Location of maximum shear stress for I section under torsion

You may want to check out the AISC Design Guide for torsion (9 I think). They have good diagrams showing the stress distribution through the section.

I think that you'd have two components of shear stress involved:

1) St. Venant torsion stress. I'd expect the maximum stress to occur at the top and bottom of the flanges (assumed thicker than the web).

2) Warping torsion. Since the flanges act more or less as two independent plates flexing in plane, the max stress would occur at mid-width of the flange.

In a wide flange beam, warping torsion should dominate.

So I guess that my final answer would be that the max shear stress due to torsion would occur at top of the top flange and the bottom of the bottom flange, both at the centerline of the cross section.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.