IFC 4.3.0.1 (IFC4X3) development

# 7.10.3.5 IfcStructuralActivity

ABSTRACT This definition may not be instantiated

## 7.10.3.5.1 Semantic definition

The abstract entity IfcStructuralActivity combines the definition of actions (such as forces, displacements, etc.) and reactions (support reactions, internal forces, deflections, etc.) which are specified by using the basic load definitions from the IfcStructuralLoadResource.

The differentiation between actions and reactions is realized by instantiating objects either from subclasses of IfcStructuralAction or IfcStructuralReaction respectively. They inherit commonly needed attributes from the abstract superclass IfcStructuralActivity, notably the relationship which connects actions or reactions with connections, analysis members, or elements (subtypes of IfcStructuralItem or IfcElement).

*Coordinate Systems*:

The following coordinate systems are distinguished:

• The so-called global coordinate system is the coordinate system shared by all items and activities which are grouped in a common IfcStructuralAnalysisModel. This coordinate system is established by an ObjectPlacement. (This coordinate system is not necessarily the same as the IfcProject's world coordinate system.)
• The so-called local coordinate system is a coordinate system local to a structural item (connection or member). This coordinate system is established by a Representation in conjunction with further use definitions and attributes of subtypes of IfcStructuralItem.

Representation items in topology representations are always given within the ObjectPlacement, i.e. in so-called global coordinates (global with respect to the IfcStructuralAnalysisModel to which this activity belongs).

Locations of the load objects in the AppliedLoad attribute (if of type IfcStructuralLoadConfiguration) are always given in local coordinates.

Directions of the load objects in the AppliedLoad attribute refer to global or local coordinates according to the GlobalOrLocal attribute.

The ObjectPlacement and Representation are sometimes not explicitly instantiated; instead they may be implied as described below. Global and local coordinate systems are then determined in the same way as with explicit placement and representation.

*Topology Use Definitions*:

Instances of IfcStructuralActivity which are connected with a structural item of same dimensionality, i.e.

shall not have an ObjectPlacement nor a Representation. It is implied that the placement and representation of the IfcStructuralActivity is the same as the ones of the IfcStructuralItem.

Instances of IfcStructuralActivity which are connected with

shall have a topology representation as specified below. It includes a placement and a product representation. The IfcProductRepresentation shall be given by an item in a Representation of type IfcTopologyRepresentation.

Instances of IfcStructuralActivity which are connected with

shall have a shape representation as specified below. It includes a placement and a product representation. The IfcProductRepresentation shall be given by items in a Representation of type IfcShapeRepresentation. Shape representation and topology representation may be combined.

Local Placement

The local placement for IfcStructuralActivity is defined in its supertype IfcProduct. It is defined by the IfcLocalPlacement, which establishes a global coordinate system which shall be common to all items and activities in an IfcStructuralAnalysisModel.

Topology Representation

Instances of IfcStructuralActivity which act on parts of a surface item shall have a topology representation given by a face with underlying surface geometry, IfcFaceSurface, which should be the single item of IfcTopologyRepresentation.Items. The surface establishes a local coordinate system of the activity:

• The origin of surface parameters u,v is the origin of the local coordinate system.
• The local x and y directions follow the tangents on the surface and are in parallel with and directed like u and v respectively.
• The local z direction is in parallel with and directed like the surface normal.
• RepresentationIdentifier: 'Reference'
• RepresentationType: 'Face'

Instances of IfcStructuralActivity which act on a curve on a surface item shall have a topology representation given by an edge (IfcEdge or subtype), which should be the single item of IfcTopologyRepresentation.Items. The curve geometry shall be compatible with the surface geometry of the connected item. In conjunction with this surface, the curve establishes a local coordinate system of the activity:

• The origin of the curve parameter u is the origin of the local coordinate system.
• The local x direction follows the tangent on the curve and is directed like u.
• The local z direction is in parallel with and directed like the surface normal of the connected surface item.
• The local x,y,z directions form a right-handed Cartesian coordinate system.

Instances of IfcStructuralActivity which act on a single point on a curve or surface item shall have a topology representation given by an IfcVertexPoint, which should be the single item of IfcTopologyRepresentation.Items. The point geometry shall be compatible with the curve or surface geometry of the connected item. The local coordinate system of the activity is oriented by the curve or surface geometry of the connected item as described above for activities with edge or face topology.

• RepresentationIdentifier: 'Reference'
• RepresentationType: 'Vertex'

Shape Representation

Instances of IfcStructuralActivity which act on a surface item and are specified by isocontours (level sets) shall have a shape representation given by a set of curves on a surface, IfcPCurve. The basis surface shall comply with or preferably be identical with the surface of the structural item to which the activity is connected. The representation identifier and type of this geometric representation is:

• RepresentationIdentifier: 'Level set'
• RepresentationType: 'GeometricCurveSet'

## 7.10.3.5.4 Property sets

• Pset_Risk
• RiskName
• RiskType
• NatureOfRisk
• RiskAssessmentMethodology
• UnmitigatedRiskLikelihood
• UnmitigatedRiskConsequence
• UnmitigatedRiskSignificance
• MitigationPlanned
• MitigatedRiskLikelihood
• MitigatedRiskConsequence
• MitigatedRiskSignificance
• MitigationProposed
• AssociatedProduct
• AssociatedActivity
• AssociatedLocation
• Pset_Tolerance
• ToleranceDescription
• ToleranceBasis
• OverallTolerance
• HorizontalTolerance
• OrthogonalTolerance
• VerticalTolerance
• PlanarFlatness
• HorizontalFlatness
• ElevationalFlatness
• SideFlatness
• OverallOrthogonality
• HorizontalOrthogonality
• OrthogonalOrthogonality
• VerticalOrthogonality
• OverallStraightness
• HorizontalStraightness
• OrthogonalStraightness
• VerticalStraightness
• Pset_Uncertainty
• UncertaintyBasis
• UncertaintyDescription
• HorizontalUncertainty
• LinearUncertainty
• OrthogonalUncertainty
• VerticalUncertainty
• Qto_BodyGeometryValidation
• GrossSurfaceArea
• NetSurfaceArea
• GrossVolume
• NetVolume
• SurfaceGenusBeforeFeatures
• SurfaceGenusAfterFeatures

## 7.10.3.5.6 Formal representation

ENTITY IfcStructuralActivity
ABSTRACT SUPERTYPE OF (ONEOF
(IfcStructuralAction
,IfcStructuralReaction))
SUBTYPE OF (IfcProduct);
END_ENTITY;