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Fire Induced Thermal Fields in Window Glass II - Experiments.


pdf icon Fire Induced Thermal Fields in Window Glass II - Experiments. (742 K)
Joshi, A. A.; Pagni, P. J.

Fire Safety Journal, Vol. 22, No. 1, 45-65, 1994.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Keywords:

glass; windows; computer models; fire models; mathematical models; radiation; thermal stresses; vents; equations; temperature profiles; heat flux

Abstract:

The authors' previously presented model determines the time to breakage of window glass exposed to a compartment fire. The physical and mechanical properties of glass and the history of the compartment fire are required. Among the mechanical properties of glass, the breaking stress is the least well known. Here, experiments on 59 plate glass samples using the four-point flexure method are described to determine the breaking stress distribution. This distribution is by a three-parameter cumulative Weibull function with parameters. A breaking stress of 40 M Pa (5800 psi) was determined to be a reasonable value to use in breaking calculations for ordinary window glass. The breaking patterns of the test specimens suggest that fractures initiate at edge imperfections rather than at surface flaws. Some experiments to estimate the heat transfer coefficient inside the compartment and the emissivity of the hot layer are also described and values are suggested for use in the model.