NIST Special Publication
1000-2
NISTIR 6942
December 9, 2002
Progress Report on NIST Building and Fire Investigation into the
World Trade Center Disaster
Summary:
The National Institute of Standards
and Technology (NIST) announced its 24-month building and fire safety
investigation of the World Trade Center (WTC) disaster on August
21, 2002. NIST also released the final plan for its investigation
at the same time. This plan, which reflects comments received in
writing and at a June 24, 2002 public meeting held in New York City
may be found at http://wtc.nist.gov.
This public update summarizes the
progress made by NIST and the cooperation it has received from a
variety of organizations since the August announcement. This report
covers:
- Availability of funding to support
the investigation element of the NIST public-private response
plan;
- Passage of the National Construction
Safety Team (NCST) Act and new authorities for the WTC investigation;
- Progress toward the establishment
of an Advisory Committee as called for by the NCST Act;
- Access to the work of technical
experts involved in the insurance litigation related to the WTC
towers;
- NIST’s use of a balance of analytical,
experimental, and numerical tools to evaluate alternative collapse
hypotheses;
- Progress in identifying and collecting
materials relevant to the investigation from the building owner,
leaseholder, their consultants and contractors, New York City
authorities, and other sources, with more information still needed;
- Selection of external experts to
augment the NIST team in the area of occupant behavior and evacuation;
- The outline of a systematic data
collection methodology for studying occupant behavior, evacuation,
and emergency response;
- Status of steel and its analysis,
photographic and video image collection and analysis, and contracting
plans;
- Exchange of information and discussions
with the New York City Department of Buildings related to the
activities of its World Trade Center Building Code Task Force;
and
- Progress in NIST’s concurrent WTC
Research and Development (R&D) Program and the Dissemination and
Technical Assistance Program (DTAP).
The highlights of this update include:
- initial NIST efforts to identify
steel recovered from the WTC towers and characterize the elevated
temperature properties of the primer paint used on perimeter columns;
- outline of a three-pronged sampling
methodology developed by NIST to obtain new data on evacuation
and emergency response through face-to-face interviews, paper
and web-based questionnaires, and focus group interviews with
occupants, first responders, and families of victims;
- important types of documents obtained
by NIST from the owner, leaseholder, insurers, and local authorities,
and the specific documents and materials that have not yet been
located or provided to NIST;
- a summary of NIST’s photographic
and video image collection efforts, the need for access to unpublished
photos and non-broadcast video footage from media sources, and
call for specific types of photos and videos to document initial
damage and subsequent fire growth;
- NIST’s use of a balance of analytical,
experimental, and numerical tools to evaluate alternative collapse
hypotheses for the WTC towers; and
- the status of the Advisory Committee
that is being established pursuant to the National Construction
Safety Team Act (P.L. 107-231) signed into law October 1, 2002
by President Bush and that provides NIST with lead agency authorities
to investigate building failures.
Goals of WTC Investigation:
- To investigate the building construction,
the materials used, and the technical conditions that contributed
to the outcome of the WTC disaster.
- To serve as the basis for:
- Improvements in the way buildings
are designed, constructed, maintained, and used;
- Improved tools and guidance
for industry and safety officials;
- Recommended revisions to current
codes, standards, and practices; and
- Improved public safety, and
business and insurance stability.
Objectives of WTC Investigation:
The objectives of the NIST investigation
of the WTC disaster are to:
- Determine why and how WTC 1 and
WTC 2 collapsed following the initial impacts of the aircraft
and why and how WTC 7 collapsed;
- Determine why the injuries and fatalities
were so high or low depending on location, including all technical
aspects of fire protection, occupant behavior, evacuation, and
emergency response;
- Determine what procedures and practices
were used in the design, construction, operation, and maintenance
of WTC 1, 2, and 7; and
- Identify, as specifically as possible,
areas in current building and fire codes, standards, and practices
that warrant revision.
Fact-Finding Focus of Investigation:
NIST is a non-regulatory agency of
the U.S. Department of Commerce. The NIST investigation is focused
on fact-finding, not fault-finding. No part of any reports, data,
and findings resulting from a NIST investigation can be used in
any legal proceedings (15 USC 281a; P.L. 107-231).
NIST Public-Private Response
Plan:
The NIST public-private response
plan consists of three program elements. The first is a 24-month
building and fire safety investigation that will
study the factors contributing to the probable cause (or causes)
of collapse of the 110-story WTC towers (WTC 1 and 2) and the 47-story
WTC 7 and to the associated fatalities and injuries. What is learned
in examining WTC 1, 2, and 7 is expected to benefit new and existing
buildings.
Parallel to the investigation is
a proposed research and development (R&D) program
to provide the technical basis for specific improvements to building
and fire codes, standards, and practices, particularly to facilitate
implementation of recommendations that result from the WTC investigation.
