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Starkloff, Hans-Jörg. "Stochastic finite element method with simple random elements." Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200800596.
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We propose a variant of the stochastic finite element method, where the random
elements occuring in the problem formulation are approximated by simple random
elements, i.e. random elements with only a finite number of possible values.
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Mackenzie, Donald. "A study on simple piping elbow finite elements." Thesis, University of Strathclyde, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336119.
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Lundqvist, Erik. "Simple volumes : - Spatial complexity." Thesis, KTH, Arkitektur, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-263060.
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In this thesis project, I have explored ways to reach spatial complexity through the use of a simple system of volumetric building elements. The ambition has been to draw an apartment building with emphasis on a variety in the apartment layouts as well as to let the functions of circulation, which I define as both shared and private functions such as stairs, elevators and passages, become an integrated part of the architectural expression. The volumetric building element, with proportions derived from our infrastructural norms as it requires transformation on a truck, is today an ubiquitous object or even an architectural typology of its own. When they are assembled, it can both become a system of similar parts or one new, larger object. The project has then also been a search for an architectural ambivalence between hiding and exposing the fact that a building is the outcome of a system.
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Gunther, Jan-Stefan. "The flexible, low-tech environment : a kit of simple architectural elements." Virtual Press, 2002. http://liblink.bsu.edu/uhtbin/catkey/1231349.
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This creative project focuses on the research, planning, design and field-testing of a kit of basic architectural elements that can be used to build simple spaces and small constructions. These elements are reusable, easy to handle, and allow for a nearly infinite number of configurations.The environment in which the system was developed is a setting of an improvisational outdoor theatre, called 'Live-Action-Role-playing-Games'- (LARP). Therefore the system does not provide a high quality indoor space, but rather focuses on the critical requirements of theatrical stages, such as flexibility, ease of erection and variety. Additionally, the system dealt with the pragmatic issues of affordability and cost-effectiveness.The design process commenced with great attention being paid to the very special requirements of LARP and attempting to test initial assumptions. It included two surveys of LARP participants and use of charrettes to incorporate users input into the design process. Prototype elements were then constructed and field-tested during a full-scale replication of an actual LARP-event over afour-day testing period.Following this an evaluation was made, lessons were learned, and the information gained was incorporated in to the final design.This document then records the entire design process and concludes with extensive documentation of the system.Department of Architecture
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Niland, Haven Sierra. "The Effects of Common and Uncommon Elements on the Emergence of Simple Discriminations." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1505220/.
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A computerized program was designed to test whether arranging a common element in two, otherwise independent, 2-term correlations (stimulus-stimulus and response-stimulus) would result in emergent simple discriminative-stimulus properties for the antecedent stimulus relative to an arrangement with no common elements programmed. Data from 8 adult participants in this experiment indicate that common element arrangements led to relatively high rates of responding in the presence of the putative discriminative stimulus and relatively low rates or no responding in the presence of the putative s-delta during testing in extinction. Conversely, the uncommon element arrangements produced no clear discriminative control. The current data reflect a comparison of arrangements across subjects. These data support Sidman's (2000) suggestion that common elements among contingencies are sufficient to produce stimulus classes and cause class mergers. The data also have implications for thinking about the mechanism by which and the conditions under which discriminative control develops. Finally, these data have the potential to inform the programming and implementation of reinforcement contingencies in applied settings.
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Llorens, Sulivera Joan. "Experimental study of simple and multi-leaf masonry slender elements under compressive stress loaded parallel to the face." Doctoral thesis, Universitat de Girona, 2020. http://hdl.handle.net/10803/671027.
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The thin-tile vault is a structural system widely used in the Mediterranean area. The most spectacular development took place through modernist-style buildings designed by architects such as Antonio Gaudí o Luís Domènech and Muntaner among the others.
Thin-tile vault, from a morphological standpoint, is made up of one or more leaf of thin-tile lay flat, and joined with plaster or mortar. As a particularity of this arrangement, the load is applied parallel to the face of the thin-tile as opposed to the load-bearing walls masonry, where the load is applied perpendicularly to it. Deepening the knowledge of this type of masonry is the main objective of this thesis.
In masonry, normally the compressive strength of the constituent materials is used to analytically establish the compressive strength of the masonry. This thesis, and based on the experimental results on one-, two- , and three-leaf thin-tile specimens, analyse stress-strain law, failure modes, and mechanical properties and compared with those corresponding to different masonries presented in the literatureLa volta catalana és un sistema estructural àmpliament utilitzat en l'àrea mediterrània. Es a través d'edificis d'estil modernista d’arquitectes com Antoni Gaudí o Lluís Domènech i Muntaner que presenta el seu màxim esplendor. La volta catalana, des d'un vessant morfològica, està constituïda per una combinació d'una o diverses fulles de rajoles col·locades planes, i unides amb guix o morter. Una particularitat d'aquesta fàbrica és l’aplicació de la càrrega paral•lela a la cara de la rajola en contraposició a la fàbrica de rajol de parets on aquesta és aplicada perpendicular. Aprofundir en el coneixement d’aquest tipus de fàbrica es el principal objectiu d’aquesta tesis. En fàbrica, habitualment la determinació analítica de la resistència a compressió es determina a partir dels materials constituents (peça i morter). La tesi, i a partir dels resultats experimentals sobre provetes de fàbrica de rajola d'una, dues i tres fulles, analitza el comportament tensió-deformació, el mode de falla i les propietats mecàniques i els compara amb diferents fàbriques presents en la literatura
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Ramaccini, Giovanna Verfasser], Alexander von [Akademischer Betreuer] [Kienlin, and Paolo [Akademischer Betreuer] Belardi. "Perugia in particular. The architectural survey of simple elements in the historic city / Giovanna Ramaccini ; Alexander von Kienlin, Paolo Belardi." Braunschweig : Technische Universität Braunschweig, 2019. http://d-nb.info/1191365441/34.
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Ramaccini, Giovanna [Verfasser], Alexander von [Akademischer Betreuer] Kienlin, and Paolo [Akademischer Betreuer] Belardi. "Perugia in particular. The architectural survey of simple elements in the historic city / Giovanna Ramaccini ; Alexander von Kienlin, Paolo Belardi." Braunschweig : Technische Universität Braunschweig, 2019. http://d-nb.info/1191365441/34.
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GRADWOHL, GERARD. "Les doigt a zinc de la poly(adp-ribose) polymerase, elements de reconnaissance de coupures simple brin dans l'adn : etude structurale et fonctionnelle." Université Louis Pasteur (Strasbourg) (1971-2008), 1991. http://www.theses.fr/1991STR13012.
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La poly(adp-ribosyl)ation est une modification post-traductionnelle des proteines impliquee dans la modulation de la structure de la chromatine et dans les mecanismes de reparation de l'adn chez les eucaryotes. La poly(adp-ribose) polymerase (parp) qui catalyse la reaction est fortement stimulee par la presence de coupures dans l'adn. En reponse a ces signaux et en presence de nad#+ comme substrat, l'enzyme catalyse la polymerisation de l'unite adp-ribose du nad#+ en un homopolymere, le poly(adp-ribose). Ce polymere est attache de facon covalente a des proteines nucleaires acceptrices. Le travail presente ici concerne l'etude des interactions parp-adn au niveau moleculaire et leurs consequences sur la stimulation de l'activite enzymatique. Les resultats obtenus montrent que la parp contient deux ions zinc localises dans un fragment n-terminal de 29 kda inclus dans le domaine de liaison a l'adn de l'enzyme. Les experiences de protection a la dnase i ont demontre que la parp se fixe specifiquement par le domaine de liaison du zinc a une coupure simple brin dans l'adn, de facon zinc dependante. Ces resultats sont en accord avec la presence de deux motifs hypothetiques (fi et fii) de doigt a zinc (cys-x#2-cys-x#2#8#,#3#0-his-x#2-cys)#2 dans le polypeptide 29 kda de la sequence humaine. Par mutagenese dirigee, nous avons identifie les ligands du zinc et analyse la consequence de l'alteration de la structure des doigts sur la liaison a l'adn et la stimulation de l'activite enzymatique. Il apparait que le doigt a zinc fii determine la specificite de reconnaissance des coupures simple brin dans l'adn et que fi est absolument requis pour la stimulation de l'activite enzymatique par les interruptions dans l'adn. Ces resultats suggerent que la parp contient un nouveau type de doigt a zinc, en terme de structure et de fonction. La parp au meme titre que d'autres proteines impliquees dans les mecanismes
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Pescatore, Jeremie. "Maillages Homotopiques tétraèdriques des tissus de la tête pour le calcul du probleme direct en magnéto/electro-encephalographie." Phd thesis, Télécom ParisTech, 2001. http://tel.archives-ouvertes.fr/tel-00005670.
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L'électroencéphalographie (E.E.G.) et la magnétoencéphalographie (M.E.G.) permettent de mesurer à la surface de la tête des champs électromagnétiques résultant des activités neuronales du cerveau. La localisation des sources d'activités neuronales à partir des signaux mesurés à la surface de la tête nécessite de modéliser la propagation des champs électromagnétiques à l'intérieur des tissus de la tête. Cette modélisation consiste à résoudre les équations de Maxwell pour toutes les configurations de sources neuronales possibles par des techniques de calcul numérique (intégrale de surface, différence finies et éléments finis), qui nécessitent de disposer d'un maillage surfacique ou volumique des tissus et d'affecter à chaque élément du maillage une valeur de conductivité électrique du tissu correspondant. L'objectif de cette thèse est de construire des modèles réalistes des tissus de la tête sous forme de maillages tétraédriques adaptés aux méthodes d'éléments finis. Ces maillages tétraédriques sont construits à partir de données anatomiques individuelles obtenues en imagerie par résonance magnétique (I.R.M.). Nous montrons, tout d'abord, l'importance que revêt une modélisation volumique des tissus de la tête, en particulier pour la M.E.G. et l'E.E.G. Ainsi, nous mettons en évidence les contraintes géométriques et topologiques que doit respecter un maillage voumique pour la résolution du problème direct en M.E.G. et E.E.G. à partir de la méthode des éléments finis. Dans ce cadre, nous proposons alors de développer une méthode de maillage volumique fondée sur une décomposition spatiale du domaine d'interêt suivie de transformations préservant la topologie. Dans les méthodes aux éléments finis, la qualité des tétraèdres influence la précision du calcul numérique. En effet, des tétraèdres avec un mauvais rapport de forme produisent des matrices mal conditionnées. Nous montrons qu'il est possible de construire des tétraédrisations presques régulières (T.P.R.) de l'espace où tous les tétraèdres sont identiques et ont des arêtes presque égales. Nous introduisons, ensuite, une caractérisation originale des déformations homotopiques d'un objet discret s'appuyant sur un maillage tétraédrique. Nous avons étendu la notion d'éléments simples par rapport aux trames discrètes classiques (pixels et voxels) des images numériques en appliquant des résultats issus de la théorie de l'homologie au cas des maillages tétraédriques. De nombreux outils locaux peuvent être utilisés à des fins d'adaptation de maillages tétraédriques. C'est pourquoi, nous présentons une adaptation fondée sur des modifications locales d'une T.P.R. et contrôlant la taille des arêtes. La dernière partie de ce manuscrit présente une méthode de maillage volumique des tissus de la tête s'appuyant sur les propriétés topologiques et géométriques que nous avons exposées précédemment. Ainsi, nous construisons d'abord une T.P.R. à partir d'une I.R.M. segmentée des tissus de la tête dont le nombre d'éléments est compatible avec le coût d'une F.E.M. puis nous effectuons un étiquetage homotopique du maillage où nous attribuons à chaque tétraèdre une étiquette optimale fonction de son contenu tissulaire et des contraintes topologiques. Une des originalités de notre méthode de maillage volumique réside dans la notion de région homotopiquement déformable qui permet d'injecter dans un maillage volumique des connaissances a priori topologiques sur les objets à mailler. Ces maillages permettent également de construire des maillages surfaciques adaptés aux méthodes d'intégrales de frontière sans risques d'intersection entre les surfaces de tissus proches. Des premiers tests effectués à la Pitié-Salpétrière ont d'ailleurs montré l'adéquation entre les maillages proposés et la résolution du problème direct en M.E.G. et E.E.G.
