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

This paper is concerned with the eccentric load behavior of L-shaped concrete-filled steel tubular (CFT) stub columns with binding bars. Eight specimens with binding bars and one without binding bars were tested to examine the effects of horizontal spacing and diameter of binding bars, load eccentricity ratio, and load angle on the failure modes, bearing capacity and ductility of L-shaped CFT stub columns. Experimental results demonstrate that the local buckling of the steel tube can be postponed by setting binding bars, and the bearing capacity and curvature ductility of the L-shaped CFT stub columns are at most 1.04 and 3.31 times those without binding bars, respectively, and the plane section assumption can also be satisfied. Based on a modified stress–strain relationship of confined concrete, the fiber element analysis is applied to predict the bearing capacity of the specimens, and the predicted results agree well with the experimental ones. Then the parametric studies using the proposed theoretical model are carried out to further study the fundamental behavior of eccentrically loaded L-shaped CFT stub columns with various steel yield strengths, sectional steel ratios, cube strengths of concrete, confinement coefficients of binding bars, sectional aspect ratios and load angles. Finally, simplified interaction formulas are put forward to predict the Mx/Mx′–My/My′ curves for the L-shaped CFT stub columns with or without binding bars subjected to biaxial eccentric load, and the theoretical results predicted by the simplified formulas agree well with those predicted by the fiber element analysis program.

► 9 eccentrically loaded L-shaped CFT 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 spacing of bars increase ductility remarkably.
► The constitutive relation of concrete is modified to conduct the numerical analysis.
► A theoretical model is proposed to predict the Mx/Mx′–My/My′curves for the columns.