Theses and Dissertations - Department of Civil, Construction & Environmental Engineering

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    Experimental and FEA Study of Structural Behavior of CLT Shear Walls for Wood Building Applications
    (University of Alabama Libraries, 2021) Chowdhury, Farhan A.; Dao, Thang N.; Aaleti, Sriram; University of Alabama Tuscaloosa
    Cross Laminated Timber (CLT) is emerging as a sustainable alternative to traditional building construction materials for tall buildings in high seismic regions. However, before they can be incorporated into the building codes, different categories of CLT shear wall systems need to be fully characterized and novel solutions must be implemented to overcome the limitations of existing timber systems. This dissertation addresses analytical modelling of unbonded post-tensioned (PT) CLT rocking wall (CLTRW) system for its use in both rectangular and nonrectangular configurations. A set of laboratory experimental tests and nonlinear finite element analysis (FEA) were compared to investigate and characterize the flexural and lateral behavior of CLTRW system. The flexural performance was studied using a full-scale, 5-layer rectangular CLT panel testing in three-point loading configuration. A three-dimensional (3D) finite element (FE) model with nonlinear geometry and contact properties was developed in ABAQUS using measured material properties. The FE model was validated using the experimental data from the CLT panel bending test. Based on the validated FE model, additional FE models of previously tested post-tensioned CLTRW panels with different wall aspect ratios and tendon configurations were also developed. A close agreement between the measured and FEA models was found in the stiffness behavior, which suggested that the proposed nonlinear FE modelling approach can be employed to predict the performance of other CLTRW systems. This research further analytically investigates shear behavior of high stiffness web-to-flange connections for nonrectangular CLTRW system. The proposed shear connections use spatially arranged self-tapping screws (STS) together with ultra-high-performance concrete (UHPC) shear-keys. 3-D nonlinear FE models for connections with and without UHPC were validated using the available experimental data, which showed that the inclusion of UHPC would significantly improve the stiffness of the connections. The FEM technique for connections was subsequently used to evaluate the lateral load performance of a 36-ft tall, T-shape CLTRW wall with multiple connections. The results from this model were compared to a T-wall without shear-key connections. It was found that the wall with high-stiffness shear-key connections showed better lateral load performance compared to traditional connection wall.
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    Fate of Polycyclic Aromatic Hydrocarbons and Petroleum Biomarker Compounds in Road Asphalt
    (University of Alabama Libraries, 2021) Kinali, Kubra; Clement, T. Prabhakar; University of Alabama Tuscaloosa
    Almost six thousand types of petroleum-based products are being used all around the world on a regular basis. Some of these petroleum products can have a devastating effect on water, air, and soil environments. For instance, oil spills pose large-scale threats to water and soil quality and also can impact human health due to the carcinogenic and toxic components in petroleum. Asphalt, which is commonly used to pave roads, is an interesting petroleum byproduct that contains some toxic and carcinogenic polycyclic aromatic hydrocarbons (PAHs) and can pose considerable risk to the environment. Runoff from the asphalt surfaces can generate contaminated stormwater that can pollute water bodies. Recently, it has been estimated that the world asphalt usage is approximately 102 million tons per year. Therefore, understanding the fate of PAHs and other hazardous compounds in asphalt is an important environmental problem.In this study, a newly paved parking lot at the University of Alabama was used as a sampling site to track the fate of PAHs under natural weathering conditions. The asphalt samples were collected for over two years, 2019-2021, to determine the weathering levels of PAHs and petroleum biomarkers (terpanes) with time. All asphalt samples were analyzed using a GC/MS method run in the selected ion monitoring (SIM) mode. The results show that the most dominant PAH compounds in all the asphalt samples are chrysene, which is well-known as a toxic chemical. Concentrations of some of the lighter PAHs, such as naphthalene, degraded rapidly; however, several heavy PAHs concentrated over the same time period. Our study also showed that some of the lower molecular weight tricyclic terpanes such as TR21, TR22, TR23 and TR24 weathered slightly during this period. All the pentacyclic terpanes remained stable and resisted weathering over the two-year period.
