Error Help: Rigid Body Modes

Grasshopper Karamba3D
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1

Hi, I am trying to model and analyze using Karamba a series of trusses. I have set up the model, but when I try to go and analyze I get an error that says:

“1. There are 138 rigid body modes in the system. This means some parts can move freely without causing deformation.
Try to use the ‘Eigen Modes’-component and activate the display of local coordinate axes: The first eigen-mode will be the rigid body motion.
If this does not help, check whether you have a pinned support directly attached to a hinge. A hinge introduces an extra node which may cause the problem.
When analyzing a flat shell structure one has to lock the rotation perpendicular to the plate in at least one node.”

From what I have seen on the forum, other people who have received this error had geometric issues with them having duplicate points causing the structure to not be fully connected. I tried to identify whether this was the issue in my case too, but could not seem to figure it out.

I am using Lunchbox in order to create my trusses. I was wondering whether this could in any way interfere with the Karamba analysis?

Any help on how to sort this problem out would be greatly appreciated :slight_smile:

the grasshopper file and associated model are linked below.

Timber Non-Form Active Improved.gh (27.8 KB)

Model.3dm (44.3 KB)

2

Hi, here are some tips you can use to troubleshoot your definition.

  • check your data structures as you have multiple branches

  • flatten your inputs in the ModelView

  • use the connected parts component to see if there are unconnected elements

  • check if your joint definitions or beams/trusses are actually stable

  • use the eigenmodes component to identify any issues