Reanalysis for Structures with Close Frequencies Based on an Improved CA Method

Researches on modification and optimization of structures with close frequencies are valuable and of wide interest in the industrial applications. In this paper, an improved combined approximations technique, which can estimate the number of basis vectors according to the modifications in advance, is proposed for solving the perturbed Eigen problem with close frequencies rapidly. With this method, the number of basis vectors can be automatically pre-estimated by the modification of structure. This paper suggests that the number of basis vectors should be less than 10% of the degrees of freedom. This method is benefit to improve the efficiency, avoid the sickness of reduced equations and keep the computation stability of CA method. A numerical example of a spring-mass structure is solved by this method, which proves that the method can solve the perturbation response problem with fewer computing times and higher precision.