Ships tie up to wharves with lines fastened to mooring fittings such
as bollards, corner mooring posts, cleats, chocks, and pad eyes (Figure
· Bollards, single- or double-bitt, are steel or cast-iron posts
to which large ships are tied. They prevent ships' lines from riding up
off the post. Bollards may have waist diameters smaller than ton diameters
and may have caps, or projecting, rounded horns. Double-bitt bollards
are also known as double bitts or double steamship bitts. Bollard bodies
may be hollow for filling with concrete after installation They are usually
designed to take line pulls of about 35 tons.
· Corner mooring posts are usually designed to take pulls of
up to 60 tons.
· Cleats are generally cast iron, with arms extending horizontally
from a relatively low body. The base may be open or closed. Cleats are
used for securing smaller ships, tugs, and workboats.
· Open or closed chocks, generally made of cast iron, are used
for directing and snubbing lines when working a ship into or out of its
berth. A closed chock must be used when there is a change in both vertical
and horizontal directions of a line.
· Pad eyes are metal rings mounted vertically on a plate and
intended to receive a ship's line spliced with thimble and shackle. They
are used only for securing small craft.
Proper installation requires that the vertical and horizontal stress
on any structural unit on which mooring hardware is attached be partially
transferred to the wharf structure. This is done by increasing the number
and size of stringers under the hardware installation, and by providing
anchorage for mooring hardware bolts that will transfer the stress through
the pile cap of one or more bents to several piles.
The number and size of stringers are increased at the location of major
hardware items. When base widths of hardware are greater than 12 inches,
but less than 24 inches, at least two 12- x 12- inch stringers are needed.
For base widths greater than 24 inches, but less than 36 inches, three
12 x 12-inch stringers are needed; and so forth. Stringers are laid close
together and are spiked to each other and at each bearing point. Mooring
hardware bolts pass through stringers, filler blocks, and anchorage timbers.
Standard wharf structures use the following mooring hardware:
· Pier, 90 x 500 feet—six large double-bitt bollards on
each side on 100-foot centers and five 42- inch cleats on each side centered
· Offshore marginal wharf, 60 x 500 feet— six large double-bitt
bollards and five 42-inch cleats spaced as above on the outshore side
· Lighterage quay 35 x 500 feet—eleven 42-inch cleats on
For nonstandard wharf structures, mooring hardware should be installed
in numbers, types, and spacing approximately that of standard wharves.
When cleats and pad eyes are not available, every third fender pile
must be extended 3 to 4 feet above the wharf deck. Fender-pile extensions
may be used to steady a ship in the berth, but not to winch a ship into
On berths located near enough to the shore, bollards or mooring posts
may be located onshore.
Bollards and other mooring hardware are placed clear of cranes and traffic
and as close to the curb as possible. Onshore mooring anchors should be
located so that the lines will not have to be moved for traffic.
ANCHORAGES FOR HARDWARE
The following paragraphs explain the different types of hardware and
Location Between Pile Bents
To provide anchorage for heavy items of mooring hardware located between
pile bents, a grillwork of 12 x 12 timbers is bolted underneath the pile
cap (Figure 11-15). Each of the four piles directly affected by the upward
pull on the grillwork is strapped to the pile cap with 3- x 3/8-inch steel
strapping. The straps are spiked to piles and pile caps. Filler blocks
of 12 x 12 timbers are centered to receive the mooring hardware bolts.
Location on Pile Bents
Mooring hardware is also located directly over the outside bearing pile
of a bent as shown in Figure 11-16. Mooring hardware with 22-
to 26-inch bolt centers is
anchored as follows:
· Two 12 x 12 by
timbers are bolted
under the pile cap over
which the hardware is
located and to both sides
of three piles of the bent.
· 12 x 12-inch filler timbers
approximately 4 feet long
are bolted to the wharf
pile cap under the
hardware bolt location.
· Each of the three piles
directly affected by the
upward pull on the
grillwork is strapped to the pile cap with steel strappings as described
above (see Figure 11- 15).
Items of mooring hardware with bolt centers greater than 26 inches require
using timber wider than 12 inches or doubling the number of timbers, or
locating the hardware between bents using the timber grillwork anchorage
The wharf structure is longitudinally braced at the location of bollard
installations. Diagonal bracing is done from just below the pile caps
to about low-water level at the location of each bollard. The cross bracing
is bolted to each pile.
Installation of Light Items
Light items of mooring hardware with bolt centers less than 8 inches,
such as cleats, chocks, and pad eyes, are bolted through the stringpiece,
blocking, decking, and stringer end piece.