Classification for IFC
In ARCHICAD, you can optionally assign certain classifications to any project element. Such a classification assigns special parameters and functions to these elements for use by other applications: to interpret data, to make models transparent, to locate elements, for listing purposes, to share exact data, etc.
For each construction element, classifications can be set in the Categories and Properties panel of its Settings dialog box.
While each ARCHICAD element type has a default counterpart in IFC, you can assign any other element type to a particular element - for example, if there is no specific ARCHICAD tool corresponding to the IFC element type you want to map it to.
Element classification affects the IFC export process, because each element will be saved to the IFC model in accordance with the element type chosen for it. In the Categories and Properties panel (under IFC Properties), the “IFC Type” item displays the IFC entity corresponding to the classification (and naturally, the exported element will be of this type). Thus, if you classify a slab as a ceiling in ARCHICAD, the target program will interpret this element as a ceiling (depending, of course, on the program’s capabilities).
In collaborating with partners who are using structural programs, you can export your ARCHICAD model to IFC format: the Structural Function classification (assigned in ARCHICAD) automatically adds the “load-bearing” property to structural elements in the export file.
Note: By default, Revit Structure will display only walls that have the “load-bearing” property in the “Structural” discipline views. But, if you forget to classify required walls as “Load-Bearing Elements” in ARCHICAD, the structural engineers can also change the bearing function of walls, or they can apply another display discipline (e.g. “Architectural”) in order to show all walls exported from ARCHICAD.
The current IFC standard supports the export of the “load-bearing” IFC property only for the following elements: Wall, Slab, Column, Beam, Roof; elements classified as such in ARCHICAD; and objects having these sub-types. Thus, the Structural Function classification of elements such as Stair, Ramp, and Curtain Wall will have an effect only within ARCHICAD - for example, for the purposes of Find & Select, Scheduling, or Partial Structure Display.
If you have classified model elements as “Load-Bearing Elements”, then you can use the Partial Structure Display “Core of Load-Bearing Elements Only” option to display those elements only. This is particularly useful if you wish to export only load-bearing elements to a structural engineer: in this case, just use the “visible elements” export mode on a view that uses this Partial Structure Display option.
This classification is useful for listing purposes - for example, you can calculate the materials needed for all load-bearing walls or columns, separately from materials of non-load-bearing elements. Criteria in the Find & Select dialog box include: search for those elements that have been defined as load-bearing or non-load-bearing, or whose Structural Function classification is “Undefined”. Since IFC export can be limited to selected elements only, you can - for example - export all selected elements defined load-bearing (not just their Core only, as described in the example above).
“Structural Function” lets you limit the exported IFC model to load-bearing elements only, thereby streamlining the collaboration process.
The load-bearing data is also a standard property of exported elements. Moreover, if other applications (such as a structural program) also classify elements according to their load-bearing function, ARCHICAD can filter these elements upon importing them, and such elements will show up in the ARCHICAD model with that classification.
This classification is useful if you plan to send an IFC file to partners (e.g. energy analyzers) who are able to differentiate elements by their location in the building. When you export the ARCHICAD model to IFC format, your model elements that are classified as “Interior” or “Exterior” will carry this information to the partner’s application via IFC.
Naturally, the opposite is also true. Since Position (IsExternal) is a standard IFC property for certain building elements (e.g. Wall, Slab, Column, or Beam), if an imported IFC model contains such data, then the appropriate classification is automatically added to the respective elements.
Criteria in the Find & Select dialog box include: search for elements classified as either “Exterior” or “Interior”, or whose position is “Undefined”.
Interactive Schedule Criteria are also available to differentiate listed elements by Position, as defined here.
Note: Within ARCHICAD, the Position classification is fully usable as an ARCHICAD property (e.g. in Find & Select and Interactive Schedule). However, it will not be exported as an IFC property for certain element types (e.g. Ceiling (IfcCovering)) which are not supported by the IFC standard.