Effect of stirrups on the bond behavior of lap spliced GFRP bars in concrete beams

Abstract

Although the bond behavior of fiber-reinforced polymer (FRP) bars with concrete differs from that of steel bars with concrete, limited studies are available on the bond performance between FRP bars and concrete. To investigate the bond performance of glass FRP (GFRP) bars in concrete, lap splice tests were performed on 22 beam specimens. The test parameters included the spacing of stirrups along the bar splice length, bar diameter, loading type, and type of spliced bar. As with the counterpart specimens, five lap splice specimens using steel bars were also tested. All beam specimens using GFRP bars experienced splitting bond failure. The test results showed that the existence of stirrups along the splice length increased the bond strength of GFRP bars, and the bond strength decreased with the increase of stirrup spacing in the GFRP beam specimens. The bond strength contribution by stirrups was more effective in the GFRP beam specimens with a diameter of 20 mm than that of GFRP beam specimens with a diameter of 28 mm. The digital image correlation (DIC) technique was used to investigate the evolution of cracks in the beam specimens that failed by splitting failure. The current design methods and proposed design method were applied to the test results including existing test results, and the proposed design method predicted well the test results.