Interfacial stress transfer of near surface-mounted FRP-to-concrete joints

Adhesively bonding carbon FRP (CFRP) plates to the surfaces of reinforced concrete structures is now a well-established form of retrofitting with advanced design rules and mathematical models that quantify the debonding mechanisms. However, externally bonded plates tend to debond at low strains which limits the effectiveness of this retrofitting technique. Tests have shown that near surface-mounted CFRP plates, where the FRP plate is inserted and bonded to the grooves cut into the concrete cover, substantially increase the debonding strain which in turn leads to significant increases in material efficiency as well as flexural strength and ductility. In this paper, mathematical models and design equations are developed for predicting the intermediate crack debonding capacities of near surface-mounted plates and their accuracy is demonstrated by comparisons with test results.