Vibration Mitigation Of Stayed Cable Subjected To Influence Of Deck Motion

In recent decades, cable-stayed bridges have mushroomed all over the world with particularly strong momentum of development. Since the new millennium came, remarkable achievements have been made in the development of cable-stayed bridge in China, leading the world's advanced level, and the spans of cable-stayed bridges have been refreshed constantly by the Chinese bridge experts. Cable functions as the important force transfer and force structure, and the costs of the cable design and construction are normally accounted for 25% -30% of the whole bridge, as a matter of which the cable design and construction play a key role in the full bridge.However, recently the tremendously economic lost and the disruptions of traffics caused by the cable damage induced by vibration are often found in newspaper coverage. The easily damaged property of stayed cable is determined by its own, such as slender flexible structure, its own small damping, light weight per unit length of cable and a long period of high dynamic stress state, which attributes to the varieties of mechanisms of cable vibration easily induced by the external disturbances. Thus as the weakness of cable property is present, developing a strategy to enhance the vibration suppression capability of stayed cable has become very necessary and urgent.This paper will study the use of tuned mass damper (TMD) and magnetorheological damper (MRD) respectively as the vibration suppression damper of cable with sag. On the basis of studies done by previous researchers, this paper intends to cite the deck motion, cable damping and stiffness to sag cable-damper theoretical model. First of all, the theoretical derivations on two sorts of cable-damper system would be accomplished, with the damping and stiffness of the cable itself included in cable-TMD damping system, establishing the non-coupling cable-MRD-bridge model as well as the modified coupling cable-MRD-bridge model. Then, the two kinds of vibration model will be accurately solved through complex modal frequency method, and after that the parameters optimization curves of the coupling as well as uncoupling system modal damping ratio verse the dimensionless parameters such as cable inclination, sag, cable damping ratio, the installation location and cable tension weight ratio would be drawn. Furthermore, we could obtain that damping coefficients of cable and the damper are beneficial for the upgrading of both TMD and MRD damping systems without being affected by the mode of deck motion, with the stiffness parameters of cable and damper performing the opposite effects while the effects generated by the coefficients of damper installation position and cable sag making contribution for the system damping depend on the type of the absorber system, with exception of the cable inclination relying on mode of deck effects. Finally, making reference to the damper design, installation, vibration mitigation capacity and the development prospects of dampers, comparisons of TMD damping system with MRD damping system would be made and then calculation and analysis of vibration suppression performance of two damping systems will be based on the real project example with the new optimized parameters offered by applying the above optimization curves. The real project would be made to verify the correctness of the cable-TMD model with cable damping and stiffness considered and to correct the previous non-coupling cable-MRD model which may overestimate the vibration mitigation capability of real MRD damping system.