On the fire safety features super-tall steel Foshan construction and fire safety design
With the rapid economic development, high-rise construction from the initial rare and gradually spread. China's reform and opening up has brought vigorous economic and social development, urban construction with each passing day, but during this period of significant fire appeared grim trend, according to statistics, l991 to 2000 decade, a total of 888,485 since the onset of fire , 24,564 people dead, 43,422 injured people, the direct property losses 11.64 billion yuan. These four figures accounted for 25.8% of the total fires past 50 years, 14.7%, 13.6% and 58.8%, highlighting the seriousness of the super high-rise construction, including fire safety, including a new question, the urgent need to reform the traditional means of fire , to the satisfaction of the needs of the new era of the situation.
First, the definition and classification of super high-rise construction
With economic development, the city quickly increased, the plight of the shortage of land have become increasingly prominent, high-rise construction can more fully use of limited space, conservation of land, laying on the ground by focusing on a variety of underground pipelines and the decline of investment in public works. And a collection of super high-rise construction in the construction of the city, construction, machinery and equipment, building materials and construction techniques highest achievement and all technology, the performance of the urban social, economic and cultural extent and pace of modernization, many super high-rise construction is to become a city or important landscapes and landmarks region. In addition, high-rise construction area, the variety of functions, such as offices, hotels, apartments and shopping complex in a construction, the convenience of the people's lives.
China's construction specification does not clearly define the rules of "super high-rise construction", but to go beyond 24 meters in height constructed public construction and more than ten layers and 10 layers built residence are considered "high-level civil construction." In 1972, the construction of high-level international conference in the US city of Bethlehem, Pennsylvania, held on the definition of high-rise construction has made a more unified understanding of the high-rise construction is divided into four categories: first class level of construction: 9-16 layer (up to 50m) ; second class level of construction: 17 to 25 layers (up to 75m); high-rise construction of the third category: 26 to 40 layers (up to 100m); fourth class super high-rise construction: 40 storeys (100m height above). China "senior civil construction design for fire protection" Although there is no clear rules for super high-rise, but the height beyond 100m, layers beyond the construction of 32 layers in exile layer, apron, fire water pressure, save facilities, positive and smoke Active fire alarm areas have special requirements.
Second, the fire safety features of super high-rise construction
Ultra-high-rise construction as a region and symbol of the city, the construction of costly, involving the construction of a series of questions about construction, equipment, fire, transportation, power, environment, etc., is a comprehensive crystallization of a regional economy, science and technology, aesthetics. However, due to the high altitude of this construction material, personnel, equipment and piping systems messy, dangerous fire accidents, it is difficult to resist or prevent natural disasters (earthquakes, strong winds), internal equipment system failure accidents, fires and other man-made case Once the onset of fire, distributed and remedies are finally will have a direct threat to the safety of life and property, so the fire is the number one enemy of super high-rise construction, which has become one of the primary questions about fire safety inevitable.
(A) function uses the clutter, ignition sources and more
Ultra-high-rise construction of the main construction, function messy, most built in the bottom of the main construction of the podium, used as shopping malls, restaurants, entertainment and other business functions, as most of the main construction of residential, office, hotel and other uses. Electrical equipment and many kinds of super high-rise construction, large quantities, overload, short-circuit, the onset of the appearance of a small spark increased; more garage parking, storage volume; the flow of personnel, many people smoke; the appearance of lightning, fire and other flying surroundings Ultra-high-rise construction is also possible onset of fire ignition sources, fire load density.
(B) the vertical tube wells and more concentrated fuel, easy to form a chimney effect
Internal construction of super-tall straight stairwells, elevator shafts, tube wells, cable wells, exhaust ports, road and other blocking spam imprecise many types of vertical tube wells, most of its furnishings and decoration materials are flammable and combustible materials Once the onset of fire, easily and rapidly extending along these vertical tube wells. These vertical tube wells and a seat like tall chimneys, fire, easy to form a chimney effect, contributing to extend the flue gas fire. The higher the height of the construction, the more intense the chimney effect. Experimental data shows that the construction of super-tall fire smoke along a straight stairways, elevator shafts and other vertical shaft speeds rise straight up to 3 to 4 meters per second, sometimes even up to 8 meters per second.
