A Framework for Performance-Based Fire Following Earthquake Engineering

Abstract

The occurrence of fires igniting during and immediately following a seismic event represents an important design scenario that should be accounted for. Building concentration, construction type, weather conditions, and other factors can combine to create a situation in which fire following an earthquake is the principal cause of damage. Records from past earthquakes show that the damage caused by the subsequent fire can be very significant, often exceeding the damage caused by the earthquake. The current seismic design philosophy permits certain degree of damage during earthquakes, making the structures more vulnerable when exposed to the additional demand of fire loading. Fire resistance of steel frames is implemented using passive or active fire resisting systems, which have shown high variability in their sustained damage due to the seismic event. In this paper, a new framework for performance-based fire following earthquake engineering is developed and discussed. The framework is established through combining stability analysis of isolated columns with system-level finite element analysis of a steel building while accounting for randomness in parameters associated with post-flashover fire, passive fire protection, and mechanical loads. Fragility surfaces for column instability as a function of various levels of fire load density and inter-story drift ratios are produced. The results demonstrate that instability can be a major concern in steel structures, both on the member and system levels, under the sequential events and highlights the need to develop provisions for the design of steel structures subjected to fire following earthquake.