Building fire protection is an important issue in architectural design. The requirements of building fire partitions and fire partitions often make architects in a dilemma between building decoration effects and building fire protection. The emergence of fireproof glass has solved this problem, and fireproof glass curtain wall and fireproof glass partition are widely used in more and more buildings. Fire-resistant glass curtain walls are widely used in the building's closed refuge floors, closed evacuation stairs (such as Shanghai Grand Theater, Hong Kong HSBC Bank), and the partition needs of large-scale venues' building fire protection zones (such as Guangdong Olympic Stadium, Nanning Convention and Exhibition, etc.). Partition with fireproof glass. Fireproof glass curtain wall and fireproof glass partition are building components with a certain fire resistance limit, which are used to control and prevent fire from spreading to other parts of the same building vertically or horizontally. However, as a special fire protection product, if its design and material selection are improper, it may not be able to form a real fire partition and achieve the purpose of reducing fire losses.
1. Fire protection of fireproof glass curtain wall and fireproof glass partition
Building fire protection is mainly composed of passive fire protection system and active fire protection system, while taking into account the safety evacuation requirements of people in the building. Passive fire protection is mainly based on the basic principle of combustion, taking measures to prevent the occurrence of burning conditions or weaken the development of burning conditions, and prevent the spread of fire. Such as setting up firewalls, etc.; the active fire prevention system mainly takes measures to detect fires as early as possible, destroy the formed combustion conditions, extinguish or control the fire within a certain range, and reduce fire losses, such as setting up automatic fire alarms, fire extinguishing facilities and smoke prevention and exhaust systems. Wait.
Fireproof glass curtain wall and fireproof glass partition belong to passive fire protection system, and its main function is to prevent the spread of fire. There are four ways of building fire spread, including flame spread, heat conduction, heat convection and heat radiation, which are accompanied by the spread of smoke. Except the first way is that the flame spreads the fire by directly igniting the combustible material, the latter three ways all use different heat transfer processes to ignite the combustible material to cause the fire to spread. Therefore, the design of fireproof glass curtain wall and fireproof partition is focused on how to prevent the spread of fire.
According to relevant codes, the fire resistance rating of a building is to ensure that the building will not collapse in a short period of time in a fire. Fireproof glass curtain walls and partitions are part of the building, and their function is to ensure that they remain intact for a certain period of time after a fire occurs, that is, fire resistance. Therefore, the selection of its fire resistance rating during design should be determined according to the fire resistance rating of the building where it is located and the fire protection requirements of the part of the building where it is located.
2. Functional requirements of glass curtain wall and fireproof glass partition
According to the way the fire spreads in the building and the function of the fireproof glass curtain wall and the fireproof glass partition, it should have the following basic characteristics:
2.1 Smoke-proof. That is, when a fire occurs, it can prevent the smoke generated by the fire from passing from the side that is exposed to the fire to the side that is behind the fire. This is the most basic requirement. Reasonably and effectively blocking the flue gas generated by the fire and avoiding the formation of the chimney effect is the basis for controlling the spread of the fire and ensuring that the evacuation channel is unblocked or the refuge is effective.
2.2 Fire integrity. That is, in the event of a fire, when one side is exposed to fire, it can prevent the flame from penetrating or prevent the flame from appearing on the back fire side for a certain period of time. According to the design requirements of building fire protection, the fire glass curtain wall or fire partition should have good integrity. If there is a burn and collapse, or the fire fails to meet the requirements of the fire prevention time limit, the fire will spread, and the purpose of reducing fire losses cannot be achieved.
2.3 Fire resistance and heat insulation. That is, in the event of a fire, when one side is exposed to fire, the temperature of the back fire surface can rise within a certain period of time so as not to ignite the items in the back fire area. If the smoke isolation is satisfied, the integrity is ensured, but because the heat generated by the fire passes through the fireproof glass, a large amount of thermal radiation causes the flammable materials on the back fire side to burn, and it does not play a role in fire prevention.
3. Design of fireproof glass curtain wall and fireproof glass partition
Fireproof glass curtain wall is first and foremost a curtain wall, and it must have all the characteristics of a curtain wall. Such as wind pressure, rain, air leakage, in-plane deformation and other properties. The design requirements of these aspects have been clearly specified in the JGJ102 specification, and will not be repeated here. As a glass curtain wall with fire protection function, in addition to the above functions, the more important thing is the function of fire protection. Similarly, the design of fireproof glass partitions should first consider the safety of its own structure, and then consider the requirements of fire protection.
