Endurance Time Method for Rapid Collapse Safety Assessment of Earthquake-Damaged Buildings

Abstract

Post-earthquake building safety assessment must rapidly evaluate structural integrity before imminent aftershocks to guide safe reoccupation decisions. While studies have quantified residual collapse capacity following seismic damage, computational demands of conventional Incremental Dynamic Analysis (IDA) methods pose challenges for urgent, real evaluations. This research proposes an efficient framework using the Endurance Time (ET) method to estimate rapidly the residual collapse capacities needed for post-earthquake building safety assessment. The ET method leverages an incrementally scaled acceleration function in a single Nonlinear Response History Analysis (NRHA) to simulate the demands across intensity levels up to complete collapse. We develop a procedure adapting ET for mainshock-aftershock damage assessment, introducing Representative Damage States (RDSs) as an alternative to IDA's iterative analyses at fixed damage states. This paper demonstrates the framework's steps on a steel moment frame benchmark modeled with OpenSees and subjected to earthquake scenarios emulating the 2015 Nepal event. The findings show the ET method can efficiently generate the complete residual collapse capacity diagram for a mainshock-damaged building, covering all potential damage states with minimal nonlinear analyses. This computational efficiency is advantageous for overcoming barriers in emergency assessments, enabling rapid evaluation of building collapse safety after significant seismic events.