This program addresses work in critical areas such as structural
fire safety, mitigation of progressive collapse, building vulnerability
reduction tools, and equipment standards for first responders. This
includes experimental validation of computer analysis tools. The
rate at which the recommendations of the investigation can be implemented
will depend on the level of funding available to the R&D program.
An industry-led dissemination
and technical assistance program (DTAP) is the third part
of the NIST response plan. The DTAP is designed to engage leaders
of the construction and building community in the implementation
of proposed changes to practices, standards, and codes. Also, it
will provide technical guidance and tools to better prepare facility
owners, contractors, architects, engineers, emergency responders,
and regulatory authorities to respond to future disasters. The DTAP
is crucial for timely adoption and widespread use of proposed changes
to practice, standards, and codes resulting from the WTC investigation
and the R&D program.
Funding Status for the WTC Public-Private
Response Plan:
On September 9, 2002, $16 million
in funding to support the WTC investigation was transferred to NIST
by the Federal Emergency Management Agency (FEMA). These funds were
made available from the emergency supplemental appropriation passed
by Congress and signed into law on August 2, 2002.
In FY 2002, total funding of $19.4
million was allocated to support NIST’s WTC response plan, including
the above $16 million for the investigation.
In FY 2003, the President’s budget
requests $4 million to support selected portions of the WTC response
plan, focused on the R&D and DTAP program elements. This request
is currently pending in Congress. Like much of the federal government,
NIST is operating on a continuing resolution. This provides NIST
with about one half of the requested level of funding in FY 2003
until a final appropriation is received.
National Construction Safety Team
Act:
The National Construction Safety
Team Act (P.L. 107-231) signed into law October 1, 2002, by President
Bush establishes NIST as the lead agency to investigate building
failures. The Act, modeled after the National Transportation Safety
Board (NTSB) for investigating transportation accidents, provides
NIST with significant additional authorities. The NCST Act applies
to the NIST WTC investigation in response to the attacks of September
11, 2001.
The NCST Act provides for the establishment
of investigative teams to assess building performance and emergency
response and evacuation procedures in the wake of any building failures
that has resulted in substantial loss of life or that posed significant
potential of substantial loss of life. The purpose of investigations
conducted under the Act is to improve the safety and structural
integrity of buildings in the United States. The Act gives NIST
the responsibility to dispatch teams of experts, where appropriate
and practical, within 48 hours after major building disasters. Investigation
teams will include outside experts.
Consistent with NIST’s public-private
WTC response plan, the Act gives the teams an explicit mandate to:
- Establish the likely technical cause
of building failures;
- Evaluate the technical aspects of
procedures used for evacuation and emergency response;
- Recommend specific changes to building
codes, standards, and practices;
- Recommend any research or other
appropriate actions needed to improve the structural safety of
buildings, and/or changes in emergency response and evacuation
procedures; and
- Make final recommendations within
90 days of completing an investigation.
NIST will report to Congress on actions
taken as a consequence of its recommendations.
The Act gives NIST and its teams
comprehensive investigative authorities to:
- Access the site of a building disaster;
- Subpoena evidence and witnesses;
- Access evidence such as records,
documents, materials, and artifacts; and
- Move and preserve evidence.
The Act also authorizes that NIST may
confer with employees and request the use of services, records, and
facilities of state and local governmental authorities.
NIST plans to work with all interested
parties in an investigation and, if necessary, judiciously exercise
its new subpoena authority. NIST will issue subpoenas if needed
to obtain documents, materials, oral testimony, or other evidence.
Establishment of the NCST Advisory
Committee:
The Charter for an Advisory Committee
to be established pursuant to the National Construction Safety Team
Act was approved November 5, 2002. The Committee will advise the
NIST Director on carrying out the responsibilities assigned to NIST
under the Act. This Advisory Committee applies to the WTC investigation
and to future NIST investigations under the Act. Both the Act and
the Charter for the Advisory Committee may be found at the NIST
WTC web site at http://wtc.nist.gov.
On November 12, 2002, NIST issued
an announcement requesting nominations of individuals for appointment
to the National Construction Safety Team Advisory Committee by November
27, 2002. NIST has received a large number of excellent nominations
in response to this request, in addition to nominations previously
submitted. NIST is reviewing potential candidates for appointment
to this select committee that will consist of at least five but
no more than 10 members. A total of 84 nominations have been received.
Announcement of the selections will be made as soon as the vetting
process for appointments under the Federal Advisory Committee Act
is complete. The NIST Director will make the selections and his
decisions are final. Portions of the Committee’s meetings are expected
to be open to the public. One or more of the meetings are expected
to take place in New York City.
Access to Technical Information
Developed in WTC Towers Insurance Litigation:
In July 2002, representatives of
Silverstein Properties, the leaseholder for the WTC towers and WTC
7, offered to provide NIST with full access to critical information,
materials, and data relevant to the NIST investigation. This included
the large body of technical work completed by its experts as part
of the insurance litigation involving the WTC towers.
In early October 2002, the group
of insurance companies involved in the same insurance litigation
offered to provide NIST with the technical work completed independently
by its experts.
