 10.2.8 Define any other requirements 229 A series of 3" by 6" access holes are designed in the portal frame beam for pre-stressing of cables 229 10.2.9 Design each connection 230 Detailing a typical joint type (glass panes + cable system) – the rear elevation part (interior part) 231 vii Detailing a typical joint type (glass panes + cable system) – the front elevation part (exterior part) 239 Chapter XI Case study four – Ha-Lo, Niles, Illinois 247 11.1 Introduction 247 11.1.1 Project information 247 11.1.2 Images 250 11.2 Detailing process for a typical section 255 11.2.1 Identify the building infrastructure 256 11.2.2 Determine modular size 256 11.2.3 Identify the back up structure 257 11.2.4 Make a checklist of all elements based on four categories 257 11.2.5 Define the position, shape and size of each element 258 11.2.6 Define all connections based on nine categories 259 11.2.7 Define the material and method for each connector 261 11.2.8 Define any other requirements 267 Special details are considered when steel plates are bolted to toughed glass fins 267 11.2.9 Design each connection 268 Detailing a typical joint type (glass fin + glass wall) 268 Chapter XII Conclusions 279 12.1 Feedback from peers and professionals 279 12.2 Suggestions for future research 284 12.3 Useful sources 286 Bibliography 288 Appendix A Sample web pages developed for the detailing methodology 293 viii List of Tables Table 2-1 Eight rules 11 Table 2-2 The nine points of the detailing process 12 Table 3-1 Sample list of existing representative PSG wall projects 16 Table 4-1 The properties of the materials used in a typical PSG walls 23 Table 4-2 Nominal composition of clear float glass 24 Table 4-3 Glass types 25 Table 4-4 Glass design thickness 29 Table 4-5 Glass type from the strongest to the weakest 31 Table 4-6 Functional requirement checklist of glass facades 35 Table 4-7 The relationship between the sizes of the bolt and the spreader plate 46 Table 5-1 General principles 69 Table 5-2 U and R values for various glass combinations using 4mm thick glass and 12mm air cavity 88 Table 6-1 A checklist of elements based on four categories 113 Table 6-2 A checklist of all connections based on nine categories 114 Table 7-1 Overview of the detailing process applied to each case study 127 Table 8-1 General project information of case study #1 138 Table 9-1 General project information of case study #2 169 Table 9-2 Case study #2 - Illustration and description of step 5 (1) 176 Table 10-1 General project information of case study #3 213 Table 10-2 Case study #3 - Illustration and description of step 5 (1) 220 Table 11-1 General project information of case study #4 249 Table 11-2 Case study #4 - Illustration and description of step 5 (1) 258 Table 11-3 Case study #4 - Illustration and description of step 6 (1) 259 ix List of Figures Fig. 1-1 Macro scale design and micro scale design 2 Fig. 1-2 The general aspects to consider in detail design 5 Fig. 1-3 A morphological box shows how to develop the aspects step by step 6 Fig. 1-4 Edge-supported glass wall (left) and point-supported glass wall (right) 8 Fig. 1-5 Typical spider fitting attached to metal pipes 9 Fig. 3-1 Detail designs conveying different design concepts and resulting in different building appearances 15 Fig. 3-2 Springs are used to keep cables in tension 18 Fig. 3-3 Mock-up testing example 20 Fig. 3-4 An example of field quality control description by ASI 21 Fig. 4-1 Regular Crystal molecule structure and Irregular molecule structure of glass 24 Fig. 4-2 Pilkington float glass process 25 Fig. 4-3 Production range of the glass panes 28 Fig. 4-4 The silicone joints in the New Exhibition Center in Leipzig, Germany (1) 33 Fig. 4-5 The silicone joints in the New Exhibition Center in Leipzig, Germany (2) 33 Fig. 4-6 Components in a typical PSG wall (plan) 34 Fig. 4-7 Components in a typical PSG wall (section) 34 Fig. 4-8 The PSG wall in the University of Connecticut 35 Fig. 4-9 Cable net joint in Hotel Kempinski at Munich Airport 40 Fig. 4-10 Glass fin joint in the Ha-lo building 41 Fig. 4-11 Five types of mechanical point-fixing system with perforation 42 Fig. 4-12 Willis Faber & Dumas building designed by Norman Foster 43 Fig. 4-13 Patch fitting and suspended assembly design 45 Fig. 4-14 Exploded axonometric of Planar Bolted double glazed fixing 47 Fig. 4-15 Articulated bolt system 48 Fig. 4-16 Glazing support attachments 49 x Fig. 4-17 Five types of back up structures 51 Fig. 4-18 Metal frame supported example – Kadoorie Biological Science Building 52 Fig. 4-19 Metal frame supported example – Western Morning News 53 Fig. 4-20 Metal frame supported example – TGV Railway Interchange 53 Fig. 4-21 Truss shapes 54 Fig. 4-22 Truss support example – Sydney Convention and Exhibition Centre South 54 Fig. 4-23 Truss supported example – Arup Hong Kong Station 55 Fig. 4-24 Truss supported example – the New Exhibition Center 56 Fig. 4-25 Tension cable shapes 56 Fig. 4-26 Tension cable supported example – Shanghai New Opera House 57 Fig. 4-27 Glass fin supported example – Luxembourg City History Museum 58 Fig. 4-28 Glass fin supported example – Main Public Library in Memphis 59 Fig. 4-29 Glass fin supported example – Samsung Jong-Ro Building in Korea 60 Fig. 4-30 Cable net supported example – Hotel Kempinski in Munich 61 Fig. 4-31 Cable net supported example – the new AOL/Time-Warner Corporate 62 Fig. 4-32 Double-curved cable net structures examples 63 Fig. 4-33 Horizontal infrastructure diagram 63 Fig. 4-34 Horizontal infrastructure example – American Yazaki 21 64 Fig. 4-35 Horizontal infrastructure example – Le Palais des Beaus-arts de Lille 65 Fig. 4-36 Vertical infrastructure diagram 65 Fig. 4-37 Vertical infrastructure example – Hanamaki Gymnasium 66 Fig. 4-38 Vertical infrastructure example – The Greenhouses of the Parc Citroen 66 Fig. 4-39 Grid infrastructure diagram 67 Fig. 4-40 Grid infrastructure example – La Villette Museum in Paris (1) 67 Fig. 4-41 Grid infrastructure example – La Villette Museum in Paris (2) 68 Fig. 4-42 Grid infrastructure example – the New Museum of Modern and Contemporary Art in France 68 xi Fig. 5-1 Macro scale design of a glazed structure 70 Fig. 5-2 An integration approach of building and solar design 76 Fig. 5-3 Two examples describing the concept of synergy 78 Fig. 5-4 Synergy examples 79 Fig. 5-5 Lighting design framework 80 Fig. 5-6 Different glares 81 Fig. 5-7 Contrast grading 82 Fig. 5-8 Integration of lighting and architecture 84 Fig. 5-9 Wind load effect 85 Fig. 5-10 Earthquake risk 86 Fig. 5-11 Concentric plans vs. eccentric plans 87 Fig. 5-12 Remedy to deal with wing intersections 87 Fig. 5-13 Remedy to deal with height difference 88 Fig. 5-14 Summary of various types of shading and their associated values 90 Fig. 5-15 The same fixing type used in both single and double glazing 92 Fig. 5-16 Transportation cost example 93 Fig. 5-17 Example of tolerance need 96 Fig. 5-18 Methods to deal with tolerance 97 Fig. 5-19 Drilling process for a countersunk hole 98 Fig. 5-20 On site assembly of the articulated bolt 99 Fig. 5-21 Window frame installation process 99 Fig. 5-22 The difference between prefabricated welds and on site welds 101 Fig. 5-23 Special glass fitting design (a) 102 Fig. 5-24 Special glass fitting design (b) 102 Fig. 5-25 Labyrinth principle for water proof design 103 Fig. 5-26 Air barrier used in a joint for water proof 104 xii Fig. 5-27 Water tightness designed for an exterior glass floor 105 Fig. 5-28 Extruded silicone joints used in the La Villette Museum 106 Fig. 5-29 Different detail designs affect maintainability 108 Fig. 5-30 Detail design for maintenance equipment in La Villette Museum 108 Fig. 5-31 Glass fixings attached to the exterior glass façade - Avenue Montaigne 109 Fig. 6-1 Different cable connections 116 Fig. 6-2 Some examples of bolted connections to tubular members 117 Fig. 6-3 Examples of pinned connection (a & b) and sliced connection (c) 118 Fig. 6-4 Joint noding of tubular members in a welded connection with concentricity and modest eccentricity 118 Fig. 6-5 Examples of right-angle connection 119 Fig. 6-6 Examples of tube to tube splices 119 Fig. 6-7 Splice connection with (a) and without (b) cover plate; and tube to tube connections by welding (c) or by gusset plate (d) 120 Fig. 6-8 Examples of cable connections using clamp 120 Fig. 6-9 A socked termination for cables and wire ropes 121 Fig. 6-10 A typical anchorage for a cable or wire rope end connection to rigid boundaries 122 Fig. 6-11 Examples of swaged connection 122 Fig. 6-12 Threaded coupling for bars (a) and typical coupling between stainless steel bars (b) 123 Fig. 6-13 Example of gusset plate (welded fins) connections of cable and tube members 124 Fig. 7-1 Overview of the four case studies 125 Fig. 7-2 Tempered glass failure in the Palais de Justice, Bordeaux 134 Fig. 7-3 Laminated glass failure in the Mache Saint-Honore, Paris 135 Fig. 8-1 Stamford climate data 136 Fig. 8-2 Site plan and first floor plan of the building of the University of Connecticut 140 Fig. 8-3 Exploded axonometric 141 Fig. 8-4 Exterior and interior photos of the building of the University of Connecticut 142 xiii Fig. 8-5 Interior views, description, elevation and section of the glass wall 143 Fig. 8-6 Case study #1 - Illustration and description of step 1 144 Fig. 8-7 Case study #1 - Illustration and description of step 2 144 Fig. 8-8 Case study #1 - Illustration and description of step 3 145 Fig. 8-9 Case study #1 - Illustration and description of step 4 145 Fig. 8-10 Case study #1 - Illustration and description of step 5 146 Fig. 8-11 Case study #1 - Illustration and description of step 5 - Example of structural calculations 147 Fig. 8-12 Case study #1 - Illustration and description of step 6 149 Fig. 8-13 Case study #1 - Illustration and description of step 7 150 Fig. 8-14 Case study #1 - Illustration and description of Step 8 153 Fig. 8-15 Case study #1 - Illustration and description of Step 9 - Eccentric and concentric conditions of the joint 154 Fig. 8-16 Case study #1 - Illustration and description of Step 9 - Flow chart of the detailing process starting from concentric connection 155 Fig. 8-17 Case study #1 - Illustration and description of Step 9 - Illustration of each image shown in Fig. 8-16 156 Fig. 8-18 Case study #1 - Illustration and description of Step 9 - Flow chart of the detailing process starting from an eccentric connection 160 Fig. 8-19 Case study #1 - Illustration and description of Step 9 - Illustration of each image shown in Fig. 8-18 161 Fig. 9-1 Las Vegas climate data 167 Fig. 9-2 Exterior view of McCarren International Airport 170 Fig. 9-3 Interior view of the glass wall of McCarren International Airport 171 Fig. 9-4 Enlarged photo of glass fitting detail and tension rod joint 172 Fig. 9-5 Plan, elevation and sections of south glass wall 173 Fig. 9-6 Case study #2 - Illustration and description of step 1 174 Fig. 9-7 Case study #2 - Illustration and description of step 2 174 Fig. 9-8 Case study #2 - Illustration and description of step 3 175 xiv Fig. 9-9 Case study #2 - Illustration and description of step 4 175 Fig. 9-10 Case study #2 - Illustration and description of step 5 (2) 177 Fig. 9-11 Case study #2 - Illustration and description of step 6 178 Fig. 9-12 Case study #2 - Illustration and description of step 7 179 Fig. 9-13 Case study #2 - Illustration and description of step 8 190 Fig. 9-14 Case study #2 - Illustration and description of step 9 - Flow chart of detailing process for joint A 194 Fig. 9-15 Case study #2 - Illustration and description of step 9 - Illustration of each image shown in Fig. 9-14 195 Fig. 9-16 Case study #2 - Illustration and description of step 9 - Flow chart of how to detailing JOINT B starting from a concentric connection 200 Fig. 9-17 Case study #2 - Illustration and description of step 9 - Illustration of each image shown in Fig. 9-16 201 Fig. 9-18 Case study #2 - Illustration and description of step 9 - Flow chart of how to detailing JOINT B starting from an eccentric connection 204 Fig. 9-19 Case study #2 - Illustration and description of step 9 – Illustration of each image shown in Fig. 9-18 205 Fig. 10-1 Chicago climate data 211 Fig. 10-2 Exterior and interior photos of the glass lobby 215 Fig. 10-3 Plan and elevations of the glass lobby 216 Fig. 10-4 Case study #3 - Illustration and description of step 1 217 Fig. 10-5 Case study #3 - Illustration and description of step 2 217 Fig. 10-6 Case study #3 - Illustration and description of step 3 218 Fig. 10-7 Case study #3 - Illustration and description of step 4 220 Fig. 10-8 Case study #3 - Illustration and description of step 5 (2) 221 Fig. 10-9 Case study #3 - Illustration and description of step 6 222 Fig. 10-10 Case study #3 - Illustration and description of Step 7 223 Fig. 10-11 Case study #3 - Illustration and description of Step 8 229 Fig. 10-12 Case study #3 - Illustration and description of Step 9 - Overview of the detailing process for a typical glass fitting joint 231 xv Fig. 10-13 Case study #3 - Illustration and description of Step 9 - Detailing process for rear elevation 232 Fig. 10-14 Case study #3 - Illustration and description of Step 9 - Illustration of each image in Fig. 10-13 233 Fig. 10-15 Case study #3 - Illustration and description of Step 9 - Detailing process for front elevation 240 Fig. 10-16 Case study #3 - Illustration and description of Step 9 - Illustration of each image in Fig. 10-15 241 Fig. 11-1 Niles climate data 247 Fig. 11-2 Exterior photos of Ha-Lo 250 Fig. 11-3 Plan and elevation of Ha-Lo 251 Fig. 11-4 Interior glass wall photos of Ha-Lo 252 Fig. 11-5 Typical section and enlarged photo of the glass-fin wall of Ha-Lo 253 Fig. 11-6 Enlarged glass fitting photos of Ha-Lo 254 Fig. 11-7 Glass wall elevation and plans 255 Fig. 11-8 Case study #4 - Illustration and description of step 1 256 Fig. 11-9 Case study #4 - Illustration and description of step 2 256 Fig. 11-10 Case study #4 - Illustration and description of step 3 257 Fig. 11-11 Case study #4 - Illustration and description of step 4 257 Fig. 11-12 Case study #4 - Illustration and description of step 5 (2) 258 Fig. 11-13 Case study #4 - Illustration and description of step 6 (2) 260 Fig. 11-14 Case study #4 - Illustration and description of step 7 261 Fig. 11-15 Case study #4 - Illustration and description of step 8 267 Fig. 11-16 Case study #4 - Illustration and description of step 9 - Overview of the detailing process for a typical glass fitting joint 269 Fig. 11-17 Case study #4 - Illustration and description of step 9 - Illustration of each image in Fig. 11-16 270 Fig. 11-18 Case study #4 - Illustration and description of step 9 - Splice boot alternatives shown in Fig. 11-16 277 xvi Fig. 11-19 Case study #4 - Illustration and description of step 9 - An example of splice boot alternatives 278 Fig. A-1 Sample webpages – Homepage 293 Fig. A-2 Sample webpages – Rules 294 Fig. A-3 Sample webpages – Process 294 Fig. A-4 Sample webpages – Demonstrations (1) 295 Fig. A-5 Sample webpages – Demonstrations (2) 295 xvii Abstract Architectural detailing is primarily left to experience in professional practice rather than formal education. This thesis assumes a methodology can be developed to teach students and young architects architectural detailing. The methodology is based on rules and a process, considering assembly, installation, tolerance, functionality, and aesthetics. It is illustrated and demonstrated on case studies of Point-Supported-Glass (PSG) walls, which present some of the most complex detailing challenges with potential flaws, ranging from assembly problems to leaks. 1 Introduction This thesis presents a methodology to teach architectural detailing, illustrated and demonstrated on case studies of Point-Supported-Glass (PSG) walls. The methodology is based on rules and process. Chapter I defines detailing and PSG wall. It also explains the choice of detailing and PSG walls as research topics. Chapter II describes the research methods used in the thesis. It provides an overall review of the thesis structure, the research process, as well as the final product. Chapter III introduces the eight general rules developed for the detailing methodology. Subsequently, chapter IV, V and VI, discuss three of the eight general rules in detail respectively. Chapter IV explores detailed information of PSG walls. Chapter V describes the principles involved in the detailing methodology. Chapter VI describes the detailing process in detail. Chapter VII provides an overall introduction of the four case studies provided by ASI (Advanced Structures Incorporated), and a preliminary exploration of the PSG projects with failures. The following four chapters, chapter XIII, IX, X, and XI present the four case studies separately. Chapter VIII shows the first case study, the University of Connecticut located in Stamford, Connecticut, which is a tension cable supported structure. Chapter IX introduces the second case study, the McCarren International Airport in Las Vegas, which is truss-supported. Chapter X discusses the third case study, a cable-net supported glass wall of the UBS Building at One North Wacker Drive in Chicago, Illinois. Chapter XI describes the fourth case study, a glass-fin supported glass wall of the Halo building in Niles, Illinois. Chapter XII draws conclusions, including feedback from peers and experts, suggestions for future studies, as well as useful sources for the study of architectural detailing and PSG wall systems. Chapter I Why teach detailing and PSG (Point-Support Glass)? 1.1 What is detailing? 1.1.1 Definition of detailing The dictionary definition of “detail” is: “Particulars considered in individually and in relation to a whole.” (www.dictionary. com) Detailing is the process of creating details. “God is in the details” (Mies van der Rohe, 1959). Many famous architects, such as Norman Foster, Helmut Jahn, and Renzo Piano, emphasize architectural detailing. They use details to reinforce their design concepts, assure high quality designs and control the final look and performance of the building. The same architectural designs with different details would make the building look dramatically different. A bad detail design may affect the building’s visual effect, energy efficiency, cost, constructability and even construction time. A good detail design, however, will not only improve a building’s performance, but also make the structure into an amazing piece of art. 1.1.2 The relationship of design and detailing employed in this thesis In this thesis, design and detailing are not separate conceptions throughout thesis. They are related, because detailing is a smaller scale of design. There are different scales of design ranging from macro scale design to micro scale design (Fig. 1-1). This thesis focuses on detailing at the micro scale. Fig. 1-1 Macro scale design and micro scale design Designers must be concerned that macro scale design and micro scale design are related to each other, yet they have different concentrations. For instance, in macro scale design more emphasis 2 3 is taken on issues regarding building safety, energy and so on. Therefore such topics as structure type and building orientation need to be decided in the macro scale design. In micro scale design, however, more emphasis is taken on issues like tolerance, water tightness and constructability. Topics such as the design of joints and the installation sequences need to be considered in the micro scale design. Please refer to chapter 5 for more information on macro and micro scale design. 1.2 Reasons for detailing methodology Detailing links the design process and construction. Detailing needs to be not only consistent to the design concept, but also to be a good guideline for manufacturers and contractors to actually build it. In most American architectural schools, students learn primarily how to design in macro scale, but not much about how to detail. In Europe, things are different. Most European architects learn both design and detailing. For them, detailing is part of design (T. Spiegelhalter, personal communication, 2004). This is an ideal way to make details. But currently most US architecture schools separate design and detailing, and emphasize schematic design rather than detailing. Experienced architects may have learned good detailing from practical experience. However, architecture students require good methods for learning detailing. If an architecture student wants to make a detail design of a concrete wall section, for example, what will he or she do? He or she may go to the library and find a book on concrete details. The student may find books introducing concrete buildings with a few small images showing detail drawings. These small drawings may have no material description or dimensions and no information regarding the detail rationale. Now consider books dealing specifically with detailing. A student may find many books with names like “Architectural detailing,” or “Detailing method,” but these books are either a mere collection of detail drawings without explanation, or abstract theory without case studies. Some publications have both theories and simple examples (like a wall section) but no case studies of a real building. The student may copy a detail drawing without understanding the rationale. Therefore, it will be very helpful if there is a book teaching students how to design detailing step by step. But before students are ready to do detailing, they should have an overall understanding 4 of the aspects they need to consider. They can start asking a few questions: What do they want to achieve? How are they going to achieve it? What is the relation between macro design and detail design? What’s the purpose of a detail? After answering all of these questions, students will better understand what they need to do. The step-by-step method can help students to design details. This thesis introduces a methodology for detail design, using a step-by-step methodology, examples, and case studies 1. 2. 1 Overview of existing detailing methods and their advantages and disadvantages Methods based on detail drawing collections These are the most common methods. The advantages are that readers can get a lot of existing drawings within a short time and have an overall clue of what the details look like. They can also get different solutions for a specific problem, such as the different ways to connect wall and roof. Nonetheless, readers have no clue of why or how these details are made. Why is one drawing different from another one? Why does the connection look like that? In other words; these methods show the product but not the process. Methods based on pure theories The typical example is the book Principles of Architectural Detailing (Emmit et al. 2004) (see Fig. 1-2 and Fig. 1-3). Although this book provides clear basic principles of detailing, some students may find its theories too abstract. It may help experienced architects to understand, but is too vague for architecture students. (G. G. Schierle, personal communication, 2004) Fig. 1-2 The general aspects to consider in detail design (Emmit et al. 2004) 5 Fig. 1-3 A morphological box shows how to develop the aspects step by step (Emmit et al. 2004) 6 7 Methods based on case studies For example, books named “Glass buildings,” or “concrete buildings,” often provide very good information on case studies. Readers can get information about real projects and learn their details. It is a very effective way to learn some specific examples. But because there are no theories or step-by-step method, it is hard for student readers to understand how to develop details. Again, these books focus on the product rather than the process. They expect the reader to figure out the process alone. 1.2.2 Advantages of methods based on combined issues Principles + methodology + worked examples + case studies This thesis introduces a method to combine principles, methodology, worked examples and case studies. Principles deal with “what” and “why” issues. For example, before detailing one must define an objective. Or what is the purpose(s) of the detail? One answer is: the building must be safe. Another answer may be the building must be within the budget. Only after defining a complete list of constraints can one produce a method to solve these issues. A methodology deals with the question of “how” – how to solve problems? How to make a building safe? One needs to analyze the structural behavior, figuring out what kind of forces to notice, such as bending, shear, or overturning moment. Material is another important issue because different materials have different structural performances. A process of detailing is finding an answer for each “how” question. It will be even better if the methodology can be illustrated by worked examples, which are different from case studies. The case studies, which will also be used in the thesis, provide complete information for existing projects, including plan, elevation, section, detail drawings, photos as well as specifications. The worked examples, however, will only be part of a project; and therefore will only illustrate a specific point of the methodology. Most of these worked examples are supposed to be involved in point-supported glass wall systems, but in some cases, some very good examples of other structural types can explain the methodology very well. An edge-supported glass building with very good seismic design or daylight control design can also be used to illustrate the methodology. This thesis will introduce case studies to demonstrate the methodology. These case studies are projects by Advanced Structure Incorporated (ASI). One of the reasons for choosing ASI projects as case studies is because ASI does good point-supported glass buildings; and ASI not only makes detail designs, but actually builds them. The second reason is that it is easier to get detailed information from ASI than other firms. Each of these case studies will demonstrate some points of the methodology, depending on different features of the projects. Theoretically, all of the points of the methodology should be covered by the case studies. Through the combination of principles, methodology, worked examples and case studies, this thesis will produce an effective way for architectural students to learn detailing. 1.3 What is PSG wall? In a PSG (point-supported glass) wall system, glass panels are held at points and supported by glass fittings, (or hardware, or devices), such as steel spider (see Fig. 1-4, left), rather than by edge elements, such as mullions (see Fig. 1-4, right). The emergence of PSG systems is largely the result of architectural requirement: architects want the building enclosure as transparent as possible. Faculty of Economics, Utrecht, The Netherlands (http://www. washington. edu/) University of Connecticut, Stamford, Connecticut (http://www. structural. de/) Fig. 1-4 Edge-supported glass wall (left) and point-supported glass wall (right) 8 The first point-supported glass system was called patch plate system, invented by Pilkington and was first used in Europe in the 1970’s. In 1982, Pilkington invented another system called Planer TM system. In patch plate system there is no hole drilled in the glass. In Planer TM system countersunk holes are drilled and bolts are inserted into the holes to hold the glass. The Planer TM system now is the most popular system used in point-supported glass buildings. Other companies are also introducing new systems onto the market, but the basic concepts are the similar. There are different types of glass fittings. The choice of glass fittings is dependant on the types of glass. It is also dependant on the type of backup structure (see chapter 3. 2 for more details about back up structures). Fig. 1-5 below shows a typical spider fitting attached to metal pipes. The glass panels are joined by black structural silicone. Fig. 1-5 Typical spider fitting attached to metal pipes (A PSG wall in Las Vagas, photo by the author) 1. 4 Why choose PSG wall systems for demonstration? 1. 4. 1 The wide usage of point-support glass wall systems Firstly, glass façades are widely used in buildings. Advanced technology makes structure elements smaller in size, producing larger and larger glass façades. Glass-fins, cables and trusses make it possible to get maximum transparency. Glass as a building material can create quite different images for buildings: They can be colored, translucent or reflective; they can even be changeable due to sunlight. All of these reasons make glass façades favorable for architects. 9 10 Glass façades include glass roofs and glass walls. Because of the different loads and different orientation imposed on roofs and walls, their structural characteristics are different. Therefore the detailing requirements for them are different as well. For example, dead load and gravity live load are the main loads for beams, while lateral wind and seismic loads need to be considered for wall detailing. This thesis will focus mainly on glass walls so that the detailing methods can be demonstrated for a clear purpose. Although glass façades are widely used nowadays, they are relatively new compared to concrete, masonry or other types of façades. As a result, there are not many publications providing systematical introduction and analysis of glass façade buildings and detailing. Also, because glass walls can be designed into many different types, there are no standard categories to define the glass wall types. These factors make it hard for inexperienced architects or architecture students to start glass wall design. For this reason, this thesis will provide an overall study and analysis of existing glass wall systems; give a standard category to define the glass wall types; and then use point-support glass wall as demonstration to teach how to detail a glass wall step-by-step. 1.4.2 PSG wall systems represent advanced technology in architecture Compared to edge-supported glass wall systems which have been used for quite a long time, PSG wall systems are relatively new. They reduce the opaque area to the minimum, therefore have higher requirement for structure issues. It also requires special consideration for waterproofing, assembling process, maintenance, etc. 1.4.3 Point-supported glass walls involve many aspects required for detailing Firstly, the consideration of light and thermal control is important in the design of glass structures. For example, lighting may not be a key issue for concrete walls. Secondly, glass walls have high requirement for structural design because of the material properties. To design a glass wall withstanding wind load is obviously more challenging than to design a concrete or steel wall. Thirdly, glass walls, especially PSG walls, have high requirement for precision, such as precise manufacture, assembly and installation, which are generally not discussed in many architectural schools. 11 Chapter II Research Methodology 2. 1 Statement Architectural detailing is primarily left to experience in professional practice rather than formal education. There are few publications discussing strategies of detailing with demonstrations using a specific type of structure. This thesis presents a methodology to teach architectural detailing illustrated and demonstrated on case studies of Point-Supported-Glass walls. 2. 2 Hypothesis This thesis assumes a methodology can be developed to teach students and young architects architectural detailing. The methodology is based on rules and process, considering assembly, installation, tolerance, functionality and aesthetics using PSG walls as demonstrations. 2. 3 Thesis structure and research process The methodology developed in this thesis is based on rules and process. The eight rules are listed in Table 2-1 as below. Rule 1 Know basic requirements of PSG wall systems Rule 2 Know design concept Rule 3 Know principles Rule 4 Study from good designers and good detail examples Rule 5 Consult with manufacturers as needed Rule 6 Create detail design (process) Rule 7 Mock-up examples and test as needed Rule 8 On site supervision as needed Table 2-1 Eight rules These eight rules are introduced in detail in Chapter 3. Besides, Rule 1, 3, and 6 are further studied in Chapter 4, 5, and 6 respectively. The thesis then explores a process which may be a guide to follow to create detail design. The process includes nine points, as shown in Table 2-2 (see chapter 6 for details). The thesis firstly introduces the nine points, one by one, and then uses four case studies to illustrate and support the nine points. 12 1. Find out the infrastructure 2. Determine modular size 3. Determine the back up structure 4. Make a checklist of all elements based on four categories Category 1 – Infrastructure elements Category 2 – Glass wall elements Category 3 – Elements for openings Category 4 - Additional devices 5. Determine the position, shape and size of each element 6. Find out all connections based on nine categories Category 1 – Connections within glass wall Category 2 – Connections within openings Category 3 – Connections within additional devices Category 4 – Connections between glass wall and additional devices Category 5 – Connections between glass wall and openings Category 6 – Connections between openings and additional devices Category 7 – Connections between glass wall and infrastructure Category 8 – Connections between openings and infrastructure Category 9 – Connections between additional devices and infrastructure 7. Determine the material and method for each connector 8. Any other special requirements 9. Detailing each connection Table 2-2 The nine points of the detailing process In order to make the process easy to understand and follow, during the case studies, the thesis introduces a sequence for the nine points. This sequence, however, is only one of possible sequences. If choosing different sequence, the result might be different. But how to determine the sequence, and what is the effect, are not going to be discussed in the thesis. The first eight points are to make preparation for the ninth point, which is “detailing each connection. ” Because different connections have different requirements and emphasis in detailing, it is advisable to provide a method for each typical connection type. The four case studies (Chapter 8, 9, 10 and 11) each gives one or two examples of the possible process to detailing typical connection types. To make the detailing process easy to follow, a flow chart is developed to explain each step visually. (See 8.2.9, 9.2.9, 10.2.9, and 11.2.9 respectively). Each of the four case studies represents a typical structural type of PSG wall system. They are cable truss, truss, cable net and glass-fin, respectively. For each project, a typical PSG wall section is used to illustrate and support the detailing process developed for the methodology. 13 The thesis also makes a brief study of some projects with detail failures (see 7.2). Detailed research for projects with failures is left for future studies. At the end of the thesis, a conclusion is drawn from the research (see Chapter 12 for details). 2.4 Products The research results in two products. One main product is the written thesis and the other one is a supplemental web site of the methodology. The thesis provides the complete description of the research, including the hypothesis, research methods, and research results. The web site is proposed to be used as a teaching tool for students and young architects to study the detailing methodology (see Appendix A for sample web pages). 14 Chapter III Eight general rules 3. 1 General This chapter describes the eight rules mentioned in 2.3 in detail. Note there is not a fixed sequence of the eight rules. The rules form a general guide for a designer to create PSG wall details which are both functionally and aesthetically successful. 3.2 Learning the eight rules 3.2.1 Know basic requirements of PSG wall systems Before starting to detail PSG walls, a designer should have a good understanding of this system. Because currently there is no a publication giving out a systematic and standard introduction for PSG wall systems, the thesis produces its own way to describe this special system, including an introduction of the material and a definition of a PSG wall based on different components. See chapter 4 for detailed information. 3.2.2 Know design concept A good detail design should correctly convey the design concept, and even reinforce the concept. Before starting to make a detail, a designer should answer the question: what is the design concept of this project? For instance, some adjectives can be used to describe a project: is it light or heavy, classic or modern, simple or complex, prominent or obscured, and so on. Different design concepts will determine the basic detailing needs. The following three images (Fig. 3-1) show how details affect the design concept and building appearance. Media building, Toolo Bay, Helsinki, Finland. Architect: Sarc Architects (Davey 2000) Banque Populaire de L'Ouest et de L'Armorique-Rennes-France (Rice and Dutton 1995, p.116) Sony Center (Blaser 2002, p.48) Fig. 3-1 Detail designs conveying different design concepts and resulting in different building appearances 3.2.3 Know principles This introduces the principles which should be considered in detail design. These principles are described in detail in chapter 5. Two types of principles are discussed: general principals and important principles. The general principles include function, structure type, structure behavior, material property, life cycle analysis (LCA), maintenance, light control, thermal control, ventilation, cost control, sound control, water proof, aesthetics, integration, fire resistance, water proof, and synergy. These general principles are normally more emphasized during macro design scale, which is not the focus here; therefore they are only briefly introduced in 5.2. Among these general principles, four are described in detail in 5.2.3, which are light control; structural behavior; thermal control; and cost control. The reason for this is because the author considers that in general these four points are more critical to detailing of PSG walls than other points. The important principles are generally more emphasized during micro design scale, which is the focus of the methodology. They are: tolerance; manufacture, assembly and installation; water resistance; maintenance; and aesthetics. See 5.3 for details. 15 16 3.2.4 Study good designers and good detail examples To see how other people make details is a good way to make better details of ones own. Many world famous architects are also good detailing designers, such as Renzo Piano, Norman Foster, Ackermann, Schulitz, SOM, HOK, etc. In addition, there are some firms specifically focusing on steel and glass façade projects, such as ASI, Dewhurst Macfarlane and Partners, James Carpenter Design Associates Inc, etc. The more a designer knows, the easier he can create his own details. To help readers to start, some existing representative PSG wall projects are listed below. Examples are listed based on different types of back-up structure: metal frame, truss, tension cable, cable net, glass fin and other types. Architects Project name Location Metal frame Nicholas Grimshaw & Partners Financial Times Print Works London, UK Nicholas Grimshaw and Partners Western Morning News Plymouth, England J. M. Ibos and M. Vitart Architects Le Palais des Beaux-Arts de Lille Lille, France Avery Associates Imax Cinema Waterloo, London Ben Van Berkel Shopping Center in Emmen Emmen, The Netherlands N/A Kadoorie biological Sciences Building, The University of Hong Kong Hong Kong Sar, PRC Helmut Jahn / Werner Sobek Charlemagne – European Union Truss Tate & Snyder Architects McCarren International Airport Las Vegas, Nevada HOK and Nikken Sekkei Sendai International Airport Sendai, Japan Nicklaus Grimshaws and Partners UK pavilion at Barcelona Exhibition British Odile Decq and Benoit Cornette Banque Populaire de L'Ouest et de L'Armorique-Rennes Rennes, France Von Gerkan, Marg & Partner New Exhibition Center Leipzig, Germany Polshek Partnership The Rose Center for Earth and Space New York City, NY Botti Rubin Arquitetos Associates British Brazilian Center Sao Paulo, Brazil Nicholas Grimshaw & Partners Paddington Station Paddington, London, UK Ancher Mortlock Woolley Pty Ltd Sydney Convention and Exhibition Centre South Darling Harbour, Sydney, Australia Table 3-1, Continued on next page 17 Tension cable Epstein, Glialman and Vidal 50 Avenue Montaigne Paris, France Helmut Jahn / Werner Sobek FKB Airport Cologne/Bonn, Germany Arte Jean-Marie Charpentier et Associes New Opera House Shanghai, China Richard Rogers Partnership Channel 4 Headquarters London Adrien Fainsilber in cooperation with Rice Francis Ritchie (RFR) La Villette Museum Paris, France N/A Princeton University Genomics Institute Princeton, New Jersey N/A The Kimmel Center for the Performing Arts Philadelphia, Pennsylvania Riken Yamamoto & Field Shop Saitama Prefectural University Koshigaya, saitama, Japan Cable net Jan Stormer Entrance Hall to University of Bremen Germany Helmut Jahn / Ove Arup + Partners Hotel Kempinski Munich Germany Lohan Associates, Inc UBS Building Chicago, Illinois Glass fin Conny Lentz, Luxembourg Reperages Architects, Paris Luxembourg City History Museum Luxembourg Francoise Jourda & Gilles Perraudin Architects Palais de Justice Melun Murphy/Jahn Architects Ha-Lo Niles, Illinois N/A The public library in Memphis Memphis N/A Samsung Jong-Ro Building Seoul, Korea Fox & Fowle Architects Entry Pavilion in Avaya Headquarters Renovation basking Ridge, New Jersey Helmut Jahn / Werner Sobek / Matthias Schuler Bayer Ag konzernzentrale Leverkusen, Germany Other types Helmut Jahn / Ove Arup + Partners Sony Center Berlin, Germany Helmut Jahn / Werner Sobek / Matthias Schuler Galleria Kaufhof Chemnitz, Germany Table 3-1 Sample list of existing representative PSG wall projects 3.2.5 Consult with manufacturers as needed Useful tips: If necessary, consult with manufacturers as early as possible Study manufacture, assembly, and installation process To save money and time, use available items as much as possible The more one knows the easier changes can be made For example, in tension cable structures the cables need to be kept in tension otherwise they will slack and become unstable. Study how to keep the cables in tension. A good way is to use springs, because they adjust for temperature variations. Consult with manufacture. Designers may find that the springs themselves can be a very interesting part for architectural design. Although the functions of the springs are the same, the images below show that the design of different forms of springs can bring very different architectural expression. If designers have no background understanding of manufacture, assembly and installation, they probably will not know that a spring can be designed like that. Interior view showing the springs used at the bottom of each cable Enlarged images of the springs Another type of spring Entrance Hall to University of Bremen , by Jan Stormer Architect Fig. 3-2 Springs are used to keep cables in tension (Anon 4 , Detail, May 2001, p.876-880) 18 19 3.2.6 Create detail design (process) A detailing process which may help (see chapter 6 for details) Always remember the principles, especially tolerance, manufacture, assembly, installation, water tightness, and maintenance (see chapter 5 for details) Look how other designers make it. But do not copy; adapt them creatively. Generally, for small buildings, use what is available as much as possible. For important big buildings, unique new designs may be applied. Adapt complex mass-produce items rather than redesign them. (high cost) Change the parts which will not cost too much. (Any part made by very expensive machines will cost a lot if changed.) 3.2.7 Mock-up examples and test as needed In some case, testing may be needed, especially for unique new designs. PSG wall systems usually require a high attention to mock-up testing for the following reasons: The technology of PSG walls is relatively new compared to traditional structures The inherent properties of glass are not well defined To verify the reliability of complex joints between glass and its supports The wide range of types of PSG walls According to Loughran (2003), mock-up testing systems typically include the test of sound transmission, fire resistance, air and water leakage, overall condensation resistance, structural loads, and thermal transmission. The author also recommends that: “While it is not possible to replicate every condition on the building, at least the size of the mock-up must be large enough to include all major elements and perimeter transition conditions. It is not usually necessary to repeat the actual building frame used to support the enclosure, but it is crucial that all actual details of the enclosure are incorporated into the mock-up. ” (Loughran, 2003) Besides mock-up testing, field testing is another important and very effective method. Field testing can verify many “quality control measures” which happen in laboratory conditions. Materials may get eroded during transportation; field installation may not be as expected. In these cases, a random field testing can be very useful. For example, a “standard hose test” on site can easily detect water leakage caused by fabrication or installation faults. A “random sealant adhesion field test” can verify whether the sealant material is installed correctly and working properly. Ideally, the workers constructing the mock-up should be the same ones constructing the real projects. (Loughran, 2003, p.74-81) Fig. 3-3 below shows a mockup cable net glass wall during a test for water tightness. A sophisticated cable net glass wall is tested for water leakage. Fig. 3-3 Mock-up testing example (ASI) 3.2.8 On-site supervision as needed A good design is not automatically a good final product. Assembly and installation will make a big difference. The purpose of on-site supervision is to make sure the following issues: The installation process is correct. The materials are properly protected. The components are properly installed. The design requirements are all satisfied. 20 21 Especially for the construction of PSG walls, on-site supervision can detect faults which may cause structural failure. For example, the scratches on the glass surface may cause glass breakage. If discovered in time, the glass can be replaced to prevent failure after the completion of the building. Also, a timely detection on-site may prevent stainless steel from rusting if its surface is damaged during transportation. Another important operation which needs to be supervised on site is welding. Generally, if a weld is made in the factory, no additional supervisors are needed. But if a weld is made on site, an inspector is needed to assure its quality. The following (Fig. 3-4) is excerpt from the General Notes sheet of the McCarran International Airport from ASI, showing an example of field quality control as described by ASI. Field quality control: 1. Provide visual inspection of all welded and bolted connections. A. Measure 25% of welds, selected randomly. B. Check 25% of bolts, selected randomly, with calibrated torque wrench. C. Provide certification of pre-stress values in tension rods after pre-stressing is complete. 2. Inspect bolted connections in accordance with AISC specifications. 3. Weld tests: A. Ultrasonic inspection B. Liquid penetration inspection Fig. 3-4 An example of field quality control description by ASI 22 Chapter IV Exploring PSG wall systems 4.1 General As described in chapter 01, a PSG (Point-Supported-Glass) wall system is a light-weight wall system in which the glass panels are supported at local points, rather than traditional mullions, so called edge-support (or linear-support) systems. One of the first PSG buildings is the office of Willis, Faber & Dumas in Ipswich designed by Norman Foster in conjunction with the glass manufacturer Pilkington in 1971-1975. The building features a suspended glazing system: each pane is hung from the one above it, and the glass façade is suspended from the beam or floor above. The glass panels are clamped together by patch fittings which protrude beyond the glazing surface. In 1982, Norman Foster collaborated with Pilkington to design the Renault Centre in Swindon. He used the Planer system in which glass fittings do not project beyond the surface and therefore a flush appearance was achieved. In this building, the glazing is screwed to the supporting frame rather than suspended from above. In 1986, Adrien Fainsilber and RFR (Peter Rice, Martin Francis and Ian Ritchie) designed the La Villette Museum in Paris which successfully uses suspended glazing system and Pilkington Planar system simultaneously. (Schittich et al.1999, p.50-51) The materials generally used in a PSG wall are glass, steel, stainless steel, aluminum and silicone. (Please see 4.2 for more details.) A typical PSG wall consists of five parts: glazing panels, glass fittings, glazing support attachment, glass support structure and building infrastructure. (Please see 4.3 for more details) 4.2 Materials The materials generally used in a PSG wall are: Glass – used as envelope material Steel – generally used in load bearing structures Stainless steel – generally used in fasteners and profiles, and also more and more used in load bearing structures if higher corrosion resistance is required Aluminum – generally used as fasteners because of its formability and lightness Silicone – generally used as sealants, also increasing the structural performance of the glazing wall The following table describes the material properties of glass, steel, stainless steel and aluminum. (Kallioniemi 1999, p.10) Table 4-1 The properties of the materials used in a typical PSG walls (Kallioniemi1999, p.10, excerpted) The properties of glass are described in detail in 4.2.1. The properties of steel, stainless steel and aluminum are described in 4.2.2. The properties of silicone are described in detail in 4.2.3. 4.2.1 Glass What is glass? Glass has a history of about 7,000 years. It is one of the oldest man-made materials whose main component is silicon dioxide (SiO 2 ). It is an amorphous material. Encyclopedia defines glass as a “hard substance, usually brittle and transparent, composed chiefly of silicates and an alkali fused at 23 high temperature. ” Krewinkel (1998) indicates that it is the difference between the regular molecular structures of crystal and the irregular molecular structure of glass that makes the different lighting behavior of the two materials: glass is transparent while crystal can only be translucent (Fig. 4-1). Regular Crystal molecule Irregular molecule Fig. 4-1 Regular Crystal molecule structure and Irregular molecule structure of glass (Gibbs 1996, online) The raw materials composed in clear float glass include seven key elements as shown in Table 4-2. Component Weight % SiO 2 sand (quartz) 73 Na 2 O 13. 8 CaO 6. 6 MgO 3. 6 Al 2 O 3 0. 17 Fe 2 O 3 0. 12 SO 3 0. 3 Table 4-2 Nominal composition of clear float glass (Loughran 2003, p.13, excerpted) Glass manufacturing processes Annealed float glass process Previously, the common methods of producing flat glass included sheet glass process and plate glass process. In 1959, Pilkington invented the float glass process, which now comprises more than 90% of the world’s flat glass. In this process, molten glass is poured onto a large bed of molten tin and then cooled slowly through an annealed lehr. (Button et al.1993, p.355) The whole process including: introduce raw materials; mixing; melting; refining; molten tin float bath; cooling; cutting; breaking; and storage (Loughran 2003, p.14). See Fig. 4-2 for the Pilkington float glass process. 24 Fig. 4-2 Pilkington float glass process (http://www.glassrecruiters.com/info. asp) Rolled glass process Wired glass, patterned glass, figured glass, obscured glass, cast and rolled glass are produced by a rolling process, in which “the semi-molten glass is squeezed between metal rollers to produce a ribbon with controlled thickness and surface textures or patterns. ” (Button et al.1993, p.357) Glass type Glass comes in many types. Generally, there are the following types available: annealed glass, safety glass, heat strengthened glass, security glass, solar control glass, bent glass, insulating glass and decorative glass. See Table. 