Search Results (1 - 25 of 752 Results)

Sort By  
Sort Dir
 
Results per page  

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

Mohammed, Alahmad SuleimanElectrochemical and Electroflotation Processes for Milk Waste Water Treatment
Doctor of Engineering, Cleveland State University, 2017, Washkewicz College of Engineering
The dairy industry generates abundant milk waste waters characterized by high biochemical oxygen demand (BOD) and chemical oxygen demand (COD) concentrations that can be very harmful to the environment, if left untreated. Electrocoagulation (EC) has been in use for waste water treatment. The treatment application uses aluminum electrodes and iron or the combined hybrid Al/Fe electrodes. Milk waste water contains high concentration organic pollutants and the main constituents of those organics are carbohydrates, proteins and fats, originating from the milk. The process of separating the flocculated sludge from waste water that has been treated using the electrocoagulation process can be accomplished by the flotation processes. The electroflotation technology is effective in removing colloidal particles, oil, grease, as well as organic pollutants from waste water. This study uses electrochemical and electroflotation treatment of milk waste water by means of an aluminum electrode with specific parameters including total organic carbon (TOC), pH, turbidity, transmittance, and temperature. Even though the electrochemical and electroflotation treatment processes have been around for some time, it has not been thoroughly studied. This study is going to highlight the importance of this technique as a pre-treatment method of milk waste water and its contribution to the reduction of pollutants in the milk processing industry. Furthermore, the process of electroflotation and electrochemical flotation continuously prove to be effective in remediation of varieties of pollutants of different chemical compositions and have the ability to achieve a very high treatment efficiency.

Committee:

Yung-Tse Hung, Ph.D. (Committee Chair); Walter Kocher , Ph.D. (Committee Member); Lili Dong, Ph.D. (Committee Member); Chung-Yi Suen, Ph.D. (Committee Member); Saili Shao, Ph.D. (Committee Member)

Subjects:

Civil Engineering; Engineering; Environmental Engineering

Keywords:

Electrochemical, electroflotation and electrocoagulation;Total organic carbon;Chemical oxygen demand; Biochemical oxygen demand ;Transmittance;Turbidity and pH

