How to Account for Uncertainty in Soil Properties in Offshore Monopile Design by Means of Probabilistic Analysis

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2022-2-28

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Orakcı, Olgu

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Offshore wind turbines gain more importance worldwide as they contribute to reduce greenhouse gas emissions and achieve a low-carbon future producing sustainable energy. Monopile is the most commonly employed foundation type for offshore wind turbines. Monopile design requires a comprehensive assessment of seabed soil properties with depth. However, seabed soils involve inherent variability and uncertainty in material properties. Modifications to deterministic design approaches are suggested in the literature to account for uncertainties and achieve target reliability. This study aims to incorporate the uncertainty of soil properties in a probabilistic approach to reach a more reliable and cost-efficient design. Thus, a one-dimensional analysis by the p-y method is conducted to check structural stability and serviceability according to American Petroleum Institute (API) and Det Norske Veritas - Germanischer Lloyd (DNV-GL) guidelines. Hence, nonlinear springs are assigned along the length of the monopile to account for the soil-structure interaction. Analyses are conducted using OpenSees as a nonlinear solver and Python for batch runs. Monte Carlo Simulation is employed to generate random fields. Firstly, the analysis method is verified by comparing the deterministic analysis for a case study in Denmark. Then, probabilistic analysis is applied to the case study and a newly designed monopile in Belgium offshore. Results show that seabed soil variability can affect the probability of unsatisfactory performance (PUP) depending on the specific soil conditions (Denmark Case Study less than 1%, Belgium Case Study 12%). Furthermore, the selection of soil parameter distribution function can affect PUP for high coefficient of variation values.

Subject Keywords

offshore wind turbines, probabilistic, uncertainty, monopiles

URI

https://hdl.handle.net/11511/96719

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

O. Orakcı, “How to Account for Uncertainty in Soil Properties in Offshore Monopile Design by Means of Probabilistic Analysis,” M.S. - Master of Science, Middle East Technical University, 2022.