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Holcombe, Evan W.Multi-Scale Approach to Design Sustainable Asphalt Paving Materials
Master of Science (MS), Ohio University, 2017, Civil Engineering (Engineering and Technology)
The continuous use of recycled material in asphalt pavement mixtures, specifically Reclaimed Asphalt Pavement (RAP), Recycled Asphalt Shingles (RAS) and Re-Refined Engine Oil Bottoms (REOB), have developed an increasing need to further evaluate the performance of these mixtures at the micro and macro-levels, as the use of such materials reduces cost of virgin materials and energy consumption. Although asphalt binder, including recycled or additive materials, may meet a desired performance grade (PG) using macro-scale tests, they may lack critical nano-mechanical properties that largely affect long-term performance, such as adhesion and diffusive efficiency between virgin and recycled binders. These commonly overlooked properties can correlate with performance behaviors such as fatigue and low temperature cracking during field performance. This study was conducted in two major parts. Part one was performed with the intent to evaluate the nano-mechanical and blending-diffusive efficiency of toluene and trichloroethylene extracted RAP and RAS binder using tapping mode imagery and force spectroscopy using Atomic Force Microscopy (AFM). Furthermore, this study was set to correlate the findings from micro-testing to macro-scale laboratory performance tests including Semi-Circular Bending (SCB) to evaluate fatigue cracking resistance at intermediate temperatures, Asphalt Concrete Cracking Device (ACCD) to evaluate low temperature cracking and AASHTO 283 ITS to study moisture damage susceptibility of intermediate course mixtures with high RAP and RAS contents. Results showed that tear-off RAS material have a significant effect on fatigue and low temperature cracking performance, primarily at long-term aged conditions. Neither tear-off nor manufactured waste RAS binder blend well with virgin binder, whereas RAP shows a zone of blending. AFM imaging indicated all extracted RAS binder had a much rougher surface texture than RAP or virgin binders and did not contain any “bee” structures. The procedure of splitting RAP material for sampling during the volumetric mix design process has a significant effect on the optimal virgin binder content design, which in turn has a large effect on performance properties. Part two of this thesis summarizes the results of laboratory tests that were conducted to evaluate the microstructure, adhesion and other mechanical properties of asphalt binders meeting the same Performance Grade (PG) but produced using different processes and modifiers. Atomic Force Microscope (AFM) tapping mode imaging and force spectroscopy experiments were conducted on different straight run and modified asphalt binders meeting the same performance grade. In addition, Bitumen Bond Strength (BBS) and Semi-Circular Beam (SCB) tests were conducted on the different binders evaluated and mixes prepared using those binders, respectively, for comparison. The AFM images indicated that the microstructure of the modified binders was different than those of the straight run binders. The AFM force spectroscopy test results showed that binders with same PG grade could have significantly different adhesion properties. The results of the SCB tests indicated that the fatigue performance was affected by the adhesion properties of the binders evaluated. The AFM bonding energy had a very good correlation with the flexibility index parameter obtained from SCB test results. The results of this part suggests that the adhesion properties of asphalt binders should be included in their evaluation process and specifications.

Committee:

Munir Nazzal, Dr. (Advisor)

Subjects:

Civil Engineering; Materials Science

Keywords:

reclaimed asphalt pavement; recycled asphalt shingles; re-refined engine oil bottoms; atomic force microscopy; fatigue cracking; adhesion; diffusion, moisture damage; thermal cracking

Abounia Omran, BehzadApplication of Data Mining and Big Data Analytics in the Construction Industry
Doctor of Philosophy, The Ohio State University, 2016, Food, Agricultural and Biological Engineering
In recent years, the digital world has experienced an explosion in the magnitude of data being captured and recorded in various industry fields. Accordingly, big data management has emerged to analyze and extract value out of the collected data. The traditional construction industry is also experiencing an increase in data generation and storage. However, its potential and ability for adopting big data techniques have not been adequately studied. This research investigates the trends of utilizing big data techniques in the construction research community, which eventually will impact construction practice. For this purpose, the application of 26 popular big data analysis techniques in six different construction research areas (represented by 30 prestigious construction journals) was reviewed. Trends, applications, and their associations in each of the six research areas were analyzed. Then, a more in-depth analysis was performed for two of the research areas including construction project management and computation and analytics in construction to map the associations and trends between different construction research subjects and selected analytical techniques. In the next step, the results from trend and subject analysis were used to identify a promising technique, Artificial Neural Network (ANN), for studying two construction-related subjects, including prediction of concrete properties and prediction of soil erosion quantity in highway slopes. This research also compared the performance and applicability of ANN against eight predictive modeling techniques commonly used by other industries in predicting the compressive strength of environmentally friendly concrete. The results of this research provide a comprehensive analysis of the current status of applying big data analytics techniques in construction research, including trends, frequencies, and usage distribution in six different construction-related research areas, and demonstrate the applicability and performance level of selected data analytics techniques with an emphasis on ANN in construction-related studies. The main purpose of this dissertation was to help practitioners and researchers identify a suitable and applicable data analytics technique for their specific construction/research issue(s) or to provide insights into potential research directions.

Committee:

Qian Chen, Dr. (Advisor)

Subjects:

Civil Engineering; Comparative Literature; Computer Science

Keywords:

Construction Industry; Big Data; Data Analytics; Data mining; Artificial Neural Network; ANN; Compressive Strength; Environmentally Friendly Concrete; Soil Erosion; Highway Slope; Predictive Modeling; Comparative Analysis

Murphy, Julianna E.Catalytic Effect of Iron Oxidizing Bacteria on the Production of Pigment from Acid Mine Drainage
Master of Science (MS), Ohio University, 2017, Civil Engineering (Engineering and Technology)
Abandoned and underground mines have been the known source of a persistent pollutant known as acid mine drainage. Coalmines are abundant in the Appalachian area, which results in multiple heavily polluted streams and waterways. The iron leached from the mines coats the streambeds with a thick orange slurry destroying the aquatic habitat. Specifically, for this research, the Sunday and Raccoon Creek watershed were investigated. The objective of this thesis was to manipulate the environment in order to optimize the growth and catalytic oxidation effects of locally collected iron oxidizing bacteria during the production of a viable iron oxide pigment. Temperature and pH of the environments were controlled to find prime conditions for the bacteria to thrive. While it was found that the pigment created in the lab had minimal hiding power and did not form goethite, the iron oxidized with bacteria oxidized at rates averaging at least 30 times faster than those without at all pH values. Through statistical comparison, it was found that all seeps oxidized iron at a faster rate than the sterile control at a confidence value of 95%. While there was no statistical difference found between the Carbondale Seep’s oxidations rates, both were found to have the faster oxidation rates then Batgate. All oxidation rates were found to be significantly faster at the higher temperature and high pH. The failure in the production of goethite was found to be a consequence of the overabundance of sulfate within the tanks, estimated at least 6 times the concentration at the seeps.

