Post-earthquake fire collapse performance and residual story drift fragility of two-dimensional structural frames

Structural systems have deteriorated seismic performance as they are exposed to thermal effect due to dependency of material properties to temperature. Following an earthquake, once structure has already some residual displacement, fire ignition is very likely to occur. This makes it necessary to evaluate structural response of a building considering the fire event which follows an earthquake to have robust evaluation of structural response. Thus, it is required to model structural systems with consideration of both earthquake and thermal loads to capture multi-hazard behavior. In this study, performance of two-dimensional steel frames in case of fire following an earthquake is evaluated and collapse parameters of frames are calculated. Fragility curves related to collapse and residual story drift demands are given, and comparison of results between earthquake and fire-following-earthquake is illustrated. In addition, collapse probability of frames in fifty years is also given. Results of collapse performance evaluation are adjusted with the consideration of expected seismic hazard on site. Median collapse capacity decreases more than 30% and there is an apparent increase in collapse probability of fire-exposed frames in fifty years, which is more than three times for some frames.