Dhungel, HariInvestigating the Temporal and Spatial Variability of Flow and Salinity Levels in an Ungaged Watershed for Ecological Benefits:A Case Study of the Mentor Marsh Watershed
Master of Science in Engineering, Youngstown State University, 2018, Department of Civil/Environmental and Chemical Engineering
The Mentor marsh was the first declared a National Natural Landmark in 1966 and became a nature preserve in 1971 in the State of Ohio. Despite being affected by salt pollution and other physical challenges, it still has a tremendous economic value, and will rise if it is restored. The Marsh was specifically dominated by catastrophic salt pollution due to the development of different human and industrial activities, especially between the late 1950’s and late 1970’s. The water salinity of the marsh varied from oligosaline (500 to 5,000) mg/L to hypersaline (above 40,000 mg/L) during that period. Salinity is a crucial environmental problem in the Mentor Marsh leading to profound consequences in wetland plants and aquatic habitats; including the rapid development of Phragmites australis in the downstream marshland. These Phragmites australis were very vulnerable to capture fire. While several studies were conducted in the past in the Mentor marsh, hydrologic investigation of the watershed has not been conducted yet, due to the lack of monitoring stations and long-term data records. Since the Mentor marsh watershed is a small ungaged watershed, and data is only being collected for a short duration, the prediction of flow with limited data invites certain degree of uncertainty. Therefore, monitoring stations were established in two small tributaries of Blackbrook Creek and Marsh Creek, for real time data recording of flow stage, water conductivity, water temperature, and atmospheric pressure in hourly mode using Levelogger and Barologger data logging devices. Similarly, the creek cross-section, water velocity and water stage were recorded intermittently with direct field observation to develop a rating curve and generate the continuous streamflow data. The hydrologic model, Soil and Water Assessment Tool (SWAT), was developed using climate data from National Climatic Data Center (NCDC) and Digital Elevation Model (DEM), land cover and soil data from the United States Department of Agriculture (USDA). The model was calibrated on the monthly scale with a Nash Sutcliffe Efficiency (NSE) of 0.86, the Root Mean Square Error (R2 ) of 0.87, and Percentage bias (PBIAS) of -2.9% using the observed data from Blackbrook monitoring station from the period of November 2016 to August 2017. Similarly, it was validated with NSE (0.78), R2 (0.87) and PBIAS (-13%), respectively, using the observed data records from the period of September 2017 to March 2018. The total monthly salinity loading from Blackbrook Creek was in the range of 10.23 ton to 163.98 ton, whereas it was in the range of 65.63 ton to 2028.13 ton in Marsh Creek. The median monthly salinity loading in Blackbrook Creek and Marsh Creek were 55 ton and 329 ton, respectively. The analysis showed that the Marsh creek had higher salinity loading than that of Blackbrook creek during direct field bservation. This was mainly because of the relatively large size of Marsh Creek catchment compared to Blackbrook Creek. However, the salinity concentration was higher in Blackbrook Creek compared to the Marsh Creek except in the month of winter and early spring seasons. The salinity loading was linearly correlated with streamflow in daily (R2 = 0.72) and monthly scale (R2= 0.83) in Blackbrook Creek. Similarly, the daily and monthly R2 of streamflow with salinity in Marsh Creek was 0.86 and 0.76, respectively. Furthermore, the correlation of salinity loadings with simulated streamflow from the SWAT model was utilized to generate the salinity loadings in streamflow events of various years at historical period. The monthly simulated salinity loading in Blackbrook and Marsh Creek in the historical period (2000-2016) illustrated that Marsh Creek contributed more than 10 times higher salinity loading than that of Blackbrook Creek. Similarly, the results showed that Blackbrook and Marsh Creek had higher median salinity loading in spring season. The salinity loading simultaneously decreased in summer and fall in both creeks and vice versa in winter season, most likely due to road salt application. The result also showed that wet years such as 2008 and 2011, experienced higher salinity loading in both creeks. Likewise, the analysis showed that annual median salinity loading in a historical period of 2000 to 2016 from Blackbrook and Marsh Creek were 620 ton and 8334 ton salt load respectively, which contributed to downstream marsh.

Committee:

Suresh Sharma, PhD (Advisor); Tony Vercellino, PhD (Committee Member); Peter Kimosop, PhD (Committee Member)

Subjects:

Civil Engineering; Environmental Engineering; Hydrologic Sciences; Hydrology; Water Resource Management

Keywords:

Creek, Phragmites, Salinity, Marsh, SWAT, Levelogger, Barolloger, Mentor Marsh Watershed

Kodsy, AntonioEFFECT OF ELECTROKINETICS ON PULLOUT RESISTANCE OF SHEET PILE WALLS
Master of Science in Civil Engineering, Cleveland State University, 2018, Washkewicz College of Engineering
This research was conducted to evaluate the feasibility of reducing the pullout resistance of metal sheet piles embedded in clay soils by Electrokinetic (EK) conditioning. Pullout tests were conducted on bench scale thin stainless-steel metal plates ( 8 cm wide and 46 cm long) implanted in pure kaolinite clay, and mixtures of kaolinite clay and sand. The pullout resistances were determined after 20, 40, and 60 minutes residence times of steel plates in the soils before and after EK conditioning under an electric gradient of 1500 V/m. The pullout resistances of the steel plates embedded in kaolinite clay reduced linearly with the duration of EK conditioning. As much as 60% reduction in pullout resistance was observed after 60 minutes EK conditioning. For the kaolinite-sand mixtures, the pullout resistances reduced by about 70% and 80% for 20% and 30% sand contents respectively after 20 minutes EK conditioning and showed no significant improvement with the increase in treatment duration. It was demonstrated that the electrokinetic process could be utilized to reduce the pullout resistance of metal plates embedded in clay and clayey soils.

