Nonlinear Analysis For Ultimate Load-Capacities Of Concrete-Filled Steel Tubular Arches

Owing to many advantages such as high load capacities, good fire and earthquake resisting behavior and convenience for construction. Concrete-Filled Steel Tubular (CFST) arches have been more and more widely used in practical constructions especially in highway and city arch bridges. The fundamental failure modes of CFST arches are loss of stability and loss of material strength. The process of a CFST arch from initial loading to the arrival of ultimate load-capacity before failure is a process of complicated nonlinearity. The main objective of this paper is to predict this complete load-deformation process for none-hinge CFST arches using numerical techniques.In this paper, the double nonlinear finite element analysis with considering the material and geometric nonlinear properties is presented. In the analysis, a CFST arch (single tube) is first divided into a finite number of straight beam elements. According to the virtual work principle and the modified Newton-Raphson iteration method the tangent stiffness matrix considering double nonlinear properties is established. With regard to the non-equilibrium forces, the material nonlinear property along the height of the section and the length of the element is considered and the computation accuracy is improved as a result. The final nonlinear algebraic equation set is solved using the step-by-step Newton-Raphson iteration and the deformed curves for the corresponding state of each load increment can be determined. Through iteration for all incremental steps the ultimate load can finally be found. Using the present method the ascending segment of the load-deformation curve can be obtained.considering of the effect of stability and material strength.A computer program based on the above theoretical formulation is developed by means of the Visual Fortran code. Numerical examples of a single circular CFST arch in two loading cases are presented. The complete load-deflection and load-strain relation curves in the two loading cases are numerically obtained and the numerical results are compared with test results. This demonstrates the validity and accuracy of the proposed method. Meanwhile the effects of loading modes and steel ratio on the behavior of the CFST arches are numerically analyzed and discussed...