Shear behaviour of concrete V-shaped beams with and without steel fibres

Abstract

This research paper studies the shear behaviour of beams with V-shaped webs (V-beams) containing steel fibres in various volumes (0, 0.6 and 1%). Asymmetrical three-point bending tests were performed to investigate the shear behaviour of V-beams and the potential of fibres being used as minimum shear reinforcement. Shear strength, normalised shear stresses, shear cracking (angles and pattern) and shear crack widths at ultimate resistance are compared for the various V-beam types and fibre volumes. A simple shear prediction model found in literature is modified to accommodate the cross-sections of V-beams which accurately predicts shear capacities of V-beams with slight conservatism. It is found that fibres significantly enhance the shear capacity of V-beams and allow beams to resist higher loads at wider crack widths compared to beams containing no fibres. Furthermore, the shape of the web influences shear capacity tremendously and higher shear strengths are reached by beams with larger web cross-sectional areas. It is known that the widely used assumption that shear is entirely resisted by the effective rectangular portion of the web, determined by the narrowest part of the beam $$\left( {b_{\text{w}} } \right)$$ and by the effective depth $$\left( d \right)$$ , often results in over-conservative shear predictions which ultimately leads to an inefficient use of concrete. This research indicates how the shear strength increases in beams with identical values of $$b_{\text{w}}$$ but increasing web areas.