Author(s)

Y.-M. Chen & C. Hsiao

Abstract

Antenna structure commonly exhibits a symmetric arrangement due to its simplicity in analysis and attractive structural responses under loading conditions. The dynamic responses of repetitive structures are relatively sensitive to modification where slight changes in the geometric parameters can destroy the structure symmetry. This paper presents an analytically derived computational model based on the Rayleigh-Ritz method for the periodic structure such as antenna structure. The Rayleigh-Ritz method is relatively useful in treating continuous structure with non-uniform mass and/or stiffness properties. The antenna structure is represented by a number of cantilever beams elevated at an angle and built-in into a hub and coupled by springs. Both free and force responses are determined. Optimisation with objective function targeting by minimizing the tip displacement is then carried out searching for a set of tip masses attached to the free end of the cantilever beams. The structural vibration properties resulting from adding additional tip-masses to the periodic structure are discussed in detail. 1 Introduction A periodic structure consists fundamentally of a number of identical structural components [9], i.e., periodic elements which are joined together end-to-end and/or side-by-side to form the whole structure. Structures such as multi-story buildings, multi-blade turbines and rotary compressor, stiffened plates are commonly treated as periodic structures [10]. Considerations of the vibration levels likely to be caused by the time-dependent force, pressure to be encountered in service life of the structure are essential during the design stages

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