Foundation slab (Geometry)

Foundation slab property	Description
Icon
Modules where available
Reference plane position	Horizontal
Geometry	Any shape
Thickness	Constant or variable
Hole	Available
Eccentricity	Available for display and calculation
Edge connection	Rigid elastic (spring) linear or non-linear
Material	Concrete
Orthotropic feature	Available
Load direction	Vertical
Load type	Point load (force and moment), Line load (force and moment), Surface load, Surface temperature variation load, Surface stress load, Surface support motion
Available analysis results	Displacement, internal forces, stresses, stability and vibration shape
Available design	Foundation design
Default Short Command	FSL

Table: Foundation slab properties

Definition steps

1. If needed, set a proper position for the working plane.
2. Start  Foundation slab command from  tabmenu and choose  Define.
   

3. Set the properties of the new plate at  Default settings:

    

   • 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.

     Eccentricity 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:

5. Modify the default edge connections with  . 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).

   Active  link button assigns the stiffness value typed in the Compression field to the Tension field. Inactive icon  lets to define stiffness values separately.

   Predefined types
   Click   to set all motion and rotation components to “rigid”. The result will be a “totally rigid” connection.
   Click   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   to set all components to free. This tool gives the possibility to virtually connect independently moving elements.
   Behavior
   Click   to assign the stiffness value defined in the Compression field to the Tension field by components.
   Click   not to allow tension for all connection components.
   Click   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.

6. Add hole with   tool.

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

8. Modify the Foundation slab properties with the  Properties tool of the Foundation slab tool palette.

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

10. 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.