Kangaroo_tesegrity structure: elongation and strain

Hallo Daniel,

I have tried the tensegrity-structure example file and noticed the struts getting shorter; I know theoretically it somehow happen to compression parts. But the strain about 30 cm doesn’t look realistic!

(To get 1 mm deformation from a solid steel volume (1 cm x 1cm x 1 meter) we need almost 2100 KN.)

I was thinking it could be caused by stiffness, so I put higher stiffness for struts in order to minimum its strain, but by 16.000 units the whole structure 'explored'!

Even I tried to vary the stiffness of struts and make it 5-10 times than cables, the strain on struts are still there.

But as I said, the deformation is still too much and not realistic...

So here are the questions:

- What dose those units for stiffness and 'gravity' really means? And:

- How we simulate a forced element (in my case struts) to obtain the realistic strain?

Attachments:

tensegritydemo-modified.ghx, 281 KB

Replies to This Discussion

Permalink Reply by Daniel Piker on November 12, 2013 at 12:04pm

Hi Frank,

Kangaroo can be used for either form-finding, or simulation of actual structures, but these are often quite separate things.

For example, using a soap-film like behaviour to model a tensile fabric structure - during the form-finding process, the area of the surface changes a huge amount, whereas when it is actually built the change in area from the untensioned shapes that are cut out to their final form is much smaller.

I'll try and make a better example definition for tensegrity structures later. Are you aiming for equal tensions in the cables ? I've also been trying some new force-density based stuff that might be useful here

Permalink Reply by Jon on November 14, 2013 at 7:52am

Hi Daniel,

Exactly reversed. I think in most of case we could accept various tension parts rather than struts coz the local adjustment take place during the erection (depends on details).

What I was wondering is, as I at beginning mentioned about, that there is a huge amount of strain on struts: in the example-file it gets shorter approximately 30 units for struts…! (Fortunately even the strain the struts ‘almost’ keep equal length!)

I would be glad the seeing the update of definition for tensegrity structure!

Thanks Daniel!

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