Seismic Demand of the Liquefaction Potential with Equivalent Number of Cycles for Probabilistic Seismic Hazard Analysis: Fid-Bau Portal

Seismic Demand of the Liquefaction Potential with Equivalent Number of Cycles for Probabilistic Seismic Hazard Analysis

Kishida, Tadahiro / Tsai, Chi-Chin

Abstract

Equivalent number of cycles ( $N_{cyc}$ ) is a significant factor in assessing liquefaction potential during earthquakes. However, the effects of $N_{cyc}$ are considered a deterministic value by using a magnitude scaling factor, and the uncertainties of these effects have not been included in the current design practice. This paper calculates $N_{cyc}$ within the soil mass by deconvolution analysis as a function of the period of soil layer from the ground surface ( $T_{s}$ ) and the soil property ( $b$ ) using a wide range of acceleration time histories. The predictive model of $N_{cyc}$ is developed as variable dependent on earthquake magnitude, peak ground acceleration (PGA), and ratio of spectral acceleration, $T_{s}$ and $b$ . Then, the $N_{cyc}$ model is combined with the ground-motion prediction equation of PGA and the prediction equation of seismic shear-stress reduction coefficient ( $r_{d}$ ) to obtain the prediction equation of the seismic demand of the liquefaction potential ( $K_{1 cyc}$ ). The standard deviation of $K_{1 cyc}$ is also modeled on the basis of the aleatory variability of PGA, $r_{d}$ , and $N_{cyc}$ with correlations between these residuals. This predictive model of $K_{1 cyc}$ is implemented in probabilistic seismic hazard analysis (PSHA) to show the impact of these uncertainties on design practice.