Stone FEM analysis

Replies to This Discussion

Permalink Reply by Romain Mesnil on February 29, 2016 at 8:11am

Hi Maurizio,

the analysis performed by Brocato and Mondardini uses volumic elements, nonlinear contact (with Mohr Coulomb criterion). All these things do not exist in Karamba.

It's a very difficult computation, because of all the contacts between the blocks and arising nonlinearities. Two remarks:

• If you want to assess the deformation of the structure, you have to go into this kind of detail. I would recommend exporting the geometry into another finite-element software...
• If you are interested in the stability of the structure (application of the lower-bound theorem for the stability of structures), you can use discrete elements like done here.

Maybe the best thing to do is to use a discrete elements formulation, but be careful with the modelling. If not done correctly, your analysis can be very innacurate without any warning or feedback from the software.

I hope this helps,

Best,

Romain

Permalink Reply by Maurizio Barberio on February 29, 2016 at 10:18am

Hi Romain,
Thanks for your reply. So, in your opinion, is it correct to use form-finding techniques applied to a mesh and, after found the wanted shell, discretizing or tessellating it?
In other words does a tessellated shell has the same behaviour of a continue shell?

Best,

Maurizio

Permalink Reply by Romain Mesnil on February 29, 2016 at 10:32am

Hi Maurizio,

I think that form-finding cannot hurt, especially if you want compression only structure. The question that arise after this is the stability of the structure. Stone structures rely on friction between blocks: with compression forces orientated following the cuts between blocks, there is no problem, but when forces are not aligned with the interface, you have to add a yield criterion for the joint (Mohr-Coulomb for example). Form-finding won't guarantee that the structure is stable when you get more into this kind of detail. Think of flat Abeille's vault: one of the papers by Brocato and Mondardini shows that they are stable even though stones experience bending: at this point classical form-finding is useless, and other tools have to be used.

There are some very interesting papers on the analysis of stone structures, among them Maurizio Brocato and Lucia Mondardini, but also this one. For design, discrete elements are probably a better choice than finite elements, as it's very tricky to justify that the assembly behaves as a continuous shell.

Best,

Romain

Permalink Reply by Maurizio Barberio on February 29, 2016 at 10:49am

Thanks Romain for your kind explanation. I know that paper by Fallacara et al, the stone tree prototype with the cantilevered branches is part of my MArch thesis :)

I'll look at discrete elements more deeply!

Best,

Maurizio