“Seismic fragility assessment of RC framed structures under varying ground motion duration”

Abstract

Earthquakes are considered as the major unpredictable natural phenomenon often resulting in major disasters. Here in this study, the effect of the duration is isolated from other parameters related to ground motion like amplitude, and response spectral shape by assembling spectrally equivalent long and short duration pairs of records using Seismomatch and Seismosignal. The performance of buildings constructed in accordance with Nepal's National Building Codes of Practice in relation to seismic design is carried out. Incremental dynamic analysis is performed using SAP2000. From results, it shows that the lateral story displacements increase with the increase in duration. The collapse prevention state for lower story buildings is attained at higher values of Peak ground acceleration compared to higher story buildings with a decrement in value of PGA at collapse by 8.8%, 15.38%, 18.32% and 29% respectively for long-duration motions for 4 to 7 story building respectively. The fragility curve shows the increase in the probability of collapse by 40%, 30%, 45 % and 50% respectively for 4 to 7-story buildings with decreasing value of PGA. Also, there is an increase of collapse capacity ratio respectively for higher-story building when significant duration value increased from 2 to 4 times. So, it is concluded that longerduration earthquakes have significant effects on seismic responses of the structure.