bluuebunny/crossref_metadata_2025_split huggingface dataset:
An upper-bound rigid–plastic solution for the shear failure of concrete beams without shear reinforcement
Authors: Kemp K. O. , Al-Safi M. T. 
Published: October 2009

Synopsis In recent years research workers at the Technical University of Denmark and elsewhere have shown that simple rigid–plastic methods of analysis can be used to predict closely the experimental shear failure loads of reinforced and prestressed concrete beams. The method has proved sufficiently attractive in Europe to be considered as a basis for new code of practice formulations for shear failure, but has so far been rather neglected in the United Kingdom. In this paper, rigid–plastic analysis is applied to the shear failure of reinforced or prestressed concrete beams without shear reinforcement. A new upper-bound solution for this problem is derived and compared with the previous ‘exact’ solution derived by Nielsen and Braestrup. The new upper-bound solution is shown to produce lower failure values of shear stress for certain ratios of compression to tension steel.
Effect of boundary conditions upon the behaviour of concrete under concentrations of load
Authors: Kotsovos Michael D. , Newman John B. 
Published: October 2009

Synopsis A non-linear finite-element technique incorporating a constitutive model of concrete behaviour has been used to analyse plain concrete structural forms under concentrations of load induced by a wide range of boundary conditions. The influence of boundary conditions upon strength, deformation and fracture processes has been investigated and the most critical boundary conditions are identified. The predicted behaviour is found to be in close agreement with experimental values when the boundary conditions assumed for the analysis simulate closely those imposed by the testing techniques.
The splitting strength of concrete prisms subjected to surface strip or patch loads
Authors: Oehlers D. J. , Johnson R. P. 
Published: October 2009

Synopsis Analyses of computer studies and of over 200 tests lead to a method of predicting the load at which a concrete prism splits or bursts when subjected to a concentrated surface strip or patch load, and the range over which this splitting determines the ultimate strength. The effects upon the splitting strength of eccentricity of loading, the length of the prism, external lateral restraint and internal reinforcement are also determined.
Constitutive relationships and a failure criterion for concrete based on fundamental material properties
Authors: Montague P. , Kormi K. 
Published: October 2009

Synopsis The functional stress-strain relationships obtained by Kotsovos from his application of regression analysis to empirical data are used as the basis for a derivation of multiaxial constitutive relationships, for concrete subjected to compressive stresses, which distinguish between loading and unloading. A model is proposed in which internal cracking is accompanied by an internal transfer of energy from the deviatoric stress system to the spherical stress system, resulting in modified values of the effective internal spherical and shear stresses and of the shear strain. This transfer of energy is regarded as an irreversible process which can only take place during loading and internal crack propagation. The proposed failure criterion is that failure of the material takes place when, under any system of applied compressive stresses, the internal shear stress reaches a unique value equal to that which exists at failure in a uniaxially compressed solid cylindrical specimen of 100 mm diameter and250 mm length. For any other general compressive stress state which generates a modified octahedral shear stressless than this unique value, the concrete will retain its load-bearing capacity.
Forces in the vicinity of edge columns in flat-slab floors
Authors: Hall A. S. , Rangan B. V. 
Published: October 2009

Synopsis Tests were carried out on four half-size models of flat-slab floors. Each model represented two panels at the edge of a building. They were tested under simulated uniformly distributed load with the object of investigating the distribution of moments and shears on the three faces of an edge column. The three force components at the pin support at the foot of the test column were measured; strain gauges were also attached to the reinforcement. From these measurements, expressions are developed which predict what proportions of the total panel moment and shear enter the column directly as bending and shear at the column face. The remainder enters via the spandrel beam or spandrel-strip. Statics then enables the torsion, shear and bending in the spandrel to be calculated,
Compression testing and cracking of plain concrete
Authors: Shrive N. G. 
Published: October 2009

Synopsis Flaws such as pores and voids are present in cement paste, and thereforein concrete. These flaws act as stress-raisers and cause the initiation of cracks in compressive stress fields. By analysing the stress state in compressive test specimens – recognizing that testing machines apply displacement conditions – and examining the stresses which may then exist around a spherical void, it is possible to explain the typical cracking patterns observed in such specimens. It is also possible to explain the cracking patterns and apparent changes in strength observed under externally applied biaxial stress conditions. This analytical work is restricted to elastic isotropic media and spherical voids, so the potential effect of aggregate particles is examined. Aggregate is shown to cause stress variation on a local basis, which may aid crack formation close to aggregate particles, andthe extension of cracks around aggregatelcement paste interfaces. It is concluded that cracks are initiated at flaws such as pores or voids. It is suggested that, since fracture mechanics deals with the fracture of heterogeneous non-brittle materials, it may be worth while considering the application of appropriate fracture mechanics methods to the fracture of concrete.
Factors affecting concrete permeability to cryogenic fluids
Authors: Hanaor Ariel , Sullivan Patrick J. E. 
Published: October 2009

