Experiments were conducted to investigate the shear behaviour of large deep beams subjected to uniform load. Six tests were performed on specimens with identical cross sections and reinforcing, but under different loading configurations. Variables included: span, degree of cracking prior to loading, proximity to a disturbed region near a reaction, and type of flexural stress on the loaded face. The findings indicate a specific set of variables resulting in unconservative predictions made using a strut-and-tie model for simply-supported beams subjected to uniform load, confirming and validating recent results by other researchers. A fanning strut model is proposed and is shown to provide more conservative results. The emerging trend of high capacity in continuous uniformly-loaded specimens is supported by the experimental results, as is the high capacity of specimens uniformly-loaded on their flexural tension face. Further, the high strength of specimens with suboptimal crack orientations supports recent experimental work.

Experiments were conducted to investigate the shear behaviour of large deep beams subjected to uniform load. Six tests were performed on specimens with identical cross sections and reinforcing, but under different loading configurations. Variables included: span, degree of cracking prior to loading, proximity to a disturbed region near a reaction, and type of flexural stress on the loaded face. The findings indicate a specific set of variables resulting in unconservative predictions made using a strut-and-tie model for simply-supported beams subjected to uniform load, confirming and validating recent results by other researchers. A fanning strut model is proposed and is shown to provide more conservative results. The emerging trend of high capacity in continuous uniformly-loaded specimens is supported by the experimental results, as is the high capacity of specimens uniformly-loaded on their flexural tension face. Further, the high strength of specimens with suboptimal crack orientations supports recent experimental work.

Geosynthetics are used in conjunction with soil/particulate materials to serve various functions like reinforcement, drainage, filtration and containment. The shear behavior of soil-geosynthetic interfaces hugely depends upon on the morphological properties of particulate materials and surface characteristics of geosynthetics. However, many researchers have ignored the effects of morphology, owing to the difficulty in finding the morphological characteristics of sand particles. Few of them used visual, manual and imaged based quantifications, which are not very effective. Also, the effects of particle size and morphology are often combined and the individual effect of these parameters cannot be easily separated. In addition to this, there are very few studies which have given importance to quantitative understanding of surface features/roughness of geosynthetics and almost all of them are limited to 2D surface measurements. The objective of this thesis is to understand the interface shear mechanisms of sand-geosynthetic systems through modified large interface direct shear tests coupled with morphological characterization of sands using advanced image based and optical techniques and surface topographical analysis of geosynthetics using 3D interferometry. The individual effects of particle size and morphology on interface shear mechanism are investigated by carefully selecting the sands having specific size fractions and different morphological characteristics. A new computational method based on image analysis is proposed in this study to quantify the morphology of sands (roundness, sphericity and roughness) more accurately by writing several algorithms and implementing them in MATLAB. The roundness and sphericity of sand particles in this method are quantified as per Wadell (1932) and Krumbein and Sloss (1963) respectively and the root mean square roughness is used as a measure of surface roughness. Out of total four sands, namely coarse sand (CS), medium sand (MS), fine sand (FS) and angular coarse sand (ACS) used in this study, CS, MS and FS have similar morphology and different particle sizes, whereas CS and ACS have same size and dissimilar morphology. The effects of size and morphology of sand particles on the interface shear behavior are examined through direct shear tests on dilative and non-dilative interfaces. After examining the boundary effects on deformation patterns analyzed using shear bands in conventional, fixed box and symmetric interface direct shear tests, symmetric interface direct shear test is observed to show uniformity in stresses and deformations across the shear box and hence the same is adopted in this thesis. Test results revealed that the peak interface friction and dilation angles in case of dilative interfaces are hugely dependent upon the interlocking between the sand particles and the asperities of geosynthetic material, which in turn depend on the relative size of sand particles and asperities. Highest interface shear strength is observed when the asperity size of the geosynthetic material matches with the mean particle size of sand, which is also manifested in terms of highest shear band thickness. Direct shear tests on non-dilative interfaces (sand-smooth geomembrane) revealed that interface friction angle depends on the number of effective contacts rather than the particle size. Morphology of sands is found to have major influence on the interface shear strength among all the parameters investigated. Results from interface shear tests are examined in the light of topographical analysis of sand particles and shear induced surface changes in geomembrane. Possible shearing mechanisms at the interface and the influence of particle size, morphology and normal stress on sliding or plowing are brought out from 3D surface roughness measurements using 3D optical profilometer. The stress-shear displacement response of sand-geomembrane interfaces are correlated to the surface changes on sheared geomembranes through visual observations and roughness quantifications. Medium sand used in this study could make more number of effective contacts with deeper grooves, resulting in highest interface friction. The number of grooves are less in case of coarse sand and the depth of grooves is less in case of fine sand, resulting in lesser interface friction for these two sands compared to medium sand, supporting the results of interface shear tests.

