Decoupling criterion for elastic-plastic seismic analysis of large-scale complex piping systems in nuclear power plants

This paper proposes an elastic-plastic-based decoupling criterion that can be applied to the seismic analysis of large-scale complex piping systems in nuclear power plants under beyond design basis earthquakes. First, the existing elastic-based decoupling criteria for seismic analyses were critically reviewed. Next, the effect of plasticity on the decoupling criteria was investigated by considering the equivalent damping and stiffness reduction. Finally, the decoupling criterion considering plasticity was developed based on the changes resulting from existing decoupling criteria. The validity of the proposed decoupling criterion was confirmed through its application to an analysis of a real piping system.