大跨径悬索桥吊索高温力学性能研究

Study of Mechanical Properties of Slings of Long Span Suspension Bridges Under High Temperatures

为了获得大跨径悬索桥的最危险火灾场景和抗火救援时间,以某三塔四跨悬索桥为背景,采用ANSYS软件建立全桥三维空间热-结构耦合有限元模型,选用随温度变化的热工参数和不同火源燃烧升温曲线对桥梁结构施加热荷载,分析各类汽车在主跨跨中及边墩处燃烧时吊索温度场分布特征及力学性能时变规律。结果表明:升温曲线的选用对确定火灾下吊索破坏时间影响很大;油罐车在桥梁主跨跨中最外车道发生燃烧为悬索桥最危险火灾场景,此场景下吊索的破坏时间最短为24min,破坏时的温度为473℃,吊索此时的抗拉强度降低到540 MPa,桥梁的抗火救援时间应在此时间内;油罐车通过桥梁时应采用引导车的方式从中央分隔带旁车道通过。

To acquire the most dangerous fire disaster situation and the best fire fighting time of the slings of long span suspension bridges, a three-tower and four-span suspension bridge was taken as an example and the three-dimensional finite element model of thermal-structure coupling for the whole bridge of the bridge was established, using the software ANSYS. The temperaturevarying thermal parameters and temperature rise curves of the different fire source burning were selected, the thermal loads were applied to the bridge and the time-varying laws of the temperature field distribution characteristics and mechanical properties of the slings of the bridge at the time the different vehicles were burning at the midspan of the main span and at the side piers of the bridge were analyzed. The results show that the selection of the temperature rise curves has great influ-ence on the determination of the destruction time of the slings exposed to the fire. The burning of the oil tank truck on the outermost lane at the midspan of the main span is the most dangerous fire disaster situation to the suspension bridges. In the situation of such kind, the destruction time of the slings is the shortest and is 24 min. The temperature at the time can reach 473 °C , the tensile strength of the slings can fall to 540 MPa and the fire fighting of the slings should immediately start before the time. When the oil tank truck passes through the bridge, the truck should preferably travel on the lane close to the medial strip, following the guiding car.