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Naidoo, Vaughn. "Policy Based Network management of legacy network elements in next generation networks for Voice Services." Thesis, University of the Western Cape, 2002. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5830_1370595582.
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Havlasová, Zuzana. "Modely obnovy skupinově homogenních prvků." Master's thesis, Vysoká škola ekonomická v Praze, 2008. http://www.nusl.cz/ntk/nusl-12419.
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The aim of this diploma thesis is to explain the branch of renewal models and clear up their application in examples. The first part of the thesis is concerned with the characteristics of renewal models provided that the elements are homogeneous. The reliability theory is also described because it's closely associated with renewal models. The second part of the thesis explains the problematic of group-homogeneous elements renewal models, their assumptions and solution. The final part of the diploma thesis point out practical application of individual models in objective examples.
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Chinchay, Poma Deybi Alejandro. "Análisis de elementos finitos de concreto simple en comprensión simple y triaxial." Master's thesis, Pontificia Universidad Católica del Perú, 2017. http://tesis.pucp.edu.pe/repositorio/handle/123456789/8737.
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En este estudio se ha empleado el modelo constitutivo UBCSAND disponible en el programa
de elementos finitos TNO Diana. Este modelo basado en plasticidad es empleado en la
literatura para evaluar el fenómeno de licuefacción de arenas saturadas. En esta investigación
el UBCSAND es adaptado y empleado para predecir el comportamiento del concreto simple
en ensayos triaxiales a partir de la calibración de la data experimental de ensayos de compresión
uniaxial. El modelo es empleado para predecir el incremento de la resistencia y ductilidad
debido al confinamiento sobre elementos de concreto. Cualquier confinamiento en el material
puede ser considerado y los efectos de la falla del concreto debido al confinamiento pueden ser
modelados. Para estimar los parámetros del modelo se usan datos de ensayos de probetas de
concreto sometidas a compresión uniaxial. Esto permite que el modelo de elementos finitos
realice la predicción del comportamiento generalizado del concreto bajo carga de compresión
triaxial. Con el mismo propósito se utilizan tres modelos constitutivos implementados en el
programa de elementos finitos TNO Diana. Estas relaciones constitutivas basadas en
deformación total y concebidas para predecir el comportamiento esfuerzo-deformación del
concreto son los modelos de Thorenfeldt, Parabólico y Maekawa. Dichos modelos de manera
similar al UBCSAND son calibrados con base en ensayos de concreto en compresión uniaxial.
Después, el modelo de Thorenfeldt es empleado junto al criterio de falla “Hsieh-Ting-Chen”
para predecir el comportamiento del concreto en compresión bajo esfuerzos de confinamiento.
También es realizado un análisis comparativo entre los modelos UBCSAND, Thorenfeldt,
Parabólico y Maekawa mediante un indicador de bondad de ajuste con base en los modelos
calibrados de los ensayos de compresión uniaxial. Para este fin se emplea el coeficiente de
determinación mostrando el buen desempeño del modelo UBCSAND para reproducir las
curvas esfuerzo-deformación del concreto bajo compresión uniaxial en relación con los
modelos numéricos concebidos para concreto. Esta precisión es alcanzada hasta el pico de
resistencia, ya que el UBCSAND, al estar formulado en el espacio de esfuerzos, no puede
predecir el ablandamiento del material post pico. Finalmente, se realiza una comparación de la
predicción del comportamiento del concreto en compresión triaxial entre los modelos
UBCSAND y Thorenfeldt. El desempeño de los modelos está en buen acuerdo con los
resultados experimentales tanto en la predicción del incremento de la resistencia, así como en
la predicción del incremento de la ductilidad para distintos niveles de confinamiento. Los
resultados del análisis comparativo demuestran la utilidad del modelo UBCSAND, concebido
inicialmente para modelar arenas, como una herramienta para predecir el comportamiento del
concreto bajo compresión simple y confinada.Tesis
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MATTAR, NETO MIGUEL. "Elementos finitos simples de placa." reponame:Repositório Institucional do IPEN, 1989. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10274.
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Made available in DSpace on 2014-10-09T12:36:47Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:57:33Z (GMT). No. of bitstreams: 1 04284.pdf: 1503589 bytes, checksum: 2edbafe6bd5d8ce87342f894ae47bd43 (MD5)
Tese (Doutoramento)
IPEN/T
Escola Politecnica, Universidade de Sao Paulo - POLI/USP
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Anilkumar, A. K. "NEW PERSPECTIVES FOR ANALYZING THE BREAKUP, ENVIRONMENT, EVOLUTION, COLLISION RISK AND REENTRY OF SPACE DEBRIS OBJECTS." Thesis, Indian Institute of Science, 2004. http://hdl.handle.net/2005/80.
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Vikram Sarabhai Space Centre,TrivandrumIn the space surrounding the earth there are two major regions where orbital debris causes concern. They are the Low Earth Orbits (LEO) up to about 2000 km, and Geosynchronous Orbits (GEO) at an altitude of around 36000 km. The impact of the debris accumulations are in principle the same in the two regions; nevertheless they require different approaches and solutions, due to the fact that the perturbations in the orbital decay due to atmospheric drag effects predominates in LEO, gravitational forces including earth’s oblateness and luni solar effects dominating in GEO are different in these two regions. In LEO it is generally known that the debris population dominates even the natural meteoroid population for object sizes 1 mm and larger. This thesis focuses the study mainly in the LEO region. Since the first satellite breakup in 1961 up to 01 January 2003 more than 180 spacecraft and rocket bodies have been known to fragment in orbit. The resulting debris fragments constitute nearly 40% of the 9000 or more of the presently tracked and catalogued objects by USSPACECOM. The catalogued fragment count does not include the much more numerous fragments, which are too small to be detected from ground. Hence in order to describe the trackable orbital debris environment, it is important to develop mathematical models to simulate the trackable fragments and later expand it to untrackable objects. Apart from the need to better characterize the orbital debris environment down to sub millimeter particles, there is also a pressing necessity of simulation tools able to model in a realistic way the long term evolution of space debris, to highlight areas, which require further investigations, and to study the actual mitigation effects of space policy measures. The present thesis has provided newer perspectives for five major issues in space debris modeling studies. The issues are (i) breakup modeling, (ii) environment modeling, (iii) evolution of the debris environment, (iv) collision probability analysis and (v) reentry prediction. The Chapter 1 briefly describes an overview of space debris environment and the issues associated with the growing space debris populations. A literature survey of important earlier work carried out regarding the above mentioned five issues are provided in the Chapter 2. The new contributions of the thesis commence from Chapter 3. The Chapter 3 proposes a new breakup model to simulate the creation of debris objects by explosion in LEO named “A Semi Stochastic Environment Modeling for Breakup in LEO” (ASSEMBLE). This model is based on a study of the characteristics of the fragments from on orbit breakups as provided in the TLE sets for the INDIAN PSLV-TES mission spent upper stage breakup. It turned out that based on the physical mechanisms in the breakup process the apogee, perigee heights (limited by the breakup altitude) closely fit suitable Laplace distributions and the eccentricity follows a lognormal distribution. The location parameters of these depend on the orbit of the parent body at the time of breakup and their scale parameters on the intensity of explosion. The distribution of the ballistic coefficient in the catalogue was also found to follow a lognormal distribution. These observations were used to arrive at the proper physical, aerodynamic, and orbital characteristics of the fragments. Subsequently it has been applied as an inverse problem to simulate and further validate it based on some more typical well known historical on orbit fragmentation events. All the simulated results compare quite well with the observations both at the time of breakup and at a later epoch. This model is called semi stochastic in nature since the size and mass characteristics have to be obtained from empirical relations and is capable of simulating the complete scenario of the breakup. A new stochastic environment model of the debris scenario in LEO that is simple and impressionistic in nature named SIMPLE is proposed in Chapter 4. Firstly among the orbital debris, the distribution of the orbital elements namely altitude, perigee height, eccentricity and the ballistic coefficient values for TLE sets of data in each of the years were analyzed to arrive at their characteristic probability distributions. It is observed that the altitude distribution for the number of fragments exhibits peaks and it turned out that such a feature can be best modeled with a tertiary mixture of Laplace distributions with eight parameters. It was noticed that no statistically significant variations could be observed for the parameters across the years. Hence it is concluded that the probability density function of the altitude distribution of the debris objects has some kind of equilibrium and it follows a three component mixture of Laplace distributions. For the eccentricity ‘e’ and the ballistic parameter ‘B’ values the present analysis showed that they could be acceptably quite well fitted by Lognormal distributions with two parameters. In the case of eccentricity also the describing parameter values do not vary much across the years. But for the parameters of the B distribution there is some trend across the years which perhaps may be attributed to causes such as decay effect, miniaturization of space systems and even the uncertainty in the measurement data of B. However in the absence of definitive cause that can be attributed for the variation across the years, it turns out to be best to have the most recent value as the model value. Lastly the same kind of analysis has also been carried out with respect to the various inclination bands. Here the orbital parameters are analyzed with respect to the inclination bands as is done in ORDEM (Kessler et al 1997, Liou et al 2001) for near circular orbits in LEO. The five inclination bands considered here are 0-36 deg (in ORDEM they consider 19-36 deg, and did not consider 0-19 deg), 36-61 deg, 61-73 deg, 73-91 deg and 91- 180 deg, and corresponding to each band, the altitude, eccentricity and B values were modeled. It is found that the third band shows the models with single Laplace distribution for altitude and Lognormal for eccentricity and B fit quite well. The altitude of other bands is modeled using tertiary mixture of Laplace distributions, with the ‘e’ and ‘B’ following once again a Lognormal distribution. The number of parameter values in SIMPLE is, in general, just 8 for each description of altitude or perigee distributions whereas in ORDEM96 it is more. The present SIMPLE model captures closely all the peak densities without losing the accuracy at other altitudes. The Chapter 5 treats the evolution of the debris objects generated by on orbit breakup. A novel innovative approach based on the propagation of an equivalent fragment in a three dimensional bin of semi major axis, eccentricity, and the ballistic coefficient (a, e, B) together with a constant gain Kalman filter technique is described in this chapter. This new approach propagates the number density in a bin of ‘a’ and ‘e’ rapidly and accurately without propagating each and every of the space debris objects in the above bin. It is able to assimilate the information from other breakups as well with the passage of time. Further this approach expands the scenario to provide suitable equivalent ballistic coefficient values for the conglomeration of the fragments in the various bins. The heart of the technique is to use a constant Kalman gain filter, which is optimal to track the dynamically evolving fragment scenario and further expand the scenario to provide time varying equivalent ballistic coefficients for the various bins. In the next chapter 6 a new approach for the collision probability assessment utilizing the closed form solution of Wiesel (1989) by the way of a three dimensional look up table, which takes only air drag effect and an exponential model of the atmosphere, is presented. This approach can serve as a reference collision probability assessment tool for LEO debris cloud environment. This approach takes into account the dynamical behavior of the debris objects propagation and the model utilizes a simple propagation for quick assessment of collision probability. This chapter also brings out a comparison of presently available collision probability assessment algorithms based on their complexities, application areas and sample space on which they operate. Further the quantitative assessment of the collision probability estimates between different presently available methods is carried out and the obtained collision probabilities are match qualitatively. The Chapter 7 utilizes once again the efficient and robust constant Kalman gain filter approach that is able to handle the many uncertain, variable, and complex features existing in the scenario to predict the reentry time of the risk objects. The constant gain obtained by using only a simple orbit propagator by considering drag alone is capable of handling the other modeling errors in a real life situation. A detailed validation of the approach was carried out based on a few recently reentered objects and comparison of the results with the predictions of other agencies during IADC reentry campaigns are also presented. The final Chapter 8 provides the conclusions based on the present work carried together with suggestions for future efforts needed in the study of space debris. Also the application of the techniques evolved in the present work to other areas such as atmospheric data assimilation and forecasting have also been suggested.
