Analyze solids

Hi,

A few friends and I, recently started modelling a bench made out of concrete (GRFC concrete). The legs of the bench are circular and an angle and the whole bench is an irregular form. 

One of our options is using karamba. From the tutorials and the manual I saw a few examples of elements modeled with shells, however there is no solid option.

The area where people will sit is thin, so it can be modelled as a shell, however does anyone know if there is a workaround for the modelling of the legs, made out of solidly cast concrete?

My idea is to model the legs in a number of strips, therefore having many shells. But from what I know the shells will not recognize that there is shell connected to their surface.

Thank you in advance for any input.