Comparative study on the bond performance of near-surface mounted fiber-reinforced polymer bars.

• The bond performance of NSM-FRP bars are governed by the adhesive type. • The shear strength of the adhesive has a significant influence on the bond strength of the NSM-FRP bars. • The NSM-CFRP bars showed the highest bond strength as compared to their BFRP, GFRP, and SS counterparts. • The texture of the NSM-FRP bar dictates its mode of failure. • The BPE model can be used to describe the bond-slip relationship for the NSM-FRP bars. This paper presents the experimental and analytical results of a large study on the bond performance of near-surface mounted (NSM) fiber-reinforced polymer (FRP) bars. The investigated parameters included the bar material (basalt-FRP (BFRP), glass-FRP (GFRP), carbon-FRP (CFRP), and stainless steel (SS) bars), the bar surface configuration (deformed and sand-coated bars), the filling adhesive (NSM-Gel, Sikadur-30, and Sika Grout-214), and the bonded length of the bar (6, 12, and 24 times its diameter). Sixty-six C-shape concrete specimens were tested under direct pullout loading configuration. The bond strength, the free-end and loaded-end slip, the strains in the NSM bar, and the modes of failure of the tested specimens are reported and discussed. The NSM-Gel adhesive outperformed other adhesives in developing the bond strength of the tested specimens regardless of their bar material. Both the deformed and sand-coated NSM-BFRP and GFRP bars showed almost similar bond strengths while the NSM-CFRP bars showed the highest strengths. The images obtained from the scanning electron microscope confirmed the obtained results in terms of the modes of failure and the bond failure mechanism. Analytically, the BPE model was calibrated using the experimental results to describe the bond stress-slip relationships of the FRP bars. [ABSTRACT FROM AUTHOR]