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    Behavior of Residential Safe Room Walls Impacted by Windborne Debris
    (University of Alabama Libraries, 2021) Pierce, Blair Butler; Song, Wei; University of Alabama Tuscaloosa
    Tornadoes and hurricanes are among the most devastating storms on the planet. Much of the damage from these storms occurs when debris is picked up by high winds and strikes structures. Safe rooms are often constructed in commercial and residential buildings to protect occupants from windborne debris. The process for designing safe rooms requires all components to pass the large missile test, in which a 2x4 wood missile is fired at high speeds at safe room assemblies. Prescriptive designs may be utilized for residential safe rooms; however, these designs can be costly and difficult to construct. The purpose of this research is to 1) Test safe room wall assemblies constructed with conventional steel sheets and alternative materials in order to decrease the cost and improve constructability of safe rooms, and 2) Develop an experimental procedure to measure full-field deformation of safe room wall assemblies under impact during large missile test. High speed photographs are taken of each impact and digital image correlation technology is used to obtain the deformation of the wall assemblies. Additionally, the stiffness and effective mass are measured for each specimen to verify the results. While the alternative materials tested as part of this research were not successful in resisting debris impact, the non-contact measurements obtained for the passing specimens produced fair results. These measurements are further used to evaluate the behavior of the passing specimens, providing insights that go beyond the qualitative pass/fail method used in previous research.
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    A Safe Systems Approach to Vulnerable Road User Safety Issues in Ghana
    (University of Alabama Libraries, 2021) Agyemang, William; Jones, Steven; University of Alabama Tuscaloosa
    Approximately, 90% of global road traffic deaths occur in low-and middle-income countries (LMICs), and vulnerable road users (VRUs) constitute 54%, even though these countries have about 60% of the world’s vehicle population. VRUs are particularly prone to injuries and fatalities because they are not protected by any external vehicular body and their vulnerability is higher in mixed traffic conditions. There have been efforts by many countries across the globe to reduce road traffic deaths and injuries, but progress varies significantly between different regions and countries. In Ghana, VRUs account for a high proportion of crashes, with pedestrians and motorcyclists making up about 60% of total crashes every year. Motorcycle-related road safety has become topical due to the recent rapid rise in commercial motorcycle activities attributed to the problem of urban traffic congestion and the general lack of reliable and affordable public transport in rural areas. Additionally, uncontrolled interaction between human and high-speed vehicular activities in and around settlement areas throughout Ghana has resulted in numerous pedestrian deaths and injuries. The phenomenon has been attributed to the land-use and right-of-way planning practices as well as lack of safe crossing facilities for VRUs, comprising pedestrians, bicyclists, and motorcyclists (both two- and three-wheelers). This dissertation is the result of three distinct, but interrelated research efforts addressing VRU safety issues in Ghana. Ghana, like many other countries in sub-Sahara Africa (SSA), is a rapidly developing nation with a rising middle-income population that is driving the urbanization and motorization processes. Nonetheless, a vast majority of the population rely on walking and motorcycles for their daily travel needs. Pedestrians and motorcyclists, both drivers and pillions, make up a significant proportion of VRU fatalities in the country. This dissertation seeks to throw more light on the VRU safety concerns in the country by a) understanding how local transport professionals perceive pedestrian and motorcycle safety issues and the adoption of the Safe Systems approach as a countermeasure tool to address them, and b) conducting data-driven analyses to identify factors contributing to these crashes so that potential countermeasures can be developed based on local conditions and input from local road safety professionals. The dissertation consists of three major areas related to VRU safety in the country. The first part of the study assessed opinions of local transport professionals on the complex safety issues relating to VRUs using the Safe Systems approach to explore how local context could guide the implementation of countermeasures. The Safe