The shear behavior of CFRP strengthened RC beams

The primary objective of this paper is to study the effectiveness of using externally applied CFRP composites as a method of shear strengthening. The parameters investigated in this study included CFRP amount and distribution (i.e., sheet versus strips), bonded surface (i.e., web sheet versus U-wrap), and fiber orientation (i.e., 90° fiber direction versus 45° fiber direction). Firstly, a novel Nonlinear Finite Element Analysis (NLFEA) model is created and validated. Then, five RC beams (150×225×1500 mm) have been constructed. The overall behavior of the NLFEA beams loaded up to failure, the onset of the cracking, and crack development with increased load and ductility were described. The NLFEA results showed that externally bonded CFRP increased the shear capacity of the strengthened RC beams significantly depending on the variables investigated. The beams strengthened with 90° CFRP U-wrap sheet provided a large increase in the ultimate load carrying capacity compared to beams strengthened with 90° CFRP web strips of 50 mm width. Decreasing the spacing between the strips is also efficient, while using 45° strips rather than 90° strips does not produce a remarkable increase in the shear capacity. The externally bonded CFRP can increase the shear capacity of the beam significantly by 34−62 % than that of the control beams, depending on the variables investigated. The inclination of the primary shear crack influenced the shear strength contribution of the external strengthening. Finally, an inclusive assessment of the NLFEA results, as well as three other well-known shear strength models, is conducted using a large test database. It is shown that the proposed shear strength, Chen and Teng, and the Chen et al. models give consistently good correlation with test data with an acceptable coefficient of variation as well as ACI Model shows unsatisfactory performance probably owing to its empirical nature and the use of an inappropriate model for the effective FRP bond length.