NISTNCSTAR1-2A Federal Building and Fire Safety Investigation of the World Trade Center Disaster
Reference Structural Models and Baseline Performance Analysis of the World Trade Center Towers
William
J.
Fasclian
Ridiard B. Garlocl<
National Institute of Standards and Technology
Technology Administrofion • U.S. Deportment of
Commerce
NIST
NCSTAR
1-2A
Federal Building and Fire Safety Investigation of the World Trade Center Disaster
Reference Structural Models and Baseline Performance Analysis of the World Trade Center Towers
William
J.
Faschan
Richard B. Garlock Leslie E. Robertson Associates. R.L.L.P.
September 2005
i %
U.S. Department of
Commerce
Carlos M. Gutierrez, Secretary
Technology Administration Michelle O'Neill. Acting Under Secretary for Technology National Institute of Standards and Technology William Jeffrey, Director
Abstract
•
Development of estimates of design gravity and into the reference structural
models and use
wind load cases were considered
wmd loads
in the baseline
in this study, including
on the towers for implementation perfonnance analysis. Various
wind loads used
in the original
WTC design, wind loads based on two recent wind tunnel studies conducted in 2002 by Cennak Peterka
Peterson, Inc. (CPP) and
Rowan
for insurance litigation concerning the towers,
NIST from
critical
Williams Davies and Irwin,
The following
(RWDl)
and refined wind load estimates developed by
assessment of infonnation obtained from the
state-of-the-art considerations.
Inc.
CPP and RWDl
three loading cases
reports
were considered
and
for the
baseline perfonnance analysis:
-
Original
WTC design
WTC design -
in
loads case. Loads included dead and live loads as in original
conjunction with original
(NYCBC
2001)
live loads;
scaled in accordance with
-
Loads included dead
Slate-of-the-practice case.
Code
WTC design wind loads.
NYCBC 2001
New York City Building RWDl wind tunnel study,
loads; cuirent
and wind loads from the
wind speed.
Refined NIST estimate case. Loads included dead loads; live loads from the current
American Society of Civil Engineers Standard Minimum Design Loads Other Structures
(ASCE
7-02);
The global tower models were analyzed using
and
and the refined wind load estimates developed by NIST.
the various gravity and
The
baseline performance results were obtained.
for Buildings
wind loading
cases,
and the
results included:
wind loads
•
Total and inter-story drift under
•
Demand/capacity
•
Axial forces in the exterior columns, including shear lag effects and presence of tensile forces
•
Perfonnance of splice cormections
at the exterior
•
Towers' resistance
and oveituniing under wind loads.
Similarly, the typical floor
ratios for the
primary structural components of the towers
to shear sliding
walls
models were analyzed under gravity loading conditions, and the baseline
perfonnance results were obtained. The results included: •
Floor mid-span deflections
•
Demand/capacity
ratios for the
Keywords: Columns, floor system, gravity
primary structural components of the
floors.
wind
load.
World Trade
NISTNCSTAR
1-2A,
WTC
load, load, model, structural, truss,
Center.
iv
Investigation
1 3 8 1
Table of Contents
Abstract
iii
Table of Contents
v
List of Figures
ix
List of Tables
xiii
List of Acronyms
xv
and Abbreviations
Preface
xvii
Executive
Chapter
Summary
xxvii
1
Introduction 1
.
1
1
WTC Structural System
Description of 1.1.1
Global Structural System
1.1.2
Floor Structural System
1
1
4
Chapter 2
Development
of Structural
2.1
Introduction
2.2
Description of the
Databases for the
WTC
Towers
1
2.3
WTC Structural Documents Over\ iew of the WTC Structural Database (WTC-DB)
2.4
Methodology
2.5
2.6
1
for the
1
1
WTC-DB Development
14
2.4.1
Data Entry
14
2.4.2
Quality Control
15
2.4.3
Cross Section Property Calculations
15
2.4.4
Relational Database
Development
16
Modifications to Database Elements
16
2.5.1
Core Column Reinforcing
2.5.2
Core Column Reinforcing Due
2.5.3
Repair
2.5.4
Tenant Alteration for an Interoffice Stair
18
2.5.5
Drawing Book Data Discrepancies
1
Due
to the
at
Floors 98 to 106 to Construction
Bombing of February
16
of Fiduciary Trust Vault
26, 1993
1
2.6.2
NIST NCSTAR
Member Designations Column Member Multiple Section Property
1-2A.
WTC
Investigation
18
20
Section Property Calculations 2.6.
17
20 Calculation
21
v
1
Table of Contents
2.7
Member
2.6.3
Spandrel
2.6.4
Section Property Calculation Comparisons
24
2.6.5
Rolled Shape Database
25
23
Multiple Section Property Calculation
Summary
26
Chapter 3
Development of Reference Structural Models
WTC
Towers
27
3.1
Introduction
27
3.2
Global Models of the Towers
27
3.2.1
Components and Systems
3.2.2
Coordinate System, Nomenclature, and Models Assembly Overview
28
3.2.3
Core Columns Modeling
32
3.2.4
Exterior Wall, Foundation to Floor 4 Modeling
35
3.2.5
Exterior Wall Trees (Floor 4 to 9) Modeling
36
3.2.6
Exterior Wall (Floor 9 to 106) Modeling
38
3.2.7
Exterior Wall (Floor 107 to
41
3.2.8
Hat Truss Modeling
3.2.9
Flexible and Rigid Floor
3.2.10 Verification of Global 3.2.11 Results of 3.3
3.4
3.5
VI
for the
in the
1
10)
Towers' Global Models
28
Modeling
41
;
Diaphragm Modeling
43
Models
43
Modal Analysis
Typical Truss-Framed Floor Model
44
—Floor 96A
46
3.3.1
Primary Trusses
48
3.3.2
Bridging Trusses
49
3.3.3
Truss
3.3.4
Viscoelastic
3.3.5
Strap Anchors
51
3.3.6
Concrete Slab and Metal Deck
52
3.3.7
Verification of the 96th Floor
Typical
Member Cover Plates
51
Dampers
Beam-Framed Floor Model
5
Model
52
—Floor 75B
53
3.4.1
Composite Beams
55
3.4.2
Horizontal Trusses
55
3.4.3
Concrete Slab and Metal Deck
55
3.4.4
Viscoelastic
3.4.5
Verification of the 75th Floor
Dampers
56
Model
56
56
Parametric Studies
NISTNCSTAR
1-2A.
WTC Investigation
0
Table of Contents
3.6
3.5.1
Exterior Wall Columns/Spandrel Typical Panels (Floors 9 to 106)
3.5.2
Exterior Wall Columns/Spandrel
3.5.3
Flexible Floor
Comer Panels
57
59
(Floors 9 to 106)
Diaphragm
61
Summary
64
Chapter 4
Gravity and
Wind Loads on the
WTC
Global Models
67
4.1
Introduction
67
4.2
Gravity Loads
68
4.3
4.4
4.2.1
Gravity Loads from Areas Outside of Core
69
4.2.2
Gravity Loads from Areas Inside of Core
70
4.2.3
Construction Sequence Loading Effects
74
Wind Loads
74
WTC Design Wind Loads
4.3.1
Original
4.3.2
State-of-the-Practice
4.3.3
Refined
4.3.4
Comparisons of Wind Loads
NIST
74
Wind Loads
78 79
Estimates
79
References
81
Chapter 5
Baseline Performance Analysis of the
WTC
Global Models
83
5.1
Introduction
83
5.2
Calculation of Demand/Capacity Ratios
83
5.2.
5.3
5.4
1
Selection of Global
Models Design Parameters
Baseline Performance Analysis of
WTC
Original
5.3.2
State-of-the-Practice
5.3.3
The Refined NIST Estimate Case
Case
Baseline Performance Analysis of 1
Original
87
1
WTC Design Load Case
5.3.1
5.4.
85
WTC
87 105
WTC 2
Design Load Case
107 109 1 1
5.4.2
State-of-the-Practice Case
128
5.4.3
The Refined NIST Estimate Case
1
30
5.5
Summary
132
5.6
References
134
NIST NCSTAR
1-2A,
WTC
Investigation
vii
Table of Contents
Chapters
Baseline Performance Analysis of Typical Floor Models
135
6.1
Introduction
135
6.2
Typical Truss-Framed Floor
1
36
Gravity Loads
1
36
Results of Baseline Analysis
137
6.2.
1
6.2.2 6.3
Typical Beam-Framed Floor
140
6.3.1
Gravity Loads
140
6.3.2
Results of Baseline Analysis
141
Chapter?
Summary Appendix
145
A
WTC Tower Structural
Drawings Index
for Large-Size
Sheets
149
Appendix B
Drawing Book 19 Modifications for Structural Elements Not Included Database
in
the
167
Appendix C
WTC
Drawing Book Flowcharts
169
Appendix D
Excel File List and Description
179
Appendix E Relational Database File List
185
and Description
Appendix F
Relational Database Tutorial
187
Appendix G
Categorization of Floor Construction Types for Areas Outside of Core
vin
NISTNCSTAR
191
1-2A,
WTC Investigation
List OF Figures
Figure P-1
.
The
eight projects in the federal building
and
fire safety investigation
of the
WTC xix
disaster
WTC tower architectural floor plan (floor 26, WTC 2) Typical WTC exterior wall, foundation to floor 9 Typical WTC tower hat truss elevation (Drawing SA 401) Typical WTC floor truss framing zones (Drawing SA-104), components of typical truss Part plan of floor 96 of WTC
2
framing system
6 7
Figure 1-7.
WTC floor panel layout plan Typical WTC floor truss elevation
Figure 1-8.
Part section t\'pical truss floor panel
8
Figure 1-9.
Floor truss with exterior wall end detail
9
Figure 1-10.
Details of the
Figure 1-1
Damping
Figure 1-1
Typical
.
Figure 1-2. Figure 1-3. Figure 1-4.
Figure 1-5.
Figure 1-6.
Figure 2-1
1.
.
Figure 2-2.
Figure 2-3.
Figure 2-5.
Typical
5
damping
unit used in the
Drawing Book
used
unit
8
in the
beam-framed
3 flowchart:
WTC
1
tmss-framed floors
9
10
floors
and
WTC 2 core columns, foundation to
floor
106
14
Core column reinforcement
17
Column
section at original
column
strap detail (taken
from drawing book
18,
Core column
19
series
300
19
Exterior column type 300. floor 9 to floor 106 (taken from drawing
book
4,
page4-AB2-18) Figure 2-6.
4
1
page 18-AB2-12) Figure 2-4.
3
Column
22
type 6000 with tapered spandrel (taken from drawing book
1,
23
pages 1-A2-27 and 28)
24
Figure 2-7.
Box
Figure 3-1
Global model coordinate axis location
29
Figure 3-2.
Typical exterior panel nomenclature
30
Figure 3-3.
Rendered isometric views of the
Figure 3—^.
Frame
.
section and a built-up
v
iew of the
column
WTC
33
model
WTC
illustrating the core
2 model: exterior wall elevation and interior section columns, core bracing, and hat truss
Figure 3-5.
Frame view and rendered view of the
NISTNCSTAR
1-2A.
WTC
1
Investigation
WTC
1
model (foundation
to floor 9)
34 36
ix
1
List of
Figures
Drawing Book
Figure 3-6.
Exterior wall tree panel (taken from
Figure 3-7.
Exterior wall tree: as-built cross sections for level
E
2,
page 2-AB2-2)
37
Drawing Book
(taken from
page 2-AB2-13) Figure 3-8.
Frame view and rendered view of an
Figure 3-9.
Typical
Figure 3-10. Figure 3-1
1.
2,
^
39
39
exterior wall tree
WTC tower exterior wall panel As-modeled plan of the WTC hat truss Rendered 3-D model of the WTC hat tmss (prior to assembly
40 42
1
1
in the unified global
42
model) Figure 3-12.
Mode
shapes of
WTC
shape (N-S), (c) Third
1
(exaggerated): (a)
mode shape
first
mode shape (E-W),
second
mode 45
Figure 3-13.
Typical truss-framed floor panels arrangement
Figure 3-14.
Typical truss-framed floor model (floor 96A), slab not
Figure 3-15.
(b)
(torsion)
47
shown
48
Typical primary truss cross-section, as-built and as-modeled transfonned truss
work 49
points
Figure 3-16.
Typical bridging truss cross-section, as-built and as-modeled transformed truss
work
points
50
Connection between bottom chords of primary and bridging trusses
5
Figure 3-18.
Strap anchors modeling
52
Figure 3-19.
Typical beam-framed floor arrangement
54
Figure 3-1
7.
Figure 3-20. Typical beam-framed floor model (floor 75B) Figure 3-21
.
Horizontal truss modehng, slab not
54
shown
55
and frame models of typical exterior wall panel
Figure 3-22.
Shell element
Figure 3-23.
Selection of column and spandrel rigidity of typical exterior wall panel
Figure 3-24.
Shell element
Figure 3-25.
Selection of column and spandrel rigidity of typical exterior wall
Figure 3-26.
Detailed and simplified model of the exterior wall
Figure 3-27.
Deflection of typical beam-framed floor model due to lateral loading
63
Figure 3-28.
Deflection of equivalent floor model due to lateral loading
63
Figure 3-29.
Deflections of the north and south faces of the floor for the detailed and equivalent floor
Figure 4-1
.
Figure 4-2. Figure 4-3.
58
and frame models of typical exterior wall comer panel
60
comer panel
60
comer panel
61
models
64
Partition groups
A, B, C, D, and E
71
Partition groups
G and F
72
Windward and leeward wind
X
57
distribution for (a) orthogonal
and
(b) diagonal
78
directions
NISTNCSTAR
1-2A,
WTC
Investigation
1
List of
Drift diagrams of
Figure 5-1.
(b)
Figure 5-2.
Figure 5-3.
Figure 5—4.
due
1
Demand' capacity below floor 9
ratios for
WTC
Demand/capacity
ratios for
(b)
600
and
1
88
under original design loads,
(a) north elevation
90 1
under original design loads,
(a)
north elevation
92
WTC
1
core columns under original design loads, (a) 500
96
line
WTC
1
due to original
WTC wind loads at (a) floor B6, 100
73
(c) floor
Tension force distribution (kip)
Figure 5-6.
AON-E- and
^
Shear lag diagrams of (b) floor"'39.
(a)
^
WTC
and
WTC wind loads,
to original
Demand/capacity ratios for and (b) east elevation
line
Figure 5-5.
WTC
A75N+E-
Figures
in the exterior wall
columns of WTC
1
under original
design dead and wind loads, (a) 100 face (north) and (b) 200 face (east)
Figure 5-7.
Drift
Drift diagrams of
Figure 5-8.
Figure 5-9.
Drift (b)
Figure 5-10.
.
106
to refined
NIST
estimate
wind
1R14PD and
loads, (a)
108
WTC wind loads,
to original
(a)
B180N+E- and 1 1
WTC 2
under original design loads,
(a)
west elevation
(b) north ele\ ation
Demand/capacity
Demand and
below
ratios for
600
(a)
(a)
WTC
2 due to original
73
(c) floor
Figure 5-1
6.
Drift (b)
Figure 6-1
.
diagrams of WTC 2 due
2R4PbN
WTC wind loads at
(a) floor
15
B6, 123
^ in the exterior
wall columns of
WTC 2 under original
and (b) 2R1
126
lower estimate, state-of-the-practice case,
to the
IPDN
129
diagrams of WTC 2 due to refined
NIST
estimate
wind
loads, (a)
2R4PD
and
2R11PD
131
Summary of WTC-design 100 psf - partition load
is
criteria
Unbraced length of truss diagonal
Figure 6-3.
Connection
Figure 6-4.
Demand/capacity
Figure 6-5.
Beam-framed
NISTNCSTAR
1-2A.
detail for
reduced
included in
Figure 6-2.
WTC
1
119
Tension force distribution (kip)
Drift
13
WTC 2 core columns under original design loads, (a) 500
design dead and wind loads, (a) 100 face (west) and (b) 200 face (north)
Figure 5-15.
1
west
line
Shear lag diagrams of
and
WTC 2 under original design load case,
floor 9
capacity ratios for (b)
(b) floor 39,
Figure 5-14.
due
1
Demand''capacity ratios for
line
Figure 5-13.
WTC
diagrams of WTC 2 due
elevation
Figure 5-12.
lower estimate, state-of-the-practice loads,
to the
B90N-E+
and 1
due
1
1R8PDN
(b)
1R8PD
(b)
Figure 5-1
diagrams of WTC
1R14PDN and
(a)
103
beam 30WF1
member groups
Investigation
of
136 138
16, floor 75
ratios for floor 75,
floor
live loads for floor design: design load
LL allowance
WTC 2:
of WTC 2
original
WTC design criteria loading
142 143 143
xi
List of
Figures
This page intentionally
Xll
left
blank.
NISTNCSTAR
1-2A.
WTC Investigation
List of
Table P-1
.
Federal building and
Public meetings and briefings of the
Table 2-1
Modifications to members of the
Table 3-1.
Approximate
Table 3-2.
Calculated
Table 3-3. Table
3^.
WTC disaster
xviii
WTC Investigation
xxi
WTC database (WTC-DB)
size of the reference structural
13
models (rounded)
35
WTC towers Calculated first six periods and frequencies with P-A effects for the WTC towers first six
periods and frequencies without P-A effects for the
Comparison of measured and calculated
WTC Table 3-5.
of the
fire safety investigation
Table P-2.
.
Tables
first
two natural frequencies and periods
46
Lateral displacement (in.) for the shell
and frame models of typical exterior wall 59
.
and frame models of typical exterior wall column and spandrel rigidities
Lateral displacement (in.) for the shell
comer panel with
Table 4—1
44
for
1
panel with varied column and spandrel rigidities
Table 3-6.
44
Original
varied
WTC design criteria loads for floor 96A model for the
61
design of columns
(typical truss floor).^
69
Table 4-2.
Grouping of the wind directions
77
Table 4-3.
A
Table
WTC Comparison of wind load estimates for WTC 2
Table 4-5.
Base shears and base moments due
Table 5-1
Statistics
.
Table 5-2.
comparison of wind load estimates for
Table 5-3.
WTC
Statistics
1
WTC
1
different building codes
81
under original design load case
89
(DCRs) for exterior wall column wind design dead and load case
of demand/capacity ratios (DCRs) for
80
from various sources
calculated demand/capacity ratios
under original
80
from various sources
wind loads from
of demand/capacity ratios for
Maximum for
to
1
WTC
1
splices
105
under the lower estimate, 107
state-of-the practice case
Table 5—4.
Statistics
of demand/capacity ratios (DCRs) for
WTC
1
under the refined NIST 109
estimate case
Table 5-5.
Statistics
of demand/capacity ratios (DCRs) for
WTC 2 under original design load 112
case
Table 5-6.
Maximum for
NISTNCSTAR
WTC
1-2A.
2 under original
WTC
(DCRs) for exterior wall column design dead and wind load case
calculated demand/capacity ratios
Investigation
splices
128
xiii
List of
Tables
Table 5-7.
Statistics
of demand/capacity
ratios
(DCRs)
for
WTC 2 under the lower estimate, 130
state-of-the practice case
Table 5-8.
Statistics
NIST
Table 6-1
.
of demand/capacity
ratios
(DCRs)
for
WTC 2 under the refined 132
estimate case
Summary of typical
truss-framed floor live loads and (reduced live loads) for areas
outside of core
Table 6-2. Table 6-3.
Area inside
137
core: loading floor 96,
Summary of maximum
WTC
137
1
deflections for typical truss-framed floor under
DL
-i-
LL
for
areas outside of core
Table
6^.
Table 6-5.
137
Statistics
of demand/capacity ratios for floor 96 under original design load case
Statistics
of demand/capacity ratios (DCRs) for floor 96 under the
ASCE
139
7-02
140
loading case
Table 6-6. Table 6-7.
Beam-framed core Statistics
area: loading floor 75,
WTC 2
141
of demand/capacity ratios for floor 75 under the original design loading
144
case
XIV
NISTNCSTAR
1-2A,
WTC
Investigation
List of
Acronyms and Abbreviations
Acronyms American
Institute
of Steel Construction
/\rntricdn irun dnu oieei insiiiuie
/Vol-'
/\iiowdDic oucss ucsign
no/"' A /RRr^
Building Officials and Code Administrators Basic Building Code construction dead load
Lrr
Cermak Peterka
Peterson, Inc.
database
ULK
demand-'capacity ratio (JcdU lUaU
F-W n vv
£Lcljl
Or
Government Furnished Information
T-
1
Qct
—
f=*ct ri r*=*r*ti r\n W' vv Col LlilCLLiUll 1
CD A LtKA
Leslie E. Robertson Associates, R.L.L.P.
LL
live ludu
I
T
I
LrvT
U
i^udu dnu iveaioidncc rdcior uesign
iviiir
mecndnicdi, ciecincdi, dnu piumuing
IVlIliN.
mccnanicdi ccjuipmeni ruoin
NIST
l^CLUKJllal JlllolllUlv \Jl OLu.llLlu.lUo uiiLI 1 ^L-iiliUlUg Y
IN
-o
IN
I
V^DV^
l>iUllIl
iNevv
— I
OUUllI
urK
Llll
v^iiy
CCLIUIJ
Duiiuing i_uue
i^piicdi \„fidrdcicr
ivecugnuiun
PANYNJ
Port Authority of New
RWDI
Rowan Williams Davies and
SDL
superimposed dead load
SQL
Structured Query Language
WL
wind load
WSHJ
Worthington, Skilling, Helle
WTC
World Trade Center
NISTNCSTAR
1-2A.
WTC
Investigation
York and
New
Jersey
Irwin, Inc.
& Jackson
XV
List of Acronyms
WTC
1
and Abbreviations
World Trade Center
1
(North Tower)
WTC 2
World Trade Center 2 (South Tower)
WTC
World Trade Center
7
7
Abbreviations
2D
two dimensional
3D
three dimensional
ft
foot
ft^
square foot
Fy
yield strength
h
hour
in.
inch
kip
a force unit equal to 1,000
ksi
1
,000 pounds per square inch
lb
pound
min
minute
pcf
pounds per cubic foot
psf
pounds per square foot
psi
pounds per square inch
XVI
pounds
NISTNCSTAR
1-2A,
WTC Investigation
Preface
Genesis of This Investigation Immediately following the Federal Emergency
terrorist attack
on the World Trade Center
Management Agency (FEMA) and
the
planning a building performance study of the disaster. The search efforts ceased, the Building Performance Study
report in
their other professional
May
2002. fulfilling
its
1
1,
2001, the
American Society of Civil Engineers began
week of October
Team went
to the site
This was to be a brief effort, as the study team consisted of experts
away from
(WTC) on September
who
7,
as soon as the rescue
and began
its
largely volunteered their time
commitments. The Building Perfonnance Study Team issued
goal "to determine probable failure
future in\ estigation that could lead to practical
and
assessment.
mechanisms and
its
to identify areas
of
measures for improving the damage resistance of buildings
against such unforeseen e\'ents."
On August
21. 2002. with funding
from the U.S. Congress through
Standards and Technology (NIST) announced
On
disaster.
October
Construction Safety
The goals of the
To
To
The
building and
fire safety investigation
2002, the National Construction Safety
Team Act
(Public
of the
Law
WTC
107-231),
was
Team Act.
investigation of the
in\ estigate the
WTC disaster were:
building construction, the materials used, and the technical conditions that
contributed to the outcome of the •
its
the National Institute of
The NIST WTC Investigation was conducted under the authority of the National
signed into law.
•
1,
FEMA,
WTC disaster.
serve as the basis for:
-
Improvements
-
Improved
-
Recommended
-
Improved public
tools
in the
way
buildings are designed, constructed, maintained, and used;
and guidance for industry and safety
officials;
revisions to current codes, standards, and practices; and safety.
specific objectives were:
1
.
Determine aircraft
2.
why and how
WTC and WTC 2 WTC 7 collapsed; 1
collapsed following the
initial
impacts of the
and why and how
Determine including
why
all
the injuries and fatalities were so high or low depending on location,
technical aspects of fire protection, occupant behavior, evacuation, and
emergency response; 3.
Determine what procedures and practices were used and maintenance of WTC
4.
1, 2,
and
7;
in the design, construction, operation,
and
Identify, as specifically as possible, areas in current building
and
fire
codes, standards, and
practices that warrant revision.
NISTNCSTAR
1-2A,
WTC Investigation
xvii
.
Preface
NIST
is
a nonregulatoiy
agency of the U.S. Department of CoiTunerce's Technology Administration. The
puipose of NIST investigations States,
and the focus
on
is
is
to
improve the safety and
NIST
fact finding.
structural integrity
in substantial loss
organizations. Further,
in the
wake of any
make
damages
Law
arising out of any matter
of life.
loss
NIST
findings of fault nor negligence by individuals or
no part of any report resulting from a NIST investigation
into a building failure or
from an investigation under the National Construction Safety Team Act may be used for
United
building failure that
of life or that posed significant potential of substantial
does not have the statutoiy authority to
in the
investigative teams are authorized to assess building
performance and emergency response and evacuation procedures has resulted
of buildings
menfioned
in
such report (15
USC
in
any
suit or action
281a, as amended by PubUc
107-231).
Organization of the Investigation
The National Construction Safety Team Dr.
Arden
L.
Bement,
was
Jr.,
led
for this Investigation, appointed
by Dr.
Shyam
S.
by the then NIST Director,
Sunder. Dr. William L. Grosshandler served as
Associate Lead Investigator, Mr. Stephen A. Cauffman served as Program Manager for Administration,
and Mr. Harold
E.
Nelson served on the team as a private sector expert. The Investigation included eight
interdependent projects whose leaders comprised the remainder of the team.
each of these eight projects in
is
available at http://wtc.nist.gov.
Table P-1, and the key interdependencies
among
Table P-1. Federal building and
fire
Practices; Project Leaders: Dr. H. S.
Lew
and Mr. Richard W. Bukowski
project
safety investigation of the
Aircraft Impact
Damage
Analysis; Project
Leader: Dr. Fahim H. Sadek
Mechanical and Metallurgical Analysis of
of
summarized
WTC
disaster.
Project Purpose
Document and analyze
the code provisions, procedures, and
practices used in the design, construction, operation, and
maintenance of the
structural, passive fire protection,
emergency access and evacuation systems of WTC Baseline Structural Performance and
is
the projects are illustrated in Fig. P-l
Technical Area and Project Leader Analysis of Building and Fire Codes and
A detailed description
The purpose of each
and
1, 2,
and
7.
Analyze the baseline performance of WTC and WTC 2 under design, service, and abnormal loads, and aircraft impact damage on the structural, fire protection, and egress systems. 1
Structural Steel; Project Leader: Dr. Frank
Determine and analyze the mechanical and metallurgical properties and quality of steel, weldments, and connections from steel
W. Gayle
recovered from
Investigation of Active Fire Protection
Investigate the performance of the active fire protection systems in
Systems; Project Leader: Dr. David
WTC
D. Evans; Dr. William Grosshandler
and
1, 2,
fate
and
WTC 7
and
1, 2,
and
7.
their role in fire control,
emergency response,
of occupants and responders.
Reconstruction of Thermal and Tenability
Reconstruct the time-evolving temperature, thermal environment,
Environment; Project Leader: Dr. Richard
and smoke movement in WTC 1 2, and 7 for use in evaluating the structural performance of the buildings and behavior and fate of occupants and responders.
G.
Gann
Structural Fire
Response and Collapse
Analysis; Project Leaders: Dr. John L.
Gross and
Dr
Therese
P.
McAllister
,
Analyze the response of the WTC towers to fires with and without aircraft damage, the response of WTC 7 in fires, the performance of composite steel-trussed floor systems, and determine the most probable structural collapse sequence for WTC 1, 2, and 7.
Occupant Behavior, Egress, and Emergency Communications; Project Leader: Mr. Jason
Analyze the behavior and fate of occupants and responders, both those who survived and those who did not, and the performance of
D. Averill
the evacuation system.
Emergency Response Technologies and Guidelines; Project Leader: Mr. J. Randall
Document of the
terrorist attacks
Lawson
WTC
7,
XVlIl
the activities of the
on
emergency responders from the time 1 and WTC 2 until the collapse of
WTC
including practices followed and technologies used.
NISTNCSTAR
1-2A,
WTC
Investigation
Preface
NIST
WTC
Investigation Projects
Analysis of
Stoictural
Steel
Collapse
Nisr Figure P-1. The eight projects in the federal building and investigation of the WTC disaster.
National Construction Safety
The NIST Director Safety
Team
Act.
initial
safety
Team Advisory Committee
also established an advisory
The
fire
committee as mandated under the National Construction
members of the committee were appointed following
a public solicitation.
These were: •
Paul Fitzgerald, Executive Vice President (retired)
FM
Global, National Construction Safety
Team Advisory Committee Chair •
John Barsom. President. Barsom Consulting, Ltd.
•
John Bryan, Professor Emeritus, University of Maryland
•
David
•
Glenn Corbett, Professor, John Jay College of Criminal Justice
•
Philip
NISTNCSTAR
1-2A.
Collins, President,
The Preview Group,
Inc.
DiNenno, President, Hughes Associates,
WTC
Investigation
Inc.
XIX
Preface
•
Robert Hanson, Professor Emeritus, University of Michigan
•
Charles Thornton, Co-Chairman and Managing Principal, The Thomton-Tomasetti Group, Inc.
•
Kathleen Tiemey, Director, Natural Hazards Research and Applications Information Center, University of Colorado
•
Fonnan Williams,
at
Boulder
Director, Center for
Energy Research, University of California
at
San
Diego This National Construction Safety Investigation and
commentary on
Team Advisory Committee provided technical
drafts of the Investigation reports prior to their public release.
has benefited from the work of many people
in the
NIST
preparation of these reports, including the National
Team Advisory Committee. The
Construction Safety
advice during the
content of the reports and recommendations,
however, are solely the responsibility of NIST.
Public Outreach During the course of this Investigation, NIST held public briefings and meetings solicit input
from the public, present preliminary
findings,
(listed in
Table P-2) to
and obtain comments on the direction and
progress of the Investigation from the public and the Advisory Committee.
NIST
maintained a publicly accessible
Web
site
during this Investigation
The
at http://wtc.nist.gov.
site
contained extensive infonnation on the background and progress of the Investigation.
NIST's
The
WTC
Public-Private
collapse of the
Response Plan
WTC buildings has led to broad reexamination of how tall buildings are designed,
constructed, maintained, and used, especially with regard to major events such as fires, natural disasters,
and
Reflecting the enhanced interest in effecting necessaiy change, NIST, with support
terrorist attacks.
from Congress and the Administration, has put
in place a
program, the goal of which
is
to develop
implement the standards, technology, and practices needed for cost-effective improvements
and
to the safety
and security of buildings and building occupants, including evacuation, emergency response procedures,
and threat mitigation.
The
strategy to
•
A
meet
this goal is a three-part
NlST-led public-private response program
federal building and fire safety investigation to study the
contributed to post-aircraft impact collapse of the building, and the associated evacuation and •
A research and
for cost-effective that
XX
improvements
7
to (a) facilitate the
implementation of
WTC Investigation, and (b) provide the technical basis
to national building
enhance the safety of buildings,
factors that
WTC towers and the 47-story WTC
emergency response experience.
development (R&D) program
recommendations resulting from the
most probable
that includes:
their occupants,
and
fire
codes, standards, and practices
and emergency responders.
NISTNCSTAR
1-2A,
WTC
Investigation
Preface
WTC
Table P-2. Public meetings and briefings of the Date
Locarion
1
New York
June 24. 2002
Principal
City,
NY
Public meeting: Public
pending
m
iiQ n f^rc ni VJ al1 1Lilt 1 5UUl 1
December
2002
9.
li.
Washington.
V'lTi iML/
DC
Investigation.
Agenda
comments on
the Draft Plan for the
WTC Investigation.
Media
briefing announcing the formal start of the Investisation.
Media
briefing
on release of the Public Update and NIST request and videos.
for photographs
April
New York
2003
8.
City.
NY
forum with Columbia University on
Joint public
first-person
inter\iews.
Apnl 29-30. 2003
Gaithersburg.
MD
NCST
WTC May
-.
2003
Ne\\'
August 26-27, 2003
York
C)X\
Gaithersburg,
.
NY
MD
Ad\'isorv
Committee meetino on nlan
Investigation with a public
Media
briefing on release of A4av
NCST Advison,'
1
7.
New York
2003
Citv'.
NY
Media and public
for
and
nropre*;*;
on
session.
2003 Pvo^vess Report.
Committee meeting on
investigation with a public
September
comment
comment
status
of the
WTC
session.
briefing on initiation of first-person data
collection projects.
December 2-3. 2003
Gaithersburg.
MD
NCST Advisory
Committee meeting on
status
and
initial results
and release of the Public Update with a public comment session. Februar>'
New
12,2004
York
City,
NY
Public meeting on progress and preliminary findings with public
comments on
issues to be considered
m
formulating final
recommpndatinns June
18.
New York
2004
June 22-23, 2004
Cit}-.
Gaithersburg,
NY
MD
Media public
briefing
NCST Ad\'isory
on release of June 2004 Progress Report.
Committee meeting on
preliminary findings fi^om the
comment August 24. 2004
system Gaithersburg,
MD
NCST set
November
22.
2004
Gaithersburg.
session.
MD
at
Advisory Committee meeting on
status
and near complete
of preliminary findings with a public comment session.
NCST Advisory'
Committee discussion on
comment
Media and public sequence for the
draft annual report to
session, and a closed session to
discuss pre-draft recommendations for
New York City, NY
WTC floor
Underwriters Laboratories, Inc.
Congress, a public
April 5, 2005
the status of and
Investigation with a public
Public viewing of standard fire resistance test of
Northbrook. IL
October 19-20. 2004
WTC
WTC
Investigation.
briefing on release of the probable collapse
WTC towers and draft reports for the projects on
codes and practices, evacuation, and emergency response.
New York
June 23. 2005
City,
NY
iviculd allU pUDIlC ullclirig Oil ICICaSC Ui all UlalL
WTC towers and September 12-13, 2005
Gaithersburg.
.MD
September 13-15, 2005
Gaithersburg.
MD
•
A
draft
and the
CpUI
IS
lUI lllc
comment.
Advisorv' Committee meeting on disposition of public comments and update to draft reports for the WTC towers.
WTC Technical
Conference for stakeholders and technical and recommendations and opportunity' for public to make technical comments. for dissemination of findings
dissemination and technical assistance program
proposed changes
1
for public
NCST
community
construction and building
recommendations
community
in
(DTAP)
to (a)
engage leaders of the
ensuring timely adoption and widespread use of
to practices, standards,
and codes resulting from the
R&D
WTC Investigation
tools to better prepare facility
program, and (b) provide practical guidance and owners, contractors, architects, engineers, emergency responders, and regulatory authorities to
respond to future disasters.
The desired outcomes
are to
make
buildings, occupants,
and
first
responders safer in future disaster
events.
NISTNCSTAR
1-2A,
WTC
Investigation
XXI
Preface
National Construction Safety
A
on the collapse of the
final report
report
on the collapse of WTC 7
that provides
Team Reports on
more
WTC towers
is
being issued as
is
the
WTC
Investigation
being issued as
NIST
NCSTAR
NIST
NCSTAR
As
such,
it
of Investigation publications
is
NIST
(National Institute of Standards and Technology). 2005. Federal Building
NIST
1
Gaithersburg,
.
MD,
NIST NCSTAR Lew, H.
S.,
R.
1
World Trade Center Disaster: Final Report on
A. Gaithersburg,
The
titles
the Collapse
and Fire
Safety
of the World Trade
September.
(National Institute of Standards and Technology). 2006. Federal Building
Investigation of the
the
NCSTAR
set
these
are:
World Trade Center Disaster: Final Report on
NIST
one of a
is
part of the archival record of this Investigation.
full set
Center Towers.
A companion
means by which
of the
Investigation of the
.
lA. The present report
detailed documentation of the Investigation findings and the
technical results were achieved.
1
the Collapse
and Fire
Safety
of World Trade Center
7.
MD.
W. Bukowski, and N.
J.
Carino. 2005. Federal Building
and Fire
Safety Investigation of
World Trade Center Disaster: Design, Construction, and Maintenance of Structural and Life Safety
Systems.
NIST NCSTAR
1-1.
National Institute of Standards and Technology. Gaithersburg,
MD,
September. Fanella, D. A., A. T. Derecho, and S. K. Ghosh. 2005. Federal Building
Investigation of the
NIST NCSTAR
and Fire
Safety
World Trade Center Disaster: Design and Construction of Structural Systems.
1-1 A.
National Institute of Standards and Technology. Gaithersburg,
MD,
September.
Ghosh,
S. K.,
and X. Liang. 2005. Federal Building and Fire Safety Investigation of the World
Trade Center Disaster: Comparison of Building Code Structural Requirements. NIST NCSTAR 1-lB. National Institute of Standards and Technology. Gaithersburg, MD, September. Fanella, D. A., A. T. Derecho, and S. K. Ghosh. 2005. Federal Building
Investigation of the
Systems.
MD,
NIST
NCSTAR
Safety to Structural
1-lC. National Institute of Standards and Technology. Gaithersburg,
September.
Grill, R. A.,
and D. A. Johnson. 2005. Federal Building and Fire
Trade Center Disaster: Fire Protection and Life Construction of World Trade Center
Occupancy. NIST
MD,
and Fire
World Trade Center Disaster: Maintenance and Modifications
NCSTAR
I, 2,
and
7
Safety'
Safet}' Investigation
of the World
Provisions Applied to the Design and
and Post-Construction Provisions Applied after
1-lD. National Institute of Standards and Technology. Gaithersburg,
September.
Razza,
J.
C, and
R. A. Grill. 2005. Federal Building
and Fire
Safety Investigation of the
World
Trade Center Disaster: Comparison of Codes, Standards, and Practices in Use at the Time of the Design and Construction of World Trade Center 1, 2, and 7. NIST NCSTAR 1-lE. National Institute
of Standards and Technology. Gaithersburg,
Grill, R. A.,
MD,
September.
Investigation of the World Trade Center Disaster: Comparison of the
xxu
and Fire Safety 1968 and Current (2003) New
D. A. Johnson, and D. A. Fanella. 2005. Federal Building
NIST NCSTAR
1-2A,
WTC Investigation
Preface
York
NIST NCSTAR
Building Code Provisions.
CiTy-
Technology. Gaithersburg,
MD,
1-lF. National Institute of Standards
and
September.
and D. A. Johnson. 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Amendments to the Fire Protection and Life Safety Provisions of the New
Grill. R. A.,
Building Code by Local Lmvs Adopted While World Trade Center
York
City-
Use.
NIST NCSTAR
1, 2,
and
Were
7
1-lG. National Institute of Standards and Technology. Gaithersburg,
in
MD,
September. Grill. R. A.,
and D. A. Johnson. 2005. Federal Building and Fire Safety Investigation of the World
Trade Center Disaster: Post-Construction Modifications
of World Trade Center
I
and 2. NIST
Technology. Gaithersburg, Grill,
MD,
NCSTAR
to
Fire Protection
and Life
Safety Systems
1-lH. National Institute of Standards and
September.
R. A., D. A. Johnson, and D. A. Fanella. 2005. Federal Building and Fire Safety Investigation
of the World Trade Center Disaster: Post-Consti'uction Modifications to Fire Protection, Safety, and Stiiictural Systems of World Trade Center 7. NIST NCSTAR I-II. National Standards and Technology. Gaithersburg, Grill, R. A.,
MD.
Life Institute
of
September.
and D. A. Johnson. 2005. Federal Building and Fire Safety Investigation of the World
Trade Center Disaster: Design.
World Trade Center Gaithersburg,
MD,
7.
Installation,
NIST NCSTAR
1-1
and Operation of Fuel System for Emergency Power
J.
in
National Institute of Standards and Technology.
September.
Sadek, F. 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster:
Baseline Structural Peiformance and Aircraft Impact Towers.
NIST NCSTAR
1-2.
Damage Analysis of the World Trade Center
National Institute of Standards and Technology. Gaithersburg,
MD,
September. Faschan,
W.
J.,
and R. B. Garlock. 2005. Federal Building and Fire Safety Investigation of the
World Trade Center Disaster: Reference Stnictural Models and Baseline Performance Analysis of World Trade Center Towers. NIST NCSTAR 1-2A. National Institute of Standards and
the
Technology. Gaithersburg,
MD,
September.
Kirkpatrick. S. W.. R. T. Bocchieri, F. Sadek, R. A. MacNeill, S. Holmes, B. D. Peterson,
R.
W.
Cilke. C. Navarro. 2005. Federal Building
Center Disaster: Analysis ofAircraft Impacts
NCSTAR
and Fire
into the
Safety Investigation of the
World Trade Center Towers, NIST
1-2B. National Institute of Standards and Technology. Gaithersburg,
MD,
September.
W. Banovic, T. Foecke, C. N. McCowan, T. A. Siewert, and J. D. McColskey. 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Mechanical and Metallurgical Analysis of Structural Steel. NIST NCSTAR 1-3. National Gayle, F. W., R.
Institute
J.
Fields,
W.
World Trade
E. Luecke, S.
of Standards and Technology. Gaithersburg,
Luecke,
W.
E., T.
A. Siewert, and F.
W.
MD.
September.
Gayle. 2005. Federal Building
and Fire
Safety
Investigation of the World Trade Center Disaster: Contemporaneous Structural Steel Specifications.
Gaithersburg,
NIST NCSTAR
1-2A,
NIST
Special Publication 1-3A. National Institute of Standards and Technology.
MD,
September.
WTC
Investigation
xxiii
Preface
Banovic,
S.
W.
2005. Federal Building
and Technology. Gaithersburg, Banovic,
S.
and Fire
MD,
of the World Trade Center
Safet}' Investigation
and Identification. NIST
Disaster: Steel Inventoiy
NCSTAR
1-3B. National Institute of Standards
September.
W., and T. Foecke. 2005. Federal Building and Fire
Safet}' Investigation
of the World
Damage and Failure Modes of Structural Steel Components. NIST National Institute of Standards and Technology. Gaithersburg, MD, September.
Trade Center Disaster:
NCSTAR Luecke,
1-3C.
W.
E., J.
T. A. Siewert,
D. McColskey, C. N.
and
W.
F.
McCowan,
S.
W. Banovic,
Trade Center Disaster: Mechanical Properties of Structural
S.
J.
Fields, T. Foecke,
NIST NCSTAR
Steels.
National Institute of Standards and Technology. Gaithersburg,
Banovic,
R.
Gayle. 2005. Federal Building and Fire Safet}' Investigation of the World
MD,
1-3D.
September.
W., C. N. McCowan, and W. E. Luecke. 2005. Federal Building and Fire Safety
World Trade Center Disaster: Physical Properties of Structural Steels. NIST 1-3E. National Institute of Standards and Technology. Gaithersburg, MD, September.
Investigation of the
NCSTAR
Evans, D. D., R. D. Peacock, E. D. Kuligowski,
W.
S.
W.
Dols, and
L. Grosshandler. 2005.
Federal
Building and Fire Safety Investigation of the World Trade Center Disaster: Active Fire Protection Systems.
NIST NCSTAR
1
National Institute of Standards and Technology. Gaithersburg,
-4.
MD,
September.
Kuligowski, E. D., D. D. Evans, and R. D. Peacock. 2005. Federal Building and Fire Safety Investigation of the
NCSTAR
NIST
2001.
World Trade Center Disaster: Post-Construction Fires Prior I
to
September
-4A. National Institute of Standards and Technology. Gaithersburg,
II,
MD,
September.
Hopkins, M.,
Schoenrock, and E. Budnick. 2005. Federal Building and Fire Safety Investigation
J.
of the World Trade Center Disaster: Fire Suppression Systems. NIST Institute
of Standards and Technology. Gaithersburg,
Keough, R.
J.,
and R. A.
Grill.
Ferreira,
M.
J.,
and
S.
M.
September.
MD,
NIST NCSTAR
1-4C. National Institute of Standards
September.
Strege. 2005. Federal Building
and Fire
World Trade Center Disaster: Smoke Management Systems. NIST Institute
of Standards and Technology. Gaithersburg,
MD,
Safet}' Investigation
NCSTAR
Pitts,
and K. R. Prasad. 2005. Federal Building and Fire
Center Disaster: Reconstruction of the Fires
in the
Pitts,
the
W. M., K. M.
Butler,
T.
J.
Ohlemiller,
Safet}' Investigation
of the World Trade
World Trade Center Towers. NIST
National Institute of Standards and Technology. Gaithersburg,
of the
1-4D. National
September.
Gann, R. G., A. Hamins, K. B. McGrattan, G. W. Mulholland, H. E. Nelson,
W. M.
1-4B. National
2005. Federal Building and Fire Safety Investigation of the World
Trade Center Disaster: Fire Alarm Systems.
and Technology. Gaithersburg,
MD,
NCSTAR
MD,
NCSTAR
1-5.
September.
and V. Junker. 2005. Federal Building and Fire
Safet}' Investigation
of
World Trade Center Disaster: Visual Evidence, Damage Estimates, and Timeline Analysis.
NIST
NCSTAR
1-5 A. National Institute of Standards
and Technology. Gaithersburg,
MD,
September.
XXIV
NIST NCSTAR
1-2A,
WTC Investigation
Preface
Hamins, A.. A. Maranghides, K. B. McGrattan. J.
Yang, G. Mulholland, K. R. Prasad.
S.
E. Johnsson, T.
J.
Ohlemiller,
Kukuck, R. Anleitner and
M. Donnelly,
T. McAllister. 2005.
Federal
and Fire Safety Investigation of the World Trade Center Disaster: Experiments and Modeling of Structural Steel Elements Exposed to Fire. NIST NCSTAR 1 -5B. National Institute of
Building
Standards and Technology. Gaithersburg, Ohlemiller. T.
J..
MD,
September.
W. Mulholland. A. Maranghides.
G.
J. J.
Filliben.
and R. G. Gann. 2005. Federal
Building and Fire Safety Investigation of the World Trade Center Disaster: Fire Tests of Single
NIST NCSTAR
Office Workstations.
MD.
Gaithersburg,
Gann, R.
G.,
M. A.
1-5C. National Institute of Standards and Technology.
September. Riley,
J.
Federal Building and Fire
M. Repp. A.
S.
Whittaker, A.
Safety' Investigation
Ceiling Tile Systems to Shocks.
Technology. Gaithersburg.
NIST NCSTAR
MD,
M. Reinhom, and
P.
A. Hough. 2005.
World Trade Center Disaster: Reaction of
of the
1-5D. National Institute of Standards and
September.
Hamins. A.. A. Maranghides, K. B. McGrattan, T.
J.
Ohlemiller, and R. Anleitner. 2005. Federal
Building and Fire Safety Investigation of the World Trade Center Disaster: Experiments and
Modeling of Multiple Workstations Burning in a Compartment. NIST NCSTAR 1-5E. National Institute of Standards and Technology. Gaithersburg, MD, September. McGrattan, K.
B., C.
Investigation of the
Bouldin, and G. Forney. 2005. Federal Building and Fire Safety
World Trade Center Disaster: Computer Simulation of the Fires
NIST NCSTAR
Trade Center Towers. Gaithersburg,
MD,
in the
World
1-5F. National Institute of Standards and Technology.
September.
Baum. 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Fire Structure Interface and Thermal Response of the World Trade Center
Prasad, K. R., and H. R.
NIST
Towers.
MD, Gross,
J.
NCSTAR
1-5G. National Institute of Standards and Technology. Gaithersburg,
September.
L..
and T. McAllister. 2005. Federal Building and Fire Safety Investigation of the World Trade
Center Disaster: Structural Fire Response and Probable Collapse Sequence of the World Trade Center Towers.
NIST
NCSTAR
1-6.
National Institute of Standards and Technology. Gaithersburg,
MD,
September. Carino, N.
J.,
M. A. Stames, J. L. Gross, J. C. Yang, S. Kukuck, K. R. Prasad, and R. W. Bukowski. and Fire Safet\- Investigation of the World Trade Center Disaster: Passive
2005. Federal Building
NIST
Fire Protection. Gaithersburg,
Gross,
J.,
MD,
NCSTAR
1
-6A. National Institute of Standards and Technology.
September.
F. Herx'ey,
M.
Izydorek,
J.
Mammoser, and
J.
Treadway. 2005. Federal Building and
Fire Safety Investigation of the World Trade Center Disaster: Fire Resistance Tests of Floor Truss Systems.
MD.
NIST
NCSTAR
1
-6B. National Institute of Standards and Technology. Gaithersburg,
September.
Zarghamee, M.
S., S.
M. Mudlock, W.
NIST NCSTAR
1-2A.
I.
Bolourchi. D.
Naguib, R.
WTC Investigation
W.
Eggers, O. O. Erbay, F.
P. Ojdrovic,
A. T. Sarawit,
P.
W. Kan,
R Barrett,
J.
Y. Kitane, A. A. Liepins, L. Gross,
and
XXV
Preface
T. P. McAllister. 2005.
Federal Building and Fire Safety Investigation of the World Trade Center
Disaster: Component, Connection,
and Subsystem
Structural Analysis.
National Institute of Standards and Technology. Gaithersburg,
Zarghamee, M.
S.,
MD,
Y. Kitane, O. O. Erbay, T. P. McAllister, and
J.
NIST NCSTAR
1-6C.
September.
L. Gross. 2005. Federal
Building and Fire Safety Investigation of the World Trade Center Disaster: Global Structural Analysis of the Response of the World Trade Center Towers to Impact
NCSTAR
Pitts,
MD,
1-6D. National Institute of Standards and Technology. Gaithersburg,
McAllister, T., R.
W. M.
Damage and Fire. NIST
W. Bukowski,
R. G. Gann,
J.
September.
L. Gross, K. B. McGrattan, H. E. Nelson, L. Phan,
K. R. Prasad, F. Sadek. 2006. Federal Building and Fire Safety Investigation of the World
Trade Center Disaster: Structural Fire Response and Probable Collapse Sequence of World Trade Center
(Provisional).
7.
Gaithersburg,
NIST
NCSTAR
I-6E. National Institute of Standards and Technology.
MD.
Gilsanz, R.. V. Arbitrio, C. Anders, D. Chlebus, K. Ezzeldin, J.
W. Guo,
P.
Moloney, A. Montalva,
Oh, K. Rubenacker. 2006. Federal Building and Fire Safety Investigation of the World Trade
Center Disaster: Structural Analysis of the Response of World Trade Center 7
and Fire.
(Provisional).
Gaithersburg,
NIST
NCSTAR
to
Debris
Damage
1-6F. National Institute of Standards and Technology.
MD.
Kim, W. 2006. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Analysis of September 11, 2001, Seismogram Data. (Provisional).
National Institute of Standards and Technology. Gaithersburg,
NIST NCSTAR
1-6G.
MD.
Nelson, K. 2006. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: The
Con Ed Substation
in
World Trade Center
7.
(Provisional).
National Institute of Standards and Technology. Gaithersburg,
Averill,
J.
NIST NCSTAR
1-6H.
MD.
D., D. S. Mileti, R. D. Peacock, E. D. Kuligowski, N. Groner, G. Proulx, P. A.
Reneke, and
H. E. Nelson. 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster:
Occupant Behavior, Egress, and Emergency Communication. NIST Standards and Technology. Gaithersburg,
MD,
NCSTAR
1-7.
National Institute of
September.
