RF‑FORM‑FINDING can be activated in the "Options" tab in the "Model - General Data" section. By activating the add-on module, a new RF‑FORM‑FINDING load case is created and an additional menu appears in the main program, allowing for the definition of prestress conditions for membrane and cable elements.
Question
How do I activate the RF‑FORM‑FINDING add-on module?
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![Generate Catenary](/en/webimage/009135/2417183/01-en-png.png?mw=512&hash=e5b08a40fd9a5a16825be6182b3138f78627561e)
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![Activated Display Option: Topology on Form-Finding Form](/en/webimage/006807/1584412/ff_en-us-png.png?mw=512&hash=94b5759319b2121bb6599f91ab7f09d306687771)
With the activated option 'Topology on Form-Finding Form' in Project Navigator - Display, the model display is optimized based on the form-finding geometry. For example, the loads are displayed in relation to the deformed system.
!["Show Preliminary Form-Finding" Option in Shortcut Menu](/en/webimage/006853/1585587/formfinding-en-us-png.png?mw=512&hash=5ac96ae2cf6fc509d84c9690ca4f8cfabc3db135)
Activating 'Show Form-Finding' in the shortcut menu leads to an automatic preliminary form-finding according to the saved form-finding properties when you change the structure of membrane surfaces. This interactive graphics mode is based on the force density method.
More Information FAQ![Foil Cushion with Material Model Isotropic Plastic 2D/3D](/en/webimage/006832/497212/Form-finding_de.png?mw=512&hash=78051e4822ef57bc2068122c169039849806ee35)
In RFEM, there is an option to couple surfaces with the stiffness types "Membrane" and "Membrane Orthotropic" with the material models "Isotropic Nonlinear Elastic 2D/3D" and "Isotropic Plastic 2D/3D" (add-on module RF-MAT NL erforderlich).
This functionality enables simulation of the nonlinear strain behavior of ETFE foils, for example.
![RFEM RF-FORM-FINDING Add-on Module | Form-Finding of Membrane and Cable Structures](/en/webimage/002861/3064920/121_Zeltgruppe_(1).png?mw=512&hash=029740dfa799337fbd84aed6cbf18113b717f8fb)
- Form-finding of:
- tension-loaded membrane and cable structures
- compression-loaded shell and beam structures
- mixed tension- and compression-loaded structures
- Consideration of gas chambers between surfaces
- Interaction with supporting structure (substructure design according to various standards)
- Surfaces as a 2D and members as a 1D element
- Definition of different prestress conditions for surfaces (membranes and shells)
- Definition of forces or geometrical requirements for members (cables and beams)
- Consideration of individual loads (self‑weight, inner pressure, and so on) in the form‑finding process
- Temporary support definitions for the form-finding process
- Automatic preliminary form-finding of membrane surfaces (more information...)
- Definition of isotropic or orthotropic material for structural analysis
- Optional definition of free polygon loads
- Transformation of form‑found shape elements into NURBS surface elements
- Possibility of combined form-finding by integration of preliminary form-finding
- Graphical evaluation of the new form using colored coordinates and inclination plots
- Complete documentation of the calculation including user-defined adaptive evaluation figures
- Optional export of the FE mesh as a DXF or Excel file