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Simulation of Monopile-Clay Soil Interaction for Offshore Wind Turbines

Hassani, Mohammad | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53977 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Raie, Mohammad
  7. Abstract:
  8. Monopiles are large-diameter with a typical diameter of 2 to 10 meters that are used for the base of offshore wind turbines. During its life, this structure is subjected to wind, wave, and sea currents, and due to the lateral displacement of the monopile, the wind turbine base structure with a considerable height can create the effect of "P-Δ". Therefore, accuracy in modeling and accurate estimation of monopile displacements and rotations is important. At present, the lateral design of monopiles is based on force-displacement (p-y) curves. P-y curves are semi-empirical curves based on experimental results obtained on piles with a diameter of less than one meter in different soils and under static and cyclic loadings. Therefore, the use of these semi-empirical curves for monopile design can have a significant error due to the semi-experimental nature of the conservative direction. The results of Continuum and Discrete finite element analyses of this study and their comparison with each other show that the displacement of the pile head will be much more than reality and the results obtained for pile design based on final lateral bearing capacity are very conservative and increase manufacturing costs and installation. The use of curves for monopiles requires revision and calibration in accordance with the experiments performed, and finite element analyses will be highly capable in this regard. The design regulations for DNV wind turbine structures state that the use of these curves is not valid for monopiles and that the need to calibrate p-y diagrams by methods such as finite element analysis. In the first stage, continuum and discrete model analysis is performed for the monopile and then in the second stage, the discrete model is calibrated based on the results of continuum mechanics analysis. In the third stage, the results are validated based on the Reece experiment (1975). Expected results at the end of this study include a comparison of continuum and discrete modeling results, force-displacement diagrams calibrated for analysis of a specific type of monopile with specific soil under lateral loading, which leads to the proposal of a modified model for the p-y spring, which gives a more accurate result in monopile designs
  9. Keywords:
  10. Lateral Loading ; Continuum Mechanics ; Soil Continum Modeling ; Monopile Substructure ; Soil-Monopile Interaction ; P-Y Springs

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