Fahy, R., and G. Proulx. 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Analysis of Published Accounts of the World Trade Center Evacuation. NIST
NCSTAR Zmud,
J.
1-7A. National Institute of Standards and Technology. Gaithersburg,
2005. Federal Building
and Fire
Safet}' Investigation
Disaster: Technical Documentation for Survey Administration. Institute
of Standards and Technology. Gaithersburg,
MD,
MD,
September.
of the World Trade Center
NIST NCSTAR
1-7B. National
September.
and R. L. Vettori. 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: The Emergency Response Operations. NIST NCSTAR 1-8. National Institute of
Lawson,
J.
R.,
Standards and Technology. Gaithersburg,
XXVI
MD,
September.
NIST NCSTAR
1-2A,
WTC
Investigation
Executive Summary
INTRODUCTION
E.1
This report presents the work conducted to estabhsh the basehne performance of the North and South
World Trade Center Towers
(WTC
1
and
WTC 2) under design gravity and wind loading conditions.
Baseline performance results include basic infomiation about the behavior of the towers, such as inter-story drift under
wind
loads, floor deflections
under gravity loads, demand/capacity
and
total
ratios for
primary structural components, exterior columns response (shear lag effects and presence of tensile forces),
performance of connections, and the towers' resistance to shear sliding and overturning.
The primary
tasks that
were undertaken
to establish the baseline
performance included the following:
structural databases for the primary structural components of the WTC WTC 2 towers from the original computer printouts of the structural documents.
•
To develop
•
To
1
and
de\ elop reference structural analysis models that capture the intended behavior of each of
the rvvo towers using the generated databases. These reference the baseline performance of the towers
models
for other phases
of the National
and also served
models were used
as a reference for
more
to establish
detailed
of Standards and Technology (NIST)
Institute
investigation.
•
•
To develop
estimates of design gravity (dead and live loads) and wind loads on each of the
two towers
for implementation into the reference structural models.
To perform the
E.2
linear, static structural
analyses to establish the baseline performance of each of
two towers under design gravity and wind
loads.
DEVELOPMENT OF STRUCTURAL DATABASES FOR THE
WTC TOWERS This task included the dev elopment of structural databases of the primary components of the
WTC 2 towers.
The
structural design
generated for use
The
electronic databases
in the
beam
utilized in the
implemented
and
were developed from original computer printouts of the
development of the reference structural models of the towers.
structural databases contained the
computer and hand-tabulated data
original
schedule. In addition,
schedule) and Drawing
was
1
documents, including modifications made after construction. The databases were
components of the towers from the columns, and
WTC
Book
Drawing Books
1
through
5,
for the primary structural
including exterior walls, core
some information from Drawing Book 6
9 (beams in the hat truss region)
were included
modeling of the towers. Some modifications
in the databases, including strengthening
both towers and reinforcing of two comer core column
that
in the
were made
(core bracing
database
of a number of core columns at floors
45
to
files as
at floors
it
were
to the towers
98 to 106 of
97 of WTC 2 due to the
construction of a concrete vault at floor 97.
NISTNCSTAR
1-2A.
WTC
Investigation
xxvii
Executive
The
Summary
task included the scanning and digitization of the original drawing books, a four-step quality control
procedure, cross section property calculations, and development of the relational databases to link the
generated database
files into a
fonnat suitable for the development of the structural models.
DEVELOPMENT OF REFERENCE STRUCTURAL MODELS FOR THE
E.3
WTC TOWERS This task included the development of reference structural analysis models that capture the intended
behavior of each of the two towers using the generated databases. These reference models were used to establish the baseline for aircraft impact
perfonnance of the towers and also served as a reference for more detailed models
damage
analysis and thermal -structural response and collapse initiation analysis.
The
main types of models developed were: •
Two for
global models of the major structural components and systems for the towers, one each
WTC
1
and
WTC 2.
The models included
all
primary structural components
in the
towers, including exterior walls (columns and spandrel beams), core columns, exterior wall
bracing in the basement floors, core bracing at the mechanical floors, core bracing at the main
lobby atrium levels, hat trusses, and rigid and flexible diaphragms representing the floor systems.
To
validate the global models, the calculated natural frequencies of
compared with those measured on
WTC
1
were
and good agreement between the calculated and
the tower,
measured values was obtained. •
One model each of the
typical tioiss-framed floor (floor
framed floor (floor 75 of WTC
2).
96 of WTC
The models included
all
1)
and typical beam-
major structural components
in
the floor system, including primai7 and bridging tmsses, beams, strap anchors and horizontal trusses, concrete slabs,
studies
and viscoelastic dampers. To validate the floor models, several
were canied out
hand calculations
to
compare
stresses
and deflections estimated from the model with
for representative composite sections.
between the model
results
Good agreement was
obtained
and hand calculations.
Parametric studies were perfonned to evaluate the behavior of typical portions of the structure and to
develop simplified models for implementation into the global models. These parametric studies included detailed and simplified
models of typical exterior and comer wall panels and floor systems.
GRAVITY AND WIND LOADS ON THE WTC GLOBAL MODELS
E.4
This task included the development of estimates of design gravity and wind loads on the towers for
implementation into the reference structural models and use in the baseline performance analysis. Various wind loads were considered
in this study, including
wind loads based on two recent wind tunnel
(CPP) and Rowan Williams Davis and Irwin,
Inc.
and wind load estimates developed by NIST from
CPP
and
RWDI
reports
and
wind loads used
studies conducted in
(RWDI) critical
in the original
WTC design,
2002 by Cermak Peterka Peterson,
Inc.
for insurance litigation concerning the towers,
assessment of information obtained from the
state-of-the-art considerations.
The following
three loading cases
were
considered for the baseline perfonnance analysis:
xxvui
NISTNCSTAR
1-2A,
WTC Investigation
Summary
Executive
WTC design
Original
•
loads case. Loads included dead and live loads as in original
WTC design in conjunction with original WTC design wind loads. •
State-of-the-practice case.
Loads included dead loads; cun'ent
(NYCBC
and wind loads from the
2001)
accordance with
live loads;
NYCBC 2001
New York
City Building
Code
RWDl wind tunnel study, scaled in
wind speed.
Refined NIST estimate case. Loads included dead loads; live loads from the American
•
(ASCE
Society of Civil Engineers
7-02) Standard (a national standard); and
wind loads
developed by NIST.
The purpose of using
WTC design loads was to evaluate the performance of the towers under
the original
original design loading conditions
and ascertain whether those loads and the corresponding design were
adequate given the knowledge available of-the-practice and the refined
successive changes
The study
NIST
at
The
the time of the design.
estimate cases
was
to better
pui"pose of considering the state-
understand and assess the effects of
codes, and practices on wind design practices for
in standards,
tall
buildings.
WTC design wind load estimates exceeded those established by the 1968. when the WTC towers were designed, and up to and including 2001. The design
indicated that the original
NYCBC prior to
values were also higher than those required by other prescriptive building codes of the time.
The two orthogonal base shear and base moment components used in the original design were in general smaller than the CPP, RWDl, and NIST estimates. However, the most unfavorable combined peaks from the original design
RWDl. and NIST
were larger than, or smaller by
estimates. This
is
due
at
most
1
5 percent than, estimates
to the conservative
based on the CPP,
procedure used to combine the loads
in the
original design.
The estimated wind-induced loads on
the towers vary
tunnel/climatological studies conducted by
Considering the differences between
CPP
RWDl
and
and
by
as
RWDl
CPP
much in
as
40 percent between the wind
2002. with
results, the
RWDl
CPP
loads
being the larger.
may be viewed
as a "lower-
estimate, state-of-the-practice case."
BASELINE PERFORMANCE ANALYSIS OF THE WTC GLOBAL MODELS
E.5 The
WTC
1
and
WTC
2 global models were each analyzed under the three loading cases described above
to establish their baseline performance.
•
Under
the original
were about 56.6 (H/263)
in the
the drifts for
N-S
WTC
is
a
summary of the
results:
WTC design loads, the cumulative drifts at the top of the WTC (H/304) and 55.7
in.
These
respectively.
The following
drifts
(H/309)
were about 51.2
direction for 1
in.
WTC
2.
in.
in the
(H/335)
1
tower
E-W and N-S directions, in the E-W direction and 65.3
in.
For the lower estimate, state-of-the-practice case,
were larger than those from the original design case by about 0.5 percent
E-W and N-S directions, respectively. For the lower estimate, statecase for WTC 2, the E-W drift was larger than that of the original design case
and 22 percent for the of-the-practice
by about 16 percent, and the N-S
drift
was smaller by about
15 percent.
The
drifts
obtained
from the refined NIST estimate case were about 25 percent larger than those from the
NISTNCSTAR
1-2A.
WTC
Investigation
state-
xxix
Summary
Executive
between the base
of-the practice case. These differences are consistent with the differences
shears for the three loading cases.
•
The demand/capacity
(DCR) were based on
ratios
the allowable stress design procedure
were estimated using the AISC Specifications (1989). The estimated from the original
results indicated that
and
DCRs
WTC design load case were, in general, close to those obtained
for the lower estimate, state-of-the practice case. For both cases, a small fraction of structural
components had
DCRs
exterior walls at the
•
These were mainly observed
larger than 1.0.
columns around the comers, where the hat
walls,
and below floor
and
at
core perimeter columns 901 and 908 for
The
refined
NIST
9;
and
columns on the 600
(2) the core
case estimated
DCRs
much
truss
line
in
both towers
at (1) the
connected to the exterior
between
floors
80 and 106
of their height.
were higher than those of the original
WTC design
estimates and the lower state-of-the-practice estimates for the following reasons: The
NIST
estimated wind loads were about 25 percent higher than those used in the lower state-of-thepractice estimate, and mixed,
wind
loads.
It is
those estimated by original
which
some higher and
noted that the
CPP
NIST
others lower than the original
(an upper estimate, state-of-the practice case). In addition, the
WTC design and the state-of-the-practice cases used NYCBC
result in
lower
WTC design
estimated wind loads are about 20 percent smaller than
DCRs
than the
ASCE
load combinations,
7-02 load combinations used for the refined
NIST
case.
•
Under
WTC design dead and wind loads, tension forces were
a combination of the original
observed in the exterior walls of both towers. The forces were largest at the base of the building and at the comers. These tensile column loads were transferred from one panel to
another through the column splices. The
DCR ratios for the exterior wall splice cormections
under the effect of the tensile forces for the two towers were shown to be •
For the towers' resistance
to shear sliding
and overturning due
to
less than 1.0.
wind, the dead loads that
acted on the perimeter walls of the towers provided resistance to shear sliding and
overtuming
at the
foundation level. Considering the resistance to shear sliding under wind
load, the factor of safety
was calculated
against overtuming ranged from
1
.9 to
to
be between 10 and
1
1.5,
while the factor of safety
2.7 for both towers.
BASELINE PERFORMANCE ANALYSIS OF THE TYPICAL FLOOR
E.6
MODELS The
typical floor
models were both analyzed under gravity
loads.
The following
is
a
summary of the-
results:
•
For the typical tmss-framed floor (floor 96 of WTC less than 1.14 for the original
ASCE
1),
the
DCRs
for all floor trusses
were
WTC Design Criteria loads and WTC Design Criteria loading, the DCR was less than less than 0.86 for the
7-02 loading. Under the original
1.00 for 99.4 percent of the floor truss components. For the area outside the core, the average ratio
of the
DCRs
under the
ASCE
Criteria loading for all floor tmsses
beams inside the core were
XXX
7-02 loading to the
was about
less than
1
.08,
DCRs
under the original
0.80. For the core area, the
and more than 99 percent had a
NISTNCSTAR
WTC Design
DCRs
for all floor
DCR of less than
1-2A,
WTC Investigation
Executive
1
.0.
1.79
Under in.,
the original
0.57
in.,
WTC
and 1.44
in.
Design Criteria loading, the for
the long span one-way
maximum
Summary
floor deflections
trusses, short
were
span one-way trusses,
and the two-way zone, respectively. •
For the typical beam-framed floor (floor 75 of WTC 2) under the original
where the
span and short span zones under the original
and 0.70
NISTNCSTAR
1-2A,
WTC Design
DCRs for all floor beams were less than .0 except for two core beams shear DCRs were 1.125 and 1.09. The maximum mid-span deflections of the long
Criteria loading, the
in.,
WTC
1
WTC Design Criteria loads were about
1.55 in.
respectively.
Investigation
xxxi
Executive
Summary
This page intentionally
xxxn
left
blank.
NISTNCSTAR
1-2A,
WTC Investigation
Chapter
1
Introduction
The
was
objective of this analysis
Trade Center Towers
(WTC
1
and
to establish the baseline
performance of the North and South World
WTC 2) under design gravity and wind loading conditions.
Baseline
perfonnance results pro\ ide basic information about the towers" behavior under design loading conditions, including total and inter-story drift under demand/'capacit\' ratios for the primary structural
wind
loads, floor deflections under gravity loads,
components of the towers, exterior columns response
(shear lag effects and presence of tensile forces), performance of connections, and the towers" resistance
and overturning. The primary tasks that were undertaken
to shear sliding
to establish the baseline
performance include the following: de\ elop structural databases for the primary structural components of the WTC WTC 2 towers from the original computer printouts of the structural documents.
•
To
•
To develop two
the
and
reference structural analysis models that capture the intended behavior of each of
tov\ ers
using the generated databases. These reference models were used to establish
the baseline performance of the towers
models
1
for aircraft
and also served as a reference for more detailed
impact damage analysis and thermal-structural response and collapse
initiation analysis.
To
•
dex elop estimates of design gravity (dead and live loads) and
wind loads on each of the
tu o towers for implementation into the reference structural models.
To perform
•
the
Chapter
1
tv\'o
performance of each of
linear, static structural analyses to establish the baseline
towers under design gravity and wind loads.
of this report presents an introduction and a brief description of the structural system of the
towers. Chapter 2 presents an outline and description of the methodology used for the development of the structural databases for both towers, along with the relational databases that are
used to link the generated
databases for use in the de\ elopment of the reference structural models. Chapter 3 presents the
development of the reference structural analysis models for
WTC
1
and
WTC
2,
including global tower
models, typical floor models, and parametric studies conducted for the development of the global models.
Chapter 4 pro\ ides a discussion on the loading cases used outlines the dex elopment of the gravity and
wind loads on
in the
baseline performance analysis and
the global tower models. Chapters 5 and 6
outline the results of the baseline perfonnance analysis for the global tower respectively.
A summary of the report
is
presented in Chapter
DESCRIPTION OF
1.1.1
Global Structural System 1
and
structure.
WTC 2 each
The
NISTNCSTAR
buildings,
1-2A.
WTC
floors models,
WTC STRUCTURAL SYSTEM
1.1
WTC
models and
7.
consisted of a
1 1
0-story above grade structure and a 6-story
which were each approximately 207
Investigation
ft
by 207
ft
below grade
square in plan and with story
1
Chapter
1
heights of typically 12
ft,
rose to heights of 1,368
ft
(WTC
1)
and 1,362
exterior walls of the towers supported part of the gravity loads
and
ft
(WTC
all lateral
above ground. The
2)
and were constructed
loads,
of steel, closely spaced built-up columns and deep spandrels. The core contained coIuituis that supported
The core area was approximately 135
the remainder of the gravity loads of the towers.
The distances between
(Fig. 1-1).
36
ft
and 60
ft.
the rectangular core
The areas outside of the core were
and
the square exterior wall
free of columns,
ft
by 87
ft
in plan
were approximately
and the floors were supported by
truss-framing in the tenant areas and beam-framing in the mechanical rooms and other areas.
..^/jt-p-e-tt^im
B
no a g a a -*ni-o-ii.a-a-^anBa n na mn na n a n n o g
Source: Reproduced with permission
Figure 1-1. Typical
The primary the
basement
of
The
B aff ana a
Port Authority of
i
New
<*
York and
WTC tower architectural floor plan
New
columns, core bracing
at the
mechanical
Jersey.
(floor 26,
structural systems for the towers included exterior columns, spandrel floors, core
-S;
aa ann g a n a a a-ti-g-a-
WTC
2).
beams, and bracing
floors, core bracing at the
in
main lobby
atrium levels, hat trusses, and the floor systems.
The
exterior wall
center.
columns from the foundation
They were
level
of the exterior wall between the Concourse level and
2
up
to elevation
built-up of steel plates and connected
363
ft
were spaced 10
ft
0
by deep spandrels. Bracings existed
the foundation (Fig. 1-2).
in.
on
in the
plane
Between elevation 363
NISTNCSTAR
1-2A,
WTC
ft
Investigation
Introduction
and floor spaced
7,
the single exterior wall
at 3 ft
4
in.
columns spaced 10
on center as shown
Source: Reproduced with permission
of
in Fig.
The
Figure 1-2. Typical
The
exterior wall
columns above
and were connected
to
ft
in.
on center transitioned
to three
columns
1-2 (see also Fig. 3-6).
Port Authority of
WTC
floor 7 that
0
New
York and
New
Jersey.
exterior wall, foundation to floor 9.
were spaced
3
ft
4
in.
each other by spandrel plates, typically 52
on center, were built-up of steel
in.
deep.
The
exterior
plates,
columns and
spandrels were pre-assembled into exterior wall panels, typically 3 -columns wide by 3 -stories
tall (refer
to Fig. 3-9).
The core columns were
typically built-up
structural steel shapes at the at 3
ft
above floor
mechanical
level.
levels,
and
upper
floors.
box members
at the
lower floors and transitioned into rolled
The core columns were
typically spliced at three-story intervals
Diagonal bracing of the core columns existed
in the
At the top of each tower, hat
at
the lobby atrium levels, the
area of the hat truss.
trusses interconnected the core
columns with the exterior wall panels and
provided a base for the antennae. The vertical members of the hat trusses were wide flange core columns.
NISTNCSTAR
1-2A,
WTC
Investigation
3
Chapter
1
The diagonals were primarily wide flange
rolled sections, with the exception of the
end diagonals
connecting the core to the exterior walls, which consisted of built-up box sections. The majority of the
members in the hat truss system were wide flange and built-up box section floor beams. The members of the hat trusses were shown in the structural drawings SA/B-400 series elevations (see
horizontal
Fig. 1-3).
Source: Reproduced with permission of The Port Authority of
Figure 1-3. Typical
WTC
New Yorl< and New
Jersey.
tower hat truss elevation (Drawing
SA 401).
Floor Structural System
1.1.2
In the typical
WTC tower floor plan, the area inside the core was framed with rolled structural steel
shapes acting in a composite fashion with formed concrete slabs. The area outside the core was framed either in trusses (typical
on tenant
floors) or in rolled structural steel shapes (typical
on mechanical
floors).
Truss-Framed Floors
—The majority of
WTC towers were tenant floors where the areas
the floors of the
outside of the core were constructed of steel trusses acting in a composite fashion with concrete slabs cast
over metal deck. The trusses consisted of double angle top and bottom chords with round bar webs and
were designed
to act in a
composite fashion with the concrete
the shear connection provided trusses pairs.
were placed
The
at
every other exterior column
Composite action was achieved by
slab.
by the web bar extending above
the top chord
line, resulting in
a 6
ft
and
Two
into the slab.
8 in. spacing
between
typical floor consisted of three truss zones: a long span zone, a short span zone,
truss
and a two-way
zone (see Fig. 1-4).
The
floor trusses
were pre-assembled
the primary trusses
was about 36
ft
into floor panels as defined in the contract drawings.
in the short direction
and 60
ft
in the
The
specifications.
The two-way zone included
the long-span direction (primary trusses) as well the bridging trusses (secondary trusses). trusses
had additional strength and connectivity
tmsses to form a two-way spanning truss grid as shown the short span truss at the
in
to act in
tandem with
all
of
trusses in
The secondary
the long spanning
zones labeled two-way area
comer of the core was heavier than
long span trusses that framed to
4
them
to enable
of
long direction. The floor panels
included prmiary trusses, bridging trusses, deck support angles, metal deck, and strap anchors,
which were defined by the contract drawings and
span"
the typical ones because
in Fig. 1-4. it
Also;
did support the
it.
NISTNCSTAR
1-2A,
WTC Investigation
Introduction
Since the relative stiffness of the bridging trusses was significant in the two-way zone compared to that of the short span trusses, and since the
comer of the
core, tw 0 directional structural behavior lighter
-
in the
sides and the
one-way zones,
comer of the
the bridging trusses
were
H
]
was dominant.
M M:
^
floor truss panel types
Drawing Book
were indicated
'
1
'
M
5
in the stmctural plans (Fig. 1-5).
7 for information regarding the
D for damper information
" -
WTC floor truss framing
Figure 1-4. Typical
Book
was supported on two
and the floor was supported on only two sides (exterior wall spandrels and core perimeter beams),
so only one-way behavior
The
floor
was developed,
components of the floor
(see Chapter 2 for
more
details).
zones. The plans
truss panels,
refer in turn to
and
to
Drawing
Drawing Book 7 provided panel by
panel layout plans (Fig. 1-6) and elevations (Fig. 1-7) of each referenced tmss. The section through a floor panel after the concrete
indicate
power and telephone
NISTNCSTAR
1-2A.
was placed
is
illustrated in Fig. 1-8.
cells within the
WTC Investigation
Note
that the
dashed
lines in Fig.
1-5
metal deck constmction.
5
Chapter
1
Source: Reproduced with permission
of
The
Port Authority of
New York and New
Jersey.
Enhanced by
NIST.
Figure 1-5. Part plan of floor 96 of
6
WTC
1 (Drawing SA-104), components of typical truss framing system.
NISTNCSTAR
1-2A,
WTC Investigation
w
Introduction
cpcxpcpoocpo cpcpcpooocpo
3>!
Stee/ Deck
/=^/a/7
II '
j
"
Oof ig oaf
^iTi.
hc^e d*'m.
L -\see schedule
M
-
\
see schedule
colc/mn reference line
^ Extfirior
y- ^d3-2 7-^sS-2
I
£4lA
C327 7
Ci2T7
»
CZ2T3
—
*
o O o o o <
(
\ £4:4
<
C22 Tl'
T 7 .4B^-2a
P/o/? Top Chord Source: Reproduced
with permission of
The
Port Authority of
Figure 1-6. Typical
NISTNCSTAR
1-2A.
WTC
Investigation
WTC
5^ New York
and
New
7434-22./
Jersey.
floor panel layout plan.
?
Chapter
1
oo Soft- bole!
o
dirmzrision -M - sea? spherule _ ''i.^jSg """\ \l4® S>'-4' - ^G'-S" \
1
IJ^I
}
tfi)
cjiy
mj
t/iji
r/?j
r-fi
/
r Bxh&rior
coUmn
Floor f/ne
\
Source: Reproduced
with permission of
The
Port Authority of
Figure 1-7. Typical
New
York and
WTC floor truss
New
!
f
Jersey.
elevation.
4
Slab on 1-1/2
in.
in.
Metal
Deck !
r
]
n T^pxq/
\ ^:
\J
\j
\J
/ \—
\J
\J
^
\l
\
//
xj-
f
rcrj
1
Primary Truss Members
Source: Reproduced with permission
r
!
-
fi ;
-Lao
>.
;
C3E^i-^ara
Bridging Truss
of
The
Port Authority of
New
York and
New
Jersey.
Enhanced by NIST.
Figure 1-8. Part section typical truss floor panel.
8
NISTNCSTAR
1-2A.
WTC
Investigation
Introduction
Viscoelastic
towers.
As
damping
units
were used
system to reduce the wind-induced vibrations of the
in the floor
the towers oscillated during
wind
excitations, part of the energy of oscillation
between the bottom chords of the floor trusses and the exterior associated detail in Fig. 1-10. The figures bolts,
show
unit.
the construction of the
and viscoelastic material dimensions. The dampers were defined
details
on the dampers design, construction, and Gusset
was dissipated
The dampers were located wall columns as shown in Fig. 1-9 and
through shear deformations in the viscoelastic part of the damping
testing, refer to
NIST
dampers along with the in
plates,
Drawing Book D. For
NCSTAR
the
further
1-1.'
plate
Source: Reproduced with permission
of
The
Port Authority of
New
York and
New Jersey.
Enhanced by NIST.
Figure 1-9. Floor truss with exterior wall end detail.
^
Holes
01
lor
high tensile bolls
~.
0.05" X 4' X 10'
Section a-a
Source: Reproduced with permission of The Port Authority of New York and New Jersey. Enhanced by NIST.
Figure 1-10. Details of the damping unit used
This reference
is
to
one of the companion documents from
this Investigation.
in
A
the truss-framed floors.
list
of these documents appears
in the
Preface
to this report.
NIST NCSTAR
1-2A,
WTC
Investigation
9
Chapter
1
Beam-Framed Floors
—The
beam- framed
typical locations of the
mechanical mezzanines, and the floors above the mezzanines
were constructed using rolled consisted of
W27 beams
spacing was 6
ft
The
8 in.
The beam framing
structural steel shapes.
in the
W16 beams
long span region and
steel
beams acted
were the mechanical
floors
(e.g., floors
floors, the
41, 42, and 43). These floors
for the typical floor
in the short
system
span region. Typical
beam
composite fashion with the nonnal weight concrete slab
in
on metal deck.
The mechanical spanned
floors
were
in the direction
5
larger,
was framed
A
2
in.
in.
metal deck outside the core. The deck
Yi in.
concrete topping slab
in.
deep.
at
6
ft
1
8
intervals
in.
was placed on top of the stmctural
The beam-framed
normal weight concrete slab on
floors
by a
slab.
beams were
The
typically
above the mechanical mezzanine
1/2 in. metal deck, while the core slab
weight concrete. The floor slabs were omitted from to provide
1
similarly to the core of the truss-framed floors, but the steel
and the concrete slab was 6
had a 7 3/4
concrete slabs on
of the primary beams and was supported typically
4C5.4 deck support channel. core area
in.
was
much of the mechanical mezzanines
8
nornial
in.
outside the core
double height space for the mechanical equipment.
Similar to the truss-framed floors, viscoelastic damping units were used in the beam-framed floors to
reduce wind-induced vibrations. The dampers were located between the bottom flanges of the floor
beams and
the exterior wall
framed floors were
between the damping floor
beams
as can
columns as shown
in Fig.
1-11.
The dampers
that
slightly longer than those used in the truss-frames floors.
units
were used
in the
beam-
Also the connections
and the floor trusses were different than those between the damping units and
be seen from Fig. 1-9 and Fig. 1-1
—
1.
Reference Exterior
column
reference
Wide-flange
z:
line
Two %" 0
floor line
beam
bolts
Two
1
Va"
0
bolts
(A490)
Two
1
"
0
bolts-
(A490)
o o Vs"
-Damping Type B
Pt-^ 2'-
unit
6" 43/4'
Figure 1-11. Beam-framing was added outside of the core.
The
Damping
unit
used
to truss-framed floors at levels
in
the beam-framed floors.
which supported escalators or
escalator floors occurred typically in the
two
levels directly
stairs in the areas
above the
mechanical rooms.
10
NISTNCSTAR
1-2A,
WTC Investigation
1
Chapter 2
Development of Structural Databases for the WTC Towers
introduction
2.1
The objective of this chapter
is
to describe the
development of electronic structural databases for the
primary structural components of the World Trade Center towers
computer printouts of the
structural documents.
development of the reference
structural
(WTC
1
and
WTC 2) from the original
These databases were generated for use
models of the towers (see Chapter
in the
3).
Section 2.2 briefly describes the structural design documents of the towers. Section 2.3 presents an
overview of the database development and contents, while Sec. 2.4 outlines the methodology used to develop the structural databases from the original computer printouts, and the relational databases used for the subsequent
development of the reference
Section 2.5 describes the modifications primar\' structural
properties
to elements
of the database based on changes made
after construction.
presented in Sec. 2.6. Section 2.7 provides a
models of the towers (see Chapter
The
3).
to the
calculation of cross section
summary of the
chapter.
description of the WTC STRUCTURAL DOCUMENTS
2.2
The
is
made
components of the towers
structural analysis
WTC structural
drawings were issued
in
two main fonnats: large-sized sheets containing plan and
elevation information and smaller book-sized drawings containing details and tabulated infonnation.
Throughout the
WTCB
denotes
WTC drawings, Tower A or WTCA denotes WTC (North Tower) and Tower B or WTC 2 (South Tower). For WTC and WTC 2, the large-size sheets are listed in 1
1
Appendix A. These large-sized drawings always make reference notes, sections,
and
details.
The
structural
drawing books for
to the structural
WTC
1
and
drawing books
in their
WTC 2 contain the following
materials:
•
Book
1
contains exterior wall information to elevation 363
ft.
(Dates: 02/1967 to 12/1968,
Approx. 213 pages.) •
Book
2 contains exterior wall information elevation 363
ft
to floor 9.
(Dates: 04/1967 to
12/1967, Approx. 62 pages.)
•
•
Book
3 contains core
Book 4
column information. (Dates: 03/1967
to 09/1969,
Approx. 137 pages.)
contains exterior wall information floor 9 to floor 110. (Dates: 04/1967 to 10/1972,
Approx. 1.080 pages.)
beam
schedule. (Dates: 05/1 967 to 08/1 969, Approx. 292 pages.)
•
Book
5 contains the
•
Book
6 contains connection details and core bracing. (Dates: 08/1967 to 05/1969,
Approx. 1,060 pages.)
NIST NCSTAR
1-2A.
WTC
Investigation
1
.
Chapter 2
;
,
7 contains truss floor panel information. (Dates: 10/1967 to 07/1969, Approx. 345
Book
•
pages.)
.
(Dates: 03/1968 to 07/1974, Approx. 926 pages.)
•
Book
8 contains concrete notes
•
Book
9 contains roof area column splice details. (Dates: 05/1 970 to 04/1971, Approx.
and
details.
440 pages.)
Book
•
18 contains strap anchor and core truss seat information. (Dates: 10/1968 to
1
1/1969,
Approx. 219 pages.)
Book
•
19 contains revisions after fabrication. (Dates: 08/1968 to 05/1975. Approx. 374
pages.)
Books
•
Book 20
•
Book D
10, 11, 12,
never used
19)
contains
damper
details.
(Dates: 03/1969 to 09/1971, Approx. 43 pages.)
and 13 contain infomiation on the sub-grade
in the original
Until fabrication
Book
contains structural steel details. (Dates: 07/1968 to 03/1971, Approx. 41 pages.)
was begun,
were modified
in
the drawings
and drawing books
commenced. At
14, 15, 16,
and 17 were
that time,
above (with the exception of
listed
keeping with requests for changes by contractor(s) and early tenant
The drawings were modified up
modifications.
Books
structure.
design documents.
Book
19
was
until
introduced.
such time as the fabrication of elements It
contained the information regarding 'revisions
after fabrication'.
Leslie E. Robertson Associates, R.L.L.P.
(LERA)
believes that the original structural drawings represent
significantly accurate 'as-builf drawings for the towers.
scope, they
became
tenant modification requests
'WTC
by
LERA
were then documented
additions to the mechanical levels) modifications were
Jersey
(PANYNJ)
openings, were
made by
in a single
book of quarter-size
all
the changes. In
made by The
other engineers. In these instances,
The few modifications made by
viewed
LERA to
1
LERA
instances (e.g.,
York and
does not have record of the work
components compiled listed in
in the
member properties
WTC structural databases.
as non-essential for the
•
WTC structural databases that
Table 2-1
9 has records of other modifications to structural elements of the
WTC towers that were
development of the reference models of the towers and as such were not
included in the structural databases.
12
the
on the global behavior of the towers are
Drawing Book
plans,
Engineering. In other instances, tenant modifications, such as adding floor
pertaining to the reference structural models and were not included in the
have an
some
Port Authority of New
completed. These modifications were considered to not significantly affect the
effect
large in
Tenant Structural Modifications Book.' Later tenant modifications were mostly
archived on a job-by-job basis without a central accounting for
New
became
separate projects (e.g.. the Fiduciary Trust Vault Project, see Sec. 2.5.2). Tenant
structural modifications designed
referred to as the
As
These modifications are outlined
in
Appendix B.
NISTNCSTAR
1-2A,
WTC Investigation
A
Development of Structural Databases
members
Table 2-1. Modifications to
of the
WTC
WTC
for the
Towers
database (WTC-DB).
WTC-DB Item
Tower
Description
WTC
Core column
1
Numerous
1
WTC WTC
Bank
WTP VV
DLrillUlUU, Ul
Modified
Archi\ ed
98-106
Core columns
Book
3
Book
2
1
V_
1 1
Col.
508B and
Col.
1008B
45-97
Core columns
Book
3
LERA
*^01.
JZH,
D-z
level
Permieter
February 1993
bracing
column and
repair
G313Aand G304A
bracing
EXCO
4
Element Effected
19
2
Vault 1. J
Floor
and
reinforcing
Fiduciary
Element
WTC
stair
26
Col. 901
1
IN
A
I
P209
PR A
P10031 18
NA
Core column
LERA P 1003249
OVERVIEW OF THE WTC STRUCTURAL DATABASE (WTC-DB)
2.3
The
original
WTC design documents were devised to limit the need for repetition in documenting the data
shared between different elements with similar characteristics. The drawing book schedules refer to
subsequent tables for infonnation the
common
to several lines of the
amount of repeated infomiation, and thereby,
book data within the databases were linked
same schedule.
the data checking of the digital
minimize
In an effort to
WTC-DB,
drawing
the
manner. In order to accurately follow the original
in a similar
flow of the drawing book links, flowcharts of the drawing books
to
be digitized were developed. These
flowcharts were used to organize the links of the digitized data within the relational database. The
flowcharts are illustrated in Appendix C. coluinns)
The
is
shown
WTC-DB
An
exainple of such flowcharts for
Drawing Book
3 (core
in Fig. 2-1.
contained the computer and hand-tabulated data for the major structural components from
beam schedule for the towers. Where infonnation from Drawing Books through 5 was modified by Drawing Book 9 and would affect the towers" modeling, the information was included in the database. In addition, some infonnation from Drawing Book 6 (core bracing schedule) and Drawing Book 9 (beams in the hat truss original
Drawing Books
1
through
5,
including exterior walls, core columns, and
1
1
region)
was included
The drawing book
in the
tables
database
were
first
files as
it
digitized
was
utilized in the finite
and stored
in Microsoft
element modeling of the towers.
Excel format
files.
The Excel
files
included several worksheets that described the evolution of the data from the drawing book to the final database format, as well as additional infonnation and notes for interpreting the data. Refer to
Appendix
The
D
for the
list
of Excel fonnat
files.
WTC relational database linked the Excel files and allowed users to view and select data through
query commands. The primai7 benefit of the relational database fonnat was the ability to
programmatically query the database for data required
The query
in
assembling the structural models of the towers.
routine allowed multiple users the ability to review, extract, and export the basic data in any
required fonn.
The
data can be manipulated using Structured Query
Language (SQL) according
desired output, for example the structure of the user's finite element model input
NISTNCSTAR
1-2A,
WTC
Investigation
to the
file.
13
Chapter 2
Core Column Number/Location and Elevation
Core Column Schedule
3-Al-2>48 [47TC] 3-B1-2 WTCA-Ukl-t
>48 [47TC]
iircri.liiiAdala.ji
Is
I
A_C«rcC.il)
ttTCH-likJ-CorcColii.Hiiala xls (U_r.>rcCol>
Base Details
Splice Details
Floor 106 Splice Details
((15))
((15))
((15))
3-AB2-20, 2!
3-AB2-4,7,8>i3, 15>!6 [lOTH]
[2D]
3-AB2-3.1>19[18D]
Shape Property Table Shape Property Table.xls
3-AB2-3 [ID]
lAB^ShapcPropI
IB.CI Splice Location
Reference Floor Elevation
((!))
((2. 3))
3-AB2-22 [ID]
3-A2-23[lTC] 3-B2-23[lTC] \\TCA-Bk3-Corer(>liiiAfloorelcv,xlslA_RcffilcvlJPR/LWR|
«TCb-Bk.1-CorcColinBtk>orclov-xls(B RctElcvlU'RyLXTOl
NOTES: 1
.
Tower A B or AB, and page number where page types include; Computer generated tables; TH - Hand wntlen tables; D - Diagrams
4-AB-* Denotes Drawing Book
Number of pages and
2.
[*TC]
3.
*.xls Excel spreadsheet file
4.
((*))
TC
5.
6.
1*1
-
4,
,
type,
name; (AB_*'**) database heading
Reference note key from original Drawing Book infonnation Relational database link
(i.e.
Figures of columns and panels are
Figure 2-1, Drawing
Book
table.
Excel column number) from previous *.xls
shown from
file.
inside of building looking out, unless otherwise noted.
WTC
3 flowchart:
1
and
WTC
2 core columns, foundation to
floor 106.
2.4
METHODOLOGY FOR THE WTC-DB DEVELOPMENT
2.4.1
Data Entry
The tabulated portions of WTC Drawing Books Tagged Image
File
Format (TIFF) image
files.
1,
then opened in an Optical Character Recognition text file.
The
characters that were not
files
and 9 were
first
scanned and stored
in
containing the tabulated information were
(OCR) program
OCR program was modified to allow
document conversion process.
14
2. 3, 4, 5, 6,
The image
that converted the infonnation into a
for the filtration of unnecessary characters during the
In other words, the user could direct the
on the actual page. As an example,
if after
program
to
block specific
reviewing a table, one recognizes that
NISTNCSTAR
1-2A,
WTC
Investigation
Development of Structural Databases
it
uniformly contains numbers and only the characters "A, B,
for the
WTC
Towers
and 'V" then the remaining characters can
be frozen out by the software. This reduced the misinterpretation, as an example, of a 'Z' for a
'2,'
or an
'O' for a 'zero.'
The raw
was then opened
text file
in a
word processing program, where
it
was compared with
the original
hardcopy drawing books. As needed, data columns were adjusted, and obvious errors were individually
The
corrected.
'cleaned' text file
was then imported
When
headings and proper ahgnment.
into a Microsoft Excel spreadsheet with
importing into Excel, "texf was the
of the scanned information to avoid the misinterpretation of fractions as dates
Excel macro was written
at this
stage to convert the text fractions into
product of this stage was an Excel
file that
(e.g.,
3/8 as
fractions.
March
The
8).
An
final
contains the information from the drawing book table.
Quality Control
2.4.2
Checking began during the
OCR data entry process, where the files being entered and the OCR software
interpretation
were viewed simultaneously. This was considered a
complete, the
file
The 'Second Check' of data
cell
—An engineer not involved during
in the
in a
check.
Once
the Excel file
The 'Cross-Check
OCR process performed a second,
was
sample
in four pages,
page was compared with the original drawing books. Discrepancies of the
Rectify'
the database provided
the
random but methodical manner. For approximately once
were then either re-entered using
litigation
first
entered the 'second check* process.
checking of the database every
number
column
format used for handling
cell
by
OCR or were
Check
—After completing
the 'second check,' the files were
a consultant for the leaseholder
concerning the towers (provided by
files
individually corrected to agree with the original books.
NIST
as
of the
compared with
WTC towers as part of insurance
Government Furnished Infonnation [GFI]) using
a
Once compared, conflicting information appeared in a yellow of compared information in the "Calculation" macro formula
cross-check macro formula worksheet. highlighted cell displaying both sets
worksheet. The
cell
was then reviewed and confirmed with the
the developed worksheet, data
were
rectified,
WTC drawing books.
and the yellow highlight
then removed by comparing the files again. If errors were from the not modified, but the cell
compared again, and the repeated to remove
all
was highlighted cell
in
blue to note that
it
the yellow cells so that only blue highlighted cells remained.
—
Finally, the files
were reviewed
as
2.4.3
The next
final
data were
were then
was
The worksheet
comparison.
for completeness, formatting,
made to find any numbers that may have been input worksheet was used to develop the member section properties. \A
files
retained for the record of the original comparison, and the updated
worksheet 'ComparisonFINAL' was retained for the record of the
check
GFI worksheet, raw GFI
had been reviewed. The
were from
worksheet was
color in the 'Calculation' worksheet changed to blue. The process
'ComparisonORlGINAL' was
Final Revien
If errors
in the 'Calculation'
and data
units.
A
final
as text letters. Following this review, the
Cross Section Property Calculations step
was
members included in the database. The moment of inertia (7), section modulus (S),
to calculate the cross section properties for the
section properties calculated included cross sectional area (A), plastic section
modulus
NISTNCSTAR
1-2A,
(Z), radius
WTC
of gyration
Investigation
(r),
and torsional constant
(J) for
both the major and minor
15
Chapter 2
axes,
where applicable. The Section Designer function of SAP2000 Version 8 (SAP2000 2002) was used
to calculate the cross section properties since
the
program
to
of the section would be input into the
The
current rolled shape database in
shapes used
streamlines the development of the models and enables
it
perform more precise code checks, as the dimensions of each plate element finite
was
part
element model.
SAP2000
constmction of the
in the
that
represents the
modem
day rolling practices. The rolled
WTC towers were from a different era and, thus, had different
properties in comparison to present day shapes. Therefore, a rolled shape database consistent with the
time of construction was developed. See Sec. 2.6.5 for further discussion about the rolled shape database.
As
Development
Relational Database
2.4.4
discussed earlier, the original
WTC drawing books were designed to avoid repeating identical
The drawing book schedules,
infonnation.
several lines of the
minimize the data
same schedule.
in the digital
therefore, refer to other tables for infomiation
In keeping with the nature of the original
WTC-DB,
the drawing
common
drawing books and
to
to
book and section property data were linked using
Microsoft Access.
The assembly of the
relational database
began with the mapping of the original
WTC drawing book into
flowcharts (see Fig. 2-1). The digitized drawing book data with the coiresponding cross sectional
member properties from
the Excel-fonnat files
program and partitioned
into tables.
The
were then imported
tables
into the Microsoft
were then joined using the
Access database
links cataloged in the
flowcharts. These tables were developed to provide the input files for the finite element modeling of the
towers as illustrated
Appendix
Chapter
The generated Microsoft Access database
3.
relational database
is
files are listed in
described in the tutorial included in Appendix F.
MODIFICATIONS TO DATABASE ELEMENTS
2.5
Most
The
E.
in
members and elements defined within the WTC-DB could be fully defined by the original As outlined in Table 2-1, however, some modifications were made, and these
original
data in the drawing books.
are described in the following sections.
Of the
items outhned in Table 2-1, items
1
and 2 were included
within the database.
Core Column Reinforcing
2.5.1
A number of core columns
in
pages 19-AB-974.1 through
from
both 4,
WTC
shows
floors 98 to 106 in both towers
1
at Floors
and
that core
98 to 106
WTC 2 were reinforced at floors 98 to
ends.
The
to the
were reinforced with
database tables of Book
was appended floors 104
19,
Three methods were used to attach
steel plates.
were welded
to the flanges; (2) the plates
webs; and (3) the plates, which were parallel to the web, were welded to the flange
plate infonnation (width, thickness, length,
three-story height)
Book
columns 501, 508, 703, 803, 904. 1002, 1006, and 1007
the reinforcing plates to the wide flange columns: (1) the plates
were welded
106.
was
3.
and yield strength) was incoiporated
into the
Since the plates varied from floor to floor, the original column (defined over a
split into typically three floor-by-floor sections,
to include either
U
(upper),
and the designation of the column
M (middle), or L (lower) designation (refer to Fig. 2-2).
and 106, the columns were two-stories high. Hence, the columns
at
these floors had only
For
U
and L designations. The section property calculations included the contributions of the reinforcing plate
16
NISTNCSTAR
1-2A,
WTC
Investigation
Development of Structural Databases
at
each
the
lev el.
column
for the
For the built-up section property data, the reinforcing plate was considered
for
its
to
WTC
Towers
be applied to
floor-to-floor height.
Col. Splice
FL
101
CC703A101U
FL 100
CC703A101M
FL99 Reinforcing Plate
CC703A101L Col. Splice
FL98 44-
Figure 2-2. Core column reinforcement.
Core Column Reinforcing Due to Construction of Fiduciary Trust Vault
2.5.2
The Fiduciary Trust Company added a concrete vault at floor 97 of WTC 2, which required reinforcing two comer core columns at the north end of the core (columns 508 and 1008). This work was included the
WTC Towers A and B
Structural
Structural
Drawing 765-S-A^ indicated
steel plates
from floors 45
up box columns (floors 45
that
WTC 2 core columns
508 and 1008 were reinforced with
to 97.
The reinforcement consisted of plates welded
to 83)
and the flanges of the rolled shape
columns
reinforcing plate modifications and the reinforcing plates' yield strength,
Book
3 data contained in the
substantially affect the
WTC-DB. The
member
to reinforce
is,
It is
presumed
that these
of the
were added
built-
These
to the original
the added plates increased the capacity
only the column splice, they were not included in
For the reinforced columns, no specific information
these elements.
F,,,
to the flanges
(floors 83 to 97).
database included plates that were long enough to
properties of the column, that
of the columns. Where the plates appeared the database.
in
Renovation Drawings Reference Manual. The Fiduciary Trust
is
available about the fireproofing of
elements were fireproofed in the same
way and
using the same
materials as other parts of the structure.
NISTNCSTAR
1-2A,
WTC
Investigation
17
Chapter 2
The reinforcing
plate data
were tabulated and incorporated into the database
the length of the plates
When was
the north and south faces of the columns,
i.e.,
the
was added
as the
to differentiate
column designation "LN"
of the plates on the north face of the column. Again, when calculating the built-up
refers to the length
column
on
same manner
in the
plates discussed in the previous section, except that a second length designation
properties, the plate
was assumed
the length of the reinforcing plate
attributed to the
to
be continuous along the floor-to-floor height of the column.
shown
in the
drawing was greater than the floor height, the plate
two column segments. Where the
plate extended over the entire height of the
segment, the length was tabulated as the height of the column segment. The remaining length of plate
was
attributed to the other
Repair Due to the Bombing of February 26, 1993
2.5.3
The 1993 bombing B-2
column segment.
level.
The
resulted in structural
face of the
damage
column toward
WTC
to
the explosion
1,
centered
was
at
developed a hairline crack. The column was reinforced locally
to
exterior
column 324 (south
bowed, and the
slightly
splice in the
wall),
column
account for the loss of steel area. The
bracing on either side was replaced with equivalent sections and attached in a similar manner as the originals.
modification to the
tenant alteration
was provided
adjacent to core column 901 A,
unknowingly resulted unbraced about for a review.
1;
its
for
found the
was made
for this repair.
Interoffice Stair
for an interoffice stair
between floors 25 and 26
was perfonned by an engineering finn
in the loss
minor axis
LERA
been made for
WTC
WTC-DB
Tenant Alteration for an
2.5.4
A
No
in
WTC
1.
This work,
LERA) and
of a core column bracing strap (refer to Fig. 2-3), leaving the column
two
stories.
column
this modification.
(other than
The
effect
PANYNJ
The
stability to
LERA
alerted
be adequate.
No
of removing the strap
to the issue,
modification to the
is
accounted for
and asked
WTC-DB
in the global
LERA has
model of
see Sec. 3.2.3.
Drawing Book Data Discrepancies
2.5.5
In the original
•
WTC drawing book data, the following discrepancies were discovered by LERA:
Book
1,
3-1/18.
page l-B-15. For member number G31 lA, the inch portion of the length
modified to be 3-1/8 •
Book
3,
is listed
as
Based on the comparison with similar bracing types in the area, this dimension was in. in
the
WTC-DB.
page 3-Al-lO. For core column 601 A between floors 86
column type
is
hsted as 213. Type 213
plates, but for this location
is
a
column type which by
no plate data were provided
with comparisons with similar columns
in plan, led to
to
89 and 89 to 92, the
definition has reinforcing
in the schedule.
This, in combination
modifying the column type
to 111.
This also applies to column 60 IB, page 3-Bl-lO between floors 86 to 89 and 89 to 92.
•
Book
3,
listed as
page 3-B1^8. For column 1008B between floors 63 6 ksi
in the table.
floors, the yield strength
was modified
to
segments, the lower sphce detail number
18
to 66, the yield strength,
F,,, is
Based on the yield strength of the columns above and below these be 36
ksi.
is listed
For the same column number and floor
as "
OIG." Based on the lower
NISTNCSTAR
1-2A.
WTC
splice detail
Investigation
Development of Structural Databases
number of the columns above and below
these floors, the
for tfie
number was modified
to
WTC
Towers
be
"301G."
STRAP PLATE
"CORE
COLUMN
PU\N
— CORE COLUMN
—
I
1/2"
DECK
Source: Reproduced with permission of The Port Authority of New York and New Jersey. Enhanced by NIST.
Column section at original column strap detail book 1 8, page 1 8-AB2-1 2).
Figure 2-3.
•
Book W],
3,
is
5.5 in.
(taken from drawing
page 3-B1-9. For core column 508B between floors 21
tabulated as
W]
equals
1
1
.25 in.
However, length
B
for this
B minus two times t2 (see Fig. 2-A). WJ was modified to be in.
correctly in the table,
column
to 24, the length is
22
in.
Hence, assuming
of plate
and thickness t2
was
1,
t2 is
listed
1 1
-4
&2
CO
\/y ////// //Y/r
New
Figure 2-4. Core column series 300.
NISTNCSTAR
1-2A,
WTC
Investigation
19
Chapter 2
Book
•
6025
1,
page l-B-23 and 1-B2-19. The
listed in the tables are not explicitly
column shapes were assumed 1000
series
to
details for
shown
column types 1024, 1025, 5024, and
in the
drawing book. For these members,
be as shown in the typical details
in
page l-B-19 for the
columns, l-B-24 for the 5000 series column, and the l-B-27 for the 6000 series
column. •
Book
3,
in the
drawing book.
page 3-AB2-6. The column type 216 does not appear
to
be assigned to any member
SECTION PROPERTY CALCULATIONS
2.6
SAP2000 sections
Section Designer
was
typically used to calculate section properties for built-up sections.
were "built-up" within SAP2000
Section orientations were defined with the
page as the
detail is
shown
in the
The
by defining plate dimensions and offsets from 0-0 location.
X-X
axis horizontal to the
bottom of the original drawing book
drawing book. ^
During the process of calculating properties there was an exception
to this orientation rule.
Core column
members CC1007A104L, CC1002A104L, CC703A106L, CC1007B104L, CC1002B104L, and CC703B106L consist of a wide flange shape and web reinforcing plates. These members were input into SAP2000 rotated 90 degrees from the orientation shown in the details to utilize the default orientation of the wide flange section in Section Designer. Once the properties were calculated, the sections were placed in the WTC-DB following the orientation of the detail (i.e., the axis was shifted back 90 degrees).
When
rolled shapes
analysis
200
was used
series core
whose
were used
to create built-up sections, the rolled shapes database
to build the sections in
SAP2000
developed for
this
Section Designer as explained in Section 2.6.5.
columns (wide flange rolled columns reinforced with
plates) are
The
examples of members
properties were calculated in this manner.
Member Designations
2.6.1
For member section property calculations and assembly of the
named using
the following general
Microsoft Excel
member
designations.
finite
element models, the members were
The member designations are
listed in the
files.
