Taboos for the design of architectural glass curtain wall profiles

[China Glass Network] First, the light roof

1. PVB laminated layer is lower than 1.14

A common phenomenon is that the laminated glass of the light-emitting top is more likely to cause failure of the PVB interlayer than the facade curtain. The main reasons may be: (1) thin laminated layer; (2) high ambient temperature; (3) gravity Uneven effect, etc. Therefore, the thickness of the PVB interlayer for the lighting roof is preferably not less than 1.14.

2. No condensate discharge design The lighting roof should have a condensate discharge structure, especially in severe cold and cold areas.

3. Flat top without drainage slope The general drainage slope is 3%, otherwise there will be water accumulation and ash accumulation in the center of the glass, which seriously affects the appearance of the lighting roof.

4. The cracked tempered glass of double tempered laminated glass has the danger of self-exposure. When the panel is large (such as more than 2.5m2), if one piece of glass bursts, another piece of glass may burst, and the whole may fall off, which is a great danger. In the lighting roof, when using oversized plates and thin double tempered laminated glass, structural measures should also be taken to prevent the glass from falling as a whole.

5. Glass beam single-glued laminated glass is a structure. Once one piece of glass is self-exposed, the remaining part should be a structure. Therefore, at least three layers of glass should be used for lamination. The glass beam is a laminated glass with structural function. Therefore, at least three layers of glass are required. The glass structure of the Apple store is basically a four-piece glass laminated glass.

6. The angle of the canopy is too small. At least 3% of the drainage slope should be at least 3% of the drainage roof. The canopy should be larger, otherwise it will be easier to accumulate and accumulate water.

7. Setting of no drainage ditch The canopy is a “face” project, and organized drainage should be carried out. Generally, a drainage ditch should be arranged on the side close to the main structure, and organized water guiding should be carried out.

8. The canopy is resistant to negative wind pressure. The load on the canopy is quite complicated. The current standard has very little regulation on it. It is generally considered that the downward direction is unfavorable in all load combinations. However, in some complicated environments, it is possible that the negative wind pressure (upward load) plays a controlling role. At this time, the conventionally designed connecting rod has the possibility of being pressed, and the pressing rod is unstable.

9. Symmetrical structure The "watermelon skin" structure, which is commonly used for asymmetric force, is a symmetrical structure. If an incompletely symmetric load is applied to some of the bars, the system will undergo asymmetric deformation and sealant tearing. Severe conditions lead to water leakage at the top of the light.

Second, point-supported curtain wall and all-glass curtain wall

1. Cable structure does not use tension protector Usually adopts point curtain wall to realize the connection between different foundation buildings, forming a continuous aesthetic concept; in recent years, the application of single-layer cable net structure has gradually become widespread. The axial stiffness of the cable in this type of structure is large. If the structure or the bearing is displaced greatly, the internal force will increase greatly, and even the cable will be broken. Therefore, it is necessary to use a protector (spring compensator). Compensation, in order to absorb the deformation of the bearing under normal conditions; in extreme conditions such as earthquakes, if the deformation is large, the preset components in the protector can be broken, but still play a role to ensure that the system does not collapse and collapse. Has residual strength.

2. Large-span roofing and facade curtain walls do not use flexible joints. Large-span roofing may cause large deformation. Generally, the general structure cannot meet the requirements. Generally, the following schemes are available:

(1) Adopting the force transmission and absorption deformation of the link mechanism, and sealing with the rubber rubber plate; (2) using the long round hole, but the adjustment amount is limited.

3. Thermal bridge problem of support points The four-corner support and the support of the side points are the main force-transmitting members of the point-supporting curtain wall, and also the thermal bridge of such curtain wall. If the treatment is improper, dew condensation will occur, and structural measures should be taken to avoid it. .

4. Glass rib and panel quilting This design method puts the glass ribs and the weak parts of the panel on the same plane, which is more prone to problems. If they are staggered, they can compensate each other. And the number of bolts spliced ​​by the glass ribs is preferably two at each end, and more than two may cause other problems.

