Layout
Girder Tendon is used to model post-tensioning tendons. In OpenBrIM, tendons are modeled as loads, and the following process is applied to determine the structural effects:
Tendon loads are determined by the forces that act along the tendon layout and affect the selected structure. When calculating the forces, prestress losses are also taken into account.
Tendon loads are discretized into smaller segments, specifically at every foot. The tendon loads within each segment are statically distributed to the nodes of the selected structural element.
Girder: Select the girder that tendon is applied. Tendon loads are distributed to the this structure.
Section Reference Edge[Top/Bottom]: Select a reference edge of the Girder. This selection affects the reference line chosen during the definition of the tendon geometry.
Layout Input Method[Path Data/ Tabular Data]: There is two possible ways to input tendon geometry: Tabular Data and Path Data. Both of these methods take their reference from the selected structural object, the Girder’s reference line.
Tabular Data:
Transverse Tendon Path:
Vertical Tendon Path:
Local Coord. X Offset [in]: X offset in local coordinates of the selected object.
Local Coord. Y Offset [in]: Y offset in local coordinates of the selected object.
Local Coord. Z Offset [in]: Z offset in local coordinates of the selected object.
Using Local Coord. Offsets would be beneficial when multiple tendons use the same layout definition.
Duct Outer Diameter [in]: Set the outer diameter of tendon duct. This parameter only affects the 3D visualization of tendons.
Properties
Material: Set the material for the tendon.
Post-tension Type[Bonded/Unbonded]:
Exposure[Internal/External]:
Anchor Set Length [in]:
Wobble Friction Coefficient [1/ft]: Enter the wobble friction coefficient.
Curvature Friction Coefficient [1/rad]: Enter the curvature friction coefficient.
Jacking
# of Strands: Enter the number of strands for the tendon.
Strand Type: Enter the strand type for the tendon. The strand type can be imported from the Properties section.
Jacking Method[Start/End/Start then End/ End then Start]: Specify the jacking method that is applied to the tendon. In the case of girder, start and end refer to downstation and endstation respectively.
Jacking Force From Start [kip]: Enter the start jacking force that is applied to the tendon. It must be specified, unless Jacking Method is selected End.
Jacking Force From End [kip]: End jacking force that is applied to the tendon. It must be specified, unless Jacking Method is selected Start.
FEA Settings
In OpenBrIM, short-term losses are calculated automatically and the effect of the short-term losses can be seen from
Load Dist. Elem. Type[FENodes/FELines]: This input affects the type of finite elements loads are distributed. FELines are used for beam elements.
Percent Loss(%): Set the percent loss for the long-term losses (Concrete Creep - Concrete Shrinkage - Steel Relaxation). This is an optional input. User can leave this input as 0 and let OpenBrIM calculate the long-term losses by CEB-FIB 1990 curve by runing the time-dependent analysis. Alternatively, user can set an approximate Percent Loss(%) value for long-term losses which reduces to the Jacking Force values of the tendon.
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