Abstract
High-cycle fatigue loads caused by environmental and parametric harmonic loads play a vital role in the design of offshore wind turbines, since cumulative damage in the structural material during the service life may lead to failure. The structural modal parameters in term of eigenfrequencies and damping ratios are random with probability distributions and cannot be fixed on deterministic values due to physical and statistical uncertainties related to the soil properties. In this paper, a comprehensive study is performed on the dynamic response of an offshore wind turbine installed on a monopile. The aim is to evaluate to what
extent a change of the soil properties affects the fatigue loads for parked conditions. Based on consistent lumped-parameter models calibrated to semi-analytical impedance functions of a monopile embedded in a linear viscoelastic soil layer, fully coupled aero-hydro-elastic simulations are conducted in the nonlinear multi-body code HAWC2. Correlation of wind speeds and waves is derived on basis of wind–wave scatter diagrams from the North Sea. Slight changes of the soil stiffness, the soil damping and the presence of sediment transportation at seabed are shown to be critical for the equivalent fatigue moment at mudline that may change with more than 30%.
extent a change of the soil properties affects the fatigue loads for parked conditions. Based on consistent lumped-parameter models calibrated to semi-analytical impedance functions of a monopile embedded in a linear viscoelastic soil layer, fully coupled aero-hydro-elastic simulations are conducted in the nonlinear multi-body code HAWC2. Correlation of wind speeds and waves is derived on basis of wind–wave scatter diagrams from the North Sea. Slight changes of the soil stiffness, the soil damping and the presence of sediment transportation at seabed are shown to be critical for the equivalent fatigue moment at mudline that may change with more than 30%.
Original language | English |
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Journal | Ocean Engineering |
Volume | 101 |
Pages (from-to) | 227-234 |
Number of pages | 8 |
ISSN | 0029-8018 |
DOIs | |
Publication status | Published - 2015 |
Keywords
- Fatigue
- Lumped-parameter model
- Soil dynamics
- Wind turbine