Generic assessment of effective bond length of FRP-concrete joint based on the initiation of debonding: Experimental and analytical investigation

Numerous studies have been so far conducted to better understand the behavior of fiber-reinforced polymer (FRP) sheets adhered to the concrete surface. In most studies, effective bond length has been known as an important concept, which beyond this length, loading capacity cannot be increased. To more scrutinize on effective bond length of FRP-concrete joints, in the present study the bond behavior of FRP-concrete joints was investigated and an attempt was made to determine the effective bond length of the joints. To this end, first, 24 concrete prisms of three grades of different compressive strengths were made and strengthened with various ranges of thickness, elastic modulus, and type of FRP composites; and the specimens were subjected to the single shear test. The particle image velocimetry (PIV) technique was employed to obtain the load-slip curves and the strain and slip profiles along the joints. An attempt was made to detect the beginning of debonding through investigating the bond behavior of FRP-concrete, and consequently, the effective bond length was measured. A simplified analytical method was then developed to predict the effective bond length such that it be independent of the bond-slip relationship. Finally, comparisons were made between the values predicted by the well-known models and those obtained from the experimental results. Moreover, the new procedure suggested in this study was found capable to predict the effective bond length with reasonable accuracy.