Effective Mass Sensitivities for Systems with Repeated Eigenvalues

THE effective modal mass, commonly referred to as effective mass, is quite important in characterizing the dynamical behavior of a base driven structure because it allows the reduction of complex structures to equivalent spring-mass systems1;2 and the identi cation of the modes that can be signi cantly excited through the interface by the base motion. These modes are called target modes, and they have to be well correlatedto the experimentalones to obtain a test veri ed nite element (FE) model.3 The effective mass sensitivities, on the other hand, can be used in optimization problems such as that of nding the optimal position of an extra payload to be added4;5 or that of the minimization of errors between experimental and numerical effective masses. In this work the calculation of effective mass sensitivities has been generalized to the case of repeated eigenvalues.