NDSU Theses & Dissertations

Permanent URI for this communityhdl:10365/26050

Research performed to achieve a formal degree from NDSU. Includes theses, dissertations, master's papers, and videos. The Libraries are currently undertaking a scanning project to include all bound student theses, dissertations, and masters papers.

Browse

Now showing 1 - 20 of 75

ADYTrack: A Model for Structural Analysis of Railroad Trackbed Using Random Finite Element Method
(North Dakota State University, 2019) Arshid, Asif
Railroads are playing pivotal role to the economic growth of United States and trackbeds ensure their safe and smooth operations. However, reliable trackbed performance prediction has always been challenging due to many reasons, for instance materials characterization, deteriorations of materials and geometries due to railways operation and environmental changes etc. All these factors exhibit varying levels of intrinsic variabilities and uncertainties. These variations and uncertainties are completely ignored in most of the state-of-the-practice problems due to lack of availability of robust models that can characterize variations in materials, geometries, and/or loadings. In this study, a Random Finite Element based three-dimensional numerical model, named ADYTrack, is developed for structural analysis of railroad trackbeds. Uniqueness of this model is the inclusion of materials’ intrinsic variabilities, geometric imperfections and/or uncertainties in axle loadings. The ADYTrack results, when compared with the analytical solution of a cantilever beam model, produced a maximum percentage difference of 0.7%; and 6% difference when compared with ANSYS software results for a single layer trackbed model; and a range of 5-20% difference was observed when validated against the actual field measurements. Sensitivity studies using RFEM based ADYTrack revealed that with the increasing variations in input parameters, measured by coefficient of variations (COV), the variations in output parameter also increased, and generally followed a bilinear trend with first linear component relatively insensitive up to around 30% COV of input parameters. However, beyond this limit, a considerable increase was observed in COVs of output parameters. For a COV of 80% in subgrade resilient modulus, a COV of 65% in vertical stress at the top of subgrade layer was observed. Additionally, the performance of any substructure layer found to be more sensitive to the variations in its own resilient modulus values. Furthermore, resilient modulus of subgrade layer was found to be the most influential input parameter, as revealed by many other studies, and so was its variations. To conclude, ADYTrack model can serve as a robust supplemental tool for railroad trackbed analysis, especially at locations that exhibit higher degrees of uncertainties and thus pose higher risk of public or infrastructure safety.
Analysis on Structural Modeling for Recycled Asphalt Pavement used as a Base Layer
(North Dakota State University, 2015) Noureldin, Ehab Magdy Salah
Reusing RAP in the base layer became a common practice in the last decade. However, some crucial issues must be resolved to succeed in using RAP satisfying the standard specifications as a base layer. The most important unknown factor is the mechanistic behavior of RAP. This question may be satisfied by understanding the role of RAP in terms of whether it just behaves as a black rock or has a stabilizing effect with traditional aggregates used for base layer. The first stage of this study is modeling the structural behavior of RAP via prediction MR. This stage then comprises comparing the predicted results to actual measured data under several field conditions. The second stage focuses on the modeling behavior of PD. This stage takes in consideration two sets of data, the first is for the measured PD data calculated from MR test. While another traditional set of measured data for PD from repeated tri-axial loading (RTL) test either single or multi-stage is collected for the same RAP sources used in the first stage. The third stage concerns on MR-PD relationship. It indicates the typical relationship for the MR-PD behavior that can be understood for the RAP in base layer. The fourth and last stage is essential to investigate the Poisson’s ratio of RAP blends and its effectiveness on both parameters MR and PD. This ratio is measured during un-confined compression test. Two main testing conditions: various water and RAP contents are taken in consideration during this measurement for different RAP/Aggregate sources. This study proves that both prediction models used in the MEPDG for prediction of both parameters MR and PD are totally significant for RAP/Aggregate blends used for pavement base layer. The prediction is at the highest accuracy at water content levels close to OMC%, MDD and with 50% to 75% RAP content. In addition, it is proved that Poisson’s ratio is an effective parameter on both MR and PD parameters especially with variation of water content. This conclusion recommends to take in consideration Poisson’s ratio as an effective parameter in MR and PD prediction models used in MEPDG software.
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.
Bounding Surface Approach to the Fatigue Modeling of Engineering Materials with Applications to Woven Fabric Composites and Concrete
(North Dakota State University, 2011) Wen, Chao
