bluuebunny/crossref_metadata_2025_split huggingface dataset:
Virgin compression of structured soils
Authors: Liu M. D. , Carter J. P. 
Published: October 2009

This paper describes a study of the virgin compression behaviour of both naturally and artificially structured soils under one-dimensional compression or isotropic compression. It is proposed that during virgin compression, the additional voids ratio sustained by soil structure is inversely proportional to the current mean effective stress. The proposed formula has been verified for 20 different naturally and artificially structured soils, and it is seen that the proposal describes well the behaviour of all these soils. Finally, a general discussion on soil structure and its features is presented, and the proposed compression equation is extended to describe the compression of structured soil along a general stress path. Cet expos&acaute; est une étude du comportement d'une consolidation vierge sur des sols structur&acuate;s de mani&gravere naturelle et artificielle, avec une consolidation unidimensionnelle on isotrope. Nous avançons que pendant la consolidation vierge, le taux de pore additionnel subi par la structure du sol est inversement proportionnel &grave la contrainte effective moyenne actuelle. La for-mule propos&acuate;e a &acuteté v&acuute;rifi&acuate;e sur vingt sols structurés de manière artificielle et naturelle et l'on volt que la proposition décrit bien le comportement de tons ces sols. Enfin, nous présentons une &acuate;tude générale de la structure du sol et de ses caractéristiques et nous d&acuate;veloppons l'équadon de consolidation proposée pour d&acaute;crire la consolidation du sol structuré le long d'une trajectoire de contrainte g&acutge;nérale.
Plastic response of circular footings on sand under general planar loading
Authors: Gottardi G. , Houlsby G. T. , Butterfield R. 
Published: October 2009

Data from a set of tests of model circular footings on dense sand are presented. The footings were subjected to a variety of combinations of vertical, horizontal and moment loading. The tests were designed to provide the information necessary to construct a complete model of the footing behaviour, based on the concepts of plasticity theory. In particular, the tests provide detailed information about the shape of the yield surface, and so allow generalization of bearing capacity calculations to cases other than purely vertical loading. Information is also obtained about the hardening law and flow rule appropriate for a plasticity model, and the elastic response within the yield surface. Nous présentons ici les données provenant d'un ensemble d'essais sur des modèles d'assises circulaires sur un sable dense. Ces assises ont été soumises à une variété de combinations de charge verticale, horizontale et de moment. Les essais avaient été con&ecil;us pour donner l'information nécessaire à la construction d'un modéle complet du comportement de l'assise, en se basant sur les concepts de la théorie de plasticité. Notamment, les essais donnent une information détaillée sur la forme de la surface d'écoulement, ce qui permet de généraliser les calculs de résistance de portée et de les Réndre à des cas autres que les cas de charge purement verticale. Iis renseignent aussi sur la loi de durcissement et la règle d'écoulement convenant à un modée de plasticitéla réastique àieur de la surface d'écoulement.
Sedimentation and self-weight consolidation: constitutive equations and numerical modelling
Authors: Toorman E. A. 
Published: October 2009

