Form-Finding of Membrane and Cable Structures

Dlubal Software for Membrane and Cable Structures

1. April 2015

The RFEM module RF-FORM-FINDING finds the shapes of membrane and cable constructions. The shape is found by using the equilibrium between the surface stress (prestress) and the natural and geometrical boundary reactions.

In the subsequent static analysis, the new form will be calculated taking into account the geometrically nonlinear method of analysis according to third order analysis (large deformation analysis).


  • Membrane as 2D and cable as 1D element
  • Simulation of membrane elements in the entire structure
  • Taking into account the semi-rigidity of the supporting structure
  • Simulation of isotropic and orthotropic membranes
  • Isotropic, orthotropic and radial prestress fields for membranes
  • Geometrical deflection, force or force density for cable elements
  • Consideration of self-weight forces for form-finding
  • Taking into account interior pressures for form-finding (pneumatic models)
  • Graphical evaluation of the new form using colored coordinate and inclination plots
  • Load of the membrane by geometry-independent free load blocks
  • Complete documentation of the calculation with user-defined adaptive evaluation figures
  • Temporary support definitions for the form-finding process
  • Simulation of mesh made of glass/PTFE and ETFE layers
  • Possibility to export the FE mesh as dxf or Excel file

Working with RF-FORM-FINDING

You first define the support conditions and properties of the membrane which specifies the prestress parameters in the membrane properties.

This is followed by an iterative form-finding process respecting the equilibrium between the defined prestresses and the boundary reactions.

After the form-finding procedure, RFEM replaces the initial input by a new shape by assigning a new "deformed" mesh in the background with the resulting stress condition from form-finding. This new model with impressed stress condition is then available for all subsequent calculations.

Moreover, the form-finding calculation displays the forces in the membrane or in the cable in the load case RF‑FORM‑FINDING after the form-finding (cable forces and cable stresses, membrane forces and membrane stresses, mesh height and mesh inclination, support reactions).

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