Made available in DSpace on 2016-06-02T20:06:00Z (GMT). No. of bitstreams: 1 1662.pdf: 571364 bytes, checksum: 6091268473b4a7cb920748fd364c2a99 (MD5) Previous issue date: 2007-03-30 / Survival data analysis models is used to study experimental data where, normally, the variable "answer"is the time passed until an event of interest. Many authors do prefer modeling survival data, in the presence of co-variables, by using a hazard function - which is related with its interpretation. The Cox model (1972) - most commonly used by the authors - is applicable when the fail rates are proportional. This model is very flexible and used in the survival analysis. It can be easily extended to, for example, incorporate the time-dependent co-variables. In the present work we propose a proportional risk model which incorporates a time-dependent parameter named "time-dependent proportional risk model". / A análise de sobrevivência tem por objetivo estudar dados de experimento em que a variável resposta é o tempo até a ocorrência de um evento de interesse. Vários autores têm preferido modelar dados de sobrevivência na presença de covariáveis por meio da função de risco, fato este relacionado à sua interpretação. Ela descreve como a probabilidade instantânea de falha se modifca com o passar do tempo. Nesse contexto, um dos modelos mais utilizados é o modelo de Cox (Cox, 1972), onde a suposição básica para o seu uso é que as taxas de falhas sejam proporcionais. O modelo de riscos proporcionais de Cox é bastante flexível e extensivamente usado em análise de sobrevivência. Ele pode ser facilmente estendido para incorporar, por exemplo, o efeito de covariáveis dependentes do tempo. Neste estudo, propõe-se um modelo de risco proporcional, que incorpora um parâmetro dependente do tempo, denominado modelo de risco proporcional dependente do tempo. Uma análise clássica baseada nas propriedades assintóticas dos estimadores de máxima verossimilhança dos parâmetros envolvidos é desenvolvida, bem como um estudo de simulação via técnicas de reamostragem para estimação intervalar e testes de hipóteses dos parâmetros do modelo. É estudado o custo de estimar o efeito da covariável quando o parâmetro que mede o efeito do tempo é considerado na modelagem. E, finalizando, apresentamos uma abordagem do ponto de vista Bayesiano.

Made available in DSpace on 2016-06-02T20:06:04Z (GMT). No. of bitstreams: 1 3437.pdf: 1348932 bytes, checksum: d4b8cd2d1775831eeea609373f32648d (MD5) Previous issue date: 2011-02-11 / Universidade Federal de Minas Gerais / Several authors have preferred to model survival data in the presence of covariates through the hazard function, a fact related to its interpretation. The hazard function describes as the instantaneous average of failure changes over time. In this context, one of the most used models is the Cox s model (1972), in which the basic supposition for its use is that the ratio of the failure rates, of any two individuals, are proportional. However, experiments show that there are survival data which can not be accommodated by the Cox s model. This fact has been determinant in the developing of several types of non-proporcional hazard models. Among them we mention the accelerated failure model (Prentice, 1978), the hybrid hazard model (Etezadi-Amoli and Ciampi, 1987) and the extended hybrid hazard models (Louzada-Neto, 1997 and 1999). Mackenzie (1996) proposed a parametric family of non-proportional hazard model called generalized time-dependent logistic model - GTDL. This model is based on the generalization of the standard logistic function for the time-dependent form and is motivated in part by considering the timeeffect in its setting and, in part by the need to consider parametric structure. The frailty model (Vaupel et al., 1979, Tomazella, 2003, Tomazella et al., 2004) is characterized by the use of a random effect, ie, an unobservable random variable, which represents information that or could not or were not collected, such as, environmental and genetics factors, or yet information that, for some reason, were not considered in the planning. The frailty variable is introduced in the modeling of the hazard function, with the objective of control the unobservable heterogeneity of the units under study, including the dependence of the units that share the same hazard factors. In this work we considered an extension of the GTDL model using the frailty model as an alternative to model data which does not have a proportional hazard structure. From a classical perspective, we did a simulation