共查询到20条相似文献,搜索用时 15 毫秒
1.
《Urban Water Journal》2013,10(4):287-304
The water quality in a distribution system is affected by many factors, including operational and environmental conditions as well as the condition in and around the distribution network. Lack of reliable data as well as knowledge gaps with respect to the impact of these factors on water quality make the quantification of water quality failure risk very challenging. Furthermore, the variability inherent in (sometimes) thousands of kilometers of distribution pipes presents added complexities. Major modes of water quality failures can be classified into intrusion of contaminants, regrowth of bacteria (biofilm), water treatment breakthrough, leaching of chemicals or corrosion products from system components, and permeation of organic compounds through plastic pipes. Deliberate contamination and negligence of operators have in recent years become an added concern. In earlier works by Sadiq et al. (2004, 2007), an aggregative risk analysis approach using hierarchical structure was proposed to describe all possible mechanisms of contamination. In this paper a similar structure is used as a basis for a fault-tree approach. While fault-tree analysis is widely used for many engineering applications, in this paper we specifically explore how interdependencies among factors might impact analysis results. Two types of uncertainties are considered in the proposed analysis. The first is related to the likelihood of risk events, and the second is related to non-linear dependencies among risk events. Each basic risk event (input factor) is defined using a fuzzy probability (likelihood) to deal with its inherent uncertainty. The dependencies among risk events are explored using Frank copula and Frechet's limit. The proposed approach is demonstrated using two well-documented episodes of water quality failures in Canada, namely, Walkerton (ON) and North Battleford (SK). 相似文献
2.
《Structure and Infrastructure Engineering》2013,9(7):655-667
The construction of new infrastructure requires solutions that maximise the benefit while meeting acceptable safety levels. The solution to this problem can be obtained through a structural cost-based optimisation. This paper integrates a life-cycle cost optimisation model developed by Rackwitz (2000) with a structural deterioration model that combines the action of progressive degradation (e.g. corrosion, fatigue) and sudden events (e.g. earthquakes). The structural condition at a given time is measured in terms of the system's remaining life, which can be measured in practice through any structural performance indicator (e.g. ductility). It is assumed that sudden events conform to a compound point process with shock sizes and interarrival times that are independent and identically distributed random variables. Deterministic and random progressive deterioration models are also included in the formulation. Randomness in progressive deterioration is modelled as a point process with known arrival times and random shock sizes. Structural reliability is evaluated against prescribed design and operation thresholds that can be used to establish limit states or intervention policies. The entire model is illustrated with an example that compares several life-cycle models showing the importance of taking into account the damage history in evaluating the performance of infrastructure systems. 相似文献
3.
There is much debate in the UK, North America and Australia within both crime prevention and planning concerning New Urbanism and the design of suburban housing layouts. New Urbanism promotes high-density, mixed-use residential developments in ‘walkable’ neighbourhoods close to public transport, employment and amenities. One significant factor is New Urbanism's support for permeability and the preference of the grid street layout over the cul-de-sac (Morrow-Jones et al., (2004). The authors present the evidence as it relates to the grid and the cul-de-sac across a range of inter-disciplinary issues such as crime, walkability, social interaction, travel behaviour, traffic safety, cost and sustainability and housing preferences. This paper provides a brief history of the grid and cul-de-sac, discusses their respective strengths and weaknesses and concludes that any ‘one-size-fits-all’ approach is myopic and simplistic. It calls for a more holistic approach to understanding the localized and contextual dimension to suburban street layouts and how they may affect human behaviour. The paper highlights key areas for future research and calls for more inter-disciplinary debate and cooperation, particularly between environmental criminologists, planners and town centre managers. 相似文献
4.
Moira Zellner 《Planning Theory & Practice》2013,14(4):457-478
An earlier generation of planners turned to Rittel & Webber’s 1973 conception of “wicked problems” to explain why conventional scientific approaches failed to solve problems of pluralistic urban societies. More recently, “complex systems” analysis has attracted planners as an innovative approach to understanding metropolitan dynamics and its social and environmental impacts. Given the renewed scholarly interest in wicked problems, we asked: how can planners use the complex systems approach to tackle wicked problems? We re-evaluate Rittel and Webber’s arguments through the lens of complex systems, which provide a novel way to redefine wicked problems and engage their otherwise intractable, zero-sum impasses. The complex systems framework acknowledges and builds an understanding around the factors that give rise to wicked problems: interaction, heterogeneity, feedback, neighbourhood effects, and collective interest traps. This affinity allows complex systems tools to engage wicked problems more explicitly and identify local or distributed interventions. This strategy aligns more closely with the nature of urban crises and social problems than the post-war scientific methodologies about which Rittel and Webber had grown increasingly sceptical. Despite this potential, planners have only belatedly and hesitantly engaged in complex systems analysis. The barriers are both methodological and theoretical, requiring creative, iterative problem framing. Complex systems thinking cannot “solve” or “tame” wicked problems. Instead, complex systems first characterize the nature of the wicked problems and explore plausible pathways that cannot always be anticipated and visualized without simulations. The intersection of wicked problems and complex systems presents a fertile domain to rethink our understanding of persistent social and environmental problems, to mediate the manifold conflicts over land and natural resources, and thus to restructure our planning approaches to such problems. 相似文献
5.
Strategic Planning for Long-Term Flood Risk Management: Some Suggestions for Learning How to Make Strategy at Regional and Local Level 总被引:1,自引:0,他引:1
Gérard Hutter 《International Planning Studies》2007,12(3):273-289
Often, discussions about improving long-term Flood Risk Management (FRM) refer to spatial planning as one of the most promising policy instruments (non-structural measures), especially after flood disasters like in Dresden in August 2002. However, up to now, evidence is limited that spatial planning is used intensively and systematically for long-term FRM, for instance, to reduce vulnerability in flood-prone areas by controlling developments on floodplains and providing development possibilities in non-hazardous areas (Burby et al., 2000). Based on the literature on strategic spatial planning (e.g., Albrechts, 2004a; Bryson, 2004; Healey, 2007) and risk management (e.g., Klinke & Renn, 2002), this paper presents normative conclusions from case studies conducted in Dresden and London on how to use strategic planning for improving long-term FRM.
The twin hazards of uncertainty and disagreement form an essential context for plannin?s ambitions of shaping the future. In practice, planners may retreat to shorter-range decisions with more limited consequences. Or they may resort to public relations devices that may gain agreement in superficial ways. Still another response is to hide behind technical analyses that are not fully shared with the public, neither revealing the true level of uncertainty nor exposing judgements to potential disagreements. Better methods are clearly desired for professional leadership regarding the future.
(Myers, 2001: 365)