Les zones de cisaillement constituent des objets structuraux communs de la lithosphère. À grande échelle, elles sont le siège principal des déplacements entre plaques tectoniques, accommodant de grandes quantités de déformation. La compréhension de leur comportement mécanique dans le temps et l'espace est donc essentielle pour la connaissance générale de la dynamique de la lithosphère. La température joue un rôle majeur sur la loi de comportement rhéologique qui caractérise le domaine ductile (en profondeur), réduisant alors efficacement la résistance mécanique. Chaque roche possède en outre des propriétés mécaniques intrinsèques qui varient en fonction de sa composition minéralogique, de sa texture et de sa structure interne. Or, en l'absence de grandeurs directement mesurables en profondeur, la rhéologie de la lithosphère demeure sujette à diverses interprétations. Le comportement mécanique des zones de cisaillement est d'autant plus méconnu qu'elles sont le siège d'intenses changements de la nature des roches et de perturbations thermiques majeures. En particulier, l'énergie mécanique qui y est convertie en chaleur (shear heating) peut engendrer une étroite interrelation entre thermique et mécanique. Ce travail de thèse vise à contribuer à la connaissance générale de la rhéologie des zones de cisaillement lithosphérique. Une approche originale a été mise en place, se basant sur l'évolution thermique aux abords et au sein des zones de cisaillement. Sur la base de modèles numériques thermo-cinématiques 2-D et de développements analytiques, la variabilité de premier ordre de l'évolution et de la perturbation thermique est analysée et quantifiée au regard de l'influence des trois processus thermiques majeurs que sont la diffusion, l'advection et le shear heating. Les résultats sont confrontés aux signatures thermiques métamorphiques associées aux chevauchements intra-continentaux pour lesquels les influences des processus d'accrétion et d'érosion sont également examinées. Le cas du Main Central Thrust (Himalaya), associé à une inversion thermique métamorphique bien développée, est pris comme exemple de référence. Nos résultats quantitatifs mettent en avant le rôle crucial du shear heating, notamment de la variabilité de la résistance mécanique des zones de cisaillement. L'accent est mis sur l'importance des paramètres de fluage des roches. L'étude de zones de cisaillement centimétriques développées au sein de la granodiorite du Zillertal (fenêtre des Tauern, Alpes) à la faveur de faibles variations de la composition minéralogique révèle l'extrême sensibilité de la rhéologie des roches ignées représentatives de la croûte continentale. Les conséquences de cette variabilité intense à petite échelle sont finalement discutées au regard des rhéologies classiquement considérées dans les modèles qui s'intéressent aux processus qui régissent la dynamique de la lithosphère. / Shear zones are common structural features in the lithosphere and occur at various scales (from microscopic to lithospheric). At the lithospheric scale, they concentrate most of the relative movements between tectonic plates, and therefore, accommodate a high amount of strain. Consequently, the understanding of both their spatial and temporal mechanical behaviour is crucial for the general knowledge of the lithosphe dynamics. Rheology of rocks, which define their mechanical behaviour, is controlled by physical laws that predict how they deform under some stresses. Temperature plays a major role in the creep-dislocation behaviour, which characterizes the ductile domain (in depth), decreasing efficiently the rock strength. Furthermore, each