First character:
•
•
•
•
20
—below tree-B Book 2 — wall tree-T Book — core columns-C Book 4— columns and spandrels-E
Book
1
exterior
3
exterior
NISTNCSTAR
1-2A,
WTC Investigation
Development of Structural Databases
for the
WTC
Towers
Second character: •
•
Third to
—column S—
C
spandrel and below grade exterior wall spandrel,
fifth character: (third to sixth
•
character for 4 digit
strut,
column
or bracing
e.g.,
1004)
Column number
Sixth character:
•
A—WTC
•
B—WTC 2
1
Seventh character and above:
—
•
Upper
•
U
(upper),
•
T
or
•
Detailletter (lowercase)
•
f
•
Elevation
or
B
C
splice level
M (middle), or L (lower)—column segment where reinforcing plates are added
—top
—
or bottom of nonprismatic columns
—(where more
—below
of column members had different cross sections along the
members:
Exterior
tree at level
C
in
Drawing Book
•
Exterior wall tree at level
E
in
Drawing Book 2
•
Exterior column type 300 (floor 9 to 106) in
For these three
sections
u all
member types,
2 (two different cross sections)
(three different cross sections)
Drawing Book 4 (two
left
were calculated and
database tables. In an effort to minimize repeated information, the raw input data for
were only shown
in the
rows
that
column number were not repeated
blank.
different cross sections)
the section properties of the different cross sections
corresponded to the
third (if any) cross sections, the calculated data followed in the
as the
calculated)
Multiple Section Property Calculation
•
listed in the
is
tree spandrel elevations
In the database, the following three types
length of the
than one section
face or center of nonprismatic spandrel
Column Member
2.6.2
columns
for core
Since the column
in these
number was used
rows of the
NISTNCSTAR
1-2A.
WTC
Investigation
first
all
cross section. For the second and
rows below. The constant raw data such
table,
as a link for the
only the row containing the raw input data and the
first
and
thus, the corresponding cells
were
development of the relational database,
cross section properties
were returned
in a query.
21
Chapter 2
and thus, the user must refer back information.
The
section
to the
names of the
distinguished by the last one to
two
Microsoft Access 'Tables' for the remaining section property
different cross sections along the
characters,
which
member
length were
where the section
identified the cross sections
properties were calculated.
For example, exterior column
member
(refer to Fig. 2-5).
EC339 (mechanical
The
floors) tapers over a portion
section properties above and
below
of the length of the
the spandrel
were calculated. The
column section above the spandrel was called EC339, while the column section below the spandrel was called
EC339cc. The
data for
suffix 'cc' denoted the section
EC339cc were not shown
below the spandrel. Note
in the table, as the inforaiation
was
Source: Reproduced with permission of The Port Authority of Enhanced by NIST.
the
New
same
that the
as for
York and
raw dimensional
EC339.
New Jersey.
Figure 2-5. Exterior column type 300, floor 9 to floor 106 (taken from
drawing book
22
4,
page 4-AB2-18).
NISTNCSTAR
1-2A,
WTC Investigation
Development of Structural Databases
Member
Spandrel
2.6.3
In the database, the exterior
Drawing Book
1
tables.
columns below elevation 363
had corresponding spandrels shown
ft
in
column
in the details in
The
the section properties of the different cross sections
The data were
section
listed in the
names of the
database
files as
which
series 5000, 6000,
Book
Towers
1
.
and 7000
in
There were two types of
shapes. For the tapered built-up
I
were calculated and
listed in the
database
described for columns with multiple cross sections.
different spandrel cross sections along the
the last three to four characters,
WTC
Multiple Section Property Calculation
spandrels for these members, tapered built-up box shapes and built-up
box shapes,
for the
identified the cross sections
member
length were distinguished by
where the section properties were
calculated.
For these exterior columns, there were spandrels elevation 350 first
section
(face).
ft,
was
the spandrels tapered, and
section
was
at
name had
corresponding section the spandrels
two
elevations, 332
ft
and 350
were shown
the center of the spandrel between
a Suffix
C
(center).
in the figures in the
ft
The
At
(see Fig. 2-6).
two cross section properties were
face of the exterior column, and the corresponding section
at the
The second
at
as a result
The
calculated.
name had
a Suffix
two exterior columns, and
F
the
elevations and locations of the cross sections of
"Cross Section" worksheets in the database Excel
files.
El. 363' -0
EL 350'
1
EL 332--0' SECTION (CENTER)
SECTION F (FACE)
(
a-0 EL.
318--0"
ELEVATION Source: Reproduced with permission
of
The
Port Authority of
New
York and
New
Jersey.
Enhanced by NIST.
Figure 2-6.
Column type 6000 with tapered spandrel pages 1-A2-27 and
(taken from drawing book
For example, four different section properties were calculated for exterior column 6009 first
section
was
the exterior
column
itself,
and
the section
1,
28).
name was BC6009A. The
in
WTC
1.
The
other three sections,
BS6009AB332, BS6009AT350C, and BS6009AT350F were for the spandrel sections. The suffix B332 in BS6009AB332 denoted the bottom spandrel at elevation 332 ft. Suffixes T350C and T350F in
NISTNCSTAR
1-2A.
WTC
Investigation
23
— Chapter 2
BS6009AT350C and BS6009AT350F, "C"
respectively, denoted the top spandrel at elevation 350
ft,
and the
or "F" identified the location where the section properties were calculated, see Fig. 2-6.
Section Property Calculation Comparisons
2.6.4
members whose section properties were included in the GFl database, the cross sectional GFI data were compared with the data contained within the WTC-DB. Most section property results differed between the GFI and the WTC-DB by no more than 1 percent. It was found that For
all
the
properties in the
results
from the calculations of the torsional constant,
were then used
to
confirm the accuracy of the
generated values used in the
LERA
WTC-DB
however, did vary.
J,
J calculation. For
LERA
in-house program
The approximate equation used column or box section
shown
as
core columns in
in-house programs
WTC
1
SAP2000
,
were on average 8 percent larger than J values calculated using the
in-house program, while the results provided by the
greater than
LERA
GFI database were on average
13 percent
J calculations.
to calculate in Fig.
2-7
J values by is
the
LERA
in-house program for a built-up
as follows:
2{bhy
—b + It
was found
that for
box
sections,
J values
calculated
h
(Eq. 2-1)
by the above equation matched
the
J values given
by SAP2000 Tube Section. However, for the same tube section, the J values given by SAP2000 Section Designer were greater than J given by SAP2000 Tube Section, even while
Computers and Structures,
equivalent. According to
by SAP2000 Section Designer
method
to calculate the
are
more accurate
as
Inc., the
SAP2000
all
other properties were
developer of SAP2000; the
J values given
Section Designer uses a finite element
J values, while an approximate equation
used
is
in
SAP2000 Tube
Section.
// Ay // \
4
\
tw
\ \
f
(b)
(a)
Figure 2-7. In order to
24
a built-up column.
minimize the complexity of the model, where the member cross-section was of the type
illustrated in Fig.
built-up
Box section and
2-7
box columns
(a),
in SAP2000 Tube Section. The remaining SAP2000 Section Designer.
box column members were defined
(similar to Fig.
2-7 b) were defined
in
NISTNCSTAR
1-2A,
WTC
Investigation
Development of Structural Databases
For members whose properties were not given
LERA in-house program were
in the
GFI
for the
WTC
Towers
database, hand calculations or calculations by
carried out to verify the results
from SAP2000 Section Designer for
at least
one section for each member type. La
summary,
was found
it
that
SAP2000
Section Designer provided section properties in close agreement
with calculated properties. In most cases these properties also closely matched with the properties listed in the
GFI
SAP2000 results disagreed with the GFI database, the resuhs SAP2000 calculation provided the correct properties. calculated using SAP2000 were used in the WTC-DB and the
database. In the cases where
were reviewed, and
it
was concluded
that the
Therefore, the section property results
development of the
element models of the towers.
finite
Rolled Shape Database
2.6.5
While the
members of the
majorit\' of the primary
rolled shapes
were also used. The
WTC towers'
super-stiucture were built-up
rolled shapes specified in the drawings in a
longer produced and, consequently, are not included in the rolled shape database
SAP2000. Therefore, properties.
The
result
was developed using
a rolled shape database
was
a file
named 'Shape Property
'WF Shape
'Database,' 'Excel Format.' and
Table.xls.'
Properties from SAP.'
file
are
no
embedded within
the old nomenclature
The
members,
number of cases
and section
contains three worksheets:
The following
is
a discussion of their
contents.
Data contained
in 'Database'
specific rolled shapes.
and 'Excel Format'
a single reference database for rolled shapes.
Manual of Steel Construction, American
(AISC
—Drawing Books
3, 4,
and
5 include reference to
The referenced shape names were extracted from these books and assembled
6th Edition) with
Most of the
Institute
into
section properties were obtained from the
of Steel Construction (AISC), Sixth Edition, 1963
few exceptions where cross sections were not included
in this edition.
Examples
of these exceptions include the following:
•
Section properties of
14WF455
to
14WF730 were
obtained from the Manual of Steel
Construction-Load and Resistance Factor Design, American
(AISC-LRFD
Third Edition, 2001
•
Section properties of the
•
MC-shapes
the
American
Institute
•
3rd Edition).
AISC-LRFD
18WF69 were
Institute
section properties of
of Steel Construction,
6CH12, 6CH15.1, 12CH40, 12CH45, and 12CH50 were obtained from
table in the
Section properties of
Institute
3rd Edition.
obtained from the Iron and Steel
of Steel Construction,
16H342 tabulated
1
in Iron
968.
1
Beams 1873
6WF342 was assumed
and Steel Beams 1873
to
to 1952,
have the same
to 1952, the
American
of Steel Construction, 1968.
For 7x5 tube,
Z^, Z,
.
and J were obtained from the AISC- Allowable Stress Design (ASD),
1989, 9th Edition.
•
For 2L
3 1/2 in. x 3 in. x 1/2 in.
from SAP's embedded
NISTNCSTAR
1-2A.
WTC
long leg back to back, the combined properties were taken
rolled shape database.
Investigation
25
Chapter 2
Data contained
'WF Shape Properties from SAP'
in
database was created
in
SAP2000 based on
—For
the rolled
wide flange shapes, an additional
the tabulated shape dimensions
from the AISC Manuals as
discussed above. Computers and Structures, Inc. provided an Microsoft Excel
file
named
'Proper.xls'
with a macro that allowed the accurate calculation of the section properties for use within SAP2000. This infonnation was then used by
members comprised of wide
SAP2000
Section Designer to calculate section properties for built-up
flange sections and added plates.
For calculation of the properties with Troper.xls,' dimensions of the webs and flanges, as well as the size of the
fillet,
were input
the input infonnation.
into the spreadsheet.
The
results
The macro then calculated the section properties based on
were shown
to
be
in
good agreement with the
original tabulated
properties.
SUMMARY
2.7
This chapter described the development of the electronic structural databases for the primary structural
components of the structural design
WTC towers.
These databases were developed from original computer printouts of the
documents, including modifications made
after construction.
The databases were
generated for use in the development of the reference structural models of the towers.
The
structural databases contained the
components of the towers from the
computer and hand-tabulated data for the primary
original
Drawing Books
1
through
5,
structural
including exterior walls, core
columns, and beam schedule. In addition, some information from Drawing Book 6 (core bracing schedule) and Drawing
were
utilized in the
Book
9 (beams in the hat truss region) were included in the database
modeling of the towers. Modifications
to the
databases included strengthening of a number of core columns reinforcing of two
comer core columns
at floors
45
to
files as
towers that were implemented
at floors
98
to
they
in the
106 of both towers and
97 of WTC 2 due to the construction of a concrete
vault at floor 97.
The
steps that
were undertaken
digitization of the original
to
develop the structural databases included: (1) the scanning and
drawing books,
(2) a four-step quality control procedure, (3) cross section
property calculations, and (4) the development of the relational databases to link the generated database files into
26
a format suitable for the development of the structural models.
NISTNCSTAR
1-2A,
WTC Investigation
Chapter 3
Development of Reference Structural Models for the WTC Towers
INTRODUCTION
3.1
The objective of this chapter
is
to
outHne the development of the reference structural analysis models
that
capture the intended behavior of each of the two towers. The models were used to establish the baseline
performance of the towers under gravity and wind loads. They also served as a reference for more
models used
detailed
for other phases of the National Institute of Standards
and Technology (NIST)
Investigation, including aircraft impact analysis and thennal-structural response
and collapse
initiation
analysis.
Included
in this
chapter are descriptions of the reference structural models, the
modehng
techniques, the
parametric studies utilized in the development of the models, and the methodology used to export to the
models the
from the
requisite data
relational database (see
Chapter
2).
The main types of models
developed are as follows: •
Two for
•
global models of the major structural components and systems for the towers, one each
World Trade Center (WTC)
One model each of the level) within the
All
models are
SAP2000
WTC
2.
typical truss-framed floor
impact and
linearly elastic
Structures, Inc.
and
1
and typical beam-framed floor (mechanical
fire regions.
and three-dimensional, and were developed using the Computers and
Software, Version 8
(SAP2000 2002).
Section 3.2 describes the dev elopment, contents, and verification of the global models of
WTC 2.
WTC
1
and
Sections 3.3 and 3.4 present the models for the typical truss-framed floor and beam-framed
floor, respectively.
Section 3.5 describes the parametric studies that were undertaken to facilitate the
development of the global models. Section 3.6 presents a summary of the chapter.
3.2
A
GLOBAL MODELS OF THE TOWERS
three-dimensional structural analysis computer model of the
6-story below-grade structure for each of the two towers
1
10-story above-grade structure and
was developed. The global models
for the
towers consisted of the major structural components and systems required to establish the baseline
performance of the towers under gravity and wind loads. In establishing the modeling techniques for the global models, parametric studies were performed to evaluate the behavior of typical portions of the structure
and develop simplified models
NISTNCSTAR
1-2 A.
WTC
Investigation
that
could be implemented
in the global
models (see Sec.
3.5).
27
Chapter 3
Components and Systems
3.2.1
The models included
all
at
the
the Towers' Global Models
primary structural elements
(core) columns, exterior wall bracing
bracing
in
main lobby atrium
in the towers, including exterior
basement
in the
levels, spandrel
beams, hat
trusses,
and
rigid
columns, interior
mechanical
floors, core bracing at the
floors, core
and flexible diaphragms
representing the floor systems, as developed in Sec. 3.5 of this report. While the global models did not
include the structural dampers in floor systems (see Sees. 3.3 and 3.4), the effect of the dampers on the
wind load
damping
accounted for
in the
of 2.5 percent (see Chapter
determination of equivalent
large
amount of data required
capability of the
WTC-DB
wind loads using
a total
4).
Coordinate System
to
assemble the tower models dictated
is
described in this section.
—The coordinate system
for the
model geometiy was based on
from the original drawings. Figure 3-1 shows the location of the the floor models.
The Z coordinates were based on
numbers were used throughout the models
Nomenclature
—A standard nomenclature
for
member
letter,
and floor
level.
column layout
axes for the global models and
The
original
for joints, frame names, to
and section names for use
know
in the
quickly where in the building a
names generally included
Frame element names generally included
end (second node). Section names were based on the section
the joint
as described in the
the
name
member
As an example, most nodes
28
in the building, sections
(or joints) in the
•
Column number
•
Tower
•
Floor level
•
S for column splice nodes only
•
J
letter
(A for
WTC
1
and
for
'j'
drawing book, and were
was
were named based on the frame member.
tower models were named according
B
column
at the
repeated for each steel yield strength assigned for that section. Alternatively, where the section
unique to a particular
column
identification.
located by viewing any given piece of the model. Joint
number, tower
X and Y
the
actual elevations of the towers.
models was established. The nomenclature enables the user is
that the relational database
be used (see Sec. 2.4.4). The methodology for the development of the models
using the relational database
section
static
Coordinate System, Nomenclature, and Models Assembly Overview
3.2.2
The
stresses is
ratio
to the following format:
WTC 2)
for spandrel splice nodes only
NISTNCSTAR
1-2A,
WTC
Investigation
Development of Reference
i
noT)
Structural
Models
for the
WTC
Towers
(3*2)
ir
ir
i
-
.
"
f
.
,
CORE
60±
>^-H>rK>ocM>rK -c ->c>oooo-i:K>o-c-e T»0 WAY
LDKC SPAN
6T-r
Source: Reproduced with permission from The Port Authority of
New York and New
Jersey.
Enhanced by NIST.
Figure 3-1. Global model coordinate axis location. Figure 3-2 illustrates the detailed frame and joint nomenclature for a t\pical exterior wall panel.
—
Model Assembly Oven ien .\n overv iew of the assembly of the data into the tower model herein along w ith an expanded section on the programmatic assembly of the models.
is
described
Following a basic study of modeling techniques and testing of S.AP2000. Version 8 input fonnat and capabilities,
it
was detennined
assemble them
that the best
approach w as to
di\ ide the
model
into a unified model. Manipulation of these individual parts
into six
was more
main
parts
and then
efficient than
attempting to build the whole model simultaneously.
NISTNCSTAR
1-2A.
WTC Investigation
29
Chapter 3
PANEL
COL +USLtS 1
COL2H/SL iS
C(>L3tUSl.rS
C0I..3+IJS!..+J
LSL
-
COLl iUSL
COL2HJSI
fOLJtUSL
C0L3+(USL-i)-fJ
USL-l
-
COLl-^diSL-I)
C0L2+iUSL-h
C0L3-HijSL-l)
COL3+{USL-2)+J lJSL-2
COLlnLiSL.-2)
COL2nUSL-2)
(;-OL3t(USL-2j
USL: Upper Splice Level COLl ,2 J+USL.i-J ).!-2 w Joint name EC+JOiNT ABOVE: Column name ES^.IOINT RIC5HT: Spandrel name :
Defined hy adjacent panel
TYPICAL PANEL NOMENCLATURE
Figure 3-2. Typical exterior panel nomenclature.
30
NISTNCSTAR
1-2A,
WTC Investigation
Development of Reference
The
six initial
Structural
Models
for tfie
WTC
Towers
models were:
Core columns •
Exterior wall, foundation to floor 4
•
Exterior wall trees (floors 4 to 9)
•
Exterior wall, floors 9 to
•
Exterior wall floors 107 to 110
•
Hat
1
06
truss
For the core columns and exterior walls
from queries of the
WTC-DB. The
at floors
9 to 106, most of the analysis input files were generated
other four parts of the model were assembled primarily in a
more
con\ entional manner.
Core columns and exterior wall panels
model development. Both property
\
ariations.
The
programming was used the
SAP2000
input
file
(floors 9 to 106)
parts included a large
quer\' files
were used
to gather the necessary data,
to convert the data into the
SAP2000
Joint coordinates table
•
Connectivity-frame/cable table
•
Frame
file
and then simple computer
format. Four main input tables for
section properties tables
—general —non-prismatic
-
Frame
section properties
-
Frame
section properties 5
-
Section designer properties 04
-
Section designer properties 05
-
Section designer properties
1
—shape
1
1
plate
Frame assignments
•
Gravity and wind load assignments
The remaining data were added •
Material properties
•
Frame
1/wide flange
—shape channel —shape
•
1-2A.
input
in the
section and material
were developed programmatically:
•
NISTNCSTAR
were the greatest data-intensive challenges
number of frame members and
table
directly in the
SAP2000 model;
local axis
WTC
Investigation
31
Chapter 3
•
Joint restraint
•
Insertion point
•
Constraint
After the joint coordinates, connectivity, frame section properties, and frame assignments were complete for the six parts, the individual
models were combined into a unified model. Rigid floor diaphragms,
flexible floor diaphragms, core bracings, gravity loads,
wind
loads,
and masses were then added
was spot-checked, and
the
The development of the
model was executed
WTC
1
and
to verify
1
model. While there were only minor differences
lower levels in
in section
are
in the basic structural
systems of the two towers, there
and material properties, and additional column transfers
at the
WTC 2.
Isometric views of the complete
model
perfonnance.
WTC 2 models were separate and consecutive endeavors. The WTC model were applied to the development of the WTC 2
lessons learned in the assembly of the
were significant differences
its
to the
model elements
unified model. After assembly of the model, the assignment of properties for selected
shown
in Fig.
A
3^.
WTC
1
model are shown
summary of the
WTC 2
Elevations of the complete
in Fig. 3-3.
of the global models of WTC
size
1
and
WTC 2
is
presented in Table 3-1. The following presents the details of each of the six parts used in the
development of the unified global models
for
WTC
Core Columns Modeling
3.2.3
Core column coordinates were tabulated based on the typically referenced at their centerlines.
Columns on
drawings along most of their height according (i.e.,
WTC 2.
and
1
WTC
1
lines
to the face
their
dimensions given
in the
varied along the height of the towers (typically
was chosen
to define the
1
to
which
1/2 in.
at this level,
The
in
plan
the floor trusses frame
centerline of these
drawing books. Where these column centerlines
column node. Thus,
constant along the tower height because
locations were
500 and 1000, however, were located
of the column
north face for 500 columns and south face for 1000 columns).
columns was based on
location
Column
structural drawings.
between three-story pieces), a representative
the
column coordinate
at floor
106 was used as a
these columns aligned with the hat truss above.
Offsets were not used to shift the column locations because the floor framing needed to equilibrate such offsets
was not included
The spandrel
in the
model.
centerline elevation
and used also for core columns.
was
were no spandrels
in exterior panels, reference elevations
used for the core columns. The reference elevations were defined
corresponded to the elevations of the top of the concrete
There were over 5,000 nodes
Database input and
later
table of
in the core
SAP2000 be
set
in the original
were
drawings and
floor.
column model. This amount of data required
that the Interactive
up using a macro. These data were converted
to text file format
imported into SAP. Built-up sections were defined as Section Designer sections, and wide
flange shapes were defined directly from "Section WFl. pro" identical to those in the database.
file
(see Sec. 2.6.5). All section
Around 1,280 Section Designer
imported through the Interactive Database function of
32
columns
selected as the representative floor elevation for exterior
If there
SAP2000
sections
to the
were defined
names were
in this
model and
model.
NISTNCSTAR
1-2A,
WTC
Investigation
Development of Reference
Structural
Models
for the
WTC
Towers
finiiHiiuMiiHiiiitiiititiiimiiMind
itiitiMiiiK
I
Ilium
iiiiiiiiini
II
I
It
itiiiiiiiiiii
I
mil iin mil HUM
IE
iiiiiiiiiiiii
I
Hill mill
i
ii
II
i
ii
iMiiilliiiiilimiiiiiiiiilliliiliiil
I
II
liiiiiMiiimiimiim iiiMiimiiit
i
it;
mum
I
iiiiiifiiiimiimiimiiiiiiimi 11)11
III III
III
mill mill
mil
m
it
nil
mi ii mi n
iiii
III
iiiiiiimii
I
I
I
Hill
III
I
I
I
mil
III
iiiuiHiin tiiniiiiiE lum iiiMiiiMiiii nil
I
I
I
mil!
III
I
mm
Ill
III
I
mill
II
mil III
II
I
iiiiitiiiiu
ittti
III
I
milt III
I
It
III
in IK
HI
I It
III
inmiiii iiiiiiiii iimiimiii iiiimii III III
iiie iiii
iiitliiil nil:
III
m lu
iiiiR nil
II
Em li
mil
IIII I liiniii II fill
II
I
II
II
II
I
II
It
II
It nil iimiti titimiMitt
I
II
I
itiiuinniiiinrti
I
II
I
1
11
I
itmiiii nil iHiiiniiiiii itiiiiiiiim
IIII
I
lilt;
miiiit iiimitiiit: mil ut II! nil nil III nil iiiE mil III mil It nil imiiiii iiii itiiim iiiiiiiii nil
mum mum
I
mil urn m iiit itmifmimiiiimiimntiiiitmii \m ml inimiimiimmii mil nil iiiiiiiiiiiiiiiiinii! mitiitr nil nil imiiiiiiiiiiiiiiiiiiM nil 11 nil i
I
1
1
I
1
1
iiiiiniiiiiiiiiiiuiiiiiiiiiiiiiiiiiiiiiir i
i
1
11
ure 3-4. Frame view of the WTC 2 model: exterior wall elevation and interior section illustrating the core columns, core bracing, and hat truss.
NISTNCSTAR
1-2A,
WTC Investigation
Development of Reference
Structural
Models
for the
WTC
Towers
Table 3-1. Approximate size of the reference structural models (rounded).
Number Model
Number
Degrees of
of
Number
of
of
Total
Number
Joints
Freedom
Frame Elements
Shell Elements
of Elements
WTC global model' WTC 2 global moder
53.700
218,700
73.900
10.000
83,900
51.200
200,000
73.700
4.800
78,500
Txpical truss-framed model
28.100
166,000
27.700
14.800
42,500
6.500
35.700
7.500
4,600
12,100
1
TNjjical a.
beam-framed model
Model does not include
floors except for flexible
The core columns were defined
(i.e.,
was considered
occur
to
(Drawing Book
Most
the section
ft
to
later.
node
above the floor
at the
level.
and nodes were only defined
three-story
representative floor
In the models, however, at
these levels
column pieces were unique, as tabulated
in the
A section for each three-story piece was defined and then assigned to each
3).
of the three frame members that
show
17 floors as explained
members spanning from node
at the floor level,
typically at spandrel centerlines).
WTC-DB
at
Splices in core columns occurred typically 3
elevations.
the splice
as frame
diaphragms
made up
that
column. Using the SAP2000 shading feature to graphically
on the model, each frame was rotated
to its proper orientation
based on the structural
drawings.
In the as-designed drawings, there
were
strap anchors connecting the core
At floor 26 of WTC
slab to provide lateral bracing for the column.
removed during a renovation project
that
The
Associates, R.L.L.P. (see Sec. 2.5.4).
column from
releasing the
The models of the
ft,
locations
all
in the direction
the straps at
column 901 were
a finn other than Leslie E. Robertson at this
of the
location
was included
in the
model by
straps.
shown
in the
ft
were developed manually, assigning joints and
drawings. The elevation drawings show that below elevation at
10
ft
and braced with spandrels and diagonals. Joints were
where diagonals braced the columns. However, when coordinates were not given
drawings, joint coordinates were determined based on the geometry of the diagonal. Details in
WTC Drawing Book ft
as
columns were typically spaced
defined at
253
of the straps
exterior wall up to elevation 363
members connectivity
in the
diaphragm
loss
1,
to the concrete floor
Exterior Wall, Foundation to Floor 4 Modeling
3.2.4
363
the
was engineered by
columns
(level
1
show
that the
column-diagonal intersections had continuity. Joints
at
elevation
B-5) were defined only where the diagonals connect to the columns, since the tower floor did
not frame into the exterior spandrels
at that floor.
W'here noted in elevation drawings, spandrel centerline elevations were used to define joint coordinates. Additionally, joints were defined at the spandrel splice 3 in. (floor 3)
and
at
elevation 329
The majority of the elements
at
ft
midway between two columns
at elevation
350
ft
3 in. (floor 2) to allow for section type transitions.
these levels were defined as Section Designer sections, except for
box
shapes, which were defined as "Box/Tube." Channel shapes were defined directly from the
"Section WFl. pro"
Around 200
file (see
Sec. 2.6.5). All section
sections were defined in this
which was used
NISTNCSTAR
to
1-2A,
names were
model using
identical to those in the database.
the Interactive
Database function of SAP2000,
import data into the model.
WTC
Investigation
35
Chapter 3
Typical columns were connected from bottom to top, and typical spandrels were connected from right.
The SAP2000 program allows assignment of rigid zone
the overlap of cross sections.
At the
intersection of
column and the spandrels were assigned due
SAP2000 shading
end offsets
the section
to
account for
rigidity for the
of both columns and spandrels. Using the
to the large size
show
feature to graphically
factors to frame
columns and spandrels, 100 percent
left to
on the model, each frame was rotated
to
its
proper orientation based on the structural drawings.
Refer
WTC
to Fig. 1
3-5 for a frame view and rendered view of the exterior wall (foundation to floor 9) of the
model. The figure also shows the core columns and core bracings.
Figure 3-5. Frame view and rendered view of the
The panels of the
exterior wall
exterior wall trees.
spacing of 10
ft
between elevation 363
At the exterior wall
to a spacing
indicates that each panel
of 3
ft
4
was divided
ft
model (foundation to floor
and elevation 41 8
trees, the typical exterior
in.
9).
that level, the three
A typical exterior wall tree panel
extended
down
columns were connected by a horizontal
to elevation
In the model, the tree
was
363
also the location
column
11 1/2 in.
rigid
where the column
to the centerline
(see Fig. 3-6), the location of the spandrel transitioned
reference line to the center of this reference
line.
spandrel
at level
to
is
shown
and
F.
in Fig.
3—6, which
For each panel
in the
down to level D. At become one member, which
continued
element
to
columns
to
insertion point transitioned
from 6
1/2 in. offset
B
and
D
from the exterior column
columns was not included because frame end length
account for the rigidity of the spandrels.
(Fig. 3-6).
model the tapering columns. The columns
B, and ceased to taper
from the inside
of the lower column. Between levels
Through the height of level C, the box-shaped columns tapered
members were used
were called
Within the floor 9 spandrel, the exterior columns
tapered; however, in the model, the tapering of the to the
1/2 in.
1 1
ft.
face (at the spandrel) of the upper
were assigned
ft
ft
wall columns transitioned from a
into five different levels: B, C, D, E,
model, the three exterior columns from above elevation 418
36
1
Exterior Wall Trees (Floor 4 to 9) Modeling
3.2.5
offsets
WTC
at the
In the
model, non-prismatic
started to taper at the
top of the spandrel at level D.
bottom of the
The dimensions of the
NISTNCSTAR
1-2A,
WTC Investigation
A
Development of Reference
columns
at
the spandrel edges
were defined
B
the centerline of the spandrel at level level
D below).
to
1
in the
at
the joints
WTC
at level
Towers
D (see discussion
were interpolated based on the dimensions of the section
spandrel edges
shown
to vary linearly
between the two sections. Frame end length
account for the
rigidit>'
WORTHINGTON
in the
for
at the
drawing book. The section properties of the tapering column were assumed
of the spandrel
5K1LLING, HELLE &
at level
B
offsets
were assigned
and the one foot dimension
JACKSON
Civil
to the
at level
columns
to
D.
& SfJUCtura! Engineers
-4-7
PAh'BL BLB'/AjlOtj
£x re/5 .'oe y/Atu
WORLD TRADE CENTER
r/Zg
for the
drawing book. In the model, the column extended from
below the top of the spandrel
ft
Models
Therefore, in order to obtain the correct section properties along the length, the
dimensions of the section
PHOJECT
Structural
- •£x^Vf/<:'r-
c^/ofyf} A
*
Joint
X Lcv&i
//v-re
Joint offset
B
-
-far
types 4
po9es
Lcve./ C
for types
-
L£ve/ D
-
Lsve./
£
•
Lavs-I
F
-
-^or-
c'eJ'
'J-ABi--^-
4
fhr-u&
asra/ts
types 4d&ttit/s
for fyf>as 4d&ttn/3 rh'''j'6 see. /z>ase.i
-for TyjssS 4.ae.TaitS
s&c po^e 2- Ass.-
Section A-
Source: Reproduced with permission
of
The
Port Authority of
New
York and
New
Figure 3-6. Exterior wall tree panel (taken from Drawing At
level D,
the three
member
two
transitions occurred in the model.
columns coming down from
level
C
The
first transition
Jersey.
Book
was
2,
Enhanced by NIST.
page 2-AB2-2).
for the exterior columns,
where
were connected by a horizontal rigid element to become one
member consisted of the three exterior columns and the member of the same section properties with the spandrel plate was and connected between the neighboring exterior wall trees. This member connected the
at the
bottom of the
tree.
This frame
spandrel plate. Another horizontal also defined
neighboring exterior wall trees and provided lateral bracing for the columns. Frame end length offsets
NISTNCSTAR
1-2A.
WTC
Investigation
37
Chapter 3
were assigned
to the spandrel to account for the overlap
which also included the spandrel
assumed
to
occur
at
The
plate.
transition
of the spandrel plate with the frame member,
of the three members into one member was
one foot below the top of the spandrel
D to
at level
account for the fact that the
spandrel becomes engaged with the exterior columns after being connected to the exterior columns for a certain distance. Hence, the joints
There was a second transition typically defined at 6 1/2 level
D
line.
As
offset
in.
were defined
at level
offset
D
of 6 1/2
assigned
at the
column member
was assigned
in.
at
The nodes
(Fig. 3-6).
for the exterior wall
from the exterior column reference
in the exterior wall tree, the joint
a result, for the
one foot below the top of the spandrel
at
at level
columns were
but for the joints
line,
D.
and below
at
coordinates were defined along the exterior column reference
framed between the nodes
that
the top of the
member
at levels
B
and D, a
rigid joint
using a rigid body constraint, while no offset
was
bottom. Therefore, the column remained a vertically straight element while being
connected to nodes that were not aligned vertically.
At
level E, the exterior
panel, the exterior
The
in Fig. 3-7).
columns tapered and had two
different types of cross section (Fig. 3-7).
column transitioned from Section b-b
in Fig.
3-7
into a
For each
box-shaped column (Sec. c-c
location of the transition between the different types of cross section varied for different
column types from
5
ft
8 in. to 6
ft
4
in.
measured from the bottom of level E.
In the model, the transition
was assumed to be at 6 ft measured from the bottom of level E. For each panel, the exterior column at level E was modeled as two non-prismatic members. The top section of the first non-prismatic member consisted of three box-shaped columns and a middle plate, while the bottom section
column
The
(Sec. c-c in Fig. 3-7).
properties were
The second non-prismatic member was the properties
were assumed
a tapering
assumed
to vai"y linearly
box shaped column (Sec.
between the two
to vary linearly
sections.
At
was
a
box-shaped
between the two
c-c in Fig. 3-7),
sections.
and again,
level F, the exterior wall tree
columns were prismatic box-shaped columns.
The
final
model of a
is
illustrated in Fig. 3-8.
Exterior Wall (Floor 9 to 106) Modeling
3.2.6
In plan,
6 1/2
typical tree
in.
column and spandrel members connected from the exterior column reference
at
nodes located
line (see Fig. 3-9).
node using an insertion point located
'inserted,' at this
at
the outside face of the spandrel,
The columns were
at the centerline
of plate
3.
offset horizontally, or
Insertion points
not adjusted for spandrel thickness. With this modeling, gravity and wind loads could be applied
were
at the
spandrel location.
In elevation, the
columns and spandrel members connected
below the reference need for
offsets to
floor elevation (Fig. 3-9).
at
be defined. The effect of applying loads
reference floor elevations
was
studied,
and
it
the spandrel centerline, typically 12 1/2 in.
The spandrels were then located
was found
that
at it
coirectly without the
both the spandrel centerlines and the resulted in a negligible difference in
spandrel stresses.
For typical exterior wall panels
(i.e.,
three
were defined. The models included nodes centerlines) as well as the upper
floor levels
columns wide by three at the three
and lower column
where concrete slabs existed
stories high),
nodes
at five
elevations
representative floor levels (defined at the spandrel
splices.
Diaphragms were assigned
to represent the high in-plane stiffness
to all
nodes
at
of the concrete floor
slabs.
38
NISTNCSTAR
1-2A,
WTC
Investigation
Development of Reference
Structural
Models
for the
WTC
Towers
Vari,e.s,
par Ses.
gala's
"?
r-hr-u
*7
Sah. 2-lk\iB:-'iri--v
3
Ncte I Double beve/ comp/efe peneTration groove weld 12' long at top.
-\--
V \ V
^
V.
Vx column refsre.nce /me.
4
Sec /^/O/^ Source: Reproduced
with permission of
The
Port Authority of
C-C
New York
and
New
Jersey.
Figure 3-7. Exterior wall tree: as-built cross sections for level E (taken from Drawing Book 2, page 2-AB2-13).
Figure 3-8. Frame view and rendered view of an exterior wall tree.
NISTNCSTAR
1-2A.
WTC
Investigation
39
Chapter 3
Cp Cp Cp
Spandrel JSLiSl
j,, i
[
See Eel.
i-^i-
^varies ^'^ Varies
Fl
107
4-AB2-iS
\Tyclcal
Extcrlur Colusm Reference Line
Column
Spandrel fl&te (See t-AB2-ll)
••c-c'
Source: Reproduced with permission of The Port Authority of NIST.
Figure 3-9. Typical
New York and New
WTC tower exterior wall
The SAP2000 program allows assignment of rigid zone
factors to frame
Jersey.
Enhanced by
panel.
end offsets
to account for the
overlap of cross-sections. In the global model, 50 percent rigidity for the column and 100 percent rigidity for the spandrels
detailed shell that,
were assigned
for the typical exterior wall panels to
match the
model of the panel based on the parametric study resuhs
lateral deflection
(see Sec. 3.5.1
).
It
was
of the
also found
due to the relatively large depth of the spandrels and the close spacing between the columns, the
spandrels contributed to the axial stiffness of the columns in the panels. This contribution was estimated to range
from 20 percent
to
28 percent increase
in the vertical stiffness
of the panels. Therefore, a frame
property multiplier for the exterior wall column's cross-sectional area was used to provide a 25 percent increase in columns' axial stiffness (see Sec. 3.5.1).
For exterior wall comer panels, 25 percent
rigidity for the
columns and 50 percent
rigidity for the
spandrels were assigned based on the parametric study results (see Sec. 3.5.2). Also, an area modifier
40
NISTNCSTAR
1-2A,
WTC
Investigation
Development of Reference
was used
to provide a
comer panels
25 percent increase
No
(Sec. 3.5.2).
in the axial stiffness
Structural
Models
WTC
for the
Towers
of the two continuous columns of the
modifier was used for the 100, 200, 300, and 400 series intennittent
columns. Exterior column t>'pes were defined in
mechanical
floors,
and 400
yield strengths that varied
material properties at the
to
500
from 36
Drawing Book
4.
A few types (100 series typical,
300
series at
series at corners) repeated extensively throughout the towers, with steel
ksi to 100 ksi.
member assignment
Since
stage, the
SAP2000 does
not allow for the assignment of
number of different
steel strengths
was
determined for each exterior column type, and sections were defined for each. The section name included the section
number and
the yield strength as tabulated in the drawing books.
Typical spandrels and comer panels were defined as rectangular shape and Section Designer section with stiffener, respectively.
The top and bottom
stiffener
of each comer spandrel were included
parametric study and the global models. The detail shows that the stiffeners were 6
matching plate 2
in the
in.
in
both the
plates of thickness
comer column.
Exterior Wall (Floor 107 to 110) Modeling
3.2.7
Spandrel depths varied
at floors
108 and 110.
A
weighted average of spandrel depth was detennined
in
order to define the average centerline elevation of the spandrels and therefore, the node elevation for the entire floor.
For the 7 X 5 structural tube sections that were used Institute
in these floors, sections
from the current American
of Steel Construction (AISC) Manual were assigned, and modification factors of 1.04 were
applied to the section properties. The modifiers were used to match the section properties from the 6th Edition
The
AISC Manual. members from Where not shown in
exterior wall
Fy =50
ksi.
10 were typically rolled shapes with F,.=42 ksi or
1
=50
ksi,
Fy =42 ksi was used.
Hat Truss Modeling
3.2.8
In both
floors 107 to
the drawings as F,
WTC
1
and
WTC 2, a tmss system referred to as a 'hat tmss'
and the roof The hat tmss system was intended to interconnect the exterior walls to the core.
to support the load
The
hat truss
was constmcted between
floor 107
of the antenna on top of the tower and
was made up of four
trusses spanning
perpendicularly to the long direction of the core and four tmsses spanning perpendicularly to the shortdirection of the core (refer to Figs.
Frame members between
3-10 and 3-1
floors 107
and
1
10 were assigned to the model according to plan and elevation
drawings of the hat tmss. Node locations were exterior wall.
shown
in
1).
set to coincide with the centerline
Columns, diagonals, and beams were included
in the
drawings SA/B-^00 through SA/B-404 were included
participate in the hat truss
system were not included
in the
of spandrels
at the
model. All columns and diagonals
in the
model. Floor beams that did not
model, unless they were used to transfer truss
chords or core columns. Flexible floor diaphragms were used in this area.
NISTNCSTAR
1-2A,
WTC
Investigation
41
Chapter 3
Coordinates were generally not given slab.
at floor 109, as this level
did not contain a complete concrete floor
The geometi-y of the diagonals, columns, and beams was used
to
detennine the location of the node
where the diagonal would intersect floor 109. Unless othewise noted in the drawings, diagonals and
/ -
—
\
X
y
/
/ /
\
-
I
\X
/
X\ X
Figure 3-10. As-modeled plan of the
Figure 3-1 1
.
Rendered 3-D model of the
WTC
1
/
WTC
1
hat truss.
hat truss (prior to assembly in the
unified global model).
42
NISTNCSTAR
1-2A,
WTC Investigation
Development of Reference
columns were assumed
to
Structural
Models
WTC
Towers
be non-composite, and floor beams were assumed to be composite. Hat truss
main chords, and main columns were modeled with continuous joints. Hat
diagonals,
for the
truss
beams,
however, had pinned ends.
and Rigid Floor Diaphragm Modeling
Flexible
3.2.9
For most
diaphragms provide for a sufficiently accurate representation of the flow of forces
floors, rigid
and defomiations for global structural response. This analyses. In cases
is
a customary engineering practice for lateral force
where the flow of forces and deformations would be affected
significantly
by the use
of rigid diaphragms, the floors were modeled as flexible diaphragms.
The
floor
models described
in Sees. 3.3
utilized within the global models.
diaphragm shell
and 3.4 were used
to
develop the flexible diaphragm stiffness
Section 3.5.3 outlines the study for the detennination of the in-plane
of the detailed floor models, using that in-plane stiffness to aixive
stiffness
at
an equivalent
element floor model. The equivalent shell element floor was used to represent the in-plane floor
model. The shell elements attached to
stiffness in the global
all
columns and core columns.
exterior wall
Flexible diaphragms were used at the floors of the towers in the core of the atrium area, in the mechanical floors,
and
5, 6, 7,
in the floors
of the hat trusses. The floors modeled using flexible diaphragms were floors
3, 4,
9 (atrium levels); 41, 42, 43, 75, 76, 77 (mechanical levels); 107, 108, 109, 110, and roof (hat truss
region) of both towers. For the floors of the hat trusses, the stiffness of the flexible diaphragms
reduced by
a factor
diaphragm
strength.
of twenty, which resulted
in
diaphragm forces
was
were consistent with the
This was done to achieve a reasonable agreement between the as-modeled stiffness
of the floor diaphragm and the strength of the diaphragm to concrete floor slabs
that
at the
resist the forces
it
attracts.
top and bottom chords of outrigger trusses or hat trusses,
consistently that floor slabs
modeled
at
nominal uncracked
it
of
In the case
has been found
stiffness attract forces completely out
of scale
with the strength of the slabs. Based on parametric studies for a series of major high rise buildings,
became
a
customary engineering practice to reduce the
was found, based on the parametric
stiffness
of such floor
slabs.
it
This reduction factor
This reduction accounts for cracking and
studies, to be about twenty.
other factors that are consistent with the expected behavior of the floor diaphragms.
Verification of Global
3.2.10
Several steps were taken to verify the
Models model
input.
SAP2000 Version
model has been buih with frame section assignments. This allows program interpreted
their input.
for verifying the orientation
The shading option was
(i.e.,
local axes)
8 offers a 'shading' option
the user to
once a
view the members as the
and
helpful for using section-designed shapes,
of members. Note
that shading
is
not correct
when two
Section Designer sections are used in non-prismatic members, so orientations for these sections were verified
by reviewing
their local axis
engineers not associated with the
Once
the
member properties. The work was
initial
independently reviewed by
model development.
models were completed, checks for gravity and wind loads were performed. The overall
performance of the tower models under these loads was found
to
be reasonable by checking deforaiations,
stresses, reactions, etc.
NISTNCSTAR
1-2A,
WTC
Investigation
43
Chapter 3
Results of Modal Analysis
3.2.11
Verification of the global models also included comparing the calculated natural frequencies with
frequencies measured from accelerometers placed atop
WTC 2
global models were estimated using
modal
WTC
analysis.
1.
The
natural frequencies for
the construction and superimposed dead loads only (see Chapter 4 for further details).
used
in estimating the floor
frequencies for
P-A
effects.
WTC
The
first
1
and
three
WTC
1
and
The mass of the towers was estimated from
masses for the modal analysis. The calculated
first six
No
live loads
were
periods and
WTC 2 are presented in Table 3-2 without P-A effects and in Table 3-3 with mode shapes
Table 3-2. Calculated
first six
are presented in Fig. 3-12.
periods and frequencies without P-A effects for the WTC towers.
WTC
WTC 2
1
Direction
N-S
E-W
Frequency
Frequency
of
Motion
Mode
(Hz)
Period
1
0.088
2
0.093
Mode
(Hz)
Period
11.4
2
0.093
10.7
10.7
1
0.088
11.4 5.2
(s)
Torsion
3
0.192
5.2
3
0.192
N-S
4
0.233
4.3
5
0.263
3.8
E-W
5
0,263
3.8
4
0.238
4.2
Torsion
6
0.417
2.4
6
0.417
2.4
Table 3-3. Calculated
first six
WTC
(s)
periods and frequencies with P-A effects for the WTC towers.
WTC 2
1
Direction of
Motion
N-S
44
Frequency
Frequency
Mode
(Hz)
Period
(s)
Mode
(Hz)
Period
1
0.083
12.1
2
0.089
11.2
E-W
2
0.088
11.3
1
0.083
12.1
Torsion
3
0.189
5.3
3
0.192
5.2
N-S
4
0.227
4.4
5
0.250
4
E-W
5
0.250
4
4
0.227
4.4
Torsion
8
0.455
2.2
8
0.455
2.2
NISTNCSTAR
1-2A,
(s)
WTC
Investigation
Development of Reference
(b)
(a)
Figure 3-12. (b)
NISTNCSTAR
1-2A,
Structural
Models
for the
WTC
Towers
(c)
Mode shapes of WTC 1 (exaggerated): (a) first mode shape (E-W), second mode shape (N-S), (c) Third mode shape (torsion).
WTC
Investigation
45
Chapter 3
3^ presents a comparison of the calculated first three natural frequencies and periods (N-S direction, E-W direction, and torsion) against measured frequencies and periods obtained from WTC based on analyzing acceleration records obtained from accelerometers installed on the top of WTC Table
1
1.
The
table also includes the values of the natural periods
The
table
shows good agreement between
and frequencies predicted
the calculated
and measured periods, especially for the periods
estimated without P-A effects, thus indicating that the reference global model
No measured periods
representation of the actual structure.
in the original design.
is
a reasonable
or frequencies were available for
Table 3-4. Comparison of measured and calculated periods for WTC 1.
first
two natural frequencies and
Frequency (HZ) Data Source/ Event Date
Period
Direction of Motion
Wind Speed &
N-S
Direction
WTC 2.
(s)
Direction of Motion
E-W
Torsion
N-S
E-W
1
Torsion
Historical Data
11.5 mph, E/SE
0.098
0.105
0.211
10.2
9.5
4.7
January 24, 1979
33 mph, E/SE
0.089
0.093
0.203
11.2
10.8
4.9
March 21, 1980
41 mph, E/SE
0.085
0.092
0.201
11.8
10.9
5.0
0.087
0.092
11.5
10.9
NW NW
0.085
0.093
0.204
11.8
10.8
4.9
0.085
0.094
0.199
11.8
10.6
5.0
W
0.094
0.094
0.196
10.6
10.6
5.1
0.081
0.091
12.3
11.0
11.4
10.6
11.9
10.4
October
1978
11,
Deem be!-
11,
February
2,
1992
1993^
March
13, 1993^
March
10, 1994^
December
20 mph, 32 mph, 14 mph,
25, 1994^
N
Average of Measured Data Average
0.088
Orginal Design Theoretical Value
-
0.094
0.202
4.9
Predicted Values
0.084
0.096
Reference Global Model
LERA/NIST
-
WTC
1
without P-Delta
LERA/NIST
-
WTC
0.088
0.093
0.192
11.4
10.7
5.2
0.083
0.088
0.189
12.1
11.3
5.3
1
with P-Delta
Notes:
^Reported frequency value
^Reported frequency
is
is
the average of the
SW
based on center core data
corner,
NE
only.
TYPICAL TRUSS-FRAMED FLOOR
3.3
In order to select the typical truss-framed floor within the the drawings for floors 80 to 100
review
is
corner and center core frequency measurements.
were reviewed
MODEL— FLOOR 96A expanded impact and
fire
to identify structural similarities.
zones of both towers,
The summary of this
provided in Appendix G, which shows a summary of the construction type and space usage for
each floor, along with a categorization and description of floor types for both towers. floor
46
96 of WTC
1
(96A) represented the typical truss-framed floor
in the
It
was found
expanded impact and
NISTNCSTAR
1-2A,
that
fire
WTC Investigation
Development of Reference Structural Models
region for
WTC
89A
(floors
1
to 103 A).
The only exception
had an increased dead load capacity required
96A was
Floor
(floors
in this
region of
Specifically, floor
was
1
Towers
floor 92.
which
for the support of secondary water lines.
also representati\ e of the typical truss-framed floor in the
74B-88B).
WTC
WTC
for the
96A was
expanded region
similar to the truss framing at floor
for
74B and
WTC
floors
2
84B
through 88B. Floors 78B and 79B were sky lobby and upper escalator floors, respectively. Both contained long span trusses, which were similar to floor 96A, but also contained beam-framed floor construction in the entire short span area (where the escalators were located). Floors
had beam framing
in place
of a single truss panel
in the short
80B through 83B
span area, while the remaining area
contained trusses which were similar to floor 96A.
Based on the abo\ e
analysis, floor 96 of
floor for the majority of the
Fig. 3-14. Table 3-1 includes a
Type
Note;
All
-
1
Floors:
WTC -
24
26 50
-
40 58
Note: HI =
-
panel types within
FR1
An
selected as the overall representative truss-framed
fire
zone
in
both towers and
summary of the
size
Tower B
60 -66 68 - 74 84 - 91 93 - 105
96A
of the
1" length tolerance,
ER1
DR1
Floors;
floor model.
14-24
60 -74
26
84
-
40
50-58 except floors 10.1
CR1 BR1
described in the
model
is
shown
The following presents
in
the
1
A1
.
39, 40. 70.
B1
-
91
93-106
& 71 which are
C1
D1
within 6"-10"-
El
Floors 72-74 vary 18"-26".
F1
G1
GR1
HI
HR1
H6
CORE
J1
J1 Note: J1 =K1 =
HR1 Note:
is
isometric view of the typical truss-framed floor
Typical Truss Floor Panel Plan
0
1
was
and components of the truss-framed floor model.
structural systems
Tower A
1
expanded impact and
following sections (see Fig. 3-13).
major
WTC
H1
HR1 = HR6
Note:
GR1
F1
G1
El
D1
CI
B1
A1
BR1 CR1
DR1
ER1
(all
HI =M1 =
KR1
MR1
C32T5 Trusses)
FR1
Figure 3-13. Typical truss-framed floor panels arrangement.
NISTNCSTAR
1-2A,
WTC
Investigation
47
Chapter 3
Figure 3-14. Typical truss-framed floor model (floor 96A), slab not shown.
Primary Trusses
3.3.1
The primary chords.
The
long-span
and bottom chords, which were 29
trusses consisted of double angle top
trusses acted compositely with a 4
truss,
C32T1,
concrete slab on
in.
the top chord consisted of
two angles 2
to-back (SLB), and the bottom chord consisted of two angles 3
between the centroid of the two chords was calculated
to
in. in.
be 28.05
1
1/2 in.
by
1.5 in.
by 2 in.
in.
by 0.25
in.
