920,743 research outputs found
A method for creating a class of triangular C1 finite elements
No full textFinite elements providing a C1 continuous interpolation are useful in the numerical solution of problems where the underlying partial differential equation is of fourth order, such as beam and plate bending and deformation of strain-gradient-dependent materials. Although a few C1 elements have been presented in the literature, their development has largely been heuristic, rather than the result of a rational design to a predetermined set of desirable element properties. Therefore, a general procedure for developing C1 elements with particular desired properties is still lacking.This paper presents a methodology by which C1 elements, such as the TUBA?3 element proposed by Argyris et al., can be constructed. In this method (which, to the best of our knowledge, is the first one of its kind), a class of finite elements is first constructed by requiring a polynomial interpolation and prescribing the geometry, the location of the nodes and the possible types of nodal DOFs. A set of necessary conditions is then imposed to obtain appropriate interpolations. Generic procedures are presented, which determine whether a given potential member of the element class meets the necessary conditions. The behaviour of the resulting elements is checked numerically using a benchmark problem in strain-gradient elasticit
Data to accompany the paper in Granular Matter entitled "Discrete element simulation of railway ballast: modelling cell pressure effects in triaxial tests" by John Harkness, Antonis Zervos, Louis Le Pen, Sinthuja Aingaran and William Powrie
No full textThis data set accompanies the Granular Matter paper: "Discrete element simulation of railway ballast: modelling cell pressure effects in triaxial tests" by
John Harkness, Antonis Zervos, Louis Le Pen, Sinthuja Aingaran and William Powrie
Data for the following figures is included:
Figure 2 Lab and sim 15kPa.txt
Figure 3 lab and sim 200kPa.txt
Figure 5 vary friction angle 200kPa.txt
Figure 6 vary stiffness 200kPa.txt
Figure 7 best fit 500kPa stiffness.txt
Figure 8 cyclic loading comparison.txt
Figure 10 percentage non crushing contacts with radius.txt
Figure 11 histogram of alpha.txt
Figure 12 best fit conical damage model.txt
Figure 13 histograms of normal force 15kPa and 200kPa.txt
Figure 16 tan phi as a function of normal force.txt
Figure 17 conical damage with power law friction 15kPa.txt
Figure 18 conical damage with power law friction 30kPa.txt
Figure 19 conical damage with power law friction 200kPa.txt
Figure 20 conical damage with damage dependent friction 15kPa.txt
Figure 21 conical damage with damage dependent friction 30kPa.txt
Figure 22 conical damage with damage dependent friction 200kPa.txt
Figure 23 conical damage with damage dependent friction cyclic loading 55kPa.txt</span
Le Corbusier et Christian Zervos dans Cahiers d’art
No full textAbstract: The search has as purpose to notice the importance of Christian Zervos (Argostoli 1889 – Paris 1970), a greek art historian and founder of the magazine and publishing house Cahiers d’art, that lived in Paris from 1907 to the end of his life) with Le Corbusier, inserted in the contest of Cahiers d’art. The exceptional versatility of Zervos’s mind had allowed him to realize, through Cahiers d’art, a intellectual environment that exceeded the ordinary publishing house of that period, beacuse it was enchanted and nourished by all sector of knowledge. Zeros, inside the Cahiers d’art, made Le Corbusier protagonist of the section of Architecture, that submits to Sigfried Giedion. In fact since the first number of Cahiers d’art the work of Le Corbusier was broadly taken in examination. The articles related to the work of the Architect have gone since 1926 to 1954; the themes that touch these texts can be separate in four major topics: design, private house, great public buildings, painting. La recherche a le but de relever l’importance de Christian Zervos (Argostoli 1889-Parigi 1970), historien de l’art et fondateur des Éditions Cahiers d’art, qui vécut à Paris depuis 1907 à sa mort, et Le Corbusier, insérée dans le contexte de Cahiers d’art. L’exceptionnel éclectisme de Zervos a permis de réaliser dans Cahiers d’art un excellent