In this study, experimental modal analysis was studied. Experimental modal analysis includes modal testing, modal parameter estimation and calibration. For this purpose a 4 span skewed steel frame was constructed in Structural Mechanics Laboratory of Civil Engineering Department of METU. The model was transported to Vibration and Acoustic Laboratory of Mechanical Engineering Department of METU. The tests were conducted by cooperation with Vibration and Acoustics Laboratory. Due to lack of experimental modal analysis software in Structural Mechanics Laboratory, modal parameter estimation and finite element updating softwares were written in Matlab platform. The written softwares were executed on the data obtained from modal testing. 15 reasonable modes are extracted from the FRFs that are obtained from modal testing. 59.23 percent consistency is found for the nominal modal comparison. At the end of calibration process 76.14 percent consistency is achieved between the experimental results and analytical results.

Made available in DSpace on 2014-07-29T15:06:24Z (GMT). No. of bitstreams: 1 RENATO MENDES ROCHA.pdf: 735741 bytes, checksum: 6559707c78ce13d85086e58b691dd7f3 (MD5) Previous issue date: 2010-08-30 / In this dissertation we will defend Lewis Modal Realism (LMR), i.e., the metaphysical hypothesis about the real existence of a plurality of worlds. We will try to show the pragmatic character of Lewis arguments in support of this metaphysics of possible worlds. In this sense, we approximate Lewis (1986) and Quine (1960) and we aim to show that Lewis uses criteria for taking ontological decisions similar to those defended by Quine. These criteria are: simplicity of formulation, theoretical economy and distrust in purely intuitive criteria as only guide for Philosophy. To accomplish our intention, we divided the text in three chapters. In the first we present the philosophical benefits of LMR that demonstrate the theoretical utility of possible-worlds talk. These benefits are related to important concepts in Philosophy of Language and Epistemology, such as, Modality, Counterfactuals and a uniform treatment to Properties and Propositions. The second chapter is divided into two parts. At first we present the philosophical background we believe is related to Lewis philosophy. A neo-humean scenario and the resumption of metaphysics discussion in contemporary analytic philosophy compose this background. In the second part we present three fundamental thesis formulate by Lewis the consistence of his Modal Realism: concreteness, isolation and plenitude. In the third and latter chapter we discuss two criticism of LMR: (a) David Armstrong & Peter Forrest (1984) and (b) Susan Haack (1977). Each of these papers present criticism from distinct points of view. The first aims to identify a paradox in the metaphysics of possible worlds, and the latter focuses on semantics aspects of LMR. Finally, we show Lewis reply to objection (a) and that argument (b) could be inserted as an incredulous stare on LMR, and that it consists on a petition principi. / Nessa dissertação defenderemos o Realismo Modal de David Lewis (RML), ou seja, a hipótese metafísica acerca da existência real de uma pluralidade de mundos. A defesa que apresentaremos procura evidenciar o caráter pragmático dos argumentos a favor dessa metafísica dos mundos possíveis. Nesse sentido, aproximaremos a filosofia de David Lewis (1986) a de W. V. O. Quine (1960) e procuraremos mostrar que Lewis utiliza critérios para tomada de decisões ontológicas semelhantes aos defendidos por Quine. Esses critérios são: a simplicidade de formulação, a economia teórica e a desconfiança de critérios meramente intuitivos como guias para a Filosofia. Para cumprir nosso objetivo, estruturamos a dissertação em três capítulos. No primeiro apresentamos benefícios filosóficos do RML que demonstram a utilidade teórica do idioma dos mundos possíveis. Esses benefícios estão relacionados a noções importantes para a Filosofia da Linguagem e a Teoria do Conhecimento tais como: Modalidades, Contrafatuais, e um tratamento uniforme para Propriedades e Proposições. O segundo capítulo divide-se em duas partes. Na primeira traçamos um pano de fundo filosófico que acreditamos estar relacionado à filosofia de Lewis. Compõem esse pano de fundo: um cenário que identificamos como neo-humeano e a retomada de discussões metafísicas na Filosofia Analítica Contemporânea. Na segunda parte apresentamos três teses formuladas por Lewis para garantir a consistência e a coerência de seu Realismo Modal: a Concretude, o Isolamento e a Plenitude. No terceiro capítulo discutimos duas críticas ao RML: (a) David Armstrong & Peter Forrest (1984) e (b) Susan Haack (1977). Cada um desses artigos apresenta uma crítica diferente. A primeira procura identificar um paradoxo na metafísica dos mundos possíveis e a segunda concentra-se em aspectos semânticos do RML. Por fim, mostramos como a objeção em (a) é refutada por Lewis e como o argumento em (b) poderia se inserir no grupo de críticas que Lewis classifica como um olhar incrédulo sobre o RML. Por isso, concluímos que esse olhar consiste em uma petição de princípio.

