The mysteries of IFC

[jorisvanbosscheY8PG3]

I'm doing some tests with exporting Revit projects to IFC.

I'm using Revit 2022 with the default IFC exporter, and I'm exporting to IFC 4.

1. I've created 5 setups with each time the same 4 elements.

Element 1 = Wall

Element 2 = Structural Framing, created started from the Generic model line based.rfa

Element 3 = Generic model, created started from the Generic model line based.rfa

Element 4 = Structural Framing from the Autodesk Library (Belgium)

2. The export settings are stored in the attached rvt-file under the name 'Wyckaert'. For the IFC options I'm using the default Autodesk file 'exportlayers-ifc-IAI.rvt'. In this file you'll see that Structural Framings are exported to IfcBuildingElementProxy.

 

3. I'll check the IFC (also attached to this post) with Solibri.

- My own created StructuralFraming is mapped to 'Object'. Which I was expecting using the txt file in the IFC Options.

But why does it dissappear when I try to map it to IfcCovering in the second setup?

- The Structural Framing of Autodesk is mapped to IfcBeam. Why does this happen with the current export settings? Is there a hidden option in those families that overrides the IFC options?

- In the second setup this family is still available as IfcCovering. So this family can be mapped to another IfcClasse.

I'm not saying that the current export settings and the current families are the best settings and families, but I'm just trying to understand what's happening when creating families and exporting them to IFC.

I hope someone can explain what's happening and why...