Study On Bearing Capacity Of Axial Loaded T-Shapped Columns Composed Of Concrete Filled Square Steel Tubes

Special-shaped column, which is composed of concrete-filled square steel tubular columns, is a new type of structural system. It is formed by connecting concrete filled square steel tubular columns with lacing bars. It combines the advantages of both concrete filled steel tubular column and special-shaped column, namely, high strength and light weight, high stiffness and ductility, large energy absorption capacity and easy of construction. From architectural view, it avoids quoin at the corner and can be placed flexibly. With the efficiency, buildings can have more space and the space can be used more efficiently. There are three types of cross section for special-shaped composite concrete filled square steel tubular columns, which are L shaped, T shaped and X shaped. The T shaped one (TCFT) is investigated analytically and experimentally.The popular theories of CFST column which are the superposition method, the steel analogue method, the concrete analogue method and the uniform method are commented and compared. The experimental results show that the axial load and moment capacity of CFT columns can be predicted with reasonable accuracy using the superposition method. This method involves the calculations of concrete and steel forces separately and then combining these to determine the ultimate strength of CFST column. Referencing to the AIJ code which is also based on the superposition method, calculation formulas are presented and calibrated successfully with the test. The calculation method of T shaped composite concrete filed square steel tubular column (TCFT) is presented. The calculation of slenderness ratio of T shaped hollow steel tubular column is investigated based on the elastic stability theory. Then with reference to the superposition theory, the formulas to predict the axial load of the TCFT are presented.Analysis on buckling characteristic of the slender TCFT column under axial load with the finite element analysis software ANSYS is performed. A model of it is established and then the nonlinear bucking analysis is performed. The ultimate axial load and buckling model are obtained. The results are analysed and compared with those of the theory developed before, which verify the accuracy of the superposition method.The experimental studies on short and slender TCFT columns under axial load are...