Analytical Identification of Failure Modes and Design-Oriented Formulations in Hybrid FRP/Steel Reinforced Concrete Beams

This paper presents a simplified analytical method to identify six failure modes of hybrid fiber reinforced polymer (FRP)/steel RC beams and to predict the corresponding moment capacity. A numerical method for estimating the flexural behavior of concrete beams reinforced with hybrid FRP/steel bars in terms of failure modes, steel yielding moment and moment capacity is also developed. To demonstrate the effectiveness of the proposed methods, the outcomes obtained from the analytical and numerical analysis were compared with experimental data tested by the authors and several other researchers. The comparison showed that these methods accurately identify the failure modes and accurately predict the moment capacity of hybrid FRP/steel RC beams with an average error of approximately 5%. Moreover, a parametric study was conducted to investigate the influence of the modulus of elasticity and tensile strength of FRP bars on the failure modes, steel yielding moment and moment capacity of hybrid FRP/steel reinforced concrete beams. The results indicated that the elasticity modulus of FRP rods considerably affects both the failure modes and the ultimate loading capacity of hybrid RC beams. The increase in the elastic modulus not only increases the ultimate moment but also changes the failure modes of the beams.