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1
Waghorn, Matthew J. "Effect of initial stand spacing and breed on dynamic modulus of elasticity of Pinus radiata." Thesis, University of Canterbury. Forestry, 2006. http://hdl.handle.net/10092/1129.
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Wood stiffness or modulus of elasticity (MOE) is one of the most important wood properties for solid timber applications, and as such, the efficacy of wood use, especially for structural timber is strongly related to MOE. MOE in Pinus radiata is highly variable and poorly understood. In this study, the effect of initial stand spacing and breed on outerwood MOE and the vertical distribution of MOE of Pinus radiata was assessed. Understanding positive or negative influences of growth caused by initial stand spacing and genetic material on MOE is appealing because it could enable us to better comprehend how forest growers could adapt silvicultural operations to the demands of wood processing. Physical characteristics of different breeds and propagation methods of Pinus radiata were assessed at a variety of initial stand spacings. Stem diameter, crown height, stem slenderness and branch size were all heavily influenced by stand spacing. Breed had a marginally significant influence on diameter and stem slenderness. Internode length was not affected by stand spacing, but showed sizeable differences, especially between the long internode 870 breed and the remaining growth and form (GF) breeds. Outerwood MOE was significantly (P<0.0001) influenced by stand spacing and breed, but not their interaction (P>0.05). MOE scaled positively with stand spacing. MOE increased by 39% from 5.4 GPa at 209 stems ha-1 to 7.5 GPa at 2551 stems ha-1. The majority of this increase (33%) occurred between 209 and 835 stems ha-1. Physiologically aged cuttings of greater maturation status exhibited greater MOE, with the three-year-old cuttings being stiffer than the one-year-old cuttings, seedlings from the 870, 268 and 850 series, by 15, 17, 22 and 27%, respectively. Stem slenderness exhibited the strongest significant (P<0.0001) relationship with MOE (r2=0.49), followed by green crown height (r2=0.46) and diameter (r2=0.44). Stem slenderness and green crown height had a direct influence on MOE that explained 53% of the variance in MOE. MOE was also significantly (P<0.0001) influenced by spacing and breed when using the resonance technique to assess whole stem MOE. The vertical distribution of MOE showed that the lowest portion of the stem (bolt 1) was approximately 30% less stiff than bolts 2 and 3. After the greatest MOE value had been obtained at bolt 3, MOE gently declined to the top of the measured stem. Variation of MOE within trees was significant (58%) at the high stockings of 1457 and 2551 stems ha-1, but somewhat lower (36%) at the lower stockings. The 870 breed was approximately 8% and 16% stiffer than the 268 and 850 breeding series respectively, across all stockings, with the three-year-old cuttings being 7% stiffer than the one-year-old cuttings. At stockings of 481 stems ha-1 and less, the proportional height at which MOE was greatest within a tree was between 25% and 50% of stem height. At stockings above 481 stems ha-1 the proportional height at which maximum MOE was obtained was between 15% and 40% of stem height. Bolt slenderness was found to be the most significant factor impacting on MOE of the bolt. Regression of critical buckling height against diameter at ground level yielded a scaling exponent of 0.55, which was lower than the scaling exponent of 0.67 predicted with constant density-specific stiffness. There was a tendency for some bolts with lower mean diameter to display significantly higher safety margins than bolts with higher mean diameter, suggesting that the largest bolts, which occur at the base of tree, are the point of most likely critical failure.
2
Kocáb, Dalibor. "Experimentální stanovení faktorů ovlivňujících statický modul pružnosti betonu s využitím nedestruktivních zkušebních metod." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-355639.
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The Ph.D. thesis deals with one of the most important characteristics of hardened concrete; i.e. the modulus of elasticity. The thesis aims to describe and evaluate the important factors that affect the final value of concrete modulus of elasticity, especially those that can be influenced during construction. Another aim is to find ways to determine the static modulus of elasticity of concrete by non-destructive means (primarily ultrasonic pulse method, resonance method and use of electronic rebound hammers), thus to determine the possibility of creating calibration curve for NDT determination of the modulus of elasticity.
3
Engström, Anders, and Toma Sumbasacu. "The length effect on Norway spruce boards : An investigation on indicating properties based on axial dynamic and edgewise bending MOEs." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-49099.
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When using timber for construction purposes it is important to know its strength. One way to do this is by sorting the boards into strength classes that are defined by European standards. A commonly used method for strength grading is based on dynamic excitation in the longitudinal direction of the board to obtain an average dynamic longitudinal modulus of elasticity (MOE). This in turn correlates with the bending strength of the board in such a way that it can be used as an indicating property (IP) to bending strength. The use of MOE as an IP has proven to give the highest coefficient of determination (R2) to both bending and tensile strength in boards. Through the research described in this thesis, one might find that both reducing the length of a board to half its initial length and by removing the part containing the lowest local MOE in edgewise bending provided similar results, the axial dynamic MOE remaining within a 1% tolerance whereas the lowest IP based on local MOE in edgewise bending increased by 6–7%.
4
Kocuba, Robert. "Diagnostika a hodnocení prefabrikované železobetonové konstrukce." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372269.
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This thesis deals with inspection and constructionally technical research of reinforced concrete prefabricated construction from the second half of 20th century. In theoretical part, the research of literature, documents and valid standards is performed, with a focus on production and construction of prefabricated elements and also on the metodology of research. In practical part, the detection of reinforcement of individual elements of the construction and concrete properties is performed. The result of this work is the assessment of the state of the construction, static calculation of the ceiling panel and idea proposal for eventual reconstruction.
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Valentová, Renata. "Zjišťování dynamických modulů cihelného střepu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225668.
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This master’s thesis deals with the determination of dynamic modulus of elasticity non-destructive methods of brick body. The test samples were laboratory-made from two types of brick earth and further were used cotouts from the full brick types clinker. For measuring were used ultrasonic impulse and resonant-impact method.
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Tichý, Aleš. "Vliv velikosti a tvaru zkušebního tělesa na modul pružnosti lehkých betonů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-391974.
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The diploma thesis deals with the determination of the influence of size, shape and type of test specimen on values of modulus of elasticity of light-weight concrete. A lot of different specimens were prepared from two concrete’s mixtures for the experiment. Tests for measurement of static modulus of elasticity and dynamic modulus of elasticity by ultrasonic impulse velocity method were made. The results were assessed and summarized in tabular and graphical form.
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Halamová, Romana. "Problematika zjišťování statického modulu pružnosti betonu v konstrukcích." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265362.
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The thesis deals with the measurement of the elastic modulus of concrete in existing structures and possibilities of applicability of equations for the calculation of characteristic values of concrete compressive strength on the modulus of elasticity. The modulus of elasticity is determined by dynamic and static methods on specimens taken from the concrete blocks, whose composition varies by a water cement ratio and varying amounts of admixtures. In conclusion, the results of the measurements are compared and the characteristic values of the modulus of elasticity is determined.
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Wiberg, Johan. "Bridge Monitoring to Allow for Reliable Dynamic FE Modelling : A Case Study of the New Årsta Railway Bridge." Licentiate thesis, KTH, Civil and Architectural Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3897.
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<p>Today’s bridge design work in many cases demands a trustworthy dynamic analysis instead of using the traditional dynamic amplification factors. In this thesis a reliable 3D Bernoulli-Euler beam finite element model of the New Årsta Railway Bridge was prepared for thorough dynamic analysis using in situ bridge monitoring for correlation. The bridge is of the concrete box girder type with a heavily reinforced and prestressed bridge deck. The monitoring system was designed for long term monitoring with strain transducers embedded in the concrete and accelerometers mounted inside the edge beams and at the lower edge of the track slab.</p><p>The global finite element model used the exact bridge geometry but was simplified regarding prestressing cables and the two railway tracks. The prestressing cables and the tracks were consequently not included and an equivalent pure concrete model was identified.</p><p>A static macadam train load was eccentrically placed on one of the bridge’s two tracks. By using Vlasov’s torsional theory and thereby including constrained warping a realistic modulus of elasticity for the concrete without prestressing cables and stiffness contribution from the railway tracks was found. This was allowed by comparing measured strain from strain transducers with the linear elastic finite element model’s axial stresses. Mainly three monitoring bridge sections were used, each of which was modelled with plane strain finite elements subjected to sectional forces/moments from a static macadam train load and a separately calculated torsional curvature.</p><p>From the identified modulus of elasticity the global finite element model was updated for Poisson’s ratio and material density (mass) to correspond with natural frequencies from the performed signal analysis of accelerometer signals. The influence of warping on the natural frequencies of the global finite element model was assumed small and the bridge’s torsional behaviour was modelled to follow Saint-Venant’s torsional theory.</p><p>A first preliminary estimation of modal damping ratios was included. The results indicated that natural frequencies were in accordance between modelling and signal analysis results, especially concerning high energy modes. Estimated damping ratios for the first vibration modes far exceeded the lower limit value specified in bridge design codes and railway bridge dynamic analysis recommendations.</p>
9
Bizet, Laurent. "Caractérisation et modélisation du comportement thermomécanique des matériaux métalliques : vers la prise en compte des hétérogénéités micro-structurales intrinsèques." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAA001/document.
