Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-01-05T16:51:31Z No. of bitstreams: 1 LucasDaSilvaMoraes_DISSERT.pdf: 5039451 bytes, checksum: fb1fce3fc0cb32b8b90727afb4b2b99f (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-01-08T17:38:57Z (GMT) No. of bitstreams: 1 LucasDaSilvaMoraes_DISSERT.pdf: 5039451 bytes, checksum: fb1fce3fc0cb32b8b90727afb4b2b99f (MD5) / Made available in DSpace on 2016-01-08T17:38:57Z (GMT). No. of bitstreams: 1 LucasDaSilvaMoraes_DISSERT.pdf: 5039451 bytes, checksum: fb1fce3fc0cb32b8b90727afb4b2b99f (MD5) Previous issue date: 2014-11-03 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Os problemas relacionados ?s intera??es longitudinais em dutos enterrados se caracterizam como tridimensionais, podendo gerar in?meras situa??es particulares no comportamento solo-duto. Em rela??o ao avan?o nas pesquisas na ?rea de dutos enterrados, ainda ? pequena a aten??o ao tema ao longo das ?ltimas d?cadas, visto que a maioria dos trabalhos simplifica o problema analisado considerando-o em deforma??o plana. O presente trabalho tem como objetivo apresentar um estudo sobre o comportamento de dutos enterrados sujeitos a eleva??o ou recalque localizado, atrav?s de simula??es num?ricas em tr?s dimens?es. Como ferramenta num?rica foi utilizado o aplicativo computacional Plaxis 3D, o qual utiliza o m?todo dos elementos finitos. Foram avaliados aspectos espec?ficos da modelagem num?rica e realizadas an?lises param?tricas em que se investigaram os efeitos do arqueamento do solo de forma tridimensional. As principais vari?veis investigadas foram: densidade relativa do solo, deslocamento da zona de eleva??o ou recalque, faixa da zona elevada, altura de recobrimento e a rela??o di?metro/espessura do duto. As simula??es foram realizadas em duas etapas distintas, sendo na primeira feita a valida??o das an?lises num?ricas atrav?s dos modelos f?sicos de Costa (2005). Em seguida, foram realizadas an?lises num?ricas de um oleoduto em um caso espec?fico de obra, considerando o mesmo submetido ? eleva??o localizada. Os resultados obtidos permitiram a valida??o do modelo num?rico face aos resultados dos experimentos de Costa (2005), a iv avalia??o detalhada da redistribui??o das tens?es no maci?o e das deflex?es ao longo do duto, bem como a avalia??o do desenvolvimento do arqueamento no solo. Foi verificada a redu??o das tens?es no maci?o e nas deflex?es no duto ao se diminuir a altura de recobrimento do duto nas regi?es que possam deflagrar a eleva??o localizada. Tamb?m foi verificado que os esfor?os longitudinais foram superiores aos circunferenciais para situa??o analisada, inclusive ultrapassando as tens?es e deflex?es admiss?veis. Al?m disso, foram observados os benef?cios das t?cnicas de minimiza??o das tens?es como a falsa trincheira, ber?o compress?vel e a combina??o de ambas aplicadas ao oleoduto simulado / Problems associated to longitudinal interactions in buried pipelines are characterized as three-dimensional and can lead to different soil-pipe issues. Despite the progress achieved in research on buried pipelines, little attention has been given to the three-dimensional nature of the problem throughout the last decades. Most of researches simplify the problem by considering it in plane strain condition. This dissertation aims to present a study on the behavior of buried pipelines under local settlement or elevation, using three-dimensional simulations. Finite element code Plaxis 3D was used for the simulations. Particular aspects of the numerical modeling were evaluated and parametric analyzes were performed, was investigated the effects of soil arching in three-dimensional form. The main variables investigated were as follows: relative density, displacement of the elevation or settlement zone, elevated zone size, height of soil cover and pipe diameter/thickness ratio. The simulations were performed in two stages. The first stage was involved the validation of the numerical analysis using the physical models put forward by Costa (2005). In the second stage, numerical analyzes of a full-scale pipeline subjected to a localized elevation were performed. The obtained results allowed a detailed evaluation of the redistribution of stresses in the soil mass and the deflections along the pipe. It was observed the reduction of stresses in the soil mass and pipe deflections when the height of soil cover was decreased on regions of the pipe subjected to elevation. It was also shown for the analyzed situation that longitudinal thrusts were higher than vi circumferential trusts and exceeded the allowable stresses and deflections. Furthermore, the benefits of minimizing stress with technical as the false trench, compressible cradle and a combination of both applied to the simulated pipeline were verified

