Investigation On The Effects Of Dampers On Cable Tension Estimation For Cable Stayed Bridges

For cable stayed bridges,the stay cable is one of the most crucial load-carrying structural components.However,due to the inherent low damping characteristics of stay cables,they are often subjected to large vibration due to wind loads,greatly reducing the safety and longevity of the stay cable.Therefore,many cables are installed with different types of dampers to reduce the cables' vibration.To grasp the operation status of the cable,the cable tensions need accurately estimated.Since the installed dampers change the dynamics of cable structure,they will inevitably affects the results of cable tension estimation.But,so far,little research has been conducted on how the installed dampers affect the accuracy of cable tension estimation.In this study,the influence of the installed dampers on the accuracy of cable will be systematically investigated.Two types of dynamic models of the cable are considered herein.In the first model,the cable is modelled as a taut string without sag;in the second model,the effects of cable sag are consider.To improve the efficiency of calculating the dynamic characteristics of the cable with damping,a shape function of the static deformation of cable,subjected to unit load from the damper,is added to sin shape functions to approach the mode shape of cable-damper system.The Galerkin approach was adopted to analyze the natural frequency of the system.Two types of damper models are also considered.In the first model,in which a simple spring and viscous damper model is used to model the damper.In the second model,a nonlinear model is utilized to model the damper.To calculate the natural frequencies of the cable-damper system with nonlinear damper model,linearization technique is used.Based on the above derived models of the cable-damper system,extensive parameter study are conducted to investigate how the damper's parameters,including the damper's installation location,the damper's stiffness and the damper's damping coefficients,affect the natural frequencies of the cable-damper system as well as the results of cable tension estimation.The main conclusion about the effects of damper's parameters on cable tension estimation are summarized finally.