Abstract:
To lower the Levelized Cost of Electricity (LCOE) from wind sources, the long-term performance is essential component of such cost. The required maintenance of the wind turbine foundation during the design-life time of the wind turbine may result in escalated cost. The degradation of the foundation soils’ stiffness due to the accumulation small plastic strains resulting from operating cyclic loads. The foundation’ s stiffness degradation will result in shifting of the wind turbine system natural frequency, which may result in amplification of the wind turbine or may cause resonance. The anticipated shift of the wind turbine system natural frequency during the design-life time is investigated through numerical simulations. The numerical simulations utilize advanced nonlinear soil’ s constitutive model that captures the accumulation of such small plastic strains and the associated shift in the wind turbine system natural frequency. The finite element simulations reasonably estimated the wind turbine system natural frequency over the design-life time. The study provides guidelines to estimate such shifts in the natural frequency during the design stage, which will provide control on the O & M cost.