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In triaxial tests, it is of great importance to accurately measure the radial strain of a specimen. However, devices for radial strain measurement are relatively fewer than the ones for vertical strain measurement. In this study, a new measurement device based on the fiber Bragg grating (FBG) was developed to determine the small and large radial strains of a soil specimen. The new device includes two yokes and two compass-type mechanisms, which are mounted on diametrically opposite sides of the specimen. Metal strips bonded with FBG sensors were chosen as sensing elements and installed at two ends of two legs of a compass-type mechanism so that the small deformation of the specimen could be amplified by a constant ratio to a more detectable value with a higher signal-noise ratio. Considering the temperature sensitivity of FBG and the real working environment, the new device was carefully calibrated underwater. Validation tests on an intact triaxial specimen demonstrated that the new device can work reliably and accurately under both static and cyclic loadings. Key words: triaxial test, radial strain, small strain measurement, cyclic, fiber Bragg grating (FBG). Dans les essais triaxiaux, il est tres important de mesurer avec precision la deformation radiale d'un echantillon. Cependant, les dispositifs de mesure de la deformation radiale sont relativement moins nombreux que ceux de mesure de la deformation verticale. Dans cette etude, un nouveau dispositif de mesure base sur le reseau de Bragg a fibres (FBG) a ete developpe pour determiner les petites et grandes deformations radiales d'un echantillon de sol. Le nouveau dispositif comprend deux jougs et deux mecanismes de type compas, qui sont montes sur des cotes diametralement opposes de l'echantillon. Des bandes de metal collees avec des capteurs FBG ont ete choisies comme elements de detection et installees aux deux extremites des deux jambes d'un mecanisme de type boussole afin que la petite deformation du specimen puisse etre amplifiee par un rapport constant a une valeur plus detectable avec un rapport signal-bruit plus eleve. Compte tenu de la sensibilite a la temperature du FBG et de l'environnement de travail reel, le nouveau dispositif a ete soigneusement calibre sous l'eau. Des tests de validation sur un echantillon triaxial intact ont demontre que le nouveau dispositif peut fonctionner de maniere fiable et precise sous des charges statiques et cycliques. [Traduit par la Redaction] Mots-cles: test triaxial, deformation radiale, mesure de la petite deformation, cyclique, reseau de Bragg a fibres (FBG)., Introduction In conventional triaxial tests, it is generally acknowledged that determining the small-strain stiffness of a soil specimen accurately has been hindered by its seating and bedding errors as well [...]

In this study, experimental testing was performed on cast-in-place and precast barriers subjected to quasi-static loading and anchored to 6 m long bridge decks with a 1 m overhang. The three selected bridge barrier configurations include an ordinary concrete cast-in-place barrier, and two high performance fibre reinforced concrete precast barriers, one with and one without barrier-to-barrier connections. An experimental setup dedicated to testing the large-scale barrier-deck slab overhang specimens to failure was designed. The structural behavior of the three barrier configurations were analyzed and compared. The tests demonstrated that all three test configurations exceeded the design criteria in CSA-S6-06 and AASHTO LRFD, that the durability of the slab overhang is not adversely affected when using precast barriers, and that the shear key designed to connect the precast barriers provides adequate barrier longitudinal continuity. Key words: bridges deck, precast barrier, cast-in-place barrier, fibre reinforced concrete, barrier connection, barrier continuity, failure mode, crack opening, crack pattern. Dans la presente etude, des essais en laboratoire ont ete effectues sur des parapets coules en place et prefabriques installes sur des dalles de pont de 6 m de longueur avec un porte-a-faux de 1 m. Les trois configurations de parapets de ponts selectionnes comprennent soit un parapet coule en place en beton ordinaire, soit des parapets prefabriques en beton fibre a haute performance avec et sans continuite longitudinale. Un montage experimental a ete concu specialement pour tester jusqu'a la rupture des sections de pont a taille reelle comprenant la dalle en porte-a-faux et le parapet sous un chargement transversal. Le comportement structural des trois configurations de parapets a ete analyse et compare. Les essais ont demontre que les trois configurations de parapets surpassent les criteres de conception des codes CSA-S6-06 et AASHTO LRFD, que la durabilite de la dalle de pont en porte-a-faux n'est pas modifiee par l'utilisation de parapets prefabriques, et que les cles de cisaillement concues pour relier les parapets prefabriques procurent une continuite longitudinale adequate. [Traduit par la Redaction] Mots-cles: tablier de pont, parapet prefabrique, parapet coule en place, beton fibre, cle de cisaillement, continuite des parapets, mode de rupture, ouverture de fissure, patron de fissuration., 1. Introduction Throughout North America, reinforced concrete bridge barriers are used to force errant vehicles to remain on the roadway. The bridge barriers two primary functions are to contain errant [...]

In order to examine the role of the hyoid apparatuses of woodpeckers with respect to energy mitigation, we investigated its unique geometry using FEA (finite element analysis). It is believed that the hyoid apparatus' role is to aid in protecting the woodpecker's brain from damage by dissipating stress waves due to impact while pecking. The woodpecker's hyoid apparatus has a unique structure compared to other birds' hyoid apparatus as it starts at the tip of the beak, which is the tongue, surrounds the woodpeckers' skull, and ends at the root of the upper beak. The hyoid apparatus has cartilage at its core, and the cartilage is surrounded by muscle. In this study, we constructed the model of the hyoid apparatus using ABAQUS-explicit FEA software, applied a blast pressure, and measured the change in pressures along various locations on the apparatus. The results showed that the impending longitudinal stress wave was decreased by 97.5% at the free end of the forked geometry, while the shear stress increased 74.7% at the same free end. We believe that this is due to the spiral geometry of the hyoid apparatus. The analysis of the woodpecker's hyoid apparatus provides additional insight into energy dissipation from the perspective of novel biological structural materials. Our focus is to develop protective gear for soldiers and athletes based on such designs in nature. Keywords: Woodpecker; Hyoid; Energy dissipation; Finite element analysis, Introduction A woodpecker has a unique structure of a hyoid apparatus compared to the hyoid apparatus of other birds'. The hyoid apparatus starts at the beak tip, surrounds the skull, [...]

A very soft clay layer is highly compressible and exhibits significant creep under loading. The classical linearly elastic constitutive relationship and small-strain assumption are not suitable for the consolidation analysis of very soft clays. This paper presents a new large-strain consolidation model that incorporates the Yin-Graham elastic viscoplastic (EVP) constitutive equation for use in studying the consolidation of very soft clay layers with vertical drains under preloading. First, the large-strain fluid continuity equation and the EVP constitutive equation are incorporated into a quadratic differential equation of pore-water pressure and its integral terms. Second, the alternating-direction implicit (ADI) method and virtual node method are adopted to obtain the finite difference solution. A computer program named 'BSSDS' is developed for large-strain EVP consolidation analysis of clay layers with vertical drains, taking into account the complicated in situ conditions, such as resistance of vertical drains, smear effects, variation of permeability with void ratio, and multilayered soils. Third, the new large-strain numerical method is applied to the consolidation modeling of very soft clay layers with vertical drains under preloading at a site that is part of the Hong Kong-Shenzhen Western Corridor Link Project. It is found that the foundation settlements of the new large-strain EVP consolidation model have good agreement with the measured data. Finally, three different consolidation models are used to calculate the average degree of consolidation and settlements of the clay layers. The analysis shows that it is essential to consider both large-strain compression and creep effects in the analysis of very soft clay layers with vertical drains under loading. Key words: soft clay, consolidation, elastic viscoplastic model, large strain, vertical drain. Une couche d'argile tres molle est consideree comme tres compressible et presente du fluage significatif lors de sollicitations. La relation lineaire elastique constitutive classique et l'hypothese des faibles deformations ne sont pas appropriees lors de l'analyse de consolidation d'argiles tres molles. Cet article presente un nouveau modele de consolidation a grande deformation qui integre l'equation constitutive elastique viscoplastique (EVP) de Yin-Graham pour l'etude de la consolidation dans des couches d'argile tres molle avec des drains verticaux, soumises a des pre-charges. Premierement, l'equation de continuite des fluides a grande deformation et l'equation constitutive EVP sont integrees dans une equation differentielle quadratique decrivant la pression interstitielle et ses termes integraux. Deuxiemement, la methode implicite de direction alternative (IDA) et la methode du noeud virtuel sont adoptees pour obtenir la solution de la difference finie. Un programme informatique appele BSSDS a est developpe pour l'analyse de consolidation EVP a grande deformation de couches d'argile ayant des drains verticaux, en considerant les conditions in situ complexes, telles que la resistance des drains verticaux, les effets de souillures, la variation de la permeabilite selon l'indice des vides, ainsi que les sols multicouches. Troisiemement, la nouvelle methode numerique a grande deformation est appliquee pour la modelisation de la consolidation de couches d'argile tres molle avec des drains verticaux et soumis a des pre-charges sur un site qui fait partie du projet de Corridor Ouest Hong Kong-Shenzhen. Il est demontre que les tassements de la fondation selon le nouveau modele de consolidation EVP a grande deformation correspondent bien avec les donnees mesurees. Enfin, trois modeles de consolidation differents sont utilises pour calculer le degre de consolidation moyen et les tassements des couches d'argile. L'analyse montre qu'il est essentiel de considerer la compression a grande deformation et les effets de fluage lors de l'analyse de couches d'argile tres molle ayant des drains verticaux et soumises a des solicitations. [Traduit par la Redaction] Mots-cles: argile molle, consolidation, modele elastique viscoplastique, grande deformation, drain vertical., Introduction With rapid economic growth, the demand for infrastructure construction over reclaimed lands and soft marine clays has continuously increased in the coastal areas of many countries and regions. In [...]

