Esta pesquisa apresenta um estudo investigativo da análise modal aplicada a Sistemas de Distribuição (SDs) frente às distorções harmônicas, no contexto da Qualidade da Energia Elétrica (QEE). A partir do método de análise da ressonância modal, foi conduzido um estudo investigativo para apontar quais barramentos são mais sensíveis e permitem uma melhor observação frente às distorções harmônicas. Vale adiantar que o método de análise de ressonância modal, o qual é fundamentado na decomposição espectral da matriz de admitância do sistema elétrico, já apresenta interessantes trabalhos voltados para sistemas de transmissão. O desafio desta pesquisa foi então investigar a sua aplicação para SDs com um direcionamento às distorções harmônicas, bem como ao seu monitoramento. Dentre os resultados encontrados no desenvolvimento da pesquisa, destaca-se um melhor entendimento do problema das distorções harmônicas, o qual permitiu evidenciar a sensibilidade e a observabilidade dos SDs testes frente ao problema definido no contexto da QEE. / This research presents an investigative study of the modal analysis applied to Distribution Systems (DSs) in the context of Power Quality (PQ) considering the harmonic distortions. From the modal resonance analysis, an investigative study was conducted to indicate which bus bars are more sensitive and allow better observation in face of harmonic distortions. It is worth mentioning that the method of modal resonance analysis, which is based on the spectral decomposition of the admittance matrix of the electric system, already presents interesting applications focused on transmission systems. The challenge of this research was to investigate its application to DSs focusing on harmonic distortions, as well as their monitoring. Among the observed results of the research development, a better understanding of the harmonic distortions problem was achieved, which made it possible to highlight the sensitivity and observability of the DSs tests against the problem defined in the context of the PQ.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-09-22T20:32:01Z No. of bitstreams: 2 Lara Rodrigues.pdf: 17878503 bytes, checksum: a51778a9fbf6a31b2a71fe0c9c462105 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2014-09-23T15:24:03Z (GMT) No. of bitstreams: 2 Lara Rodrigues.pdf: 17878503 bytes, checksum: a51778a9fbf6a31b2a71fe0c9c462105 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-09-23T15:24:03Z (GMT). No. of bitstreams: 2 Lara Rodrigues.pdf: 17878503 bytes, checksum: a51778a9fbf6a31b2a71fe0c9c462105 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-02-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The aim of this work is to investigate the interaction and modal coupling phenomena on the nonlinear vibrations of simply supported cylindrical shell subject to both harmonic axial and lateral loads. The equations of motion of the cylindrical shell are deduced from their energy functionals and the strain field is based on the nonlinear Donnell shallow shell theory. Finally, the problem is reduced to a system of nonlinear ordinary differential equations by the application of the standard Galerkin method. The modal expansion that describes the transverse displacement of the shell is obtained by applying perturbation techniques, which identifies the importance of each term in the modal expansion by the power of the perturbation parameter. The Karhunen-Loève method is applied in order to verify the importance of each term in the modal expansion, quantifying the contribution of each of these terms in the total energy of the system. The starting solution used in the perturbation procedure contains two modes of vibration with the same natural frequency and their respective companion modes, yielding a modal expansion able to describe the modal interaction between these two modes. Then, the influence of modal interaction on the nonlinear behavior of the cylindrical shell, subjected to both lateral and axial harmonic load is studied. From the analysis of the resonance curves, the parametric instability and escape boundaries, the bifurcation diagrams, the basins of attraction and phase portraits of the cylindrical shell is possible to identify situations in which the consideration of modal interaction is necessary. / Neste trabalho estudam-se as vibrações não lineares de cascas cilíndricas simplesmente apoiadas sujeitas a um carregamento lateral e a um carregamento axial, ambos harmônicos, com o objetivo de se analisar fenômenos como o acoplamento e a interação modal. As equações de movimento da casca cilíndrica são deduzidas a partir de seus funcionais de energia. O campo de deformações da casca cilíndrica é descrito com base na teoria não linear de Donnell para cascas esbeltas e o problema é reduzido a um sistema de equações diferenciais ordinárias não lineares a partir da aplicação do método de Galerkin. As expansões modais que descrevem o campo de deslocamento transversal da casca são obtidas através da aplicação do método da perturbação, que identifica a importância de cada termo da expansão modal a partir da potência do parâmetro de perturbação. O método de Karhunen-Loève é aplicado a fim de se verificar a importância de cada termo da expansão modal, quantificando a participação de cada um desses termos na energia total do sistema. Utilizam-se, como solução inicial do método da perturbação, dois modos de vibração com frequência natural igual e com seus respectivos companion modes, obtendo-se uma expansão modal capaz de descrever a interação modal entre esses dois modos. Em seguida, analisa-se a influência da interação modal no comportamento não linear da casca cilíndrica submetidas a cargas laterais e axiais harmônicas. A partir da análise das curvas de ressonância, das fronteiras de instabilidade paramétrica, dos diagramas de bifurcação, das bacias de atração e dos planosfase da casca cilíndrica é possível identificar em quais situações de carregamento a consideração da interação modal se faz necessária.

