Study of point-supported glass breakage behavior with varying point-covered areas under thermal loading

Point-supported glazing assemblies are widely used in modern buildings for aesthetic elegance, as well as for economic reasons. However, the formation of vents caused by glass breakage could aggravate ventilation controlled compartment fires. The point-covered area generally varies and may constitute potential fire hazards. Accordingly, it is necessary to investigate the fire performance and breakage mechanisms in various point covered areas. In this study, a total of 12 tests, including three various point-covered area glazing, were heated by a 200 x 200 mm(2) pool fire. The breakage time, glass surface and air temperatures, incident heat flux, and crack initiation and final fall out ratio were obtained. The critical conditions for the three aforementioned various point-covered area glazing were determined. The reference breakage times, t(r), which were calculated by assigning a failure probability of 0.1 to the two-parameter Weibull distribution were 119, 140, and 166 s. It was established that a relatively small point-covered area glazing can survive longer; the smaller the point-covered area was, the larger the final fallout ratio of glazing assemblies will be. Numerical simulations were performed to investigate the stress distribution on the glass pane, with breakage times well predicted. Accordingly, these results have implications on the fire resistance design for point-supported glazing assemblies.