Flexural Bond Performance of Anchored CFRP Laminates to Concrete Beams

Abstract

Fiber-reinforced polymer (FRP) composites are being extensively used in retrofitting and strengthening of reinforced concrete (RC) members due to their superior properties such as high strength and corrosion resistance. This form of retrofitting has proven to be effective in enhancing the flexural and shear capacities of RC members. However, the premature debonding of FRP laminates from the concrete substrate prior to utilizing its ultimate strength is a major concern and often results in a brittle member failure. Recent studies have indicated that adequate anchorage systems could improve the FRP-to-concrete bond and delay early debonding of the FRP laminates. The use of carbon-FRP (CFRP) splay anchors as an anchorage system is gaining wide acceptance due to its compatibility with CFRP laminates and its ability to suit a wide range of applications. However, limited studies are available in the literature that examines the effect of different anchor parameters on the laminate bond strength. Hence, this study aims to investigate the effect of different anchor parameters and configurations on the capacity of externally bonded concrete prisms with CFRP laminates. Consequently, the experimental program consisted of 30 concrete prisms that were strengthened with CFRP laminates and anchored with CFRP splay anchors. The parameters investigated were CFRP anchor diameter, embedment depth, and dowel angle. All prisms were tested in flexure under four-point bending tests. Test results showed that anchoring the laminates significantly enhanced the capacity of the prisms and FRP strain utilization compared to the unanchored strengthened prisms. In addition, varying the embedment depth and insertion angle had a significant effect on the capacity of the specimens. The strength improvement in the anchored specimens reached up to 50% over the control unanchored specimens. In addition, bond-slip models for the strengthened specimens are developed based on the obtained experimental data. The outcomes of this study will hopefully aid engineers in the design of FRP strengthened systems anchored with FRP splay anchors. It can also be concluded that CFRP splay anchors, if properly designed, could enhance the flexural capacity of RC beams by delaying the brittle debonding failure mode.