Probabilistic Models for Residual and Peak Transient Tilt of Mat-Founded Structures on Liquefiable Soils

Abstract

This paper presents probabilistic models for predicting the residual and peak transient tilt of mat-founded structures on liquefiable ground. First, the study presents a completely empirical model based on correlating residual tilt to settlement in case histories. Second, a semiempirical model for residual tilt is developed based on an extensive numerical parametric study of soil–foundation–structure systems in 3D with more than 63,000 simulations, centrifuge tests performed by several researchers, and case history observations from several earthquakes. The model of peak transient tilt is based on centrifuge tests. The uncertainty around the estimates of each model is described using log-normal distributions, and all necessary correlation coefficients are calculated. The proposed procedure is the first methodology for estimating the seismically induced residual tilt of such structures that is not derived solely from settlement models on two sides of the foundation with different soil profiles. It therefore accounts for the influence of complex phenomena (e.g., soil–structure interaction, asymmetric loading, interlayering, and ejecta) that mechanistically affect tilt and settlement differently. The models consider various properties of the soil profile, foundation, and structure, and also characterize total uncertainty. These models constitute a fundamental component of a performance-based approach that could be combined with vulnerability functions in the future to evaluate liquefaction risks in terms of losses associated with tilt of structures.