Keywords: fibre-reinforced polymer bars, hybrid frp-steel bars, hybrid reinforcement ratio, finite element modelling, basalt fibre-reinforced polymers, glass fibrereinforced polymers, deflection.

Steel bars are the typical choice for reinforcing concrete members due to their relatively low cost, high tensile strength and ductile behaviour. However, in some applications where there might be exposure to aggressive agents such as coastal chlorides and de-icing salts, steel bars become susceptible to erosion. In circumstances where high ultimate moment capacity is needed steel bars may not provide the adequate capacity required. The use of Fibre-Reinforced Polymer (FRP) bars as sole and hybrid reinforcement bars was introduced to meet these deficiencies of steel bars. This paper focuses on concrete beams reinforced with hybrid FRP-steel bars. The FRP materials considered in this study are Glass Fibre-Reinforced Polymer (GFRP) and Basalt Fibre-Reinforced Polymer (BFRP). To the author’s best knowledge very few studies exist that compare the flexural performance of hybrid GFRP- and BFRP-steel reinforced beams. The performance of these two hybrid reinforcements is compared in terms of deflection and ultimate moment capacity, and a better understanding of the effect of the hybrid reinforcement ratio is gained. This was achieved by conducting a numerical investigation in ABAQUS, where thirteen reinforced concrete beams were modelled and tested under a four-point bending test. Results indicated that the large deflections, experienced by concrete beams reinforced solely with FRP bars can be reduced by opting for the use of hybrid FRP-steel bars as the internal reinforcement. Furthermore, results showed that concrete beams reinforced with hybrid FRP-steel bar exhibited higher ultimate capacity compared to FRP only or steel only reinforced beams. In addition, concrete beams reinforced with BFRP bars outperformed GFRP bars in terms of deflection and ultimate capacity, albeit slightly, both as sole FRP reinforcement and in hybrid FRP-steel scenarios. Lastly, the study found that the hybrid reinforcement ratio can be used to control the deflection and ultimate capacity of hybrid FRP-steel bar reinforced concrete beams. The results of this study provide a better understanding of the two types of FRP materials considered in this study. Knowing how the hybrid reinforcement ratio affects the behaviour of hybrid FRP-steel reinforced concrete beams can help design beams that meet required performance early in the design stage.

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