Alignment 2D Vertical Segment Circular Arc |

Item | SPF | XML | Change | Description |
---|---|---|---|---|

IFC4x1 Release Candidate 1 |
||||

IfcAlignment2DVerSegCircularArc | ADDED | |||

IFC4x1 Release Candidate 2 |
||||

IfcAlignment2DVerSegCircularArc | ||||

ToVertical | ADDED | |||

IFC4x1 Release Candidate 3 |
||||

IfcAlignment2DVerSegCircularArc | ||||

LayerAssignment | ADDED | |||

StyledByItem | ADDED |

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:

- x = offset as length measure relative to start of curve segment (i.e. 0 is at head).
- g
_{1}=*StartGradient*as ratio measure - R =
*Radius*as length measure

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 StartHeightinstanteneous 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 StartHeightinstanteneous gradient provided by StartGradient, and length provided by HorizontalLength | |

Figure 314 — Alignment vertical arc segment concave |

# | Attribute | Type | Cardinality | Description | G |
---|---|---|---|---|---|

8 | Radius | IfcPositiveLengthMeasure | radius of the circular arc | X | |

9 | IsConvex | IfcBoolean | 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 |

# | Attribute | Type | Cardinality | Description | G |
---|---|---|---|---|---|

IfcRepresentationItem | |||||

LayerAssignment | IfcPresentationLayerAssignment @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 IFC4 CHANGE The inverse attribute | X | |

StyledByItem | IfcStyledItem @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 | X | |

IfcGeometricRepresentationItem | |||||

IfcAlignment2DSegment | |||||

1 | TangentialContinuity | IfcBoolean | ? | 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 |

2 | StartTag | IfcLabel | ? | Tag to annotate the start point of the alignment segment. | X |

3 | EndTag | IfcLabel | ? | Tag to annotate the end point of the alignment segment. | X |

IfcAlignment2DVerticalSegment | |||||

4 | StartDistAlong | IfcLengthMeasure | Distance along the horizontal alignment, measured along the IfcAlignment2DHorizontal given in the length unit of the global IfcUnitAssignment. | X | |

5 | HorizontalLength | IfcPositiveLengthMeasure | Length measured as distance along the horizontal alignment of the segment. | X | |

6 | StartHeight | IfcLengthMeasure |
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 | |

7 | StartGradient | IfcRatioMeasure |
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 | |

ToVertical | IfcAlignment2DVertical @Segments | S[1:1] | X | ||

IfcAlignment2DVerSegCircularArc | |||||

8 | Radius | IfcPositiveLengthMeasure | radius of the circular arc | X | |

9 | IsConvex | IfcBoolean | 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 |

` <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>

```
ENTITY IfcAlignment2DVerSegCircularArc
```

SUBTYPE OF (IfcAlignment2DVerticalSegment)**;**

Radius : IfcPositiveLengthMeasure;

IsConvex : IfcBoolean;

END_ENTITY;