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The paper addresses forced vibrations in piping subsystems, which are induced due to the formation and separation of turbulent vortices in the flow of a fluid being transported. The excitation frequency is not a constant number but can take on values from a certain range, thus leading to difficulties and ambiguities in the vibration analysis of piping. To solve this problem, a so-called energy approach is put forward which enables one to determine the most physically governed frequencies of forced vibrations. The approach essentially consists in searching for the natural frequencies and modes of the fluid hydrodynamic vibrations whereby the minimum amount of energy leaves the piping subsystem, while the maximum one remains inside. The validity of the proposed approach is verified by test examples. The proposed methods have been used to analyze piping forced vibrations induced by turbulent vortices in the steam flow in the secondary coolant piping of nuclear power plants with WWER-1000 reactor. Natural frequencies and modes of mechanical, hydrodynamic, and coupled hydrodynamic vibrations have been determined; some recommendations of how to minimize the level of vibrations have been worked out. [ABSTRACT FROM AUTHOR]

The paper describes the method of initial parameters which is used for stress analysis of complex branched piping systems under static loading as well as under natural and forced harmonic vibrations, including the case of kinematic loading by displacement amplitudes. For the purpose of modeling arbitrary curved elements, in particular three-dimensional ones, the authors propose an inertialess rotary element of zero length, which turns coordinate axes of neighbor elements. The paper demonstrates the potentialities of the method for vibrodiagnostics of piping. [ABSTRACT FROM AUTHOR]