Civil & Environmental Engineering Masters Theses

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An Anisotropic Damage Mechanics Model for Concrete with Applications for Fatigue Loading and Freeze-Thaw Effects
(North Dakota State University, 2013) Reberg, Andrew Steven
It is well known that the formation and propagation of microcracks within concrete is anisotropic in nature, and has a degrading effect on its mechanical performance. In this thesis an anisotropic damage mechanics model is formulated for concrete which can predict the behavior of the material subjected to monotonic loading, fatigue loading, and freeze-thaw cycles. The constitutive model is formulated using the general framework of the internal variable theory of thermodynamics. Kinetic relations are used to describe the directionality of damage accumulation and the associated softening of mechanical properties. The rate independent model is then extended to cover fatigue loading cycles and freeze-thaw cycles. Two simple softening functions are used to predict the mechanical properties of concrete as the number of cyclic loads as well as freeze-thaw cycles increases. The model is compared with experimental data for fatigue and freeze-thaw performance of plain concrete.
Application of Damage Mechanics to Describe the Behavior of Concrete under Fatigue and Freeze-Thaw Processes
(North Dakota State University, 2015) Saboori, Ashkan
Concrete has been used in dams, bridges, and highway pavements in which freeze-thaw process and cyclic loading are important factors affecting its mechanical behavior. Damage caused by frost expansion is a primary concern when designing concrete structures in cold regions. The onset of damage within concrete can be accelerated when a freeze-thaw cycle occurs while a structure is subjected to an external loading. Also, concrete under fatigue loading gradually loses its strength with an increase in the number of load cycles. It is widely accepted that concrete shows more flexible behavior under freeze-thaw process and fatigue loading due to wide-spread microcracks occurred during both conditions. Therefore, concrete deteriorates under such processes and its mechanical properties such as strength, stiffness, and ultimate strain will change. In order to predict the mechanical behavior of concrete under such circumstances, a rate independent model is extended to cover fatigue loading and freeze-thaw cycles.
Assessment of Molecularly Imprinted Polymers as Phosphate Sorbents
(North Dakota State University, 2017) Ritt, Cody
Wastewater effluents and agricultural runoff are major sources of phosphorus overloading in surface waters. Phosphorus overloading ignites eutrophication, which devastates aquatic ecosystems. On the other hand, phosphorus, which is currently produced from phosphate rock, is a critical component of fertilizer mixes. However, the world is predicted to face a shortage of phosphate supply beyond 2033 due to unsustainable mining. This research aims to develop a polymeric sorbent that recovers low-concentration phosphorus for eutrophication prevention and fertilizer reuse. Available polymer-based products have underwhelmed expectations by having poor selectivity or lacking appropriate biodegradation rates. This research identified molecularly imprinted polymers (MIPs) as possible sorbents for overcoming the deficiencies of reported technologies. Screening of several MIPs resulted in one potentially feasible MIP for phosphate sorption. Further studies showed a sorption capacity of ~28 mg PO43--P/g and partial phosphate-selectivity. Potential phosphate removal mechanisms were identified, providing foresight into MIPs’ viability as phosphorus sorbents.
Calibrating Smartphones for Monitoring Road Condition on Paved and Unpaved Roads
(North Dakota State University, 2018) Hu, Liuqing
Transportation agencies report the localization of roadway anomalies that could cause serious hazards to the traveling public. However, the high cost and limitations of present technical prevent scaling the road monitoring to all roadways. Especially the unpaved road, because of the complexity of unpaved road. Using smartphone application as road condition data collection tool offer an attractive alternative because of its potential to monitor all roadways in real time and its low cost. However, the sensor sensitivity and sampling frequency of different smartphones may vary significantly, which challenge the confidence of using smartphones for actual pavement condition assessment applications. This study tends to solve this challenge by calibrating different smartphones using two different calibrating methods including calibrating towards reference or average road roughness.