Mine developments, such as haulage drifts, cross-cuts, and intersections, are the only way to access valuable ore from mining zones; they link mine developments with the nearest ore access points. Thus, they must remain stable throughout their service life or production plan. Mine development instability can cause production delay, loss of reserves, as well as damage to equipment and injury to miners. This paper presents a stepwise methodology to assess the stability of mine development intersections with respect to the mine production plan. A case study, the #1 Shear East ore-body at Vale Garson Mine in Sudbury, Ontario, is presented. A three-dimensional, elastoplastic, finite difference model (FLAC 3D) is created to simulate the development of an intersection situated 1.5 km below ground surface. The unsatisfactory performance of the intersection is evaluated in terms of strength-to-stress ratio with respect to mining sequence. A failure criterion is defined by a minimum strength-to-stress ratio of 1.4, and is used for mine developments (temporary openings). The intersection stability is evaluated at various mining stages and the modified 'point-estimate method' (PEM) of ([2n.sup.2] +1) is then invoked to study the probability of drift instability at the intersection. The results are presented and categorized with respect to probability, instability, and mining stage. Key words: mine developments, numerical modelling, point-estimate method (PEM). Les puits d'extractions, les intersections et les galeries sont des lieux de passage necessaires pour extraire les mineraux de la zone d'exploitation dans une mine. Ils relient les fronts d'exploitation aux lieux de decharge et de stockage et doivent par consequent rester stables tout au long de la duree d'exploitation prevue lors de l'etape de planification. Des instabilites des de ces developpements miniers peuvent conduire a des delais d'exploitation supplementaires, des pertes de ressources, une distribution de contraintes induites accrue, ainsi que des dommages aux equipements et au personnel d'exploitation. Cet article presente methode d'affirmation pas a pas une de la stabilite d'une intersection de galeries tout en respectant le plan de production. Une etude de cas du gisement Shear Est #1 dans la mine de Garson exploitee par Vale a Sudbury, Ontario est presentee. Une modelisation numerique trois-dimensionelle en comportement elastique-plastique avec le logiciel FLAC 3D est realisee pour simuler le comportement d'une intersection de galeries a une profondeur de 1500 m. La probabilite de performance insatisfaisante est calculee aux differentes etapes de la sequence miniere grace au ratio contrainte/resistance. Le facteur de securite est fixe a 1,4 (ouvertures temporaires). La methode de << point estimate >>([2n.sup.2] +1) est utilisee pour calculer la probabilite de performance insatisfaisante. Les resultats sont presentes et classes selon les probabilites, le type d'instabilite et l'etape de la sequence miniere. Mots-cles: developpements miniers, modelisation numerique, point-estimation de la methode (PEM)., Introduction The sublevel stoping mining method with delayed backfill has been widely adopted by many Canadian metal mines. In this method, ore is mined out in stopes (blocks) that are [...]

Numerous thin concrete walls failed in compression during the 2010 Chile earthquake. Experiments on small wall elements indicate that thin concrete walls without tied vertical reinforcement may fail very suddenly at uniform compression strains as low as 0.001 due to the thin layer of concrete between two layers of reinforcement becoming unstable. A test on a wall subjected to axial compression and strong-axis bending demonstrated that unlike a tied column, a thin concrete wall can suddenly lose all axial load-carrying capacity. Nonlinear response history analysis of a typical Chilean high-rise shear wall building indicates small global drift demands and correspondingly small curvature and compression strain demands when subjected to the ground motions measured in Santiago, which explains why most buildings were not damaged. Nonlinear finite element analysis of a typical wall step-back irregularity indicates the increase in maximum compression strains due to a reduction in wall length is much larger than predicted by a sectional analysis. Based on all the results of the current study, a number of significant changes are proposed for the 2014 edition of CSA A23.3 to avoid compression failures of thin concrete walls, including limiting the axial compression force applied to thin bearing walls, accounting for unexpected strong- axis bending of thin bearing walls, and limiting the compression strain demands on thin concrete shear walls. Key words: building codes, compression, concrete walls, earthquake damage, high-rise buildings, nonlinear analysis, seismic design, testing. Plusieurs murs minces en beton ont defailli par rupture en compression lors du seisme de 2010 au Chili. Des experiences sur des petits echantillons de mur indiquent que les murs minces en beton sans renforcement vertical attache pouvaient defaillir tres soudainement a des contraintes uniformes en compression aussi faibles que 0,001 en raison de la mince couche de beton entre deux couches d'armature qui devenait instable. Un essai sur un mur soumis a une compression axiale et en flexion dans l'axe principal a demontre qu'un mur mince en beton, contrairement a une colonne attachee, peut soudainement perdre toute sa capacite de charge axiale. Une analyse historique de la reponse non lineaire d'un immeuble de grande hauteur typique au Chili, bati en utilisant des murs de contreventement, indique des petites demandes de glissement globales et des petites demandes correspondantes de contraintes en courbure et en compression lorsque ces murs sont soumis aux mouvements de sol mesures a Santiago. C'est ce qui explique pourquoi la majorite des immeubles n'a pas ete endommage. Une analyse non lineaire par elements finis de l'irregularite typique de retrait d'un mur souligne que l'augmentation des contraintes maximales en compression causee par une reduction dans la longueur du mur est beaucoup plus grande que celle prevue lors de l'analyse sectionnelle. En se basant sur tous les resultats de cette etude, plusieurs changements importants sont proposes pour l'edition 2014 de la norme CSA A23.3 afin d'eviter les defaillances en compression des murs minces en beton, incluant la limitation de la force axiale en compression appliquee a de minces murs porteurs, tenant compte d'une forte flexion inattendue de l'axe principal des murs porteurs minces et limitant les demandes de contraintes en compression des murs de contreventement minces en beton. [Traduit par la Redaction] Mots-cles: codes du batiment, compression, murs de beton, dommage de seisme, immeubles de grande hauteur, analyse non lineaire, conception sismique, essais., Introduction Although only a few buildings completely collapsed during the magnitude M8.8 earthquake that occurred in the Maule region of Chile on 27 February 2010, many buildings were badly damaged [...]

