Optimize cross section

Hello there,

I am trying to optimize cross sections in the structure. I have two sets of members ( divided with member IDs A & B) and I want to optimize only members of set A. Seems like if I plug my cross sections list into the optimize module I can get only one of the lists (either A or B). Can you give me please some suggestions what might be wrong?

thanks

Daniel

Attachments:

3_6_09.gh, 70 KB

Replies to This Discussion

Permalink Reply by Karamba3D on April 10, 2017 at 1:03pm

Hello Daniel,

the family names of the cross sections which you want to optimize and the family names of those which can be substituted for them need to be the same (see manual and attached definition).

Best,

Clemens

Attachments:

3_6_09_cp.gh, 62 KB

Permalink Reply by Daniel on April 10, 2017 at 4:53pm

thank you for your help, Ive looked into the manual but apparently I didnt reproduce / understood it completely.

I have one more question, is there a nonlinearity such as tension only member ? Like rope/cable for example? I want to reproduce cable prestressed structure. Also, is there any other way how to prestress members except initial strain?

with kind regards,

Daniel

Permalink Reply by Karamba3D on April 11, 2017 at 1:03am

There are no tension-only members in Karamba (version 1.2.2.) yet. There is however a component called 'Tension/Compression Eliminator' which iteratively removes tensioned or compressed members.

The example 'Analyze_ThII_Truss.gh' under '.../Rhinoceros 5 (64-bit)\Plug-ins\Karamba\Examples\TestExamples\' deals with a prestressed structure - maybe this is helpful for you.

Regarding prestress: In order to capture the geometric stiffness induced by axial forces you can define NII directly via the 'Modify Element'-component. In that case set 'MaxIter' of 'Analyze ThII' to one so that the NII values do not get updated.

Another way of prestresssing elements would be to impose displacements at the supports.

Best,

Clemens

Permalink Reply by Daniel on April 14, 2017 at 12:04pm

Thank you for your valuable response. It took me quite a while to respond because I was experimenting a bit. I'm getting pretty close in my comparison with RFEM/RSTAB (I'm getting almost exact numbers with beam element structures, even with really complex structures) but with II order I'm not there yet.

In the meanwhile, as I've been playing with strain, (as a prestress) I think found some problem with RSTAB STP(DStV) conversion module (might be that I'm doing something wrong). As I define strain load -3 (mm/m) and convert it to RSTAB 8 it gets converted as a temperature, but with positive sign (+)! Shouldn't it be negative ? (-). It might be something wrong with the definition in RSTAB as well. Can you give me some feedback on this "problem"?

With the deformations (global max) I'm about 100mm off (KARAMBA = 390mm, RFEM/RSTAB = 490mm). Can you maybe give me some hints on my definition? There are "cable-like-members" defined in karamba in the roof structure, which are ment to be prestressed. (Please, find attached file)

Thank you very much again.

With kind regards,

Daniel

Attachments:

2_1_09.gh, 72 KB

Permalink Reply by Karamba3D on April 18, 2017 at 12:41pm

Daniel,

thank you for the bug report regarding Karamba's DStV output of prestress.

In RFEM one has several options for doing geometric non-linear analysis. The 'Analysis ThII'-component in Karamba is based on the assumption of small displacements. Make sure to activate the corresponding calculation option in RFEM/RStab.

You could reduce the size of the model by taking advantage of the symmetry of your structure. Did you try out a small test example involving Th. II?

Best,

Clemens

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