Portland State University. Department of Civil & Environmental Engineering
Term of Graduation
Date of Publication
Doctor of Philosophy (Ph.D.) in Civil & Environmental Engineering
Civil and Environmental Engineering
1 online resource (xiv, 256 pages)
Extensive loss of stiffness and strength in liquefied soils can cause large ground deformations during strong earthquake shaking. One of the major sources of damage in pile foundations in liquefied soil is the excessive deformation due to lateral spreading. Pile-supported wharves subjected to earthquake motions are expected to accommodate inertial loads imposed at pile head from the superstructure as well as the kinematic loads imposed on piles from the lateral ground deformations. Current design codes significantly vary on how to combine inertia and kinematic demands. Recent research on soil-foundation-structure interaction suffers from lack of experiment-based data. There is a serious need to fill the knowledge gap and help designers to better evaluate risk and design cost-effective pile foundations. In this research, the interaction of inertial and kinematic demands is investigated using data from five well-instrumented centrifuge tests on pile-supported wharves. The observations from these tests were used to investigate the time- and depth-dependent nature of kinematic and inertial demands on the deep foundations during earthquake loading. The test results were analyzed to provide the relative contributions of peak inertial loads and peak soil displacements during critical cycles, and the data revealed the depth-dependency of these factors. The results were used to refine existing guidelines for design of pile-supported wharves subjected to foundation deformations. The observations from centrifuge tests were then used to evaluate the accuracy of the equivalent static analysis (ESA) procedure using p-y models for the design of pile-supported wharves subjected to lateral ground deformations during earthquake loading. The piles in these centrifuge tests were subjected to the combined effects of wharf deck inertial loads and ground deformations. The experiments included soil properties ranging from nonliquefiable to fully liquefied cases which provided a wide range of conditions against which the ESA method could be evaluated. Finally, a nonlinear dynamic model of a pile-supported wharf was created and calibrated using recorded data from a centrifuge test. The objective of the numerical modeling was to create a calibrated numerical model that captures key responses of the wharf and the soil in order to be used in subsequent studies that are too costly and time-consuming to do using physical modeling. The calibrated numerical model was then used in an incremental dynamic analysis to evaluate the effects of ground motion duration on the dynamic response of a pile-supported wharf subjected to liquefaction-induced lateral ground deformations. The analysis results provided insights on the relative contribution of inertial and kinematic demands on the response of the wharf with respect to motion duration.
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Souri, Milad, "Development of a Design Guideline for Pile Foundations Subjected to Liquefaction-Induced Lateral Spreading" (2021). Dissertations and Theses. Paper 5695.