Matching Items (8)

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The development and engineering application of a fiber reinforced hybrid matrix composite for structural retrofitting and damage mitigation

Description

Civil infrastructures are susceptible to damage under the events of natural or manmade disasters. Over the last two decades, the use of emerging engineering materials, such as the fiber-reinforced plastics (FRPs), in structural retrofitting have gained significant popularity. However, due

Civil infrastructures are susceptible to damage under the events of natural or manmade disasters. Over the last two decades, the use of emerging engineering materials, such as the fiber-reinforced plastics (FRPs), in structural retrofitting have gained significant popularity. However, due to their inherent brittleness and lack of energy dissipation, undesirable failure modes of the FRP-retrofitted systems, such as sudden laminate fracture and debonding, have been frequently observed. In this light, a Carbon-fiber reinforced Hybrid-polymeric Matrix Composite (or CHMC) was developed to provide a superior, yet affordable, solution for infrastructure damage mitigation and protection. The microstructural and micromechanical characteristics of the CHMC was investigated using scanning electron microscopy (SEM) and nanoindentation technique. The mechanical performance, such as damping, was identified using free and forced vibration tests. A simplified analytical model based on micromechanics was developed to predict the laminate stiffness using the modulus profile tested by the nanoindentation. The prediction results were verified by the flexural modulus calculated from the vibration tests. The feasibility of using CHMC to retrofit damaged structural systems was investigated via a series of structural component level tests. The effectiveness of using CHMC versus conventional carbon-fiber reinforced epoxy (CF/ epoxy) to retrofit notch damaged steel beams were tested. The comparison of the test results indicated the superior deformation capacity of the CHMC retrofitted beams. The full field strain distributions near the critical notch tip region were experimentally determined by the digital imaging correlation (DIC), and the results matched well with the finite element analysis (FEA) results. In the second series of tests, the application of CHMC was expanded to retrofit the full-scale fatigue-damaged concrete-encased steel (or SRC) girders. Similar to the notched steel beam tests, the CHMC retrofitted SRC girders exhibited substantially better post-peak load ductility than that of CF/ epoxy retrofitted girder. Lastly, a quasi-static push over test on the CHMC retrofitted reinforced concrete shear wall further highlighted the CHMC's capability of enhancing the deformation and energy dissipating potential of the damaged civil infrastructure systems. Analytical and numerical models were developed to assist the retrofitting design using the newly developed CHMC material.

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2013

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Populating and facilitating urban sustainability transition arenas

Description

Urban areas face a host of sustainability problems ranging from air and water quality, to housing affordability, and sprawl reducing returns on infrastructure investments, among many others. To address such challenges, cities have begun to envision generational sustainability transitions, and

Urban areas face a host of sustainability problems ranging from air and water quality, to housing affordability, and sprawl reducing returns on infrastructure investments, among many others. To address such challenges, cities have begun to envision generational sustainability transitions, and coalesce transition arenas in context to manage those transitions. Transition arenas coordinate the efforts of diverse stakeholders in a setting conducive to making evidence-based decisions that guide a transition forward. Though espoused and studied in the literature, transition arenas still require further research on the specifics of agent selection, arena setting, and decision-making facilitation. This dissertation has three related contributions related to transition arenas. First, it describes a process that took place within Phoenix that focused on identifying, recruiting, and building the capacity of potential transition agents for a transition arena. As part of this, a first draft suggestion of plausible steps to take for identifying, recruiting, and building a team of transition agents is proposed followed by a brief discussion on how this step-by-step process could be evaluated in subsequent work. Second, building on such engagement, this dissertation then offers criteria for transition agent selection based on a review of the literature that includes the setting in which a transition arena occurs, and strategies to support successful facilitation of decision-making in that setting. Third, those criteria are operationalized to evaluate the facilitation of a specific decision (draft of a new transportation plan) in a specific transition arena: the Citizens Committee for the future of Phoenix Transportation. The goal of this dissertation is to articulate a first-draft framework for guiding the development and scientific evaluation of transition arenas. Future work is required to empirically validate the framework in other real-world transition arenas. A feasible research agenda is provides to support this work.

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2015

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Utilization of metaheuristic methods in the holistic optimization of municipal right of way infrastructure management

Description

This dissertation presents a portable methodology for holistic planning and optimization of right of way infrastructure rehabilitation that was designed to generate monetary savings when compared to planning that only considers single infrastructure components. Holistic right of way infrastructure planning

