Dear Dlubal Support Team,
In RFEM 6 I have a steel pipe (cylindrical surface) and I want to add a concrete pipe next to it, with a contact between the two surfaces that transfers all loads (normal and shear) between steel and concrete.
The problem is that the contact surface feature only works for "plane" surfaces — not pipe, trimmed, or curved surfaces — so I cannot connect my two cylindrical surfaces.
How can I create a load-transferring contact between two curved (cylindrical) surfaces?
Hi waelnoaman,
welcome to the community!
Surface contacts for curved surfaces are planned.
As an alternative, you can use the contact volume already known from RFEM 5 in RFEM 6:
https://www.dlubal.com/de/downloads-und-infos/dokumente/online-handbuecher/rfem-6/000042
Best regards
Stefan Hoffmann
Hello Mr. Hoffmann,
Thank you very much for your response.
May I quickly ask: Do you mean that I should model the two cylinders as volume bodies (solids) instead of surfaces and then create a contact volume in between? As far as I understand, the contact volume only works between volume bodies.
In the meantime, I have created the solution shown in the attachment: I divided the two cylinders into small sub-surfaces and then defined a surface contact between each sub-surface and the opposing sub-surface.
Is this a sensible approach, or do you instead recommend modeling with volume bodies and contact volumes?
Thank you in advance.
Best regards
Wael Noaman
Hi waelnoaman,
thank you for your inquiry.
A contact volume can easily connect 2 regular surfaces. You do not need to create additional volumes for the cylinders.
Your approach to approximate the round structure with flat surfaces is also possible.
However, if you quarter the cylinders and connect each with a contact volume, this should be more accurate in the modeling. I cannot assess whether the "error" caused by the approximation will be significant.
Best regards
Stefan Hoffmann
Hello Mr. Hoffmann,
Thank you very much for your reply.
I tried to create the contact volume as described between the two cylinders, but it does not work for me—apparently because these are surfaces and not volumes (see screenshot attached).
Did I misunderstand something here? Could you please briefly explain to me exactly how the contact volume between two (curved) surfaces must be defined?
Thank you in advance.
Best regards
Wael Noaman
Hi waelnoaman,
Thank you for your message!
To analyze the problem more precisely, the model file would be very helpful before you generate the contact volume:
Click on File → Save As and choose the following settings to reduce the file size:
Then upload the file here (e.g., *.rf6, *.rs9) – so the community can also help find a solution.
Don't want to share the file publicly? No problem – send it to me via direct message: click on my profile picture or my username → Message.
Best regards
Stefan Hoffmann
Hello Mr. Hoffmann,
Thank you very much for your message.
Attached you will find the model file, saved with the settings you specified. The model contains only the two cylinders (steel and concrete), between which I want to create a contact for full load transfer.
Thank you very much for your support
trial.rf6 (1.3 MB)
Hi waelnoaman,
thank you for your model. I have added the 4 necessary side surfaces from the volume and then defined the contact volume. I had no problems with that.
trial_mod.rf6 (1.0 MB)
Best regards
Stefan Hoffmann
Please update RFEM to the current version:
https://www.dlubal.com/de/support-und-schulungen/support/faq/005108
Hello Mr. Hoffmann,
thank you very much for your help and for the corrected model.
Unfortunately, I cannot update to the latest version: I share the model with colleagues who also have to work with it, so I have to stay with my current version. Therefore, I am unable to open your file.
Could you please send me a few screenshots instead, showing what you did in the model? In particular, I would be interested in which 4 side surfaces you added and how you subsequently defined the contact volume.
Thank you very much in advance.
Best regards
Wael Noaman
Hi waelnoaman,
attached is a video.
Best regards
Stefan Hoffmann
Hello Mr. Hoffmann,
Thank you very much for the video – it was exactly what I needed! Now I understand which areas need to be added and how to define the contact volume.
Thank you for your quick and detailed support.
Best regards
Wael Noaman
Hello Mr. Hoffmann,
Thank you again for your help.
Unfortunately, even this simple model cannot be calculated – the calculation does not complete. I have attached the model for your review.
trial.rf6 (1.3 MB)
Hi waelnoaman,
the contact volume is possible if you follow the specifications.
However, you can also approximate it with your modeling. I can hardly predict any potential problems.
Best regards
Stefan Hoffmann
Thank you very, very much!
