Frequency spectra characteristics of strong-motion acceleration recordings at liquefied sites

To understand the characteristics of earthquake action on buildings at potentially lique-fiable sites, 11 acceleration records from the selected liquefied sites were analyzed to discuss the characteristics of ground motion. The results showed that the acceleration amplitudes were remarkably reduced after initial site liquefaction and that the long-period components increased significantly with apparent " spikes” recorded. Comparison of the design spectra widely used in seismic design codes, both domestically and internationally, with the acceleration spectra obtained in this study shows that: in the short period range T＜0.3 s, the design spectra were consistent with the recorded response spectra; in the medium and long period range 0.3 s＜T＜1.5 s, the design spectra were smaller significantly than the recorded response spectra; in the long period range T＞1.5 s, the design spectra was a little smaller than the recorded spectra. Five typical numerical methods are used to simulate liquefaction acceleration, the results demonstrated that the numerical methods could satisfactorily predict response spectral values for the period range T＜1.0 s, but generally lower than the spectral values for the long-period T＞1.0 s.