Evaluation of Deflection Calculation for Hybrid-Reinforced Concrete with Fiber-Reinforced Polymer and Steel Bars

This study presents a critical evaluation of the deflection calculation for hybrid-reinforced concrete (hybrid-RC) with fiber-reinforced polymer (FRP) and steel bars by employing existing expressions for the effective moment of inertia I e . A new rational and simple approach is proposed to account for concrete shrinkage restraint caused by both steel and FRP bars and modify the existing reduction factors in the expressions from ACI 318-19 and ACI CODE440.11-22. The calculated deflections by the modified expressions, as well as Branson's equation and the method specified in CSA S806-12, are compared with the experimental values from a database including 119 hybrid-RC members. The comparisons indicate that the modified expression from ACI 318-19 provides the most accurate deflection predictions. Moreover, the modified expression from ACI CODE-440.11-22, which further includes the consideration of varied stiffness along the member span, proves to be particularly effective for cases with relatively lower reinforcement ratios.