Читать книгу Rethinking Prototyping - Группа авторов - Страница 68

Frei Otto’s exclamation in 1977 „Stop building the way you build!“ is still resonating.His works are continuously published in manifold contributions.How can we apply Otto’s approaches to structural and architectural design using modern design tools?

The fundamental research of Frei Otto and his team on lightweight structures reveals basic principles about geometries in nature and building. Within given boundary conditions, structural shapes with an inherent logic are found. The approach of form-finding can be seen as a different kind of prototyping - with a clear differentiation from classical structural theory: It is not the thinking in elements but the thinking in conditions that sets up the design driver.

In structural teachings and design, this approach is very descriptive and aesthetic in a profound way. Approaching structures through thinking in deformations provides a very good understanding about how structures work and about how they can be designed. Deformations relate directly to spans; the distribution of internal forces, bending moments, principal moments or principal stresses, can be derived from a given design task in order to develop a structural geometry.

A design study based on these principles was carried out in a study at the Biberach University of Applied Sciences. The Neue Nationalgalerie in Berlin, an icon of classical modern architecture designed by Ludwig Mies van der Rohe and first opened in 1968, was taken as role model for the design task to develop a waffle slab with its geometry being derived from the support conditions of a square ground plan. The dimensions in ground plan of approximately 65m span were given as a design constraint; the layout of the waffle slab (with the built one measuring 1.80 m in height) was subject to the design. First studies show the interaction of support positions and the correspondent deformations of a continuous slab.

Fig. 3 Analysis models of a point supported slab with varying position of supports; deformation of the slab (with deformations superelevated)

Translating these deformations into an appropriate structure, the relation between span and deformation becomes clear. The support conditions can be transformed directly as a design driver for structural dimensions. They are of course only one singular aspect in design, since internal forces (here: predominantly bending moments and shear forces) are not a priori taken into account. However, a feasible approach to design is found.

The derivation of a structure from the deformation of a reduced model produces an aesthetic, feasable and understandable geometry, as shown in Fig. 4.

Fig. 4 Structural geometry of a point-supported waffle slab derived from its support conditions and correspondent deformations

Taking into account other aspects such as bending moments or principal moments produces different results for the same design task. Comparing the design results shows a great variety of proposals, while all of them are driven by structural constraints: With a very simple structural approach, a great variety of architectural designs can be developed.