The strength and testing of window glass

Abstract

This paper presents some of the background to the new Canadian General Standards Board (CGSB) standard on the structural design of glass for buildings. It also describes strength testing of window glass at the Institute for Research in Construction of the National Research Council of Canada using three quite different testing machines. (i) A dynamic glass testing rig, with a large 2.35 m diameter piston, applies dynamic air pressures to large panes of glass in the vertical position. Results of 107 tests to failure show the considerable effect of loading rate on strength. (ii) A loading table applies linearly increasing pressures to panes of glass in the horizontal position. Results from 47 fifteen-year-old windows confirm assumptions about the deterioration of strength with in-service use in the new CGSB standard on the structural design of glass for buildings. (iii) A ring-on-ring tester applies linearly increasing loads to small 180 × 180 mm samples; the equivalent of coupon tests for steel or cylinder tests for concrete. The resulting uniform tensile stress fields avoid failures starting at the edges of the samples. Some results are given. Testing provides the basis for the structural design of glass cladding as it does for other structural materials. A great deal more testing of window glass is required. Key words: glass strength, window strength, testing, strength deterioration, rate effect, dynamic loading.