Effect of confining FRP overlays on bond strength enhancement

In this study, changes in the bond strength of reinforcing bars due to external confinement, through FRP overlays, was investigated. Eccentric pullout specimens with insufficient bond length and with two different normal strength concrete levels were reinforced with single deformed bars placed with a small cover thickness. Three reinforcing bar sizes and two FRP types, each having two different number of layers, were used in the experiments. Significant enhancement in bond strength due to FRP confinement was observed in all specimens. Although the increase in bond strength was closely related to the clamping force developed by the FRP overlays, the effectiveness of the invoked clamping force reduces beyond a limiting value. The orientation of the splitting cracks was also affected by the existence of the FRP overlays.