Damping Performance Of Longitudinal TMD And Tower-beam Damper System For Long-span Bridges

The long span cable-stayed bridge and suspension bridge system will produce significant longitudinal vibration under vehicle load,wind load and earthquake,so the longitudinal damping system is one of the key problems in the design of this kind of long span bridge.Double tower three-span cable-stayed bridge and single span suspension bridge usually arrange counterweight on the side span to balance the negative reaction force of bearings,thus creating conditions for using tuned mass damper with large massratio(TMD)to reduce longitudinal vibration.In order to compare the performance of longitudinal vibration damping system of long-span bridge,this thesis explores the parameter scheme of TMD longitudinal vibration damper designed by counterweight,and makes a comparative analysis with the longitudinal eddy current damper system.The main research contents and main conclusions are as follows:(1)single degree of freedom structure dynamic magnification coefficient was deduced the optimal weight of the TMD-type counterweight optimization parameters,based on Zhang Gao line right branch design of suspension Bridges and sutong bridge scheme,the equivalent parameters of eddy current damper are proposed,The corresponding single degree of freedom model is established,The displacement peak damping ratio of TMD scheme and eddy current damper scheme under different dynamic loads is studied,The results show that TMD-type counterweight can reduce the vibration of random loads to a certain extent,but it has better effect on harmonic loads,while eddy current damper has better effect on random loads such as earthquake loads.(2)Three-dimensional finite element models of long-span suspension Bridges and cable-stayed Bridges are established,The longitudinal vibration characteristics of main girder structure under harmonic load,seismic load,three-dimensional fluctuating wind load and random traffic load are analyzed,The peak value of the longitudinal movement,the vibration reduction rate of the longitudinal displacement and the RMS value of the longitudinal displacement of the bridge are taken as the optimization control objectives,The damping control effect of TMD-type counterweight scheme is studied.The results show that the vibration reduction effects of single-span suspension bridge and three-span cable-stayed bridge under seismic response are 39.98%and 16.06% respectively.(3)Based on the THREE-DIMENSIONAL finite element model,the damping performance of the two Bridges with different eddy-current dampers is analyzed.The results show that the eddy-current dampers can reduce the stress of the steel beams and prolong the fatigue life of the steel beams.The split-type arrangement of damper can ensure the same damping effect and be more convenient for installation.The damping effect of parallel spring and eddy current damper is studied,The results show that the damping effect of the scheme is limited compared with that of the single damper scheme,but it can effectively reduce the deformation of beam end under static load,thus reducing the length of bridge expansion joint。...