IfcMember

Semantic definitions at the entity

Entity definition

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 orientation of the member (being horizontal, vertical or sloped) is not relevant to its definition (in contrary to IfcBeam and IfcColumn). An IfcMember represents a linear structural element from an architectural or structural modeling point of view and shall be used if it cannot be expressed more specifically as either an IfcBeam or an IfcColumn.

NOTE The representation of a member in a structural analysis model is provided by IfcStructuralCurveMember being part of an IfcStructuralAnalysisModel.

The IFC specification provides two entities for member occurrences:

IfcMemberStandardCase used for all occurrences of members, that have a profile defined that is swept along a directrix. The profile might be changed uniformly by a taper definition along the directrix. The profile parameter and its cardinal point of insertion can be fully described by the IfcMaterialProfileSetUsage. These beams are always represented geometricly by an 'Axis' and a 'SweptSolid' or 'AdvancedSweptSolid' shape representation (or by a 'Clipping' geometry based on the swept solid), if a 3D geometric representation is assigned. In addition they have to have a corresponding IfcMaterialProfileSetUsage assigned.
NOTE View definitions and implementer agreements may further constrain the applicable geometry types, such as by excluding tapering from an IfcMemberStandardCase implementation.
IfcMember used for all other occurrences of members, particularly for members with changing profile sizes along the extrusion, or members defined by non-linear extrusion, or members having only 'Brep', or 'SurfaceModel' geometry.

HISTORY New entity in IFC2x2 Addendum 1.

Attribute definitions

#	Attribute	Type	Cardinality	Description	B
9	PredefinedType	IfcMemberTypeEnum	[0:1]	Predefined generic type for a member that is specified in an enumeration. There may be a property set given for the predefined types. NOTE The PredefinedType shall only be used, if no IfcMemberType is assigned, providing its own IfcMemberType.PredefinedType.	X

Formal Propositions

Rule	Description
CorrectPredefinedType	Either the PredefinedType attribute is unset (e.g. because an IfcMemberType is associated), or the inherited attribute ObjectType shall be provided, if the PredefinedType is set to USERDEFINED.
CorrectTypeAssigned	Either there is no member type object associated, i.e. the IsTypedBy inverse relationship is not provided, or the associated type object has to be of type IfcMemberType.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	B
IfcRoot
1	GlobalId	IfcGloballyUniqueId	[1:1]	Assignment of a globally unique identifier within the entire software world.	X
2	OwnerHistory	IfcOwnerHistory	[0:1]	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 - either as addition, deletion or modification.	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
	HasAssignments	IfcRelAssigns @RelatedObjects	S[0:?]	Reference to the relationship objects, that assign (by an association relationship) other subtypes of IfcObject to this object instance. Examples are the association to products, processes, controls, resources or groups.	X
	Nests	IfcRelNests @RelatedObjects	S[0:1]	References to the decomposition relationship being a nesting. It determines that this object definition is a part within an ordered whole/part decomposition relationship. An object occurrence or type can only be part of a single decomposition (to allow hierarchical strutures only).
	IsNestedBy	IfcRelNests @RelatingObject	S[0:?]	References to the decomposition relationship being a nesting. It determines that this object definition is the whole within an ordered whole/part decomposition relationship. An object or object type can be nested by several other objects (occurrences or types).	X
	HasContext	IfcRelDeclares @RelatedDefinitions	S[0:1]	References to the context providing context information such as project unit or representation context. It should only be asserted for the uppermost non-spatial object.
	IsDecomposedBy	IfcRelAggregates @RelatingObject	S[0:?]	References to the decomposition relationship being an aggregation. It determines that this object definition is whole within an unordered whole/part decomposition relationship. An object definitions can be aggregated by several other objects (occurrences or parts).	X
	Decomposes	IfcRelAggregates @RelatedObjects	S[0:1]	References to the decomposition relationship being an aggregation. It determines that this object definition is a part within an unordered whole/part decomposition relationship. An object definitions 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	-		This attribute is out of scope for this model view definition and shall not be set.
	IsTypedBy	IfcRelDefinesByType @RelatedObjects	S[0:1]	Set of relationships to the object type that provides the type definitions for this object occurrence. The then associated IfcTypeObject, or its subtypes, contains the specific information (or type, or style), that is common to all instances of IfcObject, or its subtypes, referring to the same type.	X
	IsDefinedBy	IfcRelDefinesByProperties @RelatedObjects	S[0:?]	Set of relationships to property set definitions attached to this object. Those statically or dynamically defined properties contain alphanumeric information content that further defines the object.	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
	ReferencedBy	IfcRelAssignsToProduct @RelatingProduct	S[0:?]	Reference to the IfcRelAssignsToProduct relationship, by which other products, processes, controls, resources or actors (as subtypes of IfcObjectDefinition) can be related to this product.	X
IfcElement
8	Tag	IfcIdentifier	[0:1]	The tag (or label) identifier at the particular instance of a product, e.g. the serial number, or the position number. It is the identifier at the occurrence level.	X
	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 IfcRelVoidsElement relationship that creates an opening in an element. An element can incorporate zero-to-many openings. For each opening, that voids the element, a new relationship IfcRelVoidsElement is generated.	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. This containment relationship has to be hierachical, i.e. an element may only be assigned directly to zero or one spatial structure.
	PositionedFrom	IfcRelPositions @RelatingElement	S[0:1]	Indicates a constrained placement, where the ObjectPosition must match positioning defined according to the referenced positioning element.	X
IfcBuildingElement
IfcMember
9	PredefinedType	IfcMemberTypeEnum	[0:1]	Predefined generic type for a member that is specified in an enumeration. There may be a property set given for the predefined types. NOTE The PredefinedType shall only be used, if no IfcMemberType is assigned, providing its own IfcMemberType.PredefinedType.	X

Definitions applying to Bridge View

Instance diagram

Members are used to represent linear members with primary function of axial loading such as angles as part of cross-bracing. The general definition IfcMember defines a fixed shape, while the subtype IfcMemberStandardCase allows for parametric resizing.

