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Articles 31 - 60 of 85
Full-Text Articles in Engineering
Nanoindentation Characterization Of Elastic Properties Of Shales And Swelling Clay Minerals, Shengmin Luo
Nanoindentation Characterization Of Elastic Properties Of Shales And Swelling Clay Minerals, Shengmin Luo
Doctoral Dissertations
Oil and gas shales are a class of multiscale, multiphase, hybrid inorganic-organic sedimentary rocks that consist of a generally uniform, preferentially oriented clay matrix with randomly embedded silt and sand particles as solid inclusions. A thorough understanding of the mechanical properties of shales is crucial for the exploration and production of oil and gas in the unconventional shale reservoirs, but it can be a challenging task due to their nature of compositional heterogeneity and microstructural anisotropy. In efforts to better characterize the mechanical properties of shales across different length scales and to fundamentally understand the laws of upscaling from individual …
Computational Modeling Of Laminated Veneer Bamboo (Lvb) Dowel Joints, Niloufar Khoshbakht
Computational Modeling Of Laminated Veneer Bamboo (Lvb) Dowel Joints, Niloufar Khoshbakht
Doctoral Dissertations
Laminated veneer bamboo (LVB) is a sustainable building material that has been gaining interest in the construction industry of late. As a relatively new product, little is known about its connection performance, specifically, its failure behavior in dowel type joints and possible similarities it may have to engineered wood products in terms of failure mechanisms. Research is needed to aid in the understanding of LVB dowel connection failure behavior and to quantify the failure mechanism and key factors associated with LVB dowel connection strength. Modeling, as conducted in this research, is a valuable tool to help devise safe standards and …
Finite Element Simulation Of Bonded And Mechanically Anchored Shear Interfaces Of Externally Applied Frp Sheets To Concrete And Wood-Concrete Composites, Alaa Al-Sammari
Finite Element Simulation Of Bonded And Mechanically Anchored Shear Interfaces Of Externally Applied Frp Sheets To Concrete And Wood-Concrete Composites, Alaa Al-Sammari
Doctoral Dissertations
Composite construction is prevalent in advanced structural systems where components of different materials are combined in the same structure to improve the performance of strong and economic structural sections. Maintaining continuity between the different structural components to produce monolithic structural behavior is challenging because of differences in the mechanical properties of these materials in terms of stiffness, strength, and ductility. The different components of the composite section are typically joined using adhesives and/or mechanical anchors to produce partial or full composite action. This dissertation discusses two types of shear interfaces intended to result in structural composite behavior. The first type …
Northeastern Species In Hybrid Cross Laminated Timber, Hamid Kaboli
Northeastern Species In Hybrid Cross Laminated Timber, Hamid Kaboli
Doctoral Dissertations
Known in the building industry throughout the world, Cross Laminated Timber (CLT) is a massive timber building material with outstanding structural, fire, and seismic properties. CLT is a cost-competitive, sustainable construction material is a good candidate as a substitute material for concrete, masonry, and steel, in mid-rise and high-rise buildings. CLT is perpendicular layers of dimensional lumbers usually laminated together and forming a massive structural panel. This dissertation explores the viability of utilizing Massachusetts grown Eastern Hemlock and Eastern White Pine in CLT panels as pure or in conjunction with other high-value wood products. 59% of Massachusetts’ lands are covered …
Evaluation Of The Effect Of Bottom Bar Splice Location On Performance Of Beams In Reinforced Concrete Perimeter Frames, Jorge Rivera Cruz
Evaluation Of The Effect Of Bottom Bar Splice Location On Performance Of Beams In Reinforced Concrete Perimeter Frames, Jorge Rivera Cruz
Doctoral Dissertations
The American Concrete Institute (ACI) Building Code Requirements for Structural Concrete and Commentary (ACI 318-14) indirectly accounts for resistance to progressive collapse by providing requirements for structural integrity in concrete structures. ACI 318-14 structural integrity requirements are intended to provide alternate load paths so that progressive collapse is avoided in the event of the unintended loss of an interior support. ACI 318-14 §9.7.7.5 requires that splices of structural integrity reinforcement be designed as Class B splices near mid-span for top reinforcement and near the support for bottom reinforcement. However, ACI 318-14 does not provide a clear definition for the support …
