The Vibration Frequencies of Wind Turbine Steel Tower by Transfer Matrix Method

Large-scale wind turbine structure is simplified as a slender cantilever beam with variable sections subject to complex loads configuration. An analytical procedure to estimate not only natural frequencies but also vibration mode shapes of thin-walled tubular beam by transfer matrix method is presented. The dynamic transfer matrixes of bending and torsional vibration are derived from directly solving the governing differential equations of motion for bending and torsion vibration of a straight beam. A computer code is developed to finish the details of the frequencies and mode shapes of vibrations beam, while a transfer matrix procedure has been used in developing the code. Illustrative examples are worked out to show the excellent accuracy of the presented method by comparison with exact solutions by FEM simulation. It is believed that, transfer matrix method, which is simple, effective and validate, will be useful to the designer in obtaining dynamic behaviours of wind turbine structure for fairly complex beam loads.