Abstract
Two analytical methods are introduced by which changes of the natural frequencies, the natural modes and the dynamic response due to alteration of the local physical properties (i . e ., mass, stiffness, damping, shell thickness etc.) of a structure can be predicted easily, using the modal parameters of this structure before alteration. A computer program by one of these methods is made for practical use. The values of change in the physical properties of a structure necessary for alteration of the natural frequency to specified value can also be calculated using this program. The time necessary for calculation with this program is far shorter than by direct use of the finite element method. The calculated results with this program are in good agreement with the experimental ones and the results of the finite element analysis.
