跨线钢箱梁斜拉桥列车风荷载及风致振动

Train Wind Loads Applied on a Fly-over Steel Box Girder Cable-stayed Bridge and Wind-induced Bridge Vibrations

为获得高速列车下穿时的列车风和桥梁振动响应特性,以某独塔无背索钢箱梁斜拉桥为工程背景,采用CFD仿真获得钢箱梁不同部位的列车风荷载,并基于桥梁动力模型研究施工阶段和运营阶段的风致振动响应。结果表明:高速列车下穿时,钢箱梁翼缘板、腹板及底板的表面风压均表现出明显的“头波”“尾波”特性;随着车-桥间距和距轨道中心线距离的增加,风压极值逐渐衰减,底板和腹板处的衰减速率较翼缘板处更快;在距轨道中心线20 m处,梁体受到的升力、阻力及扭矩极值分别下降为轨道中心线处的28%,23%和11%;当车速为350 km/h、轨面距梁底为7.25 m时,合龙前梁端最大竖桥向位移为9.89 mm、最大竖桥向加速度为164.58 mm/s^(2),运营阶段跨中最大竖桥向位移为3.24 mm、最大竖桥向加速度为91.95 mm/s^(2)。

In order to obtain the characteristics of train winds and wind-induced bridge vibrations during the under-passing of high-speed trains,a fly-over steel box girder cable-stayed bridge with a single tower and no back cable is selected as the background engineering.The CFD simulation is used to analyze the train wind loads applied on different panels of the steel box girder.Furthermore,the bridge dynamic analysis models are built to explore wind-induced vibrations in the construction and operation stages.Results show that the surface wind pressures applied on the flange plate,web and bottom plate of the steel box girder exhibit obvious“head wave”and“tail wave”characteristics due to the under-passing of high-speed trains.With the increase of train-bridge distance and the distance to track centerline,the extreme wind pressures decrease continuously,and the attenuation rates at the bottom plate and the web are faster than that at the flange plate.At the location that is 20 m away from the track centerline,the lift force,drag force and torque force applied on the steel box girder are about 28%,23%and 11%of those at the track centerline.When the train speed is 350 km/h and the distance between track surface and bridge bottom is 7.25 m,the maximal displacement and acceleration at the beam-end are 9.89 mm and 164.58 mm/s ^( 2) respectively before the bridge closure;while during the operation stage,the maximal displacement and acceleration at mid-span are 3.24 mm and 91.95 mm/s^( 2) respectively.