Trust force induced vibration analysis of offshore wind turbine tower with fixed monopile platform

Trust force is one of the most dynamic forces that in all periods of wind turbine operation is to be expected. Usually, dynamic response of the wind turbine tower under trust forces is calculated using the finite element method. Finite element method has high accuracy but it can considerably increases the computational works depending on the modeling type of foundation and modeling axial force variations. In this paper, transfer matrix method is used to reduce computational works and increase the speed of analysis instead of the finite elements method. For this purpose, the wind turbine foundation is modeled using DS model and required relations are extracted to determine of wind turbine response.Then, factors affecting the dynamic response such as induction factor, wind speed variations and nacelle mass variations are examined in several case studies. Finally, the transfer matrix method obtained results are compared with the results of the finite elements method, multi body dynamics, analytical method and experimental data which show good agreement in spite of low computational cost. The study shows that the vibrations from thrust force, wind turbine towers is resonance at frequencies equal to twice the natural frequency. Therefore, in the design of wind turbine towers, tower response at 0.5×ωn also be studied.