Offshore Foundations: Tripod
Image © 1997 Ramboll
The tripod foundation draws on the experiences with light weight and cost efficient three-legged steel jackets for marginal offshore fields in the oil industry.
From a steel pile below the turbine tower emanates a steel frame which transfers the forces from the tower into three steel piles. The three piles are driven 10 to 20 metres into the seabed depending on soil conditions and ice loads.
Advantages of the Tripod
The advantage of the three-legged model is that it is suitable for larger water depths. At the same time only a minimum of preparations are required at the site before installation.
The foundation is anchored into the seabed using a relatively small steel pile (0.9 m diameter) in each corner. Because of the piling requirement, the tripod foundation is not suited for locations with many large boulders.
Erosion will normally not be a problem with this type of foundation.
Suitable for Larger Water Depths
This type of foundation is not suitable at water depths lower than 6-7 metres. The main reason for this is that service vessels at low water depths will face problems approaching the foundation due to the steel frame.
Cost by Water Depth for Tripod Foundations
As in previous page, the basic difference between costs in the North Sea and the Baltic Sea is that waves determine dimensioning in the North Sea, whereas ice is decisive in the Baltic Sea. The costs include installation (1997 prices).
© Copyright 1997-2003 Danish Wind Industry Association
Updated 10 May 2003