Statement of
Dr. Arden L. Bement, Jr.

 National Institute of Standards and Technology
United States Department of Commerce

Before the

Committee on Science
House of Representatives
United States Congress

“Learning from 9/11: Understanding the Collapse of the
World Trade Center”

March 6, 2002


    Good afternoon Chairman Boehlert, Ranking Member
Hall, and Members of the Committee.  I want to thank
you for this opportunity to testify on the
investigation into the collapse of the World Trade
Center Towers.  The tragedy that the United States
experienced on September 11, 2001, was unprecedented
when compared with any prior accident, natural
disaster, or terrorist/war attack.  The collapse of
the twin World Trade Center towers was the worst
building disaster in human history.  Engineers,
emergency responders, and the nation did not
anticipate, and were largely unprepared for, such a
catastrophe.  Among other national needs, these events
highlight the following technical priorities:
To establish the probable technical causes of the
collapses and derive the lessons to be learned;
To develop and disseminate immediate guidance and
tools to assess and reduce future vulnerabilities; and

To produce the technical basis upon which
cost-effective changes to national practices and
standards can be developed.
    Shortly after the attacks on the World Trade
Center, NIST’s building and fire researchers began
assisting federal and local agencies in many ways to
investigate the spread of fire through the buildings
and their subsequent collapse.  Our researchers used
previously developed models along with preliminary
information from videos of the attack and other
sources to simulate the spread of fire and smoke in
the buildings.  At the request of the Federal
Emergency Management Agency (FEMA), NIST conducted a
comparison and analysis of the current building and
fire codes of New York City with national codes, and
we contributed to the Army Corps of Engineers’ study
of the structural and fire damage to the Pentagon.
In addition, NIST experts participated in the initial
assessment of the collapse conducted by the American
Society of Civil Engineers (ASCE) Coalition that
comprised a Building Performance Assessment Team
(BPAT) funded by FEMA.  The ASCE Coalition Team also
included professional members of the Society of Fire
Protection Engineers (SFPE), the National Fire
Protection Association (NFPA), the American Institute
of Steel Construction (AISC), and the Structural
Engineers Association of New York (SEAoNY). NIST is
lending its expertise in structural disasters to ASCE
and the Structural Engineers Association of New York
(SEAoNY) to store WTC steel at its Gaithersburg, MD,
headquarters for further scientific study.
    However, more needs to be done.  A growing number
of technical experts, industry leaders, and families
of victims are pressing for a broad-based Federal
investigation to study the building construction, the
integrity of the materials used, and all the technical
conditions that combined to cause the building
disaster at the World Trade Center [Witness would like
to submit for the record, letters received supporting
a federal investigation].  NIST has begun working
informally with a coalition of organizations ­
representing key industry, standards, codes, and
professional groups ­ in an effort to launch a
comprehensive public-private response program that
includes such an investigation.  NIST is also working
very closely with FEMA, since an in-depth technical
investigation would go well beyond the scope of the
building performance assessments conducted by FEMA
following major disasters.   The implementation of the
results of such an investigation would be critical to
restore public confidence in the safety of tall
buildings nationwide, enhance the safety of fire and
emergency responders, and better protect people and
property in the future.  To cite one example, the
February 4th issue of “Crain’s New York Business”
reports that an increasing number of tenants are
leaving the Empire State Building, which is again the
tallest building in New York City, because of fears of
another terrorist attack.  Anecdotal evidence also
suggests that building vacancy rates have doubled in
Manhattan, despite the 15 million square feet of space
that was lost on September 11th.
    NIST has received policy approval from the
Secretary of Commerce to initiate and, after
consultation with local officials, to conduct an
independent and comprehensive “National Building and
Fire Safety Investigation of the World Trade Center
Disaster” under NIST’s existing legislative
authorities (15 U.S.C. 281a).  Among Federal
laboratories, NIST is uniquely qualified to conduct
such a comprehensive investigation.  The Building and
Fire Research Laboratory is the foremost fire research
laboratory in the United States, and through the
National Earthquake Hazards Reduction Program (NEHRP)
NIST is the principal agency for research and
development to improve building codes and standards.
NIST has extensive experience and expertise in
conducting disaster investigations following
structural/construction failures, fires, earthquakes,
hurricanes, and tornadoes.  These have included the
well-known investigations into the 1981 collapse of a
walkway in the Kansas City Hyatt Regency Hotel, the
1986 Dupont Plaza Hotel fire in San Juan Puerto Rico,
the 1994 Northridge earthquake collapses, and the 1995
Kobe, Japan earthquake building collapses, to name
just a few.  In compliance with statutory requirements
NIST has already consulted with local authorities in
New York, including the Port Authority of NY & NJ, the
Mayor’s Office of Emergency Management, the New York
City Department of Design and Construction, and the
Fire Department of New York.  These organizations have
expressed support for NIST and agreed to cooperate in
it’s investigation.

