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Revolution und Kontinuität im Holzbau
2016 ¥ 1/2 ∂
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Hotel Ammerwald in Reutte, 2009 Architekten: Oskar Leo Kaufmann, Albert Rüf 8 Energieeffizienter Wohnungsbau in Ansbach, 2013 Architekten: Deppisch Architekten 9, 11 Kapelle St. Loup, 2008 Architekten: localarchitecture 10 Elemente der Holztafelbauweise 7
Ammerwald Hotel in Reutte, 2009 architects: Oskar Leo Kaufmann and Albert Rüf 8 Energy-efficient apartment building in Ansbach, 2013 Deppisch Architekten 9, 11 St Loup Chapel, 2008 local architecture 10 Panelised wood components
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The basic component of contemporary wood construction is no longer the stick – it’s the panel.1 In 1999, Andrea Deplazes formulated the expectation that modern wood construction would move away from sticks – or studs – toward panelised construction, and consequently, panelised tectonics. The re-orientation that wood construction underwent at the turn of the millennium continues to leave its mark – it was a fundamental change. The new possibilities inspire designers and heighten expectations – also with regard to ecological criteria to be met by the construction industry. The technological leap occurred against the backdrop of a politically charged worldwide re-conception of what “thinking green” means – a re-conception spurred by global warming. In this context, several developments in construction materials took place around the year 2000; in addition, materials and assemblies that already existed were developed further and used in new applications. Since the 1990s, for example, oriented strand board – which was developed in the 1950s in the USA – has been increasingly important in Germany in panelised construction.
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Wood-concrete composite floor: Back in 1922 Paul Müller obtained the first patent for the development of a floor of wood planks or boards standing on edge with a layer of concrete on top of them – the first known patent for a wood-concrete composite load-bearing component in the German-speaking lands. The intention was to reduce the consumption of steel and concrete, which were relatively expensive materials, during the period of austerity between the world wars. During the 1980s the research on this construction method resumed, and a decade later it led to a large number of novel connections and assemblies. The goal is no longer to reduce the use of concrete, but to improve the fire safety and acoustic performance, as well as to increase the stiffness. Edge-fixed timber elements: Back then, edge-fixed timber elements had already been in circulation for decades. But instead of connecting the boards with nails, as was the original practice, they are now connected my means of well-dried obliquely inserted hardwood dowels. In this way, the elements as a whole can be treated as solid wood, which
causes less wear and tear on the tools. Building components that can support large loads with a minimised cross-section and completely free of adhesives can be produced using simple, inexpensive planks. Timber box-element floors: The development of the timber box-element floor is heading in the opposite direction: the combined forces of structural members act in response to the anisotropy and linearity of the loads. By gluing the ribs to the panels, the members are unified structurally in a single cross-section. In this way the required structural depths of the components and the ribs’ cross-sections can be reduced. The dimensions of the timber box elements are limited only by their transportability. The elements can span in two directions and their supports are situated at intervals. Cross laminated timber (CLT): This material best represents the sweeping changes in wood construction. Not only does its odd number of cross-wise stacked, glued layers of boards minimise wood’s lack of homogeneity and its anisotropy, but at the same time it is a dimensionally stable planar building material whose behaviour can be predicted. Its size is theoretically undefined and limited only by the parameters of the production sequence. CLT and, analogous to it, the other less prevalent materials veneer plywood and laminated veneer lumber (LVL) are high-performance materials that are easy to handle. The classical prerequisites for wood construction – profound knowledge of the material and its applications – appear to no longer hold sway. In the mid-19th century the veneer lathe was invented, and towards the end of the century it facilitated the mass production of plywood. The development of construction materials employing multiple layers of veneers followed a trajectory from the single ply to the board: a considerable amount of time after such multiple-ply boards had been introduced into the market, cross-laminated timber made its appearance as universal element for loadbearing walls, floor constructions and roofs. KLH (“Kreuzlagenholz”, or CLT), produced in Austria and Merk Dickholz, produced in Germany, received first approvals in 1988. They constitute a milestone in the develop-