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

Abstract

SUMMARYThe 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.

Physical Modelling of Offshore Wind Turbine Foundations for TRL (Technology Readiness Level) Studies

“…One of the important considerations is the change in dynamic performance due to the application of cyclic loading. This change may be significant in the presence of loose deposits, which may liquefy as a result of cyclic loadings [26,[35][36][37]. One of the ways to White noise testing was trialed because it offered the possibility of acquiring data at more frequent intervals during long-term tests due to its greater potential for automation over free vibration tests.…”

Pushover analysis for flexible and semi‐flexible pile‐supported wharf structures accounting the dynamic magnification factors due to torsional effects

“…Combining the high seismicity with the soil characteristics (clay), a liquefaction risk exists 24,33,44,45 ; which is a process where the immersed sediments suffer a loss of resistance and let be a solid to become a viscous liquid. The measures to reduction the liquefaction risk consist in, for instance, soil replacement and intrusive retrofit methods.…”

Seismic analysis of pile in liquefiable soil and plastic hinge

“…Maheshwari and Sarkar (2011) and Sarkar and Maheshwari (2012) used the Drucker-Prager soil model of work hardening to investigate the 3D behaviour of single piles and pile groups. Lombardi and Bhattacharya (2016) and Dash et al (2017) adopted a new set of p-y curves that can be obtained by modifying the conventional p-y curves (for non-liquefied soils) in such a way that replicates the strain hardening behaviour aforementioned. In this research, the non-linear spring stiffness (p-y curves) of the liquefied soil are used to evaluate soil-pile interaction analysis performed pile bending moments.…”

“…Liquefaction happens when, during earthquake shaking, the pore water pressure of loosely deposited sandy soil layers increases rapidly and sufficiently and the effective stress in the soil can decrease to zero (Booth, 1994: p. 277). Collapse and damage of pile-supported structures due to liquefaction are still observed in many major earthquakes (Lombardi and Bhattacharya, 2016). The pile-supported structures' response to liquefiable soils during a major earthquake depends on the stiffness of the pile foundation, response of soil surrounding the pile and soil-pile interaction effects.…”