Surface Support

Glossary Term

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A surface support is used to support surfaces in RFEM. The support conditions ux, uy and uz as well as the shear springs vxz and vyz can be defined here. Furthermore, you can define whether to apply the nonlinearity in the uz-direction. In this dialog box, you can also find the option to activate spring constants for the surface support determined in the RF-SOILIN add-on module.

A surface support can be assigned to each surface entered in RFEM either graphically or in tables. The support conditions can either be set completely "rigid" or defined as "elastic" by entering a spring stiffness.

Support or springs in C u, x , C u, y , C u, z

The direction of the supports or springs refers to the local coordinate system of the respective surface to which the surface support is assigned. To display the local coordinate system of the surfaces, use the Display navigator or the shortcut menu.

The support perpendicular to the surface is controlled by entering C u, z . The entries for C u, x and C u, y describe the resistance to the displacement of the plate in x- and y-direction.

Shear springs C v, xz , C v, yz

An input in these fields has the effect that the shear resistance of the soil in the direction of the surface axes x or y is taken into account. In most cases, the Pasternak constant C v is between 0.1 ⋅ C u, z (low shear resistance) and 0.5 ⋅ C u, z (medium shear resistance). Generally, C v, xz = C v, yz can be applied. If the support in u z has been set as "rigid" (see Figure 01), it is therefore not possible to enter data for the shear springs C v, xz and C v, yz .

Theoretical background

The theoretical background to the "effective soil model" implemented in RFEM is documented in Section 4.9 of the RFEM manual.

Results for surface supports

As soon as surface supports are used in a model, the contact stresses σ z , τ yz and τ xz are available as a result after the calculation. In Table 4.21 "Surface - Contact Stresses", the columns H - J with the reaction forces R x , R y, and R z are also available for the entire surface.


Surface support Support Foundation Surface elastic foundation



RFEM Main Program
RFEM 5.xx

Main Program

Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements

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