Design of optimum viscoelastic dynamic neutralizers by response reanalysis

Resumo

In the past decades, response reanalysis techniques have been widely used to predict the dynamic effects
of localized structural modifications, for they offer the advantage of circumventing the need to reprocess the whole
set of information relative to the system of concern at each modification stage. Some recent works addressed the
issue of evaluating the effects of inserting a viscoelastic dynamic neutralizer into a primary system by means of
reanalysis, but none of them tackled the problem of finding the optimum modal parameters for the device based
on these techniques. In this context, the present work aims to investigate the use of two response reanalysis
techniques - in matrix formulation - to iteratively predict the response of the modified system after alterations in
the parameters of a single-degree-of-freedom neutralizer, which provides a convenient method to find the optimal
modal characteristics for the device. The considered primary system consists of a cantilever steel beam, the
vibrations of which are meant to be kept under control. A finite-element model for the beam is implemented and
a combination of a genetic algorithm and a local Nelder-Mead technique is used to ensure that global minimum
vibration levels are achieved. The results show promising evidence for generalizing the use of the technique to
multiple-degree-of-freedom devices and for applying the method to specific, large scale systems, such as overhead
transmission line conductor cables.