RELIABILITY-ANALYSIS OF WINDOW GLASS FAILURE PRESSURE DATA

Results are presented for reliability analyses of 14 samples of new, full-size, simply supported monolithic glass plates and PVB laminated glass units that were tested to destruction. In all, the data base includes 318 specimens that were tested to failure under uniform lateral pressure and under controlled laboratory experimental conditions. Six probability distributions are employed in the reliability analyses. Results indicate that, from a structural design perspective, the 2-parameter Weibull distribution consistently produces conservative (but not unduly low) estimates of sixty-second constant failure pressures (P60) at target reliabilities of 0.992 and 0.999. Normal and 3-parameter Weibull distributions appear to be usable for reliability analyses of architectural glass failure pressures, but they are not as consistent in producing reasonable lower bounds of glass failure pressures as is the 2-parameter Weibull distribution. Lognormal distributions (2- and 3-parameter) and the Gumbel extreme value distribution do not always produce meaningful results. At room temperature, the reliability analysis results do not support the presence of a 0.75 strength factor in building codes for specifying the lateral pressure resistance of PVB laminated glass units relative to that of monolithic glass plates. In fact, reliability analysis results herein indicate comparable nominal resistances to lateral pressure for monolithic glass plates and PVB laminated glass units at room temperature. At elevated temperatures, the "relative strength issue" becomes more complex; compared to test results at room temperature, a strength reduction clearly occurs in PVB laminated glass units tested at 170-degrees-F (77-degrees-C), but little strength reduction appears to occur at 120-degrees-F (49-degrees-C).