Displacement-based seismic fragility assessment of a high-rise reinforced concrete building

This study presents a displacement-based seismic fragility assessment of a high-rise reinforced cement concrete (RCC) building designed in compliance with Indian seismic codes. The selected structure, a G+19 ordinary moment-resisting frame (OMRF), is modelled in ETABS with realistic material properties, geometric irregularities, and design loads as per IS 875 and IS 1893 provisions. Seismic performance evaluation is conducted through Incremental Dynamic Analysis (IDA) using a suite of ground motion records from FEMA P695, scaled progressively to capture structural response from elastic behaviour to collapse. Peak Ground Acceleration (PGA) and spectral displacement serve as intensity measures, while inter-storey drift ratio is adopted as the primary damage parameter. Fragility curves are developed for key performance levels based on maximum allowable drift limits. The results reveal significant sensitivity of the high-rise frame to torsional irregularities, with drift concentration occurring predominantly in the mid-height storeys. Probabilistic fragility functions indicate that the probability of exceeding life safety limits increases sharply beyond a PGA of 0.25g. Comparison with previous studies confirms that displacement-based assessment provides a more accurate representation of seismic vulnerability than force-based methods, particularly for irregular high-rise configurations. The findings emphasize the necessity for enhanced design considerations, including stiffness regularity and supplemental damping systems, to improve resilience in Indian high-rise RCC buildings. This research contributes a performance-based seismic assessment framework adaptable for both new designs and retrofitting strategies in similar structural systems.