Dynamic models of piled foundations

The vibration behavior of piled foundations is an important consideration in fields such as earthquake engineering, construction, machine-foundation design, offshore structures, nuclear energy, and road and rail development. This paper presents a review of the past 40 years' literature on modeling the frequency-dependent behavior of pile foundations. Beginning with the earliest model of a single pile, adapted from those for embedded footings, it charts the development of the four pile-modeling techniques: the "dynamic Winkler-foundation" approach that uses springs to represent the effect of the soil; elasticcontinuum-type formulations involving the analytical solutions for displacements due to a subsurface disk, cylinder, or other element; boundary element methods; and dynamic finite-element formulations with special nonreflecting boundaries. The modeling of pile groups involves accounting for pile-soil-pile interactions, and four such methods exist: interaction factors; complete pile models; the equivalent pier method; and periodic structure theory. Approaches for validating pile models are also explored. Copyright © 2013 by ASME.

Numerical analysis of shallow foundations under combined horizontal and torsional loading

Foundations of subsea infrastructure in deep water subjected to asymmetric environmental loads have underscored the importance of combined torsional and horizontal loading effects on the bearing capacity of rectangular shallow foundations. The purpose of this study is to investigate the undrained sliding and torsional bearing capacity of rectangular and square shallow foundations together with the interaction response under combined loading using three-dimensional finite element (3D-FE) analysis. Upper bound plastic limit analysis is employed to establish a reference value for horizontal and torsional bearing capacity, and an interaction relationship for the combined loading condition. Satisfactory agreement of plastic limit analysis (PLA) and 3D-FE results for ultimate capacity and interaction curves ensures that simple PLA solution could be used to evaluate the bearing capacity problem of foundation under combined sliding and torsion.

Isolating shallow foundations from seismic loading

Most modern design codes do not allow for movement between a shallow foundation and the underlying soil during seismic loading. Consequently, the full magnitude of seismic energy is transmitted from the soil to the foundation during an earthquake. This energy either has to be dissipated before reaching the superstructure via engineering solutions such as base isolation systems, or the structure itself must withstand the full impact of the earthquake resulting in high material usage and expensive design. However, the inherent hysteric behaviour of soil can be used to isolate a foundation from the underlying soil. As part of a study into the soil-structure-interaction of shallow foundations, methods to optimise foundation isolation were investigated. In this paper the results from centrifuge tests investigating two of these methods are compared to results when no special foundation layout was implemented and the impact of the proposed isolation methods is discussed. © 2010 Taylor & Francis Group, London.

Centrifuge modeling of seismic liquefaction effects on adjacent shallow foundations

Shallow foundations built on saturated deposits of granular soils in seismically active areas are, regardless of their static bearing capacity, critical structures during seismic events. A single centrifuge experiment involving shallow foundations situated atop a liquefiable soil deposit has been performed to identify the mechanisms involved in the interaction between liquefaction-induced effects on neighboring shallow foundations. Centrifuge test results indicate that liquefaction causes significant settlements of footings, which are affected by the presence of neighboring foundations and can be extremely damaging to the superstructure. The understanding of these interaction effects is very important, mainly in densely populated urban areas. The development of high excess pore-pressures, localized drainage in response to the high transient hydraulic gradients, and earthquake-induced vertical motions to the footings are also important effects that are discussed to assist in enhancing current understanding and ability to predict liquefaction effects on shallow foundations. © 2014 Taylor & Francis Group.

Foundations for offshore wind turbines

Offshore wind turbines impose unique combinations of loads on their foundations. They impose large lateral loads in relation to vertical loading which must be resisted, but are also subject to approximately a million cycles of loading through their design life. As the performance of these systems is dominated by their dynamic response, the stiffness of the foundations becomes critical in design. Conventional design codes which are conservative by virtue of predicting a lower stiffness than might be observed in practice may not be conservative for these problems. By utilizing centrifuge modeling the behaviour of monopile foundations in both sands and clays under cyclic loading can be investigated in order to predict the dynamic behaviour of these systems. © 2010 Taylor & Francis Group, London.

Optimal displacement mechanisms beneath shallow foundations on linear-elastic perfectly plastic soil

An energy method for a linear-elastic perfectly plastic method utilising the von Mises yield criterion with associated flow developed in 2013 by McMahon and co-workers is used to compare the ellipsoidal cavity-expansion mechanism, from the same work, and the displacement fields of other research by Levin, in 1995, and Osman and Bolton, in 2005, which utilise the Hill and Prandtl mechanisms respectively. The energy method was also used with a mechanism produced by performing a linear-elastic finite-element analysis in Abaqus. At small values of settlement and soil rigidity the elastic mechanism provides the lowest upper-bound solution, and matches well with finite-element analysis results published in the literature. At typical footing working loads and settlements the cavity-expansion mechanism produces a more optimal solution than the displacement fields within the Hill and Prandtl mechanisms, and also matches well with the published finite-element analysis results in this range. Beyond these loads, at greater footing settlements, or soil rigidity, the Prandtl mechanism is shown to be the most appropriate.

