Seismic risk assessment of reinforced concrete buildings in India using cumulative damage index‐based vulnerability functions

This study proposes a framework to evaluate probabilistic seismic risk of buildings in regions exposed to both crustal and subduction earthquakes. Ground motions from subduction earthquakes are typically longer in duration, causing higher damage to structure due to increased inelastic demand as compared to ground motions from crustal earthquakes having the same peak intensity. The increased vulnerability to structural damage from subduction earthquake ground motions needs to be accounted for in seismic loss assessment studies. This study investigates the same for India. The north and northeast of India are exposed to both crustal and continental subduction seismic sources, and Peninsular India is exposed to crustal seismic sources. Nonlinear analytical models are developed for a set of modern Indian code‐compliant reinforced concrete special moment frame buildings located at 20 different sites in India. Incremental dynamic analysis (IDA) of building models using spectrally equivalent ground motions from crustal and subduction earthquakes is used for developing tectonic‐region‐type‐specific (crustal and subduction) building vulnerability functions. The cumulative damage index is used as the engineering demand parameter to capture the increased inelastic demand from subduction earthquakes on buildings. For seismic risk assessment, the total seismic hazard at a site is separated into its contribution from crustal and subduction sources and combined with respective building vulnerability functions. The seismic risk of buildings is quantified by average annual loss ratio (AALR) through event‐based probabilistic seismic risk analysis. For buildings located in high seismic zones of India, this study finds that AALR can be up to 40% higher on average as compared to studies not accounting for increased building vulnerability from subduction earthquakes.