Hidden dangers are around us, are glass curtain walls safe?

On August 26, 2016, the curtain wall glass of a hotel in Jinan, Shandong suddenly fell, and the splashed glass fragments caused accidental injuries to pedestrians; on August 29, a piece of glass from the Huade Building in Xining, Qinghai fell on the sidewalk ...Incidences of falling glass curtain walls that have occurred in various places have made some people a little worried. How to solve the hidden dangers of existing glass curtain walls, and how to avoid such problems in the future?

According to statistics, in recent years, the proportions of various curtain walls (public buildings and low-rise buildings) in buildings have been respectively For example, glass curtain walls account for 45%, aluminum panels account for 26%, stone and other materials account for 29%, and engineering glass curtain walls over 500 meters account for almost 100%. Since the weight of glass curtain walls is relatively small, generally 49-90 kilograms per square meter, which is equivalent to 1/8 to 1/5 of traditional materials, almost all buildings above 500 meters use glass curtain walls, which cannot be achieved by any other material. For example, the Saudi Kingdom Building is 1,007 meters tall, and the weight of the glass curtain wall accounts for 1% of the total weight. The height of Shanghai World Financial is 495 meters, the total volume is 420,000 tons, and the weight of glass curtain wall is 5,000 tons, accounting for 1/80. This is an objectively existing law.

Glass is an irreplaceable wall structure material. Its irreplaceability determines its indispensable use, because glass has four major characteristics at the same time: light transmission, light weight, high strength, and durability. No other material has these four characteristics at the same time. It is high-strength and opaque. Concrete is neither high-strength nor light-transparent. Metallic materials can also be used in buildings, but design masters don’t like metal textures, so they decided to use glass in super The status of high-rise buildings cannot be replaced.

Review of related accidents

In 2013, the facade glass on the balconies of many homeowners in Nanhu International Community, Jiujiang City, Jiangxi Province cracked one after another, and they were refused repairs by the property management company. The reason is that the glass curtain wall is located on the balcony of the owner's home, and it is the owner's responsibility to handle it.

On March 1, 2010, on the second floor of a commercial plaza in Yuexiu District, Guangzhou City, Guangdong Province, a 4-meter-long and 1.5-meter-wide window glass suddenly burst, and fragments flew into the air. The old lady was scratched by the debris and was sent to the hospital for treatment.

In 2006, the new Beijing Capital Museum had just been completed and opened for operation. One day after closing, a pane of glass exploded without warning. Small fragments fell from a height of 30 meters and smashed a table in the cafe on the first floor.

Analysis of the cause of the accident

Technical defects and material defects

The tempered glass of the curtain wall breaks without external force. The fundamental reason for the self-explosion of the tempered glass lies in the glass. Containing nickel sulfide and other particulate impurities, the temperature changes after exposure to the sun, causing the glass to expand, causing the glass to self-explode.

There are also risks caused by the aging of the glass curtain wall, risks caused by improper construction such as gluing the glass curtain wall and fitting it with the frame during the installation process.

Maintenance and management responsibilities are not fully implemented

Once the curtain wall glass self-explodes, as long as it is handled promptly within 3 to 4 hours, it will not fall. Therefore, the inspection of curtain wall glass is particularly important. In addition, the service life of glass curtain walls is generally about 10 years. Exterior wall materials that have "overaged their service" cannot be reinforced and must be replaced.

The property company does not care, the developers do not care, and the owners do not care. This is the most serious problem faced by glass curtain walls after entering the "risk outbreak period".

How lethal is the glass curtain wall?

Physical examination fee

The "comprehensive physical examination fee" of the glass curtain wall is expensive. Experts calculated the inspection cost per square meter. It can cost hundreds of RMB, and a single inspection fee for a large glass curtain wall commercial building may cost hundreds of thousands of RMB. Therefore, most of the so-called "maintenance" nowadays involves cleaning, and it is rare to ask professionals to repair or replace it.

Usage

Since my country's glass curtain wall industry started in 1983 after the reform and opening up, it reached a climax in the mid-1990s. The market usage of glass curtain wall has averaged 500 per year. With a growth rate of 10,000 square meters, it has developed very rapidly over the years. As of 2012, China's existing glass curtain walls accounted for 85% of the global total.

