Field Observation And Vibration Control Of Vortex-induced Vibration Of Stiffening Cables Of Multi-tower Cable-stayed Bridges

With the development of national transportation,cable-stayed bridges have been used more and more in long-span bridges.In practical engineering applications,the characteristics of long-span cable-stayed bridges,such as long length,flexibility and low damping,make them very sensitive to wind action and prone to severe windinduced vibration.Vortex-induced vibration of stay cables usually occurs at low wind speed,although the amplitude is not large,but it occurs at a high frequency,resulting in visual insecurity,and may also lead to fatigue damage of anchorage end of stay cables,affecting the safety and normal use of cable-stayed bridges.Therefore,windinduced vibration of super-long stayed cables must be effectively suppressed.Based on the field measurement of the stiffening cables of a long-span three-pylon cable-stayed bridge,the wind field of the bridge and the wind-induced vibration response of the stiffening cables are obtained.The multi-modal vortex-induced vibration characteristics and mechanism of the stiffening cables of the long-span threepylon cable-stayed bridge are studied,and the multi-modal vortex-induced vibration control of the stiffening cables is attempted.The main contents of this paper include:(1)The multi-modal vortex-induced vibration of the stiffening cables of a longspan three-tower cable-stayed bridge in China is studied by field measurement.The characteristics of the multi-modal vortex-induced vibration of the stiffening cables are analyzed,and the correlation between the vibration characteristics of the stiffening cables and the characteristics of the incoming wind is studied.(2)The free vibration equation of the cable and the vibration equation of the cabledamper system are derived.The dynamic characteristics of the cable are modeled and analyzed by ANSYS finite element method,and the modal frequencies and modes of the cable are obtained.(3)The finite element model of the stiffening cable-damper system is established,and the general optimization design curve is used to guide the optimal design of the damper's damping value.By optimizing the damping coefficient and the installation position of the damper,the high-order modal damping ratio of the stiffening cable is improved to realize the multi-modal high-order eddy-induced vibration control of the stiffening cable.In this paper,through field measurement of the stiffening cables of the three-tower cable-stayed bridge and relevant data analysis,it is found that the stiffening cables will produce multi-mode high-order vortex-induced vibration under low wind speed,and then through the establishment of the stiffening cable-damper system,finite element simulation analysis,in order to achieve the multi-mode high-order vortex-induced vibration control of the stiffening cables.It provides an important reference for the health monitoring and maintenance of the cables of the three-tower cable-stayed bridge.