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Al, Karkour Khaleel. "Unreinforced masonry walls and flange effect: a parametric study through block-based modeling." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
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This study reported in this thesis shows the flange effect in unreinforced masonry walls subjected to in-plane loading. Previous studies showed the importance of capturing the in-plane behaviour of flanged masonry walls for seismic studies. A generative tool was developed using Dynamo and Abaqus Scripting Interface (ASI) to make a parametric model covering most cases of constructing the flange wall. The analysis was held using Finite Element Method through ABAQUS software and masonry wall was modelled through block-based modelling strategy. Large parametric study was carried out to investigate the effects of several parameters on the collapse load and failure type. The effect of aspect ratio, length of flange part, location of the main part, vertical applied load and the applied boundary condition are represented in this thesis.
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Altran, Daniele Araujo. "Procedimento numérico para análise de vigas de alvenaria estrutural submetidas à flexão simples /." Ilha Solteira : [s.n.], 2010. http://hdl.handle.net/11449/91465.
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Orientador: Rogério de Oliveira RodriguesBanca: Jefferson Sidney Camacho
Banca: Rodrigo Piernas Andolfato
Resumo: A Engenharia de Estruturas é uma área de grande importância na construção civil, uma vez que sua essência é a otimização de projetos. Para atender essa necessidade, os métodos numéricos são excelentes ferramentas, que auxiliam os profissionais a obterem, com maior agilidade, projetos de alta qualidade, diminuindo custos e prazos. Além disso, a alvenaria estrutural é um sistema que satisfaz essa procura por projetos otimizados, devido à agilidade na construção, com projetos modulados, equipe e equipamentos especializados, que garantem rapidez e diminuição de custos. Nesse cenário, o presente trabalho aborda um procedimento numérico para análise do comportamento não-linear de dois modelos de vigas de alvenaria estrutural submetidos à flexão simples. Um formado somente por blocos canaleta de concreto, sobrepostos em duas fiadas; e outro, composto pela fiada inferior de blocos-canaleta e a superior, por blocos vazados, ambos os modelos grauteados. As vigas foram discretizadas com o elemento finito prismático regular linear, sendo que, para o bloco, a argamassa e o graute, se utilizou o Critério Mohr-Coulomb, para prever a ruptura e os redutores de rigidez baseados na diminuição do módulo de elasticidade. Ao final, foram comparados os resultados numéricos, obtidos com presença e ausência dos redutores de rigidez, com os observados em modelos experimentais desenvolvidos no Núcleo de Ensino e Pesquisa da Alvenaria Estrutural (NEPAE) da Faculdade de Engenharia, Campus de Ilha Solteira, UNESP. As análises numéricas realizadas produziram resultados satisfatórios para os dois modelos de vigas abordados, sendo também possível observar o aumento de rigidez da viga com blocos-canaleta e blocos vazados.
Abstract: The Structural Engineering is a very important area in civil construction, since its essence is the optimization of designs. To attend the actual necessities, the numerical methods come to be excellent tools, which help professionals to obtain, with more agility, high quality designs, reducing the costs and deadlines. Besides, that structural masonry is a system that satisfies the searching for optimized projects, due to its agility in constructions, with modulated designs, specialized staff and equipments that warrant fast and low costs. In this scenario, this paper deals with numerical proceeding for analyzing the nonlinear behavior of two models of structural masonry beams subjected to bending. One, formed only for "U" blocks of concrete overlapping in two rows; and another, composed of channel blocks in the bottom row and the upper row made of hollow blocks, both models entirely grouted. The beams were discretized with linear regular prismatic finite element, and for the block, mortar and grout it was used the Mohr- Coulomb Criteria, to expect the rupture and reducers of rigidity based on the decreasing of strain modulus. In the end, the obtained numerical results with the presence and absence of reducers of rigidity were compared, with those observed in experimental models developed at the Structural Masonry Study and Research Center, Faculty of Engineering Ilha Solteira Campus, UNESP. The accomplished numerical analys produced satisfactory results for the two beam models, and it has been also possible to observe the increase of rigidity in the beam with channel and hollow blocks.
Mestre
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Dhar, Vikas B. "A simple finite element for the dynamic analysis of rotating composite beams." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-05022009-040512/.
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Altran, Daniele Araujo [UNESP]. "Procedimento numérico para análise de vigas de alvenaria estrutural submetidas à flexão simples." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/91465.
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A Engenharia de Estruturas é uma área de grande importância na construção civil, uma vez que sua essência é a otimização de projetos. Para atender essa necessidade, os métodos numéricos são excelentes ferramentas, que auxiliam os profissionais a obterem, com maior agilidade, projetos de alta qualidade, diminuindo custos e prazos. Além disso, a alvenaria estrutural é um sistema que satisfaz essa procura por projetos otimizados, devido à agilidade na construção, com projetos modulados, equipe e equipamentos especializados, que garantem rapidez e diminuição de custos. Nesse cenário, o presente trabalho aborda um procedimento numérico para análise do comportamento não-linear de dois modelos de vigas de alvenaria estrutural submetidos à flexão simples. Um formado somente por blocos canaleta de concreto, sobrepostos em duas fiadas; e outro, composto pela fiada inferior de blocos-canaleta e a superior, por blocos vazados, ambos os modelos grauteados. As vigas foram discretizadas com o elemento finito prismático regular linear, sendo que, para o bloco, a argamassa e o graute, se utilizou o Critério Mohr-Coulomb, para prever a ruptura e os redutores de rigidez baseados na diminuição do módulo de elasticidade. Ao final, foram comparados os resultados numéricos, obtidos com presença e ausência dos redutores de rigidez, com os observados em modelos experimentais desenvolvidos no Núcleo de Ensino e Pesquisa da Alvenaria Estrutural (NEPAE) da Faculdade de Engenharia, Campus de Ilha Solteira, UNESP. As análises numéricas realizadas produziram resultados satisfatórios para os dois modelos de vigas abordados, sendo também possível observar o aumento de rigidez da viga com blocos-canaleta e blocos vazados.
The Structural Engineering is a very important area in civil construction, since its essence is the optimization of designs. To attend the actual necessities, the numerical methods come to be excellent tools, which help professionals to obtain, with more agility, high quality designs, reducing the costs and deadlines. Besides, that structural masonry is a system that satisfies the searching for optimized projects, due to its agility in constructions, with modulated designs, specialized staff and equipments that warrant fast and low costs. In this scenario, this paper deals with numerical proceeding for analyzing the nonlinear behavior of two models of structural masonry beams subjected to bending. One, formed only for “U” blocks of concrete overlapping in two rows; and another, composed of channel blocks in the bottom row and the upper row made of hollow blocks, both models entirely grouted. The beams were discretized with linear regular prismatic finite element, and for the block, mortar and grout it was used the Mohr- Coulomb Criteria, to expect the rupture and reducers of rigidity based on the decreasing of strain modulus. In the end, the obtained numerical results with the presence and absence of reducers of rigidity were compared, with those observed in experimental models developed at the Structural Masonry Study and Research Center, Faculty of Engineering Ilha Solteira Campus, UNESP. The accomplished numerical analys produced satisfactory results for the two beam models, and it has been also possible to observe the increase of rigidity in the beam with channel and hollow blocks.
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Medeiros, Nathalie Nunes Freire Alves de. "Efeito do tipo de treino discriminativo sobre a observação de estímulos compostos e de seus elementos." reponame:Repositório Institucional da UnB, 2016. http://dx.doi.org/10.26512/2016.02.D.20526.
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Dissertação (mestrado)—Universidade de Brasília, Instituto de Psicologia, Departamento de Processos Psicológicos Básicos, Programa de Pós-Graduação em Ciências do Comportamento, 2016.O presente trabalho investigou, em dois estudos, o efeito do tipo de treino e do tempo de exposição a estímulos compostos sobre a extensão do controle de estímulos e sobre o padrão das respostas de observação com estudantes universitários. No Estudo 1, nove estudantes universitários foram submetidos a três condições experimentais com treinos e testes de discriminações simples simultâneas entre quatro estímulos apresentados por 1,5 s. Nos treinos das duas condições DM, foram programadas discriminações baseadas em diferenças múltiplas entre estímulos compostos por três elementos. Nos treinos da Condição DOR, as tentativas eram formadas por duas etapas. A primeira etapa apresentava estímulos compostos por três elementos com discriminações baseadas em diferenças críticas e, a segunda, elementos separados. Os testes apresentavam estímulos com recombinações entre os elementos dos compostos e com os elementos separados. No Estudo 2, as respostas de observação foram medidas por meio de um equipamento de registro ocular e três novos participantes realizaram as condições na ordem DM1-DOR-DM2, sendo ampliada para 3,0 s a duração de apresentação dos estímulos. Os resultados mostraram que o DOR foi eficaz, quando em vigor e após a sua retirada, em reduzir o controle restrito. Também foi observado um aumento na extensão do controle de estímulos ao longo das condições experimentais. O tempo de exposição aos estímulos demonstrou ser uma variável relevante, tanto para determinar a amplitude do controle de estímulos, quanto no controle do padrão de observação. O DOR e o tempo maior de exposição aos estímulos aumentaram a ocorrência de observação aos estímulos incorretos (S-s) e correto (S+). Padrões de observação mais amplos não foram sistematicamente relacionados a desempenhos mais precisos.
