Micro-Steel Fiber-Reinforced Self-compacting Concrete-Filled Steel-Tube Columns Subjected to Axial Compression

Experimental and analytical investigations of steel-tube specimens filled with micro-steel-fiber-reinforced self-compacting concrete are presented in this study. The purpose of this study was to investigate the influence of micro-steel fibers on the strength and behavior of concrete-filled steel-tube (CFST) specimens with different wall thicknesses, length/diameter (L/D) ratios, and micro-steel fibers. Because concrete has weak tensile properties, the use of steel fibers is essential for enhancing the strain-softening characteristics. Hence, crimped micro-steel fibers with an aspect ratio of twenty-five were blended with self-compacting concrete and used as the infill for the CFST specimens. Sixty-four CFST specimens with thicknesses of 2 and 3 mm and L/D ratios of 3, 4, 5, and 6, along with micro-steel fibers with volume percentages of 0%, 0.5%, 1.0%, and 1.5%, were subjected to axial compression. The failure report includes the following modes of failure: ultimate capacities, deformation curves accompanying the effect of parameters such as the strength index, percentage of contribution of steel and concrete, confinement effect, and ductility index on the axial capacity of the CFST columns. The results indicated that the use of micro-steel fibers enhanced the ultimate capacity and ductility as well as delayed the local buckling of the specimens. The ultimate capacities of the columns were compared using design codes, such as the Eurocode (EC4), Australian code (AS5100), American code (AISC 360-10), American Concrete Institute (ACI-318), and Chinese code (DBJ13-51). An equation was proposed to determine the axial capacity, and the predicted results were close to the experimental test results and experimental data collected from 93 CFSTs in previous studies. The failure mechanism, buckling patterns, and deformation curves of all specimens were examined using the ABAQUS/CAE software, and the results were consistent with the experimental results.