Systems approach takes a holistic view of road safety, and this framework is based on the basic premise that humans are prone to errors, mistakes, and mishaps and that as a result are vulnerable to crashes and must therefore be protected systemically. The Safe Systems approach addresses: behavioral issues that may result in crashes (speeding, driving under the influence, aggressive or distracted driving, etc.) under its safer people pillar; issues related to vehicle design and condition under safer vehicles; emphasis on infrastructure designed and constructed to prevent or reduce the severity of crashes through the safer roads pillar; and finally the promulgation of policies that promote safer speeds, especially where vehicular traffic is mixed with VRUs. The study used a Multi-Criteria Decision-Making tool, the Analytic Hierarchy Process (AHP), to develop a framework based on knowledge and opinions gleaned from a survey of local road safety professionals to prioritize countermeasures for VRUs (i.e., pedestrians and motorcyclists) using a Safe Systems approach. This initial work provided a reference frame for two subsequent data-driven analyses of motorcycle and pedestrian crashes throughout the country. The motorcycle crash study emphasized the differences among crashes that occur in rural versus urban areas. The pedestrian study focused explicitly on crashes that occurred on inter-urban highways in Ghana. It is anticipated that the findings of the dissertation research will provide a basis for the development of targeted and appropriate countermeasures to reduce the number of VRU deaths and injuries in Ghana. The recommendation for a localized Safe Systems approach and a data-driven strategy to address VRU safety issues is expected to result in improved overall road safety in the country, and other countries with similar characteristics in the region. The proposed Safe Systems framework developed, and its results can be used by transport professionals to prioritize localized efforts to improve the safety of VRUs.
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    Multi-Scale Risk and Impact Assessment of Potential Dam Failure in the United States
    (University of Alabama Libraries, 2021) Song, Junho; Jones, Steven; Kam, Jonghun; University of Alabama Tuscaloosa
    Aging water infrastructure in the United States (U.S.) is a growing concern. According to the 2018 National Inventory of Dams (NID) database, there are more than 90,000 dams registered in the U.S, and their average age is 57 years. The compounding impact of climate change with aging dams has increased the potential for and exposure risk of dam failure-driven floods. At the national level, dam failure with an absence of a state dam safety program and Emergency Action Plans (EAPs) trigger local-economic collapse causing malfunction of flood control, economic paralysis, and fatalities with property losses. Since the 1950s, which is known as the Dam nation period, dams have been providing sustainable water resources for the entire continental United States (CONUS). Dams are considered a vital infrastructure providing water and water ways to communities and industries, therefore, a dam safety program is required along with increasing economics. At the state level, dams play a significant role as well (e.g., agriculture, navigation, and recreation) to increase the quality of life. Therefore, a scheduled inspection of dams inevitably leans on dam management agencies and private owners for protecting benefits from the existing dams. However, due to the various regional characteristics and legislations by the states, such as topography, privacy, and security issues, systematic administrating of dams is poorly conducted. Dams in the Black Belt areas of Alabama, home to some of the most socioeconomic vulnerable communities in Alabama, indicate an extremely low level of regular dam inspection based on the NID. At the site level, hyper-resolution inundation floodplain mapping for dam breach is crucial to improve EAPs and to minimize adverse impacts of the dam failure. However, hyper-resolution 2D modeling for hydrodynamics and costly bathymetric surveys limit understanding of the impact of antecedent flow conditions on flood mapping at the site level.This dissertation proposes a multiple-scale risk and impact assessment of potential dam failure in the United States with a focus on the state of Alabama, the only state in the CONUS with no formal dam safety legislation, in order to better understand 1) how the risk and preparedness of potential dam failure in the United States vary at a range of spatial scales (site-level to national-level), 2) how the economic benefits of the existing dams vary across the U.S. states in terms of the marginal cost of water use, and 3) what are the values of