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La prédiction de la géométrie d'une pièce mise en forme par déformation plastique grâce à un logiciel de calcul par éléments finis (EF) s'effectue en suivant séquentiellement différentes étapes : la caractérisation thermo-mécanique du matériau, la modélisation de son comportement et son intégration dans un logiciel EF, puis la mise en données et la simulation de l'opération de formage. La phase de modélisation consiste entre autre à identifier quel type de modèle de comportement est le plus approprié pour prédire les réactions du matériau lors de l'opération de formage. Ces modèles sont essentiellement développés dans le cadre de la mécanique des milieux continus (MMC). L'hypothèse forte, si ce n'est centrale, de la MMC consiste à considérer que les variables qui servent à déterminer le comportement du matériau sont continues et dérivables. Cependant, les connaissances les plus élémentaires de métallurgie indiquent que les grandeurs locales dans les matériaux métalliques sont discontinues. La majorité des modèles de comportement mécanique des matériaux métalliques repose sur la définition d'un volume élémentaire représentatif dont la taille est assez grande pour permettre une homogénéisation de la description du comportement en gommant l'influence des hétérogénéités localesL'objet de ces travaux est de montrer que la prise en compte des hétérogénéités locales dans la modélisation du comportement des matériaux métalliques est pertinente et contribue à l'amélioration de la prédiction des simulations d'opérations de mise en forme en élargissant le potentiel prédictif des modèles ainsi construits. Un modèle élasto-plastique prenant en compte les hétérogénéités locales est alors proposé<br>To obtain a relevant shape of a formed part during its finite element simulation, several steps are needed: thermo-mechanical caracterization of the material, definition of the most relevant model and integration of this model in the FE software and finally after data converting and computing processes. The modelling step include, among other things, the identification of the most appropriate model to fit the experimental material behaviour. Those models are essentially developped within the framework of continuum mechanics (CM). A strong, if not the main assumption of the CM consists in considering that mechanical description variables are continuous and differentiable. However, the basic knowledge of metallurgy indicates that local data in metallic materials are discontinuous. For metallic materials, the majority of constitutive models are based on the definition of a representative elementary volume (REV). This REV is supposed to be large enough to erase the incidence of local heterogeneities. Then those constitutive models are assumed to be homogeneous.The aim of this work is to show that introducing local heterogeneities in the description of constitutive models is relevant and contribute to improve the simulation accuracy. Those models also provide an enlargement of the simulation predictive potential. Then an elasto-plastic model, based on local heterogeneities description, is proposed
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Sousa, Fernando Henrique Fernandes. "Avaliação da relação entre os módulos de elasticidade estático e dinâmico de concretos produzidos com agregados graúdos reciclados em substituição aos agregados graúdos naturais." Universidade do Vale do Rio dos Sinos, 2018. http://www.repositorio.jesuita.org.br/handle/UNISINOS/7170.
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Previous issue date: 2018-05-28<br>Nenhuma<br>O módulo de elasticidade é um parâmetro que mensura a rigidez do concreto, sendo uma das propriedades que é levada em consideração na verificação da segurança estrutural, pois expressa as condições dos estados limites último e de serviço. Quando é avaliada - a influência da substituição de agregados graúdos naturais por agregados graúdos reciclados - o comportamento elástico do concreto torna-se imprescindível, uma vez que não é similar ao comportamento de resistência à compressão, que por sua vez pode alcançar resistências superiores ao concreto produzido inteiramente com agregados graúdos naturais. Nesse sentido, o uso da resistência à compressão como parâmetro único, para se estimar o módulo de elasticidade do concreto produzido com agregados graúdos reciclados, tem sido cada vez mais questionável. Tratando-se da influência do uso de agregado graúdo reciclado no módulo de elasticidade do concreto, poucos são os estudos que apresentam os valores de módulo de elasticidade estático e módulo de elasticidade dinâmico. Diante disso, o objetivo desta pesquisa é avaliar a relação entre o módulo de elasticidade estático e o módulo de elasticidade dinâmico de concretos produzidos com agregados graúdos reciclados em substituição aos agregados graúdos naturais, com o intuito de relacionar o tipo de agregado graúdo ao módulo de elasticidade. Para tal, foram utilizados agregados graúdos reciclados de concreto e agregados graúdos reciclados de cerâmica vermelha em taxa de substituição de 30% em relação ao agregado graúdo natural. Os concretos foram produzidos em três traços experimentais, sendo eles: traço pobre (maior relação a/c), traço intermediário e traço rico (menor relação a/c). As propriedades dos concretos foram avaliadas aos 28 dias, sendo elas: massa específica do concreto no estado fresco e endurecido; porosidade; resistência à compressão; módulos de elasticidade estático e dinâmico. Como principais resultados, verificou-se que o tipo de agregado graúdo reciclado de modo geral influenciou negativamente o módulo de elasticidade, sendo essa influência mais pronunciada no módulo de elasticidade dinâmico; não foi possível obter uma relação entre o módulo de elasticidade estático e dinâmico dos concretos produzidos com agregados graúdos reciclados; o módulo de elasticidade estático dos concretos produzidos com agregados graúdos reciclados é mais fortemente relacionado à resistência e à compressão; o módulo de elasticidade dinâmico possui maior relação com a porosidade dos concretos produzidos com agregados graúdos reciclados; os módulos de elasticidade estimados por equações algébricas apresentam elevada variabilidade.<br>Modulus of elasticity is a parameter that measures the stiffness of the concrete, being one of the properties taken into account in the structural safety check, since it expresses the conditions of the ultimate and service boundary state. When the influence of the replacement of natural aggregates by recycled aggregates is evaluated, the elastic behavior of the concrete becomes essential, since it cannot be compared to the behavior of compressive strength, usually lower than the concrete produced with natural aggregates. The use of compressive strength as a single parameter to estimate the modulus of elasticity of concrete produced with recycled aggregates has been increasingly questionated. Considering the influence of the use of recycled aggregate on the modulus of elasticity of concrete, only a few studies have compared the values of static elastic modulus and dynamic modulus. This research aims to evaluate the relationship between the static elastic modulus and the dynamic elastic modulus of concrete produced with recycled aggregates in replacement of natural aggregates, in order to correlate the type of aggregate to the modulus of elasticity, verifying the relationship between the two procedure of determination of elasticity modulus. Aggregates made of recycled concrete and of ceramic bricks were used in a replacement rate of 30% to the natural aggregate. The concretes were produced in three experimental proportions (lower w/c ratio, intermediate w/c ratio and higher w/c ratio). The properties evaluated at 28 days are: bulk concrete mass; porosity; compressive strength; static and dynamic modulus of elasticity. The main conclusions are: the recycled aggregate decrease the modulus of elasticity, mainly the dynamic modulus; there are no relationship between the static and dynamic modulus of elasticity of concrete produced with recycled aggregates; the static modulus of concrete produced with recycled aggregates has a higher relationship to the compressive strength; the dynamic modulus of elasticity is higher related to the porosity of concrete produced with recycled aggregates; the moduli of elasticity estimated by algebraic equations present high variability.
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Almeida, Sandra Freire de. "Análise dinâmica experimental da rigidez de elementos de concreto submetidos à danificação progressiva até a ruptura." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-20092005-183049/.
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Uma das aplicações da análise modal experimental é a avaliação da integridade estrutural. O ensaio dinâmico fornece os valores de freqüência natural, cujas variações podem ser utilizadas para identificar a presença e a magnitude do dano e determinar a rigidez equivalente de peças já fissuradas. Atualmente, as pesquisas sobre o efeito dinâmico nas estruturas civis estão se tornando mais freqüentes. Dentre os vários aspectos de interesse relacionados ao comportamento dinâmico das estruturas de concreto armado, cita-se como relevante a questão da danificação progressiva de seus elementos. Com a evolução da fissuração, existe uma diminuição da freqüência natural e um aumento do amortecimento. Essa variação dos parâmetros permite obter os valores de rigidez equivalente para os diversos estágios de fissuração da peça, o que pode indicar a proximidade da ruptura. Neste trabalho foi avaliada a integridade de elementos estruturais de concreto, discutindo os resultados da análise modal experimental em função do nível de danificação. Foram realizados ensaios em elementos de concreto simples para avaliação do módulo de elasticidade, tanto pelo método estático como pelo método dinâmico, observando a sua variação em função da microfissuração, resistência à compressão e idade do concreto. Os ensaios experimentais foram realizados em corpos-de-prova cilíndricos e prismáticos, sendo os resultados dos ensaios de vibração livre comparados aos resultados obtidos com os ensaios estáticos usuais. Também foram realizados ensaios estáticos e dinâmicos em vigas de concreto armado, de tamanho reduzido, para análise do comportamento de parâmetros dinâmicos ao longo de um processo de danificação. Demonstra-se a viabilidade dos ensaios não-destrutivos dinâmicos para a determinação das propriedades do material e dos elementos de concreto armado, além das vantagens econômicas, facilidade de execução e confiabilidade<br>Structural integrity assessment may be performed by experimental modal analysis. The dynamic tests provide natural frequencies values whose changes may be used to identify existent damage and to estimate the equivalent stiffness of cracked elements. Nowadays more researches about dynamic effects on civil structures are becoming available. Among all aspects related to the dynamic behaviour of reinforced concrete structures, the progressive damage of their elements is one of great relevance. According to the damage progress, the natural frequencies decrease and the damping factors increase. These dynamic characteristics changes allow getting the equivalent stiffness values for the various degrees of cracking, even indicating the closeness to failure. The objective of this research is to assess the concrete elements integrity and to discuss the results from experimental modal analysis due to different damage levels. There were carried through dynamic and static experiments to evaluate the modulus of elasticity of concrete. It was observed its changes related to concrete micro-cracking, compression strength and age. The experimental testings had been carried through in cylindrical and prismatic specimens. The results obtained from free vibration tests were compared with the ones obtained from the usual static tests. Reinforced concrete beams were also subjected to static and dynamic testings to assess the behavior of the dynamic parameters throughout a damage process. The dynamic non-destructive tests can be used to find out concrete and reinforced beam properties, beyond its economic advantages, easiness to do and trustworthiness
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Watson, Liam. "Evaluating the effects of initial stocking, physiological age and species on wood stiffness." Thesis, University of Canterbury. School of Forestry, 2013. http://hdl.handle.net/10092/9901.
