#### IfcStair

Natural language names

##### Semantic definitions at the entity

Entity definition

Definition from ISO 6707-1:1989: Construction comprising a succession of horizontal stages (steps or landings) that make it possible to pass on foot to other levels.

A vertical passageway allowing occupants to walk (step) from one floor level to another floor level at a different elevation. It may include a landing as an intermediate floor slab.

The stair is a container entity that aggregates all components of the stair, it represents. The aggregation is handled via the IfcRelAggregates relationship, relating an IfcStair with the related flights (IfcStairFlight) and landings (IfcSlab with type 'Landing').

> HISTORY: New Entity in IFC Release 2.0.

Property Set Use Definition:

The property sets relating to the IfcStair are defined by the IfcPropertySet and attached by the IfcRelDefinesByProperties relationship. It is accessible by the inverse IsDefinedBy relationship. The following property set definitions specific to the IfcStair are part of this IFC release:

- Pset_StairCommon: common property set for all stair occurrences

Geometry Use Definitions:

The geometric representation of IfcStair is given by the IfcProductDefinitionShape, allowing multiple geometric representations. Independent geometric representations should only be used when the IfcStair is not defined as an aggregate. If defined as an aggregate, the geometric representation is the sum of the representation of the components within the aggregate.

Local placement

The local placement for IfcStair is defined in its supertype IfcProduct. It is defined by the IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations.

- The PlacementRelTo relationship of IfcLocalPlacement shall point (if given) to the local placement of the same IfcSpatialStructureElement that is used in the ContainedInStructure inverse attribute or to a referenced spatial structure element at a higher level.
- If the relative placement is not used, the absolute placement is defined within the world coordinate system.

If the LocalPlacement is given for the IfcStair, then all components, which are aggregated to the stair should use this placement as their relative placement.

Geometric Representation

If the IfcStair has components (referenced by SELF\IfcObject.IsDecomposedBy) then no independent geometric representation shall defined for the IfcStair. The IfcStair is then geometrically represented by the geometric representation of its components. The components are accessed via SELF\IfcObject.IsDecomposedBy[1].RelatedObjects.

If the IfcStair has no components defined (empty set of SELF\IfcObject.IsDecomposedBy) then the IfcStair may be represented by an IfcShapeRepresentation with the RepresentationType = 'Brep'.

Illustration:

| IfcStair defining only the local placement for all components.

Attribute definitions

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
9 | ShapeType | IfcStairTypeEnum | [1:1] | Predefined shape types for a stair that are specified in an Enum. | X

Formal Propositions

Rule | Description
--- | ---
WR1 | Either the stair is not decomposed into its flights and landings (the stair can have independent geometry), or the geometry shall not be given at IfcStair directly.

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
IfcRoot
1 | GlobalId | IfcGloballyUniqueId | [1:1] | Assignment of a globally unique identifier within the entire software world. | X
2 | OwnerHistory | IfcOwnerHistory | [1:1] | Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object, NOTE: only the last modification in stored. | X
3 | Name | IfcLabel | [0:1] | Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule. | X
4 | Description | IfcText | [0:1] | Optional description, provided for exchanging informative comments. | X
IfcObjectDefinition
| IsDecomposedBy | IfcRelDecomposes @RelatingObject | S[0:?] | Reference to the decomposition relationship, that allows this object to be the composition of other objects. An object can be decomposed by several other objects. | X
| Decomposes | IfcRelDecomposes @RelatedObjects | S[0:1] | References to the decomposition relationship, that allows this object to be a part of the decomposition. An object can only be part of a single decomposition (to allow hierarchical strutures only). | X
| HasAssociations | IfcRelAssociates @RelatedObjects | S[0:?] | Reference to the relationship objects, that associates external references or other resource definitions to the object.. Examples are the association to library, documentation or classification. | X
IfcObject
5 | ObjectType | IfcLabel | [0:1] | The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute PredefinedType is set to USERDEFINED. | X
| IsDefinedBy | IfcRelDefines @RelatedObjects | S[0:?] | Set of relationships to type or property (statically or dynamically defined) information that further define the object. In case of type information, the associated IfcTypeObject contains the specific information (or type, or style), that is common to all instances of IfcObject referring to the same type. | X
IfcProduct
6 | ObjectPlacement | IfcObjectPlacement | [0:1] | Placement of the product in space, the placement can either be absolute (relative to the world coordinate system), relative (relative to the object placement of another product), or constraint (e.g. relative to grid axes). It is determined by the various subtypes of IfcObjectPlacement, which includes the axis placement information to determine the transformation for the object coordinate system. | X
7 | Representation | IfcProductRepresentation | [0:1] | Reference to the representations of the product, being either a representation (IfcProductRepresentation) or as a special case a shape representations (IfcProductDefinitionShape). The product definition shape provides for multiple geometric representations of the shape property of the object within the same object coordinate system, defined by the object placement. | X
IfcElement
8 | Tag | - |  | This attribute is out of scope for this model view definition and shall not be set. |
| ConnectedTo | IfcRelConnectsElements @RelatingElement | S[0:?] | Reference to the element connection relationship. The relationship then refers to the other element to which this element is connected to. |
| HasOpenings | IfcRelVoidsElement @RelatingBuildingElement | S[0:?] | Reference to the Voids Relationship that creates an opening in an element. An element can incorporate zero-to-many openings. | X
| IsConnectionRealization | IfcRelConnectsWithRealizingElements @RealizingElements | S[0:?] | Reference to the connection relationship with realizing element. The relationship then refers to the realizing element which provides the physical manifestation of the connection relationship. | X
| ConnectedFrom | IfcRelConnectsElements @RelatedElement | S[0:?] | Reference to the element connection relationship. The relationship then refers to the other element that is connected to this element. | X
| ContainedInStructure | IfcRelContainedInSpatialStructure @RelatedElements | S[0:1] | Containment relationship to the spatial structure element, to which the element is primarily associated. | X
IfcBuildingElement
IfcStair
9 | ShapeType | IfcStairTypeEnum | [1:1] | Predefined shape types for a stair that are specified in an Enum. | X

