> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/templates/concrete-box-girder-bridge-workflow/tendon-cbg/tendon-cbg.md). # Tendon \[CBG] This object defines a post-tensioning tendon applied to a concrete box girder. The tendon is referenced to a girder, given a 3D layout (either as a path or as tabular data), assigned material and jacking properties, and exported both as 3D detailing geometry and as finite elements for prestressing analysis. ## 3D Reference **Girder:** Pick the girder the tendon runs along. The tendon's geometry and station references are computed relative to this element. Exactly one girder must be selected. ## Layout **Section Reference Edge \[Middle/Top/Bottom]:** Edge of the girder cross-section the tendon's vertical offsets are measured from — the section middle, top, or bottom. Must be provided. **Layout Input Method \[Path Data/Tabular Data]:** Choose how the tendon path is entered. With Path Data the tendon is described by separate transverse and vertical path tables that support curve variations; with Tabular Data the path is given as a single table of station/offset points. **Tabular Data:** Table of tendon control points used when the input method is Tabular Data. Each row gives the support line, station distance, and transverse/vertical offsets that define the tendon point. Visible only when Layout Input Method is Tabular Data. **Transverse Tendon Path:** Table describing the tendon's transverse (horizontal) layout when the input method is Path Data. Each row defines the support line, station, offset, variation type, and curve parameters between control points. Visible only when Layout Input Method is Path Data; a value is required in that case. **Vertical Tendon Path:** Table describing the tendon's vertical (elevation) layout when the input method is Path Data. Each row defines the support line, station, offset, variation type, and curve parameters between control points. Visible only when Layout Input Method is Path Data; a value is required in that case. **Local Coord. X Offset:** Rigid shift of the whole tendon path along the local X axis, applied after the layout is computed. **Local Coord. Y Offset:** Rigid shift of the whole tendon path along the local Y axis, applied after the layout is computed. **Local Coord. Z Offset:** Rigid shift of the whole tendon path along the local Z axis, applied after the layout is computed. ## Properties **Material:** Material assigned to the tendon, selected from the project's defined materials. Drives the tendon weight and modulus used in analysis. A value must be provided. **Post-tension Type \[Bonded/Unbonded]:** Whether the tendon is grouted to the surrounding concrete (Bonded) or free to slip inside its duct (Unbonded). This affects how prestress force interacts with the section in analysis. **Exposure \[Internal/External]:** Whether the tendon runs inside the concrete section (Internal) or outside it (External), e.g. deviated external tendons. **Anchor Set Length:** Seating slip of the anchorage at lock-off, used to compute anchor-set friction losses near the jacking end. A typical value is about 0.375 in. **Wobble Friction Coefficient:** Friction loss per unit length due to unintended duct misalignment (wobble), per AASHTO LRFD 5.9.5.2.2b. A common starting value is 0.0002 per unit length. **Curvature Friction Coefficient (1/rad):** Friction loss coefficient for tendon curvature, per AASHTO LRFD 5.9.5.2.2b. A common value is about 0.18 (1/rad). ## Jacking **# of Strands:** Number of strands bundled in the tendon. Combined with the strand area this sets the total tendon cross-sectional area. **Strand Type:** Strand selected from the project's defined strands; supplies the strand area and material grade. A value must be provided. **Jacking Method: Jacking type \[Start/End/Start then End/End then Start]:** Which end (or sequence of ends) the tendon is stressed from. This governs where anchor-set and friction losses accumulate. **Jacking Force From Start: applied jacking force to the start of tendon.:** Jacking force applied at the start end of the tendon. **Jacking Force From End: applied jacking force to the start of tendon.:** Jacking force applied at the end of the tendon. ## FEA Settings **Load Dist. Elem. Type \[FENodes/FELines]:** Whether the tendon's prestress is applied to the structure through the finite-element nodes (FENodes) or along the finite-element lines (FELines). **Percent Loss (%):** Lump-sum percentage reduction applied to the jacking force to approximate prestress losses, when detailed loss calculation is not used. ## 3D Settings **Show Tendon(Detailing)\[No/Yes]:** Toggles whether the tendon is drawn in the 3D detailing view. ## Quantities **Min Section Area:** Smallest cross-sectional area along the tendon. Computed from the geometry. (Read-only) **Max Section Area:** Largest cross-sectional area along the tendon. Computed from the geometry. (Read-only) **Total Surface Area:** Total surface area of the tendon volume. Computed from the geometry. (Read-only) **Min Cross Section Perimeter:** Smallest cross-section perimeter along the tendon. Computed from the geometry. (Read-only) **Max Cross Section Perimeter:** Largest cross-section perimeter along the tendon. Computed from the geometry. (Read-only) **Volume:** Total volume of the tendon. Computed from the geometry. (Read-only) **Min Length Path:** Shortest path length of the tendon. Computed from the geometry. (Read-only) **Length @COG Path:** Tendon length measured along the center of gravity of the path. Computed from the geometry. (Read-only) **Max Length Path:** Longest path length of the tendon. Computed from the geometry. (Read-only) **Weight:** Total tendon weight, the volume times the material density. Computed from the geometry. (Read-only) ## 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 to export the tendon (default `IfcTendon`). **Predefined Type\[Bar/Coated/Strand/Wire/Userdefined/Notdefined]:** IFC predefined-type enumeration for the selected IFC type (default `STRAND`). **Parent\[Bridge/Superstructure/Deck/Substructure/Foundation/Approach\_Structure/Retaining\_Structure]:** IFC parent assembly the tendon is nested under on export (default `SUPERSTRUCTURE`). --- # Agent Instructions This documentation is published with GitBook. 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