3 Replies Latest reply on Jan 2, 2018 3:22 PM by Ryan Dark

    Shell vs Solids

    Tsvetan Donov

          Hi,

      I am a Rhino user. One of my tasks now is to create a bench out of GFRC concrete (concrete with no actual steel reinforcement). I did a parametric study and found that one of the legs of the bench is about 0.2m diameter. In Rhino (Grasshopper) the only type of FEA analysis is with shell elements (both Karamba and Millipede support it), however I think that 0.2m diameter is too thick to analyze it with shell elements, therefore needing solids.

      At my university on a few machines there are Solidworks licences, therefore I tough why not export my model and try to use solids in Solidworks.

       

      My question is for a circular element - 0.15 - 0.20m diameter and 0.4-0.5m in height, is it necessary to use solids. In one of the manual I read that there is ratio of 0.05 between height to span ratio, which in my case I need to use shells, but what suggestions would you give me?

       

      If I create a mesh out of shells, touching each other (multiplayers), do you think this will give accurate results, rather than trying to model the bench out of solids?

       

      Best Regards,

       

      Tsvetan Donov

        • Re: Shell vs Solids
          Ryan Dark

          Hi Tsvetan,

          If your legs have solid-cores then, given your dimensions, it would be best to analyze these with solid elements.  If they are not solid-cores what is wall thickness of your legs?

            • Re: Shell vs Solids
              Tsvetan Donov

              Hi,

              Thanks for the quick reply. Currently me and my mates are building our grasshopper model, to do a parametric study, that is why we can’t yet give proper dimensions. I am guessing it is will be around 40cm high and 15-20cm thick. The legs will be solid concrete.

              Is there a way to use solid elements for them, as from what I am reading in the manual, the FEA build into karamba is programmed to have only shells.

              However now I am thinking if the elements that we have made in Rhino are solids is karamba going to take them as solids after meshing them?

              I have attached a photo of how the model is supposed to look like, however the dimensions are not final because we don’t have a full grasshopper model build yet.

               

              Best Regards,

              Tsvetan

              Capture.PNG

                • Re: Shell vs Solids
                  Ryan Dark

                  I can't speak to the capabilities of Rhino or Karamba but in SOLIDWORKS Simulation such a model would be analyzed using solid (tetrahedral) elements.  Shell elements in SOLIDWORKS Simulation are for analyzing thin walled objects or thin plates.  From your image and description it seems that your design is neither of these so solid elements would be required.