Strengthening of flat slabs with fibre reinforced polymers using the externally bonded reinforcement on grooves method: a review

The application of fibre reinforced polymer (FRP) composites has been proved to be an effective method for strengthening of reinforced concrete (RC) structures. The attachment of relatively light and high-strength FRP sheets on structural members can lead to a significant increase of the load bearing capacity without compromising the architecture or increasing the self-weight of the structure. However, the bond between FRP and the existing concrete surface remains the weak point of this strengthening system, often leading to an underutilization of the materials used for strengthening (i.e., failure occurs below the strength of FRP composites due to debonding of FRP from the substrate). Externally Bonded Reinforcement on Grooves (EBROG) is a technique that has been shown to improve bond between FRP composites and concrete while maintaining simplicity of application. In flat slabs, a concentration of stresses occurs near the supports, which can lead to a punching shear failure that has been shown to be catastrophic on several occasions in the past. This paper reviews different FRP flexural and flexural-punching strengthening methods that have been used for improving the punching shear capacity and behaviour of flat slabs subjected to gravity loading and focuses on the application of EBROG method by reviewing and summarizing the results from recently published tests. The efficiency of the EBROG technique in improving the behaviour of flat slabs is discussed and compared with that of the conventional Externally Bonded Reinforcement (EBR) method. The effect of flexural strengthening on punching shear capacity is discussed. The experimental results are used to apply the Critical Shear Crack Theory (CSCT) and gaps in analytical capacity assessment of FRP strengthened slabs are addressed.