UTSA Electronic Theses and Dissertations
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This collection contains electronic UTSA theses and dissertations (ETDs), primarily from 2005 to present. The collection is not comprehensive; search the UTSA Library Catalog for a complete list of UTSA theses and dissertations.
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Browsing UTSA Electronic Theses and Dissertations by Department "Civil and Environmental Engineering"
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Item A best-fit rigid pavement back-calculation method based on site-specific finite element simulations(2009) Marchant, JuanTraditional best-fit back-calculation methods for rigid pavements seek to determine the slab modulus E and the modulus of the subgrade reaction k by minimizing the squared errors between estimated and measured pavement deflections. The estimated deflections are obtained using theoretical relationships (i.e., Kelvin-Bessel functions). This method is used for back-calculating the rigid layer moduli stored in the LTPP database. The measured deflections are obtained using a Falling Weight Deflectometer (FWD). This paper describes an innovative best-fit back-calculation approach for improving this traditional method. It allows estimation of the modulus of subgrade reaction supporting the slab using best-fit techniques. It introduces two main innovations: (1) It utilizes the finite element method (FEM) for obtaining the estimated surface deflections by simulating the site-specific field conditions, (slab geometry, dowel/reinforcement configuration and environmental conditions). (2) It assumes that the modulus of the Portland concrete slab is known (i.e., it can be readily obtained through non-destructive wave-propagation techniques). The new approach is tested using the LTPP database. It utilizes the FEM model EverFE for obtaining the site-specific deflection estimates. Comparisons are made between the subgrade back-calculated moduli using the traditional best-fit method and the proposed best-fit method. These comparisons are focused on LTPP sites that have elastic moduli data for the Portland cement concrete slab (i.e., obtained from core measurements using ASTM C 469), as well as traditional best-fit back-calculated moduli. The new approach shows a marked improvement in predicting moduli of subgrade reaction compared to the traditional best-fit method.Item A Comprehensive Study of the Electromagnetic Energy Harvesting Technology from Roadways Systems(2019) Gholikhani, MohammadrezaEnergy harvesting technology in roadway infrastructure has attracted significant attention recently due to its capacity to generate sustainable low power. According to the review paper, the latest work failed to include an electromagnetic approach, which is believed to be one of the most promising energy technologies for roadways. Thus, in this study, different mechanisms of electromagnetic energy harvesting technology were explored. Four mechanisms were developed and examined: the rack-pinion mechanism, linear generator (stator-translator) mechanism, rotational mechanism, and cantilever mechanism. All of these mechanisms function on principles based on Faraday's law. The Maxwell–Faraday equation, the general form of Faraday's law, states that a time-varying magnetic field will always accompany a spatially electric field, and vice versa. Some prototypes were designed and fabricated based on these four mechanisms. The performances of these prototypes in generating electrical power were examined through laboratory and in-field tests. The results showed promise for using each of these electromagnetic energy harvesting mechanisms, but the power output of the mechanisms varied in scale. The maximum power output for the rack-pinion, linear generator, rotational, and cantilever mechanisms in laboratory tests were approximately 16 W, 80 mW, 90 mW, and 1.1 W, respectively. The maximum power output for the rack-pinion mechanism in-field tests was 6.7 W. The ease of installation and the limited negative effects on a roadway's performance make electromagnetic technology an ideal candidate for energy harvesting in roadways. However, it must be noted that the technology is in its beginning stage, and it must be developed in all phases.Item A field-based evaluation of the effects of spatial and temporal variability on water quality along Geronimo Creek watershed in Guadalupe County, Texas(2010) Ovuegbe, Emeka HawkynsWith the exploding human population coupled with the advancements in technology and sophistication in life style, water quality is constantly being compromised and has lately been getting the desired attention from all the stakeholders. Following the monitoring results on Geronimo creek by Guadalupe-Blanco River Authority (GBRA) as reported in the 2004 and subsequent Texas Water Quality Inventory (TWQI) and the Federal Clean Water Act (CWA) 303(d) List, bacteria concentrations exceeded the standard for normal recreational use (mean of 162 organisms/100 mL) while the nitrate-nitrogen level was documented as high and increasing (mean concentration of 11.0 mg/L). This study monitored water quality for twelve months along the Geronimo Creek in Guadalupe County, Texas in order to conduct an assessment of pollutants, their estimates and likely sources. It also examined the influence of spatial and temporal variability on the water quality along the entire segment of Geronimo creek. The study goal was to conduct and present a Texas Commission on Environmental Quality Clean Rivers Program (TCEQCRP) quality assurance-compliant water quality monitoring and data analysis