Using OpenSees for analyzing a 9-story steel building under post-earthquake fires

Post-earthquake fires are major hazards with possible intense consequences. Civil engineering design is moving towards the concept of resilient cities, which requires buildings with structural systems to perform adequately after extreme hazards and ensure human safety. This paper provides a step towards developing a methodology to evaluate the resilience of steel buildings under post-earthquake fires. With the newly added fire module in OpenSees, the software has the capacity to perform structural analysis for both seismic and fire loads. This way, system-level analysis is performed in one software and interaction of members with each other, under both seismic and fire events, is considered together. This paper presents the challenges to seamlessly transfer from seismic to thermal analysis in OpenSees. The current constitutive material model for thermal analysis does not properly capture behavior of the frame for fire that follows earthquake. The constitutive model is therefore modified to capture effect of plastic strains, and strain reversals during heating or cooling. The new model is used to analyze a 9-story building under two earthquake hazard levels and multiple fire locations.