Ristaniemi, Aapo

Nuclear power plant piping systems exhibit dynamic behaviour, and piping supports keep the displacements of the pipes within acceptable limits. The aim of the research is the development of a simplified way to take into account the nonlinear displacement behaviour of the supports in linear dynamic piping analyses. The research was started as a Master's thesis with focus on supports with gaps and friction and was further continued regarding supports with gaps. The linearization procedure and methods are found in literature and they were further developed in this study. The goal is to represent the nonlinear system as accurately as possible by an equivalent linear system. The linearization procedure was investigated in time-domain and frequency-domain analyses using simplified piping systems. Frequency-domain is of particular interest as nonlinearities cannot be incorporated into classical mode-based methods. Equivalent linear systems were determined for the selected load cases and comparison was made between the equivalent linear and original nonlinear systems, time-domain and frequency-domain linearization results and three different linearization methods. Correspondence between equivalent linear and original nonlinear systems was not found accurate, time- and frequency-domain linearization gave similar results and different linearization methods resulted in equivalent linear systems very close to each other

Linearization of supports with gaps in dynamic piping analyses

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