House Science Committee Hearing on The Investigation of the World Trade Center Collapse: Findings, Recommendations and Next Steps

I want to welcome everyone here today to our second hearing on the collapse of the World Trade Center. In many ways, this hearing is a continuation of the discussions we began at our first hearing on March 6, and, indeed, we have the exact same panel of witnesses before us today as we did two months ago.

On March 6, we delved into the procedures that were followed to assess what had caused the towers to collapse in those indelible moments of September 11^th. We were not happy with what we learned. We found that the study of the collapse had been hampered by bureaucratic confusion, hesitation and delay; by a lack of investigative tools and by excessive restrictions on the flow of information.

But we also learned that, despite these severe impediments, the team led by the American Society of Civil Engineers (ASCE), as well as other researchers, were able to draw some preliminary conclusions about the collapse, and that the National Institute of Standards and Technology (NIST) was willing to pick up where the ASCE team had left off, even though NIST officials couldn’t tell us much at that point about exactly what that meant.

First, the ASCE team will describe the conclusions of their study – and it will become the subject of full-blown, public deliberation for the first time.

Second, NIST will tell us exactly what it intends to do in its follow-up investigation, for which the Administration has requested $16 million.

And third, we will release and open up the public discussion on legislation to ensure that the problems that hamstrung the ASCE study never, ever recur.

Let me turn first to the legislation, which I have drafted with Mr. Weiner. The bill, known as the “National Construction Safety Team Act,” is designed to remedy each and every impediment that was encountered in the Trade Center investigation.

At the March 6 hearing, we uncovered four ways in which the status quo was unacceptable. First, no federal agency was clearly charged with investigating building failures. The bill solves that problem by giving NIST clear responsibility to handle the investigations. Second, nothing ensured that investigations would begin quickly enough to preserve valuable evidence. The bill solves that problem by requiring NIST to act within 48 hours of a building failure. Third, no federal agency had the investigative authority it needed to ensure access to all needed information. The bill solves that problem by giving NIST clear authority to enter sites, access documents, test materials and move evidence, as well as clear authority to issue subpoenas. Fourth, nothing ensured that the public was kept informed of the progress of the investigation. The bill solves that problem by requiring NIST to provide regular public briefings and to make public its findings and the materials that led to those findings.

We listened closely on March 6, and we have responded with a measure targeted precisely to remedy the issues that came to our attention. And we based the bill on a highly successful model – the National Transportation Safety Board, the federal agency that investigates airline crashes.

We want to begin to get comments on the draft bill today, and we intend to introduce it – along with several colleagues on this Committee and in the Senate – within about a week. I expect our Committee to approve the bill by the end of the month, and I would like to see it come to the House floor as soon as possible.

While the bill is mostly prospective in its focus, all the investigative tools it would provide to NIST, including subpoena power, would be available to conduct the World Trade Center investigation.

But what will that investigation entail? That’s the key question this Committee needs to pursue today with NIST. There is an almost unlimited universe of questions that NIST could address, but time and money are not unlimited. NIST needs to focus on those matters that are most likely to result in changed codes and practices – including evacuation and emergency response procedures -- in a wide variety of buildings.

The investigation can’t be driven by mere curiosity or political pressures, and it can’t be based on the assumption that unlimited dollars will flow for future research. It has to be driven by the desire to save the maximum number of lives in the future – and to making the changes needed to save those lives as rapidly as possible. I hope that NIST will be able to assure us today that it is doing exactly that.

But regardless of the precise NIST agenda, the lab needs the $16 million that the Administration has requested for it in the Supplemental Appropriations bill that the House will consider later this month. The Administration is to be applauded for this request, although they have, unfortunately, complicated matters by asking that the money be provided to FEMA for transfer to NIST. We will work with the appropriators to get this money to NIST – directly, if possible; indirectly, if necessary.

So we still have plenty of questions as we pick up where we concluded on March 6. I want to assure the public in general, but especially the families of the victims, that this panel is committed to following this issue in the months and years ahead. We will not rest until we learn all we need to know to prevent future tragedies and until we implement what we have learned.

Let me conclude the same way I did on March 6: We are here because the only way to move forward is to try to understand what happened on a day that was so incomprehensible.

“The Investigation of the World Trade Center Collapse: Findings, Recommendations and Next Steps”

Chairman Boehlert, Ranking Member Hall, and Members of the Committee, I want to thank you for this opportunity to testify on the National Institute of Standards and Technology’s proposed investigation into the collapse of the World Trade Center (WTC) buildings.

I will outline the proposed NIST response plan today, and show how it complements and is responsive to the efforts of the Building Performance Assessment Team, or BPAT, led by the American Society of Civil Engineers (ASCE) and sponsored by the Federal Emergency Management Agency, FEMA. The response plan addresses all major recommendations contained in the BPAT report. I commend Dr. Gene Corley and the BPAT members for their excellent report and detailed recommendations. The National Institute of Standards and Technology (NIST) has also identified other critical issues that need study, especially in areas that impact life safety and engineering practice.

The NIST proposed response plan consists of three key program elements – including an investigation – to be conducted in parallel (graphic to be projected on video monitors). 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 we learn in examining WTC 1, 2 and 7 would 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 to demonstrate and gain acceptance of proposed changes to practice, standards, and codes. This program element addresses BPAT recommendations for the training and education of stakeholders.

All the BPAT recommendations can be seen to map into the three above elements in this graphic (graphic on screen).

We have shared the overall response plan approach extensively with public and private sector organizations and have welcomed their inputs since the middle of October 2001. The plan was modified in January 2002 when FEMA requested NIST to initiate an investigation under NIST's unique legislative authorities to conduct structural and fire investigations. This request was in direct response to a growing demand for a broad-based federal investigation into the World Trade Center disaster from technical experts, industry leaders, and families of building occupants and first responders who lost their lives on September 11, 2001. We continue to revise the plan as more technical information becomes available and to be responsive to the suggestions and needs of these many stakeholders.

