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In dit afstudeerverslag wordt een onderzoek naar de risico's en de faalkansen van jetgroutlagen uiteengezet. Eerst worden de voordelen van een jetgroutlaag ten opzichte van andere waterremmende lagen opgesomd waarna de verschillende soorten jetgroutlagen worden besproken. Na het onderzoeken van de optredende onnauwkeurigheden en afwijkingenis een risico-analyse model voor jetgroutlagen voor 2 rastertypen opgesteld. Om indicatiewaarden van veilige ontwerparameters te krijgen is vervolgens de relatie tussen enkele parameters onderzocht aan de hand waarvan een aantal simulaties voor jetgroutlagen is gedaan. De resultaten hiervan zijn in Hoofdtuk 4 en in de bijlagen terug te vinden. Jetgrouting is een techniek waarbij onder hoge druk grond los wordt gesneden en grotendeels vervangen door een water/cement-mengsel. Door dit proces trekkend en roterend tegelijk uit te voeren worden ronde groutkolommen verkregen. Door dit volgens een van te voren bepaald stramien uit te voeren wordt als het ware een ondergrondse vloer gerealiseerd, een zogenaamde jetgroutlaag. Jetgroutlagen kunnen worden toegepast bij de aanleg van verdiepte constructies. Het doel van een jetgroutlaag is te zorgen dat tijdens en na bemaling en afgraving van een bouwput geen grondwater zal toetreden. Tevens kan de jetgroutlaag dienen als stempeling na afgraving van de kuip.

Reliability analysis of the Caldicot Levels flood defence system by using Dutch reliability methods for flood defences F.A. Buijs In the light of the shift to a risk-based safety assessment of flood defences in the UK a project called RASP, Risk Assessment of Strategic Planning, is carried out at among others HRWallingford. Part of this project is to develop a detailed level methodology supporting decision-making at the scale of one flood defence system. In this Msc thesis the reliability-based tools as applied to flood defences in the Netherlands are tested on a flood defence system in the UK, the Caldicot Levels flood defence system, in order to support an evaluation of the appropriateness of these tools as part of the detailed level methodology in RASP. The Caldicot Levels flood defence system is located at the south coast of Wales in the UK. The system borders the Severn Estuary in the south, the river Usk in the west and a distinct line of hills in the north and east. In the Severn estuary one of the largest tidal ranges in the world occurs, a range that varies between 9 and 15 meter. The River Usk is a small river, however the water levels can reach quite high values especially in case of high water levels at the Severn Estuary. The Dutch reliability methods for flood defences mainly consist of two parts. Software called PC-Ring which calculates the probability of failure of a flood defence system. Second, a process that selects the flood defence sections which are most representative of the systems probability of failure. The first step in the reliability analysis is the definition of the system. This step points out the relevant defence length for the calculation of the probability of inundation and the area which suffers consequences in case the flood defence system fails. The second step is to define the systems components, or the defence types that occur in the flood defence system. Part of the second step is to determine the different failure modes which can cause failure of the components. The third step is to select for each failure mode the weak cross sections in the flood defence system which contribute most to the total probability of failure. The last step is gather the data connected to the selected cross sections and perform the calculations with PC-Ring. The results point out the weakest links in the system and which random variables contribute most to the variance of the total probability of failure. Apart from the probability of failure of the present system, the probability of failure of the system with improvements is regarded. The Dutch reliability-based methods for flood defences prove to be suitable for relatively highly engineered systems with a high data availability - compared to UK standards. Adaptations of PC-Ring to the UK site point out that the set-up of the program is not very flexible. However, considering the diverse nature of the flood defences in the UK and the often relatively low data availability, a flexible reliability-based computer program for flood defences will be required in the UK.

At the moment, there are no Dutch regulations giving criteria for the design of bored tunnels. These regulations are necessary to prove that the required safety and serviceability are guaranteed by the proposed design. The scope of the study presented in this report consists of a reliability analysis of a SFRC tunnel lining. This consists of the definition of the load and resistance factors that are considered necessary to make a design of a SFRC lining and the calculation of the failure probability of the tunnel in the ultimate limit state. The study carried out in this report is based on the ITM tunnel design case with a lining thickness of 0,40 m and a radius of 4,70 m. The tunnel lining can fail by several mechanisms. The mechanism that is examined in this study, consists of the failure of the tunnel lining under strain of the soil stresses in the ultimate limit state. The analysis is executed with a level II probabilistic design method. The basis of this method is that the parameters used in the structural design are not specified constants, but stochastic variables. The most advanced method of this level is the so-called Approximate Full Distribution Approach (AFDA). This method is used for the reliability analysis executed in this report. First of all, the reliability of the tunnel design is approached with a linear calculation model, i.e. with the analytical Duddeck model. The most remarkable conclusion drawn from the linear reliability analysis, is that the safety requirements are on the whole better met in case of more flexible and thinner inings. As this conclusion does not meet the expectations and as the use of a (simple) linear model has a real benefit, the impact of non-linear effects on the cross-section forces is examined in order to determine whether the assumption of linearity is likely to be acceptable within the limitations of the non-linear tunnel analysis. An important conclusion drawn from the non-linear reliability analysis is that the safety decreases with decreasing lining thickness. The latter refutes the conclusion drawn at the linear reliability analysis that the safety increases with decreasing lining thickness. Moreover, from the non-linear reliability analysis follows that it is not safe to use the (linear) analytical Duddeck method for the design of slender constructions. In general, it can be concluded that the examination of the safety of a tunnel lining is very extensive and that still a lot of work is left to be done.

