Mitigation of intermediate crack induced debonding of FRP strengthened RC members using FRP spike anchors

Abstract The prevention of intermediate crack-induced (IC) debonding failure in reinforced concrete (RC) members strengthened with fiber-reinforced polymer (FRP) materials is a key challenge in structural strengthening applications. This study examines the effectiveness of FRP spike anchors in mitigating IC debonding failures, focusing on variables such as anchor placement, dowel diameter, and fan length. An experimental program involving thirteen beams strengthened with externally bonded FRP sheets and secured with FRP spike anchors of varying diameters (3, 5, 6.5, 8, and 10 mm) is presented. Anchors were positioned either across the entire span, within the shear span, or concentrated at the ends of the FRP sheets. The findings are reported in terms of load capacity for each configuration and the utilization of FRP strain prior to failure. Load–deflection behavior and the analysis of failure modes are discussed for all samples, revealing a maximum load increase of 9.4% compared to unanchored beams. Anchors placed solely in the shear span demonstrated superior performance over those distributed across the span, producing more uniform FRP strain distributions in peak moment areas. Further, anchors located at the ends of the sheets improved peak displacements at failure by 40%.