TY - BOOK AU - McAllister,Therese AU - Corley,Gene ED - United States ED - Greenhorne & O'Mara ED - United States TI - World Trade Center building performance study: data collection, preliminary observations, and recommendations SN - 0160673895 AV - HD7293 L5567 2002 PY - 2002/// CY - Washington, DC PB - Federal emergency management agency KW - World TRade Center New York, N.Y KW - Design and construction KW - Local KW - Skyscraper KW - New York (State) KW - New York KW - September 11 Terrorist Attacks , 2001 KW - Office buildings KW - Fires and fire prevention KW - Tall buildings KW - Building failures N1 - "Produced by Greenhorne & O' Mara, Inc. (G&O) under contract EMW-99-CO-0267"- - T.p. verso; Includes bibliographical references; Table of Contents: Executive Summary -- 1 Introduction -- 1.1 Purpose and Scope of Study 1-1 -- 1.2 WTC Site 1-2 -- 1.3 Timeline and Event Summary 1-4 -- 1.4 Response of the Engineering Community 1-8 -- 1.4.1 Local Authorities 1-8 -- 1.4.2 SEAoNY Participation 1-10 1.5 Overview of Building Codes and Fire Standards 1-15 -- 1.5.1 Building Codes 1-15 -- 1.5.2 Unusual Building Loads 1-16 -- 1.5.3 Overview of Fire Structure Interaction 1-17 -- 1.5.3.1 ASTM E119 Standard Fire Test 1-18 -- 1.5.3.2 Performance in Actual Building Fires 1-18 -- 1.6 Report Organization 1-20 -- 1.7 References 1-21 -- 2 WTC 1 and WTC 2 -- 2.1 Building Descriptions 2-1 -- 2.1.1 General 2-1 -- 2.1.2 Structural Description 2-1 -- 2.1.3 Fire Protection -- 2.1.3.1 Passive Protection 2-12 -- 2.1.3.2 Suppression 2-12 -- 2.1.3.3 Smoke Management 2-13 -- 2.1.3.4 Fire Department Procedures 2-13 -- 2.1.4 Emergency Egress 2-13 -- 2.1.5 Emergency Power 2-14 -- 2.1.6 Management Procedures 2-14 -- 2.2 Building Response 2-15 -- 2.2.1 WTC 1 2-15 -- 2.2.1.1 Initial Damage From Aircraft Impact 2-15 -- 2.2.1.2 Fire Development 2-15 -- 2.2.1.3 Evacuation 2-21 -- 2.2.1.4 Structural Response to Fire Loading 2-24 -- 2.2.1.5 Progression of Collapse 2-27 -- 2.2.2 WTC 2 2-27 -- 2.2.2.1 Initial Damage From Aircraft Impact 2-27 -- 2.2.2.2 Preliminary Structural Analysis 2-32 -- 2.2.2.3 Fire Development 2-34 -- 2.2.2.4 Evacuation 2-35 -- 2.2.2.5 Initiation of Collapse 2-35 -- 2.2.2.6 Progression of Collapse 2-35 -- 2.2.3 Substructure 2-35 -- 2.3 Observations and Findings 2-36 -- 2.4 Recommendations 2-39 -- 2.5 References 2-40 -- 3 WTC 3 -- 3.1 Design and Construction Features 3-1 -- 3.2 1993 Attack 3-5 -- 3.3 2001 Attacks 3-5 -- 3.3.1 Fire and Evacuation 3-5 -- 3.3.2 Building Response 3-6 -- 3.4 Observations 3-8 -- 3.5 Recommendations 3-8 -- 3.5 References 3-8 -- 4 WTC 4 , 5, and 6 -- 4.1 Design and Construction Features 4-1 -- 4.1.1 Structural Design Features 4-1 -- 4.1.2 Fire Protection Features 4-2 -- 4.2 Building Loads and Performance 4-4 -- 4.2.1 Impact Damage to WTC 5 4-7 -- 4.2.2 Fire Damage 4-9 -- 4.3 Analysis of Building Performance 4-10 -- 4.3.1 Steel and Frame Behavior 4-10 -- 4.3.2 WTC 5 Local Collapse Mechanisms 4-12 -- 4.4 Observations and Findings 4-16 -- 4.5 Recommendations 4-21 -- 4.6 References 4-21 -- 5 WTC 7 -- 5.1 Introduction 5-1 -- 5.2 Structural Description 5-3 -- 5.2.1 Foundations 5-3 -- 5.2.2 Structural Framing 5-4 -- 5.2.3 Transfer Trusses and Girders 5-4 -- 5.2.4 Connections 5-8 -- 5.3 Fire Protection Systems 5-10 -- 5.3.1 Egress Systems 5-10 -- 5.3.2 Detection and Alarm 5-10 -- 5.3.3 Compartmentalization 5-11 -- 5.3.4 Suppression Systems 5-12 -- 5.3.5 Power 5-13 -- 5.4 Building Loads 5-13 -- 5.5 Timeline of Events Affecting