The sum of the
distances, thus,
was 28.05 +
1.93
= 29.98
out-to-out of the
by 0.37
in.,
in.,
short legs back-
SLB. The distance
The distance from the centroid of
the top chord to the neutral axis of the transfonned composite slab with top chord 1.93
in.
metal deck. For a typical
in. (Fig.
was calculated
to
be
3-15). Dimensions for the
short-span trusses were essentially identical to those for the long-span trusses. Therefore, in the model,
30.0
in.
was taken
as the typical distance
between the top and bottom chords for both short- and long-span
primary trusses. In the long-span truss zone, the
two individual primary
trusses,
which were part of the same floor panel
and attached to the same column, were separated (typically) by a distance of 7
between panels, the distance between the abutting long-span trusses was 7 model, 7 1/2
in.
was used
as the spacing
between
all
zone, two individual trusses which attached to the
between 4 7/8
48
in.,
5 in.,
and
5 1/4 in. In the
1/8 in.
At the joint
1/2 in. Therefore, in the
long-span primary trusses. In the short-span truss
same column were separated by
model, the typical spacing between
all
a distance that varied
short-span double
NISTNCSTAR
1-2A,
WTC Investigation
Development of Reference
trusses
was
The long span
5 in.
Structural
Models
for the
two-way zone had an as-modeled length of 58 the one-way zone had an as-modeled length of 59 ft 8 in.
while the long span trusses in
trusses in the
ft
WTC
10
Towers
in.,
C32T1 (Primary Truss Section)
Web member ^
/
4
extension
2.48"
inio slab into siao
t/—
V-A 4" Slab
If,
N.A.
i0.414"
29.98" = 30"
L2 X 1.5 X 0.25 28.05"
Combined Slab +
Primary Truss Double L
13x2x0.37
^-^]-L^ 0.537"
(Note: 2"" Truss of Pair Not
ACTUAL
Shown)
IVIODEL
Figure 3-15. Typical primary truss cross-section, as-built and as-modeled transformed truss work points. The diagonal web bars double angle shapes
for the primary trusses
in the
primary trusses,
This holds true for primarv' trusses
The
as-built truss diagonals
diagonals
is
v\
had end
1
were most often
.09 in.
was taken
1
.09
here bar diameters varied between 0.92
fixitv'.
member
in.,
and therefore, an end offset of
trusses, the actual
was 30.66
In the model, the
combined
in.
1
.8 in.
was used
Therefore, an end offset of 0.83 all
.
1
4
in.
To
mitigate the effect
model unbraced
at
in.,
in.
The
length.
while the modeled
as-built
member
length
both ends. Similarly, for the bridging
was used
at
both ends.
in.,
while the modeled
A rigid zone factor of
offset zones.
deck support angles, typically
truss top
1
by 2
3 in.
in.
by 0.75
in.
were located
in the
same plane
as
chord and composhe slab centroid.
Bridging Trusses
3.3.2
The bridging 24T1
trusses
1,
were 24
in.
deep, edge-to-edge, with double angle chords. For a typical bridging
the top and bottom chords consisted of
distance between the centroid of the top and bottom chords for the
and
unbraced length for a typical diagonal of a bridging truss was 29
100 percent was used for
truss,
in.
approach, end length offsets were used for the truss diagonals to compensate for
unbraced length for a typical diagonal in a primary' truss was 32.4
the
between the two angles.
but were considered pinned for the analysis. Pinning the
the difference in the as-built diagonal unbraced length and the
length
diameter bars. Therefore, for
conserv ative and pro\ ides an upper bound of the gravity' load stresses.
of the pinned
was 36.05
in.
as the distance
all
two chords was 23.26
NISTNCSTAR
1-2A.
WTC
in.
1.5 in.
The
bridging trusses was taken as 23.25
work points of the top chord of the bridging
equivalent slab plate for truss
two angles
24T1
1
Investigation
truss
was calculated
by
1.25
in.
by 0.23
in.,
distance used as the offset
in. (Fig.
SLB. The between the
3-16). The distance between
and the top chord of the primary trusses and
to
be 3.39
in.
This distance was selected for
all
49
Chapter 3
bridging trusses to be 3.375
in.
As
in the as-built structure, the
bridging truss was not connected along
its
length to the slab shell elements in the model. At the intersection of the top chords of the primary and the
bridging trusses, the intersection was modeled using vertical rigid links, connected
elements representing the concrete
in turn to the slab shell
slab.
24T11 (Bridging Truss Section)
Combined Slab + Primary Truss Double L
N.A.
0.368"
MODEL
ACTUAL
Figure 3-16. Typical bridging truss cross-section, as-built and as-modeled transformed truss work points.
The
original contract
drawings indicated that the bottom chord of the primary trusses was connected to
the bottom chord of the bridging trusses along the length of the primary trusses only on
149, 311, and 349.
The connection consisted of double angles 2
primary and bridging truss lower chord members
in.
by
1
1/2 in.
by 0.25
column in.
lines 111,
welded
to
both
as shown in Fig. 3-17. These connection angles were
included in the model. The Laclede (the manufacturer of the floor truss panels) shop drawings indicated that the
bottom chords of the primary trusses were similarly connected
bridging trusses
at all their intersections for
to the
bottom chords of the
construction purposes. These were conservatively not
included in the models.
50
NISTNCSTAR
1-2A.
WTC
Investigation
Development of Reference
\
I
Structural
Models
for the
WTC
Towers
k'rc72!.o6y—r /4
V 3€G ecr.
side
^ Priman tmss lower chord Source: Reproduced with permission
of
The
Port Authority of
New York and New
Jersey.
Enhanced by NIST.
Figure 3-17. Connection between bottom chords of primary and bridging trusses. For bridging trusses
in the
varied between 0.75
in.
in.
was used
angle gap
for trusses with
web
bar diameters that
in.
Truss Member Cover Plates
3.3.3
In
model, a 0.75
and 0.98
30 percent of the floor area, truss members were supplemented with cover plates. The members with
web members, and most typically bottom chords. Section SAP2000 Section Designer. The primary truss top chords were
additional plates included top chords,
properties were calculated with
reinforced with an additional set of double angles at truss end connections. At these locations, the
work
points for the section were located at the centroid of the composite double angle and concrete slab.
The Laclede shop drawings indicated plates 3/8 in. by 3 in. connecting the bottom chord of the primary truss pairs together at each end and where intersected by a bridging truss. These plates were included in the model.
Viscoelastic
3.3.4
Dampers
Viscoelastic dampers were located where the bottom chords of the long span, short span, and bridging trusses intersected the exterior
columns (see Chapter
and quasi-static loads (such as gravity loads)
static
at
1
for description
3.3.5
in the
model
at the
damper
details).
The dampers
resisted
the time of load application. Immediately following
load application, the dampers shed load until the stress in the dampers
element was located
and
was
dissipated.
A placeholder
location.
Strap Anchors
Exterior columns not supporting a truss or truss pair were anchored to the floor diaphragm by strap
anchors. TTiese strap anchors were connected to the columns by complete penetration welds.
The
strap
anchors were then connected to the slab with shear stud connectors and to the top chords of the trusses by fillet
welds. The straps were included in the model and located in the plane of the centroid of the
NISTNCSTAR
1-2A.
WTC
Investigation
51
.
Chapter 3
composite top chord. Also,
used a rigid link
to attach
model
in the
back
the
work points
intersected with the centerline of the
column and
3-1 8).
to the spandrel (see Fig.
— i
1
*
Trusses
\
/ Straps
/ )
/
Deck Support
Y
/
/
/
/
\.
\
/
\
\
/ /
/
'\
/
\
/
/
\
/ /
/ Rigid Link
/
Frame Elements Columns
\ Key: PL,
•
Spandrel PL
PL
to
—
^ Attachment
f
Attachment
1'
/
Slab
PL
to
Slab
Plate.
Note: Slab not shown.
Figure 3-18. Strap anchors modeling.
Concrete Slab and Metal Deck
3.3.6
Outside the core, the priinary trusses acted compositely with the 4 deck. In the inodel, the average depth of the slab plus deck
in.
concrete slab on
was modeled
as 4.35 in.
1/2 in. metal
1
The concrete
slab
consisted of lightweight concrete with a self-weight of 100 pcf and a design compressive strength, f'c= 3,000 psi.
The concrete modulus of elasticity,
calculated modular ratio, n=E/E,;
was taken
values are consistent with those included in the
Typically, inside the core, the
used for modeling was 1,810
Ec,
as 16,
where
WTC
is
the steel
Structural Design Criteria
beams acted compositely with
a
4 1/2
in.
ksi,
and the
modulus of elasticity. These Book.
fonned concrete
slab.
The
concrete slab consisted of normal weight concrete with a self-weight of 150 pcf and a design compressive strength, /V=
3000
calculated n ratio. EJE,
The
floors
of the
trench headers.
The concrete modulus of elasticity,
psi.
,
was taken
in thickness
SCA-109 3.3.7
(Floor
effects of the in-slab trench headers
from 4.35
96A
A
1
in. to
ft
8
2.35
in. in.
wide
built
were accoirmiodated
in the inodel
shell panel (the typical truss-floor shell
or 1.35
ksi,
and the
in. at
by reducing
mesh
size)
was
the trench header locations per drawing
Structural Concrete Floor Plan).
Model
Several steps were taken to verify the model input.
SAP2000 Version
8 offers a 'shading' option once a
with frame section assignments. This allows the user to view the members as the
program has interpreted
52
modehng was 3,320
as 8.7.
Verification of the 96th Floor
model has been
used for
WTC towers had an in-floor electrical distribution system of electrified metal deck and
The
the slab shell element thickness.
reduced
£(.
their input.
The shading option was helpful
for using section designed shapes,
NISTNCSTAR
1-2A.
WTC Investigation
.
Development of Reference
and for verifying the orientation
(i.e..
engineers not associated with the
Once and for
the
initial
Models
estimate deflections and
model were based on
stresses for a
For the composite truss sections, the
SAP2000 trusses
for the long-span truss
for gravity loads. All
superimposed dead loads
Hand
calculations
to
compare
were used
stress
to
simply supported composite truss under gravity loading.
steel stress
resuhs were within 4 percent of those calculated by
and 3 percent for the short-span
matched hand calculations within
5 percent to
1
truss.
Deflections for the
beams and
5 percent.
TYPICAL BEAM-FRAMED FLOOR
3.4
Towers
WTC Design Criteria; self weight was m accounted
for representative composite sections.
member
WTC
model development.
by SAP2000. To justify the modeling assumptions, several studies were performed hand calculations
for tfie
of members. The work was independently reviewed by
model was completed, checks were performed
live loads included in the
results to
As
local axes)
Structural
MODEL— FLOOR 75B
described in Section 3.3 for truss-framed floors, the structural drawings were reviewed to identify
structural similarities
between the beam-framed
towers (see Appendix G).
framed floor
in the
floors within the
It
was found
floors within the
75 of
that floor
expanded impact zone
for
WTC 2
expanded impact zone of WTC
expanded impact and
fire
zones of both
WTC 2 (75B) represented the typical beam-
(floors
74B
to 88B).
There were no beam-framed
1
WTC 2, lower and upper mechanical equipment room (MER) floors, respectively, MER floor pairs in both towers (floors 7 and 8, 41 and 42, and 75 and 76 for both WTC and WTC 2). Floor 77 of WTC 2, a lower escalator floor, was a beam-framed floor similar to the lower floor of the MER floor pairs, floor 75B.
Floors 75 and 76 of
were typical of the lower three 1
i.e.,
Based on the above
analysis, floor 75 of
floor for the
expanded impact and
Fig. 3-19).
An
fire
WTC 2 was selected as the overall representative beam-framed
zone
in
both towers and
is
described in the following sections (see
isometric view of the typical beam-framed floor model
is illustrated in
Fig. 3-20.
Table 3-1 includes a summary of the size of the 75B floor model. The following presents the major structural
systems and components of the beam-framed floor model.
NISTNCSTAR
1-2A.
WTC
Investigation
53
Chapter 3
Type 12
-
WTC Beam
Framed Floor Floor Plan Towers A& B Towers A & B Near
MER MER
Floors:
7,41,75,108
Floors:
9,43,77,107,110,Roof
Beams
CORE
Beams
Beams
Beams
Figure 3-19. Typical beam-framed floor arrangement.
Figure 3-20. Typical beam-framed floor model (floor 75B).
54
NISTNCSTAR
1-2A.
WTC Investigation
Development of Reference Structural Models
for the
WTC
Towers
Composite Beams
3.4.1
The beams
model were located at the elevation of the centerline of the concrete slab. The insertion beams was set at the beam top flange, and then the beam was offset down by one-half the
in the
point for the
thickness of the slab.
The beam was
rigidly linked with the slab to simulate the composite action. This
option provided for accurate estimation of the composite stiffness of the floor.
For beams with cover
plates, the properties
beam, and reinforcing plates were
were calculated by SAP2000 Section Designer, and the
slab,
rigidly linked.
Horizontal Trusses
3.4.2
Exterior columns which did not support a
beam were connected
to the floor for bracing
puiposes by
horizontal trusses. These exterior horizontal trusses were anchored to the columns with complete joint
penetration welds.
The
The
horizontal trusses were then connected with shear stud connectors to the slab.
truss angles (typically
In the
back
4
in.
by 4
in.
by 5/16
in.)
were then
field
welded
to the top flange
of the beams.
model, the work points intersected with the centerline of the column and used a rigid link to attach
to the spandrel.
The
truss
members were
located in the plane of the centroid of the composite top
chord (see Fig. 3-21).
*
Spandrel Plate
*
Figure 3-21. Horizontal truss modeling, slab not shown.
3.4.3
Concrete Slab and Metal Deck
Outside the core on the mechanical floors, the beams acted compositely with a 5 3/4 1
1/2 in. metal deck.
NISTNCSTAR
1-2A.
The average
WTC
cross-sectional depth of the slab in the
Investigation
in.
concrete slab on
model was taken
as 6.1
in.
The
55
Chapter 3
deck spanned between channels
spanned between the floor beams. The concrete slab
that, in turn,
consisted of nonnal weight concrete with a self-weight of 150 pcf and a design compressive strength of
The concrete modulus of elasticity, /?, was taken as 8.7.
typically /V= 3,000 psi.
calculated
modular
Typically, inside the core, the slab consisted
Ec,
used for modeling was 3,320 ksi and the
ratio,
beams acted compositely with
a 6
in.
fonned concrete
The concrete
slab.
of nonnal weight concrete with the same properties as concrete outside the core.
The mechanical
floors
had
a 2 in.
maximum
topping slab stiffness was not included
depth topping slab both inside and outside the core. The
in the
models, but the weight was accounted for
in the baseline
perfonnance analysis.
Viscoelastic
3.4.4
Dampers
Viscoelastic dampers were located exterior
columns (see Chapter
located in the
model
at the
1
below the bottom flange of the beams where the beams intersected the
for description).
damper
Verification of the 75th Floor
3.4.5
Similar to floor
for verifying the orientation
(i.e.,
engineers not associated with the
Once and
the
live loads
initial
deflections and
the
member
to
superimposed dead loads
for gravity loads. All
WTC Design Criteria; self-weight
accounted for by
is
compare
to
stresses for a simply supported composite
steel stress results
compared
to
beam under
hand calculations
gravity loading.
—around
The
percent for both
1
plates,
it
was found
Section Designer shapes were not calculating the stresses conectly, so instead, separate
—between
1
that
beam
steel stress
percent and 2 percent for both short- and long-span beams.
PARAMETRIC STUDIES
3.5
Modeling techniques employed consistent with, but often
in the
development of the global models of WTC
more advanced
design of high-rise buildings.
was
stress results
composite sections. Hand calculations were used to estimate
and plate elements drawn over each other were inserted. This method yielded very accurate results
and
members. The work was independently reviewed by
and long-span beams. Where the beams were built-up with reinforcing
SAP2000
view the members as the
for using section designed shapes,
modeling assumptions, several studies were perfonned
for representative
model yielded accurate
element was
model development.
included in the model were based on
hand calculations
short-
local axes) of
model was completed, checks were perfonned
SAP2000. To justify to
SAP2000 was used
The shading option was helpful
their input.
a placeholder
Model
Similar to the 96th floor model, the 'shading" option in
program interpreted
96A model,
location.
As
than, the techniques typically
such, building
employed
components were idealized so
replicated while appropriately reducing the computational requirements.
1
and
WTC 2 were
in the analysis
that overall
and
perfonnance
The following describes
the
studies undertaken to establish the idealizations used in the models, including typical exterior wall panels,
exterior
56
comer
panels, and flexible floor diaphragms.
NISTNCSTAR
1-2A,
WTC Investigation
Development of Reference
Structural
Models
for tfie
WTC
Towers
Exterior Wall Columns/Spandrel Typical Panels (Floors 9 to 106)
3.5.1
A parametric
study of typical three-column, three-spandrel exterior wall panels from the faces of the
towers (floors 9 to 106) was perfonned using two modeling methods (see Fig. 3-22). The
where each
a detailed shell model,
plate of each
column or spandrel was
specifically
second was a simplified frame model. Internal column stiffeners were included
first
model was
modeled, and the
in the shell
model. The
parametric study assumed that the shell model best represented the as-built panel performance, and therefore,
model
it
was used
to tune the
The
(see Sec. 3.2.6).
model with the detailed
objectives of the study were to (1) match the axial stiffness of the frame
shell
models by modifying the
perfonnance of the frame model, which was used throughout the global
model under gravity load and
rigidity
(2)
match the
of the column/spandrel intersections
inter-story drift
in the
of the two
frame model.
Figure 3-22. Shell element and frame models of typical exterior wall panel. For comparing the axial stiffness of the simplified frame model of the panel with the detailed shell model, both models were loaded vertically while pin-supported indicated that the shell
spandrel
beams
to the
model was
at the
stiffer than the equivalent
columns' axial
stiffness.
bottom of the columns. The
beam model due
results
to the contribution
of the
This was due to the rigidity of the spandrel beams and the
proximity between the columns. The parametric study on a wide range of panels over the height of the
NISTNCSTAR
1-2A.
WTC
Investigation
57
Chapter 3
towers showed that the vertical stiffness of the columns
in the
bottom
third
of the towers should be
increased by a factor in the range of 25 percent to 28 percent, and the columns in the middle and upper thirds of towers should be increased
by a
factor in the range of 20 percent to 28 percent.
Based on these
25 percent increase of the axial stiffness of exterior columns was selected as a reasonable
results,
representation for the panel vertical stiffness over the height of the towers between floors 9 and 106 (see Sec. 3.2.6).
For studying the
lateral
deformation of the exterior panels, panel properties were taken from three
different areas of the building. at points
A, B,
I,
and
II
respective spandrel and
loaded
in the
These included floors 79
(see Fig. 3-23)
to 82, 53 to 56,
and 23
to 26.
The defonnations
were studied for three different panel locations and
column thickness. The topmost columns were connected
their
via a rigid link and
plane of the panel and peipendicular to the column with a 100 kip-load. The boundary
conditions were as
shown
in Fig.
3-22.
Column
I
Spandrel
1
Figure 3-23. Selection of column and spandrel rigidity of typical exterior wall panel.
The
lateral
displacements found for the shell and frame models of typical exterior wall panels with varied
column and spandrel
intersection rigidities are reported in Table 3-5.
column
00 percent spandrel
rigidity
and
1
rigidity in the
The study found
that
frame model produced deflection
50 percent
results
consistent with the shell model.
58
NISTNCSTAR
1-2A.
WTC
Investigation
Development of Reference
Table 3-5. Lateral displacement
Structural
Models
for the
WTC
Towers
and frame models of typical column and spandrel rigidities.
for the shell
(in.)
exterior wall panel with varied
Lateral displacement
(in)
Floor 79-82 Shell
model
No
rigidity
Frame model (Rigidity) C:100%, S:100% C:50%, S:100%
A
0.60
1.04
0.59
0.35
B
0.28
0.52
0.29
0.18
0.45
0.78
0.44
0.26
0.45
0.78
0.44
0.26
1
II
Floor 53-56 Shell
model
No
ngidity
Frame model (Rigidity) C:100%, S;100% C:50%, S:100%
A
0.26
0.43
0.27
0.18
B
0.12
0.22
0.14
0.11
0.19
0.32
0.2
0.15
0.19
0.32
0.2
0.15
1
II
Floor 23-26 Shell
No
rigidity
0.21
0.37
0.21
0.12
B
0.1
0.18
0.1
0.06
0.16
0.28
0.16
0.09
0.16
0.28
0.16
0.09
II
Exterior Wall Columns/Spandrel Corner Panels (Floors 9 to 106)
3.5.2
parametric study was performed of an exterior wall
from floors 9
to 106.
increase in the axial stiffness of the
modeling the columns'
The panel from either side.
axial stiffness.
floor 53 to 56
simplified frame model of the
(Fig.
typical over each
was
frame model. For
this
it
was found
comer of the towers
that an area modifier to provide a
two continuous columns of the comer panels was
No
25 percent
suitable for
modifiers were needed for the intermittent columns.
selected to be representative, with
The objective of the study was
isolate the behavior
comer panel
Similar to the exterior typical panels, to account for the contribution of the
spandrels into the axial stiffness of the columns,
in the
Frame model (Rigidity) C;50%, S:100% C:100%, 8:100%
A 1
A
model
to
match the
comer panel by modifying the
parametric study, the panel
two additional columns attached on
inter-story drift of a detailed shell
was
rigidity
model and
a
of the column/spandrel intersections
straightened to simplify the study and to
of interest (see Fig. 3-24). The deformations
at
points Tl, T2, Bl, B2, and
M2
3-25) were studied for representative column and spandrel plate dimensions. The topmost columns
were connected via
a rigid link
and loaded
in the
plane of the panel and perpendicular to the column with
a 100 kip load.
The
lateral
displacements calculated for the shell and frame models of the typical exterior wall comer
panel with varied column and spandrel rigidities are reported
25 percent column
rigidity
and 50 percent spandrel
in
Table 3-6. The study indicated that
rigidity in the
frame model produced deflection results
consistent with the shell model.
NISTNCSTAR
1-2 A.
WTC
Investigation
59
Chapter 3
Figure 3-24. Shell element and frame models of typical exterior wall corner panel.
Column
Typclal exterior column
T1
C:50%, S:100%
-Spandrel
Ml
Corner panel Rigidity
Figure 3-25. Selection of column and spandrel rigidity of typical exterior wal corner panel.
60
NISTNCSTAR
1-2A,
WTC Investigation
Development of Reference
Structural
Models
for the
WTC
Towers
Table 3-6. Lateral displacement (in.) for the shell and frame models of typical exterior wall corner panel with varied column and spandrel rigidities. Floor 53-56 Shell
As
Corner panel
model
No
rigidity
rigidity
C:25%, S:50%
C:100%, S:100%
T1
0.227
0.236
0.222
0.152
12 Ml
0.227
0.236
0.222
0.152
0.149
0.154
0.149
0.102
B1
0.084
0.072
0.077
0.053
B2
0.084
0.072
0.077
0.053
part of the in-house
detailed shell element
NIST review of the
reference structural models (see
model of original comer panel
to test the accuracy of the simplified
(not straightened)
NIST NCSTAR
was analyzed under
frame model with 25 percent column rigidity and 50 percent
spandrel rigidity calculated above. Both the detailed and simplified models were loaded as Fig. 3-26.
The
deflections calculated from the frame
shown
in
model were consistent with those estimated from
the shell model, indicating that the rigidities estimated using the straight
represented the actual
1-2), a lateral loads
model
(Fig.
3-25) accurately
comer panel behavior.
Figure 3-26. Detailed and simplified model of the exterior wall corner panel.
Flexible Floor
3.5.3
The
floor
stiffness
Diaphragm
models developed as described
used within the
NIST NCSTAR
1-2A.
WTC
WTC
1
and
Investigation
in Sees. 3.3
and 3.4 were used
WTC 2 global models.
The
to
develop the flexible diaphragm
in-plane diaphragm stiffness of the
61
Chapter 3
detailed floor
models was detemiined and used
flexible shell element floor
model was then
an equivalent shell element floor model. This
to arrive at
inserted in the global
models
at specific floors to
capture the
in-plane flow of forces and defomiations. These flexible diaphragms were not used throughout, as the rigid
diaphragms
in the
majority of floors provided for a sufficiently accurate representation of the flow of
forces and defonnations while keeping
manageable the model's computational requirements.
global models, flexible diaphragms were used at the beam-framed floors 77, 107, 108, 109,
1
and roof of both towers. For
10,
the flexible diaphragms
was reduced
to prevent these
3, 4, 5, 6, 7, 9,
floors 107, 108, 109, 110.
and
In the
41, 42, 43, 75, 76,
roof, the stiffness of
diaphragms from attracting large forces
incompatible with the strength of the slabs (see Sec. 3.2.9). Parametric studies were performed to compare the diaphragm stiffness of two different floor models for
both the typical truss-framed floor and the beam-framed floor. The typical floor models were compared with simplified equivalent models that duplicated the representation of the exterior wall columns, exterior wall spandrels, core columns, and their boundary conditions. The floor framing, both inside and outside the core,
was replaced by
shell elements.
The
material properties of the shell
model matched the
properties of the concrete floor outside the core in the respective floor model.
The comparative
floor
models were loaded
(equivalent to 15 psf over the 12
ft
in the
plane of the floors with a lateral load of 180
story height) on both the
windward and leeward
faces.
base supports were released for the exterior wall columns along the loaded faces and for to
allow lateral translation only
in the direction
The comparative models were executed
windward and leeward
sides of the
all
core columns
of loading.
to assess the horizontal deflection
model and
lb/ft
The column
for the case
where the
of the floor on both the
lateral loads
were applied non-
concurrently along the 100 face and 200 face of the tower. Both the total horizontal deflection of the slab
and the relative displacement between the windward and leeward sides were compared between the models. The shell thickness was modified to match the in-plane stiffness detennined by the detailed floor models.
The defonnations from
the lateral load case using the 75th floor
model of WTC 2 are
illustrated in
Fig. 3-27, while Fig. 3-28 shows the deformations of the simplified floor model. Fig. 3-29 shows the lateral deflection
of the north and south sides of the floor model under
lateral load applied in the north
direction using the detailed and equivalent floor models.
62
NISTNCSTAR
1-2A,
WTC
Investigation
Development of Reference
Structural
Models
for the
WTC
Towers
Note: Exaggerated scale.
Figure 3-27. Deflection of typical beam-framed floor model due to lateral loading.
3 '
-1^
/K\
/
I
"TTT
W
'Vv
/VX
,-
Note: Exaggerated scale.
Figure 3-28. Deflection of equivalent floor model due to lateral loading.
NISTNCSTAR
1-2A.
WTC Investigation
63
Chapter 3
0.008
SUMMARY
3.6
This chapter described the development of the reference structural models for the
WTC towers.
These
reference models were used to establish the baseline performance of the towers and also served as a reference for
more
and collapse
initiation analysis.
•
Two
detailed
models for
aircraft
impact damage analysis and thermal-structural response
The main types of models developed were:
global models of the towers, one each for
primary structural components
WTC
1
and
WTC 2.
The models included
in the towers, including exterior walls
beams), core columns, exterior wall bracing in the basement floors, core bracing
mechanical floors, core bracing flexible
at the
main lobby atrium
all
(columns and spandrel
levels, hat trusses,
and
at the
rigid
and
diaphragms representing the floor systems. The models were developed using the
electronic databases described in Chapter 2.
natural frequencies of
WTC
1
To
validate the global models, the calculated
were compared with those measured on the tower and good
agreement between the calculated and measured values was obtained. •
One model each of a
typical truss-framed floor (floor 96 of
framed floor (floor 75 of WTC 2) included
all
in the
impact and
primary structural components
fire
in the floor
WTC
zones
1 )
in the
and a typical beam-
two towers. The models
system, including primary and
bridging trusses, beams, strap anchors and horizontal trusses, concrete slabs, and viscoelastic
dampers. To validate the floor models, several studies were carried out
64
NISTNCSTAR
to
compare
1-2A.
WTC
stresses
Investigation
Development of Reference
Structural
Models
for the
WTC
Towers
and deflections estimated from the model with hand calculations for representative composite sections.
Good agreement was
obtained between the model results and hand calculations.
Parametric studies were performed to evaluate the behavior of typical portions of the structure and to
develop simplified models that could be implemented
in the global
models. These parametric studies
included detailed and simplified models of typical exterior and comer wall panels, and floor systems.
NISTNCSTAR
1-2A.
WTC
Investigation
65
Chapter 3
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66
left
blank.
NIST NCSTAR
1-2A,
WTC
Investigation
Chapter 4
Gravity AND Wind Loads on the
WTC
Global Models
INTRODUCTION
4.1
This chapter outlines the estimation of the gravity and wind loads applied to the global models of the
World Trade Center (WTC) towers used
to
to establish their baseline
perfonnance. The following sources were
develop the loads for the various loading cases considered
•
Design Criteria document of the
in this study:
WTC towers, prepared by Worthington,
Skilling, Helle
&
Jackson (henceforth referred to as Design Criteria). •
WTC architectural and structural drawings (henceforth WTC Dwgs.).
•
Wind
reports prepared
by Worthington,
Skilling, Helle
development of design wind loads for the •
& Jackson,
Reports from two independent wind turmel studies concerning the
2002
for insurance litigation
Williams Davies and
New York
by Cermak Peterka Peterson,
Iru'in, Inc.
(henceforth
City Building
describing the
WTC towers (henceforth WSHJ Wind Reports). WTC towers, conducted in
Inc. (henceforth
CPP) and Rowan
RWDI).
Code (henceforth
•
Current
•
Current American Society of Civil Engineers
NYCBC 2001).
(ASCE
7)
Standard (henceforth
ASCE
7-02).
Three loading cases were considered for the baseline performance analysis. They included: •
Original
WTC design
loads case. Loads were as follows:
WTC design in accordance with Design Criteria, used in WTC design wind loads from WSHJ Wind Reports. •
Loads were as follows: Dead loads as
Stafe-of-the-practice case.
2001
live loads;
NYCBC
and wind loads from
RWDI
2001 wind speed. This wind load
•
is
wind tunnel
is
practice since, as will be explained later, the
loads on the towers and
Dead and
in original design;
ASCE
NYCBC
study, scaled in accordance with
considered as a lower estimate state of the
CPP wind
tunnel study produced larger wind
considered as an upper estimate state-of-the-practice case.
Refined NIST estimate case. Loads were as follows: Dead loads as loads from
live loads as in original
conjunction with original
in original design; live
7-02 (a national standard); and wind loads developed by National Institute
Standards and Technology (NIST) from critical assessment of infonnation obtained from the
RWDI
and
The purpose of using
CPP
reports and state-of-the-art considerations.
the original
WTC design loads was to evaluate the performance of the towers under
original design loading conditions,
and ascertain whether those loads and the corresponding design were
adequate given the knowledge available
NISTNCSTAR
1-2A,
WTC
Investigation
at the
time of the design. The purpose of considering the
state-
67
Chapter 4
of-the-practice case and the refined
NIST
estimate case
was
to better
understand and assess the effects of
successive changes in standards, codes, and practices on wind design practices for
tall
buildings.
Section 4.2 of this chapter presents the gravity loads on the towers, including: dead loads and live loads
used in the original design, and
and compares
the
in
accordance with
wind loads used
NYCBC
2001 and
ASCE
in the original design, state-of-the-practice
7-02. Section 4.3 presents
wind
loads,
and wind load
estimates developed by NIST.
GRAVITY LOADS
4.2
The
gravity loads applied to the global
WTC models consisted of dead loads (DL) and live loads (LL), Dead loads were applied to the global system (CDL) and superimposed dead loads (SDL), based
appropriately combined as stipulated in the Design Criteria.
computer models on the
in
two
parts: construction
dead loads
WTC Dwgs and the Design Criteria. •
CDL
defined as the self-weight of the structural system, including floor slabs, beams, truss
is
members, columns, spandrel beams, •
SDL
is
etc.
defined as the added dead load associated with architectural, mechanical, electrical,
and plumbing systems; such as curtain walls, equipment and ducts, transfonners, Three independent •
The
sets
of
mechanical
etc.
were combined with the dead loads:
live loads
was taken from
first set
ceilings, partitions, floor finishes,
the Design Criteria
and was used with the original
WTC design
loads case.
•
The second
•
The
was taken from
set
third set
For each
and was used for the state-of-the-practice case.
ASCE 7-02 and was used for the refined NIST estimates case. ASCE 7-02 are essentially identical to the NYCBC 2001 live loads.
was taken from
The Hve loads given
The
NYCBC 2001
in
live load set, live load reductions for
live load reductions in
NYCBC 2001
column design were taken from
their respective source.
are essentially identical to those of the
Design
Criteria.
Gravity loads were applied to the global system computer models using three methods:
•
The self-weight of the
was applied using •
The loads from
the
structural steel
SAP2000
frame for the exterior wall, core columns, and hat truss
self-weight feature.
areas outside the core of the typical truss-framed and
were taken from the reactions of the
typical floor
beam-framed
computer models (see Sec.
4.2.1
floors
)
and were
applied to the global models as concentrated loads on the columns.
•
Since the occupancy, opening layout, and floor framing in the core area varied the loads within the core area, from floor (see Sec. 4.2.2)
68
and were applied
B5
to the roof,
to the global
among
floors,
were calculated using a spreadsheet
models as concentrated loads on the columns.
NISTNCSTAR
1-2A,
WTC
Investigation
Gravity
and Wind Loads on
the
WTC
Global Models
Gravity Loads from Areas Outside of Core
4.2.1
The loads from from the
outside of core
were based on the reactions
areas outside the core area of the typical truss-framed floor
typical floor
computer model (floor 96 of WTC
was 100 psf The reduced applied
The Design
1).
Criteria live load for areas
loads for the typical tmss-framed floor for use in the
WTC design WTC Design Criteria was also used
global system computer models are summarized in Table 4-1, which shows the original criteria for gravity loads.
The
partition allowance
as the partition allowance for the
from the original
NYCBC 2001 and the ASCE 7-02. NYCBC 2001, and ASCE 7-02.
The
live load
of 50 psf is the same
for the original design criteria, the
Table 4-1. Original WTC design criteria loads for floor 96A model for the design of columns (typical truss floor).^
DL
LL
CDL"
SDL'
(psf)
(psf)
(psf)
(psO
Long Span
3.5
14
17.5
50
Short Span
3.5
14
17.5
50
Floor Area
Two-Way Zone Core The self-weight of interior and
a.
slabs
is
Total
3.5
16
19.5
50
None
None
None
None
e.xterior
columns,
not included in the tabulated loads and
e.xterior spandrels,
core frame members, and core floor
not applied to the floor computer model.
is
members
b.
The self-weight of the concrete slab and of the SAP2000. is added to these loads.
c.
Includes a 6 psf allowance for partitions.
d.
Since the loads inside the core are applied separately to the global system computer models, the live loads,
superimposed dead loads on the core
area,
structural steel
in the floor
and core frame members are reduced
system, as computed by
to zero in the floor
computer
models.
Live load reductions for columns for the original Criteria
and were
live loads
identical to those specified in
follow the
live load reductions
The influence
ASCE
WTC design
NYCBC 2001
live loads .
were taken from the Design
Live load reductions for the
7-02 tributary area provisions. For the
ASCE
7-02 loads,
at the exterior
walls
ASCE
7-02.
were calculated using an influence factor coefficient of two as defined
area for exterior wall columns
was calculated using
ASCE 7-02
in
a 45 degree spread for the distribution
of loads among the columns located below the loading point. In the floor
model, the self-weights of the exterior columns and spandrels, the interior core columns, and
interior core
beams
(not including those of the core perimeter)
were not included
in the analysis, since
these weights were already accounted for in the global models. For this purpose, the zero self-weight
frame property modifier
in
SAP2000 was
were also modified by using
used. Appropriate portions of the core slab section definition
a zero self-weight property modifier.
In addition, since the loads inside the
core were applied separately to the global models, the live loads and superimposed dead loads on the core area elements and core frame
members were reduced
to zero in the floor
computer models.
For calculating the loads outside the core, three typical floors (floor 96, 75, and 43) were selected representative of all of the floors in the tower except for the roof, the floors at and below floor 2,
mezzanine floor 43
Models of floors 75 and 96 were developed
floors.
was used
as a representative of the
model with modified loads was used typical floor
beam-framed
computer models, gravity loads on columns
NISTNCSTAR
1-2A,
WTC
Investigation
as discussed previously in Chapter 3,
floors that
to simulate this floor). at
to
were not mechanical
be
and the
and
floors (floor 75
Based on the column reactions from the other floors
were generated by applying
69
Chapter 4
conversion factors to the results from these floor computer models. The conversion factors were based on unit area loading differences
The conversion factors
factors
between
floors.
These calculations were perforaied
were calculated for CDL, SDL, and LL. For
in a spreadsheet.
CDL and SDL, the conversion CDL and SDL by their
were calculated for any given floor by dividing the overall floor
counteiparts at the representative typical floor. For LL, the conversion factors were similarly calculated,
except that the factors included also the appropriate live load reduction factor. The overall floor
SDL
were compiled using
span, short-span, and
a
CDL
and
weighted average based on the floor area for each of the floor zones: long-
two-way zone.
Loads on columns outside of the core
at the roof, floors at
and below floor
2,
and the mezzanine floors
were calculated by spreadsheet.
Gravity Loads from Areas Inside of Core
4.2.2
For the floor areas inside the core from floor B5 to the roof, gravity loads were calculated for individual
columns on the basis of tributaiy areas using
a spreadsheet.
The
calculations
were based on the
WTC Dwgs and the original Design Criteria. The
floor framing infomiation
was obtained from
the structural drawings. Occupancies
and opening
layouts (elevator and shaft layout) for each floor inside the core were obtained from the architectural
drawings. Floors with similar occupancy, opening layout, and floor framing were grouped together and
were represented by floor
a typical floor in the group.
framing were calculated
The core column loads spreadsheets. loads.
The
Floors with special occupancies, opening layouts, or
individually.
for each of the typical floors
NYCBC
In the worksheet, the tributary area of a core
region, the area
and special floors below floor 107 were calculated
2001 loads are essentially identical
was calculated from
to,
and were used for the
column was divided
the coordinates of the core
into four regions.
columns
in the
modified for each type of floor according to the opening layout specific to that
For each region, the dominant occupancy specified
in the architectural
corresponding to each occupancy, the floor worksheet referenced the file.
For each occupancy, the Load worksheet tabulated the
CDL
ASCE
in
7-02
For each
computer models, then floor.
plan was used. For the loads
Load worksheet
in the
same Excel
of the concrete slab, the SDL, and
the LL.
Dead loads weight of the concrete slab (including reinforcing
In addition to the
floor framing consisted of the weight of the structural steel beams. to calculate the
floor framing
weight of the
was
steel floor
steel
The
and metal deck), the
floor
CDL
of the
computer models were used
framing averaged over the floor area. The weight of the
steel
calculated to be 6 psf and 7 psf at floors 96 and 75, respectively.
CDL calculated for floor 96 was applied to all floors except the mechanical floors, CDL was applied. For typical occupancies inside the core, such as coixidors and elevator lobbies, the concrete slab CDL was based on the structural drawings and was listed in the Load worksheet. For special floors, the concrete slab CDL for these typical occupancies was overwritten in the The
floor framing
where the floor 75
Floor worksheet
70
to reflect the actual thickness of the concrete slab specified in the stmctural drawings.
NISTNCSTAR
1-2A,
WTC Investigation
Gravity
Where
a load
was not
listed in the
Load worksheet,
and Wind Loads on
the concrete slab
CDL
tlie
was included
WTC
Global Models
in the
Floor
worksheet.
The SDL includes the weights of partitions, beam floor finish, ceiling,
fireproofing, ductwork, electrical conduit and piping,
and mechanical equipment. The types of floor
occupancy were obtained from the architectural plans and from the drawings. The weight of finishes
with the original
was obtained from
finish
and ceiling applied
to
each
finish schedule in the architectural
the Design Criteria (Sheet BC-1-7). In accordance
WTC Design Criteria, for equipment rooms on the mechanical floors an SDL of 75 psf
was used. Partition layouts
and types were obtained from the architectural drawings, and the partition weights were
taken from the Design Criteria (Sheets BC-1-7 and BC-1-8). loads per gross area
were calculated
for seven typical
As shown
in Figs.
4-1 and 4-2. partition
opening/occupancy configurations.
A partition
weight of 20 psf per gross area was assumed for the return plenums and for areas where the occupancy
was not specified
in the architectural
drawings.
A partition weight of 6 psf,
used for tenant space. For occupancies that included an additional 75 psf in partition weight
taken over the gross area, was
SDL
for
equipment weight,
a
was not added.
Source: Reproduced with permission of The Port Authority of
New York and New Jersey. Enhanced
by
NIST.
Figure 4-1. Partition groups A, B, C, D, and E.
NISTNCSTAR
1-2A,
WTC
Investigation
71
Chapter 4
Source: Reproduced with permission Enhanced by NIST.
New
of Tine Port Authority of
York and
New
Jersey.
Figure 4-2. Partition groups Weights of concrete beam encasements were taken from the
At
floors 77, 43, 9 to B3,
G and
structural
F.
drawings and the Design
and B5, most of the core beams were concrete-encased. For the
20 psf uniformly distributed load taken on the gross tributary area was added encasement weights assumed for floors
for the concrete
concrete
beam encasement
to the
in the hat truss region.
For
Criteria.
entire core, a
dead load. See below all
other floors, the
loads were applied directly to the columns to which concrete-encased
beams
were connected.
The loads due
to the construction
of the Fiduciary Trust vault
in
WTC 2
(see Sec. 2.5.2)
were added
to the
dead loads of the original construction.
Live Loads
The
original
WTC live loads for occupancies inside the core were taken from the Design Criteria (Sheets
CC-1-2 and CC-1-3). For listed for the
ASCE7-02 listed in
a
few occupancies not
explicitly listed in the
Design
Criteria, the live load
most similar occupancy was used.
live loads
ASCE7-02,
identical to the
were taken from Table 4-1 of the standard. Where
the
ASCE
Design Criteria
live load
was used.
NYCBC
a
WTC occupancy was not
2001 hve loads are essentially
7-02 live loads and were not tabulated separately.
Live Load Reduction For use with the corresponding original
The
live loads, live load reductions for
WTC Design Criteria and on ASCE
live load reduction factors in the original
Criteria.
NYCBC
2001
column design were based on
the
7-02.
WTC design were taken from sheets DC 1-3 of the Design WTC Design Criteria
live load reductions are essentially identical to the original
and were not tabulated separately.
72
NISTNCSTAR
1-2A,
WTC Investigation
Gravity
and Wind Loads on
For the core columns, the ASCE7-02 hve load reductions were calculated area provisions of ASCE7-02. Core columns were divided into three
in
the
WTC
Global Models
accordance with the tributary
column groups based on
their
tributary' areas:
A
•
Columns 704, 705, 805, and 904
•
Columns
•
All other core columns
at the
perimeter of the core
single set of live load reduction factors
was applied
to all the
columns within the same column group.
Hat Truss Floors Except for floor 107. for the floor areas tributary
to the hat truss framing, gross tributaiy areas
were
calculated by hand. Openings were subtracted from gross tributary areas, and the resulting net areas were
entered into an Excel spreadsheet. Except for columns 704B106Z, 704B107, 705B106Z, 803B107,
804AB107, and 804B106Z. where gross and net
were calculated
areas
directly, for floor 107, the net areas
were taken from floor 106.
CDL, SDL, and LL were based on
the
Design Criteria sheets BFl-1 lA, BFl-12, BFl-13, and BFl-14.
These sheets assign uniform loads throughout 109 (mechanical
floor), sheet
criteria for other
mechanical
SDL = 75
BCl-3
indicates
entire floors (both outside
LL =
floors, this live load
and inside the
core).
For floor
150 psf However, for consistency with the design
was applied
in
two
parts, as
LL =
75 psf and additional
psf.
For some occupancies elsewhere in the
107
in the core for floors
to the roof, the
occupancy-specific live load given
WTC Design Criteria exceeded the unifonn live load specified for the entire floor.
these occupancies, the higher live load
was applied
to the
For
computer model. These occupancies are
summarized below;
LL=1 00 psf (instead of the uniform LL=75
•
Stair:
•
Corridors:
LL=
100 psf per
psf)
WTC Design Criteria or 80 psf per ASCE 7-02
(instead of the
uniform LL=75 psf)
Note
of the uniform LL=75 psf)
Ser\ ice room:
•
Window washer storage LL= 25 psf (instead of 75 psf)
that
1
beams,
models and
and diagonals
girders,
that their self weights
20 psf uniform load that
LL= 1 00 psf (instead
•
at
gravity loads
NISTNCSTAR
1-2A,
part of the hat truss
system were included
were calculated by SAP2000 and added
the weight of concrete encasement.
and were used for the
The antenna
were
to the
CDL.
in the global
In addition, a
every level (floor 107 to roof) was used to account for the weight of structural steel
was not modeled and
identical to
that
WTC
NYCBC
ASCE
7-02 loads were essentially
2001 loads.
were also considered
Investigation
The
in the
WTC
1
global model.
73
Chapter 4
Construction Sequence Loading Effects
4.2.3
Located between floor 107 and the roof in both towers, the hat truss interconnected the core columns and the
columns of the exterior
The
walls.
between the core and the exterior
However,
the
CDL
of the hat truss system were not distributed through the hat
between those loads distributed through the hat sequence was considered
The
effects
in the
wind loads
hat truss system distributed both gravity loads and
walls.
SDL
and
put in place prior to the completion
In order reasonably to differentiate
truss.
system and those
truss
that
were
not, the construction
computer models.
of construction sequence on the distribution of gravity loads was modeled using the nonlinear
staged construction analysis function in SAP2000. The primary puipose of this step in the analysis was to provide, at the top of the towers, a reasonably accurate distribution of construction and superimposed
dead loads between the core columns and the exterior wall. Accordingly, the global system computer
model was subdivided
into
two portions:
stage, the lower portion of the full
floor 106
and below, and the area above floor 106. In the
computer model was loaded with
with floor 106 and below. In the second stage, the portion of the activated,
and the
CDL
and
SDL
full
stage. This
methodology approximates well the way
4.3
WIND LOADS wind
at
the time of the design.
Wind
floor 106
first
associated
was
the towers
were
built.
in standards, codes, in the future.
is
two
objectives.
The
first is
structural design given the
better to understand
and practices, with
a
and assess the
view
to
This case study provides an opportunity
unique effectiveness.
these objectives, three independent sets of wind loads were applied to the global tower models
as explained in Sec. 4.1.
4.3.1
which
The second objective
helping improve standard provisions for wind loads to achieve this objective with
SDL
building with the hat truss engaged in the second
effects presented in this report has
on design practices of successive changes
To achieve
in
adequacy of the original wind loads and the con esponding
knowledge available effects
model above
and
^
investigation of wind loads and
to ascertain the
full
CDL
associated with the upper floors were placed on the full computer model.
Live loads on the whole model were applied to the
The
of the
all
Original
These
WTC
sets are further described as follows:
Design Wind Loads
loads were detennined for the original design of the
WTC towers through the development and
implementation of a boundaiy-layer wind-tunnel study which simulated the mean and fluctuating (turbulence) properties of the available in the 1960s.
WSHJ Wind
Reports.
The
wind from ground
original
From among
to gradient height
by using the knowledge and techniques
WTC wind loads were taken from summaries given in Part IV of the the loading cases, the
most severe were determined by comparisons
of diagrams of wind-induced shear and overturning moment. In the original
WTC wind tunnel studies, wind tunnel data were collected for each tower for wind
approaching from 24 wind directions, a,
in 15
degree increments. Part IV of the
provides equations for the wind-induced shears and overturning //, at
of coefficients
in these
74
be used
in the
towers
at
21 elevations,
z,
increments of 0.05//. For each wind direction, the reports provided sets
along the building height, to
moments
WSHJ Wind Reports
equations to obtain the static and the dynamic components of shear and
NISTNCSTAR
1-2A,
WTC Investigation
Gravity
overturning torsional
moment
in the
N-S and E-W
directions. Coefficients
and Wind Loads on
the
were also provided
WTC
Global Models
for calculating
moments. The torsional moments are associated with eccentricity of the global wind excitation
of the building with respect to the building center of rigidity. Based on these equations, shears and torsions
were calculated
for each
effectiv e static shear forces, 5,
wind
two orthogonal
direction for the
and overturning moments, M,
at
directions.
The equivalent
each level were comprised of static and
dynamic components:
S^S + S'
M^M + M' where the
first
and second terms
components. The
static
^^^"^
indicate, respectively, the
mean
or steady-state components and
dynamic
components of the shears and moments were calculated from the following
equations:
S{z)^^pV;DHC,{z)
_
.
_
(4-2)
M{z)^-pV:-DHC^{z)
where:
p
= design
= mean
air density
= 0.0023
slug/ft^
(or equivalent) design
a height of 1,500
ft
wind speed, determined
to
be 98
mph
averaged over 20 min
at
above ground.
and C^/ = shear force and overturning moment coefficients, respectively, obtained from
wind tunnel
D
and
H
tests
and provided
= dimension
in tabular
in plan
The dynamic components of the shear
form
and height of the tower
forces and overturning
moments
at
any height z were obtained
from the following equations:
H S'(z)
- An'nlA |w(z) /u{z)dz (4-3)
H
M\z) = \s\z)dz
NISTNCSTAR
1-2A.
WTC
Investigation
75
Chapter 4
where:
=
A =
natural frequency of oscillation of the tower
amplitude of oscillation
m{z) = mass per
unit height
at the
design wind speed
of the tower
= amplitude of fundamental
/j(z)
mean
top of the tower coiresponding to the
vibration
mode
height r for unit amplitude
at
at
the top of the
tower.
The wind intrinsic
loads were calculated on the basis of 2.5 percent total damping. This value includes the
damping of the
The
differential static
two
different methods:
structural
systems plus the supplemental damping provided by the dampers.
and dynamic shears between successive
The
•
The dynamic wind load
wind load
to
to
be applied
the tower height, the fundamental
wind-induced sway
Note
that for
a = 90
was detennined
at the
to
mode
each floor was based on the distribution of mass over shape, and the
dynamic component of the
component of the wind
for the
a = 270
forces for
degrees, for
that the basic data for the
WTC
WTC 2.
two towers
is
By
wind load cases
The
E-W
for
were it
by 180 degrees.
components of the building forces
listed
static
and dynamic
below, there were 96 different
for each tower.
(Static
+ Dynamic) and
E-W
(Static
+ Dynamic)
N-S
(Static
+ Dynamic) and E-W
(Static
- Dynamic)
N-S
(Static
- Dynamic) and E-W
(Static
+ Dynamic)
N-S
(Static
- Dynamic) and E-W
(Static
- Dynamic)
and dynamic shears
the overturning
static coefficients
observation of the static coefficient data,
shifted
N-S
static
WSHJ Wind Reports
Accordingly, the
1.
Considering the 24 different wind directions and the four combinations of the
components of the N-S and
lateral
roof
degrees, coefficients were not found in the microfilm of the
calculating the static
deduced from data
were calculated and distributed using
be applied to each floor was determined from the shear diagram.
•
static
levels
in the
moments were
N-S and E-W
directions
were calculated for
all
96 loading cases, and
calculated from the shears. In order to determine the most severe of the
96 loading cases for each tower, the wind-induced shears and overturning moments were compared, for each direction,
at
heights z/H
=
0.75, 0.50, 0.25 and
0.
The wind loading cases producing
the
maximum
shears in either of the two orthogonal directions were identified for application to the global models.