It has been known that the nucleation and growth of cracks and defects dominate the fatigue damage process in brittle or quasi-brittle materials, such as woven fabric composites and concrete. The behaviors of these materials under multiaxial tensile or compression fatigue loading conditions are quite complex, necessitating a unified approach based on principles of mechanics and thermodynamics that offers good predictive capabilities while maintaining simplicity for robust engineering calculations. A unified approach has been proposed in this dissertation to simulate the change of mechanical properties of the woven fabric composite and steel fiber reinforced concrete under uniaxial and biaxial fatigue loading. The boundary surface theory is used to describe the effect of biaxial fatigue loading. A fourth-order response tensor is used to reflect the high directionality of the damage development, and a second-order response tensor is used to describe the evolution of inelastic deformation due to damage. A direction function is used to capture the strength anisotropic property of the woven fabric composite. The comparisons between model prediction results and experimental data show the good prediction capability of models proposed in this dissertation.
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.
Cement Changes and their Effects on Shrinkage and Durability of Concrete
(North Dakota State University, 2018) Sharma, Achintyamugdha Surendra
In this work, the effects of different cementitious combinations on drying shrinkage and durability of concrete are investigated. Shrinkage is caused due to loss of water from concrete due to evaporation. Cement paste is the most vulnerable part of concrete to shrinkage. As concrete consists of cement paste and aggregates, the latter pose as restraints to the shrinking paste. As a result, tensile stresses are formed thereby leading to the formation of cracks. Cracks in concrete are responsible for the ingress of deleterious chemical ions such as, Chloride and Sulfate ions, which may form expansive compounds. Chloride ions also induce corrosion of steel reinforcement bars. Prior literature has indicated that coarser cementitious systems lead to less shrinkage in concrete. Additionally, tri-calcium silicate (C3S) and tri-calcium aluminate contents in cement also influence the extent of shrinkage in concrete. However, the extensive use of such cement in concrete as per current industry standards will be challenging. Therefore, in this study investigations are made with Type IL (10) portland limestone with or without supplementary cementitious materials (SCMs), such as fly ash, and engineered nanomaterials such as nanosilica, to develop concrete with similar shrinkage performance as compared to coarse ground portland cement, without adversely affecting other engineering properties of concrete. Key engineering properties include workability, degree of hydration, compressive and splitting tensile strengths, electrical resistivity, setting time, and bleeding. Portland limestone cement used in this study has a partial replacement level of 10% of portland cement with limestone. Although, ASTM C595 allows up to 15% replacement with limestone, current industry use is limited to ~5%. Micro-cracking tendency of selected concrete mixtures from this study is also investigated by using fluorescence microscopy and micro computed tomography (µ-CT). In this study, life cycle assessment (LCA) studies are conducted on select cementitious combinations to quantify the benefits of such replacement of portland cement. Additionally, life cycle cost analysis (LCCA) is also performed to determine feasibility of cost. Results show that Type IL portland limestone cement can be an effective alternative for reduced shrinkage strain and enhanced durability properties.
Characterization of Activities of Crumb Rubber in Interaction with Asphalt and its Effect on Final Properties
(North Dakota State University, 2015) Ghavibazoo, Amir
Recycling of millions of scrap tires produced everyday is crucial challenge encountered by waste management systems. Recycling tire rubbers in form of ground tire rubber, known as crumb rubber modifier (CRM), in asphalt industry was introduced in early 1960's and is proved as an effective recycling method. Interaction between CRM and asphalt is physical in nature which happens mainly due to exchange of components between CRM and asphalt and enhances the time temperature dependant properties of asphalt. In this work, the interaction between CRM and asphalt was evaluated through monitoring the evolutions of CRM in asphalt in macro and micro-level. The mechanism and extent of CRM dissolution were monitored under several interaction conditions. The composition of materials released from CRM was investigated using thermo-gravimetric analysis (TGA). The molecular status of the released components were studied using gel permeation chromatography (GPC) analysis. The composition analysis indicated that the CRM start releasing its polymeric components into the asphalt matrix at dissolutions higher than 20%. The released polymeric component of CRM alters the microstructure of the asphalt and creates an internal network at certain interaction temperatures according to viscoelastic analysis. At these temperatures, the released polymeric components are at their highest molecular weight based on GPC results. The effect of released components of CRM on the time temperature dependent properties of asphalt and its