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NIST's Investigation of the Sept. 11 World Trade Center Disaster

What is NIST?
The National Institute of Standards and Technology (NIST) is an agency of the Commerce Department’s Technology Administration. NIST develops and promotes measurement, standards, and technology to enhance productivity, facilitate trade, and improve the quality of life.

What are the goals of NIST’s investigation into the collapse of the World Trade Center buildings?
The goals are to investigate the building construction, the materials used, and the technical conditions that contributed to the outcome of the World Trade Center (WTC) disaster. The investigation will 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;
  • revisions to building and fire codes, standards, and practices; and
  • improved public safety.

What are the main objectives of the investigation?
The primary objectives of the NIST-led technical investigation of the World Trade Center disaster are to determine:

  • why and how the World Trade Center buildings 1, 2, and 7 collapsed after the initial impact of the aircraft;
  • why the injuries and fatalities were so low or high depending on location (by studying all technical aspects of fire protection, evacuation,
    and occupant behavior and emergency response);
  • the procedures and practices that were used in the design, construction, operation, and maintenance of the World Trade Center Buildings; and
  • which building and fire codes, standards, and practices warrant revision and are still in use.

Why is NIST doing this investigation?
NIST scientists and engineers are world-renowned experts in analyzing a building’s failure and determining the most probable technical cause. Since NIST is not a regulatory agency and does not issue building standards or codes, the institute is viewed as a neutral, “third party” investigator.

Additionally, under the National Construction Safety Team Act, signed into law in October 2002, NIST is authorized to investigate major building failures in the United States. The NIST investigations will establish the likely technical causes of the building failure and evaluate the technical aspects of emergency response and evacuation procedures in the wake of such failures. The goal is to recommend improvements to the way in which buildings are designed, constructed, maintained, and used.

In addition to the investigation into the collapse of the WTC buildings, is NIST conducting related research or programs?
The investigation is part of a broader NIST response plan to the World Trade Center disaster. In addition to the investigation, NIST also is concurrently conducting two related programs:

  • a multiyear research and development program to provide the technical basis for improved building and fire codes, standards, and practices; and
  • an industry-led dissemination and technical assistance program that will provide practical guidance and tools to better prepare facility owners, contractors, designers, and emergency personnel to respond to future disasters.

Will the results of the investigation lead to reforms in building and fire safety codes, standards, and practices?

NIST research typically provides the technical basis for new and improved standards, codes, and practices. NIST will actively work with organizations and bodies designed to make appropriate changes to ensure that results from the investigation are put to use. In this context, it is valuable for NIST to stay in contact with and provide support to such groups. For example, NIST and the New York City Building Code Task Force—whose areas of focus closely parallel the main areas being addressed in the NIST investigation and response plan—will work together as NIST moves forward with its response plan and New York City addresses its immediate and long-term building code needs.

Will the results of the investigation help prevent future disasters?

The NIST investigation will be valuable in establishing the probable technical causes of the disaster after aircraft impact, replacing speculative observations with objective and fact-based findings, deriving instructive information from the disaster, and identifying needed improvements to building and fire standards, codes, and practices and to the safety of tall buildings nationwide. Implementation of the results of the NIST investigation—in conjunction with those of the research and development and dissemination and technical assistance elements of the NIST response plan—will help restore public confidence by making tall buildings safer nationwide, enhance the effectiveness and safety of fire and emergency responders, and better protect building occupants and property in the future.

The results of the NIST investigation also will support and guide future work to develop and disseminate guidance and tools, assess and reduce vulnerabilities, and produce the technical basis for cost-effective changes in national practices and standards. A private-sector coalition—representing key industry, standards, codes, and professional organizations—has worked with NIST to establish the response plan to meet these longer-term needs. The goal of the longer-term program is to produce cost-effective retrofit and design measures and operational guidance for building owners and emergency responders.

How long is the investigation expected to take?

NIST’s investigation of the technical conditions that contributed to the outcome of the World Trade Center disaster on Sept. 11, 2001, started in August 2002 and will culminate with the release of a draft final report in December 2004.

