• To investigate the building construction, the materials used, and the technical conditions that combined to cause the World Trade Center (WTC) disaster.

• To serve as the basis for:
• Improvements in the way buildings are designed, constructed, and used; and
• Improved tools, guidance for industry and safety officials, revisions to codes and standards, and improved public safety.

The primary objectives of the NIST-led technical investigation of the WTC disaster are to:

• Determine why and how the World Trade Center buildings collapsed;

• Determine why the injuries were so low or high depending on location, including all technical aspects of fire protection, response, evacuation, and occupant behavior and emergency response;

• Determine 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

• Identify building and fire codes, standards, and practices that warrant revision.

The formulation of the NIST investigation plan will draw on several sources of information.  These include the FEMA/ASCE Building Performance Assessment (BPAT) study, NIST experts in building and fire safety, external experts and groups (industry and academia), and the public-at-large.  NIST will hold a public meeting to gather information that will help guide its investigation, including public comments on the proposed NIST investigation plan¹.  The refined plan will be made available for public comment before it is adopted as final.

The proposed NIST response plan consists of three key program elements – including an investigation – to be conducted in parallel.  These are:

• First, a 24-month building and fire safety investigation into the collapse of the Twin Towers (WTC 1 and 2) and WTC 7.  The goal of this program element is to investigate the building construction, the materials used, and the technical conditions that combined to cause these disasters following the initial impact of the aircraft.  While WTC 4, 5,and 6 will not be investigated specifically in this phase, what is learned in examining WTC 1, 2 and 7 is expected to benefit buildings of all designs.

• Second, a multi-year research and development (R&D) program to provide the technical basis to support improved building and fire codes, standards, and practices.  This program element addresses work in critical areas such as structural fire safety, prevention of progressive collapse, and equipment standards for first responders.  It includes BPAT recommendations for WTC 3, 4, 5, and 6, Bankers Trust, and peripheral buildings as well as recommendations for future studies to address specific issues of broader scope not covered by the BPAT.  The program outputs and recommendations will support the voluntary consensus process that is used to develop building and fire codes and standards in the United States.

• Third, an industry-led dissemination and technical assistance program (DTAP) that will provide practical guidance and tools to better prepare facility owners, contractors, designers, and emergency personnel to respond to future disasters. The DTAP will also be an important complement to the R&D effort in gaining acceptance of proposed changes to practice, standards, and codes.  This program element addresses BPAT recommendations for training and education of stakeholders.

NIST agrees with the BPAT recommendations that additional studies of the Twin Towers and WTC 7 should be conducted.  The NIST investigation – one component of the proposed NIST response plan – will focus on these buildings.  The results of such an investigation could lead to major changes in both U.S. building and fire codes and in engineering practice, despite the unique design features or circumstances under which the buildings collapsed.  The lessons to be derived from such an investigation will be applicable to a broad range of buildings types, not just the specific buildings that are studied.  The following examples are illustrative:

The Twin Towers and WTC 7 are the only known cases of total structural collapse where fires played a significant role.  These disasters provide a unique source of information to understand the complexities associated with the dynamics of building fires and the collapse vulnerability of structures to fires.   The investigation expects to analyze that information to validate generally applicable methodologies for use in fire safety design and retrofit of structures, and to evaluate the performance of fireproofing materials and connections used in steel structures.

In addition, these building disasters provide a unique source of information to study:

• The safety and performance of open-web steel trussed joists under fires.  This type of trussed joist is used widely in floor and roof systems for commercial and institutional buildings nationwide.

• New mechanisms – not considered previously – that could initiate progressive collapse in buildings as a result of fires and impact loads, and the critical role of pivotal components such as transfer girders and floor diaphragms.

• The mechanical and metallurgical behavior of many different grades of structural steel under fires using steel recovered from the WTC site that is being stored at NIST.

• Firefighting technologies and practices for tall buildings, including occupant behavior, evacuation, emergency response, and the performance of built-in fire protection systems such as sprinklers and fire alarms.

• The control of fire spread in buildings with large open floor plans, and the effectiveness of compartmentation as a means to isolate fires in such buildings.

• The performance of the design, construction, and approval processes used to assure safety whenever an innovative structural system is used or there is a need for variances from building and fire codes – and whether such practices are adequate to detect and remedy inherent vulnerabilities.

• The provision of adequate structural reserve capacity to accommodate abnormal loads such as blast, impact, and accidental fires – especially those that can be anticipated prior to construction – balanced properly against the need to achieve design efficiency.

The technical approach of the NIST investigation will include the following phases over an estimated 24-month period:

• Identification of Technical Issues and Major Hypotheses Requiring Investigation:  opportunity for public input (e.g., open meeting; website; Federal Register notice) in developing investigation plan; convene expert panels to solicit input (experts in structural and fire protection engineering; experts in construction, maintenance, operation and emergency response procedures of tall buildings); findings and recommendations of FEMA-funded study and technical issues identified by other experts; analyze inputs and establish priorities; review by Federal Advisory Committee.

• Data Collection:  inputs from the Port Authority of New York and New Jersey (PANYNJ), local authorities, consultants, and contractors; data and information collected by the FEMA/ASCE BPAT study; building and fire protection design calculations, records, plans, and specifications; construction, maintenance, operation records, building renovations and upgrades; video and photographic data; field data; interviews; emergency response records including audio communications; and other records.

• Analysis and Comparison of Building and Fire Codes and Practices: analysis and comparisons of codes and standards then and now, and specifications used for WTC buildings; review and analysis of practices used for design, construction, operation, maintenance, repair, renovations, and upgrades.

