Bending And Torsion Coupling Analysis Of Thin-walled Box Girder Considering The Shear Lag

The box section has characteristics such as high utilization efficiency and largebending torsion rigidity, so it is widely used in bridge structure. However, thelongitudinal bending shear lag phenomenon exists when the thin-walled box girderbridge under the loads. If ignore this phenomenon, the actual stress of box girderstructure will be underestimated, and the structure will not be safe. With the develop ofbox girder bridge to long cantilever plate and the big rib spacing of concise type singlebox single chamber section, the shear lag effect getting more and more attention. Inview of the actual project needs, the shear lag effect of thin-walled box girder shouldnot be ignored.This paper based on the thin-walled bar bending and torsion theory, put the boxsection girder bridge as the analysis object. The method abandons Vlasov’s assumptionthat the shear strains along the central line of the cross section are zero. Considering itsshear deformation to establish the bending and twisting Hamiltonian dual solutionsystem of box section girder bridge. This system abandons the elementary beam theoryand the assumption of umansky’s theory on longitudinal warping displacement, deducethe longitudinal warping displacement function expression based on the interpolationfunction, can show the shear lag effect well. This paper use the precise integrationmethod of boundary value problem to solve this system and compiles MATLABlanguage program to solve the generalized displacement and generalized force of thestructure. Choose different box cross section beams as examples and place differentloads on these structures. By solving specific examples and compared with othermethods from literature, show the rationality and feasibility of this method, providecertain reference for the designer of the box bridge.This paper introduces a new theory for the analysis of bridge box section,constructs a very flexible spline function interpolation system. The method usepiecewise cubic spline function to simulate warping displacement field of the crosssection, and considers the influence of shear deformation on the surface of the rods, caneffectively reflect the shear lag effect. Piecewise cubic spline function put the actualnode displacement for unknown quantity, so it is easy to coordinate the displacement ofthe cross section limbs joint. The number of nodes of each branche can be different, increases the flexibility of the method; the spline interpolation system especially for thethin-walled structure, which its cross section has some branches. The system opens up anew way for the application of spline function. The research results of this paper havecertain reference significance to the researchers and designers of bridge engineering.