Study On The Mechanical Properties Of Separation Concrete Filled Steel Tubular Members

Concrete-Filled Steel Tube (CFST) Structure has been widely applied in engineering structures for its advantages of high compressive strength, prominent seismic behavior and convenient construction. However, for various reasons, concrete in part of the CFST arch rib become separation for it can't bond well with steel wall in engineering practices. Understand and grasp the mechanical behavior of separation concrete filled steel tubes become the problems which are urgent to be solved in structure development. In this paper, the following work will be completed exploratory by using of research method which including theoretical analysis, model test and finite element analysis, in order to study the separation effects on mechanical behavior of core concrete filled steel tubular members, and to provide basic research data for further CFST study and design, construction and safety detection method in the future.(1) Based on the limit equilibrium theory, the formulas of axial ultimate capacity of separation CFST are derived, and the scope of application of the formula is proposed.(2)37 eccentric compression separation CFST's whole process compression model test is completed in this paper. According to the test results, the study is carry on the effect of Parameters on the mechanical behaviors which including the relationship of load-strain, the relationship of load-deformation, the distribution range of confinement effect, section strain ect.; on the macroscopic law of ultimate bearing capacity of eccentric compression separation CFST, Those parameters contain separation ratio, eccentricity ratio, loading mode, the length of Members ect.. And comparing the results with the calculated value of code, established a relational expression of capacity reduction factor and separation ratio,and a formulas of eccentric compression ultimate capacity of separation CFST(3)According to available research data, a stress-strain relation of core concrete is presented,in which the confinement effect of steel tube to core concrete is modified by separation ratio. A three-dimensional finite element model(FEM) of separation CFST is built up which has considered the material nonlinearity and geometric nonlinearity. Using ANSYS to calculate and analyze the finite element model, and compared result with test. The contrast analysis result show that the calculated value of FEM are near the test values, note that the way of using FEM simulate separation CFST is right, and provide an effective method and tools for study of separation CFST.