- 1988 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. A novel pole placement technique is developed for stabilizing an initially undairped (or lightly damped) structure using symmetric structural feedback. The feedback matrices are expressed in terms of prescribed symmetric, positive semidefinite submatrices and unknown scale factors (gain elements). The gain elements are designed to place a set of target eigenvalues at (or near) their desired locations by inposing state spaoe orthogonality conditions which the closed-locp structure must satisfy. A standard linear programming problem is formulated which not only places the target eigenvalues but also minimizes the modal dissipation and potential energy of the target modes and satisfies actuator force limits. In addition, the untargeted, higher frequency modes are guaranteed to be stable due to the positivity of the gain submatrices.