4-3 Glass type Sub-type notes Annealed glass Also called soda lime glass, flat glass or float glass. It is flat and visually clear. It is easy to break and produces sharp edges when shattered. Safety Glass Including: This glass does not break or breaks in a manner not causing injury under specific impact tests. It includes the following types: The glass is heated to about 700°C, and then cooled down rapidly. Qualified as safety glass, it is broken into small fragments with dulled edges. Toughed glass is 4 or 5 times stronger than float glass. Any other operations such as cutting, polishing and drilling must be done before being toughened. Toughening can not be applied to wired glass. Vertical toughening Glass is held vertically during toughening. Roller hearth toughening Glass is held horizontally on rollers during toughening, producing a roller wave effect. Chemical toughening Glass uses ion exchange; not common in architecture. Toughened (tempered) Glass Colored cladding glass Colored opaque materials are fused into the glass surface during toughening. Table 4-3, Continued on next page 25 26 It consists of two or more panes separated by interlayers of resin or plastic material. When broken, the glass fragments remain bonded to the interlayer firmly and can be used as safety glass. Laminates can be applied to many glass types, thickness and combinations, such as toughened and heat strengthened glass. Other materials such as polycarbonate can be incorporated to get specific performance. PVB laminated glass The interlayer material is polyvinyl butyral, which can be either clear or tinted. Laminated Glass Resin laminated glass The bonding material is a resin. It is made by a cast-in-place process, suitable to smaller sized custom glass products. It features a steel wire mesh embodied and tends to stay in place if cracked. It has been traditionally used in roof glazing and low-cost fire resistant for safety. patterned wired glass The thickness is usually 7 mm. Typical maximum size is 3,700 by 1,980 mm. Wired Glass polished wired glass It is made by the rolling process. The thickness is usually 6 mm. Typical maximum size is 3,300 by 1,930 mm. Heat strengthened glass It is similar to toughened glass, but not qualified as safety glass because of its breakage pattern. Its cooling process is slower, resulting in less distortion and strength. When broken, its visibility is better than toughened glass. Security Glass Including: The glass can resist specific impacts such as manual attack, bullets and explosion. Only laminated glass can be qualified as a security glass. It includes the following types: Anti-bandit glass It is designed to resist manual attack such as hammer or axe for a short period of time. Bullet-resistant glass It is designed to resist bullets. It also prevents injury from splinters of glass. Explosion-pressure- resistant glazing It is designed to resist a specified explosive blast. Solar Control Glass Including: It is designed to control the heat and light transmitted through the glass. This is usually achieved by controlling the absorption and reflectivity of the material. It includes the following types: Body Tinted Glass It absorbs short-wave radiation and re-radiates long-wave light. The transmittance of short-wave light decreases as the thickness of the glass increases. The thicker the glass is, the darker the color and the smaller the transmittance of short-wave light. Available colors are green, gray, bronze and blue. Maximum size is 3,210 by 6,000mm. Off-line coated glass cannot be bended or toughened after coating. Coatings can be combined with laminated and double glazed glass. Online coatings (Pyrolitic coating) Coatings are applied during the manufacturing of glass. The glazing can be bent or toughened. Compared to glass with offline coatings, it is harder and more durable. Off-line coatings(sputtered coating) The coatings are applied after the glass has been manufactured and cut. The thickness, nature and configuration of the coatings determine the light transmittance and color. Coated Glass Low-E coatings The coatings reduce the surface emissivity of glass. The glazing allows through visible light, while reducing the absorption and emissivity of long-wave infrared radiation. If coatings are on the outside face, it helps to keep heat inside; if coatings are on the inside face, it helps to block exterior heat to inside. Table 4-3, Continued on next page 27 Dielectric coatings Allows higher light transmission and increases the range of colors. Dichroic coatings Gazing has multi-layered coatings and exhibits different colors due to different view angles. Mirror silvering coatings A chemical process giving the glazing reflective properties. Spectrally Selective Glazing Allows the maximum amount of visible light through and cuts out as much invisible light as possible. Chromogenic Glasses Glazing can dynamically control the spectral aspect of radiation. It becomes darker or lighter due to the amount of light falling on the surface. Screen-Printed Glass A ceramic enamel frit is screen-printed and then fused into the glass during the toughening process. The frits help to reflect and absorb more solar heat, thereby reducing the solar heat transmitted through the glass. It can be combined with a body-tinted glass base or a sputtered solar control coating to enhance the solar performance. Laminated Glasses with Tinted Layers The tinted interlayer reduces the transmission of solar heat by increasing absorption and re-radiation. The interlayer chosen will determine the light transmittance of the glazing. Bent glass The glass can be pressed or bent during heating. Bending can be applied during the toughening process. The glass can also be laminated. Bends can be achieved in one or two panes. Insulating glass It consists of two or more panes which are separated by one or more spacers. The spacers serve as sealant materials to prevent air and water from entering. There is a dehydrator or desiccant in the spacer to prevent condensation. Overall, the insulating glass has a better thermal performance than single glazing. Decorative glass Including: The glass surface is treated in specific ways to achieve different decorative designs and patterns. This includes the following types: Patterned This is made by the rolled process in which a repetitive design pattern is impressed onto the surface of glass. Aciding A various degree of etched surface texture is produced during aciding. Stippling It is produced by floating grades of mica before the process of aciding. Bromesh This grained effect is achieved by interposing acid resistant substances before further aciding. Sand blasting It is produced by blasting an abrasive substance at the glass surface under pressure. Matt, peppered, shading, design patterns and other decorations can be achieved. Firing Ceramic color is fired onto the glass surface to achieve permanent colors. Engraving The glass surface is abraded by flexible drive tools such as copper wheels to produce decorative designs. Silk screen printing Combined with sand blasting, paint and other methods, a screen of nylon mesh or fine stainless steel is applied to the glass surface to achieve decorative designs and patterns. Edge working The glass edge is abraded or polished to get decorative profiles, also increasing edge strength by minimizing flaws in the edges. Table 4-3 Glass types (Button et al. 1993, p.355-364 & http://www.squ1.com, summarized) Glass size The book “Glass in Building” gives the general sizes available for float glass as follows: “Float glass thickness range from below 2 mm to over 25 mm for architectural purposes. They are usually 3, 4, 5, 6, 8, 10 and 12 mm thick, with 15, 19 and 25 mm for special uses. There is only one architectural quality for float glass. Most float lines have ribbon width just over 3 metres; available sizes depend on handling and shipping limitations rather than the manufacturing plant. Sizes which can be manufactured are not necessarily the sizes which can be directly used. Clear float is generally available in maximum size of 3,180 * 6,080 mm for all thickness of 3, 4, 5, 6, 8, 10 and 12 mm. For thick clear float (15, 19 and 25 mm) the maximum size will sometimes be smaller. ” (Button et al. , 1993, p.356) The dimensions of a glass pane are more limited by post processing machines than by manufacturing ability. From the view of economical purpose, the sizes of glass panes should not exceed specific limits; otherwise the cost of transportation and construction will rise much higher. Fig. 4-3 recommends the available glass pane size which is regarded to be economically restricted limits. Table 4-4 shows the design thickness of different glass types. Fig. 4-3 Production range of the glass panes (Kallioniemi 1999, p.13, excerpted) 28 29 Glass type Nominal thickness (mm) Typical minimum thickness (mm) 3 2. 8 4 3. 8 5 4. 8 6 5. 8 8 7. 7 10 9. 7 12 11. 7 15 14. 5 19 18. 0 Float glass 25 24 4 3. 5 Patterned 6 5. 5 6 6. 0 Wired 7 6. 0 * Toughened glass will have the minimum thickness of the glass from which it was made. Laminated glass will have the minimum thickness equal to the sum of the minimum thickness of its component glasses. No allowance should be made for the interlayer thickness in laminated glass. Table 4-4 Glass design thickness (Button et al.1993, p.135, excerpted) Glass strength An important issue designers need to know is that the effective (practical) strength of glass is significantly lower than the theoretical strength. Theoretically, the tensile strength of glass is 10 4 N/mm 2 . However, the practical tensile strength is only 30-80 N/ mm 2 , far lower than the theoretical numbers. Longer strain will further decrease the strength to only 7 N/ mm 2 (1,015 psi). Approximate treatment such as toughening can increase the tensile strength to about 120 N/ mm 2 (17,400 psi). (Compagno 2002, p.14) Glass is unlike some steel which offer pre-warning in the form of deflection under crack propagation. Glass will break without warning. This means that a designer has to make sure the glass will not be overloaded or stressed. Kallioniemi mentioned that: “There are two typical effects of the behavior of glass as a building material. First, the strength depends on the duration of the load application and on the environmental condition that can be e. g. dry, humid, or wet. Second, the probability of failure is the greater the larger the stressed surface area and the more uniformly the stresses are distributed. In most cases failure does not originate only from points of maximum tensile stresses. ” (Kallioniemi1999, p.11) 30 Many factors can affect glass strength. The impurities in glass, surface damages such as scratches, flaws in the edge, over local stresses and long time exposition of the loads can all decrease the glass strength and result in glass breakage. Hence, during the manufacturing process, every effort should be made to decrease the contents of impurities in glass. During assembly, transportation and installation, glass should be carefully protected from being damaged. Cutting and drilling should be done very carefully to prevent flaws on the edges. Structural designs should avoid local overstressing. To avoid local overstressing, the design of supporting systems is important. In a traditional edge-supported glazing system, three major constrains should be considered: allow enough clearance for movements; cover the glass edge to enough depth; avoid large deflections of the frame under loads. Firstly, enough clearance around the glass should be made to allow movement under loads or thermal variation. As a rule of thumb , the minimum clearance is 3 mm for single glazing, and 5 mm for double glazing. As the glass pane size increases, the clearance should also increase. Secondly, the size of the bearing surface holding the glass edges should be no less than the glass thickness, or minimum of 6 mm for single glazing and 12 mm for double glazing. (Button et al.1993, p.219) There are two designs to prevent glass from being over-stressed at local points in a PSG wall system. One traditional way is to separate glass and its support by an absorbing and a flexible material, such as a rubber pad or seal. Another way is a so-called “positive design”: to design the load value and load path very precisely under all load conditions. Two examples are the design of the spherical fixing and the compressed spring support fixing. (Kallioniemi1999, p.12) Table 4-5 is excerpted from Vandenberg’s book “Glass Canopies”. The table lists a detailed description of the glass types from the strongest to the weakest: toughened glass; heat strengthen glass; float glass and patterned glass; and wired glass. For overhead glazing, a safety glass must always be used except for buildings such as agricultural greenhouses. (Vandenberg 1997, p.8-9) 31 Glass type Description Safety glass? Toughened glass (known in the USA as ‘tempered glass’) A heat-treated glass that is four to five times as strong as float or patterned glass. Has the advantage of breaking into relatively safe dice rather than dangerous shards when fractured; but the disadvantage that it cannot be cut, worked or drilled after toughening and must be ordered to precise dimensions. Yes Heat strengthen glass Twice or three times as strong as float or patterned glass; breaks into sharp-edge shards when fractured No Float glass and patterned glass (the latter previously known as cast glass The two most commonly used types of annealed glass. Not particularly strong, and break into sharp shards when fractured. No Wired glass The weakest glass of all but has the advantage of holding together after fracture. (Wired glass is often used as fire- resistant glass. ) Yes Any combination of the above glasses laminated to an interlayer of plastic such as polyvinyl butyral (pvb) will form a safety glass. Table 4-5 Glass type from the strongest to the weakest (Vandenberg 1997, p.8, excerpted) Glass strength is only one of the factors which will affect the design strengths of glass. Other factors, such as deflections, also influence the design strength. For instance, the design strengths of glass should be usually lower than the stresses the glass can take in order to avoid too big deflections that are beyond visually acceptable levels. Deflection should particularly be avoided for toughened glass, which has higher strength than many other glass types. (Button et al.1993, p.234) 4. 2. 2 Steel, stainless steel and aluminum Steel is commonly used in load-bearing structures because of its high strength. Because in PSG walls steel is generally exposed, it must be protected from corrosion (e. g. water, high temperature, chemicals, etc). It also needs to be treated for fire resistance. Stainless steel does not corrode; neither does it dim in outdoor conditions. Generally, its coefficient of thermal expansion is 1. 5 times bigger than that of steel and 2 or 3 times bigger than that of glass. Therefore, specific considerations are required when making details if these materials work together. Aluminum is a light, easily formed, and corrosion free material. It is often used as fasteners and mullions. However, because of its big coefficient of thermal expansion, welding is relatively difficult, therefore it is not ideal for individual usage or small series. (Kallioniemi1999, p.15) 32 4. 2. 3 Silicone The connection between the glass panes is usually structural silicone. Silicone is a macromolecular polymer. Compared to other rubber like materials, it can be used over a wide range of temperature. (Kallioniemi1999, p.69) According to the test at La Villette Museum in Paris, silicone has a strong adhesive power under these two conditions: the glazing surface is absolutely dry and clean; the joint is not too wide in order to prevent polymerization. The test shows that when the joint width expands four times the original size, failure occurs in the joint itself instead of the glued surface. (Rice et al.1995, p.56-57) This test also indicated that silicone actually improves the structural performance of the glazing wall. An ideal sealant detail should have three functions (Rice & Button 1995, p.57): It has enough structural strength to bond the glass panes together. It has enough flexibility to allow displacements of the glass panes. It provides reliable water tightness for the joints. A successful example of silicone details is shown in the New Exhibition Center in Leipzig, Germany. In this case, a special challenge is the large displacement of the glass panes. A custom “many component sealing system” was developed which includes “prefabricated silicone profile” and “squeezable silicone”. The squeezable silicone is used to seal and bond the glass panes together, while the prefabricated silicone profile allows large displacements of the glass panes. (Kallioniemi1999, p.63) The following images (Fig. 4-4 and Fig. 4-5) show the squeezable silicone and prefabricated silicone profile in both horizontal and vertical joints in the New Leipzig Exhibition Center. Vertical joint Horizontal joint Fig. 4-4 The silicone joints in the New Exhibition Center in Leipzig, Germany (1) (Vandenberg 1997, p.45, modified) Fig. 4-5 below show how the silicone joints work under the large inter-pane displacement. Horizontal joint Vertical joint Fig. 4-5 The silicone joints in the New Exhibition Center in Leipzig, Germany (2) (Vandenberg 1997, p.46, modified) More detailed description of silicone can be found in 5. 3. 3. Readers can also get more information of silicone from the webpage of Dow Corning Corporation, one of the well-known silicone-based material manufacturers. For instance, Dow Corning 995 Silicone Building Sealant is specifically developed for structural glazing. (Anon 2 2003, online) 33 4.3 Components There are many types of glass walls. Different books describe different categories. There has been no standard category to define glass wall systems. However, without having an overview understanding of available glass wall types, it is hard to do appropriate design or detailing. Therefore, in this thesis, a new category is proposed to define the glass wall types based on structural difference. A typical PSG wall consists of five parts (Fig. 4-6 and Fig. 4-7): 1). Glazing panels – also known as cladding system 2). Glass fittings – also known as fastening system 3). Glazing support attachment – also known as profile system 4). Glass support structure (back up structure) – load bearing and transferring system 5). Building infrastructure – primary load bearing system 34 Fig. 4-6 Components in a typical PSG wall (plan) (Trebilcock 2004, p.142, modified) Building infrastructure Building infrastructure Glass support structure (Back up structure) Glass fittings Glazing support attachment Glazing panel Fig. 4-7 Components in a typical PSG wall (section) Glazing panels are the skin of the structure; glass fittings show how the glass panes are fixed to the support attachments; glazing support attachment is the component by which the glass is attached to support structures; glass support structure (or back up structure) shows how the glazing façade is braced; infrastructure support shows how the whole glass wall is fixed to the rest of the building. Together they describe a glass wall through five layers. For instance, one can describe the glass wall in the University of Connecticut as the following (Fig. 4-8): In the south façade of the library at the University of Connecticut, the glass panes are insulated double glazing, green-tined and low-E coat; the glazing is point-supported and the fixing type is Pilkington Planer System; the glazing support attachment is a stainless steel four way spider; the spiders are then supported by tension cables; then the whole glass wall is attached to horizontal infrastructure, which is roof to floor. (http://www.wwglass.com/) Fig. 4-8 The PSG wall in the University of Connecticut 4.3.1 Glazing panels Glazing panels often serve as the cladding system of buildings. They cover the structure; protect the inside from the outside; and satisfy some functions such as visual, thermal, and mechanical functions. Table 4-6 gives a checklist of these functions summarized from Button and Pye’s book Glass in Building (1993), in which each of these functions is explained in detail. Categories Notes Visual functions Admission of daylight The three user requirements are: tasking lighting, amenity lighting and energy conservation. Providing sufficient amount of light and proper distribution type for task lighting. Better quality is required for higher demanding tasks. Daylight alone can not work for the entire working day throughout the year, and therefore artificial lighting should be used as a supplement. The quantity of task lighting is determined by light transmission and the glazed area. The quality and distribution of task lighting is determined by the position, shape and orientation of the glazing, and the space nature to be lit. Providing proper amenity lighting for the appearance of an interior space and the contents inside. The target is to create light, shape and texture. It generally has a lower level than task lighting. Table 4-6, Continued on next page 35 36 The quality of amenity lighting is based on the occupant’s subjective judgment. The areas of light, the ‘flow’ of light, the light intensity and distribution, and the shading patterns, will affect the psychological feeling of the occupants. Energy conservation can be achieved by successful integration of daylight and artificial light. Factors involved may include orientation, room shape, tasks, occupancy patterns, and surrounding conditions. View in and View out View in involves light transmission and reflection, color and obscuration. View out involves the content of the outside scene, height above ground level, window area, shape and disposition, and spectator position and activity. Appearance of the facade The visual endowment of glass can be explored by glass artists, architects and glass manufacturers. Traditional glass decorative methods such as stained glass can be combined with the new technologies such as holography. Decorative effects of glass can also be incorporated with other glass functions such as solar control systems. Thermal functions Preventing heat loss in cold climate Heat loss consists of three stages: from the room surfaces to the internal glass surface; through the glass product; from the outer glass surface to exterior. Heat loss is generally qualified by the thermal transmittance of U-value in W/m2k or Btu/ft 2 h o F. The higher the U-value, the lower the ability to resist heat loss. Single glazing is relatively poor in resisting heat loss. Multi-layered glazing with one or more air cavities can increase thermal resistance. Thermal resistance increases as the width of the air space increases. However, a width after 15mm does not provide extra thermal benefit due to convection within the air space. A low emissivity (Low E) coating on the glass reduces the exchange of long wave radiation between the glass panes. The glass material, the spacers in multiple glazed units and the framing together determine the thermal transmittance of the complete window. Spacer materials should have low thermal conductivity such as rigid silicone foams and hollow polycarbonate extrusions. The usage of spacer may add up t0 10% to the window’s U-value. If using materials with high thermal conductivity as frames, such as aluminum, a thermal break should be used. Preventing heat gain in hot climate Solar control glass is often used to reduce unwanted heat gain. The type glass is usually body tinted (absorbing) or surface coated (reflecting). Body tinted and coatings can be combined in a single glass to increase the solar control ability. The thickness of body tinted glass affects its solar control properties. When used in double glazing, body tinted glass should be placed as the outer pane. Reflective coating glass provides greater production flexibility, higher solar heat attenuation, better light/heat ratios, and wider range of color appearance than body-tinted glass. Incorporating shading devices such as louvers and blinds in single double glazing and laminated glass can reduce heat gain. Variable Transmission (VT) glass which is still under research is another method for solar controlling. It generally has two types: mechanical and non-mechanical methods. The later one usually incorporates photo-chromic, thermo-chromic and electro-chromic materials. It may provide a full range of solar control response, but has higher benefit-to-cost ratio. Tilting the glass façade with the top outwards can increase the reflection of light. A light/heat ratio is often used to qualify the ability of the glass to let light in and reduce heat transmission. Table 4-6, Continued on next page 37 Keeping heat balance Keeping annual heat balance by admitting solar heat and reducing heat loss in winter; while reducing solar gain in summer. Passive solar gain design is an effective way to maintain acceptable solar gain and reducing energy consumption. Mechanical functions Durability of glass Glass is defined as a durable building material because of its chemical structure, a random and complex molecular structure which increasing the resistance to crystallization, durability of glass. The physical conditions of flat glass surfaces affect the glass durability. Different coating types applied to glass surface will affect the durability of the glass. No matter coated or uncoated, glass surfaces need to be protected from damage during three conditions: handling, storage and in service. Hardness is a term used to qualify the resistance to mechanical surface damage which including three types: scratch damage, abrasion damage, and penetration damage. Glass strength The strength of glass is adopted to measure the ability to resist both natural and man-made forces. The effective strength of glass is significantly smaller than the theoretical strength. Glass surface quality affects the glass strength. When under stress, glass deforms to a certain degree and then stops. If over-stressed, glass tends to break without warning. Glass is vulnerable to local overstressing. A thumb of rule is the usage of “avoid glass-to- metal contact” to avoid over stress at local points. Some flexible materials such as a nylon or bush can be used. In a few special cases, such as patent glazing systems, glass can be in contact with a relatively soft material such as aluminum spring wings. In PSG walls, because of the inevitable stress concentrations around the drilling hole, toughened glass should be used. The design of the glass supporting systems also affects the glass strength. Wired glass and laminated glass are not stronger than annealed glass. They are considered as safety glass because of the breakage pattern. Resistance to wind and snow The factors influencing dynamic wind pressure include effect of topography, effect of roughness of terrain, height of building, and size of component. The ability of glass to resist wind load depends on: glass types, thickness, area, shape and supporting systems. Under uniform loads, the glass types from the strongest to the weakest are toughened glass, heat strengthened glass, float glass, patterned (cast) glass, and wired glass, respectively. Snow loading should be considered as a long term loading which means a reduced design stress should be used in the design of glass. Alternatively, snow load can be considered as an equivalent wind load if applied a design factor. Snow load is generally considered as uniform load like wind load. Therefore the factors affecting the resistance to wind load also apply for snow load. But drifted snow may apply a triangular distribution. This should be taken into account when calculating stresses and deflections. Magnitudes of design wind load are from 500N/m 2 to 8000N/m 2 . The minimum magnitudes of design snow load are 500N/m 2 . Resistance to water loading In buildings like aquaria or swimming pool, if the glass is broken, the results may be catastrophic. Therefore the design of water load is very important. Water pressure is directly related to the water depth. Therefore the water load applied to glass is triangular instead of uniform. Because water pressure is a sustained pressure and glass suffers from static fatigue, the design stresses of water load are much lower than those of wind load, and therefore thick glass is required. Three glass types may be considered for water load: thick annealed glass, thick laminated glass and laminated toughened glass. It should be taken into account that some animals in aquaria will make considerable impact on the glass. Table 4-6, Continued on next page 38 Supporting structures like clamping or pinning should not be considered. The deflection of a supporting member should be sufficiently small. Most common supporting type is simple support system like four-edge supporting system. Laminated toughened glass should contain at least one more layer of glass than the design load requires. All leaves should be the same thickness. Resistance to thermal stress Thermal breakage occurs not only in hot area, but also in cold area. Any factors which increase the hot-center/cold-edge condition in glass will increase the thermal stress. Factors affecting thermal stress include: solar radiation, diurnal temperature range, absorption, multiple glazing, frame material, edge cover, internal shading, back-up materials, and internal heaters. The factors affecting thermal strength of glass include: The edge condition, glass size and thickness, and the type of glass. From the strongest to the weakest, the glass types in terms of their thermal safety are: toughened glass, heat strengthened glass, thin float glass, laminated float glass, thick float glass, thick laminated glass, cast glass and wired glass. Toughened glass is always safe for thermal stress, apart from a fire. Resistance to human impact Study shows that a 100lb boy was representative accident victim of glass breakage. For safety, glass is required either not to break, or to break safely. Safety glass includes: laminated glass, wired glass, glass with applied plastic film, and toughened glass. Hazardous areas include doors and glazed panels in the door, low level glazing, swimming pools and bathrooms, and building with special activity such as gymnasiums. The possibilities of body injuries from the biggest to the smallest are hand, head, leg, arm, other, and truck, respectively. Resistance to human attack The attack may come from human body, bricks, axes, hammers, torches and so on. Toughened glass is not idea because it is vulnerable to impacts from sharp objects, and its small fragment when broken can not hurt attackers. Annealed glass may be good because its sharp edges can hurt attackers when broken. It is especially useful when the panes are small enough to make entry difficult. But attackers may reach a door or window catch after breaking the glass. Laminated glass is idea in resisting penetration. The resistance to penetration depends mainly on thickness and number of PVB interlayers. Glass incorporating rigid polycarbonate interlayers allows the same performance as laminated glass with reduced thickness. Resistance to explosive loading Injuries caused by explosions include: burns from exposure to heat, direct injuries from the explosion pressure wave and shrapnel damage from building material like glass. The design of glass is to make glass to either remain unbroken or remain in place when broken. If the explosion pressure is under 10kN/m 2 , it can be considered as a wind load. If the pressure is over 10kN/m 2 , toughened glass is usually used. It is generally more economical to design the glass to remain in place if broken than to remain unbroken. Laminated glass with a highly plastic interlayer (PVB) should be used. In double glazing the laminated glass should be placed in the inside layer in the explosion is outside; the outside layer can be any type. Fixing methods are important. The general rules are: increasing the edge cover of glass beyond the one used in normal glazing frames; bolting the beads at frequent intervals to resist the partial vacuum after the blast; using high bond strength sealants or clamping pressure. Other methods include the usage of glass applied with blast resistant films or blast curtains. The service life of blast resistant film is shorter than laminated glass. Resistance to bullet Glass combined with multiple layered laminates with plastic, ductile and energy absorbing interlayers can be very effective in resisting bullet impact. Two major groups of glass products are: glass plies laminated with polyvinyl butyral (PVB) interlayers; glass incorporating polycarbonate within the construction. Table 4-6, Continued on next page 39 All the glass edges should be protected in strong rebate so that the glass will not be levered away to create a gap. The fixing system should be strong enough to keep the glass in the frame under explosion pressure. Other functions Fire resistance Glass products for fire resistance include three types: non-insulating, partially insulating, and insulating glass. Non-insulating glass products include wired glass and special composition glass. Partially insulating glass products are usually multi-laminated panes with an intumescent interlayer which becomes opaque when heated. Insulating glass products have two types: intumescent laminated glass and gel interlayered glass. All partially and fully insulating glass products require UV light protection if used externally. The fire resistance level of a glazing system is determined by glass, glazing materials, framing, frame retention and deflection, and beads and fixing details. The weakest components determine the quality of the whole system. Sound insulation The target of the glazing acoustic performance is to attenuate the exterior noise to a certain level that does not annoy, but is still sufficient to mask ambient noise. The Mass Law is the fundamental principle of the sound insulation of glass, which indicates that the sound insulation is increased by about 4 decibel with each doubling of glass thickness. But intrinsic resonance phenomena should be taken into account which will impair the acoustic insulation performance at certain frequencies. If separating the two main glass components with an air space over 100mm, potentially the highest sound insulation may be achieved. Other design factors influencing sound insulation include: glazing area, the distance to a noise source, building height, barriers, glazing types and fixings. Except for laminated glass, other glass types have the same acoustic performance as ordinary clear float glass. Electromagn etic shielding The purposes of electromagnetic shielding include: to exclude unwanted electromagnetic radiation; to contain radiation signals from equipment; using sensitive detecting devices to prevent interrogation of computer and data handling systems Clear or tinted float glass is not very effective in shielding. But with a thin metallic coating, its shielding ability can be significantly improved. The coatings on glass should be connected to the window frame along its periphery to maximum electrical signal shielding. Table 4-6 Functional requirement checklist of glass facades (Button et al.1993, summarized) For the purpose of drilling requirements and safety, the glazing should be toughed glass in PSG wall systems. Either single or double glazing can be used in PSG wall systems, but depending on the different back up structure, double glazing can not be used in some cases. (See 4.3.2 for more details.) The connectors of glazing panels are usually structural sealant. Please see 4.2.3 for details of the properties of sealant. 4.3.2 Glass fittings Glass fittings are the devices fastening glass panes together. Two types of fittings are used; edge supported and point supported. Edge-supported glass systems can be either mullion or glass-fin. It is also called as “linear support,” or “framed systems.” Framed systems include four-edge, three-edge, and two-edge supporting frames. In this system, the glass panes are supported by frames. Edge-supports can be mullions of wood, steel or aluminum. Mullin-support glass systems can be attached to frame, diaphragm, truss, cable, cable-truss, cable-net, or straight-cable. This thesis does not give a detailed study of this supporting system. Point-supported glass (PSG) systems are the type the thesis intends to discuss. Some books also describe point-supported systems as “point-fixing systems”. It can be done with glass perforation, or without perforation. For systems with perforation, the glass panes are fixed at bore-holes and fastened by screws. For systems without perforation, the glass panes are equipped at the local points or at their corners by fittings attached on both sides. (Behling, Sophia and Behling, Stephan 1999) PSG systems without perforation Point-supported glass (PSG) systems without perforation are commonly applied in cable-net structure are also called cable-lattice structure. An example is the Hotel Kempinski at Munich Airport, designed by Murphy/Jahn architects in 1994. The 1. 5 × 1. 5 m, 10 mm thick laminated glass panes are bonded together by specially developed clamping plates. Here, “the pocked-shaped retainers with a soft lining fitted to the corners of the panes,” allow for movement between the glass and net fixings. (Schittich et al. 1999, p.112) See Fig. 4-9 below. Cable net joint, outside view (Dobney 1995, p.184) Cable net joint, inside view (Compagno 2002, p.16) Fig. 4-9 Cable net joint in Hotel Kempinski at Munich Airport 40 Fixings without perforations are also seen in glass-fin supported glass walls. A typical example is the Ha-lo building in Niles, Illinois, also designed by Murphy/Jahn Architects in 1999. In the glass-fin supported glass wall, an aluminum pinch plate is pinned to a stainless steel boot. (See Fig. 4-10, left. ). In the glazing roof, the aluminum pinch plates are pinned to a custom designed aluminum four-way spider. (See Fig. 4-10, right.) (Wright 2001, p.38) In this case, the fixings are pinned connections in stead of drilling holes with screws. Fig. 4-10 Glass fin joint in the Ha-lo building (ASI brochure 999) Similar pinned joint fixings can also be found occasionally in cable truss glass walls, for instance, the FKB Airport designed by Murphy/Jahn Architects in 1992. Here the insulating glass panes are held by four-way spiders and fixed by pin joints. PSG systems with perforation For point-supported glass with perforation, basically, there are six types of mechanical glass support systems. They are: standard bolt, simple countersunk bolt, stud assembly, patch plate, Pilkington Planer system, and articulated bolt system (See Fig. 4-11). Within these six types, the patch plate system and the Pilkington Planer system are invented by Pilkington and are more popular nowadays compared to other types. (Rice and Dutton 1995, p.35-36) As Button mentioned in his book Glass in Building, for all types which use bolt fixings, toughened glass should be used, because in bolt fixings there is stress concentrated around the holes, making the holes weak points in laminated glass and annealed glass. (Button et al. 1993, p.220) 41 Standard bolt Simple countersunk bolt Stud assembly Patch plate Pilkington Planer system articulated bolt Fig. 4-11 Five types of mechanical point-fixing system with perforation (Rice and Dutton 1995, p.35-36) The following describe each of the six types in detail. All of them can be found in the book Structural Glass (Rice and Dutton 1995), unless otherwise specified. Standard bolt The glass weight is concentrated at the holes. Firmly fixed glass. No differential movement between supporting structure and glass is allowed. 42 Simple countersunk bolt It is possible to make a flush exterior surface with simple countersunk bolt. All glass weight and loads are concentrated around the holes; therefore high stress is concentrated in the holes. For this reason there is a very high requirement for drilling accuracy. Stud assembly It can take heavier load and at the same time allow smooth appearance. Cylindrical stud take the weight of glass and the areas surrounding the holes take other loads. Oversized holes increase the load-bearing surface, thus reducing the pressure applied to the glass. With an articulated assembly, this system can achieve required movement capacity. Patch plate It is an improvement based on the standard bolt. It has smaller drilling imperfections. “The patch plate is glued to the glass and the entire assembly is clamped together by a bolt.” (Rice and Dutton 1995, p.35) The glass weight is not only taken by the area around the hole, but also by friction against the patch plate. No differential movement allowed. The Willis Faber & Dumas building designed by Norman Foster firstly used this kind of system (see Fig. 4-12). The patch plate system was firstly used in Willis Faber & Dumas building designed by Norman Foster in 1975. In this project, the glass pane is 2 × 2. 5m, 12mm thick toughed glass. The brass patch plate is 165 ×165mm. The entire 15m high glass façade is suspended from the edge of the top floor by a single 38mm diameter bolt. Glass fins suspended from the intermediate floors resist the lateral wind load. Fig. 4-12 Willis Faber & Dumas building designed by Norman Foster (Compagno 2002, p.18) 43 44 In Pilkington’s book Glass in Building (Button et al.1993), this system is also called bolt and plate-fixings. Pilkington first designed and developed this system in the 1960. The system is generally used in suspended glass assemblies, in which the glass façade is “suspended from the building structure by hangers bolted to its top edge, and is sealed to the building in peripheral channels by means of neoprene strips or non-setting mastic.” Suspended glazing systems: Because glass works better in tension rather than in compression which causes buckling, glass is often suspended from a roof or floor. Most glass-fin supported glazing systems are suspended systems. When suspended, glass-fin is in tension only, therefore it will not buckling. (Shepphird, personal communication, 2005) Because of no buckling in the glass, thinner glass can be used. When the available maximum size of the glass pane is exceeded, several panes may be suspended from each other like a chain. Since the top of the chain is hung to the building, the bottom edges of the panes must be designed and installed in a way to allow free movement during structural movement or deflections, so that there is no restraint on the glass. One advantage of suspended glazing is that the system will continue to work if a glass panel is broken. (Schittich et al.1999, p.162) The conceptual diagram below (Fig. 4-13) shows how patch plate fixings work in a typical suspended glazing system (Button et al.1993, p.330). In a suspended assembly design, the glass panes are fitted by metal corner patch, or so called “patch fittings” in some books. Toughed glass fins are used to resist horizontal wind load. The whole glazing façade is suspended on top to the beam. Fig. 4-13 Patch fitting and suspended assembly design (Button et al.1993, p.330) Because the façade is “floating” from the primary infrastructure, it allows movement between glass façade and the building structure. This is beneficial for seismic design. A structural silicone building sealant is used at the pane-to-pane joints for water-tightness, but it also helps to improve the strength of the façade and therefore increases the safety factor. (Button et al.1993, p.329) 45 46 Because the friction against the patch plate is used to resist loads, the correct size and quality of bolts and plates are critical in design. Sometimes, additional suitable adhesive can be used at the “metal/gasket/glass interface” to enhance the friction coefficient. “The relationship between the components of a bolted fixing can be determined after the appropriate size of bolt has been chosen. The thickness of the spreader plate should be about three-quarters of the bolt diameter, but not less than 6mm. The diameter of the spreader plates should be about eight times its thickness. ” (Button et al.1993, p.220) See Table 4-7 below for some examples. Bolt diameter (mm) Spreader diameter (mm) Plate thickness (mm) 6 50 6 8 50 6 10 60 8 12 75 10 16 100 12 Table 4-7 the relationship between the sizes of the bolt and the spreader plate (Button et al.1993, p.220, excerpted) The size of suspended glass panes is limited by the relatively high stress concentrated at the points, rather than by the low deflection. According to information provided by Pilkington: “Single assemblies can be designed up to 20m in height on a 1. 5m module, and up to 23m on a 1. 2m module. If using multiple assembly design, any height of glass façade can be achieved. ” (Button et al.1993, p. 331) The main disadvantage of this system is that it cannot use double-glazing; neither can it be applied in non-vertical structures. Also, it seems that it can only be backed up by glass fins, although there is no official report about this. The Pilkington Planar system In this system, flexible washers at the points allow the glass and bolt to move in relation to the structure. This system is very common used nowadays. Planer CR system type 902 was one of the first such products and was firstly used by Norman Foster in 1982 in Renault Centre in Swindon in England. In this building, the single glazing façade is screwed instead of suspended from the supporting frames. (Schittich et al.1999, p.51) The design principle of the Planer system is exactly opposite to that of plate fixing system in which the glass façade is suspended from the top edge of the building. In Planer system, each glass pane is fixed separately, rather than supporting the glass panes below it. Therefore, the stress developed in the glass is significantly reduced. (Button et al. 1993, p.332) Compared to patch plate system, the main advantages of this system are: perfect flush appearance; it allows the usage of either single or double glazing attached to any types of structure (see Fig. 4-14); it can be applied to either vertical or sloping structures. It allows rotation of the glass due to minimal clamping size. However, because of the lack of clamping, the size of glass panes is more limited by deflection than that of patch plate system. There is no limitation on building height since the glass panes are fixed individually to the structure. (Button et al.1993, p.332) Fig. 4-14 Exploded axonometric of Planar Bolted double glazed fixing (Button et al.1993, p.334-335) Articulated bolt With an articulated bolt, the articulated assembly is located inside the plane of the glass, rather than outside. This ensures that there is no twisting or bending applied to the glass. In a stud assembly and the Pilkington Planar system, the articulated assembly is positioned outside the glass plane, therefore bending or twisting loads will be taken by the glass. Fig. 4-15 below shows a comparison between the two positions of the articulated assembly, in which, the left one shows that the articulated assembly is placed outside the glass plane, and the bending forces can occur in the glass; the right one shows that the articulated assembly is placed inside the glass plane and the bending forces are taken by the support structure member. (Rice and Dutton 1995, p.37) 47 Fig. 4-15 Articulated bolt system (Rice et al.1995, p.37) Although the articulated assembly located inside the glass avoids the stress on the glass, it is relatively difficult to combine it with other components such as tension rods compared to the assembly located outside the glass. (Schittich et al.1999, p.160) The articulated bolt was successfully used in the greenhouse of the La Villette Museum, designed by Rice and Francis and Ritchie (RFR) in 1986. In this building, the glass façade is a suspended system and has a flush exterior surface. This is different from the Willis Faber & Dumas building, in which the suspended glass façade does not have a flush appearance because it uses patch plate fittings. Some useful tips for the usage of the glass wall systems with perforations Rice and Dutton (1995, p.36) concluded four major design issues regarding the holes in the glass. They are: Point-supporting system cause high load concentrations. Drilling accuracy is very important to avoid fracture of the glass. Countersunk hole is particularly sensitive. With the help of articulated assemblies differential movements can be achieved. Larger holes can reduce the stress applied to the glass. 4.3.3 Gazing support attachment The glazing support attachment is also known as profile system. Its primary function is to transfer loads from the cladding system (glazing panels) to the load-bearing structures (back-up 48 structures or building infrastructures). The profile system and cladding system together create a “coherent close structure, a so-called light shell. ” Traditionally the material used in the profile system is aluminum, but stainless steel or plastic has also been adopted. (Kallioniemi1999, p.7-8) If glazing is not connected to a profile system, but directly mounted to the support structure, it is not easy to make adjustment to allow movement between the glass and the structure. This is why the glazing support attachment is generally used to separate glass from support structure. The most common forms of glazing support attachments are: angle brackets, pin brackets, clamping devices and spiders. Simple attachments such as angle brackets are stiffer, and spider attachments are relatively flexible. Fig. 4-16 illustrates angle brackets (a) and spider attachments (b). (Trebilcock 2004, p.146) Welded angle brackets Welded cleat and bolted angle brackets (a) Attachment to tubular sections Fig. 4-16, Continued on next page 49 (b) “Spider” attachments Fig. 4-16 Glazing support attachments (Trebilcock 2004, p.146) Design of the profile system may be done two ways: using the design of available products by manufacturers; making custom designs for specific requirements of a project. Designers should contact the manufacturers as early as possible to check the availability of the products, making sure that the usage of the products will satisfy all design requirements. Custom designs need to be tested before applied to real projects. 50 4.3.4 Glass support structure (backup structure) The glass support structure supports the whole glass façade and provides resistance to horizontal loads like wind or seismic activity. The primary function of the glass support structure is to transfer loads from the glass and its attachments to the building infrastructures. Besides the requirement for structural strength, other requirements such as fire protection and thermal expansion should also be considered. Generally, glass support structure is not necessary if the span is short enough, for instance, for a vertical span less than 12 feet, and a horizontal span less than 10 feet, for the reason that the glass walls within that span can resist horizontal loads by themselves. If the span is bigger than mentioned above, an additional backup structure is designed to resist horizontal loads. (Kallioniemi 1999, p.7 & Schierle 2004, personal communication) There are five types of backup structures listed as below: Metal frame – the glazing façade is framed by tubular metal frames (Fig. 4-17, a). Truss – the glazing façade is braced by vertical or horizontal truss (Fig. 4-17, c). Tension cable (rod) – the glazing façade is braced by vertical or horizontal cable and truss. Cables may be curved or straight (with high tension). Cables serve as tension members, and are spaced by compression members like struts (Fig. 4-17, d). Cable-net – the glazing facades is braced by cable-net (Fig. 4-17, e). Glass-fin – the glazing façade is braced by vertical or horizontal glass-fins (Fig. 4-17, b) 51 (a) (b) (c) (d) (e) Fig. 4-17 Five types of back up structures Metal frame support The glass fittings can be attached to tubular metal frames. The material used is generally steel because of its good strength and fastening properties. The following are three examples. Example one is the Kadoorie Biological Science Building in the University of Hong Kong, designed by Leigh and Orange Ltd. The metal pipes and glass fixings are placed on the exterior surface of the building. See Fig. 4-18. Fig. 4-18 Metal frame supported example – Kadoorie Biological Science Building (Anon 1 1999, Details in Architecture V3, p.110, 114) Example two is the Western Morning News, designed by Nicholas Grimshaw and Partners. In this example, the curved glass façade is supported by a series of curved metal columns. Every two columns of spiders are attached to one curved metal column through long metal arms. (See Fig. 4-19 below.) 52 Fig. 4-19 Metal frame supported example – Western Morning News (Compagno 2002, p.37 & 38) Example three is the TGV railway station at Roissy designed by ADP Architects in 1994 (Fig. 4-20). This example is similar to the second example. The difference is that the metal pipes are straight, not curved. The glass façade is 100 meters long and 17 meters high. The design of the articulated bolt fixings of this project is the same as the one used in the La Villette Museum designed by Rice, Francis and Ritchie (RFR) in 1986. Combined with the sophisticated stainless steel ‘hand’ complex, the glass fittings “restrain the glass against loads perpendicular to the surface”, and “allow differential movements such as thermal expansion, creep and deflections without loading the plane of the glass”. (Rice and Dutton 1995) Fig. 4-20 Metal frame supported example – TGV Railway Interchange (Rice and Dutton 1995, p.23, 138) 53 Truss support The glass fittings are attached to truss, which is used to take lateral loads. The depth of the truss is usually 1/15 to 1/10 of the total span. Truss-supported structures can be used in both vertical and non-vertical facades. The truss can have different shapes. (See Fig. 4-21 below.) Fig. 4-21 Truss shapes (ASI brochure 2003) Example one is the Sydney Convention and Exhibition Centre South designed by Architects; Ancher Mortlock Woolley Pty Ltd. The glazing façade is slope (Fig. 4-22). The simple trusses serve as mullions to support the glass panes. Fig. 4-22 Truss support example – Sydney Convention and Exhibition Centre South (Anon 1 1999, Details in architecture V2, p.14, 17) 54 Example two is the Hong Kong Station designed by Arup Associates in association with Rocco Design Ltd (Fig. 4-23). The glass wall is 17. 5 meters high and 106 meters long, featuring the largest “independently supported glazed wall in the world”. Because the building is located in a typhoon area and seismic zone, the structural design of the glass wall was especially important. Here trusses are used to resist wind and seismic loads applied to the huge glazing façade. (Pearce et al.2001, p.16) Fig. 4-23 Truss supported example – Arup Hong Kong Station (Pearce 2001, p.42, 41) Example three is the New Exhibition Center in Leipzig, Germany, designed by Von Gerkan, Marg & Partner in 1993 (Fig. 4-24). The vaulted glazing surface is supported by “a filigree steel frame of trussed arches and a grid shell from which the transparent glazing is suspended on the room side.” The two side glass walls are also supported by trussed arches. The laminated glass panes are attached to the cast arms by articulated point fixings. (Compagno 2002, p.132, 133) 55 Fig. 4-24 Truss supported example – the New Exhibition Center (left image: Compagno 2002, p.133) & (right image: Trebilcock 2004, color page) Tension cable support The glass fittings are attached to tension cables. The cables are used to resist lateral loads and are always in tension. The depth of the curved cable is usually 1/10 of the total span. The cable can be either curved or straight. Curved cables can have different shapes (see Fig. 4-25). Fig. 4-25 Tension cable shapes Example one is a glass wall in the Sony Center in Germany designed by Helmut Jahn Architects in 1993 (Fig. 4-26, a). The double-curved cables are used to brace the glass wall. The cables are then attached to vertical columns. 56 Example two is the Shanghai New Opera House in China designed by Arte Jean-Marie Charpentier et Associes in 1998 (Fig. 4-26, b). Vertical triangular-shaped cables act as primary back up structure; horizontal cables act as secondary back up structure. The vertical cables are attached to the building infrastructures, which are the beam and floor, and are additionally supported by columns. (a) Sony Center (Blaser 2002, p.51) (b) Shanghai New Opera House (Krampen 1999, p.59) Fig. 4-26 Tension cable supported example Sometimes straight cables are used instead of curved or angled cables. Similar to cable net structure, straight cable supported structure is able to achieve a façade with maximum transparency. Straight cables produces higher stress under loads than curved or angled cables, and therefore they must be applied with enough high pre-stress to resist certain loads. One typical example of straight cable supported structure is the Hotel Esplanade in Berlin designed by Murphy Jahn Architects as a part of Sony Center. The façade is 60 meters long and 20 meters high. The double-straight cables are vertically spanned at a spacing of 2 meters. Specially designed springs are used to provide constant pre-stress to the cables. Individual drilled point fixings are used to fix the glass panes directly to the cables. 57 Glass fin support The glass fittings are attached to glass fins which are used to resist lateral loads. Glass fins are generally made of toughened glass. The thickness is usually 10-20mm (0. 4in – 0. 8in). The maximum length of a single glass fin is 4. 5m (13. 5f) according to Nijsse (2003). The width of the glass fin is about 1/20 of the total height. Example one is the Luxembourg City History Museum designed by Conny Lentz, Luxembourg Reperages Architects in 1996 (Fig. 4-17). The whole glass façade is 12 meters in height and 14 meters in length. Each glass pane is 1. 27m-wide, 3. 76m-high and 12mm-thick toughened safety glass. Each glass pane used in the fins is 750mm-wide, 4m-high (approximately) and 19mm- thick toughened safety glass. Each fin consists of three glass panes, connected with each other “by way of stainless steel plates screwed together. At the top, they are supported by cantilevered steel beams (HEM 260), at the bottom they disappear into a plinth clad with sheet metal. ” (Krewinkel 1998, p.147) Fig. 4-27 Glass fin supported example – Luxembourg City History Museum (Krewinkel 1998, p.143, 144, 146) 58 Example two is the Main Public Library in Memphis designed by Looney Ricks Kiss Architects in 1997 (Fig. 4-28). The glass façade is 60-feet-high and 36-feet-wide. The designer of the glass wall “light veil”, Ed Carpenter, incorporated a special laminated dichroic glass into the façade, a material coated with thin layers of metallic oxides which transmit and reflect a variety of wavelength of light to create different colors when viewing from varying angles. Glass fins are used to brace the glazing façade, and connected by a way of aluminum armatures. Fig. 4-28 Glass fin supported example – Main Public Library in Memphis (Radulski 2004, p.198, 199) Example three is the Samsung Jong-Ro Building in Korea, designed by Rafael Vinoly Architects (Fig. 4-29). The glass façade is 50m wide by 50m high, suspended from 11 th floor level. It is braced by a combination of glass fins and 30 mm diameter rods. Dewhurst Macfarlane is the structural glass consultant of this project (http://www. dewmac.com/frame.htm). 