Therefore, jgjl02 specification (Revised Version) stipulates that the gap between the glass edge of open frame curtain wall and the bottom of frame groove shall meet the requirements of the following formula: 2 (c1-1.5) ×[ 1+(L1／L2) ×( C2-1.5)／(C1-l.5)]≥[ Δ u] [Δ u] It shall be determined according to 3 times of the elastic interlayer displacement limit of the main structure
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Due to the uneven temperature of different parts of the glass surface, the temperature in the central exposure area is higher, while the temperature in the cover plate or internal corner area is lower
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Hot dip treatment of tempered glass
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3
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If there is a very small solid particle between the edge of the glass and the bottom plate of the inlay groove (even if the diameter of the particle is less than LMM), it may burst due to the extrusion of the glass during expansion and contraction
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However, there are few projects adopting this method in China, because the current glass manufacturers can not meet the requirements of the process proposed by the project
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If the strength meets the design requirements, semi tempered glass shall be used to completely avoid glass self explosion from the aspect of glass properties
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Reasonable glass division
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Material factors in the process of reducing the metal iron content of glass raw materials, ultra white glass substrate will greatly reduce the content of impurities such as nickel and sulfur, and greatly reduce the self explosion rate of tempered glass from the raw material end
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4
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Hard materials shall not be set around the glass for filling, and the expansion allowance of the glass notch shall not be changed without permission during construction
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At this time, the curtain wall frame will change from rectangle to diamond
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During tempering, when the glass is heated, a large number of nickel sulfide crystals are formed in the glass
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Too high ambient temperature may promote self explosion
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In addition, the larger the plate size, it is vulnerable to the superposition effect of other loads, so as to increase the self explosion rate
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Design rationality: in the structural design of curtain wall nodes, the deformation or displacement of the glass caused by the superposition of various external load stresses shall be considered at the same time, so as to provide sufficient displacement space and disturbance deformation allowance for the glass, so as to prevent the glass from being crushed due to excessive disturbance or insufficient free expansion
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The self explosion of tempered glass is its inherent physical attribute
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This is also the glass application specification, which stipulates that a certain thickness of glass substrate corresponds to a certain area limit
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Glass raw materials contain trace nickel and sulfur
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Convert most of the nickel sulfide crystals in the tempered glass into β Phase, so that the glass containing impurities and easy to self explode can be detonated actively in the furnace
The quality of construction is also crucial
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Processing quality due to different glass cutting processes, it is generally to use a diamond knife to draw a fine wound on the glass and then cut it
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The factors of self explosion fracture are complex, among which the typical self explosion factors are: glass material, glass cutting process and edge processing quality, rationality of curtain wall node structure design, construction and installation quality, environmental conditions of glass application, deformation (displacement) of main structure, etc
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The above three measures for glass homogenization treatment (hot dip treatment) ultra white glass substrate laminated glass are mentioned in government order No
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2
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In this way, many fine cracks will be hidden at the edge of the glass, which may expand into cracks or even glass cracks under the action of external force or thermal stress
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Therefore, after cutting the glass, the edge must be treated with an edge grinder to eliminate the subtle cracks hidden around the glass
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They exist in two states: high temperature α Phase and room temperature β There are many problems in the process of rapid temperature drop of tempered glass α Phase crystals didn’t have time to convert into β Phase crystals, then they exist in the glass like a time bomb and may become phase at any time β Phase, volume expansion produces pressure, coupled with the internal tension of the glass, it may produce self explosion and fracture of the glass
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Self explosion mechanism self explosion mechanism: the material of glass itself will affect its self explosion probability
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The application environment of environmental factors is also an important external cause of self explosion
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The intact glass after hot immersion shows that it has less impurities and less possibility of self explosion
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If there is not enough gap between the glass edge and the inlaid groove edge to adapt to this displacement, it will also be crushed
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Following the previously published article on the safety regulations of building curtain walls, we combed the causes and improvement measures of self explosion of tempered glass, the most important factor of potential safety hazards of glass curtain walls, for everyone to share
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38 of the notice of the Ministry of housing and urban rural development and the State Administration of work safety on Further Strengthening the safety protection of glass curtain wall: laminated glass, homogeneous tempered glass or ultra white glass should be used for glass curtain wall, The real intention in the article is to reduce the safety problems caused by glass self explosion
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Laminated glass is used
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Displacement adaptability: the glass shall adapt to the displacement of the main structure
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When the main structure produces interlayer displacement under wind load and earthquake, the curtain wall keel will move synchronously with it
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Editor: Zhang Yuxin and Wang Yijun are better, that is, better design better innovation.
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Excessive stress may lead to glass self explosion
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The self explosion of tempered glass occurs from time to time
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Improvement measures: control the quality of structural design, glass processing and curtain wall installation, and avoid self explosion from human factors: 1
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The thermal expansion in different areas of the same glass is not synchronous, resulting in internal thermal stress
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The application of ultra white glass substrate can reduce the self explosion rate from the aspect of glass raw materials
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The larger the plate size, the greater the thermal expansion deformation and the corresponding thermal stress
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Glass thermal cracking is a common kind
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Of course, if the toughened glass adopts laminated sheet, the safety problem after glass self explosion can also be solved
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