Incremental dynamic analysis-based seismic fragility of an IS 13920:2016 RC frame in Zone IV: a HAZUS-MH comparison

Abstract Seismic fragility data for RC moment-resisting frame (MRF) buildings designed to current Indian codes are scarce. HAZUS-MH vulnerability functions are widely used as a substitute in Indian practice. Their applicability to Indian RC construction has not been rigorously tested. This study performs an Incremental Dynamic Analysis (IDA)-based fragility assessment of a seven-storey RC MRF designed to IS 456:2000, IS 1893:2016, and IS 13920:2016, located in Seismic Zone IV. Seven PEER NGA-West2 records were scaled to ten peak ground acceleration (PGA) levels between 0.2 g and 2.0 g, giving 70 nonlinear time-history runs. Maximum inter-storey drift ratio (IDR) was used as the engineering demand parameter (EDP). Lognormal fragility parameters were fitted by Maximum Likelihood Estimation (MLE) with 90% bootstrap confidence intervals for four HAZUS-compatible damage states. Median PGA capacities come out to 0.503 g and 1.141 g for Extensive and Complete damage under the corrected HAZUS-MH C1M (Mid-Rise), High-Code classification appropriate to a 7-storey building; Slight and Moderate damage sit at intensities too low for the present IDA sampling to resolve reliably. All seven records show drift concentrating at the first storey in a soft-storey-like pattern. Against the corrected C1M benchmark, the building comes out more fragile than the generic curve at Moderate damage (ratio 0.82) and less fragile at Extensive and Complete damage (1.48 and 1.26); the 90% confidence interval lower bounds do not consistently sit above the HAZUS medians. Taken together, these results do not support a general claim that HAZUS-MH is conservative for this building, and further multi-building study would be needed before drawing any broader conclusion.