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Modeling the shankThe shank is a very important part of the anchor because it transfers the forces exerted by the mooring line to the shank. The angle between the shank and the fluke is also of great importance, since this determines the penetration depth of the anchor and can be adjusted to match different soil types. The shank can be divided into three groups; a single shank, a twin shank and wires replacing the shank.
The single shank is the oldest and most common shank design today. It consists of a slender bar that is either square or streamlined. The dimensions of the bar can easily be fed in the computer program; the shape however needs more attention. Since the shank is shaped like a bar, the friction it experiences will primarily by caused by its form and not by the surface friction. This means that square shanks can be modeled by a single bar. For streamlined shanks model will be the same, but multiplied with a coefficient smaller than one because of the reduction in friction caused by streamlining the shank. Double shankThe twin shank allows the soil to pass more easily through and past it. The shank consists of two parallel plates connected to each other by cross members. The friction experienced by the shank is primarily determined by the soil scraping over the plates and less by is shape. The shape of the plates is less important and the shank can therefore be modeled by two square parallel plates with the same surface area as the real shank. For this approach to work the friction coefficient of a single plate in different soil types must be known. Wires instead of a rigid shankIn essence the wires are not that different from the rigid shank since they are thought during installation and can therefore be considered as very slender rods. The wires can be modeled in the same way as the streamlined shank, with a coefficient for the round shape. Of course the number of wires has to be taken into account. |
Copyright © 2005 Project group 1
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