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Abstract : This research has investigated the response of pile foundations subjected to lateral force applied directly to pile head and loadings arising from lateral soil movements of the surrounding ground. The behaviour of pile foundations subjected to lateral soil movements was studied through physical modelling with a specially designed testing apparatus. Laboratory experiments have been undertaken on a single pile embedded in progressive moving sand. A triangular loading block was used in the model tests to induce a progressive soil movement profile. Apart from eight general tests, sixteen tests were conducted on a single pile to examine the effects of the distance between the source where soil movements were induced and the pile location, the magnitude of axial load applied at pile head, the variation of loading block angle, varying combination of sliding and stable layer depths, and pile diameter on the responses of piles. The results of previously conducted pile tests with a uniform soil movement profile were compared with those of the current tests to examine the effect of soil movement profiles on the pile behaviour. Simple solutions were proposed for predicting the pile responses. They provided good estimate of the development of maximum bending moment and maximum shear force in the piles with soil movement. Importantly, the maximum bending moments induced by the soil movements were found to be linearly related to the maximum shear forces (sliding thrust), independent of the magnitude and depth of soil movement and soil movement profiles. Experiments have also been conducted on pile groups in progressive moving sand, including various pile group configurations and spacing. Both free-head and cappedhead fixity conditions have been considered. The findings show that the resistances of the piles to lateral soil movements significantly rely on their locations in a group, especially for piles arranged in a line parallel to the soil movement direction. The results of the pile group tests were compared with those of the single pile tests. Group factors were defined in terms of maximum bending moment and modulus of subgrade reaction to quantify the impact of group effect. The simple solutions developed were extended for predicting the response of individual piles in a group with soil movement. The static and cyclic responses of laterally loaded piles in cohesionless soils have been investigated as well. Guideline for estimating the design parameters for laterally loaded rigid piles in cohesionless soils were provided from extensive back calculation of measured responses of fifty-one pile tests. The elastic-plastic solutions presented by Guo (2008) were used in the back calculation. Simple expressions were presented for estimating the parameters used in the solutions. The reliability of the back calculation, the effects of the ratio of loading eccentricity to pile embedded length on the nonlinear pile response and lateral load capacity were investigated. Additionally, the apparatus was modified to apply cyclic lateral loading, with which a series of model tests were conducted on piles in dry sand under static and cyclic loadings. Analyses of the test results show that the cyclic load level has a greater impact on the pile behaviour than the number of cycles. It is noted that the gradient of the limiting force profile will decrease and the modulus of subgrade reaction will increase, after a number of unloading and reloading cycles. The induced maximum bending moment can be estimated from the applied lateral load, eccentricity of the load, and the depth at which the maximum bending moment occurs.
This work offers guidance on bridge design for extreme events induced by human beings. This document provides the designer with information on the response of concrete bridge columns subjected to blast loads as well as blast-resistant design and detailing guidelines and analytical models of blast load distribution. The content of this guideline should be considered in situations where resisting blast loads is deemed warranted by the owner or designer.
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.
Earthquake-induced soil liquefaction (liquefaction) is a leading cause of earthquake damage worldwide. Liquefaction is often described in the literature as the phenomena of seismic generation of excess porewater pressures and consequent softening of granular soils. Many regions in the United States have been witness to liquefaction and its consequences, not just those in the west that people associate with earthquake hazards. Past damage and destruction caused by liquefaction underline the importance of accurate assessments of where liquefaction is likely and of what the consequences of liquefaction may be. Such assessments are needed to protect life and safety and to mitigate economic, environmental, and societal impacts of liquefaction in a cost-effective manner. Assessment methods exist, but methods to assess the potential for liquefaction triggering are more mature than are those to predict liquefaction consequences, and the earthquake engineering community wrestles with the differences among the various assessment methods for both liquefaction triggering and consequences. State of the Art and Practice in the Assessment of Earthquake-Induced Soil Liquefaction and Its Consequences evaluates these various methods, focusing on those developed within the past 20 years, and recommends strategies to minimize uncertainties in the short term and to develop improved methods to assess liquefaction and its consequences in the long term. This report represents a first attempt within the geotechnical earthquake engineering community to consider, in such a manner, the various methods to assess liquefaction consequences.
Guiding the professional through the complexities of lateral-load design, this book and CD-ROM combination introduces the procedures involved in piles and pile group design. This is a problem that can only be solved by accounting for the soil resistance as related to the lateral deflection of the pile. Intricate equations are derived and fully explained, enabling the designer to find the critical loads, that will either cause a pile to be overloaded or cause too much lateral deflection. The CD-ROM contains simplified versions of two required programs that allow the reader to check the solutions of some of the examples given in the book and to find answers to related problems.
Pile foundations are the most common form of deep foundations that are used both onshore and offshore to transfer large superstructural loads into competent soil strata. This book provides many case histories of failure of pile foundations due to earthquake loading and soil liquefaction. Based on the observed case histories, the possible mechanisms of failure of the pile foundations are postulated. The book also deals with the additional loading attracted by piles in liquefiable soils due to lateral spreading of sloping ground. Recent research at Cambridge forms the backbone of this book with the design methodologies being developed directly based on quantified centrifuge test results and numerical analysis. The book provides designers and practicing civil engineers with a sound knowledge of pile behaviour in liquefiable soils and easy-to-use methods to design pile foundations in seismic regions. For graduate students and researchers, it brings together the latest research findings on pile foundations in a way that is relevant to geotechnical practice. Sample Chapter(s). Foreword (85 KB). Chapter 1: Performance of Pile Foundations (4,832 KB). Contents: Performance of Pile Foundations; Inertial and Kinematic Loading; Accounting for Axial Loading in Level Ground; Lateral Spreading of Sloping Ground; Axial Loading on Piles in Laterally Spreading Ground; Design Examples. Readership: Researchers, academics, designers and graduate students in earthquake engineering, civil engineering and ocean/coastal engineering.