written by: John Moehring
• edited by: Lamar Stonecypher
• updated: 1/12/2010
Glass is one of the most desirable building materials in use today. However, wanting to use it is the easy part. Actually installing and incorporating glass into construction projects is a little more complex.
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Traditional Form And Function
Sparkling, transparent, delicate, bullet proof, brittle, insulating, illustrative, recyclable. All are descriptions of glass as one of the most interesting and useful building materials in use today, with more applications and installation techniques constantly in development. Consequently the methods used to install these products in construction projects varies with the exact form and type of glass being used. Probably the most familiar forms are fiberglass products, used for insulation and translucent panels, transparent blocks, and window glass. Glass insulation is typically installed in prefabricated bats or as loose particles blown into cavities and ceilings using specialized equipment. Translucent fiberglass panels are installed using support framing where light but not visibility is desired. The familiar glass block is usually installed as a “brick and mortar" system. And of course transparent glass windows are usually glazed into framing and installed as a prefabricated building element.
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More advanced glass construction products, however, require more advanced installation methods. Prefabricated structural fiberglass panels use pre-molded interlocks and adhesives to achieve engineering performance approaching that of traditional steel and wood elements. These can also incorporate foam insulation as a composite element for a complete building system, especially useful for structures requiring RF transparency, high corrosion and/or weathering resistance, and lightweight building applications. Glass in its solid, float manufactured state is where it really shines in construction. Technological advances in strengthening and improving resistance to shattering have resulted in many more applications than just windows. Some of these techniques such as annealing, tempering, and laminating produce glasses with structural properties similar to that of aluminum alloys, without the ductile and malleable properties, of course. Consequently installation methods have improved as well. Frameless glazing utilizes specialized adhesives to hold glass panels in place against structural supports without exposed framework. This lends a smooth, continuous, uninterrupted effect to building exteriors, floors, and facades. Point supported glazing holds the glass in place at discreet locations as opposed to the perimeter edges, and has been used in building facades to dramatic effect. This requires engineered framing, mounting pads, and posts modeled to reduce shock and excessive stress distributions throughout the glass element.
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The Transparent Future
In some of the most extreme forms of recent construction techniques, glass has been used as supporting columns and beams. Glass not only looks dramatic when substituted for these traditional metal or wood elements, but it also has an attractive compressive strength to weight ratio. Like concrete, glass achieves its greatest strength when loaded in compression; it tends to fail catastrophically in tension. And again like concrete, post-tensioning techniques are being used to ensure these glass structural elements bear only compressive loads. Laminated vertical glass columns have also been installed with some success, as these elements are typically loaded compressively as constructed. In all of these advanced techniques, however, the basic uncertainty of brittle glass failure has led to no small amount of debate on their use in structural applications. Accordingly there are as yet no codified structural construction guides for use of these elements.
The success of any attempted construction utilizing non-traditional materials and techniques will of course depend on comprehensive testing and evaluation of the system in question, and structural glass applications will probably not be an exception for some time to come. However improved materials and construction techniques may one day allow us to peer through an entire structure made of glass…brightly!