Glazing Design By ASTM E 1300
Maximum Surface Stress and Probability of Breakage
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Overview
Abstract
ASTM E 1300 “Standard Practice for Determining Load Resistance of Glass in Buildings” defines the load resistance of a glass construction as being the load at which upon its first occurrence the probability of breakage is nominally 0.008 (8 lites per 1000). The authors have encountered many design calculations that cite values of maximum stress associated with probabilities of breakage of 8 lites per 1000 or 1 lite per 1000. The authors note that Appendix X6 in ASTM E 1300 offers “conservative” values of maximum surface stress allegedly associated with a probability of breakage of 8 lites per 1000, presumably at the first occurrence of the stress for all glass types. Appendix X6 states that the stress values are to be used for shapes other than rectangular. Appendix X6 offers no guidance for maximum surface stress values associated with a probability of breakage of 1 lite per 1000. The authors contend that many designers use maximum allowable surface stress values to design rectangular glass even though a single value of maximum principal stress does not correspond to a probability of breakage as defined in ASTM E 1300. The authors investigate this contention as well as the question concerning whether the values given in Appendix X6 are indeed conservative.
Authors
H. Scott Norville, P.E., Ph.D., F. FTI, F. ASCE, F. ASTM
Professor
Texas Tech University
scott.norville@ttu.edu
Stephen M. Morse, P.E., Ph.D., A.M, ASTM
Assistant Professor of Civil and Environmental Engineering
Michigan Tech University
stephen.m.morse@mtu.edu
James G. Soules, P.E., S.E., P.Eng., SECB, F. SEI, F. ASCE
Graduate Student, Department of Civil, Environmental, and Construction Engineering
Texas Tech University
greg.soules@ttu.edu
Keywords
Background
Glass is a brittle material. When lateral load induces tensile stresses in an annealed glass lite large enough to induce fracture, the location of the fracture origin rarely, if ever
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Maximum Surface Stress and Probability of Breakage
A flat glass lite is nothing more than a flat plate. The maximum stress in a flat plate subjected to a uniform lateral load varies with several factors. These are
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Discussion
Glass is a brittle material. Microscopic flaws (Griffith, 1920) exist on the surface of glass, even pristine, freshly manufactured glass. The existence of these flaws ensures that glass rarely, if
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Conclusion and Future Work
In terms of the definition of probability of breakage in ASTM E1300, the authors have demonstrated that any single value of maximum allowable surface stress for annealed glass results in
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Rights and Permissions
ASTM (1989): Standard practice for determining the minimum thickness of annealed glass required to resist a specific load. ASTM E 1300-89, West Conshohocken, PA.
ASTM (2000): Standard practice for determining load resistance of glass in buildings. ASTM E 1300-00, West Conshohocken, PA.
ASTM (2016): Standard practice for determining load resistance of glass in buildings. ASTM E 1300-16aε1, West Conshohocken, PA.
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