3.1 Smoke barrier design
In order to achieve the effect of smoke isolation, the structure of the curtain wall must first have good sealing, not only the sealing mentioned in the performance of our curtain wall, but also the sealing of fire, which must be better within a certain period of time when a fire occurs. sealing effect. Therefore, the open-frame curtain wall and unitized curtain wall structure with open system design is not suitable for the structure of fireproof glass curtain wall. Compared with the sealing design of ordinary curtain walls, two points should be paid attention to: First, the inner cavity of the profiles is sealed. In the design of ordinary curtain walls, the vertical materials are connected by plugging, which has the possibility of forming a chimney effect. When designing a fireproof glass curtain wall, it must be Seal the cavity with flame retardant material. On the other hand, it is necessary to consider the sealing failure caused by the local thermal expansion and deformation of the curtain wall when a fire occurs. Therefore, waist-shaped holes must be used in the connection parts of the skeleton, and sealants with good elasticity and fire resistance are used in the selection of sealing materials.
3.2 Refractory integrity design.
The curtain wall or partition should not collapse or collapse within the designed fire resistance time limit when a fire occurs, that is, the selected curtain wall or partition structure and material must have fire resistance. Therefore, the first consideration in the fire-resistant integrity design is the connection between the curtain wall or partition and the main body, and the second is the selection of materials.
3.2.1 The fireproof glass curtain wall and fireproof partition shall be complete and independent. Fireproof glass curtain wall, as the outer protective structure of the building, its function is to prevent the fire from spreading vertically. It is often just a piece or part of a curtain wall. In order to prevent it from collapsing in a fire, the skeleton structure should be completely separated from the curtain wall of the connected part and fully fixed with the main structure. If the conventional curtain wall plug connection is used, the fireproof part will fail due to the collapse of the non-fireproof part when it catches fire. The same is true for fire partitions. Independence and integrity are the basis for satisfying fire resistance.
3.2.2 Fireproof glass curtain wall and fireproof glass partition structure should have better ability to absorb thermal deformation. When a fire occurs, the metal skeleton of the curtain wall or partition will expand due to thermal expansion. If it is not handled properly, the structure will be damaged due to expansion and extrusion, and the fire prevention effect will not be achieved. Therefore, in the design, the use of long waist holes or other reserved deformation positions for the connection parts is a key issue to be considered in details. Figures 2 and 3 are the vertical connection nodes of the fireproof glass curtain wall. The upper part of the vertical material is opened with a round hole, and the lower part is opened with a vertical waist hole.
3.2.3 The material of fireproof glass curtain wall and fireproof glass partition must have fire resistance. When a fire occurs, the average temperature of the flame within 10 minutes after the fire is generally about 700°C; within 20 minutes after the fire, the flame temperature is generally about 800°C; within 30 minutes after the fire, the average flame temperature is about 840°C; within 1 hour, it can reach 925°C about. According to the fire resistance time limit of the building for the fireproof curtain wall or partition, the selection of appropriate fireproof materials is the basis to achieve the unity of function and economy. The skeleton materials of curtain walls or partitions are mostly aluminum profiles and steel profiles, but the melting point of aluminum is about 400°C. Under the action of high temperature of fire, the mechanical properties of steel such as yield strength and elastic modulus will decrease with the increase of temperature. , when the temperature is around 550℃, the reduction is more obvious, and generally it will lose its load-bearing capacity and collapse in about 15min. It can be seen that if the fire prevention treatment is not carried out, the fire will be destroyed within 15 minutes. Therefore, as the skeleton material of fireproof glass curtain wall and partition, fireproof treatment is required. Glass, as the main material of fireproof glass curtain wall and partition, naturally chooses fireproof glass. At present, there are many types of fireproof glass, and the selection should comprehensively consider the architectural decoration effect, strength, fire resistance limit and other aspects. The fire resistance of the connection part is the basis of the integrity of the whole system, and the embedded parts and connecting parts at the connection part should be provided with a fire protection layer.
4. Fireproof glass and its use
Fire-resistant glass is a special glass that can maintain its integrity and thermal insulation in the prescribed fire-resistance test, and is divided into three categories according to current specifications:
Class A fire-resistant glass: fire-resistant glass that meets the requirements of fire-resistant integrity and fire-resistant heat insulation at the same time. This kind of glass has the properties of light transmission, fire prevention (smoke insulation, fire insulation, heat radiation shielding), sound insulation and impact resistance. , see-through floors and other building components that require both transparency and fire resistance.
Class B fire-resistant glass: fire-resistant glass that meets the requirements of fire-resistant integrity and thermal radiation intensity at the same time.
