Post-earthquake progressive failure resistance of steel frames under column-removal scenarios

Abstract

Removal of primary structural components such as columns from structures may rapidly result in a progressive collapse to trigger. While investigating the progressive collapse of structures has been a demanding subject for decades, rare studies have yet been performed on post-earthquake progressive collapse. This article investigates the possibility of progressive collapse in seismically designed steel structures under post-earthquake column removal scenarios. In this line, 14 structures with different stories, span number, span length, behavior factor, and seismic hazard levels are investigated. The cases studied are first controlled for column removal scenarios under only the gravity loads. The cases are then subjected to 12 seismic accelerations with different specifications followed by column removal scenarios in arbitrary locations. Results show that not all of the cases studied can keep their robustness when faced with such scenarios. The results show that two factors, behavior factor, and seismic specifications, can highly increase the possibility of post-earthquake progressive collapse. As well, the results show that upper stories are more vulnerable toward progressive collapse rather than the lower stories. It is concluded that designing structures for seismic loads cannot necessarily guarantee structural safety under the column removal scenarios, either under the gravity loads alone or under post-earthquakes. Therefore, mitigation strategies should be adopted in advance to increase the safety levels of structures when such scenarios are the case.