A method is described for deriving constrained modes and frequencies f
rom a reduced model based on a subset of the free free modes plus the
residual effects of neglected modes. The method involves a simple modi
fication of the MacNeal and Rubin component mode representation to all
ow development of a verified constrained (filed-base) structural model
. Results for two spaceflight structures having translational boundary
degrees of freedom show quick convergence of constrained modes using
a measurable number of free-free modes plus the boundary partition of
the residual flexibility matrix. This paper presents the free-free res
idual flexibility approach as an alternative test/analysis method when
fixed-base testing proves impractical.