Fire resistance mechanism of fireproof glass

The intrinsic mechanical properties of fireproof glass directly determine its bearing capacity when heated by fire. In theory, the compressive strength and flexural strength of glass are high, but because there are many fine cracks on the surface and edge of glass in the process of practical production and processing, the measured value in practice is much lower. In practical engineering use, for safety reasons, 30 ~ 50MPa is generally used as the planned tensile strength of general glass and tempered glass, That is, the glass strength is affected by the standard effect, especially the crack standard effect, and the crack expands rapidly under the effect of continuous external force. In practice, the bending strength of glass is greatly affected by the comprehensive factors of appearance state, edge processing quality and toughening stress; Furthermore, the durable stress effect of building glass in the process of use, the reaction between water and active medium in the environment and the glass surface will also cause fatigue damage. The abrasion of the glass surface and the abrasion of the glass surface by wind and sand will reduce the glass strength.

Preloading stress on the glass surface is an effective way to improve the bending strength. Therefore, the commonly used sodium calcium silicon monolithic fire-resistant glass adopts the planning of high external stress, and the external compressive stress is even much greater than the external stress about 90 MPa in the current tempered glass specification. The research results also show that the toughening stress is closely related to the test value of bending strength. Under the same glass raw materials and processing conditions, the bending strength and toughening stress of glass agree with a linear equation, that is, with the progress of toughening stress, the bending strength increases. There are many discrete data analysis for glass with a thickness of 6 ~ 15mm, The envelope formula of ultimate flexural strength can be obtained: σ -  zero point eight two six σ Tempering + 37.826

However, the breaking strength of glass is discrete, and the determination of flexural strength is closely related to the test conditions such as loading method, loading rate and duration. Many countries often use statistical analysis methods to infer the practical use strength of glass. Generally, many glass damage test results are statistically processed, and the connection rules between planned safety factor and glass failure are given. When glass is used as building safety glass, especially as fire-proof glass, the safety factor of glass strength under the influencing factors of comprehensive load must be considered. In addition to the discrete safety factor K1 of glass strength and wood body, the safety factor K2 under the effects of various environmental loads under fire heating shall also be considered, In the technical code for glass curtain wall engineering, it is agreed that the failure probability of glass curtain wall is 0.1%, and its strength discrete safety factor K1 is 2.5. During the assessment of heating failure of fireproof glass in fire environment, the change of air pressure after fire, the randomness of burning hot spots and other factors.

In conclusion, it can be seen that there have been relatively mature research and cognitive conclusions on the fracture mechanical properties of glass. The composition and structure processing of glass data determines its inherent mechanical properties and mechanical parameters. Therefore, it is confirmed that the fire-resistant critical cracking stress borne by monolithic fire-resistant glass of different types and thicknesses. On the basis of soda lime silica glass, improve the external compressive stress of the glass by means of physical and chemical strengthening, improve the external surface and marginal micro cracks of the glass through precision processing, and improve its critical damage strength under certain standard scale and fire-resistant conditions, It is feasible.