Steel is usually at a temperature of 450 ~ 650 in the carrying capacity will be lost, the occurrence of large deformation, resulting in the steel columns, steel beams bent, because the result is too large deformation and can not continue to use, generally without fire protection of steel structures limit of about 15 minutes. This length of time with the member also endothermic speed.
Steel is a building material will not burn, it has a seismic, bending and other features. In practice, the relative increase in both steel load capacity of the building, but also meet the needs of architectural design aesthetic style, but also to avoid the concrete and other building materials can not be bent, stretched defects, so the steel construction industry has been favored, single-layer, multi-layer, skyscrapers, factories, warehouses, waiting rooms, lounges and other uses of steel are common. However, the steel as a building material and there are some unavoidable deficiencies in fire protection, its mechanical properties, such as porosity, temperature increases due to a sharp decline in the yield point, tensile strength and elastic modulus.
For Steel Materials overcome deficiencies in the practical application of fire prevention, fire protection must be treated, and its purpose is to improve the fire resistance of steel to design specification limits. Steel prevent rapid warming in the fire deformed slump, its measures are varied, the key is to take different approaches under different circumstances, such as the use of insulation, refractory steel barrier direct flame burning, reduce the speed of heat transfer delayed steel temperature, strength becomes weak time. But no matter what method adopted, the principle is the same. Here are several different fire protection of steel structures.
First, the outer cladding. Is added in the steel outer cladding, cast molding can be applied by spraying. Cast concrete cladding forming entities generally or reinforced with steel mesh to strengthen, to limit shrinkage cracks, and to ensure the strength of the housing. Spray can at the construction site on the steel surface to form a protective layer coated sand pump, sand pump can be lime or cement plaster mortar, perlite or asbestos may also be incorporated. Meanwhile cladding can also use perlite, asbestos, gypsum or asbestos cement, made of lightweight concrete panels, the use of adhesives, nails, bolted to the steel.
Second, filling water (water jacket). Water-filled hollow steel structure is most effective against fire protection measures. This method enables the steel to maintain a relatively low temperature in the fire, the water circulating in the steel structure, the absorbent material itself heated heat. After cooling the heated water can be recycled, or by the introduction of cold water pipes to replace the heated water.
Third, the shield. Steel is set in the wall or ceiling refractory composition, or the components concealed in the space between the two walls, as long as a slight increase or no increase refractories that can achieve the purpose of fire protection. This is one of the most economical method of fire.
Fourth, the expansion of the material. Using fireproof coatings protect components, this method has good fireproof insulation, steel construction without geometric restrictions, etc., generally do not need to add auxiliary facilities, and light coating quality, as well as some beautiful decorative effect, belongs to the modern advanced fire technical measures.
Currently, high-rise steel buildings is increasing, especially in some high-rise buildings, the use of steel material more widely. Once a high-rise building fire accident, the fire could not be extinguished in a short time, which requires us to architectural design, building materials to increase fire protection, in order to enhance its fire resistance, and to develop the necessary emergency inside the building programs to reduce casualties and property losses.