Because of its large span, large space, fast construction, economic and practical characteristics, steel structure building engineering gradually tends to high-rise buildings, and has been highly favored by modern architects. The quality of steel structure engineering affects the building structure and the safety of use directly, to ensure the construction quality of steel structure engineering, protect people's lives and property security, as project managers, especially the main management supervision of the construction quality of steel structure engineering construction quality control is important. Because of the poor fire resistance of steel structure, the damage to the building caused by fire is serious, so it is very important to carry out fire safety design for steel structure building.
Fire resisting performance of steel structure
The fire resistance of the steel structure depends on the steel, the steel doesn’t burn itself, but also has good heat resistance, but the steel can not resistant to high temperature, with the rise of temperature, the strength of the steel is getting hitched, and the deformation increases at the same time. Within 200 degrees, the performance of the steel has not changed greatly; the performance drops sharply between 430 and 540 degrees of temperature; the performance is very low at 600 degrees and can not bear the load.
Based on the physical properties of steel, when the fire occurs, and the temperature reaches 450 ~ 650 degrees centigrade, the steel structure will lose its bearing capacity, deformation occurs, resulting in steel column and steel beam bending, the result of deformation is too large to continue to work, or even collapse.
Once the high temperature is emerged, the deformation and disabled of the steel structure members can not be avoided. We can only improve the fire resistance as much as possible, so that the steel structure will not collapse immediately after the fire happened. According to the measured data in laboratory, the fire resistance limit of common steel structural members is only 15 ~ 30min. In the national standard "Code of Design on Building Fire Protection and Prevention" (GBJ16-87) and "code for fire protection design of high rise buildings" (GB50045-95), the fire resistance limits of fire walls, columns and load-bearing walls, staircases, walls and beams for Grade 1 fire resistant buildings are 3 and 2 hours. Contrast visible, the fire resistance limit of the steel members without covering fire protection layer is very different from the requirements of the fire code, and it can not satisfied the requirements of building fire protection in the case of fire. In order to overcome the deficiency of fire resistance of steel structure material in practical application, it is necessary to improve its fire resistance performance from various aspects so as to meet the requirements of fire resistance grade specified in the code.
Passive fire protection solution for steel structure
Passive fire protection of steel structural components is a fire protection method that does not rely on reducing the heat release rate of fire or suppressing the fire growth in the fire, and the structure is not affected by high temperature or flame seriously. It only uses the thermal characteristics of passive fire protection measures to separate structural components from high temperature smoke or flame, or absorbs the heat absorbed by the component, so that the component can still play its predetermined function under the action of fire. In general, non combustible hot inert materials are applied directly to the steel structure, or coated with steel materials with small thermal conductivity and self expansion or carbonization of heat energy directly outside the steel structure, or in the case of fire, the circulating water is added to protect the cooling system.
Direct coating protection method in the surface of steel structure or the periphery of direct application of fireproof materials, such as concrete, fire protection coating, coating fireproof plate system (fire wall, ceiling, fire, fire fire coating skirt wall) will seal the bare steel or cover it up, to improve the the ability of resisting steel structure .