Transportation and installation tests of gravity based structures successfully completed

Published: 8 December 2017

A large test campaign addressing critical aspects of the installation and transportation of gravity based structures (GBSs) has been executed successfully. The tests were carried out by the Dutch research institutes MARIN and Deltares as part of the GBS WIND Joint Industry Project (GBS WIND JIP).

Gravity based structures are support structures held in place by gravity. They are widely used in civil engineering and the oil and gas industry. Recently several designs of gravity based wind turbine foundations for offshore wind turbines have been developed. An example of this is the Blyth Offshore Wind Demonstrator, where five MHI Vestas 8MW turbines were installed on gravity based foundations designed by BAM.

 

The movements of gravity based structures during transportation and installation are not captured well by standard design methods. Nonlinear, viscous effects such as Vortex Induced Motion (VIM) and galloping in particular are not computed accurately. MARIN and Deltares have therefore executed a large test campaign as part of the ongoing GBS WIND JIP.

Better understating of the dynamic behaviour

By combining expertise and laboratory facilities, MARIN and Deltares have been able to consider the full operation, from port to fully ballasted on the seabed. “We have created a truly unique data set which has given us a better understanding of the dynamic behavior of gravity based structures during transportation and installation. We have not been able to investigate phenomena such as VIM during installation in this level of detail before.”  said Dr. Bo Terp Paulsen, project manager at Deltares. The tests were performed in three model basins over the course of 14 weeks.

In the next phase of the project, the improved numerical models will be used to drive simulators at MARIN and tugboat captains will be able to practice critical moments of the transportation and installation phases. This will provide valuable feedback for the engineers and designers so that future foundations can be optimized for stability as well as safe marine operations.

The GBS WIND JIP was initiated by: MARIN, Deltares, ECN, Witteveen + Bos and Vuyk Engineering and the following company’s joined the JIP: Deme, Besix, Saipem, Jan de Nul, Statoil, Strukton, Bureau Veritas, ALP Maritime and MonobaseWind.