Probabilistic Seismic Demand of 2-D Steel Moment Resisting Frames in Estimation of Collapse under Earthquake Ground Motions

ABSTRACT: This study concentrates on evaluation and estimation of collapse of two 3-story and 9-story steel moment resisting frames designed by SAC/ FEMA for the place of Los Angeles California. “Collapse” in this research is defined as the loss of lateral load-resisting capacity of frame structural system by the application of ground motion and by considering P-Δ effects on the dummy column. Dummy column is connected to the steel moment-resisting frame in order to consider the effects of gravity loads of the real 3-D structure while 2-D frame is extracted from 3-D frame. Estimation of collapse performance requires the relation between a ground motion intensity measures (IM) and the probability of collapse defined as collapse fragility curve as well as the relation between the same ground motion IM and the seismic hazard for the building defined as seismic hazard curve. Among two methods of estimating the collapse fragility curve; IM-based and EDP-based, the first method is carried out in this research because of its better performance in collapse limit state according to the previous research. In this approach, collapse is associated with ground motion IM and it is obtained by using Incremental Dynamic Analysis. The collapse performance criteria that are obtained from this research are compared with the collapse performance criteria recommended by Haselton and SAC/FEMA guidlines. Keywords: Incremental dynamic analysis, Fragility curve, Mean annual frequency, Seismic Hazard Curve, Probabilistic. ……………………………………………………………………………………………………………………………………………………………………………………………………………………