Carboxymethyl Cellulose Surface Treatment Method to Disperse Carbon Nanotubes in Smart Cementitious Materials
(North Dakota State University, 2019) Yang, Xinyuan
An innovative surface treatment method was proposed using carboxymethyl cellulose (CMC) to surface-treat carbon nanotubes (CNTs) for a consistent dispersion in cementitious materials to achieve high force detection sensitivity. This CMC surface treatment method was compared with two traditional methods, direct mixing and surfactant surface treatment, to validate dispersion effectiveness. Experimental results demonstrated that CMC and CNTs combined can increase force sensitivity of the smart cementitious material more than six times compared with direct mixing and more than three times compared with the surfactant surface treatment. CMC surface treatment significantly improved CNTs dispersion consistency. For CMC surface treatment, the comparison of 0.1%, 0.3% and 0.5% of CNTs by weight to cement demonstrated all percentages showed consistent laboratory dynamic force sensing results. Furthermore, CNTs percentage did not differ for force sensitivity. All experiments indicated the proposed CMC surface treatment method is an effective dispersion method for CNTs in smart cementitious materials.
Characterization of Mechanical Adhesion Failure in Epoxy Nanocomposites by Acoustic Emission Method
(North Dakota State University, 2021) Pearson, Matthew William
Polymeric nanocomposite coatings are used to protect metallic components in a variety of civil structures from corrosive agents. The adhesion between a coating and its substrate is not yet fully understood. In this study, the relationship between mechanical delamination of epoxy coating systems and the acoustic noise generated during failure was explored using acoustic emission. Three metrics were compared: a) mechanical loading data, b) post-test image processing, and c) acoustic emission data to gain insight into the coating-substrate layer. Neat epoxy and three epoxy nanocomposite systems modified with carbon nanotubes (CNTs), graphene (GNPs), and silica (SiO2) were casted on mild steel at two different thicknesses via draw-down bar. Test results demonstrated that there was a correlation between mechanical adhesion/cohesion strength and resulting acoustic noise. The findings suggested that the higher thickness in the reinforced coatings provided for a greater cohesion failure area as well as higher volume of acoustic energy.
Characterization of Surface Microtopography and Determination of Hydrotopographic Properties
(North Dakota State University, 2012) Chi, Yaping
Spatial characterization of surface microtopography is important in understanding the overland flow generation and the spatial distribution of surface runoff. In this study, fractal parameters (i.e., fractal dimension D and crossover length l) and three hydrotopographic parameters, random roughness (RR) index, maximum depression storage (MDS), and the number of connected areas (NCA), have been applied to characterize the spatial complexity of microtopography. Clear and meaningful relationships have been established between these parameters. The RR was calculated as the standard deviation of the processed elevation, and the fractal parameters were calculated with the semivariogram method. The puddle delineation program was applied in this study to spatially delineate soil surface and to accurately determine MDS and NCA. It has been found that fractal parameters can better characterize surface microtopography. More importantly, fractal and anisotropic analyses can help to better understand the overland flow generation process.
Clay Fluid Interactions in Montmorillonite Swelling Clays: A Molecular Dynamics and Experimental Study
(North Dakota State University, 2012) Patwary, Md Zillur R.
Swelling clays cause tremendous amounts of damage to infrastructure. For the effective prevention of detrimental effects of these clays, and to optimize the beneficial properties for industrial applications it is necessary to clearly understand the fundamental mechanisms of swelling of clays. In this study, we studied the effect of fluid polarity on swelling and flow properties of swelling clays using molecular modeling and experimental technique for bridging the molecular level phenomenon of these clays with microstructure change, particle breakdown and macro scale swelling and flow properties. A wide range of fluids (Dielectric Constant 110 to 2.4) were used, those are also commonly present in landfill leachates. We were able to tie the properties of swelling clays at different length scales. Then, we simulated the solvation of clay sheets, studied the effect of discrete charge distribution, contribution of edge charges on swelling clays and discussed some fundamental assumptions associated with double layer theories.
