Response analysis of a lowering operation for a three-bucket jacket foundation for offshore wind turbines

Abstract

The dynamic complex system formed during the construction process of an offshore wind turbine foundation lifting and lowering plays one of the leading roles in the construction decision-making and process control. In this paper, the lowering operation of a three-bucket jacket foundation (TBJF) with active suffocation is examined. A series of experiments are carried out to investigate the key factors affecting the foundation dynamic characteristics and attitude control mode during the TBJF lowering process. Then, a revised Morison model considering radiation force is proposed and validated to analyze the TBJF lowering operations. Moreover, a floating vessel - TBJF coupling lowering model is established to investigate the coupled interaction of the lowering system and the operation window period of the TBJF. The results suggest that the air cushion structure can reduce the lifting weight and has a buffer effect on the slamming load. Faster lowering speed can be adopted during the TBJF lowering through the splash zone. The coupling effect between the floating vessel and the TBJF of the side layout mode far outweighs the stern layout. For the short period waves, the wave effects are the most critical factor, while the vessel coupled interaction effects are found to be critical in long period waves of lowering operation.