Evaluation of seismic performance of pile-supported models in liquefiable soils

The seismic performance of four pile-supported models is studied for two conditions: (i) transient to full liquefaction condition, i.e. the phase when excess pore pressure gradually increases during the shaking; (ii) full liquefaction condition, i.e. defined as the state where the seismically induced excess pore pressure equalises to the overburden stress. The paper describes two complementary analyses consisting of an experimental investigation, carried out at normal gravity on a shaking table, and a simplified numerical analysis, whereby the soil-structure interaction (SSI) is modelled through non-linear Winkler springs (commonly known as p-y curves). The effects of liquefaction on the SSI are taken into account by reducing strength and stiffness of the non-liquefied p-y curves by a factor widely known as p-multiplier and by using a new set of p-y curves. The seismic performance of each of the four models is evaluated by considering two different criteria: (i) strength criterion expressed in terms of bending moment envelopes along the piles; (ii) damage criterion expressed in terms of maximum global displacement. Comparison between experimental results and numerical predictions shows that the proposed p-y curves have the advantage of better predicting the redistribution of bending moments at deeper elevations as the soil liquefies. Furthermore, the proposed method predicts with reasonable accuracy the displacement demand exhibited by the models at the full liquefaction condition. However, disparities between computed and experimental maximum bending moments (in both transient and full liquefaction conditions) and displacement demands (during transient to liquefaction condition) highlight the need for further studies. Copyright (C) 2016 The Authors Earthquake Engineering & Structural Dynamics Published by John Wiley & Sons Ltd.