IfcMember

Definition from IAI: An IfcMember is a structural member designed to carry loads between or beyond points of support. It is not required to be load bearing. The location of the member (being horizontal, vertical or sloped) is not relevant to its definition (in contrary to IfcBeam and IfcColumn).

The material of the IfcMember is defined by the IfcMaterial and attached by the IfcRelAssociatesMaterial. It is accessible by the inverse HasAssociations relationship.

A particular usage type for the IfcMember can be given by refering to the type object IfcMemberType, using the IfcRelDefinesByType relationship, or (if only occurrence information is given) by using the ObjectType attribute. Recommended values are 'member' (the default), 'brace', 'collar', 'member', 'post', 'purlin', 'rafter', 'stringer', 'strut'.

HISTORY New entity in IFC Release 2x2 Addendum.

IFC2x Edition 2 Addendum CHANGE The entity IfcMember has been added. Upward compatibility for file based exchange is guaranteed.

Property Set Use Definition

The property sets relating to the IfcMember 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 IfcMember are part of this IFC release:

Pset_MemberCommon: common property set for all member occurrences

Quantity Use Definition

The quantities relating to the IfcMember are defined by the IfcElementQuantity and attached by the IfcRelDefinesByProperties relationship. It is accessible by the inverse IsDefinedBy relationship. The following quantities are foreseen, but will be subjected to the local standard of measurement used:

Name	Description	Value Type
NominalLength	Total nominal length of the member, not taking into account any cut-out's or other processing features.	IfcQuantityLength
CrossSectionArea	Total area of the cross section (or profile) of the member. The exact definition and calculation rules depend on the method of measurement used.	IfcQuantityArea
OuterSurfaceArea	Total area of the extruded surfaces of the member (not taking into account the end cap areas), normally generated as perimeter * length.	IfcQuantityArea
TotalSurfaceArea	Total area of the member, normally generated as perimeter * length + 2 * cross section area.	IfcQuantityArea
GrossVolume	Total gross volume of the member, not taking into account possible processing features (cut-out's, etc.) or openings and recesses. The exact definition and calculation rules depend on the method of measurement used.	IfcQuantityVolume
NetVolume	Total net volume of the member, taking into account possible processing features (cut-out's, etc.) or openings and recesses. The exact definition and calculation rules depend on the method of measurement used.	IfcQuantityVolume
GrossWeight	Total gross weight of the member without add-on parts, not taking into account possible processing features (cut-out's, etc.) or openings and recesses.	IfcQuantityWeight
NetWeight	Total net weight of the member without add-on parts, taking into account possible processing features (cut-out's, etc.) or openings and recesses.	IfcQuantityWeight

Containment Use Definitions

The IfcMember, as any subtype of IfcBuildingElement, may participate in two different containment relationships. The first (and in most implementation scenarios mandatory) relationship is the hierachical spatial containment, the second (optional) relationship is the aggregation within an element assembly.

The IfcMember is places within the project spatial hierarchy using the objectified relationship IfcRelContainedInSpatialStructure, refering to it by its inverse attribute SELF\IfcElement.ContainedInStructure. Subtypes of IfcSpatialStructureElement are valid spatial containers, with IfcBuildingStorey being the default container.
The IfcMember may be aggregated into an element assembly using the objectified relationship IfcRelAggregates, refering to it by its inverse attribute SELF\IfcObjectDefinition.Decomposes. Any subtype of IfcElement can be an element assembly, with IfcElementAssembly as a special focus subtype.

Geometry Use Definitions

The geometric representation of IfcMember is given by the IfcProductDefinitionShape, allowing multiple geometric representations. Included are:

Local Placement

The local placement for IfcMember 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 IfcMember is part of an assembly, the PlacementRelTo relationship of IfcLocalPlacement shall point to the local placement of the container element, e.g. IfcElementAssembly.

If the relative placement is not used, the absolute placement is defined within the world coordinate system.

Geometric Representations

Currently, the use of 'SweptSolid', 'Clipping', 'Brep' and 'MappedRepresentation' representations is supported. In addition the general representation types 'SurfaceModel' and 'BoundingBox' are allowed. The geometry use definition for 'BoundingBox', 'SurfaceModel' and 'Brep' is explained at IfcBuildingElement.

SweptSolid Representation

The standard geometric representation of IfcMember is defined using the 'SweptSolid' representation. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

RepresentationIdentifier : 'Body'
RepresentationType : 'SweptSolid'

The following additional constraints apply to the 'SweptSolid' representation:

Solid: IfcExtrudedAreaSolid shall be supported
Profile: All subtypes of IfcParameterizedProfileDef and IfcArbitraryClosedProfileDef shall be supported (exclusions need to be agreed upon by implementer agreements).
Extrusion: The profile shall be extruded in any direction. The extrusion axis shall be perpendicular to the swept profile, i.e. pointing into the direction of the z-axis of the Position of the IfcExtrudedAreaSolid.