to establish an estimate, likely origin and distribution of pollutants for various planning and management needs. Statistically, monitoring data was analyzed using the two-way ANOVA to assess the impact or contribution of land use and/or season on water quality of Geronimo creek during the sampling period. Correlation analysis was also done on some of the parameters. Data was compared with established state standards to determine compliance. Consistent with the foregoing, this study focused on sampling flow, field, conventional, and bacteriological parameters to establish baseline pollutant levels for future monitoring programs. The majority of the routine water quality parameters were at levels lower than what would be considered detrimental to the stream and public health. Only TSS, total hardness, E. coli and nitrate-nitrogen values exceeded specific limits established by state agency. Metal toxicity was not an issue with this creek as the metal concentrations of both historical and current monitoring programs were far below the established standards. The Soil and Water Assessment Tool (SWAT) was applied to quantify, and predict under different control scenarios, the effects of the reported impairments and guide the development of best management practices (BMPs) for reducing the nitrate and E. coli levels. It was, however, verified that the model could not produce reliable results given the available data and location of existing stream flow monitoring station. Necessary recommendations for a reliable future data collection and better modeling results were identified.Item A methodology for prioritizing improvements in passive highway-rail crossings(2012) Kunisetty, Jaya LakshmiThe current Texas Priority Index (TPI) prioritizes high volume active crossings; therefore most high volume crossings have already received improvements in terms of active control devices. Further improvement at these active crossings is not a priority because most crashes occur in active crossings for reasons that cannot be eliminated with additional controls. For example, driving around closed gates or because the drivers are inattentive (Sétra, 2008). So the current research is focused on identifying low volume passive crossings that would benefit from improvements through warrants, then prioritizing the warranted crossings with a new Texas Passive Crossing Index (TPCI) developed for this purpose. Warrants are a series of tasks that make the crossing eligible for upgrade but they are not a substitute for engineering judgment The warrants and the TPCI were developed using data from the Texas Railroad Database (TxRAIL) and Federal Railroad Administration (FRA) database. Warrants were developed after examining existing methodologies and considering all the important attributes. In order to avoid the disadvantages of fixed thresholds found in all existing methodologies, a new percentile threshold concept was developed for the warrants. Since the warrants must ensure identification of all passive crossings that potentially benefit from improvements, they identify approximately 30% of all eligible passive crossings (1,115 out of 3,756). Since Texas Department of Transportation (TXDOT) updates only 75 to 100 crossings a year, a new Texas Passive Crossing Index (TPCI) was developed to prioritize the warranted crossings based on Utility Theory. The weighted average method was used for decision making in order to get the overall utility of the crossing. In order to get these weights, a survey questionnaire was given to railroad experts and their responses were normalized using the AHP theory. The TPCI includes 13 important attributes and the cumulative percentiles of all the relevant attributes are used as utility surrogates. Finally, a ranking procedure was developed that sorts crossings by the multiple crashes followed by the number of warrants met and then by TPCI. The developed ranking procedure results are significantly better than the existing priority indices for ranking and selection of passive railroad crossings in Texas. The new method can be easily implemented into a computerized decision support system to provide a more objective procedure for the selection of passive crossings for safety improvements.Item A Proposed Methodology to Analyze Cold-Formed Steel Trusses Subjected to Blast Loading Using Single-Degree-of-Freedom for Design and Assessment(2022) Rolater, GregoryThe following thesis proposes a methodology for analyzing Cold-Formed Steel (CFS) trusses subjected to blast loading using a non-linear Single-Degree-of-Freedom (SDOF) approach. SDOF has proven to be an effective structural dynamic analysis tool for the design of common components such structural steel, reinforced concrete, and even CFS studs in flexure. Unlike typical components, the behavior of CFS trusses when loaded beyond their peak capacity is not well understood, but data sets from small experimental samples demonstrate that CFS trusses are capable of providing residual capacity even after buckling occurs. Based on this key observation, the scope of this thesis intends to leverage existing data to develop a simplified methodology for blast analysis using SDOF. Within this scope, Finite Element (FE) modeling assumptions and techniques are developed and validated against available experimental data for analysis using LS-DYNA. Advanced topics, such as buckling and imperfections, are considered when modeling techniques are developed; however, these topics are worthy of independent research efforts that are not included in the scope of this thesis. Quasi-static strength simulations are then performed on designed trusses