Probabilistic Seismic Assessment of RC Tall Regular Buildings Having Special Moment Frames Subjected to Long-period Earthquakes

Numerous tall buildings in the world are located in cities near active faults. Generally, past near-fault earthquakes had predominant period greater than 1 sec. so called as long-period earthquakes. In such earthquakes, tall building having great natural period seems to be more vulnerable. In this research, seismic performance of RC tall buildings having special moment frames subjected to long-period earthquakes are assessed via fragility curves. Subsequently, three models of 15, 25 and 35 story buildings are modelled in OpenSEES and IDA analysis is performed under long and short period earthquakes. Considering maximum nonlinear drifts as engineering demand parameter, seismic fragility curves at different performance levels are developed. By comparing the fragility curves and their median values, the effect of earthquake predominant period on the seismic performance of high-rise buildings are discussed. It is concluded that, the RC tall buildings, are more vulnerable in Long-period earthquakes compared with short period ones. At low damage levels such as slight and moderate, this difference seems to be small but for extensive and complete damage levels the considered models are much more fragile in long period records. So that the average values of seismic fragility for 35 story building model Subjected to short-period earthquakes at partial, medium, wide and complete damage levels are equal to the values of 0.084g, 0.16g, 0.44g and 0.95g, respectively. However, these values are equal to 0.032g, 0.065g, 0.175g and 0.39g, respectively, for earth motion with high period. As in complete damage level the seismic median fragility decreased 60 % for long- period earthquakes.