The Commerce Department and NIST have received letters supporting our proposed response plan from key industry leaders responsible for U.S. building and fire standards, codes, and practices, including the American Society of Civil Engineers, the National Fire Protection Association, the American Institute of Architects, the Council on Tall Buildings and Urban Habitat, the Construction Industry Institute, the Society of Fire Protection Engineers, and the International Association of Fire Chiefs.

We agree with the BPAT recommendations that additional study of the Twin Towers and WTC 7 should be conducted. The NIST investigation will focus on these buildings. We believe strongly that 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. We also believe strongly that 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. Let me now give you some examples to illustrate why we believe this to be the case.

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 real building fires and the collapse vulnerability of buildings to fires. We expect 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, including 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.

There are equally important lessons for life safety – which were outside the scope of the BPAT study:

· 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.

There are also important lessons to be learned for engineering practice – areas that were not the focus of the BPAT study:

· 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 proposed NIST investigation will include world-class technical expertise from both within and outside NIST. External experts will be drawn from both academia and practice and several of those may well have contributed to the BPAT study.

We propose to charter a Federal Advisory Committee to guide all aspects of the NIST investigation, including the review of major investigation reports. Members of this group will be recognized for their distinguished professional service, possess broad technical expertise and experience, and have a reputation for independence, objectivity, and impartiality.

I have appointed a Secretariat within NIST to coordinate NIST-level activities in support of the WTC investigation and to maintain ongoing liaison with members of Congress, the public, and the media.

NIST will assign a special liaison to interact with the families of building occupants and first responders. We recognize 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.

We will maintain ongoing liaison with the professional communities over the course of the investigation through periodic briefings, presentations, and opportunity for comment on key investigation reports.

A summary of the proposed NIST investigation plan is attached for the record and is being made available to the general public on the NIST website beginning today. NIST will use an open and inclusive process in planning and conducting the investigation, and in publishing its findings and recommendations. We consulted extensively with technical experts and groups in developing the plan and briefed the BPAT experts at their January 2002 meeting, and again last Wednesday. Yesterday, we briefed representatives of the parent organizations comprising the BPAT coalition. We will hold a public meeting in New York City in the near future to share the details of the proposed NIST plan, which will be made available to the general public two weeks prior, and seek the public’s informed comment on its scope before we adopt the plan as final.

Following our statutory requirements, before we begin a building investigation, we consult with local authorities. In this case, we consulted with local authorities in New York, including the Port Authority of New York and New Jersey, 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 written support for NIST and agreed to cooperate in its investigation.

The Administration has expressed strong commitment for the NIST response plan and has requested $16 million as part of the Federal Emergency Management Agency’s FY 2002 supplemental budget request – now in Congress – to support the NIST investigation. The President’s FY 2003 budget request to Congress also requests an increase of $2 million in base funding to support other elements of the NIST response plan. The Building and Fire Research Laboratory within NIST has already redirected approximately $2 million of its existing base funds to support the response plan. Future resource requirements for the broader research and development and dissemination and technical assistance program will be considered in the Fiscal Year 2004 budget process and beyond.

Finally, Mr. Chairman, I look forward to working with you and members of this Committee as NIST embarks on a very important technical investigation. FEMA and NIST are committed to ensuring a smooth transition. Mr. Robert Shea and I recently signed a Memorandum of Understanding to strengthen our collaborative bonds by designating NIST to serve as a research and technical resource for FEMA. With your permission, I would like to submit a copy of that MOU for the record. We have agreed to develop and sign, by the end of May 2002, an operational protocol for a quick deployment mechanism that could be activated when a NIST response to extreme events is needed.

National Building and Fire Safety Investigation of the World Trade Center Disaster

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

o 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 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 plan [1] . 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.

· 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.

The response plan is different from and responsive to the BPAT efforts. The plan addresses all major recommendations contained in the BPAT report [2] . NIST has also identified other critical issues that need study, especially in areas that impact life safety and engineering practice.

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.

There are equally important lessons for life safety – which were outside the scope of the BPAT study.

· 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.

There are also important lessons for engineering practice that were not the focus of the BPAT study.

· 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 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.

At this point, the NIST investigation plan anticipates organizing around 10 project areas that would provide the focus for the technical work. These include: (1) aircraft impact analysis and damage prediction; (2) forensic analysis of structural steel; (3) analysis of built-in fire protection systems; (4) prediction of thermal environment; (5) structural fire response and vulnerability; (6) structural collapse vulnerability and mechanisms; (7) occupant behavior and egress; (8) fire service technologies and guidelines; (9) fire codes and standards; (10) analysis of building codes and practices. A GANTT chart with key sub-tasks for these projects and proposed timelines is attached.

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 NIST results will be supported by careful and detailed analytical and experimental work.

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.

Performance Outputs for WTC Investigation

National Building and Fire Safety Investigation of the World Trade Center Disaster

Technical Area

Outputs

Identification of Technical Issues and Major Hypotheses

·         Public Meetings to gather information to guide plan for NIST investigation.
·         Report(s) on NIST Investigation Plan Approach and Process.

Analysis of Building and Fire Codes and Practices

·         Report(s) on Analysis of Building and Fire Codes and Practices.

Aircraft Impact Analysis and Damage Prediction

·         Report(s) on Aircraft Impact Analysis and Damage Prediction.

Forensic Analysis of Structural Steel

·         Report(s) on Forensic Analysis of Structural Steel.

Analysis of Built-In Fire Protection Systems

·         Report(s) on Analysis of Built-In Fire Protection Systems.

Prediction of Thermal Environment

·         Report(s) on Prediction of Thermal Environment.

Structural Fire Response and Vulnerability

·         Report(s) on Structural Fire Response and Vulnerability.

Structural Collapse Vulnerability and Mechanisms

·         Report(s) on Structural Collapse Vulnerability and Mechanisms.

Occupant Behavior and Egress

·         Report(s) on Occupant Behavior and Egress.

