S. Shyam Sunder is the Deputy Director of the Building and Fire Research Laboratory (BFRL) at the National Institute of Standards and Technology (NIST), and he also serves as the lead investigator for the federal building and fire safety investigation of the World Trade Center (WTC) disaster.
In this brief interview, Dr. Sunder explains the methodologies NIST used in its analysis of the WTC disaster, and he offers recommendations for improving building performance, occupant evacuation and emergency response.
How did NIST determine which methodologies to use in its analysis of the World Trade Center (WTC) disaster?
Since the collapse of the two towers did not leave behind much physical evidence, we used the following methodologies in our analysis:
1. We determined the properties of the steel recovered from the collapsed buildings to analyze the performance of the building components during the aircraft impact and subsequent fires.
2. We reviewed video footage and photographs of the attacks and collapse to determine the condition of the buildings following aircraft impact, the evolution of the fires and the subsequent deterioration of the structures.
3. We established a baseline performance analysis of the WTC towers to estimate the expected performance of the towers under normal design loads and conditions and the capacity of the towers to withstand the attacks of September 11, 2001.
4. We conducted four-step simulations of the behavior of each tower on September 11, 2001. The four steps included:
1. The aircrafts' impact into the towers, the resulting distribution of aircraft fuel and the damage to the structures, partitions, thermal insulation materials and building contents.
2. The evolution of multi-floor fires.
3. The fires' heating and weakening of structural elements.
4. The response of the damaged and heated building structures and the progression of structural component failures, which lead to the initiation of the collapse of the towers.
To increase the accuracy of the simulation results, NIST used:
1. Visual evidence.
2. Eyewitness accounts from both inside and outside the buildings.
3. Laboratory tests involving large fires and the heating of structural components.
4. Formal statistical methods to identify influential parameters and to quantify variability in the analysis results.
What impact has NIST's analysis of the WTC disaster had on current national building and fire model codes, standards and safety practices since it was released? What recommendations has NIST made for the future?
We released the preliminary results of our analysis in April 2005 and the final results in June 2005. By making these reports public, NIST has positively impacted current national building and fire model codes, standards and safety practices.
For example, model code organizations are working to improve building classification systems and to require a higher fire rating for buildings over 420 feet in height. Also, the International Code Council and the National Fire Protection Association, which issues the Building Construction Safety Code (NFPA 5000), have made a commitment and established procedures to work with NIST to consider our recommendations for improving the safety of buildings, occupants and emergency responders.
NIST has issued a total of 30 safety recommendations for improvements to codes, standards and practices. Our recommendations are grouped as follows:
1. Increase structural integrity.
2. Enhance the fire resistance of structures.
3. Develop new design methods that will help structures to resist fires.
4. Improve active fire protection.
5. Improve building evacuation.
6. Improve emergency response.
7. Improve procedures and practices.
8. Provide education and training programs for fire protection engineers, structural engineers and architects.
How will fireproofing conditions in future buildings and structures be affected or improved based on NIST's analysis?
We believe that future fireproofing conditions can be improved by:
1. Establishing performance requirements for fireproofing that will determine the thermal performance and mechanical ability of the fireproofing to bond with steel.
2. Developing better inspection procedures for fireproofing in buildings as well as conformance criteria that will maintain quality control in the field commensurate with the fire rating tests that are typically conducted under tightly controlled conditions.
3. Improving the century-old fire resistance testing methods for components, assemblies and systems.
4. Developing and evaluating better fire-resistant materials and coatings.
NIST identified several areas of enhancement with respect to command and control and occupant preparedness during the WTC disaster. What specific recommendations does NIST make so that buildings in major metropolitan areas can improve emergency communications for command and control and occupant preparedness should a similar disaster occur in the future?
To improve occupant preparedness and emergency evacuation and to increase public awareness, we recommend that public agencies, non-profit building and fire safety organizations and building owners and managers develop public education campaigns and hold regular emergency evacuation drills for both occupants and first responders.
Tall buildings should also be designed with adequate egress capacity so that full-building evacuations may be completed in timely manner. Their design should accommodate self-evacuation by those who are mobility-impaired, and they should also provide emergency access for first responders. The hardened installation of fire-protected and structurally protected elevators in tall buildings may facilitate egress as well, but keep in mind that only a certain percentage of elevators in tall buildings would need to be enhanced in this way to conduct full evacuation of all occupants.
We believe that both intraoperability (within an agency) and interoperability (across agencies) are critical to improving emergency communications for command and control. Communication technology must be able to work within tall steel- and concrete-reinforced structures as well as during large-scale emergencies in which over 500 first responders may be operating at the site of an incident.
We also recommend the:
1. More efficient coordination and sharing of information among emergency responders and building occupants.
2. More robust design of emergency public address systems and emergency responder communication systems.
3. Regular use of the Integrated Public Alert and Warning System (previously known as the Emergency Broadcast System).
4. Regular inspection and testing of emergency communications systems, radio communications and associated operating protocols.
S. Shyam Sunder is Deputy Director of the Building and Fire Research Laboratory (BFRL) at the National Institute of Standards and Technology (NIST).
In this position, Dr. Sunder:
Is the chief operating officer for a $40 million-per-year enterprise with 180 employees and 100 research associates
Serves as the lead investigator for the federal building and fire safety investigation of the World Trade Center disaster
Leads NIST activities as the lead agency for the National Earthquake Hazards Reduction Program (NEHRP)
Oversees NIST activities related to the National Construction Safety Team Act
Guides the effective implementation of NIST's strategic plan within BFRL
Chairs the Interagency Committee on Seismic Safety in Construction (ICSSC)
Serves as the U.S.-side chair of the Wind and Seismic Effects Panel
Prior to joining NIST, Dr. Sunder worked in such positions as instructor, assistant professor, associate professor, principal research scientist and senior research scientist at the Massachusetts Institute of Technology (MIT).
Dr. Sunder holds a bachelor of technology degree in civil engineering from the Indian Institute of Technology. He also holds a master of science degree in civil engineering and a doctor of science degree in structural engineering both from MIT.