28 July 2005
than rail-mounted cranes. To this end, a wheel load of 110,000 lbs (4990 Kg)
minimum on 4-ft (1.2m) centers allows for a practical range of options. See Table 3-
2 for typical rated capacities of cranes for a variety of pier and wharf deck uses.
Figure 3-1 lists a sampling of wheel loads for 60 ton and 151 ton capacity portal
cranes recently procured by the Navy. These cranes were procured around
capacities of existing piers and wharves and have wheel loads that are somewhat
restrictive for new design. The values provided are typical for existing equipment
used by the Navy and are useful for design feasibility studies on existing structures.
The rail gage should be approximately 30 feet minimum for a 60 ton capacity portal
crane, and up to 40 feet for a portal crane of 100 tons capacity greater. For handling
of fuel containers at Repair or Fitting Out Piers, portal cranes with up to 151-ton
capacity are required.
See Figure 3-2 for crane configuration and wheel loads of container cranes and
Table 3-2 for the rated capacities of container cranes applicable to piers and
wharves. The configuration and wheel loads are derived from several
manufacturers and should be used only as a guide. A recent trend in the shipment
of containerized cargo is to use larger ships, and this is the driving force in the
design of container cranes. The size of the ship to be serviced will dictate the
capacity, configuration, operational characteristics, and gage of the crane. The
evolution in container crane design has been to increase the gage to 100 ft (30.5 m)
and outreach on the boom to 150 ft (45.7 m) and larger while maintaining the lift
capacity between 40 and 50 long tons. Hence, specific information on the size of
the ship to be serviced and details from the crane manufacturer needs to be
obtained for final crane design.
Wheel Load Uncertainty.
Portal and container cranes are usually procured separately from the construction
funds. The maximum allowable wheel loads are normally specified on the crane
procurement documents. The number and spacing of wheels are critical to the
structural capacity of an existing facility and structural design of a new facility.
Having established the required capacity and configuration of a crane, the designer
of a pier or wharf should consult with the Navy Crane Center and obtain wheel loads
for which the supporting structure should be designed. In the absence of hard
information, the 110,000 lb (4990 kg) wheel load presented in paragraph 3-3.4.1
may be used for portal cranes. However, the container crane wheel loads presented
in Figure 3-2 are only provided as a guide. The design characteristics noted in
paragraph 3-3.4.2 must be determined in order to determine realistic wheel loads.