bluuebunny/crossref_metadata_2025_split huggingface dataset:
The depth of influnce of loaded areas
Authors: Charles J. A. 
Published: October 2009

The depth of influence of a foundation load has to be evaluated so that the settlement which will be caused by the loading can be calculated. It also needs to be assessed for the design of schemes of ground improvement by preloading with a surcharge of fill. It is usually assumed that the variation of vertical stress with depth below a loaded area can be predicted with sufficient accuracy using linear, homogeneous, isotropic elastic theory. However, although such theory adequately predicts the depth of influence of typical foundation loads it overpredicts the depth of influence of more extensive surcharge loads. A simplified model of soil behaviour, based on the Marston analysis of stress conditions in trenches, has been used to investigate the effect of an increase in shear strength with increase in effective stress on the depth of influence of a surface loaded area. Although the effect is not significant for typical relatively small foundation loads, it is likely to be significant for much more extensive surcharge loads. Comparisons with the monitored depths of influence of surcharges on uncompacted fills confirm the behaviour predicted by the nalysis. La profondeur d'influence due à la mise en charge d'une fondation doit être évaluée afin de calculer le tassement résultant de ce chargement et d’élaborer des programmes permettant de tester le sol par préchargement à I'aide de remblais. Généralement on suppose qu'en des-sous d'une zone chargée, la variation de la contrainte verticale avec la profondeur pent être calculée avec suffisamment de précision en appliquant une théorie isotrope, homogène et linéaire. Cependant, même si de telles théories donnent une bonne estimation de la profondeur d'influence générée par des chargements typiques, elles tendent à surestimer celle occasionnée par des charges plus importantes. Un modèle simplifié de comportement, fondé sur une analyse de Marston des conditions de contraintes règnant dans une tranchée, a été utilisé afin d'étudier Pinfluence d'un accroissement de la résistance au cisaillement, dû à une augmentation de la contrainte effective, sur la profondeur d'influence dune surface chargée. Bien que les résultats ne soient pas très significatifs pour une charge typique relativement faible, ils le deviennent pour des charges beaucoup plus importantes. Les essais de mesure de profondeurs d'influence, réalisés sur des remblais non compactés et mis en charge, confirment les comportements prévus par L'analyse.
Dimensional analysis for geotechnical engineers
Authors: Butterfield R. 
Published: October 2009

Dimensional analysis is an important tool for engineers, aiding the design of experiments and concise expression of the results generated by them. The dimensionless groups, which are the output of a successful dimensional analysis, are usually developed via Buckingham's ‘Pi’ theorem. Because this alone is a necessary, but not sufficient, condition for a solution, difficulties are frequently encountered. This paper presents a general, dimensional analysis algorithm which imposes both necessary and sufficient conditions. Illustrative problems are included, together with a Mathematica program which generates all possible sets of admissible dimensionless groups for a specific problem. L'analyse dimensionnelle est un outil important pour les ingénieurs car elle les aide à concevoir des expériences et à exprimer de manière concise les résultats qui en découlent. Les groups non dénommés, qui sont le résultat d'une analyse dimensionnelle réussie, sont normalement développés au moyen du théorème ‘pi’ de Buckingham. Comme ce théorème seul est une condition nécessaire mais pas suffisante pour amener à la solution, des difficultés surviennent souvent. Cet exposé présente un algorithme général d'analyse dimensionnelle imposant des conditions nécessaires et suffisantes. Pour illustrer, nous joignons des problèmes avec un programme Mathematica qui produit tous les ensembles de groupes non dénommés admissibles pour un problème spécifique.
Computer experiments on environmentally induced stresses in unreinforced concrete pavement slabs
Authors: Illston J. M. , Tajirian A. 
Published: October 2009

