Apple Computer Inc.’s new store in SoHo, New York (completion: July 2002) uses laminated glass with DuPont™ SentryGlas® Plus structural interlayer for a glass staircase, bridge and mezzanine ensemble that look levitating, weightless, gravity-defying – and simply amazing, architecturally.
While the outstanding structural strength and clarity of DuPont SentryGlas® Plus structural interlayer is used for the stunning, ‘free-floating’ glass staircase, bridge and landing, laminated glass with Butacite® PVB is also used in Apple’s SoHo store for a skylight, vertical walls and handrails that complete the new-age glass and steel look of the store.

Architectural and structural engineering experts have said that the staircase, bridge and mezzanine represent a quantum leap forward in using the strength of glass for a self-supporting structure while demonstrating the aesthetic lightness of glass with a new minimalism.

The splendor of the stair structure is emphasized by the highly-polished, exposed edges of the stair treads which, although they contain a 1.5 mm interlayer of SentryGlas® Plus for phenomenal structural strength, give the appearance of one solid piece of transparent glass per stair thanks to the dedicated craftsmanship of laminator Depp Glass of Long Island, New York.

The staircase appears to be free-floating but in reality is held to the vertical, laminated glass sidewalls (supplied by Bischoff of Germany) on each side of it by tiny titanium inserts. This is the first time worldwide that glass has been laminated to metal on a large-scale design. The glass-titantium-glass construction around the inserts was made possible by the excellent flow and processing properties of SentryGlas® Plus. The structural flows far better around the metal inserts than PVB would have done.

The outstanding stiffness of DuPont’s structural interlayer means that the stair treads could be made 50 percent thinner than if PVB had been used and twenty times stronger, according to the rigorous load-bearing testing that took place in Germany.

Bystronic, a leading equipment supplier to the worldwide architectural and automotive glass industry, wanted to showcase state-of-the-art applications for architectural glass when it planned its new North American headquarters in Hauppauge (NY) USA. The building features an ethereal looking yet load-bearing, self-supporting staircase of laminated glass with SentryGlas® Plus structural interlayer in the entrance hall and a laminated glass curtainwall incorporating Butacite® PVB interlayer.

Architect Hans Rudolf Kaeser of Interior Concepts, New York City, said: “Bystronic wanted the entrance hall to be as light and airy as possible; we achieved this by designing glass stairs, mezzanine floor, handrails and a large skylight all in a low-iron, bluish- coloured laminated safety glass that matches Bystronic’s corporate colour. The stairs were finished with exposed edges using Bystronic waterjet machinery; even the metal stringers for the stairs were made with the company’s laser cutting machines. The use of DuPont’s structural interlayer added stiffness to the stairs and meant that the tread could be thinner than usual. This added to the visual effect of lightness.”

Laminator Wesley Depp said: “Normally, the handrails would have needed to be made of laminated heat tempered glass for extra strength. The use of SentryGlas® Plus, which provides five times the tensile strength and 100 times the rigidity of PVB, obviated the need for tempering. In addition, using a triple interlayer of the structural on the stairs meant that we could make the 6 foot wide stairs self-supporting with a tread that is just 2 inches thick.”

Bystronic president Rick Troesch said: “We are very pleased; the stairway is absolutely beautiful and has generated a lot of interest from visiting customers who always ask how it was made. Our aim is to show that laminated glass is an unbelievable material for interior concepts as well as exterior applications.”

Gateway Docklands Trunk Infrastructure Bridge (completed: 2000)

The Gateway structure is a major urban design element positioned between the central business district of Melbourne on a bridge that connects the City to the new development of Melbourne Docklands. The main features of the Gateway structure are two steel frame ‘fins’ that are clad in red laminated glass. These fins span a monumental stair and a series of stainless steel sculptures that form a ramped maze. The city of Melbourne is laid out on an orthogonal grid and is serviced by a tramway network. The glass fins are located on axis with Bourke Street and its associated tramlines which link the Gateway directly to the Parliament Building at the opposite end of the City. The form of this structure therefore relates directly to its urban context while also being seen as an iconographic architectural object operating as a sculpture within the built fabric of the city.

By working in this abstract architectural sense the structure allows direct interaction with people moving not only past it as viewers but also through the structure experiencing in it a totally ethereal way. The combined effect for the public is a place of geographic significance that is part of a broader, operating city fabric and network as well as a place of pleasure. The gateway is approximately 28 m long by 30 m wide.

The Gateway structure consists of the 180 mm thick concrete slab, one layer of waterproof membrane and 100 mm thick light grey granolithic concrete topping screed (broom finish).

Continuous handrails at 900 mm high are of polished stainless steel and are supported on 100 x 100 mm polished stainless steel staunchions at 1,500 mm nominal centres. The continuous balustrade extends 1,200 above the deck with clear laminated glass panes in between staunchions. Polished stainless steel channels are fixed to each staunchion supporting the glass infill panels top and bottom.

Project architect David Dennis of Wood/Marsh Pty of Melbourne said: “Laminated glass enabled us to meet our design goals because we used it to clad the steel structure of the Gateway element of the bridge using ‘red’ laminated glass (an inner layer of toughened glass, a middle layer of red lead light glass and an outer layer of clear roughcast glass with a total thickness of 17.6 mm). Toughened laminated glass was used primarily to protect the colour from depreciating over time and to allow for stainless steel fixings through the glass into the steel structure.”

Gerard McCluskey of laminator DMS Glass of Melbourne confirmed: “The glass construction is made up of 5 mm clear tempered internal, 0.76 mm clear Butacite® PVB,
4 mm Spectrum Red tempered, 0.76 mm clear Butacite® PVB and 5 mm roughcast tempered glass on the external side. The glass panels are 2,400 x 600 mm. They are affixed by four point fixing with rotational bolt fittings.”