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| Twisted
surfaces are boosting building technology Karel Vollers |
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| The development of twisted surfaces The use of twisted surfaces in architecture forms part of technological and cultural developments in which the building environment is displaying an increasingly greater freedom of shape. Thanks to technology, there is a growing tendency to use strongly distorted materials in extreme constructions. Architecture, in turn, stimulates these applications. Such experiments do, however, require that all involved parties coordinate their activities and innovate their products simultaneously. In the mid-80s, people became bored with the box-shaped buildings, often covered with mirrored glass. Two reactions emerged: some architects reintroduced differences in materials in the façade, making use of variations in colour and texture; others decided on making use of the effects of curved surfaces and contours which came into attention when a façadefinishing consisted of just 1 type of material. Initially, when architects started experimenting with the possibilities of manipulating shapes on their computer screens, the main interest went to the freely distorted double-curved volumes, also known as 'blobs'. In the last few years however, twisted surfaces and volumes have been 'rediscovered'. Twisted surfaces and freely double-curved surfaces have many visual associative properties in common, but due to repetition of straight lines, the twisted ones are much easier to realise. Architects who make use of this now include Frank Gehry (in the Guggenheim Museum in Bilbao) and Kas Oosterhuis (in the Salt Water Exhibition Pavilion Neeltje Jans in Zeeland NL). The geometric possibilities of twisting have up to now, been a confusing area of architecture, due to the many varieties of distortion. Their geometrical characteristics can, however, be made easier to understand when using a scheme which links up with computer manipulations (copying, moving and rotating). Traditionally, a twisted surface is described as being a surface composed of straight lines in which the adjacent lines are not parallel to each other nor do they intersect each other. According to the new definition, a twisted surface is composed of straight lines, in which the point from which the adjacent lines have been moved and rotated, has at least one component of the direction of the rotation at a straight angle to the direction of moving. |
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| Materials Untill this newly developed frame with glass, twisted surfaces have only been produced in wood, steel, stone/brickwork and concrete. Only an approximation of a twisted glasssurface has been made by means of facetting with flat windowpanels. The industry was not able to produce twisted and freely bent double-curved glass panels at an acceptable price, or at least not in the short term. The development of this new product was complex and accompanied by high costs. The investigation into the use of twisted glass demands an integrated approach. Because a completely new product is involved, one can hardly talk of a market. As the building volumes of the first projects in which a new product would normally be applied, are small, the development costs cannot be expected to be regained from just a few buildingparts. The series size of the window panes in the designs made up until now are so small that the glass mould cannot be manufactured at an acceptable price. In addition, the acceptable development time for current projects is far too short. Hence, few manufacturers are prepared to invest in the development of this product. In order to force a breakthrough, and to familiarise the building world with a product so far unknown, a test model was developed with twisted glass. In this sample situation, the relatively simple and cheap production process using warm-bent instead of tempered glass was applied. Much time has been spent on organising industrial cooperations to introduce the products onto the market. If frames were available, the application area for twisted glass would be much greater. A larger market outlet would in turn stimulate the industry to invest (more) in innovation. With this in mind, it was decided to develop a prototype which combined glass pane and window frame. Twisted glass can indeed be fitted without a frame onto a narrow linear surrounding profile, or be placed against the surrounding construction with a sealant. This, however, limits considerably the possible applications, because frameless surfaces are only applied as a separate skin around a building, such as a foyer facade or atrium roof or to make an accentuated shape like an entrance canopy. Frameless facades are, however, hardly appropriate if one has to produce many fire-proof and sound-proof connections. Furthermore, the frames are often necessary to be able to enclose the (laminated) glass, in, for example, strongly forward leaning facades. The latter will often occur in designs with twisted or double-curved facades. The frame which has been developed is a variant of the newest frame profile introduced onto the European market by Reynolds. An advantage of offering a total product is that the consumer does not become the victim of discussions between the various parties involved in the construction, concerning the connection between frames and panes. Considering the relatively complex three-dimensional shape produced by various suppliers, one could expect such discussions to occur on a regular basis. This combination of financially sound innovative companies guarantees the quality of the final product. |
