This paper presents a 3D Nonlinear Deformation Model (NDM) utilizing a fiber-discretization approach to evaluate the spatial load-carrying capacity of high-strength concrete (HSC) columns. By integrating realistic material constitutive laws that ac-count for passive confinement, the proposed model is validated against experimental databases, demonstrating a high degree of accuracy with merely a 5.6% error margin in peak axial capacity prediction (4677.6 kN vs. 4954.0 kN). Furthermore, a comprehen-sive parametric study comparing the NDM with TCVN 5574:2018 and Eurocode 2 re-veals that current design codes critically underestimate the ultimate biaxial flexural and axial capacities by approximately 50%. The findings emphasize that neglecting the triaxial confinement effect induced by transverse reinforcement leads to highly con-servative designs, highlighting the NDM as a robust tool for performance-based struc-tural assessment.