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The influence of initial stocking and physiologically aged cuttings (taken from 1-year- old and 5-year-old parents) on corewood modulus of elasticity (MOE) in 6-year-old Pinus radiata D. Don was studied in a Nelder-design experiment in Rolleston, Canterbury. In the same experiment, the influence of initial stocking on MOE in 5-year- old Eucalyptus nitens was also investigated. The study incorporated 19 different stocking levels ranging from 207 to 40,446 stems/ha. Green dynamic modulus of elasticity was assessed in standing trees using the TreeTap stress-wave method over the lower part of the stem (0.3 – 1.9m) for 151 P. radiata trees and 115 E. nitens trees.
The interaction between species and stocking significantly influenced MOE (P<0.001). MOE of P. radiata increased by 55% (or 3.9 GPa) between 271 and 40,466 stems/ha, and by 41% (or 2.2 GPa) between 271 and 4370 stems/ha. MOE of E. nitens was also influenced by stocking but the slope was significantly lower indicating that the effect of stocking was less pronounced than for P. radiata. Over the usual range of stockings for E. nitens there was an insignificant relationship between stocking and stiffness (P=0.335). Trees were also assessed for DBH, height, and stem slenderness (height/ DBH). None of these latter variables had a significant influence on MOE after the effects of stocking and species were accounted for. No effects of physiological age of cuttings were detected in this study.
The findings of this study highlight the importance of stocking as a tool that forest managers can utilize to regulate corewood stiffness in P. radiata trees. These results also suggest that for E. nitens, where wood stiffness is a priority, forest managers could reduce establishment costs by planting at much lower initial stockings. This study also highlights the superior stiffness of E. nitens in direct comparison with P. radiata, with many trees in the experiment already exceeding stiffness thresholds for structural timber in New Zealand.
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Procházka, David. "Vytvoření předpokladů pro hodnocení vlastností vysokopevnostních betonů s využitím nedestruktivních metod zkoušení." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-233795.
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High-strength concrete (HSC) belongs in the recent years to frequently used types of concrete. It allows realization of static challenging structures and also shows due to its dense structure greater durability especially against aggressive media. Currently HSC construction realization abroad is not exceptional. It’s using in the Czech Republic is still limited. When realized, then in a small scale in civil engineering works. The realization of high-strength concrete structures is closely related with the concrete construction quality verification. Good efficiency of the quality control methods can provide non-destructive testing methods (NDT), especially when investigating strength of concrete built in structure. A lack on relevant data for non-destructive testing of HSC in technical and normative rules is to be considered as a significant deficiency. Evident for HSC generally is the lack in literature on deeper analysis of the factors affecting their non-destructive testing, as well a meaningful methodology or practically usable calibration relationships. HSC differs from ordinary concrete not only by used components, but also by more compact structure with different strength – elastic characteristics. Considering these differences, HSC strength prediction can not be performed by using calibration relationships developed for ordinary concrete. Moreover, the question is to what extent the current knowledge of the NDT results influencing factors can be considered as valid. The paper presents findings on the effects of the key factors affecting the measurement results of Schmidt hardness method and ultrasonic pulse method, including recommendations for the practical application of these methods. The problematic of static vs. dynamic modulus of elasticity was also solved. Calibration equations for predicting the compressive strength of HSC from the non-destructive testing parameter were elaborated, showing high cohesion among variables and practically usability.
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Benetti, Joana Kirchner. "Avaliação do módulo de elasticidade dinâmico de concreto produzido com agregado graúdo reciclado de concreto." Universidade do Vale do Rio dos Sinos, 2012. http://www.repositorio.jesuita.org.br/handle/UNISINOS/4523.
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Previous issue date: 2012-01-13<br>Banco Santander / Banespa<br>FINEP - Financiadora de Estudos e Projetos<br>O setor da construção civil apresenta um grande potencial de geração de resíduos sólidos, caracterizando-se como um dos maiores geradores deste material no mundo. Por este motivo, é importante adotar um novo modelo de desenvolvimento, que busque, gradativamente, a não geração e a minimização de resíduo, assim como alternativas para o reaproveitamento destes resíduos na própria construção civil, e, assim, atingir um desenvolvimento mais sustentável. Neste contexto, muitos estudos sobre o concreto confeccionado com agregados reciclados de concreto vêm sendo desenvolvidos, tanto em nível nacional como internacional. Entretanto, é possível perceber que a maior parte das pesquisas tem seu foco voltado para a resistência à compressão e à tração, sendo mais escassos aqueles que dão ênfase para o comportamento elástico destes concretos. Frente ao exposto, o presente trabalho tem como objetivo analisar o módulo de elasticidade dinâmico de concretos produzidos com a utilização de agregado reciclado de concreto. Para tanto, confeccionou-se concretos que foram divididos em dois grupos. Um dos grupos empregou agregados reciclados de duas resistências (18 e 50 MPa), que foram inseridos em um novo concreto de 32 MPa, nos teores de substituição de 25%, 50%, 75% e 100%. O outro grupo empregou dois tipos de resíduos, gerados em maior quantidade por uma indústria de pré-fabricados de concreto. Um deles é o resíduo de concreto plástico, com cura convencional ao ar, e o outro é o resíduo de concreto seco, com cura térmica à vapor de água, sendo que substituiu-se 50% em volume do agregado graúdo natural pelo reciclado, em três novos concretos de distintas resistências. O módulo de elasticidade dinâmico foi calculado conforme especificado na C597 (ASTM, 2009), sendo analisada a influência da umidade do concreto no momento do ensaio, do tipo de resíduo e do teor de substituição de agregado natural pelo reciclado no módulo de elasticidade dinâmico. O tipo de agregado reciclado de concreto influenciou o módulo de elasticidade dinâmico, assim como os diferentes teores de substituição e a umidade do concreto no momento do ensaio. Para os materiais avaliados, o módulo de elasticidade não variou em função da resistência à compressão do concreto que gerou o agregado reciclado de concreto, e verificou-se correlação positiva entre o módulo de elasticidade e a resistência à compressão do concreto.<br>The construction industry is one of the largest solid waste generator. For this reason, it is important to adopt a new model aiming for thereuse of construction waste and thereby achieve a more sustainable development. In this context, studies on concrete made with recycledaggregate concrete have been developed, focused to determine compressive strength and tensile strength, with little emphasis on the elastic behavior of concrete. This work aims to analyze the dynamic modulus of elasticity of concrete produced with waste concrete as aggregate. To this end, it was made two groups of concrete using two types of waste generated in larger quantities by an industry of prefabricated concrete. The first group was made with a residue of plastic concrete, air-cured, and concrete made with of heat curing. The concrete aggregates were used to replace 50% by volume of natural coarse aggregate. In the second group recycled aggregates was produced in two strengths (18 and 50 MPa), being used to produce a new concrete of 32 MPa. The levels of substitution were 25%, 50%, 75% and 100%. The dynamic modulus of elasticity was calculated as specified in C597 (ASTM, 2009). It was analyzed the influence of moisture content and the type of waste recycled aggregate replacement in the natural dynamic modulus of elasticity. The type of recycled aggregate influenced the dynamic modulus of elasticity, as well as different levels of moisture and replacement of concrete at the time of trial. For the materials tested, the modulus of elasticity did not vary as a function of the compressive strength of recycled aggregate concrete, bu there was a positive correlation between the modulus of elasticity and compressive strength of concrete.
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Bartulíková, Radka. "Vliv provzdušnění a ošetřování na vývoj modulu pružnosti betonu." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225737.
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Master's thesis deals with influence of various factors on the concrete compressive strength and modulus of elasticity. This work concentrates mainly on the influence of early curing and air entrainment of concrete. One part of this work is the evaluation of laboratory measurement, which was carried out on cubes of standard and norm prisms. The development of elastic moduli was monitored in time to 730 days of age with respect to air entrainment and curing conditions. The second part of the experiment deals with a comparison of theoretical creep curves depending on the value of the modulus of elasticity based on different standards. Again, the air entrainment effect and influence of initial conditions are reflected.
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Balash, Alan. "Stavební průzkum a hodnocení stavu konstrukce." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392275.
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This diploma thesis is focused on building survey and evaluating of the state of the three-storey industrial hall. The diploma thesis consists of two parts - theoretical and practical. In the theoretical part is described a common procedure for evaluation of the state of existing structures, methods used in diagnostics (selected ones - more detailed), advantages and disadvantages of methods. In the practical part is carried out construction and technical survey of the industrial hall, the concrete strength evaluation and verification of presence and type of reinforcement. At the end of the work - evaluation of objects.
