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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Structural Optimization Using Ansys

Panayirci, Huseyin Murat 01 February 2006 (has links) (PDF)
This study describes the process of performing structural optimization using ANSYS. In the first part, the general concepts in optimization and optimization algorithms for different type of optimization problems are covered. Also finite element method is introduced briefly in this part. In the second part, important definitions in structural optimization are mentioned. Then the optimization methods available in ANSYS are explained with their theories. Necessary steps to perform optimization with ANSYS are described at the end of this part. In the next part, sample problems found from scientific papers are solved using ANSYS and the results are compared. At the end of the study, the results obtained from the example problems are discussed whether they came out as expected or not. Also conclusions are made about solving optimization problems and performing structural optimization with ANSYS.
72

Groundwater modeling and management using the finite element method and evolutionary optimisation techniques / by Eugene Osei Agyei.

Agyei, Eugene Osei January 1997 (has links)
Bibliography: leaves 208-221. / xi, 229 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Study initiated with the objective of using evolutionary techniques instead of the gradient-based methods to solve the optimisation problems embodied in both management and inverse models. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 1998
73

Collision free path planning algorithms for robot navigation problem

Han, Kyung Min. January 2007 (has links)
Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 29, 2008) Includes bibliographical references.
74

Relating constrained motion to force through Newton's second law

Roithmayr, Carlos. January 2007 (has links)
Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2007. / Bauchau, Olivier, Committee Member ; Hodges, Dewey, Committee Chair ; Singhose, William, Committee Member ; Costello, Mark, Committee Member ; Flannery, Raymond, Committee Member.
75

Topology optimization of plate-like structures

Khoza, Dineo. January 2005 (has links)
Thesis (M. Eng.(Mechanical and aeronautical engineering))-University of Pretoria, 2005. / Includes bibliographical references. Available on the Internet via the World Wide Web.
76

Qualitative investigation of the performance of a structural membrane roof project.

Nunes, Eliana Ferreira January 2012 (has links)
Programa de Pós Graduação em Engenharia Civil. Departamento de Engenharia Civil, Escola de Minas, Universidade Federal de Ouro Preto. / Submitted by Oliveira Flávia (flavia@sisbin.ufop.br) on 2016-01-14T15:41:06Z No. of bitstreams: 1 TESE_QualitativeInvestigationPerformance.pdf: 28313982 bytes, checksum: 7fa9b21301ee73fcec79f7676cdc021f (MD5) / Approved for entry into archive by Gracilene Carvalho (gracilene@sisbin.ufop.br) on 2016-01-14T17:57:17Z (GMT) No. of bitstreams: 1 TESE_QualitativeInvestigationPerformance.pdf: 28313982 bytes, checksum: 7fa9b21301ee73fcec79f7676cdc021f (MD5) / Made available in DSpace on 2016-01-14T17:57:18Z (GMT). No. of bitstreams: 1 TESE_QualitativeInvestigationPerformance.pdf: 28313982 bytes, checksum: 7fa9b21301ee73fcec79f7676cdc021f (MD5) Previous issue date: 2012 / This paper provides a qualitative investigation about the structural performance of the membranes, surface structures (with double curvature in opposite directions) with minimum thickness and weight, which absorb forces in form of tensile stresses in its own plane, considering two aspects: structural and design procedure. Initially, it involved the analyses of lightweight structure buildings and the observation of constructive work process in membrane roofs. These investigations allowed identifying strategies that contribute to achieve optimum system performance and the challenges encountered along the stages of designing and building. They also guided the qualitative analysis of the performance of a structural membrane roofing project, i.e., a particular situation, as example. This qualitative analysis was developed in two stages, guided by experimental and numerical data. The first stage involved the optimization procedure of the structural system under load action. This analysis showed that the flexible system performance is a result of the three-dimensional stability of the structural system (arrangement and geometry of all components), membrane surface stiffness (membrane geometry), as well as the cooperation of all components in pre-tension state. The second stage comprised the experimental investigation of the membrane material behaviour within the structure context in order to analyze the flattened membrane geometry. Such evaluation enabled to verify the difference between the theoretical model (shape of equilibrium) and the actual shape (consisting of flat panels), enabling the proper adjustment of the surface geometry so that the final shape can reveal not only the path of the forces, but also the best use of the material. The investigations, analyses and working procedure here adopted broadened the understanding of this system pointing possibilities to increase its performance and to minimize failures during the preliminary stage of design.
77

