Assessment of natural frequency of installed offshore wind turbines using nonlinear finite element model considering soil-monopile interaction

Journal of Rock Mechanics and Geotechnical Engineering

Subhamoy Bhattacharya¹  Djillali Amar Bouzid²  Lalahoum Otsmane³ 

[1]Corresponding author.

[2]Department of Civil Engineering, Faculty of Technology, University Saad Dahled of Blida, Route de Soumaa, Blida, 09000, Algeria

[3]Department of Civil and Environmental Engineering, Tomas Telford Building, University of Surrey, Surrey, GU2 7HX, UK

DOI  :  

来源: DOAJ

【 摘 要 】

A nonlinear finite element model is developed to examine the lateral behaviors of monopiles, which support offshore wind turbines (OWTs) chosen from five different offshore wind farms in Europe. The simulation is using this model to accurately estimate the natural frequency of these slender structures, as a function of the interaction of the foundations with the subsoil. After a brief introduction to the wind power energy as a reliable alternative in comparison to fossil fuel, the paper focuses on concept of natural frequency as a primary indicator in designing the foundations of OWTs. Then the range of natural frequencies is provided for a safe design purpose. Next, an analytical expression of an OWT natural frequency is presented as a function of soil-monopile interaction through monopile head springs characterized by lateral stiffness KL, rotational stiffness KR and cross-coupling stiffness KLR, of which the differences are discussed. The nonlinear pseudo three-dimensional finite element vertical slices model has been used to analyze the lateral behaviors of monopiles supporting the OWTs of different wind farm sites considered. Through the monopiles head movements (displacements and rotations), the values of KL, KR and KLR were obtained and substituted in the analytical expression of natural frequency for comparison. The comparison results between computed and measured natural frequencies showed an excellent agreement for most cases. This confirms the convenience of the finite element model used for the accurate estimation of the monopile head stiffness. Keywords: Nonlinear finite element analysis, Vertical slices model, Monopiles under horizontal loading, Natural frequency, Monopile head stiffness, Offshore wind turbines (OWTs)

【 授权许可】

Unknown