Model Uncertainty of Shear Wave Velocity-Based Method for Liquefaction Potential Evaluation

In this paper, the issue of model uncertainty is examined in detail within the framework of the first-order reliability method (FORM). The focus of the paper is on the characterization of the uncertainty of a shear wave velocity-based simplified model for liquefaction potential evaluation developed by Andrus and Stokoe. This simplified model is expressed as a boundary curve that defines liquefaction resistance as a function of the corrected shear wave velocity. The uncertainty of this simplified model is represented by a lognormal random variable, and characterization of the model uncertainty mainly involves the determination of its two statistics, namely, the mean and the coefficient of variation. A trial-and-error procedure is used to determine the two statistics of the model uncertainty based on a Bayesian mapping function that is calibrated with a database of case histories. This procedure is shown to be effective in the present study, and the uncertainty of the Andrus and Stokoeʹs model is characterized. With the known model and parameter uncertainties, the probability of liquefaction can be determined through a routine FORM analysis.