Response Analysis Of High-speed Railway Bridge With Mr Elastic Isolation Bearing In Near Fault Environment

The rapid increase of the high-speed railway network scale in China has made the percentage of high-speed railway bridge accounting for the total length of line increase as well.The probability of high-speed train running on the bridge have been increasing when earthquake happening.Simultaneously,the increasing requirement of train travelling speed makes the dynamic response of all parts of the bridge structures be more significant under the earthquake.There is no doubt that bridge serves as a crucial link in current transportation.The analysis on how to reduce the damage caused by earthquake to bridge structure is still a hot topic worthy of in-depth study.In the event of earthquake,the traditional bridge bearing often can not guarantee the safety of the bridge structure.This is caused by its uncontrollable stiffness and damping properties,so it is difficult to meet the requirements of cushioning and damping for random earthquakes.Magnetorheological elastomer isolation bearings have good performance in response control of Bridges.However,most of the existing researches focus on the research of elastomer material properties and bearing experiments of magnetorheological elastomer isolation bearings.Few scholars analyze and study the actual seismic performance of bridges in the near-fault environment.Taking the 32×5m pre-stressed concrete continuous bridge of the first section of the Beijing-Shanghai High-speed Railway as a case study.Through the action of different current,the paper simulates and analyzes the damping effect and hysteretic behavior of the continuous beam bridge of high-speed railway when the near-fault ground motion occurs.The main contents of this paper are as follows:(1)Read and summarize the description of the mechanical properties of the magnetorheological elastomers bearing in the domestic and foreign literature,and determine the mechanical properties of the magnetorheological bearing with the mechanical model of the magnetorheological damper as a reference.A mechanical model of magnetorheological bearing suitable for high-speed railway bridge in near fault environment is put forward in this paper,and the quantitative calculation formula is established for parametric calculation.(2)Through the secant stiffness experiment of hysteretic curve,it is verified that the bilinear model formula is highly applicable to the magnetorheological bearing under AASHTO specification.The experimental results show that the relative error of equivalent stiffness is controlled within 16%,which shows that the bilinear model formula can effectively solve the dynamic parameters of magnetorheological bearing under AASHTO specification.(3)Based on the finite element analysis ANSYS software,using APDL programming language,the spatial analysis model of high-speed railway continuous bridge is set up.Firstly,the modal analysis of the whole bridge has been carried out considering the influence of track irregularity and train operation.In order to ensure more safe and reliable operation of the train,when there is no earthquake,the actual running speed of the train should be kept below 350km/h,which is within the bearing capacity of vibration isolation.When there is earthquake,the influence of speed on the lateral displacement of bridge structure is negligible.Therefore,the impact of vertical vibration on the bridge structure is mainly considered.The ratio of vertical and horizontal peak acceleration V/H is adopted in the calculation.The decrease of V/H will reduce the safety of the structure's lateral displacement.When the current is increased,the fitting curve can still maintain a relatively stable state,which indicates that the bearing structure has little influence on the vibration V/H itself.(4)The model effect proposed in this paper will be analyzed from three aspects.In the aspect of the effect of damping ratio achieved an ideal effect,the damping control range is more than 35%.From the aspect of ground motion characteristics,compared with the pulsation-free ground motion,the magnetorheological elastomer vibration isolation bearing performs better in the control of near fault pulse ground motion.From the passive performance point of view,the magnetorheological elastomer isolation bearings has passive damping effect for near fault impulse ground motion and pulsation-free ground motion.