Shear behavior of FRC beams without web reinforcement using steel fibres with different aspect ratios

Abstract

An experimental study was conducted on twelve beams to examine the influence of shear span-to-depth ratio (a/d), fibre-volume fraction, fibre aspect ratio, and concrete compressive strength on the shear behavior of beams. Two shear span-to-depth ratios (2 and 3.75), three steel fibre-volume fractions (0, 0.5, and 0.75%), two fibre types (RC- 65/35-BN and RC-80/60-BN), and two concrete compressive strengths (HSC and NSC) were used in the tests. Two equal loads were symmetrically applied to the beams (fourpoint shear test). The applied load and the beam deflection at mid-span were recorded continuously until failure. The results demonstrated that the cracking stress and the ultimate shear strength increased with increasing fibre volume, decreasing shear span-to-depth ratio, and increasing concrete compressive strength. The beams with long fibres exhibited higher shear strength than the beams with short fibres. As the fibre volume increased, the failure mode changed from shear to flexure. Even with small shear span-to-depth ratios, the beams with a fibre volume of 0.75% acted like beams with web reinforcement. A fibre volume fraction of 0.75% is recommended as minimum shear reinforcement for beams. The beams having a volume fraction of 0.75% failed under flexure with high displacement values at failure.