INELASTIC RESPONSE EVALUATION METHOD OF EQUIPMENT CONSIDERING PEAK BROADENING OF RESPONSE SPECTRUM

In order to evaluate seismic responses considering the elasto-plastic properties of equipment and piping systems, nonlinear time history analyses are utilized. When the analyses are used for seismic evaluation of equipment and piping systems in nuclear power plants, it is required to consider the uncertainty in the frequencies owing to uncertainties in the material properties of the structure and soil. The Boiler and Pressure Vessel Code of ASME indicates that the analysis using floor motions with different time intervals, where the time intervals are modified corresponding to the response spectrum broadening, is applicable. However, nonlinear time history analysis of inelastic models is relatively time-consuming compared to linear analysis, and conducting several analysis cases indicated in the Code might increase the burden of analytical work. Therefore, simplified method is desirable to consider the uncertainty in time history analysis. In this paper, a simplified method using inelastic response spectrum is developed to consider the uncertainty in time history analysis. The applicability of the developed method is investigated by comparing the results of parametric survey with those of the developed method.