Technical experts for Silverstein
Properties provided detailed briefings to the NIST investigation
team on October 8, 2002 and the technical experts for the insurance
companies did likewise on October 23, 2002. NIST also has been provided
a large variety of documents, including reports on the structural
collapse, fire spread and severity, and wind tunnel test results
for the WTC towers by both parties. In addition, the experts discussed
the tenability environment and the evacuation processes in the buildings.
The structural collapse scenarios
discussed in those reports are among the critical issues NIST has
included in its investigation plan. In addition, the NIST plan goes
beyond those considerations to include issues of evacuation, emergency
response, and engineering practice.
NIST is reviewing the information
and reports that have been provided and incorporating what is learned
into its investigation. When NIST issues its analysis at the conclusion
of the investigation, it will make certain that the different scenarios
are examined, either alone or in combination, and compared with
available evidence to establish the facts rigorously and in an unbiased
way.
The leading scenarios under consideration
recognize that aircraft impact caused damage to perimeter and interior
columns and to floor systems. While the full extent of this damage
is unknown and can only be estimated through analysis, it led to
redistribution of the building loads among the columns (e.g., from
the damaged columns to the undamaged columns, aided by the hat truss
at the top of the towers) and with the floor systems.
At this stage, one hypothesis suggests
that the load carrying columns were weakened by the fires and failed,
initiating overall building collapse without the need for any weakening
or failure of the steel truss floor system. Another hypothesis suggests
that significant portions of one or more trussed floor systems sagged,
as they were weakened by fires, and pulled the columns inwards via
the connections, initiating overall building collapse through bending
failure of the columns. A variation of this hypothesis suggests
that the sagging floor system failed in shear at its connections
with the columns, before overall building collapse initiated through
buckling failure of the columns. Load eccentricities introduced
by partially damaged floor systems could also have contributed to
buckling failure of the columns. Combinations of these hypotheses
present other possibilities.
Based on an initial assessment of
the expert studies conducted as part of the insurance litigation
and other relevant data, NIST considers it to be premature to exclude
any of the potential hypotheses related to the sequence of events
between the aircraft impact and the collapse of each WTC tower.
Further work is needed to ensure that the results of any analysis
can adequately explain the observed behavior. First, neither tower
collapsed immediately upon aircraft impact. Second, the buildings
collapsed only after fires had burned and advanced through the buildings
for about 55 minutes in the South Tower (WTC 2) and about one hour
and 42 minutes in the North Tower (WTC 1).
Any analysis that suggests rapid
loss of stability or collapse without the need for a sustained fire
would be biased in favor of a critical collapse-initiating role
for structural components damaged by aircraft impact (e.g., columns)
and a lesser role for components weakened by fire (e.g., floor trusses
and connections). Likewise, any analysis that delays loss of stability
to well beyond the observed time-to-collapse for each tower would
be biased in favor of a critical collapse-initiating role for structural
components weakened by fire and a lesser role for components damaged
by the initial impact of aircraft.
Balanced Use of Analytical, Experimental,
and Numerical Tools
NIST is using a balance of analytical,
experimental, and numerical tools to help unravel the extremely
complex physical phenomena associated with the events of September
11, 2001 and to support or refute alternative collapse hypotheses.
Among the key factors that need to
be considered are:
- the variability in the speed, direction,
orientation, and point of impact of each aircraft and the mass
dispersion of the jet fuel following impact;
- the mass of the steel, concrete,
heavy machinery, and non-structural building materials and contents
that shared in absorbing the energy imparted during aircraft impact;
- the effects of gravity loads and
the energy carried by debris fragments in the aircraft impact
analysis;
- the performance of the steel components
and connections, at the high rates of loading during aircraft
impact and at elevated temperatures during subsequent fires, and
the associated failure criteria;
- the performance of the fireproofing
at high temperatures and the extent to which the fireproofing
may have been missing or knocked off during aircraft impact; and
- the growth and spread of fire through
the towers and the resulting temperature of the structural steel
as a function of time and location, including the coupling of
the fire dynamics and thermal-structural response analyses.
In its reconstruction of the thermal
and tenability environment, NIST is taking into account:
- the fire load provided by the building
contents and other sources such as jet fuel and fuel storage tanks;
- the ventilation available for combustion;
and
- the inter-compartment fire growth
through partitions, ceiling/floor systems, and air passages within
the buildings.
NIST is conducting a complementary
experimental effort that provides critical input to its analytical
and numerical work, including the validation of those results. These
studies include:
- the mechanical properties of steel
(columns, spandrels, trusses, truss seats, welds, and fasteners)
at high strain rates to support aircraft impact damage analysis;
- the thermal-insulation properties
of the fireproofing materials and the ability of the fireproofing
materials to withstand shock and impact;
- the mechanical properties of steel
(columns, trusses, truss seats, bolts, welds) at high temperatures
to support the analysis of structural response to fires;
- fire tests to study the floor truss-to-column
connections and the local load-transfer properties of the interface
between the steel truss and the concrete deck in the composite
floor system; and
- fire tests in large compartments
(12 ft x 12 ft x 24 ft) to measure the heat release, distribution,
and heat transfer rate to the compartment gases and steel specimens
(steel truss and columns, both with and without fireproofing)
for validating fire dynamics and thermal-structural analyses,
including the coupling between the two analyses.