Synopsis Substantial cost saving and enhanced safety could achieved in the construction of storage tanks for liquefied natural gas (LNG). if it could be demonstrated that prestressed concrete can be reliably used in the construction of the primary, as well as the secondary container. Available information on the mechanical properties of concrete at very low temperature is adequate in establishing its suitability as a cryogenic construction material. Very little work, however, has been done on the factors and mechanisms governing the flow of cryogenic fluids through the essentially porous material. The work presented here outlines design and analysis of an experiment aimed at establishing the effects of eight factors upon the permeability of concrete specimens to liquid nitrogen. The results suggest that the mechanisms governing the permeability of concrete at ambient and at cryogenic temperatures differ fundamentally. In particular, the aggregate plays a major role in the cryogenic permeability of concrete. A model is proposed, whereby incompatibilities between the physical and thermal properties of the aggregate and the cement paste give rise to microcracking below a certain temperature. Such a model is capable of accounting for the observed results, as well as for phenomena previously reported.
A temperature-matched curing system controlled by microcomputer
Authors: Wainwright P. J. , Tolloczko J. J. A. 
Published: October 2009

Synopsis The paper describes the design and development of a curing system for concrete using a microcomputer to control the apparatus and store the data. The adiabatic temperature rise of a concrete can be recorded and reproduced within the curing tanks in which test specimens can be stored. It is also possible to reproduce any predetermined temperature cycle, provided it lies within certain limits. The equipment is extremely versatile and precise and avoids the use of multichannel chart recorders or digital data-logging systems to measure and record the data.
Two simple techniques for testing the performance of repair materials for concrete cracks
Authors: Fattuhi N. I. 
Published: October 2009

Synopsis The paper describes two simple testing techniques for evaluating the effectiveness of a repair material in sealing cracks and in transmitting tensile stresses across cracks. The techniques also enable comparisons to be made between different repair materials used under varying conditions of temperature and moisture. For the first testing technique, grooves in concrete beams were formed during casting for crack simulation purposes, and were filled with different repair materials such as epoxy resins and mortars. Then the beams were subjected to different temperatures before testing in flexure. For the second testing technique, halved concrete cylinders were joined by repair materials and the cylinders were subjected to different temperatures before testing in splitting tension. The results indicated that the effectiveness of the repair materials in transmitting the tensile stresses varied and was reduced considerably at higher temperatures. The beam and cylinder results under the same testing conditions were generally consistent for the same material.
A photoelastic investigation of anchorage bearing stresses
Authors: Rasheeduzzafar  , Allison I. M. , Al-Saadoun Saadoun Saad 
Published: October 2009

Synopsis This investigation focuses on a number of features which have hitherto been less researched but which have been found to be critical in the behaviour and failure mechanism of anchorage zones. These include the mode of load transfer, the proximity of the anchorage unit to the surface plane and the critical role of the high sub-surface shear in the immediate vicinity of the anchorage unit. The results show the significant advantages of the embedded anchorage over the corresponding external unit and the critical dependence of the surface stresses upon the proximity of the anchorage unit. In a typical multi-anchorage end-block. the behaviour of adjacent units is found to be sensibly independent.
The shear design of in situ reinforced concrete beam–column joints subjected to monotonic loading
Authors: Sarsam K. F. , Phipps M. E. 
Published: October 2009

Synopsis Research into in situ reinforced concrete joints has been almost exclusively restricted to the study of their behaviour under seismic loading. Different research workers in different parts of the world have used widely differing cyclic loading patterns and this has led to inconsistencies in the proposals put forward for the design of a joint for shear. Even for single-cycle (static or monotonic) loading, there is widespread disagreement on how a joint should be designed. In this paper. a method is proposed for ultimate shear strength design for joints subjected to monotonic loading which gives reliable predictions for an extensive range of test results. A proposal for predicting the serviceability limit state, or the diagonal cracking strength of a joint, which may be necessary for some designs is also given.
Shear transfer in cracked reinforced concrete
Authors: Millard S. G. , Johnson R. P. 
Published: October 2009

Synopsis Tests of a new type are described in which reinforced concrete plate specimens are cracked in direct tension. The tensile force is maintained while in-plane shear forces are applied across the crack. Measurements are taken of the shear stiffness and subsequent crack widening, together with the tensile forces in the reinforcement, using strain gauges embedded within the bars. A technique of resin injection is used to study the variation in the width of a crack beneath the surface of the concrete. Contrary to the results of previous studies, no significant variation was observed. The shear stiffness of cracked reinforced concrete specimens was compared with results from previous aggregate interlock and dowel action tests. It can be predicted from available theoretical models, provided that the anchorage stiffness of the reinforcement is known.
Additional strains in unbonded tendons during loading
Authors: Iványi G. , Buschmeyer W. , Müller R.-A. 
Published: October 2009

