Long-term dynamic behavior of monopile supported offshore wind turbines in sand

• Main Authors: Lu-Qing Yu, Li-Zhong Wang, Zhen Guo, S. Bhattacharya, G. Nikitas, Ling-Ling Li, Yue-Long Xing
• Format: Article
• Language: English
• Published: Elsevier 2015-03-01
• Series: Theoretical and Applied Mechanics Letters
• Subjects: Offshore wind turbine; Long-term; Dynamic behavior; Strain accumulation; Similitude
• Online Access: http://www.sciencedirect.com/science/article/pii/S2095034915000185
• ISSN: 2095-0349

The complexity of the loads acting on the offshore wind turbines (OWTs) structures and the significance of investigation on structure dynamics are explained. Test results obtained from a scaled wind turbine model are also summarized. The model is supported on monopile, subjected to different types of dynamic loading using an innovative out of balance mass system to apply cyclic/dynamic loads. The test results show the natural frequency of the wind turbine structure increases with the number of cycles, but with a reduced rate of increase with the accumulation of soil strain level. The change is found to be dependent on the shear strain level in the soil next to the pile which matches with the expectations from the element tests of the soil. The test results were plotted in a non-dimensional manner in order to be scaled to predict the prototype consequences using element tests of a soil using resonant column apparatus.