Unusual results in steel roof bracings

[Anonymous]

  Why Nb.rd is so small ;

[Artur.Kosakowski]

Could you attach the file please? Thank you. 

[Anonymous]

I attach the rsa model

rsa model

[Artur.Kosakowski · Accepted solution]

From the 3rd RSA webinar which I strongly encourage you to watch:

"Do not change element length trying to define buckling parameters as this may result in unexpected results of code checking. This part of the dialog is only available for compatibility with older versions of Robot in which there was no option for definition of internal bracings. To define buckling parameters you should use buckling length coefficients instead."

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[rigid_joint]

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This part of the dialog is only available for compatibility with older versions of Robot in which there was no option for definition of internal bracings.

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As far as I remember these options are adopted since the millenium edition.

I think that I didn't fully understand the answer.

You mean that the user always has to set the buckling coefficient member length=1.00? Because in reality this number is not always=1.00

Or you mean that never set a value in the buckling real member length?

[StefanoPasquini6790]

Hi rigid-joint,

The second option that you wrote. Keep in mind that Robot is one of the best software in the world for steel structures, and one of the top options is the buckling settings. Artur want to suggest to use the options present in the dialog form and not type manually the values in the textboxes...

Cheers

[Artur.Kosakowski]

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As far as I remember these options are adopted since the millenium edition.

I think that I didn't fully understand the answer.

You mean that the user always has to set the buckling coefficient member length=1.00? Because in reality this number is not always=1.00

Or you mean that never set a value in the buckling real member length?

What I meant was that you should use the "green" part to set the correct buckling coefficients. You can type the value of buckling length coefficients e.g as 0.5 or 0.33 for elements design against axial force or use this part to define positions of internal bracings (recommended for combined axial force and bending or simple bending).

Or to put it plainly: Do not edit the values in the red frame 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[rigid_joint]

Thank you both for your answers. But it seems like that there is a conflict between them.  By hand calculations they lead to the same result but it looks like that robot prefers the green box solution nowadays.

[Artur.Kosakowski]

Not nowadays but from as long as I remember (since DOS V6 version). Or in other words for check according to older codes (with different rules) the difference could have been less visible. Personally I'd like to have the red part to be no longer accessible but as I wrote it is still there for compatibility reasons