A probabilistic assessment for classification of bridges against fire hazard

• Probability of fire occurrence and fire induced collapse of bridges is quantified.
• Importance factor (IF) for overcoming fire hazard in bridges is developed.
• Validity of the proposed approach to importance factor is established.
• Relevant design strategies for mitigating fire hazard in bridges is discussed.

This paper presents the development of a simplified approach for classification of bridges based on fire hazard. Statistical data from recent fires in bridges is utilized to quantify the probable risk of fire in bridges and also probability of fire-induced collapse of structural members in bridges. An importance factor is derived for identifying the vulnerability of bridges to fire hazard. The proposed importance factor, developed using weighted factor approach, takes into account the degree of vulnerability of different bridge components, critical nature of a bridge from traffic functionality point and fire mitigation strategies present in a specific bridge. 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 against previous bridge fire incidents. 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.