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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

Thesis (Ph. D.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains viii, 223 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 217-223).

Thesis (doctoral) -- Tampereen teknillisen yliopiston, 2007. / Includes bibliographical references. Also available on the World Wide Web.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

O presente trabalho busca compilar os fatores envolvidos na seguranÃa de barragens de terra, identificando os principais tÃpicos relacionados à seguranÃa e ao controle dos riscos que elas possuem. Apresenta um breve histÃrico do processo das regulamentaÃÃes sobre seguranÃa de barragem no cenÃrio internacional e nacional, enfatizando a importÃncia e os desafios no trato de questÃes legais que comprometem a seguranÃa de nossas barragens. Faz uma exposiÃÃo dos principais acidentes e incidentes registrados no perÃodo de formulaÃÃo e tramitaÃÃo da recente legislaÃÃo aprovada no Brasil sobre seguranÃa de barragens, Lei 12.334 de 20 de setembro de 2010. Descreve uma metodologia de avaliaÃÃo de risco com seus princÃpios e vantagens. Apresenta um estudo sobre o rompimento da barragem de terra AlgodÃes I, construÃda no municÃpio de Cocal, Norte do Estado do PiauÃ, enfatizando o histÃrico da obra, as caracterÃsticas do empreendimento, aspectos de projeto e seus mÃtodos construtivos. Faz uma anÃlise dos elementos de seguranÃa desta barragem com base na bibliografia consultada e aplicaÃÃo da metodologia descrita, objetivando identificar o potencial de risco que a barragem representava antes do seu rompimento. A partir da investigaÃÃo dos antecedentes e respectivas causas de vinculaÃÃo remota e imediatas ao incidente à possÃvel avaliar alguns dos fatores que contribuÃram com o rompimento da barragem, subsidiado nos relatÃrios tÃcnicos emitidos por especialista e/ou instituiÃÃes competentes. O fator condicionante para o colapso da barragem AlgodÃes I foi à ausÃncia de um dispositivo legal imperativo e a necessidade de uma fiscalizaÃÃo intensa no cumprimento dos preceitos estabelecidos pela lei para garantir a seguranÃa da barragem, e que devem ser levadas em consideraÃÃo para evitar riscos de colapso no tipo de estrutura estudado, jà que tal barragem representava um potencial de risco alto conforme metodologia especifica apresentada. / This study aims to compile the factors involved in safety earth dams, identifying key topics related to the security and control of the risks they have. Presents a brief history of the process of dam safety regulations in the international and national scene, emphasizing the importance and challenges in dealing with legal issues that compromise the safety of our dams. Gave a presentation of the main accidents and incidents recorded in the formulation and processing period of legislation passed in Brazil on dam safety, Law 12.334 of September 20, 2010. Describes a risk assessment methodology with its principles and advantages. Presents a study of the disruption of the earth dam AlgodÃes I, built in the city of Cocal, North of Piauà State, emphasizing the history of the work, project characteristics, design features and their construction methods. An analysis of the security features of this dam based on bibliography and application of the described methodology in order to identify the potential risk that the dam stood before his break. From the research of the past and the causes of remote and immediate link to the incident is possible to evaluate some of the factors that contributed to the dam break, subsidized in the technical reports issued by expert and / or competent institutions. The determining factor for the collapse of AlgodÃes I dam was the absence of a mandatory legal provision and the need for intensive supervision in compliance with the rules established by law to ensure dam safety, and that should be taken into account to avoid risk collapse on the type of structure studied, as this dam posed a high risk potential as specific methodology presented.

