Dynamic Analysis Of A Coupled Steel-Concrete Composite Box Girder Bridge-Train System Considering Complex Spatial Mechanical Effect

The steel-concrete composite box girder bridge had the advantages of light weight,strong spanning capacity,high torsional rigidity and short construction period.It had been widely used in the construction of highway and railway bridges at home and abroad.Under various loads in the operation stage,the interface slip,shear lag,constrained torsion and distortion represented by the steel-concrete composite box girder would affect the mechanical performance of the bridge structure and the safety and comfort of driving.Therefore,it is increasingly important to study the vehicle-bridge coupling dynamic problem considering the complex spatial mechanical effect.This paper will conduct indepth research on this problem.Firstly,based on the constrained torsion theory of Vlasov thin-walled bar and Umansky’s second torsion theory,the biaxial slip function,torsion warping displacement function and shear lag warping strength function of concrete slab and steel beam were introduced to establish a 2-node 26-DOF finite beam element model considering the effects of interface slip,shear lag,constrained torsion and distortion.Combined with previous literature research,the accuracy and applicability of the one-dimensional theoretical model proposed in this paper were verified through comparative analysis of examples.Then,based on the developed finite beam element model,the element stiffness matrix and mass matrix were derived through the principle of virtual work,and the damping matrix was obtained according to the Rayleigh viscous damping theory,and then the motion equation of steel-concrete composite box girder considering the complex spatial mechanical effect was established.A 27-degree-of-freedom vehicle model was selected,and the wheel-rail relationship of Kalker linear creep was simplified vertically and horizontally.Considering the wheel-rail displacement contact condition and track irregularity,the dynamic analysis model of steel-concrete composite box girder bridgevehicle coupling system was established considering the interface slip,shear lag,constrained torsion and distortion.Based on the time-varying of vehicle-bridge coupling system,Newmark-? method was used to solve the motion equation of vehicle-bridge coupling system.The accuracy of the dynamic analysis model of vehicle-bridge coupling system was verified by comparing and analyzing the measured data of the real bridge in the literature and the calculation results of the dynamic model in this paper.Finally,the 2-node 26-DOF finite beam element model was used to analyze the parameters of steel-concrete composite box girder,and the effects of slip stiffness,shear lag effect,torsional warping and the number of diaphragms on the mechanical properties of composite beams were studied.Based on the dynamic analysis model of steel-concrete composite box girder bridge-vehicle coupling system considering interface slip,shear lag,constraint torsion and distortion effect,the vehicle-bridge coupling dynamic response analysis was carried out.The effects of interface slip,shear lag effect,torsional warping and distortion warping on the dynamic response of vertical displacement,acceleration and vertical acceleration of the bridge ware studied.The constraint effect of the number of diaphragms on the dynamic response of distortion behavior was analyzed,which provides some theoretical basis and data reference for the design and application of steelconcrete composite box girder bridges in railway.