Analysis of Ultimate Load-Carrying Capacity of Crescent-Shaped Concrete-Filled Steel Tube Arch Bridge

In order to investigate the influences of structure parameters on the ultimate load-carrying capacity of crescent-shaped concrete-filled steel tube arch bridge, based on the constitutive relation of core concrete under confinement, the extreme-point stability of the arch bridge was analyzed. First, the most unfavorable load combination for ultimate load-carrying capacity was obtained by eigenvalue analysis, and then by considering the effects of the geometry nonlinearity and material nonlinearity in this loading condition, the ultimate load-carrying capacity and safety factor of stability were solved by Riks iterative solution. At last, the Shimian Dadu River Bridge was used as an example to analyze the effects of structure parameters on ultimate load-carrying capacity such as the angle between main and side arch rib, the strengths of steel and core concrete, and steel ratio. The analysis shows that the buckling mode of the crescent-shaped arch bridge is transverse deformation of the whole rib, and the structure stability mainly depends on the sustained load. The bearing capacity decreased 3% when considering geometry nonlinearity, decreased 1% when the initial imperfection increased from 1% to 10%, and decreased 55% when considering both geometry and material nonlinearities. When the steel ratio is increased by 50%, the safety factor of stability increased 19.0%; with the concrete strength increasing from C50 to C60, it increased 12.0%; with the steel strength increasing from Q345 to Q420, it increased 9.6%; with the angle between ribs increasing from 10to 25, it decreased 5.9%.