Research On Stability Of Concrete Filled Steel Tubulur Arch And Girder Combination Bridges

Arch and girder combination bridges, which combined by girder and arch, is a development to the traditional arch and integrate their merits. With the development of CFST (concrete filled steel tube) in arch bridge,bridge has being widely applied in China. As a new structral system, compared with the engineering practice, the design theories are relatively backward and the increase of the span of the brige, the stability problem becomes more and more evidence, In this thesis, the stability analysis of the structral system was carried on.Based on the engineering of Guangyuan Jialing River Bridge in the LanYu railway line, this thesis developed an integrated finite element model using the commercial software MIDAS.The linear elastic stability of the bridge during the construction phase, completed bridge phase and operation phase are analysed. Parameters influencing buckling eigenvalues of the bridge, such as the rise-span ratio, the angle of toe-in of the arch rib, the arrangement form and stiffness of the lateral brace, the stiffness of arch ribs and the stiffness of the beam are analysed, and the influencing trend on buckling eigenvalues of the bridge is achieved in aim of instructing the design of the same bridge types.The stability of the bridge is analysed by nonlinear stability buckling analysis method with the large commercial software ANSYS. The result of the calculation indicates that the safe stability coefficient draws from the eigenvalue buckling analysis is far higher and may induce non-conservative result. The safe stability coefficient only decreased a little when taking into account geometrical nonlinearity. Due to the material nonlinear influence, the result is more lower than that of eigenvalue buckling analysis method. But when the geometrical nonlinearity and material nonlinearity are all considered, the ultimate load is far lower than the former. So a conclution is made that both the geometrical nonlinearity and material nonlinearity must be considered when study the stability of the arch and girder combination structure.