topic How to model one way span slabs in Robot Structural Analysis Forum

How to model one way span slabs

Anonymous — Tue, 19 Apr 2016 21:58:05 GMT

Hi,

I have read some posts of modeling one-way slabs. (e.g. hollowcore, prefabricate one way)

I would like to have the opinion of the best way of getting the model correct (in load distribution and forces one supporting members:

1. Use of claddings only to distribute loads? Does this work with deep-beams that suspended the clading?

2. Use of calculation model of panel definition?

3. Use of orthotropic option, with small value of stifness in the minor direction?

Thank you for the support.

Re: How to model one way span slabs

Rafacascudo — Tue, 19 Apr 2016 23:14:37 GMT

1- Claddings will work well ,distributing the load acurately mainly when load is distributed on cladding whole area. For other loads (linear, concentrated, distributed on contour), the distribution can become VERY innacurate.

2- same as cladding if you set it with no FE and trapezoidal load distribution method

3- it's an option

4- another option is using linear releases (vertical shear) on the edges of the FE panel you do not want receive load

Re: How to model one way span slabs

Anonymous — Sat, 23 Apr 2016 08:07:05 GMT

Thanj you for your precise and quick answer.

Thank you also for your advices regarding the errors in distribution of concentrated and linear forces on claddings.

Your last suggestion is an interessing one. That's what the former CBS do when we model one way slab and the export the model to Robot. Although, I found this impracticable considering the errors and issues due to this type of releases in the model.

Thank you again for sharing this experiences en modeling.

Regards.

Re: How to model one way span slabs

Rafacascudo — Sat, 23 Apr 2016 16:21:14 GMT

Errors? For neighbor panels that share a Common edge ,set the release only on one of the edges. Releasing both Will cause errors

Re: How to model one way span slabs

saclovitzky — Tue, 26 Apr 2016 07:59:37 GMT

Hello Rafascudo,

How do you provide linear releases on the side of a slab that will prevent it attracting any loads?

Can you show how to do it?

Regards,

Re: How to model one way span slabs

Rafacascudo — Tue, 26 Apr 2016 12:35:43 GMT

All the load goes to the beams that support no Uz released panel edges.

Re: How to model one way span slabs

saclovitzky — Tue, 26 Apr 2016 16:28:44 GMT

Thanks Rafascudo,

I have a situation where the "roof" slab is deck slab(one-way), but its edges are connected to the supporting walls below, despite the fact that it is acting one way, there's a certain portion of the loads "attracted" to the supporting walls parallel to the direction of the load. Is it OK to apply linear releases on the "edges" of the slab parallel to the direction of the loads in order to prevent transferring of loads?

Again, thank you very much

Re: How to model one way span slabs

Rafacascudo — Tue, 26 Apr 2016 21:15:13 GMT

Why not? Try it and check if there are any loads going to the walls

Re: How to model one way span slabs

saclovitzky — Wed, 27 Apr 2016 07:56:21 GMT

Hello Rafascudo,

I have the same result with slab(shell) with linear releases and slab(deck-one way) with and without linear releases. There's always a portion of the load "spilled" on the side walls(parallel to the load direction). Is there a way to prevent it? My only workaround on this one, is modelling a slab with a 20mm gap on the sides that I do not want to be loaded. Is there any other way to do this?. The disadvantage of this, is that, because of the gap, I do not have a "restraint" on the wall?

Any ideas will be greatly appreciated.

Re: How to model one way span slabs

Rafacascudo — Wed, 27 Apr 2016 11:35:41 GMT

send the model

Re: How to model one way span slabs

saclovitzky — Fri, 29 Apr 2016 16:16:28 GMT

Hello Rafascudo,

Pls. see attached model and screenshots.

It seems to me that, based on the result, deck slab is much better to model a one-way distribution compared with shell slab (with linear releases).

Also, is there a way to have a "perfect" one way load distribution(no load shld be trasferred to non-load bearing wall)?

Regards,

Re: How to model one way span slabs

Rafacascudo — Sun, 01 May 2016 18:07:00 GMT

It will be not , if you also release the moment ( Rx) at these edges on the shell model.

Re: How to model one way span slabs

RFreund — Sun, 24 Aug 2025 20:19:37 GMT

I came across this and it was helpful. Since this is a pretty old post, I'm curious if your concerns about load distribution are still applicable?

It seems that there are more options now for one-way slabs now, notably: Deck Slab (one-way) and Load Take Down slab (one-way).

What are the pro's and con's of each?

If I want a one-way slab that can also act as either a rigid or semi-rigid slab, am I limited to one of the options?

Is it possible to use Load Take Down slab and also use another panel as a rigid/semi-rigid diaphragm?
Is it possible to have a panel that has no FE but also has stiffening in the XY plane?