Importance factor for design of bridges against fire hazard

• Importance factor (IF) for overcoming fire hazard in bridges is developed.
• Validity of the proposed approach to importance factor is established.
• Importance factor can be used to assess vulnerability of a bridges to fire hazard.
• Relevant design strategies for mitigating fire hazard in bridges is discussed.

Fire represents a significant hazard to civil infrastructure, including bridges. However, fire hazard is still not accounted for in conventional bridge design. This paper presents an approach for developing an importance factor for overcoming fire hazard in bridges. The importance factor takes into account the degree of vulnerability of a bridge to fire and also the critical nature of a bridge from the point of traffic functionality. The importance factor is derived by assigning weightage factors to key characteristics of bridges, i.e. bridge’s geometrical features, material properties and design characteristics, traffic demand, hazard (risk) likelihood, expected environmental damage, and economic consequences resulting from a fire incident. The proposed importance factor for fire design, which is similar to the one currently used for evaluating wind, and snow loading in buildings, is validated for a number of bridges where fire incidents occurred previously. It is shown through this validation that the proposed method for importance factor can be used as a practical tool for identifying critical bridges from the point of fire hazard and also for developing relevant design strategies for mitigating fire hazard in bridges.