glass transition kinetic was monitored using dynamic shear rheometer (DSR) and differential scanning calorimetry (DSC), respectively. The DSC results showed that the intensity of glass transition of the asphalt binder which is mainly defined by the aromatic components in asphalt reduced by absorption of these components by CRM. The evolution of CRM was investigated during short-term aging of the modified asphalt binder. In addition, the effect of presence of CRM and release of its component on oxidization of asphalt binder was evaluated using Fourier transform infrared spectroscopy (FTIR). The results revealed that CRM continue absorbing the aromatic components of asphalt during aging which stiffen the asphalt binder. Also, it was observed that release of oily components of the CRM, which contain antioxidant, reduces oxidization rate of asphalt significantly.
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.
Corrosion Risk Assessment System For Coated Pipeline System
(North Dakota State University, 2018) Deng, Fodan
Steel is widely used as building material for large-scale structures, such as oil and gas pipelines, due to its high strength-to-weight ratio. However, corrosion attack has been long recognized as one of the major reasons of steel pipeline degradation and brings great threat to safety in normal operation of structure. To mitigate the corrosion attacks, coatings are generally applied to protect steel pipelines against corrosion and improve durability of the associated structures for longer service life. Although have higher corrosion resistance, coated pipelines will still get corroded in a long run, as coatings may subject to damages such as cracks. Cracks on coatings could lower the effectiveness of protection for associated structures. Timely updates of up-to-date corrosion rate, corrosion location, and coating conditions to the pipeline risk management model and prompt repairs on these damaged coatings would significantly improve the reliability of protected structures against deterioration and failure. In this study, a corrosion risk analysis system is developed to detect and locate the corrosion induced coating cracks on coated steel using embedded fiber Bragg grating (FBG) sensors. The coatings investigated include high velocity oxygen fuel (HVOF) thermal sprayed Al-Bronze coating, wire arc sprayed Al-Zn coating, and soft coating. Theoretical models of corrosion risk assessment system were carried out followed by systematic laboratory experiments, which shows that the developed system can quantitatively detect corrosion rate, corrosion propagations, and accurately locate the cracks initialized in the coating in real time. This real-time corrosion information can be integrated into pipeline risk management model to optimize the corrosion related risk analysis for resource allocation. To place the sensing units of the system in the most needed locations along the huge pipeline systems for an effective corrosion risk assessment, an example case study is conducted in this study to show how to locate the most critical sensor placement locations along the pipeline using worst case oil and gas discharge analysis. Further applications of the developed system can be integrated with pipeline management system for better maintenance resource allocations.
Crack-Dependent Response of Structural Steel Members Repaired with CFRP
(North Dakota State University, 2014) Hmidan, Amer
Cracking of the lower flange in steel-girder bridges is a critical consideration because it will influence flexural behavior such as load-carrying capacity. Timely rehabilitation will save long-term repair costs and warrant sustainable performance. Carbon-fiber-reinforced polymer (CFRP) is a promising material to repair damaged steel members. This non-metallic reinforcement provides a number of benefits when compared to traditional repair materials (e.g., welded steel plates) for deteriorated steel girders: for example, a favorable strength-to-weight ratio, resistance to corrosion and fatigue, rapid installation in practice, and reduced long-term maintenance expenses. Although applying CFRP to steel members has recently attracted the rehabilitation community, its contribution to the behavior of repaired members is not fully understood. Very limited information about the interaction between the level of initial damage in steel girders and CFRP-repair is available, and also, scant research about the long-term performance and environmental durability for such repaired members has been done. This study addresses these identified research gaps based on a two-phase experimental program. The first phase focuses on CFRP-repaired steel beams having various levels of initial damage (representing multiple stages of fatigue crack propagation). The second phase is focused on testing the repaired beams when subjected to various levels of sustained intensity and cold temperature. A three-dimensional non-linear finite element (FE) model is developed to predict the flexural behavior of CFRP-repaired beams, including CFRP debonding and crack propagation across the critical section of the repaired beams. Also, the FE method is used and regression equations are proposed to predict the static strength of standard steel W Shapes repaired with CFRP, taking into consideration the material and geometric properties.
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.

Browse

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