Definitions applying to Bridge View

 Instance diagram

Cross-framing between girders may be described using templates of member configurations. Such cross framing is captured within components, using AISC shapes where applicable. For curved alignments where girders are placed at different elevations, members must be placed relative to the girders at each side, for which positioning is defined relative to alignment curves.

Figure 1 — Bridge framing model

Steel angles (AISC L shapes) are captured using IfcMember having geometry represented by IfcExtrudedAreaSolid with IfcLShapeProfileDef. Steel plates are captured using IfcPlate having geometry represented by IfcExtrudedAreaSolid with IfcRectangleProfileDef.

Each element is connected using IfcRelConnectsElements, where the connection geometry is indicated using IfcConnectionSurfaceGeometry, which enables analysis from derived structural analysis models (IfcStructuralAnalysisModel)

Such cross-framing is then instantiated as object occurrences according to repetition intervals, where each occurrence has unique connectivity relationships with corresponding girder segments. While such discrete modeling results in larger files sizes, individual elements need to be captured for any structural analysis usage.

Parameterization of such framing requires referencing other instances according to connectivity, particularly for bridges with super-elevations where adjacent girders are at different elevations. To reference values at connected elements, IfcReference expressions must traverse connectivity relationships such as:

“\IfcMember.ConnectedFrom[1]\IfcRelConnectsElements.RelatingElement\IfcBeam.Representation\IfcProductDefinitionShape.Representation[‘Axis’]\IfcShapeRepresentation.Items[1]\IfcIndexedPolyCurve.PointOnCurve[@Offset].Z”.

To adjust for offsets from web thickness or flange thickness, the beam profile may be referenced such as:

“\IfcMember.ConnectedFrom[1]\IfcRelConnectsElements.RelatingElement\IfcBeam.HasAssociations\IfcRelAssociatesMaterial.RelatingMaterial\IfcMaterialProfileSet.MaterialProfiles[1]\IfcIShapeProfileDef.WebThickness.

Performing arithmetic operations on multiple references may be accomplished using IfcAppliedValue, where ArithmeticOperation may indicate ADD or SUBTRACT, and Components includes the list of referenced parameters. To define arrays of framing at offsets along curves, each framing set (between two specific girders) must be defined explicitly once, and then may be duplicated along a repetition path using a constraint relationship, where an IfcTable may be used for specific offsets along the alignment, or IfcAppliedValue may be used to indicate positioning of each instance relative to a constant spacing using an ArithmeticOperation of MULTIPLY.

Concept usage

Object Typing

The Object Typing concept applies to this entity as shown in Table 16.

Type IfcElementAssemblyType

Table 16 — IfcElementAssembly Object Typing

Exchange
Import		O
Export		O

Element Positioning

The Element Positioning concept applies to this entity.

Exchange
Import		O
Export		O

Formal representations