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Bartoň, Vojtěch. "Metodika zkoušek historických cihel a zdiva." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409950.
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This diploma thesis is focused on methodology for sorting of solid fired bricks for reconstruction of historical buildings. The theorethical part of this thesis includes description of production technology of solid fired bricks and diagnostic methods. In practical part there are these methods aplied on the solid fired bricks, which are intended for reconstruction of the bridge in Sedlec. There are monitored changes in structure of solid fired bricks caused by repeated freezing and defrosting. This changes are monitored by resonant frequency method and ultasonic pulse method.
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Trinca, Alex Julio. "Influencia da dimensão do corpo-de-prova no ensaio destrutuvo de compressão paralela as fibras e no ensaio não-destrutivo utilizando ultra-som." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257144.
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Previous issue date: 2006<br>Resumo: é praticamente toda exportada em sua forma in natura sem que a ela seja agregado valor de beneficiamento. Um dos problemas enfrentados pela indústria moveleira é o fato da madeira não ser submetida à classificação, dificultando a elaboração de projetos e a certificação da qualidade do móvel confeccionado a partir deste material. Nesse contexto as empresas moveleiras brasileiras buscam parâmetros para composição e certificação de seu produto, sendo atualmente a norma brasileira ¿Projeto de Estruturas de Madeira¿ ¿ NBR 7190/97, o único instrumento norteador para a caracterização de propriedades da madeira. No entanto, nesse setor as dificuldades para a obtenção de corpos-de-prova nas dimensões especificadas por esse texto normativo têm gerado dúvidas quanto aos resultados de caracterização de propriedades, de maneira que este trabalho teve como objetivo principal verificar se os valores do módulo de elasticidade e da tensão de ruptura no ensaio de compressão paralela às fibras podem ser considerados estatisticamente equivalentes, desde que sejam mantidas a proporcionalidade da dimensão do corpo-de-prova. Para isso adotou-se, como alternativa ao corpo-de-prova proposto pela NBR 7190/97, a dimensão 0,03 m x 0,03 m x 0,09 m. Os ensaios foram realizados utilizando-se 7 diferentes espécies de madeira com densidades variadas, buscando-se, com essa amostragem, a generalização dos resultados. Como objetivo secundário se buscou avaliar a influência das dimensões do corpo-de-prova e da freqüência do transdutor na velocidade de propagação de ondas de ultra-som na direção longitudinal. As espécies adotadas foram: Cerejeira (Torresea sp), Perobinha (Paratecoma peroba) , Cabreúva-vermelha (Myroxylon peruiferum), Angico-preto (Anadenanthera macrocarpa), Garapeira (Apuleia leiocarpa), Eucalipto grandis ( Eucalyptus grandis) e Pinus elliotti (Pinus elliottii). Todos os corpos-de-prova foram ensaiados com aproximadamente 12% de umidade e os ensaios foram realizados em ambiente controlado (21° C ± 1°C). Os resultados permitiram concluir que a hipótese foi verdadeira para todas as espécies estudadas quando se considera a tensão de ruptura<br>Abstract: Most of the exported wood in Brazil is unprocessed, without any aggregated value. To change this scenario technology for wood processing and qualification are required. One of the problems faced by the furniture industry refers to the non classification of the wood, which cause difficulties to projects elaboration and quality certification of the furniture made from this material. In this context the Brazilian Industries of furniture seek for parameters to certificate its products, and the NBR 7190/97 standard ¿Project of Structures of Wood " is, nowadays, the only instrument for the characterization of wood properties. However, for the furniture industry it is very difficult to obtaining the dimensions specified by the standard. This research had as main objective to verify if the means values of the modulus of elasticity and rupture in compression parallel to the grain can be considerate statistically equal, when smaller specimen are used, if the proportionality is maintained. For that it was adopted, as alternative to the specimen proposed by NBR 7190/97, the dimension 0.03 x 0.03 x 0.09 m. For the experiments there were used 7 different species with varied densities. The secondary objective was to evaluate the influence of the specimen size and of the transducer frequency in the speed of ultrasound wave propagation in the longitudinal direction. The adopted species were: Cerejeira (Amburana cearensis), Perobinha (Paratecoma peroba), Cabreúva vermelha (Myroxylon peruiferum), Angico-preto (Anadenanthera macrocarpa), Garapeira (Apulleia leiocarpa), Eucalyptus grandis, (Eucalyptus grandis) and Pinus ellioti (Pinus elliottii). All specimens were tested with approximately 12% moisture content and were accomplished in controlled atmosphere (21° C ± 1°C). The results allowed concluding that the hypothesis was true for all the studied species when the rupture in compression parallel to the grain was considered. For the module of elasticity this hypothesis was not confirmed for two species, from the seven evaluated (garapeira e eucalipto). Although, the mean difference between the results obtained in the tests using both specimens size was 10%, smaller then the maximum allowed variability in mechanical tests (18%). For the ultrasonic velocity propagation four species did not presents statistical variation with the modification of the size of the specimens - cerejeira, garapeira, pinus and eucalyptus while for the perobinha, angico and cabreúva the ultrasonic wave velocity propagation could not be considered statistically equal when the dimension of the specimens was modify. On average (considering all the studied species) the relationship among the ultrasonic wave velocity propagation (VLL) in normalized specimen and in proposed specimen was 0.99, being respectively the maximum and the lower relationships of 1.02 and 0.93. The velocity of wave propagation presents larger variations for values of length of wave percolation/wave length (L/?) up to 3, being more constant above that limit. It was also possible to verify, for the studied species, that the velocity of wave propagation increases with the increase of the transducer frequency. Key words: modulus of elasticity of wood; compression strength parallel to the fiber; ultrasonic wave velocity; dynamic constant<br>Mestrado<br>Construções Rurais e Ambiencia<br>Mestre em Engenharia Agrícola
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Akhi, Taohida Parvin. "Experimental investigation of effective modulus of elasticity and shear modulus of brick masonry wall under lateral load." ISIS Canada Research Network, 2011. http://hdl.handle.net/1993/5304.
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The primary objective of this research program was to investigate the effective modulus of elasticity and shear modulus of brick masonry walls under lateral load, and to to justify using the Jaeger and Mufti method to calculate the effective modulus of elasticity and shear modulus of brick masonry walls. The experimental program involved the testing of three unreinforced brick masonry walls under in-plane and vertical loads. Linear Variable Differential Transducers were used to record the horizontal and vertical displacements of the walls. The experimental results were used to evaluate the modulus of elasticity and the shear modulus of walls under flexure. The experimental results were compared to the finite element analysis results. It was found that the finite element analysis yields similar results to the experimental results. It was also found that the Jaeger and Mufti method to calculate effective modulus of elasticity and shear modulus of brick masonry walls is effective for design purposes.
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Purssell, Tanis Jane. "Modulus reduction dynamic analysis." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25136.
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A semi-analytical method of dynamic analysis, capable of predicting both the magnitude and pattern of earthquake induced deformations, is presented. The analysis is based on a modulus reduction approach which uses a reduced modulus to simulate the softening induced in soils during cyclic loading. The effects of the inertia forces developed during dynamic loading on the induced deformations are also included through an appropriate selection of the reduced modulus.
The reduced modulus is utilized in a static stress-strain analysis to predict the magnitude and pattern of the deformations induced during earthquake loading. The appropriate modulus reduction is determined from laboratory tests on undisturbed soil samples. Three methods of computing a suitable post-cyclic modulus were investigated but only the cyclic strain approach, in which the modulus is determined from cyclic loading tests that duplicate the field stress conditions, yields reductions of sufficient magnitude to provide realistic estimates of earthquake induced deformations.
The modulus reduction analysis was used to predict the deformations occurring during dynamic loading of a model tailings slope in a laboratory shaking table test and of the Upper San Fernando Dam during the earthquake of February, 1971. These studies showed that the modulus reduction analysis is capable of reproducing the dynamically induced deformations and that reductions in the modulus of up to 1000 times may be required. Unfortunately, limitations of the testing equipment and inadequacies in the available data required that the appropriate modulus reductions could not be determined entirely through laboratory and field investigations. Some assumptions were necessary in selecting the reduced modulus values used in the analyses. Although these case studies were, hence, unable to provide full verification of the proposed method, they do demonstrate the reliability and simplicity of the analysis as a method of assessing the performance of soil structures during earthquake loading.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate
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Ip, Felix. "Compressive strength and modulus of elasticity of masonry prisms." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0019/MQ48451.pdf.
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Ip, Felix (Mong Kau Felix) Carleton University Dissertation Engineering Civil and Environmental. "Compressive strength and modulus of elasticity of masonry prisms." Ottawa, 1999.
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Busch, Amanda J. "Vacuum-Assisted Wet Shaping of Paper." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10567.
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Premium absorbent paper products (e.g., two-ply towel and tissue) can achieve higher fluid holding capacity per unit dry weight by means of increasing their void volume per unit weight. In turn, high void volume can be attained by increasing the overall thickness of each ply through molding the paper into a three-dimensional ("mini-egg-crate") structure before drying it.
