A structure is vulnerable if any damage produces consequences which are disproportionate to that damage. Conversely a structure is robust if it can withstand arbitrary damage. The theory of vulnerability developed in this thesis concerns structural form and connectivity. The purpose of the theory is to identify the "weak links" within a structure. A new theory of vulnerability for 3D structures has been developed. An entirely new approach has been derived from the 2D theory developed by Wu, Blockley, Woodman (1993), Yu(1997). New concepts of a graph model for 3D structural systems, 3D structural path and loop, structural round, string pattern of structural round, 3D structural tightness, 3D structural clusters, deterioration hierarchy of structural round etc. have been defined and introduced. A method of combining structural vulnerability analysis with structural response analysis has been developed and illustrated with three examples. 2D structural vulnerability theory as developed most recently by Yu(1997) has also been re-examined and improved. The algorithm for computer implementation of 2D structural vulnerability theory has been greatly improved. The improved algorithm provides a more complete search, always use the most up to date hierarchy and has a special treatment for structure with a mixture of types of joint. In order to create a graphical user interface for SAVE (Structural Analysis for Vulnerability Estimation) (Yu, 1997), some graphical functions have been developed. These graphical functions include: drawing the structure; drawing the cluster formation procedures; drawing the hierarchical presentation; drawing the most vulnerable failure scenarios in the structure. The theory is potentially of use in the design of protection and performance monitoring programmes for safety management and to reduce the risk of overlooking vulnerable failure scenarios

Probabilistic methods have been widely used in structural engineering to model uncertainties in loads and structural properties. The subjects of structural reliability analysis, random vibrations, and structural system identification have been extensively developed and provide the basic framework for developing rational design and maintenance procedures for engineering structures. One of the crucial requirements for successful application of probabilistic methods in these contexts is that one must have access to adequate amount of empirical data to form acceptable probabilistic models for the uncertain variables. When this requirement is not met, it becomes necessary to explore alternative methods for uncertainty modeling. Such efforts have indeed been made in structural engineering, albeit to a much lesser extent as compared to efforts expended in developing probabilistic methods. The alternative frameworks for uncertainty modeling include methods based on the use of interval analysis, convex function representations, theory of fuzzy variables, polymorphic models for uncertainties, and hybrid models which combine two or more of alternative modeling frameworks within the context of a given problem. The work reported in this thesis lies in the broad area of research of modeling uncertainties using non-probabilistic and combined non-probabilistic and probabilistic methods. The thesis document is organized into 5 chapters and 6 annexures. A brief overview of alternative frameworks for uncertainty modeling and their mathematical basis are provided in chapter 1. This includes discussion on modeling of uncertainties using intervals and issues related to uncertainty propagation using interval algebra; details of convex function models and relevance of optimization tools in characterizing uncertainty propagation; discussion on fuzzy variables and their relation to intervals and convex functions; and, issues arising out of treating uncertainties using combined probabilistic and non-probabilistic methods. The notion of aleatoric and epistemic uncertainties is also introduced and a brief mention of polymorphic models for uncertainty, which aim to accommodate alternative forms of uncertainty within a single mathematical model, is made. A review of literature pertaining to applications of non-probabilistic and combined probabilistic and non-probabilistic methods for uncertainty modeling in structural engineering applications is presented in chapter 2. The topics covered include: (a) solutions of simultaneous algebraic equations, eigenvalue problems, ordinary differential equations, and the extension of finite element models to include non-probabilistic uncertainties, (b) issues related to methods for arriving at uncertainty models based on empirical data, and (c) applications to problems of structural safety and structural optimization. The review identifies scope for further research into the following aspects: (a) development of methods for arriving at optimal convex function models for uncertain variables based on limited data and embedding the models thus developed into problems of structural safety assessment, and (b) treatment of inverse problems arising in structural safety based design and optimization which takes into account possible use of combined probabilistic and non-probabilistic modeling frameworks. Chapter 3 considers situations when adequate empirical data on uncertain variables is lacking thereby necessitating the use of non-probabilistic approaches to quantify uncertainties. The study discusses such situations in the context of structural safety assessment. The problem of developing convex function and fuzzy set models for uncertain variables based on limited data and subsequent application in structural safety assessment is considered. Strategies to develop convex set models for limited data based on super-ellipsoids with minimum volume and Nataf’s transformation based method are proposed. These models are shown to be fairly general (for instance, approximations to interval based models emerge as special cases). Furthermore, the proposed convex functions are mapped to a unit multi-dimensional sphere. This enables the evaluation of a unified measure of safety, defined as the shortest distance from the origin to the limit surface in the transformed standard space, akin to the notion used in defining the Hasofer- Lind reliability index. Also discussed are issues related to safety assessment when mixed uncertainty modeling approach is used. Illustrative examples include safety assessment of an inelastic frame with uncertain properties. The study reported in chapter 4 considers a few inverse problems of structural safety analysis aimed at the determination of system parameters to ensure a target level of safety and (or) to minimize a cost function for problems involving combined probabilistic and non-probabilistic uncertainty modeling. Development of load and resistance factor design format, in problems with combined uncertainty models, is also presented. We employ super-ellipsoid based convex function/fuzzy variable models for representing non-probabilistic uncertainties. The target safety levels are taken to be specified in terms of indices defined in standard space of uncertain variables involving standard normal random variables and (or) unit hyper-spheres. A class of problems amenable for exact solutions is identified and a general procedure for dealing with more general problems involving nonlinear performance functions is developed. Illustrations include studies on inelastic frame with uncertain properties. A summary of contributions made in the thesis, along with a few suggestions for future research, are presented in chapter 5. Annexure A-F contain the details of derivation of alternative forms of safety measures, Newton Raphson’s based methods for optimization used in solutions to inverse problems, and details of combining Matlab based programs for uncertainty modeling with Abaqus based models for structural analysis.

