Analysis Of Axial Bearing Capacity Of Steel Tube Confined High Strength Concrete Short Columns

As a new type of composite structure, steel tube confined high strength concrete(STCHSC) can make full use of the advantages of high strength concrete (HSC) under theprerequisite condition of guaranteed its ductility. So the STCHSC columns can be widelyused in high-rise and long-span buildings for their good performance in bearing capacity andseismic behavior. However, there is little theoretical study on the mechanical behavior of theSTCHSC columns at present. It is of great importance to investigate the mechanicalperformance of the STCHSC columns under axial pressure.In this paper, the bearing capacity of the STCHSC short columns is analyzed based onthe unified strength theory and the ANSYS finite element analysis program. The maincontents and conclusions are as follows:1. According to the load carrying mechanism of the STCHSC short columns, the lateralconfinement stress on the core concrete caused by steel tube is calculated based on the unifiedlimit solution of thick wall cylinder, and the axial bearing capacity of core concrete,longitudinal reinforcement and shaped steel is analyzed. Thus the calculation formulas ofultimate bearing capacity of the circular steel tube confined reinforced high strength concrete(STCRHSC) short columns and circular steel tube confined steel reinforced high strengthconcrete (STCSRHSC) short columns are deduced. Using the equal-area method, thecalculation formulas of ultimate bearing capacity of square STCRHSC short columns andsquare STCSRHSC short columns are established. A reasonable match is reached bycomparing the results calculated by the formulas with the test results by the references. Theresults show that the unified strength theory has a good applicability in the theoreticalcalculation of the STCHSC columns, which can offer theoretical reference to the practicalengineering design of the STCHSC columns. And parametric studies are carried out toevaluate the effects of the main factors on the bearing capacity.2. The bearing capacity, stress-strain curve and stress contour of the STCSRHSC shortcolumns and STCSRHSC short columns are analyzed by the ANSYS finite element analysisprogram. Compared the finite element analysis results with the test results by the references, agood agreement can be obtained. In addition, the influences of the concrete compressivestrength, the yield strength and diameter-thickness of steel tube on the peak stress andductility of the STCHSC short columns under axial pressure are discussed according to thefinite element analysis results.