Surface Spring Supports

 

 

 

Enter spring stiffness per unit supporting area of planar or solid elements to create elastic spring supports. Elastic Link elements may be created simultaneously. This function is mainly used to define a number of elastic supports on surfaces represented by the modulus of spring. For example, if the user wishes to define elastic supports for subgrades of foundations or underground structures, subgrade springs will be automatically entered at each node represented by concentrated stiffness. This function enables the user to specify the surface or line stiffness without having to worry about the discretization (sizes) of elements, which is automatically taken care of by the program.  

 

 

 

From the Main Menu select Model > Boundaries > Surface Spring Supports.

 

Select Geometry > Boundaries > Surface Spring Supports in the Menu tab of the Tree Menu.

 

 

 

 

 

 

Click to the right of Surface Spring Supports: Display the Surface Spring Supports Table

 

 

Note
The data entered in Surface Spring Supports are converted into Point Spring Supports or Elastic Link data and saved as such.

 

 

 Boundary Group Name

 

Select a Boundary Group in which the specified boundary condition is included. Select "Default" if Group assignment is unnecessary. Click to the right to prompt the "Define Boundary Group" dialog box to add, modify or delete Boundary Groups.

 

 

Surface Spring

 

Convert to Nodal Spring
Select a type of data to be created using the stiffness per unit area.

 

Point Spring: Point spring support

 

Elastic Link: Elastic link element

 

Distributed Spring
Enter the distributed spring stiffness to beam, planer or solid elements in order to consider elastic support conditions of subgrades.

 

 

 

When Point Spring is selected

 

 

Element Type
Assign the type of elements for which elastic spring supports or elastic link elements are to be created.

 

Frame: Create elastic spring supports or elastic link elements on the nodes of beam elements.

 

Width: Width of beam elements to calculate the support stiffness per unit length.

 

Planar: Create elastic spring supports or elastic link elements on the nodes of planar elements.

 

Solid (Face): Create elastic spring supports or elastic link elements on a face of solid elements.

 

Solid (Node): Create elastic spring supports or elastic link elements on the nodes of solid elements

 

Note
If the element type is selected as solid, a face of the elements must be specified.

 

Spring Type

 

Linear

 

Modulus of Subgrade Reaction: Subgrade stiffness

 

Kx: Stiffness per unit area in the node's local x- direction (GCS X-direction)

 

Ky: Stiffness per unit area in the node's local y- direction (GCS Y-direction)

 

Kz: Stiffness per unit area in the node's local z- direction (GCS Z-direction)

 

 

 Comp.-only / Tens.-only

 

Direction: Direction of the Point Spring

 

Normal(+): Normal (+ dir) to the surface (average normal direction of surfaces connected to the node defined with Point Spring)

 

Normal(-): Normal (- dir) to the surface (average normal direction of surfaces connected to the node defined with Point Spring)

 

Note

The normal direction of planar elements is defined by the right hand rule based on the node entry sequence. For solid elements, the normal direction (+) is oriented away from the surfaces of the elements.

 

UCS-x(+): UCS +x-direction (GCS +X-direction)

 

UCS-x(-): UCS -x-direction (GCS -X-direction)

 

UCS-y(+): UCS +y-direction (GCS +Y-direction)

 

UCS-y(-): UCS -y-direction (GCS -Y-direction)

 

UCS-z(+): UCS +z-direction (GCS +Z-direction)

 

UCS-z(-): UCS -z-direction (GCS -Z-direction)

 

Modulus of Subgrade Reaction: Subgrade stiffness

 

 

 

 

When Elastic Link is selected

 

 

Element Type
Assign the type of elements for which elastic spring supports or elastic link elements are to be created.

 

Frame: Create elastic spring supports or elastic link elements on the nodes of beam elements.

 

Width: Width of beam elements to calculate the support stiffness per unit length.

 

Planar: Create elastic spring supports or elastic link elements on the nodes of planar elements.

 

Solid (Face): Create elastic spring supports or elastic link elements on a face of solid elements.

 

Solid (Node): Create elastic spring supports or elastic link elements on the nodes of solid elements

 

Note
If the element type is selected as solid, a face of the elements must be specified.

 

Direction: Direction of the elastic link

 

Normal(+): Normal direction of the surface (average normal direction of surfaces connected to the node defined with Elastic Link)

 

Normal(-): Normal direction of the surface (average normal direction of surfaces connected to the node defined with Elastic Link)

 

Note
The normal direction of planar elements is defined by the right hand rule based on the node entry sequence. For solid elements, the normal direction (+) is oriented away from the surfaces of the elements.

 

UCS-x(+): UCS +x-direction (GCS +X-direction)

 

UCS-x(-): UCS -x-direction (GCS -X-direction)

 

UCS-y(+): UCS +y-direction (GCS +Y-direction)

 

UCS-y(-): UCS -y-direction (GCS -Y-direction)

 

UCS-z(+): UCS +z-direction (GCS +Z-direction)

 

UCS-z(-): UCS -z-direction (GCS -Z-direction)

 

Modulus of Subgrade Reaction: Subgrade stiffness

 

Length of Elastic Link: Length of elastic link element. The length dose not affect the analysis. It is simply required to define a vector internally in the solver.

 

Tens. Only, Comp.-Only: Check in an option to assign elastic link with tension-only or compression-only elements

 

 

 

Revision of V.7.6.1

 

When Distributed Spring is selected

 

 

Element Type
Assign the type of elements for which elastic spring supports or elastic link elements are to be created.

 

Frame: Create distribute spring supports along the length of the beam element.

 

Selection

 

Local Axis: Direction of the distributed spring

 

Width: Width of beam elements to calculate the support stiffness per unit length.

 

Planar(Face) : Create distributed spring supports on the face of planer elements.

 

Planar(Edge) : Create distributed spring supports on the edge of Planer elements.

 

Solid (Face): Create distributed spring supports on the face of solid elements.

 

Note
If the element type is selected as solid or Planar(Edge) and the selection is selected as Element, a face of the elements must be specified.

 

Spring Properties

 

Type

 

Linear Type: Enter the stiffness of linear elastic spring.

 

Compression-only/Tension-only Type: Enter the compression-only/ tension-only type elastic spring.

 

Modulus of Subgrade Reaction: Subgrade stiffness

 

 

 

 

Revision of V.7.6.1

 

Note Difference between Convert to Nodal Spring and Distributed Spring
 

When Convert to Nodal Spring is selected, springs are entered at the nodes of the elements. When Distributed Spring is selected, springs are uniformly distributed on a face or edge of the elements.

 

 

Convert to Nodal Spring

Distributed Spring (Winkler Spring)

Spring location

Nodes of elements

Distributed on the elements

Unit of reaction

kN

Beam: kN(kN/M)

Planar or Solid: kN(kN/M2)

Deformation

Concentrated at the nodes

As element stiffness increases, deformations are distributed throughout the elements.