study and an application with real data. We also used a Bayesian approach to a real data set. / Vários autores têm preferido modelar dados de sobrevivência na presença de covariáveis por meio da função de risco, fato este relacionado à sua interpretação. A função de risco descreve como a taxa instantânea de falha se modifica com o passar do tempo. Neste contexto, um dos modelos mais utilizados é o modelo de Cox (1972) sendo que a suposição básica para o seu uso é que a razão das taxas de falhas, de dois quaisquer indivíduos, sejam proporcionais. Contudo, experiências mostram que existem dados de sobrevivência que não podem ser acomodados pelo modelos de Cox. Este fato tem sido determinante no desenvolvimento de vários tipos de modelos de risco não proporcional. Entre eles podemos citar o modelo de falha acelerado (Prentice, 1978), o modelo de risco híbrido (Etezadi-Amoli e Ciampi, 1987) e os modelos de risco híbrido estendido (Louzada- Neto, 1997 e 1999). Mackenzie (1996) propôs uma nova família paramétrica de modelo de risco não proporcional intitulado modelo de risco logístico generalizado dependente do tempo (Generalized time-dependent logistic model-GTDL). Este modelo é baseado na generalização da função logística padrão para a forma dependente do tempo e é motivado em parte por considerar o efeito do tempo em seu ajuste e, em parte pela necessidade de considerar estrutura paramétrica. O modelo de fragilidade (Vaupel et al., 1979, Tomazella, 2003, Tomazella et al., 2004) é caracterizado pela utilização de um efeito aleatório, ou seja, de uma variável aleatória não observável, que representa as informações que não podem ou não foram observadas, como por exemplo, fatores ambientais e genéticos, ou ainda informações que, por algum motivo, não foram consideradas no planejamento. A variável de fragilidade é introduzida na modelagem da função de risco, com o objetivo de controlar a heterogeneidade não observável das unidades em estudo, inclusive a dependência das unidades que compartilham os mesmos fatores de risco. Neste trabalho consideramos uma extensão do modelo GTDL utilizando o modelo de fragilidade como uma alternativa para ii modelar dados que não tem uma estrutura de risco proporcional. Sob uma perspectiva Clássica, fizemos um estudo de simulação e uma aplicação com dados reais. Também utilizamos a abordagem Bayesiana para um conjunto de dados reais.

abstract: Optimization of on-demand transportation systems and ride-sharing services involves solving a class of complex vehicle routing problems with pickup and delivery with time windows (VRPPDTW). Previous research has made a number of important contributions to the challenging pickup and delivery problem along different formulation or solution approaches. However, there are a number of modeling and algorithmic challenges for a large-scale deployment of a vehicle routing and scheduling algorithm, especially for regional networks with various road capacity and traffic delay constraints on freeway bottlenecks and signal timing on urban streets. The main thrust of this research is constructing hyper-networks to implicitly impose complicated constraints of a vehicle routing problem (VRP) into the model within the network construction. This research introduces a new methodology based on hyper-networks to solve the very important vehicle routing problem for the case of generic ride-sharing problem. Then, the idea of hyper-networks is applied for (1) solving the pickup and delivery problem with synchronized transfers, (2) computing resource hyper-prisms for sustainable transportation planning in the field of time-geography, and (3) providing an integrated framework that fully captures the interactions between supply and demand dimensions of travel to model the implications of advanced technologies and mobility services on traveler behavior. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2018