O presente trabalho tem como objetivo desenvolver novas alternativas de identificação modal para estruturas sob excitações em condição de operação baseadas em funções de transmissibilidade. Recentes metodologias formuladas sobre conceitos de transmissibilidade têm surgido como alternativa para a identificação de parâmetros modais de estruturas. A identificação nestas metodologias é independente do espectro da excitação, sendo uma vantagem importante com respeito a metodologias anteriores no domínio da frequência que supõem a excitação como ruído branco. Dessa forma, aproveitando os diferentes trabalhos dirigidos a avaliar parâmetros modais com uso da transmissibilidade, são propostas três novas alternativas. A primeira delas propõe a decomposição de valores singulares sobre matrizes de funções de transmissibilidade escalar com densidade espectral para estimar frequências naturais e modos de vibração. A segunda alternativa propõe o conceito de funções de transmissibilidade multivariável com diferente referência para a identificação modal. E a terceira introduz uma melhora na primeira alternativa incluindo a possibilidade da estimação de taxas de amortecimento. Uma ferramenta computacional para a análise modal é desenvolvida como apoio para as simulações numéricas de verificação das metodologias de identificação modal propostas. Diferentes exemplos numéricos com uma viga submetida a excitações de ruído colorido mostram que os métodos propostos são capazes de identificar parâmetros modais sem a introdução das frequências adicionais devido às excitações de ruído colorida utilizadas. Além disso, os dados de um teste de vibrações sobre uma ponte em operação foram utilizados para verificar os métodos. / This research aims to develop new alternatives of modal identification for structures under excitation in operation condition based on transmissibility functions. Latest methodologies based on transmissibility concepts have been arising as alternatives for modal parameter identification of structures. Modal parameter identification in this type methodology is input spectrum independent being an important advantage with respect previous frequency domain methods that assumes white noise excitation. Different alternatives of modal identification based on transmissibility functions are proposed in this work. The first of them proposes singular value decomposition on scalar transmissibility functions matrices with spectral density to estimate natural frequencies and vibration modes (PSDTM-SVD method). A second alternative proposes the concept of multivariable transmissibility functions with different transferring outputs for modal parameter identification. And the third alternative proposes an enhanced PSDTM-SVD method, which permits to identify modal damping. Computational tool for modal analysis is developed as a support for the numerical simulations of verification of modal identification methodologies proposed. Different numerical examples of a beam model subjected to colored noise excitations show that the proposed methods are capable of identifying modal parameters without the introduction of the additional frequencies due to the excitations used. Furthermore, data from an operational vibration bridge test were used to verify the methods.

