With the rapid development of China's economy, the development of the curtain wall industry in the construction industry is also advancing by leaps and bounds. In the mid-1980s, framed glass curtain wall to hidden frame glass curtain wall, unit glass curtain wall, aluminum plate, stone curtain wall and so on. Only in 1998 did there be a point-connected curtain wall in the whole country. Since 2000, the number of point-connected glass curtain walls has increased in several major cities in Beijing, Shenzhen and Nanjing. Since this year, many building curtain walls in China have followed the fashion and are flocking to adopt such glass curtain walls regardless of the size of the buildings and whether they are needed or not. Some design and construction units, the characteristics of the docking glass curtain wall, use, design, manufacturing and safety of the lack of real understanding of the case, also dare to design, also dare to blind construction. This kind of glass curtain wall is too simple to see, the result is poor quality, glass cracking, endangering safety. Therefore, it is necessary to make a preliminary introduction to the point-connected glass curtain wall, and we should know what aspects to study and learn, especially when there is no standard for the glass curtain wall in the country.
Point-connected glass curtain wall can also be referred to as point-connected glass curtain wall. Point-connected glass curtain wall is composed of connecting joints and glass through transparent connection and back-cut connection. Glass is an important connecting piece and a stressed piece. The penetrating point glass curtain wall is a round hole in the glass through which the stainless steel connecting joint penetrates, and the connecting joint is exposed to the metal. The back-cut connecting point glass curtain wall is that the stainless steel connecting joint does not penetrate the glass, and the connecting joint penetrates about 60% of the thickness of the glass. Penetrating point-type glass curtain wall is divided into countersunk head type and floating head type. The countersunk-type barge joint sinks into the outer surface of the glass, with smooth and beautiful surface. The glass hole is a conical hole and complicated to process. The glass thickness should not be less than 10mm. The floating head joint is exposed on the glass surface. The point glass curtain wall adopts transparent white glass, which is different from the coated glass used for the hidden frame glass curtain wall. The indoor space can be directly seen from the outside. The structure without frame format affects the line of sight, and only the simple structure of tie rod and rope. In the room feel bright and open, transparent crystal effect, suitable for large public buildings, such as opera house, exhibition hall, waiting room, building lobby, lighting roof and gate entrance ceiling, etc.
Supporting structure form of 1. point type glass curtain wall
The supporting structure is an important part of the point glass curtain wall, which can transfer the wind load, temperature difference, own weight and seismic load to the main structure. Therefore, the support structure must have sufficient strength and rigidity. It has special independence relative to the main structure, and is an inseparable part of the whole building. The supporting structure should have a reliable connection with the main structure and not bear the attachment effect of the main structure on the curtain wall due to deformation. The supporting structure includes beams and columns, and some only have columns. Single rod, truss, vierendeel truss or tie rod and cable truss can be selected for point structure formation.
1. Single-pole supporting structure is a relatively simple structural form of point glass curtain wall. The supporting structure of column or beam made of aluminum alloy profile, glass rib or steel bears the load of glass surface. The column or beam is in tension and bending working state. The load is transmitted to the component by the concentrated load of point-barge joint, so the calculation is relatively simple.
2. Structural beam-column support structure, generally welded with steel into various frame forms, according to the design requirements, the frame can be made into vertical or hollow bow form. When the span of the point glass curtain wall is large, the single rod can not meet the requirements of load-bearing and rigidity. At this time, the steel should be treated with anti-corrosion on the surface.
3. Plane truss is a plane frame system composed of structural members according to certain rules. Commonly used are parallel chord trusses, parabolic trusses, triangular web trusses, etc. When the load on the glass is acting on the node, each rod has only axial force, and the stress distribution on the section is uniform, which can give full play to the role of the material. This type of structure is commonly used in large-span structures.
4. The load of the space truss structure is the load of several aspects in different directions, which is not in a plane. Therefore, several plane trusses form a space system according to a certain connection system to bear the load in all directions, so as to meet the requirements of the load and ensure the safety of the structure. The nodes of space trusses are generally regarded as spherical nodes, and the rods connecting the spheres can rotate through any axis of the hinge center. Like the plane truss, the straight rods connected by hinges at both ends are called chain rods. Each node of the space truss composed of nodes and chain rods has three degrees of freedom. The characteristics of this supporting structure can change with the shape of the curtain wall and have strong applicability. Most of the spherical surface of the glass daylighting roof adopts spherical grid point support structure.
5. The stress of the prestressed tie rod structure, the support system is formed by the reasonable combination of the tie rod parts and the application of certain prestress. The support truss formed by the tie rod truss is simple and light, especially when stainless steel is used as the tie rod, it can show the elegant temperament of the modern metal structure and make the building more modern.
6. The cable point support structure glass curtain wall is the latest type. It is only popular in the world in recent years. It has high technical content and great difficulty in design and construction. Its support structure is stainless steel wire cable through reasonable layout. After applying pretension to form prestressed suspension cable structure, also known as cable truss.
The supporting system of this kind of curtain wall is a prestressed double-layer suspension cable system, which has strong bearing capacity, light and beautiful appearance, good permeability, simple structure and various forms, and better visual effect. It is the most modern glass curtain wall with great vitality.