cutting-edge technologies are beneficial in better describing the flood inundated areas due to potential dam failure. This dissertation consists of five main chapters. In Chapter 1, the objectives and goals of this dissertation are addressed. In Chapter 2, the spatiotemporal patterns of the growth of dams and their potential hazard and economic benefit are assessed, using more than 70,000 NID-registered dams in the CONUS. In Chapter 3, the state-level risk of dam failure is assessed using more than 2,000 dams in the state of Alabama. The vulnerability of communities to dam failure is high in populated counties with high incomes while less populated counties with lower incomes show a low vulnerability to dam failure due to the relatively small storage capacities of the existing dams. In Chapter 4, the sensitivity test of inundation flood mapping to initial river depth with antecedent flow condition is also conducted using the experimental simulations of the two-dimensional hydrodynamic model with a Remotely Operated Vehicle (ROV). Applying the NID database which is updated with EAP data for the entire dams in the U.S, the results of the dissertation provide quantified data on potential economic values and hazards of dams. Therefore, the results of the dissertation are useful to not only estimate the total cost of recovery but also assess potential losses of the water cost due to dam failures. In addition, providing calculated cost of flood damage restoration would be a valuable index for flood insurances and increasing public awareness as a beginning step of dam safety. Furthermore, using an underwater drone has been successfully applied to acquire precise Digital Elevation Model (DEM) data and flood maps. If fully autonomous underwater drones are available later, the drones would play a key role in floodplain research areas as well as not only river streams, but also river basins are accessible to measure the bathymetric survey. The findings of this study can be useful data for reconsideration of the dam safety programs and EAPs, and it further emphasizes the need for careful design of EAPs accounting for antecedent flow conditions and accurate river channel depths for places that are required to establish safety programs.
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    Integration of Physically-Based and Data-Driven Modeling Approaches for Compound Coastal Flood Hazard Assessment Under Uncertainties
    (University of Alabama Libraries, 2021) Muñoz, David Fernando; Moftakhari, Hamed; University of Alabama Tuscaloosa
    Flood hazard assessment is an essential component of risk and disaster management that helps identify areas exposed to flooding as well as support decision making, and emergency response. Floods can result from isolated, concurrent, or successive drivers of (non-) extreme origin (e.g., fluvial, pluvial, and oceanic) and so put society and the environment at constant risk. Specifically, a combination of either concurrent or successive flood drivers with potential impacts larger than those from isolated drivers is defined as compound flooding (CF). Contemporary studies in compound flood hazard assessment (CFHA) and modeling have focused on simulating inundation extent, water depth, and velocities at local or regional scale. However, those studies often neglect inherent uncertainties associated with forcing data, observations, model parameters, and model structure. A comprehensive analysis of these uncertainty sources is thus imperative, but it requires advanced statistical techniques such as data assimilation (DA) to adequately account for error propagation in compound flood modeling. Chapters 1 to 4 present previous peer-review studies oriented towards a better characterization of uncertainty in CFHA. Those studies include the following research topics: (i) analysis of wetland elevation error and correction of coastal digital elevation models, (ii) compound effects of wetland elevation error and uncertainty from flood drivers, (iii) effects of model selection and model structure error on total water level prediction, and (iv) long-term wetland dynamics associated with urbanization, sea level rise, and hurricane impacts. Chapter 5 presents a cost-effective approach based on deep learning (DL) and data fusion (DF) techniques that enables efficient estimation of exposure to compound coastal flooding at regional scale. Chapter 6 presents a DA scheme based on the Ensemble Kalman Filter (EnKF) technique and hydrodynamic modeling to improve water level (WL) predictions and CFHA in coastal to inland transition zones where pluvial, fluvial, and coastal processes interact. The last section of this dissertation summarizes the main findings of these studies and discusses future research areas that are worth exploring in the context of CFHA.
