Digital Commons Network^™

Analysis Of Loading Rate, Fiber Orientation And Material Composition Through Image Processing And Digital Volume Correlation In High Performance Concrete, Aidan R. Carlson

Electronic Theses and Dissertations

Ultra High Performance Concrete (UHPC) and High Performance concrete (HPC) is characterized by high compressive strength and high toughness. This is achieved through maximizing the particle packing density in the matrix and the use of fibers to reinforce the matrix, increasing the materials toughness. The interactions of fibers and the matrix during loading is quite complex and involves several different energy dissipation mechanisms. The goal of this work and this thesis is to investigate these interactions and identify any changes in material response, and hope that these changes may be useful for the design of UHPC moving forward.

In this …

Examining The Impact Of Centerline Rumble-Strip Installation In Prevention Of Head-On And Opposite Sideswipe Collisions In Maine, Jhan Kevin Gil Marin

Electronic Theses and Dissertations

Among all traffic collisions, lane departure crashes are the leading type of serious traffic crashes in Maine, comprising 72% of state-wide traffic fatalities. To reduce these crashes, Maine Department of Transportation (MaineDOT) installed shoulder and centerline rumble strips on roadways to prevent lane departure crashes in Maine. With a total installed length of 1503 miles of rumble strips, specifically 511 miles of centerline rumble strips in bidirectional and undivided rural two-lane roadways, there is a need to understand the impact of rumble strips in reducing lane departure crashes. In this thesis, observational before-after studies with two methods: comparison group, and …

Using Probe Data To Understand The Impact Of The Covid-19 Pandemic On Roadway Safety, Ennis W. Marshall

Electronic Theses and Dissertations

Following the onset of the COVID-19 pandemic there was an observed decrease in traffic safety in the United Sates. New England was no exception to this, with traffic fatality rates increasing in Maine and Connecticut. This increase was attributed to the possibility that drivers had more opportunities to speed following the implementation of COVID-19 stay-at-home orders on roads with drastically reduced volume and decreased speed enforcement. To determine the state of research into the pandemic's effect on traffic safety around the world, an extensive critical review was conducted. The reviewed studies showed that roadways did indeed become less safe with …

Wave Attenuation Through Submerged Oyster Aquaculture Cages, Liam T. Hanley

Electronic Theses and Dissertations

Coastal erosion presents a growing issue to shorelines around the world and is especially harmful to Maine, a region where sea-level rise is higher than the global average. Green and hybrid coastal defense strategies are being implemented around the country to provide sustainable, habitat-friendly solutions to erosion control. Maine is a hotspot for commercial aquaculture, with an estimated $13.6 million economic impact. This study looks to bridge the gap between Maine aquaculture and the living shorelines initiative, by determining the wave attenuating properties of submerged oyster cages. The project will be able to inform local oyster farmers, resource planners, and …

Investigating The Effect Of Bead Geometry On Fiber Orientation And Thermomechanical Properties For Large-Format Extrusion-Based Additive Manufacturing, Joanna F. Keaton

Electronic Theses and Dissertations

In large-format extrusion-based additive manufacturing of polymer composites, the relationship between material properties and processing parameters requires further investigation. This thesis focuses on the relationship between fiber orientation and thermomechanical properties for short fiber-filled thermoplastic polymer systems manufactured by extrusion-based additive manufacturing. Fiber orientation is particularly important in determining the thermomechanical properties of the composite material as properties in the direction of deposition are expected to be higher for highly aligned fibers than randomly aligned fibers. Fiber orientation distribution, which is related to processing parameters and deposition conditions, can be efficiently represented by the orientation tensor. The orientation tensor can …

Efficient Sintering Of Lunar Soil Using Concentrated Sunlight, Diprajit Biswas

Electronic Theses and Dissertations

Construction material is one crucial need for long-term habitation on the moon. When concentrated for high heat flux, solar radiation can heat lunar soil or regolith until it sinters at temperatures above 900°C. The solid, sintered soil simulant can be used as construction material. This work explores the conditions leading to effective lunar soil sintering for both direct and indirect irradiated sintering. Lunar soil simulants were sintered using concentrated light from a xenon-arc lamp with varying heat flux intensity. During direct sintering of LHS-1, a sintering range of 860°C-1140°C corresponding to a peak heat flux of 105-120 kW/m2 was identified …