The solution of the mass balance equation for sedimentation and consolidation in sediment suspensions requires closure equations for the parameters diffusivity, permeability and effective stress. Experimental data for non-cohesive and cohesive materials are discussed. New semi-empirical relations, which are a better approximation of reality, are proposed. The non-uniqueness for cohesive sediments is explained in terms of differences in aggregation history. The numerical implementation of the unifying theory for sedimentation and consolidation faces some serious problems. Particularly, the discontinuities require the addition of artificial diffusivity to create the necessary damping to avoid overshoot-induced oscillations. Improved stability is obtained using a special finite-element technique. The model is validated with several data sets and proves to predict the right behaviour and density profile evolution for both non-cohesive and cohesive sediments. The remaining differences between measured and computed density profiles for cohesive materials are attributed to the inadequacy of the currently used constitutive equations. La solution de ĺéquation &acute;équilibrage des masses pour la sédimentation et la consolidation dans les suspensions de sédiments nécessite des équations de clôture pour les paramètres suivants: diffusivité, perméabilité et contraintes effectives. Les données expérimentales relatives aux matières non cohésives et cohésives sont discutées et de nouveaux rapports semi-empiriques, représentant une meilleure approximation de la réalite, sont proposés. Le caractère non unique pour les sédiments cohésifs est expliqué sur le plan des différences dans ĺhistoire de ĺagrégation. Ĺexécudon numérique de la théorie de ĺunification pour la sédimentation et la consolidation se heurte à de graves difficultés. En particulier, les discondnuités nécessitent ĺadjonction &acute;une diffusivité ardficielle pour créer ĺamortissement nécessaire pour éviter le dépassement des oscillations induites. Une technique spéciale aux é1éments finis permet &acute;optimiser la stabilité. Le modèle est confirmé avec plusieurs ensembles de données et preuves afin de prévoir le comportement exact et ĺévolution du profil de densité pour les sédiments non cohésifs et cohésifs. Les différences restantes entre profils de densités mesurés et calculés pour le matériel cohésif sont attribuées à ĺinsuffisance des équations constitutives actuels.
Fall cone and compression tests on clay±gravel mixtures
Authors: Kumar G. V. , Wood D. Muir 
Published: October 2009

Fall cone tests have been performed on mixtures of kaolin and fine gravel, from which both the variation of liquid limit with clay content and the link between undrained shear strength and water content for different clay contents have been determined. A sharp change in response is observed when the clay content falls below about 40%. One-dimensional compression tests have been performed in a hydraulic oedometer and in a consolidation tube: both devices gave similar results. Again a change in character of response is observed at clay contents below about 40%. For clay contents above about 35% it is the clay matrix alone which controls the mechanical behaviour of the mixture. The gravel only begins to influence the behaviour when the granular volume fraction reaches about 0·45. Nous avons fait des essais á la chute avec un cône sur des mélanges de kaolin et de gravier fin, et de lá, nous avons déterminé la variation de la limite liquide en fonction du contenu argileux et le lien entre résistance au cisaillement non draé et contenu en eau pour différentes teneurs argileuses. Nous avons observé un changement marqué des réponses quand la teneur argileuse tombe en dessous de 40% environ. Des essais de compression en une seule dimension ont été faits dans un dométre hydraulique et dans un tube de consolidation: ces deux dispositifs ont donné des résultats similaires. Encore une fois, nous avons observé un changement dans le caractére de la réponse dans les teneurs argileuses inférieures á environ 40%. Pour les teneurs argileuses supérieures á environ 35%, c’est la matrice ďargile seule qui contrôle le comportement mécanique du mélange. Le gravier ne commence á influencer ce comportement que lorsque la fraction du volume granulaire atteint environ 0·45.
Flexural tests of steel-concrete-steel sandwiches
Authors: Solomon S. K. , Smith D. W. , Cusens A. R. 
Published: October 2009

Synopsis In order to reduce the weight of roadway slab on medium- and long-span composite bridges, a possible alternative in the form of a steel-concrete-steel sandwich has been appraised. This consists of a concrete core, precast or otherwise, to which is attached reinforcement in the form of flat steel plates by means of epoxy resin adhesive. Specimens of the order of 100 mm thick were tested statically over a span of 1·8 m, and carried loads equivalent to wheels of the HB vehicle with an adequate safety margin. Accepted design procedures gave reasonable prediction of the ultimate loads.
Damage and energy dissipation in cement pastes in compression
Authors: Spooner D. C. , Pomeroy C. D. , Dougill J. W. 
Published: October 2009