rock has intrinsic mechanical properties, which depend on its mineralogical composition, texture and internal structures. However, due to the lack of data directly measurable deeper than a few kilometres, the lithosphere rheology, and in particular the continental lithosphere remains subject to drastically different interpretations. The mechanical behaviour of major shear zones is not fully understood, as they are the location of intense changes of both the rock internal nature and major thermal perturbations. Especially, the mechanical energy, converted into heat (shear heating) causes a close interaction between thermal ad mechanical evolutions. This thesis aims to better understand the rheological state of lithospheric scale shear zones. For this purpose, we used an original approach, based on the temperature field evolution around and within such shear zones. From 2D numerical thermo-kinematic models and analytical developments, the first order variability of thermal evolution and perturbation is anal- ysed and quantified with respect to the impact of three major thermal processes, defined as diffusion, advection and shear heating. Results are compared to metamorphic thermal signatures associated to intra-continental thrust zones for which the influence of both accretion and erosion was also investigated. The case of the Main Central Thrust (MCT) in the Himalayas, whose the inverse metamorphic thermal zonation has been extensively studied, was chosen as the main natural analogue. Our quantitative results highlight the crucial role of shear heating, and more particularly of mechanical strength variability within shear zones. We thus emphasise on the importance of rock creep parameters. The study of centimetre-scale shear zones, which developed within the granodiorite of the Zillertal nappe (Tauern window, Tyrol, Alps) thanks to little local variations of the mineralogical composition, reveals the extreme sensitivity of igneous rocks rheology, representative of the continental crust. The consequences of such an intense variability, revealed at small scale are finally discussed with regard to rheologies usually considered in models that focus on processes controlling lithosphere dynamics.

This thesis presents experiments and numerical analysis of a novel cold-formed steel framed shear wall sheathed with corrugated steel sheets. The objective of this newly designed shear wall is to meet the growing demand of mid-rise buildings and the combustibility requirement in the International Building Code. The strength of the novel shear wall is higher than currently code certified shear wall in AISI S400-15 so that it could be more favorable for mid-rise building in areas that are prone to earthquakes and hurricanes. Full-scale monotonic and cyclic tests were conducted on bearing walls and shear walls under combined lateral and gravity loads. Though the gravity loads had negative effects on the strength and stiffness of the shear wall due to the buckling of the chord framing members, it still shows promise to be used in mid-rise buildings. The objective of numerical analysis is to quantify the seismic performance factors of the newly design shear wall lateral-force resisting system by using the recommended methodology in FEMA P695. Two groups of building archetypes, story varied from two to five, were simulated in OpenSees program. Nonlinear static and dynamic analysis were performed in both horizontal directions of each building archetype. Finally, the results of the performance evaluation verified the seismic performance factors(R=Cd=6.5 and Ω =3.0) were appropriate for the novel shear wall system.

