A Probabilistic Model for Liquefaction Triggering Analysis Using SPT

The liquefaction resistance model developed by Cetin et al. (2004) along with a reference seismic loading model forms a performance function or limit state for liquefaction triggering analysis. Within the framework of the first order reliability method (FORM), the uncertainty of this limit state model is characterized through an extensive series of sensitivity studies using Bayesian mapping functions that were calibrated with a set of quality case histories. With the known model and parameter uncertainties, the probability of liquefaction of a future case can be fairly accurately predicted using the FORM analysis. A procedure is developed to assess the uncertainty associated with the Bayesian mapping function, which was due to use of limited observed data in the development. The effect of this uncertainty on the final assessment of model uncertainty is evaluated, and the variation in the final notional probability obtained from the FORM analysis estimated.