Use of Argand-Gauss techniques to design passive inertial dampers for multimodal oscillators: Stability and performance evaluations

Based on a geometric formalism and the use of phasors in the Argand-Gauss p lane, a sizing procedure is introduced here for the design of inertial dyna mic dampers applied to monomass oscillators; the theory is then extended an d applied to multimodal oscillators peculiar of structural engineering. Our geometrical approach to this classic theory provides an elegant method, in a language close to that of structural mechanics, for (i) sizing the dampe r parameters and (ii) evaluating the stability of the damped system and its performance limits. The aim of the work is that of exploring the use of da mpers to control the modal response of buildings under horizontal seismic a nd aerodynamic loads. Having introduced the concept of a monomass oscillato r equivalent to a given mode of vibration, we develop a multimodal multidam per model which is then used to perform numerical evaluations. Several cont rol strategies (involving changes in number and position of the dampers) ar e considered in relation to variation in bandwidth and intensity of the ext ernal forcing action. We discuss the advantages and limitations of this pas sive approach to structural control. (C) 1999 Elsevier Science Ltd. All rig hts reserved.