(C) the security dispersed tough personnel clouds, easy to form a serious injury or death
When the construction of super high-rise 40 floors above the fire, to make quickly dispersed into the ground or space finally exile. Because fire must stop using passenger elevators, fire firefighters lift mainly dedicated, highly Fire ladder truck also has a limit, so the stairwell is the only means of decentralized staff straight. However, the construction of super-tall straight disperse long distances, personnel clouds, dispersion time corresponding increase substantially. It is part of the fire test, the first layer needs a fire fighter position 150 meters from the 40th floor to the construction of ten minutes, then ordinary people or the elderly, children and so the demand for decentralized time will be longer. The flue gas flow rate of 2 straight to 4 m / s, in a straight extending direction of one minute to several tens of layers. Dispersing speed personnel slower than the flow of flue gas beyond 100 times, and dispersed with a pyrotechnic direction opposite to the extending direction, further increasing the personnel and the risk of dispersion of hard, easy to form serious injury or death.
(D) fire remedy is difficult, demanding the equipment means
Ultra-high-rise construction and general construction of comparison, the fire remedy the difficulty is relatively large. As the city of skyscrapers, the lack of action to start the fire ground venue, and from existing domestic high-rise construction, the exterior walls are mostly glass curtain wall, easily broken after the formation of ground casualties, and the destruction of ground fire vehicles and water supply equipment, plus the wall with fixed windows, firefighters approaching a fire very difficult. In addition, existing fire and rescue equipment far unable to revive demand satisfaction of super high-rise construction. Currently, the largest rescue firefighting vehicles ascend a height of about 100 meters. The construction of super-tall fire attack, save water consumption is relatively large, and sometimes needs to reach 100 l / sec. After save drill tested three series of high-power engines, water through the pump combiner, can only reach the height of 160 meters, with direct water through the water, as long as the height of 150 meters, but has not been widely used helicopter fire. Therefore, beyond the 150m floor built mainly relying almost exclusively inside their fire-fighting facilities to ensure external means little effect.
In addition, there is a danger of fire is often overlooked, that is built during the construction of super high-rise fire safety questions. Ultra-high-rise construction period of construction are generally longer, the construction site temporary flare up more electricity capacity, flammable and combustible material concentration. At the same time, did not open fire facilities, the lack of fire water and fire exits, as long as the temporary fire water, fire once the attack, can not guarantee a greater pressure and water, fire remedy the difficulty of fire water, especially in the late onset of construction in high-rise even fire the top.
Third, the design of ultra-high-rise construction fire proposal
China to build high-rise construction began in the 1970s, at which time most typical built in 1976 that is 115 meters high and 1985 Guangzhou Baiyun Hotel built in Shenzhen International Trade Center 158.95 meters high. Later, in 1996 the king built in Shenzhen reached a 81-storey building, 325 meters high; 1998 built Shanghai Jinmao Tower is 88 floors, 420.5 meters high, has become a landmark in the construction of a new generation. According to incomplete statistics, the country meters above the existing high-rise has been close to 1000. However, since China started late super high-rise construction, coupled with strict implementation of norms in former times, there are many questions about the current fire safety aspects of high-rise construction, such as fire and smoke partitions properly, strictly separated, closed or questions stairwell of more; secure safe exit stairs dispersion exists insufficient number of poor channel doubt; widespread doubt fire water capacity is too small, lack of fire water, fire special power is not guaranteed; the interior decoration of the outstanding questions about fire safety; firefighting facility management There are many questions on the protection and maintenance of nowhere.
