Cable elements in Karamba


I am trying to model the geometry of a cable-stayed bridge and I would like to ensure that the cables are only in tension. If compression is detected, then it should be in slack. Do I do this my pretensioning the elements? If so, would the Analyze (I) tool work or would I use the AnalyzeThII? Further, would I need to analyze the axial forces in the cable first then impose the strains into the cables to pretension it?

You can see that the cable elements closest to the towers (near vertical) is in compression. How do I prevent this from happening? Thank you.

Olivia (310.7 KB)

Hi, you can use the standard Analyze to calculate pretensioning of elements. You will need to check the Normal forces in the cables after the analysis to see how much pretensioning would be applied, as each element, cross section behaves slightly differently.

I cannot seem to open your definition as there are other plugins in your file.

Hi Mathew,

Thanks for replying. I have removed the plugins and the new Grasshopper script is attached here. Let me know if there are any other issues.

Would I need to calculate the pretension equivalent to the compression of the force in the cable?
applied strain = (compression force/A)/E

Do you have an example for this? I looked the Analyze_ThII example provided by Karamba, but it used the Analyze ThII algorithm (second order analysis). (303.0 KB)


Hi, you can refer to this example Space Ball – Karamba3D

Otherwise there should be some examples found in C:\Program Files\Rhino 7\Plug-ins\Karamba\Examples\TestExamples\02_Load\InitialStrainLoad