Research On The Calculation Method For Transverse Internal Force Of Concrete Box Girder Bridge

In recent years,with the increasing development of infrastructure industry in China,thin-walled box girder has been widely used in bridge production.The transverse internal force resulting from the deformation of box girder under vertical eccentric load has been gained much attention from domestic and foreign scholars.To solve the problem of transverse reinforcement on bridge deck and prevent longitudinal cracking of box girder plate,scientific researchers should put the whole heart and soul into the transverse internal force of box girder.On the basis of studying and summarizing different transverse internal force calculation methods,the influence of transverse internal force for concrete box girder deck under the vehicle load should be considered in this paper.Selecting single box single cell box girder as the research object,the main contents are as follows:(1)For single box single cell box girder,the relevant formulas for computing the traditional transverse internal force by frame analysis method were derived.Based on the properties of frame plates deformation,the improved frame model was established and its transverse displacement was computed.According to the coordination between the displacement of improved frame model and the displacement of box girder,calculation formulas for computing the transverse internal force considering the influence of distortion were derived.Through the analysis of an example,it can be seen that the relative error is not more than 5% between the improved analytical solution of frame analysis and the numerical solution obtained by the ANSYS.(2)The energy variational method is different from the frame analysis principle.Based on the principle of stationary potential energy,a fourth-order control differential equation with unknown distortion angle of box girder section is established to solve the distortion angle and calculate the transverse bending moment of the frame.The method of this paper was used to verify the calculation case and analyze the differences between the results of different transverse internal force calculation method.Compared with the traditional frame analysis method,the energy variational method is more accurate in calculating the transverse bending moment at the bottom plate corner of the box girder.The error between the energy variational method and the finite element numerical solution was not more than 7.2%.(3)Combined with practical engineering case,the transverse bending moment of the mid-span section of the box girder under the three lanes load is 5 times that of the vehicle load.Under the vehicle load,the Sawko formula and the Baider Bahkt formula is used to computed the transverse bending moment on the cantilever plate with equal thickness and variable thickness.The result show that the error is 3.93% between the calculated values of Sawko formula and Baider Bahkt formula.The bending moment of variable section cantilever plate computed by Baider Bahkt formula is more accurate than that of equal section box girder cantilever plate.(4)Introducing the transverse internal force correction factor,the change law of transverse bending moment and its correction factor were researched by analyzing load eccentricity and the geometric parameters of box girder.The results show that the load eccentricity and the bending stiffness ratio of top and web plate have a greater influence on the top plate corner of transverse bending moment and its correction factor,but the width of cantilever plate,the ratio of span to height and the ratio of height to width have a minor influence on them.The effective length of the wheel contact surface has a greater influence on the correction factor for the corner points of the top slab,while the box girder section size,beam height and effective width of the wheel contact surface have a smaller influence on the correction factor for the corner points of the top slab.