Ingeniero Civil / La ingeniería civil en Chile está constantemente generando avances en diseño y modelación de estructuras. En este sentido, los softwares de análisis estructural son herramientas muy importante y ampliamente utilizadas en el rubro. El objetivo de este trabajo es dejar una contribución a una de estas plataformas, SAFE_TB. Ésta fue creada por Rojas en 2012 y ha sido utilizada en docencia e investigación hasta la fecha. El objetivo de este trabajo es complementar la plataforma SAFE_TB implementando una nueva opción de análisis, el análisis modal espectral. Este es una metodología simplificada de análisis dinámico muy utilizada en diseño. Muchas normas alrededor del mundo recomiendan su uso, incluida la norma de diseño sísmico de edificios en Chile, NCh 433. La plataforma SAFE_TB, se encuentra desarrollada utilizando la metodología de programación orientada a objetos, por lo tanto, todas las clases incorporadas para el desarrollo del análisis deben ser compatibles con las clases originales. También la organización de las funciones del análisis modal espectral, siguen la estructura de los demás tipos de análisis ya incorporados a la plataforma. Paralelo al desarrollo del análisis, se desea incorporar a la plataforma, la opción de incluir restricciones de puntos múltiples del tipo diafragma rígido. Estas, son ampliamente utilizadas ya que asimilan el comportamiento de las losas de hormigón armado en edificios.

