Study On Longitudinal Vibration Control Of Long Span Bridges

Bridge is an important part of the transportation system.With the progress of the bridgeengineering and the development of the world economy,in order to meet people’s needs,the span of bridges is larger and larger.Cable-stayed bridges and suspension bridges are main bridge types of long-span bridge.As everyone knows,earthquake is very harmful to bridge structure,especially for long-span bridges.The longitudinal stiffness of long-span bridges is generally relatively small,which may generate over allowable structural deformation under earthquake.The earthquake will bring great kinetic energy to the structure in a short time.It is difficult for the general shock absorber to absorb so much energy in a short time.In order to improve the effect of vibration control of long-span bridges under earthquake action,inspired by the tuned mass damper(TMD),this paper introduces an accelerated oscillator damper,called AOD device.The AOD device can effectively transfer the displacement and speed of the controlled structure to the mass block by amplifying a certain multiplier through the transmission device.According to the principle of energy conservation,the AOD device absorbs a large amount of kinetic energy of the controlled structure,and the response of the controlled structure will be reduced,thus the purpose of vibration control is achieved.Firstly,this paper briefly introduces the development of long-span bridges and the research status of longitudinal vibration control for long-span bridges.Then the working principle of the AOD device is introduced in detail,and the derivation and solution of the differential equation is carried out.It is found that the control effect of the AOD device has a great relationship with the transmission ratio ‘r’ and the mass ‘m’.When ‘r’ takes 8 and ‘m’takes 1% of the quality of the controlled structure,it can get an ideal control effect.And it is verified on the three span continuous beam model.The finite element model of the Xinghai Bay Bridge is established by ANSYS,and the modal analysis is carried out.Chose three seismic waves according to the bay bridge site condition,and made some adjustment.The Xinghai Bay bridge are analyzed by time history analysis,using nonlinear longitudinal input.Although some adjustment has been made for seismic waves,it is found that the response of bridge structures to different seismic waves is quite different.The longitudinal vibration of Xinghai Bay Bridge is controlled by viscous dampers,where 8 nonlinear viscous dampers have been used at the bridge tower and anchorage.Theapplication of AOD device to the Bay Bridge,and compared the control effect of three kinds of Arrangement,in the end,the arrangement(1)was chosen.The vibration reduction rate of the beam end displacement can reach 65.6%,the top displacement displacement rate can reach 17.4%,and the tower bottom bending moment will reach 16.8%.And compared with the viscous damper,the control effect of AOD is better.