Call for a Measured Response to NIST’s WTC Recommendations
Two risk and fire-safety experts have called for a balanced, measured response to recommendations on tall building regulation and design released by the National Institute of Standards and Technology in response to the World Trade Center collapse.
“It is important that we learn all we can about how the WTC towers collapsed, but we must be careful not to take building-specific and event-specific failure information out of context,” said Brian Meacham, risk consulting team leader for London-based engineering firm Arup. “We need to recognize that not all factors that contributed to the WTC collapse may be applicable to other building designs.”
Meacham is widely regarded as a leading authority on risk-informed performance-based design and regulation. He recently participated in the National Construction Safety Team investigation of The Station nightclub fire in Rhode Island and currently chairs the Risk and Security Advisory Committee for the New York City Department of Buildings building code development effort.
“Everyone knows that there is no such thing as zero risk—in most cases the best we can hope for is to strike a balance between a tolerable level of risk and the cost of risk mitigation. People make this kind of choice every day,” Meacham said. “This understanding is also reflected in building codes. For example, buildings are not designed to withstand any earthquake that could happen. That is not practical or cost effective. Instead, a risk-informed approach recognizes that although an extreme earthquake—or an extreme fire or terrorism event—might result in building failure, for lesser events the building will perform suitably to provide life safety. Designing for any fire, blast or impact that could possibly occur, with the assumption that all protection systems fail at the time of the event, is simply not practical.”
Barbara Lane, an expert in structural fire design solutions who leads Arup’s Structural Fire group, said the NIST recommendations discussed specific fire mitigation and protection measures but needed to look more at structural solutions as well.
“While we understand the importance of hourly ratings, sprinklers and other protection measures, as emphasized by NIST, it’s our belief that the detailing of structural systems to withstand fire is the most robust way of designing tall buildings to withstand fire events,” Lane said. “This, in our view, is the best way of defending against collapse in fire, and we would like to see it forming the basis of future building codes and design of high-rise buildings.”
“We consider thermal expansion of material in fire to be the leading factor in a collapse,” she added. “This subject does not seem to have been addressed in NIST’s recommendations, but we hope it will become part of the ongoing discussion going forward.”
The comments from Arup’s experts will be expanded in a forthcoming, thorough review of NIST’s recommendation by Arup’s Fire Safety and Risk teams.
“People want to live and work in buildings that are comfortable and safe; they do not want to live and work in bunkers,” Meacham concluded.” They want openness, access to natural light, and working/living spaces that promote a sense community. To design buildings that meet all occupant expectations, we need to be careful that regulatory requirements do not limit our ability to balance all expectations through a balanced, integrated systems approach.”