Framework for fire risk assessment of bridges

Bridge fires are a major concern because of their social and economic consequences when bridges have to be closed to traffic. The concern for life safety is not significant as there are minimum reported fatalities during a bridge fire but can result in a huge economic and social consequence. Despite the frequency and consequences of bridge fires, they have been the subject of very few studies and are neglected in the different international bridge design standards. This paper presents a framework for evaluating the fire risk to the bridges. Fire risk is estimated by considering various criteria such as the social and economic impact of fire, the vulnerability of bridge structures to fire and the likelihood of a bridge fire. In this framework, each criterion, sub-criteria and alternative which can influence the fire risk of a bridge are assigned with a weighting value depending upon their importance. Analytical hierarchy process (AHP) is utilised to estimate the weightings for different factors. The proposed framework is implemented and validated using previous fire accident data. Six bridge fire incidents are considered in this study and the damage level experienced by them is found in compliance with the damage level associated with the fire risk estimated by the proposed framework. This framework presents an important methodology for the highway department and bridge engineers to estimate the fire risk for a particular bridge or entire bridge network in a region. An accurate estimation of fire risk helps the highway engineers to calculate the amount of fire protection required for bridge structures.