The Temperature Response of Suspension Bridge Cables Under Vehicle Fires: A Large-Scale Pool Fire Experiment with Polyethylene and Gasoline

Suspension cables and main cables (collectively referred to as cables) on both sides of suspension bridges are critical load-bearing components that determine overall structural stability. Cables are directly exposed to fires when burning vehicles stop in emergency or slow lanes, so investigating the temperature response of cables under vehicle fire scenarios is essential for fire-resistant design of suspension bridge cables. For this purpose, a 1:4 scaled fire test platform was constructed based on a real suspension bridge in Guangzhou, China that prohibits tanker access. Nine fire tests were conducted under 0-1.65m/s crosswind, using gasoline and polyethylene plates as fuel to simulate 50MW and 75MW heavy-duty truck pool fires, with cable temperatures measured for fires occurring in different lanes. The results show that flame coverage increases with heat release rate, and first increases then decreases with wind speed at a turning point of 1.0m/s. The most adverse scenario is a 75MW truck fire in the emergency lane at 1.0m/s wind speed, where the maximum height of 300℃ isotherm reaches 2.0m in the test, corresponding to 8.0m for the full-scale bridge. It is thus recommended that the fire protection coverage height for cables shall be no less than 8.0m. This study provides valuable reference for cable temperature evolution analysis and fire protection strategy optimization for suspension bridges.