We examined two approaches for predicting the inelastic responses of piping systems. The first enabled us to evaluate accurate responses using nonlinear time-history analysis. We focused on a material model in this approach. Plastic deformation might exhibit a cyclic-hardening effect, which is dependent on the strain ranges, and this hardening affects the dynamic responses of piping systems. Therefore, we improved the hardening model developed by Ohno and Wang (OW model), which is one of the most sophisticated models for producing kinematic hardening behavior. We modified it to produce cyclic-hardening behavior dependent on strain ranges. The second was a simplified approach to evaluate inelastic responses without time-consuming time-history analysis. We developed a tool using equivalent linearization. The tool used analysis techniques including a model of elastic beam elements using flexibility factors for pipe elbows, and modal response spectrum analysis. Equivalent linearization made it possible to apply modal analysis to inelastic analysis. We demonstrated how applicable the approaches were by conducting test simulations.

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