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Re: Plastic Design Selection Table (pg 2-15 to . . .)

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Thanks  Mr. Hardy.

You are right.  The basis for selecting which W sections have their Mp & Py
listed is directly related to the local buckling phenomenon of some sections
prior to reaching full yielding of the whole section, not just the extreme
fiber.  Nevertheless, since some sections with a F' or F''' less than Fy = 50
are still shown with an Mp equal to Z*Fy, the AISC Manual Tables must be taking
additional values into account, which I still cannot figure out.

Again, thanks for your comments.
ed gonzalez

>>> Dave Handy <dhandy(--nospam--at)trg.ca> 03/01/99 11:10AM >>>
Can't comment on AISC directly, however if a section is a class 3 or 4 then
the Mp or Zx is not relevant. The section must meet the width/thickness
ratios in order to be used up to the limits of full plastic behaviour.
Since the width/thickness ratios depend on fy, some sections may be class 2
for fy=44 but class 3 for fy=50.

Dave Handy. P.Eng.
The Thompson Rosemount Group.
Cornwall, Ontario, CANADA

At 10:37 AM 3/1/99 -0800, you wrote:
>Does anyone know why Mp and Py is not listed for certain W sections, for Fy =
>50?  
>
>I believe it has something to do with not complying with the requirements of
>Chapter N of AISC ASD Specs but the comments on pg 2-15 are not clear as to
>which part of the spec may affect the listing of Mp or Py, other than that it
>is not a " 'plastic design section' ".
>
>Thanks in advance,
>ed gonzalez
> 
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