in order to better characterize the extent of residual capacity after buckling. The data from strength simulations, along with principles of advanced structural analysis, are then leveraged to develop parameters for SDOF modeling. Finally, FE models and SDOF models are subjected to identical blast scenarios and the results are compared side-by-side. The resistance functions resulting from the proposed SDOF methodology compare favorably to the quasi-static simulation results performed in LS-DYNA. Similarly, the blast analysis results using the proposed SDOF models compare very well to the blast simulations performed in LS-DYNA. However, due to the limited amount of data produced within the scope of this thesis, it can be concluded that the results are encouraging, but only a framework for further development has been established. The conclusion section highlights several areas for improvement that were identified for additional research to ensure the methodology is better vetted. Also, design considerations and general guidance that are based on the findings from the work performed and backed by engineering principles are summarized as recommendations in the conclusions as well.Item A Structural and Environmental Assessment of Pavement Solar Panels(2021) Rahman, MusfiraThe concurrent energy shortages of non-renewable energy resources have directed attention to the potential of harvesting renewable energy resources from roadway. Strong incentives to sustainable solution to this problem have led to the design of innovative pavement solar panel technology. This research is based on designing and developing a solar panel for roadway application. The designed prototype consists of a thin film solar panel, a transparent cover to protect the solar panel and a wooden frame to support the whole configuration. Since the pavement is exposed to solar radiation throughout the daytime, the pavement embedded solar panel will be utilized to harvest the solar energy and store with the integration of storage system and convert into electricity. It should also provide service during power failures in remote areas without electrical utilities. The main challenge of the project is the selection of proper transparent cover since it should bear the traffic loads and should not impair the transparency at the same time. The types of transparent covers chosen for this study are polycarbonate samples of varying thicknesses, textured glass grit sample and textured float glass with corundum skid resistant coating on the surface. Percentage transmittance of each samples was determined using transmittance spectroscopy in the visible light range. The percentage transmittance for the 10 mm, 12 mm and 16 mm polycarbonate samples were 87%, 84% and 82% and for textured glass grit sample it was 40% at each wavelength in the visible light range. The finite element analysis was carried out to replicate the in-situ installation of the solar panels with polycarbonate shield covers to determine the structural feasibility. The prototype panel was subjected to static and dynamic loading and the stress, strain and deflection analysis was performed and compared with a typical pavement model without any transparent cover. Finite element analysis demonstrated that the panel would not fail by fatigue under the loading condition considered. Power generation data from these solar panels were collected and compared in a wide range of weather conditions and different seasons to assess the relationship of power and other environmental factors such as irradiance, illuminance, temperature, and cloud cover Since the panels were designed for pavement application, the panels were subjected to vehicular loading during the field tests to determine the decline in the power output due to shading of vehicles. Another purpose of the field test is to analyze whether the transparent covers face any disruption, damage, or failure under the wheel loading. Although polycarbonate samples and textured float glass sample can withstand traffic loads, the textured glass grit sample failed in fracture without any warning of failure under wheel loading. Experimental results also showed that 12 inch × 12 inch pavement solar panels generate an average of 2.2 W in sunny condition but produce less power in cloudy condition. Based on the power production data of SP10 from 12 PM to 6 PM, its feasibility was assessed for utilizing in the smart pedestrian system to lighten the crosswalk and alert the drivers of approaching vehicles.Item A Study of Restricted Crossing U-Turn(RCUT) Intersection(2017) Guddeti, Sathwik ReddyTransportation experts today are confronted with the test to meet the versatility needs of a steadily expanding populace with restricted assets. One possible treatment to alleviate congestion and safety issues at rural expressway intersections, while attempting to maintain a strategic distance from signalization or grade‐separation, is the Restricted crossing U-turn treatment, which has been effectively executed in Michigan, Florida, Maryland, New Jersey, and Louisiana. The treatment includes the preclusion of left‐turn and through movements from the side‐street approaches and accommodates them by requiring drivers to go right onto the main street and afterward make a u‐turn movement at a one‐way directional median opening downstream. Left‐turns from the major road approaches are executed in a way like left‐turns at a conventional intersection and are unaffected. Although this kind of intersection treatment is commonly viewed as a corridor‐wide treatment, the idea has been effectively utilized at isolated intersections to enhance traffic