Limit Plastic Strain for Welds

Every day, thousands of structural engineers design structural components using design check formulas that include the critical buckling load. But where do these old formulas come from, that Leonard Euler established over 200 years ago and that form the basis of all three structural steel design concepts?

This paper is focused on the specific aspects of designing membrane structures that have specific requirements, such as form-finding and cutting pattern generation. An integral part of the design of these structures is the process of finding suitable prestressed shapes and generating cutting patterns. The text briefly describes two basic processes in the design of membrane structures. The physical principles are explained and the individual theses illustrated by examples.

Compliance with building codes, such as Eurocode, is essential to ensure the safety, structural integrity, and sustainability of buildings and structures. Computational Fluid Dynamics (CFD) plays a vital role in this process by simulating fluid behavior, optimizing designs, and helping architects and engineers meet Eurocode requirements related to wind load analysis, natural ventilation, fire safety, and energy efficiency. By integrating CFD into the design process, professionals can create safer, more efficient, and compliant buildings that meet the highest standards of construction and design in Europe.

• Planar and geodesic cutting lines
• Flattening of double-curved surface parts of tensioned membranes or pneumatic cushions
• Definition of cutting patterns by using boundary lines which are not required to be connected
• Sophisticated flattening based on the minimum energy theory
• Welding and boundary allowances
• Uniform or linear compensation in warp and weft direction
• Possibility of different compensations for boundary lines
• Adaptable data organisation (any additional modification of input data is considered up to the final "weld")
• Graphical display of cutting patterns
• Statistical information about each cutting pattern (width, length, size)
• Option to automatically generate cutting patterns from cells

After the calculation, the "Point Coordinates" tab appears in the cutting pattern dialog box. In this tab, the result is displayed in the form of a table with coordinates and a surface in the graphical window. The coordinate table presents new flattened coordinates relative to the centroid of the cutting pattern for each mesh node. Furthermore, the cutting pattern with the coordinate system at the centroid is represented in the graphical window. When selecting a table cell, the respective node is displayed with an arrow in the graphic. In addition, the area of the cutting pattern is displayed below the node table.

Moreover, standard stress/strain results for each pattern are displayed in the RF‑CUTTING‑PATTERN load case in RFEM.
Features:

• Results in a table, including information about the cutting pattern
• Smart table relating to the graphic
• Results of flattened geometry in a DXF file
• Output of strains after flattening in order to evaluate the cutting patterns
• Results of strains after flattening for the evaluation of patterns

The "Orthotropic | Fabric | Nonlinear Elastic (Surfaces)" material model allows you to define prestressed fabric membranes using the representative microstructure-solid element model – RVE.

By considering the fabric geometry in the microstructure model, the corresponding transversal strain effect can now be considered for all force conditions in the membrane.