[pt] Esta pesquisa teve como objetivo investigar o comportamento tensão-deformação-resistência da areia da Praia de Ipanema, RJ, em ensaios de cisalhamento simples (DSS) realizados em corpos de prova secos, cisalhados a volume constante sob carregamento monótono de deformação controlada. Foi desenvolvido um procedimento para moldagem de corpos de prova de areia na condição seca para ensaios de DSS. Os corpos de prova foram moldados nos domínios de compacidade relativa (CR) fofo, médio, compacto e muito compacto. Para cada um desses domínios de CR, foram realizados ensaios de DSS sob os seguintes valores de tensão vertical inicial: 25, 50, 100, 150, 300, 500 e 750 kPa. Os resultados permitiram avaliar a influência da tensão vertical inicial e do índice de vazios pré-cisalhamento (epc) na variação da tensão vertical (variação da tensão vertical no cisalhamento) necessária para manter a altura (e o volume) do corpo de prova constante durante o cisalhamento, na taxa de mobilização de ângulo de atrito no plano horizontal em relação à distorção, no valor do ângulo de atrito máximo mobilizado no plano horizontal, no valor da tensão cisalhante na ruptura, no valor da distorção na ruptura, bem como nos valores dos módulos de cisalhamento secantes G25 e G50. / [en] This research aimed to investigate the stress-strain-strength behavior of the Ipanema Beach (RJ) sand in direct simple shear tests (DSS) carried out on dry specimens, sheared at constant volume under strain-controlled static loading. A procedure for preparing dry sand specimens was developed for DSS tests. The specimens were prepared in loose, medium, dense and very dense domains of relative density (Dr). For each of these Dr domains, DSS tests were carried out under the following initial vertical stress values: 25, 50, 100, 150, 300, 500 and 750 kPa. The results allowed to evaluate the influence of the initial vertical stressand the pre-shear void ratio (epc) on the vertical stress change (variation of vertical stress in shear) necessary to keep the specimen height (and volume) constant during shear, on the rate ofmobilization of the friction angle in the horizontal plane in relation to distortion, on the value of the maximum friction angle mobilized in the horizontal plane, on the value of the shear stress at failure, on the value of the distortion at failure, as well as on the values of the secant shear modulus G25and G50.

No description available.

Sickle cell disease is a genetic disorder that affects 100,000 Americans and millions more worldwide. Although the sickle mutation affects one protein, which is only expressed in a single cell type, it has profound detrimental effects on nearly every organ system in the body. Young children with sickle cell disease have an 11\% chance of suffering a major stroke event by the age of 16, and a 35\% chance of developing ÒsilentÓ strokes that often result in significant learning and mental disabilities. Clinical investigations suggest that stroke development in people with sickle cell disease results from luminal narrowing of the carotid and cerebral arteries due to excess matrix deposition and fragmentation of the elastic lamina; however, the underlying cellular mechanisms that initiate arterial remodeling in sickle cell disease remain relatively unknown. Cathepsins K and V are members of the cysteine family of proteases and represent two of the most potent elastases yet identified in humans. Furthermore, the role of Cathepsins has been well established in other cardiovascular remodeling diseases, such as atherosclerosis. Due to the compelling histological similarities between vasculopathy in sickle cell disease and atherosclerosis, we tested the hypothesis that the unique inflammatory milieu, in conjunction with the biomechanical vascular environment of sickle cell disease upregulates cathepsin K and V activity in large artery endothelial cells, ultimately leading to arterial remodeling and stroke. Currently, there are few therapeutic options for the prevention of stroke in sickle cell disease; those that do exist carry significant health risks and side effects. Together, this body of work has generated a more mechanistic understanding of how the sickle milieu stimulates the endothelium to initiate arterial remodeling, which has enabled us to identify important pathways (JNK, NF$\kappa$B) downstream of inflammatory and biomechanical stimuli and validate new therapeutic targets within the JNK pathway to establish preclinical proof of efficacy for the prevention of arterial remodeling in sickle cell disease.