59 Fig. 4-29 Glass fin supported example – Samsung Jong-Ro Building in Korea (From architect’s webpage: http://www. dewmac. com) Cable net support “Imagine glazing a giant tennis racket and using it as the enclosure for a building and you understand the essence of an emergent new building technology that ASI is introducing into the U. S. market place. Consider a structural system that is designed to deflect well beyond the allowable standards defined by building codes, one that will actually increase in stiffness with larger deflections; a system capable of supporting glass without the heavy mullions of a conventional curtain wall system, a system that eliminates bending stiff elements and consists solely of pre-tensioned cable members, and you will begin to understand the excitement surrounding this new building technology called cable net. ” (ASI brochure) In cable net system, a square mesh of cables (usually made of steel) serves as the primary load-bearing members to resist lateral loads. The cable nets are usually regular square meshes because of fabrication and erection requirements. All cables should be pre-stressed in order to control the deformation behavior. Compared to other types of back up structures, cable net supported glass walls have larger deformations. Therefore, the pane/net fixings must allow for movement. The glass fixings should be designed either to ensure the net can deflect relative to the glass panels, or ensure that the glass distorts in sympathy. (Schittich et al.1999, p.111, 112) If the glazing façade is completely flat, the cables need to be highly pre-stressed. If the façade is curved, the cables need less pre-stress; also, curved façade can substantially reduce deformations. (Schierle, G. G. , 2004, personal communication) 60 The glass panes in a cable net system can be fixed either at the corners of the panes without perforations, or be fixed by point fixings with perforations which can tolerate correspondingly large displacements and twist. (Schittich et al.1999, p.112) One typical example of the fixings without perforation is the Hotel Kempinski-Munich Airport Center-Walkways designed by Murphy Jahn Architects in 1994 (Fig. 4-30). The 1.5 by 1.5 m glass panes are mounted by means of cable nodes at the corners which allow free movement of the glazing with structural deformation. The glass façade is made of 10 mm thick laminated safety glass. The cables, both horizontal and vertical, are all pre-stressed by special tension devices which are anchored in the building infrastructure: horizontal cables are anchored to the concrete side walls and vertical cables are anchored to the floor slab at level 5.2m. Because horizontal cables not only carry wind load, but also the dead load of glass panes and cable systems, they are more highly stressed than vertical cables which only carry horizontal loads. (Krewinkel 1998, p.47, 49). Please also refer to 4.3.2 for more information of this project. ) Fig. 4-30 Cable net supported example – Hotel Kempinski in Munich (Compagno 2002, p.16) & (Dobney 1995) The UBS Building at One North Wacker Drive in Chicago in Illinois is the first building in the U. S. using this technology. Please see chapter 10 for details of this project. ASI is a pioneer in developing and applying the cable-net in the U. S. with several projects. Besides the UBS Building, ASI also designed and built another cable-net wall in the new AOL/Time- Warner Corporate Headquarters at Columbus Circle in Manhattan, collaborating with James Carpenter Architects (see Fig. 4-31 below). The wall is 90 feet wide and 150 feet high. A special 61 jacking technology was developed by ASI to achieve the required pre-stress of the stainless steel cables. (ASI brochure) Fig. 4-31 Cable net supported example – the new AOL/Time-Warner Corporate Headquarters (ASI brochure) The examples above are all flat wall cable net structures. A further advance on the cable structure is the double-curved cable net structure. The double-curved surface has substantially less deflections under horizontal loads compared to flat surface, and therefore considerably increased stability of the structure. ASI incorporated a double-curved cable net structure into the new Terminal One Expansion at SeaTac Airport, designed by Fentress Bradburn Architects. Unlike the three examples shown above using fixings without perforation, this glazing wall utilized drilled point fixings with insulated glass. (See Fig. 4-32 left) Another example of double-curved cable net system is the lobby for the new Washington D. C. headquarters of the Securities and Exchange Commission designed by ASI as a special consultant to architect Kevin Roche John Dinkloo & Associates. In this case both the glass roof and glass wall are double-curved cable net structures. (See Fig. 4-32 right) (ASI brochure) 62 Fig. 4-32 Double-curved cable net structures examples (ASI brochure) 4.3.5 Building infrastructure Building infrastructure is the original structure to which a glass wall is attached. It could be beam, floor, roof or column. Generally, there are three types of infrastructure support: (Schierle, G. G., 2004, personal communication) Horizontal support – glass wall is supported by horizontal element, such as roof and floor. Vertical support – glass wall is supported by vertical element, such as column, or wall. Grid support – glass wall is supported by both horizontal and vertical elements, like a grid. The three types, horizontal, vertical and grid infrastructure are explained in detail as follows. Horizontal infrastructure The most common type is a glass wall supported by horizontal elements, such as roof to floor, or floor-to-floor (Fig. 4-33). If the height between each floor is within 10 feet to 12 feet, vertical mullions are enough to support the glass. For more than 12 feet, additional structure is needed to resist wind load, such as cable, truss, or glass-fin. (Schierle, G. G., 2004, personal communication) 63 A house with strong roof and floor Vertical back up structure (for example, cable) supported by horizontal infrastructure A multiple story building with floors more closed to outside Vertical back up structures supported by floors Fig. 4-33 Horizontal infrastructure diagram The glass façade in American Yazaki 21 located in Canton of Michigan designed by architect Plantec is a typical example in which the vertically spanned back up structure (cable) is supported by horizontal infrastructure (roof and ground). See Fig. 4-34. Fig. 4-34 Horizontal infrastructure example – American Yazaki 21 (ASI brochure) The two images below (Fig. 4-35) show another example of horizontal infrastructure used in multiple story building. In the new administration building for the Palais des Beaus-Arts in Lille in France, designed by J. M Ibos and M. Vitart Architects, the story-height vertical back up structure (metal pipe) is supported by horizontal infrastructure (floor to floor). The vertical metal pipes, serve as traditional metal mullions. 64 Fig. 4-35 Horizontal infrastructure example – Le Palais des Beaus-arts de Lille (Asensio Cerver 1997, p.105 & 115) Vertical infrastructure If a building has strong walls or columns, the back up structure can be supported by the walls or columns (Fig. 4-36). A house with strong walls Horizontal back up structures (cable for example) supported by vertical infrastructure A multiple story building with columns more closed to outside Horizontal back up structures supported by columns Fig. 4-36 Vertical infrastructure diagram One example is the Hanamaki Gymnasium in Japan designed by Tetsuo Furuichi. The horizontal double-curved cables are attached to vertical walls (Fig. 4-37). 65 Fig. 4-37 Vertical infrastructure example – Hanamaki Gymnasium (Anon 1 1999, Details in Architecture V5, p.132 &133) If the building infrastructure is horizontal, the back up structure of the glass wall is vertical; if the infrastructure is vertical, then the back up structure will be horizontal. Sometimes, a glass wall involves two levels of back up structures, a primary back up structure and a secondary structure. In this case, the primary back up structure itself serves as the infrastructure to support the secondary back up structure. The Greenhouses of the Parc Citroen in Paris is one example (Fig. 4-38). In this glass wall, vertical double-curved cables act as primary back up structure supported by horizontal building infrastructure (beams). The vertical cables provide support to horizontal cables which act as secondary back up structure. Fig. 4-38 Vertical infrastructure example – The Greenhouses of the Parc Citroen (Rice and Dutton 1995, p. 124, 126) 66 Grid infrastructure Sometimes, the infrastructure is a grid structure, such as a grid of framed tube. Fig. 4-39 illustrates how vertical or horizontal back up structure can be supported by a grid infrastructure. Grid infrastructure Horizontal back up structure supported by grid infrastructure Vertical back up structure supported by grid infrastructure Fig. 4-39 Grid infrastructure diagram A typical example using grid infrastructure is the La Villette Museum in Paris designed by Adrien Fainsilber in cooperation with Rice Francis Ritchie (RFR). The glass facade is 64 meters by 64 meters. The size of each grid is 8m by 8m. Within each grid, horizontal cables are attached to vertical frame tubes, and the glass panels are suspended from the top frame tube. See Fig. 4-40. Fig. 4-40 Grid infrastructure example – La Villette Museum in Paris (1) (Rice and Dutton 1995, p. 24, 63) 67 Fig. 4-41 shows that for each grid, different types of back up structure can be applied such as vertical glass fins (left), or horizontal cables (right). Fig. 4-41 Grid infrastructure example – La Villette Museum in Paris (2) (Rice and Dutton 1995, p. 65) Another example of this kind is the New Museum of Modern and Contemporary Art, at Strasbourg in France, also designed by Adrien Fainsilber and RFR in 1996 (Fig. 4-42). The glass façade is 2400m 2 . Fig. 4-42 Grid infrastructure example – the New Museum of Modern and Contemporary Art in France (Krampen 1999, p.65, 169, 63) 68 69 Chapter V Detailing principles 5. 1 Overview Principles deal with the issues to satisfy specific requirements of the design or detailing of a building. The requirements listed in the Table 5-1 are explained in 5.2.1, and the issues concerned are explained in 5.2.2. Requirements Issues Requirements Issue descriptions Function Structure type Thermal and humidity control Structural behavior Material properties Ventilation and air tightness Water proofing Light control Safety and durability requirements Fire resistance Acoustics Energy efficiency Hygiene and air quality Environmental impact Human comfort and visual requirements Aesthetics Life Cycle Analysis Tolerance Maintenance Manufacture Sustainability, environmental and economical requirements Cost control Assembly Integration Installation Integrity requirements Synergy Constructability requirements Transportation Table 5-1 General principles It would be difficult to discuss all of the principles set for all of the requirements listed above. Compared to other principles, tolerance, manufacture, assembly, installation, and water proofing play a more critical role in detailing design, yet they are not enough emphasized in formal architectural education. Therefore, two types of principles are discussed: general principals and important principles. The general principles (see 5.2) are generally more emphasized during macro design scale. The important principles (see 5.3) are generally more emphasized during micro design scale, which is the focus of the methodology developed in this thesis. 5. 2 General principles In macro scale design, there are many important issues to be considered. In many cases, if designers do not pay enough attention to these issues in early design stage, it would be very hard to fix the problems later. For instance, if the glass façade is designed to face west, there will be big problems with thermal control. In later design stage, some strategies may reduce the degree of negative impact, like adding shading devices, but usually it will still be not as good as a south facing façade, and it will increase cost. Fig. 5.1 below illustrates the issues designers need to consider in macro scale design of a glass wall. Fig. 5-1 Macro scale design of a glazed structure 5. 2. 1 What is expected? Safe, durable, beautiful, sustainable, comfortable, within budget, smart, advanced, maintainable, constructible, legal The exploration of general principles can be started by asking the question: what are the requirements? Or what is expected? The building is expected to be safe. Safety means the building is strong enough to resist any kind of force (e. g. The dead load and live load caused by occupants, rain, snow; lateral wind or 70 71 seismic loads). Safety also means that the building can protect people from being hurt by fire, or any dangerous or unwanted effect, such as dangerous electricity, or insects. The building should be durable. Durability measures how long the building can be safely used. In order to be durable, all key elements consisting the whole building need to be durable, such as structure, material, mechanics, or controls. The building is expected to be beautiful. Different designer have different understanding of beauty. Regarding detail design, beauty mainly means harmony, elegant and delicate; also, it means correctly conveys the design concept. The building needs to be sustainable. Sustainability is one of the key issues for green building; it is an important method that ensures the “stability for both social and physical systems, achieved through meeting the need of the present without compromising ability of future generations to meet their own needs. ” (Brundtland et al.1987). In other words, sustainability requires that one should not only focus on solving the problems of current issues, but also pay attention to future situations. Regarding buildings, it means that the building is energy efficient; it has little or no negative environmental impact; and it uses reusable or recyclable materials. The building should be comfortable for occupants. Comfort is the physical or psychological feeling of human beings. A comfortable living or working space means appropriate temperature and humidity level; functional and delightful light; and quite space or pleasurable sound. The budget should be always considered. Architectural schools seldom emphasize cost control when educating students. However, in reality, cost control is very important. Architects have the responsibility to make a design that can be built by reasonable costs. Without careful cost planning, construction might be delayed significantly, and may result in unexpected low-quality materials. For developers, cost control is extremely important because it is directly related to profitability. Not only macro design influences cost, detailing decisions also influence cost. The building is also expected to be ‘smart’. In other words, the designer wants it to be intelligent. It means the building can take advantages of existing conditions, and be adjustable due to 72 different conditions. For instance, a façade with natural ventilation is a smart design, while fixed glassing may require air conditioning. The building is expected to be advanced. Advance does not mean fashion. It means a technique or a method can be more beneficial than others, and represents the most reasonable solutions for a specific problem. Generally, it means advanced technology, advanced materials, and advanced methods, and integration. The building should to be maintainable. It means that after the building is built, it is easy and also economical to be maintained. Eminence includes cleaning, repairing, and replacement. For instance, a self-cleaning glass pane makes it much easier to keep clean. The details have to be constructible. It would be very frustrating when everything is ready and satisfactory, but finally it cannot be built. For detailing, constructibility is very important. When a part does not match to another part, or when the size of one element is not available from manufacture, the whole façade cannot be built. Because constructibility is almost least educated in architectural schools, this thesis will make a big effort to explore it. (For example: L-shape window frames allow glass replacement, while U-shaped frames would require glass to be installed BEFORE completing the frame. See Fig. 5-21. ) The building must be legal. This means that the building needs to comply with all effective building codes and regulations. Different districts or different countries may have different codes. 5.2.2 What should be considered? Function, structure type, structural behavior, material property, life cycle analysis (LCA), maintenance, light control, thermal control, ventilation, cost control, sound control, aesthetics, integration, fire resistance, water proofing, synergy Each of these is explained as below. Function Need to analyze the function of the part to be detailed. Is it a roof, a wall, or a connection? Does it need waterproofing, fire or noise resistance? Different elements have different requirements. 73 Structure type Is it a concrete, steel, masonry, or glass structure? Is it a cantilever, shear wall, moment frame, braced frame, framed tube, or bundled tube? The structure type is determined during macro design. Detail design must consider the structure type. This is especially important when detailing a glass wall. Structural behavior What kinds of loads need to be considered? Dead and live load, wind load, or seismic load, or even thermal load? For examples, for glass walls, given the light dead load of glass walls, wind load is usually more critical than seismic load. Seismic load should be considered to prevent glass panes from breaking during an earthquake? Probably security glass is needed. In addition, joints should allow glass movement to prevent glass breakage. (See 5.2.3 for details. ) Material property The choice and usage of material will influence the performance of a building significantly. Is it strong? Is it ductile or brittle? Is it massive? Is it transparent? Is it reflective? Is it flammable? Is it expensive? Is it available? The properties of material may influence the structure design, sustainable design, or cost control. Detail design is also be defined by material. For instance, a single-glazing detail will be different from a double-glazing detail. Life Cycle Analysis (LCA) This is a relatively new concept considering the performance of material as a result of the increasing awareness of environmental issues. “Taking as an example the case of a manufactured product, and LCA involves making detailed measurements during the manufacture of the product, from the mining of the raw materials used in its production and distribution, through to its use, possible re-use or recycling, and its eventual disposal. ” (Anon 3 , www.gdrc. org) In architectural design, it is especially useful to compare different building materials. For example, which material is better for window frames, PVC (polyvinyl chloride or vinyl) or aluminum, from the environmental point of view? PVC has a lower embodied energy, but it is very hard to recycle. Aluminum has a higher embodied energy, but it is much easier to recycle (much lower cost 74 and fewer pollutants). Therefore, a detailed comparison of LCA of these two materials will help determine which one to choose. According to the Healthy Building Network, when taking into account its entire life cycle, PVC (over 30 million tons produced per year) is “one of the most environmentally hazardous consumer materials produced” because it posed “unique and major hazards in its manufacture, product life and disposal”; and has “contributed a significant portion of the world's burden of persistent toxic pollutants and endocrine-disrupting chemicals - including dioxin and phthalates - that are now universally present in the environment and the human population”. (http://www.healthybuilding.net/pvc/index. htm) Two other terms are also used, one is called “Life Cycle Inventory (LCI)”, and the other is called “Life Cycle Assessment (LCA)”. The three terms together provide a way to precisely assess the impact imposed on the environment. (Word Resource Foundation, www.gdrc. org) Maintenance “The work of keeping something in proper condition” (www.dictionary. com). The maintainability of a building will affect the total operation cost after the building is built; the quality of the building, as well as the life span of the building. For example, wood building has a higher maintenance cost but lower life span than concrete building. (See 5.3.4 for more details. ) Light control It has at least three purposes: providing delightful and comfortable lighting environment; providing reasonable illuminating level; and providing appropriate heating level. It is especially necessary when designing a glass wall because of the properties of glass. (See 5.2.3 for details. ) Thermal control Heating and cooling have significant influence on sustainability. Conventional HVAC systems contribute to maintain a stable heating and cooling level, but have problems of energy waste. Therefore to utilize natural energy like solar energy and wind becomes more and more important nowadays. (See 5.2.3 for details. ) 75 Ventilation How to provide fresh air into the space? How to create delightful breeze for people? Ventilation can be achieved through mechanical or natural ways, or both. If using mechanical, designers should consider how the mechanical systems are installed and how they are attached to buildings. If using natural ventilation, designers have to decide where to place openings, the openings size and how the envelope can integrate openings. Cost control Cost control is needed to make sure the project is within budget. Designers play an important role in cost control. From the original design concept to the final detailing process, every step may have influence on cost. In order to have an appropriate understanding of cost control, a good designer should have a basic clue of the cost of structure, material, technology, manufacture, labor, maintenance, and so on. (See 5. 2. 3 for details. ) Sound control Ignorance or failure in acoustic design may result in considerable uncomfortable building space. Different occupancy of buildings has different requirement for acoustic. For example, theater, conversation center or airport terminal, acoustic design is more important or even crucial. Material, shape and space can all be critical elements when considering sound control. (See 5.2.3 for details. ) Aesthetics Probably no designers will ignore this. It is closely related to the design philosophy of designers. The evaluation of aesthetics can be quite different individually. Generally, designers can define the aesthetical concepts through structure type, shape, material, interior and exterior space, contrast of light and shadow, etc. (See 5.3.5 for more details.) Integration Detail design should integrate all items (structure, mechanicel, electrical, etc.) and reinforce the basic design concept. All building components should be considered during the design stage to get the best performance. It is an effective approach to better building performance such as energy efficiency and building system integrity. Integration strategies are widely used in both design stage and detailing stage. (See 5.2.3 for details.) A typical example is that integration method used to corporate energy technologies, like passive solar solutions, photovoltaic, heat pumps and recovery, can contributes to excellent energy performance. (Faninger-Lund & Lund, 1998) “The best opportunities for energy savings exist in general in the early design phase of a building project. It is often at this stage when the fundamental decisions are made about the building energy concept, energy strategies and building components. ” (Faninger-Lund & Lund, 1998) Fig. 5.2 illustrates an example of the integration approach of building and solar design. “The building itself forms the central component around which different technologies or strategies can be built. For decision-making purpose, energy/environmental/economic impacts need to be assessed and then incorporated to the general requirements of a building project. ” (Faninger-Lund and Lund, 1998) Fig. 5-2 An integration approach of building and solar design (Faninger-Lund and Lund, 1998) 76 77 Fire resistance A building should be designed to satisfy the building code for fire resistance. For the materials that are combustible, such as wood and plastic, special methods need to be used to resist fire. For instance, for wood or steel column, the designer needs to take into account the thickness and position of the fire resistance material that will cover the column. Waterproof Waterproof requires the selection of material, construction process, and detail to be appropriate for waterproof. For examples, waterproof requires the material to prevent rain from coming into inside; or to prevent water in bathroom from leaking into other rooms. (See 5.3.3 for more details. ) Synergy “A principle which states that the whole is greater than the sum of its parts” (www.logosresourcepages.com). When applied to architecture, it means, “The components of the building are put together so that the desired overall properties emerge: Shelter, room, appearance, cost, safety, etc.” (Wieringa 2004) (See 5.2.3 for more explanations of synergy.) Professor Schierle (2004) gives out a clear explanation of synergy from the structural point of view. He mentioned that, in structural design, synergy could be described on two examples, pragmatic example and philosophical example, as shown in Fig. 5-3. Pragmatic example: Assuming there are two beams, one beam is composed of ten wooden boards, and the other beam consists of the same amount of material, but the ten wooden boards are glued together. The result is that the second beam is 10 times stronger and 100 times stiffer than the first beam. (Fig. 5-3, a) Philosophical example: Assume there is an auditorium as shown in the right image below. Structurally, the columns reduce the bending moment of roof beams by over 500%; architecturally, the columns define the horizontal circulation of the building. (Fig. 5-3, b) Single 10 single 10 boards Board boards glue-lam Beam of glued boards is: 10 times stronger and 100 times stiffer than beam of 10 single boards In an auditorium, the recessed columns: Integrate circulation Reduce beam size over 500 % (a) Pragmatic example (b) Philosophical example Fig. 5-3 Two examples describing the concept of synergy (Schierle 2004, p.3-2) Fig. 5-4 shows two examples how synergy is achieved in the design of glass façades. The left one is the “Congrexpo” congress building at Lille, France, designed by architect Rem Koolhaas/OMA in 1994. Structurally, glass fins serve as mullions to support the glass. Architecturally, the different position and angle of the glass fins become important elements in the façade design. The right image at Fig. 5-4 is the Western Morning News at Plymouth in England designed by Nicholas Grimshaw and Partners in 1992. Structurally, the curved metal frames support the glass panes to resist lateral loads. Architecturally, the shape of the metal frames matches the concave glass façade, and strengthens its feeling of a curve. The concave façade not only creates an impressive architectural form, but also reduces reflection, therefore successfully avoid discomfort glare. 78 Fig. 5-4 Synergy examples (Compagno 2002, p.21, 38) 5.2.3 Illustration of selected points Light control, Structure behavior, Thermal control, Cost control The texts above briefly describe the general principles. Due to limited space and time, the thesis does not explain all of the principles in detail. In stead, the author selects some of the principles to give further descriptions, which are light control, structure behavior, thermal control and cost control. The reason for choosing these principles for further study is either because the principles are especially concerned in the design of glazed structure (such as light control and thermal control), or because the principles should not only be considered in macro scale design, but also be concerned in micro scale design (such as structure behavior and cost control). Light control Overview One of the main reasons why architects like to utilize PSG wall systems in their design is because of the maximum transparency the systems can provide. Therefore, people might say that one of the main advantages of PSG wall systems is the maximum usage of light. The lighting design is probably the first issue to be considered when designing a glass wall. 79 The Square One web homepage introduces lighting design: “to use a structured approach with a list of the main requirements.” There are four basic requirements in lighting design: Visual amenity; Visual function; Architectural integration; Energy efficiency and maintenance. The list can be presented as a framework shown in Fig. 5-5. (http://www.squ1.com/) Architectural Integration Lighting Design Visual Amenity Costs (Capital & Operation) Visual Function Energy Efficiency Installation Maintenance Fig. 5-5 Lighting design framework (http://www.squ1.com) Illumination level and distribution This regards to visual function, the basic requirement for lighting design. “How well people wish to be able to see inside a building is a key factor that affects lighting design, occupants’ productivity and satisfaction, operation, energy-consumption, and long-term costs” (www.squ1.com). Three strategies can be used to make a well-functioned visual environment. They are: 1). Satisfy the requirements for brightness levels without causing visual discomfort or disability. The IES (Illuminating Engineering Society) handbook includes a table listing illumination levels for spaces for different occupancies as reference numbers. 2). Provide proper lighting patterns for different tasks. For instance, as a basic rule, use indirect north daylight for paintings; use direct south daylight for sculptures. 3). Provide different lighting solutions for different tasks in any space. For instance, operable louvers attached to glass facades can adjust the brightness of the inside space so that people can either read or view slides. 80 Visual comfort Visual comfort, or visual amenity, can be achieved through proper designs of the following issues: brightness level, distribution of luminance, variation in the lighting pattern, shadow patterns, color and texture. Glare is one of the most common problems causing visual discomfort. Generally there are four situations which can cause glare (www.squ1.com). One is that, when a person looks at directly the brilliant lighting source, like sun, because the source is too bight, glare occurs. This often causes a direct reduction in the person’s visual ability, so it is also called disability glare. If the illumination levels are greater than 2,323 foot-candles, glare will be experienced. (See Fig. 5-6, a.). The other is that, when there is excessive contrast between two adjacent elements, such as a bulb hanging under a black ceiling, glare will also occur. This is also called discomfort glare. See Fig. 5-6, b.) A reflection on a specular surface coming from a very bright source may also cause glare, for instance, the reflection from a swimming pool because of sunlight. This is called reflected glare. (See Fig. 5-6, c). Another kind of glare is called veiling reflection. It occurs when the reflected images of a light source are brighter than its surroundings. (a) Glare from headlights (b) Glare caused by contrast (Osaka Church, Tadao Ando) (c) Glare caused by reflection (University of Connecticut) Fig. 5-6 Different glares (www.allaboutvision. com) & (www.guardian. co. uk) & (ASI) 81 To avoid glare, designers need to define what causes the glare, and then use proper strategies to avoid it. Reduce the luminance of the glare source and the apparent size seen by people (Baker et al, 2002). For example, putting a diffuser under a light fixture can reduce the discomfort glare when people look directly at the fixture. Sunglasses use the same principle to reduce sun glare. Reduce the contrast. If there is a very bright source, due to adaptation phenomenon, people will feel less discomfort if the surrounding of the source is also bright. For instance, a bulb hanged from a black ceiling will cause glare; but if the ceiling is painted in white, the glare discomfort will be reduced. When looking out of the window, the bright outside view and the relatively darker inside walls beside the windows might also cause glare. In this case, either replace clear glazing with diffuse or translucent glazing, or hang some cardboards screens on the window, or plant some trees close to the facade to reduce the luminance level of outside. Use “contrast grading”. Baker and Steemers recommend “A glare source that is not sharply delineated against the background causes fewer glares than a sharp edge. ” Light matt colored window frames, splayed window sills, heads and sides will reduce contrast effects caused by sharp edge (Fig. 5-7). But avoid making these surfaces secondary glare sources; especially if the surfaces are specularly finished. (Baker et al.2002, p.179) 82 outside inside inside outside outside inside Greatest contrast if edges are sharp Less contrast if splaying the edges Lowest contrast if making the edges into curve surface Fig. 5-7 Contrast grading 83 Baker (2002) also provides the following three guidelines in his book to reduce contrast and increasing visual comfort: 1). Install windows in more than one wall. This will get more even distribution of light, thus decreasing glare discomfort. 2). Increase window areas if possible. According to Baker, the transparent part of the glazing should not be less than 16% of the floor area, or 30% of the window wall area, to satisfy 70% of the occupants. 3). Properly decide the sizes, shape and position of the window. Some simple rules are: The width of the window (transparent part) should be more than 55% of the wall in which it is installed. The height of the window should be at least 1. 3m. A strip window is better than a series of smaller window with the same width. A series of windows with a lower distance apart is better than those with a higher distance apart. Provide a clear view of the skyline if possible. If installing daylighting systems, like shading devices, one should be aware not to block the clear view of the skyline. Lighting and Architectural integration The delight in light cannot be achieved without reference to architectural issues, such as form, shape, and the hierarchy of different spaces. Lighting design should strengthen but not detract from the architectural concept. Fig. 5-8 shows three examples of integration of lighting and architecture. Lighting fixtures are mounted on the metal columns to which the glass wall is attached, serving as pole lights to illuminate the road. (Chan Center for the Performing Arts, Vancouver) A grid of 1. 5 inch spaced fiber-optic fixtures, perfectly matching the two bright point-fixed glass boxes, illuminates the sculpted basin. (Nagasaki National Peace Memorial Hall for the Atomic Bomb Victims) A series of flood lights are integrated into the trusses, which are the back up structure of the point-fixed glass wall. (Sendai International Airport-passenger terminal building, Sendai, Japan) Fig. 5-8 Integration of lighting and architecture (Krampen 1999, p.194) & (Laio 2004, p.196) & (HOK brochure) Energy efficiency and maintenance Square One (www.squ1.com) gives the following rules for energy efficiency and maintenance: 1). Use daylight as much as possible; 2). Bring adequate daylight for comfortable and efficient vision ; 3). Reduce the contrast between the space near windows and the space not close to windows; 4). Illuminate the areas in the back of the room to make the lighting distribution more even; 5). Use artificial light only if needed, and use dimming systems; 6). Use energy efficient fixtures; 7). Integrate daylight and artificial light; 8). The luminance supplied should change correspondently to sky luminance; 9). Keep good maintenance of both the fixtures and the illuminated surfaces. A good maintenance means that: 1). It is easy to clean the fixtures; 2).The room surfaces need to be kept clean; 3). Designers should provide detailed strategies of how to keep good maintenance. 84 Structural behavior Glass walls need to resist lateral loads, which mainly consist of wind load and seismic load. As the most destructive natural forces, wind and seismic forces should be carefully considered in structural analysis. Wind load Wind forces are dependant on many factors, including building height, form, openness, flexibility, topography, environment, as well as wind orientation and velocity. The most devastating wind are tornados which occur between Appalachian and Rocky Mountains with speeds of more than 200 mph. Hurricanes, which occur along the Atlantic and Golf coasts, range from 90 to over 150 mph. (IBC requires 150 mph but actual speed exceeded 200 mph.) Fig. 5-9 below shows wind load effects under different circumstances. (Schierle 2004) Wind load on gabled building Wind load on dome or vault Protected building inside a city Exposed tall building inside a city Wind flow around and above exposed building Wind speed amplified by building configuration Fig. 5-9 Wind load effect (Schierle 2004, excerpted) There are several factors which affect dynamic wind pressure of buildings: topography, roughness of terrain, the sizes of component, and the height of buildings, etc. (Button 1993, p.231) 85 Especially for glass walls, in most cases wind force is much stronger than seismic force because of the light weight. Seismic load Earthquakes are mainly caused by release of shear stress because of the movements of tectonic plates. Earthquakes can be also caused by underground explosion, volcanic eruptions, or similar man-made events. Buildings can be seriously damaged during an earthquake. The risk of earthquake is different in different locations. Fig. 5-10 shows an earthquake hazard map made by US Geological Survey. From the map, it can be seen that on the west coast of California there is a very high risk of earthquake. Generally, heavy weight structures are more susceptible to seismic load than to wind load. This is because heavy structures are stiffer than light structures to resist wind load. But because of the heavy weight, there will be higher shear force during an earthquake. Therefore, for concrete or masonry structures, seismic design is more critical than wind load design. But for glass or fabric buildings, wind force design is more critical. Earthquake Hazard Map of the United States (US Geological Survey) Fig. 5-10 Earthquake risk 86 In early design stage, proper designs can significantly reduce the risk of earthquake damages. For example, eccentric plans will torsion under lateral seismic load. Therefore, in early design stage, designer should arrange mass walls as concentric as possible. See Fig. 5-11. (Schierle 2004) X-direction: concentric; Y-direction: eccentric X-direction: eccentric Y-direction: eccentric X-direction: concentric Y-direction: concentric X-direction: concentric Y-direction: concentric Fig. 5-11 Concentric plans vs. eccentric plans (Schierle 2004) Wing intersections If a building has a shape like ‘L’, ‘T’, ‘U’, ‘H’, or ‘ +’, stress may occur at the intersections of the wings because the wings may have different time period during an earthquake (Fig. 5-12, left). Professor Schierle (2004) introduces three remedies to this problem (Fig. 5-12, right): 1). For low-rise building, separate wings by seismic joints (about 2” per story height). 2). For high-rise building, reinforce wing intersections 3). Prevent wings to pound one-another. Fig. 5-12 Remedy to deal with wing intersections (Schierle 2004) 87 Sometimes there is height difference within one building (Fig. 5-13, left), under lateral load, the structures will pound to each other. The remedy in this case is either to separate structures by seismic joints or to reinforce the intersections (Fig. 5-13, right). (Schierle 2004) Fig. 5-13 Remedy to deal with height difference (Schierle 2004) Glass safety In glass wall structures, the main loads applied on glass are lateral loads such as wind and seismic load. Basically, there are five factors influencing the ability of glass to resist lateral loads, which are: glass type, thickness, shape, area, and supporting systems. (Button et al.1993, p.234) Please refer to 4. 2. 1 for more details. Thermal control There has been a lot of research regarding the thermal behavior of glass; therefore the thesis will only briefly discuss the general methods used in thermal control of glass structures. Two basis terms one should know are the U-value and R-value, the measures of heat transfer through the glazing or the entire window assembly. U-value measures the rate of heat transfer; the lower of the U-value, the better the insulation is. R-value measures the resistance to heat flow, and it is the reciprocal of the U-value. These two values can be obtained from manufacturers. The table below (Table 5-2) shows typical U and R values for various glass combinations. Glass combination U value (w/m 2 k) R value (m 2 k/w) Single 5. 4-5. 8 0. 18-0. 17 Double 2. 8-3. 0 0. 36-0. 30 Double with Low E-coating 1. 7-2. 0 0. 59-0. 50 Triple with two Low E-coating 1. 0-1. 2 1. 00-0. 80 Table 5-2 U and R values for various glass combinations using 4mm thick glass and 12mm air cavity (Button et al. 1993, p.130) 88 89 The purpose of thermal control of glass structures is to reduce solar gain from outside during cooling seasons (summer) and reduce heat loss from inside during heating seasons (winter). Using passive solar gain design in winter can significantly offset most annual heat losses. “The greater the window insulation, the more closely are heat losses offset.” Besides, the maximum using of daylight can reduce the usage of artificial light and therefore saving energy. (Button et al.1993, p.181) For single-skin façades, reduction of solar gain may be achieved by decreasing the transmittance of some of the solar radiation incident. Methods include (Schittich 1999, p.76): Using solar-control glass (such as tinted glazing, reflective glazing, glazing attached with foil, glazing with patterns formed by enameling and silkscreen printing, etc) Exterior shading devices Interior shading devices Shading devices placed in the cavity if using multiple glazing (such as blinds, foil, spun glass placed in the cavity) Generally, exterior shading devices are much more effective than internal ones. But because of aesthetic, cost and mechanical reasons, external shading devices are not very widely used. A double-skin facade with shading devices placed in the ventilated cavity between the skins is an alternative in the case. (Hensen et al.2002) A parameter generally used to assess the ability to block solar gain is shading coefficient associate. The smaller the associated value, the less the heat transmitted through the structure. (See Fig. 5-14). “The shading coefficient is derived by comparing the properties of the solar control glass (or any glazing system) with a clear float glass having a total solar heat transmittance of 0. 87 (such a glass would be between 3 mm and 4 mm thick). There are two components: the short wave shading coefficient (the direct transmittance divided by 0. 87); and the long wave shading coefficient (the fraction of the absorptance that is dissipated inwards, divided by 0. 87). The total shading coefficient (the total solar heat transmittance divided by 0. 87) is the sum of the short and long wave shading coefficients. ” (Button et al.1993, p.156) 1. Unglazed, unshaded window opening 2. 6mm single glazing 3. 4-12-4 insulating glass 4. Internal dark roller blind, insulating glass 5. Tree without foliage, single glazing 6. Internal louver blind, 45 o , insulating glass 7. Internal reflective curtain, insulating glass 8. Awning, 45 o , insulating glass 9. Internal roller blind, insulating glass 10. Internal louver blind in cavity, 45 o , counter- sash window 11. Tree with foliage, single glazing 12. External roller shutter, insulating glass 13. External louver blind, insulating glass Fig. 5-14 Summary of various types of shading and their associated values (Schittich 1999, p.131) Cost Control Cost control is an important issue which will affect the feasibility of the design. A good designer should be aware of the resulting cost of the design, and adopt proper methods to control the cost, so that the process of the whole project would not be affected because of unexpected extra expense. Generally, four types of cost will affect the total cost. They are: material cost; fabrication cost; labor cost; transportation cost. From the sustainability point of view, maintenance and recycle cost should also be considered. Therefore, cost control can be achieved through the control of each of these types of cost. Material cost This means that designers need to have some basic knowledge of the cost of the materials they will choose at very early stage of the design. There are several ways which can help to reduce the material cost: Use proper material for different purposes. For instance, in housing design, the usage of double glazing in bedrooms and single glazing in kitchens can not only satisfy the requirement for insulation, but also avoid waste. Use local material as more as possible. Use recycled material as more as possible. 90 91 Fabrication cost This means that designers should understand general fabrication process, and how their designs will affect the fabrication cost. Some useful tips: Use pre-fabricated products as more as possible. Generally, for small buildings, use what is available as much as possible. For important big buildings, unique new designs may be applied. Adapt complex mass-produce items rather than redesign them. Change the parts which will not cost too much. (Any part made by very expensive machines will cost a lot if changed.) Use as less types of complex products as possible. This can be illustrated by an example explained as below (Fig. 5-15). In 1990, the architects Odile Decq and Benoit Cornette designed a bank in Montgermont near Rennes. This is the first building which uses a truss-supported glass façade with insulating glass. In this building, single glazing is used at the entrance, while insulating glazing is used at the office wing. “To be able to use the same type of fixing for both, RFR adapted the fixing with the articulated head in the plane of the glazing to fit the insulating glass.” (Schittich 1999, p.52) This way not only creates a consistent appearance, but also saves money by fabricating only one type of fixing instead of two types (Fig. 5-15). The top left shows the fixing used in single glazing; the bottom left shows the fixing used in double glazing. Fig. 5-15 The same fixing type used in both single and double glazing (Compagno 2002, p.99) Labor cost Labor costs can be best illustrated through an example. In US, steel structures are very popular, while in China, concrete buildings are more common than steel buildings. One important reason is that the labor cost in US is more expensive than in China, therefore, in US, people prefer steel buildings which need fewer labors than concrete. While in China, concrete is prefered because concrete is cheaper than steel. The choice of welding location is another example showing the importance of labor cost. Because on-site welding must be supervised by an inspector to assure quality, on-site welds costs more than shop welds. Therefore on-site welds increase labor costs. Here are some tips: Use pre-fabricated products as much as possible. For a specific location, if labor cost is expensive, use a design which needs less labor. Transportation cost Firstly, use local materials as much as possible to reduce transportation cost. Secondly, consider assembly and installation process, and determine which parts to be assembled in shop, and which parts to be assembled on site. For example: 92 “Current legislation requires that loads up to 5. 1 m wide require one month’s notice for transportation, subject to a maximum length of 27 m and a maximum height requirement of 4. 93 m. Smaller loads up to 3. 6 m wide require no specific notice (although they must observe the same height and length limits). Larger assembles should be fabricated as sub- assemblies of less than these dimensions, which are connected together on site. ” (Trebilcock 2004, p.209) Therefore, the detailing of the connections between the sub-assemblies is important. Fig. 5- 16 shows how the in-shop and on-site assembly will affect the transportation cost using an example of assembling pin-connected steel column and beam. 93 Welds Bolts Welds Bolts Welds (1) (2) (3) Welds Welds Pin joint example: (1) Weld plate to steel column in shop (2) Transport beam and column separatedly (3) Bolt steel beam to column on-site (4) To connect beam to column in shop will be very costly to transport them. Therefore, it is suggested that the plate is welded to the column in shop, and then the beam is bolted to the column on site. (4) Fig. 5-16 Transportation cost example Maintenance cost 1). Consider proper maintenance methods after the building is occupied. 2). During detail design, reduce exposure to exterior if possible. 94 3). Use materials which are resisting to the climates. For instance, metal is subject to corrosion in humid climate. Or special treatment may be used to avoid erosion. 4). Use materials which are easy to be cleaned. For instance, smooth surfaces are easier to clean than rough surfaces. 5). Use materials which are strong and durable. 6). For materials subject to temperature variation provide expansion joints, or make other adjustments. For instance, in the new cathedral in Los Angeles designed by Ralph Moneo, a special material called alabaster is used as window material. If exposed to high temperature, alabaster will lose moisture and then become opaque; therefore it is important to keep relative low interior temperature. Moneo designed a special ventilation system as well as special shading devices to control inside temperature. Recycle cost Generally, to reduce recycle cost means that designers should use materials which are easy to be recycled as much as possible. Recycle cost will affect the life cycle cost. For instance, PVC and aluminum are two common materials used in window frames. Although PVC has less embodied energy than aluminum, it costs more energy to be recycled than aluminum. Therefore, when considering the life cycle cost of these two materials, one should consider both the embodied energy cost and the recycle cost. 5. 3 Important principles 5.3.1 Tolerance There are three reasons to ensure tolerance in detail design: to allow different components to be assembled together; to allow thermal expansion and contraction; and to allow movement under different loads. Tolerances can be computed. “Appropriate tolerances should be agreed by all the parties at the start of the project, as late changes to allow for these effects can be costly.” (Trebilcock 2004, p.204) The three purposes of tolerance are explained in detail as the following. 95 Tolerance to allow components to be assembled together Note: Items of equal dimensions do NOT fit without tolerance as demonstrated by practical (and VERY costly) experience! Tolerance can occur during fabrication and construction process. In fabrication, member size may have geometric variations, which are called fabrication tolerances; in construction, there would be member deviations, which are called installation tolerances. If not considering the necessary tolerance during design stage, objects may not be able to be correctly fabricated or installed. Designers can ask manufacturers for the information of the general tolerances of their products. For instance, Pilkington provides tolerance table for every glass product they produce. Another way to get such kind of information is to refer to the official publications which provide specifications for steel and glass works. For instance, the National Structural Steelwork Specification for Building Construction lists several tables defining the criterion for tolerance, such as “acceptable tolerances for section type”, and “acceptable tolerances in general steel construction”. Tolerance to allow thermal expansion and contraction Objects intend to shrink when temperature decreases and expand when temperature increases. Tolerance needs to be defined to allow thermal movement. Without tolerance to allow free thermal movement, stress will occur in material. This is especially critical in the design of glass because glass is fragile and vulnerable to break. The consideration of thermal variation is especially important in large fluctuating temperature condition, such as areas with high diurnal temperature swings, or high summer-winter temperature differences. The dimension change caused by thermal variation is ΔL = α ΔT×L, where α = coefficient of thermal expansion, ΔT = temperature change, and L = initial length (Schierle 2004, personal communication). For instance, if a 20 feet long float glass pane of α = 5. 1 × 10-6/ oF, is exposed to a temperature change of 80oF, its change in length ΔL = 5 × 10-6/ oF × 80 oF × 240inch = 0. 096 inch ~ 0. 1 inch. Therefore, two adjacent glass panes need a joint of 2 × 0. 1 = 0. 2 inch for thermal expansion. A space of 0. 4 inch will occur when glass shrinks. Elastic joint material, like silicone, solves the problem (see Figure 5-18 c). Allow movement under variable loads Objects tend to deflect under loads, such as gravity load, wind, and seismic load. Tolerance needs to allow such movements. Without tolerances, movements get restraint, causing settlement stress. Differential deflections can be calculated for various loads Methods to deal with tolerance Basically, there are two ways to deal with tolerance, which are: (Trebilcock 2004, p.204 & Allen 1993, p.137, 140) 1). Provide clearance between two adjacent components. One example is shown in figure 5- 17. Another example is shown in Figure 5-18, a. In this case, due to fabrication and installation tolerance, a steel column is not perfectly vertical; therefore clearance is needed between cladding and column. Clearance is also needed to assure the beam can be placed in the columns (d < D). 2). Overcome local lack-of-fit by adjustment such as the usage of a shim or slot hole (Figure 5-18, b) 200cm 100cm 200cm 100cm 200cm 100cm 198cm 98cm 100cm 200cm 1cm clearance The glass can never fit into the opening. concrete opening glass For a concrete opening with a size of 200cm by 100cm, if a window frame is exactly as 200cm by 100cm, the frame will not fit into the opening. Therefore, provide tolerance for the frame can fit the opening. Fig. 5-17 Example of tolerance need 96 (a) Clearance to allow tolerance D (space of columns) d (length of beam) < D Clearance Steel column & beam Cladding Clearance (b) Shim & slot hole to allow tolerance Pocket (channel) Glass Silicone sealant Steel pipe Shim spacer Infrastructure Infrastructure Slot hole (c) Silicone joint Contraction Expansion Silicone Glass Fig. 5-18 Methods to deal with tolerance Designers should be able to define appropriate fabrication tolerances and installation tolerances. The manufacturers and construction workers can use the tolerance specified as a guide to control the quality of their products and installation process, and to ensure that different components can be assembled together. As Trebilcock mentioned in his book, designers can make stricter tolerance limits, however, that will increase the cost. (Trebilcock 2004, p.204) Therefore, designers should set up appropriate tolerance limits which are neither too loose (to control quality), nor too strict (to control cost). 