The structural analysis software RFEM designs membranes together with the supporting structure (for example cables).
Membranes can be modeled as general and quadrangle surfaces. The quadrangle surfaces are general quadrilateral surfaces whose boundary lines do not have to rest in one plane. Therefore, it is possible to model surfaces with anticlastic and synclastic curvature, which is characteristic for the membrane structures.
For the design, the surface types Membrane and Membrane-Orthotropic are available. It is possible to define different directional stiffness properties (in the warp and weft direction) for the surface type Membrane‑Orthotropic.
In addition, RFEM provides an option to model and design the connection plates, fittings, and others.
RF‑FORM‑FINDING searches for shapes of structures subjected to tension or compression, such as membrane and cable structures, shells, and so on. The shape is calculated by the equilibrium between the surface stress (specified prestress and additional load such as self‑weight, pressure, etc.), and the given boundary requirements. The prestressed model is afterwards used as the initial state for all subsequent calculations.
RF‑CUTTING‑PATTERN generates and organizes cutting patterns for membrane structures. Boundary conditions of the cutting patterns on curved geometry are determined by boundary lines and independent planar cutting lines or geodesic cutting lines. The flattening process is performed according to the minimum energy theory.
In the frame & truss analysis software RSTAB, it is possible to design the primary construction of membrane and cable structures. Form-finding and framework design may be carried out in the engineering software Easy by Technet. The modular program system Easy performs especially the geometrically nonlinear calculation of membranes and pneumatic cushions. RSTAB has a special connection to this design program used for light framework structures.
The internal forces are determined in Easy by Technet where the membrane is also dimensioned. Then, it is necessary to import the data to the structural analysis program RSTAB by Dlubal Software in order to perform the design and stability analysis.
Since the stiffnesses may affect the forces in a membrane significantly, the cross-sections optimized in RSTAB are returned to Easy for recalculation during the iterative process. After the design, RSTAB can also be used as a tool for documentation of the structural analysis including tables and graphics.
In addition to the RF-FORM-FINDING and RF‑CUTTING‑PATTERN add‑on modules for RFEM, you can find more useful add‑on modules for structural analysis of cable and membrane structures under the Steel Structures industry.
A unique roof structure was built for the main bus station in Aarau, Switzerland in 2013.
The canopy has a cloud-like shape and contains the largest single‑chamber cushion in the world. The ETFE cushion has a volume of 63,919.55 ft³ and covers an area of 11,517.38 ft².
Allianz Arena is a soccer stadium in Munich, Germany, which hosted the opening match of the 2006 FIFA World Cup.
The translucent exterior facade of the stadium emits light in various colors and thus makes the whole arena building very special.
The Eden Project is a complex of two biomes and outdoor gardens with plants from many diverse climates and environments.
The biome is a steel frame structure with cladding panels consisting of triple-layered membrane cushions made of ETFE foil.
A giant wooden airship “suspended” above the Centre for Contemporary Art in Prague, Czech Republic, has been opened to the public in December 2016.
The unique timber and steel airship structure “Gulliver” will serve as a space for literature.
![Figure 01 - Basic Shapes of Membrane Structures [4]](/-/media/Images/website/pages/support-and-learning/support/knowledge-base/001437/01-en-png.png)
This paper is focused on the specific aspects of designing membrane structures. These structures have specific requirements such as form‑finding and cutting patterns generation. These topics are the focus of many research works and there are many methods proposed to achieve the desired results. However, in this paper these issues will be discussed more from the practical point of view than from the theoretical one. The paper will be followed by examples, which will complement the discussed topic and show the special attention required during the design process.
The RF-FORM-FINDING add‑on module determines equilibrium shapes of membrane and cable elements in RFEM. In this calculation process, the program searches for such a geometric position in which the surface stress/prestress of membranes and cables is in equilibrium with natural and geometric boundary conditions. This process is called form‑finding (hereinafter referred to as FF).
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Product Video: Add-on Modules RF-FORM-FINDING & RF-CUTTING-PATTERN
Dlubal Webinar: Form-Finding and Cutting Patterns of Membrane Structures in RFEM
“RFEM is the best I have used. I have experience with RISA, STAAD, ETABS, Visual Analysis, and others. In the tensile/fabric structure world, I've tried NDN, Forten, etc. Once you get used to RFEM's interface, it has no comparison to the others. Even with typical structures, it's much easier.”
Fernando Peña, P.E.
10/20/2016
Dlubal Software is a member of the TensiNet Association.
This master thesis by Rostislav Lang deals with analysis of membrane structures using the finite element software RFEM.
Cable tensions after form-finding in RFEM
Tent structure before and after form-finding in RFEM
Form-finding for membrane-steel structure
FE mesh after form-finding
Contour lines after form-finding for a group of umbrellas
Hall with membrane roof
Group of tents | Representation of contour lines in RFEM
Tent structures at the Denver International Airport
Tension forces in cables and contour lines after form-finding in RFEM
Membrane roof structure
Contour lines after form-finding in RFEM
Tensile structure
Membrane structure before and after form-finding in RFEM
Tent structure
Cableway
Applying gas load on pneumatic cushions
Cut through a pneumatic cushion by using Clipping Plane
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
Main Program
The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions
Add-on Module
Form-finding of tensile membrane and cable structures
Add-on Module
Generation of cutting patterns for tensile membrane structures
Add-on Module
Stress analysis of steel surfaces and members
Add-on Module
Design of steel members according to Eurocode 3
Module Extension for RF-STEEL EC3
Warping torsion analysis according to the second-order theory with 7 degrees of freedom
Module Extension for RF-STEEL EC3
Plastic design of cross-sections according the Partial Internal Forces Method (PIFM) and Simplex Method
Add-on Module
Design of steel members according to the American standard ANSI/AISC 360
Add-on Module
Design of steel members according to the Swiss standard SIA 263
Add-on Module
Design of steel members according to the Indian standard IS 800:2007
Add-on Module
Design of steel members according to the British standard BS 5950-1:2000 or British Annex BS EN 1993-1-1
Add-on Module
Design of steel members according to the Chinese standard GB 50017-2003
Add-on Module
Design of steel members according to the Canadian standard CSA S16
Add-on Module
Design of steel members according to the Australian standard AS 4100-1998
Add-on Module
Design of steel members according to the Mexican standard NTC-DF 2004
Add-on Module
Design of steel members according to the Russian standard SP 16.13330.2011
Add-on Module
Design of steel members according to the South African standard SANS 10162-1:2011
Add-on Module
Design of steel members according to the Brazilian standard ABNT NBR 8800:2008
Add-on Module
Design of steel members according to Code of Practice for the Structural Use of Steel 2011 (Buildings Department - Hong Kong)
Add-on Module
Fatigue design of members and sets of members according to EN 1993-1-9
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