Surface Stiffness

Glossary Term

The stiffness of a surface describes the relation between the load acting on the surface and the elastic deformation of the surface. The stiffness depends on the material (elastic modulus, shear modulus, Poisson's ratio) as well as on the geometry (for example, length, width, height).

In general, a distinction is made between the following relative stiffnesses:

  • Bending stiffness
  • Torsional stiffness
  • Shear stiffness
  • Strain stiffness

Stiffness Types in RFEM

  • Standard (isotropic surface)
  • Without membrane tension (like Standard but failure of membrane stiffness under tension)
  • Orthotropic (orthotropic surface, different stiffnesses in the x- and y-direction of finite elements)
  • Glass (for surfaces made of glass, created by the RF-GLASS add-on module)
  • Laminate (laminate theory, created by the RF-LAMINATE add-on module)
  • Rigid (surfaces with very high stiffness)
  • Membrane (surfaces with membrane stiffnesses only)
  • Membrane - Orthotropic (different membrane stiffnesses in the x- and y-direction of finite elements)
  • Null (surfaces will be ignored in the calculation, necessary for solids)


stiffness stiffness matrix surface orthotropic