Mechanics And Mechanisms Of Fracture For An Eastern Spruce Subject To Transverse Loading Using Acoustic Emission, Parinaz Belalpour Dastjerdi

Electronic Theses and Dissertations

Due to its excellent structural qualities and accessibility, wood is among the most often utilized structural materials. Despite its ubiquity, wood poses numerous challenges. It is heterogeneous and anisotropic. It has a complex hierarchical ultrastructure, and the properties can have wide variation within a species, and indeed within an individual tree. This work aims to improve our understanding of the strength and fracture behavior of spruce-pine-fir (south) (SPFs), particularly in cross-grain direction. This study’s primary goal is to examine the relationship between crack propagation and cross grain morphology under the following loading configurations: compact tension, compression, and rolling shear. The …

Laboratory Study Of Conditions Influencing Binder Formation And Co2 Sequestration During Carbonation With Hydrated Lime, Temitope Omokinde

Electronic Theses and Dissertations

The production of lime and cement used as additives in the chemical stabilization of soil emits 9% of the total CO2 emissions. The utilization of lime in soil carbonation has a potential for soil improvement via the formation of calcium carbonate and also helps in the sequestration of an appreciable percentage of the process-related CO2 (67% of the total emissions) emitted during the production of this alkali, which would help to reduce the carbon footprint associated with the production of alkali such as calcium and magnesium bearing materials used in chemical stabilization. The research focuses on understanding the optimum soil …

Performance Of Helical Piles Retrofitted With A Novel Collar Vane Under Lateral And Torsional Loads, Juan Sebastian Carvajal Munoz

Electronic Theses and Dissertations

Helical piles are lightweight deep foundations designed to support both compressive and uplift loads by mobilizing the shear strength of soil adjacent to helical plates that are welded to an extendable shaft. Helical piles are relatively inexpensive, can be installed quickly utilizing non-specialized equipment, and they are suitable for a wide range of soil conditions. However, helical piles are precluded from many applications due to their inability to support substantial lateral and torsional loads. To overcome this limitation, a novel easy-to-install Collar Vane is implemented to augment the lateral and torsional capacity of helical piles.

The Collar Vane consists of …

Durability Of Large-Scale 3d Printed Materials For Transportation Infrastructure, Felipe Saavedra

Electronic Theses and Dissertations

Large-format extrusion-based polymer Additive Manufacturing (AM) or 3D printing has been used for transportation infrastructure applications, including culvert outlet diffusers and precast concrete formwork. This research assesses thermoplastic composite material system durability and dimensional stability under different environmental exposure conditions. Accelerated exposure in the laboratory was conducted for moisture absorption, freeze-thaw cycles, and ultraviolet (UV) weathering. Specifically, this thesis investigates the use of bio-based renewable polymer composites for transportation infrastructure applications by correlating accelerated laboratory durability tests with site-specific environmental durability for selected applications. The thesis compares the performance of bio-based composite materials, wood fiber/ polylactic acid (WF/PLA), wood fiber/amorphous …

Anthropogenic Effects On Tidal Distortion In A Tidal River, Matthew D. Fischer

Electronic Theses and Dissertations

Tidal rivers are landward portions of estuarine systems constituting the union between coastal, tidally controlled settings and rivers, where fluvial processes dominate. In these reaches, river discharge (mean flow) and tides are the two most important mechanisms in controlling geophysical flows. The processes governing water levels and current amplitudes in tidal rivers are highly nonlinear and modulated by external forcings- thus requiring sophisticated techniques for accurate prediction and forecasting. Physical oceanographers and estuarine physicists tend to limit their study area to the maximum extent of the horizontal tide (salinity intrusion), not the most landward point influenced by tidal water levels. …

Modeling The Impact Of The Covid-19 Pandemic On Speeding At Rural Roadway Facilities In Maine Using Short-Term Speed And Traffic Count Data., Amirhossein Shahlaeegilan

