悬索桥吊索高阶涡激振动及摆锤式MTMD减振技术研究

Study of Higher-Mode Vortex-Induced Vibration on Hangers of Suspension Bridge and Pendulum MTMD Vibration Mitigation Technique

为了解大跨度悬索桥吊索出现的大幅高频振动现象,并进行减振,以国内某主跨1688 m的悬索桥为背景(最长吊索长184.6 m),基于理论方法和施工期吊索大幅高频振动实测结果,分析吊索的振动类型及参数(频率、阻尼比);提出一种摆锤式多重调谐质量阻尼器(MTMD,其由一定形状的锤头提供质量参数,由钢绞线提供刚度及阻尼参数),采用有限元和室内试验的方法,分析其振动特性,并进行实桥验证。结果表明:该桥吊索振动频率范围为5~25 Hz,阻尼比低,单个吊点的多根吊索易发生同相位的高阶涡激振动;摆锤式MTMD单个锤头具有2个控制主频,自身阻尼比约10%,具有位移放大作用,对高频振动的响应灵敏,在很宽的频率范围内具有很好的减振性能;摆锤式MTMD可有效增加吊索自身阻尼比,控制吊索高阶涡激振动,实测减振效果达到90%以上,具有很好的实用性。

To make clear about the high-frequency and large-amplitude vibrations on hangers of long-span suspension bridge and carry out vibration mitigation,a suspension bridge with a main span of 1688 m in China(the longest hanger measures 184.6 m)is taken as the study background.Based on the theoretical calculation and the measured data of high-frequency and large-amplitude vibrations on hangers in the construction period,the vibration modes and parameters(like frequency and damping ratio)of hangers were analyzed.A type of pendulum multiple tuned mass damper(MTMD)is proposed,which contains pendulums with certain shape that can provide mass parameters and steel strands that can provide rigidity and damping parameters.The finite element calculation and indoor tests were conducted to analyze the characteristics of the vibrations,and the calculated and test results were verified on a real bridge.The verification indicate that the hanger vibration frequency of the bridge is within the band of 5~25 Hz,the damping ratio is low,and multiple hangers from a single hanging point are prone to generate in-phase higher-mode vortex-induced vibration.An individual pendulum of MTMD owns two dominant frequencies,the damping ratio of which is approximate to 10%,demonstrating that the pendulum can exert displacement amplification effect,is sensitive to high-frequency vibrations,and has sound vibration mitigation effect within a wide frequency band.The pendulum MTMD can effectively enhance the damping ratio of hangers and control higher-mode vortex-induced vibrations on hangers,the measured vibration mitigation effect of which is above 90%,proving its good feasibility.