Thermal performance of exposed framing glass façades in fire

Façades made of glass are viewed as one of the weakest parts of a building which can easily break in case of fire and change the compartment fire dynamic by creating a new opening for air to enter. A total of six clear glass panes were placed 750 and 500 mm away from a 500 × 500 mm² n-heptane pool fire to investigate the breakage behavior of fully exposed framing glass façades. Both float and toughened glass panes with a dimension of 600 × 600 × 6 mm³ were tested. The results presented include the time to breakage occurrence, heat release rates, incident heat flux, central gas temperatures and glass surface temperatures. The crack initiation and propagation as well as the loss of integrity of the glazing assembly were also recorded. The experimental results established that the critical temperature difference and heat flux for float glass were approximately 90 °C and 14 kW/m². All their cracks were initiated from the edge of glass pane and intersected rapidly, forming some islands, but the fraction of fallout was considerably small because of the protection of frame. However, the toughened glass did not break even though the center temperature reached a high value of 413 °C. Using finite element method, breakage mechanism of float glass pane is demonstrated, and the numerical predictions are further compared with the experimental measurements.