Committee:

Lutful Khan, Dr. (Committee Chair); Jacqueline Jenkins, Dr. (Committee Member); Ung Tae Kim, Dr. (Committee Member)

Subjects:

Civil Engineering; Geotechnology

Long, Andrew M.Design, Construction, and Evaluation of a Bioretention Cell in Marietta, Ohio
Master of Science (MS), Ohio University, 2018, Civil Engineering (Engineering and Technology)
Parking lots are a large contributor of undetained and untreated stormwater runoff in urban watersheds. Green infrastructure (GI) practices, such as bioretention cells (BRCs), can be implemented to offset the negative effects of parking lots. In this study, a BRC was designed to intercept the WQv from an existing asphalt parking lot before it entered nearby Goose Run in Marietta, Ohio. Construction errors limited the ponding storage volume of the BRC to only 18% of the design. Average infiltration rates ranged from 2.66 in/hr to 7.67 in/hr with an overall average rate of 5.24 in/hr. The ability of the undersized BRC to reduce runoff volumes, mitigate peak flows, reduce runoff temperature, and remove TSS from the parking lot runoff before it discharged to Goose Run was investigated. The BRC reduced runoff volumes by 51.1% and 76.4%, reduced peak flows by 66.4% and 81.5% and lagged peak flows by 1.01 hr to 1.58 hr. These conclusion were drawn from inflow and outflow data that were adjusted due to limitations in the monitoring methods and therefore contain some uncertainty. The BRC reduced parking lot runoff temperatures by 3°C. The BRC reduced event average TSS concentrations by 92.1% to 98.7% and EMCs by 93.4% to 97.3%. Effluent TSS concentrations were lowered once a capped orifice design was implemented to control the flows from the underdrain outlet, but further research is still needed.

Committee:

Guy Riefler (Advisor); Tiao Chang (Committee Member)

Subjects:

Civil Engineering

Keywords:

Bioretention

Gopagani, VikasPARAMETRIC STUDY OF SIX-STORY STRUCTURE WITH SELF-CENTERING CONCENTRICALLY BRACED FRAMES AND VARYING MASS PER FRAME
Master of Science in Engineering, University of Akron, 2016, Civil Engineering
Self-centering concentrically braced frames (SC-CBFs) have been developed to reduce the structural damage caused due to earthquakes. SC-CBF systems have better seismic performance than the conventional concentrically braced frame (CBF) system; SC-CBF systems exhibit less damage to structural and non-structural components under earthquake loading. Recent research has shown that low-rise or mid-rise building seismic performance is better compared to high-rise SC-CBF performance. This study includes the design procedure of the SC-CBF structural members, prototype building, and the analytical procedure considerations in analyses of the prototype structure. The engineering demand parameters (inter-story drift and the peak roof drift) are developed using the nonlinear time history analysis of the structure under a set of ground motions. Then the results are used to evaluate the performance of the structure. In this study, static pushover and dynamic analyses are performed on a 6 story SC-CBF with different numbers of frames in each direction for the same building dimensions (essentially varying the tributary mass per frame). This study proposes to investigate the performance of the structure with varying tributary mass per frame.

