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Remarks by Dr. Shyam Sunder, Lead Investigator

Building and Fire Safety Investigation of WTC Disaster

News Media Briefing

August 21, 2002

[Remarks as prepared]

Thank you, Dr. Bement. Good morning to you all. I'd like to share with you specific details on the scope of 

the investigation, some of the advanced tools we expect to use, the steel we have recovered from the 

site, the broader data collection process, our plans to deal with human subjects, and the team we have 

assembled to carry out the investigation.

The NIST building and fire safety investigation will focus exclusively on three buildings: the WTC 

Towers—or WTC 1 and 2, and WTC 7—the 47-story building that collapsed later in the day on 

September 11, 2001. 

We will strive to study the disaster holistically, paying particular attention to the interplay between the 

buildings, the occupants, and the emergency responders.

The lessons to be derived from our investigation, that were enumerated earlier by Dr. Bement, will benefit 

a broad range of new and existing buildings, not just the three specific buildings that are studied.

As part of the investigation, we plan to conduct eight specific projects that will address the overall 

objectives.

#1: Analyze the code provisions, procedures, and practices used in the design, construction, 

operation, and maintenance of the structural, fire protection, and emergency access and 

evacuation systems.

#2: Analyze the margin of safety of each of the WTC Towers and its structural components under 

design, service, and abnormal aircraft loads and evaluate the effect of the aircraft impact damage 

on the structural, fire protection, and egress systems. 

#3: Determine the metallurgical and mechanical properties and quality of steel, weldments, and 

connections from the steel recovered from these buildings.

#4: Document and evaluate the performance of the active fire-protection systems—including 

sprinklers, fire alarms, smoke management systems, standpipes and hoses, and communication 

system—and their role in fire control, emergency response, and fate of occupants and emergency 

responders.

#5: Reconstruct the time-evolving temperature, thermal environment, and smoke movement—

including the effect of the fireproofing system—for use in evaluating structural response and the 

behavior and fate of occupants and responders.

#6: Analyze the structural fire response of the WTC towers—with and without aircraft damage, 

WTC 7, and open-web steel joist floor systems—with and without fireproofing, and determine the 

most probable collapse mechanisms of each of the buildings.

#7: Determine the behavior and fate of occupants and responders—both those who survived and 

those who did not—by collecting and analyzing new information on occupant behavior, egress, 

and emergency communications, and evaluating the performance of the evacuation system on 

September 11, 2001.
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#8: Building on the work already done by the Fire Department of New York and McKinsey & Co., 

determine the fire service procedures and practices up until WTC 7 collapsed, including factors 

such as building design, aircraft impact damage, communications and fire protection system 

failures, ability to fight large fires in the upper floors of tall buildings, firefighter location and 

tracking, resources available for situation assessment and incident management, equipment 

performance, pre-planning, and training.

We intend to use advanced scientific methods and tools extensively in the investigation. As an example, 

consider the preliminary simulation of the fireball that was generated when the second aircraft crashed 

into the South Tower, WTC 2. This simulation used NIST's Fire Dynamics Simulator, or FDS. It will help 

us estimate the amount of jet fuel that was consumed in the fire balls. Other examples, included in the Broll tape provided to you, show how FDS can be used to evaluate the source strength of the fire by 

modeling the smoke plume and to analyze the fire and smoke movement within the buildings.

In the investigation, we plan to develop far more accurate representations of the WTC buildings, their 

contents and thermal properties, and air supply within them to reconstruct the time-evolving temperature 

and smoke environment using this tool. The results of these reconstructions will be used to evaluate the 

structural response of the buildings in fire, and the behavior and fate of occupants and responders.

NIST now has in its possession in excess of 100 pieces of steel from the WTC site that were identified by 

the Structural Engineers Association of New York and other BPAT members, including NIST. These 

pieces, several of which you see around here, include perimeter columns, wide-flanged beams, and 

trusses. 

We plan to determine the metallurgical and mechanical properties of the steel, weldments, and 

connections, and to document the observed failure mechanisms and damage. This work will be very 

useful in estimating the temperature conditions in the buildings before collapse, and in analyzing both the 

structural response of the buildings to fire and the damage induced by the aircraft impact on the 

structural, egress, and fire protection systems.

I would like to draw your attention to the three pieces of steel on my left. The large upstanding piece is a 

prefabricated column element that was directly impacted by the first aircraft that crashed into the North 

Tower, WTC 1. The identification markings are visible clearly. As the charts here indicate, this piece of 

steel is one of many, now at NIST, tentatively identified to be from the near vicinity of the impacted region 

of this tower. We expect to test this steel at extremely high rates of loading—typical of those that would 

be encountered in an aircraft impact—using advanced technology now under development at NIST.

The second piece is a damaged and twisted open-web steel truss. This is a rare truss specimen that 

survived the collapse and was located by engineers at the salvage yards. The WTC towers made 

extensive use of these types of trusses to support the floor system by spanning the 35- to 60-feet 

distance between the exterior and interior columns. There is great interest in understanding how these 

types of trusses perform in fires, the ability of spray-applied fireproofing to stay in place on these trusses 

under shock, vibration, or impact, and how they are connected to the columns.

The third piece is a highly deformed and wrinkled column from one of the upper floors that we 

hypothesize could have been subjected to intense heat. A metallurgical analysis, that carefully studies 

changes in the microstructure of the steel, will allow us to estimate the temperatures reached in this 

specimen.

More broadly, we intend to base all of our review, analysis, modeling, and testing work for the 

investigation on a solid foundation of technical evidence. This will require unfettered and timely access to 
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critical data such as building documents, video and photographic records, oral histories, and emergency 

response records in addition to the steel that has been recovered. 

The Port Authority of New York and New Jersey and Silverstein Properties have offered to provide NIST 

with access to all such information in their possession or in the possession of their contractors and 

consultants. New York City authorities have also offered to fully cooperate with NIST in its investigation. 

We'd like to put out a special call today for photographic and video images that could help us better 

document the initial damage and the subsequent fire growth and spread in the WTC Towers and WTC 7. 

We are especially interested in WTC 7 and views of the South and West faces of the towers. Those who 

are aware of or in actual possession of such materials are encouraged to contact us. 

Our study of occupant behavior, evacuation, and emergency response will require a systematic collection 

of new data from survivors, families of victims, witnesses, and others with operational responsibility on 

September 11, 2001.

The NIST Director has directed us to carry out the investigation to the highest technical and professional 

standards, by treating all those who experienced this disaster first hand with kindness and sensitivity, and 

in accordance with all legal and administrative requirements.

We will use established procedures to carefully review all survey and interview questions, data collection 

methods, and safeguards for maintaining privacy and confidentiality before proceeding with these critical 

data collection efforts.

Finally, NIST has assembled a seasoned world-class team to carry out the investigation. This team has 

the needed technical expertise as well as experience from significant prior investigations. Over two dozen 

NIST experts will be involved over the course of the investigation. In addition, we expect to significantly 

augment our in-house staff with external world-class experts in our project teams and as contractors.

This concludes my prepared remarks. Thank you.