UFC 4-152-01
28 July 2005
5-4.3.4
Accidental Overloads.
Also to be considered in the selection of a fender system are the consequences
of an accidental overload of the system. The buckling and side-loaded rubber
fenders "bottom out" if compressed beyond their maximum rated deflection, with
resultant high reaction forces and the potential for severe damage to the berthing
vessel and the support structure. The reaction of flexible pile fender systems will
continue to increase at a uniform rate when overloaded until the yield stress of
the pile material is reached, at which point continued deflection will occur as the
material yields with no appreciable increase in reaction. Foam-filled fenders,
when compressed beyond their maximum rated deflection, will exhibit a steadily
increasing reaction and will incur permanent deformation and consequent loss of
future energy-absorption capacity. The pneumatic fenders are normally fitted
with relief valves so that when overloaded they continue to absorb energy with no
increase in reaction beyond that which corresponds to the relief valve setting and
no permanent damage to the fender unit.
5-4.4
Fender System Design.
5-4.4.1
Ship Contact.
While the ideal berthing process would attempt to engage as many fender units
as possible, in reality, at the time of impact, the ship will be at a slight angle to
the berth and contact will be made over a small length. Design discrete fender
units such as the buckling column type or the floating type, for one unit providing
the full energy with a minimum of two units installed per berth. For the
continuous system using flexible piles and fenders, the length of contact will be a
function of the ship's hull radius at the level where contact is made, the flexibility
and spacing of fender units, and the stiffness of the chock and wale assembly in
the horizontal plane. The problem is analogous to a beam on an elastic
foundation. In the absence of more rigorous analysis, the following assumptions
for contact length may be made:
20 ft (6.1 m) for cruisers, destroyers, and frigates.
40 ft (12.2 m) for battleships, amphibious warfare ships, and
auxiliary ships.
When berthing is made with camels, assume only one camel to be in contact at
the time of impact, with a minimum of two camels installed per berth. Where the
camels are guided by fender piles, assume all the piles to be effective in sharing
the energy. When free-floating camels are used, not all the piles backing the
separator will be effective. Local experience should dictate and a more
conservative assumption should be made.
5-4.4.2
Allowable Hull Pressure.
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