Software for Form-Finding & Cutting Patterns of Membrane Structures

Calculation in RFEM

The structural analysis software RFEM designs membranes together with the supporting structure (for example cables).

Membranes can be modelled 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.

Form-Finding of Membrane and Cable Structures

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.

Cutting Patterns of Membrane Structures

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.

Calculation in RSTAB

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.

Add-on Modules for Structural Analysis of Cable and Membrane Structures

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.

Knowledge Base | Form-Finding and Cutting Patterns

  1. Figure 01 - Basic Shapes of Membrane Structures [4]

    Specific Requirements of Membrane Structures

    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.

  2. 1 - General Data

    Form-Finding in RFEM

    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). The FF calculation can be activated in RFEM globally in the "General Data" of a model, "Options" tab. After selecting the corresponding option, a new load case or a calculation process called RF-FORM FINDING is created in RFEM. An additional FF parameter is available for defining surface stress and prestress when entering cables and membranes. By activating the FF option, the program always starts the form-finding process before the pure structural calculation of internal forces, deformation, eigenvalues, etc., and generates a corresponding prestressed model for further analysis.

More Articles from Knowledge Base

Contact us

Contattaci

Do you have any questions about our products? Do you need advice for your current project? 
Contact us or find various suggested solutions and useful tips on our FAQ page.

+49 9673 9203 0

info@dlubal.com

Product Video: Add-on Modules RF-FORM-FINDING & RF-CUTTING-PATTERN

Dlubal Webinar: Form-Finding and Cutting Patterns of Membrane Structures in RFEM

The best I have used

“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.”

TensiNet

Dlubal Software is a member of the TensiNet Association.

Master Thesis on FEM Analysis of Membrane Structures

Masterarbeit Rostislav Lang

This master thesis by Rostislav Lang deals with analysis of membrane structures using the finite element software RFEM.

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

RSTAB Main Program
RSTAB 8.xx

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

RFEM Tensile Membrane Structures
RF-FORM-FINDING 5.xx

Add-on Module

Form-finding of tensile membrane and cable Structures

RFEM Tensile Membrane Structures
RF-CUTTING-PATTERN 5.xx

Add-on Module

Generation of cutting patterns for tensile membrane structures

RFEM Steel and Aluminium Structures
RF-STEEL 5.xx

Add-on Module

Stress analysis of steel surfaces and members

RFEM Steel and Aluminium Structures
RF-STEEL EC3 5.xx

Add-on Module

Design of steel members according to Eurocode 3

RFEM Steel and Aluminium Structures
RF-STEEL Warping Torsion 5.xx

Module Extension for RF-STEEL EC3

Warping torsion analysis according to the second-order theory with 7 degrees of freedom

RFEM Steel and Aluminium Structures
RF-STEEL Plasticity 5.xx

Module Extension for RF-STEEL EC3

Plastic design of cross-sections according the Partial Internal Forces Method (PIFM) and Simplex Method

RFEM Steel and Aluminium Structures
RF-STEEL AISC 5.xx

Add-on Module

Design of steel members according to the American standard ANSI/AISC 360

RFEM Steel and Aluminium Structures
RF-STEEL SIA 5.xx

Add-on Module

Design of steel members according to the Swiss standard SIA 263

RFEM Steel and Aluminium Structures
RF-STEEL IS 5.xx

Add-on Module

Design of steel members according to the Indian standard IS 800:2007

RFEM Steel and Aluminium Structures
RF-STEEL BS 5.xx

Add-on Module

Design of steel members according to the British standard BS 5950-1:2000 or British Annex BS EN 1993-1-1

RFEM Steel and Aluminium Structures
RF-STEEL GB 5.xx

Add-on Module

Design of steel members according to the Chinese standard GB 50017-2003

RFEM Steel and Aluminium Structures
RF-STEEL CSA 5.xx

Add-on Module

Design of steel members according to the Canadian standard CSA S16-09

RFEM Steel and Aluminium Structures
RF-STEEL AS 5.xx

Add-on Module

Design of steel members according to the Australian standard AS 4100-1998

RFEM Steel and Aluminium Structures
RF-STEEL NTC-DF 5.xx

Add-on Module

Design of steel members according to the Mexican standard NTC-DF 2004

RFEM Steel and Aluminium Structures
RF-STEEL SP 5.xx

Add-on Module

Design of steel members according to the Russian standard SP 16.13330.2011

RFEM Steel and Aluminium Structures
RF-STEEL SANS 5.xx

Add-on Module

Design of steel members according to the South African standard SANS 10162-1:2011

RFEM Steel and Aluminium Structures
RF-STEEL NBR 5.xx

Add-on Module

Design of steel members according to the Brazilian standard ABNT NBR 8800:2008

RFEM Steel and Aluminium Structures
RF-STEEL HK 5.xx

Add-on Module

Design of steel members according to Code of Practice for the Structural Use of Steel 2011 (Buildings Department - Hong Kong)

RFEM Steel and Aluminium Structures
RF-STEEL Fatigue Members 5.xx

Add-on Module

Fatigue design of members and sets of members according to EN 1993-1-9