28 July 2005
The working energy (Ewc) must be no more than 2/3 of the nominal
pile energy (Enc). This provides a minimum factor of safety of 1.5 in
case of overload of the pile.
Coefficient of Friction.
As the ship is berthed against the fender system, there will be force components
developed in the longitudinal and vertical directions also. As the coefficient of
friction between rubber and steel is very high, special fender front panels have
been developed with reduced friction coefficient. Ultra high molecular weight
(UHMW) plastic rubbing strips have been successfully used in front of timber
piles. The following friction coefficients may be used in the design of fender
Timber to steel ................ 0.4 to 0.6
Urethane to steel.............. 0.4 to 0.6
Steel to steel .................
Rubber to steel ................ 0.6 to 0.7
UHMW to steel ..................0.1 to 0.2
Fender piles, backing members, etc., are not affected by temperature fluctuations
and can be expected to perform normally. However, in colder temperatures,
rubber fender units become stiffer and their performance will be affected
significantly. Hence, evaluate the energy-absorbing capability of the rubber unit
and the fender system as a whole based on the lowest operating temperature
expected. Carefully design and detail UHMW rubbing strips which have a
significantly higher rate of expansion than steel or concrete to operate effectively.
Provide all corners of piers and wharves and entrances to slips with fender piles,
rubbing strips, and rubber fenders for accidental contact with ships or routine
contact with tugs. Use any of the different types of fender piles mentioned. See
Figure 5-15 for typical details.
Chains are commonly used in fender systems when a tension member is
needed. Chains are used in continuous fender systems and large buckling and
cell type units to resist the sudden energy released. For pneumatic and foam-
filled resilient fender units, the chain is used to suspend the units. Chain smaller
than 3/8 in (9.5 mm) is not recommended. For better corrosion resistance, zinc