NIST proposes 'holistic' approach to WTC study
The National Institute of Science and Technology solicited public comment in New York City last month for its proposed comprehensive look into the World Trade Center collapse and lessons learned. Released June 10, the National Building and Fire Safety Investigation of the World Trade Center Disaster plan states that it will "strive to study the disaster holistically, paying particular attention to the interplay between the building, the occupants and the emergency responders." It includes eight major projects.
The June 25 meeting came in the wake of the Building Performance Assessment Team (BPAT) report presented to the House Science Committee on May 1 by the 25-member team of structural and fire protection engineers assembled by the Federal Emergency Management Agency and the American Society of Civil Engineers (BD&C 6/02, p. 14). Their findings suggested that the WTC would have remained standing if fire had not overwhelmed its weakened structures.
On the heels of those conclusions, the agenda of many of the NIST speakers included comments on fire protection coating, or the lack of it, on the WTC's lightweight floor trusses. According to James Quintiere, a fire protection engineering professor at University of Maryland, differences in reported coating thickness told the story.
BPAT found a 3/4 in. thickness in Tower 2 and 1-1.5 in. thickness in Tower 1. The corresponding collapse times were 56 and 104 minutes, respectively. "One does not have to be an expert to see the correlation," said Quintiere.
Roger Morse, an architect and fireproofing expert, echoed Quintiere's concern about thickness variation, citing numerous cases in other buildings where he had seen material application problems. "Fireproofing is often applied from the floor, and the operator can't always see what he's doing," Morse said.
He also noted the type of insulation used is an essential issue that needs further examination. Morse pointed out that the substitute material, a spray vitreous fiber formulation once thought to be a viable asbestos substitute had since been found to have inferior durability.
Decidedly pro-concrete were numerous fire service advocates, citing several studies where fires in concrete-encased, steel-frame structures, including the Empire State Building, had done little permanent damage. But aside from fireproofing, George Miller, president of the National Association of State Fire Marshals, charged that a crucial missing consideration from the BPAT study was insufficient discussion of the WTC's contents. Items such as furniture, wall coverings, computer equipment and documents "kept the fire burning as it did. We do a great deal to calculate [requirements for] a warehouse full of goods. But we do little to restrict the fuel load where people work, live and learn," argued Miller.
Other speakers offered especially strong reminders to NIST about life safety issues that they charge are sorely missing from the BPAT study, such as firefighting technologies and practices for tall buildings, occupant behavior, evacuation procedures, emergency response, and the performance of active fire protection systems such as sprinklers, manual suppression, fire alarms, and smoke management systems.
Some at the meeting said they were members of the Skyscraper Safety Campaign, a project of parents and families of firefighters and 9/11 victims which many claim has been responsible for pushing Congress to mandate more investigation.
NIST, however, has proposed limiting the involvement of such parties, an issue that was not lost on Campaign Chair Sally Renehard, who was the meeting's first speaker. She took dead aim at the proposal, which suggests omitting those who "represent or [are] affiliated with parties affected directly by the investigation." Renehard noted that "every single member of the ASCE is 'affiliated with' either the engineering, design or construction communities which were involved with the building of the WTC."
Her group also is seeking to mandate that all local and national code-making bodies be made up of at least 50% representatives from the Fire Service and academics in Fire Science engineering.
Looking forward, a few speakers suggested studying the surrounding buildings as perhaps more relevant to the type of construction either in place or likely to be built in the near future, and thus more helpful. "Focusing on buildings 1, 2 and 7 may be too limited, in terms of good and bad performance that day," said Charles Carter of the American Institute of Steel Construction.