Behaviour of GFRP-RC continuous deep beams without web reinforcement

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Mohamed, Ahmed
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Steel-reinforced concrete (RC) deep beams are one of the major components in the superstructure of bridges, they are used for load distribution as transfer girders or bent caps and pile caps, because of their capability to sustain higher loads compared to slender beams. In North America, such elements are exposed to harsh weather, which makes them more susceptible to corrosion problems. Thus, this study aims at investigating the feasibility and performance of using the non-corrodible glass fiber-reinforced polymers (GFRPs) in reinforcing concrete deep beams. The GFRP material is known for its relatively low modulus of elasticity, with respect to steel, and its linear elastic stress-strain relationship up to failure. Also, GFRP bars have different surface and bond characteristics than those of steel, which require a longer development length. These different properties affect the behaviour of GFRP-RC structures. The effects on simply-supported beams and slabs have been studied extensively, while, the behaviour of GFRP-RC continuous deep beams has not been studied yet. In this study, twelve large-scale RC deep beam specimens were constructed and tested to failure; three simply-supported and nine continuous over two equal spans. All specimens were reinforced with GFRP headed-end bars. The test variables were the shear span-to-depth ratio, which included 1.0, 1.5, and 2.0; and the top longitudinal reinforcement ratio in continuous beams which included 1.2, 1.0, and 0.8%. The cross-sectional dimensions for all specimens were 590-mm deep × 250-mm wide. The overall length of the simply-supported specimens was 2,100, 2,600 and 3,100 mm while it was 3,500, 4,500, and 5,500 mm for the continuous beams. The test specimens were divided into four series. One series included the three simply-supported specimens, while the nine continuous specimens were divided into three series. The test results were presented in terms of ultimate strength, cracking, deflection and strains in reinforcement. In addition, the test results were compared to the predicted values by the Canadian standards CSA/S806-12 (CSA 2012) and CSA/A23.3-14 (CSA 2014), and the American Code ACI 318-14 (ACI 2014). The test results confirmed the formation of the Strut-and Tie-Model (STM). In addition, it was observed that increasing the shear span-to-depth ratio and increasing the top longitudinal reinforcement ratio led to a significant decrease in the load carrying capacity of the beam.
Deep beams, STM, Arch action, GFRP, Headed-end, Continuous beams.