Assessment of the Experimental and Numerical Bond–Slip Law of Various Strengthening Systems in Reinforced Concrete Elements

Abstract With the emergence and diversity of various strengthening methods in fibre-reinforced polymer (FRP) strengthened reinforced concrete (RC), understanding and comparing the bond behaviour and active bond mechanisms of these different methods is crucial before their application. In this context, a general method applicable to various strengthening techniques employed to develop accurate bond–slip models and identify the active bond mechanisms is proposed. This approach is based on experimental load–slip behaviour data and does not rely on a predefined model shape. To this end, this paper presents an experimental study on various strengthening techniques, including externally bonded reinforcement (EBR), externally bonded reinforcement on grooves (EBROG), hybrid bonded (HB), and near-surface mounted (NSM), all tested under a single lap-shear test. Here, the results of single-shear bond tests are analysed to examine the manifestation of different activated bond mechanics from various strengthening techniques in the bond–slip law and to compare their bond behaviours.