Drainage system design of building curtain wall in

2022-08-18
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Drainage system design of building curtain walls in coastal areas

there must be three conditions for rainwater leakage in curtain walls. The first is water, such as rain. Second, the way of water movement, such as cracks; Third, the power of water movement, such as gravity, kinetic energy, surface tension, capillary action, air flow and pressure difference, of which the pressure difference is the main reason for the leakage of curtain wall joints. For the rainwater leakage caused by the pressure difference, if the indoor pressure is greater than or equal to the outdoor pressure, even if there is a gap, the rainwater will not enter the interior of the curtain wall. The traditional waterproof method is to try to reduce the possible openings at the joints, and use various sealants and rubber strips to plug the contact joints. The modern unit curtain wall uses the isobaric principle to dredge the rainwater and lead the water out of the wall. In order to achieve equal pressure, we open some joints to balance the air pressure of the chamber with the outside. At the same time, the isobaric chamber is not a fully ventilated space, so it must be limited to a certain range, reasonable size and spacing, in order to produce isobaric effect more effectively. Isobaric principle is the core of waterproof design of unit curtain wall. Next, two typical unit curtain wall drainage systems in coastal areas are introduced, which are analyzed in combination with actual engineering cases for your reference only

2 layered drainage

"layered drainage" unit curtain wall system: rainwater is blocked by the first adhesive strip, and a large amount of rainwater will fall due to its own weight. Under a certain pressure, a small amount of rainwater may enter the front chamber, which falls due to its own weight and is discharged from the bottom of the unit plate. Only under a large pressure difference, the rainwater in the front chamber will further cross the second sealant strip and enter the rear chamber. Therefore, the amount of rainwater in the rear chamber is very small. These rainwater entering the rear chamber will also be discharged to the front chamber through the specially designed drainage holes on the aluminum alloy horizontal material under the action of self weight, and finally be completely discharged. Multiple adhesive strips are set between the unit plates of this layered drainage unit curtain wall system, which can completely cut off the rainwater collection line, so that the rainwater can be discharged in blocks according to the unit plates, greatly reducing the possibility of leakage caused by the continuous accumulation of rainwater. At the same time, the connecting screw holes, screw caps and process holes opened on the profiles for the installation of screws on the unit plates are required to be sealed with sealant, Ensure that the plate has good waterproof and sealing performance. The waterproof performance of this layered drainage form unit curtain wall is safe and reliable, and it is widely used in coastal areas

many curtain wall projects, such as Shenzhen Investment Bank building and tower e of China Resources Dayong, are located in the coastal area where typhoons and heavy rains frequently occur, and they are all high-rise and super high-rise buildings. 2. Placing the tested samples on the friction table has high requirements for waterproof performance, and this layered drainage single element curtain wall system is adopted. Three EPDM strips with waterproof function are used for sealing and waterproof treatment between the male and female columns and beams of the unit to form a basic isobaric opening at the front and two complete isobaric cavities at the inner side to effectively prevent rainwater from entering (the system schematic diagram is as follows: Figure 1, figure 2, figure 3, figure 4)

curtain wall projects such as China Resources Dayong e building and investment bank building were completed in 2013 and 2014 respectively. So far, no leakage has been found, and the waterproof effect is very good

advantages and disadvantages of this drainage method: the advantage of this drainage method is that it can discharge the water entering the unit cavity through the beam on each layer of unit plate, so as to ensure that the rainwater can be discharged quickly even when more rainwater enters the cavity; The front end of the layered drainage curtain wall adopts a dust-proof adhesive strip, which can be opened to facilitate and quickly check whether the drainage hole is blocked. The disadvantage is that because of the drainage of each layer, holes need to be opened at the dust-proof adhesive strip, which may lead to dust and debris entering the hole to block the drainage hole and affect the drainage; In addition, after the rainwater is discharged, it is easy to form water marks on the glass surface, affecting the appearance

3 column direct drainage

direct drainage unit curtain wall system: when rainwater passes through the first adhesive strip, a large amount of rainwater will fall due to its own weight. A small amount of rainwater enters the front chamber under a certain pressure, and the rainwater at the front chamber of the beam will also flow to both sides, reaching the position of the column, and the rainwater will fall due to its own weight and converge on the next floor. When a small amount of rain water in the front chamber further crosses the second sealant strip and enters the rear chamber under high pressure, a drainage cavity is set at the front end of the rear chamber of the beam on the curtain wall. When the beam is processed, holes are opened on both sides to the drainage cavity to avoid the horizontal chute position, and the rain water entering the rear chamber is discharged to the drainage cavity through the drainage hole, and then flows to the front chamber of the column on both sides of the beam through the drainage cavity, The rainwater falls to the next unit plate due to its own weight and converges on the next floor. According to this law, this drainage method is repeated for each floor. All rainwater is collected into the front water drainage channel under the lowest unit plate and then discharged outdoors

the height of Shenzhen AVIC business center is more than 200 meters, and the curtain wall is about 50000 square meters. Located in the coastal area with typhoon and heavy rain, the waterproof requirements are high, so this direct drainage system is adopted. Compared with the water covering rubber strip of the layered drainage system, the outermost collision extrusion rubber strip has a strong water blocking function, which can have a strong adsorption capacity for heavy metals cadmium, lead, copper and zinc, and more effectively prevent rainwater and sundries from entering the cavity, with a total thickness of 6mm. Use straight curtain wall system. The sealing form of the front and rear rubber strips is the same as that of the curtain wall of the layered drainage system, but the rainwater collection and dispersion channels are changed. The air tight adhesive strip at the last end and the water tight adhesive strip at the middle layer also play a great role. The front end of this system is also made into a groove shape, which can effectively collect rainwater and drain to the columns on both sides. The unit curtain wall of this drainage method is also used in a building in Guangzhou with a height of more than 500m. The feasibility of this system is verified by practical engineering. Nowadays, this drainage method is also widely used in curtain wall industry. (the system schematic diagram is as follows: Figure 5, Figure 6 and Figure 7)

the Shenzhen AVIC business center project was completed in 2013. So far, no rainwater leakage has occurred, and the watertightness is very good

advantages and disadvantages of this drainage method: the advantage of this unit curtain wall drainage method is that the drainage line only reaches the front end of the column, which can ensure that some curtain walls with appearance requirements can be designed more flexibly to meet the appearance requirements. At the same time, water stains will not be left on the glass surface of the curtain wall during the drainage process, and the surface of the curtain wall is clean. The disadvantage is that because the drainage hole is located in the front of the rear cavity, it is not easy to check the blockage of the drainage outlet, which is not conducive to the inspection of the causes of water leakage of the curtain wall. Therefore, it is required to check whether the drainage hole is blocked before plate assembly and on-site installation

to sum up, through the elaboration of two unit curtain wall drainage methods, the two methods have their own advantages and disadvantages. There are more application projects of layered drainage system, but the direct drainage system is also a mature system. In practical application, it is necessary to compare and select according to the requirements of different projects. Due to appearance restrictions, Binzhou and Zouping can't be arranged in layers, making Binzhou and Zouping the most competitive aluminum deep-processing industrial clusters in China. Direct arrangement is an option. There are restrictions on the profile section. If the width is small, layered drainage can be used

references

[1] Ministry of construction of the people's Republic of China, technical code for glass curtain wall engineering (JGJ), China Construction Industry Press

[2] Zhao Xi'an, architectural curtain wall engineering manual, China Construction Industry Press

[3] Shi Meiying, waterproof and drainage design of unit curtain wall, petrochemical construction

[4] caizhixin, material selection and control, building materials and application of unit curtain wall

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