1,720,956 research outputs found
How safe is safe enough?
No full textDisasters can never be completely ruled out. The Dutch national government has therefore committed itself to the concept of risk rather than the false promise of absolute safety. The objectives of this study were to evaluate current regulatory practices in the domains of industrial and flood safety in the Netherlands, and to formulate proposals for improvement. The outcomes of such an endeavor depend heavily on the chosen yardstick to distinguish between superior and inferior policy alternatives. Throughout the thesis, social improvements are defined in a way that is consistent with the approach followed in societal cost-benefit analyses. The three main topics covered by the thesis are: 1. The Dutch industrial and flood safety policies: underlying rationales, current practices, opportunities for mutual learning. 2. Methods for risk evaluation and their conformity with a utilitarian ethic: cost-benefit analysis, FN-criteria, the precautionary principle. 3. Dealing with losses: optimizing disaster preparedness, the (un)insurability of large-scale floods, the relations between insurance and system safety.Civil Engineering and Geoscience
Seismic Risk Mitigation in Greece: Translation of Dutch flood risk management practices
No full textSeismic risk in some regions of Greece has increased over the last decades. The reason lies in urban development in earthquake prone regions, combined with a lack of ability or interest to tackle known construction vulnerabilities of buildings. Despite the severity of risk, also confirmed by recent events, homeowners have proven unwilling to mitigate seismic risk, possibly because of their inability to pay and/or unwillingness to invest due to lack of information or awareness. As a result, significant part of the building stock remains unsafe, in comparison with the safety level of the current building code. A way to stimulate seismic risk mitigation is government intervention. Such intervention could consist of a safety plan (retrofit program, mandatory insurance, emergency planning etc.) implemented by government, subsidies, introduction of more stringent building codes, risk communication. Recent developments in Greece regarding seismic safety are mostly aimed at vulnerability and risk evaluation, the publishing of a technical building Code of Interventions, and mapping out a seismic safety plan for Greece. Meanwhile, experts ask for government intervention proposing organisational change and a distribution of roles / liabilities among different clusters. For every scheme of government program, risk estimation is vital to be able to set priorities and decide whether buildings, municipalities, or regions are safe enough. Besides economic risks, risks to life should also be considered. Instruments for quantifying fatality risks are however unavailable at present. A review of the cornerstones of Dutch flood risk management practices, especially in risk estimation and decision-making has shown that fatality risks are considered from a societal perspective and an individual one. The societal risk metric concerns the (exceedance) probabilities of larger numbers of fatalities; the individual risk metric concerns the probability of death of a person at a specific location. In the case of the Netherlands, due to the nature of the flood hazard and protection scheme (public flood defences), the government is strongly involved in flood risk mitigation. Despite differences between the protection schemes for large-scale floods (strengthening dikes rather than protecting buildings) and earthquakes (strengthening buildings), this project proposes the translation (=the act of converting) of aforementioned metrics to the case of seismic risk in Greece. To quantify those metrics for earthquakes requires knowledge of the probabilities of different hazard levels (peak ground accelerations), the extent of damage on buildings given the hazard, and the expected number of fatalities in case of damage given the extent of damage. In this study, societal risk (depicted by FN-curves) and individual risk levels are quantified using exceedance probability function of peak ground acceleration at the site under Seismic Risk Mitigation in Greece Translation of Dutch Flood Risk Management Practices consideration, as well as deterministic transfer functions for damage (vulnerability curves) and losses (mortality curves). Moreover, since economic losses of earthquakes can also be significant, societal economic risk (FL-curve) and individual economic risk are also proposed and quantified. Using recent research results about the vulnerability of buildings, inventory data for social economic characteristics and reasonable assumptions about missing information (like building size); risk can be estimated for existing and retrofitted building stocks of Greek municipalities. After sensitivity analysis of model parameters, two case studies are presented that show the use of the aforementioned risk metrics for different levels of government decision-making. One simulating top level (central government) decision making, setting priorities for retrofit between municipalities, and the second simulating medium level (local government) decision making, setting priorities for a retrofit program between different structural typologies of buildings. The case studies show that the risk metrics and the model to quantify them can be useful tools for deciding which municipality should absorb more resources, whether mitigation is urgent, which mitigation strategy is most efficient, and how alternative retrofit programs influence risk levels. Of course, the model is only a prototype further refinements are advised. There are important benefits from the implementation of the described methodology. Firstly, the decision maker only deals with probabilities and consequences, has a general overview thus he/she may distribute resources and time in a more (cost) effective way. Moreover, human life is distinguished from cost-benefit analysis (no monetization). Events with high numbers of fatalities, which can cause disruption to the whole of the country, as well as disproportional individual exposures, can be targeted directly. Finally, it gives the opportunity to monitor the progress of a safety plan, and is scalable for central and local administration. This study concludes by proposing the application of societal & individual risk metrics (for fatalities and economic loss) to support two levels (central and local) of government decision making concerning seismic risk mitigation in Greece. Furthermore, it provides a prototype model for the quantification of these metrics. Finally, this thesis proposes directions for further research, the most important being research about the costs of alternative retrofit programs, which is necessary for the debate about appropriate (efficient/feasible) societal & individual risk acceptance criteria.Design and Construction ProcessesCivil Engineering and Geoscience