Committee:

David Roke (Advisor)

Subjects:

Civil Engineering

Pamula, Abhiram Siva PrasadAdsorption and microfiltration processes to treat dye and coffee wastewater.
Master of Science in Environmental Engineering, Cleveland State University, 2018, Washkewicz College of Engineering
Wastewater from coffee processing industry creates high biological and chemical oxygen demand in the surface water. In addition to coffee wastewater from coffee industry, dyes from textile industry enter surface water affecting water quality in terms of transmissivity of light. Adsorption is an economical wastewater treatment process to remove color from dye and coffee wastewater. In the current thesis, adsorption using low-cost adsorbents like peanut hull and onion peel are used to treat combined dye and coffee wastewater. Three representative dyes including acid black 48, disperse yellow 3, crystal violet certified with processed coffee is used in preparing batch adsorption samples. Using UV-Vis Spectrophotometer, absorbance and transmittance of the wastewater samples are measured. After adsorbents reach adsorption capacity, the suspended solids are removed using Whatman 41 microfilters. To understand the change in organic carbon before and after treatment in the wastewater, NPOC (Non-Purgeable Organic Carbon) is compared using Shimadzu TOC analyzer. This thesis focuses on the two-stage treatment process of adsorption and microfiltration in a binary mixture of dye and coffee wastewater. Increasing Adsorbent dosage in the representative wastewater samples gives us the idea of optimum dosage required in the treatment process. The comparative study of adsorbent dosage with transmittance and NPOC gives us an understanding of the efficiency of low-cost adsorbents when compared to Powdered Activated Carbon.

Committee:

Yung-Tse Hung (Advisor); Walter Kocher (Committee Member); Lili Dong (Committee Member); Chung-Yi Suen (Committee Member); Howard Paul (Committee Member)

Subjects:

Civil Engineering; Environmental Engineering

Keywords:

Adsorption, Micro-filtration, Non-purgeable Organic Carbon, Dye and coffee wastewater, Total Suspended Solids

Nevins, Robert PardyGeoreferencing Unmanned Aerial Systems Imagery via Registration with Geobrowser Reference Imagery
Master of Science, The Ohio State University, 2017, Civil Engineering
Unmanned aerial systems are developing into increasingly competitive platforms for aerial image surveying in a variety of applications. Easy-to-use and relatively inexpensive, their utility is however reliant on georeferencing their imagery with respect to an earth-based coordinate system. Traditionally this requires the time-consuming and potentially cost-increasing introduction of ground control points into the scene of interest. Other techniques, such as direct georeferencing using integrated Global Navigation Satellite System receivers and inertial navigations systems, struggle to achieve comparable accuracy due to weight and cost limitations faced with highest-accuracy instrumentation. In this work, unmanned aerial system imagery was georeferenced via registration with satellite imagery downloaded from online geobrowser image databases, specifically Environmental Systems Research Institute World Imagery. This method allows the potential elimination of all fieldwork related to ground control point distribution and surveying, taking advantage instead of instantaneous access daytime, cloud-free satellite imagery provided by geobrowsers. Registration was performed both using pixel-based template matching, and successive application of pixel-based and feature-based keypoint detection and matching techniques. Test imagery was collected by unmanned aerial systems over a parking lot and surrounding area in central Ohio. Root mean square error results were calculated for both pixel-based and successive pixel-based and feature-based registration with respect to 8 ground control points measured independently by Global Navigation Satellite System survey. Using 0.3 meter reference imagery, sub-pixel accuracy was achieved with successive pixel-based and feature-based registration. Possible applications include unmanned aerial systems mapping for endeavors such as precision agriculture, and unmanned aerial systems navigation.

Committee:

Dorota Grejner-Brzezinska, Ph.D. (Advisor); Charles Toth, Ph.D. (Committee Member); Rongjun Qin, Ph.D. (Committee Member)

Subjects:

Civil Engineering

Keywords:

