Effect of variation in design acceleration spectrum on the seismic resilience of a building

Abstract

Past studies have shown that the ground motion is of a highly random nature. It was found in past literature that there exist large variations in ground motion characteristics at other sites for the same earthquake, as well as for the same site from other earthquakes. These large variations in ground motion characteristics illustrate the difficulties in accurately predicting demands of future earthquakes which always leads us to the challenge in identifying the design ground motions that gives a reasonable probability of having credible design provisions. The present study is focused on finding the effect of variations in ground motions on an important design parameter, seismic resilience of a building. The change in ground motion characteristics has been considered through the design acceleration spectrum of the Indian Standard code IS:1893–2016 (Part-1) which depends on several factors viz. Zone factor (Z), importance factor (I) and response reduction factor (R). An existing reinforced concrete building of G + 10 storey with I = 1.5 and R = 5 was considered. The behavior of the building was examined for the six combinations of I/R ratio and corresponding drop down in the functionality and the seismic resilience was evaluated. The result shows the existing building has a significant increase in the demand displacement, demand ductility and loss in seismic resilience at the combination I = 1.5 and R = 3 with increase in the cumulative damage probability of exceedance corresponding to the “Extreme” and “Collapse” state. This was due to the sudden increase in future seismic acceleration (Ah) when compared with designed seismic acceleration.