Non-linear Analysis For Curved Box Girders In Considering Shear-lag Effect

Compared with conventional section structures, curved box girder bridges are widely used because of theirs advantages ,such as light weight,large flexural and torsional rigidity ,beautiful profile, terrain adjustability. Firstly, the loaded characteristic of thin-walled curved girder is explained, The closed-form solutions of the governing differential equations are derived from differential equation operation principle. Then, combining the boundary condition, the calculation formulations of the shear lag are obtained. Moreover, an analytical theory for shear lag effect upon the curved box girders are established.According to thin-walled curved box theories and potential various principles, the three different shear lag functions to cantilever, top and bottom plate are assumed, the nonlinear governing equation of thin-walled curved box girders in considering moment, torsion, shear lag coupling is deduced. The residual equation group is obtained by spline allotting point method, which is solved with homotopy algorithms. By means of the half analytic solution of structure in the action of loads, the influence on the force properties of structure by different parameters of section and the differences in calculation between setting a unitive shear lag function and setting three shear lag functions are analyzed.Based on potential variational principles, the stiffness matrix of thin-walled curved box girders in considering the shear lag effect of flange's stress and material nonlinearity is obtained. The elastic and plastic problem of thin-walled curved box girders is solved with the spline finite point method and the section force plastics coefficient method. The research shows that the nonlinear property of the moment shear lag coefficient is more obvious than that of the displacement and torsion.Lastly, basic principle of finite element method ANSYS and modeling are briefly introduced. The results are goodly anastomosed when presenting two examples, verifying the accuracy of the present method. The conclusion of this paper is the development of the theory of curved box girder, would provide reference for engineering designing in the thin-walled curved box girder.