Volumetric behaviour is a fundamental consideration in unsaturated soil constitutive modelling. It is more complex than when the soil is saturated, as unsaturated soils exhibit a range of responses such as swelling and collapse under wetting and shrinkage and cracking during drying. While significant advances have been made, it is still difficult to generally explain all patterns of behaviour. This paper presents a new framework for modelling volumetric response of unsaturated soils with emphasis on compacted soils. The framework uses void ratio (e), moisture ratio ([e.sub.w]), and net stress (p) as the main constitutive variables and suction as a dependent variable. This choice of [e.sub.w] as a main constitutive variable is theoretically sound and is more attractive than the use of suction, which is relatively difficult to measure and displays significant hysteresis during drying and wetting. The framework incorporates the well-known compaction curve making it easily applicable to practical situations. Within the overall e-[e.sub.w]-p space, the operative space is constrained by three main surfaces; namely, loading-wetting state boundary surface, tensile failure surface, and the saturated plane. The conceptual basis for these state surfaces is described and the framework is qualitatively validated against observed behaviour of compacted soils. Key words: unsaturated soils, moisture content, soil compaction, void ratio, constitutive modelling. Le comportement volumetrique est une consideration fondamentale lors de la modelisation constitutive des sols non satures. La complexite est plus grande que lorsque le sol est sature puisque les sols non satures presentent une variete de comportements, comme le gonflement et l'effondrement durant le mouillage, et le retrait et la fissuration lors du sechage. Malgre le fait que plusieurs avancees significatives ont ete realisees, il est encore difficile d'expliquer de facon generale tous les types de comportement. Cet article presente une nouvelle approche pour la modelisation du comportement volumetrique des sols non satures, avec une emphase sur les sols compactes. L'approche utilise l'indice des vides (e), le ratio d'humidite ([e.sub.w]) et la contrainte nette (p) en tant de variables constitutives principales, et la succion en tant que variable dependante. Ce choix de [e.sub.w] comme variable constitutive principale est justifiable de maniere theorique et est plus simple que d'utiliser la succion, puisque la succion est relativement difficile a mesurer et demontre des effets d'hysteresis importants en mouillage et en sechage. Cette approche integre la courbe de compaction bien connue, ce qui la rend applicable aux situations pratiques. A l'interieur de l'espace e-[e.sub.w]-p, l'espace operatoire est contraint par trois surfaces principales: la surface frontiere de l'etat en mouillage-sechage, la surface de rupture en tension, et le plan sature. La base conceptuelle de ces trois surfaces est decrite et l'approche est validee qualitativement a l'aide d'observations du comportement de sols compactes. Mots-cles: sols non satures, teneur en eau, compaction du sol, indice des vides, modelisation constitutive. [Traduit par la Redaction], Introduction A large portion of geotechnical works is associated with unsaturated soil either as compacted fills or natural soil above the water table. In contrast to saturated soils below the [...]

The development of a new semiempirical method to predict the proper strain rate for constant rate-of-strain (CRS) consolidation tests is described herein. The validity of the proposed method is analyzed using experimental results from CRS and incremental loading tests on four types of soil: Lake Bonneville clay, Massena clay, kaolinite, and montmorillonite. It is found that the maximum allowable strain rate depends on the initial void ratio of the soil and thus is related to the compressibility of the soil. The effect of the strain rate on the distribution of the pore pressure within the sample is investigated by comparing values of effective vertical stress calculated using a linear equation published by Wissa et al. in 1971 with values of effective stress at the base of the specimen determined from measured values of pore pressure. Overall, the proposed method predicts the maximum allowable strain rate very well for three of the four soils and moderately well for the other soil. Key words: constant rate-of-strain (CRS) consolidation test, strain rate, Lake Bonneville clays. Cet article decrit le developpement d'une nouvelle methode semi-empirique pour predire le bon taux de deformation lors d'essais de consolidation a taux de deformation constant (TDC). La validite de la methode proposee est analysee a l'aide de resultats experimentaux d'essais TDC et a chargement incremental realises sur quatre types de sols : argile du Lac Bonneville, argile de Massena, kaolinite et montmorillonite. Il est demontre que le taux de deformation maximal allouable depend de l'indice des vides initial du sol et est ainsi relie a la compressibilite du sol. L'effet du taux de deformation sur la distribution de la pression interstitielle a l'interieur de l'echantillon est etudie en comparant les valeurs de la contrainte effective verticale calculees a partir de l'equation lineaire publie par Wissa et al. en 1971 avec des valeurs de contrainte effective a la base de l' echantillon determinees par les mesures de pression interstitielle. Globalement, la methode proposee predit tres bien le taux de deformation maximal allouable pour trois des quatre sols, et moderement bien pour l'autre sol. Mots-cles : essai de consolidation a taux de deformation constant (TDC), taux de deformation, argiles du Lac Bonneville. [Traduit par la Redaction], Introduction Since its development by Smith and Wahls (1969), the constant rate of strain (CRS) consolidation test has been plagued by two problems: (i) an unknown distribution of pore water [...]

This paper investigates the use of a pre-existing network of resistive strain gauges located on the girders of a single bridge span to determine the classification and estimate the weight of vehicles traveling over that span. Vehicle events on the bridge are identified automatically by a measurement filtering algorithm. Manual classification labels are then applied to a subset of these events to investigate the strain signal features that distinguish various vehicle classes. Trends in these features over time are investigated, and an estimate of vehicle weight is obtained from these features without the need for detailed knowledge of the structure's composition. Additionally, a number of neural network configurations are tested on the problem of determining vehicle class from these features. Results are tested on data from both the summer and winter seasons. Finally, estimates of vehicle weight are improved by using the classification network to filter input events. Key words: structural health monitoring, weigh-in-motion, vehicle classification, neural computing. Cet article examine l'utilisation d'un reseau existant de jauges de deformation resistives situeees sur les poutres maitresses d'une traveee de pont afin de determiner le classement et estimer le poids des vehicules voyageant sur cette travee. La circulation des vehicules sur le pont est identifieee automatiquement par un algorithme de filtrage des mesures. Des etiquettes manuelles de classement sont ensuite appliquees a un sous-ensemble de la circulation afin d'examiner les caracteristiques des signaux de contrainte qui distinguent les diverses classes de vehicules. Les tendances de ces caracteristiques dans le temps sont etudiees; une estimation du poids des vehicules est obtenue a partir de ces caracteristiques sans demander une connaissance deetaillee de la composition structurale. De plus, un certain nombre de configuration de reseaux neuronaux ont ete mis a l'eepreuve afin d'essayer de determiner la classe de vehicule a partir de ces caracteristiques. Les resultats sont examinees par rapport aux donnees estivales et hivernales. Pour completer, les estimations des poids de vehicules sont ameliorees en utilisant le reseau de classification afin de filtrer les eveenements saisis. Mots-cles: suivi de la sante structurale, pesage dynamique, classement des vehicules, neuroinformatique. [Traduit par la Redaction], 1. Introduction As the general practice of structural health monitoring (SHM) becomes more common, an increasing number of structures are now being instrumented with sensors and data acquisition equipment. The [...]

The measurement of relative displacements and deformations is important in many fields such as structural engineering, aerospace, geophysics, and nanotechnology. Optical-fiber sensors have become key tools for strain measurements, with sensitivity limits ranging between [10.sup.-9] and [10.sup.-6] [epsilon] hertz [(Hz).sup.-1/2] (where E is the fractional length change). We report on strain measurements at the [10.sup.-13] [epsilon]-[Hz.sup.-1/2] level using a fiber Bragg-grating resonator with a diode-laser source that is stabilized against a quartz-disciplined optical frequency comb, thus approaching detection limits set by thermodynamic phase fluctuations in the fiber. This scheme may provide a route to a new generation of strain sensors that is entirely based on fiber-optic systems, which are aimed at measuring fundamental physical quantities; for example, in gyroscopes, accelerometers, and gravity experiments. 10.1126/science.1195818

The popularity of the Barcelona basic model (BBM) has grown steadily since its publication in 1990, due to its ability to capture key aspects of unsaturated soil behaviour. Nevertheless, the BBM is still rarely employed by practitioners, partly because of the absence of simple and objective methods for selecting parameter values from laboratory tests. One difficulty is that, in the BBM, individual aspects of the isotropic virgin behaviour are controlled by multiple parameters, while at the same time a single parameter controls more than one aspect of soil behaviour. This has led to iterative procedures where parameter values are adjusted in turn to match experiments, which requires significant experience and can lead to the selection of widely varying parameter values depending on the user. The proposed method streamlines parameter selection with a view to increasing the appeal of the BBM for practitioners. The method adopts a 'sequential' procedure where the five parameters governing isotropic virgin behaviour are matched to degrees of freedom in the BBM, which are then fixed one at a time, in a specific order, without any assumption about other parameters. The simplicity and reduced subjectivity of the method in comparison with iterative procedures is demonstrated by selecting parameter values from laboratory tests. Key words: unsaturated soils, constitutive modelling, Barcelona basic model. La popularite du modele de base de Barcelone (MBB) est en constante augmentation depuis sa publication en 1990 en raison de sa capacite d'integrer les aspects cles du comportement non sature des sols. Cependant, le MBB est encore rarement utilise; par les praticiens, en partie dfl a l'absence de methodes simples et objectives pour selectionner les valeurs des parametres a partir d'essais en laboratoire. Une des difficultees est que dans le MBB, les aspects individuels du comportement vierge isotrope sont controls par plusieurs parametres, alors que simultanement, un seul parametre controle plus d'un aspect du comportement du sol. Ceci implique que des procedures iteratives sont utilisees pour ajuster les parametres un a un pour representer les essais en laboratoire, ce qui demande une certaine experience et qui peut mener a la selection de valeurs grandement diffeerentes pour les parametres selon l'utilisateur. La meethode proposee simplifie la selection des parametres dans le but d'augmenter l'interet des praticiens pour le MBB. La meethode adopte une procedure seequentielle dans laquelle les cinq parametres qui gerent le comportement vierge isotrope sont associeesa des degresde liberte dans le MBB, qui eux sont fixesun a la fois dans un ordre specifique, sans aucune supposition a propos des autres parametres. La simplicite et la reduction de la subjectivite de la meethode comparativement aux procedures iteratives est demontree par la selection de valeurs pour les parametres a partir d'essais en laboratoire. Mots-cles: sols non satures, modelisation constitutive, modele de base de Barcelone. [Traduit par la Redaction], Introduction The Barcelona basic model (BBM) developed by Alonso et al. (1990) is the first and best-known elastoplastic constitutive model for unsaturated soils. The BBM incorporates suction, s, as a [...]

