topic Re: Modelling a wide cap beam in Robot in Robot Structural Analysis Forum

Modelling a wide cap beam in Robot

Anonymous — Thu, 27 Jul 2017 11:22:23 GMT

Hey guys

I have difficulties modelling a wide cap beam with the dimensions of 4m*12m (in the plan) and varying thickness from 0.6m (on the edges) to 1.5m (in the middle part). 4 girders sit on the cap beam from each side. The cap beam is supported by a 4m*4m concrete box column. due to large dimensions it has to be subdivided to few elements or possibly a shell element to represent its actual behavior.

I attached a hand sketch of the cap beam. please give me an idea what to do ?

Thanks

Re: Modelling a wide cap beam in Robot

Rafacascudo — Thu, 27 Jul 2017 12:08:57 GMT

columm - bar with rigid links on top

slabs - shell with variable thickness

Something like this

You can enter the missing slab( or top of columm) part as a load on columm top node

model attached Robot 2018

Re: Modelling a wide cap beam in Robot

Anonymous — Thu, 27 Jul 2017 12:10:43 GMT

Thanks Rafael

But in fact the top surface of slap should be perfectly flat and horizontal. Also is it possible to define non-prismatic shells in 3D frame mode since this option is only available in shell mode, and when I switch to shell mode to define something and switch back to 3D frame I get errors during the analysis.

Regards

Re: Modelling a wide cap beam in Robot

Artur.Kosakowski — Thu, 27 Jul 2017 12:12:29 GMT

Hi @Anonymous

As I already started my picture Just to illustrate the way it was done by @Rafacascudo (thank you) and in case you want to model have the middle part of the cap as well

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.

Re: Modelling a wide cap beam in Robot

Rafacascudo — Thu, 27 Jul 2017 12:16:31 GMT

the slab top surface not being horizontal is just a detail . You can be sure the the correct slab stiffness will be perfctly represented even though its geometry is not according to real life.

You can only define slabs/walls (as structural members) in a shell structure type model !!

You cannot go back to frame 3d type expecting the shell objects will appear there like magic

Re: Modelling a wide cap beam in Robot

Anonymous — Thu, 27 Jul 2017 12:17:53 GMT

Thank you Artur. It was very helpful.

Re: Modelling a wide cap beam in Robot

Rafacascudo — Thu, 27 Jul 2017 12:31:37 GMT

Life is hard ...

Re: Modelling a wide cap beam in Robot

Anonymous — Thu, 27 Jul 2017 12:34:42 GMT

life really sucks, I don't know why the hell I chose engineering and why the structural engineering MSc 10 years after my BSc...?!?!

I should blame dad lol

Re: Modelling a wide cap beam in Robot

Artur.Kosakowski — Thu, 27 Jul 2017 12:36:06 GMT

Hi @Rafacascudo

With all the help you provide it is actually pretty easy

I really do appreciate it. Thank you.

Re: Modelling a wide cap beam in Robot

Anonymous — Thu, 27 Jul 2017 20:17:12 GMT

I was just wondering if there is anyway to make the section independent from points coordinate or create it using relative dimensions ?

I tried your way and it perfectly worked in Plate mode, but once I copy it to another 3D frame file the shape gets distorted. and If I define the slabs in a 3D frame file, the top surface is drawn with a slope by default.

Maybe there is way to draw it in plate mode and merge the segments and make a solid object ?!?!?

Re: Modelling a wide cap beam in Robot

Rafacascudo — Thu, 27 Jul 2017 21:07:49 GMT

"Shell"structure type = "3d frame" structure + shell objects (slabs, walls).
You will NEVER get a perfect geometry for this model. Slab face can be horizontal if you model an inclined panel as Artur suggested in his sketch. But your thicknesses (65cm,150cm) will not be vertical.

If you really need a 100% perfect geometry model , use Solid structure type.
But then your life will really become hard 🙂