When doing section properties one of the calculcated properties is the Polar moment of inertia of the section area, at the centroid.

Polar moment of inertia is a measure of a beam's ability to resist torsion.

Today I discovered that the calculation which SW uses, requires the beam's cross section to be circular.

So a shaft or a pipe is OK, but any other shape will show incorrect values.

(the other properties in the section property report screen may be OK though.

In the Help files I can't find anything about this. Therefore I suggest that either a remark should be made in the section screen that the cross sectional shape should be circular or the calculation method for non-circular shapes and channel shapes (which are weak against twist) should be altered.

If needed I can send examples.

Regards,

Jan