Made available in DSpace on 2014-12-17T14:48:12Z (GMT). No. of bitstreams: 1 JohnGBG_DISSERT.pdf: 5632038 bytes, checksum: eabbd6743af14f648742650469c3d48f (MD5) Previous issue date: 2012-07-02 / A numerical study on the behavior of tied-back retaining walls in sand, using the finite element method (FEM) is presented. The analyses were performed using the software Plaxis 2D, and were focused on the development of horizontal displacements, horizontal stresses, shear forces and bending moments in the structure during the construction process. Emphasis was placed on the evaluation of wall embedment, tie-back horizontal spacing, wall thickness, and free anchor length on wall behavior. A representative soil profile of a specific region at the City of Natal, Brazil, was used in the numerical analyses. New facilities built on this region often include retaining structures of the same type studied herein. Soil behavior was modeled using the Mohr-Coulomb constitutive model, whereas the structural elements were modeled using the linear elastic model. Shear strength parameters of the soil layers were obtained from direct shear test results conducted with samples collected at the studied site. Deformation parameters were obtained from empirical correlations from SPT test results carried out on the studied site. The results of the numerical analyses revealed that the effect of wall embedment on the investigated parameters is virtually negligible. Conversely, the tie-back horizontal spacing plays an important role on the investigated parameters. The results also demonstrated that the wall thickness significantly affects the wall horizontal displacements, and the shear forces and bending moments within the retaining structure. However, wall thickness was not found to influence horizontal stresses in the structure / O presente trabalho apresenta um estudo num?rico atrav?s do m?todo dos elementos finitos (MEF) utilizando-se o aplicativo computacional Plaxis 2D, com o objetivo de verificar aspectos do comportamento de estruturas de conten??o atirantadas em areia. As an?lises foram dirigidas ao desenvolvimento dos deslocamentos horizontais, das tens?es horizontais e dos esfor?os internos (esfor?o cortante e momento fletor) durante o processo construtivo da estrutura. As simula??es num?ricas inclu?ram avalia??es da influ?ncia do comprimento da ficha, do espa?amento horizontal entre os tirantes, da espessura da parede e do comprimento do trecho livre. O perfil de solo utilizado nas simula??es num?ricas ? representativo de uma determinada regi?o da Cidade de Natal RN, na qual s?o constru?das com frequ?ncia conten??es do tipo analisado no presente trabalho. Utilizou-se o modelo constitutivo de Mohr-Coulomb para simular o comportamento do solo e o modelo el?stico linear para simular o comportamento dos elementos estruturais. Os par?metros de resist?ncia do solo foram determinados por meio de ensaios de cisalhamento direto e os par?metros de deformabilidade foram estimados atrav?s de correla??es emp?ricas obtidas de resultados de ensaios SPT executados na regi?o em estudo. Os resultados obtidos mostraram que varia??es no comprimento da ficha praticamente n?o influenciam o comportamento da estrutura, no ?mbito dos par?metros avaliados, ao passo que o espa?amento horizontal entre os tirantes apresenta forte influ?ncia sobre essas grandezas. Verificou-se tamb?m que a espessura da parede apresenta consider?vel influ?ncia sobre os deslocamentos horizontais e sobre os esfor?os internos e pouca influ?ncia sobre as tens?es horizontais

