Design, construction, and maintenance of structural and life safety systems

282 Pages·2015·17.8 MB·English

NIST NCSTAR 1-1
Federal Building and Fire Safety Investigation of the
World Trade Center Disaster
Design, Construction, and
and
IVIaintenance of Structural Life
Safety Systems
H. S. Lew
Richard W. Bukowski
Nicholas J. Carino
National instituteofStandardsandTechnology TechnologyAdministration • U.S. DeparimeniofCommerce

NIST NCSTAR 1-1
Federal Building and Fire Safety Investigation of the
World Trade Center Disaster
Design, Construction, and
IVIaintenance of Structural and Life
Systems
Safety
H. S. Lew
Richard W. Bukowski
Nicholas J. Carino, retired
Building andFire Researcli Laboratory
National Institute ofStandards and Technology
September 2005
U.S. Department ofCommerce
Carlos M. Gutierrez, Secretary
Technology Administration
Mictielle O'Neill. Acting UnderSecretaryfor Technology
National InstituteofStandards and Technology
William Jeffrey, Director
Disclaimer No. 1
Certain commercial entities, equipment, products, or materials are identified in this document in orderto describe a
procedure orconcept adequatelyorto trace the history ofthe procedures and practices used. Such identification is
not intended to imply recommendation, endorsement, or implication thatthe entities, products, materials, or
equipment are necessarilythe best available forthe purpose. Nordoes such identification imply a finding offault or
negligence bythe National Institute ofStandards and Technology.
DisclaimerNo. 2
The policy ofNIST isto usethe International System ofUnits (metric units) in all publications. In this document,
however, units are presented in metric units orthe inch-pound system, whichever is prevalent in the discipline.
Disclaimer No. 3
Pursuantto section 7 ofthe National Construction SafetyTeam Act, the NIST Directorhas determined that certain
evidence received by NIST in the course ofthis Investigation is "voluntarily provided safety-related information"that is
"not directly related to the building failure being investigated" and that"disclosure ofthat information would inhibitthe
voluntary provision ofthattype of information" (15 (JSC 7306c).
In addition, a substantial portion ofthe evidence collected by NIST in the course ofthe Investigation has been
provided to NIST under nondisclosure agreements.
Disclaimer No. 4
NISTtakes no position asto whetherthe design orconstruction ofa WTC building was compliantwith anycode
since, due to the destruction ofthe WTC buildings, NIST could notverifythe actual (or as-built) construction, the
properties and condition ofthe materials used, orchangesto the original construction made overthe life ofthe
buildings. In addition, NIST could not verifythe interpretations ofcodes used by applicable authorities in determining
compliance when implementing building codes. Where an Investigation report states whethera system was
designed or installed as required by a codeprovision, NIST has documentary oranecdotal evidence indicating
whetherthe requirement was met, orNIST has independently conducted tests oranalyses indicating whetherthe
requirement was met.
Use in Leqal Proceedings
No partofany report resulting from a NIST investigation into a structural failure orfrom an investigation underthe
National Construction SafetyTeam Act may be used in any suitoraction fordamages arising out ofany matter
mentioned in such report (15 USC 281a; as amended by P.L. 107-231).
