28 July 2005
However, longitudinal cracking was encountered with these same types of piles
during construction of Pier D at Bremerton, Washington.
Composites made of concrete and steel, concrete and fiberglass, plastic and
fiberglass, and plastic and steel have been successfully employed in piers and
wharves. Composites offer many advantages over conventional materials but
often have limitations that need to be considered. Some advantages may
include improved corrosion resistance, lightweight, and ease of construction.
Some of the disadvantages may include low strength, UV light deterioration,
long-term durability and high cost.
Concrete and Steel.
Concrete-filled pipe piles, steel H-piles with a concrete casing, and steel beams
with concrete decks are the more common composite types. The concrete
casing or jacket for the steel H-piles may be required only in the splash or tidal
zone. However, due to instances of severe deterioration of the pile just below
the jacket, the jacket must be extended to ELW or to below mudline. Concrete
may also be added to steel pipe piles for deadweight purposes to resist uplift
forces or to increase the stiffness of the pile.
Concrete and Fiberglass.
Concrete-filled fiberglass piles have been used in facilities where high axial
capacities are not required. The lightweight fiberglass piles are easily installed
and do not require high capacity handling equipment.
Plastic and Fiberglass.
Fiberglass reinforced plastic piles and beams have been successfully used in
pier and wharf construction primarily as fender piles, wales and chocks.
Plastic and Steel.
Recycled plastic piles with steel cage reinforcement have also been used in pier
and wharf construction.
For deck-supported structures and for support of piping and conduits, aluminum
members are useful. However, do not use unprotected aluminum underwater or
in the splash zone. To prevent corrosion, aluminum should be electrically
isolated from adjacent materials by nonconductive gaskets, washers, or bolt
sleeves. Aluminum construction may be used in the superstructure of Magnetic
Treatment and Electromagnetic Roll piers, due to the nonmagnetic
characteristics of the material.