How to use properly LaDeform in load-controlled?

Hello Karamba team,

I’ll try to make it short: I’m trying to make the Large Deformation algorithm work on a mixed-structure (tubes and cables). The calculation with Analyze Th1 doesn’t provide satisfying results and I think it is based on the assumption of small displacements. That’s why I want to try with LaDeform.

But doing this I met some problems. I tried to experiment it on the small examples that are provided with Karamba:

1.LaDeform in load-controlled behavior

I know Karamba has mainly been created make form-finding and not properly precise calculations, but I’d like to evaluate deformations of my structure under certain loads (load-controlled). It is said to let it in Default value for MaxDisp (-1).

[Rhino view for deflection of the rope]

In this example derived from a Karamba example (Large_Deformation_Rope.gh), the programs shows different ways to get approximately equal max deflection. But, getting into it, I realized Load Multiplier for gravity is different from one model to another (-3.237 for Analyze TH1 and -134 for LaDeform). So what is the interest of the example if the quite similar shape of deflections are not got under the same loadings? (quite different loadings indeed)

Doesn’t it show on the contrary that LaDeform algorithm does not work properly, if you need to change the load multiplier?

The Grasshopper file is shown below.

2.MaxDisp

When I use the model is “max disp”, I command the deformation, but how can I get the value of the virtual force exerted (which I don’t know because it is now imposed)? What is its link with the imposed deflection?

Otherwise I can’t figure how to use it with displacement-controlled loading

3.Iterative process

As it seems impossible to use LaDeform process, I tried to test it by iterations, as you recommend it on the forum, saying that it is equivalent to an iterative Analyze Th1 process.

I tried to reproduce this loading but the result is not very enthusiastic as you can see. The Rhino file shows the progressive loading, with the corresponding Grasshopper files, where I

-          disassemble the model,

-          get the previous deformed model

-          put in another part of the load,

-          re-assemble and then calculate it on the previous deformed shape.

Do you have any idea why the answer is not the same ? (LaDeform seem to give like 5 times less for the same loadings) (and even controlling it by displacements the shapes do not fit the principle of the algorithm would let think)

[RhinView for Iterative process]

First step by analyze Th1, and result by LaDeform

4.Analyze Th1 after LaDeform?

Some tutorials of Karamba show that an analysis with Analyze Th1 is sometimes made immediately after a calculation in large deformations. What is its reason? It seems to sometimes change considerably the result. What is the sense of such an operation? Would it mean that LaDeform is not trustworthy?

ð  My question is then: is there a way to make the use of LaDeform for other purposes than form-finding affordable and coherent? If I mistake using it, where?

Thank you very much for your help,