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Resumo: O objetivo deste trabalho foi medir médias para algumas medidas intra e interarcos em modelos de gesso da população brasileira branca portadora de oclusão normal. Para isso, 51 modelos de oclusão normal foram digitalizados tridimensionalmente com o Microscribe duas vezes com um espaço de sete dias entre as digitações para avaliação do erro do método. Os dados conseguidos foram então trabalhados através do programa Tigaro. A estatística para estimar-se as médias foi realizada através da análise de modelo multinível e os erros sistemático e casual foram calculados através dos teste T- student e pela fórmula de Dahlberg, respectivamente. Como resultado foram estabelecidas estimativas das médias para a população brasileira com oclusão normal das distâncias intercaninos, intermolares, inter 1os pré-molares e inter 2os pré-molares, comprimento de arco, torques e inclinações dentárias, espessuras dos dentes no terço médio, altura de cúspides, profundidade da curva de Spee, overjet e overbite, angulação entre os planos oclusais, desvio de linha média e as diferenças entre as bordas oclusais dos dentes anteriores. Também a partir deste estudo, determinou-se um formato de arco padrão para a amostra estudada, que pode ser utilizado como template para arcos em ortodontia... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: The aim of this paper was to measure the average of some intra and interarches measurements in cast models of the white brazilian population with normal occlusion. In order to achieve this objective, 51 models were digitized threedimensionally with a Microscribe twice seven days apart for method error evaluation. The collected data was then worked on the software Tigaro. The statistics used was the multilevel models analysis in order to estimated the means for the measures and the systematic and random error were calculated through the t-student test and Dahlberg's formula, respectively. As a result estimated means of intercanine, intermolar and interpremolar widths, arch length, torques and inclinations, teeth mid-third widths, cusp height, deepness of the curve of Spee, overjet and overbite, angulation between the planes of occlusion, mid-line deviation and the differences of the heights of the incisal borders of the anterior teeth were established for the white brazilian population with normal occlusion. Also, through this study a pattern of arch form was established for the sample studied, that can be used as a template for orthodontic arches. / Orientador: Luiz Gonzaga Gandini Júnior / Coorientador: Haruaki Hayasaki / Banca: Ary dos Santos Pinto / Banca: Adriano Marotta Araújo / Mestre

The idea of the arch as a compression member is presented. The statical work of the arch is illustrated with experiments on photoelastic models. The search for optimal shapes of arches is discussed. A study includes historical development of the arch from the Sumerian times up into the XX century. Examples of arches have been derived from Western Europe, Middle East and Asia; there are also examples of arches in Polish architecture, not well known in the United States. A selection of modern constructions illustrates actual trends in arch applications in contemporary architecture. / M. Arch.

Este trabalho é dedicado ao estudo da estabilidade de arcos, em regime elástico linear, submetidos a carregamentos conservativos. No Capítulo I, desenvolve-se a análise de alguns importantes trabalhos dos últimos 20 anos, sobre estabilidade de arcos, apresentando-se os seus procedimentos e principais resultados. O Capítulo 2 é dedicado aos estabelecimento de conceitos básicos do cálculo tensorial necessários para o desenvolvimento claro da teoria da elasticidade em coordenadas curvilíneas e sua aplicação na formulação variacional da teoria de barras curvas, apresentadas no Capítulo 3. O Capítulo 4 é dedicado à confecção de modelo matemático para o estudo da estabilidade de arco com geometria e carregamentos conservativos quaisquer, envolvendo o estabelecimento da trajetória fundamental de equilíbrio, a determinação da carga crítica e o estabelecimento da trajetória pós-crítica na vizinhança da carga crítica. A formulação adotada é a lagrangiana, a discretização do problema é feita pelo método dos elementos finitos, e as equações não lineares de equilíbrio são resolvidas por uma combinação dos métodos das perturbações e de Newton-Raphson. / This paper deals with the stability of arches in a linear-elastic condition under conservative loads. In Chapter 1, the analysis of some important papers on arch stability written during the last 20 years is developed, together with a presentation of their procedures and main results. Chapter 2 establishes some basic concepts of tensorial calculus, required for the clear development of the elasticity theory on curvilinear coordinates and its application to the variational formulation of the curved beams theory, which are presented in Chapter 3. In Chapter 4, a mathematical model for the study of the stability of arches with any geometry and any conservative loading is presented; it involves the establishment of the fundamental equilibrium trajectory, the determination of the critical loading and the establishment of the post critical trajectory near the critical loading. The Lagrangean formulation is adopted, the problem discretization is made by the finite element method, and the nonlinear equilibrium equations are solved through a combination of the perturbation and the Newton-Raphson methods.

