Abstract:

Aiming at the growing concern over the fire risk of bridges, the fire resistance of a long-span cable-stayed bridge is analyzed by means of the performance-based method. First, different types of vehicles, namely, car, bus, van, heavy goods truck and petrol tanker, are selected as fire risk sources, and three kinds of fire scenarios on deck are designed. Next, the flame temperatures of different fire scenarios are obtained by using FDS (Fire Dynamics Simulator), and they are compared with those of the ISO834 curve. Then, the temperatures of stay cables are acquired respectively by using the FDS and the ISO834 curve, and the failure conditions of the cables are also discussed by taking into account the yield strength variation. Finally, the safety of the full bridge is assessed. The results show that (1) the flame temperatures obtained through FDS simulations are generally lower than those of the ISO834 curve, and three cables may fail in the most serious case;, and (2) that, fires have a limited influence on the overall safety performance of bridges but can weaken the using function, so it’s necessary to take effective measures to reduce the loss caused by fires.

Key words: cable-stayed bridges, fires, performance-based approach, failures of stay cables, risk assessment