IfcAsymmetricIShapeProfileDef defines a section profile that provides the defining parameters of a singly symmetric I-shaped section. Its parameters and orientation relative to the position coordinate system are according to the following illustration. The centre of the position coordinate system is in the profile's centre of the bounding box.

The overall width of the profile is implicitly given by the maximum of the bottom flange width and the top flange width.

IfcAsymmetricIShapeProfileDef can also be used to model rail profiles if the application scenario does not require a full explicit shape model of the rail profile. Alternatively, IfcArbitraryClosedProfileDef can be used to provide the exact shape of rail profiles. Either way, a reference to an external document or library should be provided to further define the profile as described at IfcProfileDef.

HISTORY  New entity in IFC2x2.

IFC2x3 CHANGE  All profile origins are now in the center of the bounding box. The attribute CentreOfGravityInY has been made OPTIONAL.

IFC4 CHANGE  Supertype changed from IfcIShapeProfileDef to IfcParameterizedProfileDef. Attributes which were inherited from IfcIShapeProfileDef are now defined directly at IfcAsymmetricIShapeProfileDef and have been partially renamed but were not reordered.
Bottom flange may be narrower than top flange.
Type of TopFlangeFilletRadius relaxed to allow for zero radius.
Trailing attribute CentreOfGravityInY deleted, use respective property in IfcExtendedProfileProperties instead.
Attributes BottomFlangeEdgeRadius, BottomFlangeSlope, TopFlangeEdgeRadius, TopFlangeSlope added.

Figure 382 illustrates parameters of the asymmetric I-shaped section definition. The parameterized profile defines its own position coordinate system. The underlying coordinate system is defined by the swept area solid that uses the profile definition. It is the xy plane of:

• IfcSweptAreaSolid.Position

By using offsets of the position location, the parameterized profile can be positioned centric (using x,y offsets = 0.), or at any position relative to the profile. The parameterized profile is defined by a set of parameter attributes. In the illustrated example, the 'CentreOfGravityInY' property in IfcExtendedProfileProperties, if provided, is negative.

Figure 382 — Assymetric I-shape profile