Laboratory Study Of The Geotechnical Properties Of Abraded Railway Ballast With Natural And Clay Mix Fouling, Andrew Rohrman
Laboratory Study Of The Geotechnical Properties Of Abraded Railway Ballast With Natural And Clay Mix Fouling, Andrew Rohrman
Doctoral Dissertations
With 140,000 miles of active track, railroad freight is the largest method of transporting goods in the United States. An important component of the railroad substructure is the gravel-size aggregate placed below the tracks, called ballast. The ballast is responsible for draining water away from the track, resisting forces from traffic loading, maintaining track position, and reducing loads to acceptable pressures for the subgrade. Ballast is typically selected to be highly angular and uniformly graded, but these characteristics are constantly changing under dynamic traffic loading. As the ballast is loaded, the particles abrade against each other, grinding off stone dust …
Mechanical Performance Of Structural Systems With Missing Members: From Buildings To Architected Materials, Panagiotis Pantidis
Mechanical Performance Of Structural Systems With Missing Members: From Buildings To Architected Materials, Panagiotis Pantidis
Doctoral Dissertations
Structural systems are potentially subjected to damage initiating scenarios throughout the course of their service time. Depending on the nature and extent of the damaging event, they may experience significant reduction or even complete loss of their mechanical performance. This dissertation delves into the mechanics of structural systems under the notion of missing members from their domain, investigating types of structural systems: a) multi-story steel framed buildings, and b) materials with a truss-lattice microstructure. Part I of the dissertation investigates the performance of multi-story steel framed buildings under a column removal scenario, developing an analytical framework for their quasi-static robustness …
Equity And Efficiency In Multi-Modal Transportation Systems, Nicholas M. Fournier
Equity And Efficiency In Multi-Modal Transportation Systems, Nicholas M. Fournier
Doctoral Dissertations
The land-use pattern for many cities is a central business district surrounded by sprawling suburbs. This pattern can lead to an inefficient and congestion-prone transportation system due to a reliance on automobiles, because high-capacity transit is not efficient in low-density areas where insufficient travelers can access transit. This also poses an equity concern as the monetary cost of faster and more expensive travel disproportionately burdens low income travelers. This dissertation presents a deterministic approximation of a discrete choice model for mixed access and mainline transportation modes, meaning that travelers may use different modes to access a mainline system, such as …
Modeling And Optimizing Routing Decisions For Travelers And On-Demand Service Providers, Xinlian Yu
Modeling And Optimizing Routing Decisions For Travelers And On-Demand Service Providers, Xinlian Yu
Doctoral Dissertations
This thesis investigates the dynamic routing decisions for individual travelers and on-demand service providers (e.g., regular taxis, Uber, Lyft, etc). For individual travelers, this thesis models and predicts route choice at two time-scales: the day-to-day and within-day. For day-to-day route choice, methodological development and empirical evidences are presented to understand the roles of learning, inertia and real-time travel information on route choices in a highly disrupted network based on data from a laboratory competitive route choice game. The learning of routing policies instead of simple paths is modeled when real-time travel information is available, where a routing policy is defined …
A Multiline Anchor Concept For Floating Offshore Wind Turbines, Casey Fontana
A Multiline Anchor Concept For Floating Offshore Wind Turbines, Casey Fontana
Doctoral Dissertations
Floating offshore wind turbines (FOWTs) hold great potential for the renewable energy industry, but capital costs remain high. In efforts to increase FOWT substructure efficiency and reduce costs, this thesis investigates a novel multiline anchor concept in which FOWTs share anchors instead of being moored separately. The goal of this thesis is to evaluate the force dynamics, design, and potential cost reduction of the system. Anchor forces are simulated using the NREL 5 MW reference turbine and OC4-DeepCwind semisubmersible platform, and multiline anchor force is computed as the vector sum of the contributing mooring line tensions. The use of a …