Two different experiments investigated the effect of different discriminative training procedures with compound stimuli and exposure time on the extent of established control over behavior and the pattern of observing response with college students. In Study 1, nine participants were submitted to three experimental conditions involving simple simultaneous discrimination training and testing of four compound stimuli presented for 1.5 s. Training in both DM conditions were programmed with discriminations based on multiple differences between stimuli composed of three elements. During training in the DOR condition the trials were comprised in two stages. The first stage presented compound stimuli of three elements with discrimination based on critical differences; in the second stage, elements were presented separately. Tests to verify extension of stimulus control were programmed with recombined compound stimuli and isolated elements. In Study 2, observation responses were measured by an eye-tracker equipment. Three new participants performed the conditions in the DM1-DOR-DM2 order, with the duration of stimulus presentation extended to 3.0 s. The results suggest that DOR was effective in reducing restricted stimulus control. Accuracy scores improved and remained high when DOR requirements were withdrawn. Improvement in the extension of stimulus control was also observed throughout the experimental conditions. Duration of stimulus presentation seems to be an important variable in determining both the amplitude of stimulus control and the observation pattern. DOR and longer exposure to stimuli increased occurrence of observing responses to correct (S+) and incorrect (S-) stimuli. Extensive observation patterns were not systematically related to accurate performance.
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Urthaler, Lapeira Yetzirah Yksya. "On simple and accurate finite element models for nonlinear bending analysis of beams and plates." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5779.
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This study is concerned with the development of simple and accurate alternative finite element models to displacement finite element models for geometrically
nonlinear bending analysis of beams and plates. First, a unified corotational beam
finite element that incorporates the kinematics of classical as well as refined beam
theories, including the Timoshenko and Reddy beam theories, is developed in a single
finite element. The governing equations are written in a "corotational" local frame
that rotates with the element and with respect to which the standard linear engineering relations between strains and internal forces are valid. The element is based
on Lagrange interpolation of the axial displacement, Hermite cubic interpolation of
the transverse displacement, and related quadratic interpolation of the rotation, and
it does not experience shear locking. The model is verified by comparisons with exact and/or approximate solutions available in the literature. Very good agreement is
found in all cases.
Next, a finite element model is developed using a mixed formulation of the first-order shear deformation theory of laminated composite plates. A p-type Lagrangian
basis is used to approximate the nodal degrees of freedom that consist of three displacements, two rotations, and three moment resultants. The geometric nonlinearity,
in the sense of the von Kõarman, is included in the plate theory. The mixed plate
element developed herein is employed in the linear and nonlinear bending analysis of a variety of layered composite rectangular plates. The effects of transverse
shear deformation, material anisotropy, and bending-stretching coupling on deflections and stresses are investigated. The predictive capability of the present model
is demonstrated by comparison with analytical, experimental, and numerical solutions available in the literature. The model provides an accurate prediction of the
global bending response of thin and moderately thick plates subjected to moderate
and moderately large rotations. The inclusion of the bending moments at the nodes
results in increased accuracy in the computation of stresses over those determined by
conventional displacement-based finite element models. The many results presented
here for geometrically nonlinear bending analysis of beams and plates should serve as
reference for future investigations.
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Qirezi, Fatmir. "Discrete schemes for thermoviscoelasticity with thermorheologically-simple nonlinear coupling." Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/13456.
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Bressan, Caroline Zanini. "Estudo numérico dos ensaios de tração simples e flexão de três pontos do aço livre de interstícios (IF) utilizando o modelo de Gurson modificado." Universidade do Estado de Santa Catarina, 2015. http://tede.udesc.br/handle/handle/2066.
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Numerical methods have received a substantial attention from Engineering Professionals especially due their capacity to provide solutions for a wide range of problems in many areas. In the last years, numerical simulation has become increasingly common and has turned into a key factor for solving numerous engineering problems in the industry as well in academia. This, however, requires the development of suitable methodological strategies to determinate constitutive law able to best describe the material behavior in the simulation. The present work is inserted within the context of metal forming, aiming to simulate 2D and 3D geometrical models of the simple tensile test and three-point bending test of a notched plate, both using the material properties of an Interstitial Free Steel, IF. For both cases, it was used a modified Gurson model available in the ABAQUS ® software, which is based on the finite elements method. Numerical modelling of the elasto-plastic process used to simulate the three-point bending and simple tensile test was discretised using structured meshes with an appropriate refinement. The experimental results for tensile tests used smooth cylindrical specimens with dimensions defined according to ASTM E 8M-01. The three point bending test was qualitatively compared with the results reported by Mashayeshi, et al (MASHAYEKHI, ZIAEI-RAD, et al., 2005). The strain hardening law used in this work was the Holomon or modified Swift law coupled with the damage evolution of the Gurson s model. The geometrical models for the tensile specimens account for axisymmetry, so that only one-quarter part of the 2D and 3D specimens was modelled. An appropriate mesh refinement in the necking region was also adopted. The numerical simulation was able to predict with success the stress-strain curve behaviour of the IF steel comparing with the experimental results. Both 2D and 3D simulation results of the simple tensile test were very similar. The prediction of porosity evolution with the applied displacement was analysed and the results indicated that the necking region in the central zone of the specimen presented the largest micro-void concentration, as expected. For the three-point bending test of a notched plate, the simulation provided a good qualitative agreement with the Mashayekhi´s numerical results, which have shown that the largest concentration of micro-voids was in the central region of the notch where the crack initiation occurs.
Métodos numéricos tem recebido uma grande atenção dos profissionais da área da engenharia em especial principalmente pelo seu caráter facilitador na solução de problemas em diversas áreas. Nos últimos tempos, a simulação numérica está se tornando cada vez mais comum e se transformando em uma peça chave para a resolução de inúmeros problemas de engenharia encontrados tanto nas indústrias quanto nas linhas de pesquisa científica das universidades. Isso, porém, exige desenvolvimento de estratégias de metodologias científicas adequadas o suficiente para determinar as leis que descrevam melhor o comportamento dos materiais a serem simulados. O presente trabalho está inserido no contexto da conformação de metais, tendo por objetivo simular, com malhas tipo 2D e 3D, os ensaios de tração simples e de flexão de três pontos de uma placa com entalhe de um aço livre de interstícios, aço IF (interstitial free steel), utilizando o modelo de Gurson modificado no programa ABAQUS ®, que utiliza o Método dos Elementos Finitos. Para o modelamento numérico do processo de deformação elasto-plástica dos ensaios de tração simples e flexão foi utilizada a lei de Gurson modificado de materiais porosos e uma malha com refinamento adequado. Os corpos de prova ensaiados experimentalmente em tração simples foram de aço IF cilíndricos preparados de acordo com a norma ASTM E 8M-01. Já o ensaio de flexão de três pontos foi simulado com o intuito de fazer uma comparação qualitativa com o resultado apresentado por Mashayekhi, Ziaei-Rad, et al. (MASHAYEKHI, ZIAEI-RAD, et al., 2005). A lei de encruamento plástico utilizada neste trabalho foi a Lei de Holomon ou Swift modificado acoplado com o modelo de evolução do dano de Gurson modificado. Após a escolha da geometria de somente quarta parte do corpo de prova, devido à simetria axissimétrica e do refinamento adequado da malha na região da estricção local, a simulação numérica foi capaz de prever com sucesso o comportamento da curva de tensãodeformação do aço IF comparando-se com os resultados experimentais. Os resultados da simulação 2D e 3D do ensaio de tração simples foram iguais. Portanto, a simulação 2D do ensaio de tração simples é mais conveniente pois é mais rápida e igualmente precisa que a simulação 3D para o presente caso de material dúctil e isotrópico. A previsão da evolução da porosidade com a deformação e a região de maior concentração de vazios foi analisada: ocorreu na região da estricção local e na zona central do corpo de prova como esperado. No caso do ensaio de flexão da placa com entalhe central, os resultados da simulação numérica mostraram uma boa concordância com os resultados de Mashayekhi, Ziaei-Rad et al. (2005), que apresentaram a maior concentração de vazios na região central do entalhe onde ocorrerá o aparecimento de trincas.
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Aydin, Selcuk Han. "The Finite Element Method Over A Simple Stabilizing Grid Applied To Fluid Flow Problems." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609467/index.pdf.
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We consider the stabilized finite element method for solving the incompressible Navier-Stokes equations and the magnetohydrodynamic (MHD) equations in two dimensions.
The well-known instabilities arising from the application of
standard Galerkin finite element method are eliminated by using the stabilizing subgrid method (SSM), the streamline upwind Petrov-Galerkin (SUPG) method, and the two-level finite element method (TLFEM). The domain is discretized into a set of regular triangular elements. In SSM, the finite-dimensional spaces employed consist of piecewise continuous linear interpolants enriched with the residual-free bubble functions. To find the bubble part of the solution, a two-level finite element method with a stabilizing subgrid of a single node is described and its applications to the Navier-Stokes equations and MHD equations are displayed. This
constitutes the main original contribution of this thesis. Numerical approximations employing the proposed algorithms are presented for some benchmark problems. The results show that the proper choice of the subgrid node is crucial to get stable and accurate numerical approximations consistent with the physical configuration of the problem at a cheap computational cost. The stabilized finite element method of SUPG type is applied to the unsteady Navier-Stokes
equations together with a finite element discretization in the time domain. Thus, oscillations in the solution and the need of very small time increment are avoided in obtaining stable solutions.
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Dias, Nestor Juvenal Gianotti Terra. "Uma formulação alternativa e enriquecida para elementos do tipo hermitiano 2-simplex." Universidade do Estado de Santa Catarina, 2014. http://tede.udesc.br/handle/handle/2060.
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The main objective of this work was to obtain an alternative formulation for the so-called Hermitian 2-simplex type-(3) elements and enrich this formulation by adding functions with null value on all the nodes of the element, however with unitary partial derivatives one node. The conventional Hermitian element is an old element with degree p=3 and the degrees of freedom are the displacements and the partial derivatives in each node of the element. The element formulated in this work and their enriched versions have C0 continuity (C1 continuity is assured only at the element nodes). The formulation of the elements is based on the Principle of Minimum Potential Energy and because it is a displacement formulation, the prescribed Neumann (partial derivatives) or the Cauchy-Robin (mixed) boundary conditions are satisfied without any difficulty at the boundary nodes. Stresses and/or fluxes are obtained without any additional post-processing of finite element solution and with precision similar to the precision obtained for displacements. In this work these elements were applied to the solution of various problems of plane elasticity, axial-symmetric elasticity, free vibration of membranes and potential problems. The main emphasis in these analyzes was to study the rates of convergence obtained with homogeneous meshes and distorted meshes. Another aspect studied was the convergence for material locking problems (EPD) and special attention was given to the analysis of error in stress (or fluxes). After several comparisons made throughout this work it was concluded that the results obtained with this type of element is better than a large majority of triangular elements available in the literature.