Hypercholesterolemia is a significant risk factor in the development of cardiovascular disease and is associated with chronic leukocyte adhesion in the microvasculature. While the underlying mechanisms behind this have yet to be determined, it may be possible that hypercholesterolemia impairs the fluid shear stress (FSS) inactivation of neutrophils through the rigidifying effect of cholesterol on membrane fluidity. FSS restricts surface expression of CD18 integrins through cathepsin B (ctsB) proteolysis, which minimizes neutrophil adhesivity. If hypercholesterolemia blocks FSS mechanotransduction, then the inhibition of CD18 cleavage may link pathologic blood cholesterol elevations with dysregulated neutrophil adhesion. We hypothesized that elevated cholesterol contributes to dysregulated neutrophil adhesion by impairing ctsB FSS-induced CD18 cleavage through membrane fluidity changes. In the first part of this study, we demonstrated that FSS-induced CD18 cleavage is a robust response of neutrophils and involves selective cleavage of macrophage 1-antigen (Mac1) through ctsB proteolysis. The second part of this study confirmed that ctsB regulates neutrophil adhesion through its proteolytic actions on Mac1, an important integrin involved in adhesion and chemotaxis. Specifically, ctsB accelerated neutrophil motility through an effect on Mac1 integrins during pseudopod retraction. Furthermore, by using a flow-based assay to quantify the mechanoregulation of neutrophil adhesivity, we demonstrated that FSS-induced ctsB release promoted neutrophil detachment from platelet-coated substrates and unstimulated endothelium. For the third part of this study, we linked cholesterol-related membrane fluidity changes with the ability of FSS to restrict neutrophil adhesion through Mac1. We also determined that pathologic cholesterol elevations associated with hypercholesterolemia could block FSS-induced Mac1 cleavage and were linked to disrupted tissue blood flow. This was accomplished using low-density lipoprotein receptor deficient (LDLR-/-) mice fed a high-fat diet. Ultimately, the results provided in the present study confirmed that cholesterol-related changes in membrane fluidity blocked the ability of ctsB to regulate neutrophil adhesion through FSS-induced Mac1 cleavage. This implicates an impaired neutrophil FSS mechanotransduction response in the dysregulation of neutrophil adhesion associated with hypercholesterolemia. Since dysregulated adhesion may be one of the earliest upstream features of cardiovascular disease associated with hypercholesterolemia, the present study provides a foundation for identifying a new mechanobiological factor in the pathobiology of microcirculatory dysfunction.

The in-plane properties of paperboard have always been of interest to paper scientists. Tensile properties are crucial when the board is fed through converting machines at high speeds. Compressive properties are essential in the later use. Inhomogeneities affect both the compressive and tensile properties. For the tensile properties, it is the inherent heterogeneity of the paperboard that might cause problems for the board-maker. Varying material properties, through the thickness of the paperboard, are on the other hand used to achieve high bending stiffness with low fiber usage. It is of interest to know how this practice affects the local compressive properties. Papers A and B aims to address this, while C, D and E focus on in-plane heterogeneities. Paper A investigates the mechanism that causes failure in the short span compression test (SCT). It was concluded that the main mechanism for failure in SCT is delamination due to shear damage. In paper B the effect of the through-thickness profiles on the local compression strength was examined. It was concluded that the local compression is governed by in-plane stiffness and through thickness delamination. The latter was in turn dependent on the local shear strength and in-plane stiffness gradients. In paper C the tensile test is investigated with focus on sample size and strain distributions. The strain behavior was dependent on the length to width ratio of the sample and was caused by activation of local zones with high strainability. Paper D focuses on the strain zones seen in C. The thermal response in paper was studied. It was observed that an inhomogeneous deformation pattern arose in the paper samples during tensile testing. It was concluded that the heat patterns observed coincided with the deformation patterns. It could be shown that