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RE: seaint Digest for 27 Jul 2004

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IMHO, I think the point the plan checker is trying to get across is that
shear tabs are weak in torsion compared to a double angle connection.  If
possible, you should consider just changing the detail to a double angle
connection.  Also, I think trying to find out the torsional resistance of a
shear tab from AISC may prove to be futile.

Brian S. Bossley, EIT
Ventura Engineering
7610 Olentangy River Rd.
Columbus, OH 43235
(614) 847-1110 x121


-----Original Message-----
From: Jordan Truesdell, PE [mailto:seaint(--nospam--at)truesdellengineering.com]
Sent: Wednesday, July 28, 2004 8:15 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: seaint Digest for 27 Jul 2004


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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