Self-explosion rate

Due to the volume expansion of impurities in the glass, tempered glass also has the risk of "self-explosion". According to industry statistics, 1% to 3% of tempered glass will suddenly shatter without warning.

Even if people use the second "quenching" method to "detonate" a batch of unstable glass in advance, the self-explosion rate of tempered glass can only be reduced to 0.1% to 0.3%, and cannot be reduced to 0. This characteristic that troubled architects was once called "glass cancer" because it was difficult to deal with.

Lethality

In 2009, the Shenzhen Municipal Public Security Bureau issued an announcement on "Strictly Prohibiting Falling Objects from High-rise Buildings", which stated that objects "the size of fingernails" were dropped from the 25th floor. The momentum created when it reached the ground was enough to penetrate a human skull. If the glass falls from an altitude of 300 meters, the speed when it reaches the ground is "no less than a bird that hits an airplane."

Who is the person responsible for maintenance, inspection, and appraisal?

Who is the person responsible for maintenance?

The safety maintenance of glass curtain walls implements the owner responsibility system, and the building is a single If it is owned by the owner, the owner shall be the person responsible for safety maintenance of the glass curtain wall; if the building is jointly owned by multiple owners, each owner shall jointly negotiate and determine the person responsible for safety maintenance, who shall take the lead in the safety maintenance of the existing glass curtain wall. .

Who will perform maintenance inspections?

One year after the completion and acceptance of the glass curtain wall, the construction unit should conduct a comprehensive inspection of the safety of the curtain wall. The person responsible for safety maintenance must conduct special inspections of existing glass curtain walls in accordance with regulations. After suffering a special accident, the person responsible for safety maintenance or the technical unit with corresponding qualifications entrusted by him or her shall conduct a comprehensive inspection of the glass curtain wall of the potentially damaged building in a timely manner, and repair the hidden danger parts in a timely manner.

Who will evaluate the safety performance?

If the glass curtain wall has reached the designed service life, the person responsible for safety maintenance should entrust a unit with corresponding qualifications to conduct safety performance appraisal of the glass curtain wall, and modifications are required. , reinforcement or demolition, units with corresponding qualifications should be entrusted with the responsibility for implementation.

How to standardize maintenance and reinforcement?

For structural maintenance and reinforcement of glass curtain walls, the structural components of the glass curtain wall must not be changed without authorization. The structural calculation and reinforcement plan should comply with relevant national standards and specifications, and exceed If required by technical standards, safety technical demonstration should be carried out. After the structural repair and reinforcement project of the glass curtain wall is completed, the owner, the unit responsible for safety maintenance or the unit responsible for daily maintenance and management shall organize acceptance inspection.

How can we avoid glass curtain wall accidents?

(1) When building a new glass curtain wall, factors such as urban landscape, surrounding environment, building properties and usage functions must be comprehensively considered, and factors such as building safety, environmental protection and Energy saving and other requirements require reasonable control of the type, shape and area of ??glass curtain walls. Encourage the use of lightweight and energy-saving exterior wall decoration materials to reduce safety hazards of glass curtain walls from the source.

(2) Newly built residences, party and government office buildings, hospital outpatient emergency buildings and ward buildings, primary and secondary schools, nurseries, kindergartens, and buildings for the elderly are not allowed to use glass curtain walls on the second floor and above.

(3) In commercial centers, transportation hubs, public cultural and sports facilities with dense population and high mobility, near roads, squares and buildings with entrances and exits and personnel passages at the bottom, it is strictly prohibited to use full-scale Hidden frame glass curtain wall. If the above buildings are equipped with glass curtain walls on the second floor or above, buffer areas such as green belts or podiums should be reasonably set up in the surrounding area below the curtain wall, and protective facilities such as overhangs and anti-impact awnings can also be used.

(4) The glass curtain wall should use laminated glass, homogeneous tempered glass or ultra-white glass. The use of tempered glass should comply with the current national standard "Toughened Glass for Building Doors, Windows and Curtain Walls" JG/T455.

(5) New glass curtain walls should be based on national laws, regulations and standards, strengthen the safety technical demonstration of scheme design, construction drawing design and construction plan, and conduct special acceptance before completion.

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