Query on IFC valid assembly structure

1

Hello All,

We received an IFC file having below assembly structure, Is it valid and acceptable IFC assembly structure ? Does this assembly structure fits in Buildingsmart standards ?

ifcProject
ifcSite
ifcBuilding
ifcBuildingstorey
ifcsite
ifcsite
ifcsite

Thank you in advance for your help.

Regards,
Amith Singh

2

Can you add indentation to show the structure unambiguously?

3

It’s not a problem to have multiple sites with the same project file.
A site object is a contiguous area of ​​land onto which you can add one or more buildings.
At some point you have one site and no buildings. Then step by step you add buildings to sites.

The mistake could be to design several sites when in reality there is only one area.

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4

Thank you Yauron, For your help.

Is it valid to have multiple ifcsite under ifcbuildingstorey ?

For example, In the example shared below, under ifcbuildingstorey, it got multiple ifcsite.

Ifcproject
ifcsite
ifcbuilding
ifcbuildingstorey
ifcsite
ifcsite
ifcsite
.

5

@AMITHSINGH ,

There should NOT be IfcSite under/within an IfcBuildingStorey. Definitely something wrong there.

IfcSite should always be near the top of the spatial/logical hierarchy, right below IfcProject. An IfcSite can contain one or more IfcBuilding and/or an IfcFacility/IfcBridge/etc., but is NOT contained by them.

Maybe the IfcSite items under IfcBuildingStorey are objects that have been incorrectly classified/assigned?

I bet members of the GA would love to see the file to see what is happening.

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6

This inclusion of IfcSite lower down is strictly allowed by the IFC schema but was immediately dis-allowed by an implementers agreement and then by the Coordination/reference view which is the convention implemented by most current authoring and analysis tools. But -for example - the Newcastle City model contains a site containing sites with each site containing multiple buildings.

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7

@nn1 Some of the “logic” of the schema just boggles my mind.

I can understand the ability to nest site(s) within a site, but "technically " allowing a site to be nested within a building/facility/buildingstorey/facilitypart? And it takes an IA /MVD to clarify?

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8

See

IfcSite "A site is a defined area [of land, possibly covered with water,] on which the project construction is to be completed.

https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/concepts/Object_Composition/Aggregation/Spatial_Composition/content.html

IfcBuilding aggregating IfcSite is in this list

9

@nn1, the link you provided says that “a spatial structure element should only be part of an element at the same or higher level” and puts IfcSite at a higher level than IfcBuilding. Definitely no, according to this site should not be part of building.

Also there are informal propositions for IfcSpatialStructureElement

  1. A site should not be (directly or indirectly) associated to a building, storey or space.
  2. A building should not be (directly or indirectly) associated to a storey or space.
  3. A storey should not be (directly or indirectly) associated to a space.

I would also like to see the file, because I am not sure, if we are actually talking about something like this:

Ifcproject
   ifcsite
      ifcbuilding
         ifcbuildingstorey
   ifcsite
      ifcsite
      ifcsite
10

Hi tausher,

Thank you for all your help.
Being the customer data, I can’t share the ifc file. But I captured a snapshot of assembly structure by opening it in BIMVision and attached over here.

Assembly_Structure
Assembly_Structure354Ă—518 40.5 KB

11

As far as I know, the site is not some sort of subdivision of Building Storey.
You must understand the purpose of hierarchical formalism: to have a universal sense of reading data. When I build an application, I need formal logic to let me be guided by this logic to build my visual representation. If you invent a new reading direction, only you will be able to display the information. BIM will then have lost all its usefulness.

12

@AMITHSINGH
Yeah, something is definitely wrong with the way the IFC data was attached to elements in the model and exported. No es bueno.

Can you give us a hint as to the objects that were classified as “Site” within the building storey?

13

I don’t want to jump to conclusions here but this is a very common issue I find coming from Revit-generated IFC models. In Revit, there is a “Site” category that people tend to use for things like street furniture or bollards or cars or whatever. In the Revit export mapping table, at least at one point it was the default to export these as IfcSite which led to this type of IFC.

If this is the case, you can just ask your model author to read the Revit guide to IFC classes which can fix it.

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