The functioning of vital infrastructures, such as energy and telecommunications infrastructure, is key to societal and economic security and well-being in modern society. The reliability of these infrastructures is thus of paramount importance. Transmission system operators (TSOs) fulfill a central role in achieving this reliability, by maintaining, operating and developing the transmission networks that form the backbone of the infrastructure. However, the TSOs have to achieve this in changing conditions and with increasing uncertainties; vital infrastructures are faced with rapidly changing market conditions and regulations, especially given the ongoing liberalization process in the European Union. Furthermore, they not only have to maintain reliability, but also other values like affordability, accessibility and sustainability. To ensure an adequate level of reliability, while also remaining efficient and profitable in a changing environment, TSOs need to continuously reevaluate their planning and investment decision making methods. To be able to do this, they need insight in the trade-off between reliability and efficiency and the different investment options to improve reliability. In this research, we aim to add to that insight by comparing three vital Dutch infrastructures (the gas infrastructure, the electricity infrastructure and the fixed line telecommunications infrastructure) using an analytical framework based on the ISO31000 Risk Management standard. By using risk management, we create a generic framework that explicitly deals with uncertainty. We focus on three elements in the risk management process: context, assessment and treatment. The study consists of a comparative case study, based on literature review and interviews with TSOs and regulators. The context has been described along a set of factors, that have been categorized as either technical, economic or institutional. The final set of 12 factors is considered to be as parsimonious, relevant and complete as possible, to give a structured and efficient overview of the different infrastructures. From analyzing the context it follows that the infrastructures are very different, but often have striking similarities on individual context factors and experience similar developments, such as internationalization and institutional fragmentation. This fact enables us to analyze the particular influence of these factors on the assessment and treatment of reliability. This final set of factors thus forms a strong basis for the rest of the analysis. Reliability is neither a simple nor an unambiguous concept for multiple reasons. First, we can identify different levels of reliability. Second, reliability risks can occur on different timescales and in different parts of the supply chain. Third, in vital infrastructures the public interest in reliability has a large influence on the perception of reliability. Finally, the discussion on reliability is often embedded in a specific infrastructure. To compare the assessment of reliability in different infrastructures, we have to deal with these complexities. Therefore, we have developed a new conceptual model that identifies different levels and dimensions of reliability and also is generic enough to be applied to all analyzed infrastructures. The assessment of reliability in gas and electricity infrastructure shows strong similarities, while in telecommunications infrastructure the assessment is radically different as a result of rapid technological developments and strong differentiation in services offered. When analyzing the treatment of reliability, it becomes clear that individual treatment options are very infrastructure specific and comparing them is difficult and of limited use. Therefore, four high-level treatment strategies have been identified, which can be compared between infrastructures. These four treatment strategies are investing in larger infrastructures, investing in smarter infrastructures, supply responsiveness and demand responsiveness. The dominant strategies of the TSO in gas infrastructure are investing in larger infrastructures and supply responsiveness; in electricity infrastructure it is supply responsiveness and in telecommunications infrastructure it is investing in larger and smarter infrastructures. Demand responsiveness is important, but not a central strategy for TSOs, because they deal with aggregated traffic flows and have no direct contracts with consumers in which to include incentives for demand responsiveness. The trade-off between reliability and efficiency is sometimes mistakenly simplified and over rationalized in the discussion between regulators and regulated TSOs. Considering that the costs of reliability risks and the investment costs to reduce these risks can be estimated, it is contended that this trade-off can be analytically optimized. However, given the multidimensionality and subjectivity of reliability and the complexity of transmission networks, this optimization is most likely false and extremely difficult. In an infrastructure where different stakeholders have different perceptions and requirements for reliability, which also change over time and as a result of incidents, an adequate level of reliability can only be determined in a political, rather than an analytical, process. Another concern is that fragmented regulatory oversight and the decoupling of public values, can lead to conflicting interventions and suboptimal decisions by the TSO. Especially when the regulation of a specific value is very stringent compared to other values (e.g. efficiency by price regulation) and the regulated TSO has only specific responsibilities and capabilities, the risk exists that the scope of the TSO is narrowed only to those responsibilities and capabilities, instead of developing and encouraging new solutions. To avoid this, regulation should be more holistic and should address conflicts between different public values instead of decoupling them. To achieve an adequate trade-off between reliability and efficiency, while dealing with institutional fragmentation and uncertainty, TSOs should employ more proactive mechanisms to efficiently and effectively utilize existing and future transport capacity. Especially the gas infrastructure lacks such mechanisms, e.g. an efficient capacity allocation mechanism. Also, while we have shown that analytically optimizing the trade-off between efficiency and reliability produces no sensible results, TSOs still need a way to determine and achieve an adequate level of reliability. Considering the political and complex nature of reliability, it is necessary to develop instruments to achieve long-term reliability in cooperation with other stakeholders.

