Rigid body mode error in Karamba


(Claire) #1

Hello again, all. I’m trying to optimise my structure using galapagos/octopus with karamba, but at the moment I’m having serious problems with the karamba bit.

I’m trying to calculate the deflection of the slab using the AnalyzeThi component, and using that value as a factor for my optimisation. However, after I added horizontal ties to my model, it’s been returning insanely high values of displacement (like 9.44 e9 metres). After fiddling with it more I ended up with a failed model and this error message:

  1. There are 86 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.

But I have no idea how to use the Eigen Modes component to fix it. I tried removing duplicate points, but nothing much seems to have changed.

Thanks in advance, everyone.

tree model.3dm (65.2 KB)
trees test 10.gh (77.5 KB)

(Claire) #2

I tried using separate lines instead of an exploded polyline, and I discovered that for some reason only two of the lines are intersecting and also appear to be in the same branch naturally.

As you can see from this screenshot, there is no branch {0}, and two items in {1}. Every other branch has just one item. I’m completely baffled as to why this is happening, given that I’m literally using the same points in the same data tree to build each line. Also, the exploded tree in the screenshot contains just one item per branch.

The above shows the only intersection, which is between lines 0-1 and 1-2. They intersect at point 1, as they should. I have no idea why they are the only two lines that are doing this.

I’m attaching the slightly updated, lines instead of exploded polyline definition below.

trees test 11.gh (80.4 KB)