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

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johnwang
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Re: [IFC Export] Problems with IFC (structural view) export/import

Postby johnwang » Thu Jan 14, 2021 9:19 pm

balrobs wrote: Thu Jan 14, 2021 2:36 pm
So I managed to come to this result:
This is cool.

Could you share a simple ifc file, I want to try to import it into Mystran/Nastran95. Thanks.
hfc series CAE workbenches for FreeCAD (hfcNastran95, hfcMystran, hfcFrame3DD, hfcSU2 and more)
balrobs
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Re: [IFC Export] Problems with IFC (structural view) export/import

Postby balrobs » Fri Jan 15, 2021 7:56 am

johnwang wrote: Thu Jan 14, 2021 9:19 pm
balrobs wrote: Thu Jan 14, 2021 2:36 pm
So I managed to come to this result:
This is cool.

Could you share a simple ifc file, I want to try to import it into Mystran/Nastran95. Thanks.
Of course!
Here is the ifc file exported from FreeCad. Be aware that it comes with the limitation described in previously posts:
Test_IFC_3_storeys_01.ifc
(16.93 KiB) Downloaded 18 times
And here the ifc files exported from RFEM after the import and a simple structural analysis (self weight):
Test_IFC_3_storeys_02.ifc
(48.15 KiB) Downloaded 22 times
Have fun with it :D
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yorik
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Re: [IFC Export] Problems with IFC (structural view) export/import

Postby yorik » Fri Jan 15, 2021 1:07 pm

balrobs wrote: Thu Jan 14, 2021 3:12 pm I can't find this Nodes property for Arch Walls. Could this be the reason why for Walls the IFC-Exporter don't work
Yes. Indeed walls don't have that property. You should either model walls using the Structure tool (change their IFC type to Wall afterwards), or use the wall tool, then use the structure tool on top of it to convert it to structure (then change the IFC type). But indeed it would be useful to add the Nodes system to walls too. I'll take care of that.

I'll also fix the end vertex for slabs. Indeed that seems obvious.

About the rest, how to manipulate things... Indeed the best way would be to be able to select the nodes and move them around like any other geometry. Maybe an interesting workflow could be this:

1) You can model node lines manually, using lines and polylines
2) You can attach such a line or polyline to a structural object, for ex. a NodeObject property. If such property is set, the struct object derives its nodes from the attached object and not automatically anymore
3) You can move, trim, edit, rotate... the lines/polylines, the nodes will be automatically adjusted

About section properties and materials, that is already done actually, if you export a hybrid model with both the IFC product (beam, column...) and IFC structural element. But not sure how many softwares out there can use that... Maybe there is some better way?
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bernd
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Re: [IFC Export] Problems with IFC (structural view) export/import

Postby bernd » Sat Jan 16, 2021 7:44 pm

None I know of. ATM materials an cros sections should be included in the structural analysis ifc.
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Re: [IFC Export] Problems with IFC (structural view) export/import

Postby balrobs » Sun Jan 17, 2021 7:46 am

yorik wrote: Fri Jan 15, 2021 1:07 pm
balrobs wrote: Thu Jan 14, 2021 3:12 pm I can't find this Nodes property for Arch Walls. Could this be the reason why for Walls the IFC-Exporter don't work
Yes. Indeed walls don't have that property. You should either model walls using the Structure tool (change their IFC type to Wall afterwards), or use the wall tool, then use the structure tool on top of it to convert it to structure (then change the IFC type). But indeed it would be useful to add the Nodes system to walls too. I'll take care of that.
Thank you so much @yorik for taking care of this issue. It would be wonderfull if walls could have a Nodes system too.
yorik wrote: Fri Jan 15, 2021 1:07 pm I'll also fix the end vertex for slabs. Indeed that seems obvious.
Awesome! That would mean that this step would no longer be necessary in the further processing software.
BTW while you are on it ... what do you think about not creating IFCSTRUCTURALCURVEMEMBER's on the slab loop but instead a IFCSTRUCTURALSURFACEMEMBER for it. IMHO this shouldn't be too difficult and would be very helpfull for further structural analysis.
I took a look at some FreeCad generated IFC file and the IFC specifications trying to understand the changes required in this regard:

