Performance of reinforced concrete structures in post-earthquake fire

Post earthquake fire (PEF) can lead to the collapse of buildings that are partially damaged in a prior earthquake that occurred immediately before the fire. Most standards for the design of structures against earthquake ignore the possibility of post earthquake fire and hence buildings designed following these codes could be vulnerable under PEF. An investigation based on FEMA 356 is performed here on the performance based safety level of structures designed to the ACI code after they are subjected to an earthquake load with the PGA of 0.30 g. This is followed by a fire analysis of the weakened structure from which the time it takes for the weakened structure to collapse is calculated. The results show that the vulnerability of structures increases dramatically when a deformed structure is exposed to PEF. While the investigation is for a certain class of structures (intermediate reinforced concrete frame, 3 stories), the results confirm the need for the incorporation of post earthquake fire in the process of analysis and design.