xl

The localization of the free modes of vibration of disordered multispan beams is investigated, both theoretically and experimentally. It is shown that small deviations of the span lengths from an ideal value may have drastic effects on the dynamics of the system. Emphasis is placed on the development of a perturbation method that allows one to obtain the strongly localized modes of vibration of the disordered system without a global eigenvalue analysis of the entire system. Such a perturbation analysis is cost-effective and accurate. More importantly, it provides physical insight into the localization phenomenon, and allows one to formulate a criterion that predicts the occurrence of strongly localized modes. Also, an experiment is described which has been carried out to verify the existence of localized modes for disordered two-span beams. Theoretical and ex-perimental results are compared in detail and excellent agreement is found, thus confirming the existence of localized modes for such weakly coupled, weakly disordered structural systems. <*i(t) d