In general, the dynamic analysis with FEM(Finite Element Mothod) of large structures requires large computer menory space and long computational time. For the purpose of economical dynamic analysis of large structures, most of all engineer want to use more efficient FEM algorithm. This paper reports modified CMS(Component Mode Synthesis) method which use more efficient algorithm than the classical CMS method. In this paper, ist is shown that Ritz vector sets can play the role of normal mode vector sets of substructures in CMS algorithm. The modified CMS method has good convergence performance compared with that of the classical CMS method.
