Enhancement of impact performance of reinforced concrete beams without stirrups by adding steel fibers

The impact strength of reinforced concrete beams without shear reinforcement is studied in this paper, with emphasis on the improvement of the impact performance achieved by using steel fiber-reinforced concrete (SFRC). Drop-weight and companion quasi-static tests have been completed on 2000 × 125 × 250 mm beams containing ordinary longitudinal steel bars. Seven SFRC mixes have been studied, including three fiber types (smooth, hooked and prismatic) and three volumetric fractions (0% i.e. plain concrete, 0.5% and 1.0%). The study has confirmed the brittle impact behavior of beams without fibers, which failed by shear. With the addition of 0.5% steel fibers, shear failures were obtained with hooked and prismatic fibers but not with smooth fibers. Finally, all beams with 1.0% steel fibers developed a flexural failure mode. The improvement of the impact behavior of beams with SFRC is also confirmed by the fact that most of the specimens which developed a flexural failure had thin diagonal cracks in the webs of the shear spans, but such cracks did not progress due to the fiber-bridging capacity. In the paper, the study is completed with an analysis of the rate sensitivity of the shear strength and the capacity for energy absorption of tested beams.