On May 18, 2021, the Shenzhen SEG Building shook, the amplitude was relatively large, the personnel in the building were worried about the collapse of the building and all were evacuated, there was no earthquake around the incident, there was no construction, and the wind speed was only level 5, so the onlookers dispersed in a confused face, after all, everyone at most guessed what the reason was.
After 2 months of investigation, the results were released on July 15, and the gust of wind caused the mast at the top of the SEG Building to vibrate, coupled with the building's natural frequency, causing the SEG Building to vibrate.
Typhoon: What will happen to the Shanghai Tower, which is taller than the Game Tower?
At 17:00 on July 24, 2021, fireworks typhoon is located at 124.20° east longitude and 27.50° north latitude in the East China Sea, about 310 kilometers southeast of Xiangshan County, Zhejiang Province, and is expected to make landfall in the coastal area from Zhoushan to Yuhuan in Zhejiang Province from the afternoon to the night of the 25th, with a wind force of typhoon or strong typhoon.
Shanghai is only more than 100 kilometers away from the landing site, almost within the ten-level wind circle of fireworks, China's tallest building - Shanghai Tower is in Lujiazui, Shanghai, with a height of 632 meters, a total of 128 floors, weighing 850,000 tons! China first, the world's second, second only to dubai's Burj Khalifa, typhoon hit, what about Shanghai Tower?
It is reasonable to say that the building weighing 850,000 tons is not afraid of any typhoon at all, after all, when the weight reaches a certain level, it is a kind of existence that cannot be ignored. However, this is not the case at all, and it is said that when the typhoon strikes, the Shanghai Tower will shake, with a maximum shaking amplitude of up to 1.4 meters.
Because the building is not a mountain, it is a social function, an angular building, in order to ensure its social function, it will be designed and built in the most usable space and the most economical way, so there will be various problems, so it must avoid many pits when designing and building.
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Buildings must consider a very important factor when designing, that is, aerodynamics, because the modern building environment is very complex, such as the building is getting higher and higher to consider the pneumatic deformation, because the building itself is not a rigid body, its large-scale structure will be deformed in the wind, the frequency of this wind vibration response may resonate.
It is also possible to cause the building to vibrate due to the vortex caused by the vortex shedding, so there are two solutions, one is to avoid as much as possible in the design, such as building a model to blow a wind tunnel at various wind speeds and in the complex environment of the surrounding building, and then using a supercomputer to achieve the best shape of the building.
The other is the internal structure of the building to prevent resonance, the early low-rise buildings are designed in the mode of semi-rigid body, at most considering the expansion joint of thermal expansion and contraction, but the building is getting higher and higher, the "rigid body" of reinforced cement is not worth mentioning in the face of wind and earthquake, and even on high-rise buildings can also throw out the effect of noodles.
How to prevent it, there are roughly two ways, one is the lower cost of structural damping to achieve, the other is relatively high cost, but the effect is better active seismic resistance to achieve.
Structural damping is not difficult to understand, the most typical is to set up energy-absorbing equipment in some parts of the building, such as the spring flat load of a truck or a hydraulic viscous damper, so that the building absorbs these shaking energy when it is blown by the wind or earthquake, so as to achieve the purpose of rapidly reducing vibration.
Of course, there is more than one kind of structural damping, the early 381-meter-high Empire State Building (built in 1931), the outer walls are made of brick or stone, and the internal partition walls are made of brick or block, and it is found through calculations that these material combinations in non-structural structures can provide sufficient damping.
However, in the curtain wall structure of the World Trade Center (World Trade Twin Tower, collapsed in the 911 incident), the keel structure was used, and there was no partition wall to provide damping, so the viscoelastic damper was introduced into the super high-rise building for the first time, and the viscoelastic damper was installed between the lower string of the floor truss and the outer frame tube.
Viscoelastic damping
The structural parts of the Bank of China Tower in Hong Kong are more interesting, its diagonal braces are only connected to the columns in its own plane, while the columns in different planes are not directly connected by nodal plates, but are bundled together by concrete, and the concrete and steel structures together form a damping structure.
Shanghai World Financial Center is a space truss structure: in the giant structural columns, giant diagonal braces and ring trusses, the giant diagonal braces are filled with concrete, which not only increases the stiffness and damping of the structure, but also prevents the bending of the diagonal bracing side panels, which is also similar to the design of the Bank of China Tower, of course, both are Robertson's landmark works, and it is inevitable to reduce costs by following the mature design.
Active damping device
The active damping device is to use the sensor to sense the direction and intensity of the building's shaking, and then use the counterweight to make the opposite movement, the shaking energy is eliminated into invisibility, so there will be a huge counterweight in the building to cancel out the shaking energy of the building, so the question is, is it placed on the top of the building or in the building or at the bottom of the building?
Maybe many friends will think that you have to be at the bottom of the building to hold the whole building, right? But this is completely wrong, just like when the top of a balance bar is maintained, you will find that the balance bar with a larger weight at the top is easier to maintain, because the mass is large, and the displacement under the same energy is small and not easy to shake.
Therefore, it is difficult to shake, and it is only necessary to adjust it slightly, such as when the Shenzhen SEG Building is shaken, it is said that the swimming pool on the roof is dried up and is being maintained, because the SEG Building does not involve active damping devices, and the swimming pool on the roof has a partial damping effect.
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The Shanghai Tower building is very distinctive, its recognition is extremely high, because from the bottom to the top is a shape that constantly twists and changes in size rapidly, first of all, from the appearance of this is an aerodynamic consideration of the vortex shedding, the frequency of vortex shedding at each height will change, each height is different, so it is difficult to form a resonance.
The other is a structural damping design, such as a giant frame in the main structure - core barrel - outstretch truss. Maximizes resistance to horizontal loads such as wind loads, as well as resistance to gravity. The suspension structure in the outer curtain wall support system is added to the radial strut (each layer rotates 1 degree upwards) plus the horizontal oblique bracing, and the deformation difference between the curtain wall structure and the main structure is reduced by telescopic support.
In addition to these designs, there are active damping devices, which are active damping devices weighing up to 1000 tons in 125 to 126 layers, which consume the energy generated by wind loads on the structure through their own inertia and damping, thereby reducing the response of the structure. Taipei 101 uses a similar active damping device, but on a smaller scale than the Shanghai Tower.
Although the damping device of Shanghai Tower is advertised as "the world's first pendulum eddy current tuning quality damper", but the principle is not much different, known as the small waist of the Canton Tower is a damping device was also transformed into a waterproof box, on the top floor of the Canton Tower installed two iron fire water tanks of 540 tons each capacity, the water tank is equipped with tracks and with control devices, usually when the damper is used, when the tower body shakes, the water tank is controlled by the computer to slide in the opposite direction to eliminate the shaking of the tower.
The Sea Center Building resisted the attack of typhoons "Lichma" and "Ambi", and the "fireworks" in the Zhejiang circle this time are small, and I believe that there will be no moths.
Damping device is the magic weapon of modern high-rise buildings to deal with earthquakes and typhoons, otherwise even if the structural strength is enough, under the sharp shaking, people will inevitably be dizzy, and the tallest building on the earth, the Burj Khalifa, has reached 828 meters, and the future does not know whether there will be 1000 meters of buildings, and what damping technology will be used?