Este trabalho propõe uma metodologia para escolha de modal de transporte a partir da aplicação do método de análise hierárquica a um conjunto de critérios levando em consideração o ponto de vista dos donos da carga. Parte-se de uma pesquisa de critérios adotados na escolha de modal sob contextos que incluem variação de cargas avaliadas, de disponibilidade de infraestrutura e serviços logísticos. Avalia-se ainda o método de análise hierárquica, AHP, que permite a decisão multicriterial com fatores quantitativos e qualitativos. Propõe-se uma metodologia de escolha de modal considerando o que é importante para o embarcador baseado no método AHP. Os critérios levantados na literatura são condensados em um conjunto hierarquizado de 3 critérios (custo logístico total; atendimento a particularidades da carga; e confiabilidade) e 7 subcritérios (custo logístico total; acessibilidade, flexibilidade, e oferta de instalações logísticas; pontualidade, perdas e danos, e informações ao cliente). A metodologia resultante é genérica e pode ser aplicada a um conjunto abrangente de situações logísticas. A título de exemplo, a metodologia é aplicada a três casos de transporte, para a escolha entre a alternativa rodoviária direto ou intermodal com ferrovia, variando-se a distância (média ou longa distância) e a carga transportada (açúcar a granel ou contêiner, para exportação). Os resultados são comparados e discutidos em termos dos pesos relativos dos critérios na escolha do embarcador, e das respectivas contribuições à decisão em face dos atributos das alternativas. Conclui-se que a avaliação multicriterial, contemplando critérios quantitativos e qualitativos, proporciona uma análise abrangente da hierarquia e contribuição dos critérios e a distinção dos pontos críticos na competição entre modais. / This study proposes a method for determining modal choice in transport problems based on an analytic hierarchy technique, considering the cargo owners point of view. Initially, a research of criteria used in modal choice in several contexts is carried out: cargos evaluated, availability of infrastructure and logistic services, standpoint of the evaluator. A review of the AHP method (which allows for multicriterial decisions with qualitative and quantitative factors) ensues. The author proposes a method for assisting in the modal choice from the cargo owners standpoint, based on the AHP technique. The criteria collected from the literature review are condensed in a hierarchical set of 3 criteria (total logistic costs; compliance with specificities of the cargo; and reliability) and 7 subcriteria (total logistic costs; accessibility, flexibility, and availability of logistic facilities; timeliness, susceptibility to loss or damage; and information to customers). The resulting method is generic and can be applied to a comprehensive range of logistic situations. The proposed method is then applied, as an example, to three freight cases, to aid the modal choice between direct roadway transportation or intermodal transport based on rail freight, with varying distances (medium or long distance haul) and the cargo being transported (bulk sugar or container, both for export). The results are compared and discussed in terms of the relative weights of each of the 7 subcriteria in the cargo owners modal decision, and the respective contributions to the decision in light of the attributes of the alternatives. The study concludes that the multicriterial evaluation, contemplating quantitative and qualitative criteria, yields a more comprehensive analysis of the important criteria hierarchy and the distinction of key issues in modal competition.

The aim of this study is to examine to what extent Swedish writers, who write in English, use the modals must, have to and have got to. The hypothesis being tested argues that the core modal must is not being challenged by the emerging modals have to and have got to in this non-native variety of English. The objective of this thesis is to be accomplished by attempting to answer the following research questions: 1) What is the frequency and usage of the English modals must, have to and have got to in the material? 2) How do the frequencies in the Swedish material compare with the frequencies in the British and American corpora and to the previous studies? 3) How do the Swedish writers use the modals with regard to epistemic and deontic meaning? The study is corpus based, and the corpora used consist of Swedish newspapers in English (SWENC) and material from blogs and tweets which are written in English by Swedes (SESMC). These are compared with the press sub-corpora in BE06 (the British 2006 corpus of CQP web at Lancaster) and in AE06 (the American 2006 corpus of CQP web at Lancaster), which represent British and American native varieties of English. The method is quantitative and the results are presented after the process of normalization. The results show that must, have to and have got to are used in SWENC and SESMC although, to greatly varying degrees. The core modal must is more frequently used in the Swedish corpus than in the British and American sub-corpora. The emerging modal have to is used more frequently than must in all three corpora. The second emerging modal have got to is very seldomly used. Additionally, a qualitative examination of the modals and their meanings reveal that the writers in SWENC and SESMC use the older modal must alongside the newer have to and newest modal have got to, but with a preference for a toned-down style of language. The conclusion drawn is that the core modal must is indeed being challenged by the emerging modal have to even in the non-native variety of English.

