Experiment Of Gap Between Square Steel Tube And Conerete And Study On Special-shaped Column Composed Of Concrete-filled Square Steel Tubes

In this paper, the result of research on concrete-filled square tubular structure was analyzed, and the calculation theories of three kind of concrete-filled square tubular column, which are unity calculation, similar steel calculation, and superposition calculation, were analyzed. This paper pays more attention on notions and theoretical foundation of simple superposition calculation.Special-shaped column composed of concrete-filled square steel tubes is a new type of structural member. Flexible section is its distinct characteristic. Indoor area and space can be enlarged, and decoration can be convenient, while special-shaped columns were designed in buildings. So, special-shaped column composed of concrete-filled square steel tubes will be used widely, with country-wide popularization of the steel structural buildings.Supersonic flaw detecting tests were carried on for the special-shaped column composed of concrete-filled square steel tubes specimen, including L-shaped section, T-shaped section and X-shaped section. According to the parameter such as velocity, frequency and the style of wave, Incision test was carried on for some specimen so as to observe and to measure the gap in section cut apart. So the conclusion is drew that there exist the gap under the exterior forces between steel and concrete and even cause totally apart; the gap and the scope of apart depend on the force. Then accuracy of Supersonic flaw detecting was tested.For calculation method, the superposition theory, which is of simple calculation, of clear conception, of reliable safe, is verified to be suitable for the calculation of concrete-filled square steel tubular column, because of the supersonic flaw detecting and the theoretical analysis. Three problems, which are distributing coefficients of axial pressure, section turning radius, increase of bearing capacity, are point out, according to analysis for existing formula of superposition theory. Then, this paper introduces a new calculation method of superposition theory.