Theoretical Analysis And Experimental Study On Special-shaped Column Composed Of Concrete-filled Square Steel Tubes

Special-shaped column composed of concrete-filled square steel tubes is a kind of composite structural member which is formed by connecting concrete-filled square steel tubular columns with bracings. The composite column has advantages of both concrete-filled steel tubular column and special-shaped column, such as better bearing capacity, earthquake resistance and fire resistance. Indoor area and space can be enlarged, and decoration can be convenient, while this special-shaped columns are used in buildings.For special-shaped column composed of concrete-filled square steel tubes, research is done by three methods: superposition theory, finite element analysis and axial compression experiment. In addition, the discussion of beam-column joints and filling walls are carried out for popularization and application of the composite column.For calculation method of special-shaped column composed of concrete-filled square steel tubes, the superposition theory is introduced and adopt to the calculation of the composite column with distributing coefficients of axial pressure deduced in this paper. For L-shaped composite column(LCFT), T-shaped composite column(TCFT) and Crisscross section composite column(XCFT), the equivalent slenderness ratios are deduced and coefficients of bearing capacity increase of steel tube is determined by existed axially compressed experiment data of concrete-filled square steel tubes.For each of LCFT, TCFT and XCFT, both a short column specimen and a slender column specimen are designed for axially compressed experiment by superposition theory in order to analysis load bearing capacity of both strength failure and buckling failure. Before axially compressed experiments are carried out, short specimens and slender specimens are simulated by general finite element programming ANSYS.When axially compressed experiments are carried out, it is prove that, results of finite element simulation, superposition theory, and axially compressed experiments are concordant so that the feasibility of superposition theory for calculating special-shaped columns composed of concrete-filled square steel tubes is verified.Supersonic flaw detecting test and incision test are carried out for each axially compressed experiment sepcimens in addition to the axially compressed experiment. Collaborative work status between square steel tube and filled concrete are learned according to the result of supersonic flaw detecting test and incision test.Based on the introduction of beam-column joints and new materials of filling wall, the discussion of beam-column joints and filling walls are also carried out for application of the special-shaped columns.Finally, this paper puts forward several problems for special-shaped columns composed of concrete-filled square steel tubes to be researched more deeply and makes an expectation of application for this composite columns.