Synopsis The paper is concerned with the computation of deflections and stresses in an unreinforced concrete pavement slab subjected only to the effects of tempera–ture and humidity. The basis of the computer simula–tion is presented in three stages: (a)the histories of material properties and environmental variables; (b)the computation of the distributions of imposed ther–mal and shrinkage strains through the depth of the slab, using finite difference techniques; (c) the compu–tation of the lift–off of the slab and the consequent stresses, using finite element techniques. It is shown that by far the largest tensile stresses are induced ifthere is external restraint of the longitudinal movement of the slab. Stresses significant enough to threaten tensile fail–ure of the concrete can also occur (in the absence of restraint) as a result of the early effects associated with the heat of hydration of the cement, and under the influence of the long–term shrinkage. Computer exper–iments are reported in which the injhences of a number of variables are examined, including those for slab dimensions, climatic changes and the curing of the concrete.
Recoverable and irrecoverable deformation of heat-cured cement paste
Authors: Parrott L. J. 
Published: October 2009

Synopsis Heat curing at temperatures up to 65°C reduced the creep and shrinkage of ordinary Portland cement pastes having a water/cement ratio of 0·47. Strain measured after unloading and after rewetting indicated that the reductions were primarily associated with the irrecoverable components of creep and shrinkage. The reductions did not correlate with differences between the combined water content or the capillary porosity of the cement pastes, but they were associated with differences in the extent of silicate polymerization within the cement hydrate. Elastic strains, creep-recovery strains and cube strengths of the cement pastes were not noticeably affected by the extent of silicate polymerization.
The effect of variations in the aggregate content of concrete columns upon the estimation of strength by the pulse-velocity method
Authors: Davis S. G. 
Published: October 2009

Synopsis The results are reported of a series of tests planned to place quantitative limits upon the accuracy of the ultrasonic-pulse-velocity method, when it is used to assess the variations in strength through the height of a lift of concrete. Changes in the mix proportions of the concrete resulting from the placing process have been monitored, and the effect of such changes upon the correlation between strength and pulse velocity has been investigated. The results suggest that, for a typical structural concrete mix, the error in the estimation of the variability of strength is likely to be in the range from 4·5 to 9%.
Effects of embedded steel bars upon ultrasonic testing of concrete
Authors: Chung H. W. 
Published: October 2009

Synopsis Ultrasonic testing of a reinforced concrete member by means of the Pundit apparatus is affected by the steel bars embedded in the concrete. An investigation of the effects of the reinforcement has been made, using the bar diameter and the concrete strength as the variables. It is found that the steel bar appears to act compositely with the surrounding concrete in transmitting ultrasonic pulses. The effective pulse velocity is somewhat between the pulse velocities in the two separate media, and varies with the diameter of the bar and the pulse velocity in the concrete. An empirical formula for the effective pulse velocity is proposed. On the basis of this formula and further theoretical consideration, the zone of steel influence is defined. A correction factor is derived whereby the measured pulse velocity in a concrete–steel medium is adjusted to give the pulse velocity in the plain concrete.
Bond strength at high temperatures
Authors: Diederichs U. , Schneider U. 
Published: October 2009

Synopsis This paper deals with the bond strength of steel and concrete at high temperatures because, although bond strength is of major importance in the determination of the behaviour of concrete structures in fire, there is no detailed information available on this problem. For this reason a test apparatus was developed which enabled pull-out experiments to be carried out on cylindrical concrete specimens with short embedment lengths. During the tests the slip at the non-loaded end of the concrete specimen and the pull-out force were reassured. In the temperature range 20 to 800°C the pull-out system enabled two different types of experiment to be carried out: force–slip measurements at thermal steady state and at non-steady state conditions. In these experiments normal-weight concrete made with Portland cement and siliceous aggregate and three different types of reinforcing steel (ribbed steel bars, plain round bars and deformed prestressing bars) were used. Differences between the results for the different types were noted, especially between the ribbed steel and plain round steel bars.
Relationships between permeability and pore structure of hardened cement paste
Authors: Nyame B. K. , Illston J. M. 
Published: October 2009

