Structural Slabs are at different height when importing IFC file into Archicad 27

[Burak]

Hello there!

We have an IFC structural model from our engineer. We want to embed it into our model, as a hotlink, so our architectural and static models are comparable all the time.

When I place them as hotlinks, or just directly open IFC files in Archicad, the slabs are at different heights (the top of slabs and columns and beams should be at the same level). If we open IFC model in an IFC viewer (like Solibri v24.5) model seems OK and with no errors; but when we introduce IFC model into Archicad, slabs are sitting at different heights.

Actually, the same problem exists with Archicad 25, I tried the same workflow a couple of years back too but no luck either... IFC Model is attached, you can check it. We all know just IFC model has been exported as IFC2x3.

edit: you can download IFC Model from here: WeTransfer Model 
It is funny that we can attach even .apx files but not .ifc files here. 🙂

Operating system used: Windows 27.5003

  

[JeffH]

are the IFC stories different than the stories in your model?

That is usually the issue with the IFC's we get from our engineers.

[Burak]

Hello Jeff,

Thanks for your reply. I've checked story settings, only our AC files are all at 0 elevation, but the federated IFC model has ground floor top elevation of 38 cm's. Story levels have the same equal heights (306 cm) on all files.

I've created another fresh Archicad file and imported our engineer's IFC file. The result is the same, slabs' top elevations are different from what they are supposed to be. I've shared screenshots. You can check story settings of AC and IFC file, but we are getting same error about model.

  

  

[JeffH]

I believe the issue is due to the 0 and -1 stories being different between the 2 models.

As soon as you bring that ifc into your model, it will attempt to adjust elements based on the settings you have selected in the hotlink manager dialog (maybe adjusting these settings will solve your issue)

I can't speak on Solibri.

I only know that every time the consultants IFC story's are different then our models it creates chaos with our models.  We always have them adjust back to the levels we have defined.

[Burak]

Hi Jeff,

Nah, probably the cause of that error has a different reason. I've created a blank new Archicad file, according to IFC's story and level settings, and placed hotlink (and tried merging model with the same steps and different translators). Results are the same: same slabs have different elevations in Archicad and Solibri (and in engineer's program too), as they are in same IFC model and file.

The interesting part is, in Archicad, slabs are at a lower elevation than they are supposed to be; but their elevation difference is equal to their thickness. I mean, a 20cm thick slab is 20cm lower than the original position in Archicad than IFC model and then 15 cm slabs are 15 cm lower in Archicad... I am guessing (like I am shooting a line here :)) that maybe there can be a problem with Archicad's reference point (top of slab) for slabs are different or working differently from our engineer's originating program (ProtaStructure 2024); as if I change reference points of slabs in Archicad, they come to their normal positions. But, as I said, I am "guessing". And this answer is not explaining much about why IFC model is normal in some viewer but not normal in Archicad...

The problem exists since several years actually, and I am sure that ProtaStructure is using IFC 2x3 Coordination View 2.0 standart.