To compare
overturning
moments
were combined vectorially
(i.e.,
for each loading case, the
the
moments
magnitude of the resultant
squares of the components, and the direction P of the resultant
76
is
in the
two orthogonal
directions
equal to the square root of the
moment
is
sum of the
the arctangent of the ratio of the
NISTNCSTAR
1-2A.
WTC
Investigation
and Wind Loads on
Gravity
the
WTC
Global Models
and .Y-components). The load cases were grouped by the angle p using an increment of 45 degrees, resulting in 8 groups of load cases. For each P group, at z/H = 0.75, 0.50, 0.25 and 0, the wind load cases V-
that generated the
maximum
moment were
resultant
identified for application to the
computer global
system models. Eight groups of maximum moment plus four directions of maximum shear in the
towers would result
produced towers.
a
As
in
48 different loading
maximum resultant moment a result, for
WTC
and/or a
cases.
maximum
1,16 loading cases were
at
four heights
However, some individual wind load cases shear at
more than one elevation
and for
identified,
WTC 2,
in the
17 loading cases were
identified.
For cases where an intermediate floor did not provide
was
distributed to the floors
For the floors modeled directions
were applied
moments were forces,
lateral
support for the exterior wall, the wind load
above and below, omitting the intermediate floor wind
in the global
model by
rigid diaphragms, the
N-S and E-W The torsional
in the
as concentrated loads at the geometric center of the building.
also taken into account. For the floors with flexible diaphragms (see Chapter 3), the
based on
tributary' areas,
were resolved
and leeward forces were applied. At these
into point loads at the perimeter
floors, the torsional
moment was
concentrated forces applied parallel to the four faces of the tower simplified
wind forces
load.
method used
at the
center columns of each face.
for applying the torsional loads at floors with flexible
any noticeable effects on the analysis
results.
columns. Both windward
represented by four identical
The
diaphragms did not have
For each loading case, the orthogonal wind forces were
subdivided into windward and leeward forces based on the direction of the wind. For this purpose, the
24 wind directions
a
(discussed previously) were divided into 8 groups as given in Table 4-2.
a=0
is
for
direction for
wind blowing from north
The wind
to south.
Table 4-2. Grouping of the wind directions.
a
Group 337.5
2
22.5
4
5
157.5
6
202.5
7
247.5
8
292.5
1
67.5
For groups
1
,
3, 5,
and 7 (orthogonal or near-orthogonal wind
distributed in accordance with Fig. 4-3a. For groups 2, 4, 6, directions), the
wind forces were
directions), the
wind forces were
and 8 (diagonal or near-diagonal wind
distributed in accordance with Fig. 4-3b.
The
factors
shown
in Fig.
4-3
were based on Figure 6-6 of ASCE 7-02 Standard.
NISTNCSTAR
1-2A.
WTC
Investigation
77
Chapter 4
0.5/1.3 Fy
0.5/1.3 Fy
Leeward
Leeward
0.5/1.0 Fx
0.5/1.0 Fx
0.8/1.3 Fx
Side
Side
Windward
0.5/1.3 Fx y,
Leeward
X
X
0.8/1.3 Fy
0.8/1.3 Fy
Windward
Windward wind Direction
A Wind Direction
(b)
a)
Figure 4-3.
Windward and leeward
and
distribution for (a) orthogonal
(b)
diagonal
wind directions. State-of-the-Practice
4.3.2
For the in
Wind Loads
WTC towers, two wind tunnel tests and wind engineering studies based thereon were conducted
2002 by independent laboratories as part of insurance
The
tests
of both studies were
made
available to
NIST; see NIST
NIST investigation. RWDI. The results
litigation unrelated to the
and studies were conducted by Cermak Peterka Peterson,
NCSTAR
Inc.
(CPP) and by
1-2 for
more
details.
For the purpose of the baseline analysis, the state-of-the-practice wind load case consisted of the wind load estimates provided by
NYCBC open
RWDI,
scaled in accordance with a wind speed equivalent to the
2001 wind speed (interpreted to be the 80
ten"ain).
These wind loads were applied
combination factors presented
The wind loads from
RWDI
in the
RWDI
mph
fastest-mile
to the global
at
30
ft
elevation over
models using the directional and torsional load
reports.
are smaller than those obtained
Considering the differences between
wind speed
from
CPP
WTC 2
for
RWDI and CPP results, RWDI practice may
(see Sec. 4.3.4).
be viewed as a "lower-
estimate, state-of-the-practice case."
The
state-of-the-practice
wind loads were
distributed in the global system
similar to that described in connection with the original design
78
wind
computer models
in a
manner
loads.
NIST NCSTAR
1-2A,
WTC Investigation
Gravity
and Wind Loads on
the
WTC
Global Models
Refined NIST Estimates
4.3.3
NIST completed an independent
wind loads
analysis to estimate the
that
would be appropriate
for use in
designing the towers based on state-of-the-art considerations. The analysis was based on results provided
by CPP and RWDI. with modifications The objective of this analysis was not to better understand
Wind
and assess the
to assess the
7-98 Standard (which
the
is
results scaled in
same
as in the
changes
baseline analysis. For details on
wind loads on
how
these
wind speed
7-02 Standard) were estimated by
ASCE
see
NIST
7-98 and
ASCE
wind loads were obtained
the towers, consistent with the
ASCE
NIST
in
ASCE
using the
7-02 Standard wind speed
number was recommended by NIST
1.15. This
and practices.
in standards, codes,
accordance with a wind speed equivalent to the
and then muhiplied by a factor of
lateral
ASCE
in M'ind engineering.
adequacy of the original design wind loads, but rather
effects of successive
loads based on recently developed knowledge and consistent with the design
RW'DI
The
draw on recently developed knowledge
that
for the refined
NCSTAR
NIST
1-2.
7-02 design wind speed
requirements, were estimated by using the effective static floor-by-floor wind loads presented in Table 5a
(without P-A effects) or Table 5b (with P-A effects) of the
RWDI report (north tower) for WTC and RWDI report (south tower) for 1
Table 3a (without P-A effects) or Table 3b (with P-A effects) of the
WTC
These effective
2.'
factors indicated in note (3) provided at the
were applied
RWDI
to the global
Comparisons
of
Tables 4-3 and 4-4 provide a
and the
WTC
2. respectively.
NYCBC.
wind loads
the
RWDI
bottom of Tables
model of each tower using
(north tower) and Table 4a of
4.3.4
wind loads were multiplied by
static floor-by-floor
RWDI
5 in
RWDI. The
loads so obtained
the load combinations presented in Table 6a of
Wind Loads
summary of the wind-induced base
The values
study, the
in
CPP
are expressed in terms of
RWDI: Most
and
and by the
(south tower).
shears and base
moments on
WTC
I
Tables 4—3 and 4-4 are based on the 1938 and 1968 versions of
study, the refined
NIST
estimates, and the original design.
The
two orthogonal components and of measures of the most unfavorable
combined peaks obtained by various methods, •
3
the factor 1.15
unfavorable peak
is
as follows:
calculated as vector
sum of weighted .v and
v peaks, with
weighting factors approximately consistent with the "principle of companion loads," the
approximations being based on engineering judgment and in-house experience. •
CPP: Most unfavorable peak
is
calculated as vector
sum of x peak and companion
time v-response, or 3; peak and companion point-in-time x-response, whichever •
For the for
P-A
is larger.
WTC design:
Most unfavorable peak is calculated as vector sum ofx and v peaks corresponding to most unfavorable wind direction. These x and/or 7 peaks may be smaller for that most unfavorable direction than the x peaks and j' peaks corresponding to wind Original
normal
"
point-in-
WTC 2
to a building face (see Sec. 4.3.1).
tower Tables 3b and 3c
effects are in fact given in
NIST NCSTAR
1-2A.
WTC
in the
RUT)I
report (South
Tower) were inadvertently switched. The loads accounting
Table 3c of the report.
Investigation
79
Chapter 4
A comparison
Table 4-3.
of
wind load estimates Base Shear
Source 1 1
NYC
\\l
IT
Building Code
Q^S yj o
1968
to
for
WTC
from various sources. Base Moment 106kip ft
1
103 kip
Most
Most
unfavorable
unfavorable
combined peak
About
About
5.3
5.3
4.2
4.2
9.3
9.3
7.7
7.7
10.1
10.5
combined peak
date
R\X/ni
/
MVP
RiiilHino
zuuz
1
1.4
zuuz
1
Z.J
10.5
13.0
12.2
Code
RWni
/
A
QPP
rPP / NYr N \^ \_ 1 1
/
1
i
7
OS
1
1
1 .J
1 1
A n 't.U
1
n 8
1 1
1 1
A .4
1 1
^ J.
1 1
NA
NA
NA
NA
NA
NA
2002
NA
NA
NA
NA
NA
NA
2004
14.1
13.0
16.1
12.4
13.1
15.1
1960"s
9.8
10.6
14.0
10.3
9.1
13.7
RiiilHinP Ul lU 11 jL>
1 1
J ci,
Code
CPP / ASCE NIST/
7-98
third-party
SOM
review Original
WTC
Design
Table 4-4. Comparison of wind load estimates for Base Shear
WTC
2 from various sources. Base
103 kip
Moment 106kip
Most
unfavorable
unfavorable
Source
NYC Building Code NYC
Building Code
combined peak
About N-S
About
E-W
combined peak
Year
N-S
E-W
1938
5.3
5.3
4.2
4.2
9.3
9.3
7.6
7.6
2002
9.7
11.1
12.3
10.1
9.2
11.3
2002
10.6
12.2
13.5
11.1
10.1
12.4
2002
NA
NA
NA
NA
NA
NA
2002
15,1
15.3
17.1
15.5
14.0
17.0
2004
1
2.2
14.0
15.5
12.8
11.6
14.3
13.1
10.1
16.5
8.8
12.6
15.2
1968
to
date
RWDI/NYC Building Code
RWDl ASCE /
CPP / NYC
7-98
Building
Code
CPP / ASCE NIST
7-98'
/third-party
SOM
review Original a.
ft
Most
Using
WTC Design
ASCE
1960-s
7-98 Sections 6.5.4.1 and 6.6.
Table 4-5 presents a summary of design base shears and base moments based on various building codes at the
time of the design. Note that the base
foundation level (rather than
80
moments presented
in
Tables 4-3 to 4-5 are calculated
at the
at the street level).
NISTNCSTAR
1-2A,
WTC
Investigation
Gravity
Table 4-5. Base shears and base
moments due
and Wind Loads on
to
the
wind loads from
WTC
Global Models
different
building codes.
Building
Code
1938
1968 to Date
1964
NYC
NYC
NY
Building
Base Shear
Code
Code
Building
State
BOCA/BBC
1967 Chicago Municipal Code
1965
Code
5.3
9.3
9.5
9.8
8.7
4.2
7.7
7.6
8.5
7.5
(10^ kip)
Base Moment (10^ kip
ft)
Tables 4-3 and 4-4 indicate that the original design wind load estimates exceed in established
by
the
NYCBC (a prescriptive minimum requirements code) prior to
WTC towers were designed, and up to and including 2001. also higher than those required
York
cases those
when
New
the 1964
and Code Administrators Basic Building Code
and the 1967 Chicago Municipal Code.
various wind-tunnel-based studies are in
the
Table 4-5 shows that the design values are
by other prescriptive building codes of the time, including
State Code, the 1965 Building Officials
(BOCA BBC),
all
1968,
It is
noted also that wind effects obtained from
cases higher than wind effects based on prescriptive codes
all
and standards.
The two orthogonal base shear and base moment components used smaller than the CPP.
RWDl, and
refined
NIST
estimates.
CPP. RWDI, and NIST
estimates. This
is
due
design are in general
However, the most unfavorable combined
peaks from the original design are larger than, or smaller, by the
in the original
at
most
to the consei"vative
1
based on
5 percent than estimates
procedure used to combine the
loads in the original design. (For example.
NIST
estimates are higher by about 15 percent than the most
unfavorable original design wind loads for
WTC
1,
unfavorable original design loads for
and lower by about
5 percent than the
most
WTC 2.)
Tables 4-3 and 4~4 indicate that the estimated wind-induced loads on the towers vary by as
40 percent between
CPP
the
wind tunnel/climatological studies conducted
being the larger. Thus,
RWDl
CPP
in
much
as
2002 by CPP and RWDl, with
loads are considered as an upper estimate, state of the-practice, while
loads are considered as a lower estimate, state of the-practice.
REFERENCES
4.4
ASCE
7-02:
American Society of Civil Engineers,
Buildings and Other Structures, Reston,
CPP
report:
ASCE
7 Standard
Minimum Design Loads
for
VA, 2002.
Data Report, Wind-Tunnel Tests - World Trade Center, Cermak Peterka Petersen,
Inc.
August 2002. Design
Criteria:
Design Criteria document for the
WTC towers developed by Worthington, Skilling, Helle
& Jackson. NYCBC
2001: Building Code of the City of New York, 2001 Edition, Gould Publications, Binghamton,
NY.
NIST NC STAR
1-2A.
WTC
Investigation
81
-
Chapter 4
RWDI
report: (north tower) Final Report,
Tower
1,
Rowan Williams Davies and
Wind-Induced Structural Responses, World Trade Center Irwin, Inc., October 4, 2002.
(south tower) Final Report, Wind-Induced Structural Responses,
Williams Davies and h-win.
SAP2000
Inc.,
October
4,
(2002), Linear and Nonlinear Static and
series
&
Structures Inc., Berkeley,
Rowan
CA.
of wind reports developed by Worthington, Skilling, Helle
outlining the development of design
2,
Dynamic Analysis and Design of Three-Dimensional
Structures Basic Analysis Reference, Computers
WSHJ Wind Reports: A
World Trade Center - Tower
2002.
wind loads
for the
& Jackson,
WTC towers (see NIST NCSTAR
1-1
).
WTC Dwgs: WTC architectural and structural drawings.
82
NIST NCSTAR
1-2A,
WTC
Investigation
Chapter 5
Baseline Performance Analysis of the
WTC
Global Models
INTRODUCTION
5.1
This chapter presents the resuks of the basehne perfonnance analysis for the World Trade Center
(WTC)
1
Chapter
and
4.
WTC 2 global models under the three gravity and wind loading cases described in WTC design load case, the lower-estimate state-of-the-
These cases include the original
practice case, and the refined National Institute of Standards and
Technology (NIST) estimate
case.
Baseline performance results include basic information about the behavior of the towers under design loading conditions, pertaining to total and inter-story
drift,
demand/capacitv' ratios of primary structural
components, exterior columns response (shear lag effects and presence of tensile forces), perfonnance of connections, and the towers' resistance to shear sliding and overturning.
Section 5.2 describes the estimation of the demand/capacit\ ratios and the selection of the design
parameters for their estimation. Section 5.3 presents the results of the baseline pertonnance analysis for
WTC
under the three loading cases. Similarly. Sec. 5.4 presents the results for
1
WTC 2.
Section 5.5
presents a summary- of the results. For both towers, detailed baseline perfonnance results are provided for the original
WTC
design loading case, while a brief summary of the results
the-practice and refined
NIST
is
provided for the state-of-
estimate cases.
calculation of demand/capacity ratios
5.2
demand capacity ratios (DCRs) for structural components were estimated using the Allowable Stress Design (ASD) procedure as specified in the American Institute of Steel Constmction (AISC) Specification for Stiiictural Steel Buildings - Allowable Stress Design and Plastic Design - 9"' For
all
anah
sis cases,
Edition, 1989.
taken
DCRs
at
the
The DCRs were
calculated by dividing
unfactored (working) loads and
for the structural
1
.
at
working
component demands by component
capacities,
stresses, not at ultimate loads or yield stresses.
components were determined
These
as follows:
The component demands were obtained from
the results of the baseline performance analysis
using the reference global models (see Sec. 3.2) and working loads based on the following
load combinations:
•
For the original
WTC design loading case and for the state-of-the-practice case, the load
combinations were those specified by the City Building
AISC
Specificafion (1989) and the
New York
Code (NYCBC) 2001:
Dead Load Dead Load - Live Load
Dead Load - Live Load ^ Wind Load
NISTNCSTAR
1-2A.
WTC
Investigation
83
—
"
Chapter 5
Dead Load + Wind Load •
NIST
For the refined
estimate case, the load combinations were those specified by the
American Society of Civil Engineers (ASCE 7-02) Standard:
Dead Load
Dead Load + Live Load
Dead Load + Wind Load Dead Load + 0.6 X
2.
The component original design
0.75 x (Live Load
+ Wind Load)
Dead Load + Wind Load
capacities
were based on
the
nominal
steel strength as specified in the
documents and using the AISC Specification (1989):
For the original design loading case and for the state-of-the-practice case (consistent with
NYCBC 2001), a one-third increase in the allowable stress was considered for load cases that included
NYCBC •
wind, as specified
AISC
2001 and
at the
time of the design and as
is
currently specified in
Specification (1989).
For the refined NIST estimate case, where loads were based on the load combinations were taken from the
ASCE
ASCE
7-02 Standard,
7-02 Standard, which does not allow the
one-third increase in allowable stress.
The
interaction equation in
two equations
for
AISC
Specifications (1989) estimates the
members subjected
— f •'
£)(^J^
r
flx\
m.\.l
_j_
to
DCR as the
larger of the following
both axial compression and bending stresses:
C
"'1
'fhy
_|_
(Eq. 5-1)
Z)Ci?
=
—
^
+
0.60F,
For the case when f^,IF^ <
F,^
0.
1
5
,
+ F,„
the following equation
is
pennitted
in lieu
of the previous two
.
equations:
where the subscripts x and v indicate the axis of bending about which a applies,
84
particular stress or design property
and
NISTNCSTAR
1-2A,
WTC Investigation
Baseline Performance Analysis of the
and
WTC
Global Models
are the axial compressive stress and compressive bending stress, respectively, that
would be permitted and
are the
if axial force
computed
alone or
axial stress
if bending
moment
alone existed.
and compressive bending
stress at a
given point,
respectively.
F'^ is the
Euler buckling stress divided by a factor of safety.
C„j is a coefficient that
A re\'iew of the basic 6th Edition of the
depends on column curvature caused by applied moment.
design equations and allowable stresses for combined axial load and bending for the
AISC
Specifications (1963), which
was
in effect at the
time of the design, indicates that
they are essentially identical to those of the 9th Edition (1989) design equations and allowable stresses.
There
are.
however, some variations between the 6th and 9th Editions of the specification. The 1963
Specification did not specifically address biaxial bending in the
combined
In addition,
stress equations.
the allow able stress fonnulations for bending with lateral torsional buckling are
somewhat
different
between the two design specifications. For the original design loading case, the SAP2000 program was used directly
to estimate the
DCRs
using
NIST estimate case, member demands under the
the above equations. For the lower-estimate state-of-the-practice case and the refined a
second order analysis that accounted for P-A effects was used
applied gravity and
wind
loads.
The P-A
the global models; as a result, the terms
analysis results in a
C,,,
and
(1
—
I
to estimate
moment
magnification in the components of
F^) were assigned a unit value in the above
DCRs. For these cases, DCRs were calculated in Excel spreadsheets, SAP2000 computer program. The calculations were spot-checked for
equations to estimate component
using results obtained by the
accuracy and to verify that the correct design infonnation was being applied. For most of the component calculations that
acceptable.
were checked, the SAP2000/Microsoft Excel spreadsheet calculations were found
When
errors
were detected, the design parameters were corrected
to provide for
to
be
an acceptable
calculation.
Selection of Global Models Design Parameters
5.2.1
For estimating the
DCRs
of the structural components under the various loading conditions, the following
design parameters were used
•
The
global models of
effective length factors,
the actual
Virtually
all
WTC
1
and
WTC 2 to yield accurate results:
K factors, for ASD coluinn design were selected by
column end conditions with
Table C-C2.1 •
in the
m the Commentary
of the 9th Edition of the
AISC ASD Manual.
core columns were designed originally as axially loaded
significant eccentric loads
and without continuity of framing
P-A moments. The
of construction are consistent with
details
comparing
the theoretical end conditions depicted in
that this
members without
would generate
significant
design approach.
Accordingly, in order to eliminate erroneous bending stresses in the interaction equations, allowable bending stresses for core columns were increased sufficiently to reduce the bending
term
NISTNCSTAR
in the interaction
1-2A,
WTC
equation to less than 0.01.
Investigation
85
Chapter 5
•
The cross-section of the
intennittent
comer columns of the tower included
web
extended beyond the flanges. The
a
web
plate that
plate extensions effectively, but inappropriately,
reduced the section modulus of the cross-section by significantly limiting the allowable stress
To correct for this bending was increased.
in the flange.
plane
•
For the floor 107, 108, and
would
resist the
1
inappropriate reduction, the allowable bending stress for in-
10 spandrel beams, for bending in the plane of the slab, the slab
tendency for the spandrels to bend preventing significant bending stresses
from developing
in the spandrels.
To achieve
this
behavior
model, the spandrels'
in the
allowable bending stress was increased sufficiently to limit the bending tenn in the interaction equation to less than 0.01, ehminating erroneous bending stresses.
•
For the floor 7 spandrels, the actual span length was insignificant due to the actual geometry of the spandrel plate construction. Since the as-modeled spandrels had a significant span and
would otherwise develop erroneous bending
stresses, the allowable
bending
stress
was
increased sufficiently to limit the bending tenn in the interaction equation to less than 0.01.
•
At the exterior wall between floors exterior
columns varied
pronounced
1
and
10, the
unbraced lengths and the properties of the
significantly along the height.
in the out-of-plane direction,
columns. The effects of variation
in
had a notable
These variations, particularly effect
on the buckling strength of the
unbraced lengths and non-prismatic coluinns are only
obliquely addressed in the equations in the
AISC
specifications for
column
capacities.
To
study the influence of unequal unbraced lengths in consecutive floors on the buckling strength of the exterior columns, an elastic buckling (eigenvalue) analysis a typical elastic
column
tree using
SAP2000. Since
buckling capacities obtained from the
the
columns buckle
SAP2000 buckling
was earned out
in the inelastic range, the
analysis were converted into
allowable inelastic buckling capacities using the procedure in Appendix E3 of the
and Resistance Factor Design (LRFD) Specification (1986). The study showed
column unsupported between
out-of-plane direction, for the typical exterior
for
AISC Load
that, in the
floors 2
and
7,
consideration of the shorter unbraced lengths above and below increased the inelastic out-of-
plane buckling capacity by about 25 percent. The default allowable buckling stress calculated by the
SAP2000 computer program
was, therefore, overwritten to reflect this
increase.
Beyond
the influence of unequal unbraced lengths in consecutive floors on the
capacity, the elastic buckling analysis
was
columns located between floors 7 and
9.
Specification (1986)
was used
Again, the procedure
to convert the elastic
into allowable inelastic buckling capacities. in the
columns buckling
also used to study the buckling capacity of the non-prismatic in
LRFD
Appendix E3 of the AISC
buckling capacities of the non-prismatic members
The average
area along the non-prismatic
member was used
conversion equations. Based on the inelastic buckling capacities of the non-prismatic members, the
allowable buckling stress at the
minimum
section of the non-prismatic
members was used
in the global
systems computer models. The resulting modifications to the design parameters were as follows:
86
- Modified F, = Calculated SAP2000 defauh
•
Floors 9 to 10: upper coluiTins
•
Floors 9 to 10: bottom columns
- Modified
F
= Calculated SAP2000
NISTNCSTAR
F
default
1-2A,
F,
x 0.89
x
1
.08
WTC Investigation
.
Baseline Performance Analysis of the
Floors 7 to
9:
F
Modified
Calculated
Floors 2 to
7:
F
Modified
=
Floors 2 to 10: C,„
SAP2000
default
(based on K=1.0 about both
1
Calculated
.0 for
Fa
x
model of WTC
baseline performance analysis of the global
computer with a
CPU
speed of 3.06
The following summarizes
15 h.
Original
5.3.1
WTC
GHz
and
1.0
GB
of RAM.
]
= 0.85
out of plane bending and
BASELINE PERFORMANCE ANALYSIS OF WTC
5.3
The
default
Global Models
X 1.43.
axes)
The
SAP2000
WTC
.26
for in plane
bending
1
was perfonned on a Pentium 4 personal The duration of the analysis was about 1
the results under the three loading cases.
Design Load Case
analysis reported in this section used the gravity and
wind loads used
in the original
design of the
towers, as explained in Chapter 4.
The
of the analysis indicated that for the dead and live loads used
results
in the original
WTC design, the
core columns and the exterior walls carried approximately 53 percent and 47 percent, respectively, of the total gravity load at the
The
calculated total
approximately 56.6
These
drifts are
basement (B6)
maximum in.
(4
ft
drift
level.
of WTC
8.6 in.) in the
equivalent to about
induced by the original
1
E-W
direction and 55.7
H/304 and H/309
H is the height of the tower from the foundation wind loads was not and compared cladding, to
part of the original
to the capability
The
and the inter-story
drift
drifts
plots are presented for the
E-W
WTC design criteria.
and
WTC design wind loads was (4
ft
7.7 in.) in the
N-S
N-S
direction.
directions, respectively,
Limitation of total building
drift
where under
were determined
Instead, inter-story drifts
of the architectural building systems such as the partitions and the exterior
accommodate these
inter-story drifts. Accordingly, there
available to which the total drifts drift)
in the
level to the roof.
in.
may be compared.
normalized by the stoiy height for
E-W
no
is
historical project-specific data
Figure 5-1 presents the deflected shape (cumulative
WTC
1
under the original design loads.
and N-S directions for the cases producing the
(wind azimuth 0 and 75 degrees for the
E-W
and N-S
directions, respectively,
maximum
cumulative
where azimuth 0
indicates tower north).
DCRs
were calculated using the SAP2000 computer program. The calculations were spot-checked for
accuracy and to verify that the correct design information was being applied. For most of the component
SAP2000
calculations checked, the
WTC The
1
global systems
calculations were found to be acceptable.
components under the
member
original
category, the
number of members,
their coefficient of variation (C.O.V.), the percentage
of components with
statistics include, for
greater than
DCR.
1
.05, the
each
number of members with
The
DCR statistics for
WTC design loading are summarized in Table 5-1
DCR greater than
1
.05,
the
mean value of the DCR,
DCR greater than
and the
Figure 5-2 shows the distribution of DCRs for the four exterior walls of
maximum
WTC
1
1.0
and
calculated
under the original
design loads. Close-up views are provided for the exterior walls below floor 9 in Fig. 5-3.
DCRs
for the
core columns are provided in Fig. 5-4.
NISTNCSTAR
1-2A.
WTC
Investigation
87
Chapter 5
Interstory Drif/Story Height for Original
Interstory Drif/Story Height for
Wind Load (E-W)
Original
1600 T
0.00
Wind Load
1600
0.40
0.20
0.60
0.00
Interstory Drift/Story Height [%]
Figure 5-1.
Drift
0.40
0.20
0.60
Interstory Drift/Story Height [%]
(b)
(a)
88
(N-S)
diagrams of V (a) AON-E-
1
due to original A75N+E-.
WTC
wind loads,
(b)
NISTNCSTAR
1-2A,
WTC
Investigation
A
1
Baseline Performance Analysis of the
Table 5-1. Statistics of demand/capacity ratios for
WTC
1
WTC
Global Models
under original design
load case.
Member Type Exterior \\
Number
Mean
c.o.v.
of
Calculated
of
Members
DCR
DCR
Percentage
Percentage
of
of
Number
of
Components Components Components
DCR
with
>
1.0
DCR
with
> 1.05
with
>
DCR
1.05
Maximum Calculated
DCR
all
Columns Below Floor
floor 1
Floor 9 to 106
Above
628
0.77
0.19
4.3
2.7
17
1,122
0.74
0.25
3.3
0.5
6
1.27
31.086
0.76
0.12
1.1
0.4
121
1.31
578
0.73
0.31
12.3
10.0
58
1.46
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1
to 9
floor
1
06
1.36
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1
tn 9
/
61U ^1 AO
0.34
836
0.35
0.69
5.219
0.86
0.14
10
Columns
2j9
0.47
0.45
0.4
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499
0.24
0.87
279
0.47
200 12
1
Floor 9 to
Above
1
06
floor
1
1
06
Core Columns
U.J
1
0.45
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1
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n ju 'X(\ u. 1
.9
.7
1
5.3
14
278
1
1
IV
.Z(S
1
.55
1.36
Hat Truss System
Braces Exterior \\
A
A
0.4
1
1
0.4
0.2
1
1.07
0.53
2.5
0.7
2
1.06
0.72
0.16
2
1
2
1.16
0.40
0.52
0
0
0
0.75
.26
all
Bracing
Below
floor
1
Above
floor
1
06
NISTNCSTAR
1-2A.
WTC
Investigation
89
Chapter 5
(b)
(a)
0 .00
0 .50
0 .75
1
.00
1
.08
Figure 5-2. Demand/capacity ratios for WTC 1 under original design loads, (a) north elevation and (b) east elevation.
90
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of the
0 .00
0 .50
Figure 5-2.
NISTNCSTAR
1-2A,
WTC
(c)
0 .75
south elevation and
Investigation
1
(d)
.00
1
WTC
Global Models
.08
west elevation (continued).
91
Chapter 5
Figure 5-3. Demand/capacity ratios for WTC 1 under original design loads, (a) north elevation below floor 9.
92
NISTNCSTAR
1-2A,
WTC Investigation
Baseline Performance Analysis of the
i
1
WTC
Global Models
i
i
;
i
.
.
r
;
.
]
:
1
!
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;
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0 .50
0 .75
1
.00
1
.OK
(b)
Figure 5-3. Demand/capacity ratios for WTC 1 under original design loads, (b) east elevation below floor 9 (continued).
NISTNCSTAR
1-2A,
WTC Investigation
93
r
Chapter 5
'TT
H
li
!
J.J.J.
''1
i
/
:i.
!
A A A A A Azt\zl\zl\ Azl\ A A A A A A A/tv4\ 0.00
0.50
0.75
1.00
1.08
(c)
Figure 5-3. Demand/capacity ratios for WTC 1 under original design loads (c) south elevation below floor 9 (continued).
94
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of the
0 .00
0 .50
0 .75
1
.00
1
WTC
Global Models
.08
(d)
Figure 5-3. Demand/capacity ratios for WTC 1 under original design loads, elevation below floor 9 (continued).
NISTNCSTAR
1-2A,
WTC
Investigation
(d)
west
95
~
—
—
——
;
'
Chapter 5
TOWER
A,
500's 501
502
503
DCR of CORE COLUMN COLUMN NUMBER 504
505
506
507
TOWER
DCR of CORE COLUMN COLUMN NUMBER
A.
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Figure 5-4. Demand/capacity ratios for WTC 1 core columns under original design loads, (a) 500 line and (b) 600 line.
96
NISTNCSTAR
1-2A.
WTC Investigation
—
^
'
— —
'
—
1
—
—
1
WTC
Baseline Performance Analysis of the
TOWER
A.
700's
702
701
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DCR of CORE COLUMN COLUMN NUMBER 704
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NISTNCSTAR
1-2 A.
WTC
700
Investigation
line
WTC
and
(d)
core columns under original design loads, 800 line (continued). 1
97
—
—
1
'
.
Chapter 5
TOWER 901
902
TOWER
DCR of CORE COLUMN COLUMN NUMBER
A,
900's
903
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f'
,,
.p
(-EJ-
H.'
094 091
u
9.1
iiM
0 92
{1 9.1
ij
094
0 9b
I et
0 92
o.9:<
U8J
0 95
ii
m.
" 8^
0
4,
>.i
^1
1'
0
9'-
n.8
U
9i<
0
111
0,90
0 92
It
0.91
0.93
086 ( HA
WO 1
...
.,
.
—
1
0 02
0 87 0 69 0 91
oa4
'
1
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fl
fi-i
0
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95 9r.
11
U
92
fii:-
0.84
0 67
0 95
.
1
111
0
0 8y
nq-i
0.91
HA
1
(1
(ice,
0 91
1
Or
U97
0 92
0 95 0 97
0.94
1
0;
1194
0 89
0 93 0 95
0 93
1
ij'-.
11
0
9.'
0 97
0 95
H.
1
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a9
iHj
I
01
0 95 -
0.96
(.P7
n-<
088
0 -n
0 85
c,:
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1-1%
us. 0 94
'
H
'^7
0 92 0 92
1
ri
^
87
1
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---^yr
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0 87
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n
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—
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-—
L!iL_
U 95
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9f.
u 85
0 89
0 89
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oaf.
090
0 90
062
0 93
0 87
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1
1
0 96 0
0.93
" '
'
'
"""rp~ "
''
''''
"
,,"
^''^
"
.
0.77
0 68
065 096
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1
00
084
1
02
1
01'
U
083 OBJ •
0
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II
97
0 88
0 8?
1187
(f
B6
0
8(1
0 96
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0 83
088 088
0 90
0 84
0 87
0 90
0 85
0 90 0 91 0 92
0 87
Pi"
0E5
fl a-i
0 85
1.1
0 87
0
R"-!
fl
8H
0
p.?
1
0
fl9
11
R7
11
SI
n 97
fl
R7
0 9^
,,
y^.
.,
a
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fl
ec.
11
8^1
0!
0 88
til-
0 64 0 85
1
1
11
84
11
MS
088
OB''-
0 87
0 90
088
0 91
u as
0 67
0 3. fl
1
0S9
0,89
(1
bb
11
a"'
fl
H"
Oflh
II fj-.
i|
9?
0
a-j
li
85
118'.
0
9lJ
0 86 O.Bfi
1
17.'
"TW
.1
n
fl7
n
8'.
0 K7
fl
096
11
0
II 1411
r.
pi
87
n ay
9fl
0 ao
bi
1
'1]
0 HO 08tt
fl
qfi
11
87
,
,
y._
y
'J
85
ti
87
fl64
1)
uas
0 88 0 89
0 85
0.86
8fo
o6<( (1 P.I-
„,
1
'11
R1
)
(11
I
'81^
fl
108
0
flT
1115^.
n
flS
II
U *i
36
0 aj
1
n 85
lift*.
0
8',
0 84
(187
[1
84
1185
0 88
0 89 0 87
0 87
•TW
oav
..m.-
0 an
87
0 88
U 87
0.91
fl
85 0 85
111
o.afl
t t
0 8S 0 86
oyi
0 91
b&y 095 06i
ObS
0 62
096
0
flfi
fl
86
87
0 88 0 69 0 an
our
0 87 0 6:
fl
0 98 0 79
0 79
0 63
0 81 0
0.7?
0.7(4
OBfi 0.83 1
I,S6
ot
0,84
0 92
,1S„ lU,.
1
..r
(1
BO
Oft"l
0 0 0 0
83
0 79
82 83
0
0 94
0 95
0,83
061
084
oei
0 79 0 86
0 95
0
8.1
0 82
0,911 7
084 0 67
82
085 0 85
1
00
0.86
0 83
f).86
0 63
0.88
086
0.88
(f)
0 .50
0 .75
Figure 5-4. Demand/capacity ratios for (e)
98
f>81
0 82
(e)
0 .00
Bfi
900
line
and
1
.00
1
c08
WTC (f)
1 core columns under original design loads, 1000 line (continued).
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of the
The npes of members
in the exterior wall that
had
DCRs
larger than
1
WTC
Global Models
were calculated for a combination
of axial load and bending under a combination of gravity and wind loads and were generally found in three types of location:
1
.
Columns
at the
comers;
2.
Where
the hat truss connects to the exterior wall; and
3.
Below
floor 9.
The members
in these locations
some of the highest
would be expected
wind
calculated forces under
to
loads.
The
hat truss-to-exterior wall connections
interconnected two major stmctural systems with large concentrated load
below floor 9 was a highly Given the extraordinary
x
ariable
and articulated
structural
set
of highest forces and
in the analysis at locations
exterior wall
of engineering calculations
perforaied almost forty years ago with relatively mdimentai^y computational tools,
were observed
The
ti-ansfers.
system that had large calculated forces.
of replicating with precision a
difficulty
comer columns had
experience large forces. The
at locations
DCRs
excess of one
in
where there was
significant
complexity of system behavior.
The core columns
that
had
DCRs
larger than
were generally located on the 600 column 901 and 908 for
much of their
height.
1
line
The
were calculated
between
due
for axial stresses
floors 80
and 106 and
to gravity loads
and
core perimeter columns
at
gravity loads on these columns were affected significantly by
assumptions about tributary areas, unit construction dead loads and superimposed dead loads, and the
sequence of construction of the hat tmss. The high degree of stress calculated
at these
core columns
is
assumptions between the original and cunent computations.
likely associated with differences in these
Figure 5-5 presents the distribution of the normal stresses due to axial loads (axial coluinn load divided
by columns cross sectional area)
in the
columns of the four exterior walls due
wind loads only
to
(gravity
The axial stresses are presented at three levels along the height of show both the tensile and compressive stresses on the columns where shear lag effects can be observed. For comer columns 101, 159, 301,
loads are not included in these plots). the tower: B6, 39, and 73.
induced by wind loading,
and 359 This
at floor 73, Fig.
likely
is
due
The
plots
5-5(c) indicates that their stresses are smaller than their neighboring columns.
to the influence
of the special comer framing
discontinuous
at that floor, i.e., the
columns and chamfered plan layout of the exterior wall framing.
The
results
of the baseline performance analyses indicated that tension forces were developed
exterior walls of
WTC
1
wind loads
tensile forces are largest at the base
These
The
axial tensile
exterior wall
tension forces for
WTC
1
are
WTC design dead and wind loads.
under the original
the combination of dead and
for
all
faces are illustrated in Fig. 5-6.
of the building and
at the
all
splice capacities
four faces of
summarized
For the tower resistance
in
WTC
1
.
to
were calculated from the
The
DCR
The
1-2A.
WTC
from
another through the column splices. original details
and compared
to the
ratios for the exterior wall splice connections for
Table 5-2.
to shear sliding
and overtuming due
to
wind, the dead loads that acted on the
perimeter walls of the tower provided resistance to shear sliding and overtuming
NISTNCSTAR
forces
figure indicates that
comers.
column loads were transferred from one panel
column
The tension
in the
Investigation
at
the foundation level.
99
Chapter 5
Considering the resistance to shear sliding under wind load, the factor of safety was estimated to be approximately
11. 5.
This was calculated by dividing the resisting force due to dead load on the perimeter
wall (a coefficient of friction of 0.7 was used) by the wind shear at the foundation level. Considering resistance to overturning due to
wind
load, the factors of safety
were estimated
and 2.6 for overturning about a north-south axis and for an east-west calculated by dividing the resisting
moment due
to
wind load taken
Tower
A:
moment due
at the
to
be approximately 2.3 This was
axis, respectively.
dead load on the perimeter wall by the overturning
foundation level.
to East Wind (AON-E-) Loads not included)
West
(Gravity
to
Tower
A:
West
(Gravity
to East Wind (AON-E-) Loads not included)
459
401
-30
300 Face (South Columns)
-
400 Face (West Columns)
FL B6
-
FL B6
(a)
Figure 5-5. Shear lag diagrams of WTC 1 due to original WTC wind loads at (a) floor B6, (b) floor 39, and (c) floor 73.
100
NISTNCSTAR
1-2A,
WTC Investigation
WTC
Baseline Performance Analysis of the
Tower
A:
Tower
West
(Gravity
to East Wind (AON-E-) Loads not included)
A:
Global Models
West
(Gravity
to East Wind (AON-E-) Loads not included)
30 20 10
259
201
0 -10 -20
-30
100 Face (North Columns)
Tower
A:
-
200 Face (East Columns)
FL 39
West
(Gravity
to East Wind (AON-E-) Loads not Included)
Tower
A:
FL 39
-
West to East Wind
(Gravity
(AON-E-)
Loads not included)
30 20
459
401
-30
300 Face (South Columns)
-
400 Face (West Columns)
FL 39
-
FL 39
(b)
Figure 5-5. Shear lag diagrams of WTC (a) floor B6, (b) floor 39, and
NISTNCSTAR
1-2A.
WTC Investigation
1
due
to original
(c) floor
WTC
wind loads
at
73 (continued).
101
Chapter 5
Tower
A:
Tower
to East Wind (AON-E-) Loads not included)
West
(Gravity
A:
West
(Gravity
30
30
20
20
10
10
0}
U
0
ra
-10
-10
-20
-20
to East Wind (AON-E-) Loads not included)
259
201
X
< -30
-30
100 Face (North
Tower
A:
-
200 Face (East Columns)
FL 73
West
(Gravity
«
Columns)
to East Wind (AON-E-) Loads not included)
Tower
A:
30
20
20
FL 73
West
(Gravity
30
-
to East Wind (AON-ELoads not included)
10
10
(A
301
S
0
1X <
-10
-10
-20
-20
459
359
-30
401
-
-30
300 Face (South Columns)
-
400 Face (West Columns)
FL 73
-
FL 73
(C)
Figure 5-5. Shear lag diagrams of WTC (a) floor B6, (b) floor 39, and
102
1
due
to original
WTC
wind loads
at
(c) floor 73 (continued).
NISTNCSTAR
1-2A.
WTC
Investigation
Baseline Performance Analysis of the
WTC
Global Models
240-249
2 50-259
(b)
(a)
0
100
500
lood
Figure 5-6. Tension force distribution (kip) in the exterior wall columns of WTC 1 under original design dead and wind loads, (a) 100 face (north) and (b) 200 face (east).
NISTNCSTAR
1-2A.
WTC
Investigation
103
Chapter 5
300-309
310-319
320-329
340-349
330-339 1
|
400-419
350-359
410-419
420-429
430439
440-449
450-459
{ {
V
(d)
(C)
100
Figure 5-6.
104
(c)
300 face (south) and
500
(d)
100(1
400 face (west) (continued).
NISTNCSTAR
1-2A.
WTC Investigation
)
Baseline
Table 5-2.
Maximum
Exterior
Exterior \\
Column
Fac6
Below 100 Face (
iNortn
1
0.26
floor
Floor
1
400 Face
State-of-the-Practice
wind tunnel
model was analyzed using
The
of
(4
in.
ft
drifts are equi\ alent to
height for
WTC
1
0.15
1
0.59
0.84
1
0.26
the lower estimate, state-of-the-practice loading case, as
NIST NCST.AR
WTC
0.36
to 9
floor 42
1-2).
NYCBC
This loading case included dead loads, live loads
Rowan Williams Da\ ies and
Irwin. Inc. (R\\'DI)
2001 wind speed.
induced by the lower estimate, state-of-the-practice case was
8.8 in.) in the
E-W
direction and 68.1
about H/303 and K''253
in the
Figure 5-7 presents the deflected shape (cumulati\ e storv'
42
2001. and wind loads from the
total drift
approximately 56.8
0.77
Case
study, scaled in accordance with
The calculated
0.26
Floor 10 to 41
Above
NYCBC
1
14
0.54
1
floor
Floor
(West)
according to the
U.
to 9
floor
Below
global
0.6j
Floor 10 to 41
Above
described in Chapter 4 (see also
0.32
floor
Moor
(South)
to 9
floor 42
Below JUU race
ui_K
0.53
1
U to 41
1
1
drift)
E-W
in. (5 ft 8.1 in.) in
and
and the
N-S
the
N-S
directions for the load combinations producing the
1
maximum
cumulative
direction.
directions, respectively.
inter-storv' drifts
normalized by the
under the state-of-the-practice case. The plots are presented for the
DCR statistics for WTC
column
0.31
Abo\'e floor 42
Abo^e
1
Global Models
0.64
1
to 9
0.96
rloor
(East)
caicuiatefl
rloor lU to 41
200 Face
WTC
WTC
Maximum
all
Splices floor
Floor
Below
The
of the
calculated demand/capacity ratios (OCRs) for exterior wall
^^ all
5.3.2
Pe rformance Analysis
E-W
and N-S
drift.
global system components under the lower estimate, state-of-the-practice
loading case are summarized in Table 5-3.
A
comparison of the mean values of the
DCRs
estimated
from the original design case (Table 5-1) with those from the state-of-the-practice case (Table 5-3) indicated that the results are very similar. Also, the distribution of the
members with DCRs
greater than
1
.0
were very similar
DCRs
and the locations of
betv\'een the original design case
and the
state-of-
the-practice case.
NISTNCSTAR
1-2A.
WTC
Investigation
105
Chapter 5
Interstory Drif/Story Height for
Interstory Drif/Story Height for
RWDI/NYCBC Wind Load (E-W)
RWDI/NYCBC Wind Load
1600
1600
0.00
0.20
0.40
0.60
0.00
0.20
0.40
0.60
0.80
Interstory Drift/Story Height [%]
Interstory Drift/Story Height [%]
(b)
(a)
Figure 5-7. Drift diagrams of
WTC
loads, (a)
106
(N-S)
1
due
to the lower estimate, state-of-the-practice
1R14PDN and
(b)
1R8PDN.
NISTNCSTAR
1-2A,
WTC Investigation
1
Baseline Performance Analysis of the
Table 5-3. Statistics of demand/capacity ratios (OCRs) for
WTC
WTC
Global Models
under the lower
1
estimate, state-of-the practice case.
Member Type
Number
Mean
Percentage
Percentage
of
of
Number
of
Components Components Components Maximum
of
Calculated
Members
UCK
c.o.v.
with
UCK
>
01
DCR
with
l.U
DCR
DCR
with
Calculated
> 1.05
> 1.05
DCR
Exterior Wall
Columns Below Floor
1
floor
628
0.77
0.19
6.1
4.0
25
1.30
1,122
0.78
0.26
13.1
5.2
58
1.15
31.086
0.78
0.13
2
0.9
281
1.44
578
0.71
0.31
10.7
7.6
44
1.36
4_U
n AQ
U.40
A
1
to 9
Floor 9 to 106
/\UUVC liUUl
Exterior
UU
J
W all
Spandrels
Below Floor
1
floor
1
A 0In u
to 9
Floor 9 to
U.J
1
106
1
/
n lU 1
.J
1
7
n u
u.ou
.7
14
1.57
278
1.36
1
.
A
''9
T)
1
1
31.160
0.32
0
836
0.35
0.70
1.9
1
5.219
0.86
0.14
9.9
5.3
Columns
239
0.45
0.50
0.4
0.4
1
1.26
Beams
499
0.23
0.93
0.2
0.2
1
1.07
279
0.41
0.60
1.1
0
0
1.03
200
0.76
0.16
2.5
2
4
1.18
12
0.35
0.47
0
0
0
0.64
Above
floor
06
1
Core Columns
Hat Truss System
Braces
Exterior
WaW
Bracing
Below
floor
1
Above
floor
1
The Refined NIST Estimate Case
5.3.3
The
WTC
(see also
ASCE
06
1
global model
The calculated (5
RWDl
and
total drift
10.6 in.) in the
equivalent to about
E-W
was analyzed using the refined NIST estimate 1-2).
7-02 Standard, and
obtained from
ft
NCSTAR
NIST
w ind loads developed by NIST based on
GPP
case, as described in Chapter
critical
of WTC
1
induced by the refined
direction and 83.9
H/244 and H'205
NIST wind
combination producing the
NIST NCSTAR
1-2A.
assessment of information
reports and state-of-the-art considerations in
in the
in.
(6
E-W
ft
1
and
NIST
1.9 in.) in the
N-S
loads.
The
maximum
N-S
WTC Investigation
was approximately 70.6
direction.
These
E-W
5-8 presents
by the story height
and N-S
in.
drifts are
directions, respectively. Figure
plots are presented for the
cumulative
wind engineering.
estimate case
the deflected shape (cumulative drift) and the inter-story drifts normalized
under the refined
4
This loading case included dead loads, live loads in accordance with the
for
WTC
1
directions for the load
drift.
107
Chapter 5
Interstory Drif/Story Height for
interstory Drif/Story IHeight for
NISTWind Load (E-W)
0.00
0.20
0.40
NiSTWind Load
0.60
0.80
0.00
Interstory Drift/Story Height [%]
0.40
0.60
0.80
Interstory Drift/Story Height [%]
(b)
(a)
Figure 5-8. Drift diagrams of (a)
108
0.20
(N-S)
WTC
1
due to refined NIST estimate wind loads, (b) 1R8PD.
1R14PD and
NISTNCSTAR
1-2A,
WTC
Investigation
1
Baseline Performance Analysis of the
WTC
DCR statistics
for
summarized
Table 5—4. The
in
original design
Global Models
NIST estimate case are truss members estimated from
global systems components under the refined
1
DCRs
for the core
columns and hat
the
and the state-of-the-practice cases (Tables 5-1 and 5-3, respectively) are generally close
to those estimated
columns and hat
from the refined NIST estimate case (Table 5^). This
truss
members do not
significantly contribute to
exterior walls, including columns, spandrels,
are larger than those estimated
from the
for the exterior walls, the ratio of the
mean DCRs from 1
.84 to 1.11.
mean DCRs from
estimate case to the
due
is
wind load
to the fact that core
resistance.
The
DCRs
for the
and bracings calculated from the refined NIST estimate case
original design
from the original design case ranged from
NIST
WTC
and the state-of-the-practice cases. For example, the refined
The
ratio
NIST
estimate case to the
of the mean
DCRs
mean DCRs
from the refined
the lower estimate, state-of-the-practice case ranged from
1.65 to 1.14.
Table 5-4. Statistics of demand/capacity ratios (DCRs) for estimate case.
Member Type
Number
Mean
rf^ \7 co.v.
of
f^alnilafpfl
of
.Members
DCR
DCR
628
1.04
0.24
1,122
1.11
0.27
31,086
1.10
578
0.81
420 610
WTC
1
under the refined NIST
Percentage
Percentage
of
of
Number
of
^ „ „ ^^^^ Components Components Components
with
DCR
with
DCR
with
DCR
Maximum Calculated
DCR
> 1.05
> 1.05
52.5
47.3
297
1.95
69.0
63.6
714
1.69
0.14
72.1
59.7
18572
2.05
0.28
19.7
14.2
82
1.57
0.81
0.46
22.
21.4
90
2.05
0.61
0.45
8.0
4.3
26
2.03
31,160
0.52
0.29
0.5
0.3
109
1.32
836
0.41
0.68
2.4
1.9
16
1.82
5.219
0.84
0.15
8.9
5.2
270
1.40
Columns
239
0.53
0.49
3.8
0.8
2
1.26
Beams
499
0.26
0.93
1.8
1.4
7
1.30
Braces
279
0.49
0.55
6.1
2.5
7
1.10
200
1.11
0.18
73.0
62.0
124
1.76
12
0.52
0.42
0
0
0
0.90
CAICI
lUI
>
1.0
TT ^11
Columns Below Floor
floor 1
1
to 9
Floor 9 to 106
Above
floor 106
Exterior Wall
Spandrels
Below Floor
floor 1
1
to 9
Floor 9 to 106
Above
floor
1
06
Core Columns Hat Truss System
Exterior Wall
Bracing
Below
floor
Above
floor 106
5.4
1
BASELINE PERFORMANCE ANALYSIS OF
The baseline performance computer with
a
CPU
WTC
2
model of WTC 2 was perfonned on a Pentium 4 personal and 1 .0 GB of RAM. The duration of the analysis was about
analysis of the global
speed of 3.06
GHz
15 h. The following summarizes the results under the three loading cases.
NISTNCSTAR
1-2A,
WTC
Investigation
109
Chapter 5
The
WTC
Original
5.4.1
Design Load Case wind loads used
analysis reported in this section used the gravity and
in the original
design of the
towers, as explained in Chapter 4.