##### Definitions applying to AISC Model View

Instance diagram

Stair shall be represented in an aggregation structure similar to the Assembly, where the stair is decomposed into stair flight and landing, and railing. Stair flight can be futher decomposed into stair steps (Building Components). However, when stair is an External Element that is not fabricated in the shop, it may not use the aggregation structure.

A stair and its components may have attributes listed below should use Defines By Property Set (IfcRelDefinesByPropertyies) in order to represent required information items listed below and are described in the corresponding sections of this document.

Piece Identification

- GUID
- Part name
- Piece mark
- Indication mark

Material Information

- Material class
- Material ID
- Material certification
- Material grade
- Material type

Status Information

- Status flags

Scheduling information

- Sequence ID
- Sequence level
- On site by date

Drawing Information

- Drawing numbers

Quantity Information

- Count

Tolerance for Layout

- Tolerance

Information Item Mapping

Steel Detailing Information | IFC Entity \ Attribute | Note
Location in space | IfcProduct \ ObjectPlacement | Location of Stair is relative to the location of IfcRelContainedInSpatialStructure \ RelatingStructure
Components | IfcRelAggregates | Pieces belong to Assembly

Concept usage

Properties on Occurrences

The Properties on Occurrences concept applies to this entity as shown in Table 24.

Property
AISC_EM11_Pset_PieceIdentification
AISC_EM11_Pset_Feature
AISC_EM11_Pset_ToleranceForLayout
AISC_EM11_Pset_Material
AISC_EM11_Pset_SurfaceTreatment
AISC_EM11_Pset_StatusInformation
AISC_EM11_Pset_VersionInformation
Table 24 — IfcStair Properties on Occurrences

Exchange |
--- | ---
Import | O
Export | O

Placement

The Placement concept applies to this entity.

Exchange |
--- | ---
Import | R
Export | R

Body Brep Geometry PolyLoop

The Body Brep Geometry PolyLoop concept applies to this entity as shown in Table 25.

Table 25 — IfcStair Body Brep Geometry PolyLoop

Exchange |
--- | ---
Import | O
Export | O

Feature Substraction

The Feature Substraction concept applies to this entity as shown in Table 26.

FeatureObjectType | Description
--- | ---
BoltHole | Represents an instance of Bolt Hole
SlotHole | Represents an instance of a Slot Hole
Cope | Represents an instance of a Cope
Opening | Represents an instance of an Opening
SkewedEnd | Represents an instance of a Skewed End, which has two axis of rotation
WeldPreparation | Represents an instance of a Weld Preparation
Table 26 — IfcStair Feature Substraction

Exchange |
--- | ---
Import | O
Export | O

Element Decomposition

The Element Decomposition concept applies to this entity as shown in Table 27.

RelatedObjects
IfcStairFlight
IfcRailing
IfcPlate
Table 27 — IfcStair Element Decomposition

W or I shaped structural steel piece (column, beam or member) can be assembled with three plates. IfcRelAggregate\RelatedObject should refer to IfcBeam, IfcColumn or IfcMember, and IfcRelAggregate\RelatedObject should refer to IfcPlate

Exchange |
--- | ---
Import | O
Export | O

Concept inheritance

# | Concept | Model View
--- | --- | ---
IfcStair
| Properties on Occurrences | AISC Model View
| Placement | AISC Model View
| Body Brep Geometry PolyLoop | AISC Model View
| Feature Substraction | AISC Model View
| Element Decomposition | AISC Model View

##### Formal representations

XSD Specification
`<xs:element name="IfcStair" type="ifc:IfcStair" substitutionGroup="ifc:IfcBuildingElement" nillable="true"/>
<xs:complexType name="IfcStair">
<xs:complexContent>
<xs:extension base="ifc:IfcBuildingElement">
<xs:attribute name="ShapeType" type="ifc:IfcStairTypeEnum" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcStair
SUBTYPE OF (IfcBuildingElement);
ShapeType : IfcStairTypeEnum;
WHERE
WR1 : (HIINDEX(SELF\IfcObjectDefinition.IsDecomposedBy) = 0) OR ((HIINDEX(SELF\IfcObjectDefinition.IsDecomposedBy) = 1) AND (NOT(EXISTS(SELF\IfcProduct.Representation))));
END_ENTITY;

EXPRESS-G diagram

`

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