Axial load behavior of L-shaped CFT stub columns with binding bars

This paper is concerned with the axial load behavior of L-shaped concrete-filled steel tubular (CFT) stub columns with binding bars provided to improve the mechanical behavior of these elements. Six specimens with binding bars and one specimen without binding bars were tested to examine the effects of horizontal spacings and diameters of binding bars, and width-to-thickness ratios of steel plates on the failure modes, maximum strength, and ductility of L-shaped CFT stub columns. Experimental results demonstrate that the local buckling of the steel tube can be delayed by setting binding bars, the confinement effects on the core concrete can be improved significantly, and the bearing capacity and ductility of the L-shaped CFT stub columns are enhanced by 7% and 26%, respectively. Based on a constitutive model of confined concrete, a method for calculating the maximum strength of L-shaped CFT columns with and without binding bars is proposed. The method is verified with experimental results from this test program and data from other experiments. The results predicted by the proposed method show better agreement with the experimental values than the values predicted by AISC (2005), BS5400 (2005), EC4 (2004) and GJB (2001).

► 7 Axially loaded L-shaped CFT stub columns with and without binding bars are tested.
► Setting binding bars changes the failure modes and postpones the local buckling.
► Setting bars and decreasing the horizontal spacing of bars increase ductility.
► The strength is enhanced when the horizontal spacing of bars is small enough.
► The proposed model for calculating the strength is of higher accuracy than the codes.