Hello
I am trying to make a bending-active structure using kangaroo2. I have used the example on GitHub provided by Dan Piker. But the bottom of my structure seems a bit weird. Can someone tell me why it turns out like this? And is there someone that could help fix it?
I am not totally sure of the strength of each component… i could maybe have something to do with this. I would like the bottom of the gridshell to be more straight, and not flattened. I have linked the Grasshopper file.
The method of form-finding a gridshell by starting from a flat grid then pushing in the sides so that it pushes up into a vault works with quad grids because the angle of the quads can change.
What start out as squares turn into rhombi. This rotation of the edges is important because it allows the shell to have double curvature.
The construction of these gridshells can then be much like the form-finding process - starting with a flat quad grid, pushing up, and only then adding diagonals for shear bracing.
When you have a tri-hex grid like that, this approach is not appropriate because there is no flexibility for the grid to deform in-plane. This means if you start flat and push in, it will buckle more like a sheet of paper as you are seeing, staying close to developable, instead of making a doubly curved vault.
You can build such tri-hex gridshells, but a different technique is needed, such as connecting the members as a curved 3 dimensional shape from the start, without ever having it lay flat.
Thank you for your answer! I have now tried to make quads instead. So if i understand you right the approach showed on the image below would work? If the red marked sides are pushed in.
Yes, though the short edges around where it is trimmed aren’t ideal. It keeps things cleaner if you can cut the grid along its main directions or along its diagonals.
There’s an example file similar to this here
