Vibration Control of Big Outdoor Ferris Wheel Structure

Vibration Control of Big Outdoor Ferris Wheel Structure

The outdoor large-scale Ferris wheel is an emerging structural form, which is now facing many severe technical challenges in a building. Compared with the strength, stability, and rigidity indexes of general steel structures, the comfort level index is more important. Since the size of the Ferris wheel increases, it will have more deformation, and the requirements on comfort level index will be much higher. As a special form of high-rise steel structure, it is more affected by wind loads and earthquakes, so it requires vibration control to meet comfort requirements.

The structure design of the big Ferris wheel is currently developing in the direction of increasing height, lightweight and high strength. Due to the continuous increase in the height of the structure and decrease of the rigidity and damping, the swing of the structure increases, which will affect normal use under the action of the lateral load. The design requirement of this type of structure is to limit the vibration acceleration speed of the structure to satisfy people's comfort level. The wind loads and earthquakes are both dynamic loads, which will cause the structure to vibrate. The vibration frequency, vibration acceleration speed, and vibration duration will affect the people's body feeling. Generally speaking, the standard for the comfort of the human body is: the limit that makes people annoyed is 15gal; the limit for very annoying is 50gal; the limit for unbearable is 150gal. Therefore, for the design of the Ferris wheel structure that people can go for viewing and sightseeing, it must also meet the comfort and deformation requirements. The design generally requires vibration control of the structure.

The structural vibration control can be divided into passive control, active control, and semi-active control in between. Passive control does not require additional energy. When the structure vibrates, it drives the control device to move. Because the control force is passively generated, it is called passive control. Active control requires additional energy. When the structure is subjected to random loads, the sensor in the control mechanism takes up the structure response (displacement, velocity, acceleration), and the computer receives this information and transmits it to the device driver after processing. The equipment controlled by the computer is selected as the optimal control force applied to the structure to control the vibration of the structure. The control device actively applies the control force by the external energy according to the optimal control rule, thus, it is called active control. Semi-active control is basically passive control. But in the control process, the parameters of the control mechanism are adjusted by additional energy to adjust the role of the control force.

Among these three types of control, active control requires additional energy, and the control mechanism is more complex. In theory, active control has the best effect, but it has not been implemented in high-rise structures in practice. At present, passive control is widely used at home and abroad on the structural vibration control.

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