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|  MIL-S-62294B(AT)
each frame member(s) shall be not greater than 50 percent of the frame material yield strength
or, when specified (see 6.2), 33 percent of the frame material yield strength. Under the above
cited conditions of loading, the main frame deflection shall be not greater than 2 inches. All
parts of the framing shall be completely electric-arc welded. The strength of the finished welds
shall be such that they will not fail or crack when the semitrailer is subjected to the loads and
performance requirements specified herein.
* 3.6.1 Frame splices. Where frame members are spliced, joints shall be reinforced to fulfill
the dynamic loading requirements of 3.3 through 3.4 and the static loading requirements of 3.6.
Splices shall be designed to avoid stress concentration. Splice welds shall be continuous.
Transition areas in the gooseneck and kickup shall be smooth and rounded to minimize stress
concentrations.
* 3.6.2 Frame construction. The frame shall be of the fixed gooseneck type. The main frame
rails shall be high tensile steel I-beams of not less than 50,000 psi yield strength. The kickup
frame and lower deck frame shall be reinforced and welded into a single structure. The
crossmembers shall be not more than 2-feet apart, except over wheels.
3.6.3 Stress analysis. The contractor shall perform a stress analysis for the semitrailer
loaded as specified in 3.4.2. The stress analysis shall include shear and moment diagrams and
deflection calculations. The strength of the floor, crossmembers, and outside frame members
shall not be included in calculations to compute the main frame maximum fiber stress; but the
weight of the floor, crossmembers, and outside frame members imposed on the main frame shall
be included in the total load imposed on the main frame. Stress calculations shall include
complete analysis of the gooseneck and kickup area.
* 3.7 Platform. The platform shall be of the two deck type. Each deck (lower and kickup)
shall be level and completely covered having no cutouts or protrusions. The kickup deck shall
be floored the same as the lower deck or may be completely covered with safety tread type steel
plate with a minimum thickness of 0.187 inch, exclusive of the raised tread. The lower deck
shall be floored with hardwood of not less than 1-5/16 inch uniform thickness. The lower deck
wood shall be apitong, white or red oak, or white ash as specified in MIL-W-3912. Apitong is
allowed for flooring provided the average weight shall be not less than 47 pounds per cubic foot
(pcf), with none of the individual pieces weighing less than 42 pcf, with no more than 15 percent
of moisture content at time of weighing. Laminated hardwood is not acceptable. Floorboards
shall be laid lengthwise with tongue-and-groove or shiplap joints. Flooring shall be secured with
corrosion-resistant screws or bolts. Not less than two securing screws or bolts shall be installed
at each cross sill and not less than two on each side of each butt joint. When secured from the
top, the floor shall be countersunk and the top of the countersunk screw or bolt head shall be not
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