Post-earthquake collapse safety of damaged buildings subjected to aftershock hazard

Reliable and quick assessment of the collapse probability of damaged buildings is a critical issue in post-earthquake response and recovery processes. Rapid and consistent evaluation of the postearthquake risk associated with the affected buildings is an essential factor in achieving resilience. This study aims to assess the post-earthquake safety of the damaged reinforced concrete buildings subjected to aftershock hazard based on their probability of collapse. The collapse probability of a damaged building is related to its aftershock fragility characteristics and the aftershock hazard exhibited at the site. Aftershock fragility is evaluated by analyzing the nonlinear response of the building subjected to mainshock-aftershock ground motion sequences. In the collapse fragility analysis, major sources of uncertainty that affect the collapse capacity (e.g. record-to-record variability, material and system uncertainty) of the building, are taken into account. In the proposed method, the aftershock hazard is assessed by a novel approach in which the observed mainshock demand at the site is explicitly considered. This approach is expected to be useful in terms of obtaining more consistent risk evaluations compared to those solely based on the engineering judgment. An example application of the proposed safety assessment approach is presented for a site in Istanbul, Turkey that is assumed to be affected by a scenario earthquake. Resulting collapse probabilities are presented for a set of buildings with different properties. Considered properties are: total number of stories, mainshock damage level, and the mainshock intensity observed at the site.