Made available in DSpace on 2014-12-17T14:55:00Z (GMT). No. of bitstreams: 1 JoabsonNC.pdf: 1023745 bytes, checksum: 5c279305bf7356a4d77b64ca8e0c6261 (MD5) Previous issue date: 2005-12-19 / This work presents a theoretical and numerical analysis using the transverse resonance technique (TRT) and a proposed MTRT applied in the analysis of the dispersive characteristics of microstrip lines built on truncated isotropic and anisotropic dielectric substrates. The TRT uses the transmission lines model in the transversal section of the structure, allowing to analyze its dispersive behavior. The difference between TRT and MTRT consists basically of the resonance direction. While in the TRT the resonance is calculated in the same direction of the metallic strip normal axis, the MTRT considers the resonance in the metallic strip parallel plane. Although the application of the MTRT results in a more complex equivalent circuit, its use allows some added characterization, like longitudinal section electric mode (LSE) and longitudinal section magnetic mode (LSM), microstrips with truncated substrate, or structures with different dielectric regions. A computer program using TRT and MTRT proposed in this work is implemented for the characterization of microstrips on truncated isotropic and anisotropic substrates. In this analysis, propagating and evanescent modes are considered. Thus, it is possible to characterize both the dominant and higher order modes of the structure. Numerical results are presented for the effective permittivity, characteristic impedance and relative phase velocity for microstrip lines with different parameters and dimensions of the dielectric substrate. Agreement with the results obtained in the literature are shown, as well as experimental results. In some cases, the convergence analysis is also performed by considering the limiting conditions, like particular cases of isotropic materials or structures with dielectric of infinite size found in the literature. The numerical convergence of the formulation is also analyzed. Finally, conclusions and suggestions for the continuity of this work are presented / Este trabalho apresenta os fundamentos te?ricos da t?cnica da resson?ncia transversa (TRT) e da t?cnica da resson?ncia transversa modificada (MTRT) aplicada na an?lise das caracter?sticas dispersivas de uma microfita considerando substratos diel?tricos isotr?picos e anisotr?picos truncados. A TRT utiliza o modelo da linha de transmiss?o na se??o transversal da estrutura, permitindo analisar o seu comportamento dispersivo. A diferen?a entre a TRT e MTRT consiste basicamente na dire??o da resson?ncia. Enquanto na TRT a resson?ncia ? calculada ao longo do eixo normal ? fita met?lica, a MTRT considera a resson?ncia no plano paralelo ? fita met?lica. Embora a aplica??o da MTRT resulte num circuito equivalente mais complexo, sua utiliza??o permite a caracteriza??o mais precisa, incluindo modo el?trico de se??o longitudinal (LSE) e modo magn?tico de se??o longitudinal (LSM), microfitas com substrato truncado, ou estruturas planares com multiplas regi?es diel?tricas. Um programa computacional utilizando a TRT e MTRT ? discutido e desenvolvido para caracteriza??o de microfitas sobre substratos isotr?picos e anisotr?picos truncados. Na an?lise, consideram-se modos propagantes e evanescentes. Assim, ? poss?vel caracterizar n?o somente o modo fundamental, mas tamb?m os modos de ordem superior da estrutura. S?o apresentados resultados num?ricos para as diversas grandezas, ou seja, permissividade efetiva, imped?ncia caracter?stica e velocidade de fase relativa para microfita com diferentes par?metros e dimens?es do substrato. S?o feitas compara??es com outros resultados dispon?veis na literatura e, tamb?m, com resultados determinados experimentalmente. Em alguns casos, os resultados s?o comparados como casos particulares de materiais isotr?picos ou de estruturas com diel?tricos de tamanho infinito encontradas na literatura, tendo sido observada uma excelente concord?ncia. Apresenta-se, ainda, um estudo de converg?ncia da formula??o proposta e, finalmente, conclus?es e sugest?es para continuidade do trabalho