TABLE I. Dimensions and clearances.
Overall length for size A and B, minimum practicable, but not more
Overall length for size C, minimum practicable, but not more than (inches)
Overall width not more than (inches)
Overall height for size A and B, not more than (inches)
Overall height for size C, not more than (inches)
Height of upper fifth wheel plate, plus or minus one inch (inches)
Landing gear clearance, radius from center of kingpin to any point 6 inches
below upper fifth wheel plate, not less than (inches)
Ground clearance, not less than (inches)
Swing radius from centerline of kingpin to most distant point on the
semitrailer nose, not more than (inches)
3.5 Frame or frameless type. Chassis construction shall be the manufacturer's standard
frame or frameless type, but in either case, the structural integrity requirements of DoT Safety
Regulation 178.345 shall be met. Structural members shall support the running gear, upper fifth
wheel plate and landing gear.
* 3.5.1 Frame. When a frame type semitrailer is furnished, the frame shall be capable of
meeting the performance requirements specified herein. The frame shall be adequately braced to
ensure stability. When the vehicle is loaded with specified payload (see 3.2.3), and when being
towed by a truck tractor, the maximum fiber stress in any frame member shall not be greater than
33 percent of the frame material yield strength. Crossmembers shall be of full width. Bolsters
shall be of sufficient width to support the tank and to distribute the stress when the tank is loaded
with specified payload. All parts of the frame shall be completely electric arc welded.
3.5.2 Frame splices. Where frame members are spliced, joints shall be reinforced to fulfill
the dynamic loading requirements and the static loading requirements. Splices shall be designed
to avoid stress concentration. Splice welds shall be continuous.
* 3.5.3 Stress analysis. A stress analysis for the semitrailer, loaded as specified in 3.4, shall be
performed. The stress analysis shall include shear and moment diagrams and deflection
calculations. This analysis shall verify compliance of the chassis and tank structural integrity
with Safety Regulation 178.345.3 and shall at least the following calculations and diagrams: