Special stairs

Welded plate formed into hollow tubular members gives the greatest freedom in design. The possibilities with cantilevers are more rewarding than standard spirals where bolted connections may loosen. The example at Arnhem City Hall in Figure 7.5a has a flair and verve that equals the finest work by Victor Horta. The imaginative use of curved rectangular tube in handrailing recreates the sinuous

Rod balustrade supporting treads

Rod balustrade supporting treads

Cross tubes or rods carry each tread

Flats

Figure 7.3a Folded steel stairs: Providing builders access as skeletal frame is erected and then used permanently

Cross tubes or rods carry each tread

Flats

Figure 7.3b Folded steel stairs: Profiles for folded sheet stairs or treads

Figure 73c Folded steel stairs: Finishes to folded plate

Figure 7.3d Folded steel stairs: Individual tread detailing

Figure 73c Folded steel stairs: Finishes to folded plate

Figure 7.3d Folded steel stairs: Individual tread detailing qualities associated with metals and is employed to maximum effect where the rails terminate as newels.

Public stairs within this idiom need to have a safe balustrade, such as I. M. Pei's detail for the new entry below the Grand Louvre pyramid (given in Case Study 12.4). Curved sheets of toughened glass or acrylic (if permitted by fire codes)

have inherent strength and sufficient rigidity to perform as a balustrade if effectively clamped to the handrail and string (Figures 7.5 b and 7.5c). The engineering to the Foster stairs and bridge at the Sainsbury Arts Centre, Norwich, had to be tested with the built example on site to satisfy the local authority in 1977, though the construction principles are

Connection bolt

Figure 7.4a Spiral stairs: Typical assembly of centre column with cantilever treads and landings (with kind permission of Weland Grating (UK) Ltd)

now fully accepted and marketed as standard balustrades.1

Glass and metal can also be combined in treads and risers. Le Corbusier used 'Nevada' lenscrete to diffuse natural lighting to the stairwell in the Maison Clarté apartment building in Geneva (Figure 7.5d). The artificial lighting was arranged through a suspended conduit in the well

Figure 7.4b Spiral stairs: Lattice frame to balustrading: detail of trussed balustrade to curving stairs at Legends night club, London, 1987, Architect: Eva Jiricna, Engineers: Dewhurst MacFarlane

serviced by naked light bulbs - replacement of the bulbs was effected by sliding the light fixture along its overhead track at the top floor and then walking down to each landing to change the bulb. The slender quality of steel profiles can reduce the impact of pre-cast concrete or timber which may be selected for treads. Ladder trusses with horizontal steel trellises will carry 'plank' treads, the upper line of the trusses forming a handrail. This motif was used frequently by Marcel Breuer for external stairs to reduce the impact or shadow from the construction interfering with the fenestra-tion (Figure 7.5e).

Connection bolt

Figure 7.4c Spiral stairs: Designer spirals beyond the limit of common sense
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