The origins of the method, which relies on the high penetration of thermal neutrons through most industrial materials, in the late 1970s and 1980s and its development up to the present time are described. The basic steps from the measurement of lattice spacing to the calculation of stress are outlined. The length scales on which strains and stresses are manifest have a bearing on the interpretation of strain in terms of stress. A number of examples of macroscopic strain or stress fields are described where these scale considerations, as well as gradients of solute concentration that affect the interpretation of strain, matter. The strains on the length scale of the grains provide useful information about the elasticity and plasticity of materials, particularly in materials of lower symmetry than cubic. Finally, a number of future directions are suggested, which are enabled by the new intense neutron sources and improved equipment built in the last few years. PACS Nos: 61.05.fm, 62.20.F-, 83.85.Lq Nous decrivons la meethode, de son origine dans les anneees 70-80 jusqu'a son developpement aujourd'hui. Elle repose sur la grande penetration des neutrons thermiques a travers la plupart des materiaux industriels. Nous soulignons les etapes de base a partir du parametre cristallin au calcul de l'effort de contrainte. Les echelles de longueur caracteeristiques des efforts et deformations influent sur l'interpretation de la deformation en fonction de l'effort. Nous decrivons des exemples de champs macroscopiques d'effort ou de deformation, oil sont importants ces considerations d'echelle et les gradients de concentration de solute; qui affectent l'interpretation de la deformation. Les deformations a l'echelle du grain fournissent des renseignements utiles sur l'eelasticite; et la plasticite des materiaux, particulierement dans les materiaux de symetrie plus basse que cubique. Finalement, nous suggerons des developpements a venir qui sont rendus possibles par la nouvelle source intense de neutrons et par le nouvel appareillage qui a este construit ces dernieres anneees. [Traduit par la Redaction], 1. Introduction The concept of using the interplanar spacing of the crystal lattice as a built-in strain gauge of the state of stress is nearly a century old [1] and [...]

Prevention of hot tearing during casting or welding of commercial alloys remains a challenge for numerous industrial applications. The tendency of an alloy to tear is related to the alloy's microstructure, solidification rate, and the stress/strain conditions it experiences during solidification. Due to technological challenges in performing accurate and reliable measurements, there remains a paucity of quantitative experimental data on the stress/strain conditions associated with the onset of hot hearing. This paper reports on a novel approach to quantify strain at the onset of hot tearing in two magnesium alloys. Neutron diffraction strain mapping was carried out and revealed that in the case of the AZ91D alloy, tensile strain of ~0.05% was associated with initiation of material's plastic damage and hot tearing, while for the AE42 alloy the critical strain was ~0.09%. PACS No: 61.05.fg La prevention de la fissuration a chaud lors de la coulee ou du soudage d'alliages metalliques demeure un defi dans beaucoup d'applications industrielles. La tendance d'un alliage a se dechirer est relieea la microstructure de l'alliage, au taux de solidification et aux conditions de contrainte et de deformation pendant la solidification. A cause des limitations technologiques actuelles, il est difficile d'obtenir des mesures precises et fiables des conditions de contrainte et deformation associees au debut de la fissuration a chaud. Nous presentons ici une nouvelle approche pour quantifier la deformation au debut de la fissuration a chaud dans deux alliages de magnesium. Une cartographie des deformations, obtenue par diffraction de neutrons, revele que dans le cas de l'alliage AZ91D, une deformation sous traction de ~0,05 % est associeee au debut du dommage plastique et de la fissuration a chaud, alors que pour l'alliage AE42, la deformation critique est de ~0,09 %. [Traduit par la Redaction], 1. Introduction Hot tears are cracks forming in a semi-solid alloy prior to its complete solidification. These cracks may be observed on the casting surface or in the casting interior [...]

Longitudinal elongation develops in reinforced concrete members that exhibit flexural yielding during cyclic loading. The longitudinal elongation can decrease the shear strength and deformation capacity of the members. In the present study, nonlinear truss model analysis was performed to study the elongation mechanism of reinforced concrete beams and the effects of various design variables on the elongation. The results showed that residual tensile plastic strain of the longitudinal reinforcement in the plastic hinge is the primary factor causing the member elongation and that the shear-force transfer mechanism of diagonal concrete struts has a substantial effect on the magnitude of the elongation. Based on the elongation mechanism found by truss model analysis, a simplified method for evaluating member elongation was developed. The proposed method was applied to test specimens with various design parameters and loading conditions. DOI: 10.1061/(ASCE)ST.1943-541X.0000201 CE Database subject headings: Beams; Reinforced concrete; Cyclic loads; Plastic hinges; Seismic design. Author keywords: Beams; Concrete, reinforced; Cyclic loads; Plastic hinges; Seismic design.

A unified methodology is proposed to compute the tendon stresses in externally prestressed beams in elastic and ultimate states, and practical design equations are developed to predict the ultimate tendon stresses. Previous test results have shown that there is an almost linear relationship between the tendon stress increment and the beam midspan deflection in both elastic and inelastic ranges. The key point is to seek this relationship and then the prediction of the tendon stress increment is transferred to the problem of calculating the beam midspan deflection. The second-order effect of external tendons is included in this deformation compatibility based analysis. Moreover, reasonable simplifications are made to establish practical design equations for the prediction of the ultimate tendon stress. The proposed equations are shown to be able to account for most of the important variables and result in good agreement with test data. It is shown that the ultimate stress increment is mainly dependent on the tendon eccentricity and the neutral axis depth, and the second-order effect can be reasonably taken into account using the stress and depth reduction factors. DOI: 10.1061/(ASCE)ST.1943-541X.0000202 CE Database subject headings: Tendon; Stress; Flexural strength; Prestressing; Inelasticity; Bonding. Author keywords: External tendon; Unbonded tendon; Stress increment; Flexural strength; Second-order effect.

This paper addresses the potential use of granulated rubber as backfill material for buried pipelines in cold regions. An experiment on a laboratory scale buried pipe was conducted to evaluate the pipe-backfill interaction upon freezing. Two backfill materials were employed. In Case 1, sand was used as backfill material. In Case 2, granulated rubber was mixed with sand. Induced circumferential and longitudinal strains along the pipe were measured with movement of the freezing front into the backfill and an estimate of the freezing soil pressure was obtained based on the measured pipe strain. Experimental results showed that the behavior of the buried pipe was influenced by the progression of the freezing front and type of backfill material. Cold temperatures advanced faster into the sand backfill compared to the rubber-sand backfill due to the good thermal characteristics of rubber. Circumferential strains increased in both backfills indicating the development of freezing soil pressure in the backfill. Dominant vertical compressive strains were observed at 0[degrees] and 180[degrees] in both backfills. A significant reduction in strain and pressure exerted on the pipe upon freezing in the rubber-sand backfill was confirmed and the application of rubber mixed with sand as backfill material is possible. DOI: 10.1061/(ASCE)MT.1943-5533.0000090 CE Database subject headings: Buried pipes; Strain; Freezing; Frozen soils; Backfills; Frost; Rubber; Water content. Author keywords: Pipe strain; Freezing front; Soil freezing pressure; Backfill; Frost penetration; Granulated rubber; Unfrozen water content.

