Research On Hysteretic Behavior Of Concrete Filled Double-skin Steel Tubular Beam-Columns

Concrete filled double-skin steel tubular (CFDST) is a new type of composite structure filled with concrete between two concentric steel tubes. It can offer many advantages, such as high bearing capacity, good plasticity and malleability, convenient construction, high fire resistance, high bending rigidity, light deadweight. The cross-section of the outer and inner steel tube are various, such as circle, square, rectangle and some others. Two kinds of CFDST section tubes were studied in this paper, that is, the outer steel tubes are circular hollow sections (CHS) or square hollow sections (SHS), while all the inner steel tubes are CHS.The hysteretic behavior of concrete filled double-skin steel tubular beam-columns is the basis of elastic-plastic dynamic response analysis for the structure, which is investigated in this paper. Based on systematic parameter analysis, simplified lateral load-lateral deflection hysteretic models were suggested.The main achievements were summarized in detail as follows:(1) The relevant researches were reviewed firstly. In this paper, lateral load-lateral deflection relationship curves of concrete filled double-skin steel tubular beam-columns subjected to cyclic loading were calculated by finite element software─ABAQUS.(2) The hysteretic curves were calculated by finite element software─ABAQUS. The carrying capacity decline and stiffness degenerate of concrete, the Bauschinger effect and strengthening effect of steel under cyclic loading are considered accurately in this analytic model. The predicted load versus deformation relationship curves are in good agreement with those of tests. The reliability of finite element model was verified.(3) Lateral load-lateral deflection relationship curves and work mechanism on concrete filled double-skin steel tubular beam-columns subjected to cyclic loading were obtained and analysed by finite element method. Failure modes of steel tube were discussed, stress distributions of steel and concrete and interactions between steel and concrete were investigated.(4) Based on the finite element method, parametric analysis was performed on the behaviors of lateral load-lateral displacement relationships for the composite beam-columns. The selected parameters were the nominal steel ratio, axial compression ratio, slenderness ratio, hollow section ratio, etc. Finally, a kind of simplified load-displacement hysteretic model of concrete filled double-skin steel tubular beam-columns are put forward, which can serve the engineering design.