Stability Behavior Of An Arch Bridge With Two Independent Inclined Steel Box Ribs

Steel structure has been widely used in civil engineering. And many arch bridges with steel box ribs have been constructed. With the background of Nanning bridge, the stability behavior of the arch bridge with two independent inclined steel box ribs is studied in this paper. The Nanning bridge consists of a horizontally curved steel box girder with a 300m span, supported by two independent inclined steel arch ribs, with no lateral bracing between the arch ribs. The arch ribs are single-closed-cell steel box girders, stiffened with transverse diaphragm, longitudinal stiffener and transverse stiffener. The statical behavior and the structure of the bridge are complicated according to the design. It's important to study the stability behavior of the ribs, which subject to coexistent compression, shear, bending and torsion. The major concerns in this dissertation are described as follows:The whole bridge was modeled by using 3-dimension beam element and the overall buckling coefficient and ultimate load coefficient under different load cases were computed under the assumption of ignoring the local instability. The influence of geometric and material nonlinear as well as the influence of different initial deflections was considered. This part of study also examined the effect of some design parameters on the buckling stability. These parameters include the stiffness of the bridge deck main girders and the stiffness of the arch ribs.The bridge was modeled with beam element and shell element to calculate the interaction between local stability and overall stability, also including the buckling coefficient and ultimate load coefficient, with considering initial local deformation. As a comparison, the local buckling coefficient was also calculated with the stability theory of the stiffened plate. The effect of some design parameters of the stiffened plate on the buckling stability, including the thickness of the skin plate and the stiffeners and the distance between stiffeners, was examined by this part of study.By the results, the local buckling stability and the overall ultimate strength determine the stability behavior of the bridge. The effect of the local buckling stability should not be ignored in the analysis.