Читать книгу Rethinking Prototyping - Группа авторов - Страница 70

Patterns, or ornaments, have a long history in building and can be found in all cultures. Traditionally, they are decoratively added elements. Adolf Loos’ essay „Ornament und Verbrechen“ (Ornament and Crime) marks a turning point in contemporary architecture: The elimination of any non-functional decorative elements sets the origin of classical modern architecture.

Studies of parametric geometries base on the systematic variation of geometrical patterns: the variation reveals characteristic elements, be it subjective aesthetical or objective structural qualities. Fig. 6 shows examples of parametric studies: Parametric geometrical studies by D‘rcy Wentworth Thompson dealing with the subject on growth and form (Thompson 1961); form-finding studies with systematic variation of boundary conditions using soap films within differently curved wires carried out by Frei Otto and his team (Bach 1988); and parametric optimisation studies carried out by the author developing optimal shapes within a given volume with varying orientation of the point loads applied to the structrure.

Fig. 6 Examples of parametric design studies

Today, the ornament seems to be back in architecture and parametric design is very fashionable in both architectural and structural design. New tools allow generating geometries adapting to variable boundary conditions - being structural demands, lighting conditions or formal conceptions. Fig. 7 shows examples of modern ornaments (left: exhibition stand Gasser Fassadentechnik, Swissbau 2012; right: Suedwestmetall facade, architects Allmann Wappner Sattler)with their design possibilities and manufacturing conditions directly related to new developments: repetition in patterns is other than some few decades or years ago redundant. Structural necessities as well as manufacturing constraints can be neglected. The focus is set on aesthetical logics and qualities.

Fig. 7 Examples of modern ornamental design

The missing link between pattern and structure can be achieved through use of structural optimisation methods. As an example, the procedure in this study shown in Fig. 8 is

 A given design space, here: a flat cuboid volume, with part of the space not being subject to the optimisation.

 A given structural system, here: evenly distributed load on the top surface; point supports.

 The optimisation formulation, here: minimum compliance as an objective, given volume fraction (15% of the design space to be filled with material) as a design constraint.

 Varying of parameters, here: systematic variation of the support points of the structure.

Fig. 8 The structural model as a plate with distributed loading + point supports, the optimisation result

The optimisation result shows the material distribution within the design space: ribs running directly between the point supports along the short distance and ribs connecting between the point supports reaching maximum height at mid-distance with the ribs merging and leaving a void in the middle.

The structural system modelled for this optimisation is a very broadly applied one: plates under distributed loadings can be inserted into many structural arrangements. The patterning is now produced through variation of the position of the points supports, which are located in the four corners of the initial model (Fig. 9).

Fig. 9 Position of point supports and bottom view of the corresponding optimisation results

Fig. 10 Possible arrangement of parametric pattern

All of the systems use the same amount of material, all of them are optimised according to the given support conditions. The result of this study is a patterning with an inherent structural logic, comprehensible to the viewer and derived from objective targets: the development of geometries relating to their structural system.

A possible application of parametrically optimised plates is shown in Fig. 10. The material of the plates could be any mouldable material adequate resistance, such as fibre reinforced concrete or plastic. The fixing points of the cladding plates are then positioned where they were located in the optimisation run.

The optimisation can basically be scaled within certain limits. Another possible application is the generation of plates at a larger scale is shown in Fig. 11. It resembles in its appearance the famous ceiling structure of the Gatti Wool Factory in Rome, designed by Pier Luigi Nervi, a pioneer in the design of aesthetic and efficient structures. To suit the support conditions determined by the optimisation procedure the columns are branched at varying heights, corresponding to the distance of the support points. Since the plates were optimised as individual structural elements, they are arranged at a distance.

Fig. 11 Pattern roof structure, referring to Nervi‘s Gatti ceiling

It was the merit of Pier Luigi Nervi to merge aesthetics, structural efficiency and construction - as he mentioned „good engineering seems to be a necessary, however not sufficient condition for good architecture“ (Nervi 1965). Modern manufacturing methods allow variations in geometry without rising costs. Nervi‘s idea of aesthetical engineering should be carried on using modern design and manufacturing tools.

Further parametric studies deal with the design of shells: the interaction of support geometries of a structure produces related shell geometries. The curvature of the shell is then directly linked to its structural system, a possibility to create structural parametric patterns in 3D space.