TM 5-850-1
(4) Tidal range construction. Where tidal
under action of winds, currents, and waves without tug
assistance.
ranges are in excess of 5 to 6 feet, provide a lower line
(2) For locations where the behavior of the
of fendering near mean low water, if possible. For open
moored ship is the governing factor, soft fenders
piers, lower fendering may be braced to pier structure.
(5) Rubbing strips.
combined with soft mooring ropes are successful in
Where vessels are
minimizing mooring forces and ship motion. A soft type
berthed against separators, use of steel or timber
fender system (e.g.
rubber-in-radial-compression
rubbing strips on fendering faces should be considered.
(6) Hardware and treatment. For pile and
fenders) tends to increase the natural oscillation period
of a moored ship so that a resonance with long-period
hung systems, use of treated timber and hardware may
waves or seiches can be avoided. The foregoing is
be optional.
Untreated timber piles should be
applicable in harbors where berthings present no
considered only for locations where mechanical damage
difficulty and are assisted with tugs; but oscillation of
is significant and where biological deterioration effect is
water in the harbor basin by seiche action is a significant
negligible. For resilient systems, timbers should be
factor governing the choice of fender.
treated and hardware galvanized, except that
(3) Where berthing operations and the
galvanizing of ogee washers may be optional. For all
behavior of moored ships seem to pose problems of
systems, cast iron bolt inserts are preferable to screw-
equal importance, it is best to choose a fender of
type inserts for attaching fenders to concrete structures.
(7) Moving parts.
intermediate type, one that can act stiffly during berthing
Minimize the use of
and softly when the ship is moored.
Hydraulic-
moving parts. When used, they should be greased and
pneumatic fender systems meet such requirements.
made of hard grade steel or fitted with hard bearing
c. Maximum allowable distance between moored
points.
ships and dock face. The distance required by the
f. Miscellaneous factors related to fender system
fender system should be limited so as to avoid
inconvenience during cargo loading and unloading.
reliability in operation, and cost of maintenance. In
Generally, the maximum limit is 4 to 5 feet. No problem
addition, evaluation of systems that have given
exists if the fender system is for a tanker berth that
satisfactory service at or near the proposed installation,
involves fuel supply only.
resistance to longitudinal component of berthing force,
d. Pier type as related to fender system selection.
and ease and economy of replacement are important.
9-4.
Design procedure.
For mooring or berthing platform, consider a resilient
a. General design procedure. The design of a
fender, since the length of the structure available for
distribution of berthing load is limited. For an open pier,
fender system is based on the law of conservation of
any type of fender system may be applicable. For a
energy. The amount of energy being introduced into the
solid pier, consider use of resilient or retractable fenders
system must be determined, and then a means devised
to minimi7e vessel damage.
to absorb the energy within the force and stress
e. Structural factors. Structural factors related to
limitations of the ship's hull, the fender, and the pier.
the fender system selection are indicated below.
General design procedure for a fender system are as
(1) Concentrated loads at pier ends and
follows:
expansion joints. Fender spacing should be reduced to
(1) Determine the energy that will be
half at those bents adjacent to expansion joints.
delivered to the pier upon initial impact (table 9-3). The
Provide clusters of fender piles at the outboard end and
selection of a design vessel should be based on
exposed corners of pier. For corners subject to berthing
recommendations from the Military Traffic Management
impact or frequent use as a turning point for ship
and Terminal Service and the Military Sealift Command.
maneuvering, resilient corner fender systems should be
(2) Determine the energy that can be
considered.
absorbed by the pier or wharf (distribution of loading
(2) Projections.
Fender systems should
must be considered). For structures that are linearly
present a smooth face to berthing vessels and bolt
elastic, the energy is one-half the maximum static load
heads should be recessed. It is of prime importance
level times the amount of deflection. Allowance should
that fenders be spaced sufficiently close together to
also be made in cases where other vessels may be
prevent the prow of a vessel from getting between the
moored at the pier. If the structure is exceptionally rigid,
fenders at angles of approach up to 15 degrees (provide
it can be assumed to absorb no energy.
wales and chocks to prevent this).
(3) Subtract the energy that the pier will
(3) Integral construction. Pile, hung, and
absorb from the effective impact energy of the ship to
retractable fenders will be tightly chocked and
determine the amount of energy that must be absorbed
constructed as an integral, interlocking unit. Chocks
by the fender.
should be recessed back of vertical fender faces.
(4) Select a fender design capable of
absorbing the amount of energy determined above
without exceeding
9-5
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