Effect of Keying Flaps on a Multiline Ring Anchor in Soft Clay
Publication: IFCEE 2021
ABSTRACT
The multiline ring anchor (MRA) was devised as a cost-effective means for securing floating offshore wind turbines (FOWTs) to the seabed. FOWTs occurring in arrays create the possibility for attaching mooring lines from multiple units to a single anchor. Additionally, the deep embedment of the MRA into relatively strong soil permits high load capacity to be achievable with a small and lighter anchor, thereby reducing anchor material, transport, and installation costs. However, since the MRA is shorter than a conventional caisson, features such as wing plates and keying flaps are needed to achieve parity in load capacity with a caisson having a comparable diameter. Preliminary studies show that attaching wing plates to MRA in soft clay is highly effective in enhancing its horizontal load capacity, but only marginally effective in improving vertical load capacity. This motivated the current study investigating the use of keying flaps to further enhance vertical load capacity. Two-dimensional finite element analyses were conducted to understand how keying flaps impact the failure mechanism of the stiffeners and provide reliable evaluations of the uplift resistance of the MRA. The results show that the thickness of the stiffener, flap length, and flap angle can affect the failure mechanism and bearing factors. For the optimal design of the stiffener, a comparative study was carried out to compare the effects of keying flaps and thickness of the stiffener. The studies show that introducing keying flaps can have comparable load capacity with thicker stiffeners and that it can be an economical solution for achieving high vertical load capacity while containing material and fabrication costs.
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REFERENCES
Aubeny, C. (2017). Geomechanics of Marine Anchors, CRC Press, Taylor & Francis Group, Boca Raton, FL.
Bhattacharya, S. (2014). “Challenges in design of foundations for offshore wind turbines.” Engineering & Technology Reference, 1(1), 922.
Chen, W.-F. (1975). Limit analysis and soil plasticity, Elsevier.
Diaz, B. D., Rasulo, M., Aubeny, C. P., Fontana, C. M., Arwade, S. R., DeGroot, D. J., and Landon, M. (2016). “Multiline anchors for floating offshore wind towers.” Proc., OCEANS 2016 MTS/IEEE Monterey, IEEE, 1-9.
Lee, J., and Aubeny, C. P. (2020). “Multiline Ring Anchor system for floating offshore wind turbines.” Journal of Physics: Conference Series, 1452, 012036.
Lee, J., Khan, M., Bello, L., and Aubeny, C. P. (2020). “Cost analysis of multiline ring anchor systems for offshore wind farm.” Proc., Deep Foundation Institute 45th Conference, In press.
Murff, J., Randolph, M., Elkhatib, S., Kolk, H., Ruinen, R., Strom, P., and Thorne, C. (2005). “Vertically loaded plate anchors for deepwater applications.” Proc., Proc Int Symp on Frontiers in Offshore Geotechnics, 31-48.
Musial, W., Beiter, P., Spitsen, P., Nunemaker, J., and Gevorgian, V. (2018). “2018 Offshore Wind Technologies Market Report.” U.S. Department of Energy (DOE), U.S. Department of Energy (DOE).
Musial, W., Heimiller, D., Beiter, P., Scott, G., and Draxl, C. (2016). “2016 Offshore Wind Energy Resource Assessment for the United States.” National Renewable Energy Lab.(NREL), Golden, CO (United States).
O’Loughlin, C., White, D., and Stanier, S. (2015). “Novel Anchoring Solutions for FLNG-Opportunities Driven by Scale.” Proc., Offshore Technology Conference, Offshore Technology Conference.
O’Neill, M., Bransby, M., and Randolph, M. (2003). “Drag anchor fluke soil interaction in clays.” Canadian Geotechnical Journal, 40(1), 78-94.
SteelBenchmarker. (2020). “Steel price history.” <http://steelbenchmarker.com/files/history.pdf>. (Mar.26, 2020).
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© 2021 American Society of Civil Engineers.
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Published online: May 6, 2021
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