Dynamic Response of Tertiary Subsystems

An efficient and accurate method is presented for dynamic analysis of tertiary subsystems mounted on primary‐secondary systems, such as control devices attached to piping in nuclear power plants. Modal properties, such as natural frequencies, damping ratios, and mode shapes, of the composite primary‐secondary‐tertiary system are derived in terms of the known subsystem properties, employing previously developed modal synthesis and perturbation results for primary‐secondary systems, which are extended here to subsystems with non‐classical damping. The method is direct in that the response of the tertiary subsystem is obtained in terms of the input excitation without the need to generate intermediate results, such as floor response spectra. Important effects of tuning, interaction, nonclassical damping, and spatial coupling are fully accounted for. The paper also presents an in‐depth analysis of the conditions and effects of tuning in primary‐secondary‐tertiary systems.