Grasshopper

algorithmic modeling for Rhino

# Form finding with Kangaroo (catenary lines)

Hello everyone,

Recently I've started to work with the Kangaroo plugin for Grasshopper for a project. The project is about the design and structure of thin concrete shells.

I was inspired by the work of Heinz Isler. He worked a lot with catenary lines and gravity. By turning the catenary line upside down, the ideal compression arch is obtained (the best for concrete).

Now I wanted to try and create some of his models with Kangaroo and Grasshopper. I am currently working with the structure of the image below:

I managed to create the two crossed catenary lines, but I can't figure out how to 'add' the mesh to the structure so it would shape as the image shows. I also tried the gravity component, but I can't figure it out...

I hope anyone can help me with this problem,

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Hi Stefan,

The key thing is to make the mesh edges also into springs. You can do this by extracting mesh edges, or use the included SpringsFromMesh component as shown.

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Hi Daniel,

Thank you for the response.

Indeed the mesh is now included in the structure with the catenary lines. But the problem is that the mesh is now no longer in the squared surface (image in previous post).

I think the goal is to sort of drape a mesh over the two catenary lines so that new catenary lines are formed between the corners of the square mesh (the edge lines of the square plane also turn into catenary lines)... I don't know if this is possible..

Ah yes, it was missing gravity applied to the mesh (it was only on the cables). With that it gives more the shape in your original post:

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Yes, that's it!

But I was wondering how it is possible that the mesh at one of the catenary lines is very smooth while the mesh hanging at the other catenary line has triangles (where it hangs)...

This is just how the mesh is being triangulated for display. If you want to control this you could triangulate the mesh in Rhino and swap edges to get the desired diagonals. Be careful though, as a triangulated mesh would behave differently when the edges are made into springs. It may be better to keep the quad mesh as the input to SpringsFromMesh, and make a copy which you triangulate and input to Geometry.

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