Le but de cette thèse est la compréhension de pourquoi certains complexes de ruthénium sont soit pasluminescents soit avec un temps de vie très courte de l’état excité. Des calculs de type théorie de lafonctionnelle de la densité (DFT) ou DFT dépendante du temps (TD-DFT) étaient effectués pour cinqcomplexes existants et aussi pour un complexe hypothétique. Selon la théorie de champs de ligand (LFT),la plus proche sont les énergies des états de type transfert de charge métal-ligand (MLCT) à un état de typemétal centré (MC), alors le plus facile est-ce à peupler l’état MC ainsi menant à une dèsexcitation nonradiative de l’état MLCT. Les calculs DFT/TD-DFT s’avéraient suffisants pour reproduire les géométrieset spectres d’absorption expérimentales. Ceci, ensemble avec la technique de densité d’états partielle,permettaient une validation de l’idée fondamentale issue du modèle LFT en confrontant les résultats denos calculs avec les temps de vie mesurés. / Density-functional theory (DFT) and time-dependent DFT (TD-DFT) were carried out for 5 rutheniumcomplexes and one hypothetical one. The goal was to understand the lack of luminescence or very shortexcited state lifetimes at room temperature in some of them. According to ligand-field theory (LFT), thecloser the energies of the metal-to-ligand charge transfer (MLCT ) and the metal-centred (MC) states,the easier it is to populate the MC state, leading to radiationless disactivation of the luminescent MLCT.DFT/TD-DFT calculations proved adequate in reproducing experimental geometries and absorption spectra.Verification of LFT explanation was done by use of partial density of states whose results agreedreasonably well with the usual hypothesis.

L'objectif de cette thèse est d'étudier la fiabilité et la cyclabilité des jonctions Tunnel magnétique pour mieux comprendre les mécanismes de dégradation et de claquage de la barrière. Une étude de l'endurance de la barrière MgO jusqu'au claquage électrique est présentée. Les échantillons ont été testés sous un mode impulsionnel. Par l'étude de l'effet de retard entre des impulsions successives, une durée de vie optimale des JTM est observée pour une valeur intermédiaire de retard entre les impulsions correspondant à un compromis optimal entre la densité moyenne de charge piégée dans la barrière et la modulation temporelle de charge. En outre, un modèle de piégeage / dépiégeage de charge a été développé qui appuie cette interprétation. L'étude souligne le rôle des pièges de charges dans le mécanisme de claquage de la barrière tunnel. Elle montre aussi que l'endurance extrêmement longue pourrait être obtenue en réduisant la densité des sites de piégeage d'électrons dans la barrière tunnel. Puis, une étude de l'endurance et le bruit basse fréquence a été dans les jonctionS CoFeB/MgO/CoFeB pour STT-MRAM ou TA-MRAM. Une corrélation a été observée et expliquée par la présence de sites de piégeage d'électrons dans la barrière de MgO et le rôle des phénomènes de charge/ décharge à la fois dans la fiabilité et la puissance du bruit en 1 / f électrique. Ces résultats prouvent que le test du bruit basse fréquence peut être utilisé comme une caractérisation prédictive de l'endurance. Enfin, en perspectives, des mesures complémentaires en été proposées pour développer plus le modèle de charge/décharge, une optimisation de la barrière pourrait ainsi être réaliser pour réduire le nombre des pièges de charge au sein de la barrière et par conséquent améliorer la fiabilité des jonctions Tunnel. / The thesis objective is to study the Magnetic Tunnel Junction reliability and cyclability to more understand the barrier breakdown mechanisms. An investigation of barrier endurance till electrical breakdown in MgO-based magnetic tunnel junctions (MTJs) is presented. Samples were tested under pulsed electrical stress. By studying the effect of delay between successive pulses, an optimum endurance of MTJs is observed for an intermediate value of delay between pulses corresponding to an optimum trade-off between the average density of charge trapped in the barrier and the amplitude of its time-modulation at each voltage pulse. Furthermore, a charge trapping/detrapping model was developed which support this interpretation. The study emphasizes the role of electron trapping/detrapping mechanisms on the tunnel barrier reliability. It also shows that extremely long endurance could be obtained in MTJs by reducing the density of electron trapping sites in the tunnel barrier. Then the write endurance and the 1/f noise of electrical origin were characterized in CoFeB/MgO/CoFeB MTJ for STT-MRAM or TA-MRAM. A correlation was observed and explained by the presence of electron trapping sites in the MgO barrier and the role of electron trapping/detrapping phenomena in both the MTJ reliability and its 1/f electrical noise power. These results suggest that 1/f noise could be used as a predictive characterization of the MTJ endurance. Finally, as thesis perspectives, some complement measurements were proposed to further investigate this model and an optimization of MgO barrier which could be carried out to reduce the density of these trapping sites was presented to ameliorate the MTJs reliability.

