Influencing Factors of Motion Responses for Large-Diameter Tripod Bucket Foundation

Abstract

Large-diameter multi-bucket foundation is well suited for offshore wind turbines at deeper water than 20 m. Air floating transportation is one of the key technologies for the cost-effective development of bucket foundation. To predict the dynamic behavior of large-diameter tripod bucket foundation (LDTBF) supported by an air cushion and a water plug inside every bucket in waves, three 1/25-scale physical model tests with different bucket spacing were conducted in waves; detailed prototype foundation models were established using a hydrodynamic software MOSES with a draft of 4.0 m, 4.5 m, and 5.0 m and with a water depth of 10.0 m, 11.25 m, and 12.5 m. The numerical and experimental results are consistent for heaving motion, while exhibiting favorable agreement for pitching motion. The results show that the resonant periods for heaving motion increased with increasing draft and water depth. The maximum amplitude for heaving motion first decreased and then increased with the increase of water depth and spacing between the buckets. The maximum amplitude for pitching motion first decreased and then increased with increasing water depth but decreased with increasing spacing between the buckets. The wider the spacing between the bucket foundations, the larger the heave response amplitude operators (RAOs). Simply improving the pitch RAOs by increasing the spacing between bucket foundations is limited and negatively affects motion performance during the transportation of LDTBF.

Floating Performance of a Composite Bucket Foundation with an Offshore Wind Tower during Transportation

“…Since the elastic stiffness of the air spring is smaller than that of the water spring, the resistance of the floating body with an air cushion is less than the resistance of the ordinary floating body with the same draft. As a result, the stability of the floating body with an air cushion may be less than that of the ordinary floating body [32][33][34]. In the towing process, in addition to paying attention to the motion response of the structure, the emphasis should also be placed on the air cushion and the interaction forces' response.…”

Air cushion barge platform for offshore wind turbine and its stability at a large range of angle

“…Their focus was the motions of CBF which just needs initial stability properties. Liu et al [20][21] studied a similar air cushion structure to that in [17], and gave only the properties of initial stability. Chenu at al.…”