This chapter shows research of stability of supporting structure of onshore wind turbine foundations based on field measurements, finite element (FE) analysis and laboratory experiment. In order to investigate the relation of action-response of tower-foundation system, long-term field measurements were carried out for two existing onshore wind turbines with/without piles for its foundations. Then, the models were built up for three-dimensional nonlinear FE analyses. The damage processes of reaching failure were examined by FE models, and limit state of foundations was individually defined by fatigue limit state of concrete. Consequently, the stress-number of cycle (S-N) diagram derived from both experiment and analysis was discussed for the assessment of existing structure.
Part of the book: Stability Control and Reliable Performance of Wind Turbines