“Measured response” needed for tall buildings

Two acknowledged US-based experts in risk and security management and fire safety have called for a “balanced, measured response” to recommendations on tall building regulation and design issued by the US Commerce Department’s National Institute of Standards and Technology (NIST) in direct response to the World Trade Centre atrocities of 9/11.

The NIST’s recommendations look set to take hold in Europe and the UK in due course.

“It is important we learn all we can about how the World Trade Centre towers collapsed, but we must be careful not to take building-specific and event-specific failure information out of context,” commented Brian Meacham, risk consulting team leader for global engineering specialist Arup.

“We need to recognise that not all factors that contributed to the collapse of the Twin Towers may be directly applicable to other building designs,” he added.

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 as engineers is to strike a balance between a tolerable level of risk and the cost of mitigating any identified risks. People make this kind of choice every day,” explained Meacham. “This understanding is also reflected in building codes. For example, buildings are not designed to withstand any earthquake that could happen. Similarly, designing for any fire, bomb blast or other 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 discuss specific fire mitigation and protection measures, but must also consider structural solutions.

Lane told SMT: “While we understand the importance of hourly ratings, sprinklers and other protection measures, it is our firm belief that the detailing of structural systems to withstand fire is the most robust way of designing tall buildings to withstand fire events. We would very much like to see this view form the basis of future building codes and the design of high-rise structures.”

Lane considers the thermal expansion of material in fire to be the leading factor in a given building’s collapse.

“This subject does not seem to have been addressed in the NIST’s recommendations, but we very much hope it will at some point.”