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RE: Analysis of pipes with large D/t ratios

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Bill,

For ASD, Troitsky recommend the same formulas as ASD, 

Fa-critical = 662/D/t) + 0.399Fy 

for 3300/Fy < D/t < 13000/(D/t)

but includes Fa-critical = 5333/(D/t) for D/t > 13000/(D/t)


Bill Scott, P.E., S.E.
Principal Engineer
VECO Alaska, Inc.
949 E. 36th Street
Anchorage, AK  99508
Phone 907-762-1655, FAX 907-762-1734

-----Original Message-----
From: Bill Allen [mailto:T.W.Allen(--nospam--at)home.com]
Sent: Thursday, October 26, 2000 10:43 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Analysis of pipes with large D/t ratios


I KNEW you would have fun with this one, Rick :o).

Nooooo, I haven't cracked open my LRFD manual yet.

In my particular problem, the D/t ratio is 7,020/Fy and stresses are due to
wind loads (seismic is miniscule).

I can't believe ASD doesn't address this problem. I know in the past (before
the HSS specifications), I've used Appendix B5.b for slender wall tubes
(i.e., 10"x10"x3/16").

Thanks,

Bill

||-----Original Message-----
||From: Rick.Drake(--nospam--at)Fluor.com [mailto:Rick.Drake(--nospam--at)Fluor.com]
||Sent: Thursday, October 26, 2000 10:22 AM
||To: seaint(--nospam--at)seaint.org
||Subject: Re: Analysis of pipes with large D/t ratios
||
||
||
||Bill:
||
||The latest and most complete slenderness ratios for
||nonseismic applications
||can be found in the LRFD specification and manual.  For
||circular HSS in
||axial compression, there is no compact section limit.  The noncompact
||section limit is 3300/Fy.  For circular HSS in flexure, the
||compact section
||limit is 2070/Fy and the noncompact section limit is 8970/Fy.
||
||For seismic applications, you need to refer to the AISC
||Seismic Provisions
||where some of the slenderness rations are tighter.  For
||circular HSS in
||axial compression or flexure, the compact section limit is
||1300/Fy.  The
||noncompact section limit is per the LRFD specification and manual.
||
||By the way, have you opened up that LRFD Manual yet?
||
||Rick Drake, SE
||Fluor Daniel, Aliso Viejo
||
||***************************************************
||
||
||
||
||
||
||"Bill Allen" <T.W.Allen(--nospam--at)home.com> on 10/26/2000 09:50:41 AM
||
||Please respond to seaint(--nospam--at)seaint.org
||
||To:   <seaint(--nospam--at)seaint.org>
||cc:
||
||Subject:  Analysis of pipes with large D/t ratios
||
||
||AISCM (ASD) Vol 9 does not really address pipe sections with large D/t
||ratios as far as I can tell. I'm sure there are local buckling issues
||related to this, but I cannot find any guidelines with the
||exception of
||Appendix B5 which addresses allowable axial stresses:
||Fa=662/(D/t)+0.40Fy.
||
||Anyone else have a better guideline?
||
||TIA,
||
||Bill Allen, S.E.