Concentrated Torque on Wide Flange

[theonlynamenottaken]

I am trying to analyze the situation of applying a concentrated torque to existing wide-flange sections. The torque is applied through a baseplate that is placed atop the top flange, and then a matching plate is placed under the bottom flange. The two plates are then connected using threaded rods (4) and effectively sandwiching the beam. I am positive that I need web stiffeners at this location due to flexure introduced to the web-flange fillet. I just don't know how to go about calculating quantity and sizing. The location of the torque application varies from midspan to immediately adjacent the end supports of the beams. The beams are simply supported by double clip angles.... any thoughts?

 

[JAE]

Wide flanges have incredibly small torsional stiffnesses so don't depend on that to stabilize whatever the WF's support.

 

[UcfSE]

Perhaps you can change the twisting moment into a couple force and design the stiffeners for that compressive couple force. There's probably some web-distortion calc you could do if you really want to check the web without stiffeners. I'd just use the stiffeners though. Other thoughts: recommend using AISC Design Guide 9. Another good reference using a difference method is "Steel Structures" by Salmon and Johnson.

 

[boo1]

The end connections must resist the end reaction.

 

[DaveAtkins]

To elaborate on what JAE hinted at, the stiffeners (if required) only resist local flange bending. The bigger issue is torsion in the overall wide flange beam. The AISC guide is an excellent resource. I have justified a double clip angle for torsion before, but an angle at each flange is better. But you must be careful how these angles are welded to the column and beam, so that you do not create a moment connection.

DaveAtkins

 

[1prsplmps1]

You can increase the torsional capacity of this WF by connecting stiffeners at the end of each side of the top and bottom flanges. Basically you'll be creating a box member, which is very efficient in torsion.