Synopsis A description is given of a steady-state method of measuring the permeability of hardened cement paste. The method takes advantage of the applied hydrostatic pressure in sealing truncated conical disc specimens at hydraulic gradients up to 150000. Relationships between saturated permeability and pore structure parameters, as determined by drying at 105°C and mercury intrusion porosimetry, are presented for hardened cement pastes of differing water/cement ratios and times of hydration. It was found that there is no unique relationship between permeability and porosity, though well defined trends were evident for the effect upon permeability of time of hydration at constant water/cement ratio. Similar trends were found between permeability and surface area at constant time of hydration. A broad-banded relationship was evident between permeability and hydraulic radius for all the grouped results. Reasonably close agreement was found between the structural parameter from hydraulic radius theory and the permeability, though with some discrepancies at low permeabilities.
Extended model for estimating the strength-developing capacity of Portland cement
Authors: Popovics Sándor 
Published: October 2009

Synopsis This paper presents a new formula for estimating the strength-developing capacity of Portland cement. This formula was obtained by the extension of a so-called exponential cement model published earlier for relative strengths. This extension is in two directions: (1) the strengths are expressed in stress units, such as N/mm2, instead ofpercentages; and (2) this new model reproduces the effect of cement fineness upon the strength development in addition to the compound composition and age of testing. Compressive and tensile strengths obtained on standard ASTM Ottawasand mortar specimens illustrate the validity of the new formula.
Static and cyclic response of reinforced concrete beams repaired by resin injection
Authors: Hewlett P. C. , Morgan J. G. D. 
Published: October 2009

Synopsis This paper covers laboratory testing, both static and cyclic (reversed loading), of reinforced concrete beams aimed at establishing the repair capability and consequences of synthetic resin injection. Beams designed to fail both in tension and in shear were tested to failure, repaired and re-tested. Unidirectional and reversed loading sequencies were applied. The purpose of cyclic loading was to establish the effect of an interposed resin layer within cracked concrete, resulting from ‘wedging’ and possible resin fatigue. The work has established that, if cracks are accessible to the resin (i.e.not less than 0·1 mm wide), failed beams can be reinstated to load-deflection and ultimate load behaviour at least as good as those of the unfailed beam. If; however, bond between reinforcement and concrete has been destroyed, or the reinforcement extended beyond its elastic limit, total reinstatement is doubtful. Extensive shear cracking can be reinstated totally and beams failed in this way are both stiffer and stronger than originally. Within the limits of this test programme, resin within a crack has no deleterious effect upon repaired beam’s behaviour under reversed loading.
The behaviour of reinforced concrete flanged beams with stiffeners
Authors: Subedi N. K. 
Published: October 2009

Synopsis The modes of failure and the ultimate strength of deep reinforced concrete flanged beams with stiffeners can be predicted. The major contributions to the ultimate strength come from the strength of the web and the main reinforcement. A simple method is proposed for the analysis of reinforced concrete flanged beams with stiffeners. Results from micro-concrete model tests and also tests carried out at the Polytechnic of Central London and Concordia University, Canada, are compared with the proposed method of analysis.
Portland–pfa cement: a comparison between intergrinding and blending
Authors: Monk Michael 
Published: October 2009

Synopsis Portland–pfa (pulverized-fuel ash) cements containing 20-40% (by weight) pfa have been prepared in the laboratory both by intergrinding the ashes with clinker and by blending with cement. The ashes were obtained from four base-load stations and the cements and clinker from two UK cement works. Cement properties have been assessed according to BS 4550 and scanning electron microscopy was used to examine the effects of grinding upon the pfa particles. The work has shown that intergrinding leads to an improvement in the water-reducing properties ofcoarse pfas and also in their pozzolanic activity as indicated by compressive strength development at later ages. Setting times have been found to be essentially the same for blended and interground cements, both being considerably longer than for typical ordinary Portland cements. The results of the work on laboratory-prepared cements have been confirmed on factory-produced cements. Thus the results of this investigation indicate that, provided pfas are chemically acceptable, they can be used for Portland-pfa cement manufacture by intergrinding irrespective of their coarseness.
Further responses of the bond in reinforced concrete to high temperatures
Authors: Royles R. , Morley P. D. 
Published: October 2009

