This thesis investigated the different aspects and mechanisms of leak-before-break (LBB) assessment. The main objective was to improve the understanding of the transition between surface and through wall defects. While existing procedures generally idealise the through-wall crack into a rectangular shape, in reality a crack propagates with a shape depending on the loading. Comparison between the related solutions from established procedures have been undertaken. The apparent variation depending on the solutions used in the assessment has been highlighted. Two different methodologies have been employed to investigate the transition of flaw: (i) non-ideal through-wall and (ii) surface-breaking flaw propagation. The first approach consists of numerical models of non-idealised flaws in order to assess the effect on LBB parameters. For the second approach, experiments have been first carried out to visualise the shape of defect growths. To further study surface-breaking flaws, both experimental and numerical studies were performed. Fatigue tests on deeply notched plates with two crack aspect ratios were carried out. Strain evolutions on the back surface were recorded along the axes parallel and perpendicular to the crack. Numerical models have been prepared to investigate a larger scope. Behaviour of growing surface-breaking defects was examined. Based on the work conducted in this research, the major findings can be summarised as follows: - The existing solutions to carry out a LBB assessment using available procedures were reviewed and discussed. For axial flaws, SIF solutions were found similar and in good agreement with FEA values. Reference stress solutions showed significant difference between BS 7910 and API 579-1/ASME FFS-1. When compared to experimental data, API's solutions were able to distinguish between leak and break cases. - Flaw geometry assumption for through-wall crack yet to become idealised did not always reflect the actual behaviour, especially for COA calculation. In this case, FEA can be used as a good predictive tool for LBB to estimate margins when assessing leak rate. - The experiment using metallic specimens showed that high stress/strain on back surface would provide a good estimate of the crack propagation as it approached break-through. This offers a more accurate monitoring mechanism. Strain-mapping devices such as gauges could be used.

Esta pesquisa não teve a pretensão de resolver ou solucionar as questões envolvidas na problemática das coberturas vivas, e nem tão pouco dizer a maneira correta de se executar, mas sim apresentar algumas sugestões e questões a serem observadas no que se diz respeito ao desenvolvimento e aplicação da cobertura viva, e servir também de apoio para interessados na tecnologia. Ao longo de toda a apresentação da pesquisa será enfatizada a necessidade de se estudar cada cobertura dentro de seus parâmetros de singularidades impostas pelo local de implantação. Para isso desenvolveu-se um estudo sobre o sistema construtivo de cobertura conhecido atualmente como \"cobertura verde\", \"teto verde\", ou \"telhado de grama\". Essa investigação teve como enfoque questões técnicas de execução, como: impermeabilização, tipos de vegetação, tipos de drenagem, substrato, irrigação, etc. Dentro da pesquisa foram investigados alguns materiais disponíveis no mercado, que possam ser adaptados e agregados à execução da cobertura viva. Uma etapa dos estudos foi estruturada em uma análise de produção de ensaios com modelos reduzidos, a fim de observar e entender mais de perto o ciclo e o funcionamento da cobertura. Este estudo apresenta observações técnicas, realizadas tanto na fase de projeto como na de execução, fornecendo subsídios para contribuir com o aperfeiçoamento desta tecnologia. Com o objetivo de evitar qualquer tipo de endurecimento dos futuros pensamentos envolvidos na resolução da problemática da singularidade da cobertura, a pesquisa não observa uma inserção em dinâmicas regionais, como por exemplo: componentes e materiais e sua disponibilidade regional, índices pluviométricos, vegetação e clima, e outros fatores envolvidos na implantação regional da cobertura viva, sendo que cada uma destas problemáticas sugerem e abrem caminhos para muitas outras pesquisas. / This research did not aim to solve or resolve the issues involved in problematic of living roofs, and neither tell the correct way to execute, but to present some suggestions and issues to be observed as regards the development and application of a living roof, and also serve to support people who are interested in this technology. Throughout the presentation of the research will emphasize the need to study each roof within the parameters of singularities imposed by deployment location. To do this it developed a study on the construction system of coverage currently known as \"green roof\", \"green cover\", or \"grass roof.\" This investigation was focused technical issues of implementation, such as waterproofing, vegetation types, types of drain, substrate, irrigation, etc. Within the research were investigated some materials that are available in the market which can be adapted and added to the execution of living roofs. A step of studies was structured in an analysis of production tests with scale models in order to observe and understand more closely the cycle and operation of the roof. This study presents technical observations, performed either in the design phase and in the implementation, providing subsidies to contribute to the improvement of this technology. With the purpose of avoid any future tightening of thoughts involved in solving the problem of uniqueness of the roof, the research does not observe an insertion in regional dynamics, such as: materials and components and their regional availability, rainfall, vegetation and climate and other factors involved in the regional deployment of living coverage, with each of these problems and suggest ways to open many other researches.