This dissertation presents a portable methodology for holistic planning and optimization of right of way infrastructure rehabilitation that was designed to generate monetary savings when compared to planning that only considers single infrastructure components. Holistic right of way infrastructure planning requires simultaneous consideration of the three right of way infrastructure components that are typically owned and operated under the same municipal umbrella: roads, sewer, and water. The traditional paradigm for the planning of right way asset management involves operating in silos where there is little collaboration amongst different utility departments in the planning of maintenance, rehabilitation, and renewal projects. By collaborating across utilities during the planning phase, savings can be achieved when collocated rehabilitation projects from different right of way infrastructure components are synchronized to occur at the same time. These savings are in the form of shared overhead and mobilization costs, and roadway projects providing open space for subsurface utilities. Individual component models and a holistic model that utilize evolutionary algorithms to optimize five year maintenance, rehabilitation, and renewal plans for the road, sewer, and water components were created and compared. The models were designed to be portable so that they could be used with any infrastructure condition rating, deterioration modeling, and criticality assessment systems that might already be in place with a municipality. The models attempt to minimize the overall component score, which is a function of the criticality and condition of the segments within each network, by prescribing asset management activities to different segments within a component network while subject to a constraining budget. The individual models were designed to represent the traditional decision making paradigm and were compared to the holistic model. In testing at three different budget levels, the holistic model outperformed the individual models in the ability to generate five year plans that optimized prescribed maintenance, rehabilitation and renewal for various segments in order to achieve the goal of improving the component score. The methodology also achieved the goal of being portable, in that it is compatible with any condition rating, deterioration, and criticality system.

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2012

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Optimal resource allocation in social and critical infrastructure networks

Description

We live in a networked world with a multitude of networks, such as communication networks, electric power grid, transportation networks and water distribution networks, all around us. In addition to such physical (infrastructure) networks, recent years have seen tremendous proliferation

We live in a networked world with a multitude of networks, such as communication networks, electric power grid, transportation networks and water distribution networks, all around us. In addition to such physical (infrastructure) networks, recent years have seen tremendous proliferation of social networks, such as Facebook, Twitter, LinkedIn, Instagram, Google+ and others. These powerful social networks are not only used for harnessing revenue from the infrastructure networks, but are also increasingly being used as “non-conventional sensors” for monitoring the infrastructure networks. Accordingly, nowadays, analyses of social and infrastructure networks go hand-in-hand. This dissertation studies resource allocation problems encountered in this set of diverse, heterogeneous, and interdependent networks. Three problems studied in this dissertation are encountered in the physical network domain while the three other problems studied are encountered in the social network domain.

The first problem from the infrastructure network domain relates to distributed files storage scheme with a goal of enhancing robustness of data storage by making it tolerant against large scale geographically-correlated failures. The second problem relates to placement of relay nodes in a deployment area with multiple sensor nodes with a goal of augmenting connectivity of the resulting network, while staying within the budget specifying the maximum number of relay nodes that can be deployed. The third problem studied in this dissertation relates to complex interdependencies that exist between infrastructure networks, such as power grid and communication network. The progressive recovery problem in an interdependent network is studied whose goal is to maximize system utility over the time when recovery process of failed entities takes place in a sequential manner.

The three problems studied from the social network domain relate to influence propagation in adversarial environment and political sentiment assessment in various states in a country with a goal of creation of a “political heat map” of the country. In the first problem of the influence propagation domain, the goal of the second player is to restrict the influence of the first player, while in the second problem the goal of the second player is to have a larger market share with least amount of initial investment.

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2016

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Modeling, analysis, and efficient resource allocation in cyber-physical systems and critical infrastructure networks

Description

The critical infrastructures of the nation are a large and complex network of human, physical and cyber-physical systems. In recent times, it has become increasingly apparent that individual critical infrastructures, such as the power and communication networks, do not operate

The critical infrastructures of the nation are a large and complex network of human, physical and cyber-physical systems. In recent times, it has become increasingly apparent that individual critical infrastructures, such as the power and communication networks, do not operate in isolation, but instead are part of a complex interdependent ecosystem where a failure involving a small set of network entities can trigger a cascading event resulting in the failure of a much larger set of entities through the failure propagation process.

Recognizing the need for a deeper understanding of the interdependent relationships between such critical infrastructures, several models have been proposed and analyzed in the last few years. However, most of these models are over-simplified and fail to capture the complex interdependencies that may exist between critical infrastructures. To overcome the limitations of existing models, this dissertation presents a new model -- the Implicative Interdependency Model (IIM) that is able to capture such complex interdependency relations. As the potential for a failure cascade in critical interdependent networks poses several risks that can jeopardize the nation, this dissertation explores relevant research problems in the interdependent power and communication networks using the proposed IIM and lays the foundations for further study using this model.

Apart from exploring problems in interdependent critical infrastructures, this dissertation also explores resource allocation techniques for environments enabled with cyber-physical systems. Specifically, the problem of efficient path planning for data collection using mobile cyber-physical systems is explored. Two such environments are considered: a Radio-Frequency IDentification (RFID) environment with mobile “Tags” and “Readers”, and a sensor data collection environment where both the sensors and the data mules (data collectors) are mobile.

Finally, from an applied research perspective, this dissertation presents Raptor, an advanced network planning and management tool for mitigating the impact of spatially correlated, or region based faults on infrastructure networks. Raptor consolidates a wide range of studies conducted in the last few years on region based faults, and provides an interface for network planners, designers and operators to use the results of these studies for designing robust and resilient networks in the presence of spatially correlated faults.

