| Tweet |
Custom Search
|
|
|
||
 MIL-HDBK-1038
sheave nests, using 75 percent of the auxiliary hoist rated hook load. (Normally
whip and auxiliary hoists of variably rated cranes have constant ratings.) For
both of these boom section analyses, the boom is assumed to be at 75 percent of
each hoist's maximum operating radius.
4) Dead load, 150 percent main hoist rated load with a vertical
impact factor. This load case is applied only to the analysis of the king pin on
roller path type of cranes. The maximum stresses are limited to 133 percent of
AISC allowable values.
b)
Portal Base.
Four load cases are considered:
1) Dead load, main hoist rated hook load with a vertical impact
factor, 40 mph wind, acceleration forces due to rotate and travel motion, and
spreading or squeezing forces. The maximum stresses are limited to 85 percent of
AISC allowable values.
2) Dead load and non-operating wind load from the front, rear, or
side with the boom at the specified radius. The upperworks is positioned with the
boom in the specified direction. The maximum stresses are limited to 133 percent
of AISC allowable values.
3) For fatigue analysis: 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 allowable stress range is
limited to 100 percent of the AISC allowable values for Loading Condition 2 (that
is, 100,000 to 500,000 cycles).
4) For fatigue analysis: the stress range is defined as the
algebraic difference between the stresses due to the upperworks load case defined
in paragraph 5.1.2.4 a) (3), for the main hoist only. 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).
c)
Machinery House and Operator's Cab.
Three load cases are
considered:
1) Dead load, 40 mph wind, and a distributed roof load of 20 psf,
or the local snow load, whichever is greater. The maximum stresses are limited to
100 percent of AISC allowable values.
2) Concentrated downward load of 250 pounds at any location on the
roof.
The maximum stresses are limited to 100 percent of AISC allowable values.
3) Dead load, snow load, and non-operating wind load from any
direction.
The maximum stresses are limited to 133 percent of AISC allowable
values.
d)
Other Structural Components. Structural components and members
which are not specifically addressed above, are to be designed according to the
criteria to which they are related.
117
|
 
|
|
|
||
