Analysis of slender FRP-reinforced concrete columns subjected to unequal end moments

The equivalent moment factor is essential for the simplified second-order analysis of the slender reinforced concrete columns subjected to unequal end moments. Various design codes for steel-reinforced concrete (steel-RC) provide the same well-established equation to estimate the equivalent moment factor. In recent years, fiber-reinforced polymer (FRP) bars have gained popularity as a means of reinforcing concrete. Design codes and guidelines for reinforced concrete are being adapted for FRP reinforcement because of their distinct material properties as compared to conventional steel bars. This paper shows that the existing equivalent moment factor expression for steel-RC columns is not sufficiently conservative to estimate the equivalent moment factor for FRP bars reinforced concrete (FRP-RC) columns. Based on the regression and percentile analysis, an equation is proposed to estimate the equivalent moment factor for FRP-RC columns. A detailed parametric study was conducted to assess the behavior and to regress the equation to estimate the equivalent moment factor for FRP-RC columns. Hence, two numerical methods, the direct curvature method (DCM) and the column deflection curve method (CDM), were implemented and validated with experimental results. Furthermore, the paper shows that the numerical method, DCM for the detailed second-order analysis with curvature distribution estimation can predict the column capacity with sufficient accuracy in comparison to the experimental results. To date, no study is available in the literature on the equivalent moment factor of FRP-RC columns, this study serves as a significant contribution and guidance for the codal committees to form design guidelines for FRP-RC columns. • Equivalent moment factor for the simplified second-order analysis of FRP-RC columns. • FRP-RC columns subjected to unequal end moments. • Numerical methods for the detailed second-order analysis of the reinforced concrete columns subjected to unequal end moments. • Equation to estimate the equivalent moment factor for FRP-RC columns.