We consider semidefinite programming (SDP) formulations of certain truss topology optimization problems, where a lower bound is imposed on the fundamental frequency of vibration of the truss structure. These SDP formulations were introduced in: [M. Ohsaki, K. Fujisawa, N. Katoh and Y. Kanno, Semi-definite programming for topology optimization of trusses under multiple eigenvalue constraints, Comp. Meth. Appl. Mech. Engng., 180: 203--217, 1999]. We show how one may automatically obtain symmetric designs, by eliminating the `redundant' symmetry in the SDP problem formulation. This has the advantage that the original SDP problem is substantially reduced in size for trusses with large symmetry groups.
CentER Discussion paper 2007-17, Tilburg University, The Netherlands, February 2007.