7.7.3.16 IfcStructuralLoadGroup

Lastgruppe / Lastkombination

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:

  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.

Common Use Definitions

The following concepts are inherited at supertypes:

 Instance diagram

Group Assignment

The Group Assignment concept applies to this entity as shown in Table 632.
TypeDescription
IfcStructuralLoadCaseStructural load cases applicable to the load group.

Table 632 — IfcStructuralLoadGroup Group Assignment




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;

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

PredefinedType : Selects a predefined type for the load group. It can be differentiated between load groups, load cases, load combinations, or userdefined grouping levels.
ActionType : Type of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE.
ActionSource : Source of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE.
Coefficient : 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.
Purpose : 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.
SourceOfResultGroup : Results which were computed using this load group.
LoadGroupFor : Analysis models in which this load group is used.

Formal Propositions:

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

Inheritance Graph:

ENTITY IfcStructuralLoadGroup
ENTITY IfcRoot
GlobalId : IfcGloballyUniqueId;
OwnerHistory : OPTIONAL IfcOwnerHistory;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ENTITY IfcObjectDefinition
INVERSE
HasAssignments : SET OF IfcRelAssigns FOR RelatedObjects;
Nests : SET [0:1] OF IfcRelNests FOR RelatedObjects;
IsNestedBy : SET OF IfcRelNests FOR RelatingObject;
HasContext : SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
IsDecomposedBy : SET OF IfcRelAggregates FOR RelatingObject;
Decomposes : SET [0:1] OF IfcRelAggregates FOR RelatedObjects;
HasAssociations : SET OF IfcRelAssociates FOR RelatedObjects;
ENTITY IfcObject
ObjectType : OPTIONAL IfcLabel;
INVERSE
IsDeclaredBy : SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects;
Declares : SET OF IfcRelDefinesByObject FOR RelatingObject;
IsTypedBy : SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects;
IsDefinedBy : SET OF IfcRelDefinesByProperties FOR RelatedObjects;
ENTITY IfcGroup
INVERSE
IsGroupedBy : SET OF IfcRelAssignsToGroup FOR RelatingGroup;
ENTITY IfcStructuralLoadGroup
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;
END_ENTITY;

Examples:

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