How to Use torsional constant "J" in AISC-13th to get torsional stres?

[RobertEIT]

I know for many AISC steel shape, torsional constant "J" differs graetly from polar moment of inertia. But are we supposed to use torsional constant "J" in AISC-13th steel shape the same way as polar moment of inertia to get the torsional stress of a AISC steel shape, i.e. Tau=T*r/J?

Thanks a lot!

 

[ash060]

The Torsional Constant does not get the shear stress due to torsion except for round shapes.

It is a little more complicated than that for open shapes like W-Flanges and Channels

Check out AISC Design Guide #9 and it will help you out.

 

[Lion06]

I suggest using R instead of J as detailed in "Design of Welded Structures" by Blodgett.

 

[JAE]

Yes - Blodgett covers it well.

 

[ship4885]

Take a look atAISC Design Guide 9, it outlines torsional analysis and design of steel members.