Fire Service Technologies and Guidelines

·         Report(s) on Fire Service Technologies and Guidelines

Fire Codes and Standards

·         Report(s) on Elevator and Fire Resistance Standards.

Technical Findings and Recommendations

·         Interim and Final Reports on the Technical Findings and Recommendations of the Investigation, including probable technical causes of the disaster.

Dissemination and Deployment of Findings

·         Dissemination and Deployment of Findings via proposed standards and codes changes and participation with industry in their adoption and acceptance into codes and standards.

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

[2] The attached graphic shows how the BPAT recommendations map into the NIST response plan.

Professor Glenn P. Corbett

John Jay College of Criminal Justice

Before the

Committee on Science

House of Representatives

United States Congress

Good afternoon Chairman Boehlert, Ranking Member Hall, and Members of the House Science Committee. Thank you for allowing me to again testify before you about the investigation of the World Trade Center disaster.

Nearly eight months have passed since the collapse of the twin towers, yet today we are only just beginning to understand exactly what happened on September 11^that the World Trade Center (WTC). While the Building Performance Assessment Team (BPAT) report that is being released at today’s hearing yields some useful information, the generalized nature of its recommendations and the limited scope of the assessment leave us with little hard evidence for which to make specific improvements to codes, design practices, and emergency response procedures. The recommendations of this report provide us with a useful starting point, but much work remains to be done.

The proposed National Institute of Standards and Technology (NIST) investigation that is under consideration today is the type of large-scale forensic inquiry that the federal government should have launched last September. I was pleased to learn that NIST plans to conduct a thorough and comprehensive investigation, incorporating the six focus areas that I identified in my testimony before this Committee on March 6^th. They intend to take a multi-disciplinary approach, allowing for the investigation to benefit from the expertise of a wide range of experts and to permit the disaster to be studied holistically. The depth and breadth of the planned investigation will provide as complete an understanding of the disaster at the World Trade Center as is now possible.

The fact-finding “leave no stone unturned” objective of the NIST investigation will allow us to develop detailed conclusions and learn the lessons about what transpired at the World Trade Center. It is the application of these hard-earned lessons, of course, that is the primary reason for conducting the investigation in the first place. These lessons must be translated into actual changes to our building and fire codes, enhancements in building design methodologies, and improvements in emergency response procedures and technologies. While NIST has laid out a comprehensive proposal for investigating and researching the lessons learned from the disaster, the key to achieving this goal lies in the details of the NIST plan. This is where I will focus my comments today.

After having reviewed several draft documents concerning the actual plan for the NIST investigation, I have identified three particular areas of concern: 1) the need for the rapid assemblage of a diverse group of individuals to form the core “Federal Advisory Committee” which will oversee the investigation; 2) the need for subpoena power for the investigation; and 3) the need for the investigation to be centered upon the development of “defensible” and detailed proposals for changes in building and fire codes as well as improvements in emergency response procedures and technologies. While I am aware that NIST is attempting to deal with these three issues, I think that it is important to highlight these concerns in light of what has happened in the preparation of the BPAT report.

The Federal Advisory Committee’s critical role will be its review of NIST’s draft plan for the investigation and in its ongoing role of monitoring the investigation. These duties are very important in light of the multidisciplinary aspects of the investigation and since some areas of the investigation involve issues that are outside of NIST’s traditional areas of expertise such as building evacuation, firefighting, and urban search and rescue. It is essential that the Committee is composed of many individuals with a broad range of expertise and experience. It is equally important that the Committee be formed as quickly as possible to allow for the rapid development and implementation of the best plan possible.

A review of NIST’s current draft plan has spotlighted the need for the guidance of the “world class experts” of the Federal Advisory Committee. For example, the “evacuation” portion of the draft plan does not propose that individual interviews of survivors be conducted but rather relies on the use of survey forms to collect information. A “one size fits all” survey form will not gather all of the critical information that is necessary to understand the evacuations that took place on September 11^th. In order to gain all valuable data including unanticipated information, actual interviews of the survivors must be conducted. In addition, the interview process itself will allow for the presence of a mental healthcare professional who can help the survivor address the emotions that will be unleashed when asking questions about how they survived. Federal Advisory Committee members with expertise in human behavior and building evacuations would be able to provide useful information for the development of such an interview plan as well as the anticipated costs.

This need for diversity of expertise became evident in my review of the BPAT report. For example, the BPAT report recommends the development of “…training materials and courses for emergency personnel with regards to effects of fire on steel.” In reality, there are several books and training materials currently available concerning building construction, including large amounts of information on steel frame buildings and the effects of fire on steel. Ironically, FEMA itself (through the United States Fire Administration) publishes a very popular training program called “Principles of Building Construction: Noncombustible.” I believe that had a firefighter been on the BPAT team, this fact would have been quickly identified.

The second area of concern is the need for subpoena power. In order to thoroughly investigate the WTC disaster, investigators must have access to all relevant information. It is only with a full set of facts that conclusions may be drawn. The experience in the preparation of the BPAT study has identified this as a key issue. The Science Committee hearing on March 6^th clearly highlighted some of the impediments the BPAT faced in obtaining key information. My fear is that the NIST investigation will be hindered by these same problems.

Information may be found in a variety of locations and may be held by many different individuals and organizations that will not provide this information voluntarily. Even though the WTC investigation is an investigation of a fact-finding nature, a legal means for obtaining information that would otherwise be unavailable must be provided for investigators.

The third area of concern is to learn as many lessons as possible and to apply these lessons. In order for changes related to building and fire codes to be applied, the NIST investigation and research reports must include specific recommended changes to specific sections of our model codes, not generalized recommendations.

For example, in the Observations, Findings, and Recommendations chapter of the BPAT study, the report states “Fireproofing needs to be tough under impact and fire conditions that deform steel members,...” This conclusion will not easily find its way into the model codes since it is not in the proper code format and lacks the corresponding necessary supporting evidence. NIST must recognize this fact if the ultimate goal is to actually improve building codes, standards, and practices.