5.3.2 Manufacture, assembly, and installation Because the three processes, manufacture, assembly and installation, are closely related to each other, they are described together here. 97 “A close working relationship with industry is a key element at the design stage and a must even before the concept is determined.” (Rice & Dutton, 1995, p. 38) This is especially true regarding point-supported glass system, because the technology of the system is largely affected by the available industrial technology. A good understanding of manufacturing process can help designers to define limitations as well as the possibilities, and then be able to make correct decisions. For instance, at the very early design stage, a designer needs to know the available sizes of glazing, the available choices of glass fittings, the positions of the holes, etc. After the design concept is determined, manufacturers will check its feasibility, and then if necessary, test it by samples. Manufacture process Manufacture process often determines available size, material, and quality of a product. Fig. 5-19 shows how a countersunk hole is produced. From left to right, the first four images show the process (drilling from both sides prevent breakage); the far right one shows that lubricating milk jet is used while drilling the hole (Rice & Dutton, 1995, p. 40). First pass Second pass Countersinking Chamfering Milk jet Fig. 5-19 Drilling process for a countersunk hole One example is that designers should know the importance of the holes drilled in the glass. For instance, the size of the hole is critical. If the size is too small, the concentration stress at the areas around the hole will be too big, increasing the risk of breakage of the glass. If the size is too big, it might influence the appearance, also cause problem for water tightness. Assembly process Assembly process defines how to make each component. Fig. 5-20 shows from left to right, the process of on site assembly of an articulated bolt. The far right image shows the bolts are fixed into the glass fitting (Rice & Dutton, 1995, p. 41). 98 Fig. 5-20 On site assembly of the articulated bolt Another example showing the importance of understanding assembly issues is that, the choice of glass fixing type is affected by the type of glazing. Double glazing system can not be used in patch plate fixing system. If a designer chooses patch plate fixing system in a building located in a cold city, it will be a big problem for energy conservation. Installation process The importance of understanding installation process in detail design can be illustrated. Fig. 5-21, (1) and (2) show one way to install the window which would not allow replacement of broken glass. The L-frame (3), (4) and (5) allows replacing broken glass. The bars are installed after the glass, so that the glass can be replaced if broken. 99 1 2 3 4 5 glass U-shape frame L-shape frame bar (1) The glass is installed at first. (2) The U-shape frames are then installed. In this way, if the glass is broken, it is very hard to replace it. Therefore the installation process is not correct. (3) The L-shape frames are firstly installed. (4) The glass is then installed. (5) Finally, the bars are installed. In this way, if the glass is broken, it is very easy to replace it just by removing the bars. So compared to the previous one, it shows an improved installation process. Fig. 5-21 Window frame installation process 100 The Purposes of understanding installation process are: 1). Understand sequence of installation 2). Understand what part will be installed on site and what part will be installed in factories (prefabricated). For instance, prefabricated products usually have size limitations for transportation. A typical example is the design of a prefabricated concrete building. The size of rooms may be restricted by transportation limits. Although this is not a PSG example, the effect is similar. Some work should be done in factory while others should be done on site. Some items require specific temperature and moisture conditions during manufacture, such as sealants; therefore they need to be installed in the shop. “In general, the smaller, highly precise, highly finished components are made in the factory, while the larger elements of the building are created on site from simple, easily fitted pieces of factory-made materials.” (Allen 1993, p.160) Some technologies, like welding, require different quality control in shop than on site. By code, site welding requires an inspector, while shop welding requires no inspector, which is an important cost factor to be considered. Rice gives out an example in his book Structural Glass on page 89. Fig. 5-22 shows the welds made in factory look thinner and more elegant that those made on site. Knowing this, designers may want to specify that only prefabrication welding can be used if the part is located at an important public space where people can see it. Or, the designers may find a way to solve the problem in design stage, for instance, to add some decoration parts covering the ugly welding Detail of a node-tube assembly showing the different types of welding: Weld type 3 (horizontal) Weld type 2 and 1 (vertical, left and right) From top to bottom: Weld type 1 (factory) Weld type 2 (on site) Weld type 3 (on site) Fig. 5-22 The difference between prefabricated welds and on site welds (Rice & Dutton 1995, p.89) Innovative details combining design and industry understandings If understanding the manufacture, assembly and installation process very well, designers can produce innovative details which not only satisfy the required functions, but also become to an important design element. For example, designers can create new form of fittings which are more compatible with their architectural concept, instead of just using available products. If manufacturers can make them, and then test the feasibility successfully, the designers’ idea can be achieved. One example is the specially designed the Natural History Museum in Darwin Center, London, by HOK (Fig. 5-23). In this façade, the designer created a ‘huge’ spider which becomes the main element of the façade. The size of the spider is about 2-3 feet in length. Although it is very different from traditional spiders, the basic principle is the same. Without the participation of the manufacturers from early design stage to final installation, the innovative design would have not been possible. 101 Exterior view (HOK: http://www.hok.com/) Glass wall detail (HOK: http://www.hok.com/) “Huge” spiders in the glass facade (HOK brochure) Fig. 5-23 Special glass fitting design (a) Such custom glass-fitting design is also shown in TGV Railway Terminal in Roissy, CDG airport, designed by architect ADP in 1994. The spiders are connected to tubular trees by long struts that cantilever on both sides. Also see Fig. 3-2 in Chapter 3 (3.2.5) for another example. Exterior view of the glass facade Detail view TGV Railway Terminal in Roissy, France (Rice & Dutton 1995, p.138) Fig. 5-24 Special glass fitting design (b) 5.3.3 Waterproof Waterproof is a very important issue in detail design, especially for joint design, because joints are the most common leakage source. 102 Four ways in the waterproof design of joints Allen (1993, p.25) summarized four means to achieve waterproof: Overhang and Drip, Capillary Break, Wash, and Labyrinth. Fig. 5-25 illustrates the principle of Labyrinth. No Labyrinth Labyrinth Horizontal joint between wall panels Vertical Labyrinth joint between wall panels Aluminum Labyrinth joint Fig. 5-25 Labyrinth principle for water proof design (Allen, 1993, p. 24) Although by the usage of the combination of the four ways, a designer can make a sealant- free joint, when there is wind passing through the joint from outside to inside, the air current can “blow or ‘pump’ water through the joints” because of the air pressure. This is why most leakages occur when it is windy and rainy. This problem can be solved by using a perfectly airtight sealant at the inside edge of the joint serving as an air barrier. When a small amount of air comes into the small empty space inside the joint, it increases the pressure of the small space. When the pressure inside the small space equals to the pressure outside the wall, water cannot be sucked into the building. (Allen 1993, p.25) See Fig. 5-26. This method is called as Pressure-Equalized Cavity Wall Construction, and it is also called as rainscreen detail. Two key components of this method are: a perfect designed air barrier at the edge of inner surface; a sufficient sized opening between the air barrier and outer space. The first building designed with the pressure-equalized strategy was the World Trade Center in New York. Because high rise buildings are especially susceptible to wind force, this pressure- equalized design is particularly important. (Loughran 2003, p. 71) 103 Fig. 5-26 Air barrier used in a joint for water proof (Allen, 1993, p. 25) The width-to-depth ratio of the joint between two panels of materials, like metal-to-metal and metal-to-glass, is critical for water proof design. Typically, the ratio should be at least 2:1. A realistic example which applied the methods mentioned above can be seen in the detail design in an outdoor glass deck in Nijmegen, the Netherlands (Fig. 5-27). This example shows “an efficient solution for guaranteed water tightness of the support detail of an exterior glass floor”. (Nijsse 2003, p.53) This example also illustrates another important principle of waterproof design, which is the usage of a second line of defense. If water passes through the first line of defense, it will be blocked at the secondary line of defense. 104 1. Glass panel (load carrying) 2. Cavity 3. Glass panel (insulating) 4. Silicon joint (first line of defense) 5. Top stainless steel inverted channel profile 6. Connecting stainless steel profile 7. Drain to gutter (external) 8. Connection to concrete floor Fig. 5-27 Water tightness designed for an exterior glass floor (Nijsse 2003, p.53) For PSG glass wall design, the important connections that will affect waterproof are: the connection between the glass panes; the connection between the glass and glass fixings; the connections between the glass and infrastructures. The connection between the glass panes The connection between the glass panes is usually sealed by structural silicone. According to Allen, the connection detail is unreliable if it only replies on the sealant joint without using any other methods such as labyrinth or rainscreen, because “any defect in the sealant will cause a water leak”. (Allen 1993, p.27) But because this method is less expensive and much simpler, currently most PSG walls use this method. Since PSG walls with structural silicone only have a history of less than 40 years, the silicone still works well within its life span, therefore the information about the leakage caused by the aging of silicone is not available yet. However, because the sealant joint is the only method for waterproofing, every effort should be made to ensure that the sealant joint works correctly. Firstly, the glass surface needs to be completely clean and dry when installing the sealant. Secondly, the width to depth ratio of a sealant joint is critical. It should be neither too narrow nor too wide. As a rule of thumb, generally, the width to depth ratio should be at least 2:1. The minimum width is ¼” (6mm), and the maximum width is 1-2” (25-50mm). The minimum depth is ¼” (6mm), and the maximum depth is ½” (13mm). Therefore, a ½” wide joint should be ¼” deep; while a 1. 5” 105 wide joint should be ½”. Also, the width of the joint cannot be left to chance. It is related to temperature change, the properties of the sealant, and the properties of the materials on both sides of the joint, the structural deflection, and the dimension of the building skin. Therefore, the determination of the width should be made not only by detail designers, but also engineers as well as material suppliers. Allen provided an equation that can be used as a preliminary guidance to calculate the width of the joint. (Allen 1993, p.35) Rice has a clear description for the usage of silicone as sealant material: It is “used either as a mastic or as extrusions glued together with mastic. The mastic is used on the small joints between glass sheets in a glass panel, and the extrusions are used on the larger joints between panels. Silicone adheres perfectly to glass when applied according to the following precautions: the glass must be absolutely clean and dry; the area of the joint must not be too wide – this could prevent its total polymerization. Under these conditions, silicone has a remarkable adhesive power. ” (Rice & Dutton 1995, p.56) In the glass façade of the La Villette Museum, extruded silicone joints are used for water- tightness (Fig. 5-28). The design of the joint must satisfy three functions: firstly, it should allow movement between adjacent glass panels; secondly, it must be water protected; and thirdly, it can not protrude from the external glass skin. Fig. 5-28 Extruded silicone joints used in the La Villette Museum (Rice & Button 1995, p.57) 106 107 The connection between the glass and glass fixings When designing the connection between the glass and the fixings, one rule is that, the glass can never directly contact hard metals, like steel. This would cause breakage of the glass and result in water leakage. Therefore, a thermoplastic spacer is generally used between the hole in the glass and the steel bolt. But some designers use pure aluminum instead because thermoplastics intend to creep after a period of time. Pure aluminum is fairly soft, and will not creep. (Rice 1995, p.37) The connections between the glass and infrastructures The design of the connection between the glass and infrastructure can use the four ways mentioned above, which are Overhang and Drip, Capillary Break, Wash, and Labyrinth. Also, an air barrier should be used to prevent water from coming through the joint caused by differential air pressure on windy days. Despite a sophisticated detail design for water proof, laboratory mock-ups and field tests are also very important, especially for the custom designs which are unique and not applied before. Also, a perfect design cannot guarantee a perfect waterproof performance without proper installation workmanship. In addition, a sealant system works best if satisfying the two conditions: it is installed in shop rather than installed on site; it is not exposed to weather. This system can be found in pressure-equalized enclosures. (Loughran 2003, p.81) 5.3.4 Maintenance How detailing affects maintainability Fig. 5-29 shows two examples of how a detail design may affect maintainability. Inside Outside SECTION mullion glass Outside Inside glass mullion SECTION Inside Outside Outside Inside (1) (2) Glass on the mullion inside creates deep shadows, but makes mullions easy to get dirty. Glass on the mullion outside creates no shadows and avoids mullion to get dirty (1) Support inside behind the glass wall protects the support structure (2) Support outside the glass wall exposes the support structure to corrosion (a) Location of mullion (b) Location of back up structure Fig. 5-29 Different detail designs affect maintainability Integration of maintenance equipment Another issue that detail design needs to consider is future requirements for maintenance. Using the La Villette Museum as an example, in the design of the bio-climatic glass façade, the designer designed two small rails suspended from each structural horizontal member, one above the tube, the other below the tube. Maintenance equipment can hang on the rails to go inside of the glass building (Fig. 5-30). The right image shows how the 6mm rails are connected to the structural tubes. Fig. 5-30 Detail design for maintenance equipment in La Villette Museum (Rice & Button 1995, p.8) 108 5.3.5 Aesthetics How detailing affects aesthetics A good detail design is not only functionally successful, but also visually successful. This can be achieved through proper color, texture, shape, and proportion in the detail design of each component. Also, detail designer should always consider the overall design concept of the building. For instance, the point fixings of glass can be mounted either inside or outside of the glass façade. Generally, they are positioned inside, because it is easier for maintenance. But in the building in Avenue Montaigne in Paris, designed by Epstein, Glaimann & Vidal in 1993, the glass fixings are mounted on the outside of the glass façade, because the architects wanted a “completely smooth glass façade” from inside view, therefore “the half-cylinder should be reflected in the glass and so create the illusion of a whole cylinder” (Schittich 1999, p.51). See Fig. 5-31. Fig. 5-31 Glass fixings attached to the exterior glass facade – Avenue Montaigne (Rice & Dutton 1995, p.132, 133) 109 110 Chapter VI Detailing process 6.1 In general The following process is a guide to detail design. The process includes nine points. Four case studies are used as demonstrations to illustrate and support the nine points (please see chapter 8, 9, 10, and 11). As introduced in 2.3, the nine points are: 1). Identify the building infrastructure. 2). Determine modular size. 3). Identify the backup structure. 4). Make a checklist of all of the elements based on four categories. 5). Define the position, shape and size of each element. 6). Define all connections based on nine categories. 7). Define the material and method for each connector. 8). Define other requirements if required. 9). Design each connection. The sequence shown here is typical and can be applied to many situations. Theoretically, a designer can start from any one of the nine points and follow a different sequence. A different sequence may lead to different result. This is another complicated topic and will therefore not be discussed in this thesis except to note that the sequence is related to several factors, such as a designer’s experience, emphasis, and/or different conditions for each project. An experienced designer may not need to follow all of the nine points. He may miss several, or even most of the steps, but still can create a good detail. He may have a very different approach to make details. But this thesis is not going to analyze the possibilities of different sequences; neither will it compare the advantages and disadvantages of different sequences. This thesis will discuss the application of one typical sequence and use four case studies to illustrate the application. 111 6.2 Learning the process 6.2.1 Identify the building infrastructure Purposes Identify location and configuration (horizontal or vertical) of the building infrastructure. Identify the materials used in the infrastructure. Identify the strength (strong or weak) and stiffness (soft or stiff) of the building infrastructure. General rules The infrastructure determines if a backup structure is needed. If the height between the roof and floor is within 12 feet, vertical mullions are enough to support the glass. If higher than 12 feet, additional backup structure (such as a truss, cable or glass-fin) is needed to resist lateral load. The infrastructure also determines whether to use a horizontal or vertical backup structure. Generally, horizontal infrastructure (roof, beam, and floor) can use vertical backup structure. Vertical infrastructure (column, shear wall) can use horizontal backup structure. Methods of connections for different materials used in infrastructure: Steel: weld or bolt Concrete: anchor bolt, anchor plate Wood: bolt or screw 6.2.2 Determine modular size Purposes Determine the module of backup structures and sub-structure members. For example, if using vertical cables, modular size means the space between each two adjacent vertical cables, as well as the space between horizontal cables as sub-structures if there are any. General rules Generally, the modular size may be based on glass panel size. If the glass pane is bigger than its maximum span without support (generally 5~10’), then additional support is needed. 112 It is recommended that the modular size is either exactly the same as glass size or at good proportion based on glass size for both structural and aesthetical consideration. 6.2.3 Identify the backup structure Purposes The backup structure is used to resist lateral loads, such as wind and seismic load. The backup structure can be metal frame, truss, tension cable, cable net or glass fin. The choice of backup structures may influence the choice of glass fittings. General rules The choice of different backup structures is based on a combination of a variety of issues ranging from profile rations, cost and maximum span to the choice of glass fittings. Generally, different types of backup structures have different maximum spans. Backup structures not only include primary structures, but also include secondary structures. For example, if a vertical truss is used as a backup structure to support the glass wall, designers also need to consider the secondary structure, which will be horizontal bracings. The backup structure is defined by architects and/or engineers; or by curtain wall designer and/or contractors; or by all participants involved. Material used generally: Truss: most likely steel Cable: normally strand, (stiffer than wire rope) Glass fin: generally made of toughened glass. Cable net: most likely steel 6.2.4 Make a checklist of all elements based on four categories Purposes: This step is to asure all of the elements involved are considered at detail designs. The checklist of all elements is prepared for the next step. The four categories are shown in table 6-1. 113 Category 1 – Elements in building Infrastructure systems Ground; Roof; Floor; Column Category 2 – Elements in glass wall systems Glass fittings (devices) Glass panels Glass fittings Backup structure slements Category 3 – Elements for openings Ventilation Entrance Other openings Category 4 - Additional devices HVAC Shading devices, daylight control devices Fire protection Table 6-1 A checklist of elements based on four categories 6.2.5 Define position, shape and size of each element. Purposes Locate each element by center line. Determine the shape of metal frames (straight or curved), trusses (rectangular or triangular, and the depth), curved cables (relative positions of the two cables), or glass fins (rectangular or slope). General rules The shape is defined by architects and/or in consultation with curtain wall designers and/or contractors. The size of each element is defined by calculation, experience and/or aesthetics. Look at both primary section and secondary section. 6.2.6 Define all connections based on nine categories. Purposes This step is to make sure all joints involved in a wall section are considered. After listing all joints, a designer may have an overall understanding of the detail designs for the complete wall section; therefore the designer may be able to make correct decisions when looking at each joint separately. The nine categories are shown in Table 6-2. 114 Category 1 – Connections within glass wall Glass + Glass Glass + Glass fittings Glass fittings + backup structure elements Connections within backup structures Category 2 – Connections within openings Category 3 – Connections within additional devices Category 4 – Connections between glass wall and additional devices Glass + additional devices Glass fittings + additional devices Backup structure elements + additional devices Category 5 – Connections between glass wall and openings Category 6 – Connections between openings and additional devices Category 7 – Connections between glass wall and infrastructure Glass + infrastructure Backup structure elements + Infrastructure Category 8 – Connections between openings and infrastructure Category 9 – Connections between additional devices and infrastructure Table 6-2 A checklist of all connections based on nine categories General rules (1) Minimize the number of expensive fittings (for examples, single cable, not too many fitting) Design connections that can be prefabricated in the shop, rather than in the field (cost, quality control) Make welded connections only in the shop and bolted connections in field. (to avoid inspector, cost) Outside support or inside support (clean, no corrosion) Always consider appropriate tolerance General rules (2) Glass to glass Water proof, airtight, expansion, silicone, movement expansion Tolerance: thermal expansion, movement, manufacture Glass to fittings Metal can not attach directly to the glass to waterproof and reduce pressure. Tolerance: to fit glass and if glass fitting moves, avoid stress on glass; make the hole bigger, about one inch. Washer, allow movement 115 Glass to roof and floor Glass cannot take vertical load; need to provide space to allow vertical movement, water tight, and tolerance. Glass fin to roof and floor No vertical load; to avoid buckling Glass fin to glass façade Either glued by silicone, or bolted. Silicone is flexible to allow movement. Cable to roof and floor Make sure the cable is pre-stressed. The roof and floor have to be strong enough to resist cable tension. Tell engineer of infrastructure how much load the roof has to take. Truss to roof and floor Truss can not resist vertical load. Use slot to allow movement. Glass fittings to backup structure Make sure no stress on glass. Cable to strut Generally, all of the cables at one point should meet at one point to avoid bending stress. If cables can not meet at one point for various reasons, (for example, the connector between cable and strut may be too big for all of the cables to meet at one point) bending stress will occur in the strut. In this case, designers should confirm with engineers to make sure the struts are strong enough to resist the bending stress. For each connection, designer needs to consider the method to connect adjacent elements. For example, when cables come to struts, there are generally two ways to join elements. One way is to let the cable go through the strut (Fig. 6-1, a &b); the other way is to make the cable separated by the strut (Fig. 6-1, c). The first way is generally cheaper because the connector is simpler. The cable is consistent and therefore there is no bending moment for the strut. The second way is generally more expensive because the joints are more complicated, but the strut is stronger. (a) Cable going through the strut La Villette Museum in Paris (Rice & Dutton 1995, p.73) (b) Cable going through he strut American Yazaki 21 (ASI brochure) (c) Cable separated by the strut University of Connecticut (ASI) Fig. 6-1 Different cable connections 6.2.7 Define material and method for each connector Purposes This step defines the material and method used for each connector listed in the previous step. Generally, different materials will result in different connection methods. General rules Glass panel connections generally use structural silicone. Connections in truss supported systems use bolted, pinned, and/or welded joints. Connections in tension cable systems use clamped, socked, swaged, and threaded joints; Connection of crossing cables use clamped joints. Cable to tube connections use gusset plates. Connection in truss supported systems Connections in trusses usually use bolted, pinned and (or) welded connections. In truss supported structures, tubular members are often used, and the material is generally stainless steel. The section of the tube can be circular, square, or rectangular. The detailing of the connections of the tubes requires the size of each tube and the connection method. The size of each tube should be determined based on structural design, fabrication, as well as aesthetic consideration. The connections between 116 tubular members typically have two forms, which are bolted and welded connections. A bolted connection generally has also some welded parts. (Trebilcock & Lawson 2004, p.87) “Bolted connections are desirable for site assembly, and large welded sub- assemblies that are prefabricated and bolted together on site at suitable locations.” (Trebicock & Lawson 2004, p.89) More information of tubes can be found in the Corus publications on tubes and pipes. The following image (Fig. 6-2) shows some examples of typical bolted connections to tubular members. (a) Projecting flange-plates This can be used in any shape and size of tubular members. (b) and (c) Welded plate with projecting fin plate The bolts are loaded in shear basically. (d) Welded fin cut into the section This connection form part of a splice connection. The bolts are loaded in shear. (e) Through bolts with internal ferrules (f) Sections with flattened ends This is only appropriate in smaller circular tubular sections. Fig. 6-2 Some examples of bolted connections to tubular members (Trebicock & Lawson 2004, p.89) Pinned connections use welded fin plates and welded end-plates. Some examples are shown in Fig. 6-3 a & b. Connections between tubular members and I-section steel beams usually use spliced connection (Fig. 6-3, c). This can be often seen is a truss-supported glass wall. The end of the truss is connected to the I-beam by a spliced connection. The spice plate used here is curved at the end for visual effect reason. The bolts are designed to transfer the shear and axial forces. (Trebicock & Lawson 2004, p.91) 117 (a) Simple pinned connection examples (b) A typical pinned connection to a foundation achieved by a single pin from a projecting plate (c) Spliced connection between the tube and I- beam Fig. 6-3 Examples of pinned connection (a & b) and sliced connection (c) (Trebicock & Lawson, 2004, p.90, 91, 96) The two images below (Fig. 6-4 & Fig. 6-5) show how to do the details of the welded joints. Ideally, the center-lines of the chords (main members) should intersect the center-lines of the branches (bracing members), which is called as “nodding” (Fig. 6-4 a). But in reality, there could be “a small degree of eccentricity of the nodes”. (Trebicock & Lawson, 2004, P99) (Figure 6-4 b, c, d) But if eccentric nodes are used, designers need to assure the bars can resist the bending stress. (a) Concentrated joint noding (ideal) (b) Gap joint with positive eccentricity (c) Partial overlap with negative eccentricity (d) Total overlap with negative eccentricity Fig. 6-4 Joint noding of tubular members in a welded connection with concentricity and modest eccentricity (Trebicock & Lawson 2004, p.99) When two tubes come together with a right angle, an end cap can be used to achieve rigidity of joint, or a flush right-angle can be achieved by welding, or a plate can be used to get greater load transfer capacity (Fig. 6-5). 118 (a) Flush right- angle connection (b) Flush right-angle connection with infill plate (c) Overshooting right-angle connection Fig. 6-5 Examples of right-angle connection (Trebicock & Lawson 2004, p.99) Connections along the length of a tubular member have two forms: One form is to weld the tubes end to end; the other way is using bolted splices (Fig.6-6). (a): Welded connections It is the neatest solution. The connection can achieve the full strength of the tube. It should only be made in shop in order to achieve correct tube alignment. (b): Flange plates The connection is more efficient for compression than tension because of bending in the plate. The bigger the loading, the thicker the plates and the more bolts are required. (c): Splice plates The joint is regarded as pinned, therefore not appropriate for members who are in compression or bending. The joint can be either exposed or covered by a circular plate to get a smooth appearance (please see the images below). (d): Partial end-plates It should be considered as pinned. Not suitable for the middle of a member subject to high-tension or bending. Fig. 6-6 Examples of tube to tube splices (Trebicock & Lawson 2004, p.93) Splice plates with and without cover plate are shown in Figure 6-7 a & b. Connections of tube to tube with different angles generally take two forms: welded tube to tube connections (Figure 6-7, c), and gusset plate connections (Figure 6-7, d), which can be used in shorter span trusses. 119 (a) Splice connection exposed (b) Splice connection with cover plate (c) Welded connection (d) Gusset plate connection Fig. 6-7 Splice connection with (a) and without (b) cover plate; and tube to tube connections by welding (c) or by gusset plate (d) (Trebicock & Lawson 2004, p.94, 100, 101) Connection in tension cable systems “Two basic types of connection may be used in tension structures using tie rods or cables: those which connect tie rod or cables to each other, and those which connect to the main structural elements. Generally, both these forms of connection require a method of adjustment to prevent sag in the member and/or to induce a specified tension.” (Trebicock & Lawson 2004, p.117) Typically, four methods are used in tension cable (or rod) systems: clamped, socked, swaged, and threaded. Clamped connection is generally used for low-tensile forces (Figure 6-8). (a) “Example of connection between net cable and boundary cable using special clamp” (b) Example of cable crossing fixings using clamp. Twinned thin cables “have many practical advantages over a single thick cable of equivalent load-bearing capacity”. Fig. 6-8 Examples of cable connections using clamp (Vandenberg 1998, p.33, 33) 120 The end connection of cables and wire ropes generally use socked and swaged termination: “Wire cables and ropes can resist very high-tensile forces but their ends cannot be threaded or welded. For low-tensile forces or for temporary connections, the cables can be clamped. For higher tensile forces, a number of methods are available, the most common of which are the socked termination and the swaged (or pressed) termination. In a socked termination, the individual wires are spread into a conical-shaped steel casting (Fig. 6-9, a) and are anchored using zinc or resin. The casting can then be attached to any particular fitting or linking device by means of a threaded coupler (Fig. 6-9, b). A swaged termination is usually provided by the manufacturer. (Fig. 6-10)” (Trebicock and Lawson 2004, p.118) (a) Splaying out of wire rope (b) Threaded coupling for wire rope sockets Fig. 6-9 A socked termination for cables and wire ropes (Trebicock & Lawson 2004, p.118) The following image (Fig. 6-10) shows a typical anchorage for a cable or wire rope end connection to rigid boundaries. 121 Fig. 6-10 A typical anchorage for a cable or wire rope end connection to rigid boundaries (Vandenberg 1998, p.30) Examples of swaged connections are shown in Fig. 6-11. Swaged cable-end Fork end Adjustable fork-end Threaded end to permit adjustment Swaged tensioner Compact tensioner Toggle fork Fig. 6-11, Continued on next page 122 Rings allowing multiple connections of ties for bracing systems Eye bolt Coupler device used for an X-braced connection Tension-coupling system for stainless steel bar Fig. 6-11 Examples of swaged connection (Trebicock and Lawson 2004, p.122, 123) The end connections of linear tension bars or tie rods using threads are shown in the image below (Fig. 6-12). (a) threaded coupling for bars or rods (b) typical coupling between stainless steel bars or rods “In tie bars or rods, the connections are formed by threading the bars. Welding is not appropriate as the bars are usually made from high-tensile steel. For the highest strength bars, the thread is not cut but is rolled onto the bars so that no cross- sectional area is lost. Left- and right-handed threads are formed onto the ends to enable couplings to be made, as shown in the image left (a). The coupler is often provided with a flattened portion to assist in turning without damaging the surface. The image left (b) shows an example of a coupler in a large stainless steel bar used in the Helsinki Sanomat building. In this case, the thread has been cut into the bar.” (Trebicock and Lawson 2004, p.118) Fig. 6-12 Threaded coupling for bars (a) and typical coupling between stainless steel bars (b) (Trebicock & Lawson 2004, p.118, 119) Cable and tube connection using clamping or gusset plate Connection between tension cable and tubular members usually use gusset plate (also called as welded fins) as the connectors (Figure 6-13). 123 The left image shows the connection of ties to tube at Cologne Airport designed by Murphy/Jahn Architects. The gusset plate is welded to the tubes, and the cable is bolted to the gusset plate. This connection is usually seen in connections where there are multiple cables connected to one tubular member. Fig. 6-13 Example of gusset plate (welded fins) connections of cable and tube members (Trebicock and Lawson 2004, p.92) 6.2.8 Define other requirements if required. Define any other special requirement for manufacture, assembly and installation, which are usually easy to ignore by architectural students or young architects. Actually, manufacture, assembly and installation should be considered during the whole detailing process to assure constructibility. This step serves an important reminder to assure these critical points are considered. Please see chapter 8 for an example. 6.2.9 Design each connection. General rules: Always remember principles (see Chapter 3) when detailing each connection. Every element is related to the center lines of the system. Different types of connections may have different detailing method and process. Reference processes may be created for typical joint types for the purpose of easy study. For each specific joint, the detailing method can be different because of different requirements and emphasis. For example, the joint between the infrastructure and the glass façade requires that the glass façade not take any vertical load, and will move freely in vertical direction without constrain. A joint between the glass panes and backup structure requires that the glass panes will not directly contact the metal pieces and the horizontal load can be transferred from the glass to the backup structures. Therefore, it is a good practice to develop different detailing methods for different types of connections. 124 Chapter VII Demonstrations overview 7.1 Introduction of the four case studies The thesis uses four PSG wall projects as case studies to demonstrate the detailing methodology. There are two main reasons to choose these four projects as cast studies: 1). They are from ASI, which not only designs, but also does fabrications and installations. 2). Each of the four case studies represents a typical structural type of PSG wall system. They are tension cable, truss, cable net and glass-fin, respectively (Fig. 7-1). Case study one – cable truss supported Case study two – truss supported Case study three – cable net supported Case study four – glass fin supported Fig. 7-1 Overview of the four case studies (ASI) 7.1.1 Case study one, cable support structure Case study one is the University of Connecticut Student Center, at Stamford, Connecticut, designed by Perlins Eastman Architects. ASI served as the glass façade consultant for this project. The 440 feet long and 35 feet high glass façade is vertically braced by double curved stainless steel cables and consists of green-tinted, low-e coated and insulated glass panels 5 feet wide and 5.8 feet high. (ASI) Please see chapter 8 for this case study. 125 126 7.1.2 Case study two, truss support structure The project is the McCarren International Airport at Las Vegas, Nevada. The designer is Tate & Snyder Architects, and the façade consultant is ASI. The building includes two slope glazing facades, both of which are supported by custom tubular steel trusses and braced with stainless steel tension rods. The south façade is 100 feet long and 60 feet high, and the north one is 50 feet long and 50 feet high. The 1.339-inch thick insulated glass panels are 11.3 feet long and 4 feet high each. (ASI) Please see chapter 9 for detailed study of this project. 7.1.3 Case study three, cable-net structure It is the UBS Building at One North Wacker Drive located in Chicago, Illinois, designed by Lohan Associates, Inc. The 40 feet high glass lobby is supported by stainless steel cable net structure. A small round cast stainless steel node on the corners of glass panes transfers loads to the pre-stressed cables. It is the first building using this type of cable net structure in the U.S. The glass used in the lobby is 5 feet wide, 5 feet high and 0.5 feet thick, monolithic tempered and heat soaked glass. (ASI) Please see chapter 10 for this case study. 7.1.4 Case study four, glass-fin support structure The project is the Ha-Lo building in Niles, Illinois, designed by Murphy/Jahn Architects. The building consists of a 4000-square-feet glass wall, of which the height is 26.5 feet. The glass wall is braced by a series of 1.5 feet wide and 1.25 inch thick laminated glass fins at a space of 5 feet. The insulated glass used in the glazing wall is 1 and 1/16 inch thick, 5 feet wide and 13-14.5 feet high. (ASI) See chapter 11 for details. 7.2 Overview of the detailing process for each case study Table 7-1 provides an overview of the detailing process (explained in Chapter 6) applied to each case study. For more details, see 8.2.1 – 8.2.9 for case study #1; 9.2.1– 9.2.9 for case study #2; 10.2.1– 10.2.9 for case study #3; and 11.2.1 – 11.2.9 for case study #4. 127 Case studies Detailing process Identify the building infrastructure Case study #1 Infrastructure type – upper beam to lower beam Infrastructure material – steel frame Case study #2 Infrastructure type – Roof to floor Infrastructure material – steel frame Case study #3 Infrastructure type – Ground to floor, column to column (grid infrastructure, horizontal and vertical ) Infrastructure material – steel frame (stiff) Case study #4 Infrastructure type – Ground and floor (horizontal) Infrastructure material – reinforced concrete (stiff) Determine modular size Case study #1 5’ × 5’ 10” based on glass pane Case study #2 4’ vertical modular size based on glass pane size 5’ 8” horizontal modular size based on half of glass pane width Case study #3 5’ × 5’ based on glass pane limitation Case study #4 5’ interval distance based on glass pane limitation and architectural elevation 11’ 1” and 14’3” vertical span due to three factors – the maximum size of glass pane; the maximum size of toughened glass-fin; and architectural elevation requirement Identify the back up structure Case study #1 Primary structure – Vertical curved tension rods are used as the back up structure; Vertical straight rods are used additionally; Horizontal strut pipes are compression members Secondary structure – Horizontal bracing rods are used to strengthen the structure; Horizontal straight rods are used additionally Material – stainless steel rod; steel pipe Case study #2 Primary structure – Vertical compression trusses and vertical tension rods are used as the back up structure Secondary structure – Horizontal bracing struts are used to strengthen the structure Material – stainless steel rod; stainless steel pipe Case study #3 Cable net structure (consisting of both horizontal and vertical cables) Vertical cables are attached to steel floor beams by connection boxes; horizontal cables are attached to composite steel and concrete perimeter columns by connection boxes Material – stainless steel cable Case study #4 Primary structure – Vertical laminated toughened glass-fins are used as back up structure. Secondary structure – Lateral bracing cables are used to strengthen the structure. Material – laminated toughened glass-fin; stainless steel rod Make a checklist of all elements based on four categories Case study #1 Category 1 – Infrastructure elements ¾ Upper beam and lower beam Category 2 – Glass wall elements ¾ Glass panels – double-glazing, green-tinted, low-E coated ¾ Glass fittings – four way spider ¾ Primary back up structure – strut pipe(spreader bar); truss rod; vertical rod ¾ Secondary back up structure – bracing rod; horizontal rod Category 3 – Elements for openings ¾ Does not apply in this case Category 4 - Additional devices ¾ Does not apply in this case Table 7-1, Continued on next page 128 Case study #2 Category 1 – Infrastructure elements ¾ Roof beam and floor beam Category 2 – Glass wall elements ¾ Glass panels – 1.339” thick double-pane insulated glass ¾ Glass fittings – Two way and four way spiders ¾ Backup structure elements – Tubular steel truss and stainless steel tension rods Category 3 – Elements for openings ¾ Does not apply in this case Category 4 - Additional devices ¾ Perforated metal sheet sunscreens Case study #3 Category 1 – Infrastructure elements ¾ Top beam, bottom beam and columns Category 2 – Glass wall elements ¾ Glass panels – Half inch thick monolithic tempered glass ¾ Glass fittings – Clamping plate cable-net fittings without perforation ¾ Backup structure elements – Cable net including horizontal and vertical cables Category 3 – Elements for openings ¾ Portal frame beam – Built up box beam TS8×6×9/18 ¾ Portal frame column – Built up box column TS6×4×1/2 ¾ Portal frame jamb – 24” ×24” concrete pocket ¾ Glass door – Three clear glass doors Category 4 - Additional devices ¾ Does not apply in this case Case study #4 Category 1 – Infrastructure elements ¾ Third floor reinforced concrete slab and ground floor reinforced concrete foundations Category 2 – Glass wall elements ¾ Glass panels – Double glazing ¾ Glass fittings – Custom designed aluminum pinch plate and stainless steel splice boots ¾ Back up structure elements – Laminated toughened glass-fins as primary back structure; lateral bracing cables as secondary back up structure Category 3 – Elements for openings ¾ Portal frame beam – Steel tube ¾ Portal frame column – Steel tube ¾ Door beam – Steel tube square ¾ Glass door – 15' opening glass doors Category 4 - Additional devices ¾ Does not apply in this case Define the position, shape and size of each element Case study #1 Find out the size of infrastructure The size of glass panels and glass fittings are determined by products The size of strut pipe and rod are determined through both calculation and experience Case study #2 Find out the dimensions and materials of glass panes and infrastructure The shape of steel truss is determined by architects The sizes of stainless steel tubes, struts and rods are determined by structural calculation or experience The shape, material and size of metal sunscreens are determined by architects, considering both aesthetical reasons and thermal performance of the building. Case study #3 Find out the sizes of given infrastructure, glass panes and glass fittings On south facade, the size of vertical cables is determined by structural calculations and/or experience; the size of horizontal cables is determined by that of vertical cables On west and east facade, the size of horizontal cables is determined by structural calculations and/or experience; the size of vertical cables is determined by horizontal cables The position, shape and size of portable glass doors are determined by architects and/or glass door manufacturers The sizes of portable frame beam and column are determined by calculation and experience Table 7-1, Continued on next page 129 Case study #4 Find out the width and shape of glass fins Find out the size of glass panes The sizes and materials of custom designed glass fittings are determined by structural calculations and aesthetics The size of horizontal bracing cables is determined by structural calculation as well as experiences The sizes of portal frame beam, portal frame column and door beam are determined by both structural and aesthetical requirements Define all connections based on nine categories Case study #1 Category 1– Connections within glass wall ¾ Glass + Glass ¾ Glass + Spider ¾ Spider + Strut ¾ Strut + Rod Category 2 – Connections within openings ¾ Does not apply in this case Category 3 – Connections within additional devices ¾ Does not apply in this case Category 4 – Connections between glass wall and additional devices ¾ Does not apply in this case Category 5 – Connections between glass wall and openings ¾ Does not apply in this case Category 6 – Connections between openings and additional devices ¾ Does not apply in this case Category 7 – Connections between glass wall and infrastructure ¾ Glass + Ground ¾ Glass + Roof ¾ Rod + Ground ¾ Rod + Roof Category 8 – Connections between openings and infrastructure ¾ Does not apply in this case Category 9 – Connections between additional devices and infrastructure ¾ Does not apply in this case Case study #2 Category 1– Connections within glass wall ¾ Class + glass ¾ Glass + truss tube ¾ Glass + strut ¾ Truss tube + rod ¾ Rod + strut Category 2 – Connections within openings ¾ Does not apply in this case Category 3 – Connections within additional devices ¾ Perforated sheet metal + stiffener ¾ Solid sheet metal + stiffener Category 4 – Connections between glass wall and additional devices ¾ Truss structure + sunshade device ¾ Tension rod structure + sunshade device Category 5 – Connections between glass wall and openings ¾ Does not apply in this case Category 6 – Connections between openings and additional devices ¾ Does not apply in this case Table 7-1, Continued on next page 130 Category 7 – Connections between glass wall and infrastructure ¾ Glass + roof beam ¾ Glass + floor beam ¾ Truss structure + roof beam ¾ Truss structure + floor beam ¾ Tension rod structure + roof beam ¾ Tension rod structure + floor beam Category 8 – Connections between openings and infrastructure ¾ Does not apply in this case Category 9 – Connections between additional devices and infrastructure ¾ Does not apply in this case Case study #3 Category 1– Connections within glass wall ¾ 　 Class + glass ¾ 　 Glass + cable (horizontal and vertical) Category 2 – Connections within openings ¾ 　 Glass door + portal frame beam ¾ 　 Glass door + portal frame column ¾ 　 Glass door + portal frame jamb ¾ 　 Portal frame beam + portal frame column ¾ 　 Portal frame beam + portal frame jamb Category 3 – Connections within additional devices ¾ 　 Does not apply in this case Category 4 – Connections between glass wall and additional devices ¾ Does not apply in this case Category 5 – Connections between glass wall and openings ¾ 　 Glass + portal frame beam ¾ 　 Glass + portal frame column ¾ 　 Vertical cable + portal frame beam ¾ 　 Horizontal cable + portal frame column Category 6 – Connections between openings and additional devices ¾ 　 Does not apply in this case Category 7 – Connections between glass wall and infrastructure ¾ 　 Glass + floor beam (top) ¾ 　 Glass + floor beam (bottom) ¾ 　 Glass + column ¾ 　 Vertical cable + floor beam (top) ¾ 　 Vertical cable + floor beam (bottom) ¾ 　 Horizontal cable + column Category 8 – Connections between openings and infrastructure ¾ 　 Portal frame beam + floor beam (bottom) ¾ 　 Portal frame column + floor beam (bottom) ¾ 　 Portal frame jamb + floor beam (bottom) Category 9 – Connections between additional devices and infrastructure ¾ 　 Does not apply in this case Case study #4 Category 1– Connections within glass wall ¾ Class + glass ¾ Glass + glass fin ¾ Glass fin + glass fin ¾ Glass fin + lateral cable Category 2 – Connections within openings ¾ Glass door + portal frame beam ¾ Glass door + portal frame column ¾ Glass door + door beam ¾ Portal frame beam + portal frame column ¾ Portal frame beam + door beam Table 7-1, Continued on next page 131 Category 3 – Connections within additional devices ¾ Does not apply in this case Category 4 – Connections between glass wall and additional devices ¾ Does not apply in this case Category 5 – Connections between glass wall and openings ¾ Glass fin + portal frame beam ¾ Glass + portal frame beam ¾ Glass + portal column Category 6 – Connections between openings and additional devices ¾ Does not apply in this case Category 7 – Connections between glass wall and infrastructure ¾ Glass + concrete slab (third floor) ¾ Glass + concrete foundation (ground floor) ¾ Glass fin + concrete slab (top) ¾ Glass fin + concrete foundation (bottom) ¾ Lateral cable + concrete slab (second floor) Category 8 – Connections between openings and infrastructure ¾ Portal frame column + concrete foundation (ground floor) Category 9 – Connections between additional devices and infrastructure Does not apply in this case Define the material and method for each connector Case study #1 Glass + Glass – structural silicone Glass + Spider – bolted together Spider + Strut – connected by a solid bar; the spider is bolted to the solid bar; the strut is welded to the solid bar Strut + Rod – connected by a steel plate; the plate is welded to the strut; the rod is bolted to the plate. Glass + Ground Glass + Roof Rod + Ground (steel tube) – connected by a plate and an anchor plate; the anchor plate is welded to the steel tube; the plate is welded to the anchor plate; the rods are bolted to the plate Rod + Roof (steel tube) – connected by a plate and an anchor plate; the anchor plate is welded to the steel tube; the plate is welded to the anchor plate; the rods are bolted to the plate Case study #2 Glass + Glass – structural silicone sealant Glass + Truss tube – Four way spider with Pilkington Planar System Glass + Strut – Two way spider with Pilkington Planar System Truss tube + Tension rod – connected by a steel plate; the plate is welded to the strut; the rod is bolted to the plate. Tension rod + concrete floor – connected by a vertical steel plate; the rod is bolted to a vertical plate; the vertical plate is welded to a horizontal plate which is bolted to the concrete floor Truss structure + sunshade device – the sheet metal covers the truss tubes all around so that the sunscreens look perfectly integrated with the truss structure Glass + roof beam – a steel pocket holds the glass pane; the pocket is bolted to a steel angle with a shim space between the pocket and the steel angle; the angle then is welded to the infrastructure Truss + roof beam – connected by three steel plates (two on top and one on bottom) that are bolted together like a Sandwich; the bottom plate has a slotted hole for pin to allow free vertical movement of truss Glass + concrete floor – a steel pocket holds the glass pane; the pocket is bolted to the concrete floor with a shim space between the pocket and concrete block Truss + concrete floor – connected by three steel plates (one on top and two on bottom) that are bolted together like a Sandwich Table 7-1, Continued on next page 132 Case study #3 Glass + Glass – structural silicone Glass + cables (horizontal and vertical) – bonded together by custom designed cast metal nodes Glass + Floor beam (top) – connected by a steel channel with a shim space between the channel and beam Vertical cable + Floor beam (top) – cable swage is screwed to a horizontal steel plate which is welded to a vertical steel plate; the vertical plate is welded to the steel beam Glass + Floor beam (bottom) – connected by a steel channel and two steel plates with a shim space between the channel and the plates Vertical cable + Floor beam (bottom) – cable swage is screwed to a horizontal steel plate which is welded to a vertical steel plate; the vertical plate is welded to the steel beam Case study #4 Glass + Glass – structural silicone sealant Glass + concrete slab – connected by custom designed steel frame Glass fin + concrete slab – connected by a stainless steel splice boot Glass + Glass fin – connected by custom designed aluminum pinch plate and stainless steel splice boot Glass fin + Glass fin – connected by stainless steel splice boot Glass fin + Lateral cable – bolted together Glass + Concrete foundation – glass is glued to steel frame by structural silicone and backer rod; the steel frame is bolted to splice boot; the stainless steel splice boot is anchored to the concrete foundation Glass fin + Concrete foundation – connected by a stainless steel splice boot Glass + Portal frame beam – glass is held by a steel plate which is welded to the door beam; the door beam is bolted to a custom designed steel plate which is then welded to the portal frame beam Glass fin + Portal frame beam – bolted together through a stainless steel portal boot Portal frame beam + Portal frame column – welded together Define any other requirements Case study #1 A gusset plate with an extra hole for pre-stressing Case study #2 A splice plate is used to connect two pieces of steel tubes with the same outside diameters but different thickness A safety anchor loop is designed on the truss tubes to allow additional structural loads applied onto the glass wall Two bracing rods in truss structure are eccentrically designed in vertical direction to allow one rod crossing over the other one Case study #3 A series of 3” by 6” access holes are designed in the portal frame beam for pre-stressing of cables Case study #4 Special details are considered when steel plates are bolted to toughed glass fins Design each connection Case study #1 Detailing a typical joint type (rod + strut) – starting from a concentric connection Detailing a typical joint type (rod + strut) – starting from an eccentric connection Six steps ¾ Step 1 – Draw (concentric or eccentric) center line connections ¾ Step 2 – Draw connector size as dotted line ¾ Step 3 – Define tolerance between connectors ¾ Step 4 – Explore connector options ¾ Step 5 – Design connector ¾ Step 6 – Make adjustment (reduce connector and check eccentric stress; concave shape of the gusset plate to allow structural movement) Table 7-1, Continued on next page 133 Case study #2 Detailing a typical joint type Joint A (rod + strut) Detailing a typical joint type Joint B (rod + strut) – starting from a concentric connection Detailing a typical joint type Joint B (rod + strut) – starting from an eccentric connection Six steps ¾ Step 1 – Draw concentric center line connections ¾ Step 2 – Draw connector size as dotted line ¾ Step 3 – Define tolerance between connectors ¾ Step 4 – Explore connector options ¾ Step 5 – Design connector ¾ Step 6 – Make adjustment Case study #3 Detailing a typical joint type (glass panes + cable system) – the rear elevation part (interior part) Detailing a typical joint type (glass panes + cable system) – the front elevation part (exterior part) Six steps ¾ Step 1 – Draw concentric center line connections ¾ Step 2 – Draw key connector size as dotted line ¾ Step 3 – List all elements to be joint together ¾ Step 4 – Define connection methods between adjacent elements ¾ Step 5 – Design connector ¾ Step 6 – Make adjustment Case study #4 Detailing a typical joint type (glass fin + glass wall) Six steps ¾ Step 1 – Draw concentric center line connections ¾ Step 2 – Draw key connector size as dotted line ¾ Step 3 – Determine position of boot bolts ¾ Step 4 – Explore connector options ¾ Step 5 – Design connector ¾ Step 6 – Make adjustment Table 7-1 Overview of the detailing process applied to each case study 7.3 Introduction of failure studies This section features research of projects that failed because of inappropriate detail designs. Firstly, general failure types are introduced briefly; secondly, several failure detailing examples are provided. Future research is expected on this topic. 