Predicting Seismic Collapse Safety of Post-Fire Steel Moment Frames

Abstract

This paper summarizes a study focused on evaluating the post-fire performance of steel Intermediate Moment Frames (IMFs) following earthquakes. To this aim, archetypes comprising 3-bay IMFs with three different heights were seismically designed, and their two-dimensional finite element models were created in OpenSees software. The post-fire mechanical properties of steel were inserted into the models based on 64 different fire scenarios. The effects of different cooling methods are scrutinized at system level. To develop seismic fragility curves, Incremental Dynamic Analysis (IDA) was performed using 50 suites of far-field and near-field records, according to FEMA-P695. Then, the Collapse Margin Ratio (CMR) of each model was calculated based on the data from the fragility analysis. The results show that the seismic resistance of structures that experienced fire declines to some extent. In addition, the lowest safety level was observed when the structures were subjected to pulse-like near-field records.