This paper presents the results of a comprehensive research study to determine the potential causes for an inordinate distress developed on a shotcrete liner material of a tunnel located near Dallas, TX. This tunnel was originally founded on a limestone material. Distress locations were identified where possible delamination of shotcrete layer and moisture leaks were either suspected or noticed. As a part of the research, rock cores and white powderlike substance behind the liner were collected around the distressed locations, and these cores and powder material were subjected to chemical, mineralogical, and engineering tests to understand the potential causes of this distress. Mineralogical tests, in particular, X-ray powder diffraction analysis on a powder material and gel-like substances collected on the liner, showed the presence of anhydrite, gypsum, and ettringite traces. High amounts of sulfate measurements in chemical and energy dispersive X-ray spectroscopy studies also showed that both gypsum and ettringite formations were possible in and around the limestone material. Upon hydration, mineral expansion of ettringite and anhydrite led to heaving and subsequent cracking of the adjacent shotcrete layer. Engineering characterization tests including unconfined compression strength (UCS), indirect tensile strength (ITS), and triaxial tests on rock cores embedded with a powder type sulfate material revealed that low strength cores were obtained near high distress zones and high strength cores were collected at low distress zones. The UCS values ranged from 6.2 (high distress) to 13.8 MPa (low distress) whereas the ITS values of the cores varied from 0.5 to 1.1 MPa for the same distress locations. This indicates the potential loss of strength of these rock materials from the presence of gypsum material in them. Possible methods to mitigate this heaving problem behind the liner are also discussed. DOI: 10.1061/(ASCE)MT.1943-5533.0000087 CE Database subject headings: Sulfates; Tunnels; Shotcrete; Gypsum; Limestone; Rocks; Differential settlement. Author keywords: Sulfate heaving; Tunnels; Shotcrete; Ettringite; Gypsum; Limestone; Rock testing.

In the analysis or design process of reinforced concrete structures, the peak stress and strain in plain concrete under triaxial stress are critical. However, the nonlinear behavior of concrete under triaxial stresses is very complicated; modeling its behavior is therefore a complicated task. In the present study, several radial basis function neural network (RBFN) models have been developed for predicting peak stress and strain in plain concrete under triaxial stress. For the purpose of constructing the RBFN models, 56 records including normal- and high-strength concretes under triaxial loads were retrieved from literature for analysis. The K- means clustering algorithm and the pseudoinverse technique were employed to train the network for extracting knowledge from training examples. Besides, the performance of the developed RBFN models was estimated by the method of three-way data splits and K-fold cross- validation. On the other hand, a comparative study between the RBFN models and existing regression models was made. The results demonstrate the versatility of RBFN in constructing relationships among multiple variables of nonlinear behavior of concrete under triaxial stresses. Moreover, the results also show that the RBFN models provided better accuracy than the existing parametric models, both in terms of root-mean-square error and correlation coefficient. DOI: 10.1061/(ASCE)MT.1943-5533.0000077 CE Database subject headings: Reinforced concrete; Stress; Strain; Neural networks; Concrete structures. Author keywords: Concrete; Triaxial stress; Peak stress; Peak strain; Neural networks.

A series of simplified rod-fastened rotors, which have different surface contact roughness are manufactured and their modal parameters under different pretightening force, are measured in free-free state. The concept of surface contact stiffness is introduced to simulate the influence of pretightening force on modal parameters of these simplified rod-fastened rotors using finite element method. The experiment measured results are compared and fitted to the finite element analysis results and the relationship between contact stiffness and contact stress is established in which the contact stress is defined by the pretightening force. The relationship is then applied on the modal analysis of a real gas turbine rotor, and its modal test results and finite element analysis results are consistent with each other, proving that the relationship and the described determination method of contact stiffness based on modal test and finite element analysis are effective. [DOI: 10.1115/1.4000591] Keywords: rod-fastened rotor, contact stiffness, contact stress, natural frequency, modal analysis

In the present paper, calculations of the stress intensity factor (SIF) in the linear-elastic range and the J-integral in the elastoplastic domain of cracked structural components are performed by using the shell-to-solid submodeling technique to improve both the computational efficiency and accuracy. In order to validate the submodeling technique, several numerical examples are analyzed. The influence of the choice of the submodel size on the SIF and the J-integral results is investigated. Detailed finite element solutions for elastic and fully plastic J-integral values are obtained for an axially cracked thick-walled pipe under internal pressure. These values are then combined, using the General Electric/Electric Power Research Institute method and the reference stress method, to obtain approximate values of the J-integral at all load levels up to the limit load. The newly developed analytical approximation of the reference pressure for thick-walled pipes with external axial surface cracks is applicable to a wide range of crack dimensions. [DOI: 10.1115/1.4001267] Keywords: finite element analysis, submodeling technique, stress intensity factor, J-integral, semi-elliptical surface crack, reference stress method

Distributed optical fiber strain sensors have attracted increasing attention in research and applications related to civil engineering because no other tools can satisfactorily detect the locations of unpredictable events. For instance, for crack detection, it is necessary to employ a fully distributed sensor because crack locations are a priori unknown. The Brillouin optical correlation domain analysis (BOCDA) system, a distributed sensor that offers high spatial resolution by using stimulated Brillouin scattering, has undergone significant development over the last decade, during which it has been used in a wide range of civil engineering applications. In this paper, we demonstrate how a BOCDA-based optical fiber strain sensor can be employed to monitor cracks in fiber-reinforced concrete. Crack monitoring is important for checking the structure of such high-performance concrete, which has enhanced strength and toughness since it incorporates fibers. In particular, early detection of tiny cracks is essential for preventing crack growth and dispersion. We carried out a concrete beam-bending test to detect crack-induced strain distribution during loading. For this purpose, we employed an improved BOCDA system that provides enhanced measurement length with high spatial resolution; hence, BOCDA can detect a tiny crack before visual recognition. Moreover, we demonstrate a field application of the BOCDA system to ensure a flawless pedestrian deck made of fiber-reinforced concrete. DOI: 10.1061/(ASCE)ST.1943-541X.0000195 CE Database subject headings: Fiber optics; Probe instruments; Monitoring; Cracking; Fiber reinforced materials; Reinforced concrete; Strain measurement. Author keywords: Fiber optics; Sensors; Monitoring; Cracking; Fiber reinforced materials; Strain measurement.

We present a quasi-static fiber optic strain sensing system capable of resolving signals below nanostrain from 20 mHz. A telecom-grade distributed feedback CW diode laser is locked to a fiber Fabry-Perot sensor, transferring the detected signals onto the laser. An [H.sup.13][C.sup.14]N absorption line is then used as a frequency reference to extract accurate low-frequency strain signals from the locked system. [c] 2010 Optical Society of America OCIS codes: 120.0120, 280.0280.

Investigations were conducted in several regions of Norway with the purpose of detecting and measuring stress-relief features and to derive from them valuable information on the shallow-crustal stress state. Stress-relief features are induced by blasting and sudden rock unloading in road construction and quarrying operations, and are common in Norway and probably in other regions of Fennoscandia, as they are in NE America. Stress relief at the Earth's surface is diagnostic of anomalously high stress levels at shallow depths in the crust and characterizes the formerly glaciated Baltic and Canadian Precambrian shields. The mean orientation of the maximum horizontal compressive stress axis, as deduced from the orientation of stress-relief features, was found to be NW-SE, consistent with North Atlantic ridge-push forces. We show that our determined stress orientations are in excellent agreement with other kinds of stress data. As a final step, we estimate ridge-push force magnitudes from gravity data in the North Atlantic region. Our computations suggest that strong ridge-push forces characterize the Baltic and Canadian shields. We conclude from this quantitative analysis and our fieldwork results that present-day stress relief, in Fennoscandia and NE America, is mostly triggered by plate-scale ridge-push forces and not by residual glacial loading stresses. doi: 10.1144/0016-76492009-136.

Notch stress-strain conversion (NSSC) rules are widely used to estimate nonlinear and history-dependent stress-strain behavior of the notch components or structures. This paper focuses on the estimation of stress and strain using the conventional NSSC rules and linear elastic analysis by considering the entire relaxation locus of the component during inelastic action. On the basis of local effects, net-section collapse, and reference stress, a simple method for estimating inelastic strain in the vicinity of stress concentrations is proposed. The accuracy of the method is compared with elastic-plastic finite element analysis for several notch configurations exhibiting two-dimensional and three-dimensional effects. [DOI: 10.1115/1.4000371] Keywords: notch stress-strain conversion (NSSC), reference stress, elastic-plastic

[1] Transform motion along oceanic transforms generally occurs along narrow faults zones. Another class of oceanic transforms exists where the plate boundary is quite large (~100 km) and includes several subparallel faults. Using a 2-D numerical modeling, we simulate the slip distribution and the crustal stress field geometry within such broad oceanic transforms (BOTs). We examine the possible configurations and evolution of such BOTs, where the plate boundary includes one, two, or three faults. Our experiments show that at any time during the development of the plate boundary, the plate motion is not distributed along each of the plate boundary faults but mainly occurs along a single master fault. The finite width of a BOT results from slip transfer through time with locking of early faults, not from a permanent distribution of deformation over a wide area. Because of fault interaction, the stress field geometry within the BOTs is more complex than that along classical oceanic transforms and includes stress deflections close to but also away from the major faults. Application of this modeling to the 100 km wide Tjornes Fracture Zone (TFZ) in North Iceland, a major BOT of the Mid-Atlantic Ridge that includes three main faults, suggests that the Dalvik Fault and the Husavik-Flatey Fault developed first, the Grismsey Fault being the latest active structure. Since initiation of the TFZ, the Husavik-Flatey Fault accommodated most of the plate motion and probably persists until now as the main plate structure. Citation: Homberg, C., F. Bergerat, J. Angelier, and S. Garcia (2010), Fault interaction and stresses along broad oceanic transform zone: Tjornes Fracture Zone, north Iceland, Tectonics, 29, TC 1002, doi: 10.1029/2008TC002415.

