Everyone who is engaged in construction, or onlythinks to get down to work, faces new concepts. For example, the limit of fire resistance of structures determines the fire safety of the structure. Let's look at some of the most commonly used materials in construction and how they meet this requirement.
The buildings of stone have a high naturalfire resistance limit. This is determined by their natural thermophysical properties and massiveness of the material itself. In case of fire, such structures are able to withstand heating up to 900 degrees, while their strength does not decrease and there are no signs of destruction. Therefore, in many cases, stone buildings do not require additional heat protection.
Reinforced concrete and concrete structures possessrelatively low thermal conductivity, well resist fire. But in our time they are made thin-walled, do not have a monolithic connection. Therefore, their safety functions in case of fire can be performed only for one hour, in some cases even less. The fire resistance limit of such structures depends on their cross-section of material and the size of the product itself. The diameter of the used reinforcement, the quality of the concrete, the grade of the filler from the load on this structure, the layout of the supports and the percentage of moisture of the concrete are taken into account. The greatest fire resistance has concrete, the humidity of which is close to 3.5%.
However, when it is more than 1200 kg / m3, it canEven with minor fire effects. This can lead to a fairly rapid destruction of the structure. The fire resistance limit for boards that have beams with the same structural parameters will be higher than for beams. In case of fire, the heating of the plate occurs on one side, whereas the beam is exposed to fire from three. In the case of support of the slab on the counter, the fire resistance limit will be significantly higher than when installed on both sides. Plates, having a solid section, made of ordinary concrete and using a protective layer of 10mm, which use valves A-III class, have a fire resistance limit of one hour.
The fire resistance of building structures made of concrete can be increased by the manufacture of a plate based on mineral fibers, perlite and vermiculite, plaster and plaster.
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The structures made of metal, aluminumalloys and cast iron, is much easier to install than reinforced concrete materials, although they are also equivalent in their bearing capacity. However, the metal has a high thermal conductivity and a low critical temperature, so the limit of fire resistance is no more than 15 minutes. It increases with this type of construction due to the use of fire protection. The most common way to protect the structure of metal from the effects of fire is the use of non-combustible building materials as a covering material, as well as plastering. For example, if the steel structure is lined in half a brick, the fire resistance limit will reach five hours. When the column is plastered using a metal mesh, the fire resistance will increase to 45 min. By increasing the plaster layer to 5 cm, it is possible to increase the fire resistance up to two hours. Also to increase resistance to the temperature of heating, asbestos-cement, expanded clay, mineral-fiber and gypsum boards are used. The use of these materials makes it possible to increase the fire resistance of the material to two hours or more.
