Study On Crack Propagation Performance And Law Of Railway Concrete Simply Supported Beam Bridge Under Train Load

With the rapid development of railway industry,a large number of railway bridges have been built in our country,and the concrete simply supported beam bridge is a common type of railway bridges in our country.Under the function of various unfavorable factors could result in the beam crack of the concrete simply supported beam bridge during operation,the existence of crack will not only affect the appearance and durability of the bridge but can reduce the overall stiffness of the structure of the bridge,the normal service state of the bridge is greatly disturbed,which may influence the safety of the train and cause potential safety hazard,in addition,the crack of the beam is likely to expand further under the action of the train load.Therefore,it is necessary to study the crack propagation property and law of the beam under the train loads.This paper takes the ordinary railway concrete simply supported T beam bridge with crack and high-speed railway concrete simply supported box girder bridge with crack under train loads as the research objects.Combine train-bridge coupling vibration analysis and crack propagation analysis to study the crack propagation property and law of the railway simply supported beam bridge under the train loads.The main research contents are as follows:(1)Based on the basic theory of multi-body system dynamics and its modeling method,the train dynamics model and the bridge finite element model are established by multi-body dynamics software SIMPACK and finite element software ANSYS under the premise of comprehensive consideration of various nonlinear factors.SIMPACK built-in port is used to transform the finite element model of the bridge into an elastomer substructure expressed by the multi-body system.Finally,based on the wheel-rail contact relationship,the coupling vibration model of train and bridge is established.(2)The finite element software ANSYS is used to build the bridge model with crack,and use singular elements to mesh crack tip.The wheel-rail force obtained from train-bridge coupling vibration analysis is extracted and applied to the bridge model with crack in the form of moving load for transient analysis,and the stress and strain data are obtained,Finally,the three-dimensional dynamic stress intensity factors at the crack tip under different working conditions are solved based on the interaction integral.The crack propagation is quantified by the defined fracture propagation evaluation parameter.(3)Based on the results of freight train-bridge coupling vibration analysis,the influences of different beam damage ratio,train weight,speed and structural damping ratio on the mid-span vertical crack propagation performance and law of ordinary railway concrete simply supported T beam bridge under the load of freight train are studied.The influence of horizontal fracture angle on the propagation performance and regularity of oblique crack at a quarter span is also studied.(4)Based on the results of CRH3 train-bridge coupling vibration analysis,the influences of different web damage degree and different high-speed train speed on the vertical crack propagation performance and law of the web in the mid-span of the high-speed railway concrete simply supported box girder bridge under the load of CRH3 high-speed train are studied.At the same time,the influence of different speed of high-speed train on the propagation performance and law of oblique crack in web at quarter span is studied.