NIST is also reviewing previously completed
tests on open-web steel truss systems, including their performance
under gravity loads and fire. The past performance of open-web steel
trusses in fires is being documented using available fire incident
and insurance investigation reports.
Status of Data Collection Efforts:
NIST is basing its review, analysis,
modeling, and testing work for the investigation on a solid foundation
of technical evidence. This requires access to critical data such
as building documents, video and photographic records, emergency
response records, and oral histories in addition to the samples
of steel that have been recovered.
NIST has received excellent cooperation
from a variety of organizations in the discovery phase of its investigation.
It has begun to receive large volumes of documentation from the
Port Authority of New York and New Jersey and its consultants and
contractors; Silverstein Properties and its consultants and contractors;
and the group of companies that insured the WTC towers and their
technical experts. NIST also has begun to receive information from
the Fire Department of New York (FDNY) and the New York City Office
of Emergency Management (OEM).
The above documents and other information
relate to the design, construction, operation, inspection, maintenance,
repair, alterations, emergency response and evacuation of the WTC
complex. They include information such as:
- the original design drawings (structural,
architectural, mechanical, electrical, plumbing) and the original
fabrication and construction drawings for the WTC towers;
- tenant alteration application (TAA)
reports, including drawings and specifications, for the WTC towers
and WTC 7, and associated construction audit reports;
- tenant design standards manuals
for structural, architectural, HVAC, fire protection, plumbing,
electrical, fire alarm, and construction review;
- emergency evacuation procedures
manuals, including fire safety guide;
- operations manuals for the fire
protection system, including sprinklers, standpipes, alarm system
and communication protocols, water and power supply;
- operations manuals for the heating,
ventilating, and air-conditioning systems;
- reports on facility condition surveys
and structural integrity inspections for the WTC towers and WTC
7;
- recent inspection and maintenance
reports for the elevators and escalators in the WTC towers;
- reports on pre-design tests of structural
components including dampers for the WTC towers;
- reports on wind tunnel tests of
the WTC towers and wind speed measurements near the WTC site;
- reports on the 1993 bombing damage
assessment and repairs, and documentation of changes made to the
evacuation system after 1993;
- documents related to the location,
approval, and inspection of fuel tanks in WTC 7;
- documents related to fire rating
and fireproofing of structural steel members in the WTC towers;
- documents related to Port Authority
building and fire code requirements and practices;
- documents related to the lease of
the WTC towers by Silverstein Properties;
- reports prepared by McKinsey and
Company for FDNY and NYPD;
- basic FDNY dispatch data, including
time of dispatch and unit identification; and
- firefighter fatality and injury
data from FDNY.
NIST has a number of requests for materials
that are currently pending with several organizations. They include
those listed above and the New York Police Department (NYPD). NIST
is working with these organizations to gain access to important information,
specifically that related to emergency response and evacuation on
September 11, 2001, including communication and operational records.
The important documents and materials
that have not yet been located and/or provided include:
- the original contract specifications
for the WTC towers that were completed in the early 1970s (the
structural steel and concrete specifications for the WTC towers
have been located);
- the final design drawings used for
construction bid for WTC 7 (NIST has documents dated near the
end of the design cycle but their status relative to the final
drawings is unclear);
- the as-built drawings of the WTC
towers and WTC 7 (NIST has the original contract drawings for
the WTC tower structures that were revised to document
significant changes during construction and early tenant modifications;
NIST also has been offered access to supplementary drawings that
document the majority of the WTC tower structural tenant
modifications);
- the construction logs for the WTC
towers and WTC 7;
- the maintenance records for the
WTC towers and WTC 7;
- documents related to the ability
of the WTC towers to withstand the abnormal load condition of
a Boeing 707 aircraft impact that was considered in the original
design;
- records of the video surveillance
system used for security purposes at the WTC complex;
- fire alarm panel sensors and modules;
and
- photographic or video documentation
of the south face of WTC 7 on September 11, 2001.
The Port Authority and Silverstein Properties
have informed NIST that most of the documents cited above were destroyed
in the collapse of WTC 1, which housed documents for the Port Authority,
and in the collapse of WTC 7 and WTC 1, which housed documents for
Silverstein Properties. As such, those documents are not available
with them. Both organizations have also informed NIST that the video
surveillance records and fire alarm panel modules were destroyed at
the WTC complex and none of those materials were recovered from the
debris.
