IfcStair

IfcStair

Definition from IAI: 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 a stair (IfcStair) with the related flights (IfcStairFlight) and landings (IfcSlab with type 'Landing').

HISTORY New Entity in IFC Release 2.0 ISSUES: See issue and change log for changes made in IFC Release 2x.

Geometry Use Definitions:

The geometric representation of IfcStair is given by the IfcProductDefinitionShape, allowing multiple geometric representation. 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 , which is used in the ContainedInStructure inverse attribute, or to a spatial structure element at a higher level, referenced by that.
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.

EXPRESS specification:

ENTITY IfcStair

SUBTYPE OF (

IfcBuildingElement);

ShapeType

IfcStairTypeEnum;

WHERE

WR1

(HIINDEX(SELF\IfcObject.IsDecomposedBy) = 0) OR ((HIINDEX(SELF\IfcObject.IsDecomposedBy) = 1) AND (NOT(EXISTS(SELF\IfcProduct.Representation))));

END_ENTITY;

Attribute definitions:

ShapeType

Predefined shape types for a stair that are specified in an Enum.

Formal Propositions:

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.

References (1):

Name

Type

Referred through

Express-G

IfcBuildingElement

Entity

Subtype

Diagram 1

Inheritance graph

ENTITY IfcStair;

ENTITY IfcRoot;

GlobalId

IfcGloballyUniqueId;

OwnerHistory

IfcOwnerHistory;

Name

OPTIONAL IfcLabel;

Description

OPTIONAL IfcText;

ENTITY IfcObject;

ObjectType

OPTIONAL IfcLabel;

INVERSE

IsDefinedBy

SET OF IfcRelDefines FOR RelatedObjects;

HasAssociations

SET OF IfcRelAssociates FOR RelatedObjects;

HasAssignments

SET OF IfcRelAssigns FOR RelatedObjects;

Decomposes

SET OF IfcRelDecomposes FOR RelatedObjects;

IsDecomposedBy

SET [0:1] OF IfcRelDecomposes FOR RelatingObject;

ENTITY IfcProduct;

ObjectPlacement

OPTIONAL IfcObjectPlacement;

Representation

OPTIONAL IfcProductRepresentation;

INVERSE

ReferencedBy

SET OF IfcRelAssignsToProduct FOR RelatingProduct;

ENTITY IfcElement;

Tag

OPTIONAL IfcIdentifier;

INVERSE

ConnectedTo

SET OF IfcRelConnectsElements FOR RelatingElement;

ConnectedFrom

SET OF IfcRelConnectsElements FOR RelatedElement;

ContainedInStructure

SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements;

ENTITY IfcBuildingElement;

INVERSE

ProvidesBoundaries

SET OF IfcRelSpaceBoundary FOR RelatedBuildingElement;

HasOpenings

SET OF IfcRelVoidsElement FOR RelatingBuildingElement;

FillsVoids

SET [0:1] OF IfcRelFillsElement FOR RelatedBuildingElement;

ENTITY IfcStair;

ShapeType

IfcStairTypeEnum;

END_ENTITY;