Simplified design formula of slender concrete filled steel tubular beam-columns

The objective of this paper is to develop a simplified method that could pr edict the strength of concrete filled steel tube (CFT) columns applicable t o high strength material under combined axial compression and flexure. The simplified method for determining the strength of CFT columns is based on t he interaction curve of the section approached by a polygonal connection of the points. These points are determined by using symmetrical properties of the CFT section. For each point, a simple equation is proposed to determin e the strength of the slender columns under compression and flexure. The si mple equation was adjusted with results of elasto-plastic analysis results. Validation of the simplified method is undertaken by comparison with data from the test conducted at Kyushu University. These results confirm the fac t that the simplified method could accurately and reliably predict the stre ngth of CFT columns under combined axial compression and flexure.