milieu intellectuell qu’il va au-delà des Éditions, car uni et nourri par chaque domaine de la connaissance. Dans les Cahiers d’art, Zervos rend Le Corbusier le protagoniste de la section d’architecture, soignée par Siegfried Giedion. Keywords: Cahiers d’art; Christian Zervos; projects. DOI: http://dx.doi.org/10.4995/LC2015.2015.1018[EN] The search has as purpose to notice the importance of Christian Zervos (Argostoli 1889 – Paris 1970), a greek art historian and founder of the magazine and publishing house Cahiers d’art, that lived in Paris from 1907 to the end of his life) with Le Corbusier, inserted in the contest of Cahiers d’art. The exceptional versatility of Zervos’s mind had allowed him to realize, through Cahiers d’art, a intellectual environment that exceeded the ordinary publishing house of that period, beacuse it was enchanted and nourished by all sector of knowledge. Zeros, inside the Cahiers d’art, made Le Corbusier protagonist of the section of Architecture, that submits to Sigfried Giedion. In fact since the first number of Cahiers d’art the work of Le Corbusier was broadly taken in examination. The articles related to the work of the Architect have gone since 1926 to 1954; the themes that touch these texts can be separate in four major topics: design, private house, great public buildings, painting. La recherche a le but de relever l’importance de Christian Zervos (Argostoli 1889-Parigi 1970), historien de l’art et fondateur des Éditions Cahiers d’art, qui vécut à Paris depuis 1907 à sa mort, et Le Corbusier, insérée dans le contexte de Cahiers d’art. L’exceptionnel éclectisme de Zervos a permis de réaliser dans Cahiers d’art un excellent milieu intellectuell qu’il va au-delà des Éditions, car uni et nourri par chaque domaine de la connaissance. Dans les Cahiers d’art, Zervos rend Le Corbusier le protagoniste de la section d’architecture, soignée par Siegfried Giedion.Sabella, MP. (2016). Le Corbusier et Christian Zervos dans Cahiers d’art. En LE CORBUSIER. 50 AÑOS DESPUÉS. Editorial Universitat Politècnica de València. 1986-2006. https://doi.org/10.4995/LC2015.2015.1018OCS1986200
The effect of boundary conditions, model size and damping models in the finite element modelling of a moving load on a track/ground system
No full textThis record contains data for the article relating to the following abstract: An investigation is presented of the use of finite element models in the time domain to represent a load moving on a railway track on a flexible ground. A systematic study is carried out to compare different sizes and shapes of finite element mesh, different boundary conditions intended for suppressing reflections from the truncated model boundaries, and different models of soil damping. The purpose is to develop guidance to assist in selecting appropriate finite element models for moving load problems. To prevent reflections from the boundaries of the finite domain two approaches are compared. A 40 m radius hemispherical finite element mesh has been used first with infinite elements around the perimeter. This approach gives good results for a point harmonic load at the centre of the domain but some problems are highlighted when it is used for moving load calculations. An alternative approach has therefore been investigated based on a cuboid mesh. The base was fixed to prevent rigid-body motions of the model and, rather than use infinite elements at the sides, these were also fixed. It is shown that, provided that a suitable damping model is used, the spurious reflections from the sides of the model can be suppressed if the model is wide enough. On the other hand, if infinite elements are used, the calculations are found to be considerably more costly with little added benefit. Different models of soil damping are also compared. It is shown that a mass-proportional damping model gives a decay with distance that is independent of frequency, making it particularly suitable for this application. The length of model required to achieve steady state has been investigated. For a homogeneous half-space it is found that the required length increases considerably in the vicinity of the critical speed, up to 130 m in the present example, whereas for the layered ground a more modest length is sufficient for all speeds.
