Finite elements method can considerably increases the computational works of free vibration analysis of offshore wind turbine with fixed monopile platform depending on the modeling type of foundation,. 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 CS, DS and AF models are used and required relations are extracted to determine the natural frequencies and mode shapes for each of the models. Then, factors affecting the frequency such as water depth and added mass coefficient 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 and experimental data which show good agreement in spite of low computational cost.

Keywords: Offshore wind turbine tower, Natural frequencies, Transfer matrix method

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