Generate tri-directional spectra-compatible time histories using HHT method

This paper proposes two algorithms to generate spectrum-compatible time histories based on two approaches recommended by USNRC Standard Review Plan 3.7.1. Hilbert-Huang Transform technique is used to analyze frequency contents and amplitudes of seed motions. Through adjusting the frequency contents and amplitudes of seed motions, spectrum-compatible time histories are obtained. The first algorithm is to generate tri-directional time histories compatible with multi-damping target design spectra (ground response spectra or floor response spectra). The second algorithm is to generate tri-directional time histories compatible with single-damping target design spectra. Examples are presented to demonstrate versatility of these two proposed algorithms to generate spectra-compatible time histories.