The glass curtain wall is widely used in modern architecture as the technical expression method of the building facade. As the material carrier of the curtain wall, glass has also been continuously improved with the continuous development of curtain wall technology. Many countries have successively issued industry standards for high-rise glass curtain walls, which stipulate that the curtain walls of buildings must use "safety glass". Other glass products made of laminated glass, such as safety insulating glass, etc.".
"safety glass" used in high-rise glass curtain walls 1
2. Comparison of technical performance of insulating glass and laminated insulating glass
Two types of insulating glass and laminated insulating glass are often used in high-rise curtain walls, both of which comply with the current national standards for safety glass. The difference between the two types of glass is only in the structure of the outer glass. In the structure of insulating glass, the outer sheet is a single piece of tempered glass; in the structure of laminated insulating glass, the outer sheet is made of laminated glass (the substrate of laminated glass can be tempered glass or semi-tempered glass). Now compare these two common glass combinations.
2.1 Structural composition
Insulating glass: It is composed of two pieces of single-piece tempered glass. Laminated insulating glass: the outer sheet is laminated and the inner sheet is a combination of single-piece tempered glass.
2.2 Specific configuration
Insulating glass: 8mm (tempered) + 12mm (hollow layer) + 8mm (tempered)
hollow glass unit, the weight of the glass is about 41.0kg/m2.
Laminated insulating glass: 8mm (semi-tempered) + 1.52mm (PVB interlayer) + 6mm (semi-tempered) + 12mm (hollow layer) + 6mm (tempered) structure of laminated insulating glass unit, the weight of the glass is about 51.2kg/m2.
2.3 Comparison of advantages
(1) Hollow glass:
①This is the most economical solution in safety glass when it meets the relevant specifications. Glass of this structure is widely used throughout China, and is even widely used in super high-rise buildings.
②Glass with this structure is lighter and easier to manufacture.
③Compared with a laminated glass of the same thickness, the strength of single-piece tempered glass is higher.
(2) Laminated insulating glass:
① When broken, the fragments will temporarily stick to the PVB interlayer, reducing the risk of glass falling from the building, and avoiding the risk of voids in the exterior wall due to glass falling off.
②The types of glass options can be increased, and various aesthetic effects and functions can be realized, such as colored PVB interlayer, laminated glass composed of the body-colored glass of different colors.
③Compared with single-piece tempered glass, laminated glass has higher sound insulation performance. The insulation performance of insulating glass using single-layer laminated glass is 3dB lower than that of insulating glass using single-piece glass.
④ When using laminated glass, the glass surface will look flatter, so it is not necessary to use tempered glass (for example, semi-tempered glass can be used). Therefore, the waviness on the glass surface is not so obvious.
2.4 Comparison of disadvantages
(1) Insulating glass
① When the glass is broken due to impact or other factors, the entire piece of tempered glass will be broken into small particles with obtuse angles similar to honeycombs. Even so, the small particles spilled from the height of the outer wall are still fatal to passers-by and cause damage to the surrounding property to a certain extent.
②As we all know, tempered glass has self-explosive characteristics, mainly due to the presence of nickel-sulfur sand particles in the glass, and the nickel-sulfur sand particles cause stress concentration on the glass during the decay. When the stress exceeds the limit, the tempered glass will explode spontaneously. According to the statistical results, if the tempered glass is not hot-dipped, the probability of self-explosion is greater. And if the tempered glass is subjected to the hot-dip test treatment following EN14179, the probability of nickel-sulfur grit degeneration may be reduced to one per 400 tons. Take a high-rise building with a total external wall area of about 82,580m2 as an example. If the outer sheet is made of 8mm thick glass for comparison, the total weight of the outer sheet is about 1690 tons: According to the statistical results, all the outer sheets are based on the EN14179 standard. In the case of the hot-dip test, the nickel-sulfur grit in all outer glass can be reduced to four. Assuming that there is only one nickel-sulfur sand grain in a piece of outer glass, only 4 pieces of glass on the exterior wall of the entire tower may explode spontaneously because of the nickel-sulfur sand grains.
