Shear strengthening of RC beams with externally bonded U- and fully-wrapped FRCM composites

Fiber-reinforced cementitious matrix (FRCM) composites have been used as externally bonded (EB) bending and shear reinforcement of existing reinforced concrete (RC) members, as well as to improve their axial behavior through confinement. While numerous experimental, analytical, and numerical investigations on the contributions of EB FRCM composites to the flexural capacity of RC beams can be found in the literature, quite limited work has been done to investigate the shear resisting force contribution of EB FRCM jackets applied to RC members. FRCM shear strengthening can be performed either side bonding, U-wrapping, or fully wrapping the reinforcement around the cross-section of beams and columns. In this paper, the shear resisting force contribution provided by a polyparaphenylene benzobisoxazole (PBO) FRCM composite is investigated with four-point bending tests of seven real-scale RC beams under-reinforced in shear. One beam is used as control whereas six are strengthened with U-wrapped or fully-wrapped FRCM. The parameters studied are the number of layers, inclination angle of textile principal direction (PD) with respect to the beam longitudinal axis, and presence of anchors. The results obtained shed light on the role of these parameters on the RC beam shear resisting force, contributing to the body of knowledge on this topic.