Lateral Undrained Capacity of a Multiline Ring Anchor in Clay
Publication: International Journal of Geomechanics
Volume 21, Issue 5
Abstract
Offshore wind energy is an attractive alternative in pursuing the nation's clean energy goals due to the significant demand for electricity in the coastal areas of the United States. Locating sites further offshore in deeper water can provide stronger, more consistent wind power resources and can mitigate aesthetic concerns. This motivates a need for improvements in the floating offshore wind turbine (FOWT) technology. As foundation costs comprise a significant fraction of the total cost for offshore wind power development, reducing the cost of the mooring system can play a significant role in making floating offshore wind economically competitive. Previous studies led to the development of a novel, efficient multiline ring anchor (MRA) system that can provide significant capital cost savings. Preliminary research shows that the MRA has a clear advantage under lateral loading by attaching wing plates to the cylindrical core of the anchor. In this study, two-dimensional finite-element (2D FE) analyses were performed to understand how wing plates affect the MRA performance under horizontal loading and provide reliable estimates of the ultimate load capacity. The results show the collapse mechanisms and bearing factors can be affected by width, the total number of wing plates, and load angles. This study also presents plastic limit analysis (PLA), based on the upper bound solution, to validate the 2D FE results by comparison and to confirm whether the postulated collapse mechanism was correct. The results obtained in the current study indicated that PLA can be a benchmark solution to evaluate the ultimate load capacity of the MRA with a satisfactory agreement with the FE-computed values.
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Data Availability Statement
All data, models, and codes generated or used during the study appear in the published article.
Acknowledgments
The authors acknowledge the support for the second author from the National Science Foundation, award number CMMI-1936901, and the Texas A&M High Performance Research Computing facility for the use of their resources in running the numerous finite-element analyses supporting this study.
Notation
The following symbols are used in this paper:
- Ap
- projected area of the MRA;
- D
- diameter of the cylinder part of the MRA;
- rate of energy dissipation;
- E
- Young's modulus;
- F
- applied load;
- H
- lateral resistance of the MRA per unit length;
- L
- characteristic width of MRA;
- Lp
- projected width of MRA normal to load direction;
- Np
- dimensionless unit lateral bearing factor;
- Npc
- H/(suD), lateral bearing factor based on D;
- Npp
- H/(suLp), lateral bearing factor based on Lp;
- Nw
- number of wing plates;
- su
- undrained shear strength;
- v0
- velocity of the anchor in the loading direction;
- vn
- v0 cos β, v0 cos δ;
- vt
- v0 sin β, v0 sin δ;
- Ww
- width of the wing plates;
- α
- adhesion factor between pile and soil;
- β, δ
- angle of the triangular wedge;
- θ
- angle between applied load and the closest wing; and
- θa
- load angle from bisector between two wing plates.
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Published In
International Journal of Geomechanics
Volume 21 • Issue 5 • May 2021
Copyright
© 2021 American Society of Civil Engineers.
History
Received: Jun 11, 2020
Accepted: Dec 2, 2020
Published online: Feb 23, 2021
Published in print: May 1, 2021
Discussion open until: Jul 23, 2021
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