flow and improve safety. This report presents design guideline recommendations for the execution of restricted crossing intersection treatments in Mississippi. Specific items tended to in this report include general design elements, cross-sectional elements, intersection and crossover design details, pedestrian accommodations, traffic control gadgets, lighting, marking, historical safety performance, development costs and phasing, and public involvement efforts. The proposals contained in this record cannot have any significant bearing to all circumstances as each venture is one of a kind and commonly require their own variations to site‐specific conditions. A significant number of the design elements suggested for the Restricted Crossing U-turn and MUT crossovers coordinate the current Texas department of Transportation practices for arterials. All references contained in this report refer to the 2014 release of the TxDOT Roadway Design Manual, which is as of now undergoing a noteworthy modification. Therefore, the planner ought to check that the latest plan criteria are being utilized preceding starting an outline.Item A study of texture on airport runways using an outflow meter and the sand patch method(2010) Aranda, Sergio C.Hundreds of aircraft take off and land safely every hour of the day, all over the world, without incident. From the perspective of the average consumer, what matters most is getting from point of origin to point of destination in a timely and safe manner. The makeup of a runway plays a major factor in landing an aircraft safely. But what does it take to accomplish this goal? A good pilot, a good airplane, good engines, clean fuel, good tires, and good brakes are some of the components. Another lesser-known but vital factor is runway texture. Texture is a major component in ensuring safe landings, and maintaining the proper texture involves regular examination and maintenance. Two airports, San Antonio International Airport (SAT) at San Antonio, Texas, and Laredo International Airport (LRD) at Laredo, Texas, were utilized in this experiment for different reasons. The airport in San Antonio was selected because at the present time, SAT operations has only one method of inspecting the airport's runways, and this method involves using a skid friction tester. On two separate occasions, skid friction testing was observed at SAT. Only after witnessing the procedures and interviewing several SAT personnel did it become apparent that SAT depends on this method exclusively. Realizing this fact was the motivation to look for a viable alternative method that would serve as a backup for the maintenance personnel at SAT. Laredo International Airport was chosen because it has neither antiquated nor modern testing equipment; instead, it employs a simple visual inspection despite the fact that, on some days, it handles more takeoffs and landings than the San Antonio facility. After interviewing personnel, the consensus was that finding a viable alternative testing method was warranted. Since LRD is undergoing changes, the operations manager at the Laredo International Airport was enthusiastic about conducting experiments with alternate testing methods in keeping with LRD's goal of maintaining the best runways possible. For this study, the alternative methods to measure texture on runways were determined by considering cost and ease of implementation. The two methods chosen for testing were an outflow meter and the sand patch. Overall, both provided favorable results but the sand patch method proved to be more reliable and accurate in determining texture.Item Activated sludge aeration waste heat for membrane evaporation of desalination brine concentrate: a bench scale collaborative study(2016) Muppavarapu, Nayana S.Desalination processes produce highly concentrated brine effluent which is costly to dispose of for inland desalination facilities. The current study uses membrane evaporation process to reduce brine concentrate volumes. Membrane evaporation was evaluated at the bench scale for different brine flow rates, airflow rates and air temperatures, extent of fouling and possible means to control fouling. The evaporation rate was found to increase with airflow rate and air temperature and decrease with brine flow rate. Model predictions, derived based upon literature values for heat and mass transfer correlations, agree well with the measured evaporation rate. The economics of the proposed process appear favorable because energy demands can be neglected when using waste heat. Fouling was observed in experiments for brine concentrate solutions with and without ferrous iron. Cleaning of the membranes by flushing the fibers with brine at higher flow rates was not able to alleviate fouling. Fouling could be alleviated when the pH of the brine concentrate solution was lowered for the durations of the studies conducted. Full evaluation of the process will require longer-term studies and future studies should also consider possible sources of supplemental waste heat to increase the overall amount of water treated.Item Adsorption of Arsenic to Titanium Dioxide Nanoparticles, and Nano-Composites: Study of Isotherms, Kinetics, Photo-Oxidation, and Individual Metal Effects(2017) Wagle, DipendraArsenic contamination in drinking and groundwater is of great challenge due to its toxic effect to human and the environment. The purpose of this study was to investigate the removal of arsenic from water via adsorption process by using nanomaterials and novel nanocomposites. The adsorption behavior of arsenic to four different sorbents: TiO2 NPs, zeolite (ZSM5), TiO2-ZSM5, and