Electronic Theses and Dissertations

The COVID-19 pandemic caused a significant change in traffic operations and safety. For instance, various U.S. states reported an increase in the rate of fatal and severe injury crashes over this duration. In April and May 2020, the comprehensive stay-at-home orders were issued across the country, including in Maine. These orders resulted in drastic reductions in traffic volume,switching working policies of noticeable number of corporations and educational administrations like universities to the remote working, closure of many organizations during the lockdown period, and people avoidance to public places to suppress the possible exposure to the virus were among the most …

Wave And Tide Driven Nearshore Processes: Implications For Tidal Asymmetry And Coastal Protection, Samuel Rickerich

Electronic Theses and Dissertations

The dynamics of the coastal ocean are driven by wind, buoyancy, tidal, and wave processes. In the context of the variability of the coastal ocean driven wave action, storm surge, and sea level rise, understanding interactions between physical processes and means to mitigate their effects is necessary. It is the goal of this study to extend the understanding of (i) wave and tidal hydrodynamics in coastal areas and (ii) explore adaptable coastal defense strategies for these environments. These goals are addressed through process-oriented hydrodynamic-wave simulations. As tides enter the coastal ocean, nonlinear interactions from bathymetry, friction, and variations in tidal …

Nutrient Removal From Recirculating Aquaculture System Water, Eliza M. Costigan

Electronic Theses and Dissertations

Recirculating aquaculture systems (RAS), where only approximately 10% of the total system water is exchanged per day, have grown in popularity in recent years due to their potential to provide a high-quality protein source in a contained environment. With increased production comes the need for RAS water treatment to mitigate recirculation and discharge of nutrients produced by fish; mainly phosphorus and nitrogen. When discharged, nutrients can contribute to eutrophication in surrounding water bodies, harming the fish and other aquatic life. Therefore, RAS effluent should be treated before discharge. One method of phosphorus removal is adsorption, a surface phenomenon that is …

Generalizing The Negative Binomial-Lindley Model For Accounting Subpopulation Heterogeneity In Crash Data Analysis, A S M Mohaiminul Islam

Electronic Theses and Dissertations

Crash data are often highly dispersed; it may also include a large amount of zero observations or have a long tail. The traditional Negative Binomial (NB) model cannot model these data properly. To overcome this issue, the Negative Binomial-Lindley (NB-L) model has been proposed as an alternative to the NB to analyze data with these characteristics. Research studies have shown that the NB-L model provides a superior performance compared to the NB when data include numerous zero observations or have a long tail. In addition, crash data are often collected from sites with different spatial or temporal characteristics. Therefore, it …

Role Of Microplastics On The Release And Adsorption Of Organic Compounds In Natural Waters, Ashton Collins

Electronic Theses and Dissertations

Microplastics in the aquatic system are among the many inevitable consequences of plastic pollution, which has cascading environmental and public health impacts. The implications lead to the production of leachate comprised of dissolved organic matter (DOM) and increasing adsorption potential of organic compounds (OCs) onto the microplastic surfaces. In this study, the adsorption potential of organic pollutants and the formation of microplastic leachate from ultraviolet (UV) light were explored. The adsorption potential was created through a summarization and critical review of the literature on the adsorption of synthetic OCs by microplastics in aqueous environments since their emergence in 2008. A …

Optimization Of A Lightweight Floating Offshore Wind Turbine With Water-Ballast Motion Mitigation Technology, William Ramsay

Electronic Theses and Dissertations

Floating offshore wind turbines are a promising technology to address energy needs utilizing wind resources offshore. The current state of the art is based on heavy, expensive platforms to survive the ocean environment. Typical design techniques do not involve optimization because of the computationally expensive time-domain solvers used to model motions and loads in the ocean environment. However, this project uses an efficient frequency domain solver with a genetic algorithm to rapidly optimize the design of a novel floating wind turbine concept. The concept utilizes liquid ballast mass to mitigate motions on a lightweight post-tensioned concrete platform, with a target …

On The Application Of Dynamical Measures Of Hydrologic Response To Prediction And Similarity Assessment In Watersheds, Prashanta Bajracharya

Electronic Theses and Dissertations

The Prediction in Ungauged Basins (PUB) initiative set out to improve the understanding of hydrological processes with an aim of improving hydrologic models for application in ungauged basins. With a majority of basins around the world essentially ungauged, this suggests the need to shift from calibration-based models that rely on observed streamflow data to models based on process understanding. This is especially important in natural infrastructure planning projects such as investments in the conservation of wetlands across the watershed, where the lack of streamflow data hinders the quantification of their benefits (such as flood attenuation), resulting in a difficulty in …

