A simplified method for inelastic piping system seismic response prediction

This paper presents a seismic response prediction method based on a simplified plastic system analysis. The analysis uses a dynamically equivalent static-g loading that has been adjusted for inelastic energy dissipation. The simplified plastic system analysis utilizes an incremental series of equivalent static-g loadings and replaces yielded components with hinge elements when a predefined hinge moment is reached. This hinge moment value is selected to result in inelastic energy absorption of the same magnitude as observed in piping component dynamic tests and analyses. Two definitions of dynamically equivalent static-g loadings are employed: One conservatively based on the peak of the design acceleration response spectrum, the other based on modal analysis results of the simplified plastic system model. Both definitions account for inelastic energy dissipation using. Newmark-type inelastic response spectrum reduction factors and displacement ductility results of the simplified plastic system analysis. A comparison of predicted results versus experimental results is provided for a high-level seismic test of a representative LWR piping system. (orig.)