Shear Performance of High-Strength Concrete (HSC) Beams Reinforced with Steel and Fiber Composite Grids

This study investigates the shear performance of high-strength concrete (HSC) beams reinforced with steel, fiber composite grids (CFRP and GFRP), and their hybrid configurations in the absence of transverse reinforcement. A total of six full-scale beams with varying reinforcement configuration and shear span-to-depth (a/d) ratios were experimentally tested under monotonic loading to evaluate their load capacity, cracking characteristics, failure modes, and serviceability behavior. The results revealed that beams reinforced solely with fiber grids exhibited significantly reduced strength and brittle shear failure. Hybrid systems incorporating both steel and fiber grids demonstrated improved strength and ductility, closely matching or surpassing control specimens with conventional steel reinforcement. Key structural parameters such as effective moment of inertia, cracking moment, shear strength, and midspan deflection were compared against analytical predictions based on ACI 318-16 and the Canadian Education Module code. While predictions generally aligned for hybrid beams, notable discrepancies were found for FRP-only systems, particularly in serviceability performance. The findings highlight the potential of hybrid reinforcement as a viable design strategy for HSC beams, offering a balance between strength, ductility, and service performance.