Popular network posters, shen boy, liu sam
On the afternoon of 18 may, the sudden swing of the 79-storey landmark building, the sage building, north of shenzhen province, triggered discussions on issues related to the safety and stability of super-high buildings. On 19 may, a public network poster journalist interviewed the persons concerned。
Sage building
There's been a tremor in the seger building that's causing concern. - yeah
According to public information, the sage building, which was completed in 1999, is an earlier group of super-high buildings in the country, with a height of 355. 8 metres, a total of 79 floors, a floor of 75 floors and a floor of 4 floors, with a total construction area of 170,000 square metres, and a landmark building in shenzhen, the north and south。
Following the incident, experts from the relevant units and scientific institutions formed the preliminary findings of the vibrations in saig square house. After an expert study in guangdong province, it is prima facie considered that: (i) the shenzhen saig building is a chain of tremors rather than a left and right shaking; (ii) the tremors are caused by a combination of factors, mainly the influence of the wind, as well as by the effects of subway operations (the two subways passed through the stairs) and the temperature (the temperature has increased by up to 8 degrees in the last two days, which has a significant impact on the steel structure); and (iii) the main structure of the seig building is secure, with strong internal structures and well-established ancillary facilities. The above-mentioned findings are preliminary and are still subject to further investigation by the group。
In addition, industry speculates from the field: first, the wind oscillation effect, the so-called “wind oscillation effect”, is the pulsive effect of a vortex under the influence of the wind in high-rise buildings and buildings; secondly, the change of ground-based earth pressure or low-frequency vibration, where there are three metro lines on the floor, where the metro will produce low-frequency vibration, where the metro's vibrations reach the inherent frequency of the building and then shakes up; and thirdly, the nitric barrier reaches the level shift limit, generally at a height of 10 metres from the ground in the normal state of wind pressure, where the wind speed is 5 metres/s, at an altitude of 90 metres and the wind speed of 15 metres/s. If up to 300-400 metres, the wind will become more powerful, i. E. When wind speeds exceed 30 metres/s, the skyscraper will shake. In order to ensure safety, residential comfort must also be taken into account in order to reduce the shaking of buildings in the event of greater wind or earthquakes. As a result, the tuning quality blocker, known as the "standing house ball", is widely used. However, there are limits to the vibrator's vibrator position and if the limit is exceeded in a given direction, the effect of vibration decays along a given direction is differential。
What's the effect of the modulating mass blocker? All the skyscrapers
U xian, assistant director general of technical research and development at the green land group regional management headquarters, introduced the journalist popular network poster journalist, which was able to result in the movement of super-high buildings mainly from seismic and wind loads。
In fact, in the current case of super-high buildings in the country, the essentially resistant wind is around class 13, i. E., the general wind power has little impact on the main building. Wu xian told the public network poster journalist: “the reason why the wind does not cause devastating damage to buildings is that superstructures typically undergo seismic vibrations and wind tunnel trials to simulate the effects of earthquakes and winds and have several lines of defence in the later design of the building.”
“in the case of zinnan's current first-highest building, the greenfield puli centre in zinan, wu zheng indicated that, although the building was not equipped with a tuning-quality barrier, it itself had two lines of defence, with a number of enhancements added to the design. As a result, it is generally possible to ensure that there is no problem with the wind that happens in 50 years, and that there may be short-lived discomfort with the wind that happens in a hundred years, but there is no problem with security。
Combination mass blocker
On the question of the blockers referred to above, wu jing said: “in some older super-high buildings, it is true that there will be more tuning quality blockers, such as the 101 building in taipei. It is commonly said to be the addition of very high-quality, or very large, spheres to buildings, which reduce energy through space shaking. However, for the time being, in the shandong region, superstructures can solve the problem with their own resilience. In the southern regions of taiwan, shenzhen and other regions, the frequency of earthquakes, typhoons and hurricanes may require additional measures on buildings.”
