Investigation of progressive collapse-resisting capability of steel moment frames using push-down analysis

In this study the vertical push-down analysis was conducted to investigate the resistance of steel moment frames for progressive collapse. The analysis was carried out by gradually increasing the vertical displacement in the location of the removed column and the vertical load in all spans corresponding to the increase of vertical displacement. The analysis results showed that the load resisting capacity increased as the number of stories and the number of spans increased. However, as the length of a span increased, the load resisting capacity against progressive collapse decreased. The load-displacement relationships obtained from push-down analyses were compared with those obtained by incremental nonlinear dynamic analyses, and the results showed that the maximum load factors resulted from the dynamic analyses were a little less than those from the push-down analyses. This implies that the push-down analysis might overestimate the inherent capacity of structures against progressive collapse.