WTC 7 on September 11 , 2001 5-16 -- 5.5.1 Collapse of WTC 2 5-16 -- 5.5.2 Collapse of WTC 1 5-16 -- 5.5.3 Fires at WTC 7 5-20 5.5.4 Sequence of WTC 7 Collapse 5-23 -- 5.6 Potential Collapse Mechanism 5-24 -- 5.6.1 Probable Collapse Initiation Events 5-24 -- 5.6.2 Probable Collapse Sequence 5-30 -- 5.7 Observations and Findings 5-31 -- 5.8 Recommendations 5-32 -- 5.9 References 5-32 -- 6 Bankers Trust Building -- 6.1 Introduction 6-1 -- 6.2 Building Description 6-1 -- 6.3 Structural Damage Description 6-4 -- 6.4 Architectural Damage Description 6-6 -- 6.5 Fireproofing 6-10 -- 6.6 Overall Assessment 6-10 -- 6.7 Analysis 6-11 -- 6.7.1 Key Assumptions 6-12 -- 6.7.2 Model Refinement 6-12 -- 6.7.3 Simulation of Nonlinear Behavior 6-13 -- 6.7.4 Connection Details 6-13 -- 6.7.5 Connection Behavior 6-14 -- 6.8 Observations and Findings 6-15 -- 6.9 Recommendations 6-16 -- 6.10 References 6-16 -- 7 Peripheral Buildings -- 7.1 Introduction 7-1 -- 7.2 World Financial Center 7-4 -- 7.2.1 The Winter Garden 7-4 -- 7.2.2 WTC 3, American Express Building 7-5 -- 7.3 Verizon Building 7-7 -- 7-4 30 West Broadway 7-13 -- 7.5 130 Cedar Street 7-14 -- 7.6 90 West Street 7-15 -- 7.7 45 Park Place 7-17 -- 7.8 One Liberty Plaza 7-17 -- 7.9 Observations and Findings 7-19 -- 7.10 Recommendations 7-19 -- 7.11 References 7-19 -- 8 Observations, Findings, and Recommendations -- 8.1 Summary of Report Observations , Findings and Recommendations 8-1 -- 8.2 Chapter Observations , Findings , and Recommendations 8-2 -- 8.2.1 Chapter 1 : Building Codes and Fire Standards 8-2 -- 8.2.2 Chapter 2. WTC 1 and WTC 2 8-2 -- 8.2.2.1 Observations and Findings 8-2 -- 8.2.2.2 Recommendations 8-5 -- 8.2.3 Chapter 3: WTC 3 8-6 -- 8.2.3.1 Observations 8-6 -- 8.2.3.2 Recommendations 8-6 -- 8.2.4 Chapter 4: WTC 4 , 5 , and 6 8-6 -- 8.2.4.1 Observations and Findings 8-6 -- 8.2.4.2 Recommendations 8-7 -- 8.2.5 Chapter 5: WTC 7 8-7 -- 8.2.5.1 Observations and Findings 8-7 -- 8.2.5.2 Recommendations 8-8 -- 8.2.6 Chapter 6: Bankers Trust 8-8 -- 8.2.6.1 Observations and Findings 8-8 -- 8.2.6.2 Recommendations 8-9 -- 8.2.7 Chapter 7: Perpheral Buildings 8-10 -- 8.2.7.1 Observations and Findings 8-10 -- 8.2.7.2 Recommendations 8-10 -- 8.2.8 Appendix C: Limited Metallurgical Examination 8-10 -- 8.2.8.1 Observations and Findings 8-10 -- 8.2.8.2 Recommendations 8-11 -- 8.3 Building Performance Study Recommendations for Future Study 8-11 -- 8.3.1 National Response 8-11 -- 8.3.2 Interaction of Structural Elements and Fire 8-11 -- 8.3.3 Interaction of Professions in Design 8-12 -- 8.3.4 Fire Protection Engineering Discipline 8-12 -- 8.3.5 Building Evacuation 8-12 -- 8.3.6 Emergency Personnel 8-12 -- 8.3.7 Education of Stakeholders 8-13 -- 8.3.8 Study Process 8-13 -- 8.3.9 Archival Information . 8-13 -- 8.3.10 SEANY Structural Engineering Emergency Response Plan 8-13 -- A Overview of Fire Protection in Buildings -- A.1 Introduction A.2 Fire Behavior A-1 -- A.2.1 Burning Behavior of Materials A-1 -- A.2.2 Stages of Fire Development A-1 -- A.2.3 Behavior of Fully Developed Fires A-4 -- A.3 Structural Response to Fire A-4 -- A.3.1 Effect of Fire on Steel A-5 -- A.3.1.1 Introduction A-5 -- A.3.1.2 Evaluating Fire Resistance . A-5 -- A.3.1.3 Response of High-rise, Steel-frame Buildings in Previous Fire Incidents A-6 -- A.3.1.4 Properties of Steel A-9 -- A.3.1.5 Fire Protection Techniques for Steel A-10 -- A.3.1.6 Temperature Rise in Steel A-14 -- A.3.1.7 Factors Affecting Performance of Steel Structures