A New Genetic Algorithm for Continuous Structural Optimization

January 2015 (has links)
abstract: In this thesis, the author described a new genetic algorithm based on the idea: the better design could be found at the neighbor of the current best design. The details of the new genetic algorithm are described, including the rebuilding process from Micro-genetic algorithm and the different crossover and mutation formation. Some popular examples, including two variable function optimization and simple truss models are used to test this algorithm. In these study, the new genetic algorithm is proved able to find the optimized results like other algorithms. Besides, the author also tried to build one more complex truss model. After tests, the new genetic algorithm can produce a good and reasonable optimized result. Form the results, the rebuilding, crossover and mutation can the jobs as designed. At last, the author also discussed two possible points to improve this new genetic algorithm: the population size and the algorithm flexibility. The simple result of 2D finite element optimization showed that the effectiveness could be better, with the improvement of these two points. / Dissertation/Thesis / Masters Thesis Civil and Environmental Engineering 2015
78

Otimização de seções transversais de concreto armado sujeitas à flexão: aplicação a pavimentos / not available

Rodrigo de Carvalho Soares 04 April 1997 (has links)
Nos tempos atuais, já existe um forte desenvolvimento computacional no que diz respeito a análise de estruturas com características geométricas, de cargas e vinculações previamente definidas. Assim como os processadores, tem-se investido bastante em pré e pós-processadores, os quais são responsáveis pela maior parte do tempo dedicado a um projeto. No entanto, pode-se dizer que a definição automática das características geométricas dos elementos estruturais deixa a desejar. Hoje, esta etapa ainda é feita pelo engenheiro, apenas com uma ajuda indireta da máquina. Este trabalho apresenta uma maneira ótima de fazer o pré-dimensionamento das vigas de um pavimento de concreto armado. Para isso, desenvolveu-se uma formulação de minimização do custo de uma seção transversal com a qual, através de um método de aproximações combinadas, obtém-se o mínimo custo do vigamento de um pavimento. As variáveis envolvidas na função que representa o custo são: a altura da viga e as áreas de aço. E as restrições do problema são: a taxa geométrica da armadura, a taxa de armadura de compressão em relação a de tração e a flecha máxima pré-estabelecida pelo usuário. / Nowadays, there is a continuous development in structural computational analysis for known geometrical, loading and boundary conditions. Much effort has been made on the pre and pos-processors, which is the main part of the time spent in designing. The automatic definition of the geometrical characteristics for the structural elements, however is poor yet. Today, this phase is still carried out by the engineer, only with an indirect machine help. This work presents an optimal method to automate the first draft design of the beams reinforced concrete floor. A formulation to achieve the cross-section minimum cost function is proposed and then extended to the whole floor by combined approximation methods. In order to obtain the cost function the following values have been considered: the beam depth and the steel area. As problem constraints, the steel geometric rate, the steel compression with the steel tension rate and the limit displacement have to be prescribed by the user.
79

Um metodo heuristico de otimização de forma de componentes estruturais no estado plano de elasticidade linear / A heuristic method of the structural components shape optimization in plane estate of linear elastidty

