Retrofitting Methods for Existing Wind Turbine Foundations and Their Responses Under Wind Loads

As the demand for renewable energy continues to rise, the wind power industry is shifting its focus from the quantity of installed turbines to higher-capacity installations. Consequently, foundation loads increase when the upper turbine is replaced with a larger one, potentially leading to insufficient connection strength between the tower and the foundation ring. To address this issue, this study proposes two retrofit methods: The internal and external combined-connection methods. These methods aim to enhance the connection strength between the wind turbine tower and the foundation by incorporating anchor bolts, additional foundation rings, and post-cast concrete. Three wind turbine-foundation-soil finite element models were established using ABAQUS: One with the existing foundation, one retrofitted using the internal combined-connection method, and one retrofitted using the external combined-connection method. Under the same wind load, the dynamic responses of the three models were compared to evaluate the effectiveness of the internal and external combined-connection methods for foundation retrofitting. This study shows that the internal and external combined-connection methods effectively reduce the stress levels in the anchor bolts, foundation ring, and foundation, with the external combined-connection method yielding better retrofit results. After retrofitting the foundation using the internal and external combined-connection methods, the maximum stresses in the anchor bolts, foundation ring, concrete, and reinforcement cage were reduced by 35.77% and 41.84%, 34.50% and 38.36%, 23.85% and 27.87%, and 39.23% and 45.38%, respectively. However, although both methods have a beneficial effect on the wind turbine structure, their improvement is limited compared to their impact on the anchor bolts, foundation ring, and foundation.