Experimental and Analytical Investigation on Bond Performance of the Interfacial Debonding in Flexural Strengthened RC Beams with CFRP Sheets at Tensile Face

Externally bonding of fiber reinforced (FRP) sheet to reinforced concrete (RC) beams has become a popular flexural strengthening method in recent years. The ultimate flexural strength of those strengthened beams can be improved efficiently, but it is often prevented by premature failure modes, such as sheets end interfacial debonding. This paper proposes an effective method to prevent sheets end interfacial debonding. Hence, an experimental and analytical study conducted to verify the efficiency of the proposed method. Therefore, nine concrete beams with dimensions of 100 mm width, 160 mm height and 1200 mm length were manufactured and tested. Eight specimens were strengthened in flexure with various numbers of CFRP layers and different sheets end strengthening methods. From the test results of this study it is conducted that the design guidance of ACI 440.2R-02 and ISIS Canada overestimates and the developed method by Toutanji et al. underestimates the flexural strength of CFRP strengthened RC beams at yielding. Also, applying the proposed method to sheets end strengthening, prevented sheets end interfacial debonding and increased load carrying capacity of those strengthened beams by 26% and 32%. The ductility (i.e. Δ_u⁄Δ_y) of those strengthened beams increased by 77% and 90%.