Research on the strengthening and retrofitting methods of existing wind turbine foundations with embedded‐ring

Higher demand for the load‐bearing ability of supporting foundations is required if its upper wind turbine is substituted by a larger one. Presently, there is a lack of strengthening and retrofitting methods for existing wind turbine foundations. A combined‐connection retrofitting method by adding anchor bolts to the existing wind turbine foundation with embedded‐ring is prompted in this study. Furthermore, a strengthening measure by adding a stiffening beam, expanding the foundation plate, and adding rock bolts to increase the ability to resist basal bending moment is proposed. Finite element analysis is conducted to analyze the effectiveness of the proposed strengthening and retrofitting methods for a 2 MW wind turbine foundation. The result shows that the peak stress of embedded‐ring is decreased by 36% by using the internal combined‐connection, and the peak tensile stress of concrete is reduced by 4.0%. When the external combined‐connection is adopted, the peak stress of the embedded‐ring is reduced by 69.3%, and the peak tensile stress of the concrete is reduced by 26.0%. It illustrates that the external combined‐connection method is more effective to increase the load‐bearing capability of the connection than the internal combined‐connection method. Additionally, the proposed strengthening measure by adding a stiffening beam, expanding the foundation plate, and adding rock bolts is effective to decrease the responses of foundation. The maximum tensile stress of concrete, the maximum compressive stress of concrete, and the maximum stress of the embedded‐ring are reduced by 19.8%, 31.3%, and 22.2%, respectively. To summarize, the proposed strengthening and retrofitting methods are capable of ensuring the safety and stability of higher‐power wind turbine operation. When upper wind turbine is substituted by the one having higher hour power generation, the height of wind turbine tower and the length of its blade will increase. There are two obstacles to reuse existing embedded‐ring foundation. Firstly, the connection strength between wind turbine tower and its embedded‐ring is not enough to resist increased basal overturning moment. Secondly, the load‐bearing capability of total foundation should be improved. Highlights are as follows: 1. A combined‐connection construction by adding anchor bolts to existing wind turbine foundation with embedded‐ring is prompted in this study. 2. A strengthening measure by adding stiffening beam, expanding foundation plate