See-through and safe: Innovations in fire-rated glazing [AIA course]

Failure modes of glass systems under the extreme heat and pressures of building fires are reasonably well known, yet still hard to predict. In a recent fire simulation on a three-story structure built in India and studied by Underwriters Laboratories, the façade system of toughened glass and aluminum composite panels performed better than expected. That is, the glass did: As the aluminum cladding’s window frames deformed and expanded under heat, “the glass panels did not break due to fire but fell to the ground in intact form,” wrote the captivated research team.

In many cases, however, glass panels and structural glazings subjected to fire do fail. “Compared to other traditional materials for buildings, standard glass is typically characterized by brittle behavior and limited tensile resistance,” according to Chiara Bedon, PhD, a professor at Italy’s University of Trieste, who has studied structural glass systems exposed to fire. “The intrinsic properties of glass—together with typically limited thickness-to-size ratios for glazing elements, the mutual interaction of glass components with adjacent constructional elements as a part of full assemblies, and the combination of mechanical and thermal phenomena—make glass structures highly vulnerable,” says Bedon.

Many of those phenomena are considered in building codes, life-safety codes, and material performance standards. Products such as wire glass—including glazings with the unique look of cast and polished wire, as well as laminated and multi-laminated glazings and glass block—are engineered to block smoke and flames and to withstand high pressures and certain effects of hose streams, all of which can occur during fire events. Many types of glazings can withstand thermal shock, another key phenomenon. Glass that is fire-rated may als

LEARNING OBJECTIVES
After reading this article, you should be able to:
• Describe the safety and security benefits of fire-rated glazing and window systems.
• Discuss the opportunities and limitations of fire-rated glazing applications.
• Compare the competing priorities, codes, and standards related to the specification and detailing of transparent enclosures.
• List and contrast the systems and products used for fire-rate glass assemblies. 

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