Force transfer characteristics of composite bucket foundation for offshore wind turbines

Abstract

This paper presents a new type of composite bucket foundation (CBF) for offshore wind turbines, which can be adapted to the loading characteristics and development needs of offshore wind farms due to its special structural form. There are seven rooms divided inside the CBF by steel bulkheads, which are arranged in a honeycomb structure. The six peripheral rooms with the skirt have the same proportions while the middle orthohexagonal one is a little larger. With the seven-room structure, the CBF has reasonable motion characteristics and towing reliability during the wet-tow construction process. Through extensive research into the force transfer characteristics of composite structure systems, a composite bucket foundation structure system with a curved transition part has been developed. The large bending moment and horizontal force of the wind turbine tower are transferred to and dispersed into the sea floor soil through a prestressed curved concrete transition section, the top cover of the bucket foundation, the bucket skirts, and the internal steel compartment plates. Particularly, this proposed CBF structure can effectively convert the extremely large bending moment of the turbine tower to limited tensile and compressive stresses within the foundation structure via a transition section.