Committee:

Guy Riefler (Advisor)

Subjects:

Civil Engineering

Keywords:

iron oxidizing bacteria; pigment; catalytic effects; oxidation rates

Razzaghi, Hesham M.Spatial Analysis of Alcohol-related Injury and Fatal Traffic Crashes in Ohio
Master of Science (M.S.), University of Dayton, 2017, Civil Engineering
Traffic crashes are considered alcohol-related if blood alcohol concentration (BAC) of a driver or non-motorist is 0.08 grams per deciliter (g/dl) or above. This thesis analyzed various socioeconomic factors that may influence alcohol-related fatal and injury crashes in Ohio at the county level in order to determine counties that may need heightened attention in terms of enforcement and education campaigns. This study used three years of Ohio traffic crash data at the county level from 2012 to 2014 obtained from the Ohio Department of Public Safety (ODPS). The objective of this study was to explore the use of an Ordinary Least Squares (OLS) regression method in identifying factors affecting alcohol-related fatal and injury crashes in Ohio at the county level. This study was done by using Geographic Information System (GIS) in order to utilize its spatial capabilities. The model of alcohol-related fatal and injury traffic crashes was initially built with 15 independent variables that may affect alcohol-related traffic crashes such as population density and household income. The variables were divided into four groups namely crash response variables, road network variables, traffic variables, and socio-demographic variables. The Moran’s I index for residuals was almost equal to zero demonstrating that there was little evidence of any autocorrelation between each other, then OLS model was deemed adequate in modeling the data used in the this study. After removing highly correlated variables, only four variables were found to be significantly affect the rates of alcohol-related traffic crashes at the county level at a 90% confidence level. The variables found significant include percent of males in the population in the county, percent of trucks in the vehicles registered in the county, percent of licensed drivers per population in the county, and elevation range in the county.

Committee:

Deogratias Eustace (Advisor)

Subjects:

Civil Engineering

Keywords:

Spatial Analysis, Alcohol-related Traffic Crashes and Ordinary Least Squares

Althoff, Eric CDetailed and Simplified Structural Modeling and Dynamic Analysis of Nuclear Power Plant Structures
Master of Science, The Ohio State University, 2017, Civil Engineering
Probability risk assessment (PRA) of nuclear power plants (NPP) has been used since the mid-1970s to evaluate the associated risks or perform a risk-informed design of NPPs. Since its inception, PRA has considered both internal and external events to evaluate the risks to a NPP site. However, external event PRA has historically been recognized as having considerable safety margin until recent events have emphasized the need for a reevaluation. This research is part of a larger project with the goal of incorporating internal and external event PRA in a common platform using state-of-the-art methods. Specifically, the focus of the research in this thesis was to develop and evaluate structural models with different levels of complexity for several structures that are vital for seismic probabilistic risk assessment (SPRA) of NPPs. For SPRA, critical structures, systems, and components (SSCs) are investigated to evaluate their risk during seismic events. To evaluate the risk of critical SSCs, structural models are needed to predict their dynamic behavior. However, due to the large number of analyses required during SPRA, simple yet sufficient models are desired to increase the computational efficiency and reduce the run-time of models. As such, the focus of this research was to develop simple yet sufficiently accurate structural models for SSCs and to evaluate the uncertainty related to those models. Three critical NPP structures are investigated in this research to illustrate the capabilities and limitations of models with varying levels of complexity. The structures included a condensate storage tank (CST), auxiliary building, and containment structure. Realistic geometric and material properties for each structure are introduced, and both detailed three-dimensional (3D) and simplified two-dimensional (2D) models are created. Detailed 3D finite element (FE) models incorporated complex mechanical behavior such as fluid- iii structure interaction and slab flexibility. Simplified 2D models developed included lumped-mass stick models and lumped-mass-spring systems. Modal and time history analyses are used to evaluate and compare the dynamic behavior and response of both detailed and simplified models to seismic events, and the capabilities and limitations of simplified models are investigated. For CSTs, several available simplified lumped-mass-spring systems are developed and compared to a 3D FE model that incorporated fluid-structure interaction. Critical failure modes for CSTs are investigated using simplified and detailed models to illustrate key differences in the models. For auxiliary buildings, several different 3D building models are developed to illustrate the effects of structural irregularity and slab flexibility on simplified models. The importance of detailed 3D models is illustrated through spatial response of the 3D models compared to the singular response of simplified stick models. Finally, simplified and detailed models for a containment structure are developed. Lumped-mass stick and 3D FE models are developed to evaluate the dynamic behavior and response of each. A polar crane system is later added to one of the 3D FE models to investigate its potential failure modes. For each structure developed, the limitations and capabilities of simplified models are evaluated, and certain scenarios where simplified models are insufficient for SPRA are illustrated.

Committee:

Halil Sezen (Advisor); Abdollah Shafieezadeh (Committee Member); Jieun Hur (Committee Member)

Subjects:

Civil Engineering

Keywords:

Structural modeling, dynamic analysis, probabilistic risk assessment, seismic probabilistic risk assessment, finite element modeling, modal analysis, transient analysis, nuclear power plants, SAP2000, ANSYS

Bardhipur, SeemaModeling the Effect of Green Infrastructure on Direct Runoff Reduction in Residential Areas
Master of Science in Civil Engineering, Cleveland State University, 2017, Washkewicz College of Engineering
Urbanization causes a serious impact on storm water systems by expansion of impervious surfaces. Low Impact Development (LID) is a technique growing in popularity to solve the issue of storm water management. However, to evaluate the benefits of LIDs is a difficult task due to realistic parametrization of LIDs and subcatchments for modeling. The goals of this study are: a) to provide a practical guideline to parameterize and simulate LIDs (bio-retention and rain barrels) in residential areas; and b) to evaluate the resulting effect on the current drainage system under various design storms. U.S. Environmental Protection Agency’s Storm Water Management Model 5 (SWMM5) was used to simulate the hydrologic performance of LID controls and their effects on reducing direct runoff from a residential area, Klusner Avenue in Parma, Ohio. This study conceptualized the study site in reasonable detail, including house, garage, backyard, tree lawn, driveway, sidewalk, and street, so that the performance of LID controls could be identified easily. Specifically, a street catchment was carefully modeled using an open-conduit routing option, which simulated the street drainage systems more effectively. SWMM5 parameters were calibrated using the observed rainfall-runoff data which was collected before implementing LID practices at Klusner Avenue. The Nash-Sutcliffe efficiency (NSE) had a value of 0.69 for the calibrated model which indicates a strong fit between the output and observed data. Finally, the calibrated model was used to add LID controls to evaluate its effects under various design storms, 1-year, 2-year, 5-year, 10-year, 25-year, and 50-year return periods. The results show that two types of LID controls, bio-retention cell and rain barrel installed in the study site reduced the total runoff volume from 9 to 13% and the peak flow by from 11 to 15% depending on rainfall intensities. The analysis of results suggested that the performance of LID controls should be based on not only their capacity and treatment area but also target design storm and unit cost.

