The Influence Of Bridge Creep On Track Irregularity And Dynamic Characteristicsof High-speed Driving

In order to ensure the high smoothness of high-speed railway,a large number of high-speed railway foundation adopts bridge instead of road to control the settlement deformation,laying ballastless track to ensure the smoothness and less maintenance of the line.Simply supported beam bridge and continuous rigid beam bridge have become the main bridge types for high-speed railway infrastructure construction due to their advantages of simple structure,convenient construction,good economy,strong crossing performance,large stiffness and good earthquake resistance.The existing operation practice shows that the long-term creep of concrete leads to the deformation of the arch and downwarping of the bridge,resulting in periodic unsmoothness of the track,which affects the safety and stability of high-speed traffic.Based on multi-body system dynamics and finite element simulation method,established the vehicle-line-bridge space coupling vibration model,the orbit of creep and random irregularities and Bridges under the action of vertical deformation superposition as foreign incentive system,further study of the bridge creep of track irregularity and affect the characteristics of the dynamic characteristics of high-speed train,and based on the requirement of high speed railway train operation stability and safety,Liang Tixu variable deformation threshold and control measures are put forward.The main research contents and conclusions are as follows:(1)Based on the finite element theory,a finite element model of the bridge was established which could take into account the effect of prestress and the creep of concrete,and the creep of the bridge structure in different service ages was predicted.The results show that the creep arch value of the simply supported beam is 8.17 mm after 10 years,and the bending value of the continuous rigid beam is 43.74 mm.(2)According to the creep characteristics of the bridge and the coordination between the track and the deformation of the beam body,the creep sine curve of the simply supported beam fitted by the arc curve or the calculated bending line under the rigid beam are superimposed into the track random irregularity spectrum,and the latest external excitation of track irregularity is generated by combining the two.(3)Based on the multi-body dynamics and finite element theory,the finite element models of vehicle,track and bridge were established respectively,and the co-simulation of um-ansys was realized through the um-fem interface.Set the condition parameters of the model under the simulation condition,extract the time-history curve of vehicle body and bridge dynamic response and the relevant peak,and compare with the data in previous studies and the specification limits to comprehensively verify the accuracy of the simulation model of the system.(4)Based on the vehicle-line-bridge space coupling vibration model,the dynamic response of high-speed vehicles under the excitation of different train speeds and track irregularity is calculated.Combined with the dynamic performance evaluation indexes of vehicle-bridge,the creep threshold value and control measures of the beam are proposed.It is suggested that the upper arch limit of 32 m simply supported beams should be 7mm.The creep limit of rigid frame girder Bridges studied in this paper should be controlled by 38 mm after completion.In order to avoid track irregularity and over-limit caused by creep of continuous rigid beam Bridges,and to ensure the stability and safety of high-speed traffic,it is suggested to postpone construction of ballastless track for at least 3 months after completion of the bridge.