Bond behavior of deformed GFRP rebars

The bond behavior of straight Glass-Fiber-Reinforced-Plastic (GFRP) reinforcing bars to concrete was experimentally investigated. Results of 48 beam and 18 pull-out specimens constructed with No. 3, 6, and 9 GFRP rebars are presented. The static tensile load was applied to the rebars in a gradual increment of load level until splitting failure of concrete, rebar pull out failure, or rebar fracture occurred. The slip between the rebars and concrete was measured at the loaded and free ends at each load level. Variables in the study included concrete compressive strength, embedment length, clear concrete cover, rebar diameter, and concrete cast depth. On the basis of the experimental results, it was concluded that the ultimate bond stress increases with higher concrete compressive strength and clear concrete cover, but decreases with larger concrete cast depth. The ultimate bond stress and the loaded end slip of the pull-out specimens were found to be greater than that of the beam specimens. Beam test data could be more realistic and accurate for use in determining the development length.