Vertical Sections
Hole locations for vertical members should be placed as shown in examples A and B on Figure 3.
Each vertical member should have two holes at each end, 180º apart and in line with the horizontal members. It is best if the holes are of equal size, and the combined area of the two holes at either end of the verticals should be at least 30% of the cross-sectional area.
Horizontal End Plates
Preferably, the fabrication is completely open. (See example C on Figure 3.)
• If H + W = 24” (61 cm) or larger, the area of the hole (plus clips) should equal 25% of the area of the tube (H x W).
• If H + W = less than 24” (61 cm) but more than 16” (41 cm), the area of the hole (plus clips) should equal 30% of the area of the tube (H x W).
• If H + W = less than 16” (41 cm) but more than 8” (20 cm), the area of the hole (plus clips) should equal 40% of the area of the tube (H x W).*
2. If full internal holes are NOT incorporated into the design (Alternative method)
A. Each external
vent must be as close to the welds as possible and must be 25% of the
I.D. of the pipe but not less than 3/8” (9.5 mm) in diameter. The
two holes at each end and at each intersection must be 180º apart and
in the proper location.
B. Vent holes in end sections or in similar sections must be 1/2”
(13 mm) in diameter.
C and D. Ends should be left completely open. Any device used for erection
in the field that prevents full openings on ends of horizontal rails and
vertical legs should be galvanized separately and attached after galvanizing.
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