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Fire safety characteristics of super high-rise buildings?

China's Code for Fire Protection Design of High-rise Civil Buildings has no explicit provisions on super-high buildings, but there are special requirements on refuge floor, apron, fire water pressure, fire extinguishing facilities, positive pressure smoke exhaust and automatic fire alarm for buildings with a height of more than 111m and more than 32 floors. Among them, what are the fire safety characteristics of super high-rise buildings? The following is an introduction to the fire safety characteristics of super high-rise buildings brought by the construction network for reference.

fire safety characteristics of super-high-rise buildings

As a symbol of a region and a city, super-high-rise buildings are costly to build, involving a series of problems such as architecture, structure, equipment, fire prevention, transportation, energy and environment, and are the comprehensive crystallization of regional economy, science and technology and aesthetics. However, due to the high height of this building, the large number of people, the complex equipment and pipeline system, and the hidden danger of fire accidents, in the case of natural disasters (earthquakes, strong winds), internal equipment system failures, man-made fires and other irresistible or preventive situations, once a fire occurs, it is very difficult to evacuate and put out, which will directly threaten the safety of life and property. Therefore, fire is the number one enemy of super-high-rise buildings, and its fire safety has become one of the inevitable primary problems.

(1) The functions and uses are complex, and there are many ignition sources

The main building of super-high-rise buildings is tall and has complex functions. Most of the main buildings have podium buildings on the ground floor, which are used as shopping malls, restaurants, entertainment and other commercial functions, and most of the main buildings are used as houses, offices, hotels and so on. Moreover, there are many types and quantities of electrical equipment in super-high-rise buildings, and the phenomena of overload, short circuit and small sparks are increasing; There are many parking in the garage and a large amount of oil storage; There are many mobile workers and many smokers; Lightning strike and the surrounding environment, such as Fei Huo, are also possible ignition sources of super high-rise buildings, and the fire load density is high.

(2) There are many vertical tube wells and combustible materials are concentrated, which are easy to form vertical stairwells, elevator wells, pipe wells, cable wells, exhaust ducts, garbage tunnels and other kinds of vertical tube wells which are not tightly sealed. Most of their furnishings and decoration materials are flammable and combustible. Once a fire breaks out, it is easy to spread quickly along these vertical tube wells. Moreover, these vertical tube wells are like towering chimneys. When there is a fire, it is easy to form stack effect, which encourages the spread of smoke fire. The higher the building height, the stronger the stack effect. Experimental data show that the fire smoke in super high-rise buildings rises vertically along vertical shafts such as stairwells and elevator shafts at a speed of 3 to 4 meters per second, and sometimes even 8 meters per second.

(3) It is difficult to evacuate safely, and people are crowded, which is easy to cause heavy casualties.

When a super high-rise building with more than p>41 floors is on fire, it is very difficult to evacuate people to the ground or refuge space quickly. Because the passenger elevator must be stopped in case of fire, the fire elevator is mainly for firefighters, and the height of the fire ladder truck is limited, so the stairwell is the only means of vertical evacuation. However, the vertical evacuation distance of super-high-rise buildings is long and people are dense, and the evacuation time is also greatly increased. According to the test of the fire department, it takes more than ten minutes for a fire fighter to get down to the first floor of the building from the 41-story position of 151 meters, so the evacuation time for ordinary people or the elderly and children will be longer. The vertical flow speed of flue gas is 2 ~ 4 m/s, and it can spread dozens of layers in 1 minutes in the vertical direction. The evacuation speed of people is more than 111 times slower than the flow speed of smoke, and the evacuation direction is opposite to the spread direction of fireworks, which further increases the difficulty and danger of evacuation and easily causes heavy casualties.

(4) Fire fighting is difficult and requires high equipment and means

Compared with ordinary buildings, the fire fighting of super high-rise buildings is relatively difficult. Because there are many high-rise buildings in the city, there is a lack of ground for fire fighting operations. Moreover, judging from the existing super-high-rise buildings in China, most of the external walls are made of glass curtain walls, which can easily cause casualties on the ground. It is very difficult for firefighters to get close to the fire point for fire fighting vehicles and water supply equipment that damage the ground and fixed windows on the external walls. In addition, the existing fire fighting equipment is far from meeting the fire fighting and rescue needs of super high-rise buildings. At present, the maximum rescue height of fire-fighting climbing car is about 111 meters. When a fire breaks out in a super high-rise building, the water consumption for extinguishing the fire is relatively large, sometimes it needs to reach more than 111 liters/second. According to the fire drill test, three high-power fire engines are connected in series, and the height can only reach 1.61 meters through the water pump connector, and the height can only reach 1.51 meters through the water hose, but the fire helicopter has not been widely used. Therefore, floors over 1.51 m can only be guaranteed by the internal fire-fighting facilities of the building, and the external means have little effect.

in addition, there is a fire hazard that is often overlooked, that is, the fire safety of super high-rise buildings during construction. The construction period of super-high-rise buildings is generally long, and there are many temporary hot works on the construction site, large electricity consumption and concentrated flammable and combustible materials. At the same time, the fire-fighting facilities are not opened, and there are only temporary fire-fighting water sources. Once a fire breaks out, the water pressure and quantity of fire-fighting water cannot be guaranteed, and it is more difficult to put out the fire, especially in the middle and high floors or even the top floors in the later stage of construction.

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