Progressive collapse is the process where a primary structural element fails, resulting in the failure of adjoining structural elements, which in turn causes further structural failure. Progressive collapses may be accidental, as the result of design deficiencies, fire, unintentional overload, material failure or natural phenomenon (e.g. erosion, wind or earthquakes). They can also be induced deliberately as a demolition method, specifically that of building implosion, or caused by acts of terrorism or war.

Notable examples

Terminology

As the resulting damage in a progressive collapse is disproportionate to the original cause, the term disproportionate collapse is frequently used in engineering to describe this collapse type.

Model code changes

Based on recommendations from the United States Commerce Department's National Institute of Standards and Technology (NIST), a comprehensive set of building code changes were approved by the International Code Council (ICC). The recommendations were based on the findings of NIST's three-year investigation of the collapses of New York City's World Trade Center (WTC) towers on September 11, 2001. The proposals addressed areas such as increased resistance to building collapse from fire and other incidents, use of sprayed fire-resistive materials (commonly known as "fireproofing"), performance and redundancy of fire protection systems (i.e., automatic sprinklers), fuel oil storage/piping, elevators for use by first responders and evacuating occupants, the number and location of stairwells, and exit path markings. The model code changes consistent with the NIST WTC investigation recommendations that are now required by the IBC include: