how to use torsional constant j in aisc-13th to get torsio
 

how to use torsional constant "j" in aisc-13th to get torsio
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!
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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.
i suggest using r instead of j as detailed in "design of welded structures" by blodgett.
yes - blodgett covers it well.
take a look ataisc design guide 9, it outlines torsional analysis and design of steel members.