Synopsis Additional strains occurring in unbonded tendons during the loading of prestressed beams or slabs cannot be calculated by simple methods. Therefore in the national codes some simplified design formulae are proposed. However, the validity of such approaches is very limited. Analogously to the simple kinematic model of limit state design, in the present paper a single-crack element with real physical properties is developed. To calculate the additional strains in unbonded tendons of prestressed beams or slabs from the rotations of these elements, the single-crack elements have to be related to a compatible kinematic model. As shown in the paper, the calculated strains based upon this model agree well with the measured ones observed in bending tests on unbonded prestressed concrete slabs.
Influence of lightweight aggregates on thermal strain capacity on concrete
Authors: Brooks J. J. , Bennett E. W. , Owens P. L. 
Published: October 2009

Synopsis The tensile strain capacities of concretes with densities between 1200 and 2300 kg/m3 are determined by means of a short-term stressing technique. The thermal strain capacity of lightweight aggregate concrete is up to 2½ times greater than that of flint gravel concrete of similar workability and strength. Lightweight aggregate concretes also have lower coeficients of thermal expansion and reach slightly higher maximum temperatures due to hydration. It is demonstrated that the main influencing parameter on tensile strain capacity is the strengthlelastic modulus ratio.
Concrete strength evaluation through the use of small diameter cores
Authors: Yip W. K. , Tam C. T. 
Published: October 2009

Synopsis When cores are tested to establish the in situ strength of hardened concrete, it is current practice to use 100 or 150 mm diameter cores. For various reasons. such as the small size of a member or congestion of reinforcement, drilling of smaller cores is preferred, but these are not yet fully recognized in standards and guidance documents. The compressive strengths of 50mm diameter cores are compared with the strengths of 100mm diameter cores and control cubes. Other effects on the measured strengths of 50 and 100mm diameter cores are studied, including diameter, length/diameter ratio, direction of drilling, curing conditions, age of concrete and location of cored specimen. The results are compared with available published data. Results obtained. involving over 1000 samples, support the viability of using 50mm diameter cores to estimate the in situ strength of hardened concrete.
Salinity modelling for the Sabine—Neches Estuary, Southeast Texas
Authors: Mantz P. A. 
Published: October 2009

A two-dimensional, depth averaged, computer code was used to model salinities for the Sabine–Neches Estuary in Southeast Texas, USA. The model bathymetry was set to the mean sea level of 1996, and channel friction was adjusted to give an optimised Manning's n value for the annual, 6-minute water level data at eight stations.The simulated velocities were checked using flow discharges measured at six estuary sections for a three-day survey period. Three dispersion methods were used to calibrate the model for salinity. The data used were a 6 month record for 1996 at seven estuary stations, and a 7-year partial record from 1990 to 1996 for two stations at the Upper and Lower ends of Sabine Lake. The first method used a constant salinity dispersion coefficient and the second used a velocity related coefficient; they were accurate to within an annual mean value of about 5 ppt. For the third method, a two dimensional dispersion function was derived, which modelled to within an annual mean value of about 1 ppt. The ultimate purpose for the study was to estimate salinity increase for Sabine Lake with designed, fresh water flow extractions from the catchment. A maximum salinity increase of about 2 ppt for a 50 year return period was estimated.
Calibration of facies proportions through a history-matching process
Authors: Ponsot-Jacquin Catherine , Roggero Frédéric , Enchery Guillaume 
Published: October 2009

Abstract
The facies-proportion calibration method is a new history-matching technique, which modifies facies proportions within a fine geological – geostatistical model until a good match of the field data is reached.
The initial facies proportions in the model are usually locally constrained by well data, for example, but their spatial tendencies may be unreliable in some parts of the reservoir. The algorithm presented in this paper introduces average proportion ratios between facies groups in order to calculate new facies proportions while taking into account their initial values. It can be applied locally on specific regions or globally on the whole reservoir for stationary or non-stationary facies distributions. The proportion ratios can be manually adjusted or iteratively computed through an optimization process. The method has been successfully applied to a real field case.
New radiolarian assemblages from La Désirade Island basement complex (Guadeloupe, Lesser Antilles arc) and Caribbean tectonic implications
Authors: Cordey Fabrice , Cornée Jean-Jacques 
Published: October 2009

