Study On Seismic Reduction And Isolation Control Of High-speed Railway Continuous Girder Bridges Under The Action Of Spatially Varying Earthquakes

High-speed railway long-span bridges in high-intensity earthquake areas often require seismic isolation design to meet seismic requirements.With the continuous accumulation of seismic disaster experience,the spatial variation characteristics of ground motion should also be considered in seismic analysis of long-span bridges.In this paper,the mechanical parameters of long-span high-speed continuous beam bridge bearings with different seismic isolation devices are optimized and analyzed in detail under the excitation of seismic waves with different spectral characteristics.And the effect and numerical rules of its vibration reduction and isolation are studied.For the traveling wave effect in the spatially varying ground motion effect,study its influence on the shock absorption effect of each vibration isolation device.The main research contents completed are as follows:(1)Using power spectral density function model and coherence function model to describe spatially varying ground motion fields from different angles.Summarizes the principles of seismic wave selection for time history analysis.Based on the general-purpose finite element software,a full-bridge finite element model of a large-span continuous beam bridge with a main span of 128m,which is commonly used in high-speed rail,is established.Trial adjustment of bearing parameters using the general connection unit that comes with the software.Simulate viscous dampers and hyperboloid spherical vibration isolation bearings,and the structure models of the bridges with seismic isolation bearings are established.(2)The mechanical parameters of long-span high-speed continuous beam bridge bearings with different seismic isolation devices are optimized and analyzed in detail under the excitation of three kinds of seismic waves with the same peak value and different spectral characteristics.The result shows that:Three types of seismic waves with the same acceleration peak but different spectral components have different optimization results for the mechanical parameters of the same seismic isolation bearing model.When selecting the actual bearing parameters,the ground motions with corresponding spectral characteristics should be selected for optimization analysis according to the site conditions where the bridge is located,and determined in combination with the requirements of the bearing structure size.Under the action of Taft waves,except for the relative displacement of the fixed pier,the seismic response of the bridge structure is reduced,especially the internal force and the top displacement of the pier at the fixed pier No.2 have a shock absorption rate of more than 74%;Under the action of El centro wave and Tianjin wave,the internal force and displacement response of the fixed pier of No.2 decreased significantly,and the shock absorption rate reached more than 81%.The internal forces and displacements of other piers increased,but the increase was not large compared to the response of fixed piers.Since the other piers share the earthquake action of the fixed piers,the forces on the bridge piers tend to be uniform and reasonable,avoiding the situation where the fixed piers are subjected to large forces.(3)Traveling wave effects in consideration of spatially varying ground motion effects,the seismic response analysis of the bridge model with ordinary bearings,hyperboloid spherical isolating bearings,and viscous dampers is performed.And gives the comparison of the response effects of each model under the wave passage effect.The result shows that:For ordinary bearing bridges,the traveling wave effect will amplify the response of the shear force and bending moment at the bottom of the pier,and the effect on the relative displacement of the pier beam is not obvious.When the wave velocity is 500m/s,the response of the internal force at the bottom of each pier and the relative displacement of the pier beam is the largest.For a hyperboloid spherical isolating bearing bridge,when the apparent wave velocity is 500m/s,the internal force of each pier increases significantly,and the relative displacement of the pier beam decreases significantly.For bridges with viscous dampers,the traveling wave effect will reduce the response of the internal force of each pier and the relative displacement of the pier beam.The smaller the apparent wave velocity,the larger the response value of the bending moment of the main pier,and the smaller the response value of the shear force and the relative displacement of the pier beam.In this paper,through a combination of theoretical analysis and numerical simulation,the mechanism of vibration reduction and isolation of high-speed railway continuous beam bridges under uniform excitation and spatially varying ground motion is analyzed.The effectiveness and accuracy of high-speed rail continuous beam bridge isolation and isolation control are improved,which can provide a reference for high-speed rail continuous beam bridge isolation and isolation design,and lay the foundation for further research on other spatially varying ground motion effects.