Moreover, with regard to the shaking of the shenzhen sage building, wu xian believes that there may also be a cause for resonance。
How can the “first height” be stable
The zhinan greenfield puli centre (hereinafter referred to as the “zinan green land centre”), located at the triangle of puli street, chinan city in shandong province and east hsu river street and the ycl road, is 303 metres high, top of which is the first high building in shandong province, and the first building of over 300 metres on top of shandong province, which became operational in 2015。
Chinan green land center
According to wu, the green ground centre as a whole has a triangulation structure, with the main tower structure being a steel mix frame structure, the core cylinder being a concrete structure, the outer column being a steel tube filled with concrete pillars, the frame and the floor beam are steel structures, with a steel-pressed steel plate surface on the floor; the core cylinder structure is shaped in a six-side shape, with a dynamic steel pillar placed at the six corners, and with an external stretching of steel beams and outer frame pillars. “in this case, in the event of a windy weather, the building forms two layers of defence, one core barrel defusing wall structure and the other six steel tube concrete pillars. If there is some damage to the interior reduction wall, then the external second line of defence can also withstand the external force.”
There are two lines of defence in the building design of greenfield center
With regard to the performance design of such super-high-rise buildings, wu xian stated: “the greenfield centre is generally able to withstand major winds of class 13 and earthquakes below level 9, and can perform normal undamaged construction, and special major natural disasters (such as earthquakes, hurricanes, etc.) can cause minor damage, without prejudice to the evacuation of personnel and may continue to be used after the building itself has been repaired and certified for testing”
So, during the construction process, for example, to ensure quality security in superstructured buildings? Wu xian told the mass media that “such high-rise buildings will be placed under temporary support during construction to maintain structural stability; at the same time, the health monitoring system will be increased, as in normal times when we have a medical examination or when we make an electrocardiogram of a detection chip on the body, any minor change in the building will be reported to the police”
How can it be safe and stable for zinan, who is building a cbd project with a height of over 400 metres
In addition, journalists are concerned about the ongoing construction of the shandong international finance centre (ifc), located at the heart of the cbd, in chinan, as part of the green land group project. Upon completion, it will become the first super-highest building of more than 400 metres in the east of the mountain and will replace the green land centre as the “first height of zinan”. So what is the safety and stability of the project
Impact chart of shandong international finance centre
Wu xin told the public network poster journalist that the shandong international finance centre had undergone seismic vibrating and wind tunnel trials to model the most unfavourable conditions for design, that building safety and stability met the requirements, and that building comfort was a leading level in the industry。
In accordance with national norms, high-level concrete structures with a height of not less than 150 metres should meet the requirements of wind perturbation comfort. Under the 10-year wind load standard set by the current national standard, the maximum acceleration of wind direction and cross-wind vibration at the top of the structure should not exceed 0. 25 m/s2. The maximum acceleration of wind direction and cross-wind vibration at the top of the structure may be calculated in accordance with the relevant provisions of the technical instructions for high-level civil construction steel structures, which are currently the industry standard。
According to wu, the main structure of the main tower of the shandong international finance centre (ifc) is based on the construction of steel walls with reinforced concrete, with a cross-stretch and reinforced concrete construction of the outer column, which meets the design requirements for effective protection against wind loads; the design and real-time control of the front stage of the main tower meets the computational requirements and has a greater presence on the inside of the corner and the high-level retreat processing, which allows for a better sharing of the resistance to wind loads; and, in addition, the maximum wind-shield limits of the main tower of shandong international finance centre and the results of the wind-hole tests meet the requirements。
Is it a quality problem or normal
It is worth mentioning that, today, high-rise buildings are not limited to commercial structures, and many residential projects are designed as super-high-rise buildings. Thus, many netizens have questioned how to distinguish between the real quality of the building or the normal swing caused by the wind in the case of top-rise shaking
The netizens questioned how to distinguish between construction quality problems and normal phenomena
According to wu, “the minimum threshold in the construction industry is quality security, so that the quality security of most buildings is guaranteed, requiring that the maximum acceleration of wind direction and cross-wind vibration at the top of the building should not exceed 0. 25 m/s2. But people are very sensitive, and if the acceleration reaches 0. 1 m/s2 ~ 0. 15 m/s2, people feel uncomfortable, and therefore the comfort of the human being is taken into account when designing buildings. As a result, construction has been added to meet people's requirements for comfort.”
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