#### 6.1.3.9 IfcSlabStandardCase

| Decke / Dachfläche / Bodenplatte - Standard
| Dalle 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 representation
- 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 IfcSlabStandardCase.

> HISTORY New entity in IFC4.

## Plumbing System Design

The following concepts are inherited at supertypes:

- IfcSlab: Voiding

Instance diagram

Identity

The Identity concept applies to this entity.

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Object Typing

The Object Typing concept applies to this entity as shown in Table 36.

Type
IfcSlabType
Table 36 — IfcSlabStandardCase Object Typing

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 109 illustrates assignment of IfcMaterialLayerSetUsage and IfcMaterialLayerSet to the IfcSlabStandardCase as the slab occurrence and to the IfcSlabType. The same IfcMaterialLayerSet shall be shared by many occurrences of IfcMaterialLayerSetUsage. This relationship shall be consistent to the relationship between the IfcSlabType and the IfcSlabStandardCase.

Figure 109 — Slab type definition

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Material Layer Set Usage

The Material Layer Set Usage concept applies to this entity.

The material of the IfcSlabStandardCase is defined by IfcMaterialLayerSetUsage and attached by the IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship. Multi-layer slabs can be represented by refering to several IfcMaterialLayer's within the IfcMaterialLayerSet that is referenced from the IfcMaterialLayerSetUsage.

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. See Type Use Definition for additional agreements for standard slabs.

Figure 110 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 110 — Slab material layers

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Body Geometry

The Body Geometry concept applies to this entity as shown in Table 37.

RepresentationType | Geometry
--- | ---
SweptSolid | IfcExtrudedAreaSolid
Clipping | IfcBooleanClippingResult
Table 37 — IfcSlabStandardCase Body Geometry

Currently, the use of 'SweptSolid' and 'Clipping' representations is supported. In addition the general representation type 'BoundingBox' is allowed. The geometry use definitions for 'BoundingBox', is explained at IfcBuildingElement.

> 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 IfcSlabStandardCase.

SweptSolid Representation

The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used for the 'SweptSolid' representation:

- RepresentationIdentifier : 'Body'
- RepresentationType : 'SweptSolid'

The following additional constraints apply to the swept solid representation:

- Solid: IfcExtrudedAreaSolid is required,
- Profile: IfcArbitraryClosedProfileDef, IfcRectangleProfileDef, IfcCircleProfileDef, 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 'SweptSolid' representation.

Figure 111 illustrates a 'SweptSolid' geometric representation.

> NOTE 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 111 — Slab body extrusion

Clipping representation

The 'Clipping' geometric representation of IfcSlabStandardCase is defined using the swept area geometry with additional clippings applied. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

- RepresentationIdentifier : 'Body'
- RepresentationType : 'Clipping'

The following constraints apply to the 'Clipping' representation:

- Solid: see 'SweptSolid' shape representation,
- Profile: see 'SweptSolid' shape representation,
- Extrusion: see 'SweptSolid' shape representation,
- Material: see 'SweptSolid' shape representation,
- Boolean result: The IfcBooleanClippingResult shall be supported, allowing for Boolean differences between the swept solid (here IfcExtrudedAreaSolid) and one or several IfcHalfSpaceSolid.

Figure 112 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 112 — Slab body clipping

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XSD Specification:

<xs:element name="IfcSlabStandardCase" type="ifc:IfcSlabStandardCase" substitutionGroup="ifc:IfcSlab" nillable="true"/>
<xs:complexType name="IfcSlabStandardCase">
<xs:complexContent>
<xs:extension base="ifc:IfcSlab"/>
</xs:complexContent>
</xs:complexType>

EXPRESS Specification:

ENTITY IfcSlabStandardCase

| SUBTYPE OF (IfcSlab);

| WHERE

HasMaterialLayerSetusage | : | SIZEOF (QUERY(temp <* USEDIN(SELF, 'IFCKERNEL.IFCRELASSOCIATES.RELATEDOBJECTS') | ('IFCPRODUCTEXTENSION.IFCRELASSOCIATESMATERIAL' IN TYPEOF(temp)) AND ('IFCMATERIALRESOURCE.IFCMATERIALLAYERSETUSAGE' IN TYPEOF(temp.RelatingMaterial)) )) = 1;

END_ENTITY;

Formal Propositions:

HasMaterialLayerSetusage | : | A valid instance of IfcSlabStandardCase relies on the provision of an IfcMaterialLayerSetUsage.

Inheritance Graph:

ENTITY IfcSlabStandardCase

| ENTITY IfcRoot

GlobalId | : | IfcGloballyUniqueId;
OwnerHistory | : | OPTIONAL IfcOwnerHistory;
Name | : | OPTIONAL IfcLabel;
Description | : | OPTIONAL IfcText;

| ENTITY IfcObjectDefinition

| INVERSE

HasAssignments | : | SET OF IfcRelAssigns FOR RelatedObjects;
Nests | : | SET [0:1] OF IfcRelNests FOR RelatedObjects;
IsNestedBy | : | SET OF IfcRelNests FOR RelatingObject;
HasContext | : | SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
IsDecomposedBy | : | SET OF IfcRelAggregates FOR RelatingObject;
Decomposes | : | SET [0:1] OF IfcRelAggregates FOR RelatedObjects;
HasAssociations | : | SET OF IfcRelAssociates FOR RelatedObjects;

| ENTITY IfcObject

ObjectType | : | OPTIONAL IfcStrippedOptional;

| INVERSE

IsDeclaredBy | : | SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects;
Declares | : | SET OF IfcRelDefinesByObject FOR RelatingObject;
IsTypedBy | : | SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects;
IsDefinedBy | : | SET OF IfcRelDefinesByProperties FOR RelatedObjects;

| ENTITY IfcProduct

ObjectPlacement | : | OPTIONAL IfcObjectPlacement;
Representation | : | OPTIONAL IfcProductRepresentation;

| INVERSE

ReferencedBy | : | SET OF IfcRelAssignsToProduct FOR RelatingProduct;

| ENTITY IfcElement

Tag | : | OPTIONAL IfcStrippedOptional;

| INVERSE

ConnectedTo | : | SET OF IfcRelConnectsElements FOR RelatingElement;
IsInterferedByElements | : | SET OF IfcRelInterferesElements FOR RelatedElement;
InterferesElements | : | SET OF IfcRelInterferesElements FOR RelatingElement;
HasOpenings | : | SET OF IfcRelVoidsElement FOR RelatingBuildingElement;
ProvidesBoundaries | : | SET OF IfcRelSpaceBoundary FOR RelatedBuildingElement;
ConnectedFrom | : | SET OF IfcRelConnectsElements FOR RelatedElement;
ContainedInStructure | : | SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements;

| ENTITY IfcBuildingElement

| INVERSE

| ENTITY IfcSlab

PredefinedType | : | OPTIONAL IfcStrippedOptional;

| ENTITY IfcSlabStandardCase

END_ENTITY;

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