IfcMemberType
Definition from IAI: The element type (IfcMemberType) defines a list of commonly shared property set definitions of a structural member and an optional set of product representations. It is used to define a structural member specification (i.e. the specific product information that is common to all occurrences of that product type).
NOTE: The product representations are defined as representation maps (at the level of the supertype IfcTypeProduct, which gets assigned by an element occurrence instance through the IfcShapeRepresentation.Item[1] being an IfcMappedItem.
A structural member type is used to define the common properties of a certain type of a structural member that may be applied to many instances of that type to assign a specific style. Structural member types may be exchanged without being already assigned to occurrences.
The occurrences of the IfcMemberType are represented by instances of IfcMember.
HISTORY New entity in Release IFC2x Edition 2.
IFC2x2 ADDENDUM CHANGE: The entity IfcMember has been added to serve as the occurrence object for all member types.
Use definition for steel members
When using the IfcMemberType as the underlying type for steel members within steel construction aware applications the following additional conventions apply:
Material association:
The IfcMemberType is
associated with exactly one instance IfcMaterial by the
IfcRelAssociatesMaterial relationship. This material association assigns
a common material to all occurrences (IfcBeam, IfcColumn or
IfcBuildingElementProxy) of the IfcMemberType. If an individual
occurrence has its own material assignment (see IfcMember), then this
overrides the material assignment given at the IfcMemberType.
Geometric representation:
The IfcMemberType
type has (at least) one representation map assigned through the
RepresentationMaps relation. The representation map has a full geometric
representation given by:
The attribute ProfileName of the extruded IfcProfile instance may contain a standardized name according to local standards. However, a geometric representation of the profile is necessary as specified below. An importing application is allowed to check for the existence of the profile name: in case of identifying it as a standardized name, the corresponding profile geometry and possibly other cross sectional properties can be read from a library. Otherwise the explicit IFC geometry and possible non geometric IfcProfileProperties have to be used.
Only 'SweptSolid' representation should be used to represent steel members. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:
The following additional constraints apply to the 'SweptSolid' representation:
In addition to the full 'SweptSolid' representation a simple representation for the axis of gravity can be used., i.e. as a second IfcRepresentationMap. It represents the neutral axis of stress which is not necessarily in the profiles center of gravity. In this case the following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:
Position number:
The position number is specified in
the attribute IfcTypeProduct.Tag.
Non geometric profile properties:
Non geometric
profile properties (for instance mechanical properties) are specified through
IfcProfileProperties (and its specific subtypes). These properties are
attached to IfcMemberType by the relationship
IfcRelAssociatesProfileProperties. If an individual occurrence has its
own profile property assignment (see IfcMember), then this overrides the
profile property assignment given at the IfcMemberType.
Quantity related properties:
Quantity related
properties, which do not relate to the profile, are specified through
IfcElementQuantity (and its specific subtypes). These properties are
attached to the IfcMemberType by the relationship
IfcRelDefinesByProperties. If an individual occurrence has its own
element quantity assignment (see IfcMember), then this overrides the
quantity assignment given at the IfcMemberType. The following quantities
are foreseen, but will be subjected to the local standard of measurement
used:
| Name | Description | Value Type |
| NominalLength | Total nominal length of the member, not taking into account any cut-out's or other processing features. | IfcQuantityLength |
| CrossSectionArea | Total area of the cross section (or profile) of the member. The exact definition and calculation rules depend on the method of measurement used. | IfcQuantityArea |
| OuterSurfaceArea | Total area of the extruded surfaces of the member (not taking into account the end cap areas), normally generated as perimeter * length. | IfcQuantityArea |
| TotalSurfaceArea | Total area of the member, normally generated as perimeter * length + 2 * cross section area. | IfcQuantityArea |
| GrossVolume | Total gross volume of the member, not taking into account possible processing features (cut-out's, etc.) or openings and recesses. The exact definition and calculation rules depend on the method of measurement used. | IfcQuantityVolume |
| NetVolume | Total net volume of the member, taking into account possible processing features (cut-out's, etc.) or openings and recesses. The exact definition and calculation rules depend on the method of measurement used. | IfcQuantityVolume |
| GrossWeight | Total gross weight of the member without add-on parts, not taking into account possible processing features (cut-out's, etc.) or openings and recesses. | IfcQuantityWeight |
| NetWeight | Total net weight of the member without add-on parts, taking into account possible processing features (cut-out's, etc.) or openings and recesses. | IfcQuantityWeight |
EXPRESS specification:
|
| PredefinedType | : | Identifies the predefined types of a linear structural member element from which the type required may be set. |
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