Section check not analized despite getting forces??

[Anonymous]

Hello,

I don't understand why robot doesn't analize the members. I get some warnings of instablities but robot runs the calculations. The moments diagrams and deformations are the expected ones.

I'm trying to simulate a 2span beam supported in shorts arms. Like a facade purlins.

Purlins are user section database of less than 3mm. (I Already know the program doesn't run a thin walled section check for users sections. But I just want to check as a normal section in elastic field (class 3).

Whats going on?

Thanks

[Artur.Kosakowski]

Ay and  Az being 0s when you have shear forces. Try to save this section in the user section database with C shape type or edit these areas entering some values.

BTW: if you ryun manual check for axial force and bending (shears as )s you will get the results).

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.

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.

[Anonymous]

Hello,
I am aware that Ay and Az are 0. But I believe that is not the issue.

Try to delete all the releases and you will find out that then robot makes the checks (also without shear áreas).

[Artur.Kosakowski]

The difference is not the lack of releases but the presence of axial force. IMHO the check of section defined in this way (without assigned section type and some parameters missing e.g. thickness of web, flanges etc.) could only be done for pure tension (axial force) as FX/AX compared to resistance. 

You may consider one of these two solutions:

- save this section in the user database in one of the ways described below:

http://knowledge.autodesk.com/support/robot-structural-analysis-products/troubleshooting/caas/sfdcar...

http://knowledge.autodesk.com/support/robot-structural-analysis-products/troubleshooting/caas/sfdcar...

- define section by properties and assign it the type using these dialogs

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.

[Anonymous]

Hi,
Definitely the axial load plays a role here. (please have a look to the attached example).

When an axial load is applied, robot makes the verification, when there is no axial load don't. (with the same section as before, without shear áreas and other section properties).

It doesn't make sense to me.

[Artur.Kosakowski]

That's what I tried to explain  

My point is that for section which is defined "incorrectly" in a sense that it hasn't got all the parameters required by the Steel design module the verification may be done incorrectly (e.g. C shape verified with formulas that are not intended for C shape) and the only "reasonable" check is for pure tension. The recommend workflow is to define a section in a way it is expected by the steel design module. 

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.

[Anonymous]

Hello,

I've just realised that the gamma of the bar is involved in this issue.

From the attached file, I reach the conclusion that: robot doesn't perform the member check when the bar has bending moment in z axis (weak) and there is no axial load.

To me totally non sense.

[Artur.Kosakowski]

Please attach your user section database with this profile.

[Anonymous]

Hello,
I sent you the database privately.
Thanks

[Artur.Kosakowski · Accepted solution]

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.