    The proposed investigation would involve
world-class experts from industry, academia, and other
laboratories to complement NIST’s excellent in-house
technical expertise.  Supplementing the outstanding
work done through the building performance assessment
team initially assembled through FEMA, NIST would
delve deeper into the factors related to the collapse.
 NIST would use the results of the soon to be released
ASCE Coalition team’s study as a valuable source of
input into the investigation.  The objectives of the
NIST investigation would be to determine technically:

Why and how the World Trade Center buildings collapsed
following the impacts of the planes;
Why the injuries were so high or low depending on
location, including all technical aspects of fire
protection, response, evacuation, and occupant
behavior and emergency response;
Whether or not state-of-the-art procedures and
practices were used in the design, construction,
operation, and maintenance of the World Trade Center
Buildings; and
Whether there are new technologies or procedures that
should be employed in the future to reduce the
potential risks of such a collapse.
    The NIST investigation would focus primarily on
World Trade Center Buildings 1 and 2 (the Twin Towers)
for several reasons.  First, the collapse of the
Towers was the triggering event that caused much of
the collateral damage to the adjacent properties.
Second, many structural and fire protection design
features and construction details found in the Towers
are widely used in the building construction industry.
 Third, to study procedures and practices used to
assess the safety of innovative structural systems and
building designs not covered by existing building
codes or prior in-use experience as was the case of
the twin towers, and whether such practices are
adequate to detect and remedy inherent
vulnerabilities.  Fourth, to study procedures and
practices used to provide adequate structural reserve
capacity to resist abnormal loads (e.g. blast,
explosion, impact due to aircraft or flying debris
from tornadoes, accidental fires, and faulty design
and construction), especially those that can be
anticipated prior to construction (e.g. impact of a
Boeing 707).  Fifth, the Twin Towers would provide the
opportunity to study the effectiveness of fire
protection and firefighting technologies and practices
for tall buildings, including emergency mobility and
egress, and communication systems.  And lastly, the
analytical tools used in these investigations would be
experimentally verified and widely applicable to other
building types. Besides the Towers, the investigation
would possibly consider examining WTC Building 7,
which collapsed later in the day.
    NIST would use an open and inclusive process in
formulating its work plan for the investigation.  This
would involve the participation of technical experts
from industry, academia, and other laboratories as
well as liaison with federal, state, and local
authorities. NIST would expect to complete its
investigation and issue a final report in 24 months.

    The results of the proposed investigation would be
extremely valuable in establishing the probable
technical causes of the disaster and deriving the
lessons to be learned, but it would be meaningless
unless we take the knowledge gained and put it to
practical use.  That is why NIST, in partnership with
FEMA and a number of private sector organizations, has
developed a broader response program.  This broader
program would address critically and urgently needed
improvements to national building and fire standards,
codes, and practices that have begun to be recognized
in recent years. The events of September 11th have
brought even more focus and priority to this already
important issue.

    The goal of this broader program would be to
produce cost-effective retrofit and design measures
and operational guidance for building owners and
emergency responders.  The program would develop and
disseminate guidance and tools to assess, and produce
the technical basis and recommendations for
cost-effective changes to reduce vulnerabilities.

    Over the course of the proposed investigation and
broader program there would be a number of short-term
and interim work products that would provide guidance,
tools, and technical assistance to better prepare
facility owners, contractors, designers, and emergency
personnel for future disasters.  Some of these
products, based on prior NIST work, would be
disseminated broadly as soon as possible.  Others that
need further refinement would be disseminated within a
year, and the rest after the completion of the
investigation.  I would like to note that the
President’s FY 2003 budget request for NIST contains a
$2 million funding increase, which will go towards
this effort and related research.

