Shear Behavior of Macro-Synthetic Fiber-Reinforced Concrete Beams Without Stirrups

Twenty-seven large-scale beams were instrumented and tested under monotonic centerpoint loading to determine the effect of a newly developed high-modulus macrosynthetic fiber on the shear strength and failure behavior of longitudinally reinforced concrete (RC) beams without stirrups. Slender and short beams with respective shear span-depth ratios (a/d) of 3.5 and 2.3 were tested. The length of the beams varied between 1.9 and 3.2 m (75 and 126 in.), and the macrosynthetic fibers were added at volume fractions of 0.50, 0.75, and 1.0%. Deflection of the beam, strain in the concrete and in the flexural reinforcing bars, and the cracking pattern were monitored during the test at different stages of the monotonic loading until failure. The results showed that the addition of macrosynthetic fibers significantly improved the shear strength and ductility of the RC beams and modified the cracking and failure behavior. The ultimate shear strength of slender and short beams was increased up to 30% compared to the control RC beams.