Estimation of the Shear Strength of RC Members with Externally Bonded, Fully-Wrapped FRCM Composites

Externally bonded (EB) fiber reinforced cementitious matrix (FRCM) composites have been proven to be an effective solution for shear strengthening existing reinforced concrete (RC) members. Different layouts, namely U- and full-wrapping, of the EB composite can be adopted depending on the geometry and type of RC member. In the case of RC beams, the fully-wrapped layout is not always possible due to the presence of the slab. However, this layout is particularly attractive in the case of RC columns, where the composite can be applied easily and may provide significant strength increase. Although FRCM composites are attracting interest, the availability of analytical design models is still quite limited. In particular, few studies regarding the evaluation of the shear strength of FRCM fully-wrapped RC members are available in the literature. In this paper, an analytical model for the estimation of the contribution of fully-wrapped FRCM composites to the shear strength of RC members is proposed. The model is based on the truss analogy commonly adopted by various codes and guidelines for the estimation of the shear strength of RC beams and for fiber reinforced polymer (FRP) strengthened RC beams. The analytical model estimates the contribution of the FRCM to the member shear strength accounting for the bond behavior of the specific composite employed, which is an important aspect since FRCM composites have reported different bond behavior than FRP composites externally bonded to concrete substrates. The accuracy of the model provisions is assessed by comparing analytical and experimental results of RC beams fully-wrapped with a carbon FRCM composite