Mitigating the effects of a tanker truck fire on a cable-stayed bridge

Fire represents one of the most severe threats to the integrity of our built infrastructure. This study focuses on the effects of open-air hydrocarbon pool fires that may result from a tanker truck crash or sabotage since the quantity and flammability of its contents poses one of the worst-case hazards to a nearby bridge. In general, the calculation of a bridge’s response to a vehicle-based fire hazard consists of four steps:(1) calculate the fire’s characteristics and geometry; (2) calculate the heat transfer from the fire to the structural elements via radiation heat flux; (3) calculate the temperature increase of the structural elements; and (4) calculate the resulting material and mechanical response of the structural elements. The authors have developed a streamlined framework for efficient calculation of these steps which synthesizes numerous models based on both first principles and empirical data to quantify the extent of damage caused by a specified fire threat. Due to its efficiency, this approach can be used to calculate the effects of a range of fire types, sizes, and locations to develop an envelope of performance for which the risk of damage and the effectiveness of potential fire protection measures can be evaluated. The methodology is used to demonstrate the design process for determining fire protection on a cable-stayed bridge. This design example shows that explicitly modeling the fire, rather than using the UL 1709 fire curve, better quantifies the extent of fire effects and potentially reduces the required fire protection based on the available capacity.