Crack-Based Evaluation of Internally FRP-Reinforced Concrete Deep Beams without Shear Reinforcement

The maintenance or replacement of critical infrastructure exposed to aggressive environments is a major problem in many countries. To address this issue, alternative noncorrosive materials, such as fiber-reinforced polymers (FRPs), have been proposed to substitute conventional steel bars. However, large-scale tests of beams with small shear-span-to-depth ratios (deep beams) and FRP bars have shown a significant reduction of shear strength compared to similar beams with steel reinforcement. Therefore, the main objective of this paper is to model and explain the mechanisms that govern the reduction in strength. Twelve test specimens from the literature are analyzed based on a crack-based assessment framework for steel-reinforced concrete members, which is extended to account for FRP bars. The crack-based approach shows that large strains in the flexural FRP reinforcement diminish the aggregate interlock resistance and cause premature shear-induced flexural failures in members without shear reinforcement. It is also shown that the model adequately captures local and global deformations, as well as the effects of beam slenderness, longitudinal reinforcement axial stiffness, concrete strength, and crack geometry on the shear response of internally FRP-reinforced concrete deep beams without shear reinforcement.