A finite element model is developed to study the behaviour of unstiffened steel plate walls. The model includes both material and geometric nonlinearities and strain rate effects. The model is first validated using the results from quasistatic and dynamic experimental programs. The validated finite element model is then used to study the performance of four storey and eight storey steel plate walls with moment-resisting beam-to-column connections under spectrum compatible seismic records for Vancouver and Montreal. Two different steel plate wall types defined in the current Canadian standard CAN/CSA-S16-01 are considered, namely, Type D (ductile) and Type LD (limited-ductility) plate walls. All the Type D walls, designed according to the capacity design provisions, exhibit better inelastic seismic responses than the Type LD plate walls. The analyses of eight storey steel plate walls show that in high seismic regions, such as Vancouver, medium- to high-rise Type LD plate walls may exhibit yielding in columns in intermediate floors. The study also shows that in more moderate seismic regions, like Montreal, Type LD plate walls behave in a stable and ductile manner and can be used for low- to medium-rise buildings. Key words: capacity design, ductility, strain rate, finite element, P-delta, pushover analysis, seismic analysis, seismic design, seismic performance, steel plate wall. Un modele d'elements finis est developpe afin d'etudier le comportement de murs non renforces en plaques d'acier. Le modele tient compte des non-linearites geometriques et des materiaux ainsi que des effets du taux de sollicitation. Le modele est le premier modele valide en utilisant les resultats de programmes experimentaux dynamiques et quasi statiques. Le modele d'elements finis valide est ensuite utilise pour etudier le comportement de murs en tole forte de quatre et de huit etages comportant des assemblages poutre-poteau a cadre rigide au moyen de sismogrammes compatibles au spectre pour Vancouver et Montreal. Deux differents types de murs en tcole forte definis dans la norme canadienne actuelle CAN/CSA-S16-01 sont considers, le Type D (ductile) et le Type LD (ductilite limite). Tous les murs de Type D, concus selon les dispositions de calcul de la capacite, montrent de meilleures reponses sismiques inelastiques que les murs en plaques d'acier de Type LD. Les analyses pour les murs de tole forte de huit etages montrent que dans les regions a forte sismicite, telles que Vancouver, des murs de tole forte de Type LD pour batiments de moyenne et de grande hauteur peuvent presenter une propagation des zones inelastiques dans les poteaux des etages intermediates. L'etude demontre egalement que dans les regions a sismicite plus moderee, telles que Montreal, les murs en ttole forte de Type LD se comportent de maniere stable et ductile et peuvent etre utilises dans les batiments de faible et de hauteur moyenne. Mots-cles: calcul de la capacite;, ductilite,elements finis, P delta, analyse de renversement, analyse sismique, conception sismique, comportement sismique, mur en plaques d'acier, taux de sollicitation. [Traduit par la Redaction], 1. Introduction Steel plate walls (SPWs) are increasingly being used as the primary lateral load resisting system in buildings. They consist of steel plates installed vertically within building frames and [...]

A unique formulation for the elastic torsional buckling analysis of columns is developed in this paper based on the principle of stationary complementary energy. It is well known that in displacement based numerical formulations, discretization errors lead to stiffer behavior; hence convergence from above. On the other hand, discretization errors in complementary energy based numerical formulations lead to softer behavior in linear elasticity problems, which is a desired feature from the engineering view point. However, complementary energy based formulations can only overpredict the buckling loads for the flexural buckling problems of columns unless the physical conditions are compromised. In this study a formulation based on the principle of stationary complementary energy is considered for the elastic torsional buckling analysis of columns. The complementary energy expression is obtained from the well known total potential energy functional by using Frederichs' transformation. In contrast to flexural buckling analysis of columns, it is shown that when the principle of stationary complementary energy is used, the torsional buckling loads can be underpredicted. A mathematical proof is provided to elucidate this property. The convergence behavior of the approximate solutions is illustrated through numerical examples for several columns with different boundary conditions. DOI: 10.1061/(ASCE)EM.1943-7889.0000061 CE Database subject headings: Buckling; Torsion; Convergence.

Fiber Bragg grating (FBG) sensors have attracted a considerable amount of interest for their superior characteristics. However, the FBG sensors made on bare fibers are easily damaged. For their safe use in engineering, the glass core of optical fibers is coated with softer low modulus protective coatings. A portion of the host material strain is absorbed by the protective coatings when the strain transfers from the host material to the fiber core, and hence only a segment of structural strain is sensed. By introducing the shear modulus of the host material, a novel analytical model is developed for evaluating the sensing strain of the embedded FBG sensors in composite structures based on the strain in a host material. The average strain transfer ratio is deduced to describe the percentage transferred to the optical fiber core from the host material. It is concluded that the shear modulus of the host material influences strain transmission, especially when it is much lower than the modulus of the fiber core. Then, the strain transfer ratio of an optical fiber sensor embedded in a multilayered structure is developed in a similar way. The factors that affect the efficiency of strain transfer on the optical fiber sensor are deduced and discussed in detail based on the theoretical analysis. Finally, the theoretical results are verified through laboratory experimentation with the FBG sensors. DOI: 10.1061/(ASCE)0733-9399(2009)135:12(1343) CE Database subject headings: Strain distribution; Probe instruments; Experimentation; Young's modulus; Parameters.

The development of strain in two 31 and 56 m long instrumented postdriving grouted cylinder piles at a site west of Busan, South Korea, were monitored during 200 days after construction, whereupon a static loading test was performed. Initial strain measurements showed unexpected elongation of the pile, probably due to swelling from absorption of water but as the soil reconsolidated, the elongation changed into shortening, probably due to imposed residual load in the pile. The resulting compression of the pile eventually offset the swelling of the pile. To investigate the cause of the strain changes more closely and enhance the evaluation of the field data, two short pile pieces were prepared and placed free-standing above ground in an outside laboratory. One piece was from a cylinder pile of which central void was grouted and one was made up by grouting inside a temporary casing. The monitoring showed that the short pieces appeared first to shorten and then to elongate due to the heating and cooling from the hydration process. When strains and temperature had stabilized 150 days after start of the study, both pieces were submerged to introduce swelling of the concrete. For the first 100 days after submerging, the swelling strains in both short pieces amounted to 100 [micro][epsilon]. Seven hundred days after submersion, the total swelling strains were 150 and 250 [micro][epsilon]. DOI: 10.1061/(ASCE)GT.1943-5606.0000124 CE Database subject headings: Instrumentation; Piles; Grouting; Strain; Measurements; Swelling; Monitoring.

Mechanistic-empirical pavement design guide for flexible pavements as per the AASHTO design guide requires characterization of subgrade soils using the resilient modulus (MR) property. This property, however, does not fully account for the plastic or permanent strain or rutting of subgrade soils, which often distress the overlying pavements. Soils such as silts exhibit moderate to high resilient moduli properties but they still undergo large permanent deformations under repeated loading. This explains the fallacy in the current pavement material characterization practice. A comprehensive research study was performed to measure permanent deformation properties of subgrade soils by subjecting various soils under repeated cycles of deviatoric loads. This paper describes test procedure followed and results obtained on three soils including clay, silt, and sandy soils. The influence of compaction moisture content, confining pressure, and deviatoric stresses applied on the measured permanent deformations of all three soils are addressed. A four-parameter permanent strain model formulation as a function of stress states in soils and the number of loading cycles was used to model and analyze the present test results. The model constants of all three soils were first determined and these results were used to explain the effects of various soil properties on permanent deformations of soils. Validation studies were performed to address the adequacy of the formulated model to predict rutting or permanent strains in soils. DOI: 10.1061/(ASCE)GT. 1943-5606.0000163 CE Database subject headings: Strain; Subgrades; Models; Repeated load; Triaxial tests; Experimentation.

