|Decke / Dachfläche / Bodenplatte - Standard|
The standard slab, IfcSlabStandardCase, defines a slab with certain constraints
for the provision of material usage, parameters and with certain constraints for the geometric representation. The
IfcSlabStandardCase handles all cases of slabs, that:
- have a reference to the IfcMaterialLayerSetUsage defining the material layers of the slab with thicknesses
- are based on an extrusion of a planar surface as defined by the slab profile
- have a constant thickness along the extrusion direction
- are consistent in using the correct material layer set offset to the base planar surface in regard to the shape
- are extruded either perpendicular or slanted to the plane surface
The definitions of slab openings and niches are the same as given at the supertype IfcSlab. The same agreements to the
special types of slabs, as defined in the PredefinedType attribute apply as well.
NOTE If the IfcSlabStandardCase is of type Landing
and is used within an IfcStair or IfcRamp, the
special agreements to handle stair and ramp geometry will also
affect the geometric representation of the
HISTORY New entity in IFC4.
Common Use Definitions
The following concepts are inherited at supertypes:
- IfcRoot: Identity, Revision Control
- IfcElement: Box Geometry, FootPrint Geometry, Body SurfaceOrSolidModel Geometry, Body SurfaceModel Geometry, Body Tessellation Geometry, Body Brep Geometry, Body AdvancedBrep Geometry, Body CSG Geometry, Mapped Geometry
- IfcBuildingElement: Surface 3D Geometry
- IfcSlab: Object Typing, Property Sets for Objects, Quantity Sets, Material Layer Set, Spatial Containment, Surface Geometry, Element Voiding, Product Assignment
Material Layer Set Usage
The Material Layer Set Usage concept applies to this entity.
Multi-layer slabs can be represented by refering to several
IfcMaterialLayer's within the IfcMaterialLayerSet
that is referenced from the
Material information can also be given at the
IfcSlabType, defining the common attribute data for all
occurrences of the same type. It is then accessible by the
inverse IsDefinedBy relationship pointing to
IfcSlabType.HasAssociations and via
IfcRelAssociatesMaterial.RelatingMaterial. The IfcSlabStandardCase defines in addition that the
IfcSlabType should have a unique IfcMaterialLayerSet,
that is referenced by the IfcMaterialLayerSetUsage
assigned to all occurrences of this IfcSlabType.
Figure 212 illustrates slab material usage, where the following conventions shall be met:
- The reference coordinate system is the coordinate system established by the IfcExtrudedAreaSolid.Position.
- The reference plane is the plane defined by the extruded profile of IfcExtrudedAreaSolid.SweptSolid. The IfcMaterialLayerSetUsage.OffsetFromReferenceLine is given as a distance from this plane.
- The IfcMaterialLayerSetUsage.DirectionSense defines how the IfcMaterialLayer's are assigned to the reference plane. POSITIVE means in direction to the positive z-axis of the reference coordinate system.
- The IfcMaterialLayerSetUsage.OffsetFromReferenceLine is the distance parallel to the reference plane and always perpendicular to the base (XY) plane of the reference coordinate system. This is independent of a potential non-perpendicular extrusion given by IfcExtrudedAreaSolid.ExtrudedDirection <> 0.,0.,1. A positive value of IfcMaterialLayerSetUsage.OffsetFromReferenceLine would then point into the positive z-axis of the reference coordinate system.
- The Thickness of each IfcMaterialLayer shall be the parallel distance (measured perpendicular to the base plane). The TotalThickness of the IfcMaterialLayerSet is the sum of all layer thicknesses and in case of a perpendicular extrusion identical with IfcExtrudedAreaSolid.Depth
- The IfcMaterialLayerSetUsage.LayerSetDirection is always AXIS3.
Figure 212 — Slab material layers
The Product Placement concept applies to this entity as shown in Table 172.
Table 172 — IfcSlabStandardCase Product Placement
The following restriction is imposed:
- The local placement shall provide the location and directions
for the standard slab, the x/y plane is the plane for the
profile, and the z-axis is the extrusion axis for the slab body.
Body SweptSolid Geometry
The Body SweptSolid Geometry concept applies to this entity.
The following additional constraints apply to the swept solid
- Solid: IfcExtrudedAreaSolid is required,
- Profile: IfcArbitraryClosedProfileDef,
IfcEllipseProfileDef shall be supported.
- Extrusion: The profile can be extruded perpendicularly
or non-perpendicularly to the plane of the swept profile.
- Material: The definition of the
IfcMaterialLayerSetUsage, particularly of the
OffsetFromReferenceLine and the
ForLayerSet.TotalThickness, has to be consistent to the
EXAMPLE Figure 213 illustrates a 'SweptSolid' geometric representation. The following interpretation of dimension parameter applies for polygonal slabs (in ground floor view):
IfcArbitraryClosedProfileDef.OuterCurve: closed bounded curve interpreted as area (or foot print) of the slab.
Figure 213 — Slab body extrusion
Body Clipping Geometry
The Body Clipping Geometry concept applies to this entity.
The following constraints apply to the 'Clipping'
- Solid: see 'SweptSolid' shape representation,
- Profile: see 'SweptSolid' shape
- Extrusion: see 'SweptSolid' shape
- Material: see 'SweptSolid' shape
- Boolean result: The IfcBooleanClippingResult
shall be supported, allowing for Boolean differences between the
swept solid (here IfcExtrudedAreaSolid) and one or several
EXAMPLE Figure 214 illustrates a 'Clipping' geometric representation with definition of a roof slab using advanced geometric representation. The profile is extruded non-perpendicular and the slab body is clipped at the eave.
Figure 214 — Slab body clipping
XSD Specification: <xs:element name="IfcSlabStandardCase" type="ifc:IfcSlabStandardCase" substitutionGroup="ifc:IfcSlab" nillable="true"/>
|HasMaterialLayerSetusage|| : ||SIZEOF (QUERY(temp <* USEDIN(SELF, 'IFCKERNEL.IFCRELASSOCIATES.RELATEDOBJECTS') |
('IFCPRODUCTEXTENSION.IFCRELASSOCIATESMATERIAL' IN TYPEOF(temp)) AND
('IFCMATERIALRESOURCE.IFCMATERIALLAYERSETUSAGE' IN TYPEOF(temp.RelatingMaterial))
)) = 1;|
|HasMaterialLayerSetusage|| : ||
A valid instance of IfcSlabStandardCase relies on the provision of an IfcMaterialLayerSetUsage.
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