De observatiemethode in de geotechniek: De theorie achter de methode
No full textDe observatiemethode wordt gedefinieerd als een geegreerd bouw- en ontwerpproces waarbij de uiteindelijke bouwwijze of het uiteindelijke ontwerp wordt vastgesteld door gebruik te maken van meetgegevens tijdens de bouwfase (naar Van de Kamp en Van Baars, 2003). Hoewel de observatiemethode in de geotechniek al vaker is toegepast en volgens Eurocode 7 is toegestaan, ontbreekt een risicotechnische onderbouwing van de methode. Zonder dit inzicht is het veelal onmogelijk om vooraf te stellen dat toepassing van de observatiemethode een goede beslissing is. De hoofdvraag van dit afstudeeronderzoek is tweeledig: wat bepaalt het rendement van de observatiemethode? Wat betekent dit voor het toepassingsgebied en de vormgeving van de observatiemethode? Om de hoofdvraag te beantwoorden is een risicobenadering gevolgd, waarbij de verwachtingswaarden van de kosten van een conventioneel Risk Based Optimised-ontwerp en een ontwerp met observatiemethode zijn vergeleken. Om het onderzoek te structureren is onderscheid gemaakt tussen onzekerheden in de tijd en onzekerheden in de ruimte. De bevindingen zijn uiteindelijk getoetst door deze te vergelijken met beschrijvingen van toepassingen van de observatiemethode in de literatuur. Ook zijn de bevindingen getoetst met casestudies: sterk geschematiseerde projecten die met een wiskundig programma zijn gesimuleerd. Een belangrijke beperking voor de analyses wordt gevormd door de afhankelijkheden van de kanscomponenten bij een ontwerp met observatiemethode. Zo beloeden de waarnemingsresultaten de faalkansen en de kansen op volgende waarnemingsresultaten. Ook zijn de faalkansen afhankelijk van de kans dat het ontwerp wordt aangepast. Vaak is MonteCarlo simulatie door het grote aantal benodigde trekkingen geen optie om vooraf de verwachtingswaarde van de kosten van een ontwerp met observatiemethode te berekenen. Bestaande voorwaarden voor toepassing van de observatiemethode zijn beoordeeld en waar nodig aangepast. Ook zijn aanvullende voorwaarden opgesteld. Verder is gekeken naar de situaties waarin toepassing van de observatiemethode het grootste potentieel heeft om kostenbesparingen te leveren. Er zijn enkele algemene aanbevelingen gedaan ten aanzien van de vormgeving van de methode. Het gaat dan om de keuze voor het startontwerp en de opzet van het monitoringsprogramma. In de bestaande literatuur over de observatiemethode zijn enkele onvolkomenheden geconstateerd. Zo is de vaak gehanteerde conclusie dat toepassing van de observatiemethode (vooraf) gunstig was omdat deze (achteraf) een besparing leverde, niet valide gebleken.Civil Engineering and Geoscience
A risk-informed approach to coastal zone management
No full textEconomic and population growth have led to an unprecedented increase in the value at risk in coastal zones over the last century. To avoid excessive future losses, particularly in the light of projected climate change impacts, coastal zone managers have various instruments at their disposal. These primarily concern land-use planning (establishing buffer zones) and engineering solutions (beach nourishment and coastal protection). In this paper, we focus on risk mitigation through the implementation of buffer zones (setback lines). Foregoing land-use opportunities in coastal regions and protecting coasts is costly, but so is damage caused by inundation and storm erosion. Defining appropriate setback lines for land-use planning purposes is a balancing act. It is however unclear what level of protection is facilitated by current approaches for defining setback lines, and whether this is, at least from an economic perspective, sufficient. In this paper, we present an economic model to determine which setback lines would be optimal from an economic perspective. The results provide a useful reference point in the political debate about the acceptability of risk in coastal zones. The main conclusions are (i) that it is useful to define setback lines on the basis of their exceedance probabilities, (ii) that the exceedance probability of an economically efficient setback line will typically be in the order of magnitude of 1/100 per year, (iii) that it is important to distinguish between situations in which morphological conditions are stationary and non-stationary, and (iv) that long-term uncertainties (e.g. due to climate change) influence the exceedance probability of efficient setback lines but only to a limited extent.Hydraulic EngineeringCivil Engineering and Geoscience
The use of individual and societal risk criteria within the Dutch flood safety policy-nationwide estimates of societal risk and policy applications
No full textThe Dutch government is in the process of revising its flood safety policy. The current safety standards for flood defences in the Netherlands are largely based on the outcomes of cost-benefit analyses. Loss of life has not been considered separately in the choice for current standards. This article presents the results of a research project that evaluated the potential roles of two risk metrics, individual and societal risk, to support decision-making about new flood safety standards. These risk metrics are already used in the Dutch major hazards policy for the evaluation of risks to the public. Individual risk concerns the annual probability of death of a person. Societal risk concerns the probability of an event with many fatalities. Technical aspects of the use of individual and societal risk metrics in flood risk assessments as well as policy implications are discussed. Preliminary estimates of nationwide levels of societal risk are presented. Societal risk levels appear relatively high in the South Western part of the country where densely populated dike rings are threatened by a combination of river and coastal floods. It was found that cumulation, the simultaneous flooding of multiple dike rings during a single flood event, has significant impact on the national level of societal risk. Options for the application of the individual and societal risk in the new flood safety policy are presented and discussed.Hydraulic EngineeringCivil Engineering and Geoscience
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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