Passive Dampers For Vibration Mitigation Of Cables Based On Numerical Simulation And Field Experiment Of The Bridge

As the primary load transmission components in cable-stayed/suspension bridge,the stay/ suspender cable,which is the most vulnerable part,owns the properties of slender and flexible.The service state of stay/suspender cable is essentially significant during the whole service life of long-span bridge.Suffered from reciprocating vibration for a long period,stay/suspender cable is prone to fatigue damage,which may eventually lead to the reduction of its service life.Under certain extreme weather conditions,stay/suspender cable is prone to large vibration.The phenomenon is a serious threat to bridge structure and traffic satety.Researches on vibration mitigation for stay/suspender cable has recenetly attracted a lot of scholars and engineers.It has the positive effect on stay/suspender cable’s service life by taking effective vibration control measures.Numerical simulation analysis and in-field experiment of vibration mitigation have been conducted for stay cable and suspender cable in this article respectively.Firstly,two kinds of suitable Tuned Liquid Damper(TLD)have been proposed based on the structural form of stay cable.Then,the vibration mitigation test of suspender cable by adopting Four-wire Pendulum Tuned Mass Damper(FWPTMD)is carried out on Xinghai Bay Cross Sea Bridge.(1)A damper,which is called Sloped Ring-shaped Tuned Liquid Damper-1(SRSTLD-1),is proposed in the first section.Its base surface is perpendicular to the cross section of the stay cable.SRSTLD-1 is only applicable to stay cable with an inclination greater than 45 degrees.By selecting proper cylindrical coordinate system,the first order sloshing frequency and time varying control force of SRSTLD-1 can be deduced based on classical linear potential flow theory.According to the mathematical expression of SRSTLD-1’s dynamic charateristics,its size is designed and optimized for certain existing stay cable.Modal and transient anlaysis are conducted on the comparative group of the stay cable to be controlled in MATLAB software.The vibration mitigation effect of SRSTLD-1 is analyzed by cable’s modal information and comparative group’s midpoint dynamic response together.(2)A damper,which is called Sloped Ring-shaped Tuned Liquid Damper-2(SRSTLD-2)is proposed in the second section.Its base surface is parallel to the groud.Similarly,damper’s second-order control Laplace differential equation and its corresponding boundary conditions are given.The solution with undetermined coefficients are provided based on transformation of coordinates.However,undetermined coefficients have not been figured out due to the mathematical complexity.To further work out this problem,the comparative group model of certain existing stay cable has been simulated and established in ADINA software.Dynamic responses at the target node position are solved by using implicit-dynamics solution method.SRSTLD-2’s size is optimized through simulation outcomes.(3)Based on the Four-wire Pendulum Tuned Mass Damper(FWPTMD),the real brigde test is conducted on Dalian Xinghai Bay Cross Sea Bridge to validate the damper’s vibration mitigation effect.Time history analysis of test load cases is done in ANSYS software.Midpoint velocity responses of the comparative group have been gathered under the same sinusoidal excitation.The vibration mitigation effect of FWPTMD has been demonstrated by both of the experimental results and numerical results.The researches above have indicated that the proposed passive damper can be used to mitigate the vibration of stay/suspender cable.Their first modal damping ratio have also been improved.The proposed passive damper has a positive effect on prolonging cable’s service life,which is esstential.