MIXED-BASIS SUPERPOSITION METHOD FOR THE PERTURBATION ANALYSIS OF EIGENSOLUTIONS

The modal superposition method is often used for computing the perturb ation of eigenvectors in structural modification and model correction. However, it will bring about significant errors in the solution when the high-frequency modes are truncated. This paper presents a new meth od, which uses known modes construct a new basis of the N-dimensional Euclidean space (say, the mixed-basis), to calculate the first and sec ond order perturbations of the known eigenvectors. In the present meth od only the known modes are used. The accuracy of this method not only has no relation to number of the truncated modes but is better than t he truncated modal superposition method, in which only the known modes are employed. A numerical example of a truss structure with 36 degree s of freedom is given to illustrate the effectiveness of the method.