Objetivo principal deste trabalho foi obter uma formulação alternativa para os chamados elementos Hermitianos 2-simplex do tipo (3) e enriquecer esta formulação adicionando funções com valor nulo em todos os nós do elemento, porém com derivadas parciais unitárias em apenas um destes nós. O elemento Hermitiano convencional é um elemento antigo na literatura, possui grau p=3 e os graus de liberdade do elemento são os deslocamentos e suas derivadas parciais em cada nó. O elemento formulado neste trabalho e sua versão enriquecida possuem continuidade C0 (a continuidade C1 só é assegurada nos nós do elemento). A formulação dos elementos é baseada no Princípio da Mínima Energia Potencial e por se tratar de uma formulação de deslocamento as condições de contorno de derivadas (Neumann) ou mistas (Cauchy-Robin) que são prescritas no contorno são satisfeitas sem nenhuma dificuldade. As tensões e/ou fluxos são obtidos sem nenhum pós-processamento adicional e com precisão semelhante à dos deslocamentos. Neste trabalho estes elementos foram aplicados para a solução de diversos problemas da elasticidade plana e axi-simétrica, problemas de vibração livre de membranas e problemas de potencial. A ênfase principal nestas análises foi o estudo das taxas de convergência com malhas homogêneas e com malhas distorcidas. Outro aspecto estudado foi a convergência para os problemas de locking de Poisson e especial atenção foi dada para as análises de erro em tensões (ou fluxos) pontuais que é o ponto forte deste tipo de elemento. Após diversas comparações realizadas ao longo deste trabalho concluiu-se que os resultados obtidos com este tipo de elemento são melhores do que a grande maioria de elementos triangulares disponíveis na literatura.
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Yoneda, Adrian Yu. "Avaliação do desempenho da defensa metálica maleável simples utilizada nas vias brasileiras, em diversas condições de instalação." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-13052014-150101/.
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A aplicação do método de elementos finitos como ferramenta de análise vem crescendo na indústria ao longo dos anos, sendo que uma das áreas em desenvolvimento corresponde ao estudo de impacto e avaliação de resistência ao choque. O objetivo deste trabalho é avaliar a eficiência da defensa metálica maleável simples utilizada nas rodovias do Brasil, no que diz respeito à capacidade de conter um veículo desgovernado de 2000 quilogramas a 100 quilômetros por hora, através da simulação numérica pelo método dos elementos finitos. Para possibilitar a execução das análises, são realizados ensaios experimentais de corpos de prova retirados de um dos componentes da defensa metálica para a caracterização do material. Além disso, são desenvolvidas simplificações no modelo para permitir a realização de análises com baixo custo computacional. A partir do modelo elaborado, são avaliados os comportamentos de impacto na defensa metálica maleável simples em diversas condições de instalação encontradas em vias brasileiras com grande volume de veículos, incluindo-se condições inadequadas. As avaliações indicam que a defensa é incapaz de reter o veículo, ocorrendo o rompimento dos parafusos que unem as lâminas. As defensas em condições irregulares de manutenção apresentam resultados mais catastróficos, colocando mais risco aos ocupantes e pedestres. Por fim, é recomendada a elevação da classe do parafuso para 5.8, permitindo que a defensa retenha o veículo do teste 3-11 do NCHRP Report 350.The application of Finite Element Method as an analysis tool in industry has been increasing over the years, so that one of the development areas corresponds to the study of impact and crashworthiness. The objective of this work is to assess the efficiency of a guardrail model used on Brazilian roads, with respect to the ability of containing a runaway vehicle of 2 ton at 100 miles per hour, through numerical simulation using finite element analysis. Experimental tests of samples taken from a component of the guardrail are performed to enable material characterization for the analysis. Furthermore, model simplifications are developed to permit the analysis with low computational cost. The impact behaviors are evaluated in various guardrail installation conditions found on high movement roads, including some inadequate ones. The analysis show that the guardrail is unable to retain the vehicle, shearing the W-beam splice bolts. The irregular maintenance condition guardrails present more catastrophic results, endangering even more the occupants and the pedestrians. Finally, it is recommended that the bolts are upgraded to 5.8, enabling the vehicle retention under test 3-11 of NCHRP Report 350.
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Dabeet, Antone. "Discrete element modeling of direct simple shear response of granular soils and model validation using laboratory tests." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/48510.
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The direct simple shear (DSS) device is one of the most commonly used laboratory testing tools to characterize the shear behavior of soils. In the Norwegian Geotechnical Institute (NGI) version of the DSS test, where a cylindrical soil specimen is confined by a wire-reinforced membrane, only normal and shear stresses on the horizontal planes are measured. The knowledge of these stresses alone does not provide adequate information to calculate friction angles for use in geotechnical design. Further, the absence of complementary shear stresses at the soil-membrane interface causes stress non-uniformities within DSS specimens, which makes the task of interpreting DSS testing results even more difficult. With the recent advances in computers, it is now possible to model soil in a realistic manner as a collection of particles using the discrete element method (DEM). With this background, a DEM model of a cylindrical DSS specimen was developed to provide insight on the state of stress and strain in DSS specimens. A laboratory DSS testing program was undertaken on glass beads as part of this study. The results of the glass beads tests were used for comparison with the DEM model results. Further, free-form sensors (paper-thin flexible pressure sensors mounted on the reinforced part of the DSS membrane) were used to measure lateral stresses acting on reconstituted Fraser River silt specimens. It was shown that: i) the adopted DEM modeling approach is effective in capturing the salient characteristics of the DSS behavior of the tested glass beads; ii) during the shearing phase, the distribution of shear strains across the specimen is more uniform at lower shear strain levels; iii) significant stress non-uniformities during shearing are limited to a narrow zone of about two particles diameter near the lateral boundaries, while stresses at central specimen locations are relatively more uniform (i.e. most representative of “ideal” simple shear conditions); and iv) at large shear strains, the horizontal plane becomes the plane of maximum obliquity, and the friction angle calculated using the stress state on the horizontal plane is a good approximation to the mobilized friction angle at such strain levels.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Orassi, Vincenzo. "Finite element study of fractured mandible in human and sheep." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17819/.
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Osteosynthesis is one of the most discussed and investigated subjects in the orthopaedic literature. Mandible fractures are reported as one of the main causes of facial injury and their impact on patient life may bring serious consequences, compromising masticatory function, speech and facial aesthetics.
Current treatments for mandibular simple fractures include the use of load-sharing devices such as titanium miniplates and screws, which have the role of fixing the fracture ends and restore the facial continuity. Fixation systems ultimately aim to
generate the optimum mechanical strains within the fracture region, which will promote the bone healing process. However, there is not a clear understanding of the influence of fixation stability on the biomechanics of stabilized mandibular
fractures, particularly when using biomaterials different from titanium. The aim of this study is to investigate the biomechanical response of fractured mandible using traditional titanium miniplates and alternative fixation systems made of magnesium alloys. With a view on future preclinical evaluation of these new devices, both human and sheep models are investigated.
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Fletcher, Eric Matthew. "FE-ANN based modeling of 3D simple reinforced concrete girders for objective structural health evaluation." Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/32497.
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Master of ScienceDepartment of Civil Engineering
Hayder A. Rasheed
The structural deterioration of aging infrastructure systems is becoming an increasingly important issue worldwide. To compound the issue, economic strains limit the resources available for repair or replacement of such systems. Over the past several decades, structural health monitoring (SHM) has proved to be a cost-effective method for detection and evaluation of damage in structures. Visual inspection and condition rating is one of the most commonly applied SHM techniques, but the effectiveness of this method suffers due to its reliance on the availability and experience of qualified personnel performing largely qualitative damage evaluations. The artificial neural network (ANN) approach presented in this study attempts to augment visual inspection methods by developing a crack-induced damage quantification model for reinforced concrete bridge girders that requires only the results of limited field measurements to operate. Simply-supported three-dimensional reinforced concrete T-beams with varying geometric, material, and cracking properties were modeled using Abaqus finite element (FE) analysis software. Up to five cracks were considered in each beam, and the ratios of stiffness between cracked and healthy beams with the same geometric and material parameters were measured at nine equidistant nodes along the beam. Two feedforward ANNs utilizing backpropagation learning algorithms were then trained on the FE model database with beam properties serving as inputs for both neural networks. The outputs for the first network consisted of the nodal stiffness ratios, and the sole output for the second ANN was a health index parameter, computed by normalizing the area under the stiffness ratio profile over the span length of the beam. The ANNs achieved excellent prediction accuracies with coefficients of determination (R²) exceeding 0.99 for both networks. Additional FE models were created to further assess the networks’ prediction capabilities on data not utilized in the training process. The ANNs displayed good prediction accuracies (R² > 0.8) even when predicting damage levels in beams with geometric, material, and cracking parameters dissimilar from those found in the training database. A touch-enabled user interface was developed to allow the ANN models to be utilized for on-site damage evaluations. The results of this study indicate that application of ANNs with FE modeling shows great promise in SHM for damage evaluation.
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Lens, Luciani Neves. "Modelos para análise de fratura do concreto simples empregando interfaces coesivas." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/17645.
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O concreto é um material de comportamento quase-frágil na ruptura, desenvolvendo uma zona de processo de fratura relativamente grande na ponta de uma fissura principal, na qual ocorrem fenômenos complexos. Modelos de fratura discretos são adequados para estudar tais fenômenos. Neste contexto, o presente trabalho estuda diferentes modelos de fratura discreta em concreto simples, em situação de modo I puro e modo misto (modo I e modo II, simultaneamente) empregando dois modelos constitutivos da zona coesiva, um acoplado e outro desacoplado. Considerando que a malha de elementos finitos não é adaptada durante a análise, fissuras não coincidem exatamente com as superfícies reais de fratura, resultando em componentes de tração e corte nas interfaces coesivas da frente de fissuração, as quais também não coincidem com os valores reais. Tais componentes devem diminuir com a abertura da fissura. Neste trabalho é demonstrado que apenas o modelo acoplado é capaz de lidar com as componentes espúrias do vetor tensões, e que a variável-chave é o potencial plástico empregado na integração deste vetor. Os modelos apresentados são comprovados por estudos experimentais, no caso de fratura em modo I puro com testes de flexão de vigas a 3 pontos e no caso do modo misto com testes em viga com 1 entalhe e dois entalhes a 4 pontos, viga com entalhe excêntrico ensaiada a 3 pontos e placa com duplo entalhe. Parâmetros do modo II podem ser alterados em uma faixa grande sem alterar visivelmente os resultados, pelo menos nos exemplos testados. Por outro lado, a lei coesiva para metodologia das interfaces coesivas necessita de uma lei de pré e pós-pico. Para o pós-pico, três leis são utilizadas, a saber: lei linear, bi-linear e exponencial. A escolha da lei interfere tanto no comportamento de pós-pico, como no valor de carga máxima a ser alcançado. A região de pré-pico define aberturas e deslizamentos elásticos fictícios, porém necessários para metodologia das interfaces coesivas. Neste trabalho, uma equação é proposta para determinar a lei constitutiva de pré-pico, que elimina efeitos de malha tornando a análise objetiva.Plain concrete behaves as a quasi-brittle material in rupture, developing a relatively large process zone at the crack tip. Complex phenomena occur in this zone. Discrete fracture models are indicated to study such rupture process. In this context, the present work studies different plain concrete fracture models for mode I and mixed mode (coupled mode I and II) using two constitutive models for the cohesive zone: one is a coupled model and the other is uncoupled. Considering that the finite element mesh is not adapted during the analysis, cracks do not coincide exactly with the real fracture surfaces, resulting in components of the traction vector at the cohesive zone that are not coincident with the real values either. Such components must decrease with crack opening. In this work it is demonstrated that only the coupled model is able to deal with the spurious components of the traction vector and that the key variable in this regard is the plastic-potential used in the tractions integration. The presented models are verified by experimental tests. In the case of the pure mode I, threepoint beams are used and in the case of the mixed mode three-point and four-point beams as well as double-notched plates are used. Mode II parameters can be changed in a large range without a noticeable change in results, at least for the tested examples. On the other side, the cohesive law used in the methodology needs a pre-peak and a post-peak relation. For the postpeak, three different shapes are used: linear, bi-linear and exponential. The shape has influence in the overall post-peak behavior of the body, as well as in the peak loading reached. Pre-peak relation defines the fictitious elastic opening and the sliding necessary to complete the description of the cohesive interface methodology. In this work an equation is proposed for the pre-peak constitutive law that eliminates mesh effect problems, turning the analysis objective.
