New Developments in Predicting the Strength of Glass after 20 or more Years of Use in Buildings

Ignatius Calderone

It is well known that the strength of the glass varies with load duration. Therefore existing models for predicting the behaviour of glass subjected to wind pressure involve simplifications using an assumed short duration for the design wind pressure and using the corresponding glass strength for this load duration. However, the wind pressures, which load the glass, are fluctuating during all windstorms and tests have shown that breakage frequently occurs at a "gust" pressure lower than was previously resisted during the test. Therefore, the cumulative effect needs to be computed over the entire load history.

This paper presents a new proposed method of determining the effective strength of glass that has previously been subjected (over many years) to the fluctuating wind loads. The method includes the effect of the non-linear relationship between applied pressure and stress for the application of Brown's Integral. Actual wind pressures versus time data were integrated together with the actual glass breakage data of 20-year-old glass taken from a building. Comparing the results with the equivalent 3-second breakage pressure for new glass breakage data indicated that the method could be used to predict the strength of even older glass.

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The Authors

Dr. Ignatius Calderone Director Calderone and Associates Pty Ltd Dr Ignatius Calderone is a Director of Calderone and Associates Pty Ltd, Consulting Engineers based in Melbourne Australia. His expertise is in the areas of building façade design particularly with re... Read more