- Offshore wind turbines are designed to balance cyclic loading from wind, the rotating machinery and the waves against the fatigue limits of the materials used. A proper understanding of the structural dynamics of the completed structure is necessary for an accurate fatigue life calculation. Early designs underestimated the initial stiffness of the soil-structure interaction of monopiles. As a result, the design models underestimated the natural frequencies, and so the fatigue life. Recent farms still see some mismatch in structural dynamics between design and the real world. The current publication will discuss the results of a unique operational modal analysis campaign that was conducted during the installation of an offshore wind farm inside the scope of SoilTwin project aiming to further improve the understanding of how offshore wind turbines behave once installed. It will be also discussed how the intermediate stages of the turbine can be used to further improve structural models.
