f Nateghi-A - International Institute of Earthquake Engineering and Seismology, Tehran, Iran
n Parsaeifard - International Institute of Earthquake Engineering and Seismology, Tehran, Iran

Progressive collapse is a kind of failure in which the collapse of one or several load bearing elements is ended in partial or total collapse of structures. If earthquakes induce progressive collapse, seismic and gravityloads cause initial failure propagating to other parts of structures. Therefore, seismic progressive collapse canoccur in structures regardless the number of stories. In this paper the behavior of a one story steel building isstudied to investigate the effect of initial damaged column position on the seismic progressive collapse. In this regard the critical position of damaged column has been identified first and then, the effect of damaged column is studied. Accordingly, nonlinear dynamic analysis has been used to obtain the fragility curves of the structure and investigate its failure probability. A damage index has also been used to validate the results. Based on the results obtained in this research, the initial failure of a middle column can increase the failure probability of structures during earthquakes. Besides, among the evaluated design parameters, the failure probability is changed significantly in the columns in accordance with their axial loads.

Failure probability /Fragility curve/ Nonlinear dynamic /Progressive collapse