Suspension bridges are prone to vibration due to their long span and high flexibility when vehicles pass by. The vibrational differential equations of the vehicle-bridge system were established by using dynamic equilibrium theory and finite element method to investigate the vehicle-excited vibration of suspension bridges. Aizhai bridge in western Hunan province was taken as a case study and the dynamic responses of the suspension bridge structure such as displacements of main girders, the stresses of main cables, hanger rods and web members were analyzed by mathematically simulating bridge deck pavement surface roughness and using computer software when vehicle streams pass by the bridge with different velocities and weights. The results calculated indicate that the dynamic responses of the bridge structure usually increase with increasing vehicle velocity or weight except for the lateral vibration displacement that exhibits indefinite trend with the change of vehicle velocity. The vehicle operational parameters have significant influences on the vertical displacement of main girders and relatively insignificant influences on the lateral displacement. The dynamic responses of the bridge structure are more susceptible to the variation of vehicle velocity than that of vehicle weight.%悬索桥跨度大,柔性高,在车辆通过时,易发生振动.为了研究其车激振动问题,利用动力平衡原理和有限元法,建立车桥系统振动微分方程.以湘西矮寨大桥为背景,通过对桥面不平顺进行数学模拟,利用计算机软件ANSYS分析大跨度悬索桥在车流分别以不同速度和车重运行时主梁跨中位移、主缆、吊杆和腹杆的动力响应.研究结果表明:随着行车速度或车重的增加,结构响应通常增大,但主梁跨中横向振动位移随车速的变化具有不确定性;车辆运行参数对主梁竖向振动位移的影响显著;而对主梁横向振动位移的影响较小;结构动力响应对车速的变化比对车重的变化更为敏感.
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