28 July 2005
In this system, individual fender units like the end-loaded, rubber shear, or
buckling type, are attached directly to the pier or wharf face. For narrow tidal
range in solid piers and wharves, and for narrow vessel size range, this system
may be cost-effective for direct berthing of surface ships. Although this system is
very popular in commercial piers and wharves throughout the world, it may not
be suitable for some Naval facilities. This system is subject to damage from
snagging on ship protrusions at levels of 8 to 10 ft (2.4 to 3.5 m) above the water
line and from vertical loads resulting from snags on rails and protrusions during
falling tides or from lateral loads due to snags on protrusion during longitudinal
movement of the ship.
a. End-Loaded Rubber Fenders. These work by elastic compression of
hollow rubber cylinder elements with small length-to-diameter ratios. As
shown in Figure 5-8(A), steel fender panels with special rubbing material
facing are usually required to minimize wear. The reaction force is an
exponential function of the deflection. These fenders are usually attached
directly to the pier or wharf structure in the form of a "cell fender."
b. Rubber Shear Fenders. The potential energy in these units is stored
as elastic shear deformation of the rubber. Usually, a solid rubber block is
vulcanized between two metal plates and the force is transferred through
a fender frame or panel, as shown in Figure 5-9. These fenders are highly
sensitive to proper manufacturing and installation as they depend on the
bond between steel plates and the rubber. The force-deflection
relationship is essentially linear.
c. Buckling Fenders. These fenders operate on the buckling column
principle, in which a molded column of rubber is loaded axially until it
buckles laterally. The end-loaded cylinder fenders described earlier are
actually a buckling fender in principle. Most buckling fenders are not well
suited for direct contact with a moving ship and hence are used with an
abrasion or protector panel, as shown in Figure 5-10. The reaction force
is linear up to a level when the pure compression behavior changes to the
buckling mode. Hence, initially a relatively high reaction is built up with a
small deflection, which then stays constant through the rest of the
deflection range. Because buckling fenders are intended to buckle in a
predetermined direction, any lateral deflection can significantly reduce
their effectiveness. When lateral loads in either direction (parallel to
length of berth or up/down) are anticipated, a cell-type fender is preferred.
These fenders are becoming increasingly popular for berthing very large
ships as they can absorb very high energy with a constant reaction force.
Side-Loaded Rubber Fenders.
These are hollow rubber units available in trapezoidal, circular, square, or D-
shapes that, when loaded at their side, deform by trying to flatten out. See
Figure 5-8(B). The potential energy is stored by a combination of compression