Influence of geometric parameters on bent CFRP and GFRP spike anchors: Experimental investigation and design recommendations

Fiber-reinforced polymer (FRP) spike anchors have been widely used for structural strengthening applications. While previous studies have demonstrated their effectiveness, substantial variability in their performance has been reported, primarily due to differences in geometric parameters, fabrication methods, and installation practices. To date, no existing model has systematically quantified the bend strength of fanned FRP spike anchors as a function of bend ratio, strength ratio, and fan angle across a range of anchor sizes. Existing prediction models often rely on FRP stirrup/rope databases or use anchors of uniform size without fan configurations. In this study, these limitations are addressed through an extensive experimental program involving 78 FRP-strengthened concrete specimens. The test specimens featured either CFRP or GFRP anchors with various anchor strength ratios, anchor hole bend radii, fan lengths, and fan angles. The experimental results indicate that the bend ratio, anchor strength ratio, and fan angle significantly influence the anchor strength at the bend region. Based on these findings, a multiple linear regression model incorporating these critical parameters is proposed to accurately predict the bend strength of FRP anchors.