This contribution extends the common documented approach of integrity through Protection Levels in Satellite-Based Augmentation System (SBAS) positioning for aeronautics, to reliability on the basis of statistical hypothesis testing, and as such provides a safeguard against model misspecifications as anomalies and outliers in the measurements. It is shown that when integrity is monitored through Protection Levels and reliability added through Reliability Levels, the availability of the SBAS position solution is more than 99% for APV-I precision approach. The availability for CAT-I is currently just a few percent. When the Galileo constellation is added, and current performance is copied ahead, the percentage for CAT-I increases to beyond 95%.

In the future, a large-scale expansion of offshore wind energy is expected in the Netherlands. For this large-scale expansion, a well-designed offshore network is needed. Different network configurations will lead to other availability of the offshore network and therefore also the offshore wind energy. This research studies the contribution of offshore wind energy to the reliability of the Dutch power system, taking into account the availability of the wind power production and the offshore network. In this research, different configurations for the offshore wind energy network are defined, like individually connected wind parks, clusters of wind parks of 1 GW, and two main clusters of offshore wind parks. For each configuration, the availability of the offshore network is determined. Then the offshore wind energy, the offshore network and the Dutch power system are combined into one reliability model for the combined system. Conclusions are drawn about the availability of the different offshore networks and the usefulness of the combined reliability model developed.

Critical Infrastructures are the arteries and veins of Western, urbanized societies. The services and products provided by these large-scale, complex systems are considered essential. However, in recent years, more and more new problems seem to crop op after these infrastructures were opened up to market forces. What has happened in these critical infrastructures that we have come to depend upon? How did restructuring affect the reliability of their services? This study takes the reader beyond the debate between states and markets and focuses on the daily control and management of critical infrastructures - the world of control rooms. How has restructuring influenced the ability of those who operate these critical infrastructures to provide reliable services? And how do they cope with the effects of restructuring? Networked reliability presents first-hand accounts from electricity and telecommunications. It reconstructs the operations of the California Independent System Operator (CAISO) during California's electricity restructuring and the resulting electricity crisis. The second case study describes how KPN Mobile managed its mobile network in the liberalized mobile telphony market in the Netherlands. Networked reliability sheds new light on the effects of restructuring and institutional fragmentation in critical infrastructures that are of interest to reliability scholars, reliability professionals and policy makers involved in critical infrastructure restructuring. One of the most important findings is that the reliability of critical infrastructures becomes increasingly reliant on real-time control room operations. This study shows how those inside the control rooms employ unconventional means to ensure the reliable services under the increased volatility and unpredictability of their new environments.

The study presented in this manuscript investigates the patterns that describe reliability of water distribution networks focusing to the node connectivity, energy balance, and economics of construction, operation and maintenance. A number of measures to evaluate the network resilience has been developed and assessed to arrive at more accurate diagnostics of regular and irregular demand scenarios. These measures have been proposed as a part of the methodology for snap-shot assessment of network reliability based on its configuration and hydraulic performance. Practical outcome of the research is the decision support tool for reliability-based design of water distribution networks. This computer package named NEDRA (NEtwork Design and Reliability Assessment) consists of the modules for network generation, filtering, initialisation, optimisation, diagnostics and cost calculation, which can be used for sensitivity analyses of single network layout or assessments of multiple layouts. The study concludes that none of the analysed aspects develops clear singular patterns. Nevertheless, the proposed network buffer index (NBI) and the hydraulic reliability diagram (HRD) as visual representation of the network resilience give sufficient snap-shot pointing the composition of the index value, and displaying possible weak points in the network that can be hidden behind the averaged values of various reliability measures.