This research investigates the effect of three types of parameters: mold geometrical, operational, and paper parameters. These variables are examined with respect to their effect on the resulting overall thickness. Because the experimental research is fundamental in nature, it employs molding structures of a simplified geometry (produced via rapid prototyping techniques) rather than the geometrically complex molding fabrics used commercially.
A goal of the project is the understanding of the physics of the wet shaping process, in which vacuum is used to deform the wet paper web into the openings in the molding structure. Another goal is identification of limitations or boundaries of the wet shaping
process (e.g., conditions for which "pinholes" occur in the paper). Supporting theoretical analysis of the shaping/molding problem is performed, to provide bases for correlating experimental data and for the optimization of molding geometrical parameters. The result of this study provides quantitative information for some variables that affect the final sheet thickness.
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Bhattacharjee, Chandan. "Bayesian prediction of modulus of elasticity of self consolidated concrete." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2467.
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Vukovic, Nikola. "Comparison of laboratory and field modulus of elasticity of rocks." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/MQ44047.pdf.
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Schoppe, Brett Michael. "SHRINKAGE & MODULUS OF ELASTICITY IN CONCRETE WITH RECYCLED AGGREGATES." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/500.
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This paper presents results on experimental research for concrete produced using recycled coarse aggregates (RCA). Five types of coarse aggregates were used in this study, four of which were RCA. The main purpose of this research was to examine how different types and properties of coarse aggregate affected compressive strength, modulus of elasticity, and shrinkage in concrete when natural coarse aggregates were replaced with RCA. Concrete batches were made with water-cement (w/c) ratios of 0.30, 0.45, and 0.60, and substitution percentages ranged from 0% to 100% of natural aggregate with RCA. Test results clearly show that compressive strength, modulus of elasticity, and shrinkage greatly depend on the quality and type of coarse aggregate used. In addition to testing of hardened concrete, predictive models for elasticity and ultimate shrinkage were developed to formulate and reinforce proposed conclusions about the properties and performance for the different RCA.
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Škapová, Pavla. "Problematika testování stříkaných betonů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226742.
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The master‘s thesis focuses on testing the shotcrete prepared in laboratory conditions. The main observed properties are compresive strenght of shotcrete and modulus of elasticity. The aim is assessment of methods for measuring those parameters. The calibrating correlations for strenght characteristics of shotcrete are given by obtaining the results of used methods. The shotcrete composition, amount and type of accelerating additive as well as economic aspect of using shotcrete is also assessed.
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Nortemann, Markus. "Characterisation of Young's modulus and loss factor of damping materials." Thesis, Nelson Mandela Metropolitan University, 2014. http://hdl.handle.net/10948/d1021036.
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Given the importance of simulation techniques in automotive engineering, there is a lack of implementation regarding these techniques in the acoustics of damping materials for air-borne sound. Biot’s calculations have proven its abilities to simulate the acoustic characteristics of these damping materials. However, the characterisation of essential structural parameters, such as Young’s modulus and loss factor, in order to conduct Biot’s calculations have been inconclusive. Thus, the primary research objective of this study is to propose a new measurement system for the structural Biot parameters. After a comprehensive literature review has been undertaken on damping materials, as well as measurement apparatuses for Young’s modulus and loss factor of damping materials, two causes of measurement errors have been identified. Unknown stresses in measurement apparatuses and inhomogeneous, polytrophic and viscoelastic behaviour of specimens. A new measurement system that does not affect the specimens with unknown stresses and accounts for their complex behaviour required investigation. Non-contact ultrasound had been selected as a solution to determine the aforementioned parameters, since these methods do not necessarily touch or compress the specimen, which led to unknown stresses and neglection of the complex specimen behaviour with the aforementioned techniques. Although ultrasound had been used to determine structural parameters on various types of materials, it has never been used to measure soft porous damping materials. In order to find possible solutions, various sources using ultrasonics to investigate struc- tural parameters had been reviewed. In order to calculate structural parameters, the longitudinal and transversal wave velocity inside the specimen had to be determined. The main findings showed that non-contact ultrasound will be able to evaluate the Young’s modulus, loss factor as well as Poisson’s ratio. Consequently, it was shown that longitudinal velocity measurements could be conducted using well known transmission measurements. However, well known approaches would not be sufficient measuring the transversal wave velocity in soft damping materials. This problem was addressed with a special gas to be used, with lower sound speed velocity in the fluid than in the solid. Moreso, a new method determining the transversal wave velocity had been found, as it would enable the use of an even larger range of damping materials, especially ones with heavy frames and lower porosity. It will use refracted waves inside the specimen and the determination of the convertion position of the transversal to the longitudinal wave at the rear specimen surface. At the end of the study, hardware components were selected and a test rig was constructed, which should be able to prove that a determination of structural Biot parameters with non-contact ultrasound is possible with less errors instead of using mechanical transfer function systems. The development of measurement software as well as the testing of the measurement system and its validation was not under investigation in this dissertation. This study has expanded on the body of literature knowledge regarding non-contact ultrasound. Furthermore, a significant contribution has been made towards a new measurement system measuring Young’s modulus and loss factor which circumvents errors in mechanical transfer function systems. This will contribute to more precise simulations of damping materials and damped enclosures, which may ultimately result in enhanced efficiency of damping materials as well as the acoustic packaging of cars.
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Borgomano, Jan. "Dispersion des modules élastiques de carbonates saturés : étude expérimentale et modélisation." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEE021/document.
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Pour les roches saturées, la comparaison entre les mesures ultrasoniques (1 MHz) au laboratoire et les mesures sismiques (100 Hz) ou de diagraphie (10 kHz) sur le terrain n’est pas directe à cause de la dispersion des vitesses des ondes. Les mécanismes impliqués dans la dépendance en fréquence sont les écoulements de fluides à différentes échelles provoqués par le passage de l’onde. La dispersion et l’atténuation des modules élastiques de roches carbonatées ont été étudiées expérimentalement. Les calcaires étudiés sont : un Lavoux, un Indiana intact et craqué thermiquement, un calcaire Urgonien de Provence (Rustrel), et un coquina pré-sel du Congo. Les mesures ont été faites sur une large gamme de fréquence, en combinant les techniques d’oscillations forcées (10-3 to 102 Hz) et ultrasoniques (1 MHz) dans une presse triaxiale, pour différentes pressions effectives. Le forçage peut être hydrostatique pour mesurer un module d’incompressibilité, ou axial pour mesurer le module de Young et le coefficient de Poisson. Pour étudier l’effet de la viscosité, les mesures ont été faites en condition sèche, puis saturée en glycérine et en eau. Le drainage global et le mécanisme d’écoulement crack-pore ont été caractérisés, en termes d’amplitude de dispersion, d’atténuation viscoélastique, et de fréquence de coupure. Pour nos échantillons, la théorie de Biot-Gassmann s’est montrée valide pour les fréquences sismiques (10-100 Hz) sauf pour l’Indiana craqué thermiquement. La dispersion liée à des écoulements crackspores a été observée pour tous les échantillons sauf le Lavoux. Les fréquences de coupures de ceux-ci sont toutes dans la gamme des fréquences des diagraphies (10 kHz) pour des conditions de saturation en eau. Un modèle simple, combinant poroélasticité et milieux effectifs, a été développé pour prédire la dispersion des modules sur toute la gamme de fréquence, et s’est montré généralement en accord avec les résultats expérimentaux<br>For fluid-saturated rocks, comparing ultrasonic measurements (1 MHz) in the laboratory and seismic (100 Hz) or logging (10 kHz) measurements in the field is not straightforward due to dispersion of the bodywave velocities. The frequency-dependent mechanisms involved are wave-induced fluid flows that occur at different scales. The dispersion and the attenuation of the elastic moduli of four fluid-saturated carbonate rocks have been studied experimentally. The selected limestones were a Lavoux, an intact and thermally cracked Indiana, a Urgonian limestone from Provence (Rustrel), and a presalt coquina from offshore Congo. Measurements were done over a large frequency range, by the combination of forced oscillations (10-3 to 102 Hz) and ultrasonic measurements (1 MHz) in a triaxial cell, at various effective pressures. The forced oscillations were either hydrostatic to deduce the bulk modulus, or axial to deduce Young’s modulus and Poisson’s ratio. The measurements were done in dry-, glycerinand water-saturated conditions to investigate the effect of viscosity. For all our samples, the global drainage and the squirt-flow mechanisms were characterized experimentally, in terms of amplitude of dispersion, amount of viscoelastic attenuation, and cut-off frequencies. Biot- Gassmann’s theory was found to be valid at seismic frequencies (10-100 Hz) for all the samples except the thermally cracked Indiana. Squirt-flow transitions were observed for all the samples, except the Lavoux. The cut-off frequencies were all in the range of logging frequencies (10 kHz), for watersaturated conditions. A simple model, combining poroelasticity and the noninteraction approximation effective medium, was developed to predict the dispersion of the moduli over the whole frequency range, and was generally in agreement with the experimental results
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Bert, Stephen M. "Using Maturity to Predict Girder Camber." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/32852.
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The objective of this research was to determine if differential camber of prestressed concrete girders could be reduced by accurate prediction of initial camber at release of prestress. Maturity at prestress transfer was used to calculate modulus of elasticity for predicting camber at release. The research consists of a literature review of maturity methods, testing of a standard concrete mix to determine strength and modulus functions and measurement of girder camber and maturity.