The
of the analysis indicated that for the dead and live loads used
results
core coluinns and the exterior walls of
WTC 2
The calculated 51.2
in.
(4
total drift
3.2 in.) in the
ft
E-W
building drift under wind loads data
is
direction and 65.3
was not
available to which the total drifts
(cumulative
drift)
and the inter-story
E-W
cumulative
respectively,
DCRs were
under the original
DCRs
for accuracy
were found
WTC design wind loads was approximately 5.3 in.) in the
to
N-S
and accordingly, no Fig.
and N-S directions
1,
historical project-specific
WTC 2 under the original
for the cases
producing the
E-W and N-S
directions,
north).
SAP2000 computer program. As was done and
drifts are
WTC
Similar to
5-9 presents the deflected shape
normalized by the stoiy height for
E-W
These
direction.
directions, respectively.
(wind azimuth 180 and 90 degrees for the
calculated using the
the calculations
N-S
may be compared.
drifts
where azimuth 0 indicates tower
were spot checked
of the
drift
in. (5 ft
and
a design criterion
design loads. The plots are presented for the
maximum
level.
of WTC 2 induced by the original
equivalent to about H/335 and H/263 in the
WTC design, the
earned approximately 53 percent and 47 percent,
basement (B6)
respectively, of the total gravity load at the
in the original
to verify that the
be acceptable. The
for
WTC
1,
the calculations
conect design information was being applied, and
DCR statistics for WTC 2
global systems components
WTC design loading are summarized in Table 5-5. Figure 5-10 shows the distribution WTC 2 under the original design loads. Close-up views are
for the four exterior walls of
provided for the exterior walls below floor 9
in Fig.
5-1
1
.
DCRs
for the core
columns are
illustrated in
Fig. 5-12.
The types of members
in the exterior wall that
had
DCRs
larger than
1
were calculated for a combination
of axial load and bending under a combination of gravity and wind loads and were generally found
in
three types of location:
1
.
Columns
at the
comers;
2.
Where
the hat tmss connects to the exterior wall; and
3.
Below
floor 9.
The members
in these locations
some of the highest
would be expected
calculated forces under
wind
to experience large forces.
loads.
The
The comer columns had
hat tmss-to-exterior wall connections
interconnected two major structural systems with large concentrated load transfers. The exterior wall
below floor 9 was a highly variable and Given the extraordinary
difficulty
articulated structural system that
of replicating with precision a
set
had large calculated
performed almost 40 years ago with relatively rudimentary computational
were observed
in the analysis at locations
of highest forces and
forces.
of engineering calculations tools,
at locations
DCRs
in
excess of one
where there was
significant
complexity of system behavior.
110
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of
WTC
Global Models
Interstory Drift/Story Height for
Interstory Drift/Story Height for Original
ttie
Wind Load (E-W)
Original
Wind Load
(N-S)
1600
1600
1400
—
1200
^
1000
800 600 o)
400 200
0.00
0.20
0.40
0.60
0.00
Interstory Drift/Story Height [%]
(b)
(a)
WTC
Investigation
WTC
due to original B180N+E- and (b) B90N-E+.
Figure 5-9. Drift diagrams of
1-2A.
0.60
Interstory Drift/Story Height [%]
(a)
NISTNCSTAR
0.40
0.20
2
WTC wind
loads,
111
71
Chapter 5
Table 5-5. Statistics of demand/capacity ratios (OCRs) for
WTC
2 under original design
load case.
iTiiiriiiuci
1 >
ijc
Number
Mean
of
Calculated
\'1 pin
hp t*c
Percentage
Percentage
of
of
Number
of
Components Components Components c.o.v.
DCR
with
ncR
DCR
with
>
DCR
with
fi^
1
Maximum Calculated 1/V
IX
Exterior Wall V UIUII1II3
Rplnw Flnor r luui
flnnr
1
1
Flnnr Q tn
Above
1
" tn lu Q 1
(\f\
floor 106
^ n
T
1
0. /4
0,22
1,122
0.73
0,25
2.3
0.7
8
31,086
0.81
0,12
4.1
2.9
91
Q Q y.y
J
5
J
/ /
/
o
U.
/
4.2
J
1
1
1
C"?
.53
1.19 1.37 /
1
.J J
Exterior Wall
Spandrels
Below
floor
Floor
to 9
408
0,47
0.47
594
0.38
0.47
31.160
0.34
0.30
0
836
0.34
0.71
J. J4 J
U.OO
238
0.50
0.58
4.6
Beams
504
0.24
0.80
Braces
283
0.44
0.57
227
0,70
12
0.31
1
1
Floor 9 to 106
Above
floor 106
Core Columns
1.7
7
1.37
.3
8
1
0
0
0.86
1.7
1.4
12
1.59
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1 1
.3
1
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.47
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Hat Truss System
Columns
o
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0.2
0
0
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3.5
1.1
3
1,09
0.16
1,3
0
0
1,04
0.41
0
0
0
0,52
1
,48
Exterior Wall
Bracing
Below
floor
Above
floor 106
112
1
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of the
WTC
Global Models
i
j
i!
(b)
fa)
0 .50
0 .00
0 .75
1
.00
1
Figure 5-10. Demand/capacity ratios for WTC 2 under original design loads, elevation and (b) north elevation.
NISTNCSTAR
1-2A.
WTC
Investigation
(a)
west
113
1
Chapter 5
0 .00
Figure 5-10.
114
0 .50
(c)
0 .75
east elevation and
1
(d)
.00
1
.08
south elevation (continued).
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of the
0 .00
0 .50
0 .75
1
.00
1
WTC
Global Models
.08
(a)
Figure 5-11. Demand/capacity ratios for WTC 2 under original design load case, (a) west elevation below floor 9.
NISTNCSTAR
1-2A,
WTC
Investigation
115
Chapter 5
i.
.
j .
j
1
M
i
}
j
i
!
0 .00
i
;
J
;
I
0 .50
0 .75
1
.00
1
.08
(b)
Figure 5-11. Demand/capacity ratios for WTC 2 under original design load case, (b) north elevation below floor 9 (continued).
116
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of the
0 .00
0 ,50
0 .75
1
.00
1
WTC
Global Models
.08
(c)
Figure 5-11. Demand/capacity ratios for WTC 2 under original design load case, (c) east elevation below floor 9 (continued).
NISTNCSTAR
1-2A,
WTC
Investigation
117
Chapter 5
i
I
it ..t-J....|...t.,.|..
l-.i-
mini
0 .00
0 .50
0 .75
1
.00
1
.ON
(d)
Figure 5-11. Demand/capacity ratios for WTC 2 under original design load case, (d) south elevation below floor 9 (continued).
118
NISTNCSTAR
1-2A.
WTC Investigation
——
— —-
,
WTC
Baseline Performance Analysis of the
TOWER
B.
500's
501 I
502
I
503
I
TOWER
DCR of CORE COLUMN COLUMN NUMBER 504
I
505
I
506
U
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603
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NISTNCSTAR
1-2A,
WTC
0,76
0.98
094
098
0.94
088 0.99
0.84
0.99
(b)
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0 .00
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Investigation
(a)
500
1
WTC
line
.00
2 core
and
(b)
1
.08
columns under
600
original design
line.
119
— — —
—— ^
—— !
1
— —
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Chapter 5
TOWER B. DCR of CORE COLUMN 700's COLUMN NUMBER
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120
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and
1
WIG (d)
,00
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800
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columns under
original design
line (continued).
NISTNCSTAR
1-2A,
WTC Investigation
—
—
^ ^ —^ ^
-"
— —
^ a «
,
^— — ——
——
—
,
WTC
Baseline Performance Analysis of the
TOWER
B.
9O0's
901
I
902
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903
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0 ,50
loads,
WTC
0.88
064
1.07
0.64
0.87
1
00
1
01
(f)
Figure 5-12. Demand/capacity ratios for
1-2A.
0 88
0,79 07
1
(e)
NISTNCSTAR
Oh
n U7
1 rz
.» ...
^
1^ FL
ti ii
^— 1
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;
o.eb
1 re.
OcFl
02 Fl 01 FL Bl FL
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— — — —
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—
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T-
27Tl
-~a7-
35 FL
(e)
Investigation
900
line
and
1
WTC (f)
.00
1
.08
2 core columns under original des 1000 line (continued).
Chapter 5
The core columns
that
have
generally located on the 600
much of their height. The
DCRs>l were column
line
calculated for axial stresses due to gravity loads and were
between floors 80 and 106 and
gravity loads on these
columns were affected
at
columns 901 and 908
significantly
for
by assumptions
about tributary areas, unit construction dead loads and superimposed dead loads, and the sequence of
constmction of the hat
truss.
The high degree of stress
calculated
at
these core columns
is
likely
associated with differences in these assumptions between the original and current computations.
Figure 5-13 presents the distribution of the nonnal stresses due to axial loads (axial column load divided
by columns cross sectional area)
in the
loads are not included in these plots). the tower: B6, 39,
columns of the four exterior walls due
The
to
wind loads only
(gravity
axial stresses are presented at three levels along the height
and 73. The plots show both the
tensile
and compressive
of
on the columns
stresses
induced by wind loading, where shear lag effects can be observed. For corner columns 101, 159, 301,
and 359 This
is
at floor
likely
73, Fig. 5-1 3(c) indicates that their stresses are smaller than their neighboring columns.
due
to the influence
of the special comer framing
at that floor, i.e. the
discontinuous
columns and chamfered plan layout of the exterior wall framing.
The
results
of the baseline performance analysis indicated that tension forces were developed in the
exterior walls of
WTC 2 under the original WTC design dead and wind loads.
the combination of dead
and wind loads for
all
The tension
faces are illustrated in Fig. 5-14.
The
forces from
figure indicates that
forces are largest at the base of the building and at the comers.
These axial
The
tensile
exterior wall
tension forces for
WTC
2 are
column loads were transfeiTed from one panel
column all
splice capacities
four faces of
summarized
in
WTC 2.
to another through the
were calculated from the
The
original details
column
splices.
and compared
to the
DCR ratios for the exterior wall splice connections for
Table 5-6.
For the tower resistance to shear sliding and overtuming due to wind, the dead loads that acted on the perimeter walls of the tower provided resistance to shear sliding and overturning
at the
foundation level.
Considering the resistance to shear sliding under wind load, the factor of safety was calculated to be
approximately 10. Considering resistance to overturning due to wind load, the factors of safety were calculated to be approximately 1.9 and 2.7 for overturning about a north-south axis and for an east-west axis, respectively.
122
NISTNCSTAR
1-2A,
WTC Investigation
WTC
Baseline Performance Analysis of the
Tower
B:
West
(Gravity
to East Wind (BON+E+) Loads not included)
Tower
B:
West
(Gravity
20
20
15
15
Global Models
to East Wind (BON+E+) Loads not included)
10 tn
i.
5
5
201 0
.159
259 -5
5
-10
-10
-15
-15
-20
-20
100 Face (West Columns)
-
FL B6
200 Face (North Columns)
-
FL B6
Figure 5-13. Shear lag diagrams of WTC 2 due to original WTC wind loads at (a) floor B6, (b) floor 39, and (c) floor 73.
NISTNCSTAR
1-2A.
WTC Investigation
]23
Chapter 5
Tower
B:
to East Wind (BON+E+) Loads not included)
B:
West
(Gravity
to East Wind (BON+E+) Loads not included)
201
159
101
100 Face (West
Tower
Tower
West
(Gravity
B:
Columns)
-
200 Face (North Columns)
FL 39
Tower
West
(Gravity
to East Wind (BON+E+) Loads not included)
B:
-
FL 39
West
(Gravity
to East Wind {BON+E+) Loads not included)
20 15 10
5
359
301
0 -5
-10
-15 -20
300 Face (East Columns)
-
400 Face (South Columns)
FL 39
-
FL 39
(b)
Figure 5-13. Shear lag diagrams of WTC 2 due to original WTC wind loads at (a) floor B6, (b) floor 39, and (c) floor 73 (continued).
124
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of the
Tower
B:
Tower
West
(Gravity
to East Wind (BON+E+) Loads not included)
B:
WTC Global Models
West
(Gravity
to East Wind (BON+E+) Loads not included)
20 15 10 (0
JC
5
259
la (fl
o
0
159 *5 Axi
101
201
-5
-10 -15 -20
100 Face (West Columns)
Tower
B:
-
FL 73
200 Face (North Columns)
West
(Gravity
Tower
to East Wind (BON+E+) Loads not included)
FL 73
West
(Gravity
20
to East Wind (BON+E+) Loads not included)
20
15 10
B:
-
15
„
^-
10
'«
i
5
i,
301
359
_
-5
5
w ^
0
?
-5
.2
<
-10
-10
-15
-15
-20
-20
300 Face (East Columns)
•
400 Face (South Columns)
FL 73
-
FL 73
(C)
Figure 5-13. Shear lag diagrams of WTC 2 due to original WTC wind loads at (a) floor B6, (b) floor 39, and (c) floor 73 (continued).
NISTNCSTAR
1-2A,
WTC
Investigation
125
Chapter 5
100-109
110-119
120-129
130-139
140-149
1
50-159
200-209
210-219
220-229
230-239
240-249
250-259
m (a)
(b)
0
100
500
Figure 5-14. Tension force distribution (kip) original design
126
dead and wind loads,
(a)
lood
the exterior wall columns of WTC 2 under 100 face (west) and (b) 200 face (north). in
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of the
300-305
310-319
I
320-329
330-339
340-349
350-359
400-419
410-419
0
Figure 5-14.
1-2A.
WTC
430-439
Global Models
440-449
450-459
(d)
(c)
NISTNCSTAR
420429
WTC
100
(c)
300 face (east) and
Investigation
500 (d)
1000
400 face (south) (continued).
127
Chapter 5
Maximum
Table 5-6.
calculated demand/capacity ratios (OCRs) for exterior wall iLAicrior
iLAicrior
Column
Wall Face
Below 1
no
Fcirp
F1r\r\r r joor
(West)
Below Finnr rioor
Above Below
mo Fare
Flnnr
Above Below 400 Face
Floor
Above
State-of-the-Practice global model
according to the the
NYCBC
NYCBC
0.83
floor
0.10 u.
1
tn lo Q 7
0.99
floor 42
1
tn
0.13
A
floor
Q
floor to
floor
"7
C
1
0 3^ 0.96
floor 42
1
/u
U.J)D
0.16
0.60
1
9
0.33
0.84
Floor 10 to 41
(South)
WTC 2
U.04
1
floor 42
1 J
DCR
tn 10 Q 7
Floor 10 to 41
(East)
42
0.21
Case
was analyzed using
described in Chapter 4 (see also
1 1
Floor 10 to 41
(Norths
The
Calculated
Floor 10 to 41
Above
5.4.2
i>i
>> dii
Splice
floor
column
NIST
the lower estimate, state-of-the-practice loading case, as
NCSTAR
1-2).
2001, and wind loads from
This loading case included dead loads, live loads
RWDl
wind tunnel study, scaled
in
accordance with
2001 wind speed.
The calculated
total drift
of
WTC 2
induced by the lower estimate, state-of-the-practice case was
E-W direction and 55.9 in. (4 ft 8.1 in.) in the N-S direction. These drifts are equivalent to about H/287 and H/307 in the E-W and N-S directions, respectively. approximately 59.7
in.
(4
ft
1
1.7 in.) in the
Figure 5-15 presents the deflected shape (cumulative story height for
the
E-W
and
N-S
DCR statistics
drift)
and the inter-story
WTC 2 under the lower estimate, state-of-the-practice case.
for
directions for the load combinations producing the
drifts
The
maximum
nonnalized by the
plots are presented for
cumulative
drift.
WTC 2 global systems components under the lower estimate, state-of-the-practice
loading case are summarized in Table 5-7.
A comparison
of the mean values of the
DCRs
estimated
from the original design case (Table 5-5) with those from the state-of-the-practice case (Table 5-7) indicated that the results are very similar. Also the distribution of the
with
DCRs
DCRs
and the locations of members
greater than 1.0 were very similar between the original design case and the state-of-the-
practice case.
128
NIST NCSTAR
1-2A.
WTC Investigation
Baseline Performance Analysis of the
WTC
Global Models
Figure 5-15. Drift diagrams of WTC 2 due to the lower estimate, state-of-the-practice case, (a) 2R4PDN and (b) 2R11PDN.
NISTNCSTAR
1-2A.
WTC
Investigation
129
Chapter 5
Table 5-7. Statistics of demand/capacity ratios (DCRs) for
WTC
2
under the lower
estimate, state-of-the practice case.
Mean Number i> li. Ill
Ui.
Percentage
of
of
Number
of
Components Components Components
of Calculated I
Percentage
c.o.v.
DCR
with
with
DCR
with
DCR
nr"R
3
Maximum Calculated 17V
I\
Exterior Wall
Columns Dclow Flonr
iioor
F1/^nr loor Q 10 r y tn
Above
1
1
577
0.70
0.20
1,122
0.72
0.26
31,086
0.77
0.13
1.8
U.
U.jU
C 7/ o.
1
tn Q
1
HA UD
floor 106
J
/
o
/
1
.30
1.4
8
1.1
12
1.16
0.6
189
1.21
3.1
J
1
1
Exterior Wall
Spandrels
Below
floor
408
0.45
0.47
1
.7
0.7
3
594
0.37
0.44
0.7
0.7
4
1.19
31,160
0.31
0.27
0
0
0
0.73
836
0.33
0.70
1.7
1.4
12
1.47
U.86
0.
6.6
345
1
.36
238
0.48
0.57
3.8
2.5
6
1
.35
Beams
504
0.23
0.82
0.2
0
0
1.01
Braces
283
0.40
0.57
0.7
0
0
1.04
227
0.69
0.17
0.9
0.4
1
12
0.27
0.31
0
0
0
Floor
1
to 9
1
Floor 9 to 106
Above
floor
1
06
Core Columns
1
5
J
0.8
1.15
Hat Truss System Columns
Exterior Wall
Bracing
Below
floor
Above
floor 106
1
The Refined NIST Estimate Case
5.4.3
The
1.13
0.41
WTC 2 global model was analyzed using the refined NIST estimate case as described in Chapter 4
(see also
cun-ent
NIST
ASCE
NCSTAR
1-2).
This loading case included dead loads, live loads
NIST based on
7-02 Standard, and wind loads developed by
infonnation obtained from
RWDl
and
CPP
in
critical
accordance with the
assessment of
reports and state-of-the-art considerations in
wind
engineering.
The
calculated total drift of
(6
3.6 in.) in the
ft
E-W
WTC 2
induced by the refined
direction and 70.8
equivalent to about H/227 and H/242 in the
in. (5 ft
1 1
NIST
in.) in
E-W and N-S
the
estimate case was approximately 75.6
N-S
direction.
These
directions, respectively. Fig.
5-16 presents the
deflected shape (cumulative drift) and the inter-story drifts normalized by the story height for
under the refined
NIST wind
combinations producing the
130
loads.
The
plots are presented for the
maximum cumulative
E-W
and
N-S
in.
drifts are
WTC 2
directions for the load
drift.
NIST NCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of
Interstory Drift/Story Height for
NISTWind Load
1600
1400
-
[ft.]
1200 1000
>
(N-S)
-
1200 1000
-
m
800
-
> O
600
-
—I UD
to
> o
Global Models
1600
1400
m
WTC
Interstory Drift/Story Height for
NISTWind Load (E-W)
> »
ttie
800 600
-
-
TO
£
400
400
-
.2"
'S
'
X
200
X
-
0
200 0
0.00
0.20
0.40
0.60
0.80
0.00
Interstory Drift/Story Height [%]
(a)
WTC
Investigation
0.60
(b)
Figure 5-16. Drift diagrams of
1-2A.
0.40
Interstory Drift/Story Height [%]
(a)
NISTNCSTAR
0.20
WTC
2 due to refined NIST estimate wind loads,
2R4PD and
(b)
2R11PD.
131
Chapter 5
DCR statistics for WTC summarized
in
original design
2 global systems components under the refined
DCRs
Table 5-8. The
for the core
columns and hat
NIST estimate case are members estimated from
from the refined NIST estimate case (Table 5-8). This
truss
members do
not significantly contribute to
exterior walls, including columns, spandrels, are larger than those estimated
the
for the exterior wall, the ratio
of the mean
estimate case to the
between 1.65 and
is
wind load
due to the
fact that core
resistance.
The DCRs
for the
and bracings estimated from the refined NIST estimate case
from the original design and the state-of-the-practice cases. For example,
DCRs
from the original design case ranged between
NIST
truss
and the state-of-the-practice cases (Tables 5-5 and 5-7, respectively) are generally close
to those estimated
refined
columns and hat
1
from the refined NIST estimate case
.60
and
mean DCRs from
The
1.11.
ratio
of the mean
to the
DCRs
mean DCRs
from the
the lower estimate, state-of-the-practice case ranged
1.17.
•
Table 5-8. Statistics of demand/capacity ratios (DCRs) for NIST estimate case.
WTC
2 under the refined
Percentage
Percentage
of
of
Number
of
Maximum
Number
Mean
of
Calculated
Members
DCR
577
0.96
0.25
42
41.1
229
1.95
1,122
1.04
0.27
63.7
58.0
651
1.69
31,086
1.09
0.14
73.5
60.9
18,941
1.78
578
0.83
0.28
19.6
15.1
87
1.66
408
0.73
0.46
15.9
13.7
56
1.78
594
0.61
0.44
7.7
5.2
31
2.02
31,160
0.51
0.28
0.4
0.2
61
1.21
836
0.39
0.68
2.0
1.9
16
1.73
5,245
0.83
0.16
10.6
6.0
315
1,42
Columns
238
0.59
0.59
14.3
10.5
25
1.95
Beams
504
0.28
0.82
1.0
0.8
4
1.12
Braces
283
0.49
0.52
3.9
2.8
8
1.09
227
1.01
0.18
48.0
38.8
88
1.04
12
0.43
0.31
0
0
0
0.64
Member Type
Components Components Components c.o.v.
with
DCR
>
of
DCR 1.0
with
>
DCR
with
>
1.05
DCR
1.05
Calculated
DCR
Exterior Wall
Columns Below
floor
Floor
1
1
to 9
Floor 9 to 106
Above
floor 106
Exterior Wall
Spandrels
Below Floor
floor 1
1
to 9
Floor 9 to 106
Above
floor
1
06
Core Columns Hat Truss System
Exterior Wall
Bracing
Below
floor
1
Above
floor
1
5.5
06
SUMMARY WTC and WTC 2 global WTC design load case, (2) the lower-
This chapter presented the results of the baseline performance analysis for the
models under three gravity and wind loading cases:
(1) the original
estimate, state-of-the-practices case, and (3) the refined
132
NIST
1
estimate case. The baseline perforaiance
NISTNCSTAR
1-2A,
WTC
Investigation
WTC
Baseline Performance Analysis of the
results included total
and
inter-stoi^ drift,
and presence of tensile
effects
demand/capacity
ratios, exterior
Global Models
columns behavior (shear lag
of exterior wall splice connections, and the towers'
forces), behavior
resistance to shear sliding and overturning.
Under 56.6
the original
in.
WTC design loads, the cumulative drifts at the top of the WTC
(H 304) and 55.7
about 51.2
in.
drifts for
WTC
design case by about 0.5 percent and 22 percent for the
E-W
lower estimate, state-of-the-practice case for design case by about 16 percent, while the are consistent with the differences 4).
The
drifts
tower were about
(H/309) in the E-W and N-S direction, respectively. These drifts were E-W direction and 65.3 in. (Hy263) in the N-S direction for WTC 2. For the
in.
(H/SSS) in the
lower estimate, state-of-the-practice case, the
Chapter
1
1
were larger than those from the
and
N-S
directions, respectively.
original
For the
WTC 2, the E-W drift was larger than that from the original
N-S
drift
was smaller by about
15 percent. These differences
between the base shears for the two cases (see Tables 4-3 and 4-4 of
obtained from the refmed
NIST
estimate case were about 25 percent larger than
those from the state-of-the practice case.
The demand capaciry original
(DCR) were based on
ratios
AISC
estimated using the
Specifications (1989).
the allowable stress design procedure and
The
results indicated that
These were mainly observ ed
where the hat line
were
estimated from the
WTC design load case were, in general, close to those obtained for the lower estimate, state-of-
the practice case. For both cases, a small fraction of structural
600
DCRs
truss
in
connected
both towers
to the exterior walls,
between floors 80 and 106 and
The DCRs obtained
for the
and below floor
9;
and
(2) the core
core perimeter columns 901 and 908 for
state-of-the-practice load cases,
owing
The NIST estimated wind loads were higher than those used the-practice case
scaled to the
DCRs
larger than 1.0.
columns around the comers,
columns on the
much of their
to the following reasons:
in the
lower estimate, state-of-
by about 25 percent (about 10 percent difference between the
NYCBC 2001
wind speed and
RWDI
loads scaled to the
ASCE
RWDl
CPP •
The
NIST
It is
noted
estimated wind loads were about 20 percent smaller than those estimated by
(an upper estimate state-of-the practice case, see Chapter 4).
original
WTC design and the state-of-the-practice cases used NYCBC
combinations, which resuh the
loads
7-02 wind
speed, in addition to the 15 percent increase estimated by NIST, see Sec. 4.4.3). that the
height.
refmed NIST estimate case were higher than those from the original
WTC design and the lower estimate, •
at
components had
at (1) the exterior walls: at the
refmed NIST
in
lower
DCRs
than the
ASCE
load
7-02 load combinations used for
case.
WTC design dead and wind loads, tension forces were developed in the exterior walls of WTC and WTC 2. The forces were largest at the base of the building and at the Under
a combination of the original 1
comers. These tensile column loads were transferred from one panel splices.
The
were shown
DCR ratios for the to
be less than
to
another through the coluinn
exterior wall splice connections under these tensile forces for both towers
1.0.
For the towers' resistance to shear sliding and overturning due to wind, the dead loads perimeter walls of the towers provided resistance to shear sliding and overtuming
that acted
at the
on the
foundation level.
Considering the resistance to shear sliding under wind load, the factor of safety was calculated to be
NISTNCSTAR
1-2A.
WTC
Investigation
133
Chapter 5
between 10 and
1
1.5,
while the factor of safety against overturning ranged from 1.9 to 2.7 for both
towers.
REFERENCES
5.6
AISC
Specification 1989:
Buildings
ASCE
7-02:
American
- Allowable
Stress
Institute
Design and
of Steel Construction, Specification for Structural Steel Plastic
American Society of Civil Engineers,
Buildings and Other Structures, Reston,
NYCBC 2001
:
VA,
Design - 9* Edition, Chicago, IL, 1989.
ASCE
7 Standard
Minimum Design Loads
for
2002.
Building Code of the City of New York, 2001 Edition, Gould Pubhcations,
Binghamton, NY.
134
NISTNCSTAR
1-2A,
WTC
Investigation
Chapter 6
Baseline Performance Analysis of Typical Floor Models
INTRODUCTION
6.1
This chapter presents the resuhs of the baseline perfoiTnance analysis for the typical floor models
discussed in Chapter
[WTC]
Center
1.
For application
3.
These models included the typical truss-framed floor (floor 96 of World Trade
see Sec. 3.3) and the typical
to the floor
beam-framed
floor (floor 75 of
The self-weight of the
automatically generated in SAP2000.
and mechanical
electrical
drawings and on the original
Two
SDL
CDL
and
floor trusses, floor
is
plumbing systems
The
ducts, transformers, etc.)
SDL
(ASCE
defined as the self-weight of
beams, and concrete slabs were
(curtain wall, floor finishes, mechanical
were based on the
WTC architectural and structural
in
combination with the dead loads. The
New York
City Building
Code
(NYCBC
American Society of Civil Engineers (ASCE) 7-02
reductions were taken from the original
Institute
working
.
Live load
Standard, each for
(DCRs)
for structural
Design (ASD) procedure as specified
component demands by component
5.
The
in the
DCRs
were
capacities, taken at unfactored (working) loads
stresses, not at ultimate loads or yield stresses.
were determined
1
Stress
ratios
of Steel Construction (AISC) Specification (1989), see Chapter
calculated by dividing at
was taken
2001) are
live loads.
WTC Design Criteria and from the ASCE 7-02
components were estimated using the Allowable
and
first
respective live loads.
For the baseline performance analysis for the floor systems, demand/capacity
American
equipment and
WTC Design Criteria and the second from the American Society of Civil Engineers
essentially identical to the
its
is
WTC Design Criteria.
7-02) Standard. The live loads in the
use with
CDL
defined as the added dead load associated with architectural
independent sets of live loads were applied
from the original
3.4).
models, gravity loads were separated into three categories: construction dead
loads (CDL), superimposed dead loads (SDL), and live loads (LL). the structural system.
WTC 2, see Sec.
These
DCRs
for the structural
components
as follows:
The component demands were taken from
the results of the baseline performance analysis
using the reference floor models, making use of working loads.
2.
The component in the original
capacities
were determined based on the nominal
design documents and using the
AISC
steel strength as specified
Specification (1989).
This chapter reports on the results of the baseline performance analysis for the floor systems under gravity loading. Sections 6.2 and 6.3 present the loading and baseline performance analysis results for the truss-
framed floor and the beam-framed
NISTNCSTAR
1-2A,
WTC
floor, respectively.
Investigation
135
Chapter 6
TYPICAL TRUSS-FRAMED FLOOR
6.2
The
analysis of the typical truss-framed floor
WTC
1
was perfonned on
the computer
(see Sec. 3.3). This section describes the gravity loads applied to the
model of floor 96 of model along with
the results
of the baseline perforaiance analysis.
Gravity Loads
6.2.1
Areas Outside Core The
CDL
was
typically
was calculated based on 1
the
member's geometiy and material
properties.
WTC Design Criteria reduced
psf to 13.5 psf outside the core. Figure 6-1 shows the
1.5
live load for the floor design.
Table 6-1 provides a comparison between the
WTC Design Criteria, NYCBC 2001, and the ASCE 7-02
The SDL allowance
live loads
from the
Standard.
cm. i
tip
Op
'
1 n.KK.M'KVrV
Long Span Two-Way
Two-\\ ay VV/ Bridging
55 psf
55 psf
70 psf
T i
a.
I
D. 00
^ *-
B. 9C
6X)
CORE
s
» e O
CD
t •Wi'-Jl"
T Long Span
Two-Way
W/
55 psf
Two-Way
WTC TYPiCAL TOWER FLOOR PLAN
Bridging 55 psf 70 psf
V
T»0 wit
I
LONG
I
^AN
Cms)
Source: Reproduced with permission
Figure 6-1.
136
61© of
The
Port Authority of
New
York and
New
Jersey.
Enhanced by NIST.
Summary
of WTC-design criteria reduced live loads for floor design: design load of 100 psf - partition load is included in LL allowance.
NISTNCSTAR
1-2A,
WTC Investigation
.
Baseline Performance Analysis of Typical Floor Models
Summary
Table 6-1.
Design
Criteria
NVTC Design
NYC
1
T\vo-\\ ay
Zone
and (reduced
Long Span
Short Span
live
loads) for
Partition
Criteria
Floor
100 psf (55psf)
100 psf (70 psf)
100 psf (82.5 psf)
Code
Floor
50psf (25
psf)
50 psf (39 psf)
50 psf (47 psf)
6 psf
Floor
50 psf (25 psf)
50 psf (39 psf)
50 psf (47 psf)
6 psf
Building
ASCE
of typical truss-framed floor live loads areas outside of core.
7-02
Included
in
LL
Areas Inside Core Table 6-2 shows the
CDL
SDL
and
WTC Design Criteria. NYCBC
used inside the core area along with the
2001. and the
ASCE
live loads
from the
7-02 Standard. Loads are shown for the various
occupancies within the core area.
Table 6-2. Area inside core: loading floor 96, Loading
WTC
1
(psf)
Live Load for Floor Design
CDL
Area Tenant Space
Varies
Toilets Stair. Serv ice.
See Original
Closet
WTC Design
ASCE
SDL
Criteria
7-02
NYCBC 2001
33
100
50
50
49
40
40
40
29
100
100
100
41
75
80
80
29
75
75
75
Structural
Ele\ ator Lobby. Corridor
Drawings
Telephone. Electric Closet
Results of Baseline Analysis
6.2.2
The maximum mid-span original
deflections for each of the long-span, short-span, and
WTC Design Criteria and ASCE
Table 6-3.
Summary
of
T\\o-\\ ay
WTC Design Criteria NYCBC ASCE 7-02
1.44
1.14
For the components of the truss-framed
made
for the top
bridging trusses, and for the steel angles plus the
total
floors,
Zone
Long Span 1.79
in.
0.57
in.
in.
1.43
in.
0.44
in.
DCRs were
floor
calculated using the
SAP2000 program.
verticals of the
primary and
girders of the core. Since the top chords consisted of a pair of
concrete slab, the capacity of the concrete slab predominated and
was much
than the capacity of the top chord; therefore, a calculation of the stress in the slab seemed
would have required significant
under
Short Span
in.
and bottom chords, the diagonals and the
beams and
for the
loads are provided in Table 6-3.
maximum deflections for typical truss-framed DL + LL for areas outside of core.
Criteria
Calculations were
7-02
two-way zones
inter\'ention to
SAP's post-processor
to establish a
greater
irrelevant
and
proper design
calculation.
NISTNCSTAR
1-2A.
WTC
Investigation
137
Chapter 6
DCRs
The
were not calculated
for the following elements in this
computer model:
•
Strap elements
•
Damper elements
•
Frame connections assigned
•
Rigid links
•
Core columns, spandrels, and exterior columns
•
Deck support angles
•
Core perimeter channel members within close proximity
_
..
as "plate" elements and similar connectors
to supports
calculations were spot checked for accuracy and to verify that the correct design infoiTnation
applied. For
were found
was
most of the component calculations checked, the standard SAP2000-generated calculations
to
be acceptable; however, for some components, the computer model did not accurately
represent the actual construction, and for other components, the standard
eiToneous results. As a
result, for
estimating the
DCRs
SAP2000
calculations yielded
of the structural components, the following
adjustments to the design parameters were applied to the floor model to yield accurate results:
•
Length factors were assigned
to
tmss web members
to reflect the length
of the actual
constructed member. For example, in the model, to account for the participation of the
composite
slab, the distance
was taken
as
was applied
30
in.
to the
between the top and bottom chord of the primary
However,
this distance
primary truss diagonals
general, the length modifier
was to
actually 28
in.
floor trusses
Therefore, a length modifier
account for the actual length of the diagonal. In
was determined by measuring
the diagonal distance from the
underside of the top chord to the centerline of the bottom chord (see Fig. 6-2).
Theoretical unbraced length
=
30.1 inches,
measured from the face of top chord centerline of the bottom chord.
to the
The unbraced length is adjusted in the SAP2000 computer model by a factor of 30.1"/ 36.0" = 0.84
Figure 6-2. Unbraced length of truss diagonal. •
Significant out-of-plane bending
is
not expected in the
members of planar
trusses subjected to
concentric vertical loading. However, due to the complexity of the floor model, significant out-of-plane
(i.e.,
minor
axis)
bottom chord members. As a
bending moments were observed result, the
in
some
truss diagonals
and
allowable minor axis bending stress was
substantially increased to effectively eliminate these
bending moments from the
DCR
calculation.
138
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of Typical Floor Models
•
The allowable shear
stress for truss diagonals
substantially increased since for these
with additional bar reinforcement was
members, the SAP2000 program computed an
erroneous shear area.
For the area outside the core, the
DCRs
for all floor trusses
were
less than 1.14 for the original
WTC Design Criteria and less than 0.86 for the ASCE 7-02 loading and (by comparison) for the NYCBC WTC Design Criteria loading, the DCR was less than 1.00 for
2001 loading. Under the original
99.4 percent of the floor truss components. For the core area, the core were less than
1
.08
and more than 99 percent had a
DCR statistics for the truss-framed floor model are ASCE of the DCRs estimated from the ASCE
DCRs
for all floor
DCR of less than
summarized
in
Table
1
beams
inside the
.0.
6^ for the original design
loading case and in Table 6-5 for the
7-02 loading case. For the area outside the core, the average
ratio
7-02 loading to the
Criteria loading for all floor trusses
was about
DCRs from the
original
WTC Design
0.80.
Table 6-4. Statistics of demand/capacity ratios for floor 96 under original design load case. Percentage of Percentage of Number of Mean Components Components Components Maximum Calculated with DCR with DCR Number of Calculated C.O.V. of with DCR > 1.0 > 1.05 > 1.05 Member T}-pe Members DCR DCR DCR One-\\ ay Long
Span Zone
W eb members
1,792
0.44
0.61
3.7
1.28
23
1.14
Bottom chord
1.038
0.74
0.26
0
0
0
0.99
Web members
640
0.33
0.61
0
0
0
0.92
Bottom chord
288
0.37
0.32
0
0
0
0.55
Web members
3,086
0.30
0.80
0.3
0.26
8
1.06
Bottom chord
2,035
0.48
0.54
0
0
0
0.94
Web members
692
0.16
1.25
1
0
0
1.02
Bottom chord
327
0.12
1.33
0
0
0
0.95
1.361
0.33
0.67
0.9
0.3
4
1.07
686
0.36
0.58
1.0
0.6
4
1.08
members
One-W ay Short Span Zone
members Two-\\ ay Zone
members Bridging Trusses within One-\\ ay
Span Zones
members Core Beams
Beams
within core
Core perimeter channels
NISTNCSTAR
1-2A.
WTC
Investigation
139
Chapter 6
Table 6-5. Statistics of demand/capacity ratios (DCRs) for floor 96 under the loading case. Percentage
of
Components
Components
Mean
of
Calculated
C.O.V. of
Members
DCR
DCR
with DCR > 1.0
Web members
1,792
0.35
0.60
Bottom chord members
1.038
0.59
0.25
C+U
V./.0
.108
A in U.jU
7-02
Percentage
of
Number
Member Type
ASCE
with
DCR
Maximum Calculated
> 1.05
DCR
0
0
0.86
0
0
0.80
U.O J
u
U.J J
A u A u
U.07
n u
A u A u
A U. 78 / 0
One-Way Long Span Zone
wiie-vvd\ oiiuri opaii
Zone
Web members Bottom chord members
Two-Way Zone Web members
U.Jo
U.J J
A u A u
j.Uou
U. /y
Bottom chord members
A A1 U.4J
A /4 U. lA
Bridging Trusses within
One-Way Span Zones Web members
692
0.11
1.55
0
0
0.95
Bottom chord members
327
0.09
1.44
0
0
0.81
1.361
0.28
0.64
0.1
0.1
1.05
686
0.28
0.61
0
0
0.86
Core Beams
Beams
within core
Core perimeter chamiels
TYPICAL BEAM-FRAMED FLOOR
6.3
The
analysis of the typical
beam-framed
floor
was perfonned on
Sec. 3.4). This section describes the gravity loads applied to the
the
model of floor 75 of WTC 2
model along with
(see
the results of the
baseline performance analysis.
6.3.1
Gravity Loads
Comparing
the live loads from the original
Standard for
was
this floor,
it
was found
WTC design criteria, NYCBC 2001, and the ASC E7-02
that the three sets
75 psf
in
NYCBC 2001,
and 80 psf in
ASCE
7-02.
of loads were nearly
identical.
The only difference
WTC design criteria. As a resuh, only the original WTC design criteria
that the live load for the corridor within the core
was 100 psf in
the original
loads were applied to the computer model.
In the areas outside of the core, the superimposed dead load
was taken from
the original design criteria as
141 psf, including 75 psf for equipment loads, and the live load was 75 psf.
Table 6-6 shows the
CDL
and
SDL
used inside the core area along with the live loads from the
WTC Design Criteria, NYCBC 2001, and the ASCE 7-02
Standard. Loads are
shown
for the various
occupancies within the core area.
140
NISTNCSTAR
1-2A,
WTC Investigation
Baseline Performance Analysis of Typical Floor Models
Table 6-6. Beam-framed core area: loading floor 75, Loading
WTC
2.
(psf)
Live Load for Floor Design
CDL
Area
WTC-DC
SDL
ASCE
NYCBC
7-02
Return Air Plenum
66
75
75
75
Toilets
66
40
40
40
25
100
100
100
66
100
80
75
See Original
141
75
75
75
Structural
141
75
75
75
141
75
75
75
141
75
75
75
141
75
75
75
66
75
75
75
Stair, Serv ice.
Closet
Corridor
Varies
Motor Generator Room
Pump
Platform
2001
Drawings Electric Sub-Station
Mail
Room
Secondary Motor
Room
Unassigned Space
Results of Baseline Analysis
6.3.2
The maximum mid-span
WTC
deflections of the long-span and short-span zones under the original
Design Criteria loads were approximately 1.55
Using the SAP2000 computer program.
The
DCRs were
in.
and 0.70
in.,
respectively.
calculated for the components of the floor framing.
calculations were spot checked for accuracy and to verify that the correct design information
was
being applied. For most of the component calculations checked, the SAP2000 calculations were found
to
be acceptable.
DCRs
were not calculated for the bridging members and anchor straps as they were not a part of the
primary floor framing system. Also,
DCRs
were calculated
Except for the tw o
in the
30WF1
columns 501 and 508 (see for the original
load and
WTC
moment
1
6
DCRs were
global systems computer models.
beams running
Fig. 6-3), the
in the east-west direction
DCRs
for all
is
beam
beam-framed
and cantilevering from the core
floor
components were
design criteria loading. For the two beams cited above, the
interaction equation
were
less than 1.0,
These shear DCRs occurred in the section of the 30x 10 V2 WF^ and the centerline of the column.
This
not calculated for the spandrels and columns as their
while the shear
30WF1 16 beams
designation was used in original contract drawings to indicate a 30
DCRs
DCRs
less than 1.0
from the
were 1.125 and
axial
1.09.
located near the support between
in.
beam
deep wide flange beam with cover plates and
used here for consistency.
NISTNCSTAR
1-2A.
WTC
Investigation
141
Chapter 6
SKILLING ='TW;r
30x10
V2
-
HELLE
-
CHRISTIANSEN
-
ROBERTSON
WOJ?LD TRAOE CENTBRX
Slruclutal & Civil En
CONNBCT ION DETAIL SiSA
WF
Source: Drawing reproduced with permission
of
The
New
Port Authority of
York and
New
Jersey.
Enhanced by NIST.
Figure 6-3. Connection detail for Figure
6^ shows the distribution of DCRs for the floor framing.
two beams with in
beam 30WF116,
DCR greater than
1
.0.
DCR statistics
Table 6-7 for the original design loading case. The
shown
142
for the
The
floor 75 of
figure
shows
WTC
2.
the location of the
beam-framed floor model are summarized
statistics are
provided for
member groups
that are
in Fig. 6-5.
NISTNCSTAR
1-2A,
WTC
Investigation
Baseline Performance Analysis of Typical Floor Models
0 .00
0 .50
0 .75
Figure 6-4. Demand/capacity ratios for floor 75,
1
.00
WTC
1
2: original
WTC
loading.
Core
Figure 6-5. Beam-framed floor
NISTNCSTAR
1-2A.
WTC Investigation
member
.08
groups.
design
criteria
Chapter 6
Table 6-7. Statistics of demand/capacity ratios for floor 75 under the original design
Mean
of
Calculated
C.O.V. of
Calculated
Members
DCR
DCR
DCR
Long Span Beams
156
0.64
0.16
0.83
Short Span Beams
84
0.65
0.12
0.89
Core Beams
156
0.31
0.77
1.13
Corner Beams
32
0.49
0.35
0.90
Member Type
144
Maximum
Number
NISTNCSTAR
1-2A,
WTC Investigation
Chapter 7
Summary
This report presented the work conducted to estabhsh the baseline performance of the North and South
(WTC
World Trade Center Towers
1
and
WTC 2) under design gravity and wind loading conditions.
Baseline perfonnance results include basic information about the behavior of the towers, such as total and inter-story drift
under wind loads, floor deflections under gravity loads, demand/capacity
ratios for
primary structural components, exterior columns response (shear lag effects and presence of tensile forces under a combination of dead and wind loads), performance of connections, and the towers' resistance to shear sliding and overturning.
The follow ing
were undertaken
tasks
to allow
performing the baseline performance analyses of the
towers:
•
De\ elopment of structural databases of the primary components of the
The
towers.
electronic databases
structural design
were developed from
original
documents, including modifications made
WTC
1
and
WTC 2
computer printouts of the
after construction.
The
task
included the scanning and digitization of the original drawing books, a four-step quality control procedure, cross-section property calculations, and development of the relational
databases to link the generated database
files into a
format suitable for the development of the
structural models.
•
Development of reference
models
structural analysis
that captured the intended behavior
of
each of the two towers using the generated databases. These reference models were used to establish the baseline
detailed
models
perfonnance of the towers and also served as a reference for more
collapse initiation analysis.
-
Two
damage analysis and thermal-structural response and The main types of models developed were:
for aircraft impact
global models of the major structural components and systems for the towers, one
each for
WTC
and
1
WTC 2.
The models included
the towers, including exterior walls (coluinns exterior wall bracing in the
hat trusses,
and
rigid
basement
all
primary structural components in
and spandrel beams), core coluinns,
floors, core
bracing
at the
main lobby atrium
levels,
and flexible diaphragms representing the floor systems. To validate
the global models, the calculated natural frequencies of
WTC
1
were compared with
those measured on the tower, and good agreement between the calculated and measured values
-
was obtamed.
One model each of the
typical truss-framed floor (floor 96 of
framed floor (floor 75 of WTC 2) included
all
major
structural
in the
impact and
components
fire
WTC
1 )
and typical beam-
zone of the towers. The models
in the floor system, including
primary and
bridging trusses, beams, strap anchors and horizontal trusses, concrete slabs, and viscoelastic dampers.
compare
NISTNCSTAR
1-2A.
WTC
stresses
To
validate the floor models, several studies were carried out to
and deflections estimated Irom the model with hand calculations for
Investigation
145
5
Chapter 7
Good agreement was
representative composite sections. results
obtained between the model
and hand calculations.
Parametric studies were perfonned to evaluate the behavior of typical portions of the structure and to
develop simplified models for implementation into the global models. These parametric studies included
comer wall panels and
detailed and simphfied models of typical exterior and
•
Development of estimates of design gravity and wind loads on into the reference structural
models and use
wind load cases were considered
in the baseline
in this study, including
floor systems.
the towers for implementation
perfonnance analysis. Various
wind loads used
in the original
WTC design, wind loads based on two recent wind tunnel studies conducted in 2002 by Cermak Peterka
Rowan Williams Davies and
Peterson, Inc. (CPP) and
for insurance litigation concerning the towers,
from
critical
and wind load estimates
assessment of infonnation obtained from the
of-the-art considerations.
The following
(RWDI) developed by NIST
Iru in, Inc.
CPP and RWDI
three loading cases
reports and state-
were considered for
the baseline
performance analysis:
-
Original
WTC design
WTC design, -
in
conjunction with original
WTC design wind loads.
Loads included dead
State-of-the-practice case.
(NYCBC)
loads;
2001 live loads; and wind loads from the
accordance with
-
loads case. Loads included dead and live loads as in original
NYCBC
New York
RWDI
City Building
wind tunnel
Code
study, scaled in
2001 wind speed.
Refined NIST estimate case. Loads included dead loads; live loads from the American Society of Civil Engineers
The purpose of using
(ASCE
the original
7-02) Standard; and wind loads developed by NIST.
WTC design loads was to evaluate the performance of the
towers under original design loading conditions and ascertain whether those loads and the corresponding design were adequate given the knowledge available
The purpose of considering
was
to better
practices on
at the
the state-of-the-practice case and the refined
understand and assess the effects of successive changes
wind design practices
The study indicated established by the
.
NIST
estimate case
in standards, codes,
and
for tall buildings.
that the original
NYCBC prior to
and including 2001
time of the design.
WTC design wind load estimates exceeded those when the WTC towers were designed, and up to
1968,
The design values were
also higher than those required
by other
prescriptive building codes of the time.
The two orthogonal base shear and base moment components used were,
in general,
smaller than the CPP,
RWDI, and NIST
in the original
estimates.
unfavorable combined peaks from the original design were larger, or smaller by percent, than estimates based on the
CPP, RWDI, and NIST
design
However, the most
estimates. This
is
most
at
due
1
to the
conservative procedure used to combine the loads in the original design.
The estimated wind-induced loads on wind tunnel/climatological
146
the towers varied
studies conducted
by
by as much as 40 percent between the
CPP and RWDI
in
2002.
NISTNCSTAR
1-2A,
WTC
Investigation
Summary
The
WTC
1
and
WTC 2 global models were each analyzed under the three loading cases described above The following
to establish their baseline performance.
•
Under These
drifts
(H/304) and 55.7
in.
were about 51.2
direction for
summary of the
a
results:
WTC design loads, the cumulative drifts at the top of the WTC
the original
were about 56.6
is
WTC 2.
in.
in.
(H/335)
(H/309) in the
in the
E-W
and
N-S
E-W direction and 65.3
in.
(H/263)
For the lower estimate, state-of-the-practice case, the
were larger than those from the
original design case
by about
1
tower
direction, respectively.
0.5 percent
in the
drifts for
E-W
for
WTC 2. the E-W drift was larger than that from the original design case by about
N-S
percent, and the
NIST
refined
For the lower estimate, state-of-the-practice case
directions, respecti\ ely.
N-S
drift
1
and 22 percent for
the
and
N-S
WTC
was smaller by about 15
percent.
The
drifts
16
obtained from the
estimate case were about 25 percent larger than those from the state-of-the
practice case. These differences are consistent with the differences
among
the base shears for
the three loading cases.
•
The demand capacity
ratios
(DCRs) were based on
were estimated using the American ( 1
989).
The
Institute
DCRs
results indicated that
the allowable stress design procedure and
of Steel Construction (AISC) Specifications
estimated from the original
WTC design load case
were, in general, close to those obtained for the lower estimate, state-of-the practice case. For
DCRs
both cases, a small fraction of structural components had
mainly observ ed in both towers at (1) the exterior walls:
where the hat
truss
at
the
larger than 1.0.
connected to the exterior walls, and below floor
columns on the 600
line
between floors 80 and 106 and
at
These were
columns around the comers, 9;
and
(2) the core
core perimeter columns 901 and
908 for much of their height. •
The
refined National Institute of Standards and
were higher than those of the
original
WTC
Technology (NIST) case estimated
DCRs
design estimates and the lower state-of-the-
The NIST estimated wind loads were about 25
practice estimates for the following reasons:
percent higher than those used in the lower state-of-the-practice estimate, and mixed, some
WTC design wind loads.
higher and others lower than the original
It is
noted that the
estimated wind loads are about 20 percent smaller than those estimated by estimate, state-of-the practice case). In addition, the original
the-practice cases used
•
7-02 load combinations used for the refined
Under
a combination of the original in the exterior
column
NIST
case.
WTC design dead and wind loads, tension forces were WTC and WTC 2. The forces were largest at the base of
walls of
the building and at the comers. to another through the
WTC design and the state-of-
NYCBC load combinations, which result in lower DCRs than the
ASCE
developed
CPP
NIST
(an upper
1
These splices.
tensile
The
column loads were transferred from one panel
DCR ratios
for the exterior wall splice
connections under the effect of the tensile forces for the two towers were shown to be less than
•
1.0.
