[IFC Export] Problems with IFC (structural view) export

balrobs · June 15, 2021, 6:27am

So if I got it correctly it would be preferable to have only one material for both disciplines with all its properties.
I will try to understand the existing FreeCAD code and see how I can modify it to fit this needs.

Thank you @Moult for your valuable contribution
Kind regards

Jesusbill · June 15, 2021, 9:25am

@balrobs I am kind of leaning towards the use of a common material where possible. Certainly I would not be in favour of duplicate materials with the same name, as materials are non-root entities and there is no way to tell one of the other. At the end of the day, we want to promote collaboration between disciplines, so I think that in a general use case one can think that the architect uses a general “Beton” material for all concrete elements.
Then, the engineer, specifies for each element the specific grade/class so he is enhancing the available information relative to his domain. In that case it would make sense in my opinion that this new piece of information propagates back to the 3D model IfcElement related entities

@bernd the link Dion provided gives the thread, these comments are the most relevant https://community.osarch.org/discussion/comment/944/#Comment_944

PS: Nice screencast by the way!

Jesusbill · June 15, 2021, 10:00am

Found also this related thread https://community.osarch.org/discussion/99/ifc2ca-short-presentation
Had forgotten about it

bernd · June 15, 2021, 10:53am

Sorry for the late reply. Yes, Reference is more correct than Analysis.

IFC materials do not distinguish between architectural and structural. All IFC materials can store properties (e.g. youngs modulus) regardless of which discipline uses it. The same Ifc Material may be shared between disciplines (in an ideal, integrated world).

The relationship between the architectural model (i.e. body shapes) and structural model (i.e. stick model with analysis) is given by IfcRelAssignsToProduct.There are some discussions here: https://community.osarch.org/discussion/9/integration-of-code-aster-in-an-ifc-driven-workflow-for-structural-analysis/p1

So if I got it correctly it would be preferable to have only one material for both disciplines with all its properties.
I will try to understand the existing FreeCAD code and see how I can modify it to fit this needs.

IMHO and AFAIK. As said the hybird ifc just saves both models into one ifc file. They are totally independent from each other. They are just in one file. As long as they are independent you would have to create spearate materials for architecutral and for structural data.

On the contrary, if you would like to start to make one model out of it, no longer a hybrid out of two independent ones, it makes sense to use just one material for structural data and for architectur data.

BTW: these hybrid modells might not be standard according buildingSMART. We schould make sure they are before start to connect them.

balrobs · June 15, 2021, 3:28pm

Thanks @Jesusbill for the links!
a lot to learn … will read it carefully.
Kind regards

balrobs · June 15, 2021, 3:55pm

I’m not quite sure about that. Studying @Yoriks IFC-exporter I found this lines of code, which should bind architectural (product) and structural objects (structobj) together

# associate with structural analysis object if any

        if structobj:
            exportIFCStructuralTools.associates(ifcfile,product,structobj)

I totally agree!
Before deciding how to procede we should check this and come to a consensus!
Maybe this two hybrid IFC files genereated for my test structure could be helpfull.
Proposal1: Material duplication (one for architectural one for structural elements)
prop1_hybrid_model.ifc (55.3 KB)
Proposal2: No material duplication (one material both for architectural and structural elements)
prop2_hybrid_model.ifc (53.1 KB)