GMNIA-Based Buckling Analysis of Offshore Wind Turbine Tower: A Numerical Study Using Ansys Vestas

The rapid expansion of offshore wind energy requires reliable and cost-effective structural solutions for wind turbine towers. These towers are tall, slender shell structures whose load-bearing capacity is highly sensitive to imperfections. Current design codes, such as EN 1993-1-6, provide conservative rules developed for silos and tanks, but they are not fully suited to the unique geometry and loading of wind turbine towers. This thesis investigates the buckling behavior of an offshore wind turbine tower using Geometrically and Materially Nonlinear Analysis with Imperfections (GMNIA). Finite element simulations are conducted to capture the combined effects of geometric nonlinearity, material plasticity, and fabrication-induced imperfections. Both global imperfections, such as out-of-straightness, and local imperfections, such as circumferential weld depressions, are examined under axial compression and bending. The numerical results are compared with Eurocode-based reduction factors to evaluate the adequacy of current design approaches. The study demonstrates that GMNIA provides a more realistic representation of tower behavior, especially in capturing the critical influence of local imperfections. The findings highlight the limitations of simplified design formulas and underline the potential of advanced nonlinear simulations as a verification tool for offshore wind turbine towers. By clarifying imperfection sensitivity and structural resistance, this work contributes to the development of future design methods that improve safety, efficiency, and cost competitiveness in offshore wind energy.