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PAMPLONA, Matheus Kenji Yoshikawa. "Resistência ao fendilhamento de elementos estruturais de concreto simples e armado com agregados reciclados de concreto." Universidade Federal do Pará, 2018. http://repositorio.ufpa.br/jspui/handle/2011/10187.
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A reciclagem de resíduos sólidos de construção civil é apresentada como uma alternativa sustentável e economicamente viável, principalmente se aplicada em um contexto industrial, como a produção de estruturas pré-moldadas de concreto. Entretanto, a utilização de agregados graúdos reciclados de concreto (AGRC) para produção de estruturas ainda gera muitas incertezas devido às variáveis relacionadas à própria origem do material. Neste contexto, este trabalho busca analisar o comportamento e a resistência ao fendilhamento de elementos estruturais com AGRC. Um programa experimental foi desenvolvido com 36 espécimes prismáticos locais com objetivo de avaliar a influência de parâmetros como a taxa de substituição de agregados naturais por agregados reciclados (0%, 30% e 100%), concentração de carregamento e a atuação das armaduras transversais. Todos os espécimes romperam por fendilhamento, e foram analisadas a resistência, modo de ruptura, deslocamentos e deformações no concreto e nas armaduras. Os resultados foram comparados com os de outros trabalhos na literatura e com estimativas de resistência do ACI 318 (2014), fib Model Code 2010 (2013), Eurocode 2 (2004) e ABNT NBR 6118 (2014). Não foram encontradas evidências de uma influência significativa no comportamento e resistência ao fendilhamento de elementos estruturais com uso de AGRC em diferentes taxas de substituição. Entretanto, foram observados que fatores como a concentração de carregamento e uso de armaduras transversais interferem na maneira como se distribuem as tensões na estrutura, podendo aumentar ou reduzir a ductilidade e resistência ao fendilhamento, embora sejam parâmetros que possam estar sendo negligenciados por recomendações normativas para projetos de estruturas de concreto.
Recycling of solid construction waste is presented as a sustainable and economically viable alternative, especially when applied in an industrial context, such as the production of precast concrete structures. However, the use of recycled concrete aggregates (RCA) for the production of structures still generates many uncertainties due to the variables related to the origin of the material itself. In this context, this work seeks to analyze the behavior and the strength to splitting failure of RCA structural elements. An experimental program was developed with 36 local prismatic specimens to evaluate the influence of parameters such as the rate of replacement of natural aggregates by recycled aggregates (0%, 30% and 100%), loading concentration and the performance of transverse reinforcement. All specimens failed by splitting, and the strength, rupture, displacements and strains in concrete and reinforcement were analyzed. The results were compared with other studies in the literature and with standard codes of ACI 318 (2014), fib Model Code 2010 (2013), Eurocode 2 (2004) and ABNT NBR 6118 (2014). No evidence was found of an influence on behavior and strength to splitting failure of structural elements using RCA at different replacement levels. However, it was found that factors such as loading concentration and use of transverse reinforcement interfere in the way the strains are distributed in the structure, which can increase or reduce the ductility and splitting strength, despite being parameters that could be neglected by normative recommendations for concrete structures projects.
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Zweigart, Michael. "Diktatur der Vernunft und Demokratie des Lebens lebensphilosophische Elemente (Georg Simmel) in den Henri-Quatre-Romanen Heinrich Manns." Frankfurt, M. Berlin Bern Bruxelles New York, NY Oxford Wien Lang, 2007. http://d-nb.info/99060201X/04.
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Taghinezhadbilondy, Ramin. "Extending Use of Simple for Dead Load and Continuous for Live Load (SDCL) Steel Bridge System to Seismic Areas." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2986.
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The steel bridge system referred to as Simple for Dead load and Continuous for Live load (SDCL) has gained popularity in non-seismic areas of the country. Accordingly, it results in many advantages including enhanced service life and lower inspection and maintenance costs as compared to conventional steel systems. To-date, no research studies have been carried out to evaluate the behavior of the SDCL steel bridge system in seismic areas. The main objective of this research was to extend the application of SDCL to seismic areas.
The concept of the SDCL system was developed at the University of Nebraska-Lincoln and a complete summary of the research is provided in five AISC Engineering Journal papers. The SDCL system is providing steel bridges with new horizons and opportunities for developing economical bridge systems, especially in cases for which accelerating the construction process is a priority. The SDCL steel bridge system also provides an attractive alternative for use in seismic areas.
The SDCL concept for seismic areas needed a suitable connection between the girder and pier. In this research, an integral SDCL bridge system was considered for further investigation. The structural behavior and force resistance mechanism of the proposed seismic detail considered through analytical study. The proposed connection evaluated under push-up, push-down, inverse and axial loading to find the sequence of failure modes. The global and local behavior of the system under push-down forces was mainly similar to non-seismic detail. The nonlinear time history analysis indicated that there is a high probability that bottom flange sustains tension forces under seismic events. The finite element model subjected to push-up forces to simulate the response of the system under the vertical component of seismic loads. However, the demand-capacity ratio was low for vertical excitation of seismic loads. Besides finite element results showed that continuity of bottom flange increased ductility and capacity of the system. While the bottom flange was not continuous, tie bars helped the system to increase the ultimate moment capacity. To model the longitudinal effect of earthquake loads, the model subjected under inverse forces as well as axial forces at one end. In this case scenario, dowel bars were most critical elements of the system. Several finite element analyses performed to investigate the role of each component of preliminary and revised detail. All the results demonstrated that continuity of the bottom flange, bolts area (in the preliminary detail), tie bars over the bottom flange (in the revised detail) were not able to provide more moment capacity for the system. The only component increased the moment capacity was dowel bars. In fact, increasing the volume ratio of dowel bars could be able to increase the moment capacity and prevent premature failure of the system.
This project was Phase I of an envisioned effort that culminated in the development of a set of details and associated design provisions to develop a version of the SDCL steel bridge system, suitable for the seismic application. Phase II of this project is an ongoing project and currently the component specimen design and test setup are under consideration. The test specimen is going to be constructed and tested in the structures lab of Florida International University. A cyclic loading will be applied to the specimen to investigate the possible damages and load resistance mechanism. These results will be compared with the analysis results. In the next step, as phase III, a complete bridge with all the components will be constructed in the structures lab at the University of Nevada-Reno. The connection between steel girders will be an SDCL connection and the bridge will be subjected to a shake table test to study the real performance of the connection due to earthquake excitation.
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Rosa, Cláudia Mesquita da. "Um modelo macro - mesoscópico para a simulação de fratura em concreto simples." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/35613.
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Com a finalidade de estudar processos de fratura em concreto simples, este trabalho propõe uma escala intermediária de análise. Sendo assim, é apresentado um modelo simplificado de duas fases, o qual representa alguns elementos da microestrutra do concreto. Uma fase representa os agregados e a outra a matriz de cimento. Os agregados são considerados elástico-lineares e são representados pelos elementos finitos. Toda a não-linearidade do concreto e do processo de fratura é considerada na matriz de cimento. Tal fase é representada por interfaces coesivas, de espessura zero, entre os elementos finitos. Enquanto o modelo considera propriedades microscópicas do concreto como entrada, tem-se o comportamento macroscópico da estrutura como saída, o que é uma grande vantagem da escala proposta. Efeitos como a relação água/cimento e a densidade de agregados são introduzidos no modelo. Os resultados mostram que o modelo é capaz de captar, pelo menos qualitativamente, efeitos os quais somente são possíveis de obter com um modelo de três fases.An intermediate scale of analysis is proposed here in order to study the fracture of plain concrete. A simplified two phases model is proposed as a concrete microstructure. One phase is the aggregate and other is the cement matrix. Aggregate is considered elastic linear and is represented by finite elements. All the non-linearity of the concrete and the fracture process is considered in the cement matrix. This phase is represented by a zero thickness cohesive interface between finite elements. While the model considers microscopic properties of the concrete as input, it delivers the macroscopic behavior of the structure as output, which is a great advantage of the proposed scale. Effects like water-cement ratio and density of aggregates are introduced in the model. Results show the model is able to capture, at least qualitatively, effects only possible to obtain by a three phases model.
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Linares, López-Lage Rita María. "Elemento, átomo y sustancia simple. Una reflexión a partir de la enseñanza de la Tabla Periódica en los cursos generales de Química." Doctoral thesis, Universitat Autònoma de Barcelona, 2004. http://hdl.handle.net/10803/4709.
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Mesecke-Rischmann, Simone [Verfasser]. "Modellierung von flachen piezoelektrischen Schalen mit zuverlässigen finiten Elementen / Simone Mesecke-Rischmann." Hamburg : Helmut-Schmidt-Universität, Bibliothek, 2004. http://d-nb.info/1002138809/34.
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Beegle, David J. "Three-dimensional modeling of rigid pavement." Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1176842076.
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Viviescas, Jaimes Alvaro. "Modelos simples para el análisis de muros de obra de fábrica cargados en su plano." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/6171.
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El estudio del comportamiento mecánico-resistente de la obra de fábrica, como material de construcción, empleado en diversidad de edificaciones tanto de carácter histórico como actual, ha sido materia de interés relativamente reciente. Lo anterior, si consideramos lo vasto de los trabajos a nivel científico, realizados a otro tipo de materiales de construcción como el hormigón. Para contribuir en ese campo se ha desarrollado la investigación presentada en esta tesis doctoral, la cual ha estado orientada hacia la búsqueda de métodos simples que permitan de una manera práctica y fácil estimar la carga máxima que pueden soportar los muros en obra de fábrica, sometidos a la acción combinada de cargas verticales de compresión y horizontales de corte.