National Institute ofStandards and Technology National Construction SafetyTeam Act Report 1-1
Natl. Inst. Stand. Technol. Natl. Constr. Sfty. Tm. Act Rpt. 1-1, 278 pages (September2005)
CODEN: NSPUE2
U.S. GOVERNMENT PRINTING OFFICE
WASHINGTON: 2005
Forsale bythe Superintende—nt ofDocuments, U.S. Gov—ernment Printing Office
Internet: bookstore.gpo.gov Phone: [phone] Fax: [phone]
Mail: Stop SSOP, Washington, DC 20402-0001
Abstract
The collapse ofWorld Trade Center (WTC) 1, 2, and 7 resulted from structural damage fromdirect and
indirect effects ofaircraft impact and the ensuing fires. Thus, forcollapse analyses ofthese buildings,
knowledge ofthe physical state ofthe structural and fire safety systems priorto the aircraft impact is
essential. To obtain infonnation forthe collapse analysis ofthe buildings. National Institute ofStandards
and Technology reviewed design and construction documents, correspondence, andmemoranda related to
the building projects; interviewed individuals involved in the design, construction, and maintenance ofthe
buildings; obtained information from regulatory and emergency services agencies ofNew York City; and
WTC
reviewed books and publishedjournal and magazine articles related to the building projects,
hiformation obtained from various sources are synthesized and summarized in this report. Specifically,
this report presents (1) provisions used to design and construct the structural, fire protection and egress
systems ofthe buildings; (2) tests performed to support the design ofthese systems; (3) criteria that
governed the design ofthe structural and fire protection systems; (4) methods usedto proportion
structural members and other components ofthe buildings; (5) innovative features, technologies and
materials that are incorporated in design and construction ofthe structural and fire protection systems;
(6) details ofdeviations to the contract documents granted by Port Authority ofNew York and
New Jersey; (7) fabrication and inspection requirements atthe fabrication yard; and (8) inspection
protocols during construction.
This report also documents the fuel system forthe diesel generators that supplied emergency powerto
many ofthe tenants in WTC 7.
Findings from the synthesis ofthe information collected andresulting issues are presented.
Keywords: Buildings, codes, construction, design, egress, elevators, fire, loads, maintenance, regulations,
standards, World Trade Center.
NISTNCSTAR 1-1, WTC Investigation iii
Abstract
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IV NISTNCSTAR 1-1, WTC Investigation
Table of Contents
Abstract
iii
List ofFigures xi
List ofTables xiii
List ofAcronyms and Abbreviations xv
Metric Conversion Table xix
Preface xxiii
Acknowledgments xxxiii
Executive Summary „ xxxv
Chapter
1
Introduction
1
Background
1.1 1
1.2 Scope ofReport 1
WTC
1.3 Design and Construction Requirements for 1, 2, and 7 4
1.4 Organization ofReport 5
Chapter 2
Description of WTC 1, 2, and 7 7
2.1 Site Plan ofWTC Complex 7
WTC WTC
2.2 Description of 1 and 2 7
2.2.1 Building Description 7
2.2.2 Structural Description 9
WTC
2.3 Description of 7 13
2.3.1 Building Description 13
2.3.2 StructuralDescription 14
Chapter 3
Development of Building Codes 37
3.1 Building Code Development in the United States 37
3.2 New York City Building Code 38
3.3 Port Authority Policies forDesign and Modifications to Buildings 40
3.3.1 Procedures forPANYNJ Owned Projects 40
3.3.2 Review ofTower Plans by New York City Department ofBuildings 41
NISTNCSTAR 1-1, WTC Investigation v
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3.3.3 Procedures forTenant Alteration Projects 42
Chapter 4
Code Provisions for Structural Design 43
4.1 Contemporaneous Codes 43
4.2 Loads 44
4.2.1 Dead Loads 44
4.2.2 Live Loads 45
4.2.3 Wind Load 47