Development Of Ultra High Performance Composite Impact Panels Using Emaa, Jeffrey Hollstein

Electronic Theses and Dissertations

UHPC with the addition of fibers is recognized for its increased impact resistance compared to typical strength concrete. To further increase the resilience, recent studies have been conducted to reinforce the UHPC with CFRTP on the front and rear face to create sandwich panels. These studies used PETg/E-glass CFRTP bonded to the UHPC using EMAA (Surlyn) in a stamp thermoforming process. Impact tests conducted on these panels have shown that delamination has been the initial and detrimental failure to the sandwich composite. Increasing the composites resistance to debonding will increase the impact energy required to debond the composite. In this …

Road Salt Use Analysis In The Context Of Changing Winter Weather Conditions, Dikshya Parajuli

Electronic Theses and Dissertations

The research is inspired by the past and current patterns of road salt use, changing weather patterns, and management strategies in Maine. The historical road salt application has led to long-term impacts on the environment pressing the need for strategic use of road salt. Winter Severity Indices (WSIs) find their application in the field by aiding in interpreting weather forecasts and planning for strategic salt application. This study uses existing indices: Accumulated Winter Season Severity Index (AWSSI), Strategic Highway Research Program (SHRP) index, Illinois Salt days index, and Accumulated Freezing Degree Days to quantify long-term changes in winter weather conditions. …

Mixing Processes In Tidally Pulsed River Plumes: Mechanisms, Significance, And Variability, Preston Spicer

Electronic Theses and Dissertations

River plumes form at the river-ocean interface when fresh, buoyant river water merges with salty, dense ocean water and can significantly modify coastal water properties and circulation. It is important to understand how plumes physically mix into the ocean to inform predictive modeling of river-borne tracers to coastal seas. In tidally energetic regions such as New England, river plumes can form and evolve with each new tide and are referred to as “tidally pulsed”. In this dissertation, we explore the numerous mechanisms which can contribute to mixing tidally pulsed plumes (i.e., frontal, stratified shear [interfacial], and bottom-generated tidal mixing) their …

Joining Methods For Continuous Fiber Reinforced Thermoplastic Composites In Structural Applications, Andrew Moran

Electronic Theses and Dissertations

Continuous fiber reinforced thermoplastic (CFRTP) composites have been proposed as an alternative to metals in structural applications. CFRTP composites can be used to create structures that are lighter weight, have better resistance to environmental factors, and have the potential to be recycled. However, one of the main challenges to CFRTP composites is connections between structural members. The goal of this thesis is to investigate the feasibility of joining CFRTP composites to both similar and dissimilar materials through literature review, coupon testing, design of a structural joint, and a small scale laboratory prototype of the joint. To achieve this goal the …

Statistical Analysis Of Frequency And Severity Of Lane Departure Crashes In Maine, Alainie A. Sawtelle

Electronic Theses and Dissertations

Lane departure crashes account for approximately 34% of all roadway crashes, and over 70% of all roadway fatalities in Maine. Despite an 18% decrease in average daily traffic volume during the half of the year with colder weather, the months of November to April comprise over 64% of the yearly lane departure crashes. The majority of roadways and roadway crashes in Maine are in rural regions. Moreover, Maine has aging infrastructure, houses the oldest population in the United States, has diverse terrain and land use, and experiences several extreme weather events. The combination of these factors impacts the frequency and …

Non-Destructive Evaluation Of Concrete Using Electrical Resistivity And Ultrasonic Wave Propagation, Justin Harris

Electronic Theses and Dissertations

With the intent to investigate the relationship between concrete physical properties and non-destructive evaluation techniques (NDE), several experiments were performed. Specimens were made at varying geometries using a range of different concrete mixes under several different curing conditions. These specimens were subjected to a combination of electrical resistivity and ultrasonic wave propagation measurements. One part of this study investigated determining the orientation of steel fibers using electrical resistivity. This resulted in the fabrication of a four-probe square device with the potential capabilities of determining fiber orientation. The other part of this research applied ultrasonic wave propagation via through-transmission along with …

Development Of Thermoplastic Composite External Reinforcing Of Concrete Decking System, Jackman A. Mickiewicz

Electronic Theses and Dissertations

The use of reinforced concrete is very common in the construction of a wide variety of structures. In buildings it is used for floors, beams, columns, and walls. It can also be used in infrastructure as parts of bridges, dams, pavements, etc. Typically, concrete is reinforced with steel, primarily rebar, to carry tensile stresses.