in Fire A-14 -- A.3.2 Effect of Fire on Concrete A-17 -- A.3.2.1 General A-19 -- A.3.2.2 Properties of Lightweight Concrete A-19 -- A.3.3 Fire and Structural Modeling A-19 -- A.4 Life Safety A-22 -- A.4.1 Evacuation Process A-23 -- A.4.2 Analysis , A-24 -- A.5 References A-24 -- B Structural Steel and Steel Connections A-26 -- B.1 Structural Steel B-1 -- B.2 Mechanical Properties B-2 -- B.3 WTC 1 and WTC 2 Connection Capacity B-4 -- B.3.1 Background B-4 -- B.3.2 Observations B-5 -- B.3.3 Connectors B-5 -- B.4 Examples of WTC 1 and WTC 2 Connection Capacity B-7 -- B.4.1 Bolted Column End Plates B-7 -- B.4.2 Bolted Spandrel Connections B-8 -- B.4.3 Floor Truss Seated End Connections at Spandrel Beam and Core B-9 -- B.4.4 WTC 5 Column-tree Shear Connections B-12 -- B.5 References B-14 -- C Limited Metallurgical Examination C-1 -- C.1 Introduction C.2 Sample 1 (From WTC 7) C-1 -- C.3 Summary for Sample 1 C-5 -- C.4 Sample 2 (From WTC 1 or WTC 2) C-5 -- C.5 Summary for Sample 2 C-13 -- C.6 Suggestions for Future Research. C-13 -- D WTC Steel Data Collection D-1 -- D.1 Introduction D-1 -- D.2 Project Background D-2 -- D.3 Methods. D-2 -- D.3.1 Identifying and Saving Pieces D-5 -- D.3.2 Documenting Pieces D-8 -- D.3.3 Getting Coupons D-10 -- D.4 Data Collected D-13 -- D.5 Conclusions and Future Work D-13 -- D.6 References Aircraft Information General Specifications E-1 -- F Structural Engineers Emergency Response Plan -- G Acknowledgments -- H Acronyms and Abbreviations -- I Metric Conversions -- Tables -- Table 1.1 Timeline of Major Events 1-10 -- Table 2.1 Estimated Openings in Exterior Walls of WTC 1 2-23 -- Table 5.1 WTC 7 Tenants 5-2 -- Table 5.2 WTC 7 Fuel Distribution Systems 5-14 -- Table 7.1 DoB/SEANY Cooperative Building Damage Assessment - November 7, 2001 7-3 -- Table A.1 Peak Heat Release Rates of Various Materials ( NFPA 92B and NFPA 72 ) A-3 -- Table A.2 Fire Duration in Previous Fire Incidents in Steel-frame Buildings A-10 -- Table A.3 Critical Temperatures for Various Types of Steel A-15 -- Table A.4 Test Methods for Spray-applied Fireproofing Materials A-18 -- Figures -- Chapter 1 -- Figure 1-1 WTC site map 1-3 -- Figure 1-2 Approximate flight paths of aircraft 1-5 -- Figure 1-3 WTC impact locations and resulting fireballs 1-5 -- Figure 1-4 Areas of aircraft debris impact 1-6 -- Figure 1-5 Fireball erupts on the north face of WTC 2 as United Airlines Flight 175 strikes the building 1-7 -- Figure 1-6 View of the north and east faces showing fire and impact damage to both towers 1-7 -- Figure 1-7 Schematic depiction of areas of collapse debris impact, based on aerial photographs and documented damage 1-9 -- Figure 1-8 Seismic recordings on east-west component at Palisades , NY , for events 1-9 at WTC on September 11 , 2001 , distance 34 km 1-11 -- Figure A Satellite photograph of the WTC site taken before the attacks. 1-12 -- Figure 1-9B Satellite photograph of the WTC site taken after the attacks 1-13 -- Figure 1-10 Comparison of high-rise building and aircraft sizes 1-19 -- Chapter 2 -- Figure 2-1 Representative floor plan (based on floor plan for 94th and 95th floors of WTC 1) 2-2 -- Figure 2-2 Representative structural framing plan, upper floors. 2-4 -- Figure 2-3 Partial elevation of exterior bearing-wall frame showing exterior wall module construction 2-6 -- Figure 2-4 Base of exterior wall frame 2-7 -- Figure 2-5 Structural tube frame behavior 2-7 -- Figure 2-6 Floor truss member with details of end connections 2-8 -- Figure 2-7 Erection of prefabricated components, forming exterior wall and floor deck units 2-9 -- Figure 2-8 Erection of floor framing during original construction. 