Committee:

Ung Tae Kim, Ph.D. (Committee Chair); Jacqueline Jenkins, Ph.D. (Committee Member); Yung Tse Hung, Ph.D. (Committee Member)

Subjects:

Civil Engineering

Keywords:

Low Impact Development; Storm Water Management Model; Bio-retention; Rain Barrels; Green Infrastructure; Modeling

Gutierrez Soto, MariantonietaMULTI-AGENT REPLICATOR CONTROL METHODOLOGIES FOR SUSTAINABLE VIBRATION CONTROL OF SMART BUILDING AND BRIDGE STRUCTURES
Doctor of Philosophy, The Ohio State University, 2017, Civil Engineering
The protection of large infrastructure is a critical and complex issue facing civil engineers. Earthquakes are especially unpredictable and pose a great threat to critical infrastructure that directly affect people’s lives. To tackle this problem, the latest innovation is the development of intelligent structures. Intelligent structures have technology installed to dampen the movement caused by forces of nature. The goal is to develop a new generation of smart structures equipped with sensors and control devices that can react in real-time during an earthquake. Structural control methods have been the subject of significant research in the past 20 years but still face limitations. This investigation consists of four parts. In Part I, four ideas are introduced for vibration control of smart structures: decentralized control, agent-based modeling, replicator dynamics from evolutionary game theory, and energy minimization. Two new control algorithms are presented: 1) a single-agent Centralized Replicator Controller (CRC) and a decentralized Multi-Agent Replicator Controller (MARC) for real-time vibration control of smart structures. The use of agents and a decentralized approach enhances the robustness of the entire vibration control system. The proposed control methodologies are applied to vibration control of a 3-story steel frame and a 20-story steel benchmark structure subjected to two sets of seismic loadings: historic earthquake and artificial accelerograms and compared with the corresponding centralized and decentralized conventional control algorithms. In Part II, the aforementioned control algorithms are integrated with a multi-objective optimization algorithm in order to find Pareto optimal values for replicator dynamics parameters with the goal of achieving maximum structural performance with minimum energy consumption. The patented neural dynamic model of Adeli and Park is used to solve the multi-objective optimization problem. Vibration control of irregular structures subjected to earthquake excitations is a complex civil engineering problem with associated torsional vibrations. In Part III, the replicator dynamics concepts are adapted for active/semi-active control of multi-story irregular base-isolated structures. The control algorithm is evaluated using a 3D base-isolated benchmark structure subjected to major historical earthquakes. In Part IV, the idea of combining the conventional base isolation with an active or semi-active control system to create a smart bridge structure is investigated. A control algorithm based on game theory and replicator dynamics is employed for hybrid vibration control of highway bridge structures equipped with both a passive isolation system and semi-active control devices subjected to earthquake loadings. The efficacy of the model is demonstrated by application to a benchmark example based on interstate I-5/91 overcrossing highway bridge in southern California subjected to near-field historical earthquake excitations. Substantial reduction in both mid-span displacement and deck acceleration is achieved compared with the conventional base-isolated bridge.

Committee:

Hojjat Adeli (Advisor); Ethan Kubatko (Committee Member); Kevin Passino (Committee Member); Daniel Pradel (Committee Member)

Subjects:

Civil Engineering

Keywords:

smart structures, vibration control, earthquake, resilience, decentralized, agent, multi-agent, replicator dynamics, game theory, bridges, base isolation, benchmark, MR damper, semi-active, structural dynamics, modeling, high performance, computing

Penumatsa, GowthamCorrosion Detection in Reinforced Concrete Using Acoustic Emission Technique
Master of Science, University of Toledo, 2016, Civil Engineering
Corrosion of reinforcing steel is the major cause for deterioration of concrete structures. Corrosion of these steel bars potentially reduces the service life and ductility of the structures causing early failure of structure, this involves signifi cant cost for inspection and maintenance. Early detection of corrosion is necessary for the proper diagnosis and effective prevention of failure. Therefore, damage induced due to corrosion of reinforcing steel should be detected in the early stages and the severity of corrosion should be properly anticipated by means of non-destructive testing techniques for the safety of the structure. The available methods of corrosion detection in concrete structures are generally electrochemical, such as half-cell potential (HCP) measurements and linear polarization resistance (LPR). These methods are intrusive as they require a physical connection to the corroding steel. Furthermore, these methods only provide information about local corrosion and are usually used after corrosion damage is discovered visually. Acoustic emission is sensitive enough to be a feasible nondestructive testing technique to detect early corrosion. Therefore a corrosion monitoring cell to detect corrosion in reinforced concrete beams using acoustic emission is setup for the rst time at The University of Toledo and experiments are conducted. This thesis presents the fi rst use of acoustic emission to detect corrosion in rein- forced concrete at The University of Toledo. The tasks accomplished includes setting up a corrosion cell and understanding the AE hardware and software equipment. A literature review of corrosion monitoring in reinforced concrete using acoustic emission technology is provided in order to understand the AE technology advancement to date. Corrosion monitoring experiments were designed in the laboratory to initiate corrosion in reinforced concrete in a short time span and continuously monitor with an AE data acquisition system. Electrochemical half-cell potential method is used to anticipate the initiation of corrosion and to correlate AE data with potentials at di fferent stages of the experiment. Steel rebar and two reinforced concrete beams are corroded immersing in 3.5% NaCl solution and using constant potential. The corrosion in these rebar and concrete specimens are monitored continuously using Mistras Pocket Corpac with R15 sensors. Half cell potential measurements are also conducted to understand the method and used to establish correlation with AE. The experiments conducted helped to understand the corrosion process and detect corrosion using AE. The results of the experiments using acoustic emission were found consistent with those in the literature and the conclusions were con rmed using half- cell potential measurements.