Este trabalho aborda a introdução da segurança baseada em métodos probabilísticos, aplicados nos cálculos em estados limites, apresentando informações com o objetivo de esclarecer o meio técnico em geral a respeito dos fundamentos teóricos e das vantagens que tal método apresenta frente ao tradicional método das tensões admissíveis. Apresenta-se ainda alguns exemplos de cálculo, mostrando a determinação do índice de confiabilidade e dos coeficientes adotados no método dos estados limites, os quais são calibrados em relação aos tradicionais coeficientes de segurança do método das tensões admissíveis. / This work is about structural safety based in the probabilistic methods, applied in the structural design at limit states. Informations about theoretical background and advantages that this method shows related to traditional allowable stress design method are presented. In addition, some examples are presented, showing the determination of the reliability index and limit states factors, which are adjusted to original safety factors of the allowable stress design method.

Aborda-se a importância da avaliação de desempenho em sistemas construtivos inovadores, relatando inicialmente os sistemas de avaliação utilizados em alguns países estrangeiros e também, no Brasil. As edificações térreas de uso unifamiliar devem satisfazer determinadas exigências dos usuários, dentre as quais aquelas de segurança estrutural, durabilidade e estanqueidade. Para cada uma destas exigências estão estabelecidos requisitos e critérios de desempenho que devem ser atendidos quando o produto for avaliado. Tendo como objetivo a avaliação estrutural de sistemas construtivos inovadores, tomou-se como estudo de caso a Vila Tecnológica de Ribeirão Preto, com 111 habitações distribuídas em onze sistemas construtivos inovadores, implantada através do projeto PROTECH, programa instituído pela secretaria Geral da Presidência da República, e da COHAB-RP. O objetivo do empreendimento é criar centros de experimentação, demonstração e difusão de inovações tecnológicas, incentivando a produção industrial, aliando redução de custos à melhoria da qualidade da habitação. Cada sistema construtivo foi submetido a ensaios, realizados no campo, em um protótipo escolhido aleatoriamente. Para comparação e controle dos resultados, uma habitação convencional, \"padrão COHAB\", foi submetida aos mesmos ensaios, servindo como valores de referência. Apresentam-se então os resultados da avaliação, referentes à segurança estrutural, como também, a metodologia utilizada e o desempenho de cada sistema inovador frente ao padrão de referência adotado. / This work discusses the performance evaluation of innovative construction systems, starting with an account of the evaluation systems used in Brazil as well as in some foreign countries. Single storey one-family houses must satisfy several of the users\' basic expectations, among them structural safety, durability and watertighness. Prerequisites and performance criteria to satisfy each of these expectations have been established and must be met when the product is evaluated. The \"Vila Tecnológica de Ribeirão Preto\" was taken as a case study to perform a structural evaluation of innovative construction systems. The \"Vila Tecnológica\" has 111 homes distributed under eleven innovative construction systems, built through the PROTECH project, a program instituted by the Secretaria Geral da Presidência da República (General Bureau of the Presidency of the Republic) and by COHAB-RP (a federal housing program for low in come families). The aims to create centers for project experimention, demonstration and dissemination of innovative building technologies, and to stimulate production on an industrial scale, combining the advantages of reduced costs to improved housing quality. Each construction system was submitted to field tests performed on a randomly selected prototype. For purposes of comparison and control of the results, a conventional \"standard COHAB\" house was submitted to the same tests, the results thereof serving as reference values. The results of the evaluation of structural safety are presented herein, as well as the methodology utilized and the performance of each innovative construction system compared to the standard of reference adopted.