La primera etapa de la investigación estuvo dedicada a la recopilación y análisis minucioso de la literatura existente y referida al estudio del comportamiento mecánico-resistente de muros en obra de fábrica, bien sea a nivel experimental o analítico. Lo anterior, y tal como se muestra en el documento, no descartó el continuar con la consulta permanente en las diferentes fuentes de información para conocer los avances que, sobre la materia, se han ido presentando a medida que avanzaba el desarrollo de la investigación aquí realizada. Las campañas experimentales seleccionadas, sobre muros en obra de fábrica, fueron utilizadas en las etapas siguientes como fuente de calibración y/o validación en los estudios numéricos realizados.
Posteriormente, se procedió a seleccionar un micromodelo numérico para ser utilizado como herramienta para verificar y/o ajustar las propuestas iniciales de modelos simples. Estos modelos están basados en el método de las bielas y tirantes, el cual utiliza bielas para representar los campos de compresión y tirantes para las tracciones, formando un mecanismo resistente. Se buscaba que el micromodelo numérico permitiese predecir satisfactoriamente la carga última y los mecanismos de rotura observados experimentalmente en las campañas realizadas sobre muros de obra de fábrica disponibles en la literatura.
Los datos disponibles de las campañas experimentales, permitieron validar los micromodelos numéricos utilizados en los dos casos de carga vertical estudiados, compresión y parcial o concentrada. A continuación se realizó un estudio paramétrico para analizar la sensibilidad del comportamiento estructural de muros en obra de fábrica, con el fin de determinar la influencia en la respuesta de diversas variables geométricas y propiedades resistentes. Los resultados del estudio anterior permitieron evaluar la capacidad de los modelos simples para representar, en la respuesta del muro, la influencia de los factores analizados.
Para el caso de carga vertical uniforme se pudo evidenciar que, en general, los modelos simples presentaban un satisfactorio comportamiento en la predicción de la respuesta última de los muros evaluados. El caso de carga vertical parcial o concentrada, requirió la necesidad de modificar las propuestas iniciales de modelos simples para incluir en ellos otros factores que, según los resultados obtenidos, inciden en la respuesta del muro. Esto se realizó utilizando las diferentes distribuciones de las tensiones obtenidas numéricamente y su contrastación con el mecanismo resistente propuesto por los modelos simples.
Como resultado final del desarrollo de la investigación se presentó una propuesta de método simplificado para el análisis de muros simples en obra de fábrica sometidos a estados biaxiales (compresión y corte) de solicitaciones en su plano.
Finalmente, se presentan las conclusiones encontradas en el estudio y se plantean unas líneas de investigación futuras que permitan dar continuidad al trabajo realizado.
The study of the mechanical-resistant behavior of blocky masonry as construction material, used in a variety of historical and current buildings, has been a relatively recent area of interest. This, considering the vastness of the scientific work conducted for other construction materials like concrete.
In order to contribute in this area of knowledge, a research was developed and it is presented in this thesis. It has been oriented towards the search of simple methods that allow in practical way, to estimate the maximum load that can be supported by masonry walls subjected to the combined action of compressive vertical and horizontal shear loads.
The first phase of this research was dedicated to the collection and analysis of the state of the art related to the study of the mechanical-resistant behavior of masonry walls, in either experimental or analytical level. This literature review was continued throughout the whole process of the research. In subsequent stages, results of selected experimental campaigns on masonry walls were used to calibrate and/or validate the performed numerical studies.
Subsequently, a numeric micro-model was selected to be used as a tool to verify and/or adjust the initial proposals of simple models. These simple models are based on the struts and ties method which uses the struts to represent the compressive stress fields and the ties for tension zones, both of them forming a resistant mechanism. The objective was to predict satisfactorily, by means of the numeric micro-model, the ultimate loads and mechanisms of fracture observed in the experimental campaigns on masonry walls reported in the literature.
The available data from experimental campaigns, helped to validate the numerical micromodels that were used in the two cases of vertical load studied, uniform and partial or concentrated loads. Then a parametric study was conducted in order to determine the influence of several variables and geometrical properties on the structural behavior of masonry walls. The results of this study allowed us to evaluate the ability of simple models to represent the
influence of the analyzed factors on the response of the wall.
In the case of uniform vertical load was evident, in general, that simple models presented a satisfactory performance in predicting the ultimate response of the evaluated walls. The case of partial or concentrated vertical load required the modification of the original simple models proposals in order to include other factors that influence the response of the wall according to the numerical results. This modification was done by contrasting different stress distributions stresses obtained numerically with the proposed resistant mechanism of the simple models.
The final result of this research consists on the proposal of a simplified method for the analysis of simple walls in masonry under biaxial states (compressive and shear) of solicitations on its plane.
Finally, the conclusions drawn from the current research are summarized and recommendations for future works are given.
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Mata, Luciene Antinossi Cordeiro da. "Análise nao-linear pelo método dos elementos finitos de ligações por chapa simples levando em conta o comportamento semi-rígido." Universidade Federal de Minas Gerais, 1998. http://hdl.handle.net/1843/PASA-89GJQ9.
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The single plate framing connections are those where a plate is shop welded to the support element, either a beam or a column, and field bolted to the web of the supported beam. Usually, a single plate connection is assumed to be flexible but, actually, it is semi-rigid. This connection type was studied mainly by Richard, and his tests indicated that a significant moment can be developed at the end of the supported beam. Nonlinear finite element analyses of single plate framing connections are carried out. The assumed Load-Deformation behaviorof single bolt connections was based on the tests made by Richard. Shell and beam elements are used, suitable for plastic analyses with large displacements. Nonlinear spring elements are associated with the individual Load-Deformation behavior of the bolts. This research is extended to the case of beams connected to column webs. All the results are presented as Moment-Rotation curves and relevant ultimate strengths.As ligações por chapa simples são aquelas em que uma chapa é usualmente soldada de fábrica ao elemento suporte, podendo o mesmo ser uma viga ou um pilar, e tal chapa é parafusada, no campo, na alma da viga apoiada. Na prática, uma ligação por chapa simples é considerada flexível, porém, na verdade, é semi-rígida. Este tipo de ligação foi estudado principalmente por Richard, e seus ensaios indicaram que pode-se desenvolver um significativo momento na extremidade da viga apoiada. Neste trabalho, apresenta-se ummodelo de elementos finitos para a análise não-linear de ligações por chapa simples, onde os comportamentos Carga-Deslocamento de ligações com um parafuso são os obtidos por Richard. Utilizam-se elementos de casca e de barra, adequados para análise plástica com grandes deslocamentos, e elementos de molas não-lineares, aos quais foi associado o comportamento Carga-Deslocamento individual dos parafusos. Estendeu-se o estudo ao caso de vigas apoiadas em almas de pilares. Todos os resultados obtidos são apresentados sob a forma de curvas Momento-Rotação e de resistências últimas aplicáveis.
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Griebel, Matthew Alexander. "Viscoelastic Anisotropic Finite Element Mixture Model of Articular Cartilage using Viscoelastic Collagen Fibers and Validation with Stress Relaxation Data." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/743.
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Experimental results show that collagen fibers exhibit stress relaxation under tension and a highly anisotropic distribution. To further develop the earlier model of Stender [1], the collagen constituent was updated to reflect its intrinsic viscoelasticity and anisotropic distribution, and integrated with an existing mixture model with glycosaminoglycans and ground substance matrix. A two-term Prony series expansion of the quasi-linear viscoelastic model was chosen to model the viscoelastic properties of the collagen fibers. Material parameters were determined by using the simplex method to minimize the sum of squared errors between model results and experimental stress relaxation data of tissue in tension. Collagen elastic fiber modulus was calculated by fitting to the equilibrium data and viscoelastic parameters were determined by fitting to the relaxation curve. Results of newborn (~1-3 week old) untreated bovine articular cartilage explants from the patellar femoral groove as well as explants cultured in transforming growth factor-β1 (TGF-β1), from both the superficial (~0-0.5 mm from the articular surface) and middle (~0.5-1.0 mm from the articular surface) layers were compared to examine the effects of TGF- β1. TGF-β1 has been shown to maintain or even enhance mechanical properties of articular cartilage in compression and tension [2, 3] and this study continues with the hope that it may be used to improve tissue engineering of mature cartilage to better survive implantation in vivo for the successful repair of articular cartilage defects. Results show that TGF-β1 has a maturational effect on collagen, causing the tissue to become stiffer through an increase in elastic collagen fiber modulus and less viscous through shorter relaxation time and less stress relaxation (tissue retained a higher percentage of residual stress). The results of this study further advance the understanding of the effects of location and treatment with TGF-β1.
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Taylor, Robert Paul. "Finite Element Analysis of the Application of Synthetic Fiber Ropes to Reduce Seismic Response of Simply Supported Single Span Bridges." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34051.
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Movement of a bridge superstructure during a seismic event can result in damage to the bridge or even collapse of the span. An incapacitated bridge is a life-safety issue due directly to the damaged bridge and the possible loss of a life-line. A lost bridge can be expensive to repair at a time when a region's resources are most strained and a compromised commercial route could result in losses to the regional economy. This thesis investigates the use of Snapping-Cable Energy Dissipators (SCEDs) to restrain a simply supported single span bridge subjected to three-dimensional seismic loads. SCEDs are synthetic fiber ropes that undergo a slack to taut transition when loaded.
Finite element models of six simply supported spans were developed in the commercial finite element program ABAQUS. Two seismic records of the 1940 Imperial Valley and 1994 Northridge earthquakes were scaled to 0.7g PGA and applied at the boundaries of the structure. The SCEDs were modeled as nonlinear springs with an initial slackness of 12.7mm. Comparisons of analyses without SCEDs were made to determine how one-dimensional, axial ground motion and three-dimensional ground motion affect bridge response. Analysis were then run to determine the effectiveness of the SCEDs at restraining bridge motion during strong ground motion. The SCEDs were found to be effective at restraining the spans during strong three-dimensional ground motion.Master of Science
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Andriankaja, Andry. "La régulation transcriptionnelle du gène MtENOD11 au cours des endosymbioses racinaires : caractérisation des éléments cis-régulateurs spécifiques de la réponse aux facteurs Nod." Toulouse 3, 2006. http://www.theses.fr/2006TOU30033.
