Control of FRP Debonding in Strengthened RC Beams

When RC beams are externally bonded with FRP sheet (FRPs) on the tension-side surface, mainly two types of failure mode are expected: flexural compression failure (FCF) type and sheet debonding failure (SDF) type. If the RC beam failed with the latter mode, the calculated load-carrying capacity may not be ensured because FRPs may be debonded before reaching the compression failure of upper concrete. In this paper, in order to control FRPs debonding and to ensure the calculated load-carrying capacity, the applications of U-shape jacketing approach and side-surface bonding approach are proposed, and those debond-controlling effects were experimentally confirmed. The results obtained from this study were: (1) if shear span ratio of RC beam is large, side-surface bonding approach will be useful; and (2) applying U-shape jacketing approach, flexural reinforcing FRPs can be rationally restrained from debonding in spite of a magnitude of shear span ratio.