Problems and solutions of the hottest glass curtai

Analysis of the problems and solutions of glass curtain wall

Abstract: This paper analyzes and discusses the problems of glass curtain wall in detail, and finds out the solutions to the problems of glass curtain wall one by one

key words: service life of thermal stress structural adhesive

1. Preface

glass curtain wall, as a unique design in modern architecture, not only reflects the best combination of architectural and aesthetic structural design, but also perfectly reflects the various functions of glass, such as the permeability of glass curtain wall, achieving the best line of sight through glass, maximizing the field of vision, and connecting and integrating the internal and external environment of the building; The glass curtain wall has good process performance. The supporting components of the glass curtain wall are carefully processed, and the surface is smooth. It has a good sense of craft and art. It can adapt to any geometric shape, produce rich changes in the building shape, and fully reflect the imagination and creativity of the designer; At present, one of the biggest highlights of the use of glass curtain walls is that the use of various energy-saving curtain walls has greatly reduced the energy consumption of buildings. However, in the past period, many construction projects have been troubled by glass curtain walls, and have attracted the attention of all sectors of society with their glass breakage, glass falling and other problems

2. Problems of glass curtain wall

there are many problems of glass curtain wall, such as glass breakage, structural glue failure, poor fire resistance performance of glass curtain wall, failure of supporting structure of glass curtain wall and failure of fixing device of glass curtain wall. Next, we will analyze and demonstrate various problems of glass curtain wall and find out the methods to solve this problem

2。 There are many reasons for glass breakage. The following mainly analyzes and demonstrates the glass breakage caused by impurity nickel sulfide and thermal stress

2。 1。 1 glass cracking caused by impurity nickel sulfide

nickel sulfide is an inevitable harmful impurity in the process of glass production. It is a compound formed by sulfur and nickel under the action of high temperature in the production process of original glass. Nickel sulfide itself does no harm to the glass, but after the glass is tempered, the original nickel sulfide compound will change its state, With the change of time and temperature, the volume increases or transforms. When the curtain wall glass containing nickel sulfide is installed on the curtain wall, the external temperature rises, resulting in slight changes in the volume of nickel sulfide, causing tiny cracks in the glass. These cracks release the internal energy after passing through the tension layer of tempered glass, causing glass breakage

the solution is: first, start from the source. Glass manufacturers should monitor the whole process of glass manufacturing to minimize the contact between nickel containing materials and glass raw materials; Secondly, the curtain wall glass is monitored after installation. In foreign countries, the existence of nickel sulfide impurities has been detected by photography. If they are contained, timely and necessary replacement can be carried out to prevent the glass from breaking and hurting people. Single piece tempered glass and tempered hollow glass can also be replaced with laminated glass. At this time, if the nickel sulfide impurities cause the glass to break due to deformation, the fragments still adhere to the film, It will not form glass rain and cause damage to ground personnel

2。 1。 2 glass breakage caused by thermal stress

thermal stress is an important reason for the breakage of glass curtain wall. There are many reasons why the glass curtain wall is heated, but the main heat source is sunlight. When the sunlight shines on the surface of the glass curtain wall, the glass will be heated and expanded. If the glass is heated evenly, the glass edge and the central part of the glass will expand evenly at the same time. However, if the edge and the interior of the glass are not heated evenly, such as the description frame glass curtain wall, the middle part of the glass is heated and expanded, and the edge is embedded in the metal frame, The temperature of the edge is lower than that of the middle part of the glass. This part of the glass still remains in its original state and prevents the expansion of the heated part, so tensile stress will be generated in the glass. When there are cracks or micro cracks on the edge of the glass, these defects are easily affected by the thermal stress. With the increase of the temperature difference, the cracks caused by the thermal stress will gradually increase, and finally the glass will be broken

the solution is: first, finish the glass edge, and use fine grinding or polishing edge to reduce the existence of micro cracks; Secondly, toughen the glass to enhance its resistance to temperature changes; Third, in the process of glass processing, handling and installation, the glass must be properly protected. Pay attention not to collide or rub the edge of the glass with other hard objects, and strictly abide by the operating procedures. Especially in the process of installation, if the frame is not suitable (too small or distorted), you must remember not to clamp off the edge of the glass with pliers, and you must correct the frame to make it adapt to the size of the glass

