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of hairy cracks on glass surfaces in the course of resisting wind loads and also when subjected to natural or man-made scratches.

The equivalent 60-s pressure of the testing results and output by NAShell [13] are tabulated in Table 29.2. The average ratio of failure load to the predicted breaking load by NAShell is 2.51. This ratio is considered to be in a reasonable range because the failure stress used in NAShell has included the probability of failure of 8/1000. Not a single sample has a failure load lowered than the predicted load, indicating the reliability of the suggested method in the design of in-service glass panels.

The standard deviation, however, for the failure loads is quite large and is equal to 0.62. This demonstrates the variability of glass strength in practice and also that the nature and behavior of glass strength can only be represented as a probability of failure.

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