The paper presents a study of the influence of grain-size distribution curve on the small strain shear modulus [G.sub.max] of quartz sand with subangular grain shape. The results of 163 resonant column tests on 25 different grain-size distribution curves are presented. It is demonstrated for a constant void ratio that while [G.sub.max] is not influenced by variations in the mean grain-size [d.sub.50] in the investigated range, it significantly decreases with increasing coefficient of uniformity [C.sub.u]=[d.sub.60]/[d.sub.10] of the grain-size distribution curve. Well-known empirical formulas (e.g., Hardin's equation with its commonly used constants) may strongly overestimate the stiffness of well-graded soils. Based on the RC test results, correlations of the constants of Hardin's equation with [C.sub.u] have been developed. The predictions using Hardin's equation and these correlations are in good accordance with the test data. Correlations of the frequently used shear modulus coefficient [K.sub.2,max] with [C.sub.u] and empirical equations formulated in terms of relative density, are also given in the paper. A comparison of the predictions by the proposed empirical formulas with [G.sub.max]-data from the literature and a micromechanical explanation of the experimental results are provided. Correction factors for an application of the laboratory data to in situ conditions are also discussed. DOI: 10.1061/(ASCE)GT.1943-5606.0000096 CE Database subject headings: Shear modulus; Sand; Coefficients; Grain size; Strain.

Lithospheric strength profiles generated for a shortening continental lithosphere generally predict excessively high differential stresses in the sub-Moho continental mantle; this seems inconsistent with the relative scarcity of earthquakes at this depth. This inconsistency was put forward as evidence for weak mantle rheology. However, this argument implicitly assumes that strength envelopes are valid in actively deforming regions. We test this assumption on two end-member model lithospheres having identical upper crustal rheologies, but with (1) a weak lower crust and strong mantle, and (2) a strong lower crust and weak mantle. For this purpose, we compare one-dimensional (l-D) with 2-D visco-elasto-plastic numerical models of continental shortening. The 2-D models show that strongly heterogeneous deformation typically follows initially homogeneous deformation. Lithospheric-scale buckle folds and shear zones result in strain rate variations of as much as three orders of magnitude. Differential stresses in the upper crust are close to yield, as predicted by 1-D models. Stresses in deeper lithospheric regions, however, are significantly smaller than in 1-D models, especially in actively deforming regions. Systematic numerical simulations as a function of temperature and deformation rate reveal that 1-D models are reliable in hot and/or slowly deforming lithospheres only. The relative scarcity of earthquakes at mantle levels should thus be interpreted as an intrinsic consequence of strong lithospheric deformation rather than as evidence for a weak upper mantle.

Diffusion profiles in garnet are used to determine the duration of movement on shear zones. In the Musgrave Block, central Australia, Grenville age granulites were overprinted at depths of ~40 km by high-strain zones during the intracratonic Petermann orogeny (ca. 550 Ma ago). In these zones, quartzofeldspathic mylonites contain garnet from the early granulite facies event that developed compositional gradients during the high-pressure overprint. The diffusion of Ca into garnet is linked with the release of Ca in plagioclase (the only calcic mineral in the rock) during neocrystallization of sodic feldspar during high-strain deformation. Available diffusion data on garnet directly define the duration of high-strain deformation at eclogite facies. Our results indicate that the integrated time scales of movement in individual high-strain zones were short lived (between 0.07 Ma and 1.4 Ma), and that wide shear zones were active longer than narrow ones. In addition, we find that relict K-feldspar in one of the narrow eclogite facies shear zones yields a [sup.40]Ar-[sup.39]Ar age that is partially reset, indicating that the thermal event was also short lived. These short time scales support the hypothesis that shear heating was the dominant source of heat for the eclogite facies overprint.

Ground strains were estimated from vibrations measured during pile driving operations at a buried, prehistoric archeological site to monitor potential construction impacts. Subsurface characteristics of the site were investigated using multiple cone penetration test (CPT) soundings and the shear wave velocity profile was measured using the seismic CPT method. Embedded geophones and surface accelerometers were then used to measure ground vibrations during pile driving. Displacement gradients were estimated from the vibrations using the following three methods: (1) the difference between adjacent displacements divided by sensor spacing; (2) peak particle velocity divided by depth-dependent wave velocity (i.e., at the depth where the sensor was placed); and (3) peak particle velocity divided by frequency-dependent wave velocity from a measured dispersion curve. Methods (1) and (3) agreed well, while method (2) caused errors that depended on depth of embedment of the sensors and distance from pile driving. Errors in (2) were attributed to a mismatch between the depth-dependent wave velocity and the wave velocity on the frequency band that carried the largest velocity pulse through the dispersive soil profile. Ground strains were related to displacement gradients based on theoretical solutions of harmonic body waves and Rayleigh waves in dispersive elastic media. The peak estimated ground strains were smaller than the threshold volumetric shear strain, but a few centimeters of settlement were nevertheless observed at the site. The spatial extent of the settlement is characterized using attenuation rules fit to the vibration data, and by calibration with a settlement gauge. Ground cracking and vertical offsets that could potentially mask the archaeological history of the site were neither observed nor predicted from the observed vibration amplitudes. Estimated impact on archeological interpretation of artifacts in their stratigraphic context was likely insignificant except in the immediate region where the piles were driven. This insight will assist in future planning at sites with similar subsurface stratigraphy. DOI: 10.1061/(ASCE)GT. 1943-5606.0000031 CE Database subject headings: Vibration; Pile driving; Archaeology; Wave measurement; Foundation construction.

This study critically discusses the fundamental concepts used for evaluating the flexural and axial resistance of structures under blast. Simplified methods based on single degree of freedom are emphasized. The paper begins with how to estimate the blast parameters for a given charge size and standoff distance. These parameters include side-on and reflected pressures, positive phase duration, and side-on and reflected impulses. Subsequently, blast damage criteria are defined in accordance with prevailing guidelines and some of their short comings are discussed. To assess the impact of blast on the flexural safety and performance of structures, some simple methods are presented. The methods are either empirical or are based on the principles of energy and momentum conservation. The analytical results are in closed-form or in the form of pressure-impulse (P-I) diagrams. The effect of strain rate on both blast-induced flexural deflection and strength of structures, with particular emphasis on reinforced concrete structures, is discussed. Key words: blast, beam, column, concrete, pressure, impulse, strain rate. Cette etude analyse les concepts fondamentaux utilises pour evaluer la resistance en flexion et axiale des structures soumises a un souffle d'une explosion. L'accent est mis sur des methodes simplifiees basees sur un seul degre de liberte. Cet article debute en expliquant comment estimer les parametres du souffle pour une charge et une distance de l'explosion donnees. Ces parametres comprennent les pressions laterales et reflechies, la duree de la phase positive ainsi que les impulsions laterales et reflechies. Par la suite les criteres de dommages causes par le souffle sont definis selon des lignes directrices applicables et quelques inconvenients sont abordes. Certaines methodes simples sont presentees afin d'evaluer l'impact du souffle sur la securite et le comportement en flexion des structures. Les methodes sont soit empiriques ou basees sur les principes de conservation de l'energie et du moment. Les resultats sont sous forme analytique ou sous forme de diagrammes pression-impulsion (P-I). L'effet du taux de contraintes sur la flexion induite par le souffle et sur la resistance des structures est aborde, avec une attention speciale aux structures en beton arme. Mots-cles : souffle, poutre, colonne, beton, pression, impulsion, taux de contraintes. [Traduit par la Redaction], Introduction Recent events have created concern about the vulnerability of buildings and other structures to blast loads. The effect of blast on a building depends on the amount and location [...]

We present a fiber sensor scheme for discriminative measurement of temperature and strain by space division multiplexing high-birefringence-fiber loop mirrors (HBFLMs). Discriminative measurement of temperature and strain can be realized by sequentially measuring the resonance wavelength shifts of two HBFLMs constructed with the same high-birefringence fiber. Experimental results show that the temperature and strain resolutions reach [+ or -] 0.5[degrees]C and [+ or -]10 [micro][epsilon], respectively. This scheme can provide not only high resolutions in temperature and strain but also has potential applications in distributed HBFLM sensing. OCIS codes: 060.2310, 060.2370.

