Advancing Slender FRP RC Column Design: A Novel Analytical Equation for Predicting Effective Flexural Stiffness

This paper presents a groundbreaking contribution to the field of slender fiber-reinforced polymer (FRP) reinforced concrete (RC) column design, addressing a critical aspect in the context of ACI 318-19 methodology—the prediction of effective flexural stiffness. Acknowledging the inherent differences in the properties of FRP bars compared to steel bars, this study introduces a novel analytical equation derived from an extensive simulation of 11,520 FRP RC columns. The proposed model meticulously accounts for key parameters influencing column behavior, including the concrete strength, longitudinal reinforcement ratio, modulus of elasticity of FRP bars, eccentricity ratio, and column slenderness ratio. To validate the efficacy of the new formula, a comprehensive verification was conducted on 71 FRP RC columns, combining data from existing literature (63 columns) and experimental results obtained by the authors (eight columns, detailed in a separate publication). Notably, the newly proposed equation demonstrates a conservative approach, predicting lower flexural stiffness while exhibiting no specimens in the failure zone. This conservative yet accurate prediction underscores the proposed model’s potential superiority over existing models, emphasizing the necessity for different equations tailored to the distinct properties of FRP bars. The results of this study contribute significantly to advancing the understanding and design methodologies for slender FRP RC columns, providing engineers with a reliable tool for predicting flexural stiffness in a manner that aligns with the unique characteristics of FRP materials and the latest advancements in structural engineering.