The Breakage Behavior Of Float Glass Under The Combined Effect Of Wind Loading And Thermal Loading

More and more high-rise buildings are constructed in modern cities with the development of the society. Because of its good daylighting performance, energy saving, transparency, glass is increasingly more widely used in construction. Even through the glass has a lot of incomparable advantages, it still haunts architects because it is the weakest part in architecture. Especially glass breaking in compartment fires is an important practical problem since a window acts as a wall before breaking and a vent after breaking, The glass breakage behavior may significantly affected by the compartment fire and environmental wind in high rise building.In this work, the frame supported glass panes, with a dimension of 600 × 600 × 6 mm3, are employed to study the glass breakage behavior. The glass breaking time, crack initiation and propagation are obtained, and the maximum temperature difference on the glass is calculated. With the increase of wind speed, the temperature difference on the glass panel gradually decreased when crack initiated. The time to first crack for glass facade also gradually decrease with wind velocity increasing. Compared with the glass breakage under thermal radiation only, the combination of environmental wind accelerates collapse of the glass. The results provide useful knowledge for the fire protection of glass facades.In this study, a total of 27 experiments were designed,15 of which glasses are mounted by frame-supporting. In the frame-supporting glass installation, before glass breaking, thermal convection was the dominant heat transfer types, which account for 75% of heat flux. And heat convection between air inside combined cabinet and glass is 3.12 kW/m2-3.91 kW/m2, far more than that between air outside space and glass surface (less than 1.1 kW/m2). When there were isolated islands presenting, the larger wind speed was, the glass was more prone to falling out. But whether isolated islands formed on the glass facade had no obvious relationship with wind speed in this study. In point-supporting glass installation, the position of crack on the glass tends to occur at the aperture for supporting the glass. However, wind loading can lead that crack initiated on the edge of glass. Wind load change stress distribution inside the glass, so that the crack are more complex in the glass surface.Glass with point-supported installation exhibit better fire safety than frame-support installation under the same experimental conditions. For example, under the effect of wind load, it take 829s for the glass with point-supported installation to first break, but it takes 629s for the glass with frame-supported installation.Wind had a significantly cooling effect on the heated glass ambient surface either installation. The larger wind velocity was, the more significant the cooling effect. The wind load significantly affects the response characteristics of glass breakage:When glass facade is under the combined effect of wind loading and thermal loading, the wind load can accelerate the glass fracture.The temperature difference between glass surfaces when crack initiated are 63.5/ 78℃ when the wind speed is 0 m/s. With the wind speed increasing to 8m/s, it change to 43.4/62℃. Therefore, breakage behavior of glass is the result of joined action of wind load and thermal load. And effects of wind and thermal load is additive. The greater compressive stress induced by wind loading is when crack initiated on the glass, the higher thermal stress induced by radiation.