| WHARF SUPERSTRUCTURE
After the timber pile
bents have been aligned,
braced, and capped, the
construction of the wharf
superstructure is begun.
Building the
superstructure consists of
installation of the
stringers, the decking,
and the curbs or
stringpieces; and erection
of the fender systems.
Figure 11-10 shows
stringers and decking in
place.
STRINGERS
Stringer positions are
measured from the
centerline of the wharf. The stringers are toenailed to the pile caps
with two 3/8- x 10-inch spikes at each bearing point. The ends of the
stringers overlap to provide complete bearing on the pile caps. Spacer
blocks are toenailed between stringers with two 60d nails.
DECKING
Standard decking consists of 4- x 8-inch planks, which are spiked to
each stringer with two 5/16- x 7-inch spikes, and set with 1/4-inch spacing.
Openings greater than 1/4 inch may be used between planks in areas that
are subject to heavy rains.
STRINGPIECES
The stringpiece (or curb)
is placed on 2- x 10-inch
blocking, 24 inches long,
spaced on 48-inch
centers along the edge of
the deck. Stringpiece
bolts are countersunk
and the hole is seated
with bituminous
material. (Figure 11-11
shows a wharf-edge
cross-section of a timberpile
wharf.)
· When the
stringpieces are
parallel to the direction of
the wharf stringers, the
stringpieces are bolted
through the blocking, the
decking, and the stringer
end pieces.
· When the stringpieces are
perpendicular to the
direction of the stringer,
they are bolted through
the blocking, the decking,
alternate stringers, and
the pile cap.
FENDER PILES AND
CHOCKS
Timber is the most suitable
material for wharf fenders in
TO construction. Fender piles
serve the following purposes:
· They cushion a wharf from the impact of ships and protect the
outer row of bearing piles from damage.
· They protect the hulls of craft from undue abrasion.
The 3- or 4-foot extension of a fender pile above the deck level of
a wharf supplements wharfmooring hardware, but is not used for warping
a ship into or out of the berth.
Since fender piles are not part of the structural support of the wharf,
they are easier to replace than bearing piles.
Protection of Fender Piles
Protective devices that lengthen the life of fender piles are--
· A heavy timber wearing ribbon, which may easily be replaced.
It is sometimes installed along a line of fender piles at the elevation
receiving the heaviest abrasion.
· Floating logs or camels (floating fenders).
· Rope wrappings, particularly on corner fenders.
Fender Piles for Quays
Structures that are almost completely rigid, such as solid-fill quays,
sometimes have fender piles backed up with heavy springs to give a combination
of yield and resistance.
Installation of Fender Piles
Fender piles are driven at a slight batter (angle). Usually 1 to 12
fender piles are used along the outside edge of all rows of bearing piles,
except on the extreme inshore wharf sections. Every third fender pile
may extend 3 to 4 feet above the curb. The others are cut off flush with
the top of the curb.
Chocks and Wales
Chocks are timber braces placed between fender piles at the level of
the stringpiece or pile cap to hold them in position and give them lateral
stability. Chock ends should be firmly seated against the piles.
· On timber-pile wharves, each chock is fastened with two bolts
through the stringer endpiece or pile cap.
· On steel-pile wharves, each chock is bolted by 12- x 12-inch
blocks driftpinned to the ends of the stringers or bolted to the ends
of the wharf pile cap.
Wales (horizontal beams) are used at mean low water elevation when tidal
currents are swift or tidal variations are great. Wales add rigidity to
fender piles. A 12- x 12-inch continuous longitudinal timber wale is bolted
to the back fender of each pile. Timber chocks are placed between fender
piles and bolted to the line wales.
PILE CLUSTERS AND CORNER FENDERS
Pile clusters, whether at the faces or corners of wharves or acting
as dolphins (isolated pile clusters), must combine beam strength, rigidity,
and stability against horizontal stresses.
Therefore, the individual
piles that make up the cluster
must be joined so that the
cluster will act as a unit.
Mooring Piles
Clusters of three or more
piles are used to supplement
or replace wharf-mooring
hardware. The top of the
cluster is lashed together.
Mooring piles are placed at
intervals along the wharf face
when bollards and other
mooring hardware are not
avail able. A maximum of
three piles of each cluster
extends 3 feet or more above
the wharf deck.
Corner Fenders
Piles clustered at exposed
corners of the wharf, bolted
and lashed together, are
provided so that a ship may
use the corner to pivot when warping in and out of the berth. The wharf
is strongly reinforced at the corners with layers of diagonal planking
laid one across the other. This reinforcing is backed up with diagonal
batter piles.
The standard corner-fender cluster is made up of 10 piles battered for
adequate spacing at the points. Timber connectors may be used in conjunction
with the bolts to tie the piles more firmly into a single rigid member.
To avoid undue abrasion to ship hulls and to outside pile surfaces, heavy
rope mats may be lashed to the clusters at the level of contact. To supplement
mooring hardware, the corner piles extend 3 to 4 feet above deck level.
Deck Reinforcing on Wood-Pile Wharves. Before stringers are set, wooden
piles battered inward are driven to support a cap, set diagonally across
each corner, and bolted to the bottom face of the other caps. Another
piece of cap timber is set to act as a strut between the fender cluster
and the diagonal cap.
The space between the cluster and the diagonal cap is then floored over
with two layers of plank each 6 inches thick, laid diagonally (and transversely
to
each other) to fill the thickness between the cap timbers. To
complete the reinforcement, stringers are set close and
spiked together over the outer half of each corner panel.
Deck Reinforcing on Steel-Pile Wharves. In steel-pile
marginal wharves and piers with corner fenders, the deck in
each corner panel is similarly reinforced with timber. Wood
piles battered inward carry a diagonal cap timber bolted to
the bottom flanges of the steel-pile caps. The diagonal cap is
strutted against the fender cluster, the diagonal layers of
plank are applied, and the stringers are set close and spiked
together, as described above for wood-pile wharves.
FLOATING LOG FENDERS (CAMELS)
Floating logs are used to absorb part of the impact shock
when a ship is berthed. They protect the surface of fender
piles while a ship is tied up. The simplest type of fender is a
single line of floating logs, each secured by two or more
lengths of 1/2-inch galvanized chain fastened to 3/4-inch
eyebolts in the fender log and the wharf pile. Some
arrangement, such as loose steel collars around the wharf
piles, is provided to allow the logs to rise and fall with the
tide.
Floating clusters of logs or strongly constructed rafts are
called camels. In addition to absorbing impact shock and
protecting fender piles from the sliding friction of a ship
moving in the berth, camels may be required to breast a
ship off the face of the wharf into deeper water.
PILE-MOORING DOLPHINS
Dolphins (Figure 11-12 and Figure 11-13, page 11-10) are isolated clusters
of piles to which a ship may be moored. The center of the cluster, called
a king pile, may be a single pile or a cluster driven vertically and wrapped
to act as a unit. The other piles are driven in one or more concentric
rings around the king pile, each
battered towards the center.
The king pile is normally
left somewhat longer than
the others for use as a
mooring post.
When composed of a cluster,
the king pile is wrapped
with at least six turns of 1-
inch diameter galvanized
wire rope, stapled to each
pile at every turn.
Two wrappings of the type
described above are used for
the pile cluster. One
wrapping is located near
the top of the cluster and
the second about 2/3 the distance above mean low water.
To further ensure that the cluster will act as a unit, the piles are
chocked and bolted together approximately 2 feet above mean low water.
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