ANALYSIS AND DESIGN OF AX3ALLY LOADED SHORT CONCRETE FILLED STEEL TUBES

Axial compressive strength of short concrete filled steel tubes, CFT, is at least equal to the sum of the strengths of its components. Recent experimental and analytical research work revealed that the compressive strength of CFT could exceed the sum of its components strengths due to confinement effect of the steel tube surrounding the concrete core. In this work, the finite element analysis of short CFT subjected to axial loading was conducted using the general-purpose finite element program, ANSYS. The analysis was verified by comparison to test results published in the literature. An extensive parametric analysis was conducted to investigate the effect of steel tube slenderness ratio, concrete compressive strength, and steel tube yield strength on compressive strength of CFT. The analysis revealed that the compressive strength of concrete core might increase by 68% whereas the overall compressive strength of CFT might exceed the sum of its components strength by 14% due to confinement effect of steel tube. Numerical results indicated that current code design rules underestimated the compressive strength of CFT. A new design formula was proposed for axially loaded short CFT.