IFC 4.3.x development

7.11.3.16 IfcStructuralLoadGroup

Change log

IFC4

additionswhere_rulesHasObjectType

7.11.3.16.1 Semantic definitions at the entity

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 Factor_s 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:

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

7.11.3.16.1 Attributes

# Attribute Type Description
IfcRoot
1 GlobalId IfcGloballyUniqueId Assignment of a globally unique identifier within the entire software world.
2 OwnerHistory OPTIONAL IfcOwnerHistory 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.

> IFC4 CHANGE  The attribute has been changed to be OPTIONAL.
3 Name OPTIONAL IfcLabel 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.
4 Description OPTIONAL IfcText Optional description, provided for exchanging informative comments.
IfcObjectDefinition
HasAssignments SET [0:?] OF IfcRelAssigns FOR RelatedObjects 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.
Nests SET [0:1] OF IfcRelNests FOR RelatedObjects 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).

> IFC4 CHANGE  The inverse attribute datatype has been added and separated from Decomposes defined at IfcObjectDefinition.
IsNestedBy SET [0:?] OF IfcRelNests FOR RelatingObject 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).

> IFC4 CHANGE  The inverse attribute datatype has been added and separated from IsDecomposedBy defined at IfcObjectDefinition.
HasContext SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions 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.

> IFC4 CHANGE  The inverse attribute datatype has been added.
IsDecomposedBy SET [0:?] OF IfcRelAggregates FOR RelatingObject 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).

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
Decomposes SET [0:1] OF IfcRelAggregates FOR RelatedObjects 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).

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
HasAssociations SET [0:?] OF IfcRelAssociates FOR RelatedObjects 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.
IfcObject
5 ObjectType OPTIONAL IfcLabel The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute PredefinedType is set to USERDEFINED.
IsDeclaredBy SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects Link to the relationship object pointing to the declaring object that provides the object definitions for this object occurrence. The declaring object has to be part of an object type decomposition. The associated IfcObject, or its subtypes, contains the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.

> IFC4 CHANGE  New inverse relationship, change made with upward compatibility for file based exchange.
Declares SET [0:?] OF IfcRelDefinesByObject FOR RelatingObject Link to the relationship object pointing to the reflected object(s) that receives the object definitions. The reflected object has to be part of an object occurrence decomposition. The associated IfcObject, or its subtypes, provides the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.

> IFC4 CHANGE  New inverse relationship, change made with upward compatibility for file based exchange.
IsTypedBy SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects 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.

> IFC4 CHANGE  New inverse relationship, the link to IfcRelDefinesByType had previously be included in the inverse relationship IfcRelDefines. Change made with upward compatibility for file based exchange.
IsDefinedBy SET [0:?] OF IfcRelDefinesByProperties FOR RelatedObjects 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.

> IFC4 CHANGE  The data type has been changed from IfcRelDefines to IfcRelDefinesByProperties with upward compatibility for file based exchange.
IfcGroup
IsGroupedBy SET [0:?] OF IfcRelAssignsToGroup FOR RelatingGroup Reference to the relationship IfcRelAssignsToGroup that assigns the one to many group members to the IfcGroup object.

> IFC4 CHANGE  The cardinality has been changed from 1..1 to 0..? in order to allow the exchange of a group concept without having already group members assigned. It now also allows the use of many instances of IfcRelAssignsToGroup to assign the group members. The change has been done with upward compatibility for file based exchange.
IfcStructuralLoadGroup
6 PredefinedType IfcLoadGroupTypeEnum Selects a predefined type for the load group. It can be differentiated between load groups, load cases, load combinations, or userdefined grouping levels.
7 ActionType IfcActionTypeEnum Type of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE.
8 ActionSource IfcActionSourceTypeEnum Source of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE.
9 Coefficient OPTIONAL IfcRatioMeasure 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.
10 Purpose OPTIONAL IfcLabel 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.
SourceOfResultGroupSET [0:1] OF IfcStructuralResultGroup FOR ResultForLoadGroupResults which were computed using this load group.
LoadGroupFor SET [0:?] OF IfcStructuralAnalysisModel FOR LoadedBy Analysis models in which this load group is used.

7.11.3.16.2 Entity inheritance

dot_inheritance IfcStructuralLoadCase IfcStructuralLoadCase IfcStructuralLoadGroup IfcStructuralLoadGroup IfcStructuralLoadCase->IfcStructuralLoadGroup IfcGroup IfcGroup IfcStructuralLoadGroup->IfcGroup IfcGroup_children 4 more... IfcGroup_children->IfcGroup IfcObject IfcObject IfcGroup->IfcObject IfcObject_children 5 more... IfcObject_children->IfcObject IfcObjectDefinition IfcObjectDefinition IfcObject->IfcObjectDefinition IfcContext IfcContext IfcContext->IfcObjectDefinition IfcRoot IfcRoot IfcObjectDefinition->IfcRoot IfcTypeObject IfcTypeObject IfcTypeObject->IfcObjectDefinition IfcPropertyDefinition IfcPropertyDefinition IfcPropertyDefinition->IfcRoot IfcRelationship IfcRelationship IfcRelationship->IfcRoot

7.11.3.16.3 Definitions applying to General Usage

7.11.3.16.3.1 Classification Association

Any object occurrence or object type can have a reference to a specific classification reference, i.e. to a particular facet within a classification system.

7.11.3.16.3.2 Group Assignment

7.11.3.16.3.3 Identity

IfcRoot assigns the globally unique ID. In addition it may provide for a name and a description about the concept.

7.11.3.16.3.4 Object Predefined Type

7.11.3.16.3.5 Object Typing

Any object occurrence can be typed by being assigned to a common object type utilizing this concept. A particular rule, restricting the applicable subtypes of IfcTypeObject that can be assigned, is introduced by overriding this concept at the level of subtypes of IfcObject.

7.11.3.16.3.6 Object User Identity

An attribute Name and optionally Description can be used for all subypes of IfcObject. For those subtypes, that have an object type definition, such as ifcBeam - IfcBeamType, the common Name and optionally Description is associated with the object type.

7.11.3.16.3.7 Property Sets for Objects

Any object occurrence can hold property sets, each being a set of individual properties having name, description, value(s) and unit(s). A reference to applicable property sets, being part of this specification, is introduced at the level of sub types of IfcObject.

7.11.3.16.3.8 Property Sets with Override

Any object occurrence can hold property sets, either directly at the object occurrence as element specific property sets, or at the object type, as type property sets. In this case, the properties that are provided to the object occurrence are the combinations of element specific and type properties. In case, that the same property (within the same property set, is defined both, in occurrence and type properties, the property value of the occurrence property overrides the property value of the type property.

7.11.3.16.3.9 Revision Control

Ownership, history, and merge state is captured using IfcOwnerHistory.

7.11.3.16.4 Formal representations

ENTITY IfcStructuralLoadGroup
 SUPERTYPE OF (ONEOF
	(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 [0:?] OF IfcStructuralAnalysisModel FOR LoadedBy;
 WHERE
	HasObjectType : (
  (PredefinedType <> IfcLoadGroupTypeEnum.USERDEFINED) AND
  (ActionType <> IfcActionTypeEnum.USERDEFINED) AND
  (ActionSource <> IfcActionSourceTypeEnum.USERDEFINED)
) OR EXISTS(SELF\IfcObject.ObjectType);
END_ENTITY;