5. The glass ribs for the support are not supported by the glass ribs. The glass ribs are structural members. At present, there is not much experience accumulated. In GB/T21086-2007 "Building Curtain Wall", the glass rib deflection limit requirements are not given. However, in practical applications, there is often a design in which the glass ribs are not laminated, and as the glass structure, it is necessary to have reliability, so laminated glass must be used. In the lighting roof, that is, the glass beam is also a difficult point in the design of the lighting roof. In the “Technical Regulations for the Lighting Roof and Metal Roofing Engineering” that has been approved, the glass beam is not specified. The curtain wall design should be cautious.

6. The supporting structure of the supporting structure building curtain wall with large difference between positive and negative wind pressure bearing capacity should be able to withstand positive and negative wind pressure. Some structures may have better bearing capacity in positive pressure direction and poor negative wind pressure direction. Avoid using it, especially in areas where negative wind pressure controls. If a pre-stressed method is used to obtain a reliable structural system, it should be checked regularly to avoid safety problems.

7. Planar trusses without plane support Large-span plane trusses have many applications in curtain walls. For these structures, lateral instability check should be carried out. If necessary, lateral support should be added to avoid lateral instability and improve structural reliability.

8. Gravity cable missing gravity cable has more applications in point support curtain wall. In recent years, the design tends to abolish the gravity cable, which is a misunderstanding. Some structures use gravity cables, which not only meet the force transmission requirements of the system, but also are used to fix the position of the panel and reduce the bending moment of the panel near the connection point, thereby improving the reliability of the system.

9. The lateral ribs of the glass ribs are unstable and laterally unstable. For the projects with large spans, structural measures should be taken to strengthen and avoid instability.

10. Unreasonable hanging height Hanging glass is a reasonable structure for the transmission of glass gravity, so general engineering can be used, but it will bring about cost improvement. According to the provisions of GB50210, when the height of the glass exceeds 4m, the hanging structure is adopted, which is too harsh.

11. When the hanging glass gravity transmission is unreasonable, the lower part should be suspended, so that the absorption glass may be elongated or shortened due to the structure, temperature, etc., and the pad may not be used for padding.

12. Hanging the whole glass curtain wall The lower sealing wall does not transmit the force. The full glass curtain wall mainly transmits the load on the panel and the glass rib. Therefore, the upper and lower ends of the glass rib should be fixed, and the large-surface glass should also have corresponding structure treatment to transfer the horizontal load.

Third, the glass curtain wall

The glass curtain wall is a widely used exterior wall system. The dominant position in the exterior wall of the building cannot be shaken, and many fine projects have appeared.

1. The fluorocarbon coating is directly bonded to the structural adhesive. Some structural sealant and fluorocarbon coatings do not meet the requirements of the curtain wall. Therefore, between the sub-frame and the glass of the hidden frame curtain wall glass assembly, the fluorocarbon coating The sealing of the indirect seam part of the panel shall take measures to improve the adhesion. There are a variety of options to choose from: (a) Priming, and then injecting structural adhesives, but some experts believe that this method is not reliable, is a "two-layer skin", and there is no convincing positive report. This method is indeed effective, so further observation and research are needed; (b) using a composite profile structure, directly bonding the structural adhesive portion to the other portions of the profile, and directly bonding the structural adhesive portion to anodizing; (c) fluorocarbon During the spraying process, the part to be bonded is shielded, and the surface is still anodized; (d) Remedial measures are taken to remove the coating of the surface to be bonded with sandpaper or the like, by natural oxidation (about 5 μm).

2. Self-tapping screw connection The self-tapping screw connection is a general connection or a positioning connection, and as a structural connection, its reliability is poor.

3. Steel and aluminum profiles mixed (aluminum-clad steel)

The inner surface of the square steel pipe is not easy to be shot blasting, and the quality problem is easy to occur when hot galvanizing, resulting in low corrosion resistance; the steel and aluminum fit clearance should be tight, otherwise it will not reach the common force, which will prevent the bimetal electrochemical corrosion. .

