Abstract
Bond plays a critical role in strengthening and upgrading of concrete structures using FRP bonding technology. Since the interfacial surface may be heterogeneous and bond failure is typically brittle, the size effect can be significant, making the bond parameters obtained with small specimens unsuitable to full-scale applications. This paper is to examine the size effect on the bond properties in concrete structures strengthened externally with bonded FRP sheets. A unique apparatus was developed for large-sized specimens with 350mm width. As suggested by Lu et.al., increasing a ratio between FRP sheets width (bf) and concrete width (bc) decreased Gf values. However, it was found that a function of stiffness of interface between FRP sheets and concrete could be larger than that suggested by Lu et.al. as a result of experiments. Moreover, effective transfer length of FRP sheets is not affected by the size effect. Gf of specimens anchored with U-shape FRP sheets are no larger than that of no-anchored specimens, but the ductility in the final debonding becomes larger.
