![]() | zusammengesetztes Element |
![]() | Element Assembly |
![]() | Assemblage d'éléments |
Item | SPF | XML | Change | Description | IFC2x3 to IFC4 |
---|---|---|---|---|
IfcElementAssembly | ||||
OwnerHistory | MODIFIED | Instantiation changed to OPTIONAL. | ||
PredefinedType | MODIFIED | Instantiation changed to OPTIONAL. | IFC4 to IFC4 ADD1 | |
IfcElementAssembly | ||||
HasCoverings | ADDED | IFC4x1 to IFC4x2 | ||
IfcElementAssembly | ||||
PositionedFrom | ADDED |
The IfcElementAssembly represents complex element assemblies aggregated from several elements, such as discrete elements, building elements, or other elements.
EXAMPLE Steel construction assemblies, such as trusses and different kinds of frames, can be represented by the IfcElementAssembly entity. Other examples include slab fields aggregated from a number of precast concrete slabs or reinforcement units made from several reinforcement bars. Also bathroom units, staircase sections and other premanufactured or precast elements are examples of the general IfcElementAssembly entity
NOTE The IfcElementAssembly is a general purpose entity that is required to be decomposed. Also other subtypes of IfcElement can be decomposed, with some dedicated entities such as IfcWallElementedCase and IfcSlabElementedCase.
The assembly structure can be nested, i.e. an IfcElementAssembly could be an aggregated part within another IfcElementAssembly.
NOTE View definitions and/or implementer agreements may restrict the number of allowed levels of nesting.
The geometry of an IfcElementAssembly is generally formed from its components, in which case it does not need to have an explicit geometric representation. In some cases it may be useful to also expose an own explicit representation of the aggregate.
NOTE View definitions or implementer agreements may further constrain the applicability of certain shape representations at the IfcElementAssembly in respect of the shape representations of its parts.
HISTORY New entity in IFC2x2.
Informal Propositions:
# | Attribute | Type | Cardinality | Description | B |
---|---|---|---|---|---|
9 | AssemblyPlace | - | This attribute is out of scope for this model view definition and shall not be set. | ||
10 | PredefinedType | IfcElementAssemblyTypeEnum | [0:1] | Predefined generic types for a element assembly that are specified in an enumeration. There might be property sets defined specifically for each predefined type. | X |
Rule | Description |
---|---|
CorrectPredefinedType | Either the PredefinedType attribute is unset (e.g. because an IfcElementAssemblyType is associated), or the inherited attribute ObjectType shall be provided, if the PredefinedType is set to USERDEFINED. |
CorrectTypeAssigned | Either there is no element assembly type object associated, i.e. the IsTypedBy inverse relationship is not provided, or the associated type object has to be of type IfcElementAssemblyType. |
# | 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 | |
IfcElementAssembly | |||||
9 | AssemblyPlace | - | This attribute is out of scope for this model view definition and shall not be set. | ||
10 | PredefinedType | IfcElementAssemblyTypeEnum | [0:1] | Predefined generic types for a element assembly that are specified in an enumeration. There might be property sets defined specifically for each predefined type. | X |
Cross-framing between girders may be described using templates of member configurations. Such cross framing is captured within components, using AISC shapes where applicable. For curved alignments where girders are placed at different elevations, members must be placed relative to the girders at each side, for which positioning is defined relative to alignment curves.
![]() |
Figure 1 — Bridge framing model |
Steel angles (AISC L shapes) are captured using IfcMember having geometry represented by IfcExtrudedAreaSolid with IfcLShapeProfileDef. Steel plates are captured using IfcPlate having geometry represented by IfcExtrudedAreaSolid with IfcRectangleProfileDef.
Each element is connected using IfcRelConnectsElements, where the connection geometry is indicated using IfcConnectionSurfaceGeometry, which enables analysis from derived structural analysis models (IfcStructuralAnalysisModel)
.Such cross-framing is then instantiated as object occurrences according to repetition intervals, where each occurrence has unique connectivity relationships with corresponding girder segments. While such discrete modeling results in larger files sizes, individual elements need to be captured for any structural analysis usage.
Parameterization of such framing requires referencing other instances according to connectivity, particularly for bridges with super-elevations where adjacent girders are at different elevations. To reference values at connected elements, IfcReference expressions must traverse connectivity relationships such as:
“\IfcMember.ConnectedFrom[1]\IfcRelConnectsElements.RelatingElement\IfcBeam.Representation\IfcProductDefinitionShape.Representation[‘Axis’]\IfcShapeRepresentation.Items[1]\IfcIndexedPolyCurve.PointOnCurve[@Offset].Z”.
To adjust for offsets from web thickness or flange thickness, the beam profile may be referenced such as:
“\IfcMember.ConnectedFrom[1]\IfcRelConnectsElements.RelatingElement\IfcBeam.HasAssociations\IfcRelAssociatesMaterial.RelatingMaterial\IfcMaterialProfileSet.MaterialProfiles[1]\IfcIShapeProfileDef.WebThickness.
Performing arithmetic operations on multiple references may be accomplished using IfcAppliedValue, where ArithmeticOperation may indicate ADD or SUBTRACT, and Components includes the list of referenced parameters. To define arrays of framing at offsets along curves, each framing set (between two specific girders) must be defined explicitly once, and then may be duplicated along a repetition path using a constraint relationship, where an IfcTable may be used for specific offsets along the alignment, or IfcAppliedValue may be used to indicate positioning of each instance relative to a constant spacing using an ArithmeticOperation of MULTIPLY.
Object Typing
The Object Typing concept applies to this entity as shown in Table 16.
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Table 16 — IfcElementAssembly Object Typing |
Exchange | ![]() |
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Import | O | |||
Export | O |
Element Positioning
The Element Positioning concept applies to this entity.
Exchange | ![]() |
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Import | O | |||
Export | O |
# | 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 | |
IfcElementAssembly | ||
Object Typing | Bridge View | |
Element Positioning | Bridge View |
<xs:element name="IfcElementAssembly" type="ifc:IfcElementAssembly" substitutionGroup="ifc:IfcElement" nillable="true"/>
<xs:complexType name="IfcElementAssembly">
<xs:complexContent>
<xs:extension base="ifc:IfcElement">
<xs:attribute name="PredefinedType" type="ifc:IfcElementAssemblyTypeEnum" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
ENTITY IfcElementAssembly
SUBTYPE OF (IfcElement);
AssemblyPlace : OPTIONAL IfcStrippedOptional;
PredefinedType : OPTIONAL IfcElementAssemblyTypeEnum;
WHERE
CorrectPredefinedType : NOT(EXISTS(PredefinedType)) OR
(PredefinedType <> IfcElementAssemblyTypeEnum.USERDEFINED) OR
((PredefinedType = IfcElementAssemblyTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType));
CorrectTypeAssigned : (SIZEOF(IsTypedBy) = 0) OR
('IFCPRODUCTEXTENSION.IFCELEMENTASSEMBLYTYPE' IN TYPEOF(SELF\IfcObject.IsTypedBy[1].RelatingType));
END_ENTITY;