Research On Cable Vibration Control By Using STF Damper

Cable-stayed bridge has become the predominance of medium and long span bridges.As one of main stress components of cable-stayed bridge,cable is prone to vibrate when stimulated by the external excitation.The vibration aggravates the fatigue damage of the cable,and it also causes a disaster when it is out of control.So the vibration mitigation of the cable is critical to its normal performance.In the main vibration control methods,damper is the most extensive and effective approach.STF(shear thickening fluid)is a kind of material with superior energy dissipation,and can change the characteristics adaptively with the change of shear rate.Therefore,after combining the structural advantages of modern dampers and the performance advantages of STF materials,this paper develops a STF damper and applies it to the vibration control of cable.On the basis of validating the effectiveness of the solution,the relevant parameters analysis is made for a better application of STF damper.In order to study the characteristics of STF damper,the related experiments were carried out.This chapter analyzes the characters of the STF material,selects the reasonable damper structure,designs and makes the prototype STF damper and carries out the sine wave and seismic wave loading test on the MTS 793 system.The hysteresis curve of sine wave test showed that the characteristics of STF damper change with different loading frequency,and the results of seismic wave test show that the damper can perform stable and excellent energy dissipation.For studying the characteristics and effectiveness of STF damper,a method for solving free vibration of cable-STF damper system is established.Based on the results of dynamic characteristic experiments,the phenomenonlogical model of STF damper is proposed,the numerical model of cable-STF damper system is established,and the iterative method is introduced to the study.According to the velocity at the STF damper location,the whole decay process is divided into five stages.The representative cycles are selected at each stage.The velocity and damping force at STF damper location and the change of the realtion between displacement and damping force in each cycle are analyzed.By comparing with the viscous damper,the effectiveness of STF damper on the free vibration control of cable is validated.The decay of midspan displacement is divided into three stages,and it is found that the damping characteristics of STF damper have the combined characteristics of viscous damping and friction damping.And the character of either friction damper or viscous damper predominates at different stages of the decay process.The parameters affected the effectiveness of STF damper in free vibration control of cables are analyzed,and the suggestions are given.The free vibration of cable-STF system with different amplitude,different damper location and different cable end is studied.Increasing amplitude will increase the number of cycles in the first stage of the decay process.The damper location is more close to midspan,the height is hinged,the STF damper is more effective.