Rebar export-Export rebar sets as one instance

[COWItvo]

Familiar with issue #75 Revit need to improve the visualization of rebar layouts for the user in native IFC. It would be a huge improvement to get the possibility to export rebar sets as grouped instances. Today the IFC export from revit will split the revit rebar sets in to separate IFCelements that have a relation to a group.
Selecting a IfcReinforcingBar in a IFC viewer don`t give the user any information of the distribution length to the group of the selected element. The user need to use a grouping tool like ITO in Solibri or a classification to show the distribution.

Please see attached screenshot

[Nordlenningen]

This function should be implemented as an option, not as the only choise. Groups can be problematic to handle in a "ordering system", when you need to order only parts of groups.

[eibre]

@WawanSolihin Maybe this is a change from IFC 2x3 to 4 ?

A reinforcing bar is usually made of steel with manufactured deformations in the surface, and used in concrete and masonry construction to provide additional strength. A single instance of this class may represent one or many of actual rebars, for example a row of rebars.

http://www.buildingsmart-tech.org/ifc/IFC4/final/html/schema/ifcstructuralelementsdomain/lexical/ifcreinforcingbar.htm

I would say that in most cases it would be more user friendly to have the rebars exported as sets, the same way we are used to work with them in Revit, and the same way that e.g. Tekla does it.

[WawanSolihin]

I am not very familiar with the detailed behavior for the rebar. Are you saying that in IFC2x3 the rebar is created as one geometry with multiple items for the individual rebar, whereas in IFC4 they become individual objects that are grouped into an IfcGroup?
Currently if you export the rebar in Revit 2019 for IFC2x3, do you still get one geometry with multiple items, or is it the same as the IFC4 as a group?

[eibre]

@WawanSolihin Hope this clarifies:
I just noticed a difference in the definition of a IfcReinforcingBar given by Building Smart between IFC2x3 and IFC4. The following is added in IFC4:

A single instance of this class may represent one or many of actual rebars, for example a row of rebars.

In Revit we have both single bars, and rebar sets which is a rebar distributed along some distance and with a given spacing.

I was wondering if the decision to break the sets into individual bars was made because ifc2x3 seems to define IfcReinforcing bar as a single bar?

Groups

IFC-export from Revit 2019 both 2x3 and 4 gives the same result, individual IfcReinforcingBars that are grouped:

Unfortunately the groups doesn't add much value:

• Few IFC viewers has the functionality to select groups by clicking in 3D view. (Nor Solibri og BIMCollab, but BIMVison lets your right click and select group)
• The group is only a logical collection of objects and can't hold info about the rebar set that it represents. A rebar set should at least give info about the spacing and number of bars in a set, And also a Rebar Number and all the properties that are common to the bar in the set.
• We always group several rebar sets together in Revit to prevent rebars from beeing edited accidentally after they are sent to production. The rebar groups are then replaced by this group:
  

Conlusion:

It would be better to give us the opportunity to export a Revit Rebar Set to a IfcReinforcingBar.

[COWItvo]

Any progress from Autodesk side on this request? We also see that there are a issue with filesize when it comes to use of single rebar instances. The IFC files are huge. According to one on our projectteam that have analyzed the IFC models, the revit export of rebar is duplicating the propertyset definition multiple times. Use of SimpleBIM on a IFC with Revit reinforcement got reduced from 200mb to 70mb because it combined all the similiar definitions. Original file had 29123 prop set and simpleBIM reduced it to 74. Could this also be taken into account when improving the IFC export of rebars?

[AngelVelezSosa]

Let me ask the rebar team especially about this second issue. Sounds like there is an easy performance gain there. Do you have a trivial example with, say, 4 rebar that have 4 property sets when they should share one?

[eibre]

I see the same issue with files sizes, here is a comparison of files sizes in my current project:

[eibre]

Here is a zip containing three different ifc files, much smaller but still the same relative differences in file size:

Three different rebar IFC files.zip

@AngelVelezSosa

[eibre]

@AngelVelezSosa Has the rebar team looked into this yet?

[COWImgbj]

Any progress on this?

We're experiencing difficulties with our QA in Solibri due to the number of objects in the reinforcement IFC-files. Plus, contractors have problems working with our IFC-files due to their size. Reinforcement IFC-files from Tekla are way easier to work with.

[tomoluf]

Any progress on this?

[AngelVelezSosa]

Suggestion: Can we share the geometry for rebar that have the same exact geometry?

[eibre]

@AngelVelezSosa: I'm no expert, but a rebar set is exactly what you are describing: A rebar set is a collection of rebars with the exact same geometry (material, shape, diameter and length) which is distributed a long a path with a certain spacing. I guess it would make sense that these rebars would share the same geometry,

[COWImgbj]

@AngelVelezSosa: I'm no expert, but a rebar set is exactly what you are describing: A rebar set is a collection of rebars with the exact same geometry (material, shape, diameter and length) which is distributed a long a path with a certain spacing. I guess it would make sense that these rebars would share the same geometry,

For varying rebar sets and continuous length rebar (where the rebar measurements are stated as "varies") this might not be the cause though. It would still be beneficial to have these as one in the IFC export, but the geometry for all the rebar would be different.

In my experience, the crucial information for continuous and varying rebar sets is the total length of the set. It may be enough to display the measurements range for the whole set (A=1000-2000 mm) and the complete length of the set. Or list all the different A values in a special property or something.

[Hafft0r]

I assume that there is still no solution for this problem, right?

We are rolling-out a complete paper less construction project on a 500mil CHF Hospital building next year. The reinforcement models need to be structured in a way that a worker on site can easily hide a complete reinforcement position after having it distributed on the dedicated place. At the moment revit does not suport this kind of grouping in IFC (2x3 an 4) where as for instance Allplan Engineering and Tekla do.

If by any chance this can be implemented within the next couple of months that would be a real game changer for our tool setup.

[COWImgbj]

Any progress on this issue?

[rober-ac]

Hi!
Has it been any updates on this problem?
I guess not, but maybe someone has some new insights on it :)