Response analysis of tuned mass dampers to structures exposed to vortex loading of Simiu-Scanlan type

Vortex-induced loads on slender one-dimensional structures vibrating at loc k-in conditions consist of a self-induced part in phase with the velocity o f the structure in addition to an additive, almost harmonially varying comp onent representing the: same type of load as the vortex-induced force on a fixed cylinder. Simiu and Scanlan (1996 Wind effects on Structures. New Yor k: John Wiley & Sons Inc.) have proposed a widely used model for the self-i nduced part of the load based on a van der Pol oscillator. The aim of this paper is to investigate the optimal design of tuned mass dampers for such a load model. The method of analysis is based on the averaging method (Krylo v-Bogoliubov-Mitropolsky first order perturbation analysis) for weakly non- linear systems. Several interesting findings have come out of the analysis. First, it is shown that, if the additive loading is omitted, the vibration s will be completely removed in an interval of the frequency tuning in cont rast to the case of harmonic loading, where total damping of the primary sy stem at optimal tuning is only possible when no structural damping is prese nt. The stability of the theoretically possible motions is checked at diffe rent levels of viscous damping in the tuned mass damper. From this analysis it is concluded that introducing less damping than used for harmonic load, in order to achieve optimal results, may prove more efficient as far as va n der Pol oscillator load model is concerned. The theory has been applied t o passive damping control of the Rio-Niteroi steel girder bridge, Rio de Ja neiro, which is occasionally severely exposed to vortex-induced vibrations. (C) 2001 Academic Press.