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The elasticity of fenders is related to the ability to release the stored energy during berthing of vessels. However, it has no effect on the reaction force and the deflection of fender system. The amount of energy that a fender can absorb is dependent on the reaction-deflection curve and is represented by the area under the curve. The higher is the reaction force, the higher amount of energy would be absorbed by the fender provided that the resistance of ships’ hull is sufficient to withstand the force without permanent deformations.
Although stiff and soft fender may have the same deflection under the same maximum reaction force acting on the berthing vessel, the amount of energy absorbed by stiff fenders is much higher than that of soft fenders. Consequently, stiff fenders should be employed for berthing purpose.
On the other hand, in mooring operations where vessels are constantly subject to wave action, it is desirable to keep the tension force on the rope to a low value. In this connection, it is recommended to use soft fenders.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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One comment on "Should stiff or soft fenders be designed for berthing in piers?"
Energy absorbing is just one purpose of the fendering.
Any port, anywhere is however constructed just for one goal, for loading/unloading of ships…
During this phase the fenders also play a vital role.
Soft fenders, withstanding high shear forces, have in this respect great advantages compared with, low friction fenders, etc.
Maintained contact ships hull with fender surface is best provided when elasticity of ropes and dito of fenders are similar, etc.
Any ship that start surging along the berth, contemporarily twisted away from quay, must in some way be brought to a stop, by absorbing the inertia of ship…
If the ropes are the only contributing for this and ropes are elongating 30% this prohibits swift cranes handlings, etc…
Robust friction fenders have all advantages for a robust port!