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    Measurement of Soil and Water-Quality Parameters to Understand Subsurface Transport Processes
    (University of Alabama Libraries, 2021) Sheikh Memari, Sama Sheikh; Clement, T. Prabhakar; University of Alabama Tuscaloosa
    The goal of this dissertation is to contribute toward a better understanding of the flow and transport dynamics in saturated and unsaturated soils. In the first phase of this study, we have focused on understanding the impacts of climate change driven hydrological processes such as excess rainfall and/or draught cycles on saltwater intrusion processes with a focus on managing freshwater resources in island aquifers. As part of this effort, we used a combination of laboratory experiments and numerical simulations to study the impacts of changes in rainfall patterns on saltwater intrusion dynamics. In the second phase of this study, we have focused on understanding soil moisture storage processes in unsaturated soils. The knowledge of water stored in unsaturated soil is indispensable for several hydrological and geoenvironmental processes. The accuracy of the soil moisture transport models used in these studies depends on the precise characterization of saturated and unsaturated soil properties. In this effort, we developed novel experimental methods and modeling tools for developing soil characteristic models such as the van Genuchten and Brooks and Corey models using measured soil moisture and capillary pressure data. Also, in recent years, there has been increasing interest in developing remote sensing tools to measure soil moisture at multiple scales. As part of this research, to benchmark a novel radar technology, we collaborated with the remote sensing center to develop in-situ soil moisture datasets at a test facility in fine spatiotemporal scales.
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    Planning and Design of Seawater Pumped Hydro Storage Systems (S-PSS) Under Future Climate Change Scenarios Using Machine Learning Techniques in California
    (University of Alabama Libraries, 2021) Arslan, Orhan; Moradkhani, Hamid Hm; University of Alabama Tuscaloosa
    Climate change is one of the most critical global issues today due to its widespread impacts on water resources, energy, and agriculture. In order to reduce the emission of greenhouse gases (a major contributor to climate change), California plans to generate 100% of its energy demand from renewable energy sources by 2045. Two major renewable energy sources are solar and wind energy; however, due to differences in the peak hour of energy generation (during afternoon hours) and the energy demand (during late evening), a load balancing system is crucial. Moreover, the future impacts of climate change on energy demand and source are unknown. Therefore, this study aims to plan and design a Seawater Pumped Hydro Storage (S-PSS) to balance curtailments and load balancing. The overarching objectives are (i) comparing five different Global Climate Models (GCMs) from Coupled Model Intercomparison Project-6 (CMIP6) and using the best GCM in predicting the future precipitation and average temperature, (ii) projecting monthly electricity demand and renewable energy supply by 2035, and (iii) developing an ArcToolbox to identify possible S-PSS sites. The oversupply of electricity by the year 2035 was estimated using bias-corrected precipitation and average temperature under the SSP (shared socioeconomic pathway) 245 climate change scenario, using several machine learning algorithms and time series techniques. In order to store this oversupply of electricity, an ArcToolbox was created to locate new S-PSS facilities. The main findings of this study are (a) BCC-CSM2-MR and CanESM5.0.3 CMIP6 GCMs were best suitable for the projection of precipitation and average temperature respectively, (b) Random Forest and autoregressive integrated moving average (ARIMA) methods outperformed other methods in terms of the prediction of demand and supply, respectively, and forecasted 16,231 MWh oversupply, and (c) using the created ArcToolbox, a site for S-PSS was located with a calculated storage capacity of 521 MWh. The detailed quantitative analysis from this study can be useful for both the authorities in California and the grid operators that produce electricity to solve the load-balancing problem arising from the spread of renewable electricity supply.