Abstract
New radiolarian assemblages of Late Jurassic age were extracted from seven chert localities of the basement complex of La Désirade Island (Guadeloupe), the oldest geological unit of the Lesser Antilles arc and the eastern Caribbean region. These fauna range in age from Kimmeridgian or early Tithonian to early or early late Tithonian, showing that La Désirade cherts are not all coeval, contrary to what was established by previous studies. Furthermore, the close spatial association of cherts and volcanic elements composed of basaltic flows and volcaniclastics suggests a mixed setting of hydrothermal siliceous deposits and biogenous sedimentation consistent with an arc-related oceanic setting rather than an ophiolite-type oceanic crust. As the youngest age is obtained to the northwest of the basement complex whereas older data are found to the southeast, it also suggests that La Désirade basement complex may have undergone some structural stacking consistent with an accretion-type geodynamic setting. Our biochronological data provide a preliminary tectonic model of an eastward subduction zone for Lesser Antilles arc basement emplacement during the Mesozoic.
The late Cretaceous-Eocene instability of the Apulian passive margin in Albania (Kruja carbonate platform) and its impacts on sedimentation
Authors: Heba Grigor , Prichonnet Gilbert 
Published: October 2009

Abstract
A detailed sedimentological analysis (facies F1–F15) and a precise biostratigraphy of the Lower Cretaceous, Upper Cretaceous (CsB1–CsB7 biozones), Paleocene and Eocene are established for the shallow-water carbonates in the Kruja platform (Kulmaka massif), located along the Apulian passive margin of Albania. Two distinct periods of evolution were recognized : (1) a period of pre-Santonian stability leading to neritic inner platform sedimentation, despite the regression close to the end of the Cenomanian followed by the deepening during the Turonian recorded on other platforms of the Apulian domain; (2) a period of instability, during Upper Santonian-Upper Eocene interval, causing in “the western zone” major hiatus (16–47 Ma, and locally 60 Ma) and Eocene polygenic breccias, whereas the neritic sedimentation continued in “the eastern zone” with moderate fluctuations.
This instability has also been reported for the same period in the Gavrovo platform (Greece), similar to the Kruja platform, reflecting a regional feature. This instability is attributed to strike-slip movements along NNW-SSE faults between the Kruja-Gavrovo platform and the Ionian Basin following the collision of Apulian and European plates at the Cretaceous-Eocene times. Two erosional phases are proposed for the Kulmaka massif (Kruja platform), during Upper Santonian-Upper Eocene interval. Following Upper Santonian time, strike-slip movements generated horst and grabben structures in the inner cretaceous platform and caused erosion of the cretaceous series in “the western zone” that produced up to 450 m thick slope breccias in the Ionian Basin. This instability induced a differentiation of sedimentary conditions across-strike of the platform since the Upper Maastrichtian time : pelagic in “the western zone” and neritic external platform in “the eastern zone”. During Paleocene and Middle-Upper Eocene times, the second phase generated new hiatus, identified throughout the Kruja-Gavrovo platform, and polygenic breccias in “the western zone” of Kulmaka massif. The difference in sedimentation between these two zones of the massif is preserved during the Middle-Upper Eocene time. Finally, the Oligocene flysch, resulting from a major distensive event of the Alpine orogeny, cover unconformably the carbonate platform.
Morphosedimentological record and human settlements as indicators of West-African Late Holocene climate variations in the littoral zone of the Iwik peninsula (Banc d’Arguin – Mauritania)
Authors: Barusseau Jean-Paul , Certain Raphaël , Vernet Robert , Saliège Jean-François 
Published: October 2009

Abstract
The geomorphological, sedimentological and archaeological studies of coastal features in the Iwik-Aouatil area show two categories of coastal sedimentary units: very extensive sand flats and linear relief features covered by a thin veneer of anthropogenic Anadara senilis shell-middens. These units provide an opportunity to discuss the return to arid conditions in western Sahara during the Late Holocene, when climate changes induced the alternating occurrence of more or less dry episodes, from around 5 ka until today.
These constructions reflect the global climate change within the general framework known for the region. Two different processes occurred: (1) constant deposition of wide sand-flats and (2) construction of sedimentary ridges at specific moments. These processes demonstrate the existence of (1) constant sand discharge during the whole period as sand availability is not a limiting factor and (2) a substantially increased sand influx during the 4.2-3.2 ka episode. Because of sea-level stability in the Banc d’Arguin area during the Late Holocene, the variability of morphogenetic agents is considered to be the likely cause of fluctuations, influencing sand input rate and implying that either sand was delivered in greater abundance (aridity crisis and stronger winds) or littoral drift was more powerful (stronger waves and more frequent storms in the northern part of the Atlantic ocean), or both simultaneously. The action of these two driving forces in the depositional processes observed in the Iwik-Aouatil coastal plain is evaluated with respect to the occurrence of episodes of rapid climate changes (RCCs) and North Atlantic Oscillation (NAO) changes. A climate pattern combining episodes of RCC and NAO positive (NAO+) index during the 4.5-3.2 ka period is convenient for both sand supply, which accelerates the southwestward migration of barchan’s lines, and sand transportation, which improves the efficiency of the littoral drift.