Exclude negative buckling load factors?

I've been trying out the new buckling analysis component in Karamba. It's really a great addition. I want to wrap around it with Octopus, and therefore keep the computation minimal. Specifically, I'd like to compute only the first positive buckling load factor without having to calculate enough buckling modes that one should be positive. Is there any way to achieve this right now, i.e. only calculate until it finds a positive one?

Replies to This Discussion

Permalink Reply by Karamba3D on March 2, 2015 at 12:09pm

The AnalyzeThII-component offers the option to switch off the stiffening effect of tensile forces by setting 'NoTenNII' to true. There are however cases where this does not help.

The current algorithm for calculating the buckling factors is a Van Mises iteration which always converges to the buckling factors with the smallest absolute values. In the next release of Karamba I plan to add other algorithms which allow better control.

Best,

Clemens

Permalink Reply by Diederik Veenendaal on March 3, 2015 at 1:17am

Hi Clemens,

Thanks for the reply. Can I hack into it and write my own GH component that iterates until it finds a positive one?

I'm having trouble doing this right now; Buckling(inModel.febmodel,1,2,300,1e-5)

gives me

Runtime error (ArgumentTypeException): expected Model, got Model

Permalink Reply by Diederik Veenendaal on March 3, 2015 at 1:40am

No luck with this option either:

import Karamba.Algorithms.Component_Buckling as Buckling
Buckling.solve(inModel,1,2,300,1e-5)

Permalink Reply by Karamba3D on March 3, 2015 at 12:09pm

Hi Diederik,

try the following: type 'GrasshopperDeveloperSettings' in the Rhino text window, and then set the hook at 'Memory load *.GHA...'. Otherwise GH loads Karamba.gha twice.

Best, C.

Permalink Reply by Diederik Veenendaal on March 4, 2015 at 11:40am

Unchecking that worked!

For my next question; FromInd in the buckling component doesn't seem to work. For example, in the ShellBuckling.gh example found on the Karamba3D website, changing FromInd from 1 to 2 seems to not influence the results.

Ofcourse my question is related to computing only positive load factors in a relatively efficient way.

Permalink Reply by Karamba3D on March 4, 2015 at 1:43pm

This seems to be a bug in version 1.1.0. Thank you for the report.

I think it would be a good idea to have an option-flag on the buckling-component to limit the computation to positive buckling factors only. I will include this in the next release.

Best,

Clemens

Permalink Reply by Diederik Veenendaal on March 6, 2015 at 2:07am

Ok, so until that's fixed or the option-flag is included; this is the best option I can think of to generate only positive values, within computational reason;

import clr
clr.AddReferenceToFileAndPath("C:\Users\...\AppData\Roaming\Grasshopper\Libraries\karamba.gha")
import Karamba.Algorithms.Component_Buckling as Buckling

MaxModes = 10
num = 0
FromInd = 1
MaxIter = 300
Eps = 1e-5

for i in range(MaxModes):
    num = num+i
    if num < MaxModes:
        BLFac = map(float,Buckling.solve(inModel,FromInd,i+1,MaxIter,Eps)[0])[-1]
        if BLFac >= 0:
            break
    else:
        BLFacs = map(float,Buckling.solve(inModel,FromInd,MaxModes,MaxIter,Eps)[0])
        BLFac = min([x for x in BLFacs if x >= 0 ])
        break

Permalink Reply by Karamba3D on March 13, 2015 at 1:20am

Dear Diederik, I have uploaded a new build of Karamba 1.1.0 which in case of buckling analysis returns only positive numbers as buckling load-factors.

Best, Clemens

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