7.3.1 Failure types Failures of glass structures caused by inappropriate detail designs include: Water leakage Corrosion Glass breakage because of thermal stress or structural loads Staining of glass façade Energy inefficiency 7.3.2 Failure examples Failure studies can be very useful to help designers avoid making the same mistakes. Due to the complexity of failures, additional research is needed to explore all of the failure types mentioned above. This thesis selects two examples to illustrate failure caused by glass breakage and what designers could learn from these examples. The two examples are introduced in Patrick Loughran’s book Falling Glass: Problems and Solutions in Contemporary Architecture, 2003. This book provides an informative and systematic research of the failures of glass structures. The first example is the breakage of the tempered glass used in the Palais de Justice, Bordeaux (See figure 7-2 below). Although tempered glass has greater strength than normal glass because of the compression of the outer layer, the “inherent fragile nature” of glass reminds designers that breakage can still occur without thoughtful detail designs even when using tempered glass. (Loughran 2003, p.106, 107) (a) The tempered glass fins wrapped in canvas had to be replacement due to breakage. (b) The glass fins were replaced by steel fins. (c) The detail of a steel fin, which is more ductile but less transparent than glass fin. Fig. 7-2 Tempered glass failure in the Palais de Justice, Bordeaux (Loughran 2003, p.108, 109) Another example is the breakage of the laminated glass used in the Marche Saint-Honore in Paris (Figure 7-3). 134 “Research has also determined that laminated glass behaves less like monolithic glass and more like layered glass as the temperature of laminated glass increases from normal conditions (below 100oF or 38oF) to elevated conditions (over 120oF or 49oC). This adjustment in behavior is accompanied by a loss in glass strength and deflection characteristics.” When the temperature is high (over 170oF or 77oC), “the adhesive of the interlayer is ineffective and the layers act independently.” In Marche Saint-Honore, “the double skin facade composed of an exterior insulating unit (laminated on the inside light of glass) with point-supported lights connected to a monolithic interior light of glass.” After the building was complete, glass failures occurred. “Point-supported lights of glass are extremely susceptible to high concentrated loads, which can lead to failures. Because the glass is laminated, it does not displace. This is an added benefit to the building's security; however, the project serves to remind us that laminated glass is still susceptible to the same type of glass failures as monolithic glass.” (Loughran 2003, p.114) (a) The broken laminated insulating glass pane (b) Detail view of the broken glass Fig. 7-3 Laminated glass failure in the Mache Saint-Honore, Paris (Loughran 2003, p.114) According to Loughran (2003), the lessons learned from these two examples are: Although tempered glass is stronger than many other types of glass, it is still subject to breakage under concentrated load. Therefore, the materials in direct contact with glass should be large and soft enough to assure the forces transferred to the inherently fragile glass are evenly distributed. Under high temperature and sustained load, laminated glass will lose strength and therefore is not as strong as monolithic glass of the same thickness. If one piece of glass breaks, it should not affect other pieces. 135 Chapter VIII Case study one – University of Connecticut Student Center 8.1 Introduction 8.1.1 Project information This section introduces the climate of the city (Fig. 8-1), the general project information (Table 8-1), and a brief introduction of the project. Climate The latitude of Connecticut is 41.07N, and longitude is 073.25W. Connecticut has a generally temperate climate with warm summer and mild winter. The average temperature in January is 27°F (–3°C), and in July 70°F (21°C). The lowest recorded temperature is –32°F (–36°C) in Falls Village in Feb1943, and the highest is 106°F (41°C) in Danbury in July1995. The rainfall is evenly distributed throughout the year, with an annual rainfall 46.2in (117cm) from 1971 to 2000. (http://www.city-data.com/states/Connecticut-Climate.html) The images below (Fig. 8-1) show the (a) average temperature, (b) humidity, (c) sunshine, (d) precipitation, and (e) wind speed around the year in Stamford. (a) Average temperature Fig. 8-1, Continued on next page 136 (b) Humidity (c) Sunshine (d) Precipitation Fig. 8-1, Continued on next page 137 (e) Wind speed (mph) Fig. 8-1 Stamford climate data (http://www.city-data.com/city/Stamford-Connecticut.html, excerpted) General project information (Table 8-1) Location Stamford, Connecticut Architects Perlins Eastman Architects Associate architects Dubose Associates Engineers Cosentini Associates (mechanical); Purcell Associates (structural); Allan Davis Associates (civil) Consultants Advanced Structures Inc. (structural glazing); Scott B. Page (program); Jack Curtis & Associates (landscape); Chermayeff & Geismar (graphics); Donegan & Associates (consulting architect); Ann Kale Associates (lighting) Uninsulated metal Panel Alply Insulated metal Panel Criterion Glass curtain wall Pilkington Aluminum windows Vistawall, Pilkington Insulated glass Pilkington, Viracon Skylights Architectural Skylight Glass entrance doors Blumcraft Cherry veneer doors Weyerhauser Lighting Zumtobel, Bega Total Cost $40 million Total area 253,000 SQFT Unit cost $158/SQFT Table 8-1 General project information of case study #1 (ASI) Brief introduction Stamford campus building is located in downtown Stamford. It is the renovation of an old building of which only the structure and floor slab remain, but the brick skin was removed and substituted by glass and concrete. The south part of the building is a library, and the north part consists of classrooms and offices. The south-facing and 440-foot long glass façade is one of the most 138 139 impressive features of the building. It not only brings sufficient daylight into the academic concourse, but also makes the building close and friendly to pedestrian, which strengthens the designers’ idea to bring the building “closer to the community it serves.” The whole glass façade is divided into two parts by a concrete slab. The lower part is about 11 feet, supported by regular mullion. The 36-foot glazing of the upper part is pointed fitted, and supported by cable (rod) truss. This part is what ASI developed. For this project, ASI was hired by Pilkington as a subcontractor to provide the design and detailing of the glass wall and support system. The glass panes and fittings were not the responsibility of ASI; in stead, they were designed by W&W Glass Systems, Inc., another subcontractor of Pilkington. (Langdon 1998) The glass façade is the “nation's first Pilkington Planar glazing system supported by the longest, clear span, lenticular cable truss. The facade was made up of green-tinted, low-e coated, insulated glass panels supported by stainless steel, four-point castings.” The glass wall includes “several 900 corners supported by custom-designed corner trusses. The key feature of the support structure was the pretensioning methodology created to adequately support this unique clear span structure.” (http://www.wwglass.com/) 8.1.2 Images The following images are the site plan & first floor plan (Fig. 8-2), exploded axonometric (Fig. 8-3), exterior and interior photos (Fig. 8-4) of the building. Site plan: 1. Stamford Campus Building 2. Parking garage 3. Franklin Plaza 4. C.L.”Whitey” Heist Park 5. Rippowam River 6. St. Andrew’s Church First floor plan: 1. Entrance 2. Concourse 3. Library 4. Bookstore 5. Conference center entrance 6. Light spine 7. Auditorium 8. Classroom 9. Multiuse area 10. Mechanical Fig. 8-2 Site plan and first floor plan of the building of the University of Connecticut (Langdon 1998) 140 Fig. 8-3 Exploded axonometric (Langdon 1998) 141 (b) North facade (Langdon 1998) (a) South façade (Langdon 1998) (c) Inside view looking from east to west (Langdon 1998) (d) South façade (http://www.wwglass.com/) (e) Inside view from north to south (Langdon 1998) (f) In side view looking from east to west (http://www.wwglass.com/) Fig. 8-4 Exterior and interior photos of the building of the University of Connecticut 142 Two detailing processes are introduced in this chapter, using case studies. Firstly, a typical wall section is used to explain the detailing process of a typical PSG wall (see Chapter 8.2). Secondly, a specific joint is selected to illustrate the detailing process of a typical joint of cable and strut (see Chapter 8.2.9). Fig. 8-5 shows the interior views, description, elevation and section of the glass wall used to illustrate the detailing process. 143 The 440 feet long and 35.4 feet high south glazing facade of the Student Center, University of Connecticut, features 5 feet wide and 5.83 feet high glass panes of double-glazing, green-tined and low-E coated glass. (http://www.wwglass.com/) The glazing is point- supported, and the fixing type is Pilkington Planer System. The glazing support attachments are stainless steel four-way spiders, attached to stainless steel double-curved tension rods. The glass wall is attached to horizontal infrastructure of two square-tube steel beams. (a) Interior view (b) Description of the PSG wall based on five layers 6' Square steel tube 7'-2" 5' 5.83' Square steel tube Strut pipe Glass Rods 35.4' A typical joint used in Step 8 and Step 9 (see 8.2.8 & 8.2.9) (c) Interior view of the wall (d) Elevation (e) Section Fig. 8-5 Interior views, description, elevation and section of the glass wall (ASI, modified) 8.2 Detailing process for a typical section 8.2.1 Identify the building infrastructure (Fig. 8-6) Building infrastructure (http://www.wwglass.com/) (ASI, modified) Infrastructure type – upper beam to lower beam (horizontal) Infrastructure material – steel frame (stiff) In this example, the infrastructure consists of two horizontal beams (see the wide lines in the image left above). This means that the back up structure is a vertical structure. Here, vertical cable trusses are used. The materials of the beams are steel, which is generally strong, and can resist the cable tension. Fig. 8-6 Case study #1 - Illustration and description of step 1 8.2.2 Determine modular size (Fig. 8-7) 5' 70" Infrastructure (roof) Glass fitting Infrastructure (ground) Truss 1 2 70" 70" 70" 70" 70" Glass Left image: (1) Section of primary back up structure, see Fig. 8-8, a (2) Section of secondary back up structure, see Fig. 8-8, b Glass pane (ASI, modified) Modular size based on glass pane (ASI, modified) 5’ × 5’ 10” based on glass pane limitation In this project, the modular size of the glass wall was determined by the size of glass pane, which is 5 feet width and 5’ 10” height. Fig. 8-7 Case study #1 - Illustration and description of step 2 144 8.2.3 Identify the back up structure (Fig. 8-8) Vertical rods Truss rods Strut pipe Horizontal rods Diagonal rods (a) Section of primary back up structure (Drawn based on ASI drawings) (b) Section of secondary back up structure (Drawn based on ASI drawings) Primary structure – Vertical curved tension rods are used as the back up structure; Vertical straight rods are used additionally; Horizontal strut pipes are compression members Secondary structure – Horizontal bracing rods are used to strengthen the structure; Horizontal straight rods are used additionally Material – stainless steel rods; steel pipe Fig. 8-8 Case study #1 - Illustration and description of step 3 8.2.4 Make a checklist of all elements based on four categories (Fig. 8-9) Category Elements Two horizontal beams (like roof and ground) Top beam Bottom beam Category 1 – infrastructure Steel beam: TS 16×20 Steel grid: TS 16×14 Steel beam: TS 18×14 Steel rid: W 14×? Glass panels Glass fittings Back up structure elements Category 2 – Glass wall elements Double glazing, green-tinted, low- E coated Four way spider Strut pipe Truss rod Vertical rod Bracing rod Horizontal rod Category 3 – Elements for openings N/A Category 4 - Additional devices N/A Fig. 8-9 Case study #1 - Illustration and description of step 4 (ASI, summarized) 145 8.2.5 Define the position, shape and size of each element (Fig. 8-10, Fig. 8-11) Cable span L = 35' D=4'-6" 7'-2" 5'-11" Device (spider) 1/2" O Truss rod 2 3/8" O Strut pipe 3/8" O Vertical rod 1/4" O Horizontal rods 1/4" O Diagonal rods (bracing rods) Section of primary back up structure Plan of secondary back up structure 3/8" 2 3/8" 1/2" 1/2" Glass and fittings (by W&W) Size is determined by available products Struts and rods (by ASI) Size is determined by calculation and experience (ASI, modified) Identify the size of the given infrastructure The size of glass panels is defined by architects and/or glass manufacturers. The size of glass fittings is determined by manufacturers and/or in consultation with architects. The size of strut pipe and rod are determined through calculation and experience. Fig. 8-10 Case study #1 - Illustration and description of step 5 Example of structural calculation The following (Fig. 8-11) gives out an example of how to determine the size of the key elements including strut pipe, truss rod, vertical rod, horizontal rod, and diagonal rod, through calculation. 146 147 The sizes ASI used for these key elements are as the following: Strut pipe: 2 3/8” Ф (Diameter) Truss rod: three different sizes were used: Typical truss rod 1/2” Truss rod at corner: 3/4” Truss rod next to gate: 5/8” Vertical rod: 3/8” Horizontal rod and diagonal rod: 1/4” (this number is estimated from the DWG drawing by ASI) The calculation in the following will show how ASI determined these sizes. The size of truss rod: We need to consider the following load: Gravity load – 10psf Gravity load includes dead load and live load. In this case, we only consider the dead load because there is no live load. Gravity load is critical for seismic load. The bigger the gravity load is, the higher the seismic load. Since glass wall is lightweight structure, in most cases, the seismic load can be ignored. Seismic load – 2 psf V=CsW Cs: 20% W: 10psf V = 20%×10psf = 2psf Wind load – 30 psf for typical locations; 45psf for corners Since the seismic load (2psf) is much smaller than the wind load (30psf), consider the wind load only. Thermal load – Temperature range: ±75 o F Thermal stress f t = α ∆t E f t – Thermal stress α – Coefficient of thermal expansion ∆t – Temperature range E – Elastic modulus In this case, stainless steel rod is the bearing structure, so we need to consider the thermal stress of rod. The Coefficient of Thermal Expansion ( α) of steel is 6.5 × 10 -6 o F. The Elastic Modulus of steel is 29 × 10 6 psi. The temperature range is 75 o F. Therefore, the thermal stress of rod is: f t = α ∆t E = 6.5 × 10 -6 o F × 75 o F × 29 × 10 6 psi = 14137 psi ≈ 14 ksi Tension of truss rod (the curved rods are also called truss rods): Truss rod space: 5’ Allowable truss rod load: 10,000 LBS Allowable rod stress: Fa = 50 ksi (high stress steel) Wind load: 30 psf Truss rod length (L): 35’ Truss rod depth (D): 4.5’ Tributary area: 5’ Fig. 8-11, Continued on next page 148 Tributary load on each truss rod (uniform load): W = 30 psf × 5’ = 150 plf Global moment: M = WL 2 /8 = 150 plf × (35’) 2 / 8 = 22969 lbf Horizontal reaction: H = WL/2 = 150 plf × 35’ / 2 = 2625 # Vertical reaction: V = M/D = 22969 lbf / 4.5’ = 5104 # Tension: T = (V 2 + H 2 ) ½ = (2625 2 + 5104 2 ) ½ = 5739 # Metallic cross section required: Am = T/Fa = 5739 / 50 ksi = 0.115 in 2 Gross cross section (70% metallic) Ag = Am/0.70 = 0.115 / 0.70 = 0.164 in 2 Rod diameter Ф = 2(Ag/ π) ½ = 2 (0.164 / 3.14) ½ = 0.456 in Use Ф = ½ inch, therefore the cross area is: A = π ( Ф/2) 2 = 3.14 × (0.5/2) 2 = 0.196 in 2 Check if the total maximum stress of rod is equal or less than the allowable stress: Ultimate stress of rod: US = T/A = 5739 / 0.196 = 29281 ≈ 30 ksi Pre-stress of rod: PS = ½ US = 15 ksi Thermal stress is 14 ksi In winter, rod shrinks, causing bigger tension Stress is 15ksi + 14kis = 29 ksi In summer, rod expands, causing smaller tension, Stress is 15ksi – 14ksi = 1ksi > 0, ok! Total maximum stress of rod: f = ½ US + PS + TS = 15ksi + 15ksi + 14ksi = 44ksi < 50 ksi, ok! Size of strut pipe: Wind load: 30 psf Strut length: 5’ Tributary area: 5’ × 5.8’ = 29 f 2 Tributary load on each strut: W = 30 psf × 29 f 2 = 870 #, check <Manual of Steel Construction> Fig. 8-11 Case study #1 - Illustration and description of step 5 - Example of structural calculations (Instructed by G.G. Schierle, 2005) 8.2.6 Define all connections based on eight categories (Fig. 8-12) Glass + Spider Strut + Rod Spider + Strut Rod + Infrastructrue Glass + Infrastructure Glass + Glass (ASI, modified) Category 1– Connections within glass wall ¾ Glass + Glass, Glass + Spider, Spider + Strut, Strut + Rod Category 2 – Connections within openings (Does not apply in this case) Category 3 – Connections within additional devices (Does not apply in this case) Category 4 – Connections between glass wall and additional devices (Does not apply in this case) Category 5 – Connections between glass wall and openings (Does not apply in this case) Category 6 – Connections between openings and additional devices (Does not apply in this case) Category 7 – Connections between glass wall and infrastructure ¾ Glass + Ground, Glass + Roof, Rod + Ground, Rod + Roof Category 8 – Connections between openings and infrastructure (Does not apply in this case) Category 9 – Connections between additional devices and infrastructure (Does not apply) Fig. 8-12 Case study #1 - Illustration and description of step 6 8.2.7 Determine the material and method for each connector (Fig. 8-13) From step 6, we can see that there are eight connections. They are: Glass + Glass, Glass + Spider, Spider + Strut, Strut + Rod, Glass + Ground, Glass + Roof, Rod + Ground, and Rod + Roof. 149 Silicone sealant & backer rod (Back rod can be removed after curing) 10-16-6 or 12-16-6 DG Armourplate Planar 10 or 12 + 4 mm Pilkington Planar Typicall detail of double glazed joint TM Glass + Glass Connected by structural silicone. The left image shows the typical detail of double glazing insulating glass joint in Pilkington Planar system. (http://sweets.construction.com/) Dimensions of a typical four way spider (unit in millimeters) (http://www.wwglass.com/) Glass Spider Threaded bolt Spider section (ASI, modified) Glass + Spider Bolted together. Using standard Pilkington Planar System, one can get perfect smooth exterior surface. The connection detail of Glass + Spider is usually from the manufacturer who provides the spider. Fig. 8-13, Continued on next page 150 Strut pipe Weldings Bolt hole Glass Steel spider Glass fixing (Pilkington Planer) Threaded bolt Solid bar Spider + Strut Glass panes are fixed to the four- way spider by standard Pilkington Planer system, which creates a flush exterior surface. The spider is connected to the strut pipe by a solid bar. The spider is bolted into the solid bar, and the solid bar is welded to the strut pipe. The threaded bolt was provided by the glass manufacturer who provided glass and fixings, but the size of the bolt was dependent on the diameter of the bolt hole, which was defined by ASI. The size of the bolt (5/8” diameter, 2”deep) was defined to assure structural safety. (ASI, modified) Plate Rod Strut Bolt Weld Strut + Rod Connected by a steel plate; the plate is welded to the strut; the rod is bolted to the plate. (ASI, modified) (W&W) GLASS (BY W&W) ANGLE POCKET INFRASTRUCTURE (ROOF) (ROOF, STEEL BEAM) Glass + Roof A steel pocket holds the glass pane; the pocket is bolted to a steel angle; the angle then is welded to the infrastructure. Please notice that, the pocket should have enough height so that the glass can move vertically freely under any vertical load (such as seismic), or thermal expansion. (ASI, modified) Fig. 8-13, Continued on next page 151 ANGLE POCKET GLASS (GROUND, STEEL BEAM) INFRASTRUCTURE (ROOF) Glass + Ground See the joint of “Glass + Roof”. (ASI, modified) ANCHOR BY BERLIN PL 2 1/2x4x20 CEN. TO CEN. HOLE 1/4" VERT. SLOTTED A36 (ASI) PL. 1/2 INFRASTRUCTURE GROUND (STEEL BEAM) PRESTRESSING HOLE FOR HOLE FOR TRUSS ROD Rod + Ground (steel tube) Connected by a plate and an anchor plate; the anchor plate is welded to the steel tube; the plate is welded to the anchor plate; the rods are bolted to the plate (ASI, modified) PL. 1/2 ANCHOR (ASI) (ASI) TYP. S.S. ROD 3 1/2" 6" MIN. (ROOF, STEEL BEAM) INFRASTRUCTURE (ROOF) Rod + Roof (steel tube) Connected by a plate and an anchor plate; the anchor plate is welded to the steel tube; the plate is welded to the anchor plate; the rods are bolted to the plate (ASI, modified) Fig. 8-13 Case study #1 - Illustration and description of step 7 152 8.2.8 Define any other requirements (Fig. 8-14) A gusset plate with an extra hole for pre-stressing Gusset plate (connector) Force applied during installaion Hole for pre-stressing This step is to define special requirement for manufacture, assembly and installation, as well as any other requirements that are not covered in other steps. For example, a hole is designed in the gusset plate for pre-stressing purpose. Because the steel rods are tension members, prestress is needed to avoid compressive stress under any load (compressive stress would buckle the rods and cause instability). (ASI, modified) Fig. 8-14 Case study #1 - Illustration and description of Step 8 8.2.9 Design each connection (Fig. 8-15, Fig. 8-16, Fig. 8-17, Fig. 8-18, Fig. 8-19) A typical joint type (cable + strut) shown in Fig. 8-14 is used to illustrate the detailing process of a specific connection. Please notice that this joint is eccentric. However, when starting to detail, concentric connection should always be considered first (Fig. 8-15). The reason is that eccentric connection may cause bending stress in the joint. One should make concentric connections at first, and adjust it to eccentric connection only if needed. If eccentric connections are used, designers must check the resulting stress to ensure structural safety. The illustration of the steps will start with a concentric connection and then introduce the reasons for eccentric connection (Fig. 8-16 & Fig. 8-17). Then a detailing process starting with an eccentric connection is introduced (Fig. 8-18 & Fig. 8-19). 153 Rod Socket (Coupler) Gusset plate (Connector) Strut (a) Joint of cable + strut (ASI, modified) (b) Eccentric connection (c) Concentric connection Fig. 8-15 Case study #1 - Illustration and description of Step 9 - Eccentric and concentric conditions of the joint Detailing a typical joint type (rod + strut) – starting from a concentric connection The process to detail the joint starting from a concentric connection is: 1). Step 1 – Draw concentric center line connections 2). Step 2 – Draw connector size as dotted line 3). Step 3 – Define tolerance between connectors 4). Step 4 – Explore connector options 5). Step 5 – Design connector 6). Step 6 – Make adjustment (reduce connector and check eccentric stress). These steps are further explained in the flow chart shown in Fig. 8-16. Each image in Fig. 8-16 is described in Fig. 8-17 (Image numbers of Fig. 8-16 correspond to respective numbers in Fig. 8-17). 154 4 4.1 6 6.1 5 4.1.1 Alternate connector options 3 2 4.2 4.3 1 4.2.1 4.2.2 4.3.1 4.3.2 Fig. 8-16 Case study #1 - Illustration and description of Step 9 - Flow chart of the detailing process starting from concentric connection (Drawn based on ASI drawings) 155 156 Image 1 Principles applied: Structural behavior (concentric connection) Always consider a concentric connection at first and adjust it to eccentric connection only if needed. Concentric connection requires that the center lines for all connected elements join at one point. Five center lines are drawn, four rods and one strut. Image 2 Principles applied: Manufacture & structure (size of available cable fittings A 1 ) Structure (size of strut A 2 ) Draw the size for the elements to be connected by dotted line. Here, the size of the strut (A 2 ) and the size of sockets (A 1 ) are needed. (Sockets connect strands or rods to other elements). A 1 is provided by the strand manufacturer. A 2 is defined by structural design, based on stress, material strength, and structural length of the strut (see image below). A 2 may be also defined by needs to make connections. In this case A 1 ≈ 1 1/2”, A 2 = 2 3/8”. Image 3 Principles applied: Tolerance (tolerance between adjacent sockets) Draw the tolerance needed between adjacent elements. Here, tolerances needed for the top rods (B 1 ), and the bottom rods (B 2 ) are B 1 = B 2 = 0.5” (reference). After drawing B 1 and BB 2 , one can see that the distances between the rods and the strut (B 3 and B 4 ), are obviously bigger than 0.5”, which is ok for the necessary tolerance. Fig. 8-17, Continued on next page 157 Image 4 Principles applied: Manufacture (socket dimensions) Structure (minimum socket size C 2 ) Draw sockets connecting rods to strut. Firstly, get C 1 and C 2 from socket manufacturer (see image below) based on rod size. In this case C 1 = 1 1/4" , C 2 ≈25/32”. Image 4.1 Principles applied: Tolerance (between socket and gusset plate ) Aesthetics (connector shape) An egg-shaped gusset plate (connector) is designed to start. Note, tolerance (C 3 ) is needed between the socket and gusset plate (see image above). C 3 = 1/2" (reference). Considering the tolerance, the maximum gusset plate is defined. Image 4.1.1 Principles applied: Structure (pre-stressing to keep strands always in tension; minimum C 5 to assure enough strength to resist shear force when applying prestress) Installation (a hole to pull down the connector for pre- stressing; diameter of the hole; enough space C 4 for convenience of installation ) A hole is designed to apply pre-stress in strands. Enough space (C 4 ) is needed for installation purpose. The hole diameter (Ø 1 ) and C 5 are defined based on the prestress force applied. The prestress force is defined by structural calculations. Image 4.2 – 4.3.2 are a few examples of connector alternatives. Fig. 8-17, Continued on next page Image 5 Principles applied: Aesthetics (smooth curved edge of connector) Installation (larger space around the hole) Structure (sufficient weld length) For aesthetical reasons, the connector edge is curved. The strut ending (D 1 ) is based on aesthetics and weld length required. The minimum strut ending D 1 = 0”. (See images below). At this stage, the joint design is almost complete. However, there are still two items that could be improved: the connector looks a bit too bulky and the space around the pre- stressing hole looks too small. Image 6 Principles applied: Aesthetics (reducing connector size) Installation (increase space around prestress hole) Structure (check eccentric stress) An eccentric connection can solve these problems (see dotted lines). By separating the center lines, the strand sockets may be placed closer to the strut to reduce the joint; and the space around the prestress hole can be increased for easier installation. Image 6.1 Principles applied: Aesthetics (connector shape) Structure (allowing structural movement) An eccentric connection is designed to reduce the gusset plate and joint detail. However the eccentric joint may cause secondary stress in the strut. Thus, the strut must be designed to resist the eccentric stress in addition to any axial stress. Note, the concave shape of the gusset plate is partly because of aesthetics and partly because of functions (allowing the rods to rotate under structural movement). Fig. 8-17, Continued on next page 158 Fig. 8-17 Case study #1 - Illustration and description of Step 9 – Illustration of each image shown in Fig. 8-16 (Drawn based on ASI drawings) Detailing a typical joint type (rod + strut) – starting from an eccentric connection Fig. 8-16 and Fig. 8-17 illustrate why the concentric connection is adjusted to an eccentric connection due to the size of fittings. Fig. 8-18 shows how the detailing process works for an eccentric connection. Each image shown in Fig. 8-18 is further illustrated in Fig. 8-19. 159 Cable #1 STEP 5 STEP 6 6 5 C1 C3 C1 D2 D2 STEP 3 3 STEP 4 B4 B2 B3 B1 4 3.1.1 3.1 C2 D2 D1 A1 A2 Cable #4 Cable #3 Strut Cable #2 2 1 STEP 1 STEP 2 3.2.1 3.2 3.3.1 3.3 C2 4.1 Hole for Pre-stressing C3 3.2.3 3.2.2 3.3.3 3.3.2 C3 1 Alternate connector options 3.4.1 3.4 3.4.3 3.4.2 1 C3 Step 1 – Draw eccentric center line connections Step 2 – Draw connector size as dotted line Step 3 – Define tolerance between connectors Step 4 – Explore connector options Step 5 – Design connector Step 6 – Make adjustment (the concave shape of the gusset plate to allow structural movement) Fig. 8-18 Case study #1 - Illustration and description of Step 9 – Flow chart of the detailing process starting from an eccentric connection (Drawn based on ASI drawings) 160 Image 1 Principles applied: Structural behavior (concentric connection) Aesthetics (eccentric connection) As explained in Fig. 8-16 and Fig. 8-17, the concentric connection needs to be changed to an eccentric connection to fit the fiitings. The left image is the result of an eccentric connection, showing the five center lines of four rods and one strut. Because the eccentric joint may cause secondary stress in the strut, the strut must be designed to resist the eccentric stress in addition to axial stress. However, the principal of concentric connection is still favored: Rod #1 & Rod #3 are connected to one point; as are Rod #2 & Rod #4. Image 2 Principles applied: Manufacture & structure (size of available cable fittings A 1 ) Structure (size of strut A 2 ) Draw the size for the elements to be connected by dotted line. Here, the size of the strut (A 2 ) and the size of sockets (A 1 ) are needed. (Sockets connect strands or rods to other elements). A 1 is provided by the strand manufacturer. A 2 is defined by structural design, based on stress, material strength, and structural length of the strut (see Image 2 in Fig. 8- 17). A 2 may be also defined by needs to make connections. In this case A 1 ≈ 1 1/2”, A 2 = 2 3/8”. Image 3 Principles applied: Tolerance (tolerance between adjacent sockets) Draw the tolerance needed between adjacent elements. The distance between the top two rods and the distance between the bottom two rods are bigger than 0.5”, which is needed for necessary tolerance. Here, tolerances needed are the distances between the rods and the strut, which are B 1 = B 2 = B 3 = BB 4 = 0.5” (reference). Fig. 8-19, Continued on next page 161 Image 1 Principles applied: Structural behavior (concentric connection) Aesthetics (eccentric connection) As explained in Fig. 8-16 and Fig. 8-17, the concentric connection needs to be changed to an eccentric connection to fit the fiitings. The left image is the result of an eccentric connection, showing the five center lines of four rods and one strut. Because the eccentric joint may cause secondary stress in the strut, the strut must be designed to resist the eccentric stress in addition to axial stress. However, the principal of concentric connection is still favored: Rod #1 & Rod #3 are connected to one point; as are Rod #2 & Rod #4. Image 2 Principles applied: Manufacture & structure (size of available cable fittings A 1 ) Structure (size of strut A 2 ) Draw the size for the elements to be connected by dotted line. Here, the size of the strut (A 2 ) and the size of sockets (A 1 ) are needed. (Sockets connect strands or rods to other elements). A 1 is provided by the strand manufacturer. A 2 is defined by structural design, based on stress, material strength, and structural length of the strut (see Image 2 in Fig. 8- 17). A 2 may be also defined by needs to make connections. In this case A 1 ≈ 1 1/2”, A 2 = 2 3/8”. Image 3 Principles applied: Tolerance (tolerance between adjacent sockets) Draw the tolerance needed between adjacent elements. The distance between the top two rods and the distance between the bottom two rods are bigger than 0.5”, which is needed for necessary tolerance. Here, tolerances needed are the distances between the rods and the strut, which are B 1 = B 2 = B 3 = BB 4 = 0.5” (reference). Fig. 8-19, Continued on next page 162 Image 3.1 Principles applied: Structure and aesthetics (check D 1 and D 2 ) After setting the BB 1 = B 2 = B 3 = B 4 B = 0.5” as shown in Image 3, it turns out that the distance between the restraining bolts in the top two rods and the strut (D 1 ) is smaller than that of the bottom two rods and the strut (D 2 ). (To determine D 1 and D 2 , see Image 4. This is an example that the detailing process as shown in these images is not fixed. A designer should be able to adjust the process due to different circumstances.) Image 3.1.1 Principles applied: Structure and aesthetics (equal D 1 to D 2 ) To make the joint structurally balanced, D 1 and D 2 should be equal. Because D 1 is smaller than D 2 , D 1 is adjusted to be equal to D 2 to ensure minimum clearance (tolerance) mentioned in Image 3. Another benefit to equal D 1 to D 2 is better aesthets. The connector looks more balanced if D 1 equals to D 2 . Image 4 Principles applied: Manufacture (socket dimensions) Structure (minimum socket size C 2 ) Draw sockets connecting rods to strut. Firstly, get C 1 and C 2 from socket manufacturer based on rod size (see Image 4 in Fig. 8-17). In this case C 1 = 1 1/4" , C 2 ≈25/32”. Fig. 8-19, Continued on next page 163 Image 4.1 Principles applied: Structure (pre-stressing to keep strands always in tension) Installation (a hole to pull down the connector for pre-stressing; diameter of the hole; enough space around the hole for convenience of installation ) A hole is designed to apply pre-stress in strands. Enough space around the hole is needed for installation purpose. The hole diameter (Ø 1 ) and C 3 are defined based on the pre-stress force applied. The pre-stress force is defined by structural calculations (typically half the ultimate stress). Image 3.2 – 3.4.3 are gusset plate alternates. Image 5 Principles applied: Aesthetics (smooth curved edge of connector) For aesthetical reasons, the connector edge is curved. The strut ending (D 1 ) is based on aesthetics and weld length required. The minimum strut ending D 1 = 0”. (See Image 5 in Fig. 8-17). At this stage, the joint design is almost complete. 4.1 Hole for Pre-stressing C3 5 6 Image 6 Principles applied: Aesthetics (connector shape) Structure (allowing structural movement) The concave shape of the gusset plate is partly because of aesthetics and partly because of functions (allowing the rods to rotate under structural movement). Fig. 8-19, Continued on next page 164 Fig. 8-19, Continued on next page 165 Fig. 8-19 Case study #1 - Illustration and description of Step 9 – Illustration of each image shown in Fig. 8-18 (Drawn based on ASI drawings) 166 Chapter IX Case study two – McCarren International Airport, Las Vegas 9.1 Introduction 9.1.1 Project information Climate Las Vegas is located in the Mojave Desert, with plenty of sunshine all year round. The latitude is 36.176 o N, and the longitude is 115.137 o W. Summers are hot and dry, with an average maximum temperature 106 o F in July. Winters are mild with wind and cold nights, and the diurnal temperature swing is up to 20 o F. The average minimum temperature in winter is 33 o F in Jan. There is more rain in winter than in summer. (http://www.wordtravels.com/Cities/Nevada/Las+Vegas/Climate) See Fig. 9-1 for (a) average temperature, (b) humidity, (c) sunshine, (d) precipitation, and (e) wind speed around the year in Las Vegas. (a) Average temperature (b) Humidity Fig. 9-1, Continued on next page 167 (c) Sunshine (d) Precipitation (e) Wind speed (mph) Fig. 9-1 Las Vegas climate data (http://www.city-data.com/city/Las-Vegas-Nevada.html) 168 169 General project information (Table 9-1) Location Las Vegas, Nevada Time 1994-1996 Architects Tate & Snyder Architects Consultant architect Leo Daly Lighting consultant Lam Partners Inc. Client Nevada’s Clark County Aviation Department General contractor Sletten Companies of Nevada Main contractors Perini/Henederson Construction Manager Bechtel Infrastructure Inc. Glass curtain wall Pilkington Planar Total cost $197 million Total area 197,000 SQFT South glass façade size 100 feet in length and 60 feet in height North glass façade size 50 feet in length and 50 feet in height Table 9-1. General project information of case study #2 (ASI) Brief introduction The new satellite terminal D is the expansion of the existing facilities at McCarran Airport. Combined with the existing terminals A, B and C, the airport has a total of 104 boarding gates, recording 35 million passengers in 2002. The new terminal consumed 11400 cubit yards of concrete, and 2135 tons of steel. (Illia 2003) The terminal features two sloped south-north orientated glass walls which are supported by custom tubular steel trusses braced with stainless steel tension rods. This innovative design minimizes the steel structure profile, and therefore maximizes natural daylight and clear views to the outside (www.asidesign.com). In order to control heat gain and solar glare, designers integrated perforated metal sunscreens into the steel trusses, which minimizes direct summer sunlight while allowing direct winter sunlight. In this project, the glass panes were provided by Pilkington, and ASI provided the design and detailing of the glazing support systems. 9.1.2 Images The following images (Fig. 9-2) show the interior and exterior view of the glass façade, as well the glass fitting detail photos. (Binney 1999, p.130) (Binney 1999, p.133) (Tomei, L'ARCA, Oct 1998, p.53) (Binney 1999, p.134) Fig. 9-2 Exterior view of McCarren International Airport Fig 9-3 shows the interior photos and sections of the glass wall of the airport building. As shown in the photos, the sloped glass wall is supported by truss and tension rods, integrated with perforated metal sheet sunscreens. 170 (ASI) (ASI) (Binney 1999, p.134) (Anon 4 , L'ARCA, Oct 1998, p.54) Fig. 9-3 Interior view of the glass wall of McCarren International Airport 171 Fig. 9-4 is an example the detail design of a typical tension rod joint and glass fitting spider that are used in the glass wall back up structure. The tension rods are connected to the steel strut pipe with a round steel plate. This joint is selected to illustrate the detailing process of a typical joint in 9.2.9. Fig. 9-4 Enlarged photo of glass fitting detail and tension rod joint (ASI) 9.2 Detailing process for a typical section The south glass wall of the airport building (Fig 9-5) is selected to illustrate the detailing process of a typical glass wall section. See Fig 9-5 for plan, elevation and sections. The glass wall is supported by both truss (Fig 9-5 section 1) and tension cable (Fig 9-5 section 2). In tension cable section, Joint A (concentric connection) and Joint B (eccentric connection) are selected to illustrate the detailing process of typical tension rod connection to steel strut pipe. The detailing process is illustrated in Fig. 9.2.1 to 9.2.9. 172 SOUTH WALL ANCHOR PLAN FACE OF GLASS SOUTH WALL ELEVATION TRUSS -- FRAMING SECTION 1 CABLE BRACING -- FRAMING SECTION 2 JOINT B SHADING DEVICE 1 2 JOINT A SYMETRICAL BOTH SIDES (16 EQUAL SPACES) SAFETY ANCHOR LOOPS 5'-7 7 8 " 90'-7 13 16 " 4' 4' 55'-6" 4' 4' 4' 4' 4' 4' 4' 4' 4' 4' 3'-6" 4' Fig. 9-5 Plan, elevation and sections of south glass wall (ASI, modified) 173 9.2.1 Identify the building infrastructure (Fig. 9-6) Infrastructure (Tomei, L'ARCA, Oct 1998, p.53) (ASI, modified) Infrastructure type – roof and floor (horizontal) Infrastructure material – steel and reinforced concrete(stiff) In this example, the infrastructure consists of horizontal roof and floor beams (see the wide lines in the image left above). This means that the back up structure will be vertical structure. The material of the roof beam is steel, and material of floor is reinforced concrete. Fig. 9-6 Case study #2 - Illustration and description of step 1 9.2.2 Determine modular size (Fig. 9-7) (ASI) 4’ vertical modular size based on glass pane size 5’8” horizontal modular size based on half of glass pane width In this project, the modular size of the glass wall was 11’ 4” wide and 4’ high (defined by architectural design). Since the width of the glass pane is too big (more than 10 feet), additional support is needed. In this case, a secondary vertical rob truss structure is used in the middle of the glass panes to provide sufficient support to the glass wall. Fig. 9-7 Case study #2 - Illustration and description of step 2 174 9.2.3 Identify the back up structure (Fig. 9-8) (a) Typical truss structure (b) Custom designed truss structure (c) Typical tension rod structure (d) Custom designed tension rod structure (b & d from ASI, modified) Primary structure – Vertical compression trusses and vertical tension rods are used as the back up structure Secondary structure – Horizontal bracing struts are used to strengthen the structure Material – stainless steel rod; stainless steel pipe Fig. 9-8 Case study #2 - Illustration and description of step 3 9.2.4 Make a checklist of all elements based on four categories (Fig. 9-9) Category Elements Roof beam Floor beam Infrastructure Steel Reinforced concrete Glass panels Glass fittings Back up structure elements Two way and four way spiders Glass wall elements 1.339” thick double-pane insulated glass Tubular steel truss and stainless steel tension rods Elements for openings N/A Additional devices Perforated metal sheet sunscreens Fig. 9-9 Case study #2 - Illustration and description of step 4 (Summarized based on ASI drawings) 175 176 9.2.5 Define the position, shape and size of each element (Table 9-2, Fig. 9-10) Find out the thickness and material of glass panes, which are determined by architects and available products from manufacture. The hot and dry climate of Las Vegas also affects the selection of glass. The shape of steel truss is determined by architects for aesthetical reasons. Find out the dimension and material of infrastructure (steel roof beam and reinforced concrete floor), which are determined by architects and structural engineers. The sizes of stainless steel tubes and stainless steel bracing rods in truss structure (Fig. 9-10, left) are determined by structural calculation or experience. The size of stainless steel strut in tension rod structure (Fig. 9-10, right) is the same as the steel tubes used in the truss structure for simplify the design and installation process. Simple structural calculation or past experience is needed to verify the safety of the strut. The size of stainless steel rod is in board of the dimension of the rod used in truss for the same reasons. The shape, material and size of metal sunscreens are determined by architects, considering both aesthetical reasons and thermal performance of the building. The design loads are (ASI data): PSF (pounds per square foot) for gravity dead load of glass wall 20 PSF or 300lbs for gravity live load of sunshades (concentrated load) Gravity loading 500 lbs for gravity live load of safety loop 75 MPH (miles per hour) for lateral wind load (Exposure C and 55’6” glass wall height) Lateral loading Seismic load (zone 2B and importance factor 1.25) – Las Vegas is a city with risk of earthquake, so it is necessary to consider seismic load Thermal loading Temperature range ±70°F Prestress should be about half the stress under full load The total tension rod force is limited by the support structure Pre-stressing of tension rods 3000 PSI (pound per square inch) concrete compressive strength (the rod tension is limited by the concrete compressive strength of 3000 PSI) Other important issues According to the notes of ASI drawing sheet, “Head details have been designed based on the assumptions that the total dead weight deflection of the roof has occurred prior to installation of the trusses.” This means that when designing the connection joint of glass wall and roof beam, the vertical drift of roof beam caused by dead and live load should be considered. Table 9-2 Case study #2 - Illustration and description of step 5 (1) Steel tube TS8? (by other) 1.339" glass (by W&W) Pilkington Planar flush surface glass fitting 1/2" stainless steel rod 3 1/2" stainless steel tube Reinforce concrete floor Perforated and solid sheet metal sunshade devide 1.339" glass (by W&W) Pilkington Planar flush surface glass fitting 3 1/2" stainless steel strut 1/2" stainless steel rod Perforated and solid sheet metal sunshade devide (ASI, modified) Fig. 9-10 Case study #2 - Illustration and description of step 5 (2) 177 9.2.6 Define all Connections based on nine categories (Fig. 9-11) 8 7 11 4 10 13 6 6 1 4 2 10 11 5 3 8 12 13 12 9 Tension rod structure + sunshade device Tension rod structure + floor beam Rod+ strut Glass + strut 12 13 11 10 Tension rod structure + roof beam Truss structure + sunshade device Truss structure + floor beam Truss structure + roof beam Glass + floor beam Glass + roof beam Glass + glass 3 5 4 2 1 8 9 Truss tube + rod Glass + truss tube 7 6 (ASI, modified) Category 1– Connections within glass wall ¾ Glass + glass, glass + truss tube, glass + strut, truss tube + rod, rod + strut Category 2 – Connections within openings (Does not apply in this case) Category 3 – Connections within additional devices ¾ Perforated sheet metal + stiffener, solid sheet metal + stiffener Category 4 – Connections between glass wall and additional devices ¾ Truss structure + sunshade device, tension rod structure + sunshade device Category 5 – Connections between glass wall and openings (Does not apply in this case) Category 6 – Connections between openings and additional devices (Does not apply in this case) Category 7 – Connections between glass wall and infrastructure ¾ Glass wall+ roof beam, glass wall+ floor beam, truss structure + roof beam, truss structure + floor beam, tension rod structure + roof beam, tension rod structure + floor beam Category 8 – Connections between openings and infrastructure (Does not apply in this case) Category 9 – Connections between additional devices and infrastructure (Does not apply in this case) Fig. 9-11 Case study #2 - Illustration and description of step 6 178 9.2.7 Determine the material and method for each connector (Fig. 9-12) The material and method for the connectors are illustrated in Fig. 9-12: Glass + Glass (Fig. 9-12, a); Glass + Truss tube & Glass + Strut (Fig. 9-12, b); Truss tube + Tension rod & Tension rod + Concrete floor (Fig. 9-12, c); Truss structure + Sunshade device (Fig. 9-12, d) Glass + Roof beam & Truss + Roof beam (Fig. 9-12, e), and Glass + Concrete floor & Truss + Concrete floor (Fig. 9-12, f). (a) Glass + Glass (ASI) (http://sweets.construction.com/) The glass joint material is structural silicone sealant. The right image below shows the typical detail of double glazing insulating glass joint. (a) The material and method for connector Glass + Glass Fig. 9-12, Continued on next page 179 180 (b) Glass + Truss tube; Glass + Strut; Strut + Rod (ASI, modified) (ASI, modified) 3/8" steel plate Horizontal strut Pilkington Planar flush surface fitting D 6 = 6" D 5 = 1 3 4 " D 4 = 3 1 2 " D 3 = 1 1 4 " D 2 = 2 3/4" D 1 = 5" Glass Spider Spider steel plate Rod 5/8" by 1" slotted hole 1/2" steel plate Structual silicone Glass Coupler Vertlcal stailess steel tube (1) Glass fitting side elevation (truss) four or two way spider (ASI, modified) (2) Glass fitting side elevation (tension rod) four way or two way spider (ASI, modified) Using a standard Pilkington Planar System, provides smooth exterior surface. The connection detail of Glass + Spider is from the manufacturer who provides the spider. Image (1) shows the side elevation of a typical connection of glass and truss tube in truss structure. Image (2) is the side elevation of a connection of glass and strut in tension rod structure. They can be either four way spiders or two way spiders. Important dimensions are shown in image 1. These dimensions are determined by structural calculation, manufacturer’s products, and aesthetics. Fig. 9-12, Continued on next page Horizontal strut Glass Glass 1/2" Steel plate Vertlcal stailess steel tube 3/8" steel plate Spider Steel plate Spider 5/8" by 1" slotted hole (3) Glass fitting plan (truss) four way spider (ASI, modified) (4) Glass fitting plan (tension rod) four way spider (ASI, modified) 5/8" by 1" slotted hole Spider 3/8" steel plate 1/2" Steel plate Glass Horizontal strut Spider Steel plate Vertlcal stailess steel tube Glass (5) Glass fitting plan (truss) two way spider (ASI, modified) (6) Glass fitting plan (tension rod) two way spider (ASI, modified) Image (3) and (5) show the plan s of a typical connection of glass and truss tube in truss structure. Image (4) and (6) are the plans showing the connection of glass and strut in tension rod structure. Image (3) and (4) are for four way spider; image (5) and (6) are for two way spider. Four way spiders are used to connect four pieces of glass panel, and two way spiders are used to connect two glass panes. (b) The material and method for connector Glass + Truss tube & Glass + Strut Fig. 9-12, Continued on next page 181 182 (c) Truss tube + Tension rod; Tension rod +Concrete floor 1/2" steel plate Rod #1 Rod #2 Stainless steel tube Coupler Eccentric connection (left) and concentric connection (right) of a typical rod joint in truss structure (ASI, modified) The tension rod is connected to the truss tubes by a ½” thick connector – stainless steel plate. The coupler of the tension rod is bolted to the steel plate, and the steel plate is welded to the truss tubes. In the left image above, the joint is an eccentric connection. Although a designer should always start with a concentric connection, a concentric solution in this particular joint will result in over-sized steel plate connector (the right image above), and therefore an eccentric connection is used instead. When eccentric connection is used, the designer needs to check with structure engineer the eccentric stress to make sure structural safety. Fig. 9-12, Continued on next page Rod #3 Rod #4 3/8" plate Eccentric connection (left) and concentric connection (right) of a typical cable bracing anchor (ASI, modified) The three images above show how the tension rods are connected to reinforced concrete floor by a 3/8” thick stainless steel plate. Again, eccentric connection is used in order to get smaller steel plate connector. (c) The material and method for connector Truss tube + Tension rod & Tension rod + Concrete floor Fig. 9-12, Continued on next page 183 184 (d) Truss structure + Sunshade device Glass Perforated sheet metal Seam Solid sheet metal 3/4" diameter bolt assembly 1/2" steel plate Steel tube Spider Steel tube Sunshade device section (ASI, modified) Fig. 9-12, Continued on next page Glass Spider Perforated sheet metal Solid sheet metal Stiffener Stainless steel tube square TS3 1/2? 1/2? /8 Seam line Sunshade device plan (ASI, modified) The sunshade device is made of perforated and solid sheet metal. The sheet metal covers the truss tubes all around so that the sunscreens look perfectly integrated with the truss structure. The depth and shape of sunscreens is determined by architects, considering both aesthetics and sun screening. (d) The material and method for connector Truss structure + Sunshade device Fig. 9-12, Continued on next page 185 186 (e) Glass + Roof beam; Truss + Roof beam Steel glass connector (by W&W) Stainless steel head self drilling screws Steel tube TS8? (by other) Field trim to fit Steel tube TS5? ? /8 3/8" steel plate (double) with hole for pin 1/2" steel plate with slotted hole for pin Steel tube Rod Channel Shim space Silicone setting block Structural silicone 1.339" glass (by W&W) Field weld tube to truss D 1 = 5" D 2 = 4" D 4 = 3" D 5 = 5 1 4 " R1 3 4 " Varies 1/2" steel plate Top of truss side elevation (ASI, modified) Fig. 9-12, Continued on next page Field trim to fit Steel tube TS5??