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Foundation slab (Geometry)

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

Foundation slab propertyDescription
Modules where available1584963457098-564.png
Reference plane positionHorizontal
GeometryAny shape
ThicknessConstant or variable
EccentricityAvailable for display and calculation
Edge connectionRigid elastic (spring) linear or non-linear
Orthotropic featureAvailable
Load directionVertical
Load type
Available analysis resultsDisplacement, internal forces, stresses, stability and vibration shape
Available designFoundation design
Default Short CommandFSL

Table: Foundation slab properties

Definition steps

  1. If needed, set a proper position for the working plane.
  2. Start 1584963542559-168.png  Foundation slab command from 1584963554197-559.png  tabmenu and choose 1584963578066-756.png  Define.
  3. Set the properties of the new plate at 1584963624522-957.png  Default settings:

    1584963633474-852.png 1584963641028-868.png

    • Identifier (General)
      The program automatically generates it, but you can define custom value. Identifier (ID) number can be displayed in model view (Display settings).
    • Bedding (General)
      The horizontal one can be specified by the User. These three values define the motion spring stiffness of the automatically created surface support group under the foundation slab. By default, the horizontal values are the half of the vertical one.
    • Insulation (General)
      User can apply insulations attached to the bottom of the foundation slab. If Calculate soil as a solid element is activated, Insulations are calculated as part of the Foundation object with the user-specified parameters. Otherwise, they are ignored.
    • Geometry (General)
      Variable thicknes can be set for the foundation slab with the same method as for the Plate objects.
    • Eccentricity (General)
      Eccentricity (e) adds “virtual” distance between the reference plane and the calculation (middle!) plane if“Consider eccentricity in calculation” option is unchecked, otherwise the eccentricity has effects in the calculation. This option is useful for displaying regions with different thickness values.
      warning.pngEccentricity have no effect in calculations if “Consider eccentricity in calculation is checked off. They are only to display plate “solid” with its defined position.

      Eccentricity value can be displayed in model view (Display settings).
      The “Consider eccentricity caused by cracking in cracked section analysis” option is for Reinforced concrete slabs. With this option modeling the eccentricity changes after cracking is available. The following figure shows the eccentricity changes.
      Figure: Explaining cracked and uncracked analysis

    • Orthotropy (General)
      The ratio between the E1 and E2 elasticity modules in the main directions can be set here. So, if the value is 1, the new plate will be isotropic, otherwise it is orthotropic. The orthotropy direction can be set with the angle between E1 direction and the plate’s local x’ axis (Alpha).

    • Material
      Only concrete material can be set for Analysis and Design.

  4. Define the plate region in the model view based on the chosen geometry method.

Optional steps:

  1. Modify the default edge connections with 1584963893882-775.png . Just select the plane and then its edge(s) to set connection conditions, and finally set the requested motion and rotation settings.
    Motion-Rotation / Compression-Tension
    The x’, y’ and z’ are valid in the connection’s local system displayed in the preview and as a symbol in the middle of the edges in the model view. Choose “Rigid” or “Free” from the drop-down lists, or type stiffness values (spring connection).
    light.pngActive 1584963971885-930.png link button assigns the stiffness value typed in the Compression field to the Tension field. Inactive icon 1584963978507-412.png lets to define stiffness values separately.

    Predefined types
    Click 1584964059954-687.png  to set all motion and rotation components to “rigid”. The result will be a “totally rigid” connection.
    Click 1584964067806-246.png  to set all motion components to “rigid” and all rotation components to free (allow rotation around all directions). The result will be a hinged connection.
    Click 1584964076390-322.png  to set all components to free. This tool gives the possibility to virtually connect independently moving elements.
    Click 1584964085342-219.png  to assign the stiffness value defined in the Compression field to the Tension field by components.
    Click 1584964091566-129.png  not to allow tension for all connection components.
    Click 1584964097932-449.png  not to allow compression for all connection components.
    Setup “Rigid”
    With this option the value of “infinite” rigidity can be defined by motion and/or rotation for selected connections.
    For all edge connections, the value of “infinite” rigidity can be defined and set as project default at Settings > Calculation> “Rigid” values > Connections.

  2. Add hole with 1584964118333-611.png  tool.

  3. Modify the reference plane geometry with the Edit menu commands valid for region elements.

  4. Modify the Foundation slab properties with the 1584964140787-542.png  Properties tool of the Foundation slab tool palette.

  5. Set the display settings of plates at Settings > Display > Soil and Foundation.

  6. The Foundation slabs are stored on “Foundation” and if they modeled with Surface support group their supports will be stored at the “Support” Object layers. The color and pen width settings by selected plate elements can be modified by Edit > Properties > Change appearance.

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