How to build a firewall in the most popular 2008 O

How to build a "firewall" in the 2008 Olympic sports venues

how to build a "firewall" in the 2008 Olympic sports venues

July 31, 2007

[China paint information] with the approach of the 2008 Olympic Games, various servo valves with novel designs have been raised after the ground is pulled out and cleaned, including the National Stadium (Bird's Nest), the National Swimming Center (Water Cube) Super large space buildings such as the national stadium have become new landmarks in Beijing

while sighing the magnificent momentum of these buildings, people can't help wondering -- how do super large venues achieve fire safety and timely evacuation? Today, let's take experts to visit how large Olympic sports venues build fire barriers

structure - "real gold is not afraid of fire"

Beijing Olympic Park, which gathers many Olympic venues along the central axis of Beijing, has revealed its "true face". The "bird's nest" made of huge silver steel structure is unique. It is the main stadium of the 2008 Olympic Games, and nearly 100000 spectators will witness the grand and spectacular opening ceremony of the Olympic Games

the fire resistance of steel is not high, and generally the load-bearing steel structures are protected against fire. However, for buildings like the bird's nest, if traditional structural fire protection measures are adopted, it will undoubtedly seriously affect its construction effect and cost a lot. By introducing new design concepts, the Institute of building fire protection of the Chinese Academy of Building Sciences scientifically analyzed the possible impact of fire on the steel structure frame, and they concluded that under the condition of controlling combustibles, the bird's nest steel structure cover does not need fire protection

"according to the current code system, the fire prevention of steel structure should adopt the method of fire-proof board and fire-proof coating, so as to achieve a certain fire resistance strength. If the board is nailed outside the steel structure, the thickness of the material is increased, and the bird's nest is no longer light; spraying fire-proof coating will make the steel structure rough and ugly, and destroy the architectural appearance effect of the bird's nest." Li enging, the director of the Fire Prevention Institute, said that under the framework of the current article type specifications, personalized design and building fire prevention seem to be "fish and bear's paw"

he said that since the traditional fire protection design code is applicable to all types of buildings, some requirements are inevitably extensive and general, so the specific functions and usage of each building cannot be fully considered. Therefore, the design in strict accordance with the specifications sometimes makes the original design function of the building impossible to achieve, or causes the safety level of the building to be too high, resulting in unnecessary waste, especially for the super large creative buildings, the adaptability of the traditional specifications is poor

with the increasingly diversified and personalized architectural design, a new performance-based fire protection design method is emerging in the world, that is, a more targeted, more economical and reasonable fire protection design scheme is formed through the systematic comprehensive analysis of tailored and functional matching. With the support of the national scientific and technological research plan of the tenth five year plan, China has also carried out research on the application technology of building performance-based fire protection design. The achievements of this subject have been successfully applied in some major national engineering projects. 70% of the venues and supporting facilities of the 2008 Olympic Games have adopted performance-based fire protection design and have been put into practice

by applying performance-based fire protection design, the structural fire protection problem of bird's nest can be solved scientifically, reasonably and economically

in building fire, it is necessary to ensure that the structure will not collapse and fail under the combined action of strengthening cooperation between the upstream and downstream of conventional loads and high temperature in the fire site, which is the basic principle of structural fire safety. Li enging said that according to various calculation simulations, the temperature of the bird's nest steel structure cover in the fire is within 200 ℃, and at this time, the strength and elastic modulus of the steel are relatively unchanged. Therefore, the steel with a temperature of less than 200 ℃ is within the safety limit

the bird's nest is a semi open open open-air venue, up to 67 meters high. The Fire Prevention Institute has made a variety of designs, analyses and calculations of fire scenarios from the aspects of competition venues, stands and so on. For example, suppose that the fire in the competition field caused by the celebration float entering the stadium performance, it is estimated that the average temperature 42 meters above the ground is only 45 ℃, which will not affect the steel structure

the bird's nest is "woven" by using a large number of mutually supporting spiral steel frames on the periphery of the auditorium. The corner of the cantilever of the bird's nest steel frame is like the elbow of the human arm, which is the most stressed and fragile. If there is a fire in the stand area, can the arm close to the high-rise stand bear the fire load? The calculation results show that the maximum stress ratio of the cantilever under fire is 0.7, which is lower than the elastic bearing capacity of the steel frame, and will not affect the overall safety of the structure

"after scientific calculation and analysis, as long as the fire is controlled in a certain area, the structure of the steel frame cover of the National Stadium is safe, so there is no need to adopt additional fire protection." Li engine is very proud of this. He said that this item may save the country tens of millions of yuan

evacuation - the principle of 8 minutes

enter the "bird's nest", and the tall and magnificent buildings are breathtaking. The National Stadium will accommodate 91000 spectators. In case of fire, how long will it take for spectators to evacuate safely

