Experimental study of T-shaped CFT stub columns with binding bars subjected to eccentric load

A total of 16 T-shaped concrete-filled steel tubular(T-CFT) stub columns with binding bars and 11 specimens without binding bars were tested under eccentric compression.The influences of the loading angle,load eccentricity ratio and spacing of binding bars on the eccentric load behavior of this kind of columns were investigated.Test results indicate that setting binding bars result in the decrease of the half buckling wave length of the steel tubes,the delay of local buckling of the steel tubes,the improvement of the confinement effects on the core concrete,and the increase of load carrying capacity and ductility of the specimens.Steel plates and binding bars near the maximum compressive side exhibit obvious confinement effects on the core concrete when approaching or reaching the maximum load.The confinement effects decrease from the maximum compressive side to the minimum compressive or the maximum tensile side.The strain distribution on the column section under eccentric compression conforms to the assumption that plane section remains plane.Based on the equivalent uniaxial stress-strain relationship for the encased concrete in the T-shaped stub steel tube with binding bars,the fiber element analysis result was verified by the experiments and adopted to carry out the parametric studies to further study the fundamental behavior of eccentrically loaded T-shaped CFT stub columns.The analysis results indicate that the N/Nu-M/Mu curves will shrink inward along with the increased steel yield strength or sectional steel ratio,while will expand outward along with the increased concrete compressive strength or confinement coefficient of binding bars.