Esta pesquisa não teve a pretensão de resolver ou solucionar as questões envolvidas na problemática das coberturas vivas, e nem tão pouco dizer a maneira correta de se executar, mas sim apresentar algumas sugestões e questões a serem observadas no que se diz respeito ao desenvolvimento e aplicação da cobertura viva, e servir também de apoio para interessados na tecnologia. Ao longo de toda a apresentação da pesquisa será enfatizada a necessidade de se estudar cada cobertura dentro de seus parâmetros de singularidades impostas pelo local de implantação. Para isso desenvolveu-se um estudo sobre o sistema construtivo de cobertura conhecido atualmente como \"cobertura verde\", \"teto verde\", ou \"telhado de grama\". Essa investigação teve como enfoque questões técnicas de execução, como: impermeabilização, tipos de vegetação, tipos de drenagem, substrato, irrigação, etc. Dentro da pesquisa foram investigados alguns materiais disponíveis no mercado, que possam ser adaptados e agregados à execução da cobertura viva. Uma etapa dos estudos foi estruturada em uma análise de produção de ensaios com modelos reduzidos, a fim de observar e entender mais de perto o ciclo e o funcionamento da cobertura. Este estudo apresenta observações técnicas, realizadas tanto na fase de projeto como na de execução, fornecendo subsídios para contribuir com o aperfeiçoamento desta tecnologia. Com o objetivo de evitar qualquer tipo de endurecimento dos futuros pensamentos envolvidos na resolução da problemática da singularidade da cobertura, a pesquisa não observa uma inserção em dinâmicas regionais, como por exemplo: componentes e materiais e sua disponibilidade regional, índices pluviométricos, vegetação e clima, e outros fatores envolvidos na implantação regional da cobertura viva, sendo que cada uma destas problemáticas sugerem e abrem caminhos para muitas outras pesquisas. / This research did not aim to solve or resolve the issues involved in problematic of living roofs, and neither tell the correct way to execute, but to present some suggestions and issues to be observed as regards the development and application of a living roof, and also serve to support people who are interested in this technology. Throughout the presentation of the research will emphasize the need to study each roof within the parameters of singularities imposed by deployment location. To do this it developed a study on the construction system of coverage currently known as \"green roof\", \"green cover\", or \"grass roof.\" This investigation was focused technical issues of implementation, such as waterproofing, vegetation types, types of drain, substrate, irrigation, etc. Within the research were investigated some materials that are available in the market which can be adapted and added to the execution of living roofs. A step of studies was structured in an analysis of production tests with scale models in order to observe and understand more closely the cycle and operation of the roof. This study presents technical observations, performed either in the design phase and in the implementation, providing subsidies to contribute to the improvement of this technology. With the purpose of avoid any future tightening of thoughts involved in solving the problem of uniqueness of the roof, the research does not observe an insertion in regional dynamics, such as: materials and components and their regional availability, rainfall, vegetation and climate and other factors involved in the regional deployment of living coverage, with each of these problems and suggest ways to open many other researches.