Analyse component returns NaN (but is not red)

Hello,

The model which is in attachment shows an NaN output at the Analyse component.

Is this the same as if the component would turn red?

How can I solve this?

What is my file about:

A polyhedron geometry is taken as the base for a scissor structure.

I am not yet introducing the scissors (hinges with zero-length springs) and everything is supposed to be rigid (also the supports).

But the analyse component is not returning any value. How come?

I have a lot of coinciding points (that is necessary for the zero-length springs later), but that should not be the problem, right? Since coinciding points are just rigid connected?

Due to these coinciding points at the support points of the structure, I introduced coinciding supports. Could this be the problem? Because I tried with supports in only one of the two coinciding points, but that doesn't change anything..

I would really want to find out this problem. Because the next step would be converting this rigid frame into scissors with zero length springs at the vertices and intersection points.

Thanks

Lara

Attachments:

icosahedron polyhedron.3dm, 41 KB
scissors icosahedron_test.gh, 20 KB

Replies to This Discussion

Permalink Reply by Karamba3D on June 4, 2013 at 1:10am

Hello Lara,

your model contains beam elements of zero length (one can see this by disassembling the model and checking the length of the beam axes). These zero length beam elements are infinitely stiff and therefore lead to a NaN (= Not a Number) result for the maximum displacement.

Best,

Clemens

Permalink Reply by Lara Alegria Mira on June 4, 2013 at 7:59am

Okay, but if I convert these zero-length beam elements into springs (adding the spring cross-section to the cross section input of the assembly component). The analyze component turns red.

Is that because the vertices, where the beams come together, and the support are rigid and the springs are not?

Best

Lara

Permalink Reply by Karamba3D on June 6, 2013 at 1:27am

Specify the spring stiffnesses in such a way that no kinematic system results. Analyse the model with the Eigenmodes component in order to make sure that your model has no loose parts.

Experiment with different values for your spring stiffnesses. If the spring stiffnesses and those from the finite elements are hugely different a badly conditioned system stiffness matrix results that can not be solved.

Best,

Clemens

Permalink Reply by Lara Alegria Mira on June 4, 2013 at 8:18am

Is it like this:

If a beam is connected from nod 0 to 1 and from 1 to 4. Another from 2 to 3 and from 3 to 5.

Node 1 and 3 have the same coordinates, but are they rigidly connected or not?

Permalink Reply by Karamba3D on June 6, 2013 at 1:33am

If you put the above described geometry into a LineToBeam component nodes 1 and 3 will be merged by default. In case you specify a negative number for 'LDist' the nodes will not be merged. The same is true for the assemble-component and its 'LDist' property.

Best,

Clemens

Permalink Reply by Lara Alegria Mira on June 4, 2013 at 8:51am

I thought that maybe the "element felting component" can work. But does that work also for beams elements that intersect (at different points but with the same coordinate) (coinciding nodes)?

Permalink Reply by Karamba3D on June 6, 2013 at 1:34am

The 'element felting component' should work like described above. Did you test it?

Best,

Clemens

Permalink Reply by Lara Alegria Mira on June 10, 2013 at 11:43am

Hi!

I tested the element felting component. But I don't think it works.

See attached. I put the snap length at really small because the elements must be generated at the intersection points to introduce zero-length springs.

What am I doing wrong?

Attachments:

scissors icosahedron_test3.gh, 19 KB

Permalink Reply by Karamba3D on June 13, 2013 at 12:03am

Hi Lara,

could you please internalize the geometry or add the corresponding Rhino file?

There is a problem with the felting component for it shouldn't crash despite of the fact that there is no geometry. Thank's for the example.

Best,

Clemens

Permalink Reply by Lara Alegria Mira on June 13, 2013 at 8:06am

Hi Clemens,

The Rhino file is attached (it was also in my first discussion post).

Thanks!!!

Attachments:

icosahedron polyhedron.3dm, 41 KB
scissors icosahedron_test3.gh, 19 KB

Permalink Reply by Lara Alegria Mira on June 17, 2013 at 11:29am

Hi Clemens,

Do you think the felting component should be working for what I want?

Best

Lara

Permalink Reply by Lara Alegria Mira on June 18, 2013 at 8:02am

Hi,

I tried it on a simple example and it doesn't seem to be working for what I want.

The component doesn't accept spring cross sections, only elements from the beam type and because it won't introduce a zero-length beam as a connection element (because infinite rigid I suppose) it converts the 2 beams in 4 beams which are rigid connected at the intersection point.

So I suppose for generating scissor structures with spring elements, this component doesn't work. I don't know if you think it would be useful to let it allow to work with spring elements..

Attachments: