# Pier Stem \[STG]

The Pier Stem is a wall-type connection element between a pier cap (or column) and a foundation. OpenBrIM supports rectangular and oblong stem walls, optional circular variation along the length, and location referencing by either support line or columns.

## General

**Bounded Pier Cap? \[Yes/No]:** When YES, the top of the stem is bounded by a connected Pier Cap and the top elevation is derived from that cap. When NO, the stem top is positioned using the Top Elevation inputs directly.

**Pier Cap:** The pier cap that bounds the top of the stem wall when **Bounded Pier Cap?** is YES.

**Support Line:** The support line that defines the stem wall location when **Reference** is Support Line.

**Column(s):** One or more columns the stem wall is attached to when **Reference** is Column.

**Stem Width (Transverse Direction):** Dimension of the stem wall in the transverse direction (along the support line).

**Stem Thickness (Longitudinal Direction):** Dimension of the stem wall in the longitudinal direction (along the alignment).

**Bottom Elevation:** Global elevation of the bottom of the stem wall.

**Transverse Offset:** Offset of the stem wall from the selected support line or column, measured transverse to the alignment. The positive transverse direction in OpenBrIM places positive offsets on the right-hand side when looking upstation along the PGL.

**Longitudinal Offset:** Offset of the stem wall from the selected support line or column, measured along the alignment.

**Section Type \[Rectangular/Oblong]:** Cross-section shape of the stem wall. Oblong adds semicircular ends to the rectangular core.

**Top Elevation Mode \[Offset from Alignment/Elevation]:** Selects how the top of the stem wall is positioned. **Offset from Alignment** applies a signed offset from the PGL alignment elevation; **Elevation** sets a global elevation directly.

**Top Elevation Offset from Alignment:** Signed offset of the stem top from the alignment elevation. Used when **Top Elevation Mode** is Offset from Alignment.

**Top Elevation:** Global elevation of the stem top. Used when **Top Elevation Mode** is Elevation.

## Circular Variation

**Is Circular \[NO/YES]:** When YES, the stem wall is lofted along a circular arc rather than a straight profile.

**Radius of Curvature:** Radius of the circular arc when **Is Circular** is YES.

**Circle Direction \[Concave up/Concave down]:** Orientation of the arc when **Is Circular** is YES.

**Circle Segments:** Number of discretization segments along the arc when **Is Circular** is YES.

## FEM

**GenerateFEM \[NO/YES]:** When NO, the stem wall is omitted from the finite-element model (3D-only).

**Material:** Material assigned to the stem wall. Required when **GenerateFEM** is YES.

**Rigid Section:** Section used for the rigid links that connect the stem wall FE mesh to adjacent elements.

**Mesh Size Y Direction:** Target FE element size of the stem wall mesh in the local Y direction (along the stem width). Smaller values produce finer meshes.

**Mesh Size Z Direction:** Target FE element size of the stem wall mesh in the local Z (vertical) direction. Smaller values produce finer meshes.

## IFC

**Type \[IfcBridge/IfcBridgePart/IfcBeam/IfcColumn/IfcSlab/IfcFooting/IfcPile/IfcBearing/IfcReinforcingBar/IfcReinforcingMesh/IfcTendon/IfcMechanicalFastener/IfcAlignment/IfcPositioningElement/IfcKerb/IfcGuardrail/IfcSurfaceFeature/IfcElementAssembly/IfcCableSegment/IfcSensor/IfcDistributionElement/IfcPlate/IfcWall/IfcRail/IfcRoad/IfcDiscreteAccessory/IfcDistributionSystem/IfcMember/IfcBuildingElementProxy]:** IFC entity type used on export. Default **IfcColumn**.

**Predefined Type \[COLUMN/PIERSTEM/PIERSTEM\_SEGMENT/PILASTER/STANDCOLUMN/USERDEFINED/NOTDEFINED]:** IFC predefined type attribute. Default **PIERSTEM**.

**Parent \[BRIDGE/SUPERSTRUCTURE/DECK/SUBSTRUCTURE/FOUNDATION/APPROACH\_STRUCTURE/RETAINING\_STRUCTURE]:** Parent element in the IFC hierarchy. Default **SUBSTRUCTURE**.

## Quantities

**Total Surface Area:** Total surface area of the stem wall, including top, bottom, and side faces (Read-only).

**Side Surface Area:** Surface area of the vertical side faces only (Read-only).

**Rebar Density(per cubic yard):** Rebar mass per unit concrete volume, used to compute the rebar weight estimate.

**Rebar Weight:** Stem volume multiplied by **Rebar Density** (Read-only).

**Volume:** Computed volume of the stem wall (Read-only).

**Weight:** Stem volume multiplied by the material density (Read-only).

**Material:** Name of the assigned material (Read-only).


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