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Designing for Torsion

Designing for Torsion

Designing for Torsion

(OP)
I would like to check the torsional resistance of an I beam supporting steel joists. Originally both sides of the beam had joists - the joists meeting at the beam. The current client wants to make an openinng in one bay, leaving the loading eccentric - on one side of the beam. Any ideas on how to assess the beam's resistance under combined bending and torsion.

RE: Designing for Torsion

AISC
Design Guide 9:
Torsional Analysis of Structural Steel Members

An expert is a man who has made all the mistakes which can be made in a very narrow field

RE: Designing for Torsion

The beam doesn't have to resist torsion if the joist reaction is over the web of the beam.  The joist takes this unbalanced load in bending.  If you want to load the beam on one side of the flange, that does induce torsion, but an I beam will not resist the torsion, rather it will just twist enough to again allow the joist to take it in bending.

RE: Designing for Torsion

hokie

Re your second case; if the beam twists there is torsion in the beam.
Unless the extent of twist is limited by something other than the beam itself (eg moment connection of joist to beam) there is the possibility that the torsion is significant and must be checked.
It shouldn't be too difficult to ensure that the beam twist is limited by the joists, depending on the configuration of the connection.

ckpeng
If you're a Brit use the SCI's 'Design of Members Subject to Combined Bending and Torsion'.
If you're a Skip I believe Trahair published something in the ASI (then AISC) journal.

RE: Designing for Torsion

Just run the joist seats across the top of the beam so there is no torsion.

DaveAtkins

RE: Designing for Torsion

You could add an end plate to the joist shoe, so that the joist reaction could be considered to land over the web of the beam, but you may need to beef up the shoe so that it can handle the eccentricity which is perhaps larger than it was designed for.

BA

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