Of course, this is only a theoretical statistical value. The impurity content of the glass raw materials will affect the value of this value. In addition, the value of this value will be different for different glass production batches. Although hot dipping helps reduce the probability of self-explosion of tempered glass, the possibility of self-explosion has not been eliminated. Therefore, it should still be seen that glass fragmentation and the damage caused by it have an adverse negative impact on the commercial value of the building.
③It has more serious oil spots and arches than semi-tempered laminated glass.
(2) Laminated insulating glass:
① Higher cost.
②The strength of laminated glass depends on temperature, aspect ratio, size, thickness, and load time. The strength and rigidity will be much lower than that of a single piece of tempered glass of the same thickness. In other words, if it is replaced by laminated insulating glass of the same strength 8mm (tempered) + 12mm (hollow layer) + 8mm (tempered) thick insulating glass, the thickness will be 8 mm (semi-tempered) + 1.52mm (PVB interlayer) + 6mm (semi-tempered) + 12mm (hollow layer) + 6mm (tempered). In contrast, the self-weight of the laminated insulating glass unit is increased by about 25%. The load capacity level of the window cleaner (for glass replacement) also needs to be improved accordingly.
③Laminated glass has the risk of degumming. Film combining is a relatively complex process and requires rigorous quality control procedures. When the edge of the glass unit is in contact with silicone glue for a long time, there is still a risk of degumming the laminated edge. When small bubbles appear on the edge of silicone rubber and laminated glass and then spread to a limited degumming (generally no more than 12mm), this form of degumming is not within the scope of the glass manufacturer's quality assurance. However, this kind of variant degumming is only an appearance problem and will not affect the strength of laminated glass.
④ Compared with two-layer hollow tempered glass, the stress spots may be more obvious.
Comparison of technical performance of insulating glass and laminated insulating glass
Considering the cost, strength, safety, and feasibility, these two kinds of glass with different structures have different advantages and disadvantages. Before choosing a suitable specification of glass, it is necessary to consider and evaluate the strengths and weaknesses of each specification of glass. However, after considering all factors, the most important factor influencing the choice of glass is public safety. Although the use of single-piece tempered glass is very common and meets the relevant specifications, we cannot underestimate the danger of fragments falling from a height after the single-piece tempered glass is broken. All in all, even if the owner follows the Chinese regulations and uses safety glass in the building, there are still safety issues that need to be considered. There are many reasons for the failure of the safety glass unit. When the outer sheet is tempered unit glass, the glass will likely fall from the building after it is broken, thereby posing more potential threats to the safety of building users and the general public.
3. Curtain wall system selection
Unit glass curtain wall and frame glass curtain wall are the main two curtain wall systems.
3.1 Advantages and disadvantages of unit glass curtain wall
①The quality of the curtain wall is easy to control.
②On-site construction is simple, fast, and well managed.
③It can accommodate large structural displacement.
④Good waterproof performance.
⑤ It is easier to meet the requirements of high-performance curtain walls.
⑥It is usually able to adapt to the needs of the development level of modern buildings.
① If the installed unit block needs to be repaired or replaced, it may be difficult.
②The structural form determines the higher amount of aluminum profile for the unit curtain wall, and the cost is generally higher than that of the frame curtain wall using the same material.
3.2 Advantages and disadvantages of frame glass curtain wall
①Easy to design and flexible installation method.
②Materials are easier to store on site.
③Easy to perform maintenance.
④The cost is generally lower than the unit curtain wall.
① It is difficult to guarantee the quality and performance of curtain wall installation.
②A lot of on-site management and quality control work is required.
③ It is easy to seep water.
④ The structural displacement that can be accommodated is very limited.
⑤The construction period on site is longer.
⑥ A large number of assembly components are easily lost and damaged when stored on the floor.
⑦The quality and performance of curtain wall installation are difficult to be guaranteed.
The selection of curtain wall system 1