Steel fiber reinforced concrete beams with predetermined failure surface and no stirrups

Abstract

This paper treats an experimental study of shear problems in steel fiber reinforced concrete beams without shear reinforcement, where a specific groove in the shear span is used to specify the location of diagonal cracks, aiming to reduce the arch effect, controlling the critical crack inclination at 30°, and evaluating the assertiveness of the normative shear strength predictions. The experimental program includes four (4) beams, varying the steel fiber ratio. The results showed that the mechanism was satisfactorily induced shear failure, as expected. Also, it was observed that the ratio av/d did not influence the proposed model significantly, such behavior was expected because the shear cracks observed in the beams were more pronounced after distance av/4, making the arching action and dowel action less effective in the ultimate shear strength value. The proposed model excelled in the accuracy of the normative predictions, with a coefficient of variability between 4 and 8 %, probably to eliminate any arch effect for the ratio av/d = 1.86. However, a simplified calculation model based on the fiber residual stress distribution along the considered inclined section was proposed, and it was noted that the proposal presented better results, with an average value of 1.0 and a coefficient of variation (CoV) of only 3 %. It also showed a mean of 1.02 and a CoV of 8 % compared to the experimental results from the literature. Thus, the proposed predetermined shear failure surface and the calculation model are viable alternatives to evaluate estimates for shear resistance even with shear reinforcement or steel fibers.