Comparison of Methodologies for Seismic Fragility Analysis of Designed RC Frame Building as Per Indian Provisions

The seismic fragility analysis is widely used worldwide to compute the seismic collapse probability of structures since last two decades. The evaluation of fragility functions using nonlinear structural analysis is a crucial step in many seismic assessment techniques. In the present study, four-storey mid-rise RC frame building located in Surat city (seismic Zone-III) is designed as per IS 456, (BIS IS 1893. (2016). Criteria for earthquake resistant design of structures, Part-1 General Provisions and Buildings. New Delhi: Bureau of Indian Standards) provisions and detailed as per IS 13920 provisions. The designed RC frame is analysed using nonlinear static pushover analysis (NSPA) and incremental dynamic analysis (IDA). The response modification (R) factor is estimated for designed RC frame as per ATC-19 guidelines from the data obtained using NSPA. The results of the NSPA and IDA are used to derive the fragility curves based on assumed performance limit criteria. The fragility curves derived from the data of NSPA are fitted through approximation of the normal to binomial distribution, while in the case of IDA, the multiple stripes’ analysis is used and fragility function is fitted through maximum likelihood. The probability of various damage states is determined at performance point for seismic hazard corresponding to Zone-III, IV, and V. The R factor for RC frame is estimated as 5.72, which justifies and validates the provisions of Indian seismic code for R factor. The probability of occurrences for various damage states is ranged from 10 to 50% for study RC frame building. Comparison of NSPA and IDA approach reveals the efficiency of both approaches in estimating the probability of occurrence of various damage states and post-seismic response for RC frame.