Class C fire-resistant glass: fire-resistant glass that only meets the requirements of fire-resistant integrity. This kind of glass has the characteristics of light transmission, fire resistance and high strength. It is suitable for fireproof glass partition walls, fireproof windows, outdoor curtain walls, etc. without thermal insulation requirements. In terms of structure, fireproof glass is divided into composite fireproof glass and single-piece fireproof glass.
4.1 Composite fireproof glass. It is a kind of special colorless and transparent refractory chemical substance that can be foamed and expanded in case of fire is poured between two pieces of transparent laminated glass, and it is made after hardening. Composite glass can be made into Class A or Class B fireproof glass depending on the infusion chemical. When a fire occurs, the special transparent chemical substance poured and cured in the middle of the heat-resistant radiation type composite fireproof glass absorbs a large amount of heat in the flame, foams and expands, and at the same time becomes white when opaque, thereby preventing the flame of the glass facing the fire. The heat radiation is transferred to the back fire side, and to a certain extent, the heat transfer to the back fire side by the fire side is reduced. The glass remains intact during this process, forming a barrier that blocks the spread and spread of flames, smoke, and toxic gases from combustion. The composite fireproof glass will turn milky white and produce bubbles under long-term ultraviolet irradiation, and lose the transparent function of the glass. Therefore, it is not suitable for use on external walls, but it is used in fire partitions with fire resistance and heat insulation requirements and heat radiation protection requirements.
5.2 Monolithic fireproof glass. It is a kind of glass with fire-resistant integrity obtained by special treatment of float glass through physical and chemical methods. It belongs to Class C fire-resistant glass. The fire prevention principle of single-piece fireproof glass: in the early stage of the fire, a large temperature difference will be formed between the fire-facing surface and the back-fire surface of the single-piece glass partition. The uneven thermal stress causes the glass to burst and shatter and lose its integrity. Therefore, reducing the temperature difference between the two sides of the glass or increasing its ability to resist thermal stress is the basic way to improve its fire resistance. At present, the single-piece cesium-potassium fireproof glass produced in China can keep 84~183min without bursting under the flame impact of 1000℃, and under the same thickness, its strength is 6~12 times that of float glass; it is 1.5~12 times that of tempered glass. 3 times. It also has good processability, and can be processed into laminated safety glass, insulating glass, coated glass and point-type curtain wall glass. Therefore, monolithic fireproof glass has been more widely used.
5. Fire resistance of fireproof glass curtain wall and fireproof glass partition
The selection of fire resistance grade of fireproof glass curtain wall or partition is determined by the fire protection requirements of the building where it is located, but whether the design can meet the requirements of its fire resistance grade depends on the fire resistance performance of the selected materials on the one hand, and the curtain wall or on the other hand. partitioned structure. Structural problems are not difficult to find according to the design drawings, but the selection of materials cannot be ignored. Because the fire performance of many materials is currently in accordance with the relevant specifications, the results of the test under certain preconditions, the fire performance in the product manual may not be able to achieve the working conditions in the actual use process.
Performance testing: For example, according to the standard of "Safety Glass for Construction - Fireproof Glass" (GB 15763.1-2001), the minimum size of the test sample is 1100mm×600mm. When testing the fire resistance of the product, the test is carried out according to the minimum size, and the fire resistance time is 100min, but it may be 80min when it is larger than this size. Because fire-resistant glass is a rigid and brittle material, its fire-resistance performance depends largely on the size of the glass. The larger the size, the lower the fire resistance. Therefore, for fireproof glass, the fireproof glass whose specifications are smaller than the sample in actual use can be considered to meet the results of the test report. The sample of the same size or larger size of the component can be determined by re-testing.
Strictly speaking, for fireproof glass curtain wall and fireproof glass partition system with large area and high fire resistance performance level, representative design units should be selected for fire resistance performance test to ensure that fire protection requirements are met.
Fireproof glass curtain wall and fireproof glass partition are used by more and more buildings as a new building fire protection product, but there is no special specification and standard for the design inspection of such products. The author believes that the following three aspects should be paid attention to in the design: 1. The design of fireproof glass curtain wall and partition is not simply to change the non-refractory material used in the curtain wall or partition to refractory material, let alone ordinary glass. Switch to fireproof glass and you're all set, but consider it as a fireproof system. 2. The fire resistance level that can be achieved by fire-resistant glass curtain walls and partitions can only be determined by comprehensively considering the fire resistance level of various factors of the entire system. Subjective speculation may make mistakes, and testing tests are required to determine if necessary. 3. When designing and selecting fire-resistant glass, it is necessary to pay attention to the corresponding relationship between the size of the glass plate and the fire-resistant performance level.
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