UFC 4-152-01
28 July 2005
5-1.4
Systems Approach.
The impact energy of the berthing ship is absorbed in a complex system of
interconnected elements. For the system shown in Figure 5-1, the load passes
from the ship's hull to the camel, which is backed by a series of fender piles. The
fender piles, in turn, are supported by rubber fender units at the deck level. In
this case, the ship's energy is absorbed by the ship's hull, rubbing strips,
separator, fender piles, and rubber fenders at deck level. The system can be
modeled as shown in Figure 5-1. The energy absorbed and the force developed,
by each element can only be solved by an iterative process.
5-1.5
Functional Requirements.
5-1.5.1
Energy Absorption.
Design all fender systems for absorption of the ship's berthing energy in all the
structural types of piers and wharves.
5-1.5.2
Normal Berthing.
The fender system should be able to absorb the energy from normal berthing
operations within the working stress or acceptable deformation range as defined
in this section. Some manufacturers indicate a load deflection curve tolerance of
plus or minus 10%. If this is determined to be the case, the design reaction on
the structure should be increased by 10% and the energy absorption for design
should be decreased by 10%. Variations in the speed of testing of fenders may
affect the resulting load-deflection curves. Where the test loads are applied
rapidly, i.e., at a speed comparable to the actual ship berthing, the load-
deflection will indicate higher reaction and energy than if the test load is applied
slowly. Therefore, take care when comparing test results from different
manufacturers, and make appropriate adjustments in the factors of safety used in
design. Differences of in the order of 30% can be expected.
5-1.5.3
Accidental Berthing.
Because the fender system is less expensive than the ship or the berthing
structure, some damage to it may be permissible and acceptable. So, in the
event of an accidental situation, it is the fender system that should be
"sacrificed." Loss of the berth has a much more serious consequence than loss
of part or all of the fender system in terms of the cost and time required to restore
the facility. The cost and time to repair a damaged ship is of much greater
concern than the berth and the fender system. The accidental condition may be
caused by increased approach angle or approach velocity or a unique situation
that cannot be anticipated. In the absence of any other accident scenario,
increase the berthing energy as calculated in this chapter by at least 50 percent
and the fender system should be capable of providing this "reserve" capacity at
or near failure of the system materials.
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