2019 CSCE Annual Conference - Laval (Greater Montreal)

2019 CSCE Annual Conference - Laval (Greater Montreal) Conference

Evaluation of the Bond-Dependent Coefficient for GFRP Bars in Concrete Beams

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Mr. Cheng Shang
Dr. Karam Mahmoud, University of Manitoba
Mr. Ahmed Bediwy (Presenter)
Dr. Ehab El-Salakawy, University of Manitoba

The deterioration of reinforced concrete (RC) infrastructure such as bridges, parking garages and overpasses due to corrosion of steel reinforcement is common in North America. To overcome the corrosion-related issues, the use of glass fiber-reinforced polymer (GFRP) bars in such structures becomes a viable alternative to steel reinforcement. Due to serviceability concerns, cracking and deflections usually govern the design of GFRP-RC flexural members. Thus, there is a need to verify the crack width in FRP-RC members at service load. To account for the different bond characteristics of FRP bars, the evaluation of bond-dependent coefficient (kb) of FRP-RC members is required for serviceability design. The values of this coefficient reported in experimental studies are highly variable, resulting in unreliable crack width predictions. Recent developments in the FRP industry have led to FRP bars with different enhanced mechanical properties and surface configurations, which are expected to affect their bond performance and, consequently, the kb value. Due to the absence of comprehensive test data, the design codes and guidelines, however, recommend kb values only based on the surface configurations. Thus, this experimental study aims at investigating the kb values and verifying the dependency of the kb values on GFRP bars with different surface configurations (sand-coated and deformed/ribbed), bar diameter, concrete cover, and type of transverse reinforcement in normal-strength concrete beams. In this experimental study, a total of nine GFRP-RC beams were constructed and tested to failure. The beam specimens were 2800 mm long × 200 mm wide × 300 mm deep. All beams were tested in flexure under four-point bending configuration over a simply supported span of 2400 mm with 200 mm overhang on each side. The test results are presented in terms of applied load against slip, deflection, crack width, and strains in both GFRP bars and concrete. It is concluded that not only bar surface configuration but also bar diameter and concrete cover have a significant effect on the kb value.