Current approach: now for every edge on the slab loop:
  • create IFCEDGE
  • create IFCTOPOLOGYREPRESENTATION for IFCEDGE
  • create IFCPRODUCTDEFINITIONSHAPE for IFCTOPOLOGYREPRESENTATION
  • create IFCSTRUCTURALCURVEMEMBER for IFCPRODUCTDEFINITIONSHAPE
Proposed approach: for every slab (hopefully correct :? ):
  • create IFCEDGE for every edge on the slab loop (already done by now)
  • create IFCORIENTEDEDGE(*,*,#IFCEDGE,.T.); for every edge on the slab loop
  • create IFCEDGELOOP((list of IFCORIENTEDEDGE on the slab loop));
  • create IFCFACEBOUND(#IFCEDGELOOP,.T.)
  • create IFCPLANE (already done by now)
  • create IFCFACESURFACE((#IFCFACEBOUND),#IFCPLANE,.T.);
  • create IFCTOPOLOGYREPRESENTATION(#...,$,'Face',(#IFCFACESURFACE))
  • create IFCPRODUCTDEFINITIONSHAPE($,$,(#IFCTOPOLOGYREPRESENTATION))
  • create IFCSTRUCTURALSURFACEMEMBER('...',#...,'Slab',$,$,#..,#IFCPRODUCTDEFINITIONSHAPE,.SHELL,SLABTHICKNESS)
As an example I modeled a simple rectangular slab in FreeCad, exported the IFC file with the current approach and then modified it by hand accordingly to my proposed approach.
Screenshot.PNG
Screenshot.PNG (138.21 KiB) Viewed 1058 times
Rect_Slab.FCStd
(14.23 KiB) Downloaded 21 times
Rect_Slab_current_approach.ifc
(3.18 KiB) Downloaded 18 times
Rect_Slab_proposed_approach.ifc
(4.24 KiB) Downloaded 24 times
yorik wrote: Fri Jan 15, 2021 1:07 pm About the rest, how to manipulate things... Indeed the best way would be to be able to select the nodes and move them around like any other geometry. Maybe an interesting workflow could be this:

1) You can model node lines manually, using lines and polylines
2) You can attach such a line or polyline to a structural object, for ex. a NodeObject property. If such property is set, the struct object derives its nodes from the attached object and not automatically anymore
3) You can move, trim, edit, rotate... the lines/polylines, the nodes will be automatically adjusted
Indeed, this could be a way to go. If I understand you correctly, an advantage of this approach would be that e.g. slabs with circular borders could also be transferred to IFC. Am I right?
bernd wrote: Sat Jan 16, 2021 7:44 pm None I know of. ATM materials an cros sections should be included in the structural analysis ifc.
I will investigate further and will be back here when I found something useful!

Edit1: Corrections in proposed approach and appending sample files for a simple rectangular slab
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bernd
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Re: [IFC Export] Problems with IFC (structural view) export/import

Postby bernd » Sun Jan 17, 2021 10:08 pm

balrobs wrote: Sun Jan 17, 2021 7:46 am
bernd wrote: Sat Jan 16, 2021 7:44 pm None I know of. ATM materials an cros sections should be included in the structural analysis ifc.
I will investigate further and will be back here when I found something useful!
something to start with ... https://github.com/berndhahnebach/Ifc_S ... .ifc#L1615 and https://github.com/berndhahnebach/Ifc_S ... t.ifc#L211 there should be a surface member as well.
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Re: [IFC Export] Problems with IFC (structural view) export/import

Postby balrobs » Mon Jan 18, 2021 8:09 am

bernd wrote: Sun Jan 17, 2021 10:08 pm ...
something to start with ... https://github.com/berndhahnebach/Ifc_S ... .ifc#L1615 and https://github.com/berndhahnebach/Ifc_S ... t.ifc#L211 there should be a surface member as well.
Thank you @Bernd for the Links! :)
balrobs
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Re: [IFC Export] Problems with IFC (structural view) export/import

Postby balrobs » Tue May 18, 2021 4:05 pm

balrobs wrote: Thu Jan 14, 2021 10:43 am According to my understandig StructuralSurfaceMember are not yet supported and the StructuralCurveMember generated instead on the contour are missing the contour closing member. That's too bad :cry:
Hopefully there will be someone with the necessary skills willing to pick up this issue and improve the IFC export. IMO this feature would be extremely important for collaborations in the BIM process.
I tried to learn some Python basics and to understand the IFC export and just submitted this pull request https://github.com/FreeCAD/FreeCAD/pull/4799. to improve the IFC export for slabs.
Certainly not perfect but seems to work :D
ifc_export_test.jpg
ifc_export_test.jpg (163.62 KiB) Viewed 727 times
Attachments
ifc_export_test.FCStd
(25.89 KiB) Downloaded 8 times
paullee
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Re: [IFC Export] Problems with IFC (structural view) export/import

Postby paullee » Tue May 18, 2021 5:03 pm

balrobs wrote: Tue May 18, 2021 4:05 pm I tried to learn some Python basics and to understand the IFC export and just submitted this pull request https://github.com/FreeCAD/FreeCAD/pull/4799. to improve the IFC export for slabs.
Certainly not perfect but seems to work :D
Wow! Impressive progress ! :D

I have not much idea about IFC at the moment. Look forward to your coming contribution !
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bernd
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Re: [IFC Export] Problems with IFC (structural view) export/import

Postby bernd » Tue May 18, 2021 8:59 pm

you are a offical FreeCAD developer, welcome to the party :D https://github.com/FreeCAD/FreeCAD/comm ... or=balrobs

git commit 8ac722c1e89e