Glass masts.

Two restaurant facades in a bulky new building in London are, in contrast, essays in structural transparency, using ordinary industrialised products in an innovative way.

The sparkling column of light invented by Bere Associates when designing supports for the glass wall and roof of a small conservatory in Clapham (AR January 1996), has been made the supporting component of a structural glass system.

The system was devised by the practice, in association with glazing specialists Marcus Summers, and structural engineers Campion & Partners, when designing identical facades for two Pizza Express restaurants. Cantos Architects, the overall project architects, invited Bere Associates to detail the glass facades of the restaurants built into the concourse of Terry Farrell's elephantine Alban Gate development at London Wall.

The column's prototype consisted of a 20mm diameter high-tensile stainless-steel rod, fixed top and bottom, and threaded through glass isolators. These objects are used in the electricity industry for isolating high-voltage cables on electric pylons and, resembling a large glittering cotton reel, are shaped by a special glass-making process. Each isolator can withstand a load of 18 tonnes; so that when stacked up the rod and interspersed with cast metal or aluminium brackets, they form an immensely strong structural column with the brackets giving lateral support. Dichroic luminaires fixed to 6mm stainless lighting rods, slotted through holes in the brackets, make them seem even more insubstantial, the appearance of glittering fragility belying their real strength.

The two restaurants in Alban Gate face each other across a corridor. On plan, their facades, which are 19m long, converge on the centre of a small circus and turning the corner terminate in a slender frameless revolving door set along the curve of the circle. In both cases, the columns had to support a glass wall measuring 120 sq m and the assembly had to accommodate movement up to [+ or -]20mm within the 20-storey steel-framed building.

Bere's elegant structure is composed of sheets of glass up to 3mx2m, suspended from concealed steelwork designed to respond to building movement, and supported by double-braced columns engineered to the scale of the building and rising 6m high. Lateral stability is ensured by 950mm-wide aluminium arms extending from the columns to the centres of the larger glass panels, and providing enough stability for intermediate ones, up to 3mx1.3m.

Glass panels were attached to the arms by two adjustable knuckle joints, their design based on Marcus Summers' Admiral 90 structural bolt. Star-shaped bronze washers secure the glass to each arm, eliminating the need for countersunk holes. Instead of being an integral part of the column, lighting in the form of dichroic uplighters is embedded in the floor.

Columns can be delivered in pieces, shipped in packing cases by van. Once assembled, the column can be lifted into a steel mast-footing, turned and locked into position. The revolving door at the entrance of each restaurant is equally insubstantial looking, frameless and transparent, with the most minimal fittings.