2-9 -- Figure 2-9 Cross-section through main double trusses, showing transverse truss. 2-9 -- Figure 2-10 Outrigger truss system at tower roof. 2-10 -- Figure 2-11 Location of subterranean structure... 2-11 -- Figure 2-12 Floor plan of 94th and 95th floors of WTC 1 showing egress stairways 2-14 -- Figure 2-13 Zone of aircraft impact on the north face of WTC 1. 2-16 -- Figure 2-14 Approximate zone of impact of aircraft on the north face of WTC 1. 2-17 -- Figure 2-15 Impact damage to the north face of WTC 1 2-18 -- Figure 2-16 Impact damage to exterior columns on the north face of WTC 1 2-18 -- Figure 2-17 Approximate debris location on the 91st floor of WTC 1 2-19 -- Figure 2-18 Landing gear found at the corner of West and Rector Streets 2-19 -- Figure 2-19 Redistribution of load after aircraft impact. 2-20 -- Figure 2-20 Expansion of floor slabs and framing results in outward deflection of columns and potential overload 2-25 -- Figure 2-21 Buckling of columns initiated by failure of floor joist connections 2-26 -- Figure 2-22 Catenary action of floor framing on several floors initiates column buckling failures. 2-26 -- Figure 2-23 Aerial photograph of the WTC site after September 11 attack showing adjacent buildings damaged by debris from the collapse of WTC 1 2-28 -- Figure 2-24 Southeast corner of WTC 2 shortly after aircraft impact. 2-28 -- Figure 2-25 Approximate zone of impact of aircraft on the south face of WTC 2. 2-29 -- Figure 2-26 Impact damage to the south and east faces of WTC 2 2-30 -- Figure 2-27 Impact damage to exterior columns on the south face of WTC 2. 2-30 -- Figure 2-28 Conflagration and debris exiting the north wall of WTC 2, behind WTC 1. 2-31 --Figure 2-29 A portion of the fuselage of United Airlines Flight 175 on the roof of WTC 5 2-32 Figure 2-30 North face of WTC 2 opposite the zone of impact on the south face, behind WTC 1. 2-33 -- Figure 2-31 Plot of column utilization ratio at the 80th floor of WTC 2, viewed looking outward.... The top portion of WTC 2 falls to the east, then south, as viewed from 2-34 -- Figure 2-32 the northeast. 2-36 -- Chapter 3 -- Figure 3-1 Developed north and west elevations. 3-2 -- Figure 3-2 Developed south and east elevations. 3-2 -- Figure 3-3 Typical hotel floor plan. 3-3 -- Figure 3-4 Typical hotel floor framing plan. 3-4 -- Figure 3-5 Typical transverse bracing elevation. 3-5 -- Figure 3-6 Exterior columns from the collapse of WTC 2 falling on the southern part of WTC 3 3-6 -- Figure 3-7 Partial collapse of WTC 3 after collapse of WTC 2. 3-7 -- Figure 3-8 Remains of WTC 3 after collapse of WTC 1 and WTC 2 3-8 -- Chapter 4 Figure 4-1 Typical floor plan for WTC 5. 4-2 -- Figure 4-2 Typical column-tree system (not to scale) 4-3 -- Figure 4-3 Typical interior bay framing in WTC 5. 