/8 1/2" steel plate Steel tube 4" 1" diameter stainless steel pin 1/2" steel plate with slotted hole for pin 3/8" steel plate (double) with hole for pin Steel tube TS8? (by other) Top of truss front elevation (ASI, modified) A steel pocket holds the glass pane; the pocket is bolted to a steel angle; the angle is welded to the infrastructure. Please notice that, the pocket should have enough depth so that the glass can move vertically freely under any load (such as seismic, wind, or thermal expansion). The truss is connected to the infrastructure by three steel plates (two on top and one on bottom) that are bolted together like a Sandwich. The bottom plate has a slotted hole to allow free vertical movement of truss. According to ASI, the detailing of these joints is based on assumption that the design dead load was already applied onto the roof, and therefore most roof beam deflection already occurred. (e) The material and method for connector Glass + Roof beam & Truss + Roof beam Fig. 9-12, Continued on next page 187 188 (f) Glass + Concrete floor; Truss + Concrete floor Channel Shim space Stainless steel head self drilling screws Structural silicone Silicone setting block 1.339" glass (by W&W) Steel tubes welded into one piece 1/2" steel plate 1/2" steel plate (double) 3/8" steel plate (double) Base plate 9? ? 5/8 Drypack (by others) (4) 3/4" diameter bolts with 5 3/4" long embedment stainless steel rods/nuts Reinforced concrete D 1 = 5 1 4 " D 2 = 2 1 2 " R1 1 4 " Side elevation of truss base (ASI, modified) Fig. 9-12, Continued on next page 1" diameter stainless steel pin 1/2" steel plate with slotted hole for pin 3/8" steel plate (double) with hole for pin 1/2" steel plate Base plate 9? ? 5/8 Drypack (by others) Reinforced concrete Steel tube (4) 3/4" diameter bolts with 5 3/4" long embedment stainless steel rods/nuts D 3 = 2" D 4 = 5 3 4 " D 5 = 6" D 6 = 9" Front elevation of truss base (ASI, modified) The glass is fixed to the concrete floor through a steel pocket. The truss tubes are welded to a ½” steel plate across the tube section, and the steel plate is welded to a perpendicular ½” thick steel plate. This half inch thick steel plate is bolted to two 3/8” thick steel plates like a Sandwich. These two 3/8” steel plates are welded to a 5/8” base plate, which is anchored to the reinforced concrete floor by four ¾” diameter bolts with long embedment stainless steel rods/nuts. The shim space used between the glass steel pocket and concrete, and the Drypack between the base plate and concrete, play the same roles here – to allow installation adjustments. Note that no slotted hole is used in the steel plate because the slotted hole is already used in the joint of truss and roof beam. One slotted hole in either roof joint or floor joint is enough to assure free movement of truss. (f) The material and method for connector Glass + Concrete floor & Truss + Concrete floor Fig. 9-12 Case study #2 - Illustration and description of step 7 189 9.2.8 Any other special requirements (Fig. 9-13) Three examples are discussed here: 1). A splice plate is used to connect two pieces of steel tubes with the same outside diameters but different thickness (Fig. 9-13, a) 2). A safety anchor loop is designed on the truss tubes to allow additional structural loads applied onto the glass wall (Fig. 9-13, b). 3). Two bracing rods in truss structure are eccentrically designed in vertical direction to allow one crossing over the other one (Fig. 9-13, c). Weld backing O.D. (outside diameter) 3 1/2" stainless steel tube with thickness 0.216" Welding Splice plate O.D. (outside diameter) 3 1/2" stainless steel tube with thickness 0.600" Thinner tubes Thicker tubes Truss elevation Splice (tube connector) detail The diagram above shows how to design the connection of two steel tubes with the same outside diameters but different thickness (different inside diameters). A splice plate is welded into the thinner tube, and the thicker tube is welded to the splice plate. (a) A splice plate to connect two pieces of steel tubes (ASI, modified) Fig. 9-13, Continued on next page 190 1/2" plate 5/8" by 1" slotted hole 1/2" steel plate 3/8" plate 5/8" O safety anchor loop Glass Glass fitting Stainless steel tube Side elevation of safety anchor loop Rear elevation of safety anchor loop The safety anchor loop is designed on the truss tubes to allow additional structural loads applied onto the glass wall (see the diagrams below). The 5/8” diameter safety anchor loop is welded to a 3/8” thick steel plate, which is also welded to the steel truss tube. (b) A safety anchor loop to allow additional structural loads (ASI, modified) Fig. 9-13, Continued on next page 191 Rod #1 Rod #2 Rod #1 Rod #2 A A Section A Rod #2 Rod #1 Rod #3 Rod #4 Rod #1A Rod #1B Rod #2B Rod #2A The diagrams above shows how to detail the connection of two rods with one rod crosses over the other one, which means the center lines of the two rods are not on the same plane. In this case, in vertical direction, the rods are eccentrically connected (see the bottom middle diagram), and therefore designers should check eccentric stress. Another way is to design a round steel plate to which all rods are connected (top right diagram), making the centerlines of all rods in the same plane, and therefore creating a perfect concentric connection. But the downside of this solution is that the two crossing rods become four rods, increasing the number of joints, and therefore increasing cost. (c) Two bracing rods eccentrically located in vertical direction to allow one rod crossing over the other one (ASI, modified) Fig. 9-13 Case study #2 - Illustration and description of step 8 192 193 9.2.9 Detailing each connection The detailing process of a typical joint of rod and strut is introduced in six steps. 1). Step 1 – Draw concentric center line connections 2). Step 2 – Draw connector size as dotted line 3). Step 3 – Define tolerance between connectors 4). Step 4 – Explore connector options 5). Step 5 – Design connecter (check any eccentric stress) 6). Step 6 – Make adjustment Joint A and Joint B shown in Fig. 9-5 are selected to illustrate these six steps. Joint A is a concentric connection, and Joint B is an eccentric connection. To make it easier to understand, the detailing process of Joint B is explained in two parts. The first part shows the detailing process starting from a concentric joint, and explains why an eccentric joint is adopted. The second part shows the detailing process for an eccentric joint. The flow chart of how to detail Joint A is shown in Fig. 9-14. Each small image shown in Fig. 9-14 is enlarged and described in Fig. 9-15. The flow chart of how to detail Joint B starting from a concentric connection is shown in Fig. 9-16. Each small image in Fig. 9-16 is illustrated in Fig. 9- 17. The flow chart of how to detail Joint B starting from an eccentric connection is shown in Fig. 9- 18. Then each small image shown in Fig. 9-18 is further described in Fig. 9-19. Detailing a typical joint type Joint A (rod + strut) See Fig. 9-14. STEP 5 STEP 6 6.1 6 5 B3'' R2' B3' B3 STEP 4 STEP 3 STEP 2 STEP 1 R1 B3 4 3.1 B3 C1 R2 C2 A1 A2 B1 B2 3.2.1 3.2 B2 B3 3.2.2 1 Cable #4 Cable #2 Strut Cable #1 Cable #3 B2 B3 2 3 3.3 3.3.1 Fig. 9-14 Case study #2 - Illustration and description of step 9 - Flow chart of detailing process for joint A (Drawn based on ASI drawings) Enlarged images shown in Fig. 9-14 are explained in detail in Fig. 9-15. 194 195 Image 1 Principles applied: Structural behavior (concentric connection) Always consider a concentric connection at first and adjust it to eccentric connection only if needed. Concentric connection requires that the center lines for all connected elements join at one point. Five center lines are drawn, cable #1, #2, #3 and #4, as well as one strut. All of the elements meet at one point in order to avoid bending stress. Image 2 Principles applied: Manufacture & structure (size of available cable fittings A 2 ) Structure (size of strut A 1 ) Draw the size for the element fittings to be connected by dotted line. There are four cables coming together at one point. The easiest way is to make all of the four cables the same size because the four cables have similar loads. Making the four cables the same size not only simplifies design, but also simplifies manufacturing and installation process.) Here, A 1 is defined by calculation, or experience. A 2 is determined based on the cable fitting size, which is also defined by calculation or experience. A 1 = 3 ½”, A 2 = 1 7/32” Image 3 Principles applied: Tolerance (tolerance between adjacent sockets) Define the tolerance of each element. Firstly, make tolerance for the elements which are adjacent to each other. Generally, the space needed for tolerance between two adjacent elements (like cable to cable, and cable to strut), is 0.5 inch. In this case, there are three places which need tolerance as shown in the image left. B 1 = B 2 = B 3 = 0.5”. Check tolerances with installer Fig. 9-15, Continued on next page Image 3.3 Principles applied: Tolerance (tolerance between adjacent sockets) Aesthetics (connector shape) After finding out the tolerance, the next thing is to determine the location (or edge) of each element. In this case, B 1 , B 2, or BB 3, any of them can be the key factor governing the rest, therefore governing the location of each element. For instance, the image on left shows what will happen if B 2 B and B 3 govern. Image 3.3.1 Principles applied: Tolerance (tolerance between adjacent sockets) Aesthetics (connector shape) The location (or the edge) of each element will determine the shape of the connector connecting the cables and the strut. If B 2 and B 3 govern, designers can design the resultant shape of the connector, which is shown in the image left. As one can see, the resultant shape seems not good. It is asymmetrical. Image 3.2 Principles applied: Tolerance (tolerance between adjacent sockets) Aesthetics (connector shape) Other options can be considered. In the image left, B 2 and B 3 still govern, but place the edge of each element based on the equal distance from the central point. This will probably have a circle- shaped connector. Fig. 9-15, Continued on next page 196 Image 3.2.1 Principles applied: Aesthetics (connector shape) Image 3.2.1 shows the possible resultant circle- shaped connectors based on the previous image. Here one can see that, the connectors look better than the ones shown in the image 3.3.1. Image 3.2.2 Principles applied: Aesthetics & manufacture (connector shape) Based on the image 3.2.1, the connectors can be designed as a circle. It will not only look “perfect”, but also make it simple to manufacture. To do so, the top two cables need to be moved upward a little bit so that the distance between the top two cables and the central point is the same as the distance between the bottom two cables and the central point (R 1 shown in Image 3.1). Image 3.1 Principles applied: Tolerance (tolerance between adjacent sockets) Aesthetics & manufacture (connector shape) BB 3 becomes the only factor governing the design (see Image 3 for more information). Fig. 9-15, Continued on next page 197 198 Image 4 Principles applied: Manufacture (socket dimensions) Structure (minimum socket size C 2 ) Tolerance (maximum radius of gusset plate R 2 ) Draw sockets connecting rods to strut. Firstly, get C 1 and C 2 from socket manufacturer or catalog (see Image 4 in Fig. 8-17) based on rod size. The maximum radius of the connector (gusset plate) R 2 limited by clearance C 3 (tolerance) between the socket and the edge of gusset plate. Generally the clearance C 3 is 0.5” for small fittings (reference). Image 5 Principles applied: Structure & aesthetics (weld length of strut and gusset plate) Manufacture & aesthetics (curved shape of sockets) The strut ending is based on aesthetics and weld length required. . (see image 5 in Fig. 8-17). The cable end (socket) is drawn as manufactured. At this stage, the joint design is almost complete. Image 6 Principles applied: Tolerance (tolerance between adjacent sockets) Cost (reduce connector size) After drawing the sockets, one can see that the distance between the two adjacent sockets B 3’ is bigger than the necessary tolerance required which is generally 0.5”. Therefore, the bottom two sockets could be moved upward a little bit to make B 3’ equals to 0.5”. The benefit of doing this is to reduce connector size, which reduces material cost and improves appearance. Fig. 9-15, Continued on next page Image 6.1 Principles applied: Tolerance (tolerance between adjacent sockets) Cost & aesthetics (reduce connector size) The connector (gusset plate) size is reduced (R 2’ < R 2 ). The resultant clearance between the bottom two sockets B 3” is 0.5”. Fig. 9-15 Case study #2 - Illustration and description of step 9 – Illustration of each image shown in Fig. 9-14 (Drawn based on ASI drawings) Detailing a typical joint type Joint B (rod + strut) – starting from a concentric connection The following flow chart in Fig. 9-16 shows the detailing process of Joint B starting from a concentric connection. Each small image in Fig. 9-16 is enlarged and explained in Fig. 9-17. At the end of Fig. 9-17, one can see that an eccentric connection is needed in order to reduce the size of rod- to-strut connector. Still, the six steps are: 1). Step 1 – Draw concentric center line connections 2). Step 2 – Draw connector size as dotted line 3). Step 3 – Define tolerance between connectors 4). Step 4 – Explore connector options 5). Step 5 – Design connecter 6). Step 6 – Make adjustment 199 STEP 5 STEP 6 STEP 4 C1 C2 C4 C3 STEP 3 STEP 2 A4 A2 A1 A3 B1 B2 STEP 1 1 Cable #3 Plate Cable #4 Strut Cable #2 Cable #1 2 3 4 4.1 5 6 6.1 Fig. 9-16 Case study #2 - Illustration and description of step 9 - Flow chart of how to detailing JOINT B starting from a concentric connection (Drawn based on ASI drawings) Enlarged images in Fig. 9-16 are explained in Fig. 9-17. 200 Image 1 Principles applied: Structural behavior (concentric connection) Always consider a concentric connection at first and adjust it to eccentric connection only if needed. Concentric connection requires that the center lines for all connected elements join at one point. Six center lines are drawn, cable #1, #2, #3 and #4, as well as one strut and one steel plate. All of the elements meet at one point in order to avoid any bending stress. Image 2 Principles applied: Manufacture & structure (size of available cable fittings A 1 ) Structure (size of strut A 2 ; thickness of plate A 3 and length of plate A 4 ) Draw the size for the elements to be connected by dotted line. Here, four dimensions are needed: the size of the strut (A 2 ); the size of sockets (A 1 ); the thickness of steel plate (A 3 ) and the length of steel plate (A 4 ). (Sockets connect strands or rods to other elements). A 1 is provided by the strand manufacturer. A 2 is defined by structural design, based on stress, material strength, and structural length of the strut. A 2 may be also defined by needs to make connections. The steel plate connects the glass fitting (spider) to the strut. The thickness (A 3 ) and the length (A 4 ) are determined by structural requirements as well as installation needs which are generally provided by the glass wall manufacturer. Image 3 Principles applied: Tolerance (tolerance between adjacent sockets) Draw tolerance needed between adjacent elements. Here, tolerances needed for the top sockets (B 1 ), and the bottom sockets (B 2 ) are B 1 = BB 2 = 0.5” (reference). Fig. 9-17, Continued on next page 201 Image 4 Principles applied: Manufacture (socket dimensions) Structure (minimum socket size C 2 ) Draw sockets connecting rods to strut. Get C 1 and C 2 from socket manufacturer or catalog (see Image 4 in Fig. 8-17) based on rod size. Image 4.1 Principles applied: Structure & installation (the distance from the edge of gusset plate to restraining bolts C 3 and C 4 ) C 3 and C 4 are determined by installation requirements. They should be big enough to make the installation as convenient as possible. Image 5 Principles applied: Aesthetics & manufacture (the curved shape of gusset plate and sockets) Structure (allowing structural movement of cables) The curved shape of the gusset plate is partly because of aesthetics and partly because of functions (allowing the cables to rotate under structural movement). At this stage, the joint design is almost complete. However, the connector (gusset plate) looks a bit too long. Fig. 9-17, Continued on next page 202 Image 6 Principles applied: Aesthetics (reducing connector size) Structure (check eccentric stress) An eccentric connection can solve this problem (see dotted thick lines). By separating the center lines, the strand sockets may be placed closer to the strut to reduce the joint. Image 6.1 Principles applied: Aesthetics (connector shape) Based on Image 6, the sockets are placed closer to the strut, resulting in a shorter connector. However the eccentric joint may cause secondary stress in the strut. Thus, the strut must be designed to resist the eccentric stress in addition to any axial stress. Fig. 9-17 Case study #2 - Illustration and description of step 9 – Illustration of each image shown in Fig. 9-16 (Drawn based on ASI drawings) Detailing a typical joint type Joint B (rod + strut) – starting from an eccentric connection The flow chart showing the detailing process of Joint B starting from an eccentric joint is introduced in Fig. 9-18. Fig. 9-19 shows the enlarged images in Fig. 9-18. 203 Cable #4 Cable #2 A1 B2 STEP 5 STEP 6 A4 STEP 3 STEP 4 3 2 B1 B3 STEP 1 STEP 2 1 Plate Strut Cable #3 Cable #1 A3 A2 D3 6.1 6 5 4 C1 3.1.1 3.1 3.2.1 3.2 C2 C2 B4 B2 B4 3.1.2 3.2.2 C3 C4 D3 D2 D2 D2 D1 3.3.1 3.3 B4 C2 C2 C1 3.3.2 B4 C2 Step 1 – Draw concentric center line connections Step 2 – Draw connector size as dotted line Step 3 – Define tolerance between connectors Step 4 – Explore connector options Step 5 – Design connector Step 6 – Make adjustment Fig. 9-18 Case study #2 - Illustration and description of step 9 - Flow chart of how to detailing JOINT B starting from an eccentric connection (Drawn based on ASI drawings) 204 205 Image 1 Principles applied: Structural behavior (concentric connection) Aesthetics (eccentric connection) As explained in Fig. 9-17 and Fig. 9-18, the concentric connection can be changed to an eccentric connection to reduce the gusset plate. The left image is the result of an eccentric connection, showing the six center lines: four cables, one strut, and one steel plate. Because the eccentric joint may cause secondary stress in the strut, the strut must be designed to resist the eccentric stress in addition to any axial stress. The central point of cable #2 and cable #4 is separated from that of cable #1 and cable #3, creating an eccentric joint. However, cable #1 & cable #3 are connected to one point; and cable #2 & cable #4 are also connected to one point. Image 2 Principles applied: Manufacture & structure (size of available cable fittings A 1 ) Structure (size of strut A 2 ; thickness of plate A 3 and length of plate A 4 ) See Image 2 in Fig. 9-17. Image 3 Principles applied: Tolerance (tolerance between adjacent elements) Draw tolerance needed between adjacent elements. Here, tolerances needed are the distances between cable sockets and struct: B 1 = B 2 = B 3 = B 4 = 0.5” (reference). Obviously, the distance between the top two cables and the distance between the bottom two cables are bigger than 0.5”. Fig. 9-19, Continued on next page Image 3.3 Principles applied: Tolerance (tolerance between adjacent elements) Aesthetics (connector shape) Structure (socket dimension C 2 ) The positions of sockets will affect the shape of gusset plate, therefore when determining the positions of sockets, designers should consider the desired shape of gusset plate. The left image shows an elliptic connector. For an elliptic shape connector, all restraining bolts on the sockets should be along the line of an ellipse. Considering tolerance, cable #4 can not be moved closer to the strut, otherwise B 4 would be smaller than 0.5”, which is not OK for required tolerance. Therefore, cables #1, #2 and #3 need to be moved further to the strut. C 2 is determined by socket manufacturer based on cable size (see Image 4 in Fig. 8-17). Image 3.3.1 Principles applied: Tolerance (tolerance between adjacent elements) Aesthetics (connector shape) Structure (socket dimension C 2 ) Based on Image 3.3, cables #1, #2 and #3 are moved further to the strut, placing their restraining bolts along the line of the ellipse. Image 3.3.2 Principles applied: Aesthetics (connector shape) Structure (socket dimension) Tolerance (between socket and gusset plate ) Note, tolerance is needed between the socket and gusset plate (see Image 4 in Fig. 8-17). Considering the tolerance, the maximum gusset plate is defined. The left image shows an example of a connector shape option. Fig. 9-19, Continued on next page 206 Image 3.2 Principles applied: Manufacture (socket dimension C 1 and C 2 ) Structure (minimum socket size C 2 ) Draw sockets connecting rods to strut. Get C 1 and C 2 from socket manufacturer (see image 4 in Fig. 8-17) based on rod size. The thick dotted line in the left image means that there is a glass wall to the left of this line, which should be considered when designing the connector. For instance, the connector can not be too big or exceed the glass wall. There should be space between the glass wall and the joint. Image 3.2.1 Principles applied: Aesthetics (connector shape) Structure (socket dimension) Tolerance (between socket and gusset plate ) Note, tolerance is needed between the socket and gusset plate (see Image 4 in Fig. 8-17). Considering the tolerance, the maximum gusset plate is defined. The left image shows an alternate gusset plate. Image 3.2.2 Principles applied: Aesthetics (connector shape) Structure (socket dimension) Tolerance (between socket and gusset plate ) The left image shows another alternate gusset plate. The final product is designed based on this option. Again, tolerance is needed between the socket and gusset plate (see Image 4 in Fig. 8-17). Considering the tolerance, the maximum gusset plate is defined. Fig. 9-19, Continued on next page 207 Image 3.1 Principles applied: Manufacture & structure (minimum socket size C 2 ) Tolerance (the distance between adjacent elements B 2 and BB 4 ) The positions of the restraining bolts on the cable sockets are determined by C 2 , which is generally defined by socket manufacturers (see image 4 in Fig. 8-17). Plus, tolerance is needed between the sockets and the strut: B 2 = B 4 = 0.5” (reference). As shown in the left image, the bolts on the top tow sockets are not on the same line; and, the bolts on the bottom sockets are not on the same lines neither. To make the connector aesthetically better and structurally more balanced, the top left socket (Cable #1) should be moved upward a bit, and the bottom left socket (Cable #3) should be moved down ward a bit, so that their restraining bolts are on the same lines. Image 3.1.1 Principles applied: Structure & aesthetics (check D 1 and D 2 ) Based on Image 3.1, the restraining bolts on top two sockets are on the same line, and the retraining bolts on bottom two sockets are on the same line. After setting the BB 2 = B 4 B = 0.5” as shown in Image 3.1, it turns out that the distance between the restraining bolts in the top two sockets and the strut (D 1 ) is smaller than that of the bottom two sockets and the strut (D 2 ). Image 3.1.2 Principles applied: Structure & aesthetics (equal D 1 to D 2 ) To make the joint more structurally balanced, D 1 and D 2 should be equal. Because D 1 is smaller than D 2 , D 1 is adjusted to be equal to D 2 to ensure minimum clearance (tolerance) mentioned in image 3. Another benefit to equal D 1 to D 2 is aesthetical. The rod-to-strut connector looks more balanced if D 1 equals D 2 . Fig. 9-19, Continued on next page 208 Image 4 Principles applied: Structure & installation (the distance from the edge of gusset plate to restraining bolts C 3 and C 4 ) C 3 and C 4 are determined by both structural and installation requirements. They should be big enough to resist structural stress applied on the cables, and to make the installation as convenient as possible. C 1 is from socket manufacturer based on cable size. Considering the tolerance, the maximum gusset plate is defined (D 5 ). Image 5 Principles applied: Aesthetics & manufacture (the curved shape of gusset plate and sockets) Structure (allowing structural movement of cables) The curved shape of the gusset plate is partly because of aesthetics and partly because of functions (allowing the cables to rotate under structural movement). At this stage, the joint design is almost complete. However, the connector (gusset plate) looks a bit bulky. Image 6 Principles applied: Aesthetics & manufacture (connector shape) The dotted thick lines shown in the left image is a possible way to change the gusset plate shape. Fig. 9-19, Continued on next page 209 Image 6 Principles applied: Aesthetics & manufacture (connector shape) Based on Image 6, the gusset plate is narrowed down and lengthened a bit, making the joint more elegant. The image below shows the complete detail with glass wall. Glass Fig. 9-19 Case study #2 - Illustration and description of step 9 – Illustration of each image shown in Fig. 9-18 (Drawn based on ASI drawings) 210 Chapter X Case study three – UBS Building, Chicago, Illinois 10.1 Introduction 10.1.1 Project information Climate The latitude of Chicago is 42 o N, and longitude is 87.7 o W. Chicago is famous for its extreme climate and winds. Summers (June to the end of September) are very hot and humid, but evenings are cool because of the breezes blowing from Lake Michigan. Winters are bitterly cold, icy, and rainy, along with harsh winds and frequent snows. Spring has moderate temperature and frosty nights, but is short. Autumn is the best time of year with cool air and sunshine. The highest rainfall occurs in summer, with an average 3.67inches per month. The average maximum temperature in summer is 84 o F in July, and the average minimum temperate in winter is 30 o F. (http://www.wordtravels.com/Cities/Illinois/Chicago/Climate) See Fig. 10-1 for (a) average temperature, (b) humidity, (c) sunshine, (d) precipitation, and (e) wind speed around the year in Chicago. (a) Average temperature Fig. 10-1, Continued on next page 211 (b) Humidity (c) Sunshine (d) Precipication Fig. 10-1, Continued on next page 212 (e) Wind speed (mph) Fig. 10-1 Chicago climate data (http://www.city-data.com/city/Chicago-Illinois.html) General project information (Table 10-1) Project name UBS Building at One North Wacker Drive, Chicago, Illinois Architect Lohan Associates, Inc Lobby curtainwall fabrication and installation ASI Advanced Structures, Inc. Glass supplier and installation Trainor Glass Company Glass Schott Glass (Amiran Antireflective) Sealant Dow Corning Corp. (Anon 5 2002) General contractor AMEC Construction Management, Inc. Structure engineering Thornton-Tomasetti Engineers MEP engineering Environmental Systems design Landscape architect Peter Walker & Partners Geotechnical engineering STS Consultant, Ltd. Acoustics consultant Shiner + Associates, Inc. Concrete supplier Ozinga Chicago RMC, Inc. Crane supplier Jake’s Crane, Rigging & Transportation International Inc. Elevator supplier Otis Elevator Co. Façade supplier Antamex International, Inc (www.emporis.com) Height (structural) 651/50 feet (199m) Floors over ground 50 Floors under ground 2 Construction start 1999 Construction end Spring, 2002 Floor size (total) 1,299,990 square feet (Anon 6 ) Table 10-1. General project information of case study #2 Brief introduction The building features a 40’ high cable-net lobby wall with 5’ by 5’ glass panes. The glass façade of the lobby is supported by an innovative cable net structure. This type of structure was firstly 213 214 used in Kempinski Hotel in Munich. The UBS building in Chicago is the first building in the U.S. which uses this technology. The cables are three quarters inch in diameter. The cables are made of pretensioned stainless steel. The south façade of the lobby is 30 feet wide and 40 feet tall; both of the east and west facades measure 45 feet wide and 40 feet high. (Rothrock 2000) The glass used in the lobby is half inch thick, monolithic tempered and heat soaked glass, with a color of Schott Corp’s water white. A specific ultra thin interference layer called Amiran was coated on both sides of the glass, making the surface reflectivity of the glass less than 1%, about one seventh of that of normal glass. This brings more light into the lobby. Even when the sky is overcast, the entrance still keeps bright. Also, because of very low reflectivity, the glass panes are almost invisible, thus “creating an inviting atmosphere”, and making the customers to “enter the building without any feeling of restraint” (Prinssen & Rubmann 2003). ASI developed a full-scale mock-up of individual glass panes to test the cable-net wall. During the mock-up test, a predicted deflection of around 7 inches occurred under peak design pressures (37 psf). The wall returned to its original position without permanent displacement after removing the loads. The test also showed that the wall system could withstand wind pressures well beyond code requirements. In addition, “a pull test to verify the cable system breaking strength and the connection anchor was performed without event.” (ASI brochure) One challenge in the design was how to integrate the fixed doors into the high deflecting net wall system. According to Safford, a principal of ASI, the maximum deflection of a cable net wall is about 1/50 of the span; while in a traditional wall, the number is only 1/175. The solution was a “pin- connected structural steel portal attached to the net wall”. The glass doors are surrounded by a tapered stainless steel clad frame which keeps the doors stationary as well as providing water and air seal between the door assemblies. (Rothrock 2000) 10.1.2 Images Fig. 10-2 shows the interior, exterior and detail of the lobby glass wall. Fig. 10-2 Exterior and interior photos of the glass lobby (ASI) 215 10.2 Detailing process for a typical section Fig. 10-3 shows the plan and elevations of the glass lobby. A typical bay and a bay with glass doors (shown in dotted lines) are used to illustrate the detailing process of the glass wall. Glass lobby west elevation Glass lobby south elevation A typical bay Glass lobby east elevation 5 4 BC D BC D EF Glass lobby plan G EF G HJ 5 5 H J 4 4 210' 30' Glass doors 30' 30' 30' 30' 30' 30' 46' Fig. 10-3 Plan and elevations of the glass lobby (ASI, modified) 216 10.2.1 Find out the infrastructure (Fig. 10-4) Glass façade (http://www.ubs.com) Infrastructure type – Ground to floor, column to column (grid infrastructure, horizontal and vertical ) Infrastructure material – steel frame (stiff) In this example, the infrastructure consists of two horizontal beams and a series of columns (see the wide lines in the image above). This means that the back up structure can be either a vertical or horizontal structure, or both. A flat cable-net structure is used, with both horizontal and vertical cables. The materials of beams and columns (with concrete perimeter) are steel, which is generally strong, and can resist the tension load from the cables. Please also see the Fig00, 1, 2 &3 below. Fig. 10-4 Case study #3 - Illustration and description of step 1 10.2.2 Determine modular size (Fig. 10-5) (Glass pane, ASI, modified) 5’ × 5’ based on glass pane limitation In this project, the modular size of the glass wall was determined by aesthetic proportions and the size of glass pane, which is 5 feet width and 5’ height. Fig. 10-5 Case study #3 - Illustration and description of step 2 217 10.2.3 Identify the back up structure (Fig. 10-6) Glass fitting details: interior view (left) and exterior view (right) (Wright 2002, p.48) Fig. 10-6, Continued on next page 218 Typical glass façade elevation (Wright 2002, p.48) Cable net structure is used as the back up structure of glass. It consists of both horizontal and vertical cables. When lateral force such as wind is applied on the glass façade, the stress is evenly distributed through the cable network. (Prinssen & Rubmann 2003) Vertical cables are attached to steel floor beams by connection boxes; horizontal cables are attached to composite steel and concrete perimeter columns by connection boxes. Material – stainless steel cables Fig. 10-6 Case study #3 – Illustration and description of step 3 219 220 10.2.4 Make a checklist of all elements based on four categories (Fig. 10-7) Category Elements Beams Columns Top beam Bottom beam Category 1 – infrastructure Steel beam: W30×99 (south) W36×393 (east and west) Steel beam: W36×160 (south) W36×245(east and west) Composite steel and concrete perimeter column: 36”×36” concrete column with 5’- 0” Ø metal cover Glass panels Glass fittings Back up structure elements Category 2 – Glass wall elements Half inch thick, monolithic tempered and heat soaked glass with low reflectivity (Prinssen et al 2003) clamping plate cable-net fittings without perforation Cable net as back structure, including 19mm Ø (three quarters inch) stainless steel horizontal cables and vertical cables. Portal frame beam Portal frame column Portal frame jamb Glass door Category 3 – Elements for openings Built up box beam: ST8×6×1/2 Built up box column: ST6×4×1/2 with 10” ×10” final pocket 24” ×24” concrete pocket Two 6’11” clear glass doors and one 7’-71/4” clear glass door Category 4 – Additional devices N/A Fig. 10-7 Case study #3 - Illustration and description of step 4 (ASI, summarized) 10.2.5 Find out or determine the position, shape and size of each element (Table 10-2 and Fig. 10-8) Find out the size of given infrastructure The size of glass panels is defined by architects and/or glass manufacturers. The size of glass fittings is determined by manufacturers and/or in consultation with architects. On south façade, the size of vertical cables (19mm) is determined through calculation and experience; the size of horizontal cables is equal to vertical cables because the span of horizontal cables is less than the span of vertical cables, which means as long as vertical cables meet the structural requirements, horizontal cables with the same size are safe too. On west and east façade, the size of horizontal cables (22mm) is determined through calculation and experience; the size of vertical cables is determined by horizontal cables because the span of horizontal cables is more than the span of vertical cables. The position, shape and size of portable glass doors are determined by architects and/or glass door manufacturers. The sizes of portable frame beam and column are determined by calculation and experience. The portable beam and column should be strong enough to resist the tension load of cables. The design lateral wind load (both inward and outward) is 25PSF (pound per square foot), and 30PSF for corner, based on code requirements. Installation of glass and nodes occurs after all vertical and horizontal cables are pre-stressed and verified. Table 10-2 Case study #3 - Illustration and description of step 5 (1) Steel beam (W30×99) Steel beam (W36×160 ) Composite steel and concrete perimeter column (36"×36" concrete column with 5'-0" ? metal cover) Glass facade elevation of a typical bay Plan section Section 1/2" Schott Amiron water white monolithic tempered and heat soaked glass with low reflectivity (5' by 5') Horizontal cable Composite steel and concrete perimeter column Vertical cable 19mm (3/4in) stainless steel horizontal cable (in board of vertical cable) 19mm (3/4in) stainless steel vertical cable Steel plates cable connection box by which the horizontal cable is attached to the column Connection box by which the vertical cable is attached to the steel beam Electrically polished cast stainless steel nodes 5' 5' Elevation and sections of a typical bay (ASI, modified) Portal frame beam (TS8×6×9/18) Steel floor beam (W36×245) Portal frame column (TS6×4×1/2 ) Portal frame jamb (24" ×24" concrete pocket) Portal frame jamb Portal frame Column 22mm Stainless steel vertical cable Elevation of glass doors Sections looking at portal frame jamb (left) and column (right) Elevation and sections of glass doors (ASI, modified) Fig. 10-8 Case study #3 - Illustration and description of step 5 (2) 221 10.2.6 Define all connections based on eight categories (Fig. 10-9) 1 2 3 4 5 6 (1) Glass + floor beam (top); (2) Vertical cable + floor beam (top); (3) Glass + cables (horizontal and vertical); (4) Glass + glass; (5) Glass + floor beam (bottom); (6) Vertical cable + floor beam (bottom) Connections within glass wall and connections between glass wall and infrastructure (ASI, modified) Category 1– Connections within glass wall ¾ Class + glass, glass + cable (horizontal and vertical) Category 2 – Connections within openings ¾ Glass door + portal frame beam, glass door + portal frame column, glass door + portal frame jamb, portal frame beam + portal frame column, portal frame beam + portal frame jamb Category 3 – Connections within additional devices (Does not apply in this case) Category 4 – Connections between glass wall and additional devices (Does not apply in this case) Category 5 – Connections between glass wall and openings ¾ Glass + portal frame beam, glass + portal frame column, vertical cable + portal frame beam, horizontal cable + portal frame column Category 6 – Connections between openings and additional devices (Does not apply in this case) Category 7 – Connections between glass wall and infrastructure ¾ Glass + floor beam (top), glass + floor beam (bottom), glass + column, vertical cable + floor beam (top), vertical cable + floor beam (bottom), horizontal cable + column Category 8 – Connections between openings and infrastructure ¾ Portal frame beam + floor beam (bottom), portal frame column + floor beam (bottom), portal frame jamb + floor beam (bottom) Category 9 – Connections between additional devices and infrastructure (Does not apply) Fig. 10-9 Case study #3 - Illustration and description of step 6 222 10.2.7 Determine the material and method for each connectors (Fig. 10-10) From step 6, we can see that there are 17 connections. They are: Glass + Glass, Glass + clamping plate, clamping plate + cable, glass + floor beam (top), glass + floor beam (bottom), glass + column, cable + floor beam (top), cable + floor beam (bottom), cable + column, Glass door + portal frame beam, glass door + portal frame column, glass door + portal frame jamb, portal frame beam + portal frame column, portal frame beam + portal frame jamb, prtal frame beam + floor beam (bottom), portal frame column + floor beam (bottom), and portal frame jamb + floor beam (bottom). Glass Silicone sealant Glass + Glass Connected by structural silicone Sealant materal: Dow Corning 795 black (Left image from ASI, modified) (ASI, modified) Glass + cable net (horizontal and vertical) The glass panes and cables are connected by custom designed cast metal nodes. The glass panes are clamped together by small round clamping plates without drilling holes. The cast nodes connect the glass panes to cable systems. The left photo shows the interior view of the cast node. (ASI, modified) Fig. 10-10, Continued on next page 223 3/8" neoprene gasket Recessed front plate restrainling bolt Half inch thick monolithic tempered and heat soaked glass Stainless steel vertical cable (19mm or 22mm) Stainless steel horizontal cable (19mm or 22mm) Recessed rear plate cable restraining bolts 1 Side Elevation 2" 1" 1/8" undersize 5 3/4" gasket The left image (1) shows the side elevation of the glass node detail. Cast nodes material: stainless steel Connector of glass and steel clamping plate: 3/8” neoprene gasket 60 shore black (the neoprene avoids direct contact of glass and metal which may cause glass cracks). (ASI, modified) Fig. 10-10, Continued on next page 224 3/4" 3 Rear Elevation 2 Front Elevation 3/4" 6" rear plate 3/4" glass silicone sealant joint Rear plate Recessed rear plate cable restraining bolts 6" front plate Front plate 3/4" glass silicone sealant joint Recessed front plate restraining bolts Neoprene setting blocks Glass panel Left images are front elevation (2) and rear elevation (3) Three dimensions are important considerations here: the size of rear and front plate (6” diameter); the width of glass silicone sealant joint (3/4”); and the size of neoprene gasket. (ASI, modified) Fig. 10-10, Continued on next page 225 Steel 2" Silicone setting block Norton tape Shim space 1/2" monolithic glass Structural silicone Dow 795 black Stainless steel channel Stainless steel head self drilling screws 7/8" 1/4" Glass + floor beam (Top) The left image shows the typical solution of glass and steel beam connection. The glass is connected to the steel beam by a stainless steel channel. A shim is designed between the steel beam and steel channel for tolerance. A silicone setting block is used to avoid direct contact of glass and steel channel. The glass sealant material is structural Dow 795 black silicone. (ASI, modified) Fig. 10-10, Continued on next page 226 3/4" Steel plate Stainless steel beam 1 1/2" Steel plate Stainless steel self lubricating spherical bearing Adjusting and lock nut Stainless steel cable swage Stainless steel vertical cable 1/2" glass 2" Finish line Finish line Threaded end Vertical cable + floor beam (top) The vertical cable top attachment to the building infrastructure includes four parts: stainless steel cable swage; threaded end; stainless steel self lubricating spherical bearing; and the adjusting and lock nut. The cable threaded end is screwed to a 1 ½” thick steel plate, which is welded to a ¾” steel plate. The ¾” steel plate is either welded to or screwed to the steel beam, depending on structural engineer suggestion. (ASI, modified) Fig. 10-10, Continued on next page 227 Exterior Glass Cable swage Vertical cable Interior Finish line Threaded end Adjusting and lock nut Stainless steel self lubricating spherical bearing 1 1/2" Steel plate Stainless steel channel Shim space Stainless steel head self drilling screws 3/4" Steel plate Concrete pocket Steel beam Glass + floor beam & vertical cable + floor beam (bottom) The vertical cable is threaded into the 1 ½” thick stainless steel plate through a stainless steel self lubricating spherical hearing. The 1 ½” thick steel plate is welded to a series of vertical ¾” thick steel plate which is connected to the steel beam. The adjusting and lock nut. Allows adjustment of cable length The glass pane is also connected to the 1 ½” thick steel plate by a stainless steel channel. A shim space is used between the channel and the steel plate for tolerance. (ASI, modified) Fig. 10-10 Case study #3 - Illustration and description of Step 7 228 10.2.8 Define any other requirements (Fig. 10-11) A series of 3" by 6" access holes are designed in the portal frame beam for pre-stressing of the cables. Cable swage 3" by 6" access hole for cable pre-tensioning Glass Horizontal Cable Portal frame column Vertical section (top) & Plan section (bottom) Interior Exterior 3" 3" Glass Cable swage Vertical cable Interior Exterior Portal frame beam This step is to define special requirement for manufacture, assembly and installation, as well as any other requirements that are not covered in other steps. For example, a 3” by 6” access hole is designed in the portal frame beam (left above image) for vertical cable pre- stressing; another 3” by 6” access hole is designed in the portal frame column (left bottom image) for horizontal cable pre-tensioning. Because the steel rods are tension members, prestress is needed to minimized lateral deflection For aesthetical reasons, both access holes are designed on the interior side of the portal frames. (ASI, modified) Fig. 10-11 Case study #3 - Illustration and description of Step 8 229 230 10.2.9 Detailing each connection The typical joint of stainless steel cast nodes which connect glass panes to cable system is selected to illustrate the detailing process. 1). Step 1 – Draw concentric center line connections 2). Step 2 – Draw key connector size as dotted line 3). Step 3 – List all elements to be joint together 4). Step 4 – Define connection methods between adjacent elements 5). Step 5 – Design connector 6). Step 6 – Make adjustment There are three basis elements involved in this joint, which are horizontal cable, vertical cable and glass panes. Therefore, the detailing process needs to design: how horizontal cable is connected to vertical cable; how both cables are connected to glass panes; and how glass panes are connected to each other. To make it easier to understand, the detailing process is illustrated by two parts: rear elevation and front elevation. The rear elevation (interior) shows how the horizontal cable is connected to the vertical cable. The front elevation (exterior) shows how the glass panes are connected to the cable systems. Fig. 10-12 shows an overview of the detailing process for both rear elevation and front elevation. 3/4" horizontal cable D 2 = 6" D 1 = 5 3 4 " final STEP 6 STEP 5 STEP 4 STEP 3 3/4" horizontal cable 3/4" (19mm) vertical cable 3/4" (19mm) horizontal cable 1 8 " clearance Cable connector decoration Interior Exterior Glass center line 2" 1" Recessed rear plate cable restraining bolts Cable connector decoration Glass center line Horizontal cable Vertical cable Exterior Interior 1" Cable connector #1,2,3 Rear plate cable restraining bolts 1/16" clearance 1/16" clearance Rear plate Rear plate restraining bolt Cable connector #2 3/4" (19mm) vertical cable 3/4" (19mm) horizontal cable 3/4" (19mm) vertical cable Rear plate Cable connector #2 Rear plate restraining bolt Rear plate 7/8" notch on cable connector to hold horizontal cable 1/16" clearance 3/4" (19mm) vertical cable 3/4" horizontal cable Exterior Interior 3/4" (19mm) vertical cable 2" 1" Recessed rear plate cable restraining bolts Front plate Recessed front plate restraining bolt hole Neoprene gasket Rear plate Cable connector #1,2,3 Glass Rear plate Rear plate restraining bolt Cable connector #1 3/4" (19mm) vertical cable Cable connector Rear plate restraining bolt Rear plate Rear plate cable restraining bolts 3/4" horizontal cable 3/4" (19mm) vertical cable Glass center line Interior Exterior 1" Rear plate Cable connector #1,2,3 Cable connector #1 Rear plate restraining bolt Rear plate 1/16" clearance 7/8" notch on cable connector to hold vertical cable 3.4.3 3.4.2 3.4.1 3.2 3.3 3.4 3 4.1 4.2 4.3 4.4 5.1 6.1 Cable connector #3 Rear plate restraining bolt Rear plate Rear plate Rear plate restraining bolt Cable connector Neoprene gasket Recessed rear plate restraining bolt 2 3.1 4 5 6 STEP 2 STEP 1 3/4" (19mm) vertical cable 1 8 " 3.4.4 3.4.5 Neoprene gasket Clamping plate 1 D 1 = 5 3 4 " D 1 = 5 3 4 " D 1 = 5 3 4 " D 2 = 6" D 1 = 5 3 4 " 6.1 6 5.1 5 4.1 4 3.1 3.2 2.1 2 3/8" glass notch Front plate Front plate restraining bolt Glass Silicone sealant joint D 3 = 3 4 " Exterior Interior Front plate restraining bolt Glass Silicone setting block Rear plate Neoprene gasket Neoprene setting block Front plate Metal frame Recessed front plate restraining bolt Glass Front plate 3/4" silicone sealant joint Front plate decoration Front plate decoration Recessed front plate restraining bolt hole Front plate restraining bolt hole Front plate Neoprene gasket Glass Silicone sealant joint D 3 = 3 4 " 1/4" Neoprene setting block Metal frame Silicone setting block Rear plate Neoprene gasket final 6.2 4.3 4.2 3.3 3 2.3 2.2 Neoprene gasket Front plate restraining bolt hole 1/4" clearance Glass Silicone sealant joint D 3 = 3 4 " Rear plate Metal frame Silicone setting block 1/4" Neoprene setting block Silicone setting block Interior Exterior Rear plate Front plate Neoprene gasket Glass Front plate restraining bolt Glass Cable connector #3, 2, 1 Recessed rear plate cable restraining bolts Rear plate Neoprene gasket 3/4" horizontal cable 3/4" (19mm) vertical cable Front plate Recessed front plate restraining bolt hole 1" 2" Interior Exterior Front plate decoration Interior Exterior Recessed front plate restraining bolt hole Front plate Neoprene gasket 1 Neoprene gasket Clamping plate 1 8 " (Rear and front) Clamping plates Neoprene gasket 3/4" silicone sealant joint Clamping plate Neoprene gasket Neoprene gasket Clamping plate Rear Elevation Front Elevation Fig. 10-12 Case study #3 - Illustration and description of Step 9 - Overview of the detailing process for a typical glass fitting joint (Drawn based on ASI drawings) Detailing a typical joint type (glass panes + cable system) – the rear elevation part (interior part) Since the installation process of the glass façade is to firstly install the cable system (including apply pre-stress), and then install glass panes, the detailing process will start with the cable system (the rear elevation part, or the interior part). See Fig. 10-13. Enlarged images shown in Fig. 10-13 are explained in detail in Fig. 10-14. 231 1 2 Neoprene gasket Clamping plate 3/4" (19mm) vertical cable 1 8 " 3/4" horizontal cable 3.1 3.2 3/4" (19mm) vertical cable 3/4" horizontal cable 3.3 Rear plate 3.4.1 3.4.2 3.4.4 3.4.5 3.4.3 Cable connector #1 Rear plate restraining bolt 4.4 Rear plate Rear plate 4.3 Rear plate restraining bolt Cable connector #1 Cable connector #2 Rear plate restraining bolt 4.2 Rear plate Rear plate 4.1 Rear plate restraining bolt Cable connector #2 Cable connector #3 Rear plate restraining bolt 4 Rear plate Recessed rear plate restraining bolt 6 Cable connector Rear plate restraining bolt 3.4 Rear plate 3 Rear plate cable restraining bolts 3/4" horizontal cable 3/4" (19mm) vertical cable Glass center line Rear plate 5 Rear plate restraining bolt Cable connector 1 8 " clearance Glass center line Horizontal cable Vertical cable 5.1 Interior Exterior Exterior Interior Interior Exterior 6.1 Glass center line 1/16" clearance 3/4" horizontal cable final Exterior Interior 3/4" (19mm) vertical cable 1" 1" 2" 1" 2" 1" Rear plate Cable connector #1,2,3 7/8" notch on cable connector to hold vertical cable 3/4" (19mm) vertical cable 7/8" notch on cable connector to hold horizontal cable 1/16" clearance 3/4" (19mm) vertical cable 3/4" (19mm) vertical cable 3/4" (19mm) horizontal cable 3/4" (19mm) vertical cable 3/4" (19mm) horizontal cable Cable connector #1,2,3 Rear plate cable restraining bolts 1/16" clearance 1/16" clearance Neoprene gasket Cable connector decoration Recessed rear plate cable restraining bolts Cable connector decoration Recessed rear plate cable restraining bolts Front plate Recessed front plate restraining bolt hole Neoprene gasket Rear plate Cable connector #1,2,3 Glass STEP 6 STEP 1 STEP 2 STEP 4 STEP 3 STEP 5 Cable connector options D 1 = 5 3 4 " D 2 = 6" Step 1 – Draw concentric center line connections Step 2 – Draw key connector size as dotted line Step 3 – List all elements to be joint together Step 4 – Define connection methods between adjacent elements Step 5 – Design connector Step 6 – Make adjustment Fig. 10-13 Case study #3 - Illustration and description of Step 9 - Detailing process for rear elevation (Drawn based on ASI drawings) 232 Image 1 Principles applied: Structure & Aesthetics (concentric center line connections ) All connections are connected into one point for structural and aesthetical reasons. Image 2 Principles applied: Structure, assembly, installation & Aesthetics (the use of clamping plate and neoprene gasket as connectors, and the size of the connectors) Structure (cable net – vertical cable and horizontal cable – to support the glass wall) The glass panes are bonded together by means of clamping plates. Neoprene gasket is used between glass and metal clamping plate. The glass wall is supported by cable net structure. The size of vertical cables is determined by structural requirements (vertical span). Because the horizontal span is smaller than the vertical span, the horizontal cables can be the same size as vertical cables for installation and fabrication convenience. 3/4" horizontal cable D 2 = 6" D 1 = 5 3 4 " 3/4" horizontal cable 2 3.1 3/4" (19mm) vertical cable 1 8 " Neoprene gasket Clamping plate 1 Image 3.1 Principles applied: Structure, assembly, installation & Aesthetics (the dimension of horizontal cable) The joint of glass panes and cables includes three key parts: glass panes, vertical cable and horizontal cable. The glass panes are bonded together by steel plate; the glass panes are connected to vertical and horizontal cables by custom designed node. Image 3.1, 3.2, 3.3 and 3.4 list all key elements involved in this joint. The size of horizontal cables is the same as that of vertical cables (see image 3.2). Fig. 10-14, Continued on next page 233 Image 3.2 Principles applied: Structure & manufacture (the dimension of real plate) The diameter of vertical cable is determined by structural calculation as well as available products. Since the vertical structural span is bigger than the horizontal structural span, the theoretical required diameter of horizontal cables is smaller than that of vertical cables for structural safety. In this case, the designers made the diameter of horizontal cables the same as that of vertical cables for aesthetical reasons as well as convenient installation. Image 3.3 Principles applied: Structure & aesthetics (the dimension of stainless steel real plate) The glass panes are bonded together by two stainless steel plates: front plate and rear plate. The two plates are the same size for structural and aesthetical requirements. The left image shows the rear plate. The steel plates should be big enough to ensure enough contact area between glass panes and steel plates. If the contact area is too small, the plates can not hold the glass panes safely; besides, the glass may be broken due to stress concentration. 3/4" (19mm) vertical cable 3.2 Rear plate 3.3 Cable connector 3.4 Rear plate Rear plate restraining bolt Image 3.4 Principles applied: Structure, assembly, installation & aesthetics (the dimension and shape of stainless steel cable connector) The horizontal cables and vertical cables are connected together by custom designed cable connector through two rear plate restraining bolts. Image 3.4.1, 3.4.2, 3.4.3, 3.4.4, 3.4.5 show examples of cable connector options. Fig. 10-14, Continued on next page 234 Cable connector Rear plate restraining bolt Rear plate 3.4 3.4.1 3.4.4 3.4.2 3.4.3 3.4.5 Fig. 10-14, Continued on next page 235 Image 3 Principles applied: Structure, assembly, installation & aesthetics (the dimension and shape of real plate, horizontal cable, vertical cable and stainless steel cable connector) The left image shows the side elevation of how the horizontal cables are connected to vertical cables. Image 4.4 Principles applied: Structure, assembly, installation, tolerance & aesthetics (notch on the cable connector to hold the vertical cable) Image 4.4, 4.3, 4.2, 4.1 and 4 illustrate how the horizontal and vertical cables are connected together by the custom designed node – the cable connector. The left Image 4.4 shows there is a 7/8” wide notch on the cable connector (#1) to hold the vertical cable. There is a 1/16” clearance between the vertical cable and the cable connector. The cable connector includes three parts: cable connector #1, cable connector #2 and cable connector #3. The three pieces of cable connectors connect the horizontal cables and vertical cables by two restraining bolts. Rear plate cable restraining bolts 3/4" horizontal cable 3/4" (19mm) vertical cable Glass center line Interior Exterior 1" Rear plate Cable connector #1,2,3 3 Cable connector #1 Rear plate restraining bolt Rear plate 1/16" clearance 7/8" notch on cable connector to hold vertical cable 4.4 Rear plate Rear plate restraining bolt Cable connector #1 3/4" (19mm) vertical cable 4.3 Image 4.3 Principles applied: Structure, assembly, installation (the vertical cable is restrained by the cable connector) The left image shows that the vertical cable is restrained by the cable connector (#1) on which there is a notch to hold the vertical cable. Fig. 10-14, Continued on next page 236 Image 4.2 Principles applied: Structure, assembly, installation (the notch on the cable connector to hold horizontal cable) Cable connector (#2) is placed on top of the cable connector #1. On one side of the cable connector #2, a 7/8” notch is designed to restrain the vertical cable; on the other side is also a 7/8” wide notch to hold the horizontal cable. There is a 1/16” clearance between the notches and the cable. Image 4.1 Principles applied: Structure, assembly, installation (the horizontal cable is restrained by the cable connector) The left image shows the horizontal cable restrained by the cable connector (#2) on which there is a notch to hold the horizontal cable. Cable connector #2 Rear plate restraining bolt Rear plate 7/8" notch on cable connector to hold horizontal cable 1/16" clearance 3/4" (19mm) vertical cable 4.2 Rear plate Rear plate restraining bolt Cable connector #2 3/4" (19mm) vertical cable 3/4" (19mm) horizontal cable 4.1 3/4" (19mm) vertical cable 3/4" (19mm) horizontal cable Cable connector #3 Rear plate restraining bolt Rear plate 4 Image 4 Principles applied: Structure, assembly, installation & aesthetics (the dimension, shape and connection method of the cable connector) Cable connector #3 is placed on top of the cable connector #2. Finally, two restraining bolts screw all three cable connectors together. Fig. 10-14, Continued on next page 237 Image 5 Principles applied: Structure, assembly, installation, tolerance & aesthetics (the assembling of horizontal cables and vertical cables) The final design of the rear elevation of the cable net joint is shown as the left image and Image 5.1. Image 5.1 Principles applied: Structure, assembly, installation, tolerance & aesthetics (the assembling of horizontal cables and vertical cables) Image 5.1 side elevation. 