Synopsis A study is reported of the energy dissipated in damage and in damping when cement paste prisms are loaded in uniaxial compression. Damage, characterized both by change in initial elastic modulus during sequential loading-unloading cycles and by the energy dissipated in damage, is detected at axial strains as low as 500 to 600 × 10−6 As the axial strain increases, the initial elastic modulus falls and the energy dissipated in damage gradually increases. Volumetric strain measurements indicate that the mechanism of fracture in cement paste in uniaxial compression is basically the same as in concrete: the formation of cracks introduces a dilating effect in opposition to the normal reduction in volume of the specimen under load. Whereas energy is only dissipated in damage during the first loading over a given strain range, it can be repeatedly dissipated by the damping process. The experimental data on cement pastes indicate that the energy dissipated in damping depends uniquely upon the strain range undergone by the specimen but that it is independent of the degree of damage in the specimen.
Crack initiation in plain concrete
Authors: Walsh P. F. 
Published: October 2009

Synopsis At the tip of a sharp crack or re-entrant notch, the stresses calculated by a simple elastic analysis become infinite. Consequently, maximum-stress or -strain failure criteria and stress-concentration factors cannot be used to predict failure at such points. The linear elastic fracture mechanics theory can, however, be applied. In the paper, a brief treatment of the application of this theory to sharp cracks in concrete beams is presented and the effect of beam size is particularly examined. The same basic technique is applied to re-entrant notches. Experimental evidence of the validity of the approach is given. Theoretical results are included which allow these test data to be extended to a wide range of notch conjigurations. It is expected that this work will have considerable importance for the problem of crack initiation at corners of openings in walls etc.
An assessment of the commercial prospects for fibre- and polymer-modified concretes
Authors: Pomeroy C. D. 
Published: October 2009

Synopsis The principal effects of fibres of various types and of polymers upon the properties of Portland cement pastes, mortars and concretes are discussed briefly, and possible applications are suggested in which the special properties of the modified cement-based materials may be exploited commercially. It is concluded that structural reinforced and prestressed concretes are unlikely to be replaced by fibre or polymer concretes. It is more likely that the viable applications will exploit properties, in either the fresh or the hardened states, that are peculiar to the particular fibres or polymers incorporated in the matrix. It is also suggested that sufficient research has already been undertaken to provide data on the effects of fibres and polymers upon concrete properties and that the major effort should now be directed to the development of saleable products rather than the acquisition of additional basic information.
The expanded hysteresis loop method for measuring the damping properties of concrete
Authors: Ashbee R. A. , Heritage C. A. R. , Jordan R. W. 
Published: October 2009

Synopsis A method of measuring the damping properties of concrete is described wherein the stress-strain or load-deflection hysteresis loop is electronically modified to make it easier to examine the loop or measure its area. The logarithmic decrement for concrete is typically about 0·05 (ranging from 0·03 to 0·15) giving a length: breadth ratio for the hysteresis loop of about 100:1. This is too elongated a figure to measure accurately or to study for loop characteristics. The electronic treatment is first to make the loop upright (i.e. parallel to the load axis) and then to amplify the width in the direction of deflection. Accuracy depends upon stable, accurate amplification, but this is not difficult for the structural frequencies of interest (< 5 Hz). The experimental techniques include the use of a very stiff, servo-controlled test machine to obtain accurate stress levels, frequency, waveform of loading, etc. and steel reference specimens are tested to eliminate machine errors. The method is claimed to be a significant step forward in the study of damping and is applicable to other hysteresis systems where the two parameters can be measured electrically.
Influence of aggregate volume concentration upon the workability of concrete and some predictions from the viscosity—elasticity analogy
Authors: Hobbs D. W. 
Published: October 2009

Synopsis A simple theoretical approach is used to obtain rheological equations for concrete. It is assumed that the cement-paste phase approximates to either a Newtonian fluid or a Bingham body. The approach used predicts that changes in aggregate volume concentration give rise to large changes in fluid viscosity yield value and plastic viscosity. It is shown indirectly by using the viscosity—elasticity analogy that the resulting equations are in good agreement with experimental results on concrete.
The ultimate moment of resistance of unbonded partially prestressed reinforced concrete beams
Authors: Tam A. , Pannell F. N. 
Published: October 2009

