Assessment of shear-resisting mechanisms of steel-fibre-reinforced concrete beams

Abstract

The shear strength of 14 reinforced concrete beams, all devoid of shear reinforcement, is experimentally investigated. An analytical model is also formulated, by introducing the three main resisting mechanisms in shear, based on the contributions of the concrete compressive zone, aggregate interlock along the inclined cracks and steel fibres (dowel action is neglected). Hooked-end steel fibres 35 mm and 60 mm long are used at volume fractions ranging from 0.75 to 1.5% in the former case, and from 0.5 to 1.0% in the latter case. In all, the shear capacity resulting from the tests is higher than that predicted by the lower bound limit proposed by G. Parra-Montesinos in 2006 and by American Concrete Institute and Indian standard building codes (ACI 318 and IS 456) for fibrous concrete beams. The efficacy of the proposed model is also compared with the 12 other models proposed in the literature. The contribution of shear-resisting mechanisms, namely, compressed concrete, aggregate interlock and steel fibre, is found to be approximately 67, 15 and 18%, respectively, of the total shear strength. The effect of fibre factor (F) and longitudinal reinforcement (ρ) on the contribution of various shear-resisting mechanisms have been rigorously studied and presented.