The article was published as Shih, Jou-Yi, Thompson, David and Zervos, Antonios (2016) The effect of boundary conditions, model size and damping models in the finite element modelling of a moving load on a track/ground system. Soil Dynamics and Earthquake Engineering, 89, 1-37.</span
A review and evaluation of ballast settlement models using results from the Southampton Railway Testing Facility (SRTF)
No full textMany of the world’s railways run on ballasted track, which has for nearly 200 years provided a stable support for train operation. However, with trafficking the geometry of the track deteriorates, mainly as a result of the development of differential settlement of the track-bed (ballast and sub-base). When the geometry defects become too severe, maintenance is needed to realign the track to enable the continued safe running of trains. Maintenance is a major cost associated with ballasted railway track, which usually takes the form of tamping. However, tamping damages the ballast, resulting in a diminishing return period between maintenance interventions until eventually the track-bed requires full renewal. A major component of the differential settlement can be attributed to the ballast layer. However, differential settlement of lengths of track cannot easily be modelled or predicted either computationally or experimentally. Thus the total plastic (permanent) settlement is often used as a proxy for the potential for the development of differential settlement along a length of track in the field. Many empirical models have been developed to predict ballast settlement, usually as a function of the number of train axle passes and/or the cumulative load. However, these models may produce very different results, perhaps indicating that the input variables have not been adequately formulated. This paper describes some current empirical ballast settlement models, and evaluates them using experimental data generated using the Southampton Railway Testing Facility (SRTF). This apparatus represents a section of track consisting of a single sleeper bay 650 mm wide, confined by rigid sides that enforce plane strain conditions. The paper summarises the strengths and weaknesses of the existing models, and suggests variables that could be taken into account to improve them
Influence of thermomechanics in the catastrophic collapse of planar landslides
No full textFrictional heating has long been considered a mechanism responsible for the high velocities and long run-out of some large-scale landslides. In this work a landslide model is presented, applicable to large-scale planar landslides occurring in a coherent fashion. The model accounts for temperature rise in the slip zone due to the heat produced by friction, leading to water expansion, thermoplastic collapse of the soil skeleton, and subsequently to an increase of pore-water pressure. The landslide model, comprising equations that describe heat and pore pressure diffusion and the dynamics of the moving mass, is used to analyse the evolution of the Jiufengershan planar landslide as an example. Further, its parameter space is systematically and efficiently explored using a Taguchi parametric analysis in an attempt to quantify dominant parameters. It is shown that the process of sliding is dominated by the softening properties of the material, as expected, but also by the permeability of the slip zone and the thickness of the sliding mass. It is worth noting that the latter two parameters do not enter traditional stability analyses of uniform slope
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Some effects of particle shape on the mechanical behaviour of granular materials
No full textThe behaviour of a granular material depends on the shape, material proper- ties and packing of the grains. Starting with a particle characterization, the ability to make predictions of the macroscopic behaviour of an assembly of particles without re- course to laboratory or numerical experiments would be very useful. With this ultimate goal in mind, this work presents some first findings of an investigation into the effects on macroscopic behaviour of two key measures of particle shape: form and angularity. The form of a particle is quantified using the Longest (L), Intermediate (I) and Shortest (S) dimensions of an equivalent scalene ellipsoid; A sum of the local volumetric deviations of the particle from that ellipsoid as a ratio of the ellipsoid volume is used as a measure of angularity. Discrete element, periodic cell simulations of ellipsoidal and realistic par- ticle shapes sampled from railway ballast are used to investigate mechanical behaviour in terms of critical state friction angle. Characterization of the observed behaviour in terms of a single shape parameter is explored. It is found that deviation of particle form from that of a sphere together with increases in angularity both lead to higher angles of friction at critical state. It is argued that, at least to some extent, the higher critical state strength exhibited by non-spherical particles is due to their form and/or angularity suppressing particle rotation and leading to increased interparticle sliding, a mechanism that in comparison expends more energy
Polynomial C1 shape functions on the triangle
No full textWe derive generic formulae for all possible C1 continuous polynomial interpolations for triangular elements,by considering individual shape functions, without the need to prescribe the type of the degreesof freedom in advance. We then consider the possible ways in which these shape functions can be combinedto form finite elements with given properties. The simplest case of fifth-order polynomial functionsis presented in detail, showing how two existing elements can be obtained, as well as two new elements,one of which shows good numerical behaviour in numerical tests
Thermo-mechanical modelling for velocity prediction in catastrophic landslides
No full textThermal pressurisation has been proposed in literature as the key phenomenon to interpret the mechanics of the final collapse of large slope failures. A new thermomechanical model is proposed by improving on an existing one, applicable to large landslides and rockslides consisting of a coherent mass sliding on a thin clayey layer. The considered time window is that of catastrophic acceleration, which starts at incipient failure and ends a few seconds later, when the acquired displacement and velocity are such that the landslide is broken up into pieces. The model takes into account frictional heating, pore pressure build-up and thermoplastic collapse of the soil skeleton, leading to the vanishing of shear resistance and unconstrained acceleration. First, an existing thermo-elasto-plastic constitutive model for clays is discussed, and modified by re-formulating it in a general stress space and taking into account thermal softening. The soil constitutive model is then employed into an existing 1-D landslide model (Vardoulakis 2002), resulting in a set of three equations describing the time evolution of temperature, excess pore pressures within the shearband and slide velocity. The resulting model equations are shown to be well-posed, and then are discretised and integrated numerically to back-analyse the final stage of the case history of Vajont that occurred in Italy in 1963. Finally, a generalisation of this model and its potential applicability to the velocity back-prediction of other well-documented case histories are discussed
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