The role of FRP spike anchors in enhancing the strength of FRP fabrics

Despite the effectiveness of using externally bonded Fiber-reinforced Polymers (FRP) in structural retrofitting, premature debonding is still a critical issue. Indeed, the bond failure at the interface between the FRP and the concrete is limiting the exploit of the full composite strength. Among the different techniques proposed during the years, mechanical anchors have been demonstrated to be very effective. However, the lack of knowledge in the parameters affecting their mechanical response led to a lack of confidence in the design practice. Existing design codes and guidelines provide limited specifics for FRP spikes and this remarks the need for further research to formulate an accurate analytical model to assess the contribution of the FRP spike anchors on the strength of the FRP fabrics. This study focuses on the use of FRP spike anchors to improve the bond capacity of CFRP quadriaxial fabrics used to strengthen beam-column joints (BCJs) susceptible to premature shear failure during seismic events. This paper presents the preliminary results of an experimental campaign conducted using a novel test setup. The test results in terms of strength and strain response of the anchored fabrics are reported and discussed. Additionally, a critical review of the design models available in the literature is presented and the knowledge gaps that can be useful for future studies are discussed.