Made available in DSpace on 2014-12-17T15:14:51Z (GMT). No. of bitstreams: 1 JoaoMS.pdf: 634960 bytes, checksum: 579213d21eb24a6a8d342d2c3b15bc3d (MD5) Previous issue date: 2003-06-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this work we investigate the stochastic behavior of a large class of systems with variable damping which are described by a time-dependent Lagrangian. Our stochastic approach is based on the Langevin treatment describing the motion of a classical Brownian particle of mass m. Two situations of physical interest are considered. In the first one, we discuss in detail an application of the standard Langevin treatment (white noise) for the variable damping system. In the second one, a more general viewpoint is adopted by assuming a given expression to the so-called collored noise. For both cases, the basic diffententiaql equations are analytically solved and al the quantities physically relevant are explicitly determined. The results depend on an arbitrary q parameter measuring how the behavior of the system departs from the standard brownian particle with constant viscosity. Several types of sthocastic behavior (superdiffusive and subdiffusive) are obteinded when the free pamameter varies continuosly. However, all the results of the conventional Langevin approach with constant damping are recovered in the limit q = 1 / Neste trabalho n?s investigamos o comportamento estoc?stico de uma grande classe de sistemas com amortecimento vari?vel descritos por uma lagraniana dependente do tempo. Nossa abordagem estoc?stica ? baseada no formalismo de Langevin descrevendo o comportamento de uma part?cula browniana cl?ssica de massa m. Duas situa??es de interesse f?sico s?o consideradas. Inicialmente, uma aplica??o do tratamento padr?o de Langevin (ru?do branco) para viscosidade vari?vel ? discutido em detalhe. Na segunda abordagem, um ponto de vista mais geral ? adotado supondo uma dada express?o para o chamado ru?do branco. Em ambos os casos as equa??es diferenciais b?sicas s?o analiticamente resolvidas, e todas as quantidades fisicamente relevantes s?o explicitamente determinadas. Os resultados dependem de um par?metro arbitr?rio (q) medindo como o comportamento din?mico do sistema se afasta daquele apresentado pela part?cula browniana com viscosidade constante. V?rios tipos de comportamentos estoc?sticos (subsifusivos and superdifusivos) s?o obtidos quando o par?metro livre q varia continuamente. Contudo, no limite q -> 1, todos os resultados da abordagem de Langevin convencional s?o recuperados

This thesis examines previously unresolved issues regarding the fluid dynamics of the spread of buoyant water into a rotating environment. We focus in particular on the role that finite potential vorticity and background turbulence play in determining the flow properties. When water of an anomalous density enters into an oceanic basin, gravity-driven surface flows can be established as a result of the density difference. These flows are often of a sufficiently large scale that the dynamics are affected by the Coriolis force arising from the rotation of the earth. This causes the formation of a large outflow gyre near to the source which feeds into a propagating gravity current that is confined to the coast. Previous experimental work in this field has sought to simplify the problem through the use of a point source and a quiescent ambient. We extend this work to provide a better representation of the real-world flow by introducing a source of finite depth and background turbulence to the rotating ambient. This study seeks to answer three key questions that are critical to the understanding of the flow behaviour in this scenario. First, what is the effect of the finite potential vorticity of the outflow on the properties of the outflow vortex and the boundary current? Second, what role does the presence of the the outflow vortex play in determining the behaviour of the current? Third, what is the effect of background turbulence on the flow properties? To carry out the investigation, experiments were conducted in the laboratory and compared with a theoretical description of the flow. The currents are generated inside a rotating tank filled with saltwater by the continuous release of buoyant freshwater from a source structure located at the fluid surface. A horizontal source of finite depth is used to introduce finite potential vorticity into the outflow. The impact of background turbulence is examined by introducing an oscillating grid into the rotating tank. We find that the finite potential vorticity of the outflow plays an important role in determining the flow properties for sufficiently low Rossby and Froude number. As the value of these parameters is increased a zero potential vorticity model is able to capture the key elements of the flow behaviour. The outflow vortex is found to act as a time-varying source to the boundary current, with the current velocity fixed by the vortex velocity field. The vortex vorticity is seen to decrease with time, while the vortex radius continues to increase at late times despite the vortex having reached a limiting depth, which enables potential vorticity to be conserved and the current to be supplied with a non-zero velocity. Finally, the structure of the background turbulence is found to be key in determining the effect that it has on the flow properties, with different behaviours observed for three-dimensional and quasi- two-dimensional turbulence.

