Research On The Nonlinear Stability Of Curved Beam

In recent years, with its streamline model and rational working capcity, the thin-walled-curved beam is widely used in bridge buildings and constructions day by day. However, because of the existence of curve degree causing the complexity of its mechanics characteristic and deficiency on overall and accurate analysis to its complicated structure characteristic at present, it is restricted in application. To the thin-walled-straight beam, its broad stress-strain relational expressions of compressing, bending and warping are separate and its deformations are only limited to bending, twisting or bending-twisting .But to curved beam, its geometry equations of bending ..turning and warping are mutual coupling, its deformations are mostly crumple.The instability mode and bucking limited bearing capacity have always been big issues in curved beam application. Regarding I-shaped and box shape, two kinds of sectional circular horizontal steel curved beams, as the targets, this paper has carried on research to its instability mode and its bucking limited bearing capacity under various kinds of situations.According to the non-linear theory, this paper sets up the finite elements of I-shaped and box shape with biaxial symmetry considering both the geometic and the material non-linearity. (the paper adopts the individual unit of SOLID45). Finite element analysis adopts increment-iteration, which utilizes the Arc-Length Method to control the process of increment and iteration so as to make stable analysis and calculation of the curved beam.By making the ANSYS finite element analysis, the author draws several conclusions as follows: 1. To the horizontal I-shaped steel curved beam, under the acting of vertical uniform load, its deformation is both bending and twisting; at the limited load, its destroy form is mostly the elastic-plastic side sprain.2. To the horizontal box shape steel curved beam, the big development of the plasticity area of end beam reduces the stiffness in torsion, which lead to the instability.