Cable Net Structural Analysis

Hi Everyone,

I'm doing some exercises to explore irregular cable nets and I'm having some difficulty with the structural analysis of them.

I think I'm setting up the model alright, but when I try to release the moment joints between the elements (since they are cables, I was thinking I could analyse them as truss elements so I'd have only normal stresses and use the TenComEliminator Component to get rid of compressed elements) I get a "Singular Stiffness Matrix" and the model can't be calculated (probably because it becomes an statically indeterminate structure).

I've noticed that in some other examples with cables in Karamba, like the "Minimal Surface" example (http://www.karamba3d.com/minimal-surface/) the solution is only possible when the elements take bending, which is not really accurate for cables.

Can anyone help me figure out what am I doing wrong and possibly suggest a better way to solve this?

Best regards!

Pedro

Attachments:

Cable Net - test 1.JPG, 30 KB
Cable net - test 1.gh, 42 KB

Replies to This Discussion

Permalink Reply by Karamba3D on January 18, 2016 at 12:06pm

Hi Pedro,

you can use truss elements. In order to make them work one has to use second order theory analysis (Th.II) which takes into account the stabilizing effect of tensile forces (see attached definition). Th.II analysis is based on the assumption of small displacements. This e.g. means that a deflection of a cable perpendicular to its axis does not result in an increase of normal force in the element (see 'Analyze_ThII_Truss.gh' in '...\Rhinoceros 5.0 (64-bit)\Plug-ins\Karamba\Examples\TestExamples').

In Karamba 1.1.0 the TenComEliminator utilizes Th.I calculations and therefore will not work for your structure, the same is true for the large deformation Analysis component in version 1.1.0.

Best regards,

Clemens

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