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 strength<br />of concrete filled steel tube (CFT) columns applicable to high strength material under combined axial<br />compression and flexure. The simplified method for determining the strength of CFT columns is based on<br />the interaction curve of the section approached by a polygonal connection of the points. These points are<br />determined by using symmetrical properties of the CFT section. For each point, a simple equation is<br />proposed to determine the strength of the slender columns under compression and flexure. The simple<br />equation was adjusted with results of elasto-plastic analysis results. Validation of the simplified method is<br />undertaken by comparison with data from the test conducted at Kyushu University. These results confirm<br />the fact that the simplified method could accurately and reliably predict the strength of CFT columns<br />under combined axial compression and flexure.