Buckling Analysis

[Anonymous]

Goodmorning,

I'm modelling a curved roof made of trapezoidal hollow sections and I'm performing some benchmark checks to better understand the behaviour. I used a simple base model imported from Autocad made of some straight lines that tries to approximate the curved shape. I defined the trapezoidal section and defined a member type to joint the members and obtain the correct buckling lenghts but, as I run calculations and look at the calculation note the buckling analysis is not performed. (red X)

Does anybody tell me why this happens or better, which is the correct procedure to perform buckling analisis of a multi member group?

Does the user defined trapezoidal hollow section have some calculation issue?

Thank you,

Francesco

[Rafal.Gaweda]

File please.

[Anonymous]

Tks

[Rafal.Gaweda]

It will not work with these Automatic Buckling settings.
See help:
http://help.autodesk.com/view/RSAPRO/2016/ENU/?guid=GUID-07FF6757-9008-47EC-B497-A4CD862BCFE2

[Anonymous]

Ok, there's a lot of theory behind the automatic calculation of buckling coefficients but even in the enclosed file I cannot undestand how Robot calculates the parameters: these, compared to my hand calculations, are completely different. Where's my fault?

[Rafal.Gaweda]

See webinar 3, slide 16

"For columns in regular buildings you may use automatic buckling length option which calculates buckling length coefficient for a column based on the stiffness of elements which are defined in its top and bottom nodes."

Additionally - think about correctly creating superbars

See webinar 3, slide 7

[Anonymous]

Neither the load case that is considered as verification load case seems to be the worst one...

[Anonymous]

Sorry for asking for further explanatios again, but it's completly unclear to me what webinar tries to explain and what I have to do to create and to use "superbars", (is it a member of members?).

Isn't there any simpler tutorial that can explain clearly what are the steps to follow to create a member made of smaller members, how to connect them to perform a correct buckling analysis and how to run the analysis on the worst load combination? I'm so sorry, it's surely my fault but as far as I can see, this type of anaysis is completely incomprehensible from the webinar and from the Robot's interface.

[Rafal.Gaweda]

http://forums.autodesk.com/t5/robot-structural-analysis/manual-lt-buckling-length-in-lrfd-steel-desi...

http://forums.autodesk.com/t5/robot-structural-analysis/api-macro-for-creating-superbars-supermember...

[DennisVDijk]

Hello,

I made superbars in your model, BAR 5001to5006.

Buckling length can also be determand by the following:

I hope this would help you. Attached is your model with superbars.

Good Luck!

[Anonymous]

Thank you, finally I understood what I've to do!!!