Bending-Twisting Coupled Effect Study Based On Grillage Method For Curved Box Girder Bridge

Curved box girders have been used widely with the quick development of transportation. Based on the existed analyzed method and beam-gird method, this paper analyzes the coupling effect of bend-twist in curved box girder and does the following work:After reviewing the development of curved girder, this paper discuses various calculation theory of curved girder and further analyze the application scope and minuses of each theory.This paper analyses mathematical principle and analytical method of the coupling effect of bend-twist in curved box girder, describes and deduces the in-plane bending equation in curved girder. After that, the internal force calculation method is summarized when pure torsion is applied on the simple curved girder.This paper analyses and discusses the basic principle of beam grillage division and the value-taking method of rigidity in curved box girder. The division and calculation method is summarized to calculate the longitudinal and transversal section properties in beam grillage members. All of these can provide reference for engineers.The finite element software MIDAS-CIVIL is used to build curved prestressed box girder, which has a span of 50m and 50m. Based on the theory of beam grillage, the internal force and deformation of model is analyzed under different girder height, curvature radius, diaphragm distance and support distance. The affection of these factors in the coupling effect of bend-twist in curved box girder is analyzed. The results are listed as follows: Firstly, curvature radius has obvious affection in the deformation of curved box girder. The distance between the inner and outer deformation in middle span is greater as the curvature radius increased. This means the coupling effect of bend-twist is more obvious when the curvature radius is greater. Secondly, with the increase of girder height, the distance between the inner and outer deformation in middle span is smaller under dead load. This means, with higher girder height, the warping effect is less evident under the same load. As the beam depth is increased, the bending resistance and torsion resistance is increased. Obviously, the coupling effect of bend-twist can be ameliorated by increasing depth of girder. Thirdly, when the diaphragm distance is reduced, the stress in the same section is more uniform for curved box girder. Also, the deformation distance between inner and outer section is reduced. So, for curved box girder, the mechanics status can be improved by reduce the diaphragm spaces.