Abstract
Suction Bucket Jackets (SBJs) need to be fundamentally designed to avoid rocking modes of vibration about the principal axes of the set of foundations and engineered towards sway-bending modes of tower vibration. Whether or not such type of jackets exhibit rocking modes depends on the vertical stiffness of the caissons supporting them. This paper therefore derives closed form solutions for vertical stiffness in three types of ground profiles: linear, homogenous, and parabolic. The expressions are applicable to suction caissons having an aspect ratio (depth: diameter) between 0.2 and 2 (i.e., 0.2 < L/D < 2). The work is based on finite element analysis followed by non-linear regression. The derived expressions are then validated and verified using studies available in literature. Finally, an example problem is taken to demonstrate the application of the methodology whereby fundamental natural frequency of SBJ can be obtained. These formulae can be used for preliminary design and can also be used to verify rigorous finite element analysis during detailed design.
Highlights
IntroductionThere are new entries to the market including Taiwan (through the Formosa 1 and 2 offshore wind farms) and in the final planning stages for the
This paper aims to tackle one aspect of that where solutions are provided for rigid caissons through numerical modelling
The numerical model compares well with the formulations provided in the literature which justifies the method of extraction, the mesh used, the extent of the boundary conditions, and the rigid body assumption applied in the finite element model
Summary
There are new entries to the market including Taiwan (through the Formosa 1 and 2 offshore wind farms) and in the final planning stages for the. The limitation of the high computational cost and modelling complexities make it impractical to be utilised in preliminary design stages, yet useful in verifying the final design of the foundation. Both approaches (i.e., analytical and numerical solutions) tend to idealise the structural dynamics problem through replacing the foundation by a set of lumped springs or in the case of deep foundations distributed springs.
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