A maioria dos materiais estruturais de Construção Civil tem suas propriedades mecânicas reduzidas, quando submetidos a temperaturas elevadas. Por isso, a capacidade resistente das estruturas de concreto armado dos edifícios pode ser reduzida devido à ação térmica de incêndios. Se os meios de proteção ativa dos edifícios não forem eficientes, o incêndio desenvolve-se em proporções catastróficas. A temperatura dos elementos estruturais se eleva o suficiente para induzir à redução da resistência e rigidez e, por conseguinte, à ruptura localizada ou até ao colapso progressivo do edifício. O objetivo principal da segurança contra-incêndio é a proteção à vida dos ocupantes das edificações. Este trabalho tem o objetivo de fornecer informações às futuras revisões de normas pertinentes ao projeto de estruturas de concreto e às pesquisas subseqüentes e contribuir à escassa literatura técnica em português sobre o tema. São apresentados: os efeitos do calor sobre as propriedades térmicas e mecânicas dos materiais concreto e aço e suas influências sobre o comportamento estrutural de edifícios de concreto armado, os métodos de cálculo disponíveis na literatura técnica internacional para o projeto de estruturas de concreto armado em situação de incêndio e proposta de um método simplificado expedito mais preciso para o projeto de elementos submetidos à flexão simples e normal composta para os padrões geométricos e características do concreto usuais no Brasil. / The thermal and mechanical properties of building materials are reduced at high temperatures, and the structural resistance of reinforced concrete buildings, as well. If the means of active protection are not efficient the fire will develop and the consequential increase in temperature can take an important role on the local failure of a single member or the progressive collapse of the building. The structural design must take into account the possibility of a fire happening as an accidental action during the lifetime of the building, aiming mainly at the protection of the users lives. This doctoral thesis aims to contribute to the development of the technical references in Portuguese about the fire design of reinforced concrete structures, to stimulate further researches and afterwards standard reviews related to the structural design in fire of reinforced concrete buildings. The work reviews the heat effects on the thermal and mechanical properties of the materials and the consequential impact on the structural behaviour of reinforced concrete buildings, the calculation methods available in the international technical reference for the fire design of reinforced concrete structures and presents a proposal of an optimized simplified calculation method for the members under simple bending or composed axial-moment load, considering the geometric and concrete characteristics very usual in Brazil.

O projeto estrutural deve considerar as incertezas provenientes das variáveis envolvidas no dimensionamento dos elementos estruturais, tais como propriedades dos materiais, dimensões dos elementos estruturais e intensidade dos carregamentos atuantes. Existe também a variabilidade inerente aos métodos de análise estrutural, originária de imprecisões na idealização da distribuição das tensões e deformações dos elementos estruturais. Sendo assim, esta dissertação visa analisar a variabilidade dos desvios dos modelos de cálculo propostos por Blevot e Frémy (1967), Fusco (1994) e Santos (2013), todos baseados no método das bielas e tirantes, para blocos sobre duas, três e quatro estacas submetidos a carregamento centrado. Estes elementos estruturais possuem significativa importância, visto que atuam na transmissão dos esforços provenientes dos pilares às fundações profundas. Os modelos de cálculo foram confrontados entre si e com resultados experimentais de Blevot e Frémy (1967), Mautoni (1971), Clarke (1973), Miguel (2000) e Suzuki et al. (1998 / 1999 / 2000 / 2001) para determinação dos parâmetros estatísticos dos desvios desses modelos em relação aos ensaios. Os resultados apontaram desempenho satisfatório para os três modelos de cálculo. Em geral, todos os métodos se mostraram favoráveis à segurança nos casos avaliados para os três tipos de blocos de fundação. / Structural design must consider the uncertainties coming from the variables involved in dimensioning of the structural elements, such as material properties, dimensions of structural elements, and intensity of active loads. There is also inherent variability in structural analysis methods, originated from imprecision in idealization of the distribution of tensions and deformations of structural elements. Thus, this dissertation aims to analyze the variability of calculation models deviations proposed by Blevot and Frémy (1967), Fusco (1994) and Santos (2013), all based on strut and tie method, for two, three and four pile caps submitted to center load. These structural elements are of significant importance, since they act in transmission of loads from columns to deep foundations. Calculation models were compared with each other and with experimental results from Blevot and Frémy (1967), Mautoni (1971), Clarke (1973), Miguel (2000) and Suzuki et al. (1998 / 1999 / 2000 / 2001) to determine the statistical parameters of these model deviations in relation to the tests. Results indicated satisfactory performance for the three calculation models. In general, all methods were favorable to safety in cases evaluated for the three pile caps types.

