IfcAlignment2DVerSegCircularArc

Natural language names
Alignment 2D Vertical Segment Circular Arc
Change log
ItemSPFXMLChangeDescription
IFC4x1 Release Candidate 1
    IfcAlignment2DVerSegCircularArcADDED
IFC4x1 Release Candidate 2
    IfcAlignment2DVerSegCircularArc
      ToVerticalADDED
IFC4x1 Release Candidate 3
    IfcAlignment2DVerSegCircularArc
      LayerAssignmentADDED
      StyledByItemADDED
Semantic definitions at the entity
Entity definition

The vertical circular arc segment is defined as an arc using the inherited attributes from IfcAlignment2DVerticalSegment and the following additional curve parameters Radius as the radius of the circular arc, and IsConvex to indicate the whether the circular arc defines a sag (i.e. concave, increasing gradiant) or a crest (i.e. convex, decreasing gradiant).

The circular arc is described by:

For crest curves (where IsConvex is True), the elevation of a point along the curve (relative to StartHeight) is defined as:

start point provided by StartDistAlong and StartHeight
instanteneous gradient provided by StartGradient,
and length provided by HorizontalLength

Figure 313 — Alignment vertical arc segment convex

 

 

For sag curves (where IsConvex is False), the elevation of a point along the curve (relative to StartHeight) is defined as:

start point provided by StartDistAlong and StartHeight
instanteneous gradient provided by StartGradient,
and length provided by HorizontalLength

Figure 314 — Alignment vertical arc segment concave

 
Attribute definitions
#AttributeTypeCardinalityDescription G
8RadiusIfcPositiveLengthMeasure radius of the circular arcX
9IsConvexIfcBoolean Orientation of the circular arc, convex (Boolean=”true”) means decreasing gradient along the arc at the beginning such as at the crest of a hill, concave (Boolean=”false”) means increasing gradient along the arc at the beginning such as at the base of a valley.X
Inherited definitions from supertypes
Entity inheritance IfcAlignment2DVerticalSegment IfcAlignment2DSegment IfcGeometricRepresentationItem IfcRepresentationItem
Attribute inheritance
#AttributeTypeCardinalityDescriptionG
IfcRepresentationItem
LayerAssignmentIfcPresentationLayerAssignment
@AssignedItems
S[0:1]Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.
IFC2x3 CHANGE  The inverse attribute LayerAssignments has been added.
IFC4 CHANGE  The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.
X
StyledByItemIfcStyledItem
@Item
S[0:1]Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.
IFC2x3 CHANGE  The inverse attribute StyledByItem has been added.
X
IfcGeometricRepresentationItem
IfcAlignment2DSegment
1TangentialContinuityIfcBoolean? Connectivity between the continuous segments is not enforced per se to be tangential. Setting "TangentialContinuity" to True means that the current segment shall continue with tangential continuity to the previous one.X
2StartTagIfcLabel? Tag to annotate the start point of the alignment segment.X
3EndTagIfcLabel? Tag to annotate the end point of the alignment segment.X
IfcAlignment2DVerticalSegment
4StartDistAlongIfcLengthMeasure Distance along the horizontal alignment, measured along the IfcAlignment2DHorizontal given in the length unit of the global IfcUnitAssignment.X
5HorizontalLengthIfcPositiveLengthMeasure Length measured as distance along the horizontal alignment of the segment.X
6StartHeightIfcLengthMeasure Elevation in Z of the start point relative to the IfcAlignment coordinate system.
NOTE  It is strongly advised to not offset the IfcAlignment coordinate system from the project engineering coordinate system.
X
7StartGradientIfcRatioMeasure Gradient of the tangent of the vertical segment at the start point. It is provided as a ratio measure. The ratio is percentage/100 (0.1 is equal to 10%). It has a theoretical range of -∞ < n < ∞ using a ratio measure. The equivalent range measured in degree is -90° < n < 90°.
NOTE  For practical application of start gradient, the range of the ratio measure should be within the limits of -1 ≤ n ≤ 1 (equivalent in degree -45° ≤ n ≤ 45°). However larger limits might apply for particular usages.

Positive gradient means an increasing height at the start (or uphill), a negative gradient means decreasing height at the start (or downhill).

X
ToVerticalIfcAlignment2DVertical
@Segments
S[1:1]X
IfcAlignment2DVerSegCircularArc
8RadiusIfcPositiveLengthMeasure radius of the circular arcX
9IsConvexIfcBoolean Orientation of the circular arc, convex (Boolean=”true”) means decreasing gradient along the arc at the beginning such as at the crest of a hill, concave (Boolean=”false”) means increasing gradient along the arc at the beginning such as at the base of a valley.X
Formal representations
XML Specification
 <xs:element name="IfcAlignment2DVerSegCircularArc" type="ifc:IfcAlignment2DVerSegCircularArc" substitutionGroup="ifc:IfcAlignment2DVerticalSegment" nillable="true"/>
 <xs:complexType name="IfcAlignment2DVerSegCircularArc">
  <xs:complexContent>
   <xs:extension base="ifc:IfcAlignment2DVerticalSegment">
    <xs:attribute name="Radius" type="ifc:IfcPositiveLengthMeasure" use="optional"/>
    <xs:attribute name="IsConvex" type="ifc:IfcBoolean" use="optional"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>
EXPRESS Specification
ENTITY IfcAlignment2DVerSegCircularArc
 SUBTYPE OF (IfcAlignment2DVerticalSegment);
  Radius : IfcPositiveLengthMeasure;
  IsConvex : IfcBoolean;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

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