Numerical analysis of the mechanical behavior of the impact-damaged RC beams strengthened with CFRP

Abstract

In many places, the concrete structures suffered from impacted-damage need to be repaired. Herein, a 3-D numerical meso-scale model was established to study the mechanical behavior of the CFRP strengthened impact-damaged RC beams under 4-point loading. The strain rate effect of the strength of both of the concrete and the steel bars and the Young’s modulus of the concrete were taken into account during the impact process. In the next strengthening process, the anisotropic behavior of the CFRP was considered as well. Furthermore, the bond-slip behavior of the longitudinal bars was simulated in this model. The effectivity of the numerical model in simulating the impact behavior of concrete members and the behavior of FRP strengthened damaged RC beam was validated against experiments. Four types of strengthening schemes were designed and then compared in terms of the failure mode, failure process, strain distribution, and three mechanical indexes. It is found that the approach that strengthening the damaged beam only with the bottom FRP sheet should be avoid in practice because of the shear failure of the concrete in the shear span. Interestingly, though the loading capacity of the damaged beam gets the most significant increase by the strengthening with the U-shaped sheet, the scheme is not suggested due to its inferior ductility resulting from the failure on the FRP at the bending-shear section. Furthermore, the influence of the number of the strengthening layer on the mechanical performance of the damaged beams was discussed as well. It is found that the bearing capacity is enhanced with the increase of the strengthening layer while the ductility and the energy dissipation of the specimen decrease at the same time. In present work, four layers of bottom sheet plus average spaced U-strips in shear span is recommended to strengthen the impacted damaged RC beams.