Effect of eliminating the column on progressive collapse on seismic performance in dual steel structures

Progressive collapse is usually defined as follows: the expansion of an initial local damage within structures as a chain chemical reaction that led to the partial or total collapse of the structure. Studies in relation to the failure of structural systems in recent years highlight the importance of the phenomenon of progressive collapse caused by abnormal loading such as: accident injuries, earthquake, explosion, and etc. in order to prevent or reduce the occurrence of progressive collapse, various strategies are provided for design against progressive failure in American government documents such as: GSA and UFC. In these regulations, the loss of bearing capacity of column is considered as a promising phenomenon to investigate the performance of structure against abnormal loading. In this study, three steel structures with dual side load bearing system, average moment frame, and bracing system of 5, 10, and 15 floors were designed in Etabs 2013 software; then, using the GSA2003 regulation and selecting the method of alternative route of load transformation, foregoing structures were modeled as three-dimensional in OpenSEES software; and using nonlinear static analysis and nonlinear dynamic analysis, structures has been investigated against progressive collapse; and the results of nonlinear static analysis and nonlinear dynamic analysis compared with each other. After reviewing the results of the analysis showed that for every two analysis, removing the side column is most critical state of column elimination. In all three structures, removing the column in ground floor level creates most critical state for structure towards higher levels. By increasing the height of the structure, robustness index also is increased.