风—车—人群联合作用下浔江特大桥振动性能与舒适性评价

Vibration performance and comfort evaluation of Xunjiang cable-stayed bridges under combined action of wind-vehicle-pedestrian loadings

大跨钢箱梁斜拉桥具有频率低、阻尼小的特征,在风、车辆、人群等动力荷载作用下极易发生大幅振动,具有人行交通功能主梁的振动性能与舒适性评价是桥梁运营期普遍关注的问题。以在建的平容高速浔江特大桥(主跨636 m的大跨钢箱混合梁斜拉桥)为工程背景,通过桥梁动力响应时域理论分析,研究桥梁在风、车流、人群荷载联合作用下的振动性能、评价桥梁的振动舒适度,提出基于调谐质量阻尼器的舒适度提升措施。研究结果表明:1)在人群密度为1.5人/m^(2)的人流荷载、4级道路服务水平等级交通流车辆荷载和5 m/s风速范围内脉动风荷载联合作用下,桥梁竖向加速度峰值小于1.0 m/s^(2),横向加速度峰值小于0.2 m/s^(2),满足EN03设计指南的CL2(中等)舒适度标准。当风速超过5 m/s时,风、车流、人群联合作用下的桥梁振动加速度峰值不满足中等舒适度标准。2)人致振动响应以2 Hz附近的竖弯模态为主,车致振动响应以低阶和高阶竖弯模态为主,风致振动响应以低阶竖弯、扭转和侧弯模态为主,根据风、车流、人群联合作用下的桥梁振动特征,提出采用调谐质量阻尼器提升第1阶竖弯模态和第1阶扭转模态阻尼比的减振措施,减振后桥梁在15 m/s风、车流、人群联合作用下,桥梁振动舒适性满足CL2标准。研究成果可为类似桥梁的振动舒适性评价和减振设计提供参考。

Long-span cable-stayed bridges with steel box girdersfeature low frequency and small damping,and are prone to large-amplitude vibration under the combined action of dynamic loads such as wind,vehicles,and pedestrian.Hence,evaluating the vibration performance and comfort of main girders with pedestrian traffic function has become a common concern during bridge operation.The Xunjiang bridge(a cable-stayed bridge under construction with a hybrid box girder of a 636-mmain span)of Pingrong expressway was selected as the engineering project studied.The vibration performance and comfort of the bridge under the combined effects of wind,vehicles,and pedestrian were studied through theoretical analysis of bridge dynamic responses in time domain,whereas the comfort improvement measures were proposed.Results indicated that:(1)under the combined action of pedestrian load(with a population density of 1.5 people/m^(2)),traffic flow load(Class IV road service level)as well as fluctuating wind load(less than 5 m/s speed),the vertical peak acceleration of the bridge girder is less than 1.0 m/s^(2),and the peak lateral acceleration is less than 0.2 m/s^(2),which meets the comfort standard of CL2 level based on EN03 code;When the wind speed exceeds 5m/s,the peak acceleration of the bridge girder under the combined action of wind,vehicles and pedestrian does not meet the standard of CL2 level.(2)The human-induced vibration response is dominated by the modes with frequencies around 2 Hz,the vehicle-induced vibration response is dominated by both low-order and high-order vertical bending modes,while the wind-induced vibration response is dominated by the first-order vertical,torsion and lateral modes.According to the vibration characteristics of the bridge girder,a vibration reduction scheme using tuned mass damper(TMD)to enhance the damping of the first-order vertical bending and torsional modes was proposed.The vibration comfort of the bridge installed with TMD meets the CL2 standard under the combined action of wind with speed less than 15 m/s,vehicles,and pedestrian.This research provided a reference to the comfort evaluation and vibration reduction for similar bridges.