New vibration control device and analytical method for slender structures

Abstract

Since slender structures such as utility poles, radio masts, and chimneys, are essentially statically determinate structures, they often collapse during earthquakes. Although vibration control is the most logical method for improving the earthquake resistance of such structures, there are many practical problems with its implementation due to their very long natural vibration period. This paper proposes a new vibration control device to effectively prevent the collapse of slender structures subjected to strong earthquakes. The device consists of a pendulum, an elastic restraint and a lever, and is designed such that when it is attached to a slender structure, the second vibration mode of the structure corresponds to the first vibration mode of the same structure without the device attached. This is highly effective in causing the transverse motions of the device and the structure to oppose each other and so reduce the overall transverse vibration during an earthquake. In the present paper, the effectiveness of the vibration control device is first evaluated based on laboratory experiments and numerical studies. An example of applying the device to a tall chimney is then simulated. A new dynamic analytical method for slender structures with abrupt rigidity variations is then proposed.