Coating of NZVI Particles With Modified Starch: Colloidal Stability and Nitrate Reduction Studies
(North Dakota State University, 2015) Pate, Mary Francis
Nanoscale-zero valent iron (NZVI) is an effective groundwater remediation media because it can quickly reduce and absorb contaminants. However, NZVI quickly agglomerates in aqueous systems, reducing its remediation capacity. This work investigated coating NZVI with native and modified rice, wheat, maize, and tapioca starches to improve colloidal stability. Colloidal stability studies were conducted with native and commercially available starches; tapioca starch modified with 2-Octen-l-ylsuccinic anhydride (OSA) was the best. Four concentrations of OSA-tapioca starch were prepared (3, 15, 35, and 50% w/w). NZVI coated with 35% OSA-modified tapioca starch (concentration = 10 g L-1) kept 66% of the coated particles suspended after 2 hours (compared to 4% of bare particles, p = 0.000). Bare NZVI reduced significantly more nitrate (20 mg L-1) than coated NZVI (p =0.000). Bare and coated NZVI provided the same nitrate reduction at 40 and 60 mg L-1 (p = 0.939 and p = 0.815, respectively).
A Comparative Study of Nitrification in Fargo and Moorhead Distribution Networks
(North Dakota State University, 2012) Portlock, Daniel
Nitrification in water distribution networks has become a growing concern for water supplies in the United States. The use of chloramines as a disinfectant in distribution pipe networks has become increasingly popular to reduce the disinfectant byproducts that are formed with free chlorine. In chloraminated systems there is potential for nitrification to occur because it reduces chloramine residuals. As chloramines decompose in the network, ammonia is released. Nitrifiers oxidize ammonia into nitrites, which react with chloramines resulting in its further reduction. As this cycle continues, chloramines will be consumed faster in the network, causing regrowth of heterotrophic bacteria. A study was conducted to compare the Fargo and Moorhead distribution networks for the occurrence of nitrification and their potential to deteriorate water quality. Each distribution network was analyzed independently for variations in operational conditions and water quality parameters that can serve as indications of nitrification in a distribution network.
Comparitive Analysis of Turbidity and Organics Removal in Biological Activated Carbon and Anthracite-Sand Filters in the Moorhead Water Treatment Plant
(North Dakota State University, 2019) von Hagen, Emily
The source water for the Moorhead Water Treatment Plant (MWTP) exhibits high concentrations of total organic carbon (TOC) throughout the year and seasonal taste and odor (T&O) events. To prevent biological regrowth in the distribution system there is a need to improve organics removal in the existing biological anthracite-sand filters, especially during cold water conditions when a significant decrease in removal efficiencies are observed. Three types of granular activated carbon (GAC) were selected for a pilot study to evaluate the potential of enhanced organics and T&O removal in biological activated carbon (BAC) filters compared to anthracite-sand. Turbidity removal was also evaluated to ensure regulatory requirements could be met with BAC filters. The overall performance of the BAC filters demonstrated a significant improvement over anthracite-sand. The bituminous coal-based GACs outperformed the coconut-based GAC and exhibited surface characteristics which may have a significant impact on the removal of organics, T&O, and turbidity.
Damage Localization of Slab-on-Girder Bridges Through Vibration Characteristics
(North Dakota State University, 2015) Telste, Michael Andrew
An incompletely documented bridge 09-125-16 in Cass County, ND was tested by Bridge Diagnostics, Inc. (BDI). A Grillage numerical model is created with their field data to simulate the bridge responses due to traffic loads. A validated bridge model matching the field test data is developed. Based on the validated numerical model, loading of the corresponding bridge under different damage scenarios is performed to capture the change of displacement mode shapes. Using the difference of these displacement mode shape data, a modified curvature method is suggested for identifying damage in bridges, which is shown successfully through the modeling results of bridges with fictitious damages. An in-lab experiment of a steel plate without damage under impact forces is adopted to produce vibration data. The modified curvature is then computed using the experimental mode shape data and its change is found to correlate very well as anticipated by the suggested theory.