Concept usage

Object Typing

The Object Typing concept applies to this entity as shown in Table 32.

Type
IfcMemberType

Table 32 — IfcMember Object Typing

Exchange
Import		O
Export		O

Quantity Sets

The Quantity Sets concept applies to this entity as shown in Table 33.

Name
Qto_MemberBaseQuantities

Table 33 — IfcMember Quantity Sets

Exchange
Import		O
Export		O

Element Decomposition

The Element Decomposition concept applies to this entity as shown in Table 34.

RelatedObjects	Description
IfcReinforcingBar	Rebar including longitudinal bars and stirrups

Table 34 — IfcMember Element Decomposition

Exchange
Import
Export

Element Nesting

The Element Nesting concept applies to this entity as shown in Table 35.

Type	PredefinedType
IfcMember

Table 35 — IfcMember Element Nesting

The nesting relationship may be used to indicate nesting of member segments onto full lengths of raw material.

Exchange
Import				O
Export				O

Body SweptSolid Geometry

The Body SweptSolid Geometry concept applies to this entity as shown in Table 36.

Identifier

Type

Geometry

Body

SweptSolid

Swept Solid Geometry

Profile	Description
IfcArbitraryClosedProfileDef	Arbitrary solid profile
IfcArbitraryProfileDefWithVoids	Arbitrary hollow profile
IfcIShapeProfileDef	I-Shape with equal flange dimensions
IfcAsymmetricIShapeProfileDef	I-Shape with unequal flange dimensions

Table 36 — IfcMember Body SweptSolid Geometry

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

Solid: IfcExtrudedAreaSolid, IfcRevolvedAreaSolid shall be supported
Profile: all subtypes of IfcProfileDef (with exception of IfcArbitraryOpenProfileDef)
Extrusion: All extrusion directions shall be supported.

Figure 179 illustrates the 'SweptSolid' geometric representation. There are no restrictions or conventions on how to use the local placement (black), solid of extrusion placement (red) and profile placement (green).

Figure 179 — Beam swept solid

Figure 180 illustrates the use of non-perpendicular extrusion to create the IfcExtrudedAreaSolid.

Figure 180 — Beam non-perpendicular extrusion

Exchange
Import
Export

Annotation 2D Geometry

The Annotation 2D Geometry concept applies to this entity as shown in Table 37.

Identifier	Type	Items	Description
		IfcTextLiteralWithExtent	Piece marks.
		IfcCartesianPoint	Pop marks.
		IfcIndexedPolyCurve	Contour marks.

Table 37 — IfcMember Annotation 2D Geometry

For fabrication, piece marks, pop marks, and contour marks may be designated using the 'Annotation' representation.

Exchange
Import
Export

Surface Connectivity

The Surface Connectivity concept applies to this entity as shown in Table 38.

Type
IfcPlate

Table 38 — IfcMember Surface Connectivity

This relationship is used to indicate connections between members and other elements such as plates. The intersecting surface may be provided to indicate precisely where the member is attached, and to assist fabrication for indicating contour marking and/or weld locations.

Exchange
Import		R		R
Export		R		R

Concept inheritance

#	Concept	Model View
IfcRoot
	Software Identity	Bridge View
	User Identity	Bridge View
	Object Ownership	Bridge View
IfcObject
	Property Sets for Objects	Bridge View
IfcElement
	Element Occurrence Attributes	Bridge View
	Product Local Placement	Bridge View
	Product Assignment	Bridge View
IfcMember
	Object Typing	Bridge View
	Quantity Sets	Bridge View
	Element Decomposition	Bridge View
	Element Nesting	Bridge View
	Body SweptSolid Geometry	Bridge View
	Annotation 2D Geometry	Bridge View
	Surface Connectivity	Bridge View

Formal representations

XSD Specification

 <xs:element name="IfcMember" type="ifc:IfcMember" substitutionGroup="ifc:IfcBuildingElement" nillable="true"/>

 <xs:complexType name="IfcMember">

  <xs:complexContent>

   <xs:extension base="ifc:IfcBuildingElement">

    <xs:attribute name="PredefinedType" type="ifc:IfcMemberTypeEnum" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcMember

 SUPERTYPE OF(IfcMemberStandardCase)

 SUBTYPE OF (IfcBuildingElement);

  PredefinedType : OPTIONAL IfcMemberTypeEnum;

 WHERE

  CorrectPredefinedType : NOT(EXISTS(PredefinedType)) OR
 (PredefinedType <> IfcMemberTypeEnum.USERDEFINED) OR
 ((PredefinedType = IfcMemberTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType));
  CorrectTypeAssigned : (SIZEOF(IsTypedBy) = 0) OR
  ('IFCSHAREDBLDGELEMENTS.IFCMEMBERTYPE' IN TYPEOF(SELF\IfcObject.IsTypedBy[1].RelatingType));
END_ENTITY;

 EXPRESS-G diagram

Link to this page

Item	Change	Description
IFC2x3 to IFC4
IfcMember
OwnerHistory	MODIFIED	Instantiation changed to OPTIONAL.
PredefinedType	ADDED
IFC4x1 to IFC4x2
IfcMember
PositionedFrom	ADDED

	Stab / Stabträger
	Member
	Membre