SHEAR FLEXURAL BEHAVIOUR OF RC BEAMS STRENGTHENED BY NEAR SURFACE MOUNTED FRP BARS

Abstract

Strengthening with near-surface-mounted (NSM) fiber-reinforced-polymer (FRP) reinforcement has become a well-known technique, which provides a good bond between the FRP element and concrete. However, one of the most common failure modes of NSM-FRP strengthened beams is concrete cover separation (CCS). In this research, the shear flexural behavior of RC beams strengthened with fully and partially bonded NSM CFRP bars was studied. Two different bar configurations with straight and hooked ends were used. The hooked ends were used to act as end anchors, which might delay the CCS failure. The results indicated that the end anchoring was effective in delaying the CCS and increasing the ultimate carrying capacity. The ultimate load of the beams strengthened with two straight NSM CFRP bars increased by 166.2%, while that of the corresponding beam having end anchorage increased by 180.5% compared to the unstrengthened beam. On the other hand, unbonding the NSM bars along the mid-span zone slightly decreased the ultimate load compared with the fully bonded bars, however it slightly increased the beam deformability. Increasing the unbonded length shifted the failure mode from CCS to CCS and anchorage shearing off, which is not preferred from the point of view of the structural safety.