The Port Authority is trying to locate
the complete set of original contract specifications for the WTC
towers from its contractors and former employees. Silverstein Properties
is trying to locate any as-built drawings, construction logs, and
fire alarm records or remote logs for WTC 7. NIST will continue
to work with the Port Authority’s structural contractor to locate
and obtain documents related to the WTC towers ability to withstand
a Boeing 707 aircraft impact.
The NIST investigation team is reviewing
and analyzing the valuable and voluminous information already in
its possession. As an example, one task involves the creation of
a detailed timeline of the issues related to fireproofing of the
WTC towers. Another task involves using data generated by technical
experts for Silverstein Properties as initial input to the fire
dynamics simulation. This includes the timeline of fire events on
the external faces of the WTC towers and the state of initial damage
in these buildings.
Selection of Experts in Occupant
Behavior and Evacuation:
NIST has selected three world-class
experts as contractors to augment its investigation team in the
area of occupant behavior and evacuation. Chosen from a competitive
contract solicitation, these individuals bring extensive expertise,
including strengths in psychology and sociology, and experience
in the use of state-of-the-art sampling methods and in field data
collection strategies. These individuals are:
- Dr. Norman Groner, an independent
consultant from California. He has a doctorate in psychology and
25 years experience in the human factors field, much of it in
the area of cognitive factors related to fire safety and emergency
planning. He also has expertise and experience in interviewing
techniques. He is coordinator for the independent World Trade
Center Evacuation Initiative.
- Dr. Dennis Mileti, Director of the
National Hazards Research and Applications Information Center
within the Institute of Behavioral Science at the University of
Colorado at Boulder. He has a doctorate in sociology and 28 years
experience in risk communication and social psychology of public
action. He also has expertise in statistical sampling methods
and questionnaire design and methods.
- Dr. Guylene Proulx, Research Officer
from the Institute for Research in Construction at the National
Research Council of Canada. She has a doctorate in environmental
psychology and 15 years experience in evacuation and emergency
communications. She also has experience in post-fire egress analysis
using questionnaires and interviews. She studied the evacuation
of the WTC towers following the 1993 bombing incident.
Systematic Data Collection Methodology
for Evacuation and Emergency Response:
NIST’s study of the World Trade Center
evacuation and emergency response requires a systematic collection
of first-hand data from survivors, families of victims, and others
with operational or command authority on September 11, 2001.
The data accumulated from this effort
will be used to evaluate the role of occupant behavior, and evacuation
and emergency response technologies and practices for tall buildings,
including decision-making and situation awareness, time-constrained
evacuation strategies, communications, fire protection and firefighting,
role of fire wardens and fire safety directors, and issues concerning
people with disabilities. Additionally, observations of fire and
smoke conditions or structural damage from within the building will
be sought.
NIST will soon release a solicitation
and a white paper describing a multi-disciplinary, three-pronged
data collection methodology that includes face-to-face interviews,
paper and web-based questionnaires, and focus group interviews.
This multi-faceted approach based on well-established statistical
sampling techniques is designed to increase confidence in the findings,
enable systematic hypothesis testing and generalization, probe specific
information of particular value to the investigation, and enhance
memory recall and accuracy.
The data collection will be conducted
by a yet-to-be-selected contractor and is planned to begin as soon
as the necessary pre-work is complete. This includes preparation
of the questionnaire and detailed survey strategy, training of contractor
staff, and approval by NIST and the appropriate Institutional Review
Board (IRB) to assure compliance with federal requirements for the
protection of human subjects. NIST will use established procedures
to review all survey and interview questions, data collection methods,
and safeguards for maintaining privacy and confidentiality of all
instruments before proceeding with these critical data collection
efforts.
The white paper identifies specific
populations and the size of samples to be included in the data collection
effort. The exact numbers and populations may be modified to better
suit the investigation as additional details of the methodology
are finalized by NIST with the panel of experts and the yet-to-be-chosen
contractor.
NIST plans to perform up to 600 face-to-face
interviews of occupants. The sample population will include people
near the floors of impact in the WTC towers, in elevators and lobbies,
and from WTC 7; those with disabilities; floor wardens, fire safety
directors, and others with responsibility for safety and egress;
and family members of victims who called from the WTC towers.
The interview protocol is planned
to include four steps:
- an unimpeded open-ended narrative
account where the participant recounts his or her “story” chronologically
to the interviewer;
- a structured narrative account where
the participant reviews the story in cooperation with the interviewer
to tabulate the logical sequence of actions by identifying cues
that initiate an action, the action itself, and the reason for
taking the action;
- probing for specific information
of particular value to the investigation using open-ended questions;
and
- close-ended questionnaire items
at the end of the interview session to determine whether there
are systematic differences among the various data collection approaches.
NIST also plans to conduct face-to-face
interviews with up to 150 first responders from FDNY, NYPD,
the Port Authority Police Department (PAPD), and the firm that provided
security to the WTC complex. The FDNY population will be stratified
among firefighters, company officers, and operational command officers.
A similar stratification will be considered for other first responder
organizations.
