Collapse Assessment of Steel Moment Frames Based on Development of Plastic Hinges

Abstract

Building collapse is a level of the structure performance in which the amount of financial and life loss is maximized, so this event could be the worst incident in the construction. In this study, the collapse of low and mid-rise Regular special steel moment frames with 3, 6, and 9 story were designed by ETABS according to code guidelines and then the collapse of mentioned frames has been evaluated by nonlinear static pushover and incremental dynamic (IDA) analyses with SeismoStruct. The nonlinear static pushover analyses with three lateral load patterns were used to determine the likely location of the plastic hinges at the moment of probable failure mechanism for the mentioned frames and the nonlinear incremental dynamic analyses were used to assess the seismic intensities corresponding to form each failure mechanisms. Thus, the intensity of earthquake and the values of drift corresponding to the failure of studied frames were calculated. To perform nonlinear dynamic analyses, 10 far-fault records were used. The results of this study showed that the collapse of studied frames occurs under the far-fault records in different drifts and seismic intensities and the value of relative drift equivalent to the collapse limit varies from 2 to 5 percentage and It was also found that the collapse capacity of 3 and 6-story frames is 3.3 g and 3.4 g respectively in the uniform lateral load method and in 9-story frame, the collapse capacity of the first mode and linear lateral load methods is more and equals to 2.5 g.