Applications Of Machine Learning Methods In Macroscopic Crash Analysis For Transportation Safety Management, Somaye Garmroudi Dovirani
Applications Of Machine Learning Methods In Macroscopic Crash Analysis For Transportation Safety Management, Somaye Garmroudi Dovirani
Doctoral Dissertations
Transportation Safety Planning (TSP) is a statewide-scale tool and combines transportation planning processes with safety aims to increase safety and reduce transportation fatalities and injuries. Traffic safety, which continues to remain a critical issue worldwide, has led to a myriad of modeling techniques to improve analytical capabilities with respect to crash modeling and prediction. State and metropolitan transportation planning processes must be consistent with Strategic Highway Safety Plans. This research aims to identify models and methods to improve the ability to capture variables that have the most significant impact on traffic safety through crash prediction modeling. In order to achieve …
Application Of Ground Penetrating Radar For Use In Thermal Conductivity Site Investigations, Aaron J. Rubin
Application Of Ground Penetrating Radar For Use In Thermal Conductivity Site Investigations, Aaron J. Rubin
Doctoral Dissertations
Measurement of soil thermal conductivity in-situ is important for many practical geotechnical and civil engineering applications. However, for a variety of reasons it can be difficult to measure in-situ. A novel method to estimate the thermal conductivity of sands based on electrical relative permittivity (dielectric constant) measurements and GPR data is presented. First, an analytical model to estimate thermal conductivity of soils was developed and validated using a database of thermal conductivity measurements. The new thermal conductivity model was then compared to existing models using a larger database of new and pervious thermal conductivity measurements conducted on a wide range …
Preparing Water Supply Systems For Climate Change: The Role Of Hydrologic Forecasting In The Northeast, Leslie Decristofaro
Preparing Water Supply Systems For Climate Change: The Role Of Hydrologic Forecasting In The Northeast, Leslie Decristofaro
Doctoral Dissertations
Fresh water is a resource strongly impacted by climactic conditions. Water supply systems in the northeastern United States will see the effects of climate change on their water quality and quantity in various ways, including changes in seasonality of flows, changes in the frequency and magnitude of extreme precipitation events, and changes in the variability of precipitation and water availability. Five northeastern water supplies examined are expected to maintain at least 95% monthly reliability over a range of climates wider than the current projections. However, model results indicate that turbidity levels in New York City's Ashokan Reservoir will change with …
Experimental Investigation Of Hydraulic Fracturing Fluid On Shale And Soil, Zhenning Yang
Experimental Investigation Of Hydraulic Fracturing Fluid On Shale And Soil, Zhenning Yang
Doctoral Dissertations
Mitigation and prevention of shale-formation damage caused by hydraulic-fracturing fluid/rock interactions play an important role in well-production stability and subsequent refracturing design. This study presents three experimental investigations on the interaction of water/shale, fluid/clay, and fluid/shale. A series of experiments were designed to investigate fluid/shale interactions: hydrophilic to hydrophobic alteration through chemical-vapor deposition, nanoindentation testing on shale sample, geotechnical laboratory experiments on contaminated clay, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscope (SEM) on shale sample. A clay-matrix-based data-screening criterion is proposed for nanoindentation. The continuous-stiffness-measurment (CSM) method is proved to have better definition and characterization of …
Compressibility And Normalized Undrained Shear Behavior Of Soft Coastal Fine-Grained Soils, Arash Pirouzi
Compressibility And Normalized Undrained Shear Behavior Of Soft Coastal Fine-Grained Soils, Arash Pirouzi
Doctoral Dissertations
This thesis investigates empirical correlations between consolidation design parameters and index properties of soft fine-grained soils from coastal Louisiana region, normalized undrained shear behavior of high liquid limit organic fine-grained coastal soils, and consolidation behavior of fine-grained soils. The first phase of this research consisted of studying a database of site investigation data from 15 marsh creation projects across the coastal Louisiana region. The database includes a wide variety of fine-grained soils ranging from low-plasticity inorganic clays and silts to high-plasticity organic clays and silts with a large range of water content and liquid limit. Most of the empirical correlations …