Committee:

Douglas Nims (Advisor); Liangbo Hu (Committee Member); Dong Kim (Committee Member)

Subjects:

Civil Engineering; Engineering

Sigdel, PawanImproving Design Strategies for Composite Pavement Overlay: Multi-layered Elastic Approach and Reliability Based Models
Doctor of Philosophy, University of Toledo, 2016, Civil Engineering
Pavements need constant rehabilitation when they deteriorate with time and approach the end of their expected service lives. Overlay is the most prevalent treatment that restores its desirable condition and extends its life span of serviceability, especially for roads subjected to moderate and heavy traffic. Overlay composite design remains a major challenge due to difficulties in characterizing the complex behavior and assessing the existing condition of a combination of asphalt concrete (AC) and Portland cement concrete (PCC) layers over a soil subgrade. Deflection based design using falling weight deflectometer (FWD) deflection data offers an effective approach for overlay thickness design for composite pavements. It utilizes the deflection measurements of the pavement surface which can be used to back-calculate the subgrade and overlay composite properties and allows one to estimate the structural capacity of the existing pavement. However, the prevailing deflection based design procedure generally treats the AC and PCC as a single layer during the back-calculation and, as a result, frequently leads to less than satisfactory, usually over-conservative, design for overlay composites. The principal objective of this research is to develop improved FWD deflection based design strategies for overlay composite pavements. It is proposed that a three-layer linear elastic model be used for back-calculation of the moduli of all three layers: subgrade, PCC and AC. The structural capacity of the existing pavement is estimated using pavement surface deflections measured by FWD, the most commonly used pavement non-destructive testing (NDT) device. In the present study actual FWD deflection data for eleven construction projects are used to back-calculate the moduli of three layers. The three-layer model allows the composite pavement structure to be modeled more accurately. The elastic moduli of the asphalt concrete layer and the underlying Portland cement concrete can both be back-calculated, instead of combining them into one. The results show that the three-layer model produces higher effective thickness than the two-layer model for the same pavement structure, thereby reducing the required overlay thickness. However, there are a number of factors that can strongly influence the final overlay design thickness. The effects of computational error tolerances in back-calculation, temperature at FWD testing and variations in FWD deflection data are found significant and may cause unreliable design results and hence, two strategies to avoid excessively large or small back-calculated moduli are also explored: imposing moduli bounds and relaxing the precision convergence; they have been found very effective in mitigating the effect of large variations in deflection data. The statistical variations observed in the overlay design are also evaluated and two models are explored to improve the overall design procedure from the statistical perspective: Monte Carlo method and Point Estimation method. The effective thicknesses of existing pavement computed from reliability analysis are similar to those obtained from the proposed design method. This demonstrates the validity of the proposed design method and also the applicability of reliability based design in case the statistical parameters are available or can be obtained from engineering judgement.

Committee:

Liangbo Hu (Committee Chair); Eddie Chou (Committee Member); Brian Randolph (Committee Member); Youngwoo Seo (Committee Member); Habib Kaake (Committee Member)

Subjects:

Civil Engineering

Keywords:

composite pavement, overlay design, reliability, temperature correction

Boso, Evan M.Variable Passive Negative Stiffness Device for Seismic Protection via Apparent Weakening
Master of Science (MS), Ohio University, 2016, Civil Engineering (Engineering and Technology)
Seismic events have always been detrimental to civil engineering structures, with these events sometimes leading to structural collapse and loss of life. In order to mitigate these effects, innovative devices and design methods have been conceived. One recent method has called for the apparent weakening of the structure along with the addition of supplemental damping. This method aims to reduce the base shear, acceleration, and deformation of the structure by mimicking the post-yielding behavior. Apparent weakening is achieved through application of negative stiffness to emulate yielding before actual yielding of the structure occurs. Although there are negative stiffness devices (NSDs) that have been previously proposed, this research focuses on a new NSD, the variable passive negative stiffness device (VPNSD), that is capable of generating the ideal force versus displacement profile and improve upon drawbacks of past devices. This work will simulate the profile of this new device as well as the response of a single-degree-of-freedom structure equipped with the device and subject to various inputs. The results of the simulations showed that the VPNSD was able to create the ideal force versus displacement profile and provided reductions in base shear forces and accelerations of the model building structure.

Committee:

Ken Walsh (Advisor)

Subjects:

Civil Engineering

Keywords:

Negative Stiffness; Seismic protection; earthquake engineering; apparent weakening

Shay, Nathan MichaelInvestigating Real-Time Employer-Based Ridesharing Preferences Based on Stated Preference Survey Data
Master of Science, The Ohio State University, 2016, Civil Engineering
Expanding travel choices by providing ridesharing can improve mobility and accessibility and reduce congestion and the negative externalities associated with single occupancy automobile use. To realize these benefits, sufficient demand must be generated by matching drivers and passengers with similar origins and destinations and who are willing to travel with potential strangers. Technological developments have facilitated the provision of real-time ridesharing programs, where travelers are matched to share a ride shortly before they travel. Real-time ridesharing offers additional flexibility and the possibility of occasional use that may be desirable in an increasingly complex society with varying schedules. While initial real-time travel options have been perceived as unattractive due to reliability and personal safety concerns, the growing success of real-time ride-sourcing services suggests that perceptions may be shifting. Furthermore, large employer-based ridesharing offers additional promise due to a network of co-workers with similar work locations facilitating good matches, increased familiarity with fellow travelers, and the ability to incentivize participation. A stated preference survey of The Ohio State University community was used to analyze willingness to participate in an idealized real-time employer-based ridesharing program. Individual characteristics and travel behaviors associated with unwillingness to participate in an ideal program are analyzed. Also, the characteristics and behaviors associated with interest in a passenger or driver role in such a program are identified. Many findings support results presented elsewhere and a priori expectations, for example an increased willingness of younger travelers to participate in ridesharing, an increased willingness of females to participate as passengers, and an increased willingness of those with experience driving to participate as drivers. In addition three findings provide important insights previously unidentified about traveler preferences toward ridesharing. Firstly, it seems that those who travel in automobiles, whether shared or alone, are more likely than those who do not travel in automobiles to participate in ridesharing. Also, those who walk or use transit seem to be less willing to participate in a ridesharing program than those who do not use these alternative modes. These findings are encouraging in light of the desire to attract single occupancy vehicle users, rather than transit users or walkers, to ridesharing to realize its social benefits. Secondly, the notion that providing ridesharing expands mobility and accessibility seems to be supported by the fact that those who do not have a car available to them tend to be more interested in being rideshare passengers than those who have a car available to them. Lastly, while those living with younger dependent children are more likely to reject ridesharing due to the constraints associated with this mode, among those who are interested in ridesharing, individuals living with children—whether younger dependent ones or otherwise—are more willing to drive in a ridesharing program than those who do not live with children, possibly due to having experience traveling in vehicles with passengers.

Committee:

Mark McCord (Advisor); Rabi Mishalani (Advisor); Gulsah Akar (Committee Member)

Subjects:

Civil Engineering; Transportation

Keywords:

Real-time employer-based ridesharing; stated preference survey data; binary discrete choice model;

Zhang, RuomengEvaluation of Current Concrete Creep Prediction Models
Master of Science, University of Toledo, 2016, Civil Engineering
Creep is one of the main reasons that concrete shape changes with time. These changes may cause cracking or deflection that greatly affect the service life of the concrete structures. This study presents an evaluation of seven creep prediction models for their overall performance under the guidance of ACI codes and AASHTO codes. The prediction models include ACI 209R-92, B3, GL 2000, CEB 90, CEB 90-99, fib 2010 and AASHTO 2014. Two numerical examples were set up to carry out the calculated values for each model up to 3650 days. The results have also been compared with similar studies with historical creep performance data sets in the past decade. Prediction of creep by GL 2000 Models is found to be the best performance among these models based on this study.