4. The short-pressed cover frame curtain wall is crimped by gland. On the one hand, it is easy to realize the isostatic chamber, on the other hand, it can be engaged with the buckle cover. The use of a discontinuous gland (short gland), although it can reduce the cost, there will be problems such as uneven glass and the formation of an equal pressure chamber.

5. The connection between the beams and columns is connected by two points.

Curtain wall beams often have the phenomenon of “squeezing the head”. The reasons may be: (1) the bearing capacity of the beam does not meet the requirements; (2) the connection between the beam and the column is relatively weak, for example, the connecting piece between the beam columns uses two bolts (nail The connection, due to its poor torsional performance, causes the curtain wall beam to twist.

6. Large section decorative strip without dripping line There will be dust on the upper surface of the large section decorative strip. If no drip line is set, it will cause more flow marks on the surface of the curtain wall. If a drip line is placed at the front end of the decorative strip, it can effectively prevent the water and dust from mixing to the surface of the curtain wall.

7. The decorative cover and the live bayonet fitting decorative cover should be connected with the bayonet of the extruded profile. The bayonet has a fixed size and high precision, and can realize a reliable connection. The accuracy of the bayonet formed by the screw connection is not satisfactory, and the connection is not reliable.

8. The open cavity is not provided with hot-tight wire heat-tight wire. It has a wide application in the design of energy-saving aluminum alloy window, but it is less applied in the opening cavity of the building curtain wall, resulting in low energy-saving effect of the opening part of the curtain wall.

9. The hidden frame curtain wall adopts the non-fixed platen hidden frame curtain wall and the semi-hidden frame curtain wall. The pressure plate (clamping block) is usually used to transmit force. The spacing is generally not more than 300mm, and there are two kinds of fixed distance and non-fixed distance pressure plate. After the fixing plate is fastened by the connecting bolt, the crimping gap is relatively fixed, and the pressing force of the glass panel sub-frame is relatively uniform, which is convenient for absorbing structural and temperature deformation, reducing friction noise, and avoiding uneven pressing of the pressing block. Causes image distortion of the glass panel.

10. False frame hidden frame is not designed according to the hidden frame curtain wall. The false frame is usually installed at the joint of the hidden frame curtain wall to play the decorative effect of the framed curtain wall. This structure should be designed with the design method of hidden frame curtain wall to design hollow glass and structural adhesive, that is, the second sealant should be sealed with silicone structural adhesive. If polysulfide rubber is used as the second seal of the insulating glass, although it is not necessarily destroyed by ultraviolet radiation, there are still unsafe factors.

11. The hollow glass structural adhesive in the lower part of the glass in the hidden frame is subjected to the shearing force for a long time, which is unfavorable to the service life of the structural adhesive. Therefore, it is required to set the supporting plate in the lower part of the glass in JGJ02. The bracket and the beam are directly connected directly, and can be designed as a snap or bolt connection; the use of the bolt and the sub-frame connection of the glass component may affect the injection of the structural adhesive, and there is a quality defect, and it is recommended to use it with caution.

12. The heat-insulating strip is subjected to the shearing heat-insulating strip, which plays the role of structural transmission force and heat transfer in the heat-insulating profile, and is widely used by the curtain wall profile. In the form of a strip-type structure, the composite strip is used to forcibly press the heat-insulating strip and the aluminum alloy profile. Therefore, there is a cold work hardening phenomenon at the pressing portion of the heat insulating strip and the aluminum alloy profile, and there are even some micro crack defects. If the beam of the curtain wall is made of heat-insulating profiles, structural measures shall be taken to prevent the heat-insulating strip from being subjected to shearing force and to prevent damage to the joint between the heat-insulating strip and the aluminum alloy profile. Generally, the pallet weight or the aluminum alloy profile on the stronger side is used to bear the weight of the glass.

13. Hook-type opening fan joints are not designed to be off-handed. The curtain wall opening window usually adopts the upper hanging structure. However, due to the design flaws, the fan phenomenon often occurs in the project, and the probability of falling in individual closed projects is higher. The main reason is that these projects do not have anti-offset design, or the hook-proof design is unreasonable, or the hooking depth of the hook is not enough, or the wall thickness of the hook is too thin.

