Shear Strength Model for Reinforced Concrete Beams with U-Wrapped FRCM Composites Based on the Critical Shear Crack Width Evolution

This paper presents a new procedure to determine the different shear strength contributions of RC beams strengthened with U-wrapped externally bonded (EB) fiber-reinforced cementitious matrix (FRCM) composites. A main shear crack, named the critical shear crack (CSC), is assumed based on the compression chord capacity model (CCCM). Since the CCCM is originally an ultimate limit state model, a simplified hyperbolic function with a final value based on the CCCM is proposed to relate the concrete contribution to the CSC width, similarly to other models in the literature. Considering the truss analogy of the CCCM, i.e., adopting its angle of inclination of the compression struts, the procedure accounts for the presence of internal steel stirrups and U-wrapped EB FRCM that is modeled considering its bond behavior and tensile strength. The procedure allows for predicting the total shear strength and the different contributions, as shown by comparison between the analytical and experimental results of a 15-beam data set sourced from the existing literature. Notably, the relationship between the shear strength contributions and CSC width allows for some design advantages, particularly in terms of durability.