Mechanistic Model for Concrete Cover Separation in FRP-Strengthened RC Beams: Anchorage Optimization through Controlled Crack Propagation

This study presents an innovative artificial tooth specimen incorporating bottom-embedded anchor rods for carbon fiber–reinforced polymer (CFRP)-strengthened concrete structures. Through systematic mechanical testing, we investigated the critical CFRP strain thresholds and horizontal crack propagation patterns in concrete covers, particularly analyzing shear-induced diagonal cracks and curvature variations. The experimental program evaluated the effects of anchor-rod embedment depth, spatial arrangement, and quantity on separation resistance of the concrete cover. Key findings reveal that pullout resistance increases proportionally with embedment depth, optimal anchor placement occurs within 0.2 L from the support (where L represents the specimen length), and excessive anchor density (>3 rods per 100 mm) induces stress concentration effects. Theoretical analysis using the concrete tooth model elucidates the separation mechanism and establishes a predictive mechanical model for cover detachment in anchored systems. The derived design equations demonstrate strong correlation with experimental data (R2 = 0.92), providing practical guidelines for seismic retrofit applications.