Investigation of eccentrically loaded circular concrete-filled tubular (CFT) steel columns by fiber stress analysis (FSA) method

Abstract

The composite columns also known by the name “Concrete Filled Tubular (CFT) Steel Columns” have been preferred increasingly in the construction of high-rise buildings, bridges, towers etc. in many countries in the world. Recently, a number of research papers have been published to investigate the behavior of these structural elements in literature. In this study, a computer program, which is based on an analysis method called as “Fiber Stress Analysis (FSA)”, was developed to understand the behavior of CFT steel columns. In this computer program, the entanglement of the FSA due to the discretization of the circular composite cross section was surpassed by introducing some geometric expressions. The required concrete and steel material models were adopted from Sakino [16] in order to calculate fiber stresses. In the FSA software, a number of iterative calculations are done by computer to satisfy equilibrium equations and get a series of moment vs. curvature points of any composite column. The verification of the FSA program is executed by comparing the test results of eccentrically loaded 18 circular CFT columns performed by Fujimoto [1]. At the end of this study, it is observed that the FSA method gives accurate results and it is a rapid solution technique in the analysis of circular CFT columns. It is also seen that the steel tube strength has a positive effect on the ductility of CFT column. On the contrary, the increase of concrete strength, axial load and diameter to thickness ratio reduces the ductility of composite column.