IfcStructuralLoadGroup

BACnet MVD

#### IfcStructuralLoadGroup

Natural language names

| Lastgruppe / Lastkombination
| Structural Load Group

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC2x3 to IFC4
IfcStructuralLoadGroup |  |  |  |
OwnerHistory |  |  | MODIFIED | Instantiation changed to OPTIONAL.

##### 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:

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.

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
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. |  | X
7 | ActionType | IfcActionTypeEnum |  | Type of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE. |  | X
8 | ActionSource | IfcActionSourceTypeEnum |  | Source of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE. |  | X
9 | Coefficient | 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. |  | X
10 | Purpose | 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. |  | X
| SourceOfResultGroup | IfcStructuralResultGroup @ResultForLoadGroup | S[0:1] | Results which were computed using this load group. |  | X
| LoadGroupFor | IfcStructuralAnalysisModel @LoadedBy | S[0:?] | Analysis models in which this load group is used. |  | X

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 |  | Assignment of a globally unique identifier within the entire software world. | X | X

2

OwnerHistory

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.

X

X

3 | Name | 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. | X | X
4 | Description | IfcText | ? | 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).

> IFC4 CHANGE The inverse attribute datatype has been added and separated from Decomposes defined at IfcObjectDefinition.

X

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).

> IFC4 CHANGE The inverse attribute datatype has been added and separated from IsDecomposedBy defined at IfcObjectDefinition.

X

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.

> IFC4 CHANGE The inverse attribute datatype has been added.

X

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).

> IFC4 CHANGE The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.

X

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).

> IFC4 CHANGE The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.

X

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 | X
IfcObject

5

ObjectType

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.

X

IsDeclaredBy

IfcRelDefinesByObject
@RelatedObjects

S[0:1]

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.

X

X

Declares

IfcRelDefinesByObject
@RelatingObject

S[0:?]

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.

X

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.

> 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.

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.

> IFC4 CHANGE The data type has been changed from IfcRelDefines to IfcRelDefinesByProperties with upward compatibility for file based exchange.

X

IfcGroup

IsGroupedBy

IfcRelAssignsToGroup
@RelatingGroup

S[0:?]

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.

X

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. |  | X
7 | ActionType | IfcActionTypeEnum |  | Type of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE. |  | X
8 | ActionSource | IfcActionSourceTypeEnum |  | Source of actions in the group. Normally needed if 'PredefinedType' specifies a LOAD_CASE. |  | X
9 | Coefficient | 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. |  | X
10 | Purpose | 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. |  | X
| SourceOfResultGroup | IfcStructuralResultGroup @ResultForLoadGroup | S[0:1] | Results which were computed using this load group. |  | X
| LoadGroupFor | IfcStructuralAnalysisModel @LoadedBy | S[0:?] | Analysis models in which this load group is used. |  | X

##### Definitions applying to Design Transfer View

Concept inheritance

# | Concept | Template | Model View
--- | --- | --- | ---
IfcRoot
| Revision Control | Revision Control | Design Transfer View

##### Definitions applying to BACnet View

Concept inheritance

# | Concept | Template | Model View
--- | --- | --- | ---
IfcRoot
| Revision Control | Revision Control | Design Transfer View

##### Formal representations

XML 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 [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;

EXPRESS-G diagram

`

References: IfcStructuralAnalysisModel IfcStructuralResultGroup

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