TM 5-850-1
CHAPTER 9
FENDER SYSTEMS
9-1.
Function.
strength and feasibility for difficult seafloor conditions.
(b) Disadvantages. The disadvantages
The principal function of the fender system is to prevent
are vulnerability to corrosion and high cost.
the vessel or the dock from being damaged during the
(4) Concrete pile. Reinforced concrete piles
mooring process or during the berthing periods. Forces
are not satisfactory because of their limited internal
during the vessel berthing or anchoring may be in the
strain-energy capacity. Prestressed concrete piles with
form of impact, abrasive action from vessels, or direct
rubber buffers at deck level have been used.
pressure. These forces may cause extensive damage
(a) Advantage. The advantage is that
to the ship and structure if suitable means are not
employed to counteract them.
this pile resists natural and biological deterioration.
(b) Disadvantages. The disadvantages
9-2.
Types.
are limited strain-energy capacity and corrosion of steel
reinforcement through cracks.
General description of and applicable pertinent details
b. Retractable fender system. A retractable fender
associated with various types of fender systems are
system (fig 9-4) consists of vertical-contact posts
presented below.
a. Standard pile-fender systems.
connected by rows of wales and chocks. Contact posts
(1) Timber pile.
are normally spaced 8 feet on centers. The interval
This system (fig 9-1)
between wales is dependent on the local tide range.
employs piles driven along a wharf face bottom. Pile
Wales are fastened to holding posts suspended by pins
tops may be unsupported laterally or supported at
from specially designed brackets. The fender retracts
various degrees of fixity by means of wales and chocks.
under impact, thus absorbing energy by action of gravity
Single-or-multiple-row wales may be used, depending
and friction.
Energy-absorption capacity depends
on pile length and on tidal variations. Impact energy
directly on the effective weights, the angle of inclination
upon a fender pile is absorbed by deflection and the
of the supporting brackets, and the maximum amount of
limited compression of the pile. Energy-absorption
retraction of the system. In designing this system, the
capacity depends on the size, length, penetration, and
tide effect on weight reduction of the fender frame
material of the pile and is determined on the basis of
should be considered. Use of composite inclined planes
internal strain-energy characteristics (fig 9-2).
(a) Advantages. The advantages are
of supporting brackets and proper selection of maximum
retraction are feasible means for attaining design
low initial cost and abundant timber piles.
(b) Disadvantages. The disadvantages
capacity. Fenders are more easily removed from open
pin brackets than from slot-type. In construction, the
include:
limited energy-absorption capacity that
supporting brackets should be adequately anchored to
declines as a result of biodeterioration; susceptibility to
the associated berthing structure.
Deterioration of
mechanical damage and biological deterioration; and
timber frames does not materially reduce energy-
high maintenance cost if damage and deterioration is
absorption capacity, as is found in timber piles.
significant.
(1) Advantages. The advantages include:
(2) Hung timber. This system consists of
negligible effects of biological deterioration on energy-
timber members fastened rigidly to the face of a dock.
absorption capacity; no heavy equipment required for
A contact frame is formed that distributes impact loads
fabrication and replacement; and low maintenance cost,
(a) Advantages. The advantages are
plus minimum time loss during replacement.
(2) Disadvantages. The disadvantages are
very low initial cost and less biodeterioration hazard.
(b) Disadvantages. The disadvantages
loss of effectiveness due to corrosion or damage to
supporting brackets and high initial cost for use at open-
are low energy-absorption capacity and unsuitability for
type piers.
locations with significant tide and current effects.
c. Rubber fender systems. Rubber fenders consist
(3) Steel pile.
Steel fender piles are
of
occasionally used in water depths greater than 40 feet or
for locations where very high strength is required.
(a) Advantages. The advantages are
high
9-1
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