topic Question regarding shell modelling continuity in Robot Structural Analysis Forum

Question regarding shell modelling continuity

Ataíde — Fri, 17 Oct 2025 10:55:14 GMT

Hello!

I'm trying to make a concrete slab, and faced this modelling situation:

Modelling the slab as one, or splitting it between beams gives different results for the reinforcement maps.

I noticed this in the model I was working, and the difference was quite huge, as shown in image (the tags decided to disappear, I don't know why they do it sometimes. But on the upper side the deflection is 2.4cm, on the lower side it is 3.4cm):

So I made a simpler model to analyse it, which I share annexed (the jump isn't as noticeable, but it's there).
On top, slab modeled as one, on bottom, slab split in the beam.

Deflection u

Area reinforcement X-:

Mesh and axis considered:

I'm new to shell modelling and need to study this further, but would like to know beforehand if this is expected, and if I'm missing something. It only happens in the reinforcement maps, regular maps everything is smooth.

Thanks in advance!

Re: Question regarding shell modelling continuity

Romanich — Mon, 20 Oct 2025 23:23:42 GMT

Hi @Ataíde ,

Re: Question regarding shell modelling continuity

Ataíde — Tue, 21 Oct 2025 09:06:53 GMT

Hello @Romanich,

Thank you for your reply. The solution doesn't seem to solve the issue:

Is it a wrong modelling procedure to make the slabs separate at the beams?

Re: Question regarding shell modelling continuity

Romanich — Tue, 21 Oct 2025 14:01:33 GMT

Hi @Ataíde

Re: Question regarding shell modelling continuity

Ataíde — Tue, 21 Oct 2025 17:21:38 GMT

Hello @Romanich ,

Thank you very much for your reply.

So if I understand correctly, when working with a slab that's modelled as separated shells, in order to use the reinforcement calculation from Robot, it is needed:

For the reinforcement areas, the "globally average design forces"
For deflection, verification -> with FEM method

Without these premisses the results aren't accurate.

Is this correct?