Transfer-Function-Based Criteria for Decoupling of Secondary Systems

Abstract

New criteria for decoupling of primary-secondary systems have been recently proposed by the first writer. They are defined by a limited variation of the maximum transfer function of a secondary system that is connected to a single-degree-of-freedom primary-secondary system. In this paper, their sufficiency for decoupling is investigated when the two-degree-of-freedom primary-secondary system is subjected to a filtered white noise process of the Kanai-Tajimi power spectrum. Verifications for sufficiency of the new criteria are extended to a secondary system mounted to a multi-degree-of-freedom primary system. Effects of site condition on the criteria are also studied, by varying the characteristic frequency of the Kanai-Tajimi spectrum. The upper-bound mass ratios resulting from the criteria, above which a coupled analysis is required, are compared with the current decoupling criteria mainly used in the design of nuclear facilities. Revisions of the current decoupling criteria are suggested as a result of this study. A simple procedure is recommended and illustrated by an example to apply the new criteria into the analysis and design of secondary systems.