Design recommendations for bond of GFRP rebars to concrete

To develop design guidelines for bond of glass-fiber-reinforced plastic (GFRP) rebars to concrete, a total of 102 specimens were constructed and tested subjected to monotonic static loading. The research program was inclusive of the experimental testing of 48 beam specimens, 18 pull-out specimens, and 36 hooked rebar specimens. The tensile load was applied to the rebars in a gradual increment of load level until splitting 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 included in the study were concrete compressive strength, embedment length, clear concrete cover, rebar diameter, concrete cast depth, radius of bend, and tail length. New criteria for acceptable bond performance of GFRP rebars to concrete were developed and were used to evaluate the experimental results. Design guidelines for calculating the development lengths for straight and hooked GFRP rebars to concrete were derived. In addition, confinement factors were calculated to reflect the influence of concrete cover and casting position.