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RE: non compact pipe
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 Subject: RE: non compact pipe
 From: "Effland, Greg" <geeffland(nospamat)butlermfg.com>
 Date: Fri, 18 May 2001 12:31:48 0500
Can't
say I am 100% familiar with use of Q for pipes but here is what I am
seeing...
For 3"
O.D. 14 gage thickness
D/t =
3/.0747 =40.1
Compact Limit per Table B5.1 = 3300/Fy = 100 for 33 ksi
steel
Based
upon this it looks like D/t < limit ... Section is Compact (Qs=1, Qa=1,
Q=Qs*Qa=1) and needs no local buckling adjustments
Assuming the shape was not compact, it looks like you
are approaching it correctly:
1)
Qs=1 for all pipes, no unstiffened elements exist in a round pipe or rectangular
tube either.
2) Qa
appears to not be calculated for axially loaded circular sections since they
don't calc b sub e. Rectangular tubes should use eqn. AB57 to determine
the effective width of the legs/sides. Other sections such as I shapes
would use AB58 for their webs and Calc Qs as per B5.2.a
3)
Keep in mind it states that Fa= minimum of AB59 and section E2... longer
sections will probably tend to be controlled by E2.
4)
Bending would be as stated, eqn F33... a Q adjustment is not "visible"
since Q=1
HTH
Greg
Effland, P.E.

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