Flexural behavior of ultra-high-performance fiber reinforced concrete beams with low and high reinforcement ratios

In the study, the effects of using ultra-high-performance fiber reinforced concrete (UHPFRC) on deflection and curvature ductilities, moment capacities, flexural stiffness, and cracking behaviors of beams were experimentally investigated. Eight singly reinforced beams with four tensile reinforcement ratios (0.009, 0.019, 0.028, and 0.043) were tested under four-point loading to create a pure moment behavior in the mid region. The evaluations were made by comparing the UHPFRC beams and non-fiber beams containing UHPFRC matrix without steel fiber. Straight micro-steel fibers with volumetric ratio of 1.5% were used in the UHPFRC matrix. The results of study indicate that the use of UHPFRC for beams having especially high reinforcement ratios provides significant advantages in terms of the considered parameters. Especially high compressive strength and deformation capacity of the UHPFRC allow the use of high reinforcement ratios in beams which results in more economical sizes as long as the beam deflections ensure for both the serviceability and the ultimate limit states. In this study, however, the simplified numerical approach developed for the flexural design of fiber reinforced concrete was applied to the UHPFRC beams, as well.