Committee:

Douglas Nims (Committee Chair); Mark Pickett (Committee Member); Serhan Guner (Committee Member)

Subjects:

Civil Engineering

Keywords:

concrete creep, creep prediction models, creep coefficient, creep compliance, deflections, numerical models, time dependence

Gao, ZhichengCorrosion Damage of Reinforcement Embedded in Reinforced Concrete Slab
Doctor of Philosophy, University of Akron, 2016, Civil Engineering
Corrosion of reinforcements embedded in concrete is a worldwide problem that affects numerous reinforced concrete (RC) structures. While corrosion has always been problematic since the beginning of mining and refinery of metals, corrosion in RC structures only gained research attention during the 1960s and 1970s, following widespread use of de-icing salts on highways in United States. Since then, research has been undertaken worldwide to address corrosion issues. In this dissertation, an experimental study was conducted to characterize the structural behavior of reinforced concrete slabs subjected to accelerated corrosion in the lab. In order to make the experimental condition similar to the real service environment, the test specimens were introduced with pre-existing cracks and sustained loading was applied during the corrosion process. Accelerated corrosion of tensile steel reinforcements in RC slabs was facilitated by an accelerated corrosion process. Three different test conditions were induced in the corrosion test program: specimens without pre-existing cracks and sustained loading, specimens with pre-existing cracks but no sustained loading, and specimens with pre-existing cracks and sustained loading. In addition, different wetting and drying cycles were incorporated in the corrosion process. Expansion of longitudinal cracks along the tensile reinforcements and transverse cracks crossing the tensile reinforcements were recorded during the corrosion testing. Multiple desired corrosion levels-from low level (1%) to high level (20%)- were applied to different specimens. The gravimetric metal loss along the longitudinal direction of reinforcements was measured after the bending test. An empirical relationship was developed based on the representative specimens corroded with pre-existing cracks and sustained loading conditions for all desired corrosion levels. The epoxy-coated reinforcements and polypropylene (PP) fibers were used during casting experimental specimens to assess their corrosion resistance properties. By using the constant electric current, 10 and 20% desired corrosion levels were applied to most specimens, and 40% desired corrosion level was also applied to several test specimens with PP fibers additives to simulate the severe corrosion condition. The surface defects of epoxy-coated reinforcements and two different quantity ratios of PP fibers - 4.5 kg/m^3 and 6 kg/m^3 were considered in this study. The ultimate capacity of corroded specimens was tested after corrosion process. The average metal loss, the reduced yield strength of corroded reinforced bars and the effective cross section of the specimens can accurately predict the theoretical ultimate capacity loss compared with testing results. The critical inner expansive pressure from XFEM was applied to the developed numerical model to predict the cracking time of the cover concrete, which is defined as the severability limitation of the corroded RC structures. The proposed prediction model had been validated by comparing with the existing experiment data of uniform corrosion condition and the results show that the accuracy of developed model was acceptable to predict the serviceability of reinforced structures with corrosion damage. The effect of non-uniform corrosion condition on cracking pressure from XFEM and cracking time using developed prediction model was discussed.

Committee:

Robert Liang (Advisor); Anil Patnaik (Advisor); Zhe Luo (Committee Member); Yalin Dong (Committee Member); En Chen (Committee Member)

Subjects:

Civil Engineering

Keywords:

corrosion; reinforced concrete; cracks; metal loss

Wilson, Kevin EA Finite Element Investigation of Non-Orthogonal Moment Connections in Steel Construction
MS, University of Cincinnati, 2015, Engineering and Applied Science: Civil Engineering
Modern architectural designs for buildings often require innovative and unconventional structural solutions such as the use of non-orthogonally framed connections. Moment frames are seismic force resisting systems that provide architectural liberty when these unconventional designs are encountered. While a braced frame or a structural wall can be more cost efficient, a moment frame allows for the building space to be more efficiently utilized. Additionally, the moment frame allows for architectural liberty. When the seismic demand requires the use of an intermediate or special moment frame per the ASCE/SEI 7 specification, the document requires that the designing engineer implement a prequalified connection from the ANSI/AISC 358 document. However, the connections presented within this document do not account for non-orthogonally framed connections. Therefore, the designing engineer must either perform cyclic qualification of the proposed connection, or make a potentially ambiguous decision for the use of the connection based on their engineering judgment alone. The research investigates the effects of non-orthogonal connection framing of two connections presented in the ANSI/AISC 358 document with solid element finite element analyses. The responses of the connections are compared with traditional orthogonally framed connections validated from experimental testing. The results of the analyses provide insights on the expected behaviors as well as design recommendations that should be considered for practicing engineers.

Committee:

Gian Rassati, Ph.D. (Committee Chair); Uwe Aschemeier (Committee Member); James Swanson, Ph.D. (Committee Member)

Subjects:

Civil Engineering

Keywords:

Non-Orthogonal;Skewed;Sloped;Special Moment Frame;Reduced Beam Section;Welded Unreinforced Flange-Welded Web

Ng, Vincent LaphangA Study of Deterioration in Ride Quality on Ohio's Highways
Master of Science, University of Toledo, 2015, Civil Engineering
As pavement condition raises more and more concerns in the highway system across the United States, a new challenge emerges in developing reliable pavement deterioration prediction models that are easily applicable by highway pavement management system in state departments of transportation and other agencies. Transportation agencies typically employ a process to evaluate pavement performance on a regular basis and identifying sections with a need for maintenance or rehabilitation. Some states in the U.S. utilize an index based on ride quality alone, while others utilize a pavement rating system that is based solely on visible surface distresses in order to regularly perform evaluation of pavements. This thesis looks at the differences among the combinations of pavement types and priority systems and what effects they have on pavement roughness within the Ohio state highway system when compared with annual snowfall, quantified by the International Roughness Index (IRI). Simple correlation studies between one of Ohio’s pavement condition indices, the Pavement Condition Rating (PCR), and RIRI were conducted in attempt to find a meaningful relationship. When little to no correlations were found, this thesis then separated the highways based on pavement type, priority system, and annual snowfall region to develop an annual average IRI increase trend for each combination. Statistical testing were performed to ensure results were generated with a 90% confidence level. Slope regression and frequency prediction methods were used in three cases of annual snowfall to analyze the snowfall-¿RIRI relationship: one was split into four snowfall regions, and the other two were by different amount of snowfall thresholds—30 and 40 inches per year. Results from both methods confirmed that there exists a direct, positive correlation between the amount of annual snowfall and the increase of International Roughness Index per year in nearly all combinations of pavement-priority highways in Ohio.