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    Modelling the Potential Benefits of Irrigation with Nutrient-Rich Treated Municipal Wastewater Effluent for Growth of Loblolly Pine
    (University of Alabama Libraries, 2021) Gunaydin, Serhat; Elliott, Mark A.; University of Alabama Tuscaloosa
    This thesis research was initiated in the context of a wastewater management project in rural Alabama to investigate whether irrigation of loblolly pine (P. taeda) with nutrient-rich effluent generated by decentralized wastewater treatment systems could benefit the local forestry industry while addressing the wastewater management needs of underserved rural communities. In this study, the benefits of irrigation are considered in the local context based on recent years with actual precipitation, all wet years, and all dry years. Influent wastewater with nitrogen concentrations representative of the high, medium, and low strength municipal wastewater were included. Scenarios were tested for wastewater influent streams treated with three different nutrient removal levels relevant for decentralized wastewater treatment systems and representative of a range of nitrogen-removal performances. The growth of loblolly pine on the study site, modeled in FASTLOB annually for volume and mass over five-year intervals, is reported for all of these conditions (precipitation, influent wastewater strength, wastewater treatment efficiency) and compared with equivalent irrigation practices with pure water containing no nutrients. Irrigation with nutrient-rich wastewater treatment effluent yielded substantial benefits to loblolly pine growth (volume and mass) under all conditions tested. Over five years of growth, tree volume increased was 12.53% to 26.66 % greater with nitrogen plus phosphorous compared to irrigation with no nutrient; likewise, tree mass increased between 28.04% to 71.91% more. The greatest benefits to growth were modeled under low precipitation conditions, with poorly performing wastewater treatment technologies and high strength influent wastewater, because they yielded the highest net nitrogen loadings. It was observed that irrigation provided a higher contribution than expected. Even in the worst scenario in terms of fertilization, growth showed a significant increase. The study results show that this application will both increase land productivity and have positive effects on a big problem such as treated wastewater discharge.
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    Evaluating Transportation Network Mobility and Enhancing Traffic Signal Operations Performance Using Probe Data and Connected Vehicle Technology
    (University of Alabama Libraries, 2021) Talukder, MD Abu Sufian; Hainen, Alexander M.; University of Alabama Tuscaloosa
    High-quality, reliable, and robust data is key to better understanding performance and improvement needs for transportation infrastructure. Predominantly, transportation systems performance has been evaluated using infrastructure-based data, which is often limited by high costs, small sample size, and potential inaccuracy. With recent advancements in technology, previously unobtainable large high-fidelity data, such as probe data and connected vehicle (CV) data, can now be utilized to address many challenges related to transportation systems. This dissertation investigates various research and practical oriented applications for such emerging transportation data sources. The first part of this dissertation develops a novel methodology for characterizing mobility of transportation networks. Using probe vehicle travel times, a route-based travel time reliability metric is proposed for assessing and comparing transportation system’s performance from one geographic area to another. The second part of this dissertation uses CV-technology to develop methodology for improving operational efficiency at a signalized intersection. Two innovative traffic signal control algorithms are established to demonstrate real-time delay optimization for both connected and non-connected vehicles. The third part of this dissertation extends the use of CV-technology to facilitate prioritized freight movement in a signalized corridor. An estimated time of arrival (ETA)-based priority logic is developed, and the proposed priority system is deployed along US-82 in Northport and Tuscaloosa, Alabama. Finally, this dissertation explores the application of emerging transportation data collection technologies to characterize and evaluate transportation systems performance. The techniques presented in this dissertation will be helpful to transportation agencies, planners, and practitioners to assess existing performance and need for future transportation infrastructure.
