Global (overall) buckling of the particular space frame?

[george]

I downloaded your RSTAB 7 and got pretty amazed by its abilities.
Before this I was using SAP2000.

The thing that amazed me the most was the simplicity by which program functions were created. Very simple, convenient and functional ! Fantastic work !


I tried to experiment a little bit, a got stuck with particular problem:

How can I calculate the global (overall) buckling of particular space frame?

The .dxf file of the space truss is in the .zip file, in attachment. Also two images of space truss can be found in the attachment.
I can not send you the RSTAB file, as I am not able to save it.



Thank you for the reply.

I wish you all the best with further development of the RSTAB, it really is a great application, and it seems you are breaking your way through the competition. Keep it that way.

[Walter Rustler]

AW: Global (overall) buckling of the particular space frame?

Hello George,

To get the overal buckling modes for the structure you need to use the addon module RSBUCK. It can get you the critical load factors and the corresponding buckling modes for the structure.
I imported the dxf file you attached, but I miss the section properties and the material properties of the three sections. If I could get those as well I can do the analysis for you based on a certain load.

Another thing: If you do a second order analysis you can also find the critical load by gradually increasing the load until the matrix will be singular and you will get an instability message. There is a feature in RSTAB that allows you to do this automatically (See details for load groups). But you will not get much information about the mode of failure. This would be better to do in RSBUCK.

Best Regards
Walter Rustler, Ing.Software Dlubal

[george]

AW: Global (overall) buckling of the particular space frame?

Thank you for the reply Mr. Rustler,
To be more precise, this what I would like to do:

I want to compare a simple beam, loaded with, let`s say 10kN compressional force; with .dxf space frame loaded with force of the same intensity and direction (10kN compressional). Like this:



So what I want to know is: what would be the comparison factors?
Buckling loads, Buckling lengths, Critical Load factor, Eigenvectors by Node, Eigen vectors by Member ... ???

My point is to prove how this space frame structure is better than a regular simple beam.
And I do not know which factors related to the buckling, I need to take compare to.


Any help please.

Vielen Dank

[Walter Rustler]

AW: Global (overall) buckling of the particular space frame?

Hello,

You need to look at the critical load factor and the buckling mode. When you analyze the truss you must make sure that the buckling mode of the smallest critical load factor does not show local buckling, ie failure of a single member. The buckling mode of the truss structure must be the "same" as for the first buckling mode of the single member. It should show overall buckling of the structure an not local failure of one member.

Best Regards
Walter Rustler, Ing.-Software Dlubal

[george]

AW: Global (overall) buckling of the particular space frame?

Dear Mr. Rustler,

Thank you for the answer, and sorry for the late reply.

But I am not sure, I understood you.

Can you show me how to fet a global buckling a particular space frame?
For example, here is the one, on which I want to calculate the global buckling:



.dxf file can be downloaded from here:
http://ifile.it/o5ym4qa/spaceframe.dxf

I can not save my RSTAB project for some reason, this is why I am sending you the .dxf file.

The position of the supports is not important.

Any chance you can show me how to calculate a global buckling for this space frame? A video maybe?

Vielen Dank