Toscana Thermal Pools, Bad Sulza, Germany, Ollertz Open structure-free space under the shell roofs. Timber Showroom, Hergatz,

hall is also walled-off to avoid any structural protrusions into the hall. As well as its functional suitability, this structure-and-skin combination has won over critics by its elegance of detail and sheer transparency. The nightly drama of printing is now highly visible from a nearby road. By their very nature, shell structures are supported at their perimeters. Although any associated structural elements, such as the ribs that might increase the strength of a shell are usually constructed inside the exterior skin, their structural depths are so shallow as to not reduce space usage significantly. The Toscana Thermal Pools, Bad Sulza, enclosed by glue- laminated timber ribbed-shells, benefit from planning freedom uncon- strained by structure Figs 5.4 and 5.5. Free-flowing interior spaces surround the main pools. As well as providing openness in plan, the shells’ ribbed interior surfaces contribute to the attractive interior ambience. The interior portal frames of the Timber Showroom, Hergatz, are repre- sentative of most interior perimeter structures whose vertical members intrude into the building plan Fig. 5.6. Sometimes, floor plan edge- zones whose widths equal the structural depths can be incorporated unobtrusively into the overall building function. Take Gothic churches, for example, where numerous side chapels slot between deep internal but- tresses adjacent to the aisles. At Hergatz, it is of little consequence that structure does not integrate with an edge-zone function. The glue- laminated timber columns are quite shallow, and the exposed frames pos- sess an unusual attractiveness. Here, a conventional engineering system, often relegated to light-industrial buildings, is transformed into one with intrinsic beauty by virtue of its detailing quality. Curves soften the appear- ance of the frames and invite new architectural interpretations of their BUILDING FUNCTION 83 ▲

5.4 Toscana Thermal Pools, Bad Sulza, Germany, Ollertz

Ollertz, 1999. Timber shell structures. ▲

5.5 Open structure-free space under the shell roofs.

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5.6 Timber Showroom, Hergatz,

Germany, Baumschlager-Eberle, 1995. Timber columns project into the showroom. form. Member tapering bestows a lightness and elegance, while unobtru- sive connections, such as at the eaves joints, avoid any discordant notes. At the Sainsbury Centre, Norwich, the perimeter structure lies com- pletely inside the skin Fig. 5.7. Tubular-steel triangular trusses span between columns of identical cross-section. Although the 2.5 m thick structural walls are unusually bulky, mechanical services, storage and service areas fully occupy all of the space within them. The location and integration of all these secondary functions within the structural depth allows the remainder of the interior to function as a public space free of both vertical structure and ‘servant spaces’. Exhibition Hall 3, Frankfurt, also exemplifies the instance of perimeter structure located within the building envelope well that is integrated with building function Fig. 5.8. Over the upper exhibition level, tubular- steel arched roof beams span 160 m between triangulated buttresses that are expressed on the end elevations. The buttress depths on each side of the building accommodate the main concourse areas, both hor- izontal and vertical circulation systems, and service areas. As at the Sainsbury Centre, the entire distance between these perimeter structural zones where measured across the building can be used for exhibition purposes. The first floor structure consists of pairs of storey-deep steel trusses spaced a corridor-width apart in plan, and overlain by beams and a concrete slab. The 32 m spacing between ground floor columns results in a structural grid that also provides a high degree of flexibility for exhibition layouts. 84 STRUCTURE AS ARCHITECTURE ▲

5.7 Sainsbury Centre for Visual Arts, Norwich, England, Foster