SPATIAL EFFICIENT BI-NONLINEAR FINITE ELEMENT ANALYSIS FOR CONCRETE FILLED STEEL TUBULAR ARCH

The structural system of long-span concrete-filled steel tube space truss arch bridge is mostly sophisticated, which challenges the implementation of finite element analysis and raises more rigorous requirements for the calculation accuracy and efficiency of nonlinear analysis method. In this paper, firstly, based on the linear relationship between strain and the deformation with rigid body displacement excluded in co-rotational coordinate system, a tangent stiffness matrix for material nonlinearity of perfectly-bonded concrete-filled steel tube beam element is derived without iterations in co-rotational coordinate system by means of virtual work. Then, according to field consistency, a tangent stiffness matrix in global coordinate system for concrete filled steel tube beam element is developed considering geometric and material nonlinearity. An effective algorithm for spatial nonlinear analysis of concrete-filled steel tube arch considering both material and geometry nonlinearity is also obtained. A corresponding computer program is developed. The analysis of in-plane and out-of-plane loading conditions for concrete-filled steel tube arch model is performed. The results demonstrate that the calculation accuracy and efficiency can satisfy the requirement.