TiO2-ZSM5-MoS2 was studied. TiO2 NPs and nano composites were characterized by using surface morphology, surface area, and point of zero charge. Scanning electron microscopy (SEM) images showed that TiO2 NPs was about 20 nm, and zeolite (ZSM5) was several microns. The surface area of TiO2-ZSM5, and TiO2-ZSM5-MoS2 were 132.9 m2/g, and 106.8 m2/g respectively. The PZCs of TiO2 NPs, ZSM5, TiO2-ZSM5, and TiO2-ZSM5-MoS2 were 5.1, 4.6, 5.9, and 5.1 respectively. The isotherm and kinetic study showed that the adsorption capacity of sorbents to As (V) was greater than As (III), and As (V) adsorption rate was greater than As (III). As (V) adsorption was increased at pH below the PZC. The photocatalytic behavior of TiO2 NPs, and TiO2-ZSM5-MoS2 nano composite to oxidize As (III) to As (V) was investigated. TiO2 NPs oxidized 80% As (III) within 180 min of UV irradiation; whereas, TiO2-ZSM5-MoS2 oxidized 100% As (III) within 150 min of UV irradiation. The competitive study showed that Pb (II) was more favorable for As (V) adsorption to TiO2 NPs, and TiO2-ZSM5; whereas Zn (II) was more favorable for As (V) adsorption to TiO2-ZSM5-MoS2. Multi contaminants adsorption spiking heavy metals and As (V) to San Antonio tap water showed that TiO2-ZSM5-MoS 2 has high potential to adsorb multiple contaminants simultaneously.Item Adsorption of divalent metals to metal oxide nanoparicles: Competitive and temperature effects(2011) Grover, Valerie AnnThe presence of metals in natural waters is becoming a critical environmental and public health concern. Emerging nanotechnology and the use of metal oxide nanoparticles has been identified as a potential remediation technique in removing metals from water. However, practical applications are still being explored to determine how to apply their unique chemical and physical properties for full scale remediation projects. This thesis investigates the sorption properties of Cd(II), Cu(II), Pb(II) and Zn(II) to hematite (alpha-Fe2O3) and titanium dioxide (TiO2) nanoparticles in single- and binary-adsorbate systems. Competitive sorption was evaluated in 1L batch binary-metal systems with 0.05g/L nano-hematite at pH 8.0 and pH 6.0. Results indicate that the presence of a secondary metal can affect the sorption process depending upon the molar ratios, such as increased or reduced adsorption. Thermodynamic properties were also studied in order to better understand the effects of temperature on equilibrium and kinetic adsorption capabilities. Understanding the thermodynamic properties can also give insight to determine if the sorption process is a physical, chemical or ion exchange reaction. Thermodynamic parameters such as enthalpy (DeltaH), entropy (DeltaS), and Gibbs free energy (DeltaG) were evaluated as a function of temperature, pH, and metal concentration. Results indicate that Pb(II) and Cu(II) adsorption to nano-hematite was an endothermic and physical adsorption process, while Zn(II) and Cd(II) adsorption was dependent upon the adsorbed concentration evaluated. However, metal adsorptions to nano-titanium dioxide were all found to be endothermic and physical adsorption processes; the spontaneity of metal adsorption was temperature dependent for both metal oxide nanoparticles.Item An Evaluation of Using Void Box for Slab-On-Grade Foundation on Expansive Clay(2017) Hasan, GausulThe purpose of this study was to evaluate the performance of two types of molded paper void boxes for lightly loaded residential foundation such as slab-on-grade foundation on expansive clay. Void box is a technology to isolate the foundation from soil and reduce the effect of volume change of expansive soil on slab-on-grade foundation. As the void boxes are made of recycled waste paper, this study focused on load carrying capacity of void boxes for different moisture content, rate of water absorption of slab and beam void boxes and the deformation of void box due to the soil volume change. In order to determine the compressive strength of void boxes as they absorb water, both types of void box were kept into humidity chamber at 100% humidity and were subjected to compression tests after absorbing certain amount of water. The rate of water absorption by the void boxes were also determined with time. A model test was also performed in the laboratory to assess the moisture induced volume change of expansive soil under the support and the void area of the void boxes. The results showed that both type of void boxes could carry approximately 80 kPa stress at dry situation. As the moisture content increases, both types of void boxes lose their strength at a rapid rate up to a moisture content of 25%. However, the beam void boxes showed a higher load carrying capacity than the slab void boxes at a certain water content. The strain at failure of the void boxes was in the range of 9-12%. The study showed that the rate of water absorption of beam void boxes was also lower than the slab void boxes. After 28 days in the 100% humid condition, the slab void box absorbed 100% water, whereas, the beam void box absorbed 52% water. The study also showed that the moisture induced swelling of soil under the void spaces of was significantly higher compared to that under the contact areas of the void box.Item An Extended FEM Approach for Determining Crack Growth Parameters from the Texas Overlay Tester(2021) Alrashydah, Esra'aTransverse cracking is a common form of distress in asphalt concrete pavements. There has been a multitude of efforts in studying this problem using fracture mechanics principles. Crack propagation is typically described through Paris' fracture parameters, namely A and n for elastic