Analysis On Structural Theory And Research On Supporting Forms Of Curved Girder Bridges

Due to the rapid development of highways and city roads of our country, more and more elevated roads and city overhead crossings are built, which lead to the wider application of curved girder bridges. Compared to the straight beam bridges, curved girder bridges have the particular mechanical characteristic of bending moment-torsion coupling. Different supporting forms will directly affect the whole internal force distribution in curved girder bridges. The variation of the supporting form will change the degree of bending moment-torsion coupling. In the design of curved girder bridges, the force state of the section can be adjusted by selecting suitable supporting forms. It is beneficial to the optimal design of curved girder bridges and can obtain significant economic benefit.This thesis summarized four kinds of calculation theories of curved girder bridges, in which the closed solution and finite difference method numerical solution of simple supported statically indeterminate curved girder bridges are given based on Vlasov Equation, and the basic theory of grillage analogy method to equivalently simulate box girder is studied in detail. The principles that how to divide the grillage, how to calculate the constants for longitudinal beams and transverse beams, and how to deal with the results gotten by grillage analogy in box girder bridges are analyzed systematically, and the reasonable principles are proposed.Based on the principle of grillage analogy method, the grillage finite models with different supporting forms are built to analyze their effects to curved girder bridges by MIDAS/Civil finite element software, which come to the conclusion that the change of supporting form has great impact on the torsion and has little influence on the longitudinal shear force and bending moment. This thesis puts forward three methods to reinforce the ability of anti-torsion of curved girder bridges, which are presetting support eccentricity, reducing torsional span length and increasing the distance of beam-end supportings. By the calculation of the curved girder bridges with different internal support eccentricities, this thesis also draws the conclusions that if the support eccentricity is suitable, the beam will not disengage from supportings, the inside supportings will not appear negative counterforce and the maximum and the minimum torsion can be approximately equale. At length, the thesis provides means of arranging the supportings to ensure that they can not only adapt to the force and deformation of curved girder bridges, but also guarantee for security and stability of the structures. The thesis also provides measures to adjust supportings under different construction temperatures in hope of giving some reference for the design of curved girder bridges as well as some similar practical projects.