These proposed changes and related supporting evidence developed by NIST must be laid at the feet of the code-writing organizations for inclusion in their model codes. In addition, I believe that a special, formalized code change submittal process should be developed between NIST and the code-writing bodies to address the code changes that will emerge from this investigation. This more formalized relationship will raise many difficult questions, which are likely outside the scope of this hearing. However, the Science Committee should continue to look into this issue to see what barriers must be overcome.

I believe that the proposed NIST investigation is the best course of action to learn and apply the lessons of the World Trade Center disaster. It is critical that the investigation be as comprehensive as currently planned and be funded at the necessary level to achieve this goal. It is essential that we learn exactly what happened to the structures, victims, and survivors on September 11^th and try to prevent it from ever happening again.

Thank you for allowing me to appear before you on this very important topic. I would be happy to answer any questions that you may have.

American Society of Civil Engineers
Washington Office
1015 15th Street, N.W., Suite 600
Washington, D.C. 20005-2605
(202) 789-2200
Fax: (202) 289-6797
Web: http://www.asce.org

Following the September 11, 2001, attacks on New York City's World Trade Center, the Federal Emergency Management Agency (FEMA) and the Structural Engineering Institute of the American Society of Civil Engineers (SEI/ASCE), in association with New York City and several other federal agencies and professional organizations, deployed a team of civil, structural, and fire protection engineers to study the performance of buildings at the World Trade Center (WTC) site.

Founded in 1852, ASCE represents more than 125,000 civil engineers worldwide and is the country’s oldest national engineering society. ASCE members represent the profession most responsible for the nation’s built environment. Our members work in consulting, contracting, industry, government and academia. In addition to developing guideline documents, state-of-the-art reports, and a multitude of different journals, ASCE, an American National Standards Institute (ANSI) approved standards developer, establishes standards of practice such as the document known as ASCE 7 which provides minimum design loads for buildings and other structures. ASCE 7 is used internationally and is referenced in all of our nation’s major model building codes.

The events of following the attacks in New York City were among the worst building disasters and resulted in the largest loss of life from any single building event in the United States. Of the 58,000 people estimated to be at the WTC Complex, over 3,000 lives were lost that day, including 343 emergency responders. Two commercial airliners were hijacked, and each was flown into one of the two 110-story towers. The structural damage sustained by each tower from the impact, combined with the ensuing fires, resulted in the total collapse of each building. As the towers collapsed, massive debris clouds, consisting of crushed and broken building components, fell onto and blew into surrounding structures, causing extensive collateral damage and, in some cases, igniting additional fires and causing additional collapses. In total, 10 major buildings experienced partial or total collapse and 30 million square feet of commercial office space was removed from service, of which 12 million belonged to the WTC complex.

The purpose of the FEMA/ASCE was to see what could be learned to make buildings safer in the future. Building performance studies are often done when there is major structural damage due to events such as earthquakes or blasts. A better understanding of how building respond to extreme forces can help us design safer structures in the future.

The team recommendations are presented for more detailed engineering studies, to complete the assessments and produce improved guidance and tools for building design and performance evaluation.

As each tower was struck, extensive structural damage, including localized collapse, occurred at the several floor levels directly impacted by the aircraft. Despite this massive localized damage, each structure remained standing. However, as each aircraft impacted a building, jet fuel on board ignited. Part of this fuel immediately burned off in the large fireballs that erupted at the impact floors. Remaining fuel flowed across the floors and down elevator and utility shafts, igniting intense fires throughout upper portions of the buildings. As these fires spread, they further weakened the steel-framed structures, eventually triggering total collapse.

The collapse of the twin towers astonished most observers, including knowledgeable structural engineers, and, in the immediate aftermath, a wide range of explanations were offered in an attempt to help the public understand these tragic and unthinkable events. However, the collapse of these symbolic buildings entailed a complex series of events that were not identical for each tower. To determine the sequence of events, likely root causes, and methods or technologies that may improve or mitigate the building performance observed, FEMA and ASCE formed a Building Performance Study (BPS) Team consisting of specialists in tall building design, steel and connection technology, fire and blast engineering, and structural investigation and analysis.

The SEI/ASCE team conducted field observations at the WTC site and steel salvage yards, removed and tested samples of the collapsed structures, viewed hundreds of images of video and still photography, conducted interviews with witnesses and persons involved in the design, construction, and maintenance of each of the affected buildings, reviewed available construction documents, and conducted preliminary analyses of the damage to the WTC towers.

With the information and time available, the sequence of events leading to the collapse of each tower could not be definitively determined. However, the following observations and findings were made:

Our analysis showed that the impact alone did not cause the collapse of the towers, but instead, left the towers vulnerable to collapse from any significant additional force, such as from high winds, an earthquake, or in the case of the Twin Towers, the fires that engulfed both buildings. Without that second event, the team believes the towers could have remained standing indefinitely.

Although steel is very strong, it loses some of its strength when heated. To prevent that loss of strength, structural steel is protected with fireproofing and sprinkler systems. In the towers, fires raged throughout several floors simultaneously, ignited by the jet fuel and fed by a mixture of paper and furniture. The impact dislodged some fireproofing on the structural beams and columns, which made them vulnerable to fire damage. With the sprinkler systems disabled, the fires raged uncontrollably, weakening the steel and leading to the collapse of the buildings.

Several building design features have been identified as key to the buildings' ability to remain standing as long as they did and to allow the evacuation of most building occupants. These included the following:

Similarly, several design features have been identified that may have played a role in allowing the buildings to collapse in the manner that they did and in the inability of victims at and above the impact floors to safely exit. These features should not be regarded either as design deficiencies or as features that should be prohibited in future building codes. Rather, these are features that should be subjected to more detailed evaluation, in order to understand their contribution to the performance of these buildings and how they may perform in other buildings. These include the following:

During the course of this study, the question of whether building codes should be changed in some way to make future buildings more resistant to such attacks was frequently explored. Depending on the size of the aircraft, it may not be technically feasible to develop design provisions that would enable structures to be designed and constructed to resist the effects of impacts by rapidly moving aircraft, and the ensuing fires, without collapse. In addition, the cost of constructing such structures might be so large as to make this type of design intent practically infeasible.