4-3 -- Figure 4-4 Stairway enclosure core locations in WTC 5 4-4 -- Figure 4-5 Damage to WTC 4 4-5 -- Figure 4-6 Damage to WTC 5 4-5 -- Figure 4-7 Approximate locations of damaged floor areas in WTC 5 4-6 -- Figure 4-8 Damage to WTC 6 4-8 -- Figure 4-9 Impact damage to WTC 6 4-8 -- Figure 4-10 Impact damage to the exterior façade of WTC 6 4-9 -- Figure 4-11 WTC 5 façade damage 4-10 -- Figure 4-12 Impact damage to WTC 5 4-11 -- Figure 4-13 WTC 5 on fire 4-13 -- Figure 4-14 Deformed beams in WTC 5 4-13 -- Figure 4-15 Unburned bookstore in WTC 5 4-14 -- Figure 4-16 Looking through the door into the undamaged stair tower in WTC S 4-14 -- Figure 4-17 Buckled beam flange and column on the 8th floor of WTC 5 that was weakened by fire 4-15 -- Figure 4-18 Internal collapsed area in WTC 5 4-16 -- Figure 4-19 Internal collapsed area in WTC 5 4-17 -- Figure 4-20 Internal collapsed area in WTC 5 4-18 -- Figure 4-21 Internal collapsed area in WTC 5 with closeup of connection failure at column tree 4-18 -- Figure 4-22 Connection samples 4-19 -- Chapter 5 -- Figure 5-1 Foundation plan - WTC7 5-3 -- Figure 5-2 Plan view of typical floor framing for the 8th through 45th floors 5-4 -- Figure 5-3 Elevations of building and core area 5-5 -- Figure 5-4 Fifth floor diaphragm plan showing T-sections embedded in 14-inch slab 5-6 -- Figure 5-5 3-D diagram showing relations of trusses and transfer girders 5-6 -- Figure 5-6 Seventh floor plan showing locations of transfer trusses and girders 5-7-- Figure 5-7 Truss 1 detail 5-8 -- Figure 5-8 Truss 2 detail 5-9 -- Figure 5-9 Truss 3 detail 5-10 Figure 5-10 Cantilever transfer girder detail 5-11 -- Figure 5-11 Compartmentalization provided by concrete floor slabs 5-12 -- -- Figure 5-12 Sequence of debris generated by collapses of WTC 2, 1, and 7 5-17 -- Figure 5-13 Pedestrian bridge (bottom center) still standing after WTC 2 has collapsed, sending substantial dust and debris onto the street, but before WTC 1 (top center) has collapsed 5-18 -- Figure 5-14 View from the north of the WTC 1 collapse and the spread of debris around WTC7 5-18 -- Figure 5-15 Debris from the collapse of WTC 1 located between WTC 7 (left) and the Verizon building (right) 5-19 -- Figure 5-16 Damage to the southeast corner of WTC 7 (see box), looking from West Street 5-19 -- Figure 5-17 Building damage to the southwest corner and smoke plume from south face of WTC 7, looking from the World Financial Plaza 5-20 -- Figure 5-18 WTC 7, with a large volume of dark smoke rising from it, just visible behind WFC 1 (left) 5-21 -- Figure 5-19 Fires on the 11th and 12th floors of the east face of WTC 7 5-22 -- Figure 5-20 View from the north of WTC 7 with both mechanical penthouses intact 5-24 -- Figure 5-21 East mechanical penthouse collapsed 5-25 -- Figure 5-22 East and now west mechanical penthouses gone 5-25 -- -- Figure 5-23 View from the north of the "kink" or fault developing in WTC 7 5-26 -- Figure 5-24 Areas of potential transfer truss failure 5-27 -- Figure 5-25 Debris cloud from collapse of WTC 7 5-27 -- Figure 5-26 Debris generated after collapse of WTC 7 5-28 -- Chapter 6 -- Figure 6-1 North face of Bankers Trust building with impact damage between floors 8 and 23 6-1 -- Figure 6-2 Closeup of area of partial collapse 6-2 -- Figure 6-3 Floor plan above the 2nd level (ground floor extension not shown) 6-3 -- Figure 6-4 Area of initial impact of debris at the 23rd floor 6-4 -- Figure 6-5 Approximate zones of damage - 19th through 22nd floors, 16th through 18th floors, 11th through 15th floors, and 9th through 10th floors 6-5 -- Figure 6-6 Moment-connected beams to columns 6-7 -- Figure 6-7 Column with the remains of two moment connections 6-7 -- Figure 6-8 Failed shear connection of beam web to column web 6-8 -- Figure 6-9 Suspended column D-8 at the 15th floor 6-8 -- Figure 6-10 Area of collapsed floor slab in bays between C-8, E-8, C-7, and E-7, from 15th floor 6-9 -- Figure 6-11 Bankers Trust Lobby (note debris has been swept into piles) 6-9 -- Figure 6-12 Office at north side of the 8th floor 6-10 -- Figure 6-13 3-D ANSYS model of flange and shear plate moment connection 6-14 -- Figure 6-14 3-D ANSYS model of flange and seat moment connection 6-14 -- Chapter 7 -- Figure 7-1 New York City DDC/DoB Cooperative Building Damage Assessment Map of November 7, 2001 (based on SEANY inspections of September and October 2001) 7-2 -- Figure 7-2 Southeast corner of WFC 3 7-5 -- Figure 7-3 View of Winter Garden damage from West Street, with WTC 1 debris in front of WFC 2 7-6 -- Figure 7-4 View of Winter Garden damage from West Street, with WTC 1 debris leaning against WFC 3 7-6 -- Figure 7-5 Interior damage at floor 20 of WFC 3 7-7 -- Figure 7-6 Verizon building - damage to east elevation (Washington Street) 7-8 -- Figure 7-7 Verizon building - damage to east elevation (Washington Street) due to WTC framing leaning against the building 7-9 -- Figure 7-8 Verizon building - damage to east elevation (Washington Street) 7-9 -- Figure 7-9 Verizon building - column damage on east elevation (Washington Street) 7-10 -- Figure 7-10 Verizon building - damage to south elevation (Vesey Street) 7-11 -- Figure 7-11 Verizon building - localized damage to south elevation (Vesey Street) 7-11 -- Figure 7-12 Verizon building - detail of damage to south elevation (Vesey Street) 7-12 -- Figure 7-13 30 West Broadway - south façade, oth floor to roof, looking northeast 7-13 -- Figure 7-14 130 Cedar Street and 90 West Street 7-14 -- Figure 7-15 Interior of 90 West Street showing typical construction features 7-16 -- Figure 7-16 Buckling damage at top of column on floor 8 of 90 West Street 7-17 -- Figure 7-17 Buckling damage at top of column on floor 23 of 90 West Street 7-18 -- Figure 7-18 One Liberty Plaza - south elevation, lower floors 7-19 -- Figure 7-19 One Liberty Plaza - south elevation, upper floors 7-20 -- Appendix A -- Figure A-1 Heat release rate for office module A-2 -- Figure A-2 Fire growth rates (from SFPE Handbook of Fire Protection Engineering) A-3 -- Figure A-3 Comparison of exposure temperatures in standard tests A-6 -- Figure A-4 Thermal properties of steel at elevated temperatures A-11 -- Figure A-5 Stress-strain curves for structural steel (ASTM A36) at a range of temperatures A-11 -- Figure A-6 Strength of steel at elevated temperatures A-12 -- Figure A-7 Modulus of elasticity at elevated temperatures for structural steels and steel reinforcing bars A-13 -- Figure A-8 Reduction of the yield strength of cold-formed light-gauge steel at elevated temperatures A-13 -- Figure A-9 Steel temperature rise due to fire exposure for unprotected steel column A-16 -- Figure A-10 Steel temperature rise due to fire exposure for steel column protected with 1 inch of spray-applied fireproofing A-16 -- Figure A-11 The effect of temperature on the modulus of elasticity strength of different types of concretes A-20 -- Figure A-12 Reduction of the compressive strength of two lightweight concretes (one with natural sand) at elevated temperatures A-21 -- Figure A-13 Usual ranges of variation for the volume-specific heat of normal- weight and lightweight concretes A-21 -- Figure A-14 Specific flow rate as a function of density (SPFE Handbook of Fire Protection Engineering) A-25 -- Figure A-15 Estimated evacuation times for high-rise buildings A-26 -- Appendix B -- Figure B-1 Exterior column end plates B-1 -- Figure B-2 Tensile stress-strain curves for three ASTM-designation steels B-3 -- Figure B-3 