Both the Nurse-Saul and the Arrhenius maturity models were evaluated. Maturity relationships were developed for concrete mixes containing Type II and Type III cements. A relationship of modulus as a function of maturity was developed. Seven girders were tested. Camber predictions within 0 to ¼ in. of actual camber were obtained using modulus of elasticity calculated from a maturity based function. Comparison was made between maturity based modulus and standard strength based modulus models. Camber predictions based on modulus calculated based on field cured cylinder strengths were within 0 to ½ in.<br>Master of Science
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Wang, Xin. "Elasticity of Lipid Membrane Leaflets: Determining Pivotal Plane and Tilt Modulus in Computer Simulations." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/960.
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This thesis introduces a novel protocol to measure two elastic quantities of lipid membranes, the pivotal plane of a single leaflet and the lipid tilt modulus. The key setup relies on the simulation of a buckled membrane, a configuration that had been previously proposed to measure a membrane's bending rigidity. Since this method solely depends on the geometrical analysis of the membrane shape, and can hence even be applied to existing simulation trajectories of buckled membranes, it can provide two additional physical quantities at no extra simulation cost. Due to the high precision of its result, many technical subtleties are considered throughout the derivation, pertaining for instance to higher order corrections due to Poisson ratio effects. This calculation, as shown in this thesis, can be used to provide both a reference for other study as well as deeper insight into the nature of lipid models, especially the limitation of the coarse-grained ones.
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Huang, Xuejiao. "Meshless investigation for nonlocal elasticity : static and dynamic." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24643.
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The numerical treatment of nonlocal problems, which taking into account material microstructures, by means of meshless approaches is promising due to its efficiency in addressing integropartial differential equations. This thesis focuses on the investigation of meshless methods to nonlocal elasticity. Firstly, mathematical constructions of meshless shape functions are introduced and their properties are discussed. Shape functions based upon different radial basis function (RBF) approximations are implemented and solutions are compared. Interpolation errors of different meshless shape functions are examined. Secondly, the Point Collocation Method (PCM), which is a strong-form meshless method, and the Local Integral Equation Method (LIEM) that bases on the weak-form, are presented. RBF approximations are employed both in PCM and LIEM. The influences of support domains, different kinds of RBFs and free parameters are studied in PCM. While in LIEM, analytical forms of integrals, which is new in meshless method, is addressed. And, the number of straight lines that enclose the local integral domain as well as the integral radius are analyzed. Several examples are conducted to demonstrate the accuracy of PCM and LIEM. Besides, comparisons are made with Abaqus solutions. Then, PCM and LIEM are applied to nonlocal elastostatics based on the Eringen's model. Formulations of both methods are reported in the nonlocal frame. Numerical examples are presented and comparisons between solutions obtained from both methods are made, validating the accuracy and effectiveness of meshless methods for solving static nonlocal problems. Simultaneously, the influence of characteristic length and portion factors are investigated. Finally, LIEM is employed to solve nonlocal elastodynamic problems. The Laplace transform method and the time-domain technique are implemented in LIEM respectively as the time marching schemes. Numerical solutions of both approaches are compared, showing reasonable agreements. The influence of characteristic length and portion factors are investigated in nonlocal dynamic cases as well.
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Adem, Hana Hussin. "Modulus of Elasticity Based Method for Estimating the Vertical Movement of Natural Unsaturated Expansive Soils." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/31910.
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Expansive soils are widely distributed in arid and semi-arid regions around the world and are typically found in a state of unsaturated condition. These soils are constituted of the clay mineral montmorillonite that is highly active and contributes significantly to volume changes of soils due to variations in the natural water content conditions. The volume changes of expansive soils often cause damage to lightly loaded structures. The costs associated with the damage to lightly loaded structures constructed on expansive soils in the United States alone were estimated as $2.3 billion per year in 1973, which increased to $13 billion per year by 2009. In other words, these damages have increased more than five fold during the last four decades. Similar trends in damages were also reported in other countries (e.g., Australia, China, France, Saudi Arabia, United Kingdom, etc.).
Numerous methods have been proposed in the literature over the past 50 years for the prediction of the volume change movement of expansive soils. However, the focus of these methods has been towards estimating the maximum potential heave, which occurs when soils attain the saturation condition. The results of heave estimation considering saturated soil conditions are not always useful in engineering practice. This is because most of damages due to expansive soils often occur prior to reaching the saturation condition. A reliable design of structures on expansive soils is likely if the anticipated soil movements in the field can be reliably estimated over time, taking into account the influence of environmental factors. Limited studies are reported in the literature during the past decade in this direction to estimate/predict the expansive soil movements over time. The existing methods, however, suffer from the need to run expensive and time consuming tests. In addition, verification of these studies for different natural expansive soils has been rather limited.
A simple approach, which is referred to as a modulus of elasticity based method (MEBM), is proposed in this study for the prediction of the heave/shrinkage movements of natural expansive soils over time. The proposed MEBM is based on a simplified constitutive relationship used for the first time to estimate the vertical soil movements with respect to time in terms of the matric suction variations and the corresponding values of the modulus of elasticity. The finite element program VADOSE/W (Geo-Slope 2007) for simulating the soil-atmospheric interactions is used as a tool to estimate the changes in matric suction over time. A semi-empirical model that was originally proposed by Vanapalli and Oh (2010) for fine-grained soils has been investigated and extended for unsaturated expansive soils to estimate the variation of the modulus of elasticity with respect to matric suction in the constitutive relationship of the proposed method. The MEBM has been tested for its validity in five case studies from the literature for a wide variety of site and environmental conditions, from Canada, China, and the United States. For each case study, factors influencing the volume change behavior of soils, such as climate conditions, soil cracks, lawn irrigation, and cover type (pavement, vegetation), are successfully modeled over the period of each simulation. The proposed MEBM provides good predictions of soil movements with respect to time for all the case studies. The MEBM is simple and efficient for the prediction of vertical movements of natural expansive soils underlying lightly loaded structures.
In addition, a new dimensionless model is also proposed, based on the dimensional analysis approach, for the estimation of the modulus of elasticity which can also be used in the constitutive relationship of the MEBM. The dimensional model is rigorous and takes into account the most significant influencing parameters such as matric suction, net confining stress, initial void ratio, and degree of saturation. This model provides a comprehensive characterization of the modulus of elasticity of expansive soils under unsaturated conditions for different scenarios of loading conditions (i.e., both lightly and heavily loaded structures).
The results of the present study are encouraging for proposing guidelines based on further investigations and research studies for the rational design of pavements, shallow and deep foundations placed on/in expansive soils using the mechanics of unsaturated soils.
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Torres, Donna Schulz 1972. "Effects of modulus of elasticity of collagen sponges on their cell-mediated contraction in vitro." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50056.
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Zoric, Branislav. "Modelling the influence of stocking on longitudinal and radial variation in wood properties of Pinus radiata on a warm Northland site." Thesis, University of Canterbury. School of Forestry, 2009. http://hdl.handle.net/10092/2564.
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The objective of this study was to determine how final stocking influences tree growth and radial and longitudinal variation in wood properties at a Pinus radiata D. Don plantation located at one of the warmest forest sites in New Zealand, Forsyth Downs forest in Northland. This thesis addressed both the effect of stocking on stand basal area, height, diameter and branch diameter and the effect of stocking on wood properties microfibril angle (MFA), module of elasticity and density. Finally, how ring width influences wood properties and whether this variable accounts for the treatment effects was investigated.
Stocking, height and ring number and all interactions between these variables significantly affected ring width. Ring width by itself was significant as a predictor of density, but when it was combined with other class level variables it was insignificant (i.e. does not account for treatment effects), and it did not add anything to a model with only class effects. There was a significant impact of ring number on density while ring width was insignificant in the same model.
MFA was significantly affected by ring width, height and ring number in the tree, and all interactions, apart from the three way interaction, but not by stocking. Ring width was significant in the MFA model both by itself and when it was combined with other variables. Ring width accounted for the stocking effect.
The best model of MOE included the class level effects of stocking, height and ring number within the tree, and all interactions between these variables, and ring width, as a continuous variable. While there was a significant effect between stockings this was relatively weak compared to the other main effects. Ring width largely accounted for the effect of stocking, but not that of ring number, or height.
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Gao, Liang. "Ultrasound Elasticity Imaging of Human Posterior Tibial Tendon." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/338897.