Although the attacks on the World Trade Center are a reason to question design philosophies, the BPS Team believes there are insufficient data to determine whether there is a reasonable threat of attacks on specific buildings to recommend inclusion of such requirements in building codes. Some believe the likelihood of such attacks on any specific building is deemed sufficiently low to not be considered at all. However, individual building developers may wish to consider design provisions for improving redundancy and robustness for such unforeseen events, particularly for structures that, by nature of their design or occupancy, may be especially susceptible to such incidents.

Although some conceptual changes to the building codes that could make buildings more resistant to fire or impact damage or more conducive to occupant egress were identified in the course of this study, the BPS Team felt that extensive technical, policy, and economic study of these concepts should be performed before any specific code change recommendations are developed. This report specifically recommends such additional studies. Future building codes revisions may be considered after the technical details of the collapses and other building responses to damage are better understood.

Several other buildings, including the Marriott Hotel (WTC 3), the South Plaza building (WTC 4), the U.S. Customs building (WTC 6), and the Winter Garden, experienced nearly total collapse as a result of the massive quantities of debris that fell on them when the two towers collapsed. The St. Nicholas Greek Orthodox Church just south of WTC 2 was completely destroyed by the debris that fell on it. WTC 5, WTC 7, 90 West Street, 130 Cedar Street, Bankers Trust, the Verizon building, and World Financial Center 3 were impacted by large debris from the collapsing twin towers and suffered structural damage, but arrested collapse to localized areas. The performance of these buildings demonstrates the inherent ability of redundant steel-framed structures to withstand extensive damage from earthquakes, blasts, and other extreme events without progressive collapse.

The debris from the collapses of the WTC towers also initiated fires in surrounding buildings, including WTC 4, 5, 6, 7; 90 West Street; and 130 Cedar Street. Many of the buildings suffered severe fire damage but remained standing. However, two steel-framed structures experienced fire-induced collapse. WTC 7 collapsed completely after burning unchecked for approximately 7 hours, and a partial collapse occurred in an interior section of WTC 5. Studies of WTC 7 indicate that the collapse began in the lower stories, either through failure of major load transfer members located above an electrical substation structure or in columns in the stories above the transfer structure.

The collapse of WTC 7 caused damage to the Verizon building and 30 West Broadway. The partial collapse of WTC 5 was not initiated by debris and is possibly a result of fireinduced connection failures. The collapse of these structures is particularly significant in that, prior to these events, no protected steel-frame structure, the most common form of large commercial construction in the United States, had ever experienced a fire-induced collapse. Thus, these events may highlight new building vulnerabilities, not previously believed to exist.

In the study of the WTC towers and the surrounding buildings that were subsequently damaged by falling debris and fire, several issues were found to be critical to the observed building performance in one or more buildings.

These issues above fall into several broad topics that should be considered for buildings that are being evaluated or designed for extreme events. It may be that some of these issues should be considered for all buildings; however, additional studies are required before general recommendations, if any, can be made for all buildings. The issues identified from this study of damaged buildings in or near the WTC site have been summarized into the following points:

What may be most important is that the BPS Team does not recommend any immediate changes to building codes. The Team believes that there are a number of areas that need further study, and that there are some things that building designers could do to improve safety for occupants in buildings that might be possible terrorist targets.

In general terms, the FEMA/ASCE report suggests that critical building components such as the structural frame, the sprinkler system or the exit stairwells be designed to be more redundant, more robust, or both. Redundancy means, for example, that if some structural columns were shattered, the building would be designed to transfer the weight to other columns. Robustness means making the builder stronger and better able to resist impact without collapse.

The team is also strongly urging additional study of the collapse of the buildings.

The team found that some connections between the structural steel beams failed in the fire. This was most apparent in the collapse of World Trade Center Building 5, where the fireproofing did not protect the connections, causing the structure to fail.

The team is calling for more research and analysis of the how the connections weakened and how best to strengthen their resistance to future fires. Typically, fire resistance tests are limited to steel members, not to the steel connections.

Furthermore, fireproofing is sprayed on the connections the same way it is applied to the trusses, though the steel in the trusses and joints may be made of different alloys.

The following sections present observations, findings, and recommendations specifically made in each chapter of the FEMA/ASCE report, including the discussion of building codes and fire standards and the limited metallurgical examination of steel from the WTC towers and WTC 7.

a. The decision to include aircraft impact as a design parameter for a building would clearly result in a major change in the design, livability, usability, and cost of buildings. In addition, reliably designing a building to survive the impact of the largest aircraft available now or in the future may not be possible. These types of loads and analyses are not suitable for inclusion in minimum loads required for design of all buildings. Just as the possibility of a Boeing 707 impact was a consideration in the original design of WTC 1 and WTC 2, there may be situations where it is desirable to evaluate building survival for impact of an airplane of a specific size traveling at a specific speed. Although there is limited public information available on this topic, interested building owners and design professionals would require further guidance for application to buildings.

b. The ASTM E119 Standard Fire Test was developed as a comparative test, not a predictive one. In effect, the Standard Fire Test is used to evaluate the relative performance (fire endurance) of different construction assemblies under controlled laboratory conditions, not to predict performance in real, uncontrolled fires.

a. The structural damage sustained by each of the two buildings as aircraft impacted them during the attacks was massive. The fact that the structures were able to sustain this level of damage and remain standing for an extended period of time is remarkable and is the reason that most building occupants were able to evacuate safely. Events of this type, resulting in such substantial damage, are generally not considered in building design, and the ability of these structures to successfully withstand such damage is noteworthy.