Numerical solution of differential equations having multitude of scales in the solution field is one of the most challenging research areas, but highly demanded in scientific and industrial applications. One of the natural approaches for handling such problems is to separate the scales and approximate the solution of the segregated scales with appropriate numerical method. Variational multiscale method (VMS) is a predominant method in the paradigm of scale separation schemes. In our work we have used the VMS technique to develop a numerical scheme for computations of turbulent flows in time-dependent domains. VMS allows separation of the entire range of scales in the flow field into two or three groups, thereby enabling a different numerical treatment for the different groups. In the context of computational fluid dynamics(CFD), VMS is a significant new improvement over the classical large eddy simulation (LES). VMS does away with the commutation errors arising due to filtering in LES. Further, in a three-scale VMS approach the model for the subgrid scale can be contained to only a part of the resolved scales instead of effecting the entire range of resolved scales. The projection based VMS scheme that we have developed gives a robust and efficient method for solving problems of turbulent fluid flows in deforming domains, governed by incompressible Navier {Stokes equations. In addition to the existing challenges due to turbulence, the computational complexity of the problem increases further when the considered domain is time-dependent. In this work, we have used an arbitrary Lagrangian-Eulerian (ALE) based VMS scheme to account for the domain deformation. In the proposed scheme, the large scales are represented by an additional tensor valued space. The resolved large and small scales are computed in a single unified equation, and the effect of unresolved scales is confined only to the resolved small scales, by using a projection operator. The popular Smagorinsky eddy viscosity model is used to approximate the effects of unresolved scales. The used ALE approach consists of an elastic mesh update technique. Moreover, a computationally efficient scheme is obtained by the choice of orthogonal finite element basis function for the resolved large scales, which allows to reformulate the ALE-VMS system matrix into the standard form of the NSE system matrix. Thus, any existing Navier{Stokes solver can be utilized for this scheme, with modifications. Further, the stability and error estimates of the scheme using a linear model of the NSE are also derived. Finally, the proposed scheme has been validated by a number of numerical examples over a wide range of problems.