Expanded yield portion of the tensile stress-strain curves B-3 -- Figure B-4 Effect of high strain rate on shape of stress-strain diagram B-4 -- Figure B-5 Column tree showing bolt bearing shear failures of spandrel connection B-6 -- Figure B-6 Shear fracture failure of fillet welds connecting a W-shape column to a box core column B-7 -- Figure B-7 Bent and fractured bolts at a column four-bolt connection B-8 -- Figure B-8 Typical truss top chord connections to column/spandrel beam and to the core beam B-10 -- Figure B-9 (A) Visco-elastic damper angles bolted to angle welded to spandrel plate and (B) failed bearing seat connection B-11 -- Figure B-10 (A) Bracket plate welded to the column/spandrel plate and (B) horizontal plate brace with shear connectors welded to the failed bracket B-11 -- Figure B-11 Shear failure of floor joist connections from column / spandrel plate B-12 -- Appendix C -- Figure C-1 Eroded A36 wide-flange beam C-1 -- Figure C-2 Closeup view of eroded wide-flange beam section C-2 -- Figure C-3 Mounted and polished severely thinned section removed from the wide-flange beam shown in Figure C-1 C-2 -- Figure C-4 Optical microstructure near the steel surface C-3 -- Figure C-S Another hot corrosion region near the steel surface (etched with 4 percent nital) C-3 -- Figure C-6 Microstructure of A36 steel C4 -- Figure C-7 Deep penetration of liquid into the steel C4 -- Figure C-8 Qualitative chemical analysis C-5 -- Figure C-9 Qualitative chemical analysis C-6 -- Figure C-10 Grain boundary corrosion attack C-6 -- Figure C-11 Microstructure of a typical region showing the surface and grain boundary corrosion attack of Sample 2 C-7 -- Figure C-12 Higher magnification of the region shown in Figure C-10 C-7 -- Figure C-13 Regions where chemical analysis was performed C-8 -- Figure C-14 Gradient of sulfides into the steel from the oxide-metal interface C-12 -- Appendix D -- Figure D-1 Mixed, unsorted steel upon delivery to salvage yard D-2 -- Figure D-2 Torch cutting of very large pieces into more manageable pieces of a few tons each D-3 -- Figure D-3 Pile of unsorted mixed steel (background), with sorted, large steel pieces (center) being lifted and cut into smaller pieces (left) D-3 -- Figure D-4 Engineer climbing in unprocessed steel pile to inspect and mark promising pieces D-4 -- Figure D-S Stenciled markings on WTC 2 perimeter column from floors 68-71 D-5 -- Figure D-6 Steel pieces marked "SAVE." D-6 -- Figure D-7 Engineers measuring and recording steel piece dimensions D-6 -- Figure D-8 Engineer measuring spandrel plate thickness (t.) D-7 -- Figure D-9 Measurement of 1/4 inch for web thickness (ty.) D-7 -- Figure D-10 Measured dimensions of the steel pieces Figure D-11 Burnt steel piece marked for cutting of coupon D-9 -- Figure D-12 Coupon cut from WTC 5 showing web tear-out at bolts D-9 -- Figure D-13 WTC 1 or WTC 2 core column (C-74) D-10 -- Figure D-14 WTC 7 W14 column tree with beams attached to two floors D-11 -- Figure D-15 Built-up member with failure along stitch welding D-11 -- Figure D-16 Engineer inspecting fire damage of perimeter column tree from WTC 1 or WTC 2 D-12 -- Figure D-17 Seat-connected in fire-damaged W14 column from WTC 7 D-12 -- Figure D-18 WTC 1 or WTC 2 floor-truss section with seat connection fractured along welds D-13 -- ; Also available via Internet from the web site. Address as of 6/06/02 : http://www.house.gov/science/hot/wtc/wtcreport.htm ; current access is available via PURL ER -