• Registered: 2025-10-23
  • Posts: 2

Topic: RC beam in a thin-walled steel formwork

I want to model the behaviour of a RC beam cast in thin-walled steel formwork. The idea is that the formwork is part of the load-bearing element, and I want to model their cooperation during loading. And here I have some doubt:

1. Is the only way to model thin-walled C profile (thickness 2 mm) and connect its web and flanges is to use solids and master/slave connection, or is there a way to do it with 2D elements?

2. I tried to create solids and then assign to them Shell 3D elements, but I got a message saying that there was a problem with LCSs. How to fix this? How to check and change solids to make it work?

3. I also received a message saying that they do not recommend using Shell 3D with a single layer that is only 2 mm thick. Should I be concerned about this message?

Quote Post 1

  • Registered: 2019-10-24
  • Posts: 9

Re: RC beam in a thin-walled steel formwork

Dear Ewelina,
It is possible to do it with 2D or 2D/3D Shell elements. I would recommend you to check the ATENA-Science-GiD_Tutorial_Strengthening.pdf that is in installation package. There are all these types of models explained and also the definition of LCSs.
Regarding the Shell thickness it is always recommended to use at leas 4 layers within one shell to get reasonable results.

Quote Post 2

  • Registered: 2025-10-23
  • Posts: 2

Re: RC beam in a thin-walled steel formwork

Thank you for your answer.

How can I connect the flanges to the web of the steel C profile if I use 2D surfaces to model them?

I know that this shell option recommends to have at least 4 layers and each of them at least 20 mm thick. But my profile is 2 mm thick so even with 4 layers I want't satisfy the second condition. Can I give 4 layers and ignore that they are thick enough?

Quote Post 3