materials and A' or C3 and n' or C4 for viscoelastic materials. These parameters define the rate of change in crack length per strain cycle (da/dN) as a function of the change in the stress intensity factor (SIF) denoted by ΔK or alternatively, the pseudo-energy release rate (ERR) at the crack tip denoted by ∆JR. The corresponding Paris power law cracking parameters are A, n and A', n', respectively. These material properties are obtained from laboratory testing, such as the indirect tension creep test (IDT) or the Texas overlay cyclic test (OTR). A variety of empirical and numerical methods (i.e., FEM) has been proposed for estimating the SIF. Modelling crack propagation using the FEM poses several computational challenges (e.g., particular element types needed to capture the discontinuities and the mesh needs to be redrawn as the crack grows). The Dissertation at hand proposes a new approach that allows simulating transverse cracking growth in asphalt concretes using the extended finite element method (XFEM) in ABAQUS. It describes three 3-D XFEM modelling approaches for simulating the OTR; Model 1 involving stationary cracks of various preset lengths, Model 2 involving the virtual crack closure technique (VCCT) and Model 3 involving the low cyclic fatigue (LCF) approach. Six asphalt concrete mixes used in Texas were simulated, a Stone Mastic with a type D aggregate (SMAD), Thin overlay mixture (TOM), two Standard TxDOT mixtures with type C and D aggregate gradations (Type C and Type D), and two Superpave mixes with a type D aggregate gradation (SPD1 and SPD2).Data for these six mixtures were obtained from two sources, namely the Texas Transportation Institute (TTI) and the University of Texas at El Paso (UTEP). The data obtained was analyzed to obtain the material model inputs, including the tensile Young's modulus, and critical fracture energy (GC). These models were validated by comparing the simulation results with the laboratory test results. It was shown that Model 2 is best suited for simulating the OTR for the purpose of obtaining the Paris' power low cracking parameters. Its advantages are that it allows modelling the crack propagation, it outputs the ERR directly at the peak of each cycle and finally, it requires only the tensile modulus and the GC value as input. For the six mixes analyzed, the results of the XFEM-VCCT coupled approach (i.e., Model 2) were further processed to obtain the modified Paris' power law parameters (C3 and C4). This was done by fitting a linear equation to log of the crack propagation rate (da/dN) versus the log of the estimated ERR (i.e., ∆JR). For these six mixes, the K values were estimated analytically from the estimated ERR output. Finally, the log of da/dN was plotted versus the log of K to obtain the A and n values. The results indicated that the XFEM coupled with the VCCT approach is well suited in simulating the OTR. Using the proposed model, it is possible to efficiently estimate the Paris' power law parameters for viscoelastic materials. In addition, it could be possible to differentiate between mixtures with good cracking resistance and poor cracking resistance, as reflected by the field performance of these six mixtures. The methodology used provides a straightforward tool that allows estimating directly the cracking parameters of asphalt concretes from their tensile modulus and critical fracture energy. This model could be extended by considering the asphalt concrete microstructure and the viscoelastic nature of the binder. It can be further extended in modelling the field behavior of overlays by specifying loading rates and temperature conditions that reflect field rather than laboratory conditions.Item Analysis and design of soil nail walls in high plasicity clays(2011) Yelti, NagareddyThe main objective of this research is to evaluate the method used by TxDOT in designing soil nailed walls in expansive soils and to make recommendations to improve design procedures. The end result of this research is to provide design guidelines for soil nailed walls in high plasticity soils considering the additional lateral pressures generated by soil expansion. The present TxDOT design procedure for common retaining structures in cuts, such as soil nailing, tied-back, and drilled shaft walls, is based on lateral pressures calculated from classical Rankine's or Coulomb's methods. This considers the drained shear strength parameters and does not include any lateral pressure due to moisture changes in the expansive soils. The additional lateral pressure due to changes in moisture content in expansive soils could be 10 to 20 times higher than those estimated by classical theories. This research is divided into two parts: (i) Analysis of soil nail walls in expansive soil using the GeoStudio software. (ii) Design recommendations for soil nailed wall system in expansive clay. The focus of this research study is: (1) Horizontal pressure pattern in expansive soils on soil nail retaining structures. (2) Tensile force distribution in soil nails due to expansive soil.Item Analysis of Environmental and Socio-Economic Impacts of Hydrometeorological Disasters and Recommendations for Risk Reduction(2018) Paul, Srikanto H.The U.S. experienced 32,815 fatalities and approximately $900 billion in total damage from 1960 to 2016 as a result of hydrometeorological disasters. The state of Texas ranks first in the number of fatalities, second in the number of hazard events, and fourth in damage. This dissertation dedicates the first two essays to historical analysis of hydrometeorological disasters in Texas during this same period analyzing the spatiotemporal