Evaluating Policy And Climate Impacts On Water Resources Systems Using Coupled Human-Natural Models, Hassaan Furqan Khan
Evaluating Policy And Climate Impacts On Water Resources Systems Using Coupled Human-Natural Models, Hassaan Furqan Khan
Doctoral Dissertations
Extensive human intervention in the terrestrial hydrosphere means that virtually every river basin globally reflects the interaction between human and natural hydrologic processes. Thus, sustainable watershed management needs to not only account for the diverse ways humans benefit from the environment but also incorporate the impact of human actions on the natural system. Informed policy making to address our water challenges requires a comprehensive understanding of these feedbacks and how they might be affected by future changes in climate. This work develops coupled human-natural models for improved surface water and groundwater management in water-scarce regions under future changes in climate. …
Evaluation Of The Erodibility Of Soft Clays And The Influence Of Biopolymers, Pamela Judge
Evaluation Of The Erodibility Of Soft Clays And The Influence Of Biopolymers, Pamela Judge
Doctoral Dissertations
Erosion of silts and clays is less well understood than erosion of sands. Further, current and anticipated climate change impacts along coastlines compel consideration of new approaches to coastal protection measures; seawalls and breakwaters designs now include natural and nature-based measures. The first research topic consists of the Adaptive Gradients Framework which was a theoretically-informed facilitation tool. The framework was intended to aid a collaborative and interdisciplinary decision-making process to encourage inclusion of natural and nature-based measures in coastal protection planning and design. This research is the culmination of a series of workshops and fieldtrips executed by the Sustainable Adaptive …
Flood Risk Assessment, Management And Perceptions In A Changing World, Katherine Schlef
Flood Risk Assessment, Management And Perceptions In A Changing World, Katherine Schlef
Doctoral Dissertations
Floods are a global challenge that is increasing due to changes in climate and human populations. Using an interdisciplinary approach, this work contributes novel methodologies and knowledge to three key challenges associated with floods. The first chapter builds upon the atmospheric and statistical sciences to provide a general methodology for climate informed approaches to projecting long-term flood events based on large-scale ocean-atmospheric processes. The second chapter builds upon the engineering, decision analysis, and economics disciplines to integrate climate-informed projections with decision-scaling, a decision-making under uncertainty framework, to further flood risk management. The third chapter builds upon the social sciences to …
Intersection Signal Control And Design For Improved Person Mobility And Air Quality In Urban Multimodal Transportation Systems, Farnoush Khalighi
Intersection Signal Control And Design For Improved Person Mobility And Air Quality In Urban Multimodal Transportation Systems, Farnoush Khalighi
Doctoral Dissertations
Alternative geometric designs (e.g. roundabouts) and multi-objective signal control strategies are promising measures to improve sustainability of traffic networks. However, roundabouts are mostly used because of their safety and operational advantages. There has been less attention to the environmental performance of roundabouts. Also, the existing studies have been mostly used through field measurements and current simulation models, which need high calibration efforts and they are not inclusive in terms of considering all influencing factors on vehicular emissions at roundabouts. Furthermore, the existing real-time signal control strategies do not account for the emission rates of different vehicle types (e.g. cars and …
Origins And Seasonal Variation Of Disinfection Byproduct Precursors, Ran Zhao
Origins And Seasonal Variation Of Disinfection Byproduct Precursors, Ran Zhao
Doctoral Dissertations
Disinfection byproducts (DBPs) are formed from the disinfectant (e.g., chlorine) reacting with components of natural organic matter (NOM) in water drawn from surface water supplies, and are considered as the cause of potential serious human health problems. DBP precursors originate in large reservoirs from at least three types of sources: (1) watershed or allochthonous, (2) algal or autochthonous, and (3) bottom sediments or benthic. The properties of the NOM and the DBP precursor content of that NOM are unique to each source. The first objective of this dissertation was to use temporal and spatial water quality data from a drinking …