Design of Structural Vibration Control Using Smart Materials and Devices for Earthquake-Resistant and Resilient Buildings
(North Dakota State University, 2017) Azimi, Mohsen
Major earthquakes in recent years have highlighted the big concern of modern seismic design concept for the resilience of buildings. The overall goals of this thesis aim to design structural vibration control using smart materials and devices and to elucidate the factors determining their robustness, feasibility, and adaptability for earthquake-resistant and resilient buildings. The study mainly includes a) integrated wavelet-based vibration control with damage detection; b) shape memory alloy to eliminate the residual deformations; c) a mass damper for highly irregular tall buildings; and d) soil-structure interaction effects on the buildings. The robustness, feasibility, and adaptability of these proposed studies for earthquake-resistant and resilient buildings are evaluated using various performance measures. The findings of the study reveal that the structural vibration control strategies could advance the current-of-art knowledge in seismic risk mitigation as well as high system adaptability.
Development of Operational Strategies to Minimize Bromate Formation in the Moorhead Water Treatment Plant
(North Dakota State University, 2014) Young, Kevin Bradley
A recent study at the Moorhead water treatment plant (MWTP) determined that bromate formed during ozone disinfection and, at times, exceeded the maximum contaminant level (MCL) of 10 parts per billion (ppb) in the summer months. Operational data showed that bromate formation was directly related to raw water bromide concentration and control of the ozone system. This study was conducted with the purpose of developing and implementing operational strategies to minimize bromate formation in the MWTP. Several operational changes, including selection of source water based on bromide concentration and controlling ozone addition in a manner that reduces the ozone dose used to achieve disinfection, were implemented and were effective at minimizing bromate formation in the ozone chambers. The bromate concentration in the finished drinking water was significantly reduced and only a few samples contained greater than 10 ppb bromate.
Development of Passenger Car Equivalency Values for Heavy Vehicles for Protected Left-Turn Movements at Signalized Intersections
(North Dakota State University, 2016) Deutsch, Paul
The Highway Capacity Manual (HCM) provides methods to account for the impact of heavy vehicles in the operational assessment and design of signalized intersections. However, the overall impact of heavy vehicles on the saturation flow rate, an important parameter used to calculate capacity, is not fully understood, particularly in exclusive left-turn lanes, where little research has been conducted. This research explores the limitations of the HCM default values, procedures, and recommendations regarding heavy vehicles in protected exclusive left-turn movements at signalized intersections, and makes improvements for use by the traffic engineering professional community. Passenger car equivalency (PCE) values of 1.66, 1.93, and 3.01 were developed for small, medium, and large trucks, respectively, for protected exclusive left-turn movements at signalized intersections. These PCE values, based solely on field data collected in Fargo, North Dakota, are incorporated into a revised equation used to determine the heavy vehicle adjustment factor, fHV.
Dispersion Effectiveness of Carbon Nanotube Additives in Self-sensing Cementitious Materials for Structural Health Monitoring
(North Dakota State University, 2016) Chia, Leonard
The use of self-sensing materials such as piezo-resistive cementitious materials modified by carbon nanotube (CNTs) additives may be able to achieve a potential real time structural health monitoring in structures. However, due to the small fractions of CNTs in the cementitious materials, the piezo-resistive effect for self-sensing is usually too small to be monitored accurately in field. In this study, a theoretic algorithm is developed to analyze the piezo-resistance of CNTs modified matrix with considerations of CNTs dispersing effectiveness. Three different dispersing methods were investigated using the developed algorithm to search for a method to uniformly disperse the CNTs in cementitious materials. Laboratory experiments showed that the theoretical algorithm analyzed well for all the dispersing effectiveness of the three different methods. The surfactant method is approved to be a very promising approach to disperse CNTs. Further investigation to lower the standard deviation of the co-polymer method are needed in future.
