Metal Sales Secondary Framing - Manual (Page 29)

PSF-29
Secondary Framing
© Metal Sales Manufacturing Corporation/ Subject to change without notice/ Effective Date 9/11
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1. Tabulated values are allowable superimposed loads (PLF) on normal 1/2:12 to 4:12 roof pitches. Purlin weights have not been
subtracted from them. They meet or exceed L/180 deflection criteria as indicated in the tables.
2. Weight of roofing material and other dead loads must be subtracted from tabulated values of purlins to determine net live
load capabilities.
3. Allowable loads have been calculated in accordance with the 2001 edition of AISI Specifications. These values are valid only
if the compression flange of the section is adequately supported laterally.
4. Consult with your engineer or architect for design applications such as very low or very high roof pitches (1/4:12, over 4:12),
floating SSR, and for uplift (suction) criteria. Sag rods of angle bracing are usually required when members are not laterally sup-
ported by sheeting on the compression flange.
5. For continuous girts, wind load values can be obtained by multiplying tabulated values by 1.333.
6. End bearing capacity must be checked using actual load, bearing lengths, and the bearing chart.
7. For full member capacity, 1/2" diameter A-325 bolts are recommended for all lap bolts.
8. Web stiffeners can be provided by welding or bolting a clip plate to the support rafters and connecting the purlins through
the web holes to the clip.
9. Tabulated values are based on a 6" bearing at interior supports. Reaction at end supports can be approximated by
the following equations:
Simple Span R = 0.50WL
2 Spans R = 0.375WL
3 or More Spans R = 0.40WL
10. Maximum live loads for deflection ratios other than L/180 can be calculated using the values tabulated as follows:
For L/240: Max. LL (PLF) = (180/240) x (Tabulated Value).
For L/360: Max. LL (PLF) = (180/360) x (Tabulated Value).
3"
SimPLe SPan
TWo SPan
THree or more SPanS
3" 3" 3"
3" 3" 6" 6" 6"
6"
L L L L
L L L
W - LB/FT
W - LB/FT
W - LB/FT