桥面不平引起车桥系统随机振动车速因素分析

将桥梁离散为梁单元,车辆简化为两自由度系统,桥面不平顺引起的车桥耦合振动荷载等效为虚拟激励荷载,建立移动车辆-桥梁耦合随机振动模型,运用虚拟激励法((pseudo excitation method,简称PEM)并结合模态综合叠加技术进行求解。将数值迭代结果与Monte-Carlo法对比,验证求解算法的正确性。以简支梁桥为例,在频域内对桥面不平顺引起车桥耦合随机振动的车速因素进行分析。结果表明:桥梁跨中竖向位移均方根值随车速变化较大,车速对位移和加速度功率谱曲线的1阶频率峰值和带宽影响显著;近支点加速度功率谱曲线的峰值、频率及带宽随车速变化明显。研究桥面不平顺引起的车桥耦合随机响应,车速对桥梁和车体振动影响不可忽略。

Influence Analysis of Vehicle Speeds on Random Vibration of Vehicle-Bridge Coupling Systems Caused by Deck Irregularity

A new model for a random vibration analysis of vehicle-bridge systems subjected to road roughness excitation is proposed. The bridge is modeled as beam elements and the vehicle is modeled as two-degrees of freedom mass-spring-damper system. The load caused by deck irregularity is equivalent to pseudo excitation load. The model is solved with pseudo excitation method(PEM) following by mode superposition iterative solution introduced. The validity of model and algorithm has been verified through the result of Monte-Carlo method. Taking a simple beam bridge as an example, the random vibration response of vehicle-bridge coupling caused by road roughness and vehicle speed in frequency domain proves the following conclusion. The root mean square values (RMSV) of vertical displacement at mid-span varies with the vehicle speed obviously, and the first frequency peak and band width of displacement and acceleration power spectrum density (PSD) is changed with the vehicle speed. The peak, frequency and band width of acceleration PSD adjoining the bridge bearing change with the vehicle speed obviously. The vibration response of vehicle in vehicle-bridge coupling system caused by deck irregularity varies with the vehicle speed obviously. The effect of vehicle speed on the random responses caused by deck irregularity cannot be neglected when the vehicle-bridge coupling system is researched.