Evaluating Direct Shear Performance of Steel Fiber–Reinforced Concrete

Shear stress is one of the main design parameters for structures subjected to seismic demands. Steel fibers are a viable option for the shear reinforcement of concrete elements because they tend to increase the tensile strength and post-cracking performance of concrete. This study evaluated the direct shear strength of steel fiber-reinforced concrete (SFRC) using standardized specimens. The experimental program included direct shear tests of 14 column- and beam-type specimens using three test methods: FIP, JSCE-SF6, and Z-type. The steel fibers had double hooks at the ends and an aspect ratio of 65. The nominal fiber dosages (FD) were 30 and $60\mathrm{kg}/{\mathrm{m}}^3$, which correspond to fiber contents of 0.38% and 0.76%, respectively. The analysis of 887 data points measured during direct shear tests of the 14 specimens from this study and 69 specimens reported in the literature was performed by analyzing the trends of the shear strength parameters at the first cracking, maximum strength, and residual shear as a function of the reinforcement index. The measured results showed that the shear strength of SFRC at the limit states of cracking, maximum, and residual with FD of $60\mathrm{kg}/{\mathrm{m}}^3$ was between 3% and 52%, 5% and 50%, and 29% and 63%, respectively, greater than the values associated with FD of $30\mathrm{kg}/{\mathrm{m}}^3$. The study also proposed models to estimate the toughness, and the maximum and the residual shear strengths associated with specific displacements.