    Let me now give you three examples of work that
would be accomplished through this broader program.

    First, fire played a critical and visible role in
the collapse of the WTC buildings and contributed to
damage to the Pentagon buildings.  Current building
design practice does not consider fire as a design
condition.  Instead, structural fire endurance ratings
are prescribed in building codes using standard tests
on individual components.  The current testing
standards are based on work carried out at NIST in the
1920s.  They do not represent real fire hazards in
modern buildings.  They also do not consider the fire
performance of structural connections or of the
structural system as a whole, or the multiple
performance demands on fire proofing materials.  NIST
now has the capability to simulate building fires on
the computer to explain critical events and outcomes
to an extent previously not possible.  The proposed
work would expand on this core competence in
computational methods, and adapt measurement
techniques and test methods to support the prediction
of performance of building materials, products,
structural elements, and systems up to the point of
the collapse of a tall building due to fire.  In
short, NIST would provide the technical basis and
guidance for fire safety design and retrofit of
structures, the predictive tools and test methods for
fire resistance determination, and the performance
criteria for fireproofing materials.  In addition,
NIST proposes to develop guidance and retrofit
technologies to enhance building egress in
emergencies, practical tools and guidance to enhance
the safety and effectiveness of fire and emergency
responders, and improved models of occupant behavior
and response to enhance evacuation and communication
in emergencies.

    Second, progressive collapse ­ which refers to the
spread of failure by a chain reaction that is
disproportionate to the triggering event ­ was also
responsible for the extraordinary number of deaths in
the 1995 bombing of the federal building in Oklahoma
City.  Yet, the United States has not developed
standards, codes, and practices to assess and reduce
this vulnerability.  Adding to the problem for modern
structures is their smaller margin of safety ­ and the
reserve capacity to accommodate abnormal loads ­ due
to increased efficiency in the use of building
materials and refinements in analysis techniques.  The
work carried out at NIST in the early 1970s continues
to provide the basis for the extremely limited
guidance that is available in current United States
standards.  NIST would develop cost-effective
solutions to reduce building vulnerability to
progressive collapse using a multi-hazard approach
that exploits synergies in resisting extreme loads
from blast, impact, earthquakes, and fires.

    Third, vulnerability reduction of commercial and
institutional buildings and facilities. The
overwhelming majority of buildings in public use today
are vulnerable to terrorist attack on a number of
fronts. Most lack state of the art sensing and
information management systems.  Few have electronic
representations of the building documents or models,
and standards do not exist for such representations.
Most are not protected against chemical, biological,
and radiological (CBR) threats.  While efforts are
underway to protect military buildings through
Department of Defense's “immune buildings” program,
there are no standards and practices for civilian
buildings.  NIST proposes to work with the DoD to
develop guidelines and advanced technologies to reduce
the vulnerability of such buildings to CBR attacks.
NIST also proposes to work with industry to develop
standards for building information models and
information exchange, and practicable tools for
helping building owners make reasoned economic choices
in reducing the vulnerabilities of their buildings.

    The final program element supports a
construction-industry-led roadmapping effort to
reflect changed priorities for development and
deployment of safety and security standards,
technology, and practices.  It would also support the
delivery and dissemination of practical guidance,
tools, and technical assistance to better prepare
facility owners, contractors, designers, and emergency
personnel to respond to future disasters and to speed
economic recovery within the industry following
disasters.  The effort would complement and support
parallel efforts of technical organizations to improve
standards, codes, and practices.

    In conclusion, I believe it is imperative for the
U.S. to learn from the worst-ever building disasters
in human history and take aggressive remedial action
to minimize future losses.  As the events of September
11 demonstrated, the very stability of U.S. commerce
and our economy depends upon major buildings and
critical facilities that provide a key part of our
Nation’s physical infrastructure.  In the wake of
September 11th, the private sector’s willingness to
take necessary corrective action to strengthen
building codes and standards is extraordinarily
strong.  So with the envisioned Federal technical
leadership and partners from the private sector,
changes can be made to minimize the likelihood and
consequences of future disasters.  Thank you, Mr.
Chairman.  I would be happy to take questions from the