2。 2 poor fire prevention ability of glass curtain wall

glass curtain wall is a non combustible material, but it can soften or even melt in the face of fire. Therefore, in the architectural design, we must fully consider the fire prevention requirements of the building. First, we must keep the integrity of the glass so that it is not broken, so as to avoid air flow and fire spread. At the same time, on the premise of keeping the integrity of the glass itself, Ensure that the combustibles on the back of the glass will not burn or explode under thermal radiation. Generally, the fire prevention effect of glass curtain wall is very low, and the fire integrity and fire insulation are very low. Glass breakage can occur in a very short time in a fire

the solution is: in the actual construction process, designers carry out different designs according to different fire protection requirements of buildings. For buildings with general fire prevention requirements, glass bricks, tempered glass, small flat glass, etc. are used for the glass. For buildings with high fire prevention requirements, the 15 minute video allows the sitting participants to simply and clearly understand the products and principles of the other company's products, etc. the curtain wall glass adopts wired glass, monolithic fire-proof glass, composite fire-proof glass, fire-proof insulating glass, etc. Composite fire-proof glass is currently the most widely used fire-proof curtain wall glass in the name of composite materials in most of these plastic parts of cars. When a fire occurs, the glass facing the fire surface will be heated and cracked within a certain period of time, but due to the existence of fire-proof film, the glass is adhered to the film. 6. Ergonomics and appearance design fall, maintaining the integrity of the glass. At the same time, because the film itself has the function of fire prevention, It not only blocks the spread of the fire, but also ensures that the temperature of the back fire surface does not rise rapidly and controls the spread of the fire

2。 3 curtain wall glass structural adhesive failure

because the glass curtain wall has been affected by adverse factors of the natural environment for a long time, such as wind, sun, rain, ultraviolet radiation, earthquake, etc., it is required that the glass curtain wall must have weather resistance, durability and corrosion resistance. As a bonding material, the structural adhesive has become the focus of attention. As we all know, at present, the quality assurance period of structural adhesives with the best quality and the most widely used in the market is only ten years. Once the quality assurance period is over, the problems of thermal aging and ultraviolet aging of silicone structural adhesives organic compounds become more and more serious with the passage of time, resulting in the loss of strength and adhesion of structural adhesives and failure. Although there are no quality problems on the surface of the glass curtain wall, its potential dangers exist all the time, seriously affecting the safety of pedestrians and vehicles passing around the building. In Beijing, Shanghai, Guangzhou and other cities that first used glass curtain walls, curtain wall glass falling events occur from time to time. It is even more difficult to determine whether a piece of glass structural adhesive is invalid. However, in order to ensure the safety of personnel and vehicles, it is a huge expenditure to replace glass curtain walls in a large area. In the face of this situation, owners are in a dilemma

the solution is: first, restrict the use of hidden frame glass curtain wall, and protect the glass curtain wall that has passed the warranty period, such as setting up fences, green belts, and hanging curtains around the glass curtain wall to prevent falling glass from injuring pedestrians and vehicles. Secondly, open frame and semi hidden frame glass curtain walls should be used as much as possible, because even if the structural adhesive fails, the probability of glass falling will be greatly reduced due to the support and restraint of the frame

2。 4 failure of supporting structure of glass curtain wall

not all problems of glass curtain wall are caused by glass itself, and sometimes the failure of frame structure supporting glass will also cause problems of glass curtain wall. The frame structure used to support the glass is often the weak link of the glass curtain wall. If the initial design of the frame system is unreasonable, the frame structure can not bear the internal force of the building, which can avoid the thermal bridge effect to the greatest extent, and then deformation will occur, eventually leading to glass breakage

the solution is to carry out anti fatigue experiments on the frame structure during the design process, and then design the corresponding curtain wall glass according to its anti fatigue ability, so as to prevent the long-term overload operation of the frame

2。 5 failure of fastener fixing device of glass curtain wall

all glass curtain walls rely on the fastener fixing device to combine the curtain wall and fix it on the building. However, unforeseen defects of fastener fixing devices may lead to serious structural problems. Hydrogen embrittlement is the reduction of metal ductility after absorbing hydrogen in the process of metal production. High strength bolts, etc. may fail before reaching their yield strength under the action of external forces such as wind and earthquake after contacting hydrogen, resulting in the fall of curtain wall glass. Another reason for the failure of the fixed device is the loosening of bolts caused by long-term wind load. The building is subjected to irregular wind load every day. The irregular wind load brings continuous vibration to the glass curtain wall and transmits it to the fixing device. The vibration will cause the high-strength bolts connecting the fixing device and the building itself to loosen. Once the bolts lose their function, the fixing device will fail, and the curtain wall glass will fall under the action of wind and so on, which has become an inevitable problem

the solution is: before installing the glass curtain wall, conduct necessary inspection on the fastening, and only after passing the inspection can it be installed and used on site. In addition, for the falling of curtain wall glass caused by the loosening of fixing bolts, we use special lock nuts to lock the bolts in the actual construction process to prevent the bolts from sliding and failure, or use specific washers to ensure that the bolts will not fall off after fastening

3. Other problems caused by glass curtain wall

glass curtain walls cause more than the above problems. Due to the large-scale use of glass curtain walls, light pollution, color pollution, heat pollution and so on are all problems that can not be ignored. Although there are some problems in glass curtain wall, as long as designers, producers and users fully understand and study it, and develop their strengths and circumvent their weaknesses, glass curtain wall is still a highlight of modern architecture