4.2.4 Earthquake Load 49
4.2.5 Other Loads 50
4.2.6 Distribution ofLoads 5
4.3 Design Standards 52
4.3.1 Design Standards 52
4.3.2 Load Combinations 53
4.4 Alteration ofExisting Buildings 55
4.5 Materials and Methods ofConstruction 56
4.6 Stability, Bracing, and Secondary Stresses 58
4.7 Deflection Limitations 59
4.8 Load Tests 59
Chapter 5
Structural Design ofWTC 1, 2, and 7 63
5.1 Design Criteria 63
5.1.1 Loads 63
5.1.2 Live Load Reduction 66
5.1.3 Wind Load 68
5.1.4 Aircraft Impact 70
5.2 Structural Design Requirements 71
5.2.1 Concrete Requirements 72
5.2.2 Steel Requirements 72
5.2.3 Methods Used to Proportion Structural Members 73
Chapter 6
Innovative Features Incorporated in Structural Design 87
6.1 Irmovative Features 87
6.2 Lateral-Load-Resisting System 87
vi NISTNCSTAR 1-1, WTC Investigation
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Table ofContents
6.3 Composite Floor System 88
6.4 Viscoelastic Damping Units 89
6.5 Wind Tunnel Tests 90
6.5.1 Tests Conducted at CSU 91
6.5.2 Tests Conducted at NPL 93
Chapter 7
Fabrication and Construction Inspections and Deviations 97
7.1 Introduction 97
WTC WTC
7.2 Fabrication Inspection Requirements for 1 and 2 97
7.2.1 FloorTrusses 98
7.2.2 Box Core Columns andBuilt-Up Beams 98
7.2.3 ExteriorColumns fromElevation 363 ft to the 9th Floor Splice 100
7.2.4 Exterior Columns Above the 9th floor Splice 100
7.2.5 Rolled Columns andBeams 101
7.2.6 OtherRequirements 101
WTC
7.3 Fabrication Inspection Requirements for 7 102
7.4 Inspection During Construction 102
7.4.1 Erection Marks and Marking System WTC 1 and WTC 2 103
WTC WTC
7.4.2 Quality Control and Inspection Program for 1 and 2 104
7.5 Deviations Granted 104
7.5.1 Deviations Relating to Fabrication and Erection Tolerances 105
7.5.2 Deviations Relating to Defective Components 105
7.5.3 Deviations Relating to Alternate Fabrication and Erection Procedures 106
7.5.4 Deviations Relatingto Product Substitutions 106
7.5.5 Deviations Relating to Inspection Practice 107
Chapter 8
Structural Maintenance and Modifications During Occupancy 109
8.1 Introduction 109
8.2 Tenant Construction Review Manuals 109
8.2.1 1971 Edition 110
8.2.2 1979 Edition 110
8.2.3 1984 Edition, Revised 1990 11
8.2.4 1997 Edition 112
WTC
8.3 Standards for Structural Integrity Inspection ofthe Towers 112
NISTNCSTAR 1-1, WTC Investigation vii
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8.3.1 Visual Inspections 113
8.3.2 Review ofReports 114
8.3.3 Periodic Measurements 115
8.3.4 Recordkeeping 116
8.4 Standards forArchitectural and Structural design 117
8.5 Structural Inspection Programs 1 17
WTC
8.5.1 Facility Condition Survey of 2 11
WTC
8.5.2 Facility Condition Survey of 1 121
WTC
8.5.3 Facility Condition Survey of 7 124
8.5.4 Due Diligence Condition Survey ofWTC 1 and WTC 2 124
8.5.5 Structural Integrity Inspection Program 125
8.5.6 Summary ofStructural Integrity Inspection Programs 133
WTC
8.5.7 Modifications and Repairs to Structural Framing Systems of 1, 2, and 7 133
Chapter 9
Comparison of Fire Safety Codes and Practices 141
9.1 Comparison ofFire Provisions in Building Codes 141
9.1.1 Introduction 141
9.1.2 Interrelation ofCodes, Standards, and Practices 142
9.1.3 Comparison ofNew York City and Contemporary Building Codes 142
9.1.4 Occupancy Group 148
9.1.5 Egress Systems 149
9.2 Summaiy ofDifferences between Codes 150
Chapter 10
Influence of Codes and Standards on the Design and Construction of WTC 1 and
WTC
2 153
10.1 Egress System Design 153
10.1.1 Egress Provisions from Windows on the World 154
10.1.2 Egress Provisions from Top ofthe World 158
10.2 Requirements for a Fourth Stairway 159
10.3 Elevators 161
10.4 Active Fire Protection Systems 161
10.4.1 Fire Alarm Systems 161
10.4.2 Fire Sprinklers 162
10.4.3 Smoke Management 164
viii NISTNCSTAR 1-1, WTC Investigation