Natural modes of modified structures

It is pointed out that the ever-increasing need to improve the efficiency of structural systems places a growing importance on dynamic analysis in the design or development cycle. From a knowledge of the service and load conditions, potential vibration problems can be identified. At this stage of the design cycle, the proposed structure undergoes a series of modifications aimed at eliminating such problems. The complete reanalysis of the structure may be a time-consuming task. In this context, the methods of structural dynamics modification have evolved. The present paper provides a detailed review of structural dynamics modification techniques. Techniques based on small modifications are discussed, taking into account Rayleigh's method, perturbation approaches, and the sensitivity approach. Attention is also given to techniques based on localized modifications, techniques based on modal aproximation, and applications. (G.R.)