OHSAS 18000 Occupational Health and Safety Assessment System Series have a special importance to mining. OHSAS standardization aims to provide secure, more tranquil and healthier working space to the employees by means of establishing an assessment system. As mining activities are generally carried out in high risk environments, OHSAS has been improved and has increased its importance for mining in the world. In this study, Bigadi&ccedil / Boron Work is taken as a case for the application of OHSAS 18001. Theoretical information about OHSAS and risk assessment is provided, and some exemplifying mines that implemented this standard are given to illustrate their benefits. All possible hazard sources are identified and a &ldquo / Hazard Source Inventory&rdquo / is proposed. Together with this hazard source inventory, a risk assessment method is developed for Bigadi&ccedil / Boron Work. Several tasks are evaluated according to this proposed form. In order to define policy, principles and structure of Occupational Health and Safety Assessment System, an &ldquo / OHSA Manual&rdquo / is prepared. Several sets of standard forms were prepared and recommended for Bigadi&ccedil / Boron Work. Consistency throughout the organization was established by means of these created standard documents, procedures and forms. Proposed Job Safety Analysis form can be used to identify, analyze and record the steps involved in performing a specific task, and the existing or potential safety and health hazards associated with each step. Several safe job procedures were also prepared with the help of the risk assessment process. In addition to this, an &ldquo / Emergency Plan&rdquo / is proposed for enterprise to prevent loss of life, property and information, and provide safety in case of any emergency or natural disaster. An &ldquo / OHS Audit Instrument&rdquo / is suggested for the Bigadi&ccedil / Boron Work that will play a key role for continuous improvement of the system. Audits are integral part of OHSAS in order to identify hazards, improve health and safety conditions, and check compliance with regulations. These studies also show that there are some problems in the implementation of the system. The main problem is ineffective data recording and keeping. Lack of consciousness of employees and low commitment of top management constitute another important difficulty. Although these problems are commonly encountered in practice, applying OHSAS 18000 standard is still worthwhile method of improving work environment.

Safety risk assessment forms an integral part of the design and development of Safety Critical Systems. Conventionally in these systems, standards and policies have been developed to prescribe processes for safety risk assessment. These standards provide guidelines, references and structure to personnel involved in the risk assessment process. However, in some of these standards, the prescribed methods for safety decision making were found to be deficient in some respects. Two such deficiencies have been addressed in this thesis. First, when different safety metrics are required to be combined for a safety related decision, the current practices of using safety risk matrices were found to be inconsistent with the axioms of decision theory. Second, in the safety risk assessment process, when multiple experts are consulted to provide their judgment on the severity and/or likelihood of hazards, the standards were lacking detailed guidelines for aggregating experts' judgements. Such deficiencies could lead to misconceptions pertaining to the safety risk level of critical hazards. These misconceptions potentially give rise to inconsistent safety decisions that might ultimately result in catastrophic outcomes. This thesis addresses both these concerns present in SRM processes. For the problem of combining safety metrics, three potential approaches have been proposed. Normative Decision Analysis tools such as Utility Theory and Multi-attribute Utility Theory were proposed in the first and second approaches. The third approach proposes the use of a Multi-Objective Optimization technique - Pareto Analysis. For problems in Expert Aggregation, behavioral and mathematical solutions have been explored and the implications of using these methods for Safety Risk Assessment have been discussed. Two standard documents that contain the Safety Risk Management Processes of the Federal Aviation Agency (FAA) and the U.S. Navy were used to structure the case studies. This thesis has two main contributions. First, it evaluates the use of decision analysis in safety decision process of Safety Critical Systems. It provides guidelines to decision makers on how to meaningfully use and/or combine different safety metrics in the decision process. Second, it identifies the best practices and methods of aggregating expert assessments pertaining to safety decision making. / Master of Science / Safety risk assessment forms an important part of the design and development of Safety Critical Systems. Safety Critical Systems are those systems whose failure could potentially result in the loss of human life. Commonly in these systems, standards and policies have been developed to prescribe processes for safety risk assessment. These standards provide guidelines, references and structure to personnel involved in the risk assessment process. However, in some of these standards, the prescribed methods for safety decision making were found to be deficient in some respects. Two such deficiencies have been addressed in this thesis. First, when different safety metrics are required to be combined to provide information for a safety related decision, the current practices of the safety risk assessment do not yield consistent recommendations. Second, in the safety risk assessment process, often multiple experts are consulted to provide their judgment on the criticality of a potential safety risk of the system. The standards and policies that are currently being used, do not provide clear instructions on how to synthesize the judgements of multiple experts. This lack of clear guidelines could potentially lead to an incorrect final judgement on the criticality of the risk and ultimately result in choosing an improper method to reduce the safety risk. This thesis addresses both these concerns present in safety risk assessment process of Safety Critical Systems. For the problem of combining safety metrics, three approaches have been proposed. Two of the proposed approaches make use of normative decision analysis practices and therefore the recommendations reached using these methods will be consistent with the safety objective of the decision maker. The third approach makes use of a traditional concept called -Pareto Analysis which provides a visual method to analyze the advantages and drawbacks of a given safety concern for a system. For problems in combining the judgements of multiple experts a variety of methods was studied. The methods include group consensus and mathematical techniques and the implications of using these methods in safety risk assessment was discussed. The FAA and the U.S. Navy's standard documents and policies were used to frame the discussions. This thesis has two main contributions. First, it evaluates the use of Normative Decision Analysis methods in safety decision process of Safety Critical Systems. It provides guidelines to decision makers on how to meaningfully use and/or combine different safety metrics in the decision process. Second, it identifies the best practices and methods of aggregating expert assessments pertaining to safety decision making.

