Investigation of steel fibres as minimum shear reinforcement Available to Purchase

This paper presents the results of an experimental appraisal of the American Concrete Institute (ACI) building code provisions allowing the use of deformed steel fibres as minimum shear reinforcement in reinforced concrete beams. Two types of hooked-end steel fibres of length 35 mm and 60 mm were used in the fibrous concrete mixtures at volume fractions in the range of 0·75–1·5% and 0·5–1·0%, respectively. The performance of the fibrous concrete beams was compared to that of beams detailed with the minimum web reinforcement specified in the ACI code. The results indicate that the use of hooked-end steel fibres even at a volume fraction (0·5%) lower than the ACI-specified minimum of 0·75% led to multiple diagonal cracking with crack widths smaller than permissible values. The measured shear strengths across all fibre aspect ratios and volume fractions were higher than lower bound values for steel fibrous concrete recommended in the literature and predicted values of the beams detailed with the ACI code-specified conventional minimum web reinforcement. Predictions of the measured shear strengths with varying degrees of conservatism were obtained from seven shear strength models selected from the literature and the most accurate predictions were obtained from a modified version of the model proposed by Dinh et al. The results of this investigation support the use of the deformed steel fibres used in the experiments as minimum shear reinforcement in RC beams with depths equal to those of the tested beams.