Committee:

Eddie Chou (Committee Chair); Richard Becker (Committee Member); Liangbo Hu (Committee Member)

Subjects:

Civil Engineering

Keywords:

pavement deterioration, international roughness index, ride quality, pavement condition rating

Pettersson, FridaA Study on the Behavior of Deep, Slender Wide Flange Steel Beam-Column Members in Seismic Applications
MS, University of Cincinnati, 2016, Engineering and Applied Science: Civil Engineering
To economically control the drift limits in special moment frames (SMFs), deeper columns than the traditional W14 sections have become more common. The drift of an SMF can be reduced by increasing the bending and shear stiffness of the columns in the frame, and this would also be accomplished by using deeper sections (Shen 2002). However, deeper columns need to be checked against instability since they are more sensitive to local buckling and weak-axis failure modes than stockier columns (NEHRP 2011). The SAC project investigated the behavior of steel moment resisting frame connections after the Northridge Earthquake and some results were extrapolated to column and beam members. However, the project only produced data that led to the prequalification of RBS connections for use with W12 and W14 columns. When testing was performed with deeper column sections, stability problems occurred (FEMA 2000). This study analytically investigates the behavior of deep columns with an exterior RBS connection in a special moment frame. The 40 assemblies studied were designed according to the AISC Provisions (AISC 341, AISC 358, and AISC 360) and modeled with finite element software. A floor slab was not included and monotonic loading displaced the beam tip by 6.0 in. Column sections investigated were W14x426, W24x192, W27x194, and W30x191. The columns were subjected to varying levels of axial load and had medium or weak panel zone strength. Geometric imperfections were included in all models, and some models also included residual stresses. From this study it was concluded that the column depth does not impact the behavior of the connection and deep columns can be used in SMFs. The results show that axial loads have no effect on the column behavior until very high axial loads are applied. It was also shown the twist of the column increases with increasing column depth. Columns with a doubler plate twist more than cases without a doubler plate and the column twist decreases with an increasing axial load.

Committee:

Gian Rassati, Ph.D. (Committee Chair); Thomas M. Burns, Ph.D. (Committee Member); James Swanson, Ph.D. (Committee Member)

Subjects:

Civil Engineering

Keywords:

Deep columns;W-section;SMF;RBS;Axial load;Panel zone strength

Neupane, KamalBacterial Inhibition in Waste-Water/Fracking Water Using Copper Ion Solution
Master of Science in Engineering, Youngstown State University, 2016, Department of Civil/Environmental and Chemical Engineering
Natural gas serves as a major energy supply in United States. Hydraulic fracturing is the process of extraction of unconventional natural gas from the tight sandstones, and shale's bed. Hydraulic fracturing uses fracking fluid which consists of large volumes of fresh water, proppants (e.g. Sand), slicking agents, and antimicrobial solutions. These flow back water carries a large amount of bacteria which are responsible for the biofilm formation that can eventually clog the fissures (source) and inhibit gas extraction during down-hole production. Numerous toxic chemicals are used as biocides to eliminate the biofilm. These biocides are toxic and can deteriorate the subsurface environment. There has been exploration of alternative products for viable bacterial control but none are without any human health and/or environmental impacts. To replace these biocides, the potential use of copper solution was examined as a safer alternative to traditional biocides. Copper ions or copper compounds have been used to inhibit bacteria in many forms like solid and, liquids for centuries. Copper solutions can impede the bacterial growth while reducing the harm to the environment. This research was mainly focused on two objectives: i) to test the effectiveness of copper solution against gram positive and gram negative bacteria and ii) to explore the efficacy of copper ion solution as comparison to flow back biocide solutions.

The bacteria Escherichia coli and Staphylococcus aureus were used to represent gram negative and gram positive cells. The Staphylococcus epidermis is an aerobic bacteria present in some fracking wells which can also be experimented on in the culture. The experiment was performed using 30mL copper ion solution (250ppm Cu+2) and equivalent volume of flow back water, which were added to bacteria cultured vials at 4-6 hours to investigate the ability to inhibit bacterial strains. The growth with copper treatment was impeded for approximately 12 hours for gram negative bacteria and approximately 8-10 hours for gram positive bacteria. However, flow back water was found to inhibit all bacteria growth for up to 48-56 hours as concluded using both turbidity and viable cells count test results. To mimic the flow back water antimicrobial properties, copper ion solution may need to be added at 10-12 hours interval to replace the toxic chemicals used in fracturing fluids. It is not clear what chemicals, concentrations of the chemicals or the cost of the chemical are used in flow back water. Future studies should investigate and optimize the cost and economic viability of the copper solution. Copper and its compound are considered to be benign to the environment and they can also be toxic to deleterious bacteria, this property of copper would not only help fracking industries to remove biofilm problem but also help to preserve the subsurface environment.

Committee:

Anthony Vercellino, PhD (Committee Chair); Felicia Armstrong, PhD (Committee Member); Suresh Sharma, PhD (Committee Member)

Subjects:

Chemical Engineering; Civil Engineering; Environmental Engineering

Keywords:

hydraulic fracturing; biofilms; flowback; copper solution; turbidity; viable cell count; bacterial inhibition

Bayareddy, Venkata SubbaraoDetermination of Ineffective Flow Areas in Bridge Modeling Using HEC-RAS by Locating Ineffective Flow Stations
Master of Science (M.S.), University of Dayton, 2016, Civil Engineering
The Hydrologic Engineering Center’s River Analysis System (HEC-RAS) uses a simulation model to delineate floodplains, but it may also be used to size bridges and culverts. HEC-RAS has an option for defining ineffective flow stations at bridges and culverts. An ineffective flow area is a portion of a river or stream’s cross section where there is no water flowing downstream due to the presence of a bridge or a similar structure, i.e. no conveyance. Current practice is for modelers and engineers to provide an estimate of the location of ineffective flow stations. The purpose of the research effort detailed in this document is to develop an iterative approach capable of quickly and accurately locating ineffective flow stations at bridges. The ultimate goal of the proposed research effort will be to include the methodology in future releases of the HEC-RAS model.

