Firewalls and post-earthquake fire resistance of reinforced-concrete frames

Abstract

Post-earthquake fire (PEF) contributes significantly to loss of life and property following large earthquakes in urban regions. In the absence of adequate PEF provisions in the codes and criteria, an investigation is performed on a reinforced concrete portal frame, divided into two unequal parts by a firewall. Acknowledging that firewalls could break down after earthquake, three fire exposure scenarios are assumed: only the left part exposed, only the right part exposed and the entire frame exposed. In the first two scenarios, the firewall remains intact, whereas in the third it is assumed to be broken down. The building is first pushed to displacement corresponding to the life safety level of performance based on FEMA 356 code. Then, using a natural fire curve, fire analysis is performed. Fire-alone analysis is performed to provide a point of reference. No failure occurs in any of the fire-alone scenarios, or when exposing the smaller part of the building to the PEF. In contrast, exposing the larger part and the entire frame to PEF makes the frame fail at around 50  min and 25  min, respectively. This shows the importance of firewalls to reduce vulnerability of reinforced concrete buildings in case of PEF. The approach used allows designers to choose the position and configuration of firewalls to best protect a building against PEF.