Neste trabalho estudou-se o reforço de vigas T de concreto armado tanto por meio de adição de armadura longitudinal ao bordo tracionado envolvida por um material compósito (argamassa com fibras curtas de aço), quanto pela aplicação de uma capa de pequena espessura de microconcreto de alta resistência ao bordo comprimido. Para estudar as possibilidades da aplicação prática destas duas técnicas de reforço avaliou-se o comportamento das vigas reabilitadas verificando a influência: da atuação de um pré-carregamento durante a execução do reforço, das deformações diferidas diferenciais (fluência e retração) existentes entre os materiais novos e antigos e, dos mecanismos de resistência mobilizados na transmissão de esforços na junta - formada pela ligação do substrato ao concreto do reforço - ou entre as barras de aço tracionadas preexistentes e adicionadas em função da ausência de estribos envolvendo-as. Para redimensionar as peças reforçadas no bordo tracionado foram realizados ensaios complementares para identificar, dentre as várias fibras disponíveis comercialmente, qual a que proporcionaria ao material compósito, um confinamento suficiente que evitasse a ruptura prematura da viga pela tendência de deslizamento relativo entre as barras de aço tracionadas devida à ausência de estribos neste local. Para redimensionar as peças reforçadas no bordo comprimido realizou-se ensaios complementares para determinar as propriedades viscoelásticas dos materiais usados no substrato e no reforço, tornando possível estimar as descontinuidades geradas nos estados de tensão e deformação ao longo do tempo já que tais materiais são moldados e submetidos a carregamentos em idades distintas. Os resultados dos ensaios das vigas reforçadas de seção T foram analisados e comparados com previsões teóricas feitas a partir da adaptação de métodos analíticos convencionais recomendados por norma para estruturas novas, e a partir de simulações numéricas usando um programa computacional baseado no método dos elementos finitos. Do estudo realizado foi possível: comprovar a eficiência das técnicas de reforço propostas estando as peças submetidas ou não a um pré-carregamento durante a execução da intervenção, compatibilizar alguns dos conhecimentos teóricos existentes a fim de poder usá-los na análise teórica das vigas reabilitadas, além de reunir uma série de informações úteis que podem ser exploradas na definição de estratégias e procedimentos de projeto de estruturas reabilitadas semelhantes / This paper reports on the results of a study about the behavior of reinforced concrete T-beams rehabilitated using two different techniques. The first technique consists of the addition of longitudinal reinforcement embedded in a steel fiber reinforced highperformance mortar at the bottom face of the member. The second technique consists of rehabilitation by adding a thin overlay of high-strength concrete to the compression zone. The parameters analyzed to verify the possibilities of practical applications of these techniques were: the effect of a pre-loading acting on the beams during their rehabilitation, the differential time-dependent deformations (creep and shrinkage) between the new concrete and existing base, the mechanisms of resistance mobilized along the interface formed by old and new concrete or between pre-existent steel bars and added steel bars that are not involved by stirrups. Previous tests were carried out to make it possible to redesign the intervention adequately. Theses tests yield useful information about which type and volume of steel fibers need to be added to composite mortar to avoid the premature rupture of the strengthened beam caused by relative slipping between the layers of steel tensioned bars. These tests also give information about the viscoelastic properties of the materials used to manufacture the T-beams. The test results were analyzed and compared with the results of analytic models and numeric models based on the method of the finite elements. Based on this study, it can be stated that the proposed techniques are really efficient even if the beams are submitted to a pre-loading during the process of rehabilitation. Also, existing theoretical knowledge was organized to support the theoretical analysis of the rehabilitated beams, besides gathering useful information that can be explored in the definition of strategies and procedures of similar projects of rehabilitated structures