This thesis presents the nonlinear in-plane behaviour of circular fixed arches subjected to thermal loading only. Due to the nonlinear prebuckling behaviour of arches and its effects, classical buckling theory which is founded on geometric prebuckling linearity can not predict the in-plane buckling of arches accurately. Based on a nonlinear formulation of the strain and displacement relationship and considering constant thermal distributions only, virtual work formulations are used to establish the differential equations of in-plane equilibrium and the statical boundary conditions, from which the nonlinear equilibrium equations are derived in closed form and which are suitable to use in design. By considering the adjacent buckled configurations, the differential buckling equilibrium equations are formulated from the principle of virtual work as well, and the analytical solutions for the nonlinear buckling of fixed arches are obtained. It is shown that nonlinear elastic buckling of a fixed in the plane of it curvature can not occur when it is subjected to thermal loading only, except if the arch is as a straight column. By using the algebraic representation of nonlinear in-plane equilibrium derived in this thesis, the elastic response of fixed arches at elevated temperatures and the attainment of first yield are examined in detail. The arch deflects transversely without bound in the elastic range at elevated temperatures, whereas it will yield first at the top extreme fibre of the cross section at the supports when a critical temperature is reached. The influence of several parameters such as the included angle is also considered. Based on the models of stress distributions at cross sections, the spread of yield both through the cross section and along the length of the arch is studied. It is indicated that the progress of yielding causes the first two hinges to form at the supports of the fixed arches, and then moment redistribution leads to the generation of the third hinge at the crown with an increase of temperature. Thus nonlinear plastic hinge analysis can be applied to the arch analysis under thermal loading.

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1907. / The entire thesis text is included in file. Typescript. H. Zirulick determined to by Hyman Zirulick from "Forty-First Annual Catalogue. School of Mines and Metallurgy, University of Missouri". Title from title screen of thesis/dissertation PDF file (viewed January 26, 2009)

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 1990. / Thesis Advisor(s): Salinas, David. "December 1990." Description based on title screen as viewed on April 1, 2010. DTIC Identifier(s): Arches, Stress Analysis, Weight, Finite Element Analysis, Computer Programs, Optimization, Theses, Degrees Of Freedom, FORTRAN, Stiffness, Case Studies. Author(s) subject terms: Finite Element Method, Arches, Weight Optimization. Includes bibliographical references (p. 107). Also available in print.

Thesis (M.S.) in Civil Engineering--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaf 77).

The motion of a shallow arch subjected to random loading is investigated. It is expected that the arch will vibrate about its initial stable configuration under low intensity loading, but will snap back and forth about its horizontal axis under high intensity loading. The parameter of interest is the time of first snap-through of the shallow arch under random load. This is defined as the time taken for the arch to snap to the other side of the horizontal axis. The statistics of the time to first snap-through, such as the mean time to failure as well as its probability distribution. are determined. Most of the work treats one response mode. In the first part of the study, the critical random loading for dynamic snap-through of the shallow arch was investigated using the method of computer simulation. The random excitation was assumed to be a stationary white-noise process. The primary object was to determine the critical power spectral density parameter of the random excitations. The vanishing or diminishing of the average frequency of snap-through was used to estimate this parameter. An exact value of the critical random loading parameter could not be obtained using this criterion since it was based on numerical integration of the non-linear equation of motion and computer simulation which is expensive and time-consuming. However, the critical value or range of critical values of intensity of random excitations could be estimated with a reasonable degree of accuracy. The second part of the study dealt with the first-passage problem. The exact solution of the first-passage problem is available for only a limited class of problems. In this study, the solution was obtained using numerical approximation techniques and computer simulation. For an oscillator subjected to white noise, the displacement and velocity process are governed by the Fokker-Planck-Kolmogorov (FPK) equation. The finite difference method was used to solve the derived FPK equation of the energy envelope of the equation of motion of the arch subjected to white-noise excitation. Solutions were obtained in terms of the mean time to failure, and the probability distribution function of the time to failure. A computer program for the Monte Carlo simulation of the response of the arch subjected to random loads was also developed. A large number of records of the random excitations were simulated and these were used as input in the numerical integration of the equation of motion. The Runge-Kutta method was used to obtain the time history of the displacement response, and the time at which the response exceeded the critical threshold was recorded. Statistics of the time to first snap-through were obtained and these were then used to select an empirical distribution model for the first-passage time. The results of the approximate analysis were compared with those from the simulation. Results of both methods were in close agreement. The effect of including more than one mode in the equation of motion was also studied. Multi-mode approximations of up to four modes were considered in the analysis. It was found that the results of the multi-mode approximations are significantly different from the one-mode approximation. The effect of nonstationary random excitation on the time to first snap-through was also investigated using computer simulation. / Ph. D.

The primary purpose of this study is to determine stability boundaries (interaction curves) for a three degree of freedom, shallow arch model under multiple dynamic loads. The model consists of four rigid bars connected by frictionless pins, with rotational springs and dashpots at the three interior joints, and a translational spring at the right hand exterior joint. Three independent loads (P₁, P₂, P₃) are applied to the model, one at each of the three interior joints. The model's equations of motion, which are derived from Lagrange's equations of motion, are numerically integrated, using the Newmark-Beta method (β = 1/4), to determine the buckling loads. The buckling loads are those loads for which the buckling criterion, the end bars simultaneously below the horizontal, is satisfied. The interaction curves and buckling loads are determined for a parabolic arch with damping under step loads, a parabolic arch without damping under step loads, an eccentric arch without damping under step loads, a parabolic arch without damping under impulse loads, and an / Master of Science