| Under the extremely large temperature difference conditions,the long-span arch bridges in high altitude mountainous area are inevitably subjected to reciprocating and changeable temperature-induced deformation,which will affect the track regularity and running safety of the train.However,the deformation mapping relationship between temperature-induced deformation of arch bridge and ballastless track remains unclear.Ballastless track laying on long-span bridge faces great technical challenges in terms of adaptability to large temperature difference environments,coordination of foundation structure deformation,and control of track regularity.This thesis takes a long-span arch bridge of Sichuan-Tibet Railway and CRTS I double-block ballastless track as the research objects.The temperature field of the steelconcrete composite beam is analyzed.Then,the mapping model between vertical temperatureinduced deformation of the arch bridge and track geometry is constructed and verified.Finally,the influence of temperature and key parameters of track interlayer structure on track geometry is studied.The main research contents and conclusions are as follows:(1)Based on Python and the software ABAQUS,the temperature field model of the steelconcrete composite beam is established.The temperature variations of the composite beam in typical representative days are analyzed.The distribution of temperature difference along the beam height direction is clarified.The vertical temperature gradient model of the composite beam is obtained.The results show that under the action of temperature and solar radiation during the day,the concrete bridge deck presents a temperature distribution mode of high surface temperature and low internal temperature,and the temperature decreases nonlinearly from top to bottom.The temperature distribution mode of the bridge deck at night is transformed into low surface temperature and high internal temperature.The most unfavorable vertical temperature difference curves in spring and summer are composed of concrete bridge deck curves and steel girder multi-segment broken lines,and the vertical temperature difference in summer is more unfavorable than that in spring.Compared with the current specifications,the temperature gradient proposed can reasonably describe the temperature difference distribution of the composite beam and is more unfavorable than the current specifications.(2)Based on the analysis of the rail deformation caused by temperature-induced deformation of the arch bridge,reasonable assumptions are put forward.The rail mechanical model,track slab mechanical model,and arch bridge temperature-induced deformation calculation model are constructed respectively.Then,the alignments of the bridge deck and the arch ring under the temperature load are calculated,and the temperature-induced deformation of the arch ring is transmitted to the beam in the form of forced displacement.The bridge deck alignment of the long-span arch bridge under the temperature-induced deformation is described by the temperature-induced deformation function of the arch bridge.Based on the relationship between fastener force,rail deformation,track slab deformation,and arch bridge temperatureinduced deformation,the rail deformation is represented by a matrix related to track structure parameters and arch bridge temperature-induced deformation.The mapping model between the vertical temperature-induced deformation of arch bridge and track geometry is constructed.The models are solved using MATLAB codes.(3)A finite element model is established using the software ABAQUS to validate the mapping model proposed.The alignments of the arch ring and the bridge deck calculated by the finite element model and arch bridge temperature-induced deformation calculation model under typical temperature load are analyzed,and the comparative analysis is carried out to ensure that the temperature-induced deformation function of the arch bridge is accurate.The rail deformation curve and fastener force calculated by the mapping model and the finite element model under typical working conditions are in good agreement,which verifies the accuracy of the arch bridge-track temperature-induced deformation mapping model.(4)The verified mapping model is used to study the influence of the temperature loads,the fastener vertical stiffness,and the isolation layer stiffness on rail deformation and fastener force.The results show that the rail will follow the deformation of the continuous beam on the arch.The trend of rail deformation curve caused by different temperature gradient modes is basically the same when the temperature gradient load acts on the continuous beam.The maximum value of rail deformation,the rail deformation zone,the rail deformation extension coefficient,the rail folding angle,and the peak value of fastener force change with the temperature gradient mode.Under the overall temperature change of the arch ring,the rail deformation curve is relatively flat,the rail does not appear bending angle,and the fastener force value fluctuates around 0.The temperature gradient load mainly affects the rail deformation in a certain range at the end of the continuous beam.The overall temperature change affects the rail deformation curve in the whole bridge.The fastener vertical stiffness and the isolation layer stiffness mainly affect the rail deformation extension coefficient and the peak value of fastener force,and have little effect on the maximum value of rail deformation and the abrupt change area of fastener force. |