trends of fatalities and property damage. The number of fatalities caused by hydrometeorological disasters exhibited an increasing trend over the study period and are strongly related to the population growth. The increasing trend in property damage is also related to population, but more so to the wealth of the region impacted by the disaster. Coastal regions are highly susceptible to tropical cyclones that cause destruction with a combination of high winds, storm surge and flooding. Hurricanes have unique characteristics and predominant destructive forces (hazards) that must be communicated to the public indicating the comprehensive risk of death and property damage. Two hurricanes, Florence and Michael, making landfall in September and October 2018 respectively, exemplify the difference in hazards and opportunities for better communication. The third essay provides a preliminary, though detailed, assessment of the socio-economic and environmental impacts in the immediate aftermath of hurricanes Florence and Michael with emphasis on the difference in predominant hazards responsible for the majority of the fatalities and damage. Review and post-disaster assessment of other major hurricanes that made landfall in the U.S in the last two decades provide lessons learned and opportunities for improvement to reduce risk within the various stages of the disaster lifecycle. Gaps and recommendations for improvement of mitigation efforts are suggested within the context of each stage of the lifecycle. Effective predictive modeling and communication of the comprehensive risk to include wind, storm surge, and rain-induced flooding. Pre-disaster planning and coordination of emergency response across different levels of government and private resources. Timely confirmation of post disaster metrics using federal and state guidance to allow for exploitation of the existing momentum for change. Long-term strategies such as engineering upgrades to structures and flooding diversion in high risk coastal regions and flood plains are also gaining ground but face political challenges since this may require more initial capital and reallocation of private land ownership for the greater good of the community.Item Analysis of motorcycle crashes and fatalities including the impact of distracted drivers in Texas(2016) Alshatti, FahadThe main objectives of this research are to identify the key factors yield to motorcycle crashes and fatalities and to find the impact of distraction on motorcycle crashes. Vehicle Miles Travel and Crash Record Information System databases were collected from TxDOT to support this study. Data filtration and analysis using different tools and functions was done for all databases. Firstly, all the unnecessary data were excluded from the databases. Secondly, all the crashes that are not related to motorcycles were also excluded. Thirdly, three different files were merged into a single source file for each year. Vehicles involved in motorcycle crashes were filtered by excluding poor driving conditions to approximate the distracted driving factors causing motorcycle accidents. Driving motorcycle is riskier than driving other types of vehicles as remarked by the crashes and fatalities per 10,000 VMT records. Also, only 15.2% of the motorcycle crashes involve no injuries. Data suggest that distraction and lack of motorcycle conspicuity possibly cause most of the crashes. However, the analysis indicates critical causes lead to motorcyclist fatalities in Texas such as not wearing a helmet, driving under influence, driving in dark-unlighted roads, driving in curved roads, and poor weather conditions. Vehicles with distraction driving factors may lead to an estimated 33.4% of all motorcycles crashes. The estimated economic lost for all motorcycle crashes in 2009 to 2014 is $22,068,320,000. Suggested countermeasures include; adopting the universal helmet and statewide cell phone use ban laws that could approximately decrease the total motorcycle crashes by 10% each.Item Analytical study of the behavior of beams reinforced with high strength reinforcing bars(2016) Mandadi, ShilpiThis thesis reviews the analytical research on shear behavior with attention paid to the behavior of beams with higher yield strength (fy) of 830MPa and higher compressive strength (ƒ'c) of 98.8MPa to members controlled by flexure. All the mathematical and analytical calculations are done using the ACI and AASHTO LRFD codes. The types of bars used are A706 and A1035. The main focus of this study is to use ASTM A1035 reinforcing steel since it captures behavioral aspects of high yield strength and high compressive strength. The project identified aspects of reinforced concrete design and of the AASHTO LRFD specifications that may be affected by the use of high strength reinforcing steel. Design issues were prioritized and an integrated and analytical program was designed to develop the data required to permit the integration of high strength reinforcement in design. This program included analytical studies to validate existing ACI and LRFD provisions when applied to high strength reinforcing steel.Item Analyzing and Modeling the Effects of Independent Variables on Texas Severe Work Zone Crashes(2018) Oyameda, Oziegbe JustinPrevious literature and research on work zone crashes seem to reach a similar conclusion that frequency and severity of crashes in work zones is dependent on causative factors that range from Endogenous factors (which in this study will be referred to as factors that are components of the work zone design) to exogenous factors (which in this study will be referred to as factors that