Experimental Study on the Thermal Radiation Threat of the Vehicle Fires in Lower Lane of a Double-Deck Bridge
摘要
With the increase of bridges and vehicles, bridge fire accidents are constantly reported, which seriously threaten the structural stability of bridges and traffic safety. A 1:8 large-size double-deck bridge fire experimental platform was constructed in this study. The effects of heat release rate, ambient wind and location on the heat flux of fire in the lower carriageway were investigated by 15 sets of fire experiments. In addition, the heat flux damage criterion was introduced to analyze the thermal threat of the vehicle fire. The main conclusions are as follows: (1) With the increase of heat release rate, the heat flux increases and the destructive ability increases. In a windless environment, when the heat release rate increases to 200 MW, the heat flux reaches 20 kW/m2, at which time the steel structure of the bridge will be deformed, and the probability of death is as high as 98%, showing a strong destructive capability of thermal radiation. (2) The upstream heat flux decreases due to the increase of wind speed, while the downstream heat flux is opposite. When the wind speed increases to 4.4 m/s, the upstream heat flux of the 200 MW fire is 7.5 kW/m2 and the downstream heat flux is 27 kW/m2, which is close to four times of the heat flux in the upstream. (3) The effect of lanes on the heat flux in 100 MW and 200 MW fires is not significant, and the distance of lane change can be increased in subsequent experiments to examine the mechanism of lane effect on the heat flux. The experiments conducted in this paper will be useful for subsequent large-scale bridge fire tests.