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"Crystal Palace" of laminated glass for Leipzig Trade Fair

Leipzig Trade Fair's laminated glass hall: an interior view

The city of Leipzig, in former Eastern Germany, has been hosting trade fairs since the Middle Ages. However, the new Leipzig Trade Fair building, designed by architects von Gerkan, Marg and Partner (GMP) of Hamburg and completed in 1996 at a cost of DM 1.3 billion, provides the most striking new symbol yet of the city's post-Communist renewal as a business center.

The most spectacular aspect to the Leipzig Trade Fair is undoubtedly its laminated glass hall, designed by Ian Ritchie Architects of London. The glass hall represents a late 20^th century equivalent of London's Crystal Palace – a totally glazed enclosure using laminated glass in all 28,000m² of its overhead glazing. It is the principal building through which all visitors to the Trade Fair enter and provides a surface area of 242m x 79m for reception, information and meetings. It is linked directly to the Trade Fair's exhibition halls through a series of tubular, laminated glass bridges.

TRANSPARENCY AND SAFETY

Simon Conolly, Project Architect with Ian Ritchie Architects, explained: "Transparency and safety were our two primary design objectives for the glass hall. For maximum transparency, we wanted to minimize silhouette without compromising safety. Toughened laminated glass was the only viable safety choice for such extensive overhead glazing; to improve transparency still further, our goal was to support the laminated glass with unobtrusive point fixings rather than conventional framing."

STRUCTURALLY STRONG

Mr. Connolly continued: "The project represented an unusual challenge to local building authorities in view of the quantity of overhead glazing, suspended 28 meters above visitors' heads and the weight of each glass panel – around 200 kg! A number of tests were carried out earlier on which demonstrated the high impact resistance of the toughened laminated glass, yet the design team still gave early consideration to secondary methods of retaining glass in the unlikely event of glass breakage."

The laminated glass construction is stabilized and supported by primary trusses.

"Following extensive testing and risk analysis, we were able to demonstrate the feasibility of retaining the heavy panels for various periods of time, according to the detailing of the glass fixings, in relation to the strength of the 1.5mm thick, PVB interlayer. The suspended laminated glass fixing system was accepted by the authorities. We were thus able to achieve our design goal of having no more than 15% of the total overhead glazing area covered by structure in any radial view." The glass fixings themselves also contain a spherical bearing in the plane of the glass which effectively eliminates the transfer of local bending stresses from the support structure into the glass.

The overall length of the overhead roofing (244m) would conventionally require movement joints to accommodate temperature changes, wind and snow loads and these were initially proposed by the structural engineers for the glass hall, Ove Arup and Partners of Australia. However, as Simon Conolly explained: "We were able to use the elasticity and low modulus of all the glass joints to distribute the load throughout the entire length of the glazed envelope. Because the grid shell is supported on dense neoprene blocks which undergo shear as the structure expands and contracts, there is some restraint to these movements and the net effects are well within the capabilities of the joints to absorb movement."

"FRAMELESS" LAMINATED GLASS PANELS

The 'frameless' laminated glass panels of the overhead glazing are 3.105 x 1.525m in size, made in two layers of 8mm and 8+10mm toughened glass laminated with a 1.5mm PVB interlayer. This laminated glass construction is stabilized and supported by primary trusses at 25m centers with outriggers stabilizing the grid between these.

SOLAR CONTROL

The internal environment is tempered in summer by trees internally and by white reflective fritting on the south face of the laminated glass which can be supplemented by evaporative cooling of the glass with irrigation along the crown, using stored-de-ionized rainwater. In addition, computer-controlled laminated glass louvres at the high point of the roof and at the base are motor-driven by torque tubes to open for natural ventilation.

A FOCUS FOR RENEWAL

Today, the Leipzig Trade Fair is viewed as a benchmark in contemporary trade fair design – not only in former Eastern Europe but worldwide.