Modeling Deformation Behavior And Strength Characteristics Of Sand-Silt Mixtures: A Micromechanical Approach, Mehrashk Meidani
Modeling Deformation Behavior And Strength Characteristics Of Sand-Silt Mixtures: A Micromechanical Approach, Mehrashk Meidani
Doctoral Dissertations
This dissertation is comprised of six chapters. In the first chapter the motivation of this research, which was modeling the deformation behavior and strength characteristics of soils under internal erosion, is briefly explained. In the second chapter a micromechanis-based stress-strain model developed for prediction of sand-silt mixtures behavior is presented. The components of the micromechanics-based model are described and undrained behavior of six different types of sand-silt mixtures is predicted for several samples with different fines contents. The need for a more comprehensive compression model for sand-silt mixtures is identified at the end of this chapter. This desired compression model …
An Experimental Investigation Of The Influence Of Sampling On The Behavior Of Intermediate Soils, William Lukas
An Experimental Investigation Of The Influence Of Sampling On The Behavior Of Intermediate Soils, William Lukas
Doctoral Dissertations
Laboratory tests were performed in order to determine the effects of tube sampling disturbance on intermediate soils. Synthetic soils composed of Kaolin clay and silica silt, a reconstituted natural silt, and block sample specimens of a sensitive marine clay were tested. Tube sampling disturbance was simulated in a triaxial stress path system with bender element using the Ideal Sampling Approach prior to reconsolidation and undrained shear. ISA strain cycles of ±0.5, ±1 and ±3% were used to represent progressively greater degrees of disturbance. The influence of overconsolidation ratio (OCR) was explored by testing at OCRs of 1, 1.8, 3.6 and …
Role Of Manganese Oxide In The Formation Of Disinfection Byproducts In Drinking Water Treatment, Arianne A. Bazilio
Role Of Manganese Oxide In The Formation Of Disinfection Byproducts In Drinking Water Treatment, Arianne A. Bazilio
Doctoral Dissertations
This work examined the role of manganese oxide (MnOx) in the formation of disinfection byproducts (DBPs) in drinking water treatment. DBPs are of increasing concern as more is being learned about their carcinogenicity and genotoxicity. Studies were performed to determine the impact of MnOx and free chlorine (Cl2), used for dissolved manganese (Mn(II) removal, on the formation of these undesirable byproducts. Batch experiment results showed that the presence of MnOx did not significantly increase the haloacetic acid or trihalomethane concentrations. Rates of DBP formation were also similar in the absence and presence of Mn(II) …
Microbial Competition In Bioelectrochemical Systems, Varun Srinivasan
Microbial Competition In Bioelectrochemical Systems, Varun Srinivasan
Doctoral Dissertations
Bioelectrochemical systems(BESs)/ microbial fuel fells (MFCs) are a well-studied potential technology for bioremediation and decentralized wastewater treatment. However, progress has been somewhat stalled at the bench-scale. In well controlled experiments electron recovery is high. In natural environments, wastewaters are complex and anode-respiring bacteria can be outcompeted in the presence of competing microorganisms, leading to a loss in electron-recovery and power production. Furthermore, the cathode of the MFC plays a vital role in providing flexibility for treatment options but is an understudied part of MFCs. Modelling Intracellular Competition in a Denitrifying Biocathode: One potential MFC configuration uses an organic-oxidizing anode biofilm …
Modeling Performance, Cost, Delivery, And Trip Distribution Of Demand Responsive Transit Systems With Zoning, Mahour Rahimi
Modeling Performance, Cost, Delivery, And Trip Distribution Of Demand Responsive Transit Systems With Zoning, Mahour Rahimi
Doctoral Dissertations
Demand responsive transit (DRT) services are expensive to operate, so it is crucial to understand the factors that drive the agency costs and be able to investigate and predict the effect of possible changes in specific operating parameters as well as demand and service coverage areas on total costs. In this research, we adopt the concept of the analytical model proposed by Daganzo (1978) to present continuum approximation (CA) models that can estimate important service related factors. As the first step, we propose three analytical models to approximate the operation related variables of DRT services; Fleet Size, Vehicle Hours Traveled …
Analyses Of Densely Crosslinked Phenolic Systems Using Low Field Nmr, Jigneshkumar Patel