Synopsis Tests were carried out to examine the effects of heat treatment upon the bond between concrete and steel by using direct displacement measurements and monitoring acoustic emission. A description of the experimental set-up has been given previously and, as before, it was used to test cylindrical pull-out specimens with an actual embedment length of 32 mm. The variables considered were type of bar (plain anddeformed bars of 16 mm diameter) and the effect of load cycling (for the deformed bar only) upon the bond after it has been subjected to heat treatment. The acoustic emission equipment was incorporated into the system to assess its validity in this type of testing and was used in all three of the different test situations investigated.
Measuring long-term strains in concrete by microcomputer
Authors: Hirst M. J. S. 
Published: October 2009

Synopsis A new low-cost computer interface has been developed for acoustic strain gauges. The interface will operate and read up to four gauges and brings the benefits of computer control and results processing to these robust gauges. All control programming uses standard BASIC commands. To complement the interface, a program has been developed which effectively turns the computer into a complete datalogger for acoustic strain gauges. Operational modes range from immediate display of strains to long-term monitoring of the gauges under clock control.
Simpler nodal forces for yield-line analysis of reinforced concrete slabs
Authors: Johnarry Tonye 
Published: October 2009

Synopsis An alternative scheme for nodal forces for equilibrium analysis of yield patterns is investigated. The principal features of the scheme include defining the forces in terms of: (a) the key(yie1d) moment referred to the axes of rotation: (b) the angles between the yield lines and the axes of rotation: (c) the normal moments only stated in (a), leaving out completely explicit twisting moment terms. The scheme is not another form of the work method, but leab to solutions which match those obtained by the work method. In some cases of slabs with holes, exact solutions have been found where the work method (or the existing equilibrium method) has been unable to lead directly to such results.
Properties of concrete made with crushed concrete as coarse aggregate
Authors: Sri Ravindrarajah R. , Tam C. T. 
Published: October 2009

Synopsis Effects of using recycled concrete of different qualities as coarse aggregate upon the strength and deformation of concrete are reported. Tests on the aggregates showed that the recycled concrete aggregates have lower specific gravity and higher absorption capacity than the original crushed granite aggregate. The resistance to mechanical actions such as impact, crushing and abrasion for the recycled concrete aggregates is also lower. The effects of using recycled concrete aggregates instead of natural aggregates in concrete are: reduction in compressive strength up to 25%; reduction in modulus of elasticity up to 30%; improvement in damping capacity up to 30%; and higher amounts of drying shrinkage and creep. Available methods of predicting the modulus of elasticity on the basis of compressive strength for conventional concrete overestimate the modulus of elasticity for recycled-aggregate concretes.
The effect of vibration on the rheological properties of fresh concrete
Authors: Tattersall G. H. , Baker P. H. 
Published: October 2009

Synopsis Using a set-up in which the bowl of a two-point workability test apparatus was mounted on an electro-magnetic vibrating table, measurements were made on unvibrated fresh concrete and on the same samples under vibration. It was shown that when vibration is applied the flow properties of fresh concrete are no longer represented by the simple linear Bingham model but approximate to those of a power law pseudoplastic with zero yield value. At very low shear rates behaviour approximates to that of a Newtonian fluid and, subject to the exceeding of a small threshold condition, fluidity decreases as a simple exponential function of the maximum velocity of vibration.
Hydraulic model studies for the Ghazi-Barotha hydropower project, Pakistan
Authors: Ackers J. C. , Ashraf Akhtar M. 
Published: October 2009

