Abstract
The characteristics of smoke natural filling in ultra thin and tall atriums were investigated by hot smoke test method. For the fire located on the atrium ground, the smoke touched the side wall first and then extended both upwards and downwards. The smoke plume rising velocity variation can be divided into four stages, different from the normal law in large spaces. In the very early stage of natural filling, the smoke concentration near the height of wall touching point was highest and maintained at a high level in the whole process. The linear trend of temperature increasing in plume center above the height of touching point was broken, far less than the theoretical predictions, which verified the enhancement effect of boundary heat exchange caused by plume restriction. The variation tendencies of smoke density and temperature were similar during the hot smoke test,and there existed a good linear relation between these two parameters. The height-width ratio was calculated as 3.2 averagely by the test results when smoke plume would likely touch atrium walls, and it was very close to the theoretically derived value. This ratio can be used as the definition condition for ultra thin and tall atriums.
Highlights
China has become the new center of skyscrapers after USA, Japan and West Asia
After the smoke plume rose to the ceiling, it simultaneously subsided and spread circumferentially, which showed that the alarm number of smoke detectors increased rapidly and regularly and the top smoke concentration rose leading to continuous visibility decrease of top floor
Most of the data is accumulated near the origin of axis, so plot the data above 49 m separately in Fig. 11(b) in order to zoom in. It can be seen from the figure that when the height is over 60 m, i.e. above the plume touching point, the existing linear trend is broken and the temperature increases in the smoke plume are significantly lower than the theoretical prediction ones, which verifies the enhancement effect of boundary heat exchange caused by plume restriction in ultra thin and tall atriums
Summary
China has become the new center of skyscrapers after USA, Japan and West Asia. It is estimated that by 2022, the total number of super high-rise buildings in China will reach 1318, almost 2.5 times of USA [1]. Along with the development of super high-rise buildings, a distinctive atrium form appears, which has slim body and small area but large height-usually over 50 m or even more than 100 m. Through the investigation of the atriums in Chinese super high-rise buildings, the shape factor of the ultra thin and tall atriums described in this article is very small, basically not larger than 0.1, and significantly different with the thin atriums described by those predecessors. The lack of basic research results of smoke spread and development laws in ultra thin and tall atriums has restricted their smoke control design, test and assessment as well as for the super high-rise buildings they belong to. Hot smoke test is an effective method for fire science research and building smoke control system evaluation. Hot smoke tests are designed according to GA/T 9992012 to obtain index data such as smoke temperature, velocity, density distribution and imaging data in ultra thin and tall atriums, which can lay a theoretical foundation for further optimization of smoke control strategies
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