IfcStructuralLoadGroup

Semantic definitions at the entity

Entity definition

The entity IfcStructuralLoadGroup is used to structure the physical impacts. By using the grouping features inherited from IfcGroup, instances of IfcStructuralAction (or its subclasses) and of IfcStructuralLoadGroup can be used to define load groups, load cases and load combinations. (See also IfcLoadGroupTypeEnum.)

NOTE Important functionality for the description of a load-bearing system is derived from the existing IFC entity IfcGroup. This class provides, via the relationship class IfcRelAssignsToGroup, the needed grouping mechanism. In this way, instances of IfcStructuralAction belonging to a specific load group can be unambiguously determined.

NOTE The relationship class IfcRelAssignsToGroupByFactor is used to group load cases into load combinations. The factor provided in this assignment relationship is to applied together with the optional IfcStructuralLoadGroup.Coefficient. Unlike this coefficient which always affects the load group, the IfcRelAssignsToGroupByFactor.Factor is specific for a load case—load combination pair. As many instances of IfcRelAssignsToGroupByFactor are used within one load combination as there are different Factors to be applied to load cases in the load combination. On the other hand, a load case may appear in more than one load combination and can have a different Factor in each assignment by IfcRelAssignsToGroupByFactor.

HISTORY New entity in IFC2x2.

IFC4 CHANGE Subtype IfcStructuralLoadCase added. Informal propositions and WHERE rule added. Predefined type LOAD_COMBINATION_GROUP made obsolete and removed.

Informal Propositions:

Load groups of type LOAD_GROUP shall only contain instances of IfcStructuralAction.
Load groups of type LOAD_CASE shall always be instantiated from the subtype IfcStructuralLoadCase, not directly from the generic type IfcStructuralLoadGroup itself.
Instances of IfcStructuralLoadCase shall only contain instances of IfcStructuralAction or/ and instances of IfcStructuralLoadGroup of type LOAD_GROUP.
Load groups of type LOAD_COMBINATION shall only contain instances of IfcStructuralLoadCase.

Attribute definitions

#	Attribute	Type	Cardinality	Description	B
6	PredefinedType	IfcLoadGroupTypeEnum	[1:1]	Selects a predefined type for the load group. It can be differentiated between load groups, load cases, load combinations, or userdefined grouping levels.	X
7	ActionType	IfcActionTypeEnum	[1:1]	Type of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE.	X
8	ActionSource	IfcActionSourceTypeEnum	[1:1]	Source of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE.	X
9	Coefficient	IfcRatioMeasure	[0:1]	Load factor. If omitted, a factor is not yet known or not specified. A load factor of 1.0 shall be explicitly exported as Coefficient = 1.0.	X
10	Purpose	IfcLabel	[0:1]	Description of the purpose of this instance. Among else, possible values of the Purpose of load combinations are 'SLS', 'ULS', 'ALS' to indicate serviceability, ultimate, or accidental limit state.	X
	SourceOfResultGroup	IfcStructuralResultGroup @ResultForLoadGroup	S[0:1]	Results which were computed using this load group.
	LoadGroupFor	IfcStructuralAnalysisModel @LoadedBy	S[0:?]	Analysis models in which this load group is used.

Formal Propositions

Rule	Description
HasObjectType	The attribute ObjectType shall be given if the predefined type, action type, or action source is set to USERDEFINED.

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
IfcGroup
	IsGroupedBy	IfcRelAssignsToGroup @RelatingGroup	S[0:?]	Reference to the relationship IfcRelAssignsToGroup that assigns the one to many group members to the IfcGroup object.	X
IfcStructuralLoadGroup
6	PredefinedType	IfcLoadGroupTypeEnum	[1:1]	Selects a predefined type for the load group. It can be differentiated between load groups, load cases, load combinations, or userdefined grouping levels.	X
7	ActionType	IfcActionTypeEnum	[1:1]	Type of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE.	X
8	ActionSource	IfcActionSourceTypeEnum	[1:1]	Source of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE.	X
9	Coefficient	IfcRatioMeasure	[0:1]	Load factor. If omitted, a factor is not yet known or not specified. A load factor of 1.0 shall be explicitly exported as Coefficient = 1.0.	X
10	Purpose	IfcLabel	[0:1]	Description of the purpose of this instance. Among else, possible values of the Purpose of load combinations are 'SLS', 'ULS', 'ALS' to indicate serviceability, ultimate, or accidental limit state.	X
	SourceOfResultGroup	IfcStructuralResultGroup @ResultForLoadGroup	S[0:1]	Results which were computed using this load group.
	LoadGroupFor	IfcStructuralAnalysisModel @LoadedBy	S[0:?]	Analysis models in which this load group is used.

Definitions applying to Bridge View

Instance diagram

Concept usage

Group Assignment

The Group Assignment concept applies to this entity as shown in Table 84.

RelatedType
IfcStructuralLoadCase

Table 84 — IfcStructuralLoadGroup Group Assignment

Exchange
Import		O	R
Export		O	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
IfcStructuralLoadGroup
	Group Assignment	Bridge View

Formal representations

XSD Specification

 <xs:element name="IfcStructuralLoadGroup" type="ifc:IfcStructuralLoadGroup" substitutionGroup="ifc:IfcGroup" nillable="true"/>

 <xs:complexType name="IfcStructuralLoadGroup">

  <xs:complexContent>

   <xs:extension base="ifc:IfcGroup">

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

    <xs:attribute name="ActionType" type="ifc:IfcActionTypeEnum" use="optional"/>

    <xs:attribute name="ActionSource" type="ifc:IfcActionSourceTypeEnum" use="optional"/>

    <xs:attribute name="Coefficient" type="ifc:IfcRatioMeasure" use="optional"/>

    <xs:attribute name="Purpose" type="ifc:IfcLabel" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcStructuralLoadGroup

 SUPERTYPE OF(IfcStructuralLoadCase)

 SUBTYPE OF (IfcGroup);

  PredefinedType : IfcLoadGroupTypeEnum;

  ActionType : IfcActionTypeEnum;

  ActionSource : IfcActionSourceTypeEnum;

  Coefficient : OPTIONAL IfcRatioMeasure;

  Purpose : OPTIONAL IfcLabel;

 INVERSE

  SourceOfResultGroup : SET [0:1] OF IfcStructuralResultGroup FOR ResultForLoadGroup;

  LoadGroupFor : SET OF IfcStructuralAnalysisModel FOR LoadedBy;

 WHERE

  HasObjectType : (
  (PredefinedType <> IfcLoadGroupTypeEnum.USERDEFINED) AND
  (ActionType <> IfcActionTypeEnum.USERDEFINED) AND
  (ActionSource <> IfcActionSourceTypeEnum.USERDEFINED)
) OR EXISTS(SELF\IfcObject.ObjectType);
END_ENTITY;

 EXPRESS-G diagram

Link to this page

Item	Change	Description
IFC2x3 to IFC4
IfcStructuralLoadGroup
OwnerHistory	MODIFIED	Instantiation changed to OPTIONAL.

	Lastgruppe / Lastkombination
	Structural Load Group