Bond-slip response of end-hook and half-hooked steel fibers in moderately strong SIFCON matrix

Abstract

In this study, an attempt was made to study the bond-slip performance of end-hook and half-hooked steel fibers embedded in moderately strength SIFCON matrix, to find out the cause of excessive mechanical anchorage and to further optimize the bond-slip equation of steel fibers. Used end-hook steel fibers with embedded depths 10 and 15 mm, pullout offset angles 0°, 30°, 45°, and 60°; Half-hooked steel fiber with embedded depths 10 and 15 mm, end-hook bending angles 30°, 45°, 60°, and 90°; Novel end-hook and novel half-hooked steel fibers with end-hook length doubled, which were subjected to a static pullout test at a rate of 0.01 mm/s. Experiments showed that the half-hooked steel fiber took the best end-hook bending angle at 60°; The novel end-hook and half-hooked steel fiber had a good bonded performance. The single steel fiber anchorage performance evaluation index K was proposed. Through experimental phenomena, data analysis, and X-ray flaw detection, the existence of “local damage” was proved. Based on the traditional bond-slip formulation, a new bond-slip formulation for moderately strength SIFCON substrates is proposed by adding a plastic hinge in the “local damage” region. By comparing the old and new equation, it was found that the calculation error of the maximum pullout load of end-hook steel fibers was reduced by 3.77 times and that the calculation error of the maximum pullout load of half-hooked steel fibers was reduced by 2.8 times, and the calculation equation for the peak load of secondary reinforcement of half-hooked steel fiber was supplemented, which is of application value for further optimization of the shape of steel fibers.