Difference between beams, bars and columns - Node intermediate of beam

[Anonymous]

Dear all,

I am beginner with Robot software and I would like to know what is the difference between beams, columns and bars? Have they had same degrees of freedom?

Moreover I have created a beam (number 50 on the attached picture) between 2 nodes (number 2 and 22), this beam is divided in three parts without creating intermediate beams but with 2 additional nodes 39 and 40. These nodes are atttached to adjacent beams in the frame.

Is it correct to create intermediate nodes without creating additional beams?

Thanks in advance for your answer,

Best regards,

Frédéric

[Artur.Kosakowski · Accepted solution]

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@Anonymous wrote:

Dear all,

I am beginner with Robot software and I would like to know what is the difference between beams, columns and bars? Have they had same degrees of freedom?

They are exactly the same finite element bar types (with teh sam d.o.fs) and beams or columns names should be understood as their design paths.

Moreover I have created a beam (number 50 on the attached picture) between 2 nodes (number 2 and 22), this beam is divided in three parts without creating intermediate beams but with 2 additional nodes 39 and 40. These nodes are atttached to adjacent beams in the frame.

Is it correct to create intermediate nodes without creating additional beams?

Yes, it is.

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 All,

Could you please expand on the response of "beams or columns names should be understood as their design paths"?  When using AISC 360, the design path (i.e., what equations are evaluated) is dictated by the nature of the force (e.g. Chapter E for compression, Chapter F for flexure, Chapter H for a combination of these, ...).  How does the designation of beam/bar/column affect the "design path"?  Perhaps this is different for other codes/standards?  Or do you mean to indicate something else by the term "design path"?

Please note that I also saw this link "https://forums.autodesk.com/t5/robot-structural-analysis-forum/differences-between-beam-bars-and-col...", which seemed to indicate the same thing to me.  Specifically, it seems to indicate that there is some change in how Robot applies AISC 360 based on these terms beam/bar/column however I'm not aware of what that might be - the different chapters are selected based only on the nature of the force and (in some cases) the type of cross section (e.g., W-shape, HSS, ...).  For convenience, the response in this link that suggests this to me is reproduced below:

Defining a bar as Column will lead the design module to design the bar as column,

Defining a bar as Beam will lead the design module to design the bar as beam, etc

What does this response "design as a column" mean in Robot with regard to AISC 360?  Would Chapter F (i.e., flexure - often associated with beams) then be skipped for a 'column' in Robot?  Similarly, would a 'beam' in Robot not be evaluated per Chapters D and/or E regardless of the axial force?  Does this mean that one needs to use the type 'bar' to force evaluation by all applicable AISC 360 equations?  Is there any documentation of this? 

Thanks,

Keith

[Artur.Kosakowski]

Hi @Anonymous

For steel design what matter is a bar type (set of design parameters) assigned to a particular element (bar) of a model. The name of this bar type (beam / column / bar / my own name) is irrelevant as they theoretically could have the exactly the same parameters defined. In fact thay have these parameters set differently (column having them defined in the way that are more suitable for columns e.g. way of checking SLS limit or buckling parameters whereas beams have them more as for beams) and what is important the default labels neither cannot be renamed nor edited. I'd suggest watching the recording of the 3rd Robot webinar where you can see the recommended parameters for both beams and columns.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[Anonymous]

Hi,

I think you're referring to what Robot appears to call 'Type' as found in the 'Object Inspector' in the 'General' category.  Unfortunately, Robot seems to use inconsistent language and it appears that this is called 'Bar type' in the 'Properties' section of the dialog with the title 'Bars'.  If so, all of this makes sense to me (well, except for the inconsistent language - that's undesirable) as I see the "usual" design parameters I'd typically be looking for (Ky, Kz, ...).  Please correct me if I've misunderstood anything here.  Your answer is very helpful but I think it's not what I was asking.  

My question pertains to what Robot seems to term 'Structure object', also found in the 'Object Inspector' just below the 'Type' (just mentioned above).  This is where I find the options Beam/Column/Bar (and I don't see that I can add my own - nor do I currently need to).  The question is how/where are these used and what is the difference?  Please see the attached for clarification of the terms I've referenced and where I've found them (as an aside I'd suggest that clear consistent language in the GUI makes the attachment unnecessary but it appears that Robot is not there yet).  

Thanks,

Keith

[Artur.Kosakowski · Accepted solution]

Hi @Anonymous

There is no difference apart from the fact that you can use them to identify the role of this bar element in a 'real' structure.

If one or more of these posts answered your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

[Anonymous]

OK, great.  Many thanks.  I'd like to click on 'Accept as Solution' as you suggest but I can't seem to find a link/button/control on this page that says that.  Perhaps this is because the original person already accepted it? If so, it would make sense to me to exclude that text from your reply.  Again, clear meaningful language is important - particularly for those that try to follow the instructions 🙂   

Also fyi, I'd suggest that given this "new" response, your previous accepted solution containing "names should be understood as their design paths" is conflicting and potentially misleading (well, you can see I didn't understand it anyway).  Maybe your use of the term 'names' in this reply is intended to mean what Robot calls 'Type' rather than my interpretation of the question of beams/columns/bars being about the 'Structure object'.  It is unfortunate that Robot designers are not more distinct with the terms they use (i.e., beam/columns/bars are valid choices for both a 'Structure object' and a 'Type' so just asking about these three choices is ambiguous - a sure sign of poor design).  Thanks to your help I think I've got it now.  

Thanks,

Keith