17.05: Advanced framework for suction bucket jacket design

ABSTRACT The suction bucket is a well know foundation concept from the oil and gas industry and the concept is now adopted in the foundation of jacket substructures for offshore wind turbines. The suction buckets transfer the loads from the jacket to the soil and it is essential to include the jacket‐bucket‐soil interaction. Ramboll has developed a framework for the design of suction buckets, where both in‐place and installation scenarios are included. In this paper, we will discuss the important features included in the framework and the steps required delivering an optimized and fabrication friendly bucket design. A major challenge is to determine the foundation loads and corresponding soil stiffness for the jacket design and installation support conditions for the bucket design. It is essential to assess the short and long‐term global and local interaction between jacket/bucket as well as the bucket/soil interaction during installation to ensure that the strong suction pressure can be safely applied. The interfaces between the structural and geotechnical designs are further challenging for multiple foundations in a wind farm with varying water depths and soil conditions. The importance of focus on the safe design of this thin walled structure and the importance of managing the interfaces in such projects are highlighted in this paper. The framework for verification of suction bucket foundations involves the interfaces between geotechnical design, efficient load calculation, structural design and production. A detailed design involves numerous calculations on the buckling capacity of the bucket skirt and lid subjected to ultimate loads as well as design for fatigue.