EXAMPLE: standard geometric representation.

The following interpretation of dimension parameter applies for rectangular members:

IfcRectangleProfileDef.YDim interpreted as member width

IfcRectangleProfileDef.XDim interpreted as member depth

The following interpretation of dimension parameter applies for circular members:

IfcCircleProfileDef Radius interpreted as member radius.

Advanced SweptSolid and Clipping Representation

The advanced geometric representation of IfcMember is defined using the 'SweptSolid' (enhanced by additional profile types) or 'Clipping' geometry. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

RepresentationIdentifier : 'Body'
RepresentationType : 'SweptSolid', or 'Clipping'

The following constraints apply to the advanced representation:

Solid: see standard geometric representation,
Profile: see standard geometric representation,
Extrusion: All extrusion directions shall be supported.
Boolean result: The IfcBooleanClippingResult shall be supported, allowing for Boolean differences between the swept solid (here IfcExtrudedAreaSolid) and one or several IfcHalfSpaceSolid (or its subtypes).

EXAMPLE advanced geometric representation

	Use of non-perpendicular extrusion to create the IfcExtrudedAreaSolid.
	Use of IfcBooleanClippingResult between an IfcExtrudedAreaSolid and an IfcHalfSpaceSolid to create a clipped body.

MappedRepresentation

In addition to the standard and advanced geometric representation of IfcMember that is defined using the 'SweptSolid' or 'Clipping' geometry, also the 'MappedRepresentation' shall be supported as it allows for reusing the geometry definition of the member type at all occurrences of the same type. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

RepresentationIdentifier : 'Body'
RepresentationType : 'MappedRepresentation'

The same constraints, as given for the standard 'SweptSolid' and the advanced 'SweptSolid' and 'Clipping' geometric representation, shall apply to the MappedRepresentation of the IfcRepresentationMap.

EXPRESS specification:

ENTITY IfcMember

SUBTYPE OF (

IfcBuildingElement);

END_ENTITY;

Inheritance graph

ENTITY IfcMember;

ENTITY IfcRoot;

GlobalId

IfcGloballyUniqueId;

OwnerHistory

IfcOwnerHistory;

Name

OPTIONAL IfcLabel;

Description

OPTIONAL IfcText;

ENTITY IfcObjectDefinition;

INVERSE

HasAssignments

SET OF IfcRelAssigns FOR RelatedObjects;

IsDecomposedBy

SET OF IfcRelDecomposes FOR RelatingObject;

Decomposes

SET [0:1] OF IfcRelDecomposes FOR RelatedObjects;

HasAssociations

SET OF IfcRelAssociates FOR RelatedObjects;

ENTITY IfcObject;

ObjectType

OPTIONAL IfcLabel;

INVERSE

IsDefinedBy

SET OF IfcRelDefines FOR RelatedObjects;

ENTITY IfcProduct;

ObjectPlacement

OPTIONAL IfcObjectPlacement;

Representation

OPTIONAL IfcProductRepresentation;

INVERSE

ReferencedBy

SET OF IfcRelAssignsToProduct FOR RelatingProduct;

ENTITY IfcElement;

Tag

OPTIONAL IfcIdentifier;

INVERSE

FillsVoids

SET [0:1] OF IfcRelFillsElement FOR RelatedBuildingElement;

ConnectedTo

SET OF IfcRelConnectsElements FOR RelatingElement;

HasCoverings

SET OF IfcRelCoversBldgElements FOR RelatingBuildingElement;

HasProjections

SET OF IfcRelProjectsElement FOR RelatingElement;

HasStructuralMember

SET OF IfcRelConnectsStructuralElement FOR RelatingElement;

ReferencedInStructures

SET OF IfcRelReferencedInSpatialStructure FOR RelatedElements;

HasPorts

SET OF IfcRelConnectsPortToElement FOR RelatedElement;

HasOpenings

SET OF IfcRelVoidsElement FOR RelatingBuildingElement;

IsConnectionRealization

SET OF IfcRelConnectsWithRealizingElements FOR RealizingElements;

ProvidesBoundaries

SET OF IfcRelSpaceBoundary FOR RelatedBuildingElement;

ConnectedFrom

SET OF IfcRelConnectsElements FOR RelatedElement;

ContainedInStructure

SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements;

ENTITY IfcBuildingElement;

ENTITY IfcMember;

END_ENTITY;