For the towers" resistance
to shear sliding
and overturning due
to
wind, the dead loads that
acted on the perimeter walls of the tower provided resistance to shear sliding and overturning at the
foundation level. Considering the resistance to shear sliding under wind load, the
factor of safety
was calculated
to
be between 10 and
1
1.5,
while the factor of safety against
overturning ranged from 1.9 to 2.7 for both towers.
NISTNCSTAR
1-2A.
WTC
Investigation
147
Chapter 7
Two
typical floor
models were each analyzed under gravity
loads.
The following
is
a sununaiy of the
results:
•
For the typical truss-framed floor (floor 96 of WTC
1),
the
DCRs
for all floor trusses
were
WTC Design Criteria loads and less than 0.86 for the Under the original WTC Design Criteria loading, the DCR was less than
less than 1.14 for the original
ASCE
7-02 loading.
1.00 for 99.4 percent of the floor truss components. For the area outside the core, the average ratio
of the
DCRs
under the
ASCE
7-02 loading to the
Criteria loading for all floor trusses
beams 1
.0.
1.79
inside the core
Under in.,
were
the original
0.57
in.,
was about
less than
1
.08,
0.80.
DCRs
under the original
For the core area, the
and more than 99 percent had a
WTC Design
DCRs
for all floor
DCR of less than
WTC Design Criteria loading, the maximum floor deflections were
and 1.44
in.
for the long-span
one-way
trusses, short-span
one-way
trusses,
and the two-way zone, respectively. •
For the typical beam-framed floor
(floor 75
of WTC 2) under the original
WTC Design
DCRs for all floor beams were less than 1.0 except for two core beams DCRs were 1.125 and 1.09. The maximum mid-span deflections of the long-
Criteria loading, the
where the shear
span and short-span zones under the original
and 0.70
148
in.,
WTC Design Criteria loads were about
1.55
in.
respectively.
NISTNCSTAR
1-2A,
WTC
Investigation
4 3 7
Appendix A
WTC Tower Structural Drawings Index for Large-Size Sheets
WTC Tower A Structural Steel Drawing Index Drawing
-
(18-May-73) Latest Revision
Title
Date
LA-1
Foundation loading plan
27-Apr-67
SA-1
Foundation plan
29-Aug-68
SA-2
Plan sub-level 5
SA-3
Framing plan sub-level 4
SA-4
Framing plan sub-level
3
EL. 264
07-Oct-68
SA-5
Framing plan sub-level 2
EL.274
17-Jul-68
SA-6
Framing plan sub-level
1
EL. 284
07-Oct-68
SA-7
Framing plan service
level
EL. 294
17-Jul-68
SA-8
Framing plan floor
SA-9
Framing plan intennediate
SA-10
Framing plan floor
SA-11
SA-12
EL.242
09-Apr-69 09-Apr-69
17-Jul-68
1
level
17-Jul-68
2
17-Jul-68
Framing plan floor
3
17-Jul-68
Framing plan
floor
4
17-Jul-68
SA-1
Framing plan
floor
5
17-Jul-68
SA-1
Framing plan
floor
6
17-Jul-68
SA-15
Framing plan
floor
7
17-Jul-68
SA-16
Framing plan floor
8
17-Jul-68
SA-1
Framing plan
floor
9
17-Jul-68
SA-18
Framing plan
floors
10-11
SA-19
Not used
SA-20
Framing plan
SA-21
Not used
SA-22
Not used
SA-23
Not used
SA-24
Not used
SA-25
Framing plan
floor
17
09-Oct-68
SA-26
Framing plan
floor
18
09-Oct-68
SA-27
Framing plan
floor
19
09-Oct-68
SA-28
Framing plan
floor
20
09-Oct-68
SA-29
Framing plan
floors
21-23
09-Oct-68
SA-30
Not used
NISTNCSTAR
1-2A,
WTC
Investigation
floors
12-16
09-Oct-68
09-Oct-68
149
Appendix A
r,
n Drawing
•
Drawing^ No. S A-^
1
*
Not
nlan floor llLUJl
^4
ijiuil iiVJiJl
75
laLLllH^
S A-^4
Pr^irnino" r\lan floor
SA-^'S
Fr^immcT r^lnn floor
SA-^fi
P'r^imincr nl^in floor*;
SA-^7
Mot
iicpH
o O/A
tsJot
iicpH
SA-41
Latest Revision
.L,
^
Title
Date
iiQpH
Pt'JiiTiino 1 1 uliilil^ IJldii 1
-r
11
yjy
wvi
vjo
\jy
I
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MrQiTnr^O" nl^in jridilillig Uiaii flr*r\r iiUUl
Vw/ci-oo
Pr^nTuno r^lnn floor
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f lallllll^
^A 44
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A-47
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jy
OQ-Ort-^iR
•sA
48
riallllll^ pidil llUUl
40
HQ Opt
40
n allllll^ piali
IIUUI
41
1 1
fl-Tan ftp w-Jdii-u"
rrdiiiing piaii iiuur
47
1
fl
riaiiiiny piaii iiuur
J
1
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Ih t*Q Tn n rr l q ti t1 /~\fw ri aiiiiiig pidii iiuur
44
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70
rrdiTiing pidn iiuur
4'^ ^
01
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70
rrdminii pidii iiour
4ft
1
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f\Q
ridiriiny pidn iiuor
47
1
0 Inn
ftQ
rrdiriiiiy pidii iiuur
48
77
77 Nn\/ 68
*s
'sA ST
QA
A
'^4
J
S7
ridiiiiiij^ pidii
iiuur
4Q
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150
1
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Ih
Fidllllll^ pidll ilUUIs
<\A
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1
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1
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77 Nnv 68 ZZ-INU v-uo 77 Nnv-68
S4 Jt-
^A
m n pi^Ai Ion Frdiiiiiig
Tl/^r^v iioul
JJ
77
SA-64
Framing plan
floor
56
22-NOV-68
SA-65
Framing plan
floor
57
22-NOV-68
SA-66
Framing plan
floor
58
22-NOV-68
SA-67
Framing plan
floor
59
22-NOV-68
SA-68
Framing plan
floor
60
22-NOV-68
SA-69
Framing plan
floor
61
22-NOV-68
Ih
i"Q
1
fT T\
NISTNCSTAR
1-2A,
Kln\/
68
WTC Investigation
1
WTC
Tower
Draw ing
Drawing No.
Structural
Drawings Index
for
Large-Size Sheets
Latest Revision Title
Date
SA-70
Framinc nlan
floor
62
22-N0V-68
SA-71
Framincr nlan floor
63
22-NOV-68
SA-72
Pramino' nlan flnnr
64
?2-Nov-68
Framincr nlan floor
65
2?-Nov-68
SA-74
±
Pramincr nlan Lf 1 U.11 floor 1 Wl 1 Ui 1 1111
66
12-Dec-69
Oil.
Pramincr IJlCLll floor llWVJl IClllllll^ nlan X
67
12-Dec-69
PramincT L71C111 floor llVJWl L iCllillll^ nlan
68
12-Dec-69
/
SA-77
1.
Framincr L/lClll floor llv/V^l 1 CLllllll^ nlan
69
22-NOV-68
Oil
1
Pramino" ilVJWl L'lU.ll floor 1 dXllllJ^ nlan
70
22-NOV-68
S A-7Q
l-ramino" nlan floor
71
22-Nov-68
SA-RO
Framincr nlan L/lCtll floor i.lX-'V/l ± 1 Cllllll
72
22-NOV-68
SA-Rl OAV O 1
1 icHiillliC LJiClil
Framing nlan floor liWv'l
73
22-NOV-68
FraiTiino nlan floor
74
22-NOV-68
/
o
1 im,
O/A O J
X
Framino L/XCXXX floor XX^J^-fX I dlXllll^ nlan
75
25-Sep-68
9 A-R4
FramincT nlan floor
76
25-Sep-68
SA-R'S
Framin0 LfluXl floor XCXXlXlll^ nlan 1
77
25-Sep-68
O/T ou
X
FramincT LJi clX 1 floor X 1 VJ W 1 iXlXlw. nlan
78
18-Aug-69
o/\ o
1
FramintT nlan IJlClll floor ilVJWl dXl 1111
79
Ol-Aug-69
Framino L/lclll floor XXWWX CXlllllll^ nlan
80
Ol-Aug-69
9A-RQ
Framino XlWVJl ICXllllllC^ nlan IJlull floor X
81
27-NOV-68
^ A-QO y\j o -'A
1
Framincy L/ldli floor XlWWl lullllXlc^ nlan
82
Ol-Aug-69
9 A-Q1
X
Framino iivjvji idixiiii^ nlan |jiaii floor
83
Ol-Aug-69
FramincT nlan floor Ilwwl
84 -86
Ol-Aug-69
Framino llVJVJl dilllll^ nlan jJldll floor
87
Ol-Aug-69
Framing ^Idll floor XiWWl UlllllJ^ nlan
88
Ol-Aug-69
Framino nlan floor ilUUl idllllll^ jjldil X
89
Ol-Aug-69
Framin
90,91
Ol-Aug-69
O/A.
XXlk-l^-fX
/
OO
X
CXI.
1
iL,
1
X Idllllllw, IJldll
Mnt
iiQprl
iispH Tslot LX^^vl i V,/ I '*
1
SA-96 •s
X
A-Q7
I
i
1
X
Not used
SA-99 s A-1 no
X IdllllllL^ IJldll
FramincT nlan floor llWVJl
92
Ol-Aug-69
SA-101
Framing plan floor
93
Ol-Aug-69
SA-107
X
Frammf XdiXXlli^
nlan XXWV^l L/ldXX floor
94
Ol-Aug-69
FramincJ L/ldXl floor xxvwx XdlllXXJ^ nlan
95
Ol-Aug-69
X
Framing plan
SA-105
Framing plan floor
SA-106
Not used
SA-107
Not used
SA-106
Not used
NISTNCSTAR
1-2A.
WTC
Investigation
Ol-Au0-69
floor
97-100
Ol-Aug-69
151
7
Appendix A
„
rv
.
.
Drawing^
Drawing^ No.
Latest Revision
rr'^.
^
Title
Date
h^pH
SA-107
TSJot
SA-108
Not nspd
SA-109
FraiTiinff
SA-110 SA-1
01
Ol-Aug-69
Framins? nlan floor
102
01-Au2-69
11
Framinp nlan floor
1
0^
01
-Aup-69
SA-1 12
FraiTiinp nl?in floor
104-
01
-Auo-69
SA-1
Fr^imincT nlan floor
1
OS
07-Tan-71 \j J aij 1
Framinp nlan X %A,XXXXX XJ XtmXXX floor l\J\J X
106 X \J \J
16-Jun-77 X V J \AXX ^
1
^
nlan floor
1
/
1
SA-1 14
1.
SA-111^ 1 'S Oil
Frjimino' 1 1 dllllll^
SA-1 16
Framing plan
SA-1
FmrnincT nlan floor
1
OR
70-Ort-70
SA-11 1 8 O
FramincT nlan floor
1
00
7n-Ort-70
SA-1 Q
FrarntnO" nlan floor
110
07-Inl-71 V/Z. J 111 1
SA-1 90
1Kr^minCT lailliJl^ r\lan Ulail
kjii.
1
1
1
M
1.
iL,,
nlan Uidil floor iivJUl
1
1
07 \J
1 1
/
fS-Tiin-7'' ^ U J Ull /
Void
107 upper
floor
r\ n U.ll.
1
/
07-Mav-71
rr\r\T iVJvJi
SA-Hl S A-H''
1Klr\or lU^Jl r\ani^l pailV^l Tirf*nrooTinfT 111 t-jUHJUilll^
Hold
r\lan UldlX
SA-1 7^ Floor nanf*l UdllCl
SA-1 74
1 iKjKJl
SA-1 7S
Fvt A\/all "111 VVdll to IVJ QtVi L^Al.
S A-1
7f>
r-vt 1_-Al.
SA-1
''7
SA-1
''8
S A-1 7Q
Wall
- i=»lp\/ation VVdll CltVCllUJll \x/all
fr\ Qt n IKJ >'lll
U"
07-Anr-67
/mO
wo ivia^-u
/
Pvt Wall in n iKj Qt ^Lll
_ (=*lf^\/Qti r\n cicvaiivjll
w/qII^MO Wall
07-Anr-67 ~/\ui ~u \J
Pvt
_ (^l/^\/iiti r\Y\ ClCVallxJll
n o A MM Wall t-UU
08-Mav-67
1_^AL. \x/q11 Wall
'^Q thrn L^y nil u
1
fn n "111 lU Qt ijyy
1
'
1
1 1
/
not iivji iwpH lioCli QtVi "ill
-
plp\/ation Wall ClCVaLlUll \x/all
100 i\J\J
J_/Al.
Pvt Wall aUUv'C cir\/~\\7i=» Qt ri 7L11
— f=»lf*\/otir\n /(lO Wall ^\J\J ClCVallUll \x/cill
0R-'spn-6Q
Pvt Wall aUUVC a r\r\\/f^ Qtn "111
_ f=»l/=»\/Qti r\r\ ClCVallUli
\ D\J\J
OO
n8-*spn-6Q WOoupU"
elevation wall 300
08-Sep-69
LZ-Al.
Wall
SA-143
Ext. wall
SA-1 44
144 thru 150 not used
SA-1 51
Grillage details
29-Aug-68
SA-1 52
Grillage details
15-NOV-67
SA-153
Not used
SA-154
Not used
SA-155
Not used
^-156 and above see
152
Jail
100
i\J\J
_ (=»1(=>\/Qti r\n \x/q1I ClCVaLUJlJ Wall ^\J\J
i_,Ai.
Fvt at^o\/f* LAI. \x/all Wall aUVJVC
^A-141
WU
cr*Vif*Hiilp dLllCLlUlC
above 9th
Tower A
-
& B Index
SA-401
T/V mast suppoit
el.
SA-402
T/V mast support
el.
& Imes 800, 900 &
SA-403
T/V mast support
el.
SA-404
T/V mast support
el.
lines 500,
600
700
12-Oct-70
.
1000
12-Oct-70
lines 001, 002,
003 &004
lO-Jul-70
lines 005, 006,
007 &008
lO-Jul-70
NISTNCSTAR
1-2A,
WTC
Investigation
11
WTC
Tower
Structural
WTC Tower A Structural Concrete Drawing Index
-
Drawings Index
for
Large-Size Sheets
(18-May-73)
SCA-l
Concrete plan sub level 5
SCA-2
Concrete plan sub level 4
el.
253
SCA-3
Concrete plan sub level
el.
264
-
core
17-Jan-69
SCA-4
Concrete plan sub level 3
el.
264
-
floor
23-Jan-69
SCA-5
Concrete plan sub level 2
el.
274
-
core
22-Jan-69
SCA-6
Concrete plan sub level 2
el.
274
-
floor
22-Jan-69
SCA-7
Concrete plan sub level
1
el.284
-
core
28-Jan-69
SCA-8
Concrete plan sub level
1
el.284
-
SCA-9
Concrete plan service level
el.
SCA-10
Concrete plan service level
el.
SCA-l
1
Concrete plan floor
1
el.310-core
lO-Dec-68
SCA-l 2
Concrete plan floor
1
el.310
19-Mar-69
SCA-l 3
Concrete plan intermediate level
SCA-14
Concrete plan floor 2
-
core
17-Jan-69
SCA-l 5
Concrete plan floor 2
-
floor
04-Oct-71
SCA-l 6
Concrete plan floor 3-6
SCA-l 7
Concrete plan floor 7
-
core
02-Dec-69
SCA-l 8
Concrete plan floor 7
-
floor
26-May-69
SCA-l 9
Concrete plan floor 8
-
core
SCA-20
Concrete plan floor 9
-
core
16-Mar-70
SCA-2
Concrete plan floor 9
-
floor
ll-Feb-69
SCA-22
Not used
SCA-23
Concrete plan floors 10-40
-
floor
19-Mar-70
SCA-24
Concrete plan floors 10-16
-
core
19-Mar-70
SCA-25
Not used
SCA-26
Not used
SCA-27
Not used
SCA-28
Not used
SCA-29
Not used
SCA-30
Concrete plan floor 17
-
core
15-Apr-70
SCA-3
Concrete plan floor
8
-
core
15-Apr-70
SCA-32
Concrete plan floor 19
-
core
15-Apr-70
SCA-33
Concrete plan floor 20
-
core
15-Apr-70
SCA-34
Concrete plan floors 21-23
1
el.
3
-
242
18-Dec-68 lO-Dec-68
floor
28-Jan-69
294
-
core
03-Feb-69
294
-
floor
03-Feb-69
-
floor
02-Dec-69
02-Dec-69
floor
;
-
core
16-Mar-70
15-Apr-70
SCA-35
Not used
SCA-36
Not used
SCA-37
Concrete plan floor 24
-
core
SCA-38
Concrete plan floor 25
-
core
15-Apr-70
core
15-Apr-70
SCA-39
NISTNCSTAR
1-2A,
Concrete plan floor 26
WTC
Investigation
-
12-Mar-69
153
Appendix A
SrA-40 SrA-41
r^nnPTPfp nlan floors '^R-^l
SrA-42
Not
ii^iPfl
SCA-43
Not
1I
SCA-44
Nlnt
h^pH
r^nnrrpfp nlan flnnr
onprpfp
1
Sr A-47
niJin Tlnot*
potp
-
-
pnrp
-
pnvp
i^r\Tiprptp r\lj^n flnAr
^4
-
povp
f^nnprptp
"^S -
pnrp
"nlrin
flnm'
("nnprptp V^VJlICldt r^lnn Ulu.ll TlnnrQ llVJVJlo XJi^t INVJl
iicpn UoCU
^lot
1 1
porp ^VJlt
"^fs-^CS -JvJ
1
S-Anr-70
1
S-Anr-7n
1
7-Mar-fi9
1
S-Anr-7n
1 1
'S.Anr-7n J AVpi \J 1
cpn
iiQpn \
sr A-S^ sr A-Sd
V-UIILICIC Uiail llOUI HI
V^Ui
sr A-ss
v^Ull^lClC Uiall llUUl
llUUl
1
C IV/
sr A-'^f^
1
sr A-^i?
V-UIICICIC
llUUl
LUIC
sr A-S8
V^UIICICIC UlalJ llUUl
llUUl
sr A-SQ
V_UljvlClC Ulall llVJUl
-
sr A-fio
V_UllLlwlC Ulall llVJUl
'-tH -
sr A-f>i sr A-^i''
Uld.ll
_ nnr*rf*t(=* t^lsin \„UlldClC Ulall Tlr\r\t* llUUl A.S *-r^ 1
r\U^ /w
0- Aiia-7n
lA-Opt-^^Q >
^O-FpH-TO ^wr^cu/w uy
CUIC
*i.*-r
llUUl
z.
pm"f^ ^UlC
lO-AiiP-VO
v
v-'c
1
I
cu
/
V
\„UlldClC nlcxn Ulall Tlr\rw llUUl
id.^
_ Tlr\r\T" llUUl
1
0- Aiia-7n
sr A-^s'^
r\nr'r(=*t/^ 'rtlciTi V_U11L1CIC Ulall Tlr\r\r llUOl
zl^^ HU
_ CVJl r /mt* C
1
O-AiicT-TO
sr A-64
f» nlciTi flr^OT'c A.f\ A/i 1 r^nr*T*(^f V„ CIC Ulall llUUl L> T-U^H /
1
0-AiiP-TO
sr A-^ss
V^UIICICIC Ulall llUUl
sr A-f>6 srA ^7
srA f^A /A UO sr A-68 sr A-^SQ sr A-7n sr A-71
1
r\r\r-r(^ff^
1
unci
'-r 1
-
AX ^HO
_ flr^rxt* llUVJl
CUIC
1
CUIC
\^U11L1CIC Ulall llUUl T-O
o
ocp
/
\J
1
O-AiiP-70
1
n-Aiia_7n \) W /t.U^
INUl UdCU V^UIICICIC piall ilUUlo
/H- -
llUUl
1
/
Alt n cwvcYf^i nlQn /'-+ -.\\r\cw /All ^^UIILICIC Ulall Tlr\rwc llUUlji AS^-TIA. *T-_7 llUUl V_
unci CIC Ulall llUUlo J/, JO
NI c\\
1 1
CUIC
c f*ri
sr A-77 sr A-7^ srA -74.
srA
154
7'>
TsJnt iiQpH 1
c\x\C'Tf^\e^ nlcin \^UlldClC Ulall Tlr\r\v llUUl
^zl
^^UllLlClC piall llUUl
JJ
(wp* CUl C
LUIC
SCA-76
Concrete plan floor 56
SCA-77
Concrete plan floors 57,58 -core
SCA-78
Not used
SCA-79
Concrete plan floor 59
-
-
lO-Aug-70
core
lO-Aug-70
03-NOV-69
core
NISTNCSTAR
1-2A,
WTC Investigation
WTC
IsL A-oU
Concrete plan floor 60
Tower
Structural
Drawings Index
for
Large-Size Sheets
core
lO-Aug-70
-
core
A"? XT ^.
Concrete plan floor 62
-
core
1
cr^ A cj oL. A-oj
Concrete plan floor 63
-
core
1
o<^A-o4
Concrete plan floor 64
-
core
A A nr\ lU-Aug-/U 1 A A ™ TA lU-Aug-/U
bLA-oj
Concrete plan floor 65
-
core
lO-Aug-70
C/^ A-00 A C^i
Concrete plan floor 66
-
core
01 -May -70
cr^ A bLA-0
cr^ A CI
Concrete plan floor 61
C/^ A JjL A-oz
o
-
03-NOV-69A ,
/Z
A A « TA lU-Aug-7(J . .
/
Concrete plan floor 67
-
core
15-May-70
bLA-oo
Concrete plan floor 68
-
core
15-May-70
OO tjLA-oy
Concrete plan floor 69
-
core
24-Aug-70
C/"' A
c/^ A
on
Concrete plan floors 70-73
bCA-yi
Not used
c/^ A no
Not used
C/^
A
n'3
Not used
c/"'
A
n/1
Concrete plan floor 74
!:5L,A-y4
c/^ A nc
-
-
z4-Aug-/U
core
core
z4-Aug- /U A1 A4«-., '7A Ul-May-/U
Concrete plan floor 75
-
core
ISLA-yo
Concrete plan floor 75
-
floor
c/^ A bCA-y /
m
Concrete plan floor 76
-
core
O^ A '7A zj-Aug/U C 0 A iirr TA ZJ-AUg/U
no
Concrete plan floor 77
-
core
O^ A ..^ TA zj-Aug/U
bLA-yy
c/"* A
c/^
n/i
A
Concrete plan floor 77
-
floor
C
A
1
AA
Concrete plan floor 78
-
core
ZJ-Aug- /U TA 0^ A /U zj-Aug-
C
A
1
A
Concrete plan floor 78
-
floor
O^ A 1.^^ "TA ZJ-AUg/U
C
A
1
AO
Concrete plan floor 79
-
core
Concrete plan floor 79
-
floor
Concrete plan floor 80
-
core
C/^ A
1
1
A/1
zj-AUg- /U 1 Till TA 1 3-JUl- /U 1
OC A iirr 7n ZJ-AUg/U 10 T..1 OA 13-Jul-70
SCA-105
Concrete plan floors 80,81,82
SCA-106
Concrete plan floor 81
-
core
25-Aug-70
bCA-lU/
Concrete plan floor 82
-
core
0^ Ann 7n zj-Aug/U
Concrete plan floor 106 A
-
floor
A-1 OQ A
A
1
C/^
A
111
1
1
1
T
A Inn 71 /z D-Jun-
A1 -oep- 7n ui /u
Alt Cnnrrptp nlan flnnrQ
04-Mav-70
1
8^-1 n4R-flnnr
Concrete plan tloors lU4-JUjA-lUj-lUDA-lloor
A1 C on
Concrete plan floor 83-core
0^ A iirr 7A /U Z j-AUg-
Concrete plan floors 84-86 A
1
r^^^^^*^ f\1 A Q1 A/I'D -fl/^/-v*oi-lU4r>-iloor Loncrete plan -H^z-x^r. tloors o3-lUiA1
C
1
floor
-
-
core
7n
Aiirr 70 /u Z J-AUg')'^
Not used
C/"* A
11/1
14
Concrete plan floor s7
-
core
7^ AufT 70 J-AUg/U Z
C
lie
Concrete plan floor 88
-
core
o^; Alio 70 J-/\Ug- /U Z
bCA-l A
SCA-116
Concrete plan floors 89,90,91
SCA-117
Not used
SCA-118
Not used
SCA-119
Concrete plan floor 92
NISTNCSTAR
1-2A,
WTC
Investigation
-
core
-
core
25-Aug-70
25-Aug-70
155
Appendix A
SrA-1 20 r^ntiPTPtp nl^in floor
SCA-l 22
Q4
(^nnrrpfp nl^in flnnr
1
pnrp
1 1
S-lVIar-71 iVldl /I
-
porp
1
5-Mar-71 IVldl i
1
5-Mar-71
1 »^
Concrete nlan floors 96-99A-96-1 008-core
SrA-1 24
\lnt
SrA-1 2'S
T\fnt iiQpH
-AiiP-70
1
-
/
lI
Not uqpH
SrA-1 27
r^nnprptp nlan flnnr 100
-
pnrp
SrA-128
r^ntiprptp nliin flnnr 101
-
pnrp
lS-Mar-71 1 ^ IVldl i
SrA-1 2Q
1
nnprpfp nlun flnnr
1
0'7 -
pnrp
1
SrA-HO
(^nnprpfp nlan flnnr
1
0^
-
pnrp
01i -npr-70 W l_-/tt u
srA-1 ^1 r\ J
r^nnprpfp nlan flnnr
1
04
-
cnrp
Ol-Mar-71 \J 1 IVl di i
l3V_
1
1
A-1
sr A-1 "^4 sr A-1 ^5
OS
-
pnrp
1
nTir*vf^tp nli^n Tlr\Mt"c
1
\
\f\
-
ccwp*
v_ c\x\cxf^\f* wit
nlan Uldil flnnr llUVJl 1107 U
\^ r\T\c^v(^\(^ Ulltl CIC
nlcin Uidll flr*r\T" ilUUl
unci
SCA-l 37
/
108 i V/O
'^-Mar-71
/
1
\
S-Ma^-7'> iVld\ ^
1 1
/
U
11/^/^1* — IHJVJI
pnrp t
- tVJl
. c^cwf^ tui C
/
J
Ul
/ z.
1
^>-Iiin-72
1
U
J Llil
/
^
S-Mav-7?
1
r^nnrrpfp nlan flnnr lOR
-
flnnr
01 IVldl \J 1 -Mar-71 1
i^nnprptp OQ v^uiidciv nlan Uidll flnnr iiuui 1wjy
-
pnrp cult
30-Tiil-71 JU J Ui 1
srA-i 3Q
\c\x\c^vf^\f^ v\\c\x\ \\c\r\Y \^UlltltLt Uidll liUUl
1
0 iW 1
- r*r\i*(^ tUl t
sr A-i4n
c\x\c*vf^\f^ nlc^Ti flr\Mi" v,Ulltitlt Uldil iiUUl
1
1
1 0 IW
- Tlr\/^t* llUUi
\
1
/
/
S-Mav-72
1
^O
J
Ul
/
1
SrA-141
\
QrA-14''
(^r\-nr*fptp \^uiivitit r\lanc uidiio cppnnHar\/ &ttuiiiJ.diy 1p\/p1c itvti?>
01 \J 1 -r)pr-70 i_/ct / u
^Ulldtlt
01i -Dpp-TO W i-/tt / w
c\x\c*vf^\p' v\\'AX\ V^Uiltivlt Uldil
pidll
r\pntnr\iicp UtilliiUUot
aUU
vc\c\\ iUUi —
crwp tUit
02-"NPn-71
oLdLlUllo, totalalUl pil5>
r^nr*t*f*1"f* nlcin f*l /r\A^ r\r\cf Uidll ti.Z^UT", \^UiltlClC UU?»L fp*r\c\r\Y\ ItllSlUll 1
l^UllLltlt pidli ptillllUU^t luUl
156
u
/
/
nnprpfp nlan flnnrc
\
lay
/
1
c\wcvf^\f^ T\lcin 0 / V^UIICICIC Ulail flr\r\f* ilUUl 1IW/
IV
\J i
V UlLl
lUWtl ItVtl
1 1
7-Tiil-71 Ul~ / 1 Z"J
SCA-147
Concrete plan penthouse roof upper level
SCA-l 48
Concrete plan raised floor 107
SCA-149
Concrete plan raised floor 107 -floor
1
SCA-150
Concrete plan raised floor 106
16-Jun-72
-
-
Ol-Oct-71
core
07-Jul-72
floor
NISTNCSTAR
1-2A,
6-Jun-72
WTC Investigation
WTC
Tower
Structural
WTC Tower B Structural Steel Drawing Index
-
Drawings Index
for
Large-Size Sheets
(18-May-73)
Tower B foundation loading plan
21-Mar-68
SB-1
Foundation plan
06-Sep-68
SB-2
Plan sub-level 5
SB-3
Framing plan sub-level 4
el.253
25-Sep-68
SB-4
Framing plan sub-level
el.
264
07-Oct-68
SB-5
Framing plan sub-level 2
el. 2 74
17-Jul-68
SB-6
Framing plan sub-level
el.
SB-7
Framing plan service
SB-8
Framing plan
SB-9
Framing plan intermediate
SB-Ll
floor
Framing plan floor
SB-10
el.242
3
1
level
25-Sep-68
284
07-Oct-68
294
28-May-69
el.
17-Jul-68
1
level
2
17-Jul-68 17-Jul-68
SB-11
Framing plan floor
3
SB-12
Framing plan floor
4
SB- 13
Framing plan
floor
5
17-Jul-68
SB- 14
Framing plan
floor
6
17-Jul-68
SB-15
Framing plan
floor
7
13-Mar-69
SB-16
Framing plan floor
8
17-Jul-68
SB-17
Framing plan
floor
9
17-Aug-68
SB- 18
Framing plan
floor
10
19-Mar-69
SB-19
Framing plan
floor
11
19-Mar-69
SB-20
Framing
plan floor
12
19-Mar-69
SB-21
Framing plan
floor
13
19-Mar-69
*SB-22
Framing plan
floors
14-16
09-Oct-68
SB-23
Not used
SB-24
Not used
17-Jul-68 .
17-Jul-68
*SB-25
Framing plan
floor
17
09-Oct-68
*SB-26
Framing plan
floor
18
09-Oct-68
*SB-27
Framing plan
floor
19
09-Oct-68
*SB-28
Framing plan floor
20
09-Oct-68
*SB-29
Framing plan
floors
21-23
09-Oct-68
SB-30
Not used
SB-31
Not used
SB-32
Framing plan
floor
24
09-Oct-68
*SB-33
Framing plan
floor
25
09-Oct-68
*SB-34
Framing plan
floor
26
09-Oct-68
*SB-35
Framing plan floor
27
09-Oct-68
*SB-36
Framing plan
28-31
09-Oct-68
SB-37
Not used
SB-38
Not used
NISTNCSTAR
1-2A,
WTC
Investigation
floors
157
Appendix A
Wt"o fvi n c\ ir\ '\ r\ t1 ridiiiing pidn iiuur
jZ
no
Cinf
AS
rrdrning pidn iiuor
DO
no
O/^f
AS
rrarning piaii iioor
14
r»o Or.t
AS
r raining pidn iioor
1'^
no
0/-t
AS
rrduiing pidn iioors
1A IS
no
Of-t
AS
1
<;r
UbcU
INOl
UScU
*CD An
rrdining pidn iioor
10
no
r\ni
AS
oD-f o
ridining pidn iiuur
40
no
Hr-t
AS
*CR 40
rrdining pidn iiuur
41 ^1
1
n
Tcin
AO
Framing plan
floor
47 4Z
1
n Ton AO
rrdiiiiiig pidii iiuur
41
1
n AO vj-jdn-D7
Framing plan
floor
AA
m
Framing plan
floor
A'^
77 "Mr->A/ AS ZZ-lNOV-Oo
*QR
QR
SO
1
Ce.T\
7n
*CR
'^'J
*CR
S4
Framing plan floor
A(^
77 AS ZZ-INOV-Oo
*CR
^^
Framing plan floor
A1
77 Ma-.i7 as ZZ-JNOV-Oo
*CR
'^(^
Framing plan floor
A
fi
77 XTrA-«r AS ZZ-lNOV-Do
*CR
'n7
Framing plan floor
/IQ
77 XTrM/ AS ZZ-InOV-Do
*CR
';c
Framing plan floor
sn
77 XT/->i; AS ZZ-lNOV-Oo
5>r>-jy
Framing plan
CR AO
Not used
CR
Not used
^1
floors
'n 1
77 M/->»; AS ZZ-lNOV-Oo
^A
CR
Not used
*CR
Framing plan floor
JJ
77 "VT^i/ AS ZZ-iNOV-OO
*CR
Framing plan floor
JO
77 AS ZZ-i\0V-06
*CR A^
Framing plan floor
^7
77 XT/->\; AS ZZ-iNOV-Do
*CR AA
Framing plan floor
JO
77 "^Tr^^; AS ZZ-lNOV-Oo
*CR A7
Framing plan floor
'sO jy
77 AS ZZ-lNOV-Oo
*CR
Framing plan floor
AH DU
77 ^Tr^^/ AS ZZ-lNOV-Do
A/I
Afi
*CR AO
158
iNUi
\
*CR 1C\ oJt5- /U
*CR
77 M<->i; AS ZZ-iNOV-Oo
Framing plan floor Framing plan floor
A7 OZ
77 Mz-ii; AS ZZ-lNOV-Do
71
ridming pidn iiour
^^1
77 Nnx/ AS
*CR 77
Framing plan floor
A/I
04
77 "M/->\; AS ZZ-iNOV-Do
*CR 71
Framing plan
A'^ AA 0 J,OD
77 Mr>A7 AS ZZ-IMOV-Oo
floors
CR
7/1
Not used
CR
7'v
Framing plan floor
A7 0/
77 XT/->\7 AS ZZ-rNOV-Oo
SB-76
Framing plan floor
68
22-NOV-68
SB-77
Framing plan floor
69
22-N0V-68
*SB-78
Framing plan floor
70
22-N0V-68
*SB-79
Framing plan floor
71
22-N0V-68
NISTNCSTAR
1-2A,
WTC Investigation
5 6
1
1
WTC
*CD
CI
Structural
Drawings Index
for
Large-Size Sheets
Framing plan floor
72
22-NOV-68
Framing plan floor
15
22-Nov-68
Framing plan floor
nA /4
22-N0V-68
Framing plan floor
/j
27-Nov-68
or>-o4
Framing plan floor
lb
Ol-Aug-69
brJ-oj
Framing plan floor
1
27-Nov-68
Framing plan floor brJ-0
Framing plan floor
/
* C TD O O
*CD
n1
81
27-NOV-68
floor
O 82
27-Nov-68
Framing plan floor
O1
8j
Ol-Aug-69
Framing plan floor
84-86
27-Nov-68
CT3
O/l D£>-y4
Not used
*bB-y5
rrammg
m *bB-y7
*CD no bB-ys c D nn
bB-yy *CD
1
plan floor
bB-lUU
CD A bB-lUl 1
1
rrammg rrammg
rrammg
AC
17
Frammg
plan floor
Framing plan
Not used Not used
AO
1
bo-
87
Ol-Aug-69
OO
60
Ol-Aug-69
OA
<^ 1
/TV
A
Ol-Aug-69
AA AT AT
Ol-Sep-70
A'^
27-NOV-68
floors
A
/I
94
Ol-Aug-69
ys A^ yo A^ AA y7-iuu
Ol-Aug-69
A1 JUl
A1
1
Ol-Aug-69 A /"A Ol-Aug-69 /~v
1
rrammg
plan floor
1
A
rrammg
plan floor
1
A'^
A1
Framing plan floor
1
A*?
1U3
A A n A Ol-Aug-69
1
D 111 boD
on
An
*C *C
IT
floor
plan floor
CD CD
plan floor
rrammg
Not used
1
1
plan floor
1
CD r\n bB-lU7 *CD
plan floor
rrammg plan
SB-lUo
1
plan floor
Ol-Aug-69
1
Not used
*bB-lU2
*CD
rrammg
plan floor
O
Not used
Arv
1
Ol-Aug-69
ly
rrammg
Not used
bB-yo
18-Mar-69
ncx
OA
bB-yj
*cD
no 75
Framing plan floor
rrammg plan
sie
Tower
1
1
1
1
J
1
1
J
* C D 111
102
A^.^ /CA Ul-Aug-6y A..~ ZTA Ol-Aug-69 1
. .
/I
rrammg
plan floor
104
01-Aug-6y
rrammg
plan floor
1(J5
iu-ijec-6y
rrammg
plan floor
106
iu-ijec-6y
1
AT
AC n/ 1 Oj-Mar-
Framing plan floor
1
07 upper
*SB-n7
Framing plan floor
108
05-Mar-71
*SB-118
Framing plan floor
109
05-Mar-71
*SB-119
Framing plan floor
110
02-Jul-71
SB-120
Framing plan
* C D TIC ^bB-1 1
rrammg plan
*bB-
J
1
NISTNCSTAR
1-2A,
17
WTC
1
Investigation
floor
p.h.
107
roof upper level
void
27-Sep-71
159
1
Appendix A
Fri^mincT
SR-1 21
1
SR-1 24
T^lnnr naDipl qpHpHiiIp
SR-1
2*^
Pvt wall L A. W till
SR-1J
''6
PvtI. \\/iill w
Otli y 111
-plpvatinn wall 900 d
SR-1 27
Pvt l_.Al. \A/all Wdll
Qtrl "111
-plp\/atlOn tlCVClLlVJll \A/ail Wdll
SR-12X
Fvt wall LAI. Wdll tn Qth ^111
LJ J_>
SR-1
r>l^in
KrJimino iuiilliJ^ nlfin Uldll
I
.
'>Q 1 z.
7
78.Mar-6Q ividi \jy .^o
5-Feh-68
11
5-Fph-68 1 c u uo
-plpvatinn Wdll 400 V-l C V d 11 VJll wall "V/W
1
5-Feh-68
dii
u^tu
Pvt \x/all aKo\/p QtVi wdll dL/VJVv. 7111 l^Al.
SR-141
Pvt L
SR-142
Pvt \\/all "111 -plpx/ation Wdll ^00 LjAI. Wdll aV*OA/p dU\JVC Otn CltVdllVJll \A/all
SR-141
i_/Al.
SR-1
-plpvation dCVdLUJll wall Wdll 100 1 WV
08-Spn-6Q
900 wall ahovp QtH ClCVdlUJll wall Wdll ^\J\J Wdll
08-Sen-69
Pvt w/all anr^\/p Wdll dUUVC
SR-1 ^1
4.4 tlirn
1
SO
QtVi !7lll
-plp\/atir^n tlCVdlUJll \x/all Wdll
400
08-Spr)-6Q
r»nt ii^prl
08-Spn-6Q
It VI ll^ltTpHptQllc VJlllld^C UCLdllo
SI
1
5-Fph-68
1
v\
SR-1 40
1
1
tOO -J
w V U.11VJ11
iivji
1111 ti
V UlU
-p1 pvjiti oTi wjill Wdll 100 dL.VclllUll l\J\J
to QtVi \.\J 7 111
\C\ Wj
27-Sen-71
IpvpI
tfiipK r^mrn lulllLJ 11
\.\J
SAR-144
AnpVior L>\Jll Rnlt X-/tldllo OptailQ JT-lldlVJl
SR-1
S
AnplioT iJOll Rolf P^pfailc /A-liCllVJl J_/Cldll&
SR-1
SI 1
AtipVioi" /Ali^llVJl
08-Spn-6Q 08-Spr>-6Q
.
Rolf J_/CLdllo P^pfailc OUll
08-Spr)-6Q
SR-1 S2
|-rT"l ;3 (T(^ Hpf CI 1 1 C VJlllld^C UCldllo
OQ-Fph-68
SR-1 SI
livi llrifTPriPtciilc UvLdllo vJlllidJJ.C
1
5-Nnv-67
SR-1 S4
IrvilliirTf^ vJlllldtI,C
riptmlc UCldllo
1
3-npr-67
SR
1
1 1
SS
SB-401
SB-402 SB-403
SB-404 *
n H ronf lowpr
SR-1 21
TV mast support elev. TV mast support elev. TV mast support elev. TV mast support elev.
Lines
500,600,700
05-Mar-71
Lines
800,900,1000
05-Mar-71
Lines
001,002,003,004
05-Mar-71
Lines
005,006,007,008
14-Dec-70
formerly included with tower A
160
NISTNCSTAR
1-2A,
WTC Investigation
1 1
WTC
\\
Tower
Structural
Drawings Index
for
Large-Size Sheets
TC Tower B Structural Concrete Drawing Index - (18-May-73) SCB-l
Concrete plan sub level 5
el.
242
02-Jan-70
SCB-2
Concrete plan sub level 4
el.
253
ll-Apr-69
SCB-3
Concrete plan sub level 3
el.
264
-
core
05-Aug-69
SCB-4
Concrete plan sub level 3
el.
264
-
floor
05-Aug-69
SCB-5
Concrete plan sub level 2
el.
274
-
core
05-Aug-69
SCB-6
Concrete plan sub level 2
el.
274
-
floor
05-Aug-69
SCB-7
Concrete plan sub level
el.
284
-
core
05-Aug-69
SCB-8
Concrete plan sub level
el.
284
-
floor
05-Aug-69
SCB-9
Concrete plan service level el.294
-
core
lO-Jul-69
SCB-10
Concrete plan service level el.294
-
floor
lO-Jul-69
SCB-l
1
Concrete plan floor
1
el. 3
1
0
-
core
ll-Jul-69
SCB-12
Concrete plan floor
1
el.3
1
0
-
floor
ll-Jul-69
SCB-13
Concrete plan intermediate level
1
1
*SCB-14
Concrete plan floor 2
-
core
SCB-l 5
Concrete plan floor 2
-
floor
SCB-l 6
Concrete plan floors 3-6
SCB-17 SCB-18
-
see
SCA-13
06-Dec-69
core
see
SCA-15
see
SCA-16
see
SCA-17
Concrete plan floor 7
-
core
Concrete plan floor 7
-
floor
SCB-19
Concrete plan floor 8
-
core
see
SCA-19
SCB-20
Concrete plan floor 9
-
core
see
SCA-20
SCB-2
Concrete plan floor 9
-
SCB-22
Concrete plan floor 10
-
floor
19-Mar-70
*SCB-23
Concrete plan floor 10
-
core
19-Mar-70
*SCB-24
Concrete plan floor
1 1
-
core
19-Mar-70
SCB-25
Concrete plan floor
1 1
-
SCB-26 SCB-27
floor
02-Dec-69
16-Mar-70
floor
19-Mar-70
Concrete plan floor 12
-
floor
19-Mar-70
Concrete plan floor 12
-
core
19-Mar-70
SCB-28
Concrete plan floor 13
-
floor
19-Mar-70
SCB-29
Not used
SCB-30
Concrete plan floor 17
-
core
see
SCA-30
SCB-3
Concrete plan floor
1
8
-
core
see
SCA-31
SCB-32
Concrete plan floor
1
9
-
core
see
SCA-32
SCB-33
Concrete plan floor 20
-
core
see
SCA-33
SCB-34
Concrete plan floor 21-23
see
SCA-34
SCB-35
Not used
SCB-36
Not used
SCB-37
Concrete plan floor 24
-
core
SCB-38
Concrete plan floor 25
-
core
see
SCA-38
SCB-39
Concrete plan floor 26
-
core
see
SCA-39
NISTNCSTAR
1-2A,
WTC
Investigation
-
core
15-Apr-70
161
Appendix A
SrR-40
r^nnrrpfp nl;^n flnnr 77
-
porp
r^onrrptp nl?in floor 9^-^l
SrB-42
-
porp
floor
'^'^
_
povp
(^onprpfp nlnn floor ^4
-
porp
ope
QrA-47
Porp
cpp
srA-48
dec
LJV^/A
onprpfp
nlj^Ti
otiprpfp tilan floor
-
SrR-4Q
1
onprpfp nljin floor
"^f^-^C) -
srR-^o
Mot
iicpn
srR-si
Mot
iiQpn
SrR-57
Mot
iicpn
Mot
iicpH
/
1S-Anr-70 1 /T.pi \J 1
porp
-
porp
f^onprpfp r\lan floor 41
-
floor
f^onprptp r\lan floor 47
~
porp
t
r\nr^v(^fi^ rilan V^UIILICLC Ulall T\r%r\r llUUl A.^
— r^i^rt^
f rxTxr^vf^tf^ r\\ an florw Ulall V^UllCiCLC llUUl A.^
— flr\r\T" llUUl
unci
ntavi A.A. Ulall flrvrw llUUl T-H
I^MTii^ri^^tf^* nlcin V^UIICICIC Ulall flrxrw 'T'T' llUUl AA.
Ulall fli^r^r \^U11C1CIC nl^in llUUl
4
rMnr'Vf^ff^ r\\aY\ Ulall T\r\r\v \_^U11L1CIC llUUl
4S
1
r^nr^ff^^ti^*
I
tf^ r\T\r*irf^\f^ ^UULICLC
t
V_ UllL^l
IMUl
CIC Ulall llUUl
10-Aiia-7n I u /\U^ / u
_ r^rwf^
CUIC
_ flr^i^t* llUUl
ocp
/
u
OCp
/
U
_ rrw/^* C^UIC
Qpp
_ llUUl ilr^rxt" -
cpp QPA-fS7 QPP QpA-A*^
r*fwf^ CUIC
V^UllCldC Ulall llUUlo 'tU *tO H-
cpp srA-'>6
CUIC
t\\'ay\ TXc^fw H\j piall ilUUX A.r\
V^UllCICLC Ulall llUUl
T"!/
cpp QrA-'i4
(^onprptp r^lan floor 41
t r\r\r*r(^ff* V_ CIC
^PR
SrA-41
^7
1
J
see
r\l?in flooT"
SrR-48
D
SrA-4n
XJot iiQpH
1
OV,
cee
iiQpH
r^OTiPfptp
SrR-S6
rorp
T^ot ii
Mot
QrR-44
-
opp
lJUUl
CUl C
/
HO
srA-M
opp srA-fS^
CUIC
U^CU
^
ilUUl
opp
V^UIILICIC Ulall lliJUla H"-^'T-
CUIC
cpp
V^UIICICIC Ulall ilUUl^
/
srA-6Q
Mr\t iiCi^H
M
r\t lie
Mr\t
iicf=»H
~}~J
CUIC
cpp
^rR ov„ Xj- 7^ O
^UllCltlC piall llUUI JO
LUlC
«pp ^rA-7rS
SCB-77
Concrete plan floors 57-58
SCB-78
Not used
SCB-79
Concrete plan floor 59
-
SCB-80
Concrete plan floor 60
-
V^UIICICIC Ulall ilUUl /
162
see
SCA-77
core
see
SCA-79
core
see
SCA-80
-
core
NISTNCSTAR
1-2A.
WTC Investigation
0 7
WTC
v^uiiLicic
<;rR 8^
pidn iiuur
Tower S tructural Drawings Index
for
Large-Size Sheets
-
Lurc
in A iirr 7n lU-AUg/u
d-_ -
core
POO C/^ A see j)UA-oz
v^uiiLitit pidii iiuur Di
SCB-83
A 9 J1
1
O
SCA-
Concrete plan floor 63
-
core
see
i-^uuLrcLC pidn iiuur oh-
-
core
coo bv^A-o^ A 8/1 see
r\r(^
83
DJ
-
Lurc
coo o^^A-oj A fi*; see
V-Uncrcic pidn iiour do
-
cure
7/1 Ann 7n Z4-AUg/U
QPR
87
Concrete plan floor 67
-
core
7/1 A iirr 7n z4-Aug/U
Qr"R as
Concrete plan floor 68
-
core
7/1 Ann 7n 24Aug- /U
cpR
Concrete plan floor 69
-
core
coo j>LA-oy cr' A CO see
r\n r^ff^ff^ V^UIlLltlt 1
on
Ion tiiUUi 1 f~\f~\ v pidU t>
v^oncreie pidn iioors /u-/ j
CPR
Q1
CPR
Q"?
core
-
coo A on L5L,A-yu see Qr^
Not used
M
1^^" lie* ^/"i
Not used Concrete plan floor 74
-
core
coo Cr^ A QA b^_A-y4 see
Concrete plan floor 75
-
core
see 2>CA-95
SCB-96
Concrete plan floor 75
-
floor
see
SCA-96
SCB-97
Concrete plan floor 76
-
core
see
SCA-97
SCB-98
Concrete plan floor 77
-
core
see
SCA-98
see
SCA-99
i
SCB-99
1
in
Concrete plan floor 77
in
floor
-
inn
Concrete plan floor 78
-
core
coo Qr^ A 1 nn ov^A-iuu see
QPR cpR
ini
Concrete plan floor 78
-
floor
coo cr^ A n oCA-iui see
in")
Concrete plan floor 79
-
core
coo cr" A n7 L>i_ AVI see
Qr"R
in'?
