The theory of the dual modal space structural modification method has been previously presented. This paper implements this theory on real-world structures described by three-dimensional space (i.e., x, y, z). The analytical database for the structure is built by experimental modal analysis methods. The modifications allowed are: addition or removal of a point mass at a degree-of-freedom (DOF); addition or removal of a linear spring between two DOF; and addition or removal of a linear damper between two DOF. The modifications are done entirely in modal spaces, modal space I and modal space II, for efficiency reasons. To modify the dynamic characteristics of the structure, the physical mass modification matrix, the stiffness modification matrix and the damping modification matrix which describe the physical changes to the structure are required. These general stiffness or damping modification matrices are derived. Their form provides for an easily automated way to carry out structural modifications between any pair of structural modeling points. Other methods may require dozens of modifications to be equal to one modification under this method. The technique developed requires only the geometry of the two measured points to be connected and the axial stiffness of the connecting element. The directions of the element or the points are not needed to determine the correct modification matrix. Examples are included to illustrate the modification and verify the theory.
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