topic Re: Foundation slab - different thickness in Robot Structural Analysis Forum

Foundation slab - different thickness

Anonymous — Wed, 22 Oct 2014 18:20:46 GMT

Hello,

I would like to ask you about helping me with my problem.

I would like to model foundation slab, which has two different thicknesses of panels. When I create two panels, the thickness of them starts from the axis int the middle, and I would like to have a bottom on the same level....I have no idea how to model it...

To precise, one of part is 2 x 2 m, thickness: 0,5m, and the second one: 2 x 2 m and thickness is 1,0m. I would like those parts working together of course. Is it better to make two separate panels or maybe is there any other way?

Which type of model will be the best for such construction? Is it Building design or maybe Slab Creator?

Thank you for your help 🙂

Re: Foundation slab - different thickness

Rafal.Gaweda — Fri, 24 Oct 2014 08:13:54 GMT

1. Create and mesh panels in one plane
2. Freeze meshes
3 Copy one of these panels below and delete the original one used for copying
4. Connect pairs of "edge" nodes (to connect lower and upper panels) by rigid links

Re: Foundation slab - different thickness

Anonymous — Fri, 24 Oct 2014 13:18:58 GMT

Hello,

thank you for your response.

I had made 3 points of your instruction and I stoped on 4th one.

I would like to ask, what do you mean by: "Connect pairs of "edge" nodes (to connect lower and upper panels) by rigid links"

What are rigid links? Supports..or maybe some rigid bars?

I have tried to model it as you can see on image MES in attachments, by moving all "edge" nodes of lower panel mesh to the upper one. Is it correct?

My clear model after 3 steps from your instructions looks like image MES 2 in attachments.

Thank you again 🙂

Re: Foundation slab - different thickness

Rafacascudo — Fri, 24 Oct 2014 13:43:39 GMT

Rigid links on , geometry/additional atributes/ Rigid links.

You can link the pair of nodes one by one or use " according to list" if you have many pairs of nodes to link

Re: Foundation slab - different thickness

Anonymous — Fri, 24 Oct 2014 13:50:37 GMT

Thank you very much!

Works pefectly

Re: Foundation slab - different thickness

Anonymous — Fri, 25 Sep 2015 15:45:26 GMT

Hello,

If you want to keep the level of the two different thicknesses of the slabs the same (one 600 thick and adjoing 200mm) , and are supported by on edges by RC walls, is there much merit in adopting this approach?

The wall panels would need to be adjusted too and rigid links adopted in the vertical plane. Is this introducing a complexity that is not rquired?

Many thanks

Cheers

Lee

Re: Foundation slab - different thickness

Rafacascudo — Fri, 25 Sep 2015 19:32:53 GMT

If I understood correctly , forget the rigid links , and connect the slabs directly to the wall on the appropriate levels

Re: Foundation slab - different thickness

Anonymous — Mon, 28 Sep 2015 07:00:58 GMT

Rafael,

Thanks for your reply.

I will use the rigid links for the step in slab levels abd split the walls and adjust the respective heights to suit.

Cheers

Lee

Re: Foundation slab - different thickness

Anonymous — Thu, 06 Dec 2018 06:50:20 GMT

Hi Rafacascudo,

Could this solution also be applied for a step in a slab as per attached drawing?

Re: Foundation slab - different thickness

Rafacascudo — Thu, 06 Dec 2018 13:35:36 GMT

It could be .

But If it´s a regular building slab and there are no horizontal forces involved , I would model the 2 slabs on the same level with the beam between them.

Re: Foundation slab - different thickness

Anonymous — Thu, 06 Dec 2018 13:54:51 GMT

Then how would you get the efforts in the beam that forms there?

Re: Foundation slab - different thickness

Rafacascudo — Thu, 06 Dec 2018 16:26:35 GMT

1- Model with the 2 slabs on the same level and the beam modelled as a bar element receiving the load from the slabs

2- 2 slabs on different levels with the beam modelled as a panel linking both slabs . Forces on this "beam" /panel obtained through panel cuts reduced results.

Re: Foundation slab - different thickness

Anonymous — Thu, 06 Dec 2018 16:50:00 GMT

Thanks.

And if I choose the 2nd option is there a way to see the bending moment Myy(for a beam) in the panel/beam?

If I do a panel cut along the x axis the result look strange.

Re: Foundation slab - different thickness

Rafacascudo — Thu, 06 Dec 2018 19:02:39 GMT

Reduced moment(X,Y,Z) is given on relation to global coordinate system . So like in the picture below , you will have to do several cuts along the panel/beam lenght to have the values you want/need.

I did just one cut at midspan to compare bending moment on the panel/beam with the on in bar/beam.

Re: Foundation slab - different thickness

Anonymous — Fri, 07 Dec 2018 14:48:14 GMT

Thanks Rafacascudo

Re: Foundation slab - different thickness

Anonymous — Wed, 02 Jan 2019 15:01:48 GMT

I'm reviewing a model where small steps in various slabs are modelled as panels, so this question is on my radar now.

My question is, what are the pros and cons to modelling two slab levels and putting rigid links (as suggested early-on in this thread), versus the panel or the bar approach you suggested in the latter half of this thread?

Re: Foundation slab - different thickness

Artur.Kosakowski — Wed, 02 Jan 2019 16:32:44 GMT

Hi @Anonymous

IMHO the answer what option to decide on is based on the kind of results you want to see in the 'connection':

forces in rigid links, diagrams in a bar, maps in a panel

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.

Re: Foundation slab - different thickness

Anonymous — Thu, 03 Jan 2019 09:15:12 GMT

Fair enough, thanks. I was thinking one method was far more efficient than the other, or less likely to cause computational problems. When our model has a panel in there, the mesh doesn't look much different than a series of rigid links anyways (not a highly refined mesh).