基于大涡模拟法的铁路桥梁火灾场景研究

Study of Fire Disaster Scenarios for Railway Bridge Based on Large Eddy Simulation Method

为了掌握铁路桥梁发生火灾时的温度场和桥下失火安全高度,基于大涡模拟法对火灾场景开展研究。根据铁路桥梁火灾案例调研结果,将铁路桥梁火灾场景设定为桥面列车火灾、开敞式桥下火灾、半开敞式桥下火灾3种,确定3种火灾场景的参数取值和火焰尺寸,采用FDS火灾场模拟软件建立火灾场景的模型,分析温度场和升温曲线,并确定桥下失火安全高度。结果表明:桥面列车火灾场景下,铁路桥梁温度场的升温曲线与RABT升温曲线类似;桥下火灾场景下,当桥下高度超过火焰高度的2倍时,桥面处的温度较低,桥面结构安全;桥墩在低于2倍火焰高度的部分仍需要考虑抗火安全问题。

In order to examine the temperature fields in the railway bridge in a fire disaster and the safe clearance beneath the bridge that is able to keep it from the flames,the fire disaster scenarios are studied by the method based on large eddy simulation.In accordance with the investigation results of the fire disaster cases of railway bridges,the fire disasters of railway bridges can be categorized into three types,including the train fire on the bridge deck,open fire under the bridge and the semi-open fire under the bridge.The parameters of the three fire disaster scenarios and the size of the flames are determined.The fire disaster simulation software FDS was used to build the models of the fire disaster scenarios to analyze the temperature field and temperature rising curves and determine the safety clearance beneath the bridge.The results show that the temperature rising curve of the temperature field of the railway bridge is similar to the RABT temperature rising curve in the context of the train fire disaster.When the clearance beneath the bridge surpasses two times of the height of flames,the temperature of the bridge deck is low and the bridge deck structure is safe in the context of fire under the bridge.And fire protection should be considered for the part of the pier lower than two times of the height of the flames.