Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: NDS Equation 3.3-6 (CL)

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Roger-

Well, Cd doesn't apply to short columns when they are end bearing on a plate
and Fcperp governs the design.

You wouldn't multiply the allowable stress by Cd=0.9 if the load was dead
load only?

If you don't buy Cd with regards to unbraced wood beams, what about steel
beams? If I had a cantilevered flagpole supporting a sign subjected to wind
loads and the WF flagpole had a reduced allowable stress due to unbraced
length (8th Ed. AISC F1.3), are you saying I can't multiply the allowable
stress by 1.33?

I'm sure there are many, many other examples where the capacity of a section
(using published code values) produce a reduced allowable stress which is
then multiplied by some form of a load duration factor. Yeah, yeah, I know
the "1.33" is disappearing from steel design, but it's not gone yet!

T. William (Bill) Allen, S.E. (CA #2607)
ALLEN DESIGNS (http://www.AllenDesigns.com)
San Juan Capistrano, CA

:-----Original Message-----
:From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
:Sent: Friday, April 02, 2004 10:29 AM
:To: seaint(--nospam--at)seaint.org
:Subject: RE: NDS Equation 3.3-6 (CL)
:
:Bill,
:
:When the column design requirements were based on short, medium and long
:columns, Cd could only be applied to the short and medium columns.  When,
:in
:their infinite wisdom, AF&PA rewrote the column formula into a single
:formula, they said that they (somehow) included Cd in the short and medium
:portions of the formula, but did not include it in the long portion of the
:formula.  This is an accomplishment that truly deserves recognition.  I was
:not aware that they extended this accomplishment to lateral stability which
:never was stress controlled.
:
:I don't have my NDS at hand right now, but will be looking forward to a
:response from AWC.   (No response = Cd should not be applied.)
:
:A. Roger Turk, P.E.(Structural)
:Tucson, Arizona
:
:Bill Allen wrote:
:
:. > Roger-
:
:. > What about columns (when Fcperp doesn't govern)?
:
:. > In either case, NDS allows the use of Cd.
:
:. > T. William (Bill) Allen, S.E. (CA #2607)
:. > ALLEN DESIGNS (http://www.AllenDesigns.com)
:. > San Juan Capistrano, CA
:
:******* ****** ******* ******** ******* ******* ******* ***
:*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
:*
:*   This email was sent to you via Structural Engineers
:*   Association of Southern California (SEAOSC) server. To
:*   subscribe (no fee) or UnSubscribe, please go to:
:*
:*   http://www.seaint.org/sealist1.asp
:*
:*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
:*   send to the list is public domain and may be re-posted
:*   without your permission. Make sure you visit our web
:*   site at: http://www.seaint.org
:******* ****** ****** ****** ******* ****** ****** ********



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********