Matters needing attention in fire protection design of glass curtain wall

time:2020-11-03 17:52:00source:

The glass curtain wall is a maintenance structure for the exterior wall of the building composed of metal components and glass panels. The materials that make up the glass curtain wall mainly include: steel, aluminum alloy, glass, stainless steel and adhesive sealant. In the actual curtain wall design, attention should be paid to the design of fire compartments. Fire zoning refers to dividing the plane and space of the building into several zones in the design by firewalls, fire doors and windows, fire shutters and floors with a certain fire resistance limit. The fire partition includes two parts: the horizontal partition and the vertical partition of the floor. Taking the measure of dividing fire zones in a building can effectively control the fire within a certain range in the event of a fire in the building, prevent the fire from spreading and expand, reduce fire losses, and at the same time, it can evacuate people safely and fire fighting. Provide favorable conditions. The importance of fire zoning has been proven in countless fire lessons.

1. The concept and classification of fire compartments

Fire partitions can be divided into two categories according to the function of preventing fire from expanding and spreading outside the fire partitions:

One is the vertical fire partition, which is used to prevent the vertical fire spread between the layers of multi-storey or high-rise buildings. The vertical fire partition refers to the floor slab and the wall between the windows (including the lower wall of the window) with better fire resistance performance, and the fire separation of each floor is carried out in the vertical direction of the building.

The second is the horizontal fire partition to prevent the fire from expanding and spreading in the horizontal direction. The horizontal fire compartment refers to the fire compartment that separates each floor in the horizontal direction by fire partitions such as firewalls, fire doors, fire shutters, etc. It stops the fire from spreading horizontally on the floor. Fire partitions should be separated by firewalls. If it is really difficult, a fire shutter plus a cooling water curtain or a closed water spray system can be used, or a fire separation water curtain can be used for separation.

From the point of view of fire prevention, the smaller the fire compartment is divided, the better it is to ensure the fire safety of the building. The determination of the size of the fire compartment should take into account factors such as the nature of use of the building, its importance, the risk of fire, the height of the building, the fire fighting capacity, and the speed of fire spread.

2. Vertical fire blocking design

The vertical fire blocking design is the top priority of the curtain wall fire protection design. Depending on the structure of the building, it can be divided into the following situations:

1. When there is a solid window sill wall on the inner side of the curtain wall (the standard requirements include the structural beam plate and the upper flashing height ≥800mm, according to the fire radius, the height should be 1200mm). The following points should be noted in the design of this node:

1.1 Correctly divide the plate

Curtain wall designers should correctly understand the concept of fire partitions. Floor beams and solid window sill walls are the partitions of the upper and lower fire partitions. Therefore, it is unreasonable to divide the fire partitions with window sill walls by the floor level line. , floor beams and the outer edges of solid window sill walls are divided and determined. The glass plate does not pass through the two fire compartments, and it does not contradict the relevant requirements in the specification. Even if the floor glass plate is damaged in the fire, since the upper fire blocking is not damaged, the fire blocking can still play an effective role. barrier effect. It is recommended not to use the plate division model. If this division mode must be adopted for architectural reasons, it is recommended that the glass on the floor should be fire-resistant glass, and the expansion joints of the columns should be set slightly downward to stagger the corner positions of the beams. Or add a fire block above the first beam on the floor to ensure that even if the plate on the floor is damaged, the fire block on the upper road is not damaged, and it can still effectively protect against fire. However, when viewed from indoors, this structure obviously affects the visual effect due to the high height of the window sill.

​1.2 The fireproof layer should be set as far as possible on the lower edge of the bottom of the beam and the ceiling (or flush with the bottom of the beam), and set below the beam of the curtain wall.

The purpose of this is also to protect the embedded parts, steel angle codes, etc. from the fire as much as possible (the bearing capacity of steel will decrease at 300°C-400°C, and the bearing capacity will be lost at 600°C, and the refractory temperature of aluminum profiles is lower. ). If the bearing capacity of the embedded parts and the steel angle code is seriously affected in the fire, the bearing capacity is reduced or even lost. At this time, when the entire curtain wall skeleton falls off, the consequences are extremely serious.

1.3 A smoke-proof seal should be added at the intersection of the upper part of the window sill wall and the curtain wall.

Usually, the curtain wall glass with window sill wall does not use fire-resistant glass. Once the glass is broken, due to the protection of the solid wall (including beams and slabs, etc.), it is usually difficult for the open flame to directly jump to the upper floor. A large amount of toxic fumes will enter the upper floor as the glass breaks. This problem can be basically solved if a smoke-proof seal is added at the intersection of the upper part of the window sill wall and the curtain wall.

1.4 When this structure is adopted, the fireproof layer usually uses a 1.5mm thick steel plate to support the internal fireproof mineral wool.

When designing, it should be noted that the steel plate cannot be in direct contact with the glass of the curtain wall, so as to prevent the steel plate from being heated and expanded during a fire and breaking the glass. However, the distance between the steel plate and the curtain wall glass should not be too large, so as not to be pulled off between the steel plate and the curtain wall glass under the action of negative pressure (due to the increase of indoor temperature during a fire, the indoor pressure is greater than the outdoor pressure, which is also equivalent to the negative pressure on the curtain wall). Open seams are formed, causing the smoke to rise and the fireproof layer to fail to achieve the proper fireproof effect.

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