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Re: Torsion in wide flange shapes

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In wide flange sections, torsion will induce warping normal stresses ( in your
flange ) that need to be added to your bending stresses. Therefore your
governing combined stresses would be  fa/Fa + (torsional warping normal
stresses+ bending stresses)/ Fb < 1.0 . The torsional shear stresses would be
another design check against your allowable Fv.

 Warping normal stresses can be very high. If your column cannot handle the
warping normal stresses, then you could box out your column with side plates.
Your warping stresses go away and the torsion is taken out in a pure shear
stress. Or use a tube section.


AISC's manual "Torsional Analysis of Steel Members." is a very good straight
forward design guide with a few practical examples you can easily follow.

Regards,

Nick Pitera.



|--------+------------------------->
|        |          "Harper, Mark" |
|        |          <MHarper@hdrinc|
|        |          .com>          |
|        |                         |
|        |          01/08/02 12:52 |
|        |          PM             |
|        |          Please respond |
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  |     Subject:     Torsion in wide flange shapes           |
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I have a condition where there is some torsional force introduced in the
column due to the geometry of the precast connection.  My question is
this, What unity check do I have to make if any?  Generally I would make
a combined bending  and torsional stress  check but I am not sure about
axial load and torsion.  Would it be fa/Fa + Tv/Fv <=1  Or maybe fa/Fa +
( Torsional bending stress/Fb)<=1 ???
I have ordered the AISC Steel design guide 9 on torsion, but would
appreciate any input.
Thanks,
Mark

Mark Harper PE, SE
HDR INC.
201 South Lake Ave. #705
Pasadena, CA 91101
mharper(--nospam--at)hdrinc.com
Phone: (626) 584-1706
Fax: (626) 584-1750


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