In many tunnel designs, reinforced concrete tunnel lining design is selected based on construction requirements rather than design loads. A constant cross-section is typically used along a tunnel even if the design loads change from one location to another, especially for tunnels constructed by tunnel boring machines (TBM). Factor of safety against failure is not constant along the length of tunnel and is typically high at shallow depth regions. Factor of safety during a rare event is usually much less than the ones set for service load states. Rare events such as earthquake, train derailment, explosion and long duration fires do not happen daily and generally a minor reparable damage is targeted at the structure during those types of events. The focus of this study is to analytically investigate structural fire safety of reinforced concrete circular tunnel linings in terms of reduction in service load safety and to develop recommendations for preliminary assessment of structural fire endurance of circular tunnel linings. Analytical methods accounting for thermal non-linearity, material degradation, tunnel lining-ground interaction and fire time stages are available to assess the structural fire safety of the concrete tunnel linings. Analytical results are determined to be in good agreement with tunnel key segment hydrocarbon fire test.

A maioria dos materiais estruturais de Construção Civil tem suas propriedades mecânicas reduzidas, quando submetidos a temperaturas elevadas. Por isso, a capacidade resistente das estruturas de concreto armado dos edifícios pode ser reduzida devido à ação térmica de incêndios. Se os meios de proteção ativa dos edifícios não forem eficientes, o incêndio desenvolve-se em proporções catastróficas. A temperatura dos elementos estruturais se eleva o suficiente para induzir à redução da resistência e rigidez e, por conseguinte, à ruptura localizada ou até ao colapso progressivo do edifício. O objetivo principal da segurança contra-incêndio é a proteção à vida dos ocupantes das edificações. Este trabalho tem o objetivo de fornecer informações às futuras revisões de normas pertinentes ao projeto de estruturas de concreto e às pesquisas subseqüentes e contribuir à escassa literatura técnica em português sobre o tema. São apresentados: os efeitos do calor sobre as propriedades térmicas e mecânicas dos materiais concreto e aço e suas influências sobre o comportamento estrutural de edifícios de concreto armado, os métodos de cálculo disponíveis na literatura técnica internacional para o projeto de estruturas de concreto armado em situação de incêndio e proposta de um método simplificado expedito mais preciso para o projeto de elementos submetidos à flexão simples e normal composta para os padrões geométricos e características do concreto usuais no Brasil. / The thermal and mechanical properties of building materials are reduced at high temperatures, and the structural resistance of reinforced concrete buildings, as well. If the means of active protection are not efficient the fire will develop and the consequential increase in temperature can take an important role on the local failure of a single member or the progressive collapse of the building. The structural design must take into account the possibility of a fire happening as an accidental action during the lifetime of the building, aiming mainly at the protection of the users lives. This doctoral thesis aims to contribute to the development of the technical references in Portuguese about the fire design of reinforced concrete structures, to stimulate further researches and afterwards standard reviews related to the structural design in fire of reinforced concrete buildings. The work reviews the heat effects on the thermal and mechanical properties of the materials and the consequential impact on the structural behaviour of reinforced concrete buildings, the calculation methods available in the international technical reference for the fire design of reinforced concrete structures and presents a proposal of an optimized simplified calculation method for the members under simple bending or composed axial-moment load, considering the geometric and concrete characteristics very usual in Brazil.

