Simplified method for seismic vulnerability of plan irregular RC buildings using degree of irregularity

Irregular buildings are more vulnerable to seismic loading, depending on their degree of irregularity. The degree of irregularity in vertically irregular buildings and its correlation to seismic vulnerability (SV) have been quantified in previous studies. However, these studies on plan irregular buildings were focused on only evaluating seismic performance. A simplified method, based on the degree of irregularity, is proposed to identify the SV of plan irregular reinforced concrete (PIRC) buildings. The different types of plan irregularities considered were diaphragm discontinuity, re-entrant corners, non-parallel systems and torsional irregularity. For each type of plan irregularity, numerical models were developed with varying degrees of irregularity. The numerical models were subjected to incremental dynamic analysis and the maximum interstorey drift was recorded to develop fragility curves. The proposed simplified method effectively identified the SV of the PIRC buildings based on their degree of plan irregularity. The method can help to identify the most vulnerable PIRC buildings at the initial stage of large-scale seismic simulations, such as integrated earthquake simulations of urban areas. It can thus be used as a filtering method to select the most vulnerable PIRC buildings that need detailed seismic analyses.