- Design Methodology : Initial design ideas are first sketched out freehand, as consideration is given to the purpose of the structure; a variety of different concepts might be established that would all be developed in parallel. Initial scheme design drawings are prepared using CAD, for new ideas can quickly be tried out, and conflicts shown. Fist attempts can then be made at form finding, using either sophisticated computer programmes to iteratively solve the geometry matrix for uniform stress, or by photographing soap-film models that naturally take up the shape of minimal surface. The geometry found is incorporated into the CAD drawings from which cutting patterns are prepared and small-scale models produced.
(a) (b) (c) Figure 5.1.5 (a) Soap film model, tent with bow, (b) Form finding of the membrane with CAD, (c) Computer rendering of the tent structure, SL-Rasch
- Numerical Analysis in the Design Process of Lightweight Structures : Minimal surface structures are double curved at any given point of their surface. The surface’s curvatures can be synclinal or anticlinal, defining tangential planes towards the corners. The complex geometry and the architectural appearance of these double curved structures as well as their covered spaces can only be studied in three-dimensional models. Frei Otto said “I always tried to think three dimensionally. The interior eye of the brain should be not flat but three dimensional so that everything is an object in space. We are not living in a two-dimensional world.” And – even more so with regards to the structural analysis and the manufacturing of these structures – it requires very precise 3Dmodels, which are nowadays mostly numerically generated by the computer, using particular software. In order to achieve the highest quality results the entire design process is developed in a complementary process, through the combination of CAD linked finite element software and computational fluid dynamics software. This software uses algorithms that mathematically describe tension equilibrium elements, to generate and to simulate minimal surfaces within defined boundary conditions. This software generates numerical soap films as real tension equilibrium surfaces. The computer model allows fast modification and comparison of different shapes and thereby supports the architectural design process.
Figure 5.1.6 Numerical analysis in the design process, SL-Rasch
Figure 5.1.8 AutoCAD drawing, SL-Rasch
Figure 5.1.7 Prototype as a ‘minimal shaped’ tension equilibrium form, SL-Rasch