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

The objective of this paper is to develop a simplified method that could predict the strengthof concrete filled steel tube (CFT) columns applicable to high strength material under combined axialcompression and flexure. The simplified method for determining the strength of CFT columns is based onthe interaction curve of the section approached by a polygonal connection of the points. These points aredetermined by using symmetrical properties of the CFT section. For each point, a simple equation isproposed to determine the strength of the slender columns under compression and flexure. The simpleequation was adjusted with results of elasto-plastic analysis results. Validation of the simplified method isundertaken by comparison with data from the test conducted at Kyushu University. These results confirmthe fact that the simplified method could accurately and reliably predict the strength of CFT columnsunder combined axial compression and flexure.