In contrast to typical orthotropic membranes or rope meshes, which consist of two distinct sets of ropes or fibres, there is a type of rope mesh, where only one set of quasi-parallel ropes is alternatingly interconnected and then stretched to form a mesh. A significant non-linearity in-plane, a strong interaction between x- and y-direction, and frequent local bending (a loading type uncommon for ropes) is characteristic for this type of mesh. Studies to analyse the behaviour of a single mesh cell have been performed in [1]. To simplify many structural engineering procedures, the mesh must be approximated as a surface for which an equivalent membrane stiffness must be found. Existing biaxial testing methods, which are used for conventional membranes [2], can be adjusted to apply to single-set meshes as well [3] but testing is too complex to easily compare the stiffnesses of many different mesh subtypes as varying cell sizes, rope diameters, opening angles and pre-tension-conditions. Therefore, membrane stiffnesses must be obtained based on general rules and observations. For this purpose, I have developed two approaches: - a rhombus truss model with simplified stiffness and geometry, to obtain a direct formulation of the membrane stiffness matrix - an FE-model, which considers actual rope bending stiffness and allows modelling of the non-linear stretching process The mentioned characteristics pose challenges, but both approaches have been found to yield a suitable basis for approximate membrane stiffnesses, which can be evaluated to reflect varying subtypes. In the presentation, I will show how the mesh behaviour translates into unique membrane properties. REFERENCES [1] Rosemarie Wagner, Kai Heinlein: Experimentelle Untersuchungen zu Seilnetzen aus hochlegiertem Stahl, Messtechnik im Bauwesen, Ernst & Sohn Special 2018 [2] Jörg Uhlemann, Natalie Stranghöner, Klaus Saxe: Stiffness Parameters for Architectural Fabrics: An Analysis of Two Determination Procedures. Structural Engineering International 25 (1): 9–19. doi:10.2749/101686614X14043795570291, 2015 [3] Testing by DEKRA Automobil GmbH, PR: 852-03, sample: S17/185, second part, Material type: WEBNET micro 20261-0150-025, 2019