are outside the work zone design components). While numerous studies have been undertaken on these factors, their individual influences on the resulting work zone crashes is yet to be given exhaustive analysis. Using statistical analysis and physical observations, this document will be modeling the different factors to determine their contribution to severe crash risk in work zones. For this research, crash severity will be selected as the dependent variable. Though all crashes are worthy of investigation, their significance is measured by the cost of the damages that resulted from the crashes. In this work, high crash severity refers to crashes that resulted in either Possible injury, Non-incapacitating injury, incapacitating injury or killed. By utilizing the Multinomial Regression as the modeling technique with crash severity as the dependent variable, the significance of the various parameters in terms of their contributions to work zone crash severity is represented as P value. This measures the confidence limit of the different variables to a 95% significance level. The importance of this finding is that most of the significant factors to severe work zone crashes are independent endogenous variables. These are variables that are likely to be corrected by proper work zone design and efficient temporal traffic planning.Item Analyzing End-use Electricity Consumption Data to Investigate Residential Buildings' Consumption Patterns(2018) Jafary, MarziehThe shares of total United States' retail sales of electricity in the residential sector in 2016 was 38%, and it is projected that total U.S. electricity use grows by an average of less than 1% per year from 2016 to 2040. Therefore, estimating the electricity consumption and a load of a community or neighborhood for planners, utilities, and designers become essential. Fortunately, installation of intelligent devices and smart meters lead to collecting electricity consumption data for further analysis. This dissertation implements a data analysis methodology to collect, utilize and analyze patterns of appliance electricity consumption in addition to Electric Vehicles (EV) and Photovoltaic (PV) panels for a large dataset of single-family and multi-family homes in Austin, Texas. Further, the study characterizes the significant factors that contribute to the electricity consumption in residential buildings, namely building characteristics, socio-economic factors, occupant behavior and climatic factors. Also, due to the increase in the EV market, the study also considers the EV as a plug load in the future electricity consumption portfolio of residential buildings. The micro-environment of residential buildings is created to make sense of the data by determining whether they have EV, PV, or both in more detail regarding their electricity consumption patterns and correlation with the mentioned four factors. Finally, it advances the predictive model capability by including the mentioned four factors and their correlations on appliance electricity consumption in buildings. The predictive models of the appliance electricity consumption based on socio-economic and climatic variables provide insights to the utilities and policymakers regarding the price scheme, electricity efficiency, and demand-response programs.Item Analyzing the Effect of Urbanization on Surface Runoff for Intense Rainfall Storm Events: Case Study of Olmos Creek in San Antonio, Texas(2018) Eidi, SiavashHigh intensity rainfall storms can have devastating impacts on watersheds. Rainfall events can produce flooding which is typically magnified by urbanization and land use change. This thesis investigates how urbanization affects the generation of surface runoff in terms of peak flow and runoff volume for high intensity rainfall events. The study was conducted for the Olmos Creek basin in San Antonio, Texas. A physically-based distributed hydrological model Gridded Surface Subsurface Hydrological Analysis (GSSHA) was built, calibrated (NSE = 0.83; RSR = 0.42; PEP = -5 %; PEV = 8 %; PBIAS = -8 %), and validated based on two historical events of 25th May 2014 – 29th May 2014 (calibration period) and 28th October 2015 – 31st October 2015 (validation period). In order to analyze the effect of urbanization on surface runoff for intense storms. Six scenarios of land use land cover change were considered, consisting of the National Land Cover Dataset (NLCD) 1992 to 2011 and two hypothetical scenarios (undeveloped; and a fully developed watershed). Two type II 24-hour SCS design storms, one with a 5-year return period (5.30 inches or 134.62 mm), a 100-year return period (11.9 inches or 302.26 mm), and a hypothetical Hurricane Harvey (56.1 inches or 1423.8 mm) were simulated for each scenario. Results of the simulations showed that the evolution of land use land cover change, from 1992 to 2011, increased both peak discharge and runoff volume. In the case of 5-year storm, even though the peaks and volume were much lower compared to 100-year and Harvey, the overall relative increase was greater. A 100-year storm and Harvey will result in a greater peak and volume but showed an overall smoother relative increase over time as urbanization evolves. The results suggest that, the intensification of population density will relatively increase the magnitude of storm events with shorter return period. That indicates that while flood control systems still need to be designed to address low frequency high intensity storm events, more recurrent flood events also need to be analyzed by floodplain and urban planners, in order to mitigate the adverse impacts of urbanization on water resources.