The Static Behavior Analysis And Stability Research On Long-span Combination Box Arch Bridge

ABSTRACT:As a prime style of bridge, the arch bridge has been used for over three thousand years. However, the steel-box composite arch bridge is a kind of new structure form, it is not used in practice extensively. In addition, spatial characteristics and the stability of the bridge are discussed in this paper, which are the important reference for the design of the same type bridge in the future.The research in this paper is based on the Xinkai River composite steel-box arch bridge in Harbin-Dalian Passenger Special Line. By analyzing spatial mechanical characteristics and the stability of the bridge, all kinds of factors affecting the stability of long-span steel-box composite arch bridges in order to improve the stability of steel-box composite arch bridges are discussed.Generally, the problem of stability includes two sorts. The first one can be concluded as calculation of Eigen value, and it is not difficult. Due to the effect of the material nonlinearity, geometry nonlinearity and original bug, the second one is the problem about ultimate bearing capacity which is more reasonable comparing with the true result. But the structure stability is solved by useing the Eigen value for convenience in the design. According to the existed theory at present, on the basis of the Eigen value stability, and the factors influencing the stability of steel-box composite arch bridges such as various loads, loading form, arch type, arch rib introversion, bracing style, layout and number of bracings, and position and number of booms are analyzed by the finite element program.From the calculation results, it can be found that:to steel-box composite arch bridge, out-of-plane instability occurs mostly, and the influence of dead load to the structural stability is the biggest, the second one is live load, and lateral wind load is the smallest. The linear stability coefficient of arch bridges can be increased by using composite arch style and arch rib introversion. There is no significant effect on the stability by the number of the boom, which mainly depends on the load conditions; the "X" or "K" style bracing is adopted to connect the upper and lower arch rib of steel-box composite arch bridge which could increase the structural stability significantly, and the stability coefficient will also be increased with the incresement of number of bracing. In addition, due to material nonlinearity, the stability coefficient obtained by the nonlinear stability analysis is much lower than the one calculated by Eigen value buckling analysis, so nonconservative results may be produced by linear Eigen value buckling analysis.