Vibration Control of Wind Turbines through a Novel Reduced Column Section Approach: Numerical Application to the Onshore Wind Turbine in Sassoferrato, Italy

Abstract

Abstract The Reduced Column Section (RCS) is a design approach recently proposed by the Authors to convert the transition piece of wind turbines into a passive vibration-control device. Featured with an hourglass shape and high-strength steel, the novel device combines the advantages of several approaches used in seismic engineering, such as the isolation system, the “rocking approach” design as well as the reduced beam section approach. Through proper tuning, the proposed device can be designed to modify the first natural frequency of the wind turbine and to localize the maximum stresses onto the device, protecting the remaining parts of the wind tower and foundation. In this study, the seismic response of an onshore wind turbine subjected to earthquakes is investigated. The numerical model is developed to reproduce a real onshore wind turbine located in Italy. Operational modal analysis is performed, and the experimental modal frequencies are used to validate the numerical model. Code-compliant spectrum-compatible nonlinear analyses are performed to explore the benefits obtained by adopting the novel RCS approach. Furthermore, an incremental dynamic analysis is conducted to evaluate the dynamic mitigation induced by the proposed RCS device. Results show that the proposed device is able to efficiently mitigate the effective stresses on the wind tower wall by up to 70% compared to the stresses on the existing structure.