Stiffness variation can be generated in a flexible, vibrating structure using a number of different mechanisms, including cables, variable stiffness members, and variable stiffness joints. In such structures stiffness variation results in modal disparity, a property that allows the flow of vibration energy from one set of modes of the structure to another. The purposeful introduction of modal disparity in a structure using stiffness variation can be viewed as an effort to enhance controllability and observability of the structure, whereby vibration suppression is enabled by sensing and controlling only a few select modes. In previous work by the authors ([1,2]) modal disparity was introduced by means of cables and non-structural masses, placed strategicaly on the structure. In this work we explore other mechanisms to introduce modal disparity, including various implementations of variable stiffness joints. As in [
], the objective is to facilitate the transfer of energy from modes that are not controlled to modes that are, and this is achieved by
modal disparity. This work presents a computational scheme to maximize modal disparity by placing a finite number of variable stiffness joints on a flexible frame. The scheme is based on standard methods of topoplogy optimization. The method is illustrated by an example.