Bond strength of glass fibre-reinforced polymer bars in unconfined concrete

Abstract

Glass fibre-reinforced polymer (GFRP) bars can be used to avoid steel reinforcement corrosion in bridge decks, which usually have no transverse reinforcement. In this study, 35 flexural tests of beams and slabs were carried out to experimentally determine the bond strength of spliced GFRP bars with no transverse reinforcement. The test variables included splice length, cover thickness, and bar spacing. The splice lengths were relatively large to test realistic splice lengths used in the field (longer than 30 d b in most tests). In addition, four beams with conventional steel rebar splices were also tested to compare their bond strengths with those of the GFRP bars. Test results showed that the bond strengths of the specimens with GFRP bars were lower than those of the steel rebars. Although the average bond strength of the GFRP bars decreased with increasing splice length and decreasing cover thickness/bar spacing, the bond strength of the long splice increased when c/ d b ⩾ 2.5, in which c denotes the smaller of the minimum concrete cover and 1/2 of the bar clear spacing. Two equations for predicting the average bond strength of GFRP bars in unconfined concrete are proposed based on the regression analysis of the 33 test results from the beams and slabs that failed by concrete splitting.