Wind is becoming an ever more important source of renewable energy: installed wind turbine power now stands at 60,000 MW worldwide, providing 0.6% of world electricity demand. Still it is important that the cost of wind energy is brought down further, which means that wind turbines must be designed to be exactly as strong as necessary, but no stronger. Hence there is a need to investigate whether the conventional design procedure results in the right degree of conservatism, and if not, how it may be improved. The ideal is to make the design just conservative enough, i.e. to exactly attain the target failure probability. Because wind turbines tend to be located in remote areas, the target value is primarily determined by economic considerations, rather than by public safety issues. The aims of this work are: To quantify total uncertainty in the design procedure, and to find the relative importance of stochastic parameters influencing fatigue loads and strength. To conduct a comparative review of calculation models where necessary. To derive partial safety factors giving minimum unit electricity cost. The scope of the present research is limited to fatigue issues, since extreme loads have been investigated previously to some degree. An inventory of stochastic parameters is made; for each of the parameters the distribution is estimated, and the models currently used in wind turbine design (i.e. the procedures used to estimate characteristic parameters and how to use them in calculations) are reviewed. A limit state function is derived using the concept of life fatigue damage equivalent load range. With the First Order Reliability Method (FORM) and Monte Carlo simulation, yearly failure probabilities due to fatigue are estimated for a wind turbine that is designed exactly according to the standard, and installed following common site admission rules. A simple economic model is used to establish optimal partial factors. The partial factor values found for blades are somewhat smaller than in the standard, while values for hub, nacelle and tower are higher. The explanation for the latter is that two things are currently not taken into account in design calculations according to the standard: firstly, variation and bias in fatigue life prediction; secondly, the fact that a combination of many critical locations (for example in the tower) yields a larger failure probability than just one location. The sensitivity of the partial factor optimisation to changes in various assumptions is investigated. The main conclusions of the work are threefold: Given available data, a larger partial (load or material) factor should be used in fatigue design for cast iron and weld seams. However, the effect of this on design might be limited since hidden safety exists in the construction: material quality and hence fatigue strength are better than assumed, wind turbines are placed in climates that are more benign than they were designed for, and finally, dimensions may be determined by stiffness or extreme load considerations rather than by fatigue. The variation of the limit state function is determined mainly by uncertainty on fatigue strength and fatigue life prediction. Therefore the way forward is to accurately establish fatigue properties and calibrate fatigue life predictions for materials exactly as used in wind turbines. In this way variation may be reduced (and bias removed), and failure probability estimates may be refined. If better information is available, hidden safety may be removed and smaller partial factors used in calculations. The number of critical locations and correlation of loads and fatigue strength at different locations must be taken into account in calculations to establish failure probabilities, and must have influence on the partial factors to be used. Variation and bias of fatigue life predictions must be an explicit input to fatigue design calculations.

Zoetermeer in The Netherlands. During peak hours the frequency on some trajectories is about 24 vehicles an hour. Dealing with these high frequencies and offering travelers a high quality product, according to waiting times as well as the probability of getting a seat, the operator designed a three step controlling philosophy. The first step is to prevent deviations to occur: the infrastructure is exclusive right of way as much as possible and at intersections RandstadRail gets priority over the other traffic. RandstadRail stops at every stop and never leaves before the scheduled time. The second step in the philosophy is dealing with deviations by planning extra time in the schedule at stops, trajectories and terminals. Small deviations can be solved in this way. The final step to get vehicles back on schedule is done by the traffic control centre: they have a total overview of all vehicles and they can respond to disturbances like slowing down vehicles nearby a delayed vehicle. Experiencing major disturbances rerouting and shortening of lines is possible. RandstadRail is in operation since 2007. The actual data of the performance is used to analyze the actual effects of the control philosophy. It is shown that due to the applied measures the variability of the driving times is reduced. Punctuality has increased as well. This leads to a higher level of service, creating shorter travel times, a better distribution of passengers over the vehicles.

The title of this thesis, System Reliability Assessment of Offshore Pipelines, portrays the application of probabilistic methods in assessing the reliability of these structures. The main intention of this thesis is to identify, apply and judge the suitability of the probabilistic methods in evaluating the system reliability of offshore pipelines subjected to corrosion. The analysis was first emphasized on interpreting corrosion data as random variables and probabilistic functions, through which uncertainties of the corrosion inspection tool could be taken into account. The reliability of the pipeline was initially studied by treating the structure as an independent unit. The analysis was further elaborated for pipelines arrayed as a series system of units, with the consideration of length effects. A framework for the reliability-based maintenance model was also developed in this thesis, aiming at optimizing the pipeline system operations. Herein, the analysis was mainly focused on improving the practice of releasing corrosion inhibitors into the pipeline. The use of inhibitors is considered to be the most applied maintenance practice among pipeline industries because of its simple mechanism to fight against corrosions. Last but not least, the thesis also looked into interpreting corrosions in space using theories on hydrodynamics.