UAV; UAS; Photogrammetry; Mapping; Image Matching; Image Registration

Hotz, CarlMOMENT REDUCTION ANALYSIS OF BUILT-UP I-SECTION EXPOSED TO UNIFORM CORROSION
Master of Science in Engineering, University of Akron, 2018, Engineering
With an aging infrastructure in the United States it is becoming more pressing to understand corrosion and the effects it has on structures. This knowledge will allow structural inspectors to determine the best course of action to take when dealing with a corroded member and insight so as to not take a member out of service prematurely. There are many types of corrosion that effects steel structures the form that is being studied in this report is uniform corrosion. Uniform corrosion occurs when the corrosion process attacks the surface of the steel uniformly thinning the material. This report looks at the effect uniform corrosion has on built up I sections subjected to a bending moment, and the reduction in moment strength associated with a percent loss in cross sectional area. To accomplish this lab tests were conducted on beams that were corroded in a controlled environment. With a known reduction in cross sectional area the beams were exposed to a bending test and the results were compared to moment values calculated using equations present in the American Institute of Steel Construction Steel Manual. In addition to bending tests tension tests were conducted on non-corroded tension specimens, corroded tension test specimens and corroded specimens that the corrosion byproduct was cleaned off by a chemical process. Finally finite element models were created to as another check and to see if the corrosion process could be modeled by assuming idealized uniform loss in area from corrosion

Committee:

Anil Patnail, Dr. (Advisor); Craig Menzemer, Dr. (Committee Member); David Roke, Dr (Committee Member)

Subjects:

Civil Engineering

Keywords:

Uniform Corrosion, I-Section, Structural Engineer, Moment Reduction, Finite Element Modeling, Tension Test, ASTM B117, Corrosion Tests, Environmental Chamber

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

Alin, MaishahEffect of rejuvenators on rheological properties of asphalt binders
Master of Science, University of Akron, 2018, Civil Engineering
Reclaimed Asphalt Pavement is usually used to replace the expensive virgin binder in the asphalt mixture design. Ohio Department of Transportation allows 10% RAP in the mixture design as higher percentage of recycled binder will make mixture aged. In recent years the cost of virgin binder is increasing at extremely rate. This has garnered attention to maximizing the use of RAP to minimize the production and manufacturing cost. This research project is a part of a project of Ohio Department of Transportation. The goal of ODOT’s project is to assess the feasibility of RAP in the surface course of municipal and local roadways. The objective is to develop cost effective mix design and quality control recommendations for RAP use on local roadways in Ohio that does not adversely affect the performance or durability of the asphalt mixtures. This study evaluates the effect of three rejuvenators (SylvaroadTM RP 1000, Industrial Soybean Oil and Hydrolene H90T) to restore the viscoelastic properties of PG 64-22 when mixed with recycled asphalt binder. Rejuvenators are known to reversing the aging effect in aged asphalt binder. Therefore, use of rejuvenators will allow higher percentage of RAP being used in asphalt mixture design. In this study PG 64-22 is the virgin binder and the three rejuvenators are SylvaroadTM RP 1000, Industrial Soybean Oil and Hydrolene H90T. The RAP binder percentage was used 40% of total binder’s weight. At first recycled binder was extracted from RAP material using centrifuge method and recovered by Abson method. PG 64-22 and RAP binder is mixed with two selected dosage (low and high) for each of the rejuvenators. In order to evaluate the effect of the rejuvenators at different dosages testing had been done on unaged binders, short term aged binders, and long term aged. Short term aging has been simulated using the Rolling Thin Film Oven Test (RTFO) and the long-term aging has been simulated using the Pressurized Aging Vessel (PAV). Finally, virgin binder, recycled blend without the rejuvenators and with two different dosage of rejuvenators were tested at different aging conditions using the Dynamic Shear Rheometer (DSR), and the Bending Beam Rheometer (BBR). DSR was used to evaluate viscoelastic properties at high temperatures and Bending Beam Rheometer was used to determine the effect of rejuvenator at low temperature. These observations had been used to determine an optimum dosage for each of the rejuvenators. The results had suggested that Sylvaroad exhibited the best softening capability at lower dosage. Whereas Hydrolene was unable to leave significant effect even after using higher dosage. Comparison of observations affirmed that at higher dosage Industrial Soybean Oil reverse the aging effect significantly in recycled blend.