The work presented in this thesis was undertaken as part of the safety work package of the NATURALHY project which was an integrated project funded by the European Commission (EC) within the sixth framework programme. The purpose of the NATURALHY project was to investigate the feasibility of using existing natural gas infrastructure to assist a transition to a hydrogen based economy by transporting hydrogen from its place of production to its place of use as a mixture of natural gas and hydrogen. The hydrogen can then be extracted from the mixture for use in fuel cells or the mixture used directly in conventional combustion devices. The research presented in this thesis focused on predicting the consequences of explosions and fires involving natural gas and hydrogen mixtures, using engineering type mathematical models typical of those used by the gas industry for risk assessment purposes. The first part of the thesis concentrated on modifying existing models that had been developed to predict confined vented and unconfined vapour cloud explosions involving natural gas. Three geometries were studied: a confined vented enclosure, an unconfined cubical region of congestion and an unconfined high aspect ratio region of congestion. The modifications made to the models were aimed at accounting for the different characteristics of a natural gas/hydrogen mixture compared to natural gas. Experimental data for the laminar burning velocity of methane/hydrogen mixtures was obtained within the safety work package. For practical reasons, this experimental work was carried at an elevated temperature. Predictions from kinetic modelling were employed to convert this information for use in models predicting explosions at ambient temperature. For confined vented explosions a model developed by Shell (SCOPE) was used and modified by adding new laminar burning velocity and Markstein number data relevant to the gas compositions studied. For vapour cloud explosions in a cubical region of congestion, two models were used. The first model was developed by Shell (CAM2), and was applied using the new laminar burning velocity and other composition specific properties. The second model was based on a model provided by GL Services and was modified by generalising the flame speed model so that any natural gas/hydrogen mixture could be simulated. For vapour cloud explosions in an unconfined high aspect ratio region of congestion, a model from GL Services was used. Modifications were made to the modelling of flame speed so that it could be applied to different fuel compositions, equivalence ratios and the initial flame speed entering the congested region. Predictions from the modified explosion models were compared with large scale experimental data obtained within the safety work package. Generally, (apart from where continuously accelerating flames were produced), satisfactory agreement was achieved. This demonstrated that the modified models could be used, in many cases, for risk assessment purposes for explosions involving natural gas/hydrogen mixtures. The second part of thesis concentrated on predicting the incident thermal radiation from high pressure jet fires and pipelines fires involving natural gas/hydrogen mixtures. The approach taken was to modify existing models, developed for natural gas. For jet fires three models were used. Fuel specific input parameters were derived and the predictions of flame length and incident radiation compared with large scale experimental data. For pipeline fires a model was developed using a multi-point source approach for the radiation emitted by the fire and a correlation for flame length. Again predictions were compared with large scale experimental data. For both types of fire, satisfactory predictions of the flame length and incident radiation were obtained for natural gas and mixtures of natural gas and hydrogen containing approximately 25% hydrogen.

In roadway projects, design exceptions are implemented when the project site consists of one or more substandard design elements. The objective of this thesis is to conduct an initial investigation for a monitoring program for the safety performance of design exceptions in Georgia. A total of 467 projects containing design exceptions were reported in Georgia from 1995 to 2011, and from this crash data for 179 projects from 2003 to 2008 were sampled. The crash data collected in this research pertains to all roadway segments within the projects and is not necessarily related to the design exceptions. Future efforts will be required to explore potential connections between the crash rates and design exceptions. The annual crash results generally revealed a high variability and randomness in the data. For this reason, the average 3-year crash frequencies before design exception approval date and after it were calculated to determine the safety performance for projects containing design exceptions. A method for determining expected results using the Highway Safety Manual (HSM) predictive method is also discussed. The findings will be used to guide future research on design exceptions and mitigation measures to improve roadway safety.