This thesis deals with a vibration diagnostics of objects, structures and machines. The theoretical part is divided into three chapters according to type of the measurement. The first part called Modal Analysis discusses the basis of vibration, methods of measurement, relevant technical equipment and principle of experimental modal analysis. The second and third chapters of the thesis are focused on the diagnosis of defects. Each chapter mentioned above describes diagnosed defects, used methods and procedure for the diagnosis. Another part of the thesis summarizes practical issues and results gained in the laboratory experiments. It begins with discovering parameters of the measured object using technical diagnostics – experimental modal analysis. In the next step the hardware concept design was created, including custom measuring application programmed in LabVIEW. One part of the design is the laboratory model which includes a structure for free mounting and a possibility of excitation by an electrodynamic exciter. The application is also modified to enable measurements with shaker excitation. Finally, applications cooperating with professional software ModalVIEW and BK Connect were developed in order to simplify the operation and increase the comfort.

The aim of this diploma thesis is a creation of modal parameter estimation application. Modal properties (natural frequencies, damping factors and mode shapes) are used in many dynamics analysis and their accurate determination is very important therefore the modal parameter estimation is one of the most significant part of the experimental modal analysis. Many methods have been developed for modal parameter estimation, each of them with different assumptions and with different accuracy. In the beginning of this thesis, a theory connected with modal analysis and a theory which is necessary for understanding to presented modal parameter methods are given. Then four different modal parameter estimation methods are presented - Peak Picking, Circle Fit, Least Square method and Eigensystem Realization Algorithm. The application for the modal parameter estimation is the output of this diploma thesis. In addition, the application allows performing all experimental modal analysis such as estimation of frequency response functions, animation of the found mode shapes, different kinds of comparison etc. In the conclusion, three structures are shown on which the application and modal parameter estimation methods were tested.

Cieľom tejto diplomovej práce je predstavenie Experimentálnej modálnej analýzy a štúdium a použitie algoritmov pre výpočet modálnych parametrov z odmeraných vibrácií pri Experimentálnej modálnej analýze. Bodom záujmu sú predovšetkým algoritmy, pracujúce s odmeranými dátami v časovej oblasti. Diplomová práca sa zaoberá programovaním algoritmu ITD a jeho implementáciou pre Experimentálnu modálnu analýzu. Ďaľšou časťou práce je štúdium citlivosti algoritmu na okrajové podmienky meranej sústavy pri výpočte modálnych parametrov a štúdium možnosti využitia algoritmu pri Operačnej modálnej analýze.