• Collection and Analysis of Forensic Evidence:  structural steel, material specimens and other forensic evidence to the extent they have been collected or are otherwise available; metallurgical and mechanical analysis of steel to evaluate quality and estimate maximum temperatures; analysis of fire and elevator control panels.

• Modeling, Simulation, and Scenario Analysis:  aircraft impact on structures and estimate damages to interior and core structure and residual capacities; role of jet fuel and building contents in resulting fire; fire dynamics and smoke movement; thermal effect on structures and the effect of fireproofing; effect of fire, connections, flooring system, core and exterior columns on structural response and vulnerability; occupant behavior and response including influence of communications and barriers to egress; evacuation issues including egress, control/fire panels, emergency response, and communications; fire protection system design and vulnerability; competing hypotheses for structural collapse including evaluation of system vulnerability to progressive collapse; bounds for probable collapse mechanisms.

• Testing to Re-Create Scenarios and Failure Mechanisms:  small and some real-scale re-creation tests to provide additional data and verify simulation predictions, especially effect of fires (e.g., use and adequacy of standard fire ratings, behavior of connections and assemblies).

• Technical Findings and Recommendations:  preparation of interim and final reports; review by established NIST Editorial Review Board; augmented NIST review to include senior management, legal, and public affairs; review by Federal Advisory Committee; public comment period; finalize and disseminate via published reports, web, and media.

• Dissemination and Deployment of Findings: develop and disseminate proposed changes to codes and standards based on findings; participate with industry in their adoption and acceptance into codes and standards.

The proposed NIST investigation will use world-class technical expertise from both within and outside NIST.  External experts will be drawn from academia and practice and used on an as needed basis in various phases of the investigation.  Many of these experts may well have contributed to the BPAT study.

NIST proposes to charter a Federal Advisory Committee to guide all aspects of the NIST investigation.  The Committee will provide advice on scope, approach, work plan, and schedule; review and provide advice on results, findings, and recommendations; and review and provide advice on interim and final technical reports.  Committee meetings will be announced in the Federal Register.  Members of the Panel will be recognized for distinguished professional service, possess broad technical expertise and experience, and have a reputation for independence, objectivity, and impartiality.  Members of this committee will be selected to avoid conflicts of interest – they cannot represent parties that may be affected directly, participate in the conduct of the investigation, or participate in litigation involving the World Trade Center disaster.  The primary focus of the Panel will be to ensure that the right things are being done and to provide an independent review of the investigation.

NIST will establish a secretariat to coordinate NIST-level activities in support of the proposed investigation and to maintain ongoing liaison with the Congress, the public, and the media.  NIST recognizes that there will be significant public and media interest in the investigation.  NIST will assign a spokesman to provide press announcements and media briefings during the course of the investigation.  NIST will also provide information via reports and briefings to Congress at its request.  The secretariat will include representatives of the Building and Fire Research Laboratory, Congressional and Legislative Affairs, Budget, Public and Business Affairs, NIST Counsel, Program Office, Acquisition and Logistics, and Occupational Health and Safety.

NIST will maintain 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 will assign a special liaison to interact with the families of building occupants and first responders.  NIST recognizes the vital role that those individuals and groups have to play in providing input on the scope of the proposed NIST investigation.  We also understand that it is appropriate and important to keep these families and organizations informed about the progress of the proposed investigation.

• Independent and objective technical investigation that is fully informed of the concerns and issues of all interested parties.

• Open and inclusive process in planning and conducting investigation, and in publishing findings and recommendations.

• Focus on fact-finding, validating/verifying existing knowledge, and creating new technical and/or scientific knowledge for the purpose of deriving lessons to improve practice, standards, and codes and to reduce future risks.

• Non-technical issues outside scope:  No findings of fault.  No determination as to negligence of any individual or organization.

The implementation of the results of the investigation will be critical to restore public confidence by making tall buildings safer nationwide, enhance the safety of fire and emergency responders, and better protect building occupants and property in the future.  In addition, the investigation will be valuable in establishing the probable technical causes of the disaster, deriving the lessons from the WTC disaster, and identifying needed improvements to building and fire standards, codes, and practices and to the safety of tall buildings nationwide.

Specifically, the NIST investigation will provide an authoritative technical account of:

• Why and how the World Trade Center buildings collapsed, including the probable technical causes of the disaster.

• Why the injuries and fatalities were so low or high depending on location, including all occupant behavior and response and evacuation procedures actually experienced.

• Whether or not then-current procedures were used in the design, construction, operation, and maintenance of the WTC buildings.

The results of the investigation will also underpin and guide future work to develop and disseminate immediate guidance and tools to assess and reduce vulnerabilities, and produce the technical basis for cost-effective changes to national practices and standards.  A private sector coalition – representing the key industry, standards, codes, and professional organizations – has worked with NIST to establish the response plan (see page 1) 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.

The specific consequences of not carrying out this investigation and the broader response plan include:  loss of valuable perishable data that must be collected and archived immediately, incomplete and lack of objective assessments of building failures and lessons for the future, unknown vulnerability of existing building stock and lack of vulnerability assessment tools, lack of operational guidance for building owners and emergency responders, continuing risk in the performance of fire protection systems and technical barriers to innovation, unreliable test methods, outdated design codes and standards for new construction and lack of information to provide similar guidance to retrofit existing buildings, and risks associated with ad hoc and prescriptive changes to building codes that lack technical basis.

Note 1 - The proposed NIST investigation plan, with additional details, will be made available to the general public two weeks prior to the public meeting.

Note 2 - The graphic shows how the BPAT recommendations map into the NIST response plan.