Torsion Rotation Formulas - Open Versus Closed Shapes

[Hokie93]

It is my understanding that torsion rotation (angular twist) formulas such as those shown in Section 8.2 of "Design of Welded Structures" by Blodgett are only applicable to closed shapes (such as pipes, round HSS, and rectangular HSS) and open shapes where warping is negligible (such as angles and tee-shapes). For other open shapes, such as wide-flange shapes and channels, one would have to refer to other sources such as AISC Design Guide 9 for proper determination of member rotation in response to torsional loading. Is my understanding correct?

 

[Lomarandil]

That's my understanding. My gut feel is that ignoring warping effects would give an upper bound solution on rotation, if you can live with that.

 

[Hokie93]

Thank you for the prompt response and confirmation.

 

[gravityandinertia]

A 3D Finite Element using solid/continuum element could also model this relatively easy with warping taken into consideration. Obviously, not everyone has access to that, but it's a possibility.

 

[JedClampett]

Blodgett would be conservative on rotation, but you might overstress the member.