O projeto estrutural deve considerar as incertezas provenientes das variáveis envolvidas no dimensionamento dos elementos estruturais, tais como propriedades dos materiais, dimensões dos elementos estruturais e intensidade dos carregamentos atuantes. Existe também a variabilidade inerente aos métodos de análise estrutural, originária de imprecisões na idealização da distribuição das tensões e deformações dos elementos estruturais. Sendo assim, esta dissertação visa analisar a variabilidade dos desvios dos modelos de cálculo propostos por Blevot e Frémy (1967), Fusco (1994) e Santos (2013), todos baseados no método das bielas e tirantes, para blocos sobre duas, três e quatro estacas submetidos a carregamento centrado. Estes elementos estruturais possuem significativa importância, visto que atuam na transmissão dos esforços provenientes dos pilares às fundações profundas. Os modelos de cálculo foram confrontados entre si e com resultados experimentais de Blevot e Frémy (1967), Mautoni (1971), Clarke (1973), Miguel (2000) e Suzuki et al. (1998 / 1999 / 2000 / 2001) para determinação dos parâmetros estatísticos dos desvios desses modelos em relação aos ensaios. Os resultados apontaram desempenho satisfatório para os três modelos de cálculo. Em geral, todos os métodos se mostraram favoráveis à segurança nos casos avaliados para os três tipos de blocos de fundação. / Structural design must consider the uncertainties coming from the variables involved in dimensioning of the structural elements, such as material properties, dimensions of structural elements, and intensity of active loads. There is also inherent variability in structural analysis methods, originated from imprecision in idealization of the distribution of tensions and deformations of structural elements. Thus, this dissertation aims to analyze the variability of calculation models deviations proposed by Blevot and Frémy (1967), Fusco (1994) and Santos (2013), all based on strut and tie method, for two, three and four pile caps submitted to center load. These structural elements are of significant importance, since they act in transmission of loads from columns to deep foundations. Calculation models were compared with each other and with experimental results from Blevot and Frémy (1967), Mautoni (1971), Clarke (1973), Miguel (2000) and Suzuki et al. (1998 / 1999 / 2000 / 2001) to determine the statistical parameters of these model deviations in relation to the tests. Results indicated satisfactory performance for the three calculation models. In general, all methods were favorable to safety in cases evaluated for the three pile caps types.

Aborda-se a importância da avaliação de desempenho em sistemas construtivos inovadores, relatando inicialmente os sistemas de avaliação utilizados em alguns países estrangeiros e também, no Brasil. As edificações térreas de uso unifamiliar devem satisfazer determinadas exigências dos usuários, dentre as quais aquelas de segurança estrutural, durabilidade e estanqueidade. Para cada uma destas exigências estão estabelecidos requisitos e critérios de desempenho que devem ser atendidos quando o produto for avaliado. Tendo como objetivo a avaliação estrutural de sistemas construtivos inovadores, tomou-se como estudo de caso a Vila Tecnológica de Ribeirão Preto, com 111 habitações distribuídas em onze sistemas construtivos inovadores, implantada através do projeto PROTECH, programa instituído pela secretaria Geral da Presidência da República, e da COHAB-RP. O objetivo do empreendimento é criar centros de experimentação, demonstração e difusão de inovações tecnológicas, incentivando a produção industrial, aliando redução de custos à melhoria da qualidade da habitação. Cada sistema construtivo foi submetido a ensaios, realizados no campo, em um protótipo escolhido aleatoriamente. Para comparação e controle dos resultados, uma habitação convencional, \"padrão COHAB\", foi submetida aos mesmos ensaios, servindo como valores de referência. Apresentam-se então os resultados da avaliação, referentes à segurança estrutural, como também, a metodologia utilizada e o desempenho de cada sistema inovador frente ao padrão de referência adotado. / This work discusses the performance evaluation of innovative construction systems, starting with an account of the evaluation systems used in Brazil as well as in some foreign countries. Single storey one-family houses must satisfy several of the users\' basic expectations, among them structural safety, durability and watertighness. Prerequisites and performance criteria to satisfy each of these expectations have been established and must be met when the product is evaluated. The \"Vila Tecnológica de Ribeirão Preto\" was taken as a case study to perform a structural evaluation of innovative construction systems. The \"Vila Tecnológica\" has 111 homes distributed under eleven innovative construction systems, built through the PROTECH project, a program instituted by the Secretaria Geral da Presidência da República (General Bureau of the Presidency of the Republic) and by COHAB-RP (a federal housing program for low in come families). The aims to create centers for project experimention, demonstration and dissemination of innovative building technologies, and to stimulate production on an industrial scale, combining the advantages of reduced costs to improved housing quality. Each construction system was submitted to field tests performed on a randomly selected prototype. For purposes of comparison and control of the results, a conventional \"standard COHAB\" house was submitted to the same tests, the results thereof serving as reference values. The results of the evaluation of structural safety are presented herein, as well as the methodology utilized and the performance of each innovative construction system compared to the standard of reference adopted.