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2016

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Safe-to-fail infrastructure for resilient cities under non-stationary climate

Description

Motivated by the need for cities to prepare and be resilient to unpredictable future weather conditions, this dissertation advances a novel infrastructure development theory of “safe-to-fail” to increase the adaptive capacity of cities to climate change. Current infrastructure development is

Motivated by the need for cities to prepare and be resilient to unpredictable future weather conditions, this dissertation advances a novel infrastructure development theory of “safe-to-fail” to increase the adaptive capacity of cities to climate change. Current infrastructure development is primarily reliant on identifying probable risks to engineered systems and making infrastructure reliable to maintain its function up to a designed system capacity. However, alterations happening in the earth system (e.g., atmosphere, oceans, land, and ice) and in human systems (e.g., greenhouse gas emission, population, land-use, technology, and natural resource use) are increasing the uncertainties in weather predictions and risk calculations and making it difficult for engineered infrastructure to maintain intended design thresholds in non-stationary future. This dissertation presents a new way to develop safe-to-fail infrastructure that departs from the current practice of risk calculation and is able to manage failure consequences when unpredicted risks overwhelm engineered systems.

This dissertation 1) defines infrastructure failure, refines existing safe-to-fail theory, and compares decision considerations for safe-to-fail vs. fail-safe infrastructure development under non-stationary climate; 2) suggests an approach to integrate the estimation of infrastructure failure impacts with extreme weather risks; 3) provides a decision tool to implement resilience strategies into safe-to-fail infrastructure development; and, 4) recognizes diverse perspectives for adopting safe-to-fail theory into practice in various decision contexts.

Overall, this dissertation advances safe-to-fail theory to help guide climate adaptation decisions that consider infrastructure failure and their consequences. The results of this dissertation demonstrate an emerging need for stakeholders, including policy makers, planners, engineers, and community members, to understand an impending “infrastructure trolley problem”, where the adaptive capacity of some regions is improved at the expense of others. Safe-to-fail further engages stakeholders to bring their knowledge into the prioritization of various failure costs based on their institutional, regional, financial, and social capacity to withstand failures. This approach connects to sustainability, where city practitioners deliberately think of and include the future cost of social, environmental and economic attributes in planning and decision-making.

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2018

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Anticipating and adapting to increases in water distribution infrastructure failure caused by interdependencies and heat exposure from climate change

Description

This dissertation advances the capability of water infrastructure utilities to anticipate and adapt to vulnerabilities in their systems from temperature increase and interdependencies with other infrastructure systems. Impact assessment models of increased heat and interdependencies were developed which incorporate probability,

This dissertation advances the capability of water infrastructure utilities to anticipate and adapt to vulnerabilities in their systems from temperature increase and interdependencies with other infrastructure systems. Impact assessment models of increased heat and interdependencies were developed which incorporate probability, spatial, temporal, and operational information. Key findings from the models are that with increased heat the increased likelihood of water quality non-compliances is particularly concerning, the anticipated increases in different hardware components generate different levels of concern starting with iron pipes, then pumps, and then PVC pipes, the effects of temperature increase on hardware components and on service losses are non-linear due to spatial criticality of components, and that modeling spatial and operational complexity helps to identify potential pathways of failure propagation between infrastructure systems. Exploring different parameters of the models allowed for comparison of institutional strategies. Key findings are that either preventative maintenance or repair strategies can completely offset additional outages from increased temperatures though-- improved repair times reduce overall duration of outages more than preventative maintenance, and that coordinated strategies across utilities could be effective for mitigating vulnerability.

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2019

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Toward Adaptive Infrastructure: Flexibility and Agility in a Non-Stationarity Age

Description

As technologies rapidly progress, there is growing evidence that our civil infrastructure do not have the capacity to adaptively and reliably deliver services in the face of rapid changes in demand, conditions of service, and environmental conditions. Infrastructure are facing

As technologies rapidly progress, there is growing evidence that our civil infrastructure do not have the capacity to adaptively and reliably deliver services in the face of rapid changes in demand, conditions of service, and environmental conditions. Infrastructure are facing multiple challenges including inflexible physical assets, unstable and insufficient funding, maturation, utilization, increasing interdependencies, climate change, social and environmental awareness, changes in coupled technology systems, lack of transdisciplinary expertise, geopolitical security, and wicked complexity. These challenges are interrelated and several produce non-stationary effects. Successful infrastructure in the twenty-first century will need to be flexible and agile. Drawing from other industries, we provide recommendations for competencies to realize flexibility and agility: roadmapping, focus on software over hardware, resilience-based thinking, compatibility, connectivity, and modularity of components, organic and change-oriented management, and transdisciplinary education. First, we will need to understand how non-technical and technical forces interact to lock in infrastructure, and create path dependencies.

This report has been advanced to a peer-reviewed journal publication:
Mikhail Chester and Braden Allenby, 2008, Toward adaptive infrastructure: flexibility and agility in a non-stationarity age, Sustainable and Resilient Infrastructure, pp. 1-19, DOI: 10.1080/23789689.2017.1416846.

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