SAP 2000 Shell twisting moment 1

[giofed]

Hello all,

I was convinced that the M12 component in a shell element was equivalent to the torsional moment.
But I made a benchmark with a prismatic element (1x1 sectional dimentsions), fixed at one end, with a torsional moment of 1.0 at the free edge. The element is sufficiently long (14.0).
I get M12=0.5 and not 1.0 as I expected.

However, if I make a section cut at any location, the integral value for the torsional resultant is 1.0 as expected.
Also, the nodal torsional component at each plate is 1.0 as expected.

Is there anything I am missing in the M12 interpretation?

Best

 

[JoshPlumSE]

I was convinced that the M12 component in a shell element was equivalent to the torsional moment.

Yeah, I went down that road once before. I don't think that's the best analogy.... For me, it helps to think of M12 as more like "torsional warping" stresses in a wide flange beam. It's related to torsion, but the stresses tend to distort the element rather than purely torque it.