28 July 2005
former will lose its strength completely when punctured by ship protrusions and
that the latter may lose a significant part of its energy-absorption capacity under
repeated heavy loadings.
These behaviors are illustrated in Figure 5-14.
Evaluation of Fender Systems.
Equal Energy and Reaction.
Figure 5-14(A) illustrates the reaction-deflection characteristics of the three types
of fender systems. The area under each of the reaction/deflection curves
represents the energy absorbed by that type of fender. Each of the curves in the
figure represents fender systems with equal rated reactions and equal energy-
absorption capability. It is evident from the figure that, while the fenders of the
various types illustrated provide equal energy absorption at equal rated
reactions, the energy-absorption capacity is achieved through different
deflections, with the buckling type deflecting the least.
Equal Reaction and Deflection.
A comparison of the various types of fenders may alternatively be considered on
the basis of equal rated reaction and equal deflection, as illustrated in Figure 5-
14(B). This situation often occurs when new fender units are installed in
conjunction with, and compatible with, an existing fender system. It may also
occur when a replacement fender system is installed in an existing facility with
cargo transfer equipment of limited reach. It is evident from the figure that the
buckling type fenders have considerably more energy-absorption capacity for the
same reaction and deflection than the other types.
Reaction versus Energy Absorbed.
Comparing the various types of fender systems from the point of view of the
reaction force that is developed for a given energy-absorption capacity, as
illustrated in Figure 5-14(C), it is evident that the pneumatic, foam-filled, and
side-loaded rubber type fender units are the "softest." They have greater energy-
absorption capacity at reaction levels less than their maximum rated reaction.
This characteristic makes these fenders particularly attractive at berths that must
accommodate a wide range of vessel sizes because the fenders will deflect
significantly even when subjected to relatively small berthing impacts.