The double-layer suspension system is composed of a series of concave and convex curves (wire ropes) and suspended connecting rods. The load-bearing cables, stabilizing cables and connecting rods of the double-layer cable system are all arranged in a plane. The force characteristics are similar to plane trusses, which can be referred to as cable trusses. The design form of cable truss can be varied. In addition to considering the force performance in the design, the shape of cable truss should also be considered from the artistic point of view, so as to achieve the beautiful feeling of stable and smooth appearance, dynamic feeling and light feeling.
The cable truss includes three kinds of cables: force cable, load-bearing cable and stability cable. The main force cable mainly bears wind load, positive and negative wind pressure and seismic load. In addition to the above three loads, the front and rear main force cables should also consider the temperature change. The thermal expansion and contraction coefficient of the steel cable is relatively large, and the temperature should be considered during installation. When installed at zero degrees in winter, the high temperature steel cable will change from short to long in summer, which has a significant impact on the whole cable structure. The load of the above three kinds of cable truss will change with the change of external conditions and temperature, so more factors should be considered in the design and different measures should be taken, so that the selection of the steel cable form is very important.

Processing and installation of 2. point-connected glass curtain wall
The point-connected glass curtain wall is connected with the glass through the hole on the glass, which can be connected at 4 points, or at 6 points and 8 points. The weight of the glass is supported by the upper two corners of the barge joint, the glass is always hanging on the barge joint, the other parts of the barge joint is mainly to resist the wind pressure change of the load and displacement compensation, the glass requirements are very high.
1. Requirements for glass of point-refuted glass curtain wall
① Various loads on the glass panel of the point-type glass curtain wall are transmitted to the supporting structure through the connecting claw, and there is a large stress concentration at the glass hole and the connecting joint, so it is appropriate to use tempered glass.
Tempered glass thickness generally choose 8mm, 12mm, 15mm, special circumstances to consider.
The point-barge glass curtain wall can also use tempered laminated glass, which is mainly safe and has a certain sound insulation effect.
The tempered hollow glass can choose 12 + 12A +6, 10 + 12A +8 and so on.
⑤ According to the design needs, it can also use curved tempered, curved tempered hollow, curved tempered laminated glass, etc.
Curtain wall glass vertical surface is greater than 5 degrees, or used in the roof, lighting shed, curved surface application of tempered laminated glass is safer.
The processing and production requirements for glass are very strict, such as cutting, drilling and grooving, such as inverted shuttles, chamfering and grinding on the above edges, which will not only cause stress concentration and glass cracking.
The cutting of glass is carried out by computer cutting, and manual cutting cannot guarantee the cutting accuracy. The tolerance of glass length dimension should not be greater than 1mm, the tolerance of diagonal dimension should not be greater than 2mm, and all four sides should be rounded. Glass drilling should be carried out on an automatic drilling and edging machine, and computer positioning should be carried out. Drilling and edging should be carried out in one go.
After the above processing, the glass is further finished. If you need to go through the following processes, reverse shuttle, rough grinding, fine grinding, fine grinding, round edge fine grinding, bevel edge fine grinding, fine grinding, etc., in addition to the hole after the hole, square hole size tolerance, hole edge grinding have higher specific requirements.
2. The connecting piece and claw of the point-type glass curtain wall
The connecting parts and connecting claws of the point-type glass curtain wall are all processed with different types of stainless steel. The connecting parts are mainly divided into two types: one is fixed at the head and tail, and the other is equipped with a ball head on the head. It can rotate in a universal direction. When the glass is deformed under load, the head can rotate accordingly, reducing the stress concentration of the glass hole during deformation.
The contact part between the connector and the glass should be added with a gasket, which is generally made of soft metal or non-metallic soft materials.
There are many types of connecting claws, such as X-shaped, H-shaped, two-hole, three-hole-shaped connecting claws of various angles and specifications, and 200, 210, 220 and 230 stainless steel series connecting claws. The connecting claw is made of stainless steel, stainless steel is not equal to no rust, the choice of stainless steel. General stainless steel claw parts for 316 stainless steel, the rest of the stainless steel fittings 304 stainless steel, adapter base for 235 steel. Due to the improper use of steel, some domestic connecting claws have begun to rust.
The prestressed suspension cables of the cable-connected point glass curtain wall splicing parts are all composed of stainless steel wires in various forms. The suspension cable structure is a flexible structure. Before the prestress is applied, the cable rod has no stiffness. Before the prestress is applied, the steel cable should be pre-pulled to detect the strength and increase the stiffness.
Construction Technology of 3. Point Type Glass Curtain Wall
No matter what kind of structure, the construction process of point glass curtain wall is very strict and complicated, which cannot be written in detail here. Here, the construction process is represented by the schematic procedure of suspension glass curtain wall construction sequence.
Measuring and setting out → embedded parts calibration → truss installation and welding → calibration and inspection → connecting stressed cable → applying prestress → calibration and inspection → connecting vertical bearing cable → applying prestress → overall adjustment → adjustment and inspection → gluing → repair and inspection → glass cleaning → site cleaning → final inspection.