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Wind turbine structures – recent developments regarding fatigue design

Wind energy is already significant among the renewable energies and will become even more important in future. The development of wind turbines with heights between 100 m and 160 m provides new challenges for tower structures. The towers are usually made of steel. However, hybrid towers are also common for high towers. This paper gives a brief overview on the current situation of the wind energy market and the consequent challenges for wind turbines towers. Then, the concepts of steel and hybrid towers are presented as well as typical design guidelines of wind turbines with the focus on recent developments. The paper focuses on the challenges and possible innovative solutions concerning the fatigue verification of towers made of steel. In particular, attention is paid on the recent developments regarding the influence of the size effect as well as thickness transition of thick plates of the fatigue verification.