the formation was the cause of the inhomogeneous deformation. In final paper, E, the virtual field method was applied on data from C. / Egenskaperna hos ett kartongark kan grovt delas upp i två kategorier: i-planet egenskaper och ut-ur-planet egenskaper. I-planet egenskaperna har länge varit ett område som pappersmekanister och andra pappersforskare visat intresse för. Anledningen till detta är att de är avgörande för hur väl det går att konvertera kartongen till färdiga förpackningar, samt hur väl de förpackningarna klarar sin uppgift. Dragegenskaperna prövas när kartongen dras genom tryck- och konverteringsmaskiner i hög hastighet. Tryckegenskaperna spelar stor roll för hur väl en förpackning klarar att staplas och hålla sitt innehåll intakt. Inhomogeniteter påverkar både drag och tryckegenskaper. Papprets naturliga variation påverkar dragegenskaperna hos kartongen och kan orsaka problem för kartongmakarna. Särskilt när utvecklingen går mot mer avancerade kartong utseenden. Å andra sidan så använder sig kartongmakare flitigt av egenskapsvariationer genom tjockleken på kartongen, när dom vill åstadkomma böjstyva kartonger utan att slösa med fibrer. I detta fall är det intressant att veta hur de lokala kompressionsegenskaperna påverkas av kartongens ut-ur-planet profil. Det första två uppsatserna i denna avhandling, A och B, handlar om just detta. Uppsatserna C, D och E avhandlar hur i-planet variationer påverkar kartongens egenskaper. I Artikel A undersöks vilka skademekanismer som aktiveras under ett kortspannskompressionstest (SCT). Tre flerskiktskartonger undersöktes. De hade valts så att de hade distinkt olika skjuvstyrkeprofiler. Kartongerna karakteriserades och datan användes som materialdata i en finit element modell av SCT-testet. Modellen bestod av skikt, betraktade som kontinuum, mellan vilka det fanns kohesiva ytor. Huvudmekanismen i SCT var att kartongen delaminerade på grund av skjuvskador. Den andra uppsatsen, Artikel B, var en fortsättning på den första. Denna gång undersöktes fem flerskiktskartonger framtagna så att de hade olika skjuvstyrka beroende på positionen i tjockleksled. Det konstaterades att kompressionsegenskaperna lokalt styrs av skjuvstyrkeprofilen och styvhetsgradienter. Vidare konstaterades det att mekanismerna innan kartongen delaminerar är, i huvudsak, elastiska. Den tredje artikeln, Artikel C, fokuserade på hur dragprov på kartong påverkas av provstorleken och töjningsvariationen. Tre olika flerskiktskartonger användes som provmaterial och provbitar med olika storlek analyserades. Förutom dragprov så användes digital image correlation (DIC) för analysen. Det visade sig att den globala töjbarheten varierade med storleken på provet beroende på kvoten mellan längd och bredd. DIC visade att detta i sin tur berodde på att zoner med hög töjbarhet aktiverades i provet. Dessa zoner hade samma storlek oberoende av provstorlek och påverkade därför den totala töjbarheten olika mycket. Artikel D undersöker töjningszonerna som sågs i Artikel C samt hur de påverkas av kreppning. Vidare undersöktes pappersproverna med hjälp av termografi. Termografin visade att varma zoner uppstod i proven när det töjdes. Zonerna blev synliga när provet töjdes plastiskt. Termografi kördes parallellt med DIC på några prover. Det visade sig att de varma zonerna överenstämde med zoner med hög lokal töjning. Vidare kunde det visas att dessa zoner övenstämde med papperets mikrostruktur, formationen. En finit element analys av hur papper med olika formation töjs gjordes. Delar av provningen gjordes på kreppade papper som har högre töjbarhet. Det visades sig att någon form av skada hade överlagrats på papprets mikrostruktur under kreppningen, och att den deformationen återtogs när pappret töjdes. I den sista artikeln, Artikel E, behandlas hur VFM (Virtual Field Method) kan användas på DIC-data från kartong. DIC-datan som användes hämtades från Artikel C. Detta gjordes för att visa på hur olika VFM-formuleringar kan användas för att karakterisera styvhetsvariationen hos kartong. Provet delades upp i tre subregioner baserat på den axiella töjningsgraden. VFM-analysen visade att dessa subregioners styvhet och tvärkontraktionstal sjönk monotont, men att skillnaden mellan regionerna ökade med ökande spänning. även om endast ett prov undersöktes, så indikerade resultaten att områden med hög styvhet endast förbättrar de mekaniska egenskaperna marginellt. Analysen visade också att även om subregionerna inte är sammanhängande, så har dom liknande mekaniska egenskaper. / <p>QC 20160429</p>