Vehicle Dynamics Characteristics Of Ballastless Track Culvert Transition Section Under Complex Deformation

In the transition section of a high-speed railway line,due to the difference in the underlying material,structure,strength and stiffness,the lower foundation structure often deforms under the influence of train load and different natural conditions,thus affecting the upper track structure.Therefore,the transition section of a high-speed railway line has gradually become one of the weak links.When complex deformation occurs in the transition section of the culvert,it is of certain research value to explore the deformation characteristics of ballastless track and track surface irregularity under complex deformation,and analyze its influence on the dynamics of the vehicle/track system.In this thesis,according to the structural parameters of the transition section of high-speed railway culvert and CRTS II type ballastless track,the finite element analysis model of the transition section of the ballastless track is first established,and the deformation characteristics of the interlayer deformation of the ballastless track and the uneven surface of the track are investigated when the inverted trid transition section occurs cosine settlement,folding settlement,overall settlement of culvert and subgrade frost heave deformation respectively.Then,the FE-MBD dynamic analysis model of the vehicle-Ballastless track-culture-transition section coupled with the finite element(FE)model of track structure and the multi-body dynamics(MBD)model of vehicle system is established.The static analysis results obtained above are applied to the dynamic model.The dynamic characteristics of vehicle/track system under settlement deformation and subgrade frost heave deformation in transition section of culvert are investigated respectively.The main research contents and conclusions are as follows:(1)When the cosine settlement of 10m wavelength and 20m wavelength occurs in the transition section,as the settlement increases from 5mm to 20mm,the structural displacement of each layer of the ballastless track increases,and the contact surface of the base plate and the subgrade surface produces obvious separation,and the separation value further expands with the increase of the settlement.Small gaps were also created between the track plates.The displacement of the track structure is obvious at the joint of the two track plates and the base plate.When the sedimentation wavelength increases from 10m to 20m,the settlement displacement following of ballastless track is improved,and the contact surface of each layer of track and the base plate and the subgrade surface disappear from the joint.When the transition zone produces 0.5‰ and 1‰ angular settlement,respectively.The structure of each layer of ballastless track shows good followability,and there is no obvious splitting.Under the overall settlement deformation of 3mm and 5mm culverts,the displacement settlement curve of each layer of track and rail is approximately "U",and a few small cracks are produced.(2)When the subgrade of the transition section of the culvert generates frost heave deformation of 10m wavelength and 15m wavelength,the structure of each layer of the track and the rail all produce obvious convex cosine deformation.The contact surface between the base plate and the surface of the foundation bed produces obvious crack,and the deformation between the layers of the ballastless track keeps synchronous,and no obvious crack occurs.When the amount of frost heave increases from 5 mm to 20mm,the deformation of each layer of ballastless track and the separation of joints expand.When the wavelength of frost heave increases from 10m to 15m,the deformation followability of each layer of track and rail is improved,and the gap becomes smaller.(3)The 20m wavelength cosine settlement deformation is generated in the inverted trapezoidal transition segment,and when the settlement is increased from 5mm to 20mm,the vertical vibration acceleration of the car body reaches 1.39m/s2,which is greater than the comfort standard of 1.3m/s2 of the vertical acceleration of the car body.When the inverted trapezoidal transition segment produces 0.5‰,1‰ angular settlement,the maximum vertical vibration acceleration of the car body is 0.7306m/s2,and other dynamic indicators meet the requirements.Considering the wheel flattening,the vertical force of wheel-rail increases significantly,but has little effect on the lateral force of wheel-rail,lateral vibration acceleration of car body and vertical vibration acceleration of car body.When the overall settlement deformation of culvert is produced,the dynamic indexes meet the requirements within the maximum settlement of 5mm.(4)When the inverted trapezoidal transition segment produces a 15m wavelength cosine frost heave deformation,the vertical vibration acceleration of the car body,the vertical force of the wheel-rail and the rail vibration increase significantly,but the lateral vibration of the car body and the lateral force of the wheel-rail are little affected.For cosine freeze-heaving,when the freeze-heaving amount gradually increases from 5mm to 20mm,the vertical vibration acceleration of the car body reaches 1.37m/s2,which is greater than the comfort standard of 1.3m/s2 of the vertical acceleration of the car body.Considering the influence of wheel flattening,the vertical force of the wheel-rail significantly increases compared with that without wheel flattening.The vertical vibration acceleration of the car body has little effect.