Abstract not available

In this study, a systematic approach was adopted to investigate, numerically and experimentally, localised defects and/or damage in timber bridges, such as rot, using modal based damage detection techniques. An existing damage detection method namely damage index (DI) method that utilises modal strain energy before and after damaged state was adopted. One contribution of this study was to modify the Dl method by an additional step of normalising the modal curvature, which would minimise the dominance of higher modes. In the numerical models, a comparative study of the effects of numerical integration techniques used in a damage detection process was carried out. The results show that when mode shape curvature integrations use the rectangular rule for the numerical integration, it yields better results than the trapezoidal rule. In the numerical examples using a finite element model of timber beam, the modified DI (MDI) methods were found to perform better than its original form for locating'" single and multiple damage scenarios. For the DI methods, two types of formulations were adopted and modified, and they are denoted as modified damage index I (MDI-I) and modified damage index II (MDI-II). Another modal based damage detection method, namely changes in flexibility (CIF), was adopted for locating damage. It was found that the ClF method performed reasonably well for single damage but not multiple damage scenarios. As part of the study, the modified damage index methods were utilised for evaluating severity of damage. For the :MDI-I method, the formulation was not derived to evaluate damage severity directly. Instead, a hybrid of the MDI-I and CIF methods (HMC), was proposed for evaluating severity of damage in terms of loss of '1' (moment of inertia). Using three levels of damage, i.e. light (L), medium (M) and severe (S), the HMC method is able to predict the medium and severe damage quite well, but it is less efficient for light damage scenarios. For the MDI-II method, further manipulation of the algorithm can predict the severity of damage in terms of loss of'I'. This method is able to predict the medium and severe damage quite well but is not as good for the light damage. Both methods, HMC and MDI-II, for predicting severity of damage, required some adjustment using a weighting factor in order to obtain reasonable results. An experimental modal analysis (EMA) test program of timber beams was undertaken. This was done to verify the robustness of the modified damage index methods for detecting location and estimating severity of damage. The laboratory investigation was conducted on the corresponding changes of modal parameters due to loss of section. The MDI methods were used to detect location of damage and to evaluate the severity of damage in the test beams. A mode shape reconstruction technique was utilised to enhance the capability of the damage detection algorithms with limited number of sensors. The test results and analysis show that location of damage is quite accurately estimated with the available sensors. The methods demonstrate that they are less mode dependant and can detect damage with a higher degree of confidence. The MDI methods also show that they are able to predict the severe damage well, but it is less accurate for the medium damage and not as good for light damage. The damage index II (DI-II) method extended to plate-like structures (DI-II-P) was adopted and evaluated for detecting damage. Based on finite element analysis (FEA) results of a laboratory timber bridge, the DI-II-P method which utilises two dimensional (2-D) mode shape curvature was employed to detect location of damage. The results show that the tnethod based on 2-D mode shape curvature is able to locate damage quite well, numerically. A supplementary work using the DI-II-P method in a timber plate model was carried out. The results also show that the method was able to predict the damage location well. A process of updating a laboratory timber bridge, analytically, is presented. A finite element model was developed and updated with experimental modal data. Material properties of timber beam (girders) and plywood (deck) as well as the screw connection between deck and girder were experimentally investigated. These test results were then used for the finite element modelling. The model has been developed sequentially starting with a preliminary model having very simple features. It followed by the advanced model calibrated with the experimental modal data employing a global objective function, consisting of errors of natural frequencies and modal assurance criterion. The calibrated finite element model shows a good correlation to the experimental model with minor adjustments to the real material properties and boundary conditions. The calibrated model can reasonably be used to study the damaged behaviour of the laboratory timber bridge. The bridge model was then used to verify the numerical results for detecting damage. The bridge was inflicted with various damage scenarios with loss of section similar to the timber beam models. The limited number of data was expanded using the 2-D cubic spline. Using the reconstructed data for detecting damage yields better results than just using 'as is' data. Using the undanlaged and dmnaged modal data, the D I-II -P method was employed to detect the location of damage. The results of using the first nine modes showed that generally the severe damage is able to be located by the method. It performs reasonably well for the medium damage but does not perform as good in the light damage scenarios. However, in some cases the method can present some problems in identifying severe damage, which may be due to lack of normalisation of mode shape curvature. Complementary work was undertaken using the method 'On a timber plate, experimentally. The results showed that the damage detection process in the timber plate is less efficient compared to the laboratory timber bridge. A comprehensive comparative study was carried out based on the results of the numerical and experimental investigation of damage detection on timber beam, laboratory timber bridge and timber plate. For the timber beam, both damage detection methods, MDI-I and MDI-II, were capable of detecting medium and severe damage in the numerical and experimental studies. However, the light damage was not identified well using the experimental data in the presence of noise. To estimate damage severity in the timber beam, the HMC method performed well for the medium and severe damage. The method did not work well in estimating severity of light damage. Similar conclusions can be drawn in using the MDI-II method to estimate the damage severity. The results of applying the DI-II-P method (using 9 modes) to locate damage in the laboratory timber bridge showed that numerical and experimental data are capable of detecting all severe damage for damage cases with less than three damage locations. While for light and medium damage, the experimental data did not work well as compared to the numerical one. For the timber plate (a complementary work), the numerical and experimental results also showed that they are able to detect the severe damage well. However, there were serious false positives appearing in the light damage cases in the experimental results.

The original design of a water-washed air cleaner, which developed by industry, only takes external design and assemblage into account, but the analysis of the overall performance wasn¡¦t studied. The air in the original water-washed air cleaner doesn¡¦t flow smoothly, which cause the inefficiency of the inlet and outlet flow, so there is a necessity to improve its performance. At beginning of this thesis study, the researcher designed the shape of the blades, and then analyzed the internal fluid field of the water-washed air cleaner. He also studied the impact of the efficiency of the aperture of diaphragm and the gap between blade and diaphragm. Finally, he obtained a series of result of simulation with simulating flow field produced by CFD to find out the best shape and amount of blades. The outlet flow performs better when £] is greater. However, when extreme values are between 50 degrees to 60 degrees, the smaller inclination of blade has better efficiency of the outlet flow. The amount of blades is not always positive to the efficiency. When the number of blades is more than 9, there is no significant increase of the outlet flow. The larger aperture of diaphragm has better efficiency, and decreases the gap between the blade and the diaphragm can increase outlet flow. Finally we obtained the result of optimization efficiency by Taguchi Method. After designing the best water washed air cleaner, the vibration is also simulated. The result of simulation showed that the nature frequency of overall structure is much higher than motor¡¦s, so that would not cause the resonant vibration.

Thesis (M.Eng.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves 135-140.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Young Shin, Ilbae Ham. Includes bibliographical references (p. 63). Also available online.

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