Research On Seismic Response Analysis And Shock Absorption Control Of Abutment Approach Bridge Rigid Frame Continuous Girder Bridge System Considering Collision Effect

With the development of highway transportation industry in China,there are more and more irregular long-span Bridges under complex geological and topographic conditions,and most of them are close to or even across seismic fault zones.The impact of earthquake on bridge structure system cannot be ignored.When the main bridge structure is rigid frame continuous beam,the flexible rigid frame piers not only bear most of the horizontal seismic force,but also make the collision effect between the main approach bridge and even between abutment and approach bridge significant,which leads to seismic damage such as beam fall,pier and yieldfailure.Therefore,in this paper,the seismic response of abutment-approach bridge-rigid frame continuous girder bridge structure system under collision condition is studied,and corresponding measures of shock reduction and isolation are taken according to the structural characteristics.The main work and achievements of this paper are as follows:(1)The elasto-plastic dynamic analysis model of abutment approach bridge-rigid frame continuous girder bridge system considering impact energy dissipation,pile-soil interaction,abutment and backfill interaction,and nonlinear behavior of supports and piers is established,and the influence of impact on the seismic response of the structure under seismic fortification is analyzed.The results show that the impact increases the position displacement of the approach bridge and the relative displacement between the platform and pier beams,and the maximum change rates are 146.9% and 147.9%,respectively,and the risk of falling beams increases.The internal force and deformation of the bridge pier and the section of the pile foundation are increased,and the change rate is less than 10%.Only the section of the transition pier foundation yield failure occurs.The internal force and deformation of rigid frame pier are reduced,and the maximum change rate is-13% and-4.9%,respectively.The maximum change rates of abutment displacement,section bending moment of abutment pile foundation and backfill displacement are 1230%,116.0% and 428.5%,respectively.(2)The effects of main bridge structure type,pier height,approach span number and expansion joint spacing on seismic response of structural system are studied.The results show that the internal force,deformation and impact effect of continuous girder bridge are smaller,and the piers will not yield failure.The period ratio of the main approach bridge increases with the increase of the pier height,and the impact effect of the expansion joint is strengthened.However,the internal force and deformation of the rigid pier are only affected by the increase of the pier height,and the displacement first increases and then decreases,while the shear force first decreases and then increases.The increase of the number of bridge spans and the distance between expansion joints of the main approach bridge increases and decreases the impact force of expansion joints,respectively,and the maximum change rates are 139.8% and-88.9%.At the same time,the bending moment at the bottom of the rigid frame pier decreases and increases respectively,and the maximum change rates are-11.9% and 31.6%.The top displacement of rigid frame piers decreases and increases,respectively,and the maximum change rates are-7.5%and 33.3%.(3)The effect of long period seismic wave on structural seismic response is studied.Firstly,the ground motion parameters and spectrum characteristics of long period seismic wave are analyzed.It is found that the ground motion parameters and response spectrum of long period seismic wave are larger and have low frequency pulse characteristics.The influences on the seismic response of the structure are as follows: far field type harmonic > slip thrust > forward directional > ordinary seismic wave;At the same time,the greater the pulse period of the nearfault pulse wave is,the greater the influence on the seismic response of the structure is.The analysis of the action mechanism of long period seismic wave shows that under the same peak acceleration,the far field quasi-harmonic seismic wave has the greatest influence due to the duration of strong earthquake,the slip thrust seismic wave has the greatest influence because the energy is more concentrated in the frequency domain,and the forward directional seismic wave has the characteristics of low frequency pulse,and its influence is greater than that of the ordinary seismic wave.(4)Under the action of normal seismic wave and long period seismic wave,hyperbole spherical friction pendulum isolation bearing,cable damping bearing and viscous damper are used to carry out combined or combined damping analysis on each pier and abutment respectively.The results show that the internal force of each pier and the impact effect of expansion joint can meet the requirements only when the viscous damper is installed on the abutment and the damping device is installed on the No.5 pier.At the same time,the effective damping scheme under the action of ordinary seismic wave can not achieve the expected effect under the action of near-fault pulse earthquake,so it is necessary to optimize the parameters of the damping device.