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Nous avons réalisé une analyse fonctionnelle détaillée du promoteur du gène MtENOD11 au cours des infections endosymbiotiques et en réponse aux signaux spécifiques secretés par Rhizobium appelés facteurs Nod (FNods) qui jouent un rôle clé dans l'établissement de la syymbiose fixatrice d'azote. Nous avons identifié une région promotrice de 257 pb suffisante pour diriger une expression au cours de l'infection par Rhizobium, et de l'association endoymcorhizienne et lors de l'interaction parasitaire avec les nématodes à galles Meloidogyne incognita. Nous avons caractérisé un motif riche en AT requis à la fois pour l'expression associée à l'infection par Rhizobium et par les endomycorhizes, montrant pour la première fois des mécanismes similaires de régulation lors des infections endosymbiotiques raciniares. Nous avons ensuite caractérisé pour la première fois une unité régulatrice originale (appelée NF-box) suffisante pour conférer une expression dépendante des FNods et épiderme-spécifique. Nous avons également démontré qu'au moins trois sites de liaison de facteurs trans sont importants pour cette réponse. Enfin, nous avons initié des approches gènes candidats et un criblage simple hybride chez la levure pour identifier les facteurs trans impliqués dans l'activation de gènes par les FnodsWe have undertaken a detailed functional analysis of Medicago truncatula ENOD11 gene promoter during endosymbiotic infections and in response to specific rhizobial signals known as Nod factors (NFs), which play a key role in the establishment of the N-fixing symbiosis. First, we defined a 257 bp promoter sequence sufficient to direct expression during rhizobial infection, arbuscular endomycorrhizal (AM) fungi association and Meloidogyne incognita parasitic root knot nematode interaction. We characterized an AT-rich motif required for both rhizobial- and mycorrhizal-related infection, thus providing the first direct evidence for similarities in gene regulatory mechanisms during endosymbiotic root colonization. Subsequently, we were able to define a 33 bp novel regulatory unit (named NF-box), sufficient to confer NF-dependent, epidermal-specific expression. We further demonstrated that the NF-box unit comprises at least three adjacent trans-factor binding motifs which are important for this response. Finally, we initiated yeast one-hybrid screening and candidate gene approach to identify trans-factors involved in NF-mediated activation
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Boedicker, Cathinka [Verfasser], Simone [Akademischer Betreuer] Fulda, Rolf [Gutachter] Marschalek, and Simone [Gutachter] Fulda. "Combined inhibition of BET proteins and PI3Kα reallocates BRD4 to transcriptional regulatory elements of BH3-only proteins and triggers mitochondrial apoptosis / Cathinka Boedicker ; Gutachter: Rolf Marschalek, Simone Fulda ; Betreuer: Simone Fulda." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2019. http://d-nb.info/1202297935/34.
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Boedicker, Cathinka Verfasser], Simone [Akademischer Betreuer] [Fulda, Rolf [Gutachter] Marschalek, and Simone [Gutachter] Fulda. "Combined inhibition of BET proteins and PI3Kα reallocates BRD4 to transcriptional regulatory elements of BH3-only proteins and triggers mitochondrial apoptosis / Cathinka Boedicker ; Gutachter: Rolf Marschalek, Simone Fulda ; Betreuer: Simone Fulda." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2019. http://d-nb.info/1202297935/34.
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Kitchen, Ryan L. "Improving Steering Module Efficiency for Incremental Loading Finite Element Numeric Models." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1248.pdf.
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Dealtry, Gomes Alcoforado Cavalcanti Simone [Verfasser], and Kornelia [Akademischer Betreuer] Smalla. "Adaptation and diversification of bacterial communities to pesticide contaminants in on-farm biopurification systems via mobile genetic elements / Simone Dealtry Gomes Alcoforado Cavalcanti ; Betreuer: Kornelia Smalla." Braunschweig : Technische Universität Braunschweig, 2013. http://d-nb.info/1175821934/34.
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Dekeyzer, Stefanie [Verfasser], Karin [Akademischer Betreuer] Zonneveld, and Simone [Akademischer Betreuer] Kasemann. "Minor element composition and stable oxygen isotopes of calcareous shells of the dinoflagellate Thoracosphaera heimii / Stefanie Dekeyzer. Gutachter: Karin Zonneveld ; Simone Kasemann. Betreuer: Karin Zonneveld." Bremen : Staats- und Universitätsbibliothek Bremen, 2012. http://d-nb.info/1071992988/34.
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Galdames, Francisco José. "Segmentation d'images IRM du cerveau pour la construction d'un modèle anatomique destiné à la simulation bio-mécanique." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENS007/document.
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Comment obtenir des données anatomiques pendant une neurochirurgie ? a été ce qui a guidé le travail développé dans le cadre de cette thèse. Les IRM sont actuellement utilisées en amont de l'opération pour fournir cette information, que ce soit pour le diagnostique ou pour définir le plan de traitement. De même, ces images pre-opératoires peuvent aussi être utilisées pendant l'opération, pour pallier la difficulté et le coût des images per-opératoires. Pour les rendre utilisables en salle d'opération, un recalage doit être effectué avec la position du patient. Cependant, le cerveau subit des déformations pendant la chirurgie, phénomène appelé Brain Shift, ce qui altère la qualité du recalage. Pour corriger cela, d'autres données pré-opératoires peuvent être acquises, comme la localisation de la surface corticale, ou encore des images US localisées en 3D. Ce nouveau recalage permet de compenser ce problème, mais en partie seulement. Ainsi, des modèles mécaniques ont été développés, entre autres pour apporter des solutions à l'amélioration de ce recalage. Ils permettent ainsi d'estimer les déformations du cerveau. De nombreuses méthodes existent pour implémenter ces modèles, selon différentes lois de comportement et différents paramètres physiologiques. Dans tous les cas, cela requiert un modèle anatomique patient-spécifique. Actuellement, ce modèle est obtenu par contourage manuel, ou quelquefois semi-manuel. Le but de ce travail de thèse est donc de proposer une méthode automatique pour obtenir un modèle du cerveau adapté sur l'anatomie du patient, et utilisable pour une simulation mécanique. La méthode implémentée se base sur les modèles déformables pour segmenter les structures anatomiques les plus pertinentes dans une modélisation bio-mécanique. En effet, les membranes internes du cerveau sont intégrées: falx cerebri and tentorium cerebelli. Et bien qu'il ait été démontré que ces structures jouent un rôle primordial, peu d'études les prennent en compte. Par ailleurs, la segmentation résultante de notre travail est validée par comparaison avec des données disponibles en ligne. De plus, nous construisons un modèle 3D, dont les déformations seront simulées en utilisant une méthode de résolution par Éléments Finis. Ainsi, nous vérifions par des expériences l'importance des membranes, ainsi que celle des paramètres physiologiquesThe general problem that motivates the work developed in this thesis is: how to obtain anatomical information during a neurosurgery?. Magnetic Resonance (MR) images are usually acquired before the surgery to provide anatomical information for diagnosis and planning. Also, the same images are commonly used during the surgery, because to acquire MRI images in the operating room is complex and expensive. To make these images useful inside the operating room, a registration between them and the patient's position has to be processed. The problem is that the brain suffers deformations during the surgery, in a process called brain shift, degrading the quality of registration. To correct this, intra-operative information may be used, for example, the position of the brain surface or US images localized in 3D. The new registration will compensate this problem, but only to a certain extent. Mechanical models of the brain have been developed as a solution to improve this registration. They allow to estimate brain deformation under certain boundary conditions. In the literature, there are a variety of methods for implementing these models, different equation laws used for continuum mechanic, and different reported mechanical properties of the tissues. However, a patient specific anatomical model is always required. Currently, most mechanical models obtain the associated anatomical model by manual or semi-manual segmentation. The aim of this thesis is to propose and implement an automatic method to obtain a model of the brain fitted to the patient's anatomy and suitable for mechanical modeling. The implemented method uses deformable model techniques to segment the most relevant anatomical structures for mechanical modeling. Indeed, the internal membranes of the brain are included: falx cerebri and tentorium cerebelli. Even though the importance of these structures is stated in the literature, only a few of publications include them in the model. The segmentation obtained by our method is assessed using the most used online databases. In addition, a 3D model is constructed to validate the usability of the anatomical model in a Finite Element Method (FEM). And the importance of the internal membranes and the variation of the mechanical parameters is studied
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Espinós, Capilla Ana. "Numerical analysis of the fire resistance of circular and elliptical slender concrete filled tubular columns." Doctoral thesis, Editorial Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/17579.
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El empleo de pilares tubulares de acero rellenos de honnigón (CFT) ha crecido en las
últimas décadas, debido a su excelente comportamiento estructural, que aprovecha el efecto
combinado del acero y honnigón trabajando juntos. Esta asociación ofrece una serie de
ventajas que hacen de las columnas CFT una solución interesante: su alta capacidad portante
o su eficiente tecnología constructiva pueden citarse entre sus beneficios ampliamente
conocidos, que se completan con una elevada resistencia al fuego sin necesidad de protección
externa.
Tradicionalmente, se han venido utilizando secciones huecas circulares, cuadradas y
rectangulares para formar estas columnas compuestas. Adicionalmente, la sección elíptica ha
sido recientemente introducida dentro de la gama de secciones de acero huecas disponib les
comercialmente. Su atractivo estético y su reducida intrusión visual, junto con sus ventajas
estructurales asociadas a secciones con diferentes propiedades en sus ejes fuerte y débil,
hacen a las secciones elípticas de gran interés para los diseñadores. En esta tesis se estudian
pi lares CFT de sección tanto circular como elíptica.
Pese a que el comportamiento de los pilares CFT a temperatura ambiente ha quedado
bien establecido en los últimos años, en situación de incendio la degradación de las
propiedades del material da lugar a un comportamiento extremadamente no lineal de estas
columnas compuestas, lo que hace dificil predecir su fallo. El estado del arte en el campo del
comportamiento frente al fuego de columnas CFT se revisa en esta tesis, mostrando que es
necesario profundizar en su investigación para una comprensión completa del funcionamiento
de tales columnas en situación de incendio. En el caso de las secciones elípticas, este trabajo
constituye una investigación novedosa.
El comportamiento frente al fuego de los pilares CFT se estudia en esta tesis por
medio de un modelo realista tridimensional de elementos finitos. Los valores adoptados de los
parámetros delEspinós Capilla, A. (2012). Numerical analysis of the fire resistance of circular and elliptical slender concrete filled tubular columns [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17579
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Vergas, Fernando Jorge Antunes. "Análise estrutural de um eixo autodirecional de reboque rodoviário." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14332.
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Mestrado em Engenharia MecânicaA dissertação que aqui se apresenta prende-se com a criação de um eixo autodireccional de processos e de fabrico simples, já que uma das maiores preocupações é limitar o seu custo, mas sem afetar a segurança do veículo que este equipe. Nos dias atuais, o custo associado a um novo produto representa cada vez mais um papel fulcral na sua inserção e aceitação no mercado. Para atingir esse objetivo foi feita uma pesquisa sobre os produtos similares existentes no mercado, o modo como foram fabricados e a forma como são usados. Usando o software de CAD SolidWorks 2014, conseguiu-se obter uma geometria de traçado simples. Também recorrendo ao SolidWorks 2014, foi possível simular comportamentos reais dos vários elementos e recolher dados fornecidos pelo software, que utiliza o método dos elementos finitos para a análise.
The thesis presented here deals with the creation of a self-steering axle with simple manufacturing processes, since one of the biggest concerns is to limit his cost, but without affecting the safety of the vehicle. Nowadays, the cost associated with a new product represents an increasingly role in their insertion and market acceptance. To achieve this goal was made a research on similar products on the market, the way they are manufactured and how they are used. Using CAD software SolidWorks 2014, managed to get a simple geometry. Also using the SolidWorks 2014, it was possible to simulate the real behaviors of the different elements and collect the data provided by software, which uses the finite element method for the analysis.