Estimation of Damping Correction Factors Using Duration Defined by the Standard Deviation of Phase Difference

Abstract

The damping correction factors (DCFs) to convert the 5% damping acceleration response spectra to those for other damping levels are computed for the records of 13 Japanese earthquakes. Their correlation with the standard deviation of phase difference ( σ) is also investigated in ten frequency bands. The σ-DCF relations obtained are found to be very similar across the different types of earthquakes. Further, regression analysis suggests that for damping ratios of 1% and 2%, with the increase in σ, the DCFs increase in low-frequency bands (up to 4–5 Hz), whereas they decrease in higher frequency bands. On the other hand, for damping ratios of more than 5%, with the increase in σ, the DCFs decrease in low-frequency bands (up to 1 Hz), whereas the opposite tendency is observed in higher frequency ranges. This research also discusses the applicability of the σ-DCF relations to design ground motion simulation.