Shear Behavior of Ultra-High Performance Hybrid Fiber Reinforced Concrete Beams

Current design codes require a dense array of steel reinforcement for shear-critical structural elements in earthquake-resistant structures, such as columns, walls, coupling beams, and beam-column joints. However, this leads to congested reinforcement in such elements during construction, which could cause extensively prolonged construction and reduced construction quality. This paper aims to investigate the potential of utilizing Ultra-High Performance Concrete (UHPC) with hybrid fibers to reduce shear reinforcement in shear-critical structural elements. A series of UHPC beams reinforced with longitudinal steel bars and various combinations of hybrid fibers were tested in a four-point loading setup. Two different shear span-to-depth ratios were used to evaluate the effect of the hybridization in the shear response of the beam member. The test results showed that the presence of hybrid fibers enhanced the shear cracking stress, ultimate shear stress, and crack width controlled ability of the specimens compared to the beam swith monofibers. Due to the synergy of hybrid fibers, a smaller volume fraction of fibers was required for UHPC beams with hybrid fibers to show a shear strength comparable to the UHPC beams with monofibers