Estruturas em concreto pré-moldado vêm sendo utilizadas com freqüência em sistemas reticulados do tipo multi-piso, destinados às mais variadas atividades como: estabelecimentos comerciais, estacionamentos, escolas, hospitais e etc. A utilização de ligações viga-pilar do tipo semi-rígida constitui uma alternativa interessante para o enrijecimento e para a garantia da estabilidade global deste tipo de estrutura. Atualmente, a rigidez e a resistência destas ligações têm sido determinadas por ensaios de modelos em escala real. Estes ensaios, além de apresentarem um custo elevado, têm aplicação restrita à ligação examinada o que torna esta metodologia limitada e não adequada à prática de elaboração de projeto. Apresenta-se, neste trabalho, um modelo mecânico para determinação numérica da relação força-deslocamento de uma ligação viga-pilar semi-rígida a partir da contribuição da rigidez individual de cada componente de transferência de força utilizado na vinculação. A formulação do equilíbrio do modelo é implementada em planilha eletrônica constituindo-se numa ferramenta de cálculo para o projetista, permitindo o estudo, de forma rápida e amigável, da influência do posicionamento e da rigidez individual de cada componente de transferência de força na rigidez e na resistência da ligação. Este modelo mecânico foi utilizado para o cálculo da rigidez à rotação para momento fletor positivo de uma ligação viga-pilar ensaiada em laboratório. Os valores para a rigidez da ligação obtidos em ensaio e pelo modelo mecânico ficaram muito próximos. Da formulação do equilíbrio do modelo mecânico pode-se extrair ainda uma matriz de rigidez que é utilizada na representação da ligação semi-rígida no modelo de barra da estrutura. Um programa computacional foi desenvolvido para a análise de pórticos planos com ligação viga-pilar semi-rígida considerando ainda as não linearidades físicas e geométricas do modelo de cálculo. O programa foi validado pela comparação de resultados de exemplos também processados no programa ANSYS. A não-linearidade geométrica é considerada pelo método modal, não incremental-iterativo, e que obtém a parcela não-linear da resposta estrutural pela combinação dos seus modos de flambagem. A não-linearidade física do concreto é considerada pelo método da rigidez secante no qual a rigidez de cada barra da estrutura é reduzida na análise conforme suas armaduras e o nível de sua solicitação. Para o cálculo da rigidez secante dos pilares desenvolveu-se um programa que permite a consideração de armaduras ativas e passivas na seção. A análise de alguns exemplos revelou que a protensão dos pilares é também uma alternativa interessante para o enrijecimento da estrutura. Além de exemplos práticos, outros temas pertinentes ao projeto deste tipo de estrutura como: estabilidade na fase construtiva, esforços finais após a montagem, efeitos dependentes do tempo, assimetria de rigidez e plastificação das ligações, são também abordados no trabalho. / Precast concrete multi-storey structures have been more frequently used to construct commercial buildings, parking, schools and hospitals. The use of semi-rigid beam-tocolumn connections is a good strategy to guarantee the global stability of this type of structure. Actually the rigidity and the strength of this type of connection are obtained in an experimental program using full scale prototypes. This procedure is not only expensive but limited and not adequate for design since the results are only valid for the examined connection. This research presents a mechanical model used to determine numerically the force-displacement relationship of a beam-to-column semirigid connection. The procedure uses the contribution of any individual force transfer component active in the connection. The equilibrium equation of the model is implemented in an electronic-worksheet where the designer can rapidly and friendly study the influence of the position and the individual rigidity of each force transfer component in the global rigidity and strength of the connection. For validation, this procedure was used to calculate the flexural rigidity for positive bending moment of a beam-to-column semi-rigid connection that was tested in laboratory. The numerical values of the connection rigidity obtained by test and by the mechanical model are very close. The matrix used in the formulation of the mechanical model equilibrium can also be used to represent the semi-rigid connection in the finite element model of the structure. A computational program was developed for plane frame analysis including semi-rigid beam-to-column connections and both physical and geometric nonlinearities. The program was tested by comparing the results of some examples that are also analysed in the ANSYS program. The geometric nonlinearity is considered by a modal method where the nonlinear response of the structure is obtained by a combination of its buckling modes. The physical nonlinearity of the concrete is considered by the secant rigidity method. In this method the rigidities of all concrete bars in the structure are reduced by coefficients that depend of the reinforcement in the cross section and the level of the efforts. A special computational program was developed to calculate the secant rigidity for a concrete cross section with reinforcing bar and prestressing steel. The analysis of some examples shows that the use of prestressing steel in collums is also an interesting alternative to sttifen the structure. Beyond of some practical examples, others themes related to the design of this type of structure like: stability in the erection process, efforts in the end of the erection process, time-dependent effects, non symmetrical and plastic behavior of the connections, are also treated in this work.