UFC 4-152-01
28 July 2005
and bending of the rubber elements. The reaction force is an exponential
function of the deflection and the performance curve is quite similar for all the
shapes. Fenders having a curved rather than flat external surface increase in
stiffness more gradually as the area of contact increases during deformation. All
these fenders experience a sharp and rapid increase in stiffness when the
amount of deflection completely collapses the open bore, regardless of their
external contour.
Side-loaded rubber fenders will not absorb large amounts of energy and
generally are not used alone. They are usually provided at the top of fender piles
between the wale and berthing structure. A series of diagonal chains from the
structure to the wale completes the system. When used with tight fitting joints
between chocks, wales, and pile head, and when proper tension splices that
provide compression and tension continuity along the face of the berth are used,
the system has worked very well in both naval and commercial facilities. Ships
may be berthed either directly or a floating camel may be used. When camels
are used, size the fender piling to resist the resulting bending.
Both timber and steel piles have been used successfully, with timber being the
more common. Prestressed concrete piles are also a viable alternative,
exhibiting high-energy absorption capabilities. This type of system provides good
berthing flexibility. Ships of different sizes, tug boats, submarines, and barges
can be accommodated without any modification. However, when used with
floating camels, which tend to cock between the ship and the piles, the ships
energy may become concentrated on just one or two piles. Hence, unless the
floating camel is tightly secured to the piles (guided by piles), the system may be
subject to increased damage. The pile-rubber system is not recommended for
solid and other types of piers and wharves where full deflection of the piles within
the working range will be prevented. When this system is employed throughout
the length of berth, size the rubber fender units for direct berthing of ships
(without the use of camels).
5-3.3.4
Floating Fender Units.
This system consists of pneumatic or foam-filled fender units and a backing
system. As the fender units can be positioned to float with the tide, several
surface ship types can be handled. Design the backing system to work with the
fender unit for the full tidal range. Because the floating units are usually rather
large, they provide a good standoff. The berthing structure may be designed with
the backing system at different points along the length of berth and the fender
units moved around as berthing plans change. When clustered piles or sheet
piles are used for the backing system, additional energy can be absorbed by the
piles and their support systems at the deck level.
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