On the Development of Power Spectral Density Functions Compatible With Response Spectra

Abstract The U.S. Nuclear Regulatory Commission (US-NRC) Standard Review Plan (SRP) Revision 4, section 3.7.1, outlines guidelines for developing and evaluating ground motion time histories used in dynamic analyses of nuclear facilities. These motions are primarily defined by closely matching a design response spectrum, but a secondary check is necessary to ensure adequate power distribution across the relevant frequency range. This involves comparing the ground motion’s power spectral density (PSD) to a target PSD function that is compatible with the design spectrum. SRP 3.7.1 Appendix B provides a procedure for constructing these response spectrum compatible target PSD functions. However, this approach does not explicitly consider the impact of strong motion duration on the relationship between PSD and response spectrum. Recently, an alternative methodology has been proposed that enables the construction of target PSD functions tailored to specific strong motion durations. This article further explores the influence of strong motion duration on response spectrum-compatible PSD functions and assesses the limitations of both methodologies using PSDs from actual recorded ground motions. The findings indicate that strong motion duration significantly affects the amplitudes of the spectrum-compatible PSD functions. Moreover, target PSD functions that account for strong motion duration consistently demonstrate better correlation with the actual PSD of recorded motions, suggesting their potential for improved accuracy in the development of input motions.