A role of monitoring to reduce the uncertainty in the performance of pile foundations

In typical conventional foundation design, the inherent variability of soil properties, model uncertainty and construction variability are not modeled explicitly. A main drawback of this is that the effect of each variability on the probability of an unfavorable event cannot be evaluated quantitatively. In this paper, a method to evaluate the uncertainty-reduction effect on the performance of a vertically-loaded pile foundation by monitoring the pile performance (such as pile load testing or placing sensors in piles) is proposed. The effectiveness of the proposed method is examined based on the investigation of a 120-pile foundation placed on three different ground profiles. The computed results show the capability of evaluating the uncertainty-reduction effect on the performance of a pile foundation by monitoring. © 2014 Taylor & Francis Group, London.

Foundations of Actor Semantics

The actor message-passing model of concurrent computation has inspired new ideas in the areas of knowledge-based systems, programming languages and their semantics, and computer systems architecture. The model itself grew out of computer languages such as Planner, Smalltalk, and Simula, and out of the use of continuations to interpret imperative constructs within A-calculus. The mathematical content of the model has been developed by Carl Hewitt, Irene Greif, Henry Baker, and Giuseppe Attardi. This thesis extends and unifies their work through the following observations. The ordering laws postulated by Hewitt and Baker can be proved using a notion of global time. The most general ordering laws are in fact equivalent to an axiom of realizability in global time. Independence results suggest that some notion of global time is essential to any model of concurrent computation. Since nondeterministic concurrency is more fundamental than deterministic sequential computation, there may be no need to take fixed points in the underlying domain of a power domain. Power domains built from incomplete domains can solve the problem of providing a fixed point semantics for a class of nondeterministic programming languages in which a fair merge can be written. The event diagrams of Greif's behavioral semantics, augmented by Baker's pending events, form an incomplete domain. Its power domain is the semantic domain in which programs written in actor-based languages are assigned meanings. This denotational semantics is compatible with behavioral semantics. The locality laws postulated by Hewitt and Baker may be proved for the semantics of an actor-based language. Altering the semantics slightly can falsify the locality laws. The locality laws thus constrain what counts as an actor semantics.

Competitiveness in a globalised world: Michael Porter on the microeconomic foundations of the competitiveness of nations, regions, and firms.

In this paper, we provide the text of an interview with Professor Michael Porter discussing his research and ideas relating to the microeconomic foundations of global competitiveness. The discussion provides a microeconomic perspective on some of the key issues relating to recent research on competitiveness, productivity, clusters, US economic leadership, economic growth and development.

The Epistemological Foundations of Artificial Agents

Lacey, N. J., Lee, M. H. (2003). The Epistemological Foundations of Artificial Agents. Minds and Machines, 13, 339-365.

The Implications of Philosophical Foundations for Knowledge Representation and Learning in Agents

N.J. Lacey and M.H. Lee, ?The Implications of Philosophical Foundations for Knowledge Representation and Learning in Agents?, Springer-Verlag Lecture Notes on Artificial Intelligence, Vol 2636 on Adaptive Agents and Multi-Agent Systems, 2002.

The Implications of Philosophical Foundations for Knowledge Representation and Learning in Agents

Lacey N and Lee M.H., The Implications of Philosophical Foundations for Knowledge Representation and Learning in Agents, in Proc. AISB?01 Symposium on Adaptive Agents and Multi-agent Systems, York, March 2001, pp13-24.

The political philosophy of Miki Kiyoshi: A close reading of the philosophical foundations of cooperative communitarianism

The thesis is a historical and philological study of the mature political theory of Miki Kiyoshi (1897-1945) focused on Philosophical Foundations of Cooperative Communitarianism (1939), a full translation of which is included. As the name suggests, it was a methodological and normative communitarianism, which critically built on liberalism, Marxism and Confucianism to realise a regional political community. Some of Miki’s Western readers have wrongly considered him a fascist ideologue, while he has been considered a humanist Marxist in Japan. A closer reading cannot support either view. The thesis argues that the Anglophone study of Japanese philosophy is a degenerating research programme ripe for revolution in the sense of returning full circle to an original point. That means returning to the texts, reading them contextually and philologically, in principle as early modern European political theory is read by intellectual historians, such as the representatives of Cambridge School history of political thought. The resulting reading builds critically on the Japanese scholarship and relates it to contemporary Western and postcolonial political theory and the East Asian tradition, particularly neo-Confucianism. The thesis argues for a Cambridge School perspective radicalised by the critical addendum of geo-cultural context, supplemented by Geertzian intercultural hermeneutics and a Saidian ‘return to philology’. As against those who have seen radical reorientations in Miki’s political thought, the thesis finds gradual progression and continuity between his neo-Kantian, existentialist, Marxian anthropology, Hegelian and finally communitarian phases. The theoretical underpinnings are his philosophical anthropology, a structurationist social theory of praxis, and a critique of liberalism, Marxism, nationalism and idealism emphasising concrete as opposed to abstract theory and the need to build on existing cultural traditions to modernise rather than westernise East Asia. This post-Western fusion was imagined to be the beginning of a true and pluralistic universalism.