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

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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