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Re: seaint Digest for 27 Jul 2004

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Does your effective torque really come to much when taking the reaction force times 1/2 the thickness of the girder web? You may be able to show a negligible rotation at maximum loading with 30 minutes of pencil pushing. Alternatively, you could take the same torque and divide it by your bolt-to-bolt spacing or bottom bolt to top flange spacing to get a required resisting moment. The result will likely be one to two orders of magnitude below the connection strength and therefore negligible in your strength calculation while resisting the required torsion, QED.

If someone here can quote you chapter and verse from the AISC, that would even be better (for your stated purpose).

At 03:56 AM 7/28/2004 -0400, you wrote:
I have a steel structure with a simply supported wide flange girder
adjacent to a stair opening.  The loads from the beams come primarily from
one side and are transfered using a standard AISC shear tab connection.
There is metal deck with concrete fill on top of this girder.

The plan checker is asking me to address the torsion on this beam.  My
practice has been to not explicitly address torsion in these cases since
whatever torsion there may be will be self limiting.  While the beam may
initially apply a torsion to the girder, if the girder attempts to continue
to rotate, the beam to girder connection and the beam stiffness will act to
resist any torsion.  ACI specifically addresses this situation in ACI 318
but I do not believe that AISC does.

I am trying to figure out a polite answer other than "NO", that will not
take too much time.  Probably the best answer would be to reference a
position by AISC.   Input would be appreciated.

Mark Gilligan

Jordan Truesdell, PE

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