Girder Strand [CBG]
Pretensioning strand object for the concrete box girder. Strands are routed in the same way as the box girder's longitudinal rebar — they sit between the section's already-computed 3D edge/web polylines (top/bottom slab edges, sloped exterior webs, vertical interior webs), so they follow the section transversely along the bridge as the box geometry varies. FEA force application, jacking and loss handling are inherited from the generic strand definition; only the geometry is specialised for the box.
3D Reference
Box Girder: Pick the Concrete Box Girder these strands belong to. The girder supplies the 3D edge polylines (top/bottom slab and exterior/interior webs) along the alignment that the strand rows are placed against, so the strands automatically follow the box's transverse geometry from station to station. Required.
Strand Rows: Table of strand rows. Each row specifies one band of strands placed against a single reference edge of the box section, with its own count, spacing, cover, group-center offset and longitudinal extent. Columns:
Reference Edge [Top/Bottom/Left Exterior Web/Right Exterior Web/Internal Webs]: Which face of the section this row hugs. Top and Bottom place the strands across the slab between the slab's left and right edges. Left/Right Exterior Web place them along the sloped exterior web between its top and bottom corners. Internal Webs applies the same row to every interior web at once.
# of Strands: Number of strands in this row. Distributed symmetrically about the row center. Minimum 1.
Strand Spacing: Center-to-center spacing between adjacent strands in the row, measured along the reference edge.
Distance to Reference Edge (clear): Perpendicular clear cover from the strand surface to the reference face. The strand axis is offset by this distance plus half the strand diameter.
Transverse Offset from Center: Horizontal offset of the row's center from the slab edge midpoint. Positive shifts the group toward the right side of the section. Active only when Reference Edge is Top or Bottom.
Vertical Offset from Center: Vertical offset of the row's center from the web midpoint. Positive shifts the group upward. Active only when Reference Edge is one of the webs.
Strand Positioning Mode [Girder Inset/Station Range]: How the longitudinal extent is specified. Girder Inset measures setbacks from the girder's start and end stations; Station Range takes absolute alignment stations.
Inset from Girder Start and Inset from Girder End: Distance from each girder end where the strands begin/end. Used when Strand Positioning Mode is Girder Inset.
Start Station and End Station: Absolute stations along the alignment. Used when Strand Positioning Mode is Station Range. Values outside the girder are clamped to the girder limits.
Properties
Strand Type: Pick the strand product (e.g. Grade 270 0.5″ or 0.6″ low-relaxation). Provides the diameter used to set the strand axis offset from the reference face, plus the geometric/mechanical properties consumed by FEA and the code check. Required.
Material: Material assigned to the strand for FEA. Typically the prestressing steel material associated with the chosen Strand Type.
Wobble Friction Coefficient: Friction coefficient for unintentional duct wobble used in friction-loss calculations. Express per unit length (1/length).
Curvature Friction Coefficient (1/rad): Friction coefficient for intentional path curvature used in friction-loss calculations. Express per radian.
Jacking
Jacking Method [Start/End/Start then End/End then Start]: Where the jacking force is applied. Start and End apply at one end only. Start then End / End then Start describe a sequenced two-end jacking (jack the named end first, then re-jack from the other).
Jacking Force From Start: Jacking force applied at the start end of the strand. Used as the initial tension at the start anchor for friction-loss propagation along the path.
Jacking Force From End: Jacking force applied at the end of the strand. Used when the strand is jacked from its far end; takes the same role as the start force but propagates losses in the reverse direction.
FEA Settings
Load Dist. Elem. Type [FENodes/FELines]: How the prestressing force is delivered to the FE model. FENodes applies the equivalent forces at finite-element nodes intersected by the strand path; FELines applies them along the FE line elements. Choose FELines for typical girder modeling so the force follows the strand profile continuously.
Percent Loss (%): Lump-sum percentage of the jacking force lost to time-dependent and friction effects, applied uniformly to the FEA prestressing demand. Use 0 if losses are computed separately by the code check or refined loss workflow.
3D Settings
Show Strand(Detailing) [No/Yes]: Whether to draw individual strand polylines in 3D and detailing views. Turn off on dense pretensioning layouts to keep the view responsive.
Quantities
The values in this group are computed from the generated strand geometry and material; they cannot be edited.
Min Section Area, Max Section Area: Smallest and largest cross-sectional area of strand metal across all stations. (Read-only; may be slow on recompute.)
Total Surface Area: Sum of the side surface area of every strand in the row set. (Read-only; may be slow on recompute.)
Min Cross Section Perimeter, Max Cross Section Perimeter: Smallest and largest cross-section perimeter of strand metal across all stations. (Read-only; may be slow on recompute.)
Volume: Total volume of strand metal in the layout. (Read-only; may be slow on recompute.)
Min Length Path, Length @COG Path, Max Length Path: Length of the shortest, centroidal and longest strand path in the layout. (Read-only; may be slow on recompute.)
Weight: Total weight of the strands, computed from Volume and the strand material density. (Read-only; may be slow on recompute.)
IFC
Type: IFC entity used when exporting the strand. Default IfcTendon.
Predefined Type: IFC predefined type. Default STRAND.
Parent: IFC parent assembly the strand is attached to in the export hierarchy. Default SUPERSTRUCTURE.
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