Fire protection of steel structure building
The fire protection measures of steel structure buildings are divided into active fire protection and passive fire protection. Active fire protection mainly refers to the active fire suppression measures combined with fire detection, and changes the behavior of the fire scene, such as sprinklers and firefighters' fire fighting behavior; passive fire protection mainly refers to the adoption of reasonable measures in structural design and structural measures to improve the structure Fire resistance does not change the fire scene. Mainly introduce passive fire protection, passive fire protection is mainly divided into the following 5 categories:
1) Fire prevention by wrapping method
The coating method is mainly to wrap the steel structure as a whole with solid refractory materials. The solid refractory material not only has non-combustibility, but also has a large heat capacity. Using it as a refractory protective layer can slow down the heating of the component. At present, inorganic fireproof boards are generally used in engineering, such as calcium silicate board, gypsum board, vermiculite board, etc. This method is mainly used in beams, columns and other components with regular shapes, pharmaceutical workshops with high requirements for the cleanliness of falling ash, and low- and multi-layer light steel structure houses.
2) Fire protection by spraying method
The so-called spraying method is to apply a layer of fireproof paint on the surface of the steel structure, and then form a protective film on the steel structure, using the fireproof property of the material itself or the dense thermal insulation and thermal insulation protective layer produced by foaming to delay The temperature rise time of steel structure improves the fire resistance limit of steel structure components.
According to different methods, the classification of fireproof coatings is shown in Figure 8 below. In engineering development and application, it is mainly divided into thick-coated fire-retardant coatings, thin-coated fire-retardant coatings and ultra-thin fire-retardant coatings according to coating thickness.
3) Shielding method for fire protection
The shielding method is usually used for the fire protection of steel roofs, and the fire-resistant ceiling under the roof is used to delay the temperature rise of the steel roof caused by the lower fire. The shielding method is expensive, occupies a large building space, and because of problems such as fire at the joints, there are not many engineering applications.
4) Fire prevention by water-filled cooling method
The water-filled cooling of the steel structure is to fill the hollow closed column with water. When a fire occurs, the component will transfer the heat absorbed from the fire to the water in the column, so that the temperature of the component can be maintained to about 100°C. This is an ideal fire protection method in theory, but in practice, due to the use of fewer pipe structures and the high cost of the circulation system, issues such as rust and freeze prevention must be considered, so it is rarely used in practice.
5) Refractory steel
Refractory steel is made by adding alloying elements such as molybdenum to structural steel, so that the steel can maintain high strength within the specified refractory time. It can reach the fire resistance of fire-resistant grade 4 beams without coating. In other cases, fire-resistant coatings and other fire-resistant measures are required, but the thickness of the fire-resistant coating can be greatly reduced and the cost of fire protection can be reduced. The National Grand Theater has successfully applied the refractory steel produced by Wuhan Iron and Steel, which not only guarantees fire safety, but also realizes the architect's pursuit of beauty.