b. Preliminary analyses of the damaged structures, together with the fact the structures remained standing for an extended period of time, suggest that absent other severe loading events, such as a windstorm or earthquake, the buildings could have remained standing in their damaged states until subjected to some significant additional load. However, the structures were subjected to a second, simultaneous severe loading event in the form of the fires caused by the aircraft impacts.

c. The large quantity of jet fuel carried by each aircraft ignited upon impact into each building. A significant portion of this fuel was consumed immediately in the ensuing fireballs. The remaining fuel is believed either to have flowed down through the buildings or to have burned off within a few minutes of the aircraft impact. The heat produced by this burning jet fuel does not by itself appear to have been sufficient to initiate the structural collapses. However, as the burning jet fuel spread across several floors of the buildings, it ignited much of the buildings' contents, permitting fires to evolve across several floors of the buildings simultaneously. The heat output from these fires is estimated to have been comparable to the power produced by a large commercial generating station. Over a period of many minutes, this heat induced additional stresses into the damaged structural frames while simultaneously softening and weakening these frames. This additional loading and damage were sufficient to induce the collapse of both structures.

d. Because the aircraft impacts into the two buildings are not believed to have been sufficient to cause collapse without the ensuing fires, an obvious question exists as to whether the fires alone, without the damage from the aircraft impact, would have been sufficient to cause such a collapse. The capabilities of the building fire protection systems make it extremely unlikely that such fires could develop without some unusual triggering event like the aircraft impact. For all other cases, the fire protection for the tower buildings provided in-depth protection. The first line of defense was the automatic sprinkler protection. The sprinkler system was intended to respond quickly and automatically to extinguish or confine a fire. The second line of defense consisted of the manual (FDNY/Port Authority Fire Brigade) firefighting capabilities, which were supported by the building standpipe system, emergency fire department use elevators, smoke control system, and other features. Manual suppression by FDNY was the principal fire protection mechanism that controlled a large fire that occurred in the buildings in 1975. Finally, the last line of defense was the structural fire resistance. The fire resistance capabilities would not be called upon unless both the automatic and manual suppression systems previously described failed. In the incident of September 11, not only did the aircraft impact disable the first two lines of defense, they also are believed to have dislodged fireproofing and imposed major additional stresses on the structural system.

e. Had some other event defeated both the automatic and manual suppression capabilities and a fire of major proportions occurred while the structural framing system and its fireproofing remained intact, the third line of defense, structural fireproofing, would have become critical. The thickness and quality of the fireproofing materials would have been key factors in the rate and extent of temperature rise in the floor trusses and other structural members. In the preparation of this report, there has not been sufficient analysis to predict the temperature and resulting change in strength of the individual structural members in order to approximate the overall response of the structure. Given the redundancy in the framing system and the capability of that system to redistribute load from a weakened member to other parts of the structural system, it is impossible without extensive modeling and other analysis to make a credible prediction of how the building would have responded to an extremely severe fire in a situation where there was no prior structural damage. Such simulations have not been performed within the scope of this study, but should be performed in the future.

f. Buildings are designed to withstand loading events that are deemed credible hazards and to protect the public safety in the event such credible hazards are experienced. Buildings are not designed to withstand any event that could ever conceivably occur, and any building can collapse if subjected to a sufficiently extreme loading event. Communities adopt building codes to help building designers and regulators determine those loading events that should be considered as credible hazards in the design process. These building codes are developed by the design and regulation communities themselves, through a voluntary committee consensus process. Prior to September 11, 2001, it was the consensus of these communities that aircraft impact was not a sufficiently credible hazard to warrant routine consideration in the design of buildings and, therefore, the building codes did not require that such events be considered in building design. Nevertheless, design of WTC 1 and WTC 2 did include at least some consideration of the probable response of the buildings to an aircraft impact, albeit a somewhat smaller and slower moving aircraft than those actually involved in the September 11 events. Building codes do regard fire as a credible hazard and include extensive requirements to control the spread of fire throughout buildings, to delay the onset of fire-induced structural collapse, and to facilitate the safe egress of building occupants in a fire event. For fire-protected steel-frame buildings, like WTC 1 and WTC 2, these code requirements had been deemed effective and, in fact, prior to September 11, there was no record of the fire-induced-collapse of such structures, despite some very large uncontrolled fires.

g. The ability of the two towers to withstand aircraft impacts without immediate collapse was a direct function of their design and construction characteristics, as was the vulnerability of the two towers to collapse as a result of the combined effects of the impacts and ensuing fires. Many buildings with other design and construction characteristics would have been more vulnerable to collapse in these events than the two towers, and few may have been less vulnerable. It was not the purpose of this study to assess the code-conformance of the building design and construction, or to judge the adequacy of these features. However, during the course of this study, the structural and fire protection features of the building were examined. The study did not reveal any specific structural features that would be regarded as substandard, and, in fact, many structural and fire protection features of the design and construction were found to be superior to the minimum code requirements.

h. Several building design features have been identified as key to the buildings’ ability to remain standing as long as they did and to allow the evacuation of most building occupants. These include the following:

i. Similarly, several design features have been identified that may have played a role in allowing the buildings to collapse in the manner that they did and in the inability of victims at and above the impact floors to safely exit. These features should not be regarded either as design deficiencies or as features that should be prohibited in future building codes. Rather, these are features that should be subjected to more detailed evaluation, in order to understand their contribution to the performance of these buildings and how they may perform in other buildings. These include the following:

j. During the course of this study, the question of whether building codes should be changed in some way to make future buildings more resistant to such attacks was frequently explored. Depending on the size of the aircraft, it may not be technically feasible to develop design provisions that would enable structures to be designed and constructed to resist the effects of impacts by rapidly moving aircraft, and the ensuing fires, without collapse. In addition, the cost of constructing such structures might be so large as to make this type of design intent practically infeasible. Although the attacks on the World Trade Center are a reason to question design philosophies, the BPS Team believes there are insufficient data to determine whether there is a reasonable threat of attacks on specific buildings to recommend inclusion of such requirements in building codes. Some believe the likelihood of such attacks on any specific building is deemed sufficiently low to not be considered at all. However, individual building developers may wish to consider design provisions for improving redundancy and robustness for such unforeseen events, particularly for structures that, by nature of their design or occupancy, may be especially susceptible to such incidents. Although some conceptual changes to the building codes that could make buildings more resistant to fire or impact damage or more conducive to occupant egress were identified in the course of this study, the BPS Team felt that extensive technical, policy, and economic study of these concepts should be performed before any specific code change recommendations are developed. This report specifically recommends such additional studies. Future building codes revisions may be considered after the technical details of the collapses and other building responses to damage are better understood.

