Probabilistic assessment of steel moment frames incremental collapse (ordinary, intermediate and special) under earthquake

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. Regarding to the possibility of destructive earthquakes in different parts of the world, detailed assessment of the structure's collapse has been one of the major challenges of the structural engineering. In this regard, offering models based on laboratory studies, considering the effective parameters and appropriate earthquakes could be a step towards achieving this goal. In this research, a five-story steel structure with a system of ordinary, intermediate and special moment frame (low, intermediate and high ductility) has been designed based on the local regulations. In this study, the effect of resistance and stiffness deterioration of the structural elements based on the results of the laboratory models have been considered and the ductility role in the collapse capacity of steel moment frames has been investigated as probabilistic matter. For this purpose, incremental dynamic analysis has been done under 50 pairs of earthquake records proposing FEMA P695 instruction and fragility curves of various performance levels are developed. Results showed higher collapse capacity of special moment steel frame than the intermediate and ordinary moment frames. In the 50 percent probability level, the collapse capacity of special moment frame increased 34 % compared to the intermediate moment frame and 66 % to the ordinary moment frame. Also, the results showed that for different collapse spectral accelerations, the use of special moment frame instead of intermediate and ordinary moment frames reduces the collapse probability to 30 and 50 % respectively.