Resonance characteristics of onshore wind turbine tower structure considering the impedance of piled foundations

Abstract

Piled foundation is a conventional foundation type of onshore wind turbine structure. The impedance of foundations can be increased by adding piles under the cap, thus to improve the resonance characteristics of the structures. However, current designs in terms of the resonance frequency of wind turbine structures mostly assume that the foundations of the structures are fixed rigidly and influences of foundation types are ignored. In this paper, firstly, based on the study on the horizontal-rocking dynamic impedance of piled foundation, a simplified analysis method for evaluating the resonance characteristic of the wind turbine tower considering the impedance of piled foundation is established. Then, 1-g vibration model tests were conducted. Comparisons of the results from the theoretical calculations and vibration model tests verify the rationality of the proposed analysis method. Finally, the Guohua Tongliao onshore wind farm 3rd project in Inner Mongolia of China was selected as a case study on the resonance characteristics of the onshore wind turbine and the influence of the foundation impedance. The results of the onshore wind turbine show that compared with the shallow foundation, the piled foundation significantly improves the resonance performance of the wind turbine structures.