Steel is a non-burning building material, it has the seismic, bending and other characteristics. In practice, it can not only increase the load capacity of buildings, but also meet the need of aesthetics of architectural design, and also avoid the defects that the building materials such as concrete can not be bent and stretched. Therefore, the steel is favored by the construction industry. However, steel has some unavoidable defects in fire prevention as building materials. Its mechanical properties, such as yield point, tensile strength and elastic modulus, all decline sharply due to the increase of temperature.
Steel structures usually lose their load carrying capacity at a temperature of 450 degrees Celsius to 650 degrees Celsius, and great deformation occurs. As a result, the steel columns and steel beams bend and the steel structure can not continue to be used because of excessive deformation. Generally, unprotected steel structures The fire resistance is about 15 minutes. The length of time is also related to the rate of heat absorption by the components.
In order to overcome the shortcomings of fire prevention in practical applications, fire-proofing must be carried out. Its purpose is to raise the fire resistance of steel structure to the limit specified in the design code. The measures to prevent deformation and slump when the steel structure rapidly warms up in the fire are varied. The key is to adopt different methods according to different situations. For example, adopting adiabatic and refractory materials to block the flame and directly burn the steel structure to reduce the heat transfer rate Postpone the temperature rise of steel structure, the intensity of weakening time and so on. In reality, four kinds of steel structure fire protection measures must be given attention.
First, the outsourcing. As the name suggests, is the appearance of the steel structure to add the outer layer, the use of spray construction. With a special spraying equipment on the surface of the steel structure spray "Jinma steel structure fire-resistant slurry (one-component)" to form a protective layer, according to fire safety requirements, the design of fire-retardant paste thickness to meet the fire resistance 2 to 3 hours or more, Is currently on the market performance, cost-effective fire retardant slurry.
Second, water jacket. Hollow steel structure filled with water is the most effective protection against fire protection measures. This method allows the steel structure in the fire to maintain a lower temperature, the water circulates within the steel structure to absorb the heat of the material itself. The heated water, when cooled, can be recycled or piped into cold water instead of heated water.
Third, shielding. The steel structure is arranged in the wall or ceiling of the refractory material or the component is concealed in the space between the two walls so as to achieve the goal of fire prevention with little or no increase of the refractory material. This is one of the most economical methods of fire prevention.
Fourth, the expansion of materials. The use of steel structure fire protection coating components, this method has good fire and heat insulation, construction is not limited by the geometry of the steel structure, etc., generally do not need to add ancillary facilities, and the coating of light weight, there are certain aesthetic decorative effect, Belongs to modern advanced fire safety technology and measures.
At present, the high-rise steel structures are increasing, especially in some super-tall buildings, which adopt a wider range of steel structures. This requires us to increase the fire protection of building materials in the course of architectural design so as to enhance its fire resistance limits and to formulate the necessary contingency plans within the building to reduce the casualties and property losses.