The scope of this study was not intended to include in-depth analysis of many issues that should be explored before final conclusions are reached. Additional studies of the performance of WTC 1 and WTC 2 during the events of September 11, 2001, and of related building performance issues should be conducted. These include the following:

a. During the course of this study, it was not possible to determine the condition of the interior structure of the two towers, after aircraft impact and before collapse. Detailed modeling of the aircraft impacts into the buildings should be conducted in order to provide understanding of the probable damage state immediately following the impacts.

b. Preliminary studies of the growth and heat flux produced by the fires were conducted. Although these studies provided useful insight into the buildings' behavior, they were not of sufficient detail to permit an understanding of the probable distribution of temperatures in the buildings at various stages of the event and the resulting stress state of the structures as the fires progressed. Detailed modeling of the fires should be continued and should be combined with structural modeling to develop specific failure modes likely to have occurred.

c. The floor framing system for the two towers was very complex and substantially more redundant than typical bar joist floor systems. Detailed modeling of these floor systems and their connections should be conducted to understand the effects of localized overloads and failures to determine ultimate failure modes. Other types of common building framing should also be examined for these effects.

d. The fire-performance of steel trusses with spray-applied fire protection, and with end restraint conditions similar to that present in the two towers, is not well understood, but is likely critical to the building collapse. Studies of the fire-performance of this structural system should be conducted.

e. Observations of the debris generated by the collapse and of damaged adjacent structures suggests that spray-applied fireproofing may be vulnerable to mechanical damage from blasts and impacts. This vulnerability is not well understood. Tests of these materials should be conducted to understand how well they withstand such mechanical damage and to determine whether it is appropriate and feasible to improve their resistance to such damage.

f. In the past, tall buildings have occasionally been damaged, typically by earthquakes, and experienced collapse within the damaged zones. Those structures were able to arrest collapse before they progressed to a state of total collapse. The two WTC towers were able to arrest collapse from the impact damage but not from the resulting fire when combined with the impact effects of the aircraft attack. Studies should be conducted to determine, given the great size and weight of the two towers, whether there are feasible design and construction features that would permit such buildings to arrest or limit a collapse, once it began.

WTC 3 was subjected to extraordinary loading from the impact and weight of debris from the two adjacent 110-story towers. It is noteworthy that the building resisted both horizontal and vertical progressive collapse after the collapse of WTC 2. The overloaded portions were able to break away from the rest of the structure without pulling it down and the remaining structural system was able to remain stable and support the debris load. The structure was even capable of protecting occupants after the collapse of WTC 1.

WTC 3 should be studied further to understand how it resisted progressive collapse.

a. This office building was built over an electrical substation and a power plant, comparable in size to that operated by a small commercial utility. It also had a significant amount of diesel oil storage and had a structural system with numerous horizontal transfers for gravity and lateral loads.

b. The loss of the east penthouse on the videotape records suggests that the collapse event was initiated by the loss of structural integrity in one of the transfer systems. Loss of structural integrity was likely a result of weakening caused by fires on the 5th to 7th floors. The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time. Although the total diesel fuel on the premises contained massive potential energy, the best hypothesis has only a low probability of occurrence. Further research, investigation, and analyses are needed to resolve this issue.

c. The collapse of WTC 7 was different from that of WTC 1 and WTC 2. The towers showered debris in a wide radius as their external frames essentially "peeled" outward and fell from the top to the bottom. In contrast, the collapse of WTC 7 had a relatively small debris field because the facade came straight down, suggesting an internal collapse. Review of video footage indicates that the collapse began at the lower floors on the east side. Studies of WTC 7 indicate that the collapse began in the lower stories, either through failure of major load transfer members located above an electrical substation structure or in columns in the stories above the transfer structure. Loss of strength due to the transfer trusses could explain why the building imploded, with collapse initiating at an interior location. The collapse may have then spread to the west, causing interior members to continue collapsing. The building at this point may have had extensive interior structural failures that then led to the collapse of the overall building, including the cantilever transfer girders along the north elevation, the strong diaphragms at the 5th and 7th floors, and the seat connections between the interior beams and columns at the building perimeter.

The scope of this study was not intended to include in-depth analysis of issues. Certain issues should be explored before final conclusions are reached and additional studies of the performance of the WTC 7 building and related building performance issues should be conducted. These include the following:

a. Additional data should be collected to confirm the extent of the damage to the south face of the building caused by falling debris.

b. Determination of the specific fuel loads, especially at the lower levels, is important to identify possible fuel supplied to sustain the fires for a substantial duration. Areas of interest include storage rooms, file rooms, spaces with high-density combustible materials, and locations of fuel lines. The control and operation of the emergency power system, including generators and storage tanks, needs to be thoroughly understood. Specifically, the ability of the diesel fuel pumps to continue to operate and send fuel to the upper floors after a fuel line is severed should be confirmed.

c. Modeling and analysis of the interaction between the fire and structure are important. Specifically, the anticipated temperatures and duration of the fires and the effects of the fires on the structure need to be examined with an emphasis on the behavior of transfer systems and their connections.

d. Suggested mechanisms for a progressive collapse should be studied and confirmed. How the collapse of an unknown number of gravity columns brought down the whole building should be explained.

e. The role of the axial capacity between the beam-column connection and the relatively strong structural diaphragms may have had in the progressive collapse should be explained.

f. The level of fire resistance and the ratio of capacity-to-demand required for structural members and connection deemed to be critical to the performance of the building should be studied. The collapse of some structural members and connections may be more detrimental to the overall performance of the building than other structural members. The adequacy of current design provisions for members whose failure could result in large-scale collapse should also be studied.

