1) Dead load, main hoist rated load with the main hook 5.0 feet out
from its minimum operating radius, and the barge level. The hook load is assumed
to be suddenly released (lost) and the strain energy in the wire ropes and
structural components is permitted to pull the boom towards the boom stops. If
calculations indicate that contact is made with the boom stops, then the maximum
stresses in the A-frame and the boom stops are limited to 100 percent of AISC
One additional load case is considered:
1) For fatigue analyses: dead load with the boom at minimum
operating radius. The stress range is defined as the algebraic difference between
the stresses due to: (a) the boom directly over the section, and (b) the
counterweight directly over the section. The maximum stress range in the tub and
its connections to supporting structure in the barge should be determined. The
maximum allowable stress range is limited to 100 percent of AISC allowable values
for Loading Condition 2 (that is, 100,000 to 500,000 cycles).
Other Structural Components. Structural components and members
which are not specifically addressed above, are designed according to the criteria
to which they are related.
Barge Hull. Barge hull is designed according to the criteria of ABS
and must be submitted to that organization for review and approval.
Barge hull analysis includes the tub supporting structure, boom rest
(supporting the weight of the boom), pilot house, and the cargo deck with a
distributed load of 5000 pounds per square foot (but not exceeding 1,000,000
Container Cranes. The following structural design criteria for container
cranes are derived from informal standards of industry, port authorities, and
engineering firms specializing in the design of these cranes. In the load
combinations described below, all loads are to be applied simultaneously on the
most adverse crane configuration. In lieu of the load combinations described
below, the FEM "Rules for the Design of Hoisting Appliances" may be used, subject
to NCC approval. When analyses include secondary (P-delta) effects due to elastic
deformation of the structure and joint flexibility, the maximum allowable stresses
may be increased by a factor of 1.2, provided that the structure conforms to the
stress limits when the secondary effects are not considered. For fatigue
analyses, however, the secondary effects must be considered but with no increase
in the maximum allowable stresses.
Entire Structure (Operating Configuration). In this condition, the
boom is horizontal and supported by the boom stays. Nine load cases are
considered for normal and overload conditions:
1) Dead load, trolley dead load, live load (container weighing
89,600 to 112,000 pounds), lift system (head block, spreader, wire ropes, and
sheaves), skewing force couple (5 percent of the gantry maximum wheel loads), and
150 percent of acceleration/deceleration forces (due to gantry or trolley travel).
The center of gravity of the container is assumed to be eccentric by 10 percent
from its geometric center in the longitudinal and transverse directions (4.5 feet
on a 45-foot long container, and 0.8 feet on an 8-foot wide container).