1 8 " clearance Rear plate Rear plate restraining bolt Cable connector Neoprene gasket 5 Glass center line Horizontal cable Vertical cable Exterior Interior 1" Cable connector #1,2,3 Rear plate cable restraining bolts 1/16" clearance 1/16" clearance 5.1 Cable connector decoration Recessed rear plate restraining bolt 6 Image 6 Principles applied: Aesthetics (the recessed rear plate restraining bolts and the cable connector decorations) For aesthetical reasons the restraining bolts are recessed into the surface, and the surface of the cable connector is narrowed. Fig. 10-14, Continued on next page 238 239 Image 6.1 Principles applied: Aesthetics (the recessed rear plate restraining bolts and the cable connector decorations) The side elevation shows the recessed rear plate cable restraining bolts and the decoration of cable connector. 2" 1" Recessed rear plate cable restraining bolts Cable connector decoration 6.1 final 3/4" horizontal cable Exterior Interior 3/4" (19mm) vertical cable 2" 1" Recessed rear plate cable restraining bolts Front plate Recessed front plate restraining bolt hole Neoprene gasket Rear plate Cable connector #1,2,3 Glass Interior Exterior Glass center line Final design Principles applied: Structure, assembly, installation, tolerance & aesthetics (the assembling of glass and cable net joint) This is the final design of the glass and cable net joint. Fig. 10-14 Case study #3 - Illustration and description of Step 9 - Illustration of each image in Fig. 10-13 (Drawn based on ASI drawings) Detailing a typical joint type (glass panes + cable system) – the front elevation part (exterior part) The following diagram (Fig. 10-15) shows the detailing process for front elevation (exterior) of a typical glass joint and support. Enlarged images shown in Fig. 10-15 are explained in detail in Fig. 10-16. 1 2 1 8 " 3.1 3.2 3.3 Rear plate Glass Silicone sealant joint D 3 = 3 4 " Front plate Neoprene gasket Neoprene gasket 4.3 Neoprene gasket 2.1 2.2 2.3 Front plate restraining bolt hole 1/4" clearance Glass Silicone sealant joint D 3 = 3 4 " 4.1 Rear plate 3/8" glass notch 4 Front plate restraining bolt Front plate Front plate restraining bolt hole Front plate 5 Neoprene gasket Glass Silicone sealant joint D 3 = 3 4 " 4.2 1/4" Neoprene setting block Metal frame Silicone setting block Silicone setting block 1/4" Neoprene setting block Metal frame 6 6.1 Silicone setting block Recessed front plate restraining bolt Front plate decoration Glass Front plate 3/4" silicone sealant joint 3 Interior Exterior Rear plate Front plate Neoprene gasket Glass Exterior Interior Front plate restraining bolt Glass Silicone setting block Rear plate Neoprene gasket Neoprene setting block 5.1 Front plate Metal frame 6.2 Front plate decoration Interior Exterior Front plate decoration (Rear and front) Clamping plates Neoprene gasket Neoprene gasket Clamping plate Neoprene gasket Clamping plate Clamping plate Neoprene gasket 3/4" silicone sealant joint Recessed front plate restraining bolt hole Recessed front plate restraining bolt hole Front plate restraining bolt Glass Cable connector #3, 2, 1 Recessed rear plate cable restraining bolts Rear plate Neoprene gasket 3/4" horizontal cable 3/4" (19mm) vertical cable Front plate Recessed front plate restraining bolt hole 1" 2" Interior Exterior final STEP 6 STEP 5 STEP 4 STEP 3 STEP 2 STEP 1 Clamping plate options D 1 = 5 3 4 " D 2 = 6" D 1 = 5 3 4 " D 1 = 5 3 4 " D 1 = 5 3 4 " Step 1 – Draw concentric center line connections Step 2 – Draw key connector size as dotted line Step 3 – List all elements to be joint together Step 4 – Define connection methods between adjacent elements Step 5 – Design connector Step 6 – Make adjustment Fig. 10-15 Case study #3 - Illustration and description of Step 9 - Detailing process for front elevation (Drawn based on ASI drawings) 240 241 Image 1 Principles applied: Structure & Aesthetics (concentric center line connections ) All connections are connected into one point for structural and aesthetical reasons. The center lines are the same as that of Image 1 in Fig. 10-14. Image 2 Principles applied: Structure, assembly, installation & Aesthetics (the use of clamping plate and neoprene gasket as connectors, and the size of the connectors) The glass panes are bonded together by means of clamping plates. Neoprene gaskets are used between glass and metal clamping plate. The diameter of the clamping plates (D 1 ) and the diameter of the neoprene gasket (D 2 ) are determined by both structural and aesthetical requirements. 1 D 2 = 6" D 1 = 5 3 4 " 2 1 8 " (Rear and front) Clamping plates Neoprene gasket 3/4" silicone sealant joint 3.1 Rear plate Neoprene gasket Image 3.1 Principles applied: Structure, assembly & Aesthetics (The dimensions of rear plate and neoprene gasket) Image 3, 3.1, 3.2 and 3.3 list all elements involved in the joint: rear plate, front plate, glass panes and neoprene gasket, as well as the connection methods of all elements. The glass panes are clamped together by the rear plate and front plate like a sandwich. The neoprene gasket is placed between glass and steel plates. Image 3.1 shows the rear plate and neoprene gasket. Fig. 10-16, Continued on next page Image 2.1 Principles applied: Aesthetics (The shape of clamping plates) Image 2.1, 2.2 and 2.3 are three examples of clamping plate alternatives. The left Image 2.1 shows a butter-fly shaped clamping plate. No matter what kind of shape the clamping plate is, the dimension of the plate should be big enough to ensure enough contact area of glass panes and steel plate for structural safety. Image 2.2 Principles applied: Aesthetics (The shape of clamping plates) Image 2.2 shows an apple-shaped clamping plate. D 1 = 5 3 4 " 2.1 Neoprene gasket Clamping plate D 1 = 5 3 4 " 2.2 Neoprene gasket Clamping plate D 1 = 5 3 4 " 2.3 Clamping plate Neoprene gasket Image 2.3 Principles applied: Aesthetics (The shape of clamping plates) Image 2.3 is an egg-shaped clamping plate. Fig. 10-16, Continued on next page 242 243 Image 3.2 Principles applied: Structure, assembly & aesthetics (the material of the glass sealant joint and its width ) The glass sealant material is structural silicone with the width of ¾”. The width is determined by both structural and aesthetical requirements. Image 3.3 Principles applied: Structure, assembly & aesthetics (the dimensions of clamping plate and neoprene gasket) The clamping plates bond the glass panes together like a sandwich. Neoprene gasket is used to avoid direct contact of glass and steel plates. 3.2 Glass Silicone sealant joint D 3 = 3 4 " 3.3 Front plate Neoprene gasket 3 Interior Exterior Rear plate Front plate Neoprene gasket Glass Front plate restraining bolt Image 3 Principles applied: Structure, assembly & aesthetics (the assembling of glass panes and clamping plates) Image 3 on the left shows the side elevation of how the glass panes are bonded together by two pieces of clamping plates – front plate and rear plate. Fig. 10-16, Continued on next page 244 Image 4.3 Principles applied: Structure, tolerance, assembly & aesthetics (the assembling of glass panes and clamping plates) Image 4, 4.1, 4.2 and 4.3 illustrate how glass panes and clamping plates are assembled together. Image 4.3 shows all elements that are involved in the joint: glass panes, rear plate, front plate and metal frame. Silicone sealant joint connects glass panes. Neoprene gasket and silicone setting block connect glass panes and clamping plates (rear plate and front plate). Note, there is a ¼” clearance between the metal frame and the edge of glass panes. All elements are bolted together by a restraining bolt. Image 4.2 Principles applied: Structure & tolerance (the use of neoprene setting block to hold glass panes) A ¼” thick neoprene setting block is used under the top two glass panes to avoid direct contact of glass and metal frame. 4.3 Neoprene gasket Front plate restraining bolt hole 1/4" clearance Glass Silicone sealant joint D 3 = 3 4 " Rear plate Metal frame Silicone setting block 4.2 1/4" Neoprene setting block Silicone setting block 4.1 3/8" glass notch Image 4.1 Principles applied: Installation & tolerance (glass notches designed in the corner of glass panes) As shown in the left image, a restraining bolt at the central point of the joint holds all pieces together. Therefore, a 3/8” wide glass notch is designed at the corner of each glass pane to make enough room for connection. Fig. 10-16, Continued on next page 245 Image 4 Principles applied: Assembly (front plate restraining bolt) A bolt is used to hold all pieces together. Image 5 Principles applied: Structure, assembly, tolerance & aesthetics (the design of the joint) Image 4, 4.1, 4.2 and 4.3 explore the connecting methods of glass panes and clamping plates. Based on those images, the joint is designed as shown in Image 5. 4 Front plate Front plate restraining bolt 5 Front plate restraining bolt hole Front plate Neoprene gasket Glass Silicone sealant joint D 3 = 3 4 " 1/4" Neoprene setting block Metal frame Silicone setting block 5.1 Exterior Interior Front plate restraining bolt Glass Silicone setting block Rear plate Neoprene gasket Neoprene setting block Front plate Metal frame Image 5.1 Principles applied: Structure, assembly, tolerance & aesthetics (the design of the joint) Image 5.1 shows the side elevation of the joint. At this stage, the detailing of the joint is almost complete. Fig. 10-16, Continued on next page 246 Image 6 Principles applied: Aesthetics (recessed front plate restraining bolt hole and front plate decoration) The joint is improved aesthetically in two ways: a recessed bolt is used in the front plate restraining hole; a “X” shape decoration is designed on the surface of front plate. Image 6.1 Principles applied: Aesthetics (recessed front plate restraining bolt hole and front plate decoration) Based on Image 6, the front elevation of the joint is drawn as shown in the left image. 6 Front plate decoration Recessed front plate restraining bolt hole 6.1 Recessed front plate restraining bolt Glass Front plate 3/4" silicone sealant joint Front plate decoration 6.2 Front plate decoration Interior Exterior Recessed front plate restraining bolt hole Image 6.2 Principles applied: Aesthetics (recessed front plate restraining bolt hole and front plate decoration) Based on Image 6, the side elevation of the joint is drawn as shown in the left image. Fig. 10-16 Case study #3 - Illustration and description of Step 9 - Illustration of each image in Fig. 10-15 (Drawn based on ASI drawings) Chapter XI Case study four – Ha-Lo, Niles, Illinois 11.1 Introduction 11.1.1 Project information Climate Niles is close to Chicago, and therefore has very similar climate as Chicago, with a slightly higher precipitation in August, and slightly lower precipitation in May and June compared to Chicago (see 10.1.1 for the climate description of Chicago). The Latitude is 42.04 o N, and the Longtitude is 87.78 o W. (http://www.crh.noaa.gov/forecast/MapClick.php?CityName=Niles&state=IL&site=LOT) See Fig. 11-1 for (a) average temperature, (b) humidity, (c) sunshine, (d) precipitation, and (e) wind speed around the year in Niles. (a) Average temperature (b) Humidity Fig. 11-1, Continued on next page 247 (c) Sunshine (d) Precipitation (e) Wind speed (mph) Fig. 11-1 Niles climate data (http://www.city-data.com/city/Niles-Illinois.html) 248 249 General project information (Table 11-1) Project name Ha-Lo, Niles, Illinois Architect Murphy/Jahn Architects Engineers Cosentini (M/E/P); Peller & Associates (structural); Werner Sobek Ingenieure (special structures) Client Center Point Properties Tenant Halo Industries General contractor Harbour Contractors Concrete Olsen Construction Special structures, exterior steel Bowman Contractors Electrical Indicom Electric Insulated glass Viracon Glaszing Architectural Wall Solutions Horizontal blinds Levolux House Miscellaneous metals Western Architectural Iron Raised floor Interior Systems Special glass structures and skylight ASI Advanced Structures Inc. Table 11-1 General project information of case study #2 (Sommerhoff 2003, p.86) Brief introduction The building consists of a 4000-square-feet glass wall, a 12000-square-feet skylight as well as a 17000-square-feet interior glass. Aluminum components are used to support the insulated glass at the glazing joints. “Aluminum pinch plates are pinned to either a stainless-steel boot (for the fin wall) or a custom aluminum spider (for the skylight).” The architects developed a cast aluminum system previously for a project in Europe which might be able to be used in this project too. But because of budget and time, the cast aluminum system was replaced with “CNC machined components finished with a clear satin anodizing”. (Wright 2001, p.38) “The vault skylight is constructed of primary trusses at 15-ft. centers spanning in the 60-ft. dimension. Each truss uses a rolled steel pipe top chord, vertical pipe web members and a stainless steel underslung cable.” “Spanning between trusses are alternating glass fin purlins and steel pipe purlins at 5-ft. centers. The low-iron glass fin purlins are restrained against torsional buckling by small cables that connect to the adjacent pipe purlins.” (Wright 2001, p.38) 11.1.2 Images Fig 11-2 to 11-6 show the exterior view, interior view, plan, elevation and section of the glass wall of Ha-Lo, as well as the enlarged photos of the glass fittings used in the glass-fin wall and glass roof of the building. (Otmar 2001, p.199) (Otmar 2001, p.197) (Otmar 2001, p.200) (Otmar 2001, p.198) Fig. 11-2 Exterior photos of Ha-Lo 250 The following diagrams (Fig. 11-3) are the site plan, ground plan and elevations of Ha-Lo. Site Ground plan North and south elevation East and west elevation Fig. 11-3 Plan and elevation of Ha-Lo (Otmar 2001, p.195, 201) Fig 11-4 shows the interior photos of the glass wall. 251 (ASI) (ASI) (ASI) (Otmar 2001, p.216) (Otmar 2001, p.203) Fig. 11-4 Interior glass wall photos of Ha-Lo 252 Fig. 11-5 shows the typical section of the glass-fin wall. (Otmar 2001, p.215) (Sommerhoff 2003, p.87) The left image: (8) aluminum pinch plate; (9) stainless-steel tabs; (10) stainless-steel shelf; (11) stainless-steel cables; (12) extruded aluminum mullion; (13) laminated glass mullion; (14) aluminum grille; (15) concrete footing Fig. 11-5 Typical section and enlarged photo of the glass-fin wall of Ha-Lo 253 The following images (Fig. 11-6) show the details of glass fittings used in the glass wall and glass roof of Ha-Lo. Aluminum pinch plate used in glass wall (ASI) Aluminum pinch plate used in the ceiling (ASI) Stainless steel splice boot connector (Otmar 2001, p.217) Plan of the structural glass fin mullion (Otmar 2001, p.217) Fig. 11-6 Enlarged glass fitting photos of Ha-Lo 254 11.2 Detailing process for a typical section The south glass wall (Fig 11-7) is selected to illustrate the detailing process of a typical glass-fin wall section. Fig. 11-7 Glass wall elevation and plans (ASI, modified) The detailing process is explained as from 11.2.1 to 11.2.9. 255 11.2.1 Identify the building infrastructure (Fig. 11-8) (ASI, modified) Infrastructure type – Ground and floor (horizontal) Infrastructure material – reinforced concrete (stiff) In this project, the infrastructure consists of horizontal concrete floor slab and concrete ground foundations (see the wide lines in the image left above). This means that the back up structure will be vertical structure. Fig. 11-8 Case study #4 - Illustration and description of step 1 11.2.2 Determine modular size (Fig. 11-9) (ASI, modified) 5’ interval distance based on glass pane limitation and architectural elevation 11’ 1” and 14’3” vertical span due to three factors: the maximum size of glass pane; the maximum size of toughened glass-fin; and architectural elevation requirement In this project, the horizontal modular size is determined by both glass pane limitation and architectural objectives. The vertical modular size is determined by maximum size of structural glass-fin that can be manufactured. In this case, the decision of the section of back-up structure (glass-fin) affected the modular size. Fig. 11-9 Case study #4 - Illustration and description of step 2 256 11.2.3 Identify the back up structure (Fig. 11-10) Typical glass fin structure Custom designed glass fin Horizontal back up structure (lateral cable) (The middle and right images from ASI, modified) Primary structure – Vertical laminated toughened glass-fins are used as back up structure. Secondary structure – Lateral bracing cables are used to strengthen the structure. Material – laminated toughened glass-fin; stainless steel rod Fig. 11-10 Case study #4 - Illustration and description of step 3 11.2.4 Make a checklist of all elements based on four categories (Fig. 11-11) Category Elements Top horizontal element Bottom horizontal element Infrastructure Third floor reinforced concrete slab Ground floor reinforced concrete foundations Glass panels Glass fittings Back up structure elements Custom designed aluminum pinch plate and stainless steel splice boots Glass wall elements 1 1/16” thick double glazing 1 ¼” laminated toughened glass-fins as primary back up structure; 5/16” lateral bracing cables as secondary back up structure Portal frame beam Portal frame column Door beam Glass door Elements for openings Steel tube Steel tube 1” by 2” steel tube sqaure 15’ opening glass doors Additional devices N/A Fig. 11-11 Case study #4 - Illustration and description of step 4 (Summarized based on ASI drawings) 257 11.2.5 Define the position, shape and size of each element (Table 11-2 & Fig. 11-12) Find out the width of glass fins, which is determined by vertical span. The span is determined by infrastructure (the distance between floor concrete slab and ground concrete foundations). Find out the shape of glass fins, which is determined by architectural aesthetic requirements and the shape of concrete slab. The size of glass is determined by available products in consultation with architects. The sizes of custom designed glass fittings (aluminum pinch plate and stainless steel splice boots) are determined by both structural calculation and aesthetics. The size of horizontal bracing cables is determined by structural calculation as well as experiences. The sizes of portal frame beam, portal frame column and door beam are determined by both structural and aesthetical requirements. The design loads are (ASI data): 21 PSF (per square foot) for dead load 20 PSF for live load Vertical load 25 PSF for snow load (considering the building is located in Niles) Lateral load 80 MPH (miles per hour) lateral wind load (exposure C and 94’ building height) Thermal load Temperature range ±90oF Table 11-2 Case study #4 – Illustration and description of step 5 (1) Glass wall section Glass wall section looking at portal column of glass door Glass wall plan (ASI, modified) Fig. 11-12 Case study #4 - Illustration and description of step 5 (2) 258 259 11.2.6 Define all connections based on nine categories (Table 11-3 & Fig. 11-13) Category 1 Connections within glass wall Class + glass, glass + glass fin, glass fin + glass fin, glass fin + lateral cable Category 2 Connections within openings Glass door + portal frame beam, glass door + portal frame column, glass door + door beam, portal frame beam + portal frame column, portal frame beam + door beam Category 3 Connections within additional devices Does not apply in this case Category 4 Connections between glass wall and additional devices Does not apply in this case Category 5 Connections between glass wall and openings Glass fin + portal frame beam, glass + portal frame beam, glass + portal column Category 6 Connections between openings and additional devices Does not apply in this case Category 7 Connections between glass wall and infrastructure Glass + concrete slab (third floor), glass + concrete foundation (ground floor), glass fin + concrete slab (top), glass fin + concrete foundation (bottom), lateral cable + concrete slab (second floor) Category 8 Connections between openings and infrastructure Portal frame column + concrete foundation (ground floor) Category 9 Connections between additional devices and infrastructure Does not apply in this case Table 11-3 Case study #4 - Illustration and description of step 6 (1) Connections within glass wall and connections between glass wall and infrastructure (ASI, modified) Fig. 11-13 Case study #4 - Illustration and description of step 6 (2) 260 11.2.7 Define the material and method for each connector (Fig. 11-14) Eight major connection types are discribed in this section, which are: Glass + Glass, Glass + Spider, Glass + Strut, Strut + Rod, Glass + Ground, Glass + Roof, Rod + Ground, and Rod + Roof. These connections are explained in Fig. 11-14. Glass + Glass The glass panes are connected by structural silicone and backer rod. (ASI, modified) Glass + concrete slab Glass fin + concrete slab The glass fin is connected to the concrete slab by stainless steel splice boot. The boot is connected to a tongue plate & anchor assembly by slotted bolt to allow free vertical movement of glass fin wall. The tongue plate is screwed to the reinforced concrete slab. (ASI, modified) Fig. 11-14, Continued on next page 261 262 (ASI, modified) Glass + glass fin Glass fin + glass fin Glass fin + lateral cable The double-pane glass wall is connected to the laminated toughened glass fin (the vertical glass strips perpendicular to the glass wall) by custom designed aluminum pinch plate and stainless steel splice boot. The aluminum pinch plate is clipped to the stainless steel splice plate, and the splice plate is bolted to the laminated toughened glass fin. The top glass fin and bottom glass fin is connected by the splice boot. Since glass should be avoided to have direct contact to steel (otherwise glass is easy to get cracked due to highly concentrated stress), there should be always some elastic material to separate glass and steel. In this example, the Klinger-sil C4400 with a thickness of 3/32” is used to separate stainless steel splice boot and glass fin. According to Klinger-sil manufacturer’s product brochure, Klinger-sil C4400 is a "high quality non-asbestos grade based on aramid fiber with nitrile rubber binder" that are generally used for industrial sealing applications. (ASI, modified) Fig. 11-14, Continued on next page The left image shows that a 1/8” thick PTFE setting block is used between glass fin and aluminum pinch plate. Plus, a ¼” thick PTFE setting block is used to protect glass fin from having direct contact with steel plate. The Teflon PTFE product brochure describes the PTFE as a "high performance, high quality engineered plastic components". (ASI, modified) Fig. 11-14, Continued on next page 263 Glass + concrete foundation Glass fin + concrete foundation Glass is glued to steel frame by structural silicone and backer rod; the steel frame is bolted to splice boot; the stainless steel splice boot is anchored to the concrete foundation by four 5/8” (diameter) threaded rods. The glass fin is also connected to the concrete foundation by the bottom splice boot. The bottom splice boot is connected to glass fin by screwed bolts. Because the top boot that connects glass fin to the third floor concrete slab is designed with a slotted hole to allow free vertical movement of glass fin, the bottom boot does not need slotted holes. The PTFE setting block is also used here between glass fin and fin support block. (ASI, modified) Fig. 11-14, Continued on next page 264 265 (ASI, modified) Glass + portal frame beam Glass fin + portal frame beam Portal frame beam + portal frame column The glass fin is connected to the portal beam by means of the stainless steel portal boot, which is connected to the glass fin by screwed bolts. There is a ½” clearance between the portal boot and portal frame beam to allow free vertical movement of glass fin against the fixed door frame. (ASI, modified) Fig. 11-14, Continued on next page The left image shows that a ¼” thick PTFE setting block is used between the stainless steel boot attachment plate and glass fin to prevent the glass fin from contacting the steel plate directly. (ASI, modified) Fig. 11-14 Case study #4 - Illustration and description of step 7 266 11.2.8 Define any other requirements (Fig. 11-15) Special details are considered when steel plates are bolted to toughed glass fins. The boot bolt sub- assembly detail shown in the image left is a very good example to learn how to solve problems common in glass structures. 1. A 3/32” thick Klinger- sil is used between glass fin and stainless steel splice plate to avoid direct glass-metal contact. 2. The drilling hole in glass fin is bigger than the bolt diameter to allow enough tolerance between glass fin and bolt. 3. A plastic pipe and epoxy resin are used to further protect glass fin from being affected by the stainless steel fastener. (ASI, modified) Fig. 11-15 Case study #4 - Illustration and description of step 8 267 268 11.2.9 Detailing each connection Detailing a typical joint type (glass fin + glass wall) The detailing process is explained as below: 1). Step 1 – Draw concentric center line connections 2). Step 2 – Draw key connector size as dotted line 3). Step 3 – Determine position of boot bolts 4). Step 4 – Explore connector options 5). Step 5 – Design connector 6). Step 6 – Make adjustment The detailing of this typical joint answers the following questions: how the stainless steel splice boot connects the top glass fin to the bottom glass fin; how the splice boot is connected to the aluminum pinch plate; how the aluminum pinch plate is connected to the double glazing glass wall; and how the splice boot is connected to the glass pane joint. The following flowchart (Fig. 11-16) provides an overview of the detailing process. Enlarged images shown in Fig. 11-16 are explained in detail in Fig. 11-17. Fig. 11-16 Case study #4 - Illustration and description of step 9 - Overview of the detailing process for a typical glass fitting joint (Drawn based on ASI drawings) 269 270 Image 1 Principles applied: Structure & Aesthetics (the width of glass fin A 2 ) Assembly & Installation (the distance between glass and glass fin A 3 ) Manufacture & thermal control (the width of double glazing A 1 ) Determine the minimum width of glass fin A 2 (1’6”), generally 1/20 of the vertical span of glass fin. Since the infrastrure to which the glass fin is attached is the third floor concrete slab (top) and the ground floor concrete foundation, the span of glass fin is the total height between concrete slab and concrete foundation. The width of glass fin is also affected by aesthetical reasons which are usually determined by architects. Enough space A 3 (3 7/16”) should be designed between the glass and glass fin to allow easy installation of the aluminum pinch plate that will connect the glass to glass fin. The climate of Nile where the building is located affects the selection of glazing and its width A 1 (1 ¼”). Image 2 Principles applied: Tolerance & assembly (between the top glass fin and bottom glass fin B 2 ) Structure, manufacture, installation & assembly (the joint width of glass panes B B 1 ) To prevent buckling a half inch clearance B 2 is designed between the top glass fin and the bottom glass fin. The cleanrance is also designed for the connection of lateral cable and glass fin. Due to lack of data, the detailing of lateral cable is not shown here. The width of glass pane joint B 1 (1”) is affected by selected sealant material, connection method of glass and glass fin, and structural considerations. Fig. 11-17, Continued on next page Image 3 Principles applied: Structure (the number of boot bolts, the position of bolts and the distance between the bolts H & E) F = M/2e, where F is the force on the bolt; M is the moment; e is the distance between the bolts. Increasing of e decreases F. As a general rule, H is about equal to E. Image 4 Principles applied: Structure & aesthetics (the distance between the center of boot bolt hole to the edge of boot C 1 ) Structure & aesthetics (the distance between the center of glass pane joint and the center of aluminum pinch plate C 3 ) Structure, manufacture & tolerance (the thickness of the back boot plus the distance between the back boot and glass gin C 2 ) C 1 (2 ½”) and C 3 (1’) are determined by both structural calculation and aesthetics. C 2 (3/8”) includes the thickness of the back boot plate, plus the thickness of a certain elastic material between the back boot plate and glass fin. The elastic material used here is Klinger-sil C4400, with a thickness of 3/32”. The elastic material protects the glass fin from being restrained by the metal boot. Fig. 11-17, Continued on next page 271 Image 4.1 Principles applied: Structure & aesthetics (C 1 , C 4 , C 5 and C 6 ) C 1 , C 4 , C 5 and C 6 are determined by both structural and aesthetical reasons. C 1 = C 4 = 2 ½”; C6 = 3 ½”; C 5 = 1”. Image 5 Principles applied: Structure, manufacture, assembly, installation, tolerance & aesthetics (the design of aluminum pinch plate and glass-boot connection ) See Image 5.2 (next page) for the design of aluminum pinch plate that connects the double glazing glass wall to the stainless steel splice boot. See Image 5.3 (next page) for the design of the connection of glass pane joint and splice boot. Fig. 11-17, Continued on next page 272 Image 5.1 Principles applied: Structure, manufacture, assembly, installation, tolerance & aesthetics (the design of aluminum pinch plate; the design of glass-boot connection; and the design of boot bolt ) See Image 5.2 for the design of aluminum pinch plate that connects the double glazing glass wall to the stainless steel splice boot. See Image 5.3 for the design of the connection of glass pane joint and splice boot. See image 5.4 (next page) for the design of boot bolt connection. Fig. 11-17, Continued on next page 273 274 Image 5.2 & 5.3 Principles applied: Structure, manufacture, assembly & installation (using aluminum as the pinch plate material) Structure, manufacture & tolerance (the use of elastic material PTFE setting block between aluminum pinch plate and glass, and between stainless steel plate and glass) Structure, manufacture & tolerance (the use of elastic material Klinger-sil between stainless steel splice boot and glass fin) Structure & installation (the use of stainless steel fastener and stiffener) Water proofing & structure (glass sealant material structural silicone) Aesthetics & structure (the shape and size of aluminum pinch plate) The material and methods used as shown in Image 5.2 and Image 5.3: 1. Double glazing 2. 1/8” thick PTFE setting block and silicone sealant 3. Aluminum cover plate 4. Stainless steel fastener 5. 1/8” thick PTFE setting block 6. Aluminum backing member 7. Pin with clip 8. ½” stainless steel plate 9. 5/16” thick stainless steel splice boot 10. 3/32” Klinger-sil 11. ¼” thick back boot plate 12. 1 ¼” laminated toughened glass fin 13. ¼” thick PTFE setting block 14. ½” stainless steel plate 15. Structural silicone sealant and backer rod 16. ½” stainless steel stiffener plate Fig. 11-17, Continued on next page Image 5.4 Principles applied: Structure, manufacture, assembly, tolerance & aesthetics (the design of boot bolt through laminated toughened glass fin and stainless steel splice boot ) Please see Fig 11-15 in 11.2.8 for more details. Image 6 Principles applied: Aesthetics (the final adjustment of the shape of splice boot) Curved edge of the splice boot creates more elegant details. Fig. 11-17 Case study #4 - Illustration and description of step 9 - Illustration of each image in Fig. 11-16 (Drawn based on ASI drawings) 275 276 The following images (Image 4.2 to Image 4.5) in Fig 11-18 are examples of splice boot alternatives. The splice boot can be a simple square (Image 4.2), or a simple plate with curved edge (Image 4.2.1). Another way is to cover the glass fin with splice boot all around (image 4.4). Image 4.2.2 is the front elevation in which the splice boot only covers three sides of the glass fin; Image 4.4.1 shows the front elevation in which the splice boot cover all four sides of the glass fin. In stead of a single splice boot, Image 4.3, 4.3.1 and 4.3.2 show a solution of three separate boots. In this case, the top and bottom aluminum pinch plates should be moved to align with the top and bottom boot plates. Fig. 11-18 Case study #4 - Illustration and description of step 9 - Splice boot alternatives shown in Fig. 11-16 (Drawn based on ASI drawings) 277 Image 4.5 in Fig 11-18 shows another splice boot alternate. This solution express more clearly how the connections of top glass fin and bottom glass fin reacts to the structural behavior of glass fins. Fig 11-19 (a) shows the structural behavior of glass fin under lateral wind load. Due to the lateral wind load, the glass fin will deflect, resulting tension on one side of glass fin and compression on the other side. Because of the structural properties of glass, glass fin is stronger in resisting tension than compression. The design of glass fin connector needs to fully consider the structural behavior of glass fin under lateral loads. Fig 11-19 (b) and (c) show an example of glass fin connector that successfully solves the problem. Image 4.5 in Fig 11-18 is evoked from this example. (a) Structural behavior of glass fin under lateral load (b) Interior view of a glass fin connector (c) exterior view of a glass fin connector Fig. 11-19 Case study #4 - Illustration and description of step 9 - An example of splice boot alternatives (Nijsse 2003) 278 279 Chapter XII Conclusions This chapter includes three parts: feedback from peers and professionals; suggestions for future research; and useful sources related to methodology and future research. 12.1 Feedback from peers and professionals This section discusses feedback from the three groups listed below and then offers a brief conclusion based on this information. Peers (second year graduate students of USC Master of Building Science program) Detailing professionals (people from ASI and DewMac) Thesis advisors and other people attending the thesis review (Professor Schierle, Noble, Schiler, Spiegelhalter, Kensek, and Knowles) Feedback from MBS peers In March 2005, after the author completed the major research on detailing rules and process, an experiment was made by six USC Master of Building Sciences graduate students to test the methodology. The purposes of the experiment were: to verify the feasibility of the methodology; to test the efficiency of the methodology; to find out potential flaws; and to find out possible improvements. The planned time for the experiment was around four hours. The test included three parts. Firstly, the author made a PowerPoint presentation including background research (the basic knowledge of PSG wall systems), detailing principles (the rules), and an introduction of detailing process (the steps). Secondly, the author gave a simple glass wall frame, providing limitations on several elements, such as the size of the glass wall, the size and material of the glass panels, the orientation of the building and the building infrastructure. Thirdly, the author presents the detailing process in detail using a case study as demonstrations. In the mean time, the students created their details of the given glass wall following the process presented. Finally, the details made by the students have been reviewed by both the testers and the author, and conclusions were drawn accordingly. 280 However, the experiment did not exactly go as expected. Because of limited time, the author only finished part of the presentation, and left the final five of the total nine points of the detailing process uncovered. The results of the experiment indicated that: The background research regarding the knowledge of PSG wall systems and the detailing principals turn out to be successful. The participants came to have an overall understanding of the PSG wall systems and learned useful information involved in the detailing of the systems. Angela Vargas, one of the graduate students, commented that the presentation was well organized and the contents were exactly what she wanted to learn about the PSG wall systems. As an architect for several years, she appreciated the importance of learning the detailing and construction topics covered in the thesis. Since teaching and learning the detailing process was not complete, it is hard to evaluate the feasibility or efficiency of the methodology. However, at least one conclusion can be made from this experiment: the detailing methodology developed in this thesis is not a “quick-learning-tool” that can teach students to complete the design and detailing in a short time, such as several hours or one day. It is neither a “model” or “program” that can be utilized to create details. Instead, the methodology tends to teach students the important issues involved in a detailing design, and a possible process they can follow to start and organize a detailing design. The methodology acknowledges the inherent versatility and complexity of detailing, and therefore tries to teach the students how to fish instead of giving them the fish directly. Because the methodology explores a wide range of information of the PSG wall systems, emphasizes both the rules and the steps, and provides a large number of examples as illustrations, students are expected to spend much longer time to learn it before being able to apply the method into real detailing projects. Although the experiment did not perform as expected, it was at least partially successful not only because the background research, but also because several valuable comments were made for improvement. Andrew Lee indicated that there should be a clearer statement of how the methodology defines design and detailing. It should give clear instructions of what information belongs to design 281 decisions and what belongs to detailing decisions. The thesis states that detailing is design at a small scale. A range of the detailing scales the thesis tends to explore is given (see 1.1). Elizabeth Valmont mentioned that she understood very clearly the structure of the thesis, from PSG wall systems, to the principles one needs to consider when designing details, to the detailing process one may follow to create details. She also pointed out that she prefers to do step 3 before step 2. This is again a question of the sequence of the steps. The author later provides a reason of the sequence selected in the thesis. Douglas Noble also participated in the experiment. His comments can be found in the feedbacks from thesis advisors. Feedback from ASI (Advanced Structures Incorporated) On June 07 th , the author made a presentation of the methodology to ASI in their local office. Professor Schierle attended the event. There were around 20 persons from ASI attending the presentation. Because the methodology is for architectural students and young architects, the purpose of the presentation is not to verify the feasibility or efficiency of the methodology, but to get a clue of how professionals and even experts will evaluate the methodology, and to get suggestions for improvement. The 40-minutes presentation turned out to be successful. One young lady (she had one year experience working in ASI at that time) said that the presentation was very informative, and she felt she learnt a lot of very useful information. And she mentioned she wished she had already known these things before joining ASI. Another ASI employee, Robo (he has more than 10 years of experience in ASI) commented that the webpage developed for the methodology is very well organized and informative. He suggested putting the web-page on internet to educate more people. Dr. T.J. de Ganyard suggested adding links to some manufacturers related to PSG wall systems, such as silicone manufacturers, glass manufacturers, etc. This suggestion was adopted later. Feedback from Dewhurst Macfarlane and Partners PC The author also made a presentation to Mr. Macfarlane and Ms. from Dewhurst Macfarlane and Partners PC. Mr. Macfarlane showed great interests in the thesis. He agreed with the definition and categories of PSG wall systems developed in the thesis, and gave positive comments on the 282 failure studies. He also pointed out that some of the examples used in the thesis should be straight- cable supported instead of cable-net supported. He suggested giving him a copy of the web-page of the thesis so that he could read everything in detail. Feedback from advisors and other teachers Professor Schierle thinks the methodology would be very useful for students and young architects from his long-term teaching and professional experiences. He realizes that it is impossible to cover all subjects related to detailing, and therefore he suggests focusing only on several subjects that are critical in creating a functional and constructible detailing, but are seldom formally conveyed to students, such as tolerance and water tightness, etc. He also suggests that the images illustrating each step should be big enough, and each image should be accompanied with detailed instruction, so that students can get the points easily. Professor Noble made two major comments. One was that there should be no steps in any form of design. Steps may limit the free thinking of designers, and following the steps will result in a specific type of designs. The other comment he made is to create a breakdown table to list out all of the possible ‘arguments’ regarding the selection of the elements involved in a detailing of PSG wall systems, such as the factors influencing the choice of back up structure. Regarding the first comment, the author explains the reasons of using the steps, and points out the fact that the sequence of the steps is not fixed; different sequence might lead to different results. But the exploration of the results of different sequences is left to future research. The table mentioned in the second comment is not available yet due to the complicate characteristics of PSG wall systems and lack of data. However, readers can get useful information from Chaper 4 which describes the material properties and components that are involved in PSG wall systems. Further research is still needed to make such kind of comprehensive table. Because of continuously emerging technologies, it is impossible to create a complete table that covers all issues; continuous supplement to the table is necessary. Professor Schiler suggested that there should be some guides provided in the detailing process, such as why the steps should be there, and the rules for each step. This suggestion was then adopted. For each step, a purpose is stated, and a series of rules are explored. 283 Professor Spiegelhalter gave many useful suggestions regarding both the thesis and the web page. One major comment is that the design and detailing should not be separated because they are interrelated. The other major comment was that energy and sustainable issues should be emphasized. The author completely agrees on the first comment: detailing is a smaller scale of design. For the second comment, the author tried to supplement some energy and sustainable issues that affect the detailing design. Because the focus of the thesis is not on these topics, the thesis does not include a thorough research on this part. However, detailing regarding energy and sustainability issues is a very important and meaningful topic. The author expects to do further research on this topic in the future. Professor Kensek emphasized that the detailing methodology needs to be tested by students or young architects. This is a very important point. The author then arranged an experiment with the help of Professor Noble and tried to test the methodology in around four hours. It turned out that the test was impossible to finish within such a short time frame. Further action on the test is necessary. Professor Knowles brought up the idea to study the failure projects to test the methodology from the opposite side. The author tried to collect as much information as she could, and made some progress on this topic. However, it remains unrealistic to use failure projects to test the methodology for two reasons. Firstly because of the limited number of the known projects caused by inappropriate detailing designs, and secondly because of the impossibility to know the detailing process used by the designers to make the details for these projects Nonetheless, the studies of failure detail examples are very useful in emphasizing what needs to be avoided and what needs to be enhanced in detailing designs. Future research may be conducted to further this topic. Overall From all of the feedbacks, some conclusions can be made: The research part on the exploration of PSG wall systems and the detailing principles (rules) turns out to be comprehensive and systematic. The detailing process was not completely tested yet. Although some experts like ASI, commented that the process looks useful for students and young architects, the exact feasibility and 284 efficiency of the process still remain unknown. Further experiments are needed in order to make a final conclusion. 12.2 Suggestions for future research The thesis introduces a methodology to teach architectural detailing, based on rules and steps using point-supported glass walls as case studies. Point-supported glass walls are among the most complex and challenging detailing examples. Because of the time issues, and also because of emerging new technologies and new products, the thesis is not able to cover all of the subjects related to PSG. An instructor of MIT said, “Don’t try to cover everything because it can never be done. Instead, one should try to uncover part of the subject and introduce it to the students. The students can then learn the rest by themselves. (Allen 2005, p.7). However, it is always useful to give some suggestions for future studies as listed below: Keep updating the state-of-art of case studies. Keep seeking failure detailing examples and making conclusions from the failures. Have students or young architects to test the methodology completely and thoroughly. Explore more detailing processes for typical detailing joints. Publish and improve the web-page developed for the thesis. Keep updating the state-of-art case studies. These include all “good” detailing examples that represent top achievements in considering part or all of the detailing principles, such as tolerance, water tightness and integration. They also include the projects using new technology, new materials, and new fabrication or installation methods; or projects that have significantly low cost, good maintainability, or sustainability. Keep studying failure detailing examples and make conclusions from the failures. Firstly, a complete list of failure types should be introduced, such as the failures caused by water leakage, corrosion, glass breakage because of thermal stress or structural loads, staining of glass façade, or energy inefficiency because of inappropriate details. Secondly, failure detailing examples grouped by the failure types are collected for detailed studies. Thirdly, lessons learned from these failure examples are used as a guide to avoid similar failures in the future. 285 Have students or young architects test the methodology completely and thoroughly. An ideal way to accomplish this is to select a group of students or young architects and ask them to create details for a specified PSG project and keep their details for future usage. Then make a one-week intensive training program for this group, teaching them everything involved in the thesis. At the end of training, the group is asked again to create details for the same project and their details are recorded. This group of testers returns to their detailing practice for a period of time (one month, for example, during which they can keep learning the methodology on their own if they want). Finally, this group comes back together again, and completes two tasks: first, they are asked to create details for the same project the third time; secondly, they are asked to write down on a piece of paper the answers to several questions such as what they think they learned from the training, how effective the methodology is, to what degree the introduced methodology affect their detailing work, if they continue to learn the methodology after the one week training or not, or if there is anything to improve regarding the methodology and the training program. Then, all of the details made by the group in three rounds are compared; the written answers are studied carefully; and finally conclusions may be drawn from answers to the following questions: Was the one-week training program effective? Was the methodology feasible? How does the methodology affect detailing work and to what degree? What are the differences between the details the group made in the second round and those made in the third round? Does the methodology work better after a period of time than just following the completion of a one-week training program? If the answer is yes, then the methodology again turns out to be a way to teach people to fish rather than to give them fish directly. It shows that the methodology works in a way to affect people’s thinking style and habits. This is exactly what the author expects. Are there any differences between the details made by people who continue studying the methodology during the one-month detailing practice and the ones by people who do not? 286 Are the former ones better than the latter ones? If the answers are yes, it further enhances the efficiency of the methodology. What else can be done to improve the methodology? Explore more detailing processes for typical detailing joints. Study more typical detailing items, categorize them into logical groups and provide more instructions of the possible detailing process for these items. For instance, some typical groups can be the detailing joints between the roof and glass wall, the joints between the wall and floor, and joints of the cable-net and glass panels. Publish and improve the web-page developed for the thesis. First publish the web-page. In order to do this, copyright permission of all of the images and case studies used in the web must be obtained. And then possible ways may be explored to improve the interests and efficiency of the web-based teaching tool, such as: Update the date frequently. This is especially useful to update state-of-the-art case studies. Make the teaching and learning process more interactive. For example, people may take on- line tests to make details following the introduced methodology and see the results instantly. Other ways such as the animations of detailing steps and 3D detailing models can also increase the interaction effectively. Collect instant on-line feedback to authors from a variety of reviews including teachers, detailing professionals and students, and then the authors can modify the methodology accordingly. 12.3 Useful sources Books on architectural detailing Principles of Architectural Detailing, by Stephen Emmit, John Olie, and Peter Schmid, 2004 Architectural detailing : function constructability aesthetics, by Edward Allen, 1993 Details in architecture : creative detailing by some of the world's leading architects, v.1, v.2, v.3, v.4 and v.5 287 Books on glass and glass structure Glass buildings: material, structure, and detail / Heinz W. Krewinkel; [translated into English by Gerd Söffker and Philip Thrift]. Boston, Mass: Birkhäuser Verlag, c1998. Glass canopies / Maritz Vandenberg. Chichester, West Sussex: Academy Editions; Lanhan, MD: Distributed to the trade in the U.S.A. by National Book Network, 1997. Subject: Glass canopies, Architectural. Subject: Roofs--Design and construction. Subject: Glass construction. Series: (Detail in building) Structural glass / Peter Rice, Hugh Dutton. London; New York: E & FN Spon, c1995. Glass Construction Manual, by Schittch, Staib, Balkow, Schuler, and Sobek, 1999 Falling glass, by Loughran, 2003 See complete bibliography for more information. Glass structure consultant Advanced Structures Incorporated, http://www.asidesign.com/ Dewhurst Macfarlane and Partners, http://www.dewmac.com James Carpenter Design Associates Inc, http://www.jcdainc.com Arup Associates, http://www.arup.com Glass manufacturers Pilkington, http://www.pilkington.com SAINT-GOBAIN Group Corporate, http://www.saint-gobain.com Sealants manufacturers Dow Corning, http://www.dowcorning.com 288 Bibliography ABEL, C., 1991. 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Resources from Internet http://sweets.construction.com/ http://www.allaboutvision.com http://www.asidesign.com/ ASI (Advanced Structures Incorporated) http://www.city-data.com/city/Chicago-Illinois.html http://www.city-data.com/city/Las-Vegas-Nevada.html 292 http://www.city-data.com/city/Niles-Illinois.html http://www.city-data.com/city/Stamford-Connecticut.html http://www.city-data.com/states/Connecticut-Climate.html http://www.crh.noaa.gov/forecast/MapClick.php?CityName=Niles&state=IL&site=LOT http://www.dewmac.com/frame.htm Dewhurst Macfarlane and Partners http://www.dictionary.com http://www.emporis.com/ http://www.glassrecruiters.com/info.asp http://www.guardian.co.uk http://www.healthybuilding.net/pvc/index.htm The Healthy Building Network http://www.squ1.com http://www.structural.de/ Structural Glass Design Guide http://www.ubs.com/ http://www.washington.edu/ http://www.wordtravels.com/Cities/Illinois/Chicago/Climate http://www.wordtravels.com/Cities/Nevada/Las+Vegas/Climate http://www.wwglass.com/ Appendix A Sample web pages developed for the detailing methodology Fig. A-1, Fig. A-2, Fig. A-3, Fig. A-4 and Fig. A-5 show the sample web pages developed for the detailing methodology. Fig. A-1 Sample webpages – Homepage 293 Fig. A-2 Sample webpages – Rules Fig. A-3 Sample webpages – Process 294 Fig. A-4 Sample webpages – Demonstrations (1) Fig. A-5 Sample webpages – Demonstrations (2) 295

