Research on Mechanical Property and Control Effects of In-Service Viscous Dampers for Stay Cables
After long-term service,viscous dampers of stay cables are prone to liquid leakage.This article quantitatively evaluates and analyzes the degradation of mechanical property and vibration control performance of viscous dampers caused by liquid leakage.Firstly,using performance testing methods,viscous dampers with liquid leakage on an existing bridge are selected to study their mechanical properties and explore the mechanism of slip generation.Secondly,the mechanical property of the viscous dampers with liquid leakage was numerically simulated,with the gap elements and dashpot elements connected in series.The parameters of the model were determined and verified by tests.Based on the mechanical model,the system model of stay cables and viscous dampers with liquid leakage was established to analyze the slip triggered by liquid leakage on the additional damping ratio of the stay cables.It is shown that the liquid leakage caused significant slip of the hysteresis curves of the damping forces of the viscous dampers attached to the in-service stay cables in the second and fourth quadrants.There appeared gap inside the viscous dampers after liquid leakage,and when the piston rod passes by the gap,no resistance was generated,as a result,there appeared slip platform in the hysteresis curve of the damping force,which distinctively weakened the energy dissipation capacity of the dampers.As the slip increases,the first-mode additional damping ratio became smaller,undermining the vibration control effect of the viscous dampers on the stay cables.
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