This thesis investigates the feasibility of using concrete-filled double skin steel tubes (CFDST) as an innovative design for wind turbine towers, addressing the need for lighter, stronger, and more sustainable structures in the wind energy sector. The research is motivated by the challenges faced by the industry, including the limitations of traditional tubular steel towers, the increasing size of wind turbines, and the demand for cost-effective and environmentally friendly solutions.

The primary objective of this study is to explore whether CFDSTs could reduce steel usage while maintaining or enhancing the structural integrity of wind turbine towers, particularly in resisting local buckling under axial loads. To achieve this, both experimental and numerical investigations were conducted. The experimental phase focused on analyzing the local buckling behavior of S355 steel skins, both in single and double skin configurations, filled with high-strength concrete (C60/67). A finite element model (FEM) was developed to simulate these experiments, validate the results, and provide insights into the performance of CFDSTs under axial loading conditions.

Key findings from the study indicate that the inclusion of concrete infill significantly alters the buckling mode of the steel skins, increasing the resistance, and enhancing the post-buckling capacity. This effect was particularly pronounced in sections with higher cross-section slenderness, suggesting that CFDSTs could allow for the use of thinner steel sections without compromising structural performance, provided that optimal cross-sectional dimensions are selected. The numerical models show comparable resistance to the experimental results, though further fine-tuning of the models is necessary to enhance accuracy and better align the outcomes.

The research concludes that CFDSTs offer a promising alternative for wind turbine tower design, with the potential to achieve significant steel savings. Furthermore, suggestions for future research are presented, focusing on optimizing material selection, investigating the long-term durability of CFDSTs, and enhancing the numerical model.