NIST plans to collect data via approximately
800 returned web-based questionnaires from a whole building stratification
of the WTC towers and WTC 7. The population will be selected randomly
from eight sampling strata. The towers will be segmented into three
strata each comprising an equal number of floors representing the
top, middle, and lower third of the buildings. WTC 7 will be divided
into two strata with an equal number of floors representing the top
and bottom half of the building.
NIST also plans to collect data via
approximately 450 returned mailed questionnaires from a selected-floors
stratification of the WTC towers and WTC 7. Three floors will be
selected from each of the WTC towers – one from each of three strata
with an equal number of floors below the floors-of-impact. Two floors
will be selected from WTC 7 – one from each of two strata with an
equal number of floors.
Focus groups will elicit accurate
group representations of specific events or themes (e.g., the experience
of unique types of people in unique places in the buildings). Occupant
focus groups in approximately five specialized categories will be
conducted with between five to 10 participants per group. Examples
of such specialized groups include:
- people with special responsibilities
(floor wardens, fire safety directors, etc);
- people on a specific floor such
as the 78th floor of WTC 2 and the 91st floor of WTC 1 – just
below impact;
- people in the lobbies of WTC 1 and
WTC 2; and
- people who escaped from above the
floors of impact in the WTC towers.
First responders will constitute a second
set of focus groups, and will include FDNY, NYPD, and PAPD. Ten first
responder focus groups will be conducted with five participants per
group, the typical size of an operating unit such as a fire department
company.
Status of Steel and its Analysis:
NIST has in its possession over 200
pieces of World Trade Center steel. The vast majority of the pieces
are of significant size and include perimeter prefabricated column-spandrel
elements, rectangular box beams, wide flange sections, truss sections,
and channels. NIST also has in its possession several smaller pieces,
such as bolts. NIST has cataloged most of the pieces and is in the
process of completing a database with photographic records and member
markings. In addition, NIST is reviewing additional steel and other
artifacts stored by the Port Authority at JFK airport to identify
pieces of interest to its investigation.
Based on a correlation of information
on the grades of steel used in the WTC towers and identifying marks
on the recovered steel, it has been possible to locate nine of the
12 steel strengths used for the perimeter columns and nine of the
11 steel strengths used for the spandrel beams. An ongoing effort
is seeking to locate pieces of the remaining steel grades.
Also, approximately 250 chemical
analyses have been conducted. The analyses indicate that the majority
of the perimeter columns were made of WEL-TEN 60, 70, or 80 steels.
These columns were fabricated from steel obtained from Yawata Steel,
now Nippon Steel.
Nippon Steel representatives have
offered to cooperate fully in assisting NIST and have begun to provide
useful information to the investigation, including the proprietary
specifications for their steels. So far, tests by NIST indicate
that the higher strength steels are micro-alloyed steels (similar
to modern pipeline steels) or CrMo steels that would meet U.S. specifications
for heat resisting steels. Metallographic analysis shows a range
of structures, including coarse and fine ferrite/pearlite structures
and bainite and/or tempered martensite.
NIST also has identified the fabricators
of the steel floor trusses (Laclede Steel) and has met with representatives
of the firm. The firm has been fully cooperative in providing information
on the steels used and the design and tests of the trusses. Laclede
documents show that the trusses were fabricated with ASTM A36 and
ASTM A242 or A441 steels and that Laclede’s A36 steel was routinely
made at yield strengths of 50-55 ksi (well in excess of the 36 ksi
yield strength in the specification). The other two types of steel
have minimum yield strengths of 50 ksi.
NIST has characterized the effects
of high temperature on the primer paint used on the perimeter columns.
This work indicates that microscopic “mud-cracking” of the paint
occurs at approximately 250 ºC. At this temperature there would
be little or no visible discoloration or damage to the primer paint.
The paint becomes friable and can easily crumble or become powdery
at a temperature of about 700 ºC. At this temperature there would
be visible discoloration and damage to the primer paint (and the
steel would likely have softened significantly). Thus steel that
shows little visible evidence of discoloration or damage to the
primer paint still could have experienced high temperature levels
due to the fires. NIST is continuing to investigate other methods
to measure the temperature excursions of the steel.
Status of Photographic and Video
Image Collection and Analysis:
Photographic and video images of
damage and fires in the WTC towers and WTC 7 are critical to developing
guidance on the initial conditions for modeling the fires, the rates
of fire spread through the buildings, and the floors on which the
structural collapse may have begun.
The NIST investigation team continues
to seek photographic and video images that could help it better
document the initial damage and subsequent fire growth in the WTC
towers and WTC 7. NIST is especially interested in WTC 7 and views
from the South and West faces of the WTC Towers.
Also, there continues to be a dearth
of photos of the south side of WTC 7. It has been suggested that
it is the south side of WTC 7 that was struck by debris from the
collapse of WTC 1, and that debris may have ignited the fires that
led to the ultimate collapse of WTC 7. Some eyewitness accounts
describe fires on many floors of WTC 7 while photos show only localized
fires on other sides of the building.
