Strengthening in Shear of RC T-beams with CFRP Fabrics: Multilayer Versus Monolayer

In recent years, manufacturers have developed new heavyweight CFRP sheets as an alternative to multilayer of lightweight CFRP to strengthen important RC structure components. However, there are still design and practical issues that need to be investigated, such as (i) the maximum number of CFRP plies that can be installed without exhibiting slippage or debonding, particularly when bonded on vertical surfaces; (ii) the effectiveness of shear strengthening with multilayer CFRP fabrics compared to a monolayer of equivalent total weight. The present study aims to evaluate and compare experimentally the behavior of reinforced concrete (RC) T-beams strengthened in shear with multilayer lightweight CFRP fabrics to that of a heavyweight CFRP monolayer of equivalent total weight. To this end, nine laboratory tests were performed on eight specimens strengthened with CFRP sheets in U-wrap schemes around the web and bonded continuously along the shear span, and one control specimen with no strengthening. The results are presented in terms of failure modes, gain in capacity due to CFRP, deflection, and strain responses experienced by the externally bonded CFRPs. Finally, the experimental results obtained are compared to the predictions of the current design codes and guidelines.