Research On Two Passive Dampers For Vibration Mitigation Of Large Span Bridge’s Suspender Cables

A growing number of long span bridge is and will to be in service.The suspender cable is one of the most vulnerable components in long-span bridges.Vibration of the suspender cables will induce fatigue damage under common serice state,and large vibrations of these cables under extreme weather can be a threat to traffic and structural safety.The studies about the suspender cable is attracting more and more attention nowadays.This study focuses on the vibration of suspender cable,and it is imperative to develop effective methods to mitigate such vibration.Two methods are mentioned in this paper: ring-shaped tuned liquid damper and pendulum-tuned mass damper,with relative design methods,simulation and validation.The main research contents of this paper are as follows:(1)A ring-shaped tuned liquid damper(RSTLD)for vibration mitigation of suspender cable is proposed in this paper.The study utilizes SIMULINK environment to numerically simulate the structure-RSTLD system.A 61.55 m long suspender cable of the Xinghai Bay Cross-sea Bridge was selected as the object of the field experiment to verify the RSTLD’s vibration control efficiency.Two RSTLDs with different mass ratios and filled liquids were adopted in the experiment,and the response of the RSTLD installed cable and the symmetrical cable on the other cable plane without damper was acquired for comparing controlled and uncontrolled conditions.The experimental results show that when the liquid is water and the mass ratio is 3%,the variance of the acceleration and the maximum acceleration is reduced by about 50% and 20% to 30%,respectively.When the liquid is silicone oil and the mass ratio is 1%,the variance of the acceleration and the maximum acceleration is reduced by about 30% and 20%,respectively.The vibration control effect in the experiment is close to that in simulation.If a larger liquid viscosity damping ratio or a larger mass ratio is used,the vibration control effect will increase.(2)A pendulum-tuned mass damper(PTMD)in the form of a four-wire pendulum is proposed.In this paper,the motion mechanism of the proposed PTMD is discussed and the four-wire suspension pendulum model considering the nonlinear and pendulum length changes under the large swing angle is analyzed;explore the swing amplitude under different load amplitudes;discuss the influence factors upon the mitigation effect;the simulation results show that PTMD has great damping effect on the displacement and velocity index of the response,but there is limit effect upon the acceleration..The two damper both have a good damping capacity for all excitation directions,and can alleviate the negative impact upon the bridge structure suspender cable’s safe service caused by loading which repeat changes in magnitude and orientation in the harsh external environment.Research results may have important applications in engineering and have a positive impact on improving the service life of the delicate components and reducing the burden of maintenance and maintenance of suspender cable.