Bond Behavior Between Steel Fiber Reinforced Polymer (SRP) and Concrete

Steel fiber reinforced polymer (SRP) composite materials, which consist of continuous unidirectional steel wires (cords) embedded in a polymeric matrix, have recently emerged as an effective solution for strengthening of reinforced concrete (RC) structures. SRP is bonded to the surface of RC structures by the same matrix to provide external reinforcement. Interfacial debonding between the SRP and concrete is a primary concern in this type of application. This study aimed to investigate the bond characteristics between SRP and concrete determined by single-lap direct shear tests with different composite bonded lengths and fiber sheet densities (cord spacings). Specimens with medium density fibers failed mainly due to composite debonding, whereas those with low density fibers failed due to fiber rupture. Results of specimens that exhibited debonding were used to determine the bond-slip relationship of the SRP-concrete interface and to predict the full-range load response, which was in good agreement with the experimental results. A database of SRP-concrete direct shear tests reported in the literature was also established. Four analytical equations derived for fiber reinforced polymer (FRP)-concrete debonding were evaluated based on the database results and were found to predict the maximum load within approximately 15% error on average, however, they all underestimated the effective bond length.