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Posterior tibial tendon dysfunction (PTTD) is a common degenerative condition leading to a severe impairment of gait. There is currently no effective method to determine whether a patient with advanced PTTD would benefit from several months of bracing and physical therapy or ultimately require surgery. Tendon degeneration is closely associated with irreversible degradation of its collagen structure, leading to changes to its mechanical properties. If these properties could be monitored in vivo, it could be used to quantify the severity of tendonosis and help determine the appropriate treatment. Ultrasound elasticity imaging (UEI) is a real-time, noninvasive technique to objectively measure mechanical properties in soft tissue. It consists of acquiring a sequence of ultrasound frames and applying speckle tracking to estimate displacement and strain at each pixel. The goals of my dissertation were to 1) use acoustic simulations to investigate the performance of UEI during tendon deformation with different geometries; 2) develop and validate UEI as a potentially noninvasive technique for quantifying tendon mechanical properties in human cadaver experiments; 3) design a platform for UEI to measure mechanical properties of the PTT in vivo and determine whether there are detectable and quantifiable differences between healthy and diseased tendons. First, ultrasound simulations of tendon deformation were performed using an acoustic modeling program. The effects of different tendon geometries (cylinder and curved cylinder) on the performance of UEI were investigated. Modeling results indicated that UEI accurately estimated the strain in the cylinder geometry, but underestimated in the curved cylinder. The simulation also predicted that the out-of-the-plane motion of the PTT would cause a non-uniform strain pattern within incompressible homogeneous isotropic material. However, to average within a small region of interest determined by principal component analysis (PCA) would improve the estimation. Next, UEI was performed on five human cadaver feet mounted in a materials testing system (MTS) while the PTT was attached to a force actuator. A portable ultrasound scanner collected 2D data during loading cycles. Young's modulus was calculated from the strain, loading force and cross sectional area of the PTT. Average Young's modulus for the five tendons was (0.45±0.16GPa) using UEI. This was consistent with simultaneous measurements made by the MTS across the whole tendon (0.52±0.18GPa). We also calculated the scaling factor (0.12±0.01) between the load on the PTT and the inversion force at the forefoot, a measurable quantity in vivo. This study suggests that UEI could be a reliable in vivo technique for estimating the mechanical properties of the human PTT. Finally, we built a custom ankle inversion platform for in vivo imaging of human subjects (eight healthy volunteers and nine advanced PTTD patients). We found non-linear elastic properties of the PTTD, which could be quantified by the slope between the elastic modulus (E) and the inversion force (F). This slope (ΔE/ΔF), or Non-linear Elasticity Parameter (NEP), was significantly different for the two groups: 0.16±0.20 MPa/N for healthy tendons and 0.45±0.43 MPa/N for PTTD tendons. A receiver operating characteristic (ROC) curve revealed an area under the curve (AUC) of 0.83±0.07, which indicated that the classifier system is valid. In summary, the acoustic modeling, cadaveric studies, and in vivo experiments together demonstrated that UEI accurately quantifies tendon mechanical properties. As a valuable clinical tool, UEI also has the potential to help guide treatment decisions for advanced PTTD and other tendinopathies.
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Andreadou, Anna. "Some static and dynamic finite elastic deformations." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352956.
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Granskär, Joakim. "Evaluation of SCPT-surveys as method for accessing dynamic modulus." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-68756.
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The purpose of this master thesis is to evaluate the results from the completed SCPT (Seismic Cone Penetration Test) surveys with respect to the methods ability to estimate dynamic young´s modulus. This has been done by comparing the result from SCPT to other seismic methods and dynamic parameters converted from “static” geotechnical surveys. SCPT is a relatively new method which has not been used by Sweco or in Sweden to any greater extent and is therefore of interest to be looked in to. By adding two geophones to an ordinary CPT (Cone Penetration Test) equipment as well as including strike plates, hammer and logger system one can log dynamic parameters in addition to the regular parameters logged by a CPT system. This is done by stopping the otherwise continuous CPT survey every meter and striking the strike plates, which are placed under the tracks of the drilling rig. Seismic waves will then travel through the soil down to the geophones and be used to calculate dynamic parameters. For this master thesis a total of 47 geotechnical and geophysical surveys have been considered. The location of these 47 are approximately 7 km north of Norrköping and have been conducted between the years 2016-2017 for the East Link Project. The geotechnical surveys are composed of weight-sounding, ram-sounding and CPT while the geophysical ones are SCPT, refraction-survey and MASW (Multichannel Analysis of Surface Waves). Static elastic parameters have been calculated using the geotechnical survey results according to the Swedish transportation administrations standardized methods. These have then been converted to dynamic parameters with the help of different relationships. When these have been converted they can be compared to SCPT results and other seismic survey methods which also use wave velocity, Poisson’s ratio and density to calculate dynamic elastic parameters. Based on the results from this thesis it can be concluded that the seismic test add-on to a standard CPTu survey is a good method for accessing dynamic modules and it gives extended information of the soil stratigraphy from one single survey point. After the studies and analyses conducted for this thesis it can be concluded that the proposed conversion between static and dynamic young’s modulus using the Alpan curve gives slightly higher values than the ones derived directly from shear waves using SCPT. The other conversion using cone tip resistance to shear wave velocity gives on the other hand slightly lower values than the ones measured with the SCPT. The analysis also indicate similar trends in results between the different seismic methods. These results does however also shows that the used assumptions are somewhat general for accurate comparisons between the methods.
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Hermawan, Vera. "Experimental techniques to determine the Young's Modulus of the trachea thesis submitted in partial fulfilment of the degree of Master of Engineering, Auckland University of Technology, September 2004." Full thesis. Abstract, 2004.
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Brunetti, Carlotta. "Frequency-dependent response of snow in uniaxial compression and comparison with numerical simulation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7820/.
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La determinazione del modulo di Young è fondamentale nello studio della propagazione di fratture prima del rilascio di una valanga e per lo sviluppo di affidabili modelli di stabilità della neve. Il confronto tra simulazioni numeriche del modulo di Young e i valori sperimentali mostra che questi ultimi sono tre ordini di grandezza inferiori a quelli simulati (Reuter et al. 2013). Lo scopo di questo lavoro è stimare il modulo di elasticità studiando la dipendenza dalla frequenza della risposta di diversi tipi di neve a bassa densità, 140-280 kg m-3. Ciò è stato fatto applicando una compressione dinamica uniassiale a -15°C nel range 1-250 Hz utilizzando il Young's modulus device (YMD), prototipo di cycling loading device progettato all'Istituto per lo studio della neve e delle valanghe (SLF). Una risposta viscoelastica della neve è stata identificata a tutte le frequenze considerate, la teoria della viscoelasticità è stata applicata assumendo valida l'ipotesi di risposta lineare della neve. Il valore dello storage modulus, E', a 100 Hz è stato identificato come ragionevolmente rappresentativo del modulo di Young di ciascun campione neve. Il comportamento viscoso è stato valutato considerando la loss tangent e la viscosità ricavata dai modelli di Voigt e Maxwell. Il passaggio da un comportamento più viscoso ad uno più elastico è stato trovato a 40 Hz (~1.1•10-2 s-1). Il maggior contributo alla dissipazione è nel range 1-10 Hz. Infine, le simulazioni numeriche del modulo di Young sono state ottenute nello stesso modo di Reuter et al.. La differenza tra le simulazioni ed i valori sperimentali di E' sono, al massimo, di un fattore 5; invece, in Reuter et al., era di 3 ordini di grandezza. Pertanto, i nostri valori sperimentali e numerici corrispondono meglio, indicando che il metodo qui utilizzato ha portato ad un miglioramento significativo.
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Werner, Jörn. "The influence of composition, processing and temperature on the Young's modulus of elasticity of carbon-bonded refractories." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-155296.
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Thermal shock resistance is a key property of refractory materials. Its determination and prediction is essential for the design of structural refractories as well as lining materials. Young’s modulus of elasticity (E) is a crucial parameter for the calculation of thermal shock resistance.
For all investigated carbon-bonded alumina composition a significant increase of E was observed. This increase was attributed to a mismatch of the coefficient of thermal expansion of the composite constituents. Besides others, the graphite content as well as the maximum alumina particle size were identified as crucial factors influencing E(T). Furthermore, the influence of the porosity on E was shown and existing models were fitted to the experimental data for future predictions of E. Finally a metal melt filter structure was investigated to investigate the relationship between its strut Young’s modulus and the structures’ E at high temperatures. Further research should address the filter topic since it was uncertain how to find the normal modes of those structures.
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Maknickas, Algirdas. "Modelling of elasticity properties of solids by the discrete element method." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090713_142127-91304.
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Development of numerical methods and computation environments opened the possibility of new, more sophisticated mechanical objects modelling. In this context it is natural desire of the researchers to describe macroscopic mechanical characteristics of the materials
by their microstructure, which can be adapted for simulation of the existing and future materials. For this purpose researchers are using intensively experimental
and numerical methods for the development of which the highest priority is given. Numerical experiments are used because they are cheaper and allow the interpretation of already known results of experiments and provide information
to new investigations. One of the methods used for modelling of macroscopic properties modelling is based on microscopic properties of material is discrete element
method (DEM). The DEM traditionally was applied for the granular materials. The basic idea of DEM is that any physical structure could be described as a system of moving particles. This idea could be also applied to the description of solid deformable body. Particles forming solid body and existing interaction between them are of different nature than the granular materials because their
models are often the result of physical and mathematical abstraction. The modelling of solid deformable body with the discrete elements is just at the initial stage and the unified approach to discrete elements models doesn’t exist. There are several versions of models, based on... [to full text]<br>Tobulėjant skaitiniams metodams ir kompiuterinei technikai atsivėrė galimybė naujų, sudėtingesnių mechaninių objektų modeliavimui. Turėdami naujus sudėtingesnių objektų modelius tyrėjai gali pritaikyti aprašytas ir sumodeliuotas šių objektų savybes su mikro struktūros ypatumais esamų ar busimų savybių nustatymui bei naujų medžiagų kūrimui. Tam intensyviai naudojami kaip eksperimentiniai taip ir skaitiniai metodai, kurių tobulinimui šiuo metu yra skiriamas labai didelis dėmesys. Skaitinis eksperimentas, kaip medžiagos tyrimo būdas pasitelkiamas dar ir todėl kad yra pigesnis ir leidžia interpretuoti jau žinomus eksperimentų rezultatus, o taip suteikia žinių naujiems tyrimams.
