Shear performance of steel fibers reinforced self-confinement and self-compacting concrete-filled steel tube stub columns

This paper described an experimental work for thirty-eight steel fibers reinforced self-confinement and self-compacting concrete-filled steel tube (FSSCFST) stub columns under shear load. The variables considered in the test were self-stress, thickness of steel tube, concrete strength, axial compression ratio, shear span-to-depth ratio and steel fibers volume percentage. Failure mode, shear capacity, load-deflection curve and load-strain respond were investigated. Experimental results showed that the failure mode of FSSCFST stub columns depended on the shear span-to-depth ratio (m). When m < 0.5, the specimens failed in shear; when m ≥ 0.5, the specimens failed in flexure. Self-stress improved the rigidity and shear capacity, but decreased the deformability of FSSCFST stub columns. Steel fiber improved the shear resistance and ductility of concrete through bridging the plastic cracks near the shear failure plane. This beneficial effect from steel fibers lengthened the stage of elasticity and improved the shear strength of CFST specimens. Finally, formulas were proposed to predict the shear capacity of FSSCFST, and the predictions agreed well with the test results from this study and the literatures.