Engineering Mechanics

Proceedings Vol. 17 (2011)

ENGINEERING MECHANICS 2011

Copyright © 2011 Institute of Thermomechanics, Academy of Sciences of the Czech Republic, v.v.i., Prague

 

Náprstek J., Fischer C., Pirner M.
pages 403 - 406, full text

Wind excited vibrations of slender structures such as towers, masts or certain types of bridges can be reduced using passive or active vibration absorbers. If there is available only a limited vertical space to install such a device, a ball type of absorber can be recommended. In general, it is a semispherical horizontal dish in which a ball of a smaller diameter is rolling. Ratio of both diameters, mass of the rolling ball, quality of contact surfaces and other parameters should correspond with characteristics of the structure. The ball absorber is modeled as a holonomous system. Using Lagrange equations of the second type, governing non-linear differential system is carried out. The solution procedure combines analytical and numerical processes. As the main tool for dynamic stability investigation the 2nd Lyapunov method is used. The function and effectiveness of the absorber identical with those installed at the existing TV towers was examined in the laboratory. The response spectrum demonstrates a strongly non-linear character of the absorber.

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