Like every other industry, construction is always looking at ways to advance its technology. The work outlined in this thesis looks to assist in that goal, primarily by looking at options for using a different material than the traditional steel reinforcements to create a reinforced concrete …

Thermal And Mechanical Numerical Modeling Of Extrusion-Based 3d Printed Reinforced Polymers For Selecting Manufacturing Process Parameters, Sunil Bhandari

Electronic Theses and Dissertations

Extrusion-based 3D printing of thermoplastic polymer composites manufactures parts that have nonhomogenous, orthotropic, and process-dependent macro-scale material properties. As a part of the dissertation, research works were carried out to: • improve the interlayer mechanical properties and reduce the orthotropy, • use experimentally homogenized orthotropic material properties to numerically model the mechanical behavior of the non-homogenous orthotropic 3D printed parts, • create an efficient numerical thermal model to predict the process-dependent thermal history of the 3D printed part, and • aid the manufacturing process by selecting a suitable set of processing parameters based on a simplified sequentially coupled thermomechanical model. …

Determination Of Bridge Behavior Through Live-Load Testing And Advanced Numerical Analysis, Andrew Schanck

Electronic Theses and Dissertations

Bridges represent critical nodes in the United States’ transportation network, and an accurate understanding of their strength and durability is paramount to their continued use to transport people and goods. Traditionally, bridge assessment has been conducted through conventional beam-line analysis of isolated bridge components as specified by the American Association of State Highway and Transportation Officials (AASHTO). Although this method is reasonable for relatively new structures whose behavior are well understood, it can lead to significant over-conservative estimates of live-load capacity for older structures and for new types of structure for which design bases are still being developed. For such …

Comparison Of Land Use And Flowslide Incidence In Palu Valley Following The 2018 Mw 7.5 Palu-Donggala Earthquake, Peta C. Fifield

Electronic Theses and Dissertations

The September 28 Mw 7.5 Palu-Donggala earthquake in Indonesia was the deadliest natural disaster in 2018. Five flowslides on the eastern side of Palu Valley, which were attributed to the substantial majority of deaths and economic losses in the region, occurred due to liquefaction of naturally dry alluvial deposits in gently sloping ground (2 to 6%). The requisite conditions for soil liquefaction are the presence of loose granular sediments and full saturation. Instigation of these catastrophic ground failures were linked to artificial saturation by an unlined agricultural irrigation canal. From a civil engineering perspective, the Palu ground failures on the …

Hydrodynamic Impacts Of Expanding Aquaculture, Zhilong Liu

Electronic Theses and Dissertations

Climate change may potentially change aquatic systems and bring certain risks for aquaculture development. Understanding interactions between aquaculture and the environment helps to ensure aquaculture expansion is sustainable in the future. It is critical to determine how farms influence tidal flow patterns, turbulence, mixing and material transport in estuaries. This research aims to determine the flow response of an oyster farm, predict how expanding farms and farm placement will alter estuarine dynamics, and understand how the design of a farm influences material transport.

The hydrodynamic response of a floating oyster aquaculture farm in a low inflow estuary (the Damariscotta River …

Understanding Hydrologic Risk Within The Context Of Climate Variability And Atmospheric Moisture Pathways, Ali Aljoda

Electronic Theses and Dissertations

Nonstationarity in the means and extremes of water resources (e.g., streamflow) due to climate change presents challenges to water resources management and planning. Changes in hydrologic variables such as streamflow critically impact infrastructure, water use planning and adaptation strategies, and can lead to increased societal vulnerability. As such, existing water resources infrastructure designed based on limited records of historical flow may deteriorate under future hydro-climatic changes. Thus, important scientific tasks are: a) examining and redefining the risk, reliability, and return periods under nonstationary conditions, b) understanding the changes in extreme events statistics (i.e. frequency, and magnitude), and c) linking these …