The responses of a bridge were measured under traffic load with varying vehicle speed to investigate the dynamical characteristics of continuous bridge with steel box girders under vehicle load at expansion joint. The wavelet transform method was utilized in time-frequency analysis for responses of the bridge when vehicle passed the expansion joint and the deck of the bridge. A numerical model of vehicle-bridge coupled vibration system was carried out, and responses of bridge were calculated and compared with the experimental ones. Results show that the acceleration of the bridge when vehicle reaches the expansion joint is greater than that when vehicle passes the deck. The effect of vehicle speed on vibrations of the bridge due to the impact in position of expansion joint is more significant than that when vehicle travels on deck; the vibration amplitude decreases with the increasing of the distance between the cross-section and the expansion joint; local vibrations of deck with certain amplitudes are introduced by the impact of the vehicle in expansion joint, thus the model of member structure without consideration of local vibration of deck cannot simulate the vibration of the bridge when vehicle passes the expansion joint.%为了推测伸缩缝位置跳车引起的连续钢箱梁桥结构振动特性,实测了车辆按不同速度行驶通过桥梁时的结构振动响应,并用小波变换对振动信号进行了时频分析,根据时频信号分析车辆通过伸缩缝及桥跨结构时的结构振动特性.采用车桥耦合振动算法对伸缩缝跳车响应进行了数值模拟和对比分析.结果表明,车辆通过伸缩缝时引起的冲击加速度响应大于通过桥跨时的结构振动;行车速度对冲击振动响应的影响大于对桥跨结构振动响应的影响;冲击引起的振动具有距离衰减的特点;冲击引起较强的钢桥面板局部振动响应,用杆系结构计算模型不能反映车辆通过伸缩缝时的结构振动特性.
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