INFRASTRUCTURE PROTECTIONPaving the Way for Collapse-Resistant Structures
Buildings in the U.S. are generally designed to withstand the usual suspects: rain, wind, snow and the occasional earthquake. Abnormal events such as gas explosions, vehicle impacts or uncontrolled building fires are not typically a consideration. If vulnerable buildings face any of these unanticipated events, the results could be tragic. But now, a new building standard can help engineers prevent the worst.
Buildings in the U.S. are generally designed to withstand the usual suspects: rain, wind, snow and the occasional earthquake. Abnormal events such as gas explosions, vehicle impacts or uncontrolled building fires are not typically a consideration. If vulnerable buildings face any of these unanticipated events, the results could be tragic. But now, a new building standard can help engineers prevent the worst.
The American Society of Civil Engineers (ASCE) has released the ASCE/SEI 76-23 Standard for Mitigation of Disproportionate Collapse Potential in Buildings and Other Structures, the first national building standard of its kind. Developed over the course of a decade and informed by research led by the National Institute of Standards and Technology (NIST), the standard provides design requirements and guidance to keep small, isolated failures in a structure from propagating and bringing down the entire building or a major part of it — a phenomenon the standard defines as disproportionate collapse.
“Many different loads are considered in designing a building, but if there’s an unanticipated load that you didn’t explicitly design for, it shouldn’t cause the whole building to collapse,” said NIST research engineer Joseph Main, a member of the ASCE committee that developed the standard.
Disproportionate collapse has always been a risk for large buildings, but the events are rare. For years, the need for a standard in the U.S. aimed specifically at disproportionate collapse was a contentious topic among experts.
After several notable building failures in the ‘90s and early 2000s, a consensus began to form.
In 1995, the Alfred P. Murrah Federal Building collapsed as a result of the Oklahoma City bombing, which initially destroyed three columns — damage that led to the subsequent crumbling of nearly half of the building. During the World Trade Center (WTC) disaster in 2001, the heat of unmitigated fires in the building called WTC7 caused deformations that severed a connection between a girder and column, triggering a progression of failures that brought the building down. At the conclusion of its WTC investigation, NIST highlighted the need for a standard geared at mitigating these collapses along with guidelines and tools for building design.
Based on a proposal NIST made to ASCE, the engineering society formed a new standards committee of dozens of building experts from industry, academia and the federal government.