Synopsis Existing theories for the ultimate moment of resistance of partially prestressed unbonded concrete beams are unsatisfactory on two counts—either they are too tedious to be used (involving lengthy iterations at times) or they fail to take into consideration the span/depth ratio, which is an important factor. After reporting the results of tests on eight such beams, the paper puts forward a revised theory leading to a simple design method for the ultimate load analysis of beams of this kind. It is shown that the theory gives an accurate prediction of the ultimate strength of the test beams.
Marine floating concrete made with polystyrene expanded beads
Authors: Bagon C. , Frondistou-Yannas S. 
Published: October 2009

Synopsis The performance of concrete containing expanded polystyrene beads was studied in the context of marine floating structures and compared with that of concrete containing perlite, the latter being an ultra-lightweight aggregate used for marine applications. It was found that, for an equal density of about 80% that of sea water, polystyrene concrete has a compressive strength that is 50% higher, a modulus of elasticity 100% higher, and a modulus of rupture 25% higher than those of perlite concrete. Furthermore, polystyrene concrete is much more resistant to sulphate solutions than perlite concrete even though it is less resistant than normal-weight concrete.
The strength of restrained reinforced concrete columns—a new approach
Authors: Butler Donald J. 
Published: October 2009

Synopsis The aim of the work described in this paper is to present a new approximate method for estimating the strength of reinforced concrete columns in rigid framed structures. The method employs a deteriorating stiffness stability concept combined with a modified use of the conventional short-column moment-thrust interaction diagram. When compared with ‘exact’ computer-based solutions, the method is shown to predict failure loads very accurately (mean = 99%, coefficient of variation =4%) over a broad range of significant design parameters. The scope of the work is limited to symmetrical single-curvature, no-sway cases at this time, but the results obtained suggest that the method, when properly modified, can provide a good basis for treating more general problems as well.
A comparison of creep, elasticity and strength of concrete in tension and in compression
Authors: Brooks J. J. , Neville A. M. 
Published: October 2009

Synopsis A method of manufacturing a bobbin-shaped specimen for testing concrete in direct tension is described. Direct tensile strength is related to tensile and compressive strengths as determined by standard tests and their changes with age are described. Data on the modulus of elasticity in compression and in tension at two exposure conditions are given, and the influence of age upon creep and creep recovery is established. The differences in behaviour of strength, modulus of elasticity, creep and creep recovery are discussed by considering the effects of load and storage environment upon the adsorbed water of the cement paste, and the suggested creep mechanism is a combination of the seepage and viscous shear theories.
A low-cost creep rig for concrete
Authors: Cridland L. , Bakoss S. L. , Burfitt A. J. 
Published: October 2009

Synopsis A low-cost creep rig based on a commercially available flexible-diaphragm jack (flat jack) was developed by the authors. It was designed for creep tests on 380 × 130 × 130 mm specimens at a maximum load of 170 kN. A portable hydraulic hand pump is used with the flat jack to apply the load. Thirty rigs of this type have been used, six of them for continuing tests over a period of three years. The paper describes the methods used to calibrate the jack and shows that the rig is capable of maintaining a constant load to the accuracy required by the Australian Standard.
Predicting long-term creep and shrinkage from short-term tests
Authors: Brooks J. J. , Neville A. M. 
Published: October 2009

Synopsis On the basis of experimental results from creep and shrinkage tests lasting five years and data from other investigators, it is proposed that long-term deformations can be predicted within reasonable limits of accuracy from values measured at 28 days. The expressions given are sensibly independent of a wide range of the independent variables which affect creep and shrinkage of concrete.
The Behaviour of Bamboo-Reinforced Concrete Columns Subjected to Eccentric Loads
Authors: Cook D. J. , Pama R. P. , Singh R. V. 
Published: October 2009

