Shear capacity of steel fibre reinforced concrete beams

The Critical Shear Displacement Theory (CSDT) was developed to determine the shear capacity of reinforced concrete beams based on the different shear-carrying mechanisms (concrete in the compression zone, aggregate interlock, and dowel action). This research aims at extending the CSDT to Steel Fibre Reinforced Concrete (SFRC) by adding the contribution of steel fibres. The model extension was developed based on formulations for the contribution of steel fibres to the shear capacity from the literature. With this extension to the CSDT, the shear strength of steel fibre reinforced concrete beams without stirrups could be estimated. An extensive database is developed from the literature in order to evaluate, compare, and analyse the shear capacity of SFRC beams. The analysis indicates that two models are capable of predicting the shear strength of SFRC beams with reasonable accuracy. The mean, standard deviation, and coefficient of variation are 0.9, 0.28, 0.31 and 1.1, 0.33 and 0.30 respectively. The main geometric variables of the steel fibres that influenced the shear strength are the length, diameter, and fibre type (hooked, crimped, and straight). From the comparison between the results in the database and the proposed extensions to the CSDT it is found that the critical shear displacement of Δcr = 0.025 mm, gives reasonable results for SFRC. As such, this proposed method can be used to estimate the shear strength of SDRC based on a mechanical model.