Li engine demonstrated the calculation model of safe evacuation of people in the bird's nest grandstand to the audience. The result was that the last spectator evacuated to a safe area in 7.5 minutes. He said that China's traditional building fire prevention code has no specific evacuation time limit, but has index requirements for the width of grandstand exits. The evacuation design of the 2008 Olympic venues is based on the international practice. After comprehensive analysis, it is finally determined as the 8-minute principle

for example, the British "guidelines for the safety design of sports venues" suggests that the controlled evacuation time of each emergency exit should be no more than 8 minutes, because when the time to pass through the emergency exit at normal speed is less than 8 minutes, the audience will generally not be excited, anxious and nervous. The Sydney Olympic venues are designed with an 8-minute safety evacuation standard

through simulation, technicians use the computer dynamic calculation and analysis of the grandstand evacuation scene to find the potential safety hazards that may affect the evacuation of people in all parts of the stadium, and repeatedly optimize the width and layout of the grandstand evacuation channel

looking down from the stands, the bird's nest is a bowl shaped oval building. In fact, this is the result of changes. The bird's nest was originally designed as a bowl edge with four serrations on both sides of a relatively short distance. The stands are divided into upper, middle and lower floors. Due to the dense audience in the upper stand area and the high pressure of personnel evacuation, the Fire Prevention Institute recommends reducing the audience in the upper stand. With the implementation of the Olympic "slimming" plan and the adjustment of the overall structure, the edge of the bowl was "flattened", and the evacuation pressure of the upper grandstand was relieved

walking into the top audience of the "bird's nest" makes people feel "at a glance". It is reported that it is 51 meters high, which is equivalent to standing on the roof of an 18 story building. If there is a fire, it is most likely to cause evacuation panic when there are many people crowded at high places. "We changed the exit of the high-rise stand from the original two rows of spectators to three rows, and specially added guardrails in the middle and both sides to ensure the safe evacuation of personnel." Li engine told

for the same reason, the design of stairs has also been humanized. The bird's nest has a 6-story collecting and distributing hall, and the outdoor stairs connect the collecting and distributing hall and the ground safety area. The plane length of these large stairs is 63 meters, like 24 dragons hovering on the outer wall of the bird's nest. In order to avoid the stampede phenomenon of the crowded crowd in the chaos, the researchers adjusted the dislocation of the straight big stairs, changed them into a "zigzag" shape, and increased the stair handrails to reduce the extrusion of the rear people in the evacuation to the front. It can be said that the subtlety of safety evacuation design reflects the flexibility and scientificity of performance-based fire prevention

material - membrane structure has good flame retardant performance

not far from the bird's nest, the crystal clear "Water Cube" is like a pool of blue water, attracting people's attention. The National Swimming Center uses a large number of new materials with membrane structure, and is covered with geometric shapes that look like the molecular structure of water, creating a strange effect of the magical water world

membrane structure is a structural system that combines architecture and structure perfectly. It is a space structure form that combines high-strength flexible membrane materials and support system to form a stable surface with a certain stiffness and can bear a certain external load

in recent years, membrane structures have been widely used in the construction of large venues in Europe and the United States. However, there has been little research on the performance of membrane structure, especially its combustion performance in China. Membrane structures were introduced into the National Swimming Center and the National Stadium for the Olympic Games, and the Institute of fire protection carried out solid simulated combustion tests on them

in the simulation test, the firewood and falling fire in the corner did not ignite the membrane structure. After a long time of burning, the membrane structure material carbonized into ash, and did not spread the flame. The staff of the Fire Prevention Institute told that from the perspective of fire safety, the membrane structure is a good flame retardant material, and the spectators can watch the competition with confidence when connected with the fatigue loading experiment control module

smoke exhaust - ingenious and scientific design

with a total construction area of about 80000 square meters, the National Stadium is the largest indoor venue in Beijing Olympic Park. The wavy curved roof fully reflects the light and dynamic characteristics of sports buildings. The competition hall of the competition hall is connected with the audience rest hall to form a large space, and the smoke exhaust system naturally becomes the design focus of fire prevention experts

the data shows that 80% of the casualties in the fire are not caused by fire, but by smoke. The dense smoke brought by the raging fire pervades the space, which not only affects people's vision, but also emits a large amount of toxic gas, which is more likely to suffocate people

when a fire occurs, it is extremely important to effectively control the flow and spread of smoke to ensure the safety of personnel evacuation and improve the fire-fighting conditions. The internal space of the gymnasium is tall, similar to a huge smoke storage cabin. It can accommodate a lot of smoke in the early stage of 0.5~2.0 disaster inside and outside the fire without affecting people's evacuation line of sight. Therefore, the smoke exhaust design is very different from that of ordinary buildings. According to the conventional smoke exhaust design, the smoke exhaust volume of Gymnasiums in large spaces is often very large, which brings great difficulties to the design and construction. "If you follow the conventional design, what you see when you look up at the venue is not the bright lights, but the scattered smoke pipes." Li engine said that the performance-based design determines the necessary smoke exhaust amount according to the parameters such as the possible fire scale and the design smoke layer height in the protected area

researchers first build a calculation model, and then divide the area of the venue into grids with different sizes according to the distance from the fire source, so as to realistically simulate the flow of smoke. The results show that the amount of smoke exhaust required in the event of a fire in the competition hall is 800000 cubic meters per hour, with 24 smoke vents. Within 30 minutes, the smoke layer that affects personnel evacuation will not fall to the personnel retention area, leaving sufficient rescue time

at the same time, the competition hall is also equipped with an intelligent numerical control fire extinguishing system (commonly known as water cannon). The water cannon rotates 360 degrees to automatically detect the ignition point, automatically locate and spray water, control the water volume, and automatically stop the fire. The effective combination of various measures solves the smoke exhaust design of tall space sports buildings

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