An energy-based partial pushdown analysis procedure for assessment of disproportionate collapse potential

A disproportionate (or progressive) collapse is triggered by localized structural damage that propagates throughout a large portion of a structural system. The current guidelines issued by the US Department of Defense use the alternative path method to assess the vulnerability of a structural system to disproportionate collapse. In this method, the capability of a structure to sustain local damage is evaluated by notionally removing primary load-bearing elements and checking whether the local damage can be absorbed. The assessment can be performed using linear or nonlinear static structural models or a nonlinear dynamic model. Although nonlinear dynamic analysis gives the most accurate results, it is computationally intensive and requires considerable skill to implement properly. In this paper, the vulnerability of three steel frames to disproportionate collapse is assessed using an energy-based nonlinear static pushdown analysis. The predictions are sufficiently close to the results of a nonlinear dynamic time history analysis that the method would be useful for disproportionate collapse-resistant design of buildings with regular steel framing systems.