Measurement of the natural frequency and mode shape of prefabricated concrete wind turbine towers via the DIC method

The safety of wind turbines can be severely compromised by resonance between wind turbine towers and rotors. Traditional methods for measuring the natural frequency of wind turbine towers require sensors to be placed at specific measurement points, which can be challenging due to the large sizes and complex structures of the towers. This study introduces the DIC method, which uses the random speckle patterns on an object’s surface as carriers of deformation information, enabling full-field displacement and strain analysis.

The DIC method was employed to measure the natural frequencies and mode shapes of concrete towers. The results show that the first natural frequencies of the concrete tower under three operating conditions—turbine during stoppage, stable operation, and transition from stoppage to stable operation—are 0.2631 Hz, 0.2636 Hz, and 0.2782 Hz, respectively. The second natural frequencies are 0.8624 Hz, 1.0397 Hz, and 0.8374 Hz, respectively. The first-order mode shapes correspond to unidirectional bending of the tower, and the second-order mode shapes correspond to reverse bending.

The study demonstrates that the DIC method can effectively avoid the potential safety risks and implementation difficulties associated with traditional sensor-based approaches. It is fast, convenient, and has been validated by numerous studies. The findings of this research provide a new approach for the measurement of natural frequencies and mode shapes of wind turbine towers, contributing to the safe design and operation of wind turbines. The work titled “Measurement of the Natural Frequency and Mode Shape of Prefabricated Concrete Wind Turbine Towers via the DIC Method”, was published on Prestress Technology (published on Dec.30,2024).