Analysis Of Square Concrete Filled Steel Tube's Mechanical Behavior In Finite Element Method

This paper presents a finite element method (FEM) model for the analysis of concrete filled steel tubes (CFT) based on ABAQUS. The damage plasticity model is used to describe core concrete and elastic-plasticity model to describe the steel tube. The jointed material model is used to model interface between the concrete and the steel tube. Under the condition of axial compression, simple bending and compression-bending, the effects of parameters to CFT's mechanical performance are studied. The parameters taken in account are concrete compression strength, steel ratio, steel strength.Details are listed below:1. Model verificationThe representative experiment (Kupfer, concrete biaxial material experiment) is selected for verification of the concrete damage plasticity model. Results have shown that the model is appropriate.Representative structural experiments of CFT subjected to axial compression and compression-bending are selected to verify the FEA model presented in this paper. The results of the FEM analysis agree well with the experiments. This shows that the FEA model does well with the simulation of CFT's ultimate bearing resistance and full failure process.2. Mechanical performance analysisUnder the condition of axial compression, simple bending and compression- bending, the effect of main parameters to CFT and failure mechanism are studied. The parameters taken in account are concrete compression strength, steel ratio, steel strength. With the same steel ratio, square CFT is compared with circle CFT in bearing resistence and load-deformation curves.Under axial compression, influence of interface is considered using jointed material model, and gap of interface is considered by removal of some elements. Moreover, the influence of different parameters, such as eccentricity, axial load ratio and slenderness ratio are studied under compression-bending. Also, analysis of the mechanism that ductility reduces and structure becomes brittle with increasing axial load ratio is performed.3. Method for enhancement of bearing resistenceOn the basis of the above analysis, a method is developed to improve the ultimate bearing resistance and ductility of CFT. That is to add transverse reinforcement steel bar to CFT. Computational results show that the method is efficient.