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| Double-curved surfaces Because they are composed of straight lines, the measuring and production of twisted surfaces is simpler than those of freely double-curved surfaces, but more complex than those surfaces which can be unfolded (in 1 direction curved surfaces and cones). Theoretically, freely double-curved products could be developed and be introduced onto the market right how, but this would require a large amount of investment in various industrial areas simultaneously. Extra problems which arise are the fact that the development route is full of uncertainties and that the market is not guaranteed. The development of twisted surfaces is an important interim phase in the development of the freely double-curved surfaces. Considering the window frame, the only difference between a frame for a twisted surface and for a freely double-curved surface is that in the former the horizontal profiles and the standing profiles are usually straight, while these are bent in the freely double-curved facades. Both in a twisted and in a double-curved surface, the standing framingprofiles stand for each joint under a different angle to the horizontal and vertical (sideways and forward or backward). So the joints between the profiles stay the same as in twisted facades and one only needs to bend the uprights and horizontals, to make the framing system also suitable for freely double-curved facades. But freely double-curved panels which are necessary for this, are not yet available as an industrial product. |
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| Models of buildings Parallel to the investigation into material-technical properties, urban development and architectonic properties of the twisted surfaces were also investigated. As an illustration of the possible applications, building models were designed whose plans made use of the twist in the layout. These have been projected in various possible locations. Potential clients and users have also been approached. The 150 metre high, twisted tower projected on the avenue near the ArenA in Amsterdam-Zuidoost (NL) is a characteristic application of a twisted volume. Making use of the twist, two directions are brought into contact with each other. In this case, the directions of the surrounding orthogonal roadpattern combine with the directions at the top of the building, whereas the direction of the building's façade at streetlevel is in tune with the diagonally positioned avenue. From a distance, the building's twist refers to the diagonal aspect of the avenue. Although the developer Wessels Zeist submitted a request at the planning commission for permission to build this first twisted tower, its realisation is not yet certain The building design and the technically and economically achievable material distortion counteract each other in the development process. On the one hand, materials are applied on a large scale in the building; on the other hand, after consultation with many experts, the materials are distorted on the basis of the geometry which the market will probably ask for. In the models, all facade surfaces are twisted. Such buildings will probably have a greater optic effect than rectangular structures which just have a single twisted surface. An accompanying advantage is that in completely twisted buildings such big series sizes emerge that development costs can be completely written off. The order of the development activities is different from usual and varies per building model. Because there was no question of a fixed time limit or assignment, the result is not determined by current economic, political or social processes and the various aspects of the twisting can be optimised. In the current building market, architects are not given time to develop an integral new concept, because within a few months after being commissioned to make a design, the working drawings must be ready and the buildings cost must be calculated with little tolerance. Considering the various building industries only invest in the development of new products, if these are considered realistic with regard to producibility, costs, market demand, etc, the twisted tower models were worked out in every detail. In addition, the consequences of twisted facades on the various aspects of a building (use, spatial characteristics, costs and technique) were investigated. By precisely specifying the dimensions of abnormal parts of contemporary buildings (such as the facade cleaning installation, the connection between the inner wall and the facade, and the air conditioning), uncertainties in planning and technical costs of a new geometry are reduced to an acceptable level. The first phase of this project is limited to the materialisation of a twisted facade unit. In producing a demonstration façade model, based on industrial production techniques, the participating industries have a model at their disposal within which they can optimise their own contribution. The participants, but also related and other industrial branches can link in to this, by suggesting constructive alternatives or additional products based on their specific knowledge; they may well exert a considerable influence on the construction as a whole. Who knows, other technical solutions might well be thought of, based on totally different concepts. Karel Vollers k.vollers@wxs.nl |
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| 150 m TOWER Developer: Wessels Zeist, Zeist Design: De Architecten Cie, in collaboration with Vollers Architects, Amsterdam Computer drawing: Hellevoort, Amsterdam Construction: ABT, Velp Façade: Van Dool Constructies, De Lier Frame system: Reynolds Architecture Systems, Harderwijk Glass supplier: Eijkelkamp, Goor and Glaverned, Tiel Installations: Engineering Bureau Linssen, Amsterdam TEST FRAMES Frame design: Reynolds Architecture Systems, Vollers Architecten Computer drawing: Hellevoort Glass production: F. van Tetterode, Glaverned Glass supplier: Eijkelkamp, Glaverned Frame system: Reynolds Architectural Systems Assembly: Reynolds Special Products |
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NOTE: Article by Karel Vollers in De Architekt, November 1999. This investigation is part of the Ph. D. research project being carried out at the Faculty of Architecture, TU Delft. The twisted frame, with double-glazed panels was presented at the Batimat in Paris (Fr) in November 1999 and at the Flanders Expo in Gent (B) in January 2000. |
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