Engineering Mechanics

International Conference

Proceedings Vol. 9 (2003)


May 11 – 15, 2003, Svratka, Czech Republic
Editors: Jiří Náprstek and Cyril Fischer

Copyright © 2003 Institute of Theoretical and Applied Mechanics, Academy of Sciences of the Czech Republic, v.v.i., Prague

ISBN 80-86246-18-3 (printed, Extended Abstracts)
ISSN 1805-8248 (printed)
ISSN 1805-8256 (electronic)

list of papers scientific commitee

Dynamics of a spherical vibration absorber
Náprstek J., Pirner M.
pages 214 - +9p., 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 spherical type of absorber can be recommended. In general, it is a semi-spherical horizontal dish in which a sphere of a smaller diameter is rolling. Ratio of both diameters, mass of the rolling sphere, quality of contact surfaces and other parameters should correspond with characteristics of the structure. The spherical absorber is modelled as a holonomous system. Using Lagrange equations of the second type, governing non-linear differential system is derived. The function and effectiveness of the absorber identical with those installed at the existing TV towers was examined in the laboratory of the Institute of Theoretical and Applied Mechanics. The response spectrum demonstrates a strongly non-linear character of the absorber. The response amplitudes at the top of a TV tower with spherical absorber were reduced to ¤ of their original values.

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