Those who are aware of or in possession
of such materials are encouraged to contact NIST by electronic mail
(wtc@nist.gov), facsimile (301-975-6122),
or regular mail at WTC Technical Information Repository, NIST, 100
Bureau Drive Stop 8610, Gaithersburg, MD 20899-8610.
NIST has compiled a preliminary searchable
database of over 1,900 still photos that were obtained from 55 private
or independent photographers. The collection is expected to grow
to multiples of the current size before it is complete. The photos
are organized by major traits such as buildings shown, location
and direction of shot, faces of towers that can be seen, date and
time recorded, time uncertainty, rough measure of distance, photographer,
copyright information, and original source of material. Also special
characteristics are identified such as “collapse”, “street scene”,
“debris”, “fireball”, “thermal plume”, “people and location”, and
“presence of first responders”.
NIST also has collected copies of
several video recordings. Efforts to gather photos or videos from
media sources, especially unpublished photos and non-broadcast video
footage, are in progress. NIST believes that the public and media
could significantly assist in this public safety investigation by
sharing unpublished photos and video footage. NIST will be following
up with specific news media organizations and encourages them to
contact us about photos and videos they are willing to provide to
the investigation.
NIST has begun to characterize and
analyze the photographic and video evidence already in its possession.
Initial analyses suggest that close-up photographs of the aircraft
impact on each of the towers can be used to determine important
parameters such as exactly where each aircraft struck and its orientation,
as well as the actual in-flight deformation of the loaded wings
of the aircraft as it entered the buildings.
It is also noticeable from these
external observations that the fires grew, moved, and ebbed (not
necessarily in that order) during the period between the aircraft
impact and the collapse of the towers. Further refinement of these
observations will be pivotal in estimating where the thermal conditions
presented significant threats to the occupants and the structural
components of the towers. In addition, NIST has identified some
images that could be helpful in better understanding the possible
collapse mechanisms for the towers.
NIST is still in the early stages
of its effort to obtain, catalog, and analyze photographic and video
evidence and will share the analysis results broadly once the work
is complete.
Status of Contracting Plans:
NIST has assembled a seasoned world-class
team to carry out the investigation. This team has the needed technical
expertise as well as experience from significant prior investigations.
Over two dozen NIST experts will be involved over the course of
the investigation. In addition, NIST is augmenting its in-house
staff with external experts in its project teams as contractors.
The bulk of these contract solicitations will appear in the coming
weeks. A few have already appeared and those solicitations are now
closed. Contracts have been awarded for one solicitation.
NIST will rely on full and open competition
as the preferred contracting process in most cases. Solicitations
for the investigation will be posted on the NIST WTC web site at
http://wtc.nist.gov. They will
be based on statements of work prepared by NIST as a result of a
careful and deliberate process to identify and define in detail
the specific technical areas in which external expertise is needed
to carry out each investigation project. The final investigation
plan released August 21, 2002 with descriptions of the eight component
projects is available at the above referenced web site. By going
to that web site, potential offerors may request to be added to
a mailing list that notifies them of new solicitation postings and
awards.
Competitive proposals will be reviewed
on a best value basis considering the technical and management proposal,
business proposal, and cost proposal. Offerors will be required
to disclose potential organizational conflicts of interest and to
suggest an acceptable mitigation plan for dealing with these potential
conflicts where needed. The solicitation will specify the technical
evaluation factors. All proposals will undergo a review and selection
process consistent with all federal procurement laws and acquisition
regulations.
Information Exchange with the New
York City Building Code Task Force:
On May 17, 2002, NIST representatives
met with senior officials of the New York City Department of Buildings
and with the executive committee of its World Trade Center Building
Code Task Force. At the meeting it was agreed that NIST and the
City would maintain communication and exchange information relative
to their respective activities in areas of mutual interest.
NIST representatives subsequently
participated in the August 13, 2002 forum organized by the Building
Code Task Force. Also, the Federal Emergency Management Agency (FEMA)
provided city officials with a copy of the code comparison study
completed earlier this year by NIST for FEMA. That study compared:
- the earthquake provisions of the
2001 New York City Building Code with the 1997 National Earthquake
Hazards Reduction Program (NEHRP) Recommended Provisions;
- the wind provisions of the 2001
New York City Building Code with the American Society of Civil
Engineers standard ASCE 7-98;
- the fire provisions of the 2001
New York City Building Code with the national model codes issued
by the International Code Council (2000 International Building
Code) and the National Fire Protection Association (2000 Life
Safety Code); and
- the fire provisions of the 2001
New York City Fire Code with the 2000 International Fire Code
and the 2000 NFPA Fire Prevention Code.
On November 26, 2002, New York City
officials briefed NIST representatives on the draft recommendations
of its Building Code Task Force. NIST representatives informed City
officials on the status of its investigation and broader response
plan and discussed ways in which NIST could support the city’s ongoing
activities.
