Engineering in Glass
Pilkington's initial attempts to eliminate frames and allow architects to visualise continuous weatherproof walls of glass came early in the life of float glass. The 'Pilkington Wall' used patch fittings to secure glass panels at their corners, glass mullions for lateral stiffness, and transparent silicone compounds to seal panels into a continuous expanse of glass.
From the early 1970s Pilkington Architectural researchers began working with Sir Norman Foster & Partners, the London architects, to develop new technology. In 1982 the precision engineering of the Pilkington Planar™ system replaced patch fittings with stainless steel bolts passing through countersunk holes to secure glass panels up to 4.2 by 2 metres. Up to eight bolts will secure a panel weighing as much as 315 kg to a steel frame, masonry or glass mullion system.
Glass for Pilkington Planar™ is fully toughened and heat-soaked float, the thickness for single or double glazed panels being determined by the maximum loading conditions to be encountered in service. Laminated glass is also used. Fixture holes are a critical feature, the subject of constant investigation and testing because of the stresses induced locally by wind or snow loading or by the weight of the facade. The strength and integrity of curtain walling in situations of extreme loading such as high winds and seismic disturbance depend crucially on the behaviour of properly designated fastenings.
Stresses induced round the holes in the high-performance glazing are studied, either directly with arrays of strain gauges or in computer simulations using finite element analyses. The Pilkington Planar™ system is also supported by an engineering design service that can even encompass specific earthquake or hurricane conditions.
The engineering design permits suspended assemblies as high as 18 metres. Glass can be curved, clear, body-tinted or coated, low-e or reflecting. More recent achievements of Pilkington Architectural's ingenuity include Pilkington Planarclad™, which permits windows to be opened in a building whose walls and roof may be totally clad in glass.