悬索桥多阶竖向涡激振动塔梁阻尼减振系统研究

A Tower-Girder Damping System to Control Multi-Mode Vertical Vortex-Induced Vibrations of Suspension Bridge

为控制大跨度简支体系悬索桥的多阶竖向涡激振动,提出一种塔梁阻尼减振系统(在桥塔外伸牛腿与加劲梁之间布置耗能阻尼器),以武汉鹦鹉洲长江大桥为背景进行参数分析和减振效果研究。采用ANSYS软件建立大桥整体有限元模型,采用复模态方法分析阻尼器安装位置与阻尼系数对桥梁阻尼比的影响,给出3种优化准则,以选取最优阻尼系数和阻尼器安装位置,并将该系统应用在实桥中。结果表明:塔梁阻尼减振系统能同时提高桥梁多个竖弯模态的阻尼比,在相同阻尼系数下,模态阶数越高,最大附加阻尼比越大;随阻尼系数的增大,各阶竖弯模态的附加阻尼比先增加后减小,各阶竖弯模态均存在最大附加阻尼比和最优阻尼系数;随阻尼器安装位置与桥塔中心线距离的增大,各阶竖弯模态的附加阻尼比逐渐增大,最优阻尼系数逐渐减小,有利于降低阻尼器成本;实际安装阻尼器后大桥实测阻尼比较安装前有明显的提升。说明塔梁阻尼减振系统能够有效地控制大跨度简支体系悬索桥的多阶竖向涡激振动。

Energy dissipating dampers are installed on the overhung brackets in between the tower and the stiffening girder to form a tower-girder damping system,which is able to control the multi-mode vertical vortex-induced vibrations of the long-span,simply-supported suspension bridge.The Yingwuzhou Changjiang River Bridge in Wuhan is used for a case study.The finite element model of the full bridge was developed in ANSYS to carry out complex mode calculation to analyze the effects of installation locations of the dampers and the damping coefficients on the damping ratio of the bridge.Three parameter selection options were proposed to sort out the optimal damping coefficient and locations of dampers.In the Yingwuzhou Changjiang River Bridge,the tower-girder damping system is capable of simultaneously raising the damping ratios of multiple vertical bending modes.With the same damping coefficient,higher modes indicate greater maximum additional damping ratios.As the damping coefficient increases,the additional damping ratio of each vertical bending mode increases first,but deceases afterwards,and maximum additional damping ratio and optimal damping coefficient exist in all the vertical bending modes.As the distance of the dampers to the center line of the central pylon becomes larger,the additional damping ratio of each vertical bending mode gradually increases,while the optimal damping coefficient gradually decreases,which is favorable for cost reduction.After equipped with dampers,the damping ratios of prominent vertical bending vibration modes of the bridge are notably higher than the original structure,indicating that the tower-girder damping system can effectively control the multi-mode vertical vortex-induced vibrations of the long-span,simply-supported suspension bridge.