ATTEN: Manager Liu
ADD: Longhua Development Zone, Jing County, Hengshui City, Hebei Province
Steel is a non-combustible building material, which has the characteristics of anti-seismic, anti-ligusticum and so on. In practical application, steel can not only increase the j-load capacity of buildings, but also meet the needs of architectural design aesthetic modeling. It also avoids that concrete and other building materials can not bend and stretch, which is favored by the construction industry. Steel is widely used in single-storey, multi-storey, skyscraper, workshop, warehouse, waiting room, waiting room and so on. But steel as building material has some unavoidable defects in fire prevention. Its mechanical properties, such as yield point, tensile strength and modulus of elasticity, will drop sharply due to the increase of temperature. Steel structures usually lose their bearing capacity in the temperature range of 450 to 650 degrees Celsius, and undergo great deformation, which leads to the bending of steel columns and beams. As a result, excessive deformation can not continue. Usually, the fire resistance limit of unprotected steel structure is about 15 minutes. The length of this time is also related to the speed of heat absorption. In order to overcome the shortcomings of fire prevention in practical application of steel-bonded truss materials, fire prevention treatment must be carried out. The purpose is to raise the limit of fire prevention of steel structures to the limit specified in the design code.
In order to prevent the steel bond from deforming in the fire, various measures should be taken. The key is to adopt different methods according to different situations, such as using insulation and refractory to directly burn steel structure in the flame, reducing the speed of heat transfer, delaying the time of temperature rise and strength weakening of steel structure, etc. But no matter what method is adopted, the principle is the same. Therefore, the author believes that in reality, four kinds of steel structure fire protection measures must be paid attention to. Outsourcing layer. As the name implies, the steel structure can be cast in situ or sprayed by adding an outer layer. In order to limit shrinkage cracks and ensure the strength of the shell, the cast-in-situ solid concrete outer layer is usually strengthened by steel wire mesh or reinforcing bar. Spraying method can be used to coat the steel structure surface with mortar to form a protective layer. The mortar can be lime cement or gypsum mortar, or can be mixed with perlite or asbestos. At the same time, the outer layer can also be made of perlite, asbestos, gypsum or asbestos cement, light concrete into prefabricated panels, using adhesives, nails, bolts fixed on the steel structure.
Water jacket. Water filling in hollow steel structure is the most effective protection against fire. This method can keep the steel structure at a lower temperature in the fire, circulate water in the steel structure, and absorb the heat of the material itself. Heated water can be recirculated after cooling or cooled water can be introduced into pipes to replace screen acid. Steel-bonded trusses are arranged in walls or shacks composed of refractory materials or enclosed in hollow walls between two walls, so long as a little refractory material is added or not increased, the purpose of fire prevention can be achieved. This is one of the most economical fire-proof materials. Steel-bonded fire-retardant coatings are used to protect trusses. This method has the advantages of good fire-retardant latent heat performance, construction is not restricted by the geometric shape of steel-bonded trusses. Generally, auxiliary facilities are not needed, and the quality of coatings is light, and there is a certain aesthetic decorative effect. It belongs to modern advanced fire-retardant technical measures. At present, there are more and more high-rise steel-bonded truss buildings. Especially in one high-rise building, steel-bonded truss accidents are used. Fire can not be extinguished in a short time. This requires us to increase the fire protection of building materials in architectural design, in order to enhance their endurance limit, and formulate the necessary emergency plan inside the building, so as to reduce personnel. Casualties and property losses.