UFC 4-152-01
28 July 2005
g.
Example Calculation. Compute the energy to be absorbed by a fender
system in a tug-assisted berthing of a vessel at a pier located in a sheltered
basin. The following information is furnished:
Water depth at berth
............... 35 ft (10.7 m)
Berthing draft, fully loaded .............. 28 ft (8.5 m)
Displacement, fully loaded ...............20,500 long tons
Length ............................................. 564 ft (172 m)
Beam . . . . . . . . . . . . . . . . . ............ 81 ft (24.7 m)
Cb
= Ce x Cg x Cd x Cc.= 0.5
= Wv2/g x Cb x Cm
Efender
v from Figure 5-3 = 0.27 fps
Cm
= 1 + 2D/B= 1 + 2(28/81) = 1.69
Efender = x (20,500/32.2)x(2250/1000) x 0.272 x 0.5 x 1.69
= 44.1 ft-kips
h.
Berthing Energy for Submarines. The kinetic method for calculating
berthing energy as explained above is generally applicable for submarines.
However, the formula for computing the effective mass coefficient (Cm) is not
applicable. Contact the cognizant naval agency, such as NAVSEA, for a
recommendation for Cm based on the model study for the specific class of
submarine. Because submarines will always be tug-assisted and berthed
against camels, the approach velocity as obtained from Figure 5-3 for sheltered-
to-moderate conditions may be used in the absence of more specific information.
5-2.1.2
Berthing Models.
a. Statistical Method. This method is based on actual measurements of
the energy of the impact at existing berths. This method is closely related
to the conditions of the site where the measurements were taken and is
dependent on the fender layout and construction, e.g., distance between
piles, and the loading condition of the ship.
b. Scale Model. This method, which makes use of a small-scale model
test of the berth to be designed in a well-equipped hydraulic laboratory or
ship model basin, suffers from the scale and viscosity effects and requires
experienced interpretation.
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