What are the phases that make up the investigation?

The technical approach of the NIST investigation includes the following phases over a 24-month period:

  • identification of technical issues and major hypotheses requiring investigation;
  • data collection;
  • analysis and comparison of building and fire codes and practices;
  • collection and analysis of forensic evidence;
  • modeling, simulation, and scenario analysis;
  • testing to re-create scenarios and failure mechanisms;
  • technical findings and recommendations; and
  • dissemination and deployment of findings.

What are the specific technical projects?

The NIST investigation plan includes eight projects that provide the focus for the technical work. These are:

  • analysis of building and fire codes and practices;
  • baseline structural performance and aircraft impact damage prediction;
  • forensic analysis of structural steel;
  • investigation of active fire protection systems;
  • prediction of the thermal and tenability environment;
  • structural fire response and collapse;
  • occupant behavior, egress, and emergency communications; and
  • fire service technologies and guidelines.

What useful information is NIST deriving from the investigation?

NIST is deriving useful information in several different areas from its investigation of WTC Buildings 1, 2, and 7, including structural fire protection, life safety, and engineering practice. For example, NIST is gaining a better understanding of:

  • the dynamics of building fires and the collapse vulnerability of buildings to fires;
  • methods for fire safety design and retrofit of structures;
  • the behavior of fireproofing materials, connections, and weldments, and open-web steel trusses;
  • collapse mechanisms and the role of pivotal components such as transfer girders and floor diaphragms;
  • firefighting and evacuation technologies and practices for tall buildings;
  • controlling fire spread in buildings with large, open floor plans;
  • command, control, and communication systems for fire service responders;
  • technical evaluation processes and practices used to assure safety when innovative systems are planned; and
  • margin of safety and structural redundancy to accommodate abnormal loads.

How is the investigation being funded?

The agency received $16 million for the investigation in September 2002 from the FY 2002 supplemental appropriation. NIST redirected $3.4 million in fiscal year 2002 to begin a three-part plan in response to the WTC disaster. The FY 2003 appropriation included an increase of $3 million for related research and development.

The President's FY 2005 budget request of $9 million (including a $4 million increase) focuses on using the results of the World Trade Center investigation to provide the technical basis for improving standards, technology, and practices for building construction and for the safety of emergency first responders.

Is NIST consulting with outside experts?

NIST has marshaled world-class technical expertise from both within and outside the agency. External experts have been drawn from academia, practice, and government, and used on an as-needed basis in various phases of the investigation.

Does the investigation include an examination of the “human” element?

NIST is striving to study the disaster holistically, paying particular attention to the interplay among the building, the occupants, and the emergency responders. To determine the behavior and fate of occupants and responders—both those who survived and those who did not—NIST collected and is now analyzing information on occupant behavior, human factors, egress, and emergency communications in World Trade Center Buildings 1, 2, and 7, to evaluate the performance of the evacuation system on Sept. 11, 2001.

The data are being analyzed to study the movement of people during the evacuations, decision-making and situation awareness, and issues concerning persons with disabilities.

What is the National Construction Safety Team Advisory Committee?

The National Construction Safety Team (NCST) Advisory Committee advises the NIST director on carrying out investigations of building failures conducted under the authorities of the NCST Act, which became law in October 2002. That includes providing advice on the composition and function of investigation teams and reviewing procedures and reports.

Who is on the NCST Advisory Committee?

Nine prominent building and fire experts have been appointed to serve on the National Construction Safety Team (NCST) Advisory Committee. They are:

  • John M. Barsom, president, Barsom Consulting, Ltd., Pittsburgh, Pa.;
  • David S. Collins, president, The Preview Group Inc., Cincinnati, Ohio;
  • Glenn P. Corbett, professor, public management-fire science, John Jay College of Criminal Justice, New York, N.Y.;
  • Philip J. DiNenno, president, Hughes Associates, Inc., Baltimore, Md.;
  • Paul M. Fitzgerald, formerly with FM Global, Johnston, R.I., Holliston, Mass.;
  • Robert D. Hanson, University of Michigan, professor emeritus, Walnut Creek, Calif.;
  • Kathleen J. Tierney, professor, Department of Sociology, director, Natural Hazards Research and Applications Information Center, Institute of Behavioral Science, University of Colorado at Boulder;
  • Charles Thornton, chairman and principal, Thornton-Tomasetti, New York, N.Y.; and
  • Forman A. Williams, professor, Department of mechanical and aerospace engineering, and director, Center for Energy Research, University of California at San Diego.

