Can you create a beam element model with varying thickness?

[yiviw97057]

I have a beam element which I made the cross section for in the Tools - Section Definition. It has a constant height. I was wondering if it is possible to create a beam element with varying thickness. So that for example the beam starts at 1m and goes down to 0.2m at the other end?

I am trying to model something like this, beam seen from the side:

Edit: Would be a major plus if I could change the end heights of an already existing defined beam.

[Krzysztof_Wasik]

Hi @yiviw97057 

It is possible by using tapered setction type

Geometry >Properties >Sections >New>Tapered tab

[yiviw97057]

Thanks Krzysztof,

Is there a way to get the beam to go horizontal along the red line at the top, instead of slope upwards?

[Krzysztof_Wasik]

Hi @yiviw97057 

When you draw beam , you define beam centerline. For tapered beam centerline connects endsections geometrical centers. Beam shape is only graphical member presentation. Calculations are run based on numbers representing beam properties.

You can obtain top beam flange presented horizontally by

- defining sloped centerline

- defining offsets for beam (different for both ends).

[yiviw97057]

Thank you Kryszstof, I appreciate the help, this is what I wish to model: 

To the left at the bottom is just a straight line downwards, but right bottom line has an arch, which of the options you mentioned would be easiest? I am thinking I need one beam for the left section and maybe 2-3 for the right one. 

- defining sloped centerline: Do I just define many nodes in a sloped line and define my cross section from node to node?

- defining offsets for beam (different for both ends): How can I do this, I dont see this option?

[Krzysztof_Wasik]

Hi @yiviw97057 

I would define sloped centerlines. Offset definition results in creating additional rigid links which can affect forces distribution.

Regarding offsets - Geometry >Additional attributes >Offsets

Robot Structural Analysis 2023 Help | Offset | Autodesk

[yiviw97057]

Could you please help me understand how to define sloped centerlines? I am not sure I understand correctly, is there perhaps a video I could look at?

[Krzysztof_Wasik]

Hi @yiviw97057 

Sloperd centerlines

Section display

[yiviw97057]

I see, thank you again. I have an H-beam as you see below in grey, I want for the web to keep increasing in height downwards so it becomes how you see below the red line. Is something like this possible in Robot?  

Edit: I know I can make a lot of seperate beam element with increasing web height and put them together but would rather avoid this as it would take much time. 

[Krzysztof_Wasik]

Hi @yiviw97057 

[yiviw97057]

So this is with sloped centerline; do you think it could be problematic that the beams are sloped downwards instead of being straight? I am thinking for the statics of the system, I am working on a bridge. 

[Krzysztof_Wasik]

Hi @yiviw97057 

Beam stiffness is simulated by section properties values. Graphical section presentation does not have influence on results. Defining sloped axes will have influence on statics. For instance axial forces will appear when vertical forces will be efined. If you want to avoid that define horizontal axes and neglect not expected graphical presentation.

[yiviw97057]

So if this is how my bridge span looks from the side:

And this is how the height of the cross section will vary from H1 to H2:

Is this an okay representation?

[Krzysztof_Wasik]

Hi @yiviw97057 

I think that this type of geometry gives better simulation than sloped axes.