Elastic-Plastic Seismic Response Analysis of Piping System Considering Damage to Piping Support

Abstract Numerous piping supports are installed in the piping systems of nuclear power plants to suppress the responses of the piping systems to earthquakes. In design evaluations, allowable stresses are determined for each service state, and safety is ensured by maintaining the stress of the piping systems below the allowable stress determined via elastic evaluation. However, if a large earthquake that exceeds expectations occurs, damage may occur to the piping body and supports. Therefore, clarifying the ultimate state by performing an elastoplastic evaluation that considers damage to the piping system is important. In this study, an earthquake response analysis of a piping system, considering support damage, was conducted using nonlinear spring elements that simulate the elastoplastic behavior of the supports. The employed nonlinear spring elements can simulate the load-displacement relationships of various supports and ductile fractures. The effects of the elastoplastic behavior of the piping support on the increase or decrease in the response of the piping system was confirmed by comparing the analysis results of the nonlinear and linear spring elements. In the piping system in this study, the effect of hysteretic damping was small, and the effect of changes in the natural frequency was large.