Drive-By Bridge Damage Identification Through Virtual Simulations
(North Dakota State University, 2019) Liu, Chang
With massive infrastructures built in US, timely condition assessment of these infrastructures becomes critical to daily traffic and economics. Due to high cost, long time consumption of direct condition assessment methods, such as closing traffic for sensor installation and monitoring, indirect bridge monitoring has become a promising method. However, the technology is in its initial stage and needs substantial refinement. In this research, virtual simulation approaches, both in 2D and 3D, are used to model the bridge and vehicle interaction through ABAQUS. Artificial Damages were embedded to the model according to different locations and different levels of intensities. With the modelled outcomes, the hypothesis of identifying damages through the responses of the vehicle will be tested. From the simulated vehicle responses, bridge frequencies and damage locations and sizes could be identified accurately through short time flourier transformation and mode shape difference.
Electrochemical Investigation of Corrosion Resistance of Weldments in Steel Bridges
(North Dakota State University, 2015) Al-Kaseasbeh, Qusay Adel
Welding is commonly used for connecting steel components in steel bridge fabrication and construction. Welding processes change the microstructures, properties of surrounding steel and its surface texture. In this study, an investigation of corrosion behavior of steel bridge welds was performed under simulated corrosive environments in the laboratory. Four electrochemical tests: a) open circuit potential, b) Rp/Ec Trend, c) electrochemical impedance spectroscopy and d) potentiodynamic polarization, were identified and conducted to gain fundamentals to weldment corrosion in two commonly used bridge steels (A572 and A588). In addition, three coating systems (3-coat, Calcium sulfonate alkyd, and metallizing coating) in steel bridges were deposited on the bridge steels. Test results revealed that the bridge steel welds exhibit higher corrosion initiation over base metals, regardless the types of steel or coating. The protective coating systems can delay the corrosion initiation at the welds, thus enhancing the corrosion resistance of bridge steel welds.
Energy-Saving Non-Metallic Connectors for Precast Sandwich Wall Systems in Cold Regions
(North Dakota State University, 2014) Allard, Austin
Conserving energy in large structural buildings has become very important in today's economy. A number of buildings today are constructed with sandwich wall panels. Steel connections are most commonly used in these panels. The problem with steel is that it has a tendency to reduce the thermal resistance of the insulation. This project considers glass fiber reinforcing polymers (GFRP) and carbon fiber reinforcing polymers (CFRP) as an alternate material to steel. An experimental sandwich wall panel was constructed and subjected to freezing temperatures. The results of the experimental program were compared to a theoretical model using the ANSYS computer program. The model was verified using current analytical methods that determine the heat flux of a sandwich wall panel. The methods investigated include the parallel path, zone, parallel flow, and isothermal planes methods. The results suggest that the GFRP connectors perform slightly better than the steel and CFRP connectors.
Evaluation of the Causative Factors for Slope Failures in North Dakota
(North Dakota State University, 2021) Upadhaya, Kamal Raj
A large number of landslides with damage to roads and utilities, destruction of property, and flood risks were encountered in North Dakota (ND). Using a correlation matrix, causative factors such as soil salinity, land cover, geology, average rainfall, and average snowfall were studied. With areas ranging from 103 to 6,977,692 m2, a total of 24,098 landslides were observed. Among these landslides, there were 1,497 large-scale landslides that had areas greater than 100,000 m2. When examining the influence of different parameters using a correlation matrix, more landslides were observed in the northern and western regions of North Dakota, which corresponded to areas with steep slope inclinations, absence of dissolved salt concentrations, and high groundwater tables. Similarly, the correlation matrix for large-scale landslides suggest that the steep slope, leaching of dissolved salts, presence of herbaceous vegetation, and/or presence of rainfall with wetlands was the likely causes for the occurrence of large-scale landslides.

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Browsing Civil & Environmental Engineering Masters Theses by browse.metadata.department "Civil and Environmental Engineering"