Analyses Of Densely Crosslinked Phenolic Systems Using Low Field Nmr, Jigneshkumar Patel
Doctoral Dissertations
A uniform dispersion of reactants is necessary to achieve a complete reaction involving multi-components, especially for the crosslinking of rigid high-performance materials. In these reactions, miscibility is crucial for curing efficiency. This miscibility is typically enhanced by adding a third component, a plasticizer. For the reaction of the highly crystalline crosslinking agent hexamethylenetetramine (HMTA) with a strongly hydrogen-bonded phenol formaldehyde resin, furfural has been traditionally used as the plasticizer. However, the reason for its effectiveness is not clear. In this doctoral thesis work, miscibility and crosslinking efficiency of plasticizers in phenolic curing reactions are studied by thermal analysis and spectroscopic …
Decision Analytical Methods For Robust Water Infrastructure Planning Under Deep Uncertainty, Mehmet Umit Taner
Decision Analytical Methods For Robust Water Infrastructure Planning Under Deep Uncertainty, Mehmet Umit Taner
Doctoral Dissertations
Deep uncertainties resulting from climate change, demographic pressures, and rapidly evolving socioeconomic conditions are challenging the way that water planners design and operate large-scale infrastructure systems. Conventionally, water infrastructures have been developed using stationary methods, assuming that the underlying uncertainties can be derived from historical data or experience. However, these methods are less useful under deeply uncertain climate and socioeconomic conditions, in which the future can be substantially different from the past and cannot be expressed by well-defined probability distributions. The recognition of deep uncertainties in long-term water resources planning has led to the development of “decision-analytical” frameworks that do …
Microbial Dynamics And Design Considerations For Decentralized Microbial Fuel Cell Applications, Cynthia Castro
Microbial Dynamics And Design Considerations For Decentralized Microbial Fuel Cell Applications, Cynthia Castro
Doctoral Dissertations
The purpose of this dissertation was to assess the practicality of using microbial fuel cells (MFCs) as alternative sanitation systems for wastewater treatment and energy recovery, focusing on identifying key design considerations for treating high strength wastewater and managing alternative metabolic pathways. We evaluated the energetic outputs of a lab-based pilot MFC designed to treat complex organics present in both synthetic feces and municipal wastewater. The pilot MFC produced two energetic products, methane and electricity, when treating two types of complex wastewaters. The energetic products associated with anode respiration and methanogenesis were simultaneously observed and yielded a combined energy ouput …
An Evaluation Of Traffic Control Devices And Driver Distraction On Driver Behavior At Railway-Highway Grade Crossings, Radhameris A. Gomez Gabriel
An Evaluation Of Traffic Control Devices And Driver Distraction On Driver Behavior At Railway-Highway Grade Crossings, Radhameris A. Gomez Gabriel
Doctoral Dissertations
At-grade crossings (grade crossings) are those crossings in which any part of a roadway intersects with railroad tracks. Safety at these railroad-highway grade crossings is a major concern, with traffic control warning devices serving as the main mechanisms for improving safety. There are three factors that influence a driver’s behavior at a given crossing. First, traffic control devices, including warning devices at the railroad-highway grade crossings, provide the driver with information whose impact will depend in part on the likelihood that the driver knows whether to glance in the direction of the device based on prior experience, and in part …
Modeling And Modifying Day-To-Day Travel Behaviors: Empirical Results And Methodological Advances, Yue Tang
Modeling And Modifying Day-To-Day Travel Behaviors: Empirical Results And Methodological Advances, Yue Tang
Doctoral Dissertations
The increasing availability of individual-level longitudinal data provides the opportunity to better understand travelers'\ day-to-day learning process of their choice alternatives, which enables potentially more accurate predictions of choice patterns in a network with uncertainties. In this thesis, an instance-based learning (IBL) model for travel choice is developed within route-choice context, where on each day a traveler's decision depends on her entire choice history in the past. Learning in this model is based on the power law of forgetting and practice, which is shown to be capable of capturing various psychological effects embedded in travelers'\ day-to-day learning process, including the …