The Building Performance Study Team has developed recommendations for specific issues, based on the study of the performance of the WTC towers and surrounding buildings in response to the impact and fire damage that occurred. These recommendations have a broader scope than the important issue of building concepts and design for mitigating damage from terrorist attacks, and also address the level at which resources should be expended for aircraft security, how the fire protection and structural engineering communities should increase their interaction in building design and construction, possible considerations for improved egress in damaged structures, the public understanding of typical building design capacities, issues related to the study process and future activities, and issues for communities to consider if they are developing emergency response plans that include engineering response.

National Response. Resources should be directed primarily to aviation and other security measures rather than to hardening buildings against airplane impact. The relationship and cooperation between public and private organizations should be evaluated to determine the most effective mechanisms and approaches in the response of the nation to such disasters.

Interaction of Structural Elements and Fire. The existing prescriptive fire resistance rating method (ASTM E119) does not provide sufficient information to determine how long a building component can be expected to perform in an actual fire. A method of assessing performance of structural members and connections as part of a structural system in building fires is needed for designers and emergency personnel. The behavior of the structural system under fire conditions should be considered as an integral part of the structural design. Recommendations are to:

Performance criteria and test methods of fireproofing materials relative to their durability, adhesion, and cohesion when exposed to abrasion, shock, vibration, rapid temperature rise, and high temperature exposures need further study.

Interaction of Structural and Fire Professionals in Design. The structural, mechanical, architectural, fire protection, blast, explosion, earthquake, and wind engineering communities need to work together to develop guidance for vulnerability assessment, retrofit, and design of concrete and steel structures to mitigate or reduce the probability of progressive collapse under single- and multiple-hazard scenarios. An improved level of interaction between structural and fire protection engineers is encouraged. Specific recommendations are to:

Fire Protection and Engineering Discipline. The continued development of a system for performance- based design is encouraged. This involves the following:

Building Evacuation. The following topics were not explicitly examined during this study, but are recognized as important aspects of designing buildings for impact and fire events. Recommendations for further study are to:

Emergency Personnel. One of the most serious dangers firefighters and other emergency responders face is partial or total collapse of buildings. Recommended steps to provide better protection to emergency personnel are:

Education of Stakeholders. Stakeholders (e.g., owners, operators, tenants, authorities, designers) should be further educated about building codes, the minimum design loads typically addressed for building design, and the extreme events that are not addressed by building codes. Should stakeholders desire to address events not addressed by the building codes, they should have a basic understanding of developing and implementing strategies to mitigate damage from extreme events. Stakeholders should also be educated about the expected performance of their building when renovations, or changes in use or occupancy, occur and the building is subjected to different floor or fire loads. For instance, if the occupancy in a building changes to one with a higher fire hazard, they should review the fire protection systems to ensure there is adequate fire protection. Or, if the structural load is increased with a new occupancy, the structural support system should be reviewed to ensure it can carry the new load.

Study Process. The report benefited from a tremendous amount of professional volunteerism due to the unprecedented level of national disaster. Improvements can be made that would aid the process for any future efforts. Recommendations are to:

Archival Information. Archival information has been collected and provides the groundwork for continued study. It is recommended that a coordinated effort for the preservation of this and other relevant information be undertaken by a responsible organization or agency, capable of maintaining and managing such information. This effort would include:

ASCE is proud of the work done by the BPS Team, but strongly believes that the follow up studies recommended by the FEMA/ASCE Report are critical to obtaining the technical knowledge needed by engineers for future building design.

Thank you for the opportunity to express ASCE’s views. We offer you and all of the agencies involved in the recovery efforts ASCE’s full resources to manage the nation's critical infrastructure needs. We are ready to help in any way possible, and are eager to hear from you regarding ways that ASCE’s Critical Infrastructure Response Initiative can support you as you examine our infrastructure needs in the coming months.

National Building and Fire Safety Investigation of the World Trade Center Disaster
Technical Area	Outputs
Identification of Technical Issues and Major Hypotheses	· Public Meetings to gather information to guide plan for NIST investigation. · Report(s) on NIST Investigation Plan Approach and Process.
Analysis of Building and Fire Codes and Practices	· Report(s) on Analysis of Building and Fire Codes and Practices.
Aircraft Impact Analysis and Damage Prediction	· Report(s) on Aircraft Impact Analysis and Damage Prediction.
Forensic Analysis of Structural Steel	· Report(s) on Forensic Analysis of Structural Steel.
Analysis of Built-In Fire Protection Systems	· Report(s) on Analysis of Built-In Fire Protection Systems.
Prediction of Thermal Environment	· Report(s) on Prediction of Thermal Environment.
Structural Fire Response and Vulnerability	· Report(s) on Structural Fire Response and Vulnerability.
Structural Collapse Vulnerability and Mechanisms	· Report(s) on Structural Collapse Vulnerability and Mechanisms.
Occupant Behavior and Egress	· Report(s) on Occupant Behavior and Egress.
Fire Service Technologies and Guidelines	· Report(s) on Fire Service Technologies and Guidelines
Fire Codes and Standards	· Report(s) on Elevator and Fire Resistance Standards.
Technical Findings and Recommendations	· Interim and Final Reports on the Technical Findings and Recommendations of the Investigation, including probable technical causes of the disaster.
Dissemination and Deployment of Findings	· Dissemination and Deployment of Findings via proposed standards and codes changes and participation with industry in their adoption and acceptance into codes and standards.

May 1, 2002

Professor Glenn P. Corbett

John Jay College of Criminal Justice

Before the

Committee on Science

House of Representatives

United States Congress