Quasi-static and Fatigue Responses of Concrete Slabs Internally Reinforced with Sand-Coated GFRP Bars

Glass fiber-reinforced polymer (GFRP) bars can replace conventional steel rebars as internal reinforcement in concrete structures to avoid corrosion-related damage. The mechanism of bond between the GFRP bars and concrete differs from that between steel bars and concrete. This difference extends to fatigue loading and is partially due to the different surface condition and elastic properties of the GFRP bars. This paper investigates the bond between concrete and sand-coated GFRP bars using four-point bending tests of full-scale reinforced concrete slabs. The slabs are internally reinforced with GFRP bars and are tested under quasi-static and fatigue loading conditions. The slab subjected to cyclic loading is tested in quasi-static condition after 2 million cycles. The applied load versus load point deflection responses are presented, including the fatigue cycles. Both slabs experience shear failure, where cyclic loading have marginal impact on the slab quasi-static post-fatigue response. Full field displacement and strain components on the lateral surface of the constant moment region of the slab are obtained from digital image correlation (DIC). DIC and cross-sectional analyses are used to determine the relationship between the stress in the GFRP bar and its slip with respect to concrete at the cracked cross-sections. In addition, the GFRP bar stress versus crack opening at the bottom of the slab are obtained. DIC analysis also highlights that damage in concrete in tension occurred not only at the crack locations but also in the area surrounding the cracks, which provides a new insight on the concept of tension stiffening.