6.3 Structural

Given the evolving nature of the terrorist threat, it is impossible to predict what threats may be of concern during the lifetime of the building; it is therefore prudent to provide protection against progressive collapse initiated by a localized structural failure caused by an undefined threat. Because of the catastrophic consequences of progressive collapse, incorporating these measures into the overall building design should be given the highest priority when considering structural design approaches for mitigating the effects of attacks.

Explicit design of secondary structural components to mitigate the direct effects of air-blast enhances life safety by providing protection against localized failure, flying debris, and air blast entering the building. It may also facilitate evacuation and rescue by limiting the overall damage level and improving access by emergency personnel.

Specific issues related to structural protection measures are discussed separately in the sections below.