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Re: non compact pipe

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Nuts, I divided 3300 by the square root of 33000, argh.
Thanks for continuing with the reply for non compact though.
----- Original Message -----
Sent: Friday, May 18, 2001 10:31 AM
Subject: RE: non compact pipe

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. A-B5-7 to determine the effective width of the legs/sides.  Other sections such as I shapes would use A-B5-8 for their webs and Calc Qs as per B5.2.a
3) Keep in mind it states that Fa= minimum of A-B5-9 and section E2... longer sections will probably tend to be controlled by E2.
4) Bending would be as stated, eqn F3-3... a Q adjustment is not "visible" since Q=1
Greg Effland, P.E.
-----Original Message-----
From: Mark Baker [mailto:shake4bake(--nospam--at)]
Sent: Friday, May 18, 2001 11:38 AM
To: seaint(--nospam--at)
Subject: non compact pipe

AISC, 9th Edition, ASD
For a non compact pipe, 3" dia. , 14 ga, 33ksi
Appendix B5.2.a would have you adjust allowable stress by the Q factor but.... equations for Q are for single angles, stems of tees, with no mention of an applicable Q for pipe.
Am I correct in using B5.2.b equation A-B5-9 for Fa with no Q adjustment.
Am I correct in using F3.2 equation F3-3 for Fb with no Q adjustment.