Clapis, Antonio Pedro 08 June 1999 (has links)
Orientador: Fernando Iguti / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-26T15:45:20Z (GMT). No. of bitstreams: 1 Clapis_AntonioPedro_D.pdf: 6280663 bytes, checksum: d33f59de18e79beebaf4d0bb0cbdcd98 (MD5) Previous issue date: 1999 / Resumo: Nos últimos trinta anos pesquisadores tem procurado desenvolver métodos matemáticos e ou numéricos, na busca de se otimizar a configuração geométrica de uma dada estrutura. Como a análise estrutural é uma parte integrante do processo de otimização de forma, o progresso da otimização estrutural muitas vezes depende fundamentalmente do desenvolvimento de um bom modelo de elementos finitos. Partindo-se então do pressuposto que a discretização do modelo geometricamente e fisicamente tem sentido, pode-se implementar um algoritmo iterativo de busca da forma ótima de um elemento estrutural utilizando-se um principio heurístico de desenvolvimento. Extrapola-se um método de homogeneização do erro de discretização por elementos finitos no domínio para a homogeneização da densidade de energia de deformação por distorção (von Mises) dos elementos, onde o critério de convergência é a máxima densidade de energia de distorção permitida. Um código numérico em linguagem Fortran F32 é implementado. O programa tem como principal característica a utilização de dois modelos estruturais com graus de liberdade bem distintos (modelo físico e modelo geométrico). No modelo geométrico efetua-se a relocação dos nós da discretização por elementos finitos tendo como objetivo a melhor homogeneização possível da densidade de energia de deformação por distorção do elemento. A avaliação da potencialidade do método é feita através da otimização de algumas estruturas citadas na literatura e, com os resultados obtidos verifica-se a eficiência e a razão de convergência do método proposto / Abstract: In the past thirty years researchers have sought to develop mathematical methods and/or numerical methods to optimize the geometric configuration of a structure. Since structural analysis is part of the process of shape optimization, this success in our approach depends on the development of an adequate finite element model. Assuming that the geometrical and physical discretization of the model is established, it is possible to implement an iterative algorithm to seek the optimal shape of a structural component using a heuristic principIe. A method the balancing the error of each element in the plane stress state is extrapolated. This method is used to balance the energy of distortion deformation function (von Mises) of each element and the criterion to stop is the maximum distortion energy function in the uniaxial tension testoA numerical code using Fortran F32 language is implemented. The main characteristic of this code is the execution of two distinct structural modules (physical and geometric model). In the geometric model the nodes are relocated considering the homogenization the distortion deformation energy density per element. The potentiality of the proposed method is evaluated through some examples ftom the literature. With the results the efficiency and the convergence of the method are checked. / Doutorado / Mecanica dos Solidos / Doutor em Engenharia Mecânica
80

Optimal design for linear regression with variable costs and precision requirements and its applications to forestry

Penner, Margaret January 1988 (has links)
Various criteria are discussed and as algorithms for obtaining optimal designs for use in linear regression. Linear regression is used widely and effectively in forestry but the method of quantifying the linear relationship in terms of selecting observations or designing an experiment to obtain observations is often inefficient. The experiment or study objectives must be identified to develop a criterion for comparing designs. Then a method of obtaining observations can be found which performs well under this criterion. Biometricians in forestry have been slow to take advantage of one of the assumptions of linear regression, namely that the independent variables are fixed. In part this has been due to limitations in the theory. Two important assumptions in most optimal design work, namely that precision requirements and costs are constant for all observations, are not valid for most forestry applications. Ignoring nonconstant costs can lead to designs less efficient than ones where each combination of independent variables is selected with the same frequency. The objective of this study was to develop a method of optimal sample selection that allowed for costs and precision requirements that vary from observation to observation. The resulting practical experimental layouts are more efficient for attaining the experimenter's objectives than randomly selected observations or designs constructed using the currently available design theory. Additional features of designs that consider differing costs and precision requirements are their larger sample size and their robustness to misspecification of the sample space. Traditional optimal designs concentrated observations on the boundaries of the sample space. By recognizing that these observations may be more costly and may not be of primary interest to the experimenter, more efficient designs can be constructed from less extreme observations. A computer program for obtaining optimal designs is also included. / Forestry, Faculty of / Graduate

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