The idea is that the inner frame is held in place using cables that could be pretensioned. I’ve tried using the Analyse ThII component and the AnalyseNonlin WIP, however I ran into some issues. Do you think this setup is possible in Karamba?
From what I experience is that the ThII component doesn’t correctly model the non-linear behaviour that I am looking for as there are no forces transferring from the ‘cables’ (now set as thin beam elements with bending turned off) to the inner and outer frames. Is this possible?
The AnalyseNonlin WIP doesn’t handle this workaround for modelling ‘cables’, and having cables that handle bending moment is incorrect in my setup. I wonder if you know if there is a workaround or if I should try it in Kiwi3D as I read that they do have support for modelling cables.
In case NII (which controls the geometric stiffness of the system) is known beforehand it can be set at the “NII” input-plug of the “ModifyElement”-component. For analysing the system chose either the “Analyse”-component or “Analyse ThII” with “MaxIter” set to zero. There is then no need to specify a load which actualy causes a normal force N to which NII would be updated to by the iterations done at the “Analyse ThII”-component.
If NII is not known beforehand use “Analyse ThII” and add a load (e.g. initial strain) which produces the NII forces that are needed to stabilize the system. For the first iteration it is necessary to have a preset NII force so that the system is stable. After that the updated NII forces will do the job.
In your example the frame deforms under the pre-strain load of the diagonals. This reduces the prestress there. In order to control the forces in the diagonals use an artificially soft material (e.g. E = 1) and scale up the prestrain so that the target normal force results.
