Quantitative Study On Mapping Relationship Between Bridge Deformation And Track Geometry Of High-speed Railway

The development of high-speed railway in China has been changed from massive construction to safe operation period.Under the long-term effects of settlement,earthquake,concrete shrinkage and creep,temperature variation,and vehicle dynamic loading,high-speed railway bridges may experience irreversible vertical and lateral deformations,which can affect the track smoothness and have adverse effects on safe operation of vehicles.In this study,bridge-track deformation mapping models are presented to quantify the effects of bridge deformation on the geometry of track for high-speed railway simple bridges and CRTS I ballastless track slabs.The main research contents and conclusions are as follows:(1)Based on the analyses of the influence of bridge deformations on the operation safety of high-speed trains,multiple bridge deformation modes are considered,and their limit values specified in different standards are compared.A review is performed for the computational model of high-speed railway bridge-track interaction,the deformation compatibility effect between the unballasted track strcutures,and the mapping relationship between bridge deformations and track geometry irregularity.Drawbacks in existing studies are pointed out,and the significance of this study is elaborated.(2)Based on the analysis of the mechanism of bridge-track interaction,basic assumptions for model development are presented,and then,a universal analytical model is established to describe the relationship between bridge vertical deformation and track geometry through mechanical analyses.Analytical formulae are derived for the track deformations with the influence matrix of fastener force for rail vertical deformations,the influence matrix of fastener force for track slab vertical deformations,and the the influence matrix of bridge vertical deformations.Track deformation analytical models were established for three typical bridge deformations,which are bridge pier settlement,vertical girder fault,and vertical firder rotation.The models were solved using MATLAB codes.(3)Based on the mechanism analysis of rail deformation due to the lateral bridge deformations and the mechanical analyses of CRTS I ballastless track slab,an assumption of rigid deformation of the track slab is presented.The analytic expressions of bridge-track deformation mapping model are deduced through equilibrium and the deformation compatibility equations.Lateral rail deformations are formulated with the influence matrix of bridge lateral deformations,the influence matrix of fastener force for rail lateral deformations,and the influence matrix of fastener force for track slab lateral deformations.Formulae of rail lateral deformations are derived with girder's lateral end rotation and lateral girder fault,and solved using MATLAB codes.(4)A finite element model of bridge and CRTS I ballastless track slab is established using the software ANSYS.Three typical vertical bridge deformation modes and two typical lateral deformation modes were considered.The vertical bridge deformation modes are bridge pier settlement,vertical girder fault,and vertical girder rotation.The lateral bridge deformation modes are girder's lateral end rotation and lateral girder fault.Vertical and lateral deformation mapping models are validated using the finite element model and experiments conducted by the China Academy of Railway Sciences.(5)Based on the validated mapping model,the mapping features and influence degrees are investigated for different bridge deformation modes.A concept of rail deformation extension coefficient is proposed.The effects of key properties on maximum values of rail deformation and deformation length are quantitatively studied.The key properties include the bridge deformation amplitude,bridge span,girder suspension length,the fasterner's stiffness,and the mortar layer's stiffness.On this basis,suggestions on controlling the rail deformation are put forward.