TESTING

THE

OF B U I L D I N G Glass

STRENGTH

OF L A R G E S H E E T S

GLASS

Industry

(USA),

1964,

No.

2,

pp

80-81

Translated from Steklo i Keramika, Vol. 21, No. 10, pp. 42-48, October, 1964

In view of the rise in demand for large sheets of glass in building,the Libby-Owens-Ford Company has made special tests on the strength of this glass using vertical stands. The aim of the tests was to establish the required thickness of glass in certain wind-load conditions without calculating from theoretical formulas. In some tests the pressure on the glass was raised slowly, and in others fast. The sheets of glass were placed vertically in flat frames, the internal cavities of which were connected to a vacuum. Some sheets of glass were bent during the tests before destruction to the extent of 2-3 inches. The degree of bend was measured with a special instrument; the pressure was measured with a manometer over the whole test period. The results of the tests which were made on sheets measuring 1.8 x 1.8 m to 3.1 x 6.1 m with thicknesses of 1/4 to 1/2 inch (6.35-12.7 mm) showed that the strength is determined almost exclusively by the thiekness l while the ratio of the length of the sheets to the width scarcely affects the test results. The firm suggests, however, that additional tests on sheets of other sizes of thicknesses up to 1 inch (25.4 mm) are necessary to prove this statement. It is possible that the influence of the ratio of width to length exists for tests on sheets of glass in which it is above 4: 10. In the calculations based on new data on the strength of large sheets of glass, the coefficient of reserve of strength needed in practice is about 2.5; the possibility of breaking the glass in service conditions in very adverse conditions then does not exceed 1%. The strength factors evolved for glass i/4 inch thick (6.35 ram) agree with previous data but, as tests showed, the thickness of the sheets of glass of bigger sizes, should be greater than proposed.

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