Seismic vulnerability assessment of RC high-rise building considering soil–structure interaction effects

A rapid visual survey is conducted in Patna city to understand the building stock and its characteristics. The stock is classified per FEMA 154. Reinforced concrete moment resisting frames constitute the majority of the buildings in Patna and the ratio of low-, mid- and high-rise buildings are in the ratio 2:2:1. The percentage of soft storey buildings in Patna is 23.37%. The finite element model of a representative 15-storey special moment resisting frame building is modelled utilizing the survey data. It is modelled with and without soil–structure interaction (SSI) effects to access the variation in the structural responses with and without SSI effects. The fundamental time period is underestimated in the fixed base model by 1.38 times when compared to the model with SSI effects. A set of raw acceleration time histories is obtained from PEER NGA WEST2 database and scaled to bedrock site-specific design spectra for Patna. The time histories are further checked for soil amplification and the ground motions representative of surface motions in Patna are generated. The seismic vulnerability of the representative building is assessed by Incremental dynamic analysis. Floor displacement and inter-storey drift are significantly underestimated in the fixed base model when compared to the SSI model. A realistic building located in the study region is also studied with and without soft-storey effects. The maximum IDR gets concentrated on the first floor with the ground floor as soft storey and the seismic risk is highly amplified by the use of soft storey.