Open issues in the calibration of partial safety factors for heat-treated glass

Partial safety factors for actions and resistances are used in the semi-probabilistic approach (level I method) for structural calculations. The partial factors associated with the surface prestress in heat-strengthened and thermally toughened glass proposed by standards come from practical experience and consolidated practice. Here, we attempt at a calibration by comparison with full-probabilistic (level III) methods in paradigmatic examples under environmental actions (wind and snow). The theoretically-derived factors are in general very low, as a consequence of the statistical interference between the material-strength and surface-prestress. This finding, albeit far from being exhaustive, highlights the great potentialities of heat-treated glass, that appear to be underestimated by current standards.