ANALYSIS OF ULTIMATE AXIAL LOADS OF CONCRETE-FILLED STEEL COLUMNS WITH RECTANGULAR SECTION

A method to predict the ultimate loads for short concrete-filled steel columns with rectangular section is proposed. The behavior of steel tubes is assumed as plane stress states and the filled concrete is divided into biaxial and triaxial compression regions based on stress analysis by using finite element method. Therefore,the axial load of the column can be represented as a function of hoop tensile streess in the steel tube.The stresses of the steel tube are evaluated by Mises's yield condition and the strength of filled concrete are estimated by Kupfer's envelope for biaxial regions and Richart's criterion for triaxial regions. Based on the lower bound formula in the theory of limit analysis, the maximum value of axial loads,which is regarded as the ultimate load,can be determined by using stationary conditions. Inaddition,twelve specimens were studied by this model and very good results have been gaven.