Committee:

Donald V. Chase, Ph.D., P.E. (Advisor)

Subjects:

Civil Engineering; Hydrologic Sciences; Hydrology; Transportation; Transportation Planning; Urban Planning; Water Resource Management

Keywords:

Bridge Modeling using HEC-RAS; Ineffective flow area; Ineffective flow station; Sloped bridge abutments;

Dietrich, Anthony ThomasEstimation of stormwater runoff mitigation in Lucas County, Ohio using SWMM modeling and GIS analysis
Master of Science, University of Toledo, 2015, Civil Engineering
Increases in impervious surface, a direct result of urbanization, have resulted in the impairment of the natural water cycle. The transition from pervious vegetated cover to impervious pavement and building cover results in greater surface runoff generation and decreased groundwater recharge. The increase in runoff volumes results in greater pollutant delivery to receiving streams and disrupts the natural stream hydrology. The frequency of high intensity precipitation events is increasing due to global climate change, exacerbating the effects of urban runoff on the water system. The water quantity and quality impairments associated with urban stormwater runoff can be mitigated using bioretention LID controls. The overarching objective of this project was to assist in the development of a cohesive and coordinated plan for implementation of green stormwater strategies in Toledo - Lucas County. In this study, a combination of SWMM5 modeling and GIS analyses were used to identify candidate properties for bioretention, in three urban land use types, throughout Lucas County, Ohio. The GIS analysis using soil, land-use and parcel data identified 7,159 bioretention candidate parcels in vacant residential, multi-family residential and commercial properties. SWMM5 modeling results applied to the identified parcels estimated a potential total volume reduction of over four billion liters per year, generated over 1140 treated urban hectares. The results of the study support current bioretention design standards and note the benefit of the utilization of bioretention in some Hydrologic Soil Group D soils. This work supports future studies utilizing similar methodology to plan and prioritize LID control implementation and to estimate large scale pollutant removal performance.

Committee:

Cyndee Gruden, Dr. (Advisor); Defne Apul, Dr. (Committee Member); Richard Becker, Dr. (Committee Member)

Subjects:

Civil Engineering; Engineering; Environmental Engineering; Geography; Water Resource Management

Keywords:

Green Stormwater Infrastructure; GSI; Low Impact Development; LID; SWMM model; GIS analysis; Bioretention; runoff; stormwater

Srestasathiern, PanuView Invariant Planar-Object Recognition
Master of Science, The Ohio State University, 2008, Geodetic Science and Surveying
In many photogrammetry and computer vision applications, there ultimate goals is to recognize objects of interest. Various framework for object recognition problem have been developed. Among many framework, geometric invariances have been proven to be an efficient way to recognize object under geometric transformation i.e. affine transformation. Motivated by geometric invariance framework, we propose a new method for rec¬ognizing the isolated planar object under the circumstance of geometric transforma¬tion. Namely, we assume that object shape is deformed by projective transformation. Firstly, we present a new object’s shape representation based on an assumption that the boundary of the object’s shape can be approximately represented by a set of piecewise conics. Secondly, a new projective invariant feature is derived based on the distribution of the projective relations between the conic pairs, which are estimated from the objects shape. We hypothecate that two objects of the same type, which are viewed from different viewpoints generate similar histograms, such that the distance between these two histogram is smaller than the histograms generated from other object types. The proposed method has shown promising performance our shape database in which object’s shapes are deformed by projective transformation.

Committee:

Alper Yilmaz (Advisor); Anton F. Schenk (Committee Member)

Subjects:

Civil Engineering

Theberge, Ryan C.Comparison and Testing of Various Noise Wall Materials
Master of Science (MS), Ohio University, 2014, Civil Engineering (Engineering and Technology)
Noise abatement is an ever growing need in today's world as traffic volumes increase. Noise barriers provide local resident relief from high noise levels that can be created from a high volume highway. A standard noise barrier can be constructed from multiple types of materials, such as concrete or steel. These different types each have acoustical qualities that are particular to that material. To define which materials provided the best abatement, a two-part study was conducted to compare the decibel levels for six different materials and to compare the Federal Highway Administration's (FHWA) Traffic Noise Model (TNM) to the field results. To obtain the field results, an extensive field study was performed with recording microphones placed in specific patterns behind the wall. The model was used to replicate the field setup, and the model results were compared to the results obtained in the field. The amount of noise reduction from the field recording ranged from 11 dB to 19 dB. Based on a statistical analysis, it was found that the top material choices were the clear panel, concrete panel, hollow fiberglass panel, and steel panel. The other two, acoustic fabric and earthen berm, were significantly worse. Seventeen sites were compared to the FHWA model. The statistical analysis from the model comparisons found that of the 17 sites that 5 of them were significantly different from the model. Overall, the noise barrier materials were determined and the application of the noise model was found to be limited.

Committee:

Deborah McAvoy, Ph.D (Advisor); Ben Stuart, Ph.D (Committee Member); Ben Sperry , Ph.D (Committee Member); Douglas Green, Ph.D (Committee Member)

Subjects:

Civil Engineering

Keywords:

Noise Wall Material; Noise Abatement; Traffic Noise Model; Acoustic Fabric;

Moradkhany, AliMinimizing Parking Search Time On Urban University Campuses Through Proactive Class Assignment
Doctor of Philosophy, University of Akron, 2015, Civil Engineering
Cars cruising to find a parking space represent a key component of the traffic on urban university campuses. This study introduces a bi-objective optimization algorithm to demonstrate the feasibility of minimizing the parking search time and the number of parking trials to find a free space on urban university campuses due to daily commuters. An activity-based model is developed to assess the variation in the parking search time and the number of parking trials due to different classroom assignment methods. This model is able to investigate the effect of different arrival-departure conditions as well as different parking search methods. The University of Akron campus was selected in a case study to show the parking search time reduction under variety of conditions by using the proposed optimization approach. According to the results, using this approach, the parking demand can be efficiently distributed and the search time can be effectively reduced by around 18%. Moreover, the finally optimized class assignments will result in effective mitigation of the cruising flow due to around 14.5% reduction in the total number of parking trials. The application of developed search model is not limited to the campus parking and can be expanded to many other problems. To show this flexibility, the proposed search model was applied to a special event parking search problem and the sensitivity of parking search time to various modeling parameters was investigated.

Committee:

Ping Yi (Advisor); Hamid Bahrami (Committee Member); Linda Barrett (Committee Member); Ala Abbas (Committee Member); Junliang Tao (Committee Member); Patrick Wilber (Committee Member)

Subjects:

Civil Engineering; Transportation Planning

Alfallaj, Ibrahim SalehAnalysis of Crash Location and Crash Severity Related to Work Zones in Ohio
Master of Science (M.S.), University of Dayton, 2014, Civil Engineering
Due to growth of vehicle travel using streets and highway systems in the United States, pavement repair and rehabilitation projects have increased. As a result, the presence of work zones has created traffic congestion and has increased the crash risk. The main object of this study was to identify significant factors that contribute to an increase in crash severity in the state of Ohio and recognize the most risk segment within the work zone locations. The work zone segment area is made of : (a) termination area (TA), (b) before the first work zone warning sign area (BWS), (c) advance warning area (AWA), (d) transition area (TSA), (e) activity area (AA). This study used a 5-year crash data from Ohio Department of Public Safety (ODPS) database from 2008 to 2012. In this study, classification tree modeling was used to investigate significant predictor variables of crash severity of work zone related crashes and recognize the most significant crash location within work zone areas in the state of Ohio. Classification tree modeling identified ten important variables (factors) that explain a large amount of the variation in the response variable, crash severity. These predictor variables of work zone crash severity identified include collision type, motorcycle related, work zone crashes type, posted speed limit, vehicle type, speed related, alcohol related, semi-truck related, youth related and road condition. In case of work zone location analysis results, this study identified six significant factors, which include collision type, work zone crash type, posted speed limit, vehicle type, workers present, and age of driver. Collision type is the most significant factor that affects crash severity in a work zone. Likewise, for work zone location, the work-zone crash type was the most significant factor that contributed in increasing the probability of work zone location crashes.

