Influence of Slenderness Ratio on Buckling Behavior of Reinforced Concrete Columns: A Finite Element Analysis

Reinforced concrete columns (RCCs) are critical load‐bearing elements in structural systems, where stability is often governed by buckling, particularly in slender members subjected to axial compression. While extensive studies exist on column buckling, there remains a need for integrated approaches that couple analytical formulations with advanced numerical simulations to assess slenderness ratio effects under realistic boundary conditions and nonlinear behaviors. This study investigates the nonlinear buckling response of RCCs with slenderness ratios ( λ ) ranging from 60 to 120, representing short, intermediate, and slender columns. The analysis incorporates fixed‐free boundary conditions, load eccentricities, and both geometric and material nonlinearities of concrete and steel reinforcement. Analytical predictions of critical buckling loads were obtained using the Rayleigh–Ritz energy method, while three‐dimensional nonlinear finite element simulations were performed in COMSOL Multiphysics. Validation against Euler’s classical buckling theory and experimental results from literature confirmed the accuracy of the proposed framework. Findings indicate that increasing λ substantially reduces buckling capacity, with columns at λ = 120 exhibiting approximately 35% lower critical load compared with λ = 60. Short columns primarily failed through material yielding, whereas slender columns exhibited global elastic buckling. Fixed‐free columns demonstrated up to 20% higher buckling resistance compared with partially restrained configurations. The results underscore the strength of FEM as a predictive tool and highlight the necessity of explicitly incorporating slenderness effects in RCC design to enhance resilience, optimize material usage, and improve the safety of critical infrastructure.