An aeroelastic simulation of a stiff in-plane hingeless rotor in forward flight is conducted to evaluate the feasibility of reducing lagwise root loads via an embedded absorber within the blade. A finite element analysis based on a moderate deflection beam model is employed to capture the flap, lag, and torsion deflections of the rotor blade. The mass-spring-damper absorber system is simulated as a one-degree-of-freedom rigid body with chordwise motion. By using the Hamilton principle, system equations of motion are derived based on the generalized force formulation. Dynamic responses are calculated to investigate the potential of the absorber for in-plane loads reduction. Parametric studies are conducted to explore the influence of the absorber on the dynamic characteristics of the rotor blade. From the aeroelastic analysis of the blade-absorber system, results indicate that placing an embedded absorber in the blade chordwise direction can decrease the 1 and 2/rev lagwise root bending moments by about 50 and 90%, respectively, under large load states. The effects of absorber frequency, absorber damping, chordwise position of the absorber, rotor thrust, forward speed, and trim condition are also studied. DOI: 10.2514/1.40569

The part of sand behavior that is affected by time, such as creep, relaxation, and loading rate effects are not similar to those observed for clay. To throw more light on the time effects in sand, many series of drained triaxial compression experiments have been performed on crushed coral sand. These tests were all performed with a constant effective confining pressure of 200 kPa. The test series included experiments with specimens loaded at five different strain rates with a 256-fold ratio between the extreme rates, tests with sudden changes in strain rate from slow to fast and vice versa, and tests in which axial and volumetric creep strains were observed at stress differences of 500, 700, and 900 kPa. Creep creates structuration and this has to be overcome to produce further plastic straining. Experiments were also performed in which the stress difference was dropped quickly from three different values of 500, 700, and 900 kPa followed by creep. In these stress drop-creep tests five different magnitudes of stress drops were employed: 0, 100, 200, 300, and 400 kPa. The results involving conventional creep effects and stress drop-creep effects are presented and analyzed. DOI: 10.1061/(ASCE)GT.1943-5606.0000067 CE Database subject headings: Creep; Granular materials; Sand; Soil properties; Strain rate; Time dependence; Triaxial tests.

The effects of the confining membrane in laboratory tests on soil specimens have been the subject of numerous experimental, analytical, and numerical studies over the past half-century. This technical note expands the existing knowledge base by presenting a methodology and the associated results from an experimental study that has quantified the effect of the confining membrane in biaxial shear tests conducted on medium sand. The applicability of the method of biaxial tests on clay specimens is also presented. The results show that for both tests on sands and clays, the effect of the membrane on the shear stress on the failure plane are significant and should be accounted for in the interpretation of biaxial shear test results where localization occurs. DOI: 10.1061/(ASCE)GT. 1943-5606.0000011 CE Database subject headings: Membranes; Strain; Localization; Compression tests.

For polymer matrix composites subjected to large strain rates, it is important to correctly characterize the nonlinear and strain-rate dependent response of polymers. Viscoplastic constitutive material models have been developed to account for the effects of hydrostatic effects and inelastic strains in polymer materials. The effective implementation of such viscoplastic models is important for development of composite models geared toward practical applications. Goldberg's polymer model numerical implementation into a commercial finite-element code constitutes the main objective of this paper. Special attention is given to the use of effective algorithms for solving the model nonlinear rate dependent viscoplastic equations. Existent experimental data are used to verify the accuracy and robustness of the computational polymer model. A phenomenological fiber model and a simplified iso-strain mixture theory used to obtain the resultant stresses in the composite by averaging the stresses of the individual constituents are also defined. The validation of the simplified mixture theory for the composite model will be presented later on. DOI: 10.1061/(ASCE)0893-1321(2009)22:3(304) CE Database subject headings: Strain rate; Nonlinear response; Polymers; Composite materials.

In order to evaluate the importance of stress relaxation on device performance of capacitive RF MEMS switches, stress relaxation has been measured in 1.2-[micro]m-thick Au films using a membrane bulge technique. When the residual stress in the films is small, the stress relaxation is fully recoverable and is well described by linear anelasticity (viscoelasticity) theory. A 27% reduction in the effective elastic modulus occurs over a three-day period under constant strain conditions at room temperature. The time dependence of the relaxation can be represented by a series of time constants with values extending from seconds to days. Linear superposition of the anelastic response can be used to accurately predict the stress under any time dependence of the strain. The prediction is accurate even during cyclic loading and unloading, and even when the strain is cycled at rates that are fast compared with any of the relaxation times. The restoring force available to open a capacitive RF MEMS switch is modeled for two different switch designs. The restoring force is shown to drop by approximately 7% or 20% at room temperature for the two cases presented. [2008-0263] Index Terms--Materials reliability, microelectromechanical devices, RF switch, stress measurement.

An experimentally based relationship of the cyclic local bond stress-slip response of steel bars corresponding to splitting mode of bond failure is developed. The relationship is composed of a monotonic envelope response and cyclic bond degrading response. The model accounts for both unconfined and moderately confined concrete and incorporates the effect of several critical bond parameters such as the diameter of steel bars, the ratio of concrete cover to bar diameter, the concrete compressive strength, the type of confinement such as steel ties, fiber-reinforced concrete (FRC), and fiber-reinforced polymer jackets, and the area or content of confining reinforcement. Results predicted by the model showed very good agreement with the test data. The bond-slip relationship can be utilized for evaluating the seismic behavior and bond degradation response of bond-critical regions in reinforced concrete members when confined internally with steel ties or fiber reinforced concrete or retrofitted using external FRP jackets. DOI: 10.1061/(ASCE)0733-9445(2009)135:5(509) CE Database subject headings: Bonding; Concrete; Confinement; Cyclic loads; Numerical analysis; Slip; Fiber reinforced polymers.

We present hybrid Reynolds-averaged Navier--Stokes/large eddy simulation-based analysis of the suppression of fluctuating pressure loads on the walls of a complex nonrectangular cavity using leading-edge mass blowing. The unique aspect of the concepts discussed here is the very low mass flow rates used to achieve significant suppression. The simulation results are used to gain insight into the mechanism governing the effectiveness of these jets. The jets are applied to an L/D = 5.6 cavity at supersonic conditions of Mach 1.5. The simulation results show excellent agreement with experiments demonstrating an overall reduction in fluctuating pressure levels on the order of 50% with the control concepts. The primary mechanism of reduction is the break up of the spanwise coherence in the shear layer into smaller vortical structures thus reducing the shear layer flapping and leading to a smaller imprint on the wall pressures.

Cyclic loading has been known to induce fluid flow and thus mechanotransduction in bones. In the past, four-point bending tests have been used exclusively in studying fluid flow in bones. In order to better understand the mechanism of deformation and fluid flow under loading, compression tests were done on trabecular bone specimens under drained and undrained conditions. In the drained tests, the volume change was observed, whereas in the undrained tests, excess pore fluid pressure was measured. Cyclic loading tests were conducted in addition to monotonic loading tests to observe the permanent volume change or excess pore fluid pressure with loading cycles. A fast loading rate gave a sharp rise in the excess fluid pressure compared to a slow loading rate. The strength and stiffness of the specimens appeared to deteriorate with an increased speed of loadings, but there was no appreciable difference between the results obtained from drained and undrained tests. The drained and undrained tests as described allowed a better understanding of bone behavior under loadings for a coupled stress-flow analysis. DOI: 10.1061/(ASCE)0733-9399(2009) 135:5(375) CE Database subject headings: Human factors; Biological properties; Mechanical properties; Deformation; Cyclic loads.

A simple configuration for simultaneous measurement of temperature and strain exploiting a temperature-insensitive birefringent interferometer based on a photonic crystal fiber incorporating an erbium-doped fiber (EDF) is investigated. The transmission peak power of the birefringent interferometer incorporating the EDF is changed by the temperature variation because the amplified spontaneous emission of the EDF strongly depends on temperature. The applied strain changes the peak wavelength of the birefringent interferometer connecting with the EDF, which can make it possible to discriminate concurrent sensitivities like temperature and strain. The temperature and strain sensitivities were -0.04dB/[degrees]C and 1.3 pm/[mu][epsilon], respectively. OCIS codes: 060.2310, 060.2370.

A realistic assessment of the whole life cost of rail track foundations requires analysis of the effects of the repeated loadings applied by trains. This paper reports the effects of principal stress rotation (PSR) during cyclic loading on the permanent deformations measured in a series of hollow cylinder tests. The tests were carried out on a number of reconstituted soils selected in order to simulate foundation materials on an existing heavy haul railway line. Typical loadings and track geometry together with dynamic finite-element analyses were used to define representative stress changes to be applied to these soils, which were then tested with and without principal stress rotation during loading. It is shown that principal stress rotation has a significant and deleterious impact on permanent deformation of some materials. Therefore, it is concluded that cyclic triaxial testing, which cannot impose principal stress rotation, will not necessarily give good estimates of the long-term performance of rail track foundations. As PSR cannot be ignored when evaluating permanent displacements of rail track foundations, the use of more appropriate (realistic) testing methods such as the cyclic hollow cylinder or the cyclic simple shear apparatus is required. CE Database subject headings: Cyclic loads; Laboratory tests; Shear tests; Railroad tracks; Stress.