Second material for some lines

Grasshopper Peregrine
1

Hello,

Is there the possibility to differentiate some lines in the domain to consider a second material? I am optimising a space truss and I want diagonals to be only in compression (opposed to vertical and horizontal elements that can be in compression and tension).

Best,
Robin

2

Hi Robin,

At present only a single material can be allocated to a problem. We’re working on the ability to specify multiple design domains, which could include different materials, but even so I think this might not be exactly what you want for this case. It may be that we could provide line structures with a particular material property on a per-element basis, although this would need to be considered fully and developed further.

Best regards,

Tom

3

Hi Tom,

Thanks for your response. Indeed, having separate domains would not work for my specific application. To embed this constraint, I imagine that I need to create a N x N matrix to store the different material properties in the ground structure (N being the number of nodes). Is there a way to enforce this constraint as a post-rationalisation step, by removing the lines that should not be in tension, for instance?

Regards,
Robin

4

Hi Robin,

Without the ability to differentiate between tension and compression elements this isn’t achievable at the moment. If there was a process by which one could selectively remove elements in Peregrine (functionality that exists in LimitState:FORM), it may still be that the resulting solution is then unstable and the act of acquiring stability once more may re-introduce tension into the equation!

regards,

Tom

5

Hi Tom,

I understand, thank you for your feedback.

Best,
Robin