The Object Typing concept applies to this entity as shown in Table 51.

For bridge decks following a parametized template, such template may be referenced by this relationship.

The bridge deck template (IfcSlabType may define a standardized cross-section via IfcMaterialProfileSet, and standardized aggregated components.

Exchange
Import		O
Export		O

The Quantity Sets concept applies to this entity as shown in Table 52.

Exchange
Import		O
Export		O

The Material Profile Set concept applies to this entity.

Bridge decks are modelled as IfcSlab with IfcMaterialProfileSet indicating profile sections. The concrete profile is typically described using IfcArbitraryClosedProfileDef, where the cross-section captures any superelevation and projections for fitting onto beams.

As shown in Figure 191, the profile of the slab is described using IfcArbitraryClosedProfileDef, referring to an IfcIndexedPolyCurve. The X coordinates are fixed, while the Y coordinates vary along the alignment.

Figure 191 — Bridge deck profile

For scenarios where the cross-section varies, the material profile set must reflect the cross-section at the start of the sweep, where downstream transformations may optionally be described by constraints.

The material is described using IfcMaterial, along with properties (IfcMaterialProperties) requiring particular strengths or concrete mixes.

Exchange
Import		O
Export		O

The Constraint Association concept applies to this entity.

Constraints are entirely optional, and may be exchanged to indicate the design intent and/or to allow for editing of the underlying bridge model according to design parameters. Thus, the definitive physical structure of a bridge is described by it's geometry, whereas constraints merely provide information about how such design was achieved. In a contract scenario, in case of conflict between constraint information described herein, and the resulting geometry, the geometry governs.

For curved alignments, the dimensions of the cross-section may vary along the alignment. To manage and report such information cohesively, such dimensions may be captured in an IfcTable as shown in Figure 193, where the points of the IfcArbitraryClosedProfileDef are driven by formulas bound to columns (IfcTableColumn) of the IfcTable, with each cross-section segment captured within an IfcTableRow.

Figure 193 — Bridge deck table

Each of the table columns are mapped to corresponding profile points using IfcTableColumn with IfcReference as shown in Figure 2.

Figure 193 — Bridge deck parameter

To define such geometry in a full parametric fashion – using specific formulas rather than tables, constraints may be applied to points of the arbitrary profile. However, as the profile varies along the alignment curve, such formulas must reference positions along the alignment.

To define parameters, the IfcRelAssociatesConstraint relationship is associated with the enclosing IfcSlab, and refers to an IfcObjective having ObjectiveQualifier=PARAMETER, and contains a set of IfcMetric instances for each parameter to be related.

IfcMetric.ReferencePath maps to an X or Y coordinate value within the profile definition relative to the object, such as:

“\IfcSlab.HasAssociations\IfcRelAssociatesMaterial.RelatingMaterial\IfcMaterialProfileSet.Profile\IfcArbitraryClosedProfileDef.OuterCurve\IfcIndexedPolyCurve.Points\IfcCartesianPointList2D.CoordList[4][2]”.

This expression maps to the Y coordinate (2) of the fourth point (4) of the profile. To apply the formula for such parameter that relates the Y coordinate to the position of the underlying curve, IfcMetric.DataValue is mapped to either IfcTable for discrete values or IfcAppliedValue for a formula expression.

Exchange
Import		O
Export		O

The Element Decomposition concept applies to this entity as shown in Table 53.

Bridge decks may have reinforcing detailed according to aggregation as shown in Figure 194. Reinforcing that is poured within other components (such as piers) is defined within the connected component where it is to be initially placed, even though it may protrude into the bridge superstructure.

Figure 194 — Bridge deck components

Exchange
Import		O
Export		O

The Element Positioning concept applies to this entity as shown in Table 54.

Exchange
Import		O	O	O
Export		O	O	O

The Structural Surface Assignment concept applies to this entity.

The idealized structural representation of a bridge deck may be attached using this relationship, where underlying loads, load cases, and load results may be defined. For precast decks, camber ordinates are defined at the structural surface member.

Exchange
Import		O	R
Export		O	R

The Body SweptSolid Extruded Arbitrary Geometry concept applies to this entity.

For bridge decks following a straight alignment (horizontally straight and vertically straight with possible constant incline), and constant cross-section, the geometry may be represented by IfcExtrudedAreaSolid.

Exchange
Import		O
Export		O

The Body AdvancedSwept Fixed Reference Geometry concept applies to this entity.

For bridge decks following a curved alignment with a constant cross-section that is not rotated (no super-elevation), the geometry may be represented by IfcSurfaceCurveSweptAreaSolid.

The Body AdvancedSwept Surface Curve Geometry concept applies to this entity.

For bridge decks following a curved alignment with a constant cross-section that may be rotated, the geometry may be represented by IfcSurfaceCurveSweptAreaSolid.

Figure 195 illustrates usage of advanced swept solid geometry to represent a bridge deck, with gaps inserted for illustrative purposes.

Figure 195 — Bridge deck model

Exchange
Import		O
Export		O

The Body Spine Geometry concept applies to this entity.

For bridge decks where the profile varies along the alignment curve, slabs may be represented using IfcSectionedSpine, using discrete intervals as determined sufficient for construction. If segments may be constructed as linear, then underlying curve segments may be defined as IfcPolyline; otherwise if to be constructed precisely as curved, then such segments may be defined as any other subtype of IfcBoundedCurve for arcs, B-Splines, or other.

Note that such curve geometry does not directly reference curves structures defined at IfcAlignment; rather, such geometry is based on Cartesian placement derived from the alignment curve. The rationale for such approach is compatibility with existing CAD software for bridges which represents solid geometry according to STEP-compatible Cartesian definitions, regardless of the alignment curve.

Figure 197 illustrates usage of sectioned spine geometry to represent a bridge deck, with gaps inserted for illustrative purposes.

Figure 197 — Bridge deck model

Figure 198 illustrates the corresponding design plans for the bridge deck shown.

Figure 198 — Bridge deck plans

Exchange
Import		O
Export		O