Study Of Track Constraint Effect On The Seismic Control Of Continuous Beam Bridges In High-Speed Railways

With the rapid development of high-speed railway technology,seismic isolation technology has been constantly applied to girder bridge in high-speed railways.In order to improve the accuracy of the seismic isolation design for girder bridge in high-speed railways,it is necessary to consider the influence of track constraints on its vibration isolation performance.In this paper,based on the beam-rail interaction mechanism,a rail-bridge integrated model is established for a vibration-isolated continuous beam,and the impacts of the track constraint on the vibration isolation and energy dissipation performance of the continuous beam bridge in high-speed railways installed with seismic isolation devices have been systematically studied.The main contents are as follows:(1)Based on the beam-rail interaction mechanism,a finite element model of a continuous beam with or without track constraints is established.The influence of the track constraint on its dynamic characteristics and seismic response is studied.The results show that the track constraints influence the low-order modes of the structure and also its seismic response.The increase of the longitudinal resistance of the lines reduces the relative displacement of the rail and the girder,as well as its seismic response.(2)Three typical seismic isolation devices(friction pendulum bearings,E-shaped steel damper bearings,and viscous dampers)applied in continuous girder bridge in high-speed railway have been studied.A numerical simulation was conducted to analyze the effect of rail constraint on the performance of seismic isolation devices,including energy dissipation performance and seismic response of the structure.The results indicate that the vibration reduction and energy dissipation performance of the seismic isolation devices is reduced to some extent due to track constraint,which need to be considered for the seismic isolation design of the bridges in high-speed railways.(3)The influence of the parameters such as the longitudinal resistance of the line,the number of the adjacent simply-supported beam and the length of the roadbed on the earthquake response of the continuous beam with track constraint is discussed.It is shown that the increase of the longitudinal resistance of the line reduces the displacement of the girder,girder-rail relative displacement and the energy dissipation of the isolation bearing.The increase of the number of the adjacent simply-supported beam increases the displacement of the girder,girder-rail relative displacement and the energy dissipation of the bearing.Longer roadbed decreases the displacement of the girder,girder-rail relative displacement and the seismic response of the bridge piers.(4)A simplified model of two-degree-of-freedom continuous beam with TIBD(tuned inerter based damper)installed is introduced.The optimal parameters of TIBD with or without consideration of track constraints were calculated.Moreover,the effect of the track constraint on the damping performance of the TIBD was studied.It is indicated that considering the track constraint,the optimal parameters make TIBD's damping performance better.It is suggested that the effect of the track constraint should be taken into account when using TIBD for the seismic isolation design.