Abstract (if available)

Abstract Architectural detailing is primarily left to experience in professional practice rather than formal education. This thesis assumes a methodology can be developed to teach students and young architects architectural detailing. The methodology is based on rules and a process, considering assembly, installation, tolerance, functionality, and aesthetics. It is illustrated and demonstrated on case studies of Point-Supported-Glass (PSG) walls, which present some of the most complex detailing challenges with potential flaws, ranging from assembly problems to leaks.

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University of Southern California Dissertations and Theses

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Asset Metadata

Creator Cheng, Xiaojun (author)

Core Title A methodology for detailing applied to point-supported-glass wall systems

School School of Architecture

Degree Master of Building Science

Degree Program Building Science

Defense Date 05/10/2005

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag Architecture,case study,detailing,detailing methodology,education,OAI-PMH Harvest,point supported glass,PSG

Language English

Advisor Schierle, G. Goetz (committee chair), Noble, Douglas (committee member), Schiler, Marc (committee member), Spiegelhalter, Thomas (committee member)

Creator Email xiaojuncheng@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m291

Unique identifier UC1118161

Identifier etd-Cheng-20070226 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-169052 (legacy record id),usctheses-m291 (legacy record id)

Legacy Identifier etd-Cheng-20070226.pdf

Dmrecord 169052

Document Type Thesis

Rights Cheng, Xiaojun

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Repository Name Libraries, University of Southern California

Repository Location Los Angeles, California

Repository Email cisadmin@lib.usc.edu