Committee:

Ala R. Abbas (Advisor); Anil K. Patnaik (Committee Member); Junliang Tao (Committee Member)

Subjects:

Civil Engineering; Transportation

Keywords:

reclaimed asphalt pavement, rejuvenator, asphalt, optimum content, aging process

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

Elmushyakhi, AbrahamIn-Plane Fatigue Characterization of Core Joints in Sandwich Composite Structures
Doctor of Philosophy (Ph.D.), University of Dayton, 2017, Materials Engineering
In practice, adjacent preform sandwich cores are joined with a simple butt joint without special precautions. When molded, this gap is filled with resin and creates a resin rich area. Stress risers will be amplified under cyclic load, and consequently, the serviceability of the structure will be affected. Designers and researchers are aware of this problem; however, quantifying this effect and its intensity and consequence on the service life of the structures has not yet been developed. Despite pervious findings, limited experimental data backed by a comprehensive root cause failure analysis is available for sandwich under axial static, fatigue and post-fatigue. If such a comprehensive experimental characterization is conducted, specifically understanding the nature of the damage, intensity, and residual strength, then a valid multi-scale damage model could be generated to predict the material state and fatigue life of similar composite structures with/without core joints under in-plane static and fatigue load. This research study characterized the effect of scarf and butt core joints in foam core sandwich structures under in-plane static and fatigue loads (R=0.1 and R= -1). Post-Fatigue tensile tests were also performed to predict the residual strength of such structures. Nondestructive Evaluation Techniques were used to locate the stress concentrations and damage creation. A logical blend of experimental and analytical prediction of the service life of composite sandwich structures is carried out. The testing protocol and the S-N curves provided in this work could be reproducible and extrapolated to any kind of core material. This research study will benefit composite engineers and joint designers in both academia and industry to better apprehend the influence of core joints and its consequence on the functionality of sandwich structures.

Committee:

Elias Toubia (Advisor); Paul Murray (Committee Member); Thomas Whitney (Committee Member); Youssef Raffoul (Committee Member)

Subjects:

Aerospace Engineering; Aerospace Materials; Civil Engineering; Composition; Design; Engineering; Materials Science; Mechanical Engineering; Polymers

Keywords:

Sandwich Composite Structures; Design; Fatigue; Damage; Joints; Lightweight Materials; E-glass-vinyl ester; GFRP Laminate; Modeling; Prediction; Nondestructive Testing

Miller, Tyler MatthewFleet Optimization and Failure Probability of Winter Maintenance Routes
Master of Science in Engineering, University of Akron, 2017, Engineering
For winter maintenance purposes, the Ohio Department of Transportation (ODOT) deploys a fleet of approximately 1,600 snow plow trucks that maintain 43,000 lane miles of roadway. These trucks are based out of 200 garages, yards, and outposts that also house 650,000 tons of salt (ODOT, 2011). The deployment of such a large number of trucks over a vast maintenance area creates an operational problem in determining the optimal maintenance routes and fleet size. Traditionally, ODOT has used county borders as maintenance boundaries for ODOT garages. However, by removing these borders and optimizing the snow plow routes, ODOT may benefit from a significant time and cost savings. The results of this project provides ODOT with a tool to determine the minimum number of trucks needed to maintain the necessary roadways within Districts 1, 2, and 10. In addition, the project provides ODOT a tool to assign assets to specific facilities and the most optimal routes for each truck in the district. This research has resulted in reducing the fleets within Districts 1, 2, and 10 by 29 trucks while maintaining the same level of service currently observed. In addition to the reduced fleets, the route optimization decreasing the time to treat each road in the three districts by 17 hours for one iteration.

Committee:

William Schneider, IV (Advisor); Christopher Miller (Committee Member); Stephen Duirk (Committee Member)

Subjects:

Civil Engineering

Keywords:

Winter Maintenance; Fleet Optimization; Route Optimization; Level of Service; Monte Carlo

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

Next Page