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b. At submarine berths where mooring lines go down to the submarine,
locate the mooring hardware as close as possible to the waterside edge of
the bullrail to minimize chafing of the lines. Where this is not feasible, cast
a continuous smooth member, such as a bent plate, in the concrete
bullrail, as shown in Figure 4-3.
The primary load for a mooring dolphin comes from the tension in the mooring
line. It is typically constructed as an open pile supported structure. Where filled
(solid) construction is permitted, a single sheet pile cell may be used. When a
platform is provided for the dolphin, it should be large enough to allow a 3-ft-wide
(0.9 m) walking space all around the mooring hardware.
Timber mooring dolphins can be constructed from 7, 19, or 37 wood piles with a
king pile in the center and other piles arranged in a circular pattern around the
king pile. A 19-pile dolphin is illustrated in Figure 4-4(A). Limit the use of timber
dolphins to facilities not requiring high capacity mooring points. Timber dolphins
may be required for magnetic sensitive facilities. In areas with ready access to
timber piles, timber dolphins may be popular for small craft, tugs, patrol craft and
barges. For higher loads, a concrete dolphin is preferred, which is illustrated in
Figure 4-4(B). Because both timber and concrete dolphins can be expected to
move significantly (1 to 6 in [25 to 150 mm]) from the lateral load, design and
detail the access walkway to allow for this movement. For situations where
significant pile pullout capacities are needed, consider steel spin fin piles.