William Tjaden

Civil & Environmental Engineering & Earth Sciences

Faculty Advisor: Yazen Khasawneh

Long Term Performance of Wind Turbine Foundation through Numerical Modeling

The project will utilize dynamic finite element modeling to capture the response of the wind turbine foundations to a large number of cyclic loading. The accumulation of small plastic strains will result in stiffness degradation of the foundation soils. The degradation of the foundation soils stiffness will result in a shift of the wind turbine natural frequency, bringing it closer to the operating loads frequency, which may lead to amplification of the dynamic loading and will result in excessive vibrations.

The Numerical modelling will model the foundation elements and foundation soils and track the degradation of stiffness with the number of cyclic loading. An advanced soil constitutive model that is capable of capturing the accumulation of the plastic strains and the foundation soils stiffness degradation will be utilized. The advanced soil constitutive model will be calibrated using a cyclic tri-axial laboratory data on clayey soils. The data for the calibration will be provided by Dr. Muhannad T. Suleiman from Lehigh University.

Once a soil model is calibrated, the finite element simulations will be conducted to “quantify” the foundation stiffness reduction with the number of cycles. The correlation will be used for future development in this research area. The funding for continuing the research will be seeked from the Department of Energy (DOE) and National Science Foundation (NSF.) The ultimate objective of this research is to provide guidelines for the wind turbine foundation designers to estimate the foundation stiffness during the operation design life of the wind turbines, which in turns will allow for safe operations of the wind turbine and will provide a robust technical method to evaluate wind turbine foundations for re-powering.  

William Tjaden Final Report