Vienas iš metodų, kuris modeliuoja makroskopines medžiagų savybes remdamasis medžiagos mikro savybėmis yra diskrečiųjų elementų metodas (DEM). DEM metodas remiasi idėja, kad bet kokia fizikinė struktūra gali būti aprašyta kaip judančių dalelių sistema. Ši idėja pradėta taikyti ir vientisam deformuojamam kūnui aprašyti. Skirtingai nuo biriųjų medžiagų, vientiso kūno dalelės ir tarp jų egzistuojančios sąveikos yra kitokios prigimties, o jų modeliai yra fizikinės ir matematinės abstrakcijos rezultatas.
Vientiso deformuojamo kūno modeliavimas diskrečiais elementais yra tik pradinėje stadijoje, o vientiso požiūrio į diskrečių elementų modelius dar nėra. Yra kelios hipotetinės versijos, grindžiamos skirtingais požiūriais. Taikant DEM kūnui, pirmas žingsnis būtu tampriųjų savybių modeliavimas. Tai yra... [toliau žr. visą tekstą]
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Mao, Baimin. "Predicting resilient modulus of highway subgrade soils in Ohio." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1179257407.
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Xu, Yichao. "Investigation of Effects of Moisture Susceptibility of Warm Mix Asphalt (WMA) Mixes on Dynamic Modulus and Field Performance." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/111.
Full textAbstract:
Residual moisture from incompletely dried aggregates would most likely remain in the Warm Mix Asphalt (WMA) due to its lower production and compaction temperature, resulting in harmful effects on field performance. Dynamic modulus has been recognized as a parameter that reflects the overall behavior of asphalt mixtures and possesses promising correlations with field performance. This study aims to investigate the effects of moisture susceptibility of WMA on dynamic modulus and simulate the field performance with the aid of Mechanistic-Empirical Pavement Design Guide (MEPDG) software. Four distinct sets of WMA specimens were prepared as follows: 1. fully dried aggregates without moisture conditioning; 2. fully dried aggregates with moisture conditioning; 3. incompletely dried aggregates without moisture conditioning; and 4. incompletely dried aggregates with moisture conditioning. Simple Performance Test (SPT) was employed to collect the raw data of dynamic modulus tests and master curves were constructed from the reduced data using Hirsch model. The results show that moisture can negatively influence the dynamic modulus values and moisture conditioning had more effect than residual moisture from incompletely dried aggregates. Two types of distress, fatigue cracking and rutting, were analyzed in the simulation. Moisture can significantly decrease the resistance against rutting and to a lesser extent, the resistance against fatigue cracking.
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Briggert, Andreas. "Fibres orientation on sawn surfaces : Can fibre orientation on sawn surfaces be determined by means of high resolution scanning." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-34979.
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In 2013 the European journal of wood and wood products published an article regarding a new method to predict strength in structural timber (Olsson et al 2013). By determining the fibres orientation on all four surfaces of each board in sample of timber using a high resolution scanner the authors were able to achieve a coefficient of determination, R2, as high as 0.71 between bending strength and a new indicating property (IP). For the same sample of timber Olsson et al (2013) determined the R2 by axial dynamic excitation as 0.59. However, all boards used in their investigation were planed before scanning. This study examines if a high resolution scanner could be used to determine the fibre orientation on the surfaces of sawn timber boards of Norway spruce. Both band sawn surfaces and circular sawn surfaces were examined. The procedure in this investigation is described as follows. Firstly, both the band sawn and the circular sawn boards were scanned by a WoodEye® scanner and together with dimensions, weight and the first longitudinal resonance frequency, a modulus of elasticity (MOE) profile was calculated for each board. The MOE profiles were calculated according to Olsson et al (2013) i.e. by a transformation matrix based upon the fibres orientation and a compliance matrix based on material parameters for Norway spruce. Secondly, the corresponding MOE profiles were then determined after the boards had been planed. As a result two MOE profiles were determined for each board. An indicating property (IP) was defined as the lowest value along each MOE profile. To compare the results a regression analysis was performed in which the IPs defined before planing worked as predictor variable and IPs defined after planing worked as response variable. The band sawn band boards yielded an R2 = 0.94 and the circular sawn boards an R2 = 0.93. Further the standard error of estimate was SEE = 829.1 MPa and SEE = 640.9 MPa respectively. As a last step in this investigation the SEE values achieved in this study where implemented on to the sample Olsson et al (2013) used in their investigation.
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Axson, Daniel Peter. "Ultimate Bearing Strength of Post-tensioned Local Anchorage Zones in Lightweight Concrete." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/33711.
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Currently, NCHRP Report 356 has published an equation to estimate the ultimate strength of the
local zone in normal weight concrete. The local zone is the area of concrete directly ahead of the
bearing plate. The equation can be broken into two distinct parts: unconfined bearing strength of
concrete enhanced by the A/Ab ratio and the enhancement of strength due to the presence of
confining. Research has shown that the strength enhancement of the A/Ab ratio and confining
reinforcing is less in lightweight concrete than in normal weight concrete.
To determine the strength of the local zone in lightweight concrete 30 reinforced prisms, 2
unreinforced prisms, and concrete cylinders were tested. The dimensions of the prisms were 8
in. x 8 in. x 16 in. and the cylinders were 4 in. x 8 in. cylinders. The simulated reinforcing in the
prisms extended only through the top 8 in. of the prism and consisted of either ties or spirals with
different spacing or pitch, respectively. To determine the effect of the A/Ab ratio for each
spacing or pitch arrangement of the reinforcing, one of two different size bearing plates were
used.
From the testing performed in this research and other research, it is apparent that the NCHRP
equation is unconservative when estimating the ultimate strength of the local zone in lightweight
concrete. By modifying both parts of the NCHRP equation it is possible to conservatively
predict the ultimate strength of the local zone in lightweight concrete.
Also investigated in this thesis are equations to predict the splitting cylinder strength and
modulus of elasticity of lightweight concrete. For a sand-lightweight concrete, as defined by
ACI 318-05 Building code and Commentary, the splitting tensile strength can be accurately
predicted by multiplying the square root of the compressive strength by 5.7.<br>Master of Science
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Chang, Liu. "Surface elasticity models for static and dynamic response of nanoscale beams." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/20125.
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Nanoscale beam-like structures have attracted much attention due to their superior mechanical properties for applications in nanomechanical and nanoelectromechanical systems (NEMS). Nanoscale structures are characterized by a high surface to volume ratio. The elastic response of surface layers of atoms is different from that of the bulk atoms due to reduced connectivity. Thus, surface energy has a significant effect on the response of nanoscale structures, and is associated with their size-dependent behavior. The classical continuum mechanics fails to capture the surface energy effects and hence is not directly applicable at nanoscale. To overcome this limitation, modified continuum models incorporating surface energy effects need to be developed in order to evaluate the size-dependent mechanical response of nanoscale structures.
This thesis presents a modified continuum model and finite element formulation to study the static and dynamic response of nanoscale beams. The objective is to provide NEMS designers with an efficient set of tools that can predict static deflections, natural frequencies of vibrations, and uniaxial buckling loads of nanoscale beams with different geometries, applied forces, and boundary conditions. A general beam model based on Gurtin-Murdoch continuum surface elasticity theory is developed for the analysis of thin and thick beams of arbitrary cross-section. Closed-form analytical solutions for static bending of thin and thick beams under different loadings and boundary conditions are obtained. Their free vibration characteristics are also investigated. Analytical expressions for critical buckling loads of thin beam are presented. An intrinsic length scale depending on both surface and bulk elastic properties is defined to characterize surface energy effects in beam bending problems. The finite element simulation results of static bending, free vibration and axial buckling of nanoscale beams are compared with the analytical solutions for validation. Selected numerical results are presented for aluminum and silicon beams to demonstrate their salient response features. A technique is proposed to estimate surface elastic properties from measured natural frequencies of GaAs cantilever specimen. The surface elasticity continuum mechanics and finite element models developed in this work provide designers efficient tools to predict mechanical response of beam structures in nano devices.
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Pokluda, Radim. "Stavební recykláty pro stmelené směsi vozovek." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226040.
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In the theoretical part of the thesis are generally characterized hydraulically bound mixtures, their types, classification systems, manufacturing technology and the laying. There are also described experiences from abroad with the use secondary and recycled materials in hydraulically bound mixtures. The practical part deals with the experimental verification of the possibility of the use of secondary materials in hydraulically bound mixtures in construction of road infrastructure. In road laboratory Institute of road structures Brno university of technology was the five proposed mixtures, an assessment of their parameters with regard to the possibility of using these mixtures in the road sub-base layers. The work is also aimed at comparison of results elasticity modules reached laboratory testing and experimental measurements on road polygon.
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Zhu, Ling. "Dynamic inelastic behaviour of ship plates in collision." Thesis, University of Glasgow, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324960.
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Bayoglu, Flener Esra. "Soil-structure interaction for integral bridges and culverts." Licentiate thesis, KTH, Civil and Architectural Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1715.
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