Committee:

Deogratias Eustace, Ph.D., P.E., PTOE (Advisor); Peter Hovey, Ph.D (Committee Member); Paul Goodhue, P.E. (Committee Member)

Subjects:

Civil Engineering; Transportation

Keywords:

Work zone crash location, Work zone crash severity, Classification tree modeling, Ohio

Gissentaner, Tremaine D.Development of Conductive Green Polymer Nano-Composite for use in Construction of Transportation Infrastructure
Master of Science (MS), Ohio University, 2014, Civil Engineering (Engineering and Technology)
This thesis evaluates the effects of graphite based carbon nanofibers (CNF) when incorporated within a NatureWorks Ingeo 3001D Polylactide (PLA) matrix. A film casting method was conducted in which CNF was mixed via sonication with neat PLA at 1% wt., 3% wt., and 5% wt. doses in aims of enhancing nanomechanical behavior and conductivity. A melt compounding method via twin extrusion, was also performed to fabricate PLA/CNF samples at the same CNF wt. doses as employed by the film casting method. Nanocharacterization of samples were performed via Atomic Force Microscopy (AFM) and Scanning Electron Microscopy to evaluate nanomechanical properties and nano/micro structure of PLA/CNF samples. The PLA/1%wt. CNF sample mechanically performed better than the neat PLA, 3%, and 5% CNF samples for the film cast (69,996.94 ± 4,545.29 psi) and extruded (95,111.72 ± 30,388.96 psi) methods with respect to AFM nanoindentation. Macroscale tensile testing was performed effectively extruded samples in which the PLA/3%wt. CNF loading case (Young's Modulus = 295,594.18 psi) performed the best. Conductivity measurements were also completed to evaluate the potential for PLA/CNF based nanocomposites to be considered electrical sensors for civil engineering applications. The PLA/5%wt. CNF film cast sample was found to possess the most favorable electrical resistance (859.45 O), while all other samples were deemed not conductive due to improper dispersion of CNF particulates.

Committee:

Munir Nazzal, Ph.D (Advisor); Savas Kaya, Ph.D (Committee Member); Kenneth Walsh, Ph.D (Committee Member); Douglas Green, Ph.D (Committee Member)

Subjects:

Civil Engineering

Keywords:

Nanocomposites; Nano-composites; Carbon Nanofibers; Polylactic Acid; PLA; Green Polymers

Crawford, Justin LuveneImpacts of Station Dependent Error Sources on the Implementation of the National Height Modernization Program
Master of Science, The Ohio State University, 2013, Civil Engineering
Accurate, reliable, and up-to-date heights are essential for a wide range of economic activities in many professions, including: surveying, engineering, emergency managers, Earth scientists, and natural resource managers [Veilleux, 2013b]. Historically, accurate orthometric heights have been obtained by tying into the control benchmarks of a vertical datum. Spirit leveling and gravity readings are used to establish, maintain, and update the heights of the benchmarks, which is a costly and time consuming process. Contemporary heights can also be established with the Global Positioning System (GPS) and can be combined with a geoid model for a quick and cost effective method of obtaining the orthometric heights used in a vertical datum. The National Height Modernization Program enables access to accurate, reliable, and consistent heights [Veilleux, 2013b]. This program is being employed by the National Geodetic Survey (NGS), with the goal of implementing a new vertical datum by computing the orthometric heights through the combination of GPS and gravimetric data. The expected result is a high accuracy vertical datum that will establish the orthometric heights with an accuracy that will be sufficient for a multitude of applications in science, engineering, mapping, etc. The accuracy of such a vertical datum is, therefore, dependent on the accuracy of the underlying GPS and geoid models and a better understanding of the error sources associated with the GPS ellipsoidal height and the geoid model may enable orthometric heights to be obtained with a high accuracy. This thesis will assume that an accurate geoid model exists and will focus on any inaccuracies in orthometric heights caused by the GPS-derived height. There are many error sources that may enter into the GPS observable, including: satellite and receiver clock errors, satellite orbit errors, atmospheric delays of the GPS signal caused by the ionosphere and troposphere, receiver bias, environmental multipath, and antenna phase center variation [Grejner-Brzezinska, 2011]. These error sources must be accounted for, if high accuracy heights are to be established through GPS. This thesis principally examines the effects of station dependent error sources, including phase center variations (PCV), far-field multipath reflection, and near-field multipath reflection [Berglund, 2011]. The effects of neglecting the PCVs particular to an antenna with a radome will be examined to see how much height deviation is caused by not properly accounting for how the radome alters signal reception at the antenna. The effects of multipath caused by the following near-field error sources will be examined: GPS signal interference caused by high voltage power lines, multipath reflection from a snow-covered field, the effects of a robin sitting on an antenna, and the effects of a seagull sitting on an antenna that will be modeled through simulation. In addition, an investigation will be conducted to analyze the level of height variation caused by using different antenna models to determine the height of the same point. The results of the near-field multipath experiments show that small changes in the snow depth of an area result in a consistent pattern of multipath, while drastic changes in the snow depth of the surrounding environment will alter the magnitude of the multipath reflection. Data collected around high voltage power lines suggests that major obstructions to a GPS signal could perhaps be avoided through site planning and using only those satellites less likely to be obstructed by the high voltage power lines. The test with the birds sitting on antennas showed that the amount of error a bird causes on GPS-derived heights depends on the size of the bird and that the error will eventually average out when the bird leaves the antenna, but will impact instantaneous height estimation in, for example, real-time kinematic (RTK) GPS applications.

Committee:

Dorota Grejner-Brzezinska (Advisor); Alper Yilmaz (Committee Member); Carolyn Merry (Committee Member)

Subjects:

Civil Engineering; Geographic Information Science

Keywords:

National Height Modernization program;GPS Station Dependent Error Sources;Vertical Datum;Orthometric Heights;Multipath;Near-Field Multipath;Far-Field Multipath;Antenna Phase Center Variation

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