I have tried about 10 different models in either steel or concrete using volumetric objects.
When I run the calculation I ALMOST ALWAYS get an error saying distorted element. The problem is it takes a long time to mesh even simple objects. To make the calculation run I seem to need to have an incredibly fine mesh, which takes almost an hour to create. After the hour to create the mesh I run the analysis, only to be told there is a distorted element. So off I go to refine the mesh and wait another hour or so.
Why is it so difficult to mesh a solid?
The basic rule to mesh properly solids in Robot: you have to set FE size in the way to obtain at least 2 elements across the thinest part \ plate of the model to get reasonable results.