The $2200 million Ghazi-Barotha hydro-power project—one of the largest currently under construction worldwide and expected to be completed in about 2002—will have a peak generating capacity of 1450 MW and provide an estimated annual energy output of 6600 GWh. Its main components are a gated barrage and flow diversion structure on the Indus River at Ghazi, about 7 km downstream of Tarbela dam a 52 km long power channel with a discharge capacity of 1600 m3/s, bypassing a relatively steep reach of river, including Attock Gorge a five-unit powerhouse, discharging back to the Indus at Barotha via a 2 km long tailrace an ‘emergency’ spillway providing a bypass to the powerhouse two ‘headponds’ upstream of the power intake, to provide sufficient daily storage to support diurnal ‘peaking’ of the units. The project has a number of interesting hydraulic features, many of which were developed with the aid of about a dozen physical model studies. This paper includes a brief description of the project, outlining the role of most of the model studies and then describes two of them in greater depth.
Biometrical Differentiation of the Common Snipe (Gallinago gallinago) Migrating in Autumn Through North-Eastern Poland
Authors: Meissner Włodzimierz , Koss Mikołaj 
Published: October 2009

Biometrical Differentiation of the Common Snipe (Gallinago gallinago) Migrating in Autumn Through North-Eastern Poland
The Common Snipe is a medium-sized wader with a broad range of distribution. The analysis of recoveries shows that most of Common Snipes migrating through the southern Baltic come from Scandinavia, Baltic countries and north-western and western Russia. In this paper differentiation in the biometrics of Common Snipes migrating through north-eastern Poland was described. The data were collected at two ringing stations in north-eastern Poland. No significant differences were found between biometrical parameters from these two ringing sites. The obtained results are similar to the ones from the Gulf of Gdańsk. Mean values of particular measurements and body mass of adult and juvenile birds did not differ significantly. There was no significant biometrical variance among juvenile birds between three analysed half month periods as well as between 5 years of study except for the seasonal differences in the mean value of tarsus with toe measurement. The mean values of measurements taken from the birds studied in this work are similar to the results obtained for the Gulf of Gdansk region, and higher than in the places located more inland (southern and eastern Poland). It might be caused by differences in the biometrical values among different populations. Low values of the body mass are characteristic for Common Snipes staying in places with different habitat conditions, which shows that this species migrates in autumn with very small energetic reserves, what is typical for strategy minimising energetic expenses during migration.
Droit islamique et pratiques sociales, la question de l'orphelin
Authors: Guillermet Élise 
Published: October 2009

Résumé À une démarche volontariste des ONG islamiques de participer au jihad par le secours aux membres de l’umma correspondent différents vécus. Le présent article propose de s’intéresser à la complexité de l’économie morale, construite quotidiennement par les habitants de Zinder entre normes islamiques et pluralisme juridique hérité de la période coloniale. Il prend pour objet anthropologique les pratiques de reconstruction de filiation à l’enfant « orphelin ». Il décortique tant les réappropriations des aides internationales islamiques que leur inscription dans un ensemble plus large de pratiques allant du recours à l’état civil au baptême religieux.
Les marabouts sénégalais et leur clientèle aux États-Unis
Authors: Kane Ousmane 
Published: October 2009

Résumé Une économie spirituelle mobilisant du temps, des ressources et une énergie considérables est en train de prospérer au sein de la communauté musulmane sénégalaise des États-Unis. C’est le mode opératoire de cette économie spirituelle transnationale que cet article s’efforce de décrire, en s’attachant plus particulièrement aux activités des marabouts venus pour un séjour temporaire aux États-Unis. L’auteur les classe en trois catégories : la première regroupe des lettrés qui ne se réclament d’aucune secte et s’adressent à une large audience musulmane ; la deuxième est composée de cheikhs invités par leur daïra pour bénir ses membres, les conseiller pour progresser spirituellement et recruter de nouveaux membres ; la troisième est formée des marabouts qui vendent des biens propitiatoires et déprécatoires.