14. The obtuse angle part is not arc-type crimping. The traditional fixed-position pressure plate can not meet the needs of crimping, and the angle-adjustable connection structure should be adopted.

15. When designing the invariable glass slot profile, consider the operability during construction. The variable slot can be fine-tuned and easy to install, so the fixed glass slot is not used as much as possible.

16. Slotted small unit horizontal infinite small unit panel mounting form is widely used, its plugging depth should meet the requirements, there is a fan accident in the project, for the small joint unit, because there is no sealant positioning, should Take structural measures to locate, otherwise the inter-frame fan connection may be invalid, and there is a safety hazard.

17. Insulating glass two-way sealant with leaking edge is not used. The insulating glass of the insulating glass should be sealed with two-way sealant. The two sealants of hidden frame, semi-concealed frame, false frame and point supporting hollow glass panel should be used. The silicone structural seal is sealed so as to reliably transmit force and improve the ultraviolet radiation resistance of the insulating glass, and the width should be determined by structural calculation. The polysulfide rubber has poor ultraviolet radiation resistance, so the hollow glass which is sealed by the polysulfide rubber can not be used for the above hollow glass. In some projects, due to the use of polysulfide rubber as the second sealing material, large-scale external glass falling occurs, which has become a serious safety hazard for curtain wall engineering.

18. Insulating glass size Insulating glass is made of large and small pieces. It has some advantages in some applications. In particular, it can provide more space for the design of the profile, but there are also many shortcomings: (1) Inconvenient to use mechanical injection; (2) The transmission path is unreasonable, and may even lead to relative displacement between the glass, which leads to the failure of the hollow glass leakage; (3) there are some structural large pieces of insulating glass inter-layer parts that are not used structural glue. There are also some controversies about the calculation of large and small pieces, mainly in terms of load distribution, and more attention should be paid to the design.

19. Open the fan hollow glass "big cap"

The "big cap" is an extreme form of large and small hollow glass, which is used in the design of some open fans. Once the large glass breaks, the small glass will lose its connection and fall off.

20. The hollow glass hollow layer is unreasonable, and there is a large area of ​​insulating glass, such as patching and interference. The adsorption phenomenon may occur due to the 9mm hollow layer. Therefore, the size of the hollow layer should be comprehensively determined according to the structural requirements and thermal requirements.

21. Tempered glass matte After the frosted tempered glass, the stress distribution on the glass surface is destroyed before and after tempering, and the self-exposure of the glass is easily induced. The frost-treated point supports the glass to be more dangerous. Short-length glass should not be used for short-length bearings.

22. The bending strength of the glass forcibly mounted glass will decrease over time, because the microcracks on the glass surface will continue to expand, so the curtain wall should be designed to work in a free state. However, in actual engineering, there is indeed glass working under unnecessary long-term loads, such as forced installation, crimp sealing, and the like. A project in Beijing uses a crimped seal structure, and the probability of glass breakage is high, which is worth learning.

23. Unreasonable design of deformation joints is a difficult point. Architects cannot accept the design principle that some components or panels can be destroyed after deformation. Therefore, the deformation joints should be able to absorb deformation (including the deformation of the supporting structure, load, temperature effect). And earthquakes), and can not reduce the physical properties of the site, such as air tightness, water tightness, wind pressure and insulation properties.

24. No window cleaning machine connection design Building cleaning requires a window cleaning machine, but unfortunately many of the engineering window cleaning machines do not really play a role, on the one hand may be management problems, after all, please professional team cleaning the curtain wall is more trouble-free On the other hand, there is a certain risk in the window cleaning machine, especially when the wind is relatively large, it cannot be fixed relative to the curtain wall, that is, there is no window cleaning machine connection design. In China, relying on the former curtain wall project Great Wall Hotel, there is a longer dovetail slot for window cleaning machine, which is safe and convenient.

25. Floor-standing curtain wall slab below 800mm does not use laminated glass "General Rules for Civil Building Design" GB50352 and "Residential Design Specification" GB50096 for the provision of railings on the window, for the curtain wall, generally set at 800mm position The laminated glass between the beam and the floor can be examined.