Shell offset - modal vibration

Tim_Gowing

Victor,
I have defined shell offsets and all is good for static 3d analysis. The offsets cause a pre-processor error when the analysis is switched to modal vibration 3D. Is this error to be expected? If so, is this a fundamental restriction or could it be eliminated in the future?
Tim

Victor

Unfortunately, offset shells won't be correct with dynamics because the offset is ignored in generating the mass matrix. That means the mass is at the mesh nodes while the stiffness is offset, so there's a spurious rotational inertia. If you don't mind neglecting that, you could use it anyway. But in that case, it might be just as good or better to zero all the offsets.

Tim_Gowing

Victor,
Ok, thank you for explaining, I'm fine with that.
Tim