[pt] Nessa dissertação, são avaliados os comportamentos crítico e pós-crítico de uma placa retangular fina, simplesmente apoiada, sob compressão. Um modelo não-linear para placas perfeitas e com imperfeições é desenvolvido com base na teoria não-linear de placas proposta por Marguerre. O modelo discretizado possui dois graus de liberdade que são caracterizados pela flambagem em m e (m+1) meia-ondas senoidais na direção do carregamento. Obtém-se analiticamente soluções desacopladas e acopladas através de programas de álgebra simbólica (Maple V Realese 4). Realiza- se um detalhado estudo paramétrico visando identificar todas as possíveis configurações de equilíbrio e, para cada configuração determinada, analisa-se sua estabilidade. É também estudada a influência de imperfeições geométricas iniciais, tanto na superfície de energia quanto no número e estabilidade das soluções. Os resultados mostram que o acoplamento modal tem uma grande influência sobre o comportamento pós-crítico destas placas, podendo provocar mudanças bruscas dos modos de flambagem. Finalmente, é analisada a influência das imperfeições e tensões de compressão inicias nas freqüências naturais da placa, mostrando como estas freqüências podem ser utilizadas para determinar cargas críticas sem a necessidade de execução de ensaios destrutivos. / [en] The buckling and post buckling behavior of simply supported thin rectangular plates in axial compression is considered in this dissertation. A non- linear model for perfect and imperfect plates is developed based on Marguerre non-linear plate theory. The discretized model is considered as having two degrees of freedom characterized by buckling in m and (m+1) halfsinewaves axially and uncoupled and coupled solutions are obtained analytically by the use of symbolic algebra software. A detailed parametric study is conducted to identify all possible equilibrium solutions and establish their stability. The influence of initial geometric imperfections on the energy surface, number and stability of solutions is taken into account as an indispensable part of the analysis. The results shown that modal coupling has a strong influence on the post-buckling behavior of these plates and may explain abrupt changes of waveform of plates in the post-buckling range. Also, the influence of imperfections and initial compressive stress on the natural frequencies of the plate is analyzed and it is shown how these frequencies can be used to estimate safe buckling loads of rectangular plates non-destructively. / [es] Este trabajo presenta un análisis experimental de cinco vigas de concreto, simplemente apoyadas, protendidas con cables sintéticos externos, con el objetivo de estudiar la influencia de la resistencia del concreto en la variación de la fuerza de los cables de protensión y en la resistencia a la flexión de las vigas. La protensión de las vigas fue hecha con cables sintéticos conocidos como Parafil, con resistenciaa la tracción de 1950MPa y módulo de elasticidad de 126000MPa. La única variable considerada fue la resistencia del concreto, cuyos valores fueron 36, 57, 73, 74 y 104MPa. El concreto de las vigas con resistencia de 57, 73, 74 y 104MPa fueron construidos con el uso de la microsílica y aditivo superplastificante, con excepción de la viga con resistencia de 36MPa que fue construida con concreto común. Los resultados mostraron que la influencia de la resistencia del concreto sobre la resistencia a la flexión de las vigas no es grande. Para el aumento de 189% en la resistencia del concreto, se produjo un aumento en la variación de la fuerza en el cable de apenas 13.6% y un aumento de 33% en el momento de ruptura. Comparando los resultados experimentales con los resultados de las principales normas y modelos propuestos se verificó que todos ofrecen buenos resultados y subestiman los valores experimentales. Comparando los resultados experimentales con el modelo de Campos (1993) se observó que los valores de la variación en la fuerza en el cable superestiman los valores experimentales. 1267 En esta disertación, se evalúan los comportamientos crítico y poscrítico de una placa rectangular fina, simplemente apoyada, bajo compresión. Se desarrolla un modelo no lineal para placas perfectas y con imperfecciones teniendo como base la teoría no lineal de placas propuesta por Marguerre. El modelo discretizado posee dos grados de libertad que son caracterizados al flamear en m y (m+1) medias-ondas senoidales en la dirección de sobrepeso. Se obtienen analíticamente soluciones desacopladas y acopladas a través de programas de álgebra simbólica (Maple V Realese 4). Se realiza un detallado estudio paronétrico tratando de identificar todas las posibles configuraciones de equilibrio y, para cada configuración determinada se analisa la estabilidad. También se estudia la influencia de imperfecciones geométricas iniciales, tanto en la superfície de energía como en el número y estabilidad de las soluciones. Los resultados muestran que el acoplamiento modal tiene una gran influencia sobre el comportamiento poscrítico de estas placas, lo que puede provocar cambios bruscos de los modos de flamear. Finalmente, se analiza la influencia de las imperfecciones y tensiones de compresión iniciales en las frecuencias naturales de la placa, mostrando como estas frecuencias pueden ser utilizadas para determinar cargas críticas sin necesidad de ejecución de ensayos destructivos.

Today the regional railway system lacks the capacity at the central station in order to meet the demand for both the public and freight transportation. The West link is a railway infrastructure project that is expected to both increase train commuting and also increase the train capacity at the central station in Gothenburg. The purpose of this thesis work is to do an elastic demand analysis between car traffic and the West Link in modal shift to determine how many travelers will change mode. Also traffic simulations will be made to investigate the traffic conditions around the stations when the West link has been implemeted. The simulation results showed that nowadays there are congestions on the major highways and some of the smaller low capacity roads. In the future, congestions will become more significant if no countermeasures are implemented like the West link. In the elastic demand analysis the results were overall around 47% – 51% on a demand of between 350 000 – 400 000 trips. As a conclusion it cannot be said whether the West link will ease the pressure on car traffic or not. The reasons are that the population will increase about 100 000 inhabitants until 2030 and the West link is assumed by the region to have this amount of travelers each day. This would result in the same traffic pressure as today with congestions in certain parts. If the number of West link users will be around 200 000, as the results of this thesis shows, then the West link will ease the pressure on car traffic.