Axial load behavior of rectangular CFT stub columns with binding bars

This paper presents an experimental study on the axial load behaviour of rectangular concrete-filled steel tubular (R-CFT) stub columns with binding bars. Eight specimens were concentrically loaded in compression to failure in order to investigate the effects of the binding bars, depth-to-wall thickness ratio and cross-sectional aspect ratio on the ultimate strength and ductility of the composite columns. Experimental results indicate that the binding bars increase the confinement of the concrete core and delay local buckling of the tube. The results also show that R-CFT columns with binding bars have better ductility than those without binding bars. A model is proposed to predict the ultimate strength of the specimens. A comparison of the ultimate strengths between tests and design codes shows that the proposed model gives reasonable predictions of the ultimate strength of rectangular CFT stub columns with binding bars while the codes EC4 (1996), AU (1997) and GJB (2001) conservatively estimate the ultimate strength by 17.6%, 22.9% and 9.7% respectively.