On super high-rise construction, Hong Kong is a very typical case development. As a rapidly developing cities, Hong Kong staff clouds, shortage of land, the construction of its high-level density called the world, high-rise construction also look everywhere. Therefore, in order to effectively ensure the fire safety of these high-level construction, will pay particular attention to the following questions about the construction of Hong Kong's super high-rise fire in the design:
1. Set the fire ring road, at least ensure that the construction of objects stand in front of one of the main fire vehicles can pass, and should be able to ensure the smooth operation of rescue and revive expansion;
2. Ensure that there is adequate water nearby satisfaction save water demand, water hydrant can not be less than 4000L / min, the main channel of the city water pressure of not less than 170 kPa, no conditions should reserve sufficient fire area with water;
3. Focus on the construction of structural fire resistance, and most are used in the construction of a reinforced concrete structure, fire resistance requirements for l to 4 hours.
4. Ensure escape routes, safety dispersed. Due to shortage of land, the construction of providers are reluctant to let any escape routes accounted for much of the area. But fire regulations in Hong Kong have specific requirements, you must ensure that adequate means of escape. In addition, high-rise construction in every 15 layers arranged exile layer enables security personnel in a temporary state, and then the fire brigade under the command of the organization, dispersed in an orderly manner to the final security zones.
Combined with leading national and regional experience in the construction of high-rise fire safety, we should follow the "prevention first, combining anti-consumer" fire approach, designed to fire a few good grasp on the following aspects:
1. hybrid structure. Departure from the viewpoint of fire performance, ultra-high-rise structure built hybrid structure is superior to steel construction. Strength at high temperatures, steel structure after heating, and soon there will be plastic deformation, thereby reducing the carrying capacity structure, when the temperature reaches 500 ℃, the intensity will decline by 50%, while beyond 1000 ℃, the intensity decreased exponentially, built decline accelerated the collapse of speed. "9.11" incident, in the south of the World Trade Center towers just hours after the impact, crashing collapse that destroyed much contact with their all-steel construction.
2. From left to consider the location and the overall total set super high-rise built plane. From the viewpoint of Fire, high-rise construction must be away from the fire risk for A, B Factory (library) room, A, B, C liquid and combustible gas tank and combustible materials pile thereof. To fully consider the location of fire spacing, fire road, fire remedy surface and special rooms set on the total plane.
3. Considering the construction of super-tall smoke control design that minimizes the amount of smoke generated during a fire, and quickly exhaust fumes produced by a fire, which effectively avoid smoke from the fire zone extends to non-fire zone diffusion in particular to avoid the intrusion as a decentralized channel corridors, stairwells and front room, in order to ensure a safe and secure decentralized channel time dispersion of the demand. As long as a reasonable distinction smoke partitions in order to effectively prevent the spread of smoke, will minimize the loss of life and property.
4. Security dispersion should be designed to focus. Ultra-high-rise built straight dispersion distance, staff is highly concentrated, long-time demand dispersed. And fire, the crowd dispersed the smoke flow rate is much slower than the speed, combined with the dispersion direction and pyrotechnics extended, opposite the direction of rescue workers, increasing the dispersion of difficult and dangerous. Ultra-high-rise construction in fire protection design should be dispersed as a priority, certainly should be set at a certain part of the security zone or floor construction material, such as stairwell between layers or exile exile, dispersed platforms and set the fire emergency lighting and safety instructions dispersed symbol to guide security personnel dispersed and escape self.
5. Set the required fire elevator, and the elevator shaft for effective fire. Separate elevator smoke is the main way people straight passage, set stairwell is particularly important. When the fire is not to ensure that the high temperature flue gas into the elevator shaft, the elevator should be set before the fire room, set the area in line with regulatory requirements, the door retaining facilities should be established. For natural smoke considerations, elevator before the fire room should be set by the external walls. In order to facilitate rapid and effective use of firefighters fire elevator, should be located in the first floor straight outdoor outlet, set the operation buttons designed for firefighters to use.
Furthermore, it should increase the technology content of the construction of the fire, to take a leading scientific and technological means, take the initiative to set the alarm system and active save system, personnel dispersed induction systems, occupant detection systems, intelligent systems to ensure safety of human life and property when the fire .
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