19 June 2001
Floating structures, such as buoys and landing floats, when used in
combination with closed-cell foams.
Deck hardware such as lighting posts, grating, utility line hangars,
and handrails on piers.
Filament wound piping for lightweight, low temperature pipelines
transporting steam condensate, seawater, freshwater, sewage, oil,
and potable water.
Carbon fiber sheets, strips, and rods are used to upgrade existing pier
decks. The sheets and strips can be used by bonding them to the underside of
the deck and the rods embedded into the top deck for negative reinforcement.
These techniques can increase the shear capacity of the deck to permit greater
loads. For more information see Chapter 7 on concrete.
FRP are a composite of resin and fibrous material. The common resins
are polyester and epoxy. Polyester resins are general purpose resins that cost
less than epoxy. Epoxy resins have superior strength properties, greater
resistance to chemical and water degradation, and lower shrinkage during curing.
Materials used as reinforcement for FRP include: continuous strands,
woven cloth, chopped fibers, and in some cases, glass flakes.
Plastic and Fiberglass Piles. Piles made primarily of plastic or
fiberglass are being used as replacements for timber fender piles. Among the
plastic piles are recycled plastic piles of which there are two basic types. One
type uses a steel pipe core encapsulated in a mixture of high density and low
density polyethylene. The second uses either steel or fiberglass rebar as the
reinforcement in high-density polyethylene (HDPE). Early versions of the plastic
piles had problems associated with cracking of the outer skin. Later editions of
the plastic piles have had fewer cracking problems attributed to them. In addition
to the plastic piles, there are fiberglass piles that consist of a fiberglass tube,
which can be filled with concrete for increased strength. The fiberglass piles have
performed extremely well as fender piles.
In general, the fiberglass tube type piles that are filled with concrete
provide more stiffness than the plastic piles. However, the fiberglass piles are
vulnerable to abrasion. High- density polyethylene or ultra high molecular weight
polyethylene (UHMW) should be used as a rub strip on the fiberglass fender
piles. Both the plastic and composite fender piles have been employed
successfully at many Navy piers. Most of the plastic and composite piles have
been used as part of the secondary fendering system. It is recommended that the
plastic and composite piles not be used as the primary fendering system at this
time. Furthermore, the plastic and composite piles are not recommended for use
as bearing piles. Currently, there are no ASTM or other industry standards for
these piles, but they are being developed.