Relieving "Glass**"** Needs More

The "Shenzhen Architecture Design Code" was officially implemented in recent days. This is another city that has restricted or even prohibited glass walls in some buildings after Shanghai, Jiangsu, and Fujian provinces.

In recent years, incidents involving glass curtain walls smashing or escaping have been frequently reported in newspapers, and glass curtain walls have also been referred to as “buzzers” hanging overhead. Experts in the industry believe that in the current situation where the curtain wall renovation technology and materials are still not perfected, it is feasible to prohibit the use of glass curtain walls in order to resolve outstanding conflicts in local areas. However, whether or not a glass curtain wall is completely banned in public buildings is reasonable and feasible across the country, and it needs further discussion.

Glass walls have entered the "aging period" one after another

China's earliest introduction of glass curtain walls from the 1980s to become the world's largest market took only 20 years. By 2012, China has already exceeded 500 million square meters of glass curtain walls, accounting for 85% of the world's total, and it has become the world's largest producer and user of glass curtain walls.

According to Zhou Zhiwu, the secretariat of the China Architectural Glass and Industrial Glass Association, currently in the construction industry, the design period of glass curtain walls is generally 25 years. Glass curtain wall construction in many cities in China has experienced aging for more than 20 years. In particular, glass curtain wall high-rise buildings have seen glass cracking, corrosion and deformation of metal components, weathering and cracking of sealing strips. With problems such as the loosening of force components, the danger of becoming "high-altitude **" is increasing.

“According to the relevant regulations, tempered glass must be used for glass curtain walls. If the tempered glass used is unqualified, it will leave hidden dangers of self-explosion. Although this specially treated glass will not generally fall off after the explosion, it will form particles. Shape, but the danger of self-detonation is still great.” Zhou Zhiwu said, “The basic reason for the explosion of tempered glass is that the glass contains nickel and other particulate impurities. After being changed by the temperature of the sun, it expands, causing the glass to blew ."

“Although the current quality and strength of architectural glass are adequately protected, after all, the earthquake resistance and deformation resistance of glass are insufficient. Once typhoons, earthquakes, hailstorms and sudden changes in temperature are encountered, it is likely to cause safety accidents. The management departments of the current cities do not need to properly manage these 'glass **', said Zhou Zhiwu.

Regulatory vacuum needs to be improved

There are also views that the number of years of design beyond glass curtain walls is not the most important factor in the emergence of danger. Some foreign glass curtain walls have been used for sixty or seventy years and there are no safety issues. In this regard, Xi Shizhen, a super high-rise building curtain wall expert, said that although high-rise buildings in China have also been upgraded during the process of using glass curtain walls, the security has greatly improved, but the lack of supervision and inspection similar to the nature of the annual security inspection of elevators has caused A major cause of security risks.

It is understood that as early as 1996, China promulgated the "Technical Specifications for Glass Curtain Wall Engineering", which stipulates that "in the normal use of glass curtain walls, comprehensive inspections shall be conducted every five years for glass, seals, sealants, etc." There is no punitive measure against the violation of the owner.

In 2006, the Ministry of Housing and Urban-Rural Development promulgated the “Administrative Measures for the Safety Maintenance of Existing Curtain Walls”, which stipulates “the safety maintenance of existing curtain walls and the implementation of the owner’s responsibility system.” However, administrative orders cannot be equated with compulsory measures. Many high-rise buildings are actually Check the safety of glass curtain walls by means of "external wall cleaning".

“Three things no matter”—whether the property company, the developer, or the owner is the most serious problem facing the glass curtain wall after entering the “aging period”. "The standard technology is well implemented. The question is who will perform it. For a rented office building or office building, some people say that it was built by the owner and should be tested by the owner. Some people also say that the user is using it and should be paid by the user. "When it comes to the implementation of the problem, if there is no major problem with a glass curtain wall building, the property company, developer and owner will not take the initiative to detect it unless the country imposes a mandatory requirement." After all, it's expensive.

With the introduction and application of the national green energy-saving industry standard, the regulatory vacuum of glass curtain walls needs to be improved as soon as possible from the system and details, so as to avoid a greater degree of danger. “Apart from limiting the areas where glass curtain walls are used in cities, such as residential areas, schools, and schools, which are likely to cause casualties, the use of glass curtain walls should be prohibited. It should also be passed through the law. After the building curtain wall project is delivered and used, the property owner must entrust Professional organizations regularly conduct safety appraisal and maintenance. The relevant departments should conduct a thorough inspection of the existing glass curtain wall construction as soon as possible and attach explosion-proof membranes to prevent exfoliation and injury.

Relieve "**" from the technical level**

At present, because of its light weight, high strength, and good aesthetics, glass curtain walls are still the first choice for many high-rise buildings. In particular, ultra-high-rise buildings over 400 meters all use glass curtain walls without exception. While conducting scientific supervision and maintenance of glass curtain walls, other safety measures are also essential.

The experience of Japan and other countries can be used for reference, for example, setting up barriers in the immediate vicinity of the curtain wall, not arranging facilities to attract pedestrians to stay, and not arranging booths, catering and sales locations for indoor walls, parking spaces away from the wall roots, and canopies at the entrances and exits. Or install a metal safety net.

In addition, some non-explosive glass products can also be used, such as laminated glass, wire glass, ultra-white glass, etc. It is understood that in recent years, European countries and the United States have already proposed the use of these types of glass as materials for glass curtain wall in the technical specifications, and have achieved good results.

According to Shi Xi’s introduction, the safety of laminated glass and ultra-white glass is much higher than that of tempered glass. Although the self-detonation of tempered glass cannot be avoided, ultra-white glass produced through special processes can greatly reduce the rate of self-detonation. “The normal white glass has a self-exploding rate of 3‰-5‰ after rigidification, while the ultra-white glass is a highly transparent low-iron glass, and the implosion rate can be reduced to 0.1‰ or less due to less impurities, including Shanghai Center. Many of the super high-rise buildings under construction use ultra-white glass.

Even if the laminated glass self-explodes, the glass pieces can be maintained in a sheet form by the PVB film in the interlayer, and do not spill onto the ground to injure pedestrians. “Only, the price of laminated glass per square meter is about 100 yuan more than that of tempered glass. This is just the cost of glass. If you count different processes for glass curtain walls, the price difference between the two is greater. Therefore, in order to save costs, Many real estate developers are reluctant to use laminated glass in large quantities," Xi said. He pointed out that the country’s policy guidance to actively guide builders to adopt safer architectural glass is also a crucial aspect.