Update on WTC Research and Development
Program:
The WTC research and development
(R&D) program will provide the technical basis for specific improvements
to building and fire codes, standards, and practices, particularly
to facilitate implementation of recommendations resulting from the
WTC investigation. The program involves experimentation, analysis,
verification and demonstration of improved tools to guide the building
and fire safety industries, and feeds into the voluntary consensus
process that is used to develop building and fire codes and standards
in the United States.
The R&D program addresses work in
critical areas such as structural fire safety and the mitigation
of progressive collapse, building vulnerability reduction from chemical
and biological attack, equipment standards for first responders,
and human behavior, emergency response, and mobility. This includes
experimental validation of computer analysis tools. The rate at
which the recommendations of the investigation can be implemented
will depend on the level of funding available to the R&D program.
Initial efforts have focused on developing detailed plans for the
multi-year R&D effort through workshops and partnering arrangements
as highlighted below.
NIST recently released a report (NISTIR
6890, September 2002) summarizing the proceedings of an international
workshop held earlier this year at NIST on “Fire Resistance Determination
and Performance Prediction Research Needs.” The specific objectives
of the workshop were:
- to review current practices for
achieving fire resistance;
- to explore the potential of fire
dynamics simulations and structural behavior predictions at elevated
temperatures;
- to identify new fire resistance
options stimulated by advances in materials science;
- to identify applications and needs
in advanced computational methods; and
- to identify applications and needs
for emerging measurement, instrumentation, and test methods.
The results of this workshop, attended
by nearly 70 international experts, will guide the R&D effort and
contribute to NIST’s planning efforts to establish the needs for
a possible National Structural Fire Resistance Laboratory.
In addition, NIST is working through
international organizations to address the global needs for improvements
to structural fire safety standards, codes, and practices. Thirteen
fire laboratories across the globe have already indicated their
interest in such an effort. They include laboratories in the United
Kingdom, Sweden, France, Canada, Poland, Australia, New Zealand,
Japan, China, and Taiwan.
On July 10-12, 2002, NIST sponsored
a workshop to develop a national R&D plan to provide the basis for
national codes and standards for design to prevent progressive collapse.
The proceedings of the workshop, attended by nearly 70 industry
leaders, are in the process of being finalized and will be available
in the near future.
NIST also has developed a collaborative
effort with the Risk Management and Decision Processes Center at
the Wharton School of Business to develop cost-effectiveness tools
for evaluating the management of terrorist risks for buildings,
industrial facilities, and infrastructure. Risk mitigation strategies
are based on enhanced building practices, risk transfer through
insurance or self-insurance, and economic incentives such as tax
write-offs, insurance premium reductions, and public-private cost-sharing
arrangements. The tools will provide decision-makers with the basis
for generating a disaster mitigation plan.
Update on WTC Dissemination and
Technical Assistance Program (DTAP):
The industry-led dissemination and
technical assistance program (DTAP) is designed to engage leaders
of the construction and building community in assuring timely implementation
of proposed changes to practices, standards, and codes. It also
will provide technical guidance and tools to better prepare facility
owners, contractors, architects, engineers, emergency responders,
and regulatory authorities to respond to future disasters. The DTAP
is crucial for timely adoption and widespread use of proposed changes
to practice, standards, and codes resulting from the WTC investigation
and the R&D program.
NIST was a sponsor of the September
23-24, 2002 workshop on Critical Infrastructure Protection Priorities
organized by a group of industry associations and federal agencies
that was led by the Civil Engineering Research Foundation and the
White House Office of Science and Technology Policy.
Over 90 senior industry leaders and
government officials exchanged information on the security of the
built environment and worked to address key topics of concern, raised
in publications such as Making the Nation Safer by the National
Research Council. From 17 prospectuses that were developed, four
were assigned top priorities. They are to develop and implement:
- guidance on risk assessment;
- recommended practices for addressing
terrorist threats for buildings;
- facility knowledge systems for first
responders; and
- a collaborative infrastructure security
matrix.
NIST also was a sponsor of a November
13-15, 2002 Capital Projects Technology Roadmap Workshop organized
by the non-profit industry-led FIATECH Consortium. A key focus of
this workshop was to update a recently developed industry roadmap
to assure coverage of homeland security issues and to develop specific
project plans for implementing R&D to achieve the goals defined
in the roadmap. The workshop drew representatives from a range of
construction interests, including industry, research, academia,
and regulators.
In addition, NIST has funded an effort
to benchmark homeland security construction practices that is led
by the Construction Industry Institute, a non-profit research organization
representing the nation’s top 100 facility owners and contractors.
The study will focus on chemical
manufacturing, oil production and refining, natural gas processing
and distribution, power generation and distribution, water treatment,
and possibly other critical industries needed to support the nation’s
infrastructure. Information collected as part of a series of regional
workshops and field site visits will be used to:
- establish a basis for identifying
best practices related to the security of infrastructure capital
facilities; and
- provide the basis for assessing
the impacts of these practices on key project outcomes of cost,
schedule, and safety.