Does NIST agree with the recommendations for studies put forth by the Building Performance Assessment Team?

The NIST response plan addresses all the major recommendations contained in the report issued by the Building Performance Assessment Team, or BPAT, led by the American Society of Civil Engineers and sponsored by the Federal Emergency Management Agency. The NIST plan also identifies other critical issues that need study, especially in areas that impact life safety and engineering practice.

How will NIST keep the public informed?

NIST established a secretariat to coordinate NIST-level activities in support of the investigation and to maintain ongoing liaison with the Executive Branch, Congress, the public, and the news media.

NIST has maintained an ongoing liaison with the professional community, the public, and local authorities over the course of the investigation through briefings, presentations, and opportunity for comment on key investigation reports. NIST also assigned a special liaison to interact with the families of building occupants and first responders.

Can NIST’s findings be used in court?

As part of the act, no part of any report resulting from investigations can be admitted as evidence or used in any suit or action for damages. Addition-ally, NIST employees are not permitted to serve as expert witnesses.

Has NIST previously conducted building collapse and fire investigations?

NIST has more than 30 years of experience investigating building fire and structural failures. Scientists and engineers in NIST’s Building and Fire Research Laboratory (BFRL) often lead a failure investigation. BFRL has experts in concrete and steel construction, earthquake engineering, and fire performance in structural systems. Other NIST experts, such as materials scientists, manufacturing engineers, and electronic engineers, often provide their specialized knowledge to investigations.

In addition to the building and fire safety investigation of the Sept. 11, 2001, World Trade Center fire and building collapses, NIST also is investigating the Feb. 20, 2003, fire at The Station nightclub in West Warwick, R.I.

Examples of past failure investigations that NIST either has led or participated in include:

  • terrorist bombing, Murrah Federal Building, Oklahoma City, Okla., 1995;
  • terrorist bombing, World Trade Center, New York, N.Y., 1993;
  • building fire, Happylands Social Club, Bronx, N.Y., 1992;
  • building fire, Dupont Plaza Hotel, San Juan, Puerto Rico, 1986;
  • collapse of walkway, Hyatt Regency Hotel, Kansas City, Mo., 1981; and
  • condominium collapse, Cocoa Beach, Fla., 1981.

Is NIST involved in other homeland security activities?

NIST has had a long and productive history of supporting national security. NIST’s measurements and standards provided crucial support for the development of radar, nuclear weapons, aircraft instruments, and other key technologies that helped the United States succeed in past conflicts. Now NIST provides support for technologies to help win the war on terrorism and protect our homeland.

In addition, NIST responded to the immediate aftermath of the terrorist attacks in 2001 and is supporting the technologies that will help prevent or minimize future threats. These activities include:

  • ensuring proper doses for irradiating mail to kill anthrax bacteria;
  • developing standards, protocols, and new test methods to ensure that chemical and biological compounds can be measured accurately;
  • improving technologies and standards for definitive identification of individuals, including techniques such as fingerprinting, face recognition, and DNA analysis;
  • helping develop forensic tools for investigating computer or magnetic data evidence; and
  • facilitating the development of a suite of national chemical and biological protective equipment standards to help protect first responders.

Where can I find more information?

Information on the WTC investigation is available at For information on NIST’s NCST activities, see NIST’s broader array of homeland security projects are discussed at For printed information, contact Public Inquiries, (301) 975-NIST (6478); TTY (301) 975-8295; NIST, 100 Bureau Drive, Stop 1070, Gaithersburg, MD 20899-1070;

Date created: 08/21/02
Last updated: August 3, 2005



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