SHEAR BEHAVIOUR OF STEEL FIBROUS CONCRETE BEAMS WITHOUT STIRRUP REINFORCEMENT

Abstract

Shear strength of longitudinally reinforced normalstrength and high-strength concrete beams containing either hooked-end or crimped-type of deformed steel fibres proposed to be used as minimum shear reinforcement has been investigated for various fibre aspect ratios and volume fractions. The validity of the ACI Building Code recommended flexural performance criteria governing the use of steel fibres as minimum shear reinforcement has been examined and its shortcomings are highlighted. A total of 46 simply-supported scaled beams with a shear span-to-depth ratio of 3.5 were tested to failure under monotonically-increasing, concentrated loads. The behaviour of the fibrous concrete beams was bench-marked against the performance of beams conventionally detailed with the minimum shear reinforcement recommended in the ACI Building Code and the Indian code, IS 456:2000. For both the grades of concrete, the measured shear strengths across the two fibre types, aspect ratios and the volume fractions under investigation were higher than a lower-bound value for steel fibrous concrete given in the literature as well as predicted values of the beams detailed with the code recommended minimum web reinforcement. Different degrees of accuracy were obtained when the measured shear strengths were compared with predictions of selected shear strength models available in the literature. A simple mechanics-based shear strength predictive model considering the contribution of only the compressed concrete and tensile resistance of the steel fibrous concrete has been proposed and validated