Resarch On Beam End Displacement Relevant Problems For High-speed Railway Ballastless Track Bridge

With rapid development of high speed railways in China, ballastless track is more andmore widely used. The ballastless track is a track structure which use concrete or asphaltmortar to replace the gravel ballast roadbed which features good stability, regularity anddurability. For ballastless track, the vertical corner at beam end will result in local hunch oftrack at the joint, which further cause uplift force of the fastener on one side of the joint andpressure stress of the subplate on the other side. If the uplift force acting on the track plate(or concrete slab) is larger than the weight of track plate (or concrete slab) at the supportingpoint, the whole track structure might lose stability. In addition, the corner between beams oftwo adjacent spans and that between the beam and abutment as well as faulting of beam endswill cause geometric irregularities of the track so as to influence the running comfort andsmoothness. For the above issues, influence of the beam end deformation on strength ofballastless track as well as the safety and comfort while EMU train passes by the beam endare systematically analyzed by indoor test and finite element simulation analysis so as toprovide reference for determination of limit value of beam end.By drawing on relevant researches abroad, limit values for uplift force for clip, pressurestress and rail stress as well as stability coefficient for ballastless track at beam end areproposed according to the strengths of various components of ballastless track for high speedrailways in China; the instantaneous comfort index is proposed by referring to JR evaluationstandard and taking into consideration the influencing scope of beam end deformation. Allthe above limits serve for determination of beam end deformation limit.Elastic support beam model is used to make theoretical analysis on influence of beamend deformation on fastener and rail stress; the influence line method and optimizationprinciples are applied to calculate the maximum values of midspan deflection and beam endcorner of24m,32m and40m simple support box beam under the action of ZK live load andfour types of EMUs so as to work out the proportional relationship between beam end cornerand deflection/span ratio. Finally it is concluded that the beam end corner limit is the controlfactor for rigidity design of bridge. The beam end deformation is simulated in indoor test and the rigidity curve for WJ-7fastening system is worked out. The influence scope of beam end vertical corner and beamend faulting on fastener and rail is studied.3D solid unit finite element model established byANSYS program has simulated the testing load with the result used to validate the finiteelement model; parameterized3-D solid unit model is used to analyze the influence rules ofextension elongation of beam end, spacing between fasteners, rigidity of fasteners and typeof ballastless track on additional stress on fastener and rails.Abaqus finite element program is used to establish the vehicle-track-bridge couplingdynamics analysis model which is divided into hexahedral grid, based on which four casesincluding vertical corner of beam end, vertical faulting of beam end, horizontal corner andhorizontal faulting of beam end are simulated to calculate the safety and comfort level withEMU passing by at respectively300km/h and350km/h, the variation law between the safetyand comfort level and the amplitude of displacement has been analyzed.