Bond between single and bundled high-modulus ribbed GFRP bars with short embedment lengths and concrete

Abstract

The bond between glass fiber-reinforced polymer (GFRP) rebar and concrete is one of the most important parameters in the design of GFRP-reinforced structures. This study investigates the bond behavior of single and bundled high-modulus ribbed GFRP rebars with short embedment lengths in concrete. To achieve this, a total of 48 pullout specimens were constructed and tested. The effect of various parameters, including GFRP rebar embedded length, the concrete block dimensions, GFRP surface characteristics, presence of transverse reinforcement, and bundling of rebars on the bond behavior of high-modulus ribbed GFRP rebar was studied. The experimental results indicated that the failure mode changed from pullout to splitting failure as the embedment length increased. The presence of transverse reinforcement, in many cases, changed brittle splitting failure to partial splitting failure followed by pullout failure. The variation in rebar surface characteristics resulted in differences in the bond-slip behavior of GFRP rebar in concrete. The experimental findings illustrated that rebar stress at failure for specimens with bundled GFRP was generally higher than that of corresponding individual bar with approximately same cross-sectional area. This observation suggests that the equivalent area method may serve as a conservative approach for evaluating the embedment length of bundled ribbed GFRP rebars. Furthermore, the adhesion between ribbed GFRP rebars and concrete was quantified for various bar sizes. Finally, the experimental results were employed to refine and calibrate existing bond-slip models of ribbed GFRP rebar to concrete.