Nonlinear Finite Element Analysis On Mechanical Properties Of The Joints Of Steel-encased Concrete Composite Beam To Concrete-filled Steel Tube Column

Based on the analysis of some defects about the common steel-concrete composite beam, this article puts forward a new type of steel-encased concrete composite beam. Compared with traditional composite beams, the new type of steel-encased concrete composite beam has the advantages of high bearing capacity, high stiffness, good economics, and the convenience of construction process, some improvements in mechanical behavior and fireproof performance. The research of steel-encased concrete composite beam to column joints is few, which restricts the popularization and application of the new type composite beam. Considering the characteristics of steel-encased concrete composite beam structure and the reference of joints of concrete-filled steel tube column to steel beam or reinforced concrete beam, this article designs two new type joints of steel-encased concrete composite beam to concrete-filled steel tube column. And on the basis of experimental research, this paper mainly studies force mechanism and seismic behavior of the new joints by using finite element method and also compared with the test results. The details are as followings:(1) Consider the bond-slip between steel tube and concrete, steel-encased and concrete. Choose reasonable constitutive relation and failure criterion for material. The material properties of the finite element model (FEM) are depending on the test results of material. In order to ensure the correctness of finite element analysis, simplify the test specimens and establish the FEM according to the size of specimens.(2) By using finite element analysis software ANSYS, the nonlinear finite element analysis of two joints has been conducted under the axial load and monotonic load, which mainly studies and compares the axial bearing capacity, yield load and yield displacement of joints. According to FEM results, the difference of the axial bearing capacity, yield load and yield displacement of two joints is relatively small, which shows that opening on steel tube has little influence on bearing capacity and ductility of joints.(3) On the basis of the experimental research, the nonlinear finite element analysis of two joints has been conducted under low cyclic loading. It is demonstrated that the bearing capacity, ductility and energy dissipation capacity from FEM agree well with those of the low cyclic loading tests, which verifies the feasibility of the new joints.(4) By establishing different finite element models, analyze the influence of axial compression ratio, steel ratio, steel yield strength and concrete compressive strength to hysteretic behavior of joints. Calculation models of P-â–³curves and simplified calculation method of displacement ductility factor of bending members, construction design suggestions and study expectations of concrete-filled steel tube joints are advanced according to the results of test research and computer simulation.