Fire Safety Science Digital Archive

To develop a simple model to predict the glass cracking and/or breaking, radiant heating tests were carried out on float glass and wired glass. By changing the imposed heat flux and lateral restraint of the glass, 50 experiments were carried out to measure the time to initial crack and fallout. Temperatures were measured at the center of glass pane and edge, while the strain was measured at the edge. From the experimental data, the critical heat flux was determined under which no glass cracking takes place. By using the measured temperature and stress, the ultimate tensile stress of the glass edge was calculated. The obtained values were lower than the literature values for plain glass surface where no effect of micro defects at the cutting edge is taken into account. By analyzing the post crack behavior, it was pointed out that the fallout area mainly depends on imposed heat flux and slightly on restraint. Under intense heating (more than 9kw/m²), large piece of glass tends to fall out, however under moderate heating, glass just cracks but did not fall out. Therefore it was pointed out that the application of the thermal stress model for glass breaking is limited to intensely heated scenarios. A simple prediction formula was derived for such scenarios.