Concrete plan floor 79
-
floor
coo A 1 ni see oi-^A-iuj
cr^R
1
n
Concrete plan floor 80
-
core
coo see
Qr"R
in*;
CPR
1
Qr^R
1
'I
nA
nfi
Concrete plan floor 80-82
A coo <;p n7/ Liv„A-iu see
IN 01
^r\t llCf*H
Concrete plan floor 83
1
-
WU
/"*
llUOl
-
SrA-1 09
cop see
A 117 CP A1 z
see
C/"' A 11/1 SCA-1 14
1
used i
1
in
o^
Concrete plan floor 87
-
core
1 /
Not used
SCB-1 18
Not used
SCB-1 19
Concrete plan floor 92
-
core
SCB-120
Concrete plan floor 93
-
core
SCB-1 21
Concrete plan floor 94
-
1-2A,
qpp
coo Qr^ A 111 ov^A-i see 1
core
v^oncreie pian iioors o7,7U,v i
NISTNCSTAR
1
1
core
Concrete plan floor 84-86 iNoi
A 1 C\f^ AUD
useo
1
1
1
core
yj
1
coo Qr^ A n'^ oca-iuj see
-
1 1
QPR od5-l
1
v^oncreic pian iioor oz
1 I
SCB-1 14
1
core
Qr"R oL. D-
D- 11.:
floor
A r\A AU4
-
srR-1 OV— ID I
1
1
Concrete plan floor 8 1
\_^U1JLJCIC Uldll iiUUlo 0-)
1
1
coo see
cpR.i HQ
1
-
1
WTC Investigation
core
-
core
A 1 cop sec ov^A-i
1
QPP
cr A .1
1
see
SCA- 11
1
15-Mar-71 see
SCA-121
163
Appendix A
*
SCB- 122
Concrete plan floor 95
SCB- 123
Concrete plan floors 96-100
SCB- 124
Not used
SCB- 125
Not used
SCB- 126
Not used
SCB- 127
Not used
SCB- 128
Concrete plan floor 101
-
core
seeSCA-128
SCB- 129
Concrete plan floor
02
-
core
see
SCA-129
SCB- 130
Concrete plan floor 103
-
core
see
SCA-130
SCB- 131
Concrete plan floor 104
-
core
15-Mar-71
SCB- 132
Concrete plan floor 105
-
core
18-Jun-71
SCB-133
Concrete plan floor
06
-
core
18-Jun-71
SCB-134
Concrete plan floor 107
-
floor
30-Jul-71
SCB-135
Concrete plan floor 107
-
core
30-Jul-71
SCB- 136
Concrete plan floor 108
-
core
30-Jul-71
SCB-137
Concrete plan floor 108
-
floor
Ol-Dec-71
SCB-138
Concrete plan floor 109
-
core
SCB- 139
Concrete plan floor
1
10
-
core
03-Sep-71
SCB- 140
Concrete plan floor
1
10
-
floor
03-Sep-71
SCB-141
Concrete plan penthouse roof - core
SCB-142
Concrete plans secondary levels
SCB-143
Concrete plan sub stations, escalator
SCB-•144
Sections truck ramn
SCB-•145
Concrete plan
SCB-146
Concrete plan penthouse low roof - floor
SCB-147
Concrete plan penthouse high roof
SCB-148
Core plan obsei'vation deck
1
1
el
-
core -
core
SCA-122 SCA-123
see
SCA-138
lO-Apr-72
pits
284
see
SC A- 142
see
SCA-143
ll-Jul-69
Void
post tension
el. 264,
see
see
-
26-Mar-73 22-Sep-72
floor
08-Mar-73
Formerly included with Tower A
Note- Tower
B
Concrete plan floors 14-40
Tower B Concrete
164
-
plans floors 13-16
floor see -
core see
SCA-23
SCA-24
NISTNCSTAR
1-2A,
WTC Investigation
WTC
Tower
Structural
Drawings Index
for
Large-Size Sheets
WTC Tower A & B Structural STEEL DECK Drawing Index - (18-May-73) SA-156
Steel deck plan floor
SA-157
Steel
SA-158
Steel deck plan floors
SA-159
Steel
deck plan floor
41
17-Jun-68
SA-160
Steel
deck plan floor
43
27-Aug-69
SB-160
Steel
deck plan floor
43
27-Aug-69
SAB-161
deck plan floor
7
28-Mar-69
9
28-Mar-69
19-40
28-Mar-69
Steel deck plan floor
45
17-Jun-68
Steel
deck plan floor
44
27-Aug-69
SB-162
Steel
deck plan floor
44
27-Aug-69
SAB- 163
Steel
deck plan floors
46-49
SAB- 164
Steel
deck plan floors
50-58
SAB-165
Steel deck plan floors
59-62
17-Jun-68
SAB- 166
Steel
deck plan floors
63-66
12-Dec-69
SAB-167
Steel
deck plan floors
67-70
12-Dec-69
SAB-168
Steel
deck plan floors
71-74
17-Jun-68
SAB- 169
Steel
deck plan floors
65-69
17-Jun-68
SAB- 170
Steel
deck plan floor
75
17-Jun-68
SAB-171
Steel deck plan floor
77
17-Jun-68
SAB- 172
Steel
deck plan floors
78-79
18-Mar-69
SAB- 173
Steel
deck plan floors
80-81
17-Jun-68
SAB- 174
Steel
deck plan floors
82-83
17-Jun-68
SAB- 175
Steel
deck plan floors
84-89
17-Jun-68
SAB- 176
Steel deck plan floors
90-94
17-Jun-68
SAB-177
Steel deck plan floors
95-101
17-Jun-68 02-Jul-71
SA-162
11-6-67, 6-17-
68 17-Jun-68
SB-169
SAB- 178
Steel
deck plan floors
102-106
SA-179
Steel
deck plan floor
107
08-Sep-70
SB-179
Steel
deck plan floor
107
Ol-Oct-70
SA-180
Steel
deck plan floor
108
08-Sep-70
SB-180
Steel
deck plan floor
108
Ol-Oct-70
SA-181
Steel
deck plan floor
110
08-Sep-70
SB-181
Steel
deck plan floor
110
29-Jan-72
SB-182
Steel
deck plan floor
7
28-Mar-69
SB-183
Steel
deck plan floor
9
28-Mar-69
SB-184
Steel
deck plan floor
10
28-Mar-69
SB-185
Steel
deck plan floor
11
28-Mar-69
SB-186
Steel
deck plan floor
12
28-Mar-69
13
07-NOV-69
SB-187
NISTNCSTAR
1-2A.
Steel
WTC
deck plan floor
Investigation
165
Appendix A
Miscellaneous
SX-105
Framing plan-typical
SX-144
Sewer
SX-146 7SAB-240
166
ejector
&
21-Dec-70
office floor
sump
20-Mar-69
pits
Closure tieback anchorage perimeter Floor plan
el.
229
24-Jun-68
12-Sep-66
^(original print missing)
NISTNCSTAR
1-2A,
WTC
Investigation
Appendix B
Drawing Book 19 Modifications for Structural Elements Not Included in the Database
The following
is
a table of Drawing
Book
19 (Revisions After Fabrication) changes not included in the
database because they were considered to not significantly affect the
The hsted modifications only
reference structural models.
member properties
pertaining to the
pertain to tower modifications. Modifications
outside of the towers are not included.
Drawing Number(s)
Title
19-B-913
Detail 913
19-A-914
Detail
Date 10/9/68
914
11/20/68
Description '/2
in.
by
1
in.
shim plates
for p/t cells.
Clip angle location changed for seated
connection.
19-A-918
Detail 918
1/15/69
Additional studs and flange plates for
beam
beam framed between
in
exterior wall in
19-A-921
Detail 921
1/27/69
Beam
repair det. Floor 59
10/28/70
and 92 19-A-982.1, 982.2
1,
Beam
in
WTC
1,
core and
elevation 274
Additional flange plate for
framing
19-B-975
WTC
beam
elevation 284
in
ft.
core
ft.
reinforcing for conduits passing
through core channel.
Floor 106
beam cover
1/17/71
Beam
3/15/71
Column
cover plates Floor 106.
plate 1
Column
9-B-994
splice repair Floor
Splice Repair Floor 107
107
A
19-A-lOOl.
245
19-AB-1002. 1003
Seat detail
12-9
6/5/69
Truss seat modifications Floor 10-12,
Column 246,
WTC
1
and seat
detail
dimensional modifications Floor 10-107,
WTC 19-AB- 1004.1.
Column
1004.2
procedure
19-B-2
100.1
-
2100.4
NISTNCSTAR
splice repair
Modification to pent house roof framing plan
1-2A,
WTC
Investigation
6/20/69
1
and
WTC 2.
Additional weld for exterior wall column splice connections.
9/27/71
Raised girder using stubs on roof level framing.
167
Appendix B
This page intentionally
168
left
blank.
NISTNCSTAR
1-2A.
WTC Investigation
Appendix C
WTC
Drawing Book Flowcharts
This Appendix presents the drawing books flowcharts that illustrate the flow of the drawing book links.
These flow chans were used to organize the links of the electronic databases within the database. For the flowcharts presented in Figs.
C-1 through C-9,
A B
•
"4-AB-*" denotes Drawing Book
•
[*TC] denotes number of pages and type, where page types include:
•
TC: computer generated
•
*.xls denotes
•
((*))
•
Tower
TH: hand
Microsoft Excel spreadsheet
,
or
{*} denotes relational database
hnk
(i.e.
common:
AB, and page number
written tables; and D: diagrams
file
name; and (AB_***) denotes database heading
denotes reference note key from original Drawing
previous *.xls
•
tables;
4,
relational
the following notes are
Book
information table.
Microsoft Excel column number) from
file.
Figures of columns and panels are
shown from
inside of building looking out, unless
otherwise noted.
NISTNCSTAR
1-2A.
WTC
Investigation
169
Appendix C
Exterior Column Number and Elevation
Member Number
Column Schedule
Column Schedule
Seat Details
Spandrels
Strut Schedule
[4TC]
1-A2-7, 8 [2TC]
l-B2-2>5 [4TC]
1-B2-7, 8 [2TC]
1
-A2-2 >
5
xls (B
1-A2-1017 [8TC]
-B2-I8 [ITC]
1-B2-10>17 [8TC]
\VI C A-Bk I -C.>ln)SohcdulcSpandrcl.xl> ( A_Spaiidrol
WTCH-Hkl-CiilmSchedulcSpjndrcl
Bracing, Spandrel, and
Truss Schedule
I
Spjrida-li
1D|
Truss Type
id;
1-B2-68 [ITH] WTCB-Bkl-Tnis.,T>TK(B_TnissTypc)
xls
Splice Details
Column Types
{(7, 8))
Spandrel Details
((4)) Seat Details ((4, 14))
Spandrels
((12, 13, 18, 19))
1-A2-34>37[4D] 1-B2-41>46[4D]
1-A2-18.23 [ITC] T-A2-19>22, 24>33 [4D] 1-B2-19. 24.27 [3TC]
l-A2-38>40 [3D] l-B2-47>50 [3D] |D|
-B2-20>25, 25, 26, 28>38 16D]
WH A-Bkl-t WTC
iilimniTy|iod.il.j ^Is lAJ. olT>iu'l B-Bkl-C..lumnTyiKid.itjAls IB_tolTyixl
Tower
Details
((11))
1-AB3-1>18 [20D]
]-AB3-50>66 [9TH] [20D]
Connection Details
((3))
{(6,7))
1-A2-45>57PD][6TH]
l-A2-60>66 [7D3 l-B2-69>99 [3 ID]
l-B2-55>67, 100>I02
Plaza BIdg Details
((10))
Member Type
[]6D3[7TH] WTC A-Bkl-MemhciTypc
Figure C-1. Drawing
170
Book
1
-
xls
(A_McmhciTyiic)
WTtB-Bkl-Mi;inbi;rTypi;,xls(BJVlemb>:iTyiu-)
WTC
1
and
WTC
2 exterior wall to elevation 363
NISTNCSTAR
1-2A,
ft.
WTC Investigation
I
WTC Drawing Book Flowcharts
Exterior
Column iNumber and Elevation
Exterior Wall Tree Corner Panels (Panel # = Center Column #)
Exterior Wall Tree Schedule (Panel # = Center Column #)
2-AB2-22 [ITH]
2-A1-2 > 13 [12TC]
2-AB2-17>2i [5D]
2-B1-2 > 13 [12TC]
WTC-A-Bk:-Lxi\V.illTicc_i: (.nicrP.inSdiud.xls (A
2-AB2-2 [ID]
ComPan)
WTC B-Bk2 -ExtW allTrcc'_t onKTPaiiSclicd.xls Bit ornPan) (
V.TCA-Bt2.ExtWallTtec. ColmLttBAJs (A_Coll^Bl ^^TC&-Bk2•Extttairrrc3:_ C olniLc\ B.xlM B_ColLc\ B) ftTCA-Blt2 ColraL<:\CJd>(A ColLevO \\TCB-Bie--ExtWallTree' ColmLe\-C.x]s lBj:"olLc\0 -ExiW aimer' ColraLc\D.xk lA_ColLc\D) WTCB-BL2- ExlWallTtecj "ColmLc%D.xb lB_ColLc^ D)
Column
WTCA-Bk2 ExittallTicc. 'ColmLc\E.xhlA_ColU\E) WTC
\l^
WTCA-Bk2 ExiWjUTrec CdmLe%F.xl>lA_CoILi:vF) WTCA-Bk -ExtWain rcc'spandLcvD.xIs WTCB-BIC-ExlWainror" "ColmLc\Fxl>lB C»!L
x]<
(B_SpandLcvBI i
I
A~SpaiidLt:\D)
B_SpandLc\ D
IB. H.
ib,e.h:
iB. G. l:
Column Type Level B
Column Type
((2))
{(7))
Level
M}
{Bl
Column Type
C
Level
D
((8))
:-AB2-8 [ITH] 2-AB2-8, 9,10,11
2-AB2-7 [ITH] 2-AB2-7 [ID]
2-AB2-5 [ITH] 2-AB2-4>6 [3D]
2-AB2-25 > 30 [4D]
rcc_SpaiidLcvB \1> )A_SpandLi:\ Bl
WTCB-Bk2- EvWallTrcc. "ColmL^Ej^b (B ColL« E) WTCtt-Bk: Exl\Sjinree_SpandLc%B
Column Type Level E
Column Type
((10))
((12))
2-AB2-14 [ITH] 2-AB2-12>13, 15
2-AB2-16 [ITH] 2-AB2-16[lD]
LcvD.\l>
m
IAB_Col'nypcD)
ttTrAB-Bk2-Exl\VTrec TH-LcvE.xk
[4D] UH AB-Bk:-fc\iU'lrct-_"l H-
MTCAB - B>:i-ExcwTret_THLevE.XlB iAB_Ccl87ypeBi
Splice Details
Seat Details
Splice Details
((15, 16))
((17))
((20,21))
2-AB2-23 [ITH] 2-AB2-23 [ID]
2-AB2-31>36 [7D]
2-AB2-24[lTH] 2-AB2-24[lD]
Figure C-2. Drawing
Book
2 -
Splice Details
WTC
1
and
WTC
Level F
(.
AB-Bk2-Ii\l\\Trcc_TH-U-vp (AB_Ty]n;F)
2 exterior wall tree, elevation 363
ft
xls
to
floor 9.
NISTNCSTAR
1-2A.
WTC
Investigation
171
Appendix C
Core Column Number/Location and Elevation
I
Core Column Schedule
3-Al-2>48 [47TC] 3-B1-2
>48 [47TC]
WTCA-Bk3-CorcColmAdau.xls (A CorcCol) WTCB-Uk3-CorcCalmBdala.xls lU CorcCol)
S
IG]
Base Details
Splice Details
Floor 106 Splice Details
((15))
((15))
((15))
3-AB2-20,21
3-AB2-4,7,8>13. 15>16 [lOTH]
3-AB2-3 [ID]
[2D]
3-AB2-3.1>19 [18D]
{B,C!
Shape Property Table Sliape Property Table.xls
(AB ShapcPropI
~
Splice Location
Reference Floor Elevation
((!»
((2,3))
3-AB2-22 [ID]
3-A2-23 [ITC] 3-B2-23 [ITC] \\TCA-Bk1-CoreColmAnoorclev,xls A RcfElcvUPR/LWR) WTrB-Bk3-CorcColmBnrniri-lev.\ls (U Rcltk-vUPR/LWR) (
Figure C-3. Drawing
172
Book
3
- WTC
1
and
WTC
2 core columns, foundations to floor 106.
NISTNCSTAR
1-2A,
WTC Investigation
WJC
Drawing Book Flowcharts
Core Column Number/Location and Elevation
Core Column Truss Schedule 3-B1-49 [ITC] \\TCB-Bk3-CoreColinBdataforTruss.xls (B_Truss)
Truss Elevations
Truss DetaOs
Weld Schedules
3-B3-2 > 7 [8D]
3-B3-9>16[8D]
3-B3-12,15 [2TH]
Figure C-4. Drawing
NISTNCSTAR
1-2A.
WTC
Investigation
Book
3 -
WTC
1
and
WTC
2 core
column trusses.
173
Appendix C
Exterior Column Nixmber and Elevation
Panel Schedule (Panel #
= Center Column
#)
(BOOK 2 OF 5) [298TC] (BOOK 3 OF 5) [209TC] 4-B1-2 >299 (BOOK4 0F5) [298TC] 4-B1-300 > 508 (BOOK 5 OF 5) [209TC] 4-A1-2 > 299
4-A 1-300 > 508
WTCA-Dk4-ExtW;illPanAdaUi.xls(A_Panel) WTCB-Bk4-ExtWdllPanBdala.xls (B_Panel)
IDl
\VTCA-Bk4-SpandrelPlatcAdaIa.xlb Partsl. 2 (A Spandrel) WTCB-Bk4-SpaiidrelPlateBdata.xls Pans
1,2
(B Spandrel)
|HJ,M,N,R,S|
|E,J,0|
Panel Type
Column Tvpe
((4))'
((5))
"
Column
Splice
((8.9))
WTCAB-Bk4-PandTypcdatj lAB PanclTypc)
4-AB2-15 [ITC] 4-AB2-J2>14, 1614DJ
4-AB2-8>10 [3TC] 4-AB2-8 > 10 [3D]
4-AB2-7 [ITC] I-AB2-2 > 6 [5D]
WTt AB-BkJ-C
xls
lAB
olamnTN-pcdala
WTCAB-Bk4-ColumnSplicedata.xls
\1;
(AB_UPR/LWRCoWSplice)
CiiltType)
!M,N,01 lY.Z.AAl I
no
link!
1G,HI
|S,T|
|AK,AL,AM)
|AE,AF|
Weld Electrodes Seat Details Spandrel Conn.
4-AB2-17 [ITC]
((13, 14))
WTCAB-Bk4-WeldElectuidesdata.xls
4-AB2-30 [ITC] 4-AB2-26>29 [411
(AB WfldElcct)
WTCAB-Bk4-SpandreIConnecliondala.xls
((19))
4-AB2-35 > 37 [3TC] 4-AB2-31,32, 34 [3TH] 4-AB2-31 >34 [5D]
(AB_LFT/RGTSpn#Con) WTCAB-Bk4-ScalDctailsdata.xls
lAB Spn#Col#ScaII
Figure C-5. Drawing
174
Book 4 - WTC
1
and
WTC
2 exterior wall, floors 9 to 106.
NISTNCSTAR
1-2A,
WTC Investigation
WTC
Exterior
Drawing Book Flowcharts
Column Number
and Elevation
Column and Spandrel Schedule (Panel # = Center Column #) 4-A3-2.1 >2.4 [4TH] 4-B3-2.1 >2.4 [4TH] WTCA-Bk4-ExtWalll07-l 10ColSpanSched.xls (A_107-l lOSched) WTCB-Bk4-ExtWall 107-1 10ColSpanSched.xls (B_107-l lOSched)
{D,F}
!B,C}
Column Type
Spandrel Type
4-AB3-5.2 [2TH] 4-AB3-5.2[lD]
4-AB3-6 [ITH] 4-AB3-6, 9 [2pJ
\\TCAB-Bk4.Ext Wall_ 07to 1 0 TH-ColmTypcs.xls 1
I
AB
1
WTC AB-Bk4-ExtWall_
*ColT\iic)
1
07to 1 1 0_TH-SpandTypes.xls
(AB_RGT#SpnType)
Shape Property Table
Wall Section
Column Base
Splice
Column Conn. 4-AB3-4[lD] 4-AB3-7.1,
7.2, 8
4-AB3-11 [2TH] 4-AB3-11 [ID]
[3D]
Figure C-6. Drawing
NISTNCSTAR
1-2A,
WTC
Book 4- WTC
Investigation
1
and
WTC
2 exterior wall, floors 107 to 110.
175
Appendix C
Beam Number and
Location
Beam Schedule 5-ABl-l >243 [244TC]
Shape Property Table
{E}
WTCAB-Bk5-BeamSched.xls
(ABBeam)
Shape Property Table.xls (AB_ShapcProp)
Beam Type
Support Detail
((3))
((12))
SEE
5-AB2-l>40 [40D]
Figure C-7. Drawing
176
Book
5 -
BOOK 6
WTC
1
and
WTC
2
beam schedule and
NISTNCSTAR
1-2A,
types.
WTC
Investigation
WTC
Drawing Book Flowcharts
Core Column Number/Location and Elevation
Core Bracing Schedule
6-AB5-2>4 [4D] 6-AB5-96> 101 [7D] WTCAB-BK6-CoreBracingScheduleData.xls (AB_CoreBrace)
{F}
Core Bracing Members 6-AB5-5 [ID] WTCAB-Bk6-CoreBracingMember.xls (ABCoreBraceMember)
Figure C-8. Drawing
NISTNCSTAR
1-2A.
WTC
Book
Investigation
6
-
WTC
1
and
WTC
2 core bracing schedule
and types.
177
Appendix
C
Beam Number and
Location
Member Types - Built Up
Member Types - Rolled Shapes
9-AB4-l>3 [2D], [3TH]
9-AB5-2 [ITH]
WTCAB-Bk9-BeamFL107-PH.xls (AB_107-PH_BUBeains)
/
BU
WTCAB-Bk9-BeamFL107-PH.xls PH WFBeams)
/WF (AB_107-
{B}
i Shape Property Table Shape Property Table.xls (ABShapeProp)
Figure C-9. Drawing
178
Book
9
-
WTC
1
and
WTC
2 floor 107 to penthouse
NISTNCSTAR
beam
1-2A,
schedule.
WTC Investigation
Appendix D
Excel
File List
and Description
Files with (*) include section property calculations
some members
Files with (*) include multiple section properties calculations for
Drawing Book
1
WTCA-Bkl-ColumnTypesdata.xls* A WTC Drawing Book 1: Tower A Exterior Wall
to
EL 363 Column
Tower A Exterior Wall
to
EL 363
WTCA-Bkl-CohTiScheduleSeatDet.xls WTC Drawing Book 1: Tower A Exterior Wall
to
EL
WTCA-Bkl-ColmScheduleSpandrel.xls WTC Drawing Book 1: Tower A Exterior Wall
to
EL 363 Column
WTC A-Bk
1
'
Types
-BracingScheduleData.xls
WTC Dram'ing Book I:
WTCA-Bkl-MemberTypes.xls* WTC Drawing Book 1: Tower A
Exterior Wall to
and Strut Schedule
Bracing, Spandrel
'
363' Column Schedule
'
Schedule
-
Seat Details
-
Spandrels
EL 363 Member Type '
WTCB-Bkl-ColumnTypesdata.xls* A WTC Drcrwing Book 1: Tower B Exterior Wall
to
EL 363 Column
WTCB-Bk -BracingScheduledata.xls WTC Drawing Book 1: Tower B Exterior
Wall
to
EL 363
WTCB-Bkl-ColmScheduleSeatDet.xls WTC Drawing Book 1: Tower B Exterior Wall
to
EL 363' Column Schedule
-
Seat Details
WTCB-Bkl-ColmScheduleSpandrel.xls WTC Drawing Book 1: Tower B Exterior Wall
to
EL 363 Column
-
Spandrels
'
Types
1
WTCB-Bkl-MemberTypes.xls* WTC Drawing Book 1: Tower B
Exterior Wall to
'
'
Bracing, Spandrel and Strut Schedule
Schedule
EL 363 Member Type '
WTCB-Bkl-TrussScheduledata.xls* WTC Drawing Book 1: Tower B Exterior Wall
to
EL 363
WTCB-Bk -TrussType.xls WTC Drawing Book
to
EL
'
Truss Schedule
]
NISTNCSTAR
1-2A,
WTC
1:
Tower B Exterior Wall
Investigation
363' Truss Type
179
Appendix
D
Drawing Book
2
WTCAB-Bk2-ExtWTree_TH-LevB.xls* WTC Drawing Book 2: Tower A and B Exterior Wall Tree EL 363 Level
B
Column Type
-
at
Exterior Wall Tree
EL
363' to Floor 9
Column Type
-
at
Exterior Wall Tree
EL 363
'
to
Floor 9
-
Column Type
at
Exterior Wall Tree
EL 363
'
to
Floor 9
-
Column Type
at
Exterior Wall Tree
EL 363
'
to
Floor 9
-
Column Type
at
D
WTCAB-Bk2-ExtWTree_TH-LevE.xls* A WTC Drawing Book 2: Tower A and B Level
Floor 9
C
WTCAB-Bk2-ExtWTree_TH-LevD.xls* WTC Drawing Book 2: Tower A and B Level
to
.
WTCAB-Bk2-ExtWTree_TH-LevC.xls* WTC Drawing Book 2: Tower A and B Level
'
E
WTCAB-Bk2-ExtWTree_TH-LevF.xls* WTC Drawing Book 2: Tower A and B Level F
WTCA-Bk2-ExtWallTree_ColmLevB.xls WTC Drawing Book 2: Tower A Exterior Wall Tree EL 363 Schedule at Level
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
to
Floor 9
-
Exterior Wall Tree
E
WTCA-Bk2-ExtWallTree_ColmLevF.xls WTC Drawing Book 2: Tower A Exterior Wall Tree EL 363 Schedule at Level
-
D
WTCA-Bk2-ExtWallTree_ColmLevE.xls WTC DroM'ing Book 2: Tower A Exterior Wall Tree EL 363 Schedule at Level
Floor 9
C
WTCA-Bk2-ExtWallTree_ColmLevD.xls WTC Drawing Book 2: Tower A Exterior Wall Tree EL 363 Schedule at Level
to
B
WTCA-Bk2-ExtWallTree_ColmLevC.xls WTC Drawing Book 2: Tower A Exterior Wall Tree EL 363 Schedule at Level
'
F
WTCA-Bk2-ExtWallTree_ComerPanSched.xls* WTC Drcnving Book 2: Tower A Exterior Wall Tree EL 363 Corner Panel Schedule
WTCA-Bk2-ExtWallTree_SpandLevB.xls WTC Drawing Book 2: ToM>er A Exterior Wall Tree EL 363' Spandrel Schedule at Level
B
WTCA-Bk2-ExtWallTree_SpandLevD.xls
180
NISTNCSTAR
1-2A,
WTC Investigation
Excel
WTC Drawing Book 2:
Tower A Exterior Wall Tree EL 363
File List
and Description
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
to
Floor 9
-
Exterior Wall Tree
'
Spandrel Schedule at Level D
WTCB-Bk2-ExtWallTree_ColmLevB.xls WTC Drawing Book 2: Tower B Exterior Wall Tree EL 363 Schedule at Level B
WTCB-Bk2-ExtWallTree_ColmLevC.xls WTC Dravt ing Book 2: Tower B Exterior Wall Tree EL 363 Schedule at Level
C
WTCB-Bk2-ExtWallTree_ColmLevD.xls WTC Drawing Book 2: Tower B Exterior Wall Tree EL 363 Schedule at Level
D
WTCB-Bk2-ExtWallTree_ColmLevE.xls WTC Drawing Book 2: Tower B Exterior Wall Tree EL 363 Schedule at Level
E
WTCB-Bk2-ExtWallTree_ColmLevF.xls WTC Drawing Book 2: Tower B Exterior Wall Tree EL 363 Schedule at Level
F
WTCB-Bk2-ExtWallTree_ComerPanSched.xls* * WTC Drawing Book 2: Tower B Exterior Wall Tree EL 363 Corner Panel Schedule
WTCB-Bk2-ExtWallTree_SpandLevB.xls WTC Drawing Book 2: Tower B Exterior Wall Tree EL 363 Spandrel Schedule at Level
B
WTCB-Bk2-ExtWallTree_SpandLevD.xls WTC Drawing Book 2: Tower B Exterior Wall Tree EL 363 Spandrel Schedule at Level
Drawing Book
D
3
WTCA-Bk3-CoreColmAdata.xls* WTC Drawing Book 3: Tower A Core Columns Foundation
Core Column
to
Floor 106
to
Floor 106 Reference Floor
to
Floor 106
-
Schedule
WTCA-Bk3-CoreColmAfloorelev.xls WTC Drawing Book 3: Tower A Core Columns Foundation Elevation
WTCB-Bk3-CoreColmBdata.xls* WTC Drcm'ing Book 3: Tower B Core Columns Foundation
-
Core Column
Schedule
NISTNCSTAR
1-2A,
WTC Investigation
181
D
Appendix
WTCB-Bk3-CoreColmBdataforTruss.xls* WTC Drawing Book 3: Tower B Core Columns Foundation
Core Column Truss
to
Floor 106
to
Floor 106 Reference Floor
-
Schedule
WTCB-Bk3-CoreColi-nBfloorelev.xls
WTC Drawing Book 3:
Tower B Core Columns Foundation
Elevation
Drawing Book 4 WTCAB-Bk4-Colui-nnTypedata.xls* A WTC Drawing Book 4: Tower A and B Exterior Wall above
Column
9'''
Floor (To
106'''
Floor)
9'''
Floor (To
106'''
Floor) Panel Type
Tower A and B Exterior Wall above
9'''
Floor (To 106"' Floor) Seat
WTCAB-Bk4-SpandrelConnectiondata.xls WTC Drawing Book 4: Tower A and B Exterior Wall above Connection
9'''
Floor (To
9"'
Floor (To 106"' Floor) Weld
9'''
Floor (To
Type
WTCAB-Bk4-PanelTypedata.xls WTC Drawing Book 4: Tower A and B Exterior Wall above WTCAB-Bk4-SeatDetailsdata.xls
WTC Drawing Book 4: Details
WTCAB-Bk4-WeldElectrodesdata.xls WTC Drawing Book 4: Tower A and B Exterior Wall above
106'''
Floor) Spandrel
Electrodes
WTCAB-Bk4-ColumnSplicedata.xls WTC Drawing Book 4: Tower A and B Exterior Wall above
106'''
Floor) Column
Spice
WTCA-Bk4-ExtWallPaiiAdata.xls WTC Drawing Book 4: Tower A Exterior Wall above
9'''
Floor (To 106"' Floor) Panel Schedule
9"'
Floor (To 106"' Floor) Spandrel
9'^
Floor (To 106'^ Floor) Spandrel
9"'
Floor (To 106"' Floor) Panel Schedule
9'''
Floor (To
WTCA-Bk4-SpandrelPlateAdata_pai-t 1 .xls
WTC Drawing Book 4: Schedule Part
Tower A Exterior Wall above
1
WTCA-Bk4-SpandrelPlateAdata_part2.xls
WTC Drawing Book 4:
Tower A Exterior Wall above
Schedule Part 2
WTCB-Bk4-ExtWallPanBdata.xls WTC Drawing Book 4: Tower B Exterior Wall above WTCB-Bk4-SpandrelPlateBdata_partl .xls
WTC Drawing Book 4: Schedule Part
182
Tower B Exterior Wall above
106'''
Floor) Spandrel
1
NISTNCSTAR
1-2A.
WTC Investigation
Excel
File List
and Description
WTCB-Bk4-SpandrelPlateBdata_part2.xls
WTC Drawing Book 4:
Tower B Exterior Wall above
P"'
Floor (To
1
06'^'
Floor) Spandrel
Schedule Part 2
WTCAB-Bk4-ExtWall_l 07to 1 1 0_TH-ColinTypes.xls* WTC Drawing Book 4: Tower A and B Exterior Wall Floors 107
WTC AB-Bk4-ExtWall_l 07to
0_TH-SpandTypes.xls* Tower A and B Exterior Wall Floors 107
110 Column Type
to
110 Spandrel Type
1 1
WTC Dra\ving Book 4:
WTCA-Bk4-ExtWalll07-110ColSpanSched.xls WTC Drawing Book 4: Tower A Exterior Wall Floors 107
to 1
WTCB-Bk4-ExtWalll07-110ColSpanSched.xls WTC Drawing Book 4: Tower B Exterior Wall Floors 107
to
Drawing Book
to
10 Column and Spandrel Schedule
110 Column and Spandrel Schedule
5
WTCAB-Bk5-BeamSched.xls WTC Drawing Book 5: Tower A and B Beam Schedule Drawing Book
6
WTCAB-Bk6-CoreBracingMember.xls* WTC Drawing Book 6: Tower A and B Core Bracing Members WTCAB-Bk6-CoreBracingScheduleData.xls WTC Drawing Book 6: Tower A and B Core Bracing Schedule
Drawing Book
9
WTCAB-Bk9-BeamFL107-PH.xls* WTC Drawing Book 9: Tower A and B Floors 107
to
Penthouse Beam Member Types
Included outside of the Drawing Book folders:
Shape Property Table.xls Shape Property Table
NISTNCSTAR
1-2A,
WTC
Investigation
183
Appendix
D
This page intentionally
184
left
blank.
NISTNCSTAR
1-2A,
WTC Investigation
'
Appendix E Relational Database File List and Description
(Files with
(*) include section property calculations)
some members)
(Files with (A) include multiple section properties calculations for
WTCA_DBkl.mdb*
WTC Drawing Book 1:
Tower A Exterior Wall
to
EL. 363
Tower B Exterior Wall
to
EL. 363
'
WTCB_DBkl.mdb*
WTC Drawing Book 1: WTCA_DBk2.mdb* A
WTC Drawing Book 2:
Tower A Exterior Wall Tree EL. 363
'
to
Floor 9
to
Floor 9
WTCB_DBk2.mdb*
WTC Drawing Book 2:
Tower B Exterior Wall Tree EL. 363
'
WTCA_DBk3_col_foundation.mdb* WTC Drmving Book 3: Tower A Core Columns Foundations
to
Floor 106
WTCB_DBk3_col_foundation.mdb* WTC Drawing Book 3: Tower B Core Columns Foundations
to
Floor 106
WTCB_DBk3_col_truss.mdb* WTC Drawing Book 3: Tower B Core Column Trusses
WTCA_DBk4_9-106.mdb* A
WTC Drawing Book 4:
Tower A Exterior Wall above
9'^
Floor (To 106"' Fir)
Tower B Exterior Wall above
9'''
Floor (To
WTCB_DBk4_9-106.mdb* *
WTC Drawing Book 4:
106'''
Fir)
WTCA_DBk4_107-l lO.mdb*
WTC Drawing Book 4:
Tower A Exterior Wall Floor 107
to
Floor 110
Tower B Exterior Wall Floor 107
to
Floor 110
WTCB_DBk4_107-l lO.mdb*
WTC Drawing Book 4: WTCAB_DBk5.mdb
WTC Drawing Book 5:
Tower A and B Beam Schedules and Types
WTCAB_DBk6.mdb*
WTC Drawing Book
NISTNCSTAR
1-2A.
WTC
6:
Tower A and B Core Bracing Schedules and Types
Investigation
185
Appendix
E
WTCAB_DBk9.mdb*
WTC DraM'ing Book 9:
186
Tower A and B Floor 107
to
Penthouse
Beam
Schedules
NISTNCSTAR
1-2A,
WTC Investigation
Appendix F
Relational Database Tutorial
Database Structure: The
was developed using Microsoft Access 2002. Each database was
relational database
set
up based on
WTC Drawing Book flowcharts (refer to Appendix C). Each flowchart has a separate database for WTC and WTC 2. The arrows in the flowcharts depict the links or common threads between tables. the
1
The
relational database allows the data to be
communicated are based
to the database via a
on the Drawing Book
2,
viewed and exported based on the user's preferences and
query (a type of filter). Note: All screen views and examples below
WTC
1
database
(WTC_DBk2_TWRA.mdb).
lgiWTC_DBk2_TWRA Database
li|ji'.jaixj
Viewing Tables: To view
a database table, first
make
tables are listed in the database this, left
box.
appear
The
list
^
window. To do
chck on "Tables" under Objects
J
Create table
j
Create table by using wizard
sure that the
in the
upper
a
J
in
Design view
Create table by entering data
m
AB_TypeB
EE
AE_TvpeC
of database tables should
hand box. (Fig. F-1) Note names are listed in the flowcharts of
in the right
that the table
1
Jst of
Database
Appendix C.
Tables Double-click on the desired table to open
it.
The
table will look similar to an Excel spreadsheet
with columns and rows of data.
Figure F-1. List of database tables. ^WTC_DBk2_TWRA
:
Database
^
j
J §1
Create query
iri
Design view
Create query by using wizard
B)(2_TV/RA_LevB
Bk2_TWRfl_Leve_colarea_example BK2_TV.yRA_LevC [51
BK2_TWRA_LevD
[§1
BK2_TV«A_LevE
[§)
BK2_TV./RA_LevF
Running Queries: a query, open up the query view from the main Database window by clicking on "Queries" under the Objects title in the upper left comer of
To run
the
window.
(Fig.
F-2)
A list of queries will be
displayed in the box on the right.
Double-click on the desired query to run the query.
Figure F-2. List of database queries.
NISTNCSTAR
1-2A,
WTC Investigation
187
Appendix F
Note: All of the resident queries contain the established links between different tables. These queries all
data from
linked tables.
all
To
list
Custom Queries"
include only desired data in a query, see "Creating
below.
ipWTC_DBk2_TWRA
Creating
^Ofieri
Custom Queries:
H
111
Database
X
^Design cf]New
Ohiects
Note: All custom queries must be created from
:
Ej
Create query
Ej
Create query by using wizard
[P
Bl;2_TVi'RA_LevB
[§3
BK2_TWRA_LevcM
Besl^Viev^
[§3
BK2_TWRA_LevcS
Print...
[§0
BK2_TWRA_LevE B. P^nt Preview
gl
BK2_TWRA_LevF
in
Design view
one of the original queries as the links between tables
have already been established
queries. links
Any new
in these
query would not contain these
and would require these links
to
be created
manually.
1^
jjf^"^^ ;i=l
Start
by saving
new
a
edited. Right-click
Qpen
£opy
version of the query to be
on the query
to
be edited and
Groups Export,..
select
"Save As.
." .
from the sub-menu
that
appears. (Fig. F-3)
I
1:
Jj
X
_i
Send To
*
Add to Group
>
Create Shortcut... Delete
Rename Properties
Figure F-3. Copying a query.
In the
pop-up window, type
Make
sure that "Query"
(Fig.
Figure F-4.
is
in a
name
for the
new
query.
selected in the "As" select-box.
F^)
Naming new query. |lB WTC_DBk2_TWRA
^
Qpen ^Design
:
.|n|x|
Database
fgiriew 1^
1
tf^ 1
X
*a
Lteate query 'Irea',
in
Design view
query by using wizard
-:_T'vVRA_LevE:
# \miimmm\
3 To
edit the query, select the
click
on the "Design" button on the upper
the database
window
[§3
newly copied query and
(Fig. F-5).
left
The queiy
BH'_T'*RA_LevL
[P BK2_TWRA_LevD
comer of
[§3
BK2_TWRA_LevE
[§3
Bt:2_TWRA_LevF
will appear GrCHjps
in
design (edit) view.
Figure F-5. Selecting design view for a query.
188
NISTNCSTAR
1-2A,
WTC Investigation
Relational Database Tutorial
The design view shows
all
table associations (depicted
by arrows)
for this query.
The
first
the main table. The tables to the right are the ones that are linked from the main show where the association is made. For example, "Coll Type" in the main table (table
shows
"Column"
in the
AB_CollTypeB
be displayed
when
the query
to
I? BK2_TWRA_LevB
:
is
table.
run. (Fig.
The lower
part of the
box (from
table.
A
left)
The arrows
ColLevB)
view shows the query selections
links
that will
F-6)
MM
Selec* Queqp
6 ID
ID
ID
ID
Column
Column
Column
PItB-IN
PItB-IN
PltB-lN
PHB2-IN
PItBC-IN
PltBC-IW
PltB3-IN
PltB3-IN
PltB3-IN
PItBI
PltB4
PltB4
PItBS
PltB5
PItBS
PltB6-IN
PltBo-IN
PltB6-iN
PltB7
PltB7
PltB7
PItBS
PItBB
PItBS
weldl-IN
«eldl-IN
weldl-IN
i'ield2-IN
weldC-IN
weld2-IN
-eldS-IN
weld3-IN
iveldS-IN
ll.•ld^-II^I
weld4-IN
,wld4-IN
Coll Type
CollFyBl
CollF/e2 CollFyBe CollweltC
CoEType CotZFyBl
Col2FyB2 Col2FyB6 Col2weld3
Col3Type
I'.
ColSFyBl
CotSFyBZ
weld5-m »eld6-m
CoQFyBo Col3we!d3
inks
CollSpDet
Section i
Name
•.-veld5-IN
.A«ld6-IN
weld7-INI
,veld7-IN
weld8-IN
weld8-IN
Section
Name
Ar&a-IN2
Area-IN2
I«-IN4
IJ-IM4
Section
Name
Aiea-m2
zi
I.-IN4
Figure F-6. Query design view.
Field:
First delete all the present
clicking on the top
query selections by
row of each query
selection (Fig.
F-7) and pressing the delete key on the keyboard.
Do
this until all text is deleted
from the query
selections (the boxes themselves will not disappear)
Table:
A ColLevB * A ColLevB
El AB CollTypeB, "U ABjCollTypeB
Sort;
Show; Criteria; or:
Figure F-7. Selecting query selection.
NISTNCSTAR
1-2A,
WTC
Investigation
189
Appendix F
Double-click on the data to be included in your query (see example below).
Note: Selecting the asterisk (*) at the top of each table will
How
Example:
to include the panel, the three
Note: This example
column
list all
fields in that table.
types, as well as their associated areas in one table.
an example queiy called "Bk2_TWRA_LevB_colarea_example"
is
in the
WTC Book 2 Tower A database. Once
Double-
the original query selections are deleted, select the
"Panel" field from the main table (table
double-clicking on
it.
It
A
click
ColLevB) by
"Panel"
should appear as a query
oil
Type 'Bl
selection
below
(Fig. F-8). Fieid:
TaUe:
Panel
New Qoery
A ColLevB
Sort;
Selection
j
Crfteria
r!
1
Figure F-8. Select panel
Select "CollType" table.
from the main
table.
Then, select the "Area-IN2"
from the AB_CollTypeB
For the second column, select "Col2Type" from the main table and "Area-IN2" from the
AB_Col2TypeB table. Repeat this for the third column, choosing There should now be 7 fields displaying in the Query Selection.
File
field
field.
Edit
View
Insert
i^uery
Tools
the last table for the area of the column.
To run
Window Help
this query, click
the exclamation
S
1
All
Run
button
-
top bar of the
window. Note:
on the middle
MS
Access
(Fig. F-9).
To save
either click
the query,
on the save
PltB6-IN
ID Panel
CollType
on
mark -
PitB?
button, or go to File
PitBS
-
Menu
Save.
.
i«rIH1-TM
Figure F-9.
Run query
button.
Exporting Data: Data can be exported from any query or table into a number of formats, including
To
export a query, open the query and select File
to save as (from the
190
drop-down menu) and
Menu -
text
and Excel formats.
Export. Select the location, name, and the type
click "Save All".
NISTNCSTAR
1-2A,
WTC Investigation
Appendix G
Categorization of Floor Construction Types for Areas Outside of Core
The
structural
drawings for the floors in both towers were reviewed to identify structural similarities
within the areas outside the core. Table
G-1 summarizes
the construction types and space usage for each
floor for both towers. Information regarding the categorization
are pro\ ided in floors
Figs. G-1 through
G—
4.
Based on
and description of floor construction types
this review, the typical truss-framed
and beam-framed
were selected for modeling.
NISTNCSTAR
1-2A,
WTC
Investigation
191
323
Appendix
3 2 1
G
Table G-1. Representative categorizations of floor construction types outside of core. Tower A Floor Framing Floor
PH
Roof 110 109 108 107 106 105 104 103 102 101
100
99 98 97 96 95 94 93 92 91
90 89 88 87 86 85 84 83 82 81
80 79 78 77 76 75 74 73 72 71
70 69 68 67 60-66 59 50-58
49 48 47 46
45 44 43 42 41
27-40
26 25 14-24 13 12 11
10 9 8 7 3-6 2 1
B1
192
Tower B
Floor Framing
Space Usage
Const. Type
Floor
Space Usage
Const. Type
Roof TV/Storage Upper f\^ech Fl Lower fylech Fl
Type 12 Type 12 Type 1 Type 12 12 Tvoe :JJ:S.J.t Type 10 Tvoe 1 Type 1 Type 1 Type 1 Tvoe 1 Type 1 Tvoe 1 Tvoe 1 Tvoe 1 Tvoe 1 Tvnp 1 Tvoe ypc 1 Type 1 Tvoe 2 Tvoe y^c 1 Tvnp 1 Tvoe 1
PH Roof
Observation
110 109 108 107 106 105 104 103 102
Storage
Tvnp ype 1 Tvoe ypc 1 Type 1 Tune 1 Tvnp 9 Type 9 Type 9 Type 9 Type 8 Tvnp 7 Type 12 Type 13 Type 1 Tvnp 1
87
Type 12 Type 12 Type 13 Type 12 Type 12 Tvoe 1 Tvoe 1 Type 1 Tvoe 1 Type 1 Tvoe 1 Tvoe 1 Tvoe y^c 1 Tvoe 1 Tvnp 1 Tvoe yf^c 1 Tvnp ypt; 1 Tune 1 Type 1 Tvoe 2 Type 1 Tvnp ype 1 Tvnp ype 1 Tvnp 1 Tvnp ypc 1 Tvnp 1 Type 1 Tvoe 1 Type 9 Tvnp ype Q =7
Restaurant
Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Upper Escalator Sky Lobby Lower Escalator Upper Mech Fl Lower Mech Fl Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant
Tenant Tenant Tenant Upper Escalator Sky Lobby Lower Escalator Upper Mecti Lower Mecfi Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Upper Mech Lower Mech Core Only (Storage) Plaza - Lobby Concourse EL. 294
1
1
1
1
Type 1 Tvoe 1 Tvoe 1 Type 1 Type ypc 1 Type 6 Type 1
Type2 Type 1 Type 3 Type 3 Type 3 Type 3 Type 5 TvDe 4
T^e
12
Type 1 Type 12 Tvnp 1 Tvnp 1 Tune 2 Tvnp 1 iry Tvnp 1 Tvoe 1 Type 1 Type 1 Type 12 Type 13 Type 12 '
Upper Mech Lower Mech
Fl Fl
Observation
Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant
101
100
99 98 97
96 95 94 93 92 91
90 89 88 86 85
84 83 82
1
1
1
1
1
1
1
1
1
1
1
1
'
Expanded Zone Impact Zone
I
I
Combined Zones
Refer to
Fig.
through
G-4
G-1 for
description of floor
system categories
1
81
80
79 78
77 76 75 74
73 72 71
70 69 68 67 60-66 59 50-58
49 48 47 46 45 44 43 42 41
27-40
26 25 14-24
13 12 11
10
9 8 7
NA
3-6
Type 15 Type 14 Type 14
2 1
B1
Tenant Upp6r Escslstor Sky Lobby Lower Escalator UppGr Mech Fl Lower Mech Fl Tenant Tensnt Tertsnt
Tenant Tensnt Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Upper Escalator Sky Lobby Lower Escalator I
Innpr Mpr'h
Lower Mec^ Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Tenant Upper Mech Lower Mech Core Only (Storage) Plaza ' Lobby Concourse EL 294
Type 9 Type 8 Tvnp 7 Type 1 2 Type 1 Type 1 Type 1 Tvnp ype 1 Tvoe 1 Tvoe 1 Tvoe 1 Type 1 Type 1 Tvoe 1 Type 1 Type 2 Type 1 Type 3 Type 3 Type 3 Type 3 Type 5 TvDe 4 /r^ ^ Type 12 Type 13 Type 12 i
1
*
,1
II
Tvoe 1 Tvnp 2 Type 1 Type 1 Type 1 Type 1 Type 11 Type 12 Type 13 Type 12
NA Type 15 Type 14 Type 14
^
|
NISTNCSTAR
1-2A,
WTC Investigation
Categorization of Floor Construction Types
WTC R Roors; 10
-
Typicar Truss
Roor Panel Plan Tower 6
2A
Ftoore:
26-40 50-58 Noie:
Note; HI =
26 50
Aa panel n
)'
ERl
FR1
14-24
0R1
ftoor;
CR1 BRl
60-74
40
84
•
S«
93-106
10 11. 39 40 70 & 71
A1
B1
Type
-
CI
-
\.vhich
D1
are
6'-1Q"
El
ERl
FR1
F1
G1
HR1
HI
J1
Kl
CORE
Note: J1 =K1 =
H1
GR1
G1
HR1 = HR6
Note: HI
E-
.
WTC
D1
CI
81
Al
BRl CR1
DR1
ERl
Non-Typical Truss Floor Panel Plan
(all
=M1
DR1
CR1 BRl
=
CI
D1
F1
KRl
BEAMS
E5
F5
Type 4
-
WTC
D5
C1
B1
Al
BRl CR1
DR5
ER5
FR5
BeamfTruss Sky Lobby Floor Panel Plan
ersA& B
Figure G-1. Floor construction types
El
HR1
Towers Roots: 25.59.92 secondary walsr lin«s.
Investigation
49
BEAMS
ER3
DR3 CR6
w
CO
CO
BEAN
BEAN
BEAN
C6
D3
Floor:
E3
F3
BEAMS
BEAMS
BEAMS
SEAMS
BEAMS
BEAMS
BEAMS
1
E8
D8
C8
through
B8
AS
,
\
BEAMS
CORE
BEAMS
F8
WTC
-
MR1
MRl
FRl
B1
CORE
BEAMS
1-2A,
46
M1
FR3
NISTNCSTAR
Floorsi
GR1
KRl
C32T5 Trusses)
Al
A&B
d capacity tor
A& B
Floors 72-74 vary ie*-26".
GR1
FT
Floor Panel Plan 5
wimm
HR1
2
WTC Beam/Truss
Hi
H6
Type
-
G1
J1
Note:
3
91
BR8 CR8
DR8
ER8
:
FR8
4.
193
Appendix
Type
5
•
G
WTC Beam/Tmss
Typp
Upper Escalator Floor Panel Plan
Towers A a B
ER1
FR1
ORI
CR6
BEAMS
BEAMS
BEAMS
C6
01
Floor:
WTC
7
Beam/Tr^ss Sky Lobby Floor Panel Plan
Towers A & B
45
El
F1
ER3
FR3
0R3
CR3 BR3 A3
B3
C3
03
Floor:
78
E3
F3
BEAMS
BEAMS
BEAMS
BEAMS
BEAMS
BEAMS
BEAMS
BEAMS
M1
BEAMS
BEAMS
BEAMS
BEAMS
BEAMS
BEAMS
BEAMS
G1 HI
CORE
K1
E5
F5
Type
6
-
WTC
D5
CI
BR1 CR1
A1
B1
Non-Typical Truss Floor Panel
DR5
ER5
FR5
Type
Plai
E3
F3
6
-
BEAMS
CORE
D3
WTC Beamn'mss
C3
A3
B3
BR3 CR3
ER4
DR4
CR4 BR4
A4
B4
C4
04
GR4
ER5
0R5
CR1 BR1
CI
05
BEAMS BEAMS
CORE BEAMS
BEAMS
GR1
04
C4
BR4 CR4
DR4
ER4
FR4
El
D1
CR1
C1
Figure G-2. Floor construction types 5 through
194
F5
MR1
H4
E4
E5
BEAMS
CORE HR8
F4
FR3
Towers A & 6 Floor 79
FR5
E4
ER3
Uppar Escalator Floor Panel Plan
Tower A Floor 67
FR4
DR3
DR5
8.
NISTNCSTAR
1-2A,
WTC Investigation
Categorization of Floor Construction Types
Type 9
-
WTC Beam
Floor
Above MER Floor Panel Plan
Type
Towers A & B
Same
Note;
F5
as Type
E5
3.
Floors;
80
-
1 1
-
WTC
Heavy Angle Truss Floor Panel Plan
83
Towers B
Floors;
10-13
with opposite onentatic
D5
DR5
CI
ER5
FR5
BEAMS
BEAMS MR1
CORE HR6 GR1
G1
ER1
FR1
DR1
CR1 BR1
Typejp WTC Reinforced Type -
Note:
Same
1
CI
Rtior Panel Plan
panel plan as typical floor (Type
1)
D1
Towef A
El
Floor:
106
but with reinforced trusses
DR1
D1
CORE
GR1
FR1
Figure G-3. Floor construction types 9 through 11.
NISTNCSTAR
1-2A,
WTC
Investigation
195
Appendix
Type 12
•
G
WTC Beam Framed
Type 14
Floor Floor Plan
Towers A & B Towers A & B Near
MER MER
Floors:
7.41,75.108
Floors:
9.43.77.107.1 10. Roof
-
WTC Shon Beam Framed
Floor Floor Plan
Towers
AS
B Floors- Cone. B1.B2.B3.B4.B5
E ra
QJ
00
Beams
Beams
CORE
Beams
CORE
Beams
Beams
Beam;
Beams
Figure G-4. Floor construction types 12 through 15.
196
NISTNCSTAR
1-2A,
WTC Investigation