Dynamic Optimization Of Ballastless Track Structure On High Speed Railway Bridge

During the development of high-speed railways,the requirements for safety and durability of transportation on high-speed railway bridges are getting higher and higher.Based on the ballastless track on the bridge,the vehicle-rail-bridge system model is established through finite element,and the statics,dynamics,and fatigue calculations are performed respectively.The study summarizes the characteristics of the influence of the stiffness of the fasteners and the elastic stiffness of the supporting layer on the track structure,and proposes reasonable parameters of the ballastless track structure.First,by using the finite element method,starting from the element,the dynamic equation of the track-bridge element is derived.Based on the wheel-rail contact,the contact relationship between the multi-rigid vehicle and the track is established.The vehicle-track-bridge model is established through Matlab software,and the vehicle-track-bridge spatial coupling model is established through ABAQUS,which is compared and verified with the Matlab calculation results to determine the correctness of the model.After that,the effects of different fastener stiffness and elastic stiffness of the supporting layer on the static and dynamics of the vehicle-rail-bridge system are studied.Analyze the change law of the absolute maximum value of the system response and the sensitivity of the dynamic response under each parameter structure,and based on the change law and parameter sensitivity,establish a single-objective and multi-objective vehicle-rail-bridge system optimization model.The performance of the vehicle-rail-bridge coupling is optimized through the NSGA-Ⅱoptimization algorithm.Finally,from the conclusions of statics and dynamics,from the perspective of the change of the stiffness of the fastener and the elastic stiffness of the supporting layer,the law of the fatigue life of the vehicle-rail-bridge system is analyzed.conclusion as below:（1）Under the action of train,each parameter has different effects on the track structure:the increase of fastener stiffness,rail displacement and dynamic bending stress is gradually decreasing trend,and the influence on track plate displacement and transverse longitudinal stress is small.The increase of elastic stiffness of supporting layer,the displacement of rail and track plate shows a slow decreasing trend,while the displacement of supporting layer rises slowly and the longitudinal stress of track plate decreases gradually.The increase of rail plate thickness has less effect on the displacement of each structure,which is basically unchanged,and the transverse and longitudinal stress of rail plate gradually decreases,and the longitudinal stress of supporting layer gradually decreases.Considering the rail displacement limit,the reasonable range of fastener stiffness is selected from 50 to 80kN/mm,and the range of elastic stiffness of support layer is from 200 to 500kN/mm.（2）The results of the vehicle-bridge coupling dynamics calculations show that,with the increase of the train running speed,the indicators of the vehicle track bridge system are on the rise.With the increase of the elastic stiffness of the support layer,the indicators of the vehicle track system are decreasing trend.With the increase of the fastener stiffness,the deformation and acceleration of the rail when the train passes gradually decreases,but it will increase the wheel-rail force during the train driving process.（3）Based on the NSGA-II algorithm to optimize the performance of the peak power response,for the single class target power response results show that the fastener stiffness k_ris75 kN/mm,the elastic stiffness k_bs of the support layer is 500 kN/mm,and the minimum rail positive acceleration is obtained.The fastener stiffness k_r is 80 kN/mm and the bearing layer elastic stiffness k_bs is 420 kN/mm,and the minimum rail negative acceleration is obtained.The fastener stiffness k_r is 53 kN/mm,and the elastic stiffness k_bs of the supporting layer is 470kN/mm,and the minimum positive acceleration of the rail plate is obtained.The fastener stiffness k_r is 50kN/mm,and the elastic stiffness k_bs of the supporting layer is 500kN/mm,to obtain the minimum negative acceleration of the rail plate.The fastener stiffness k_r is 50kN/mm and the bearing layer elastic stiffness k_bs is 500kN/mm,and the minimum bridge positive acceleration is obtained.The minimum bridge negative acceleration was obtained for a fastener stiffness k_r of 50 kN/mm and a bearing layer elastic stiffness k_bs of 200 kN/mm.For the multi-class target dynamic response results show that when the rail positive acceleration is combined with the rail positive acceleration and bridge acceleration to take the optimal,the fastener stiffness k_r is 75 kN/mm and the bearing layer elastic stiffness is 500 kN/mm,both parameters are greater than the average value in the optimization range.When the negative acceleration of the rail is combined with the positive and negative acceleration of the rail and the acceleration of the bridge,the minimum value of the fastener stiffness is 500 kN/mm,and the elastic stiffness of the bearing layer is 500 kN/mm,and the parameters are greater than the average value of 350kN/mm in the optimization range.（4）The increase of the fastener stiffness will reduce the fatigue life of the track plate,but its reduction is getting smaller.And the increase of the elastic stiffness of the support layer has a significant increase of the fatigue life of the track plate.