Collapse safety assessment of plan-irregular buildings considering ductility and damage

The current study focuses on seismic fragility analysis and collapse safety assessment of reinforced concrete buildings with re-entrant corner irregularity. This is conducted in a probabilistic framework on the case studies of moment-frame building archetypes with a typical L-shaped plan. A three-dimensional perspective for ductility and damage distributions is addressed for the non-linear models developed. Multi-directional pushover procedures and incremental dynamic analyses have been performed by applying ten near-field and ten far-field earthquake records for each building model. The median collapse capacity is established through developing fragility curves in terms of several earthquake intensity measures and spatially distributed displacement, ductility and damage indices. Available and acceptable collapse margin ratios (CMRs) are measured to judge the safety margin against collapse at the maximum considered earthquake shaking level. The statistics indicate that when the collapse capacity is defined in terms of the drift, ductility or damage, instead of an intensity measure, the collapse uncertainty decreases. Thus, the median collapse capacity is calculated precisely with less variability, resulting in available CMRs that exceed acceptable CMRs. With the perspective of this methodology, a satisfactory collapse safety margin was anticipated in the seismic force-resisting system by the design requirements for the targeted building class.