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Fictitious bar (Geometry)

Last modified by Iwona Budny Bjergø on 2022/01/18 12:24

 Fictitious bar propertyDescription
Modules where available1584962684624-111.png 1584962732692-104.png 1584962773171-236.png
FunctionBar elements with given stiffness values
Axis positionHorizontal in 1584962690414-195.png
 Arbitrary (horizontal, vertical and skew) in 1584962737393-483.png 1584962769662-817.png
GeometryStraight and curved
End connectionRigid and hinged, or custom defined by Point-point connection
StiffnessEditable (but, material and cross-section definition is not available)
Load directionVertical in 1584962753957-424.png
 Arbitrary in 1584962744766-662.png 1584962766851-262.png
Load typeAll point and line load
Available analysis resultsDisplacement and internal forces
Default Short CommandFICB

Table: Fictitious bar properties


Figure: Fictitious bars connect plate elements

warning.pngThe program automatically generates “rigid” fictitious bars in the end points of “bars” modeled as a shell model (end edges of shell regions; see Shell model).

Definition steps

  1. If needed (and available in the current FEM-Design module), set a proper position for the working plane.
  2. Start 1584962879806-231.png  Fictitious bar command from 1584962906033-311.png tabmenu and choose 1584962916439-504.png Define.

  3. Set the properties of the new bar at 1584962949378-219.png  Default settings:
    • Stiffness (General)
      EA, GIt, EI1 and EI2 stiffness values can be assigned to bars. No definition of material and cross-section is needed. The local y’ axis represents the 1st principal axis, and the local z’ axis defines the 2nd principal axis.
      The value of rigid stiffness (“infinite” rigidity) can be defined and set as project default at Settings > Calculation> “Rigid” values > Fictitious bar.
    • Connections
      In 1584962995892-838.png , the end connections are fully rigid.
      In 3D modules, the end connections can be set under the Connections tab similarly to Beams. Only the released motion (arrow) and rotation (two-headed arrow) components are displayed in the model view (Display settings).
  4. Define the direction of the cross-section 1st principal axis (local y’ axis; only in 3D modules).
    The y’ axis cannot be modified in the  module, so it is always parallel with the Global X-Y (working).
  5. Choose a geometry definition method for the bar reference line (axis).
  6. Define the bar in the model view based on the chosen geometry method.

Optional steps:

  1. Modify the geometry with the Edit menu commands valid for line elements.
  2. Modify the bar properties with the 1584963110342-968.png Properties tool of the Fictitious bar tool palette.
  3. The fictitious bars are stored on “Modeling tools” Object layers. At layer settings, the default color and pen width can be set for all fictitious bars.
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