SYNOPSIS Experimental and theoretical investigations to determine the characteristics of bamboo-reinforced concrete columns subjected to uniaxial and biaxial loads are described. Studies to establish the mechanical properties of the bamboo related to its use as a reinforcement are also described. Data on the behaviour of twenty-four columns, viz nine bamboo-reinforced concrete cotumns and nine unreinforced columns subjected to uniaxial load and six bamboo-reinforced concrete columns subjected to biaxial load, are given. The applicability of accepted methods for the prediction of the ultimate load of reinforced concrete columns subjected to uniaxial and biaxial loads is described and it is shown that, when cognizance is taken of the characteristics of bamboo, behaviour can be predicted with reasonable accuracy.
Osmosis as a cause of blistering of in situ resin flooring on wet concrete
Authors: Warlow W. J. , Pye P. W. 
Published: October 2009

SYNOPSIS Excessive water in concrete affects many flooring materials and leads to their early failure. In many cases the floorings are badly blistered, each blister containing an aqueous solution under compression. This paper suggests that the pressures that arise are most likely to result from osmosis. From theoretical considerations, concrete may be expected to act as a semi-permeable membrane. In a simple experiment, hardened cement paste and mortar were shown to act as such a membrane in an osmotic cell. The proposed mechanism helps to explain failures of flooring involving liquid pressures that could not have been generated by an external agency. A better understanding of the distribution and concentration of soluble salts in concrete is necessary to reduce the possibility of osmotic flow. As it is not possible to predict when conditions may lead to the formation of an active osmotic cell, as many sources of extraneous moisture as possible should be eliminated. On ground floors, therefore, the provision of a damp-proof membrane is essential to prevent ingress of ground moisture.
Computer experiments on slender beam—columns of reinforced concrete
Authors: Constantinescu Dan R. , Illston John M. 
Published: October 2009

SYNOPSIS A computer model is described which determines the behaviour under load of slender concrete beam—columns of uniform rectangular symmetrically reinforced cross-section. The various modes of deflection and failure are presented for both short-term and sustained load and the predicted results compared favourably with the results of laboratory tests. Computer experiments are reported in which the effects of various structural and material parameters are investigated. The parameters include the distribution of moment along the member, slenderness, the ratio of reinforcement, the cover to the steel, the design strengths of steel and concrete and the magnitude of concrete creep. The empirical CEB/FIP proposals for estimating the strength of slender members are corroborated by the results of the computer experiments.
The evaluation of resin systems for concrete repair
Authors: Tabor L. J. 
Published: October 2009

SYNOPSIS Although resins have been used for repairing concrete for many years, there is still a lack of convincing data about their performance in this role. This is largely due to the absence of a suitable test for evaluating the repair techniques. Details are given of a test which realistically appraises the effectiveness of the injection of resin into cracks, the repair of damaged concrete with resin mortars and the use of resin primers with fresh concrete. The test piece is a rectangular prism with either a diagonal repaired crack or a scarf joint between the original concrete and the repair material. It is subjected to compressive test and compared directly with an undamaged concrete prism of similar dimensions. Thus the repair is subjected to a high degree of shear and is appraised in the same simple terms of cube or prism strength with which the engineer assesses the quality of his original concrete.
An analysis of the ultimate strength of lapped joints of compression reinforcement
Authors: Cairns John 
Published: October 2009

Synopsis Bond failure of ribbed reinforcing bars generally takes place by splitting of the surrounding concrete cover, unless heavy confining reinforcement is present. The bond action of the bars must therefore exert a radial bursting force on the concrete cover, and so the ultimate strength of a lapped joint may be calculated by equating the bursting force produced by bond to the ultimate confining force on the lapped bars provided by the member. In this paper, expressions are derived for the relationship between the stress developed in a lapped bar and the resultant bursting force and they show that this depends mainly upon the strength of the concrete in the member and the deformation characteristics of the bar. The contribution made by bearing of the ends of lapped bars to the ultimate strength of compression laps is also evaluated. Values of lap strength calculated from the analysis are shown to be in good agreement with results obtained from tests on lapped joints in reinforced concrete columns.