12 December 2001
from wave action. Outer armoring designs range from simple concrete cubics or
rectangulars, dense natural rock, and four-legged tetrapods (with each leg projecting
from the center at an angle of 109 1/2 from each of the other three), to solid
breakwaters made of concrete or masonry. Section VI-4-4 of the CEM summarizes
specific applications of concrete in coastal construction.
STEEL. Use of steel and considerations for appropriate applications are
discussed in Section VI-4-5 of the CEM.
WOOD AND TIMBER. Wood and timber members are widely used for
the construction and maintenance of waterfront facilities due to availability, economy,
and ease of handling relative to other construction materials. Wood can be used in
coastal projects such as seawalls, revetments, bulkheads, piers, wharves, sand fences,
and floating platforms. It's also used for temporary constructions such as formwork,
bracing, and blocking. Uses of wood and timber and applicable properties, benefits,
and drawbacks are described in Section VI-4-6 of the CEM.
COMPOSITES. Though the subject of composite materials is applicable
to the design of piers and wharves, this relatively new field is not addressed in the
CEM. Nonetheless, many of the nation's leading academic institutions are investigating
the use of fiber reinforced composite materials for concrete reinforcement.
The use of fiber reinforced plastics as an outside shell has been found to
increase the load capacity and durability of piers, wharves, and bridges. These
materials offer particular advantages over traditional reinforcements, though an
understanding of their long term performance characteristics in aggressive
environments is necessary before their use is widely accepted.
GEOTEXTILES. As strong fabrics consisting of strong woven plastic
filaments, geotextiles are predominantly used as filter cloth and are sometimes called
filter fabrics, construction fabrics, plastic filter cloth, or engineering fabrics. The most
frequent use of geotextiles in coastal construction is as a filter between fine granular
sands or soils and overlying gravel or small stones that forms the first under layer of a
coastal structure such as a revetment. A discussion of their properties and design
considerations for their application is contained in Section VI-4-7 of the CEM.