Research On Shear Lag Effect Of Box Girder Of Continuous Rigid Frame And Concrete-Filled Steel Tubular Arch Combined Bridges

With the development of transportation business in China,the box girder has been extensively using in the bridge engineering because of its lightweight of structure,strong bending stiffness,strong torsional rigidity,good structural integrity,strong spanning ability,adapting to a variety of modern construction methods and having good stability in the construction and the stage of using.However,the box girder has a significant shear lag effect due to the shear deformation of the top plate and the bottom plate of the box girder.The effect result in a greater concentrated stress at the interface between the section and the web.Ignoring the shear lag effect may threaten the safety of the bridge structure.Therefore,it is significant to study the influence of shear lag on the box girder for the design of the modern bridge.In previous research,many scholars have carried out a lot of theoretical analysis,numerical simulation and experimental research about the subject of shear-lag effect in box girder,and achieved fruitful results,laid a great foundation for further research on shear lag effect of box girder.However,these studies are mostly limited to simply supported single-box single-cell box girders with simply supported beams,continuous beams,and cantilever beams.Therefore,this thesis studies on shear lag effect of double-cell box girder based on a continuous rigid frame and concrete-filled steel tubular arch combined bridge.First of all,the thesis takes the single-box double box girder with cantilever as the research object.According to the distribution law of shear flow in box girder section,the different shear lag warping displacement functions are defined respectively for box girder top,bottom plate and cantilever wing plate.The differential equations are deduced by energy variational method for the shear lag effect that considering the shear deformation of its web.The analytical solutions of the shear lag effect of box girder under different boundary conditions and different types of loads are deduced respectively based on the differential equations,and solved the corresponding section stress,deflection and shear lag coefficient.Secondly,The ANSYS finite element simulation results are compared with the analytical solution results calculated by the MATLAB program to verify the accuracy of the analytical solution.And the accuracy of four kinds of different shear lag warping displacement functions was analyzed.In addition,the geometric parameters affecting the shear lag effect of single-box double-box girder are studied based on the finite element model,and the influence laws of the shear lag effect on box girder are summarized in this paper.Finally,based on the software of Midas Civil and Midas FEA and on-site construction monitoring,the paper analyzes the shear lag effect during the construction phase and after completion of the Bo Zhou Bridge.After the numerical simulation and on-site construction monitoring,it shows that the proposed method has high accuracy and provides a certain basis for the future research and calculation of shear lag effect in practical projects.