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    Freeway Incident Management: Analyzing the Effectiveness of Freeway Service Patrols on Incident Clearance Times
    (University of Alabama Libraries, 2021) Islam, Naima; Hainen, Alexander M.; University of Alabama Tuscaloosa
    Traffic incidents caused by vehicular crashes, roadway construction, disabled and abandoned vehicles, extreme weather conditions, and planned special events, comprise about half of all traffic congestion. As the duration of traffic incidents increases, it increases the probability of severe congestion, secondary crashes, traveler delay, travel time variability, emissions and fuel consumption, air pollution, economic and social inadequacy, as well as reduces the roadway capacity and the reliability of the whole transportation system. Freeway service patrol (FSP) programs have been considered as an effective Traffic Incident Management (TIM) program for reducing incident duration and thereby minimizing the adverse effects of traffic incidents. The overarching goal of this dissertation is to assess the impact of Alabama Service and Assistant Patrol (ASAP) program based on a unique compiled dataset. The specific objectives are: (1) to merge and match four different datasets, including response data, crash data, traffic volume data and ASAP data; (2) to identify the explanatory variables of incident clearance times with an emphasis on the ASAP coverage area information; (3) to assess duration data using hazard-based duration models with the aim of determining which modeling method best fits the data; and (4) to verify the spatial transferability for the impact of ASAP coverage area. To achieve the research objectives, this dissertation is divided into three parts. The first part describes the Weibull distribution with gamma heterogeneity in identifying the explanatory variables of incident clearance times. The second part compares two advanced econometric modeling methods (random parameters and latent class) in identifying which modeling method best fits the data. The third part employs random parameters modeling method to verify the spatial transferability of the impact of the ASAP program across the state. Ultimately, this dissertation presents a data-driven assessment of the ASAP program in the state. The distinctive contribution of this research is to provide a better understanding of the significant variables that influenced the freeway incident clearance times. The findings of this dissertation are anticipated to assist TIM agencies in formulating and implementing strategic plans to reduce freeway incident clearance times while maximizing the advantages of the ASAP program.
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    Experimental Investigation of Ultra-High-Performance Concrete Panels Under Tornado Impact Loads
    (University of Alabama Libraries, 2021) Kniffin, Hannah Rose; Aaleti, Sriram; University of Alabama Tuscaloosa
    Tornado events pose a threat to millions of people living in the tornadic-prone areas of the United States. Although many tornado shelters and safe rooms are commercially available that satisfy the extreme loading conditions required by the International Code Council and National Storm Shelter Association, there is a need for a simple yet safe design which can be easily assembled and used for multiple purposes. New engineering materials, such as ultra-highperformance concrete (UHPC), have the potential to improve tornado shelter options and save lives. This study experimentally investigates the performance of thin UHPC panels subjected to impact of standard wood 2x4 projectiles, following the requirements of ICC/NSSA 500, the leading standard on storm shelter design. 1.25-inch-thick and 1.625-inch-thick UHPC panels were cast and impacted with 15-lb wood projectiles at speeds ranging from 50 mph to 100 mph to maintain a similar impact-energy-to-panel-mass ratio. The failure response of each panel was characterized by excessive flexural deflection or punching shear. In the case of excessive deflection, a single-degree-of-freedom dynamic displacement model describes the motion of the panel during impact and the profile of the maximum deflection. In the case of punching shear, a modified equation from ACI 318 predicts the capacity of the panel. The results of the impact testing show UHPC is a promising material for future tornado shelters: UHPC panels with half the thickness of a traditional concrete shelter can be built for a similar or lower price, creatively integrated into homes, and increase accessibility of the tornado shelter for residents.
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    Low-cost, ubiquitous biomolecule as next generation, sustainable admixture to enhance the performance of ordinary portland cement-based concretes
    (University of Alabama Libraries, 2021) Fang, Yi; Wang, Jialai; University of Alabama Tuscaloosa
    The production of ordinary Portland cement (OPC) is highly energy-intensive and responsible for approximately 6% of anthropogenic greenhouse gas emissions. To reduce the carbon footprint of OPC based concrete, this research proposes to use a low-cost, ubiquitous, naturally occurring compound, tannic acid (TA) as a small-dose additive to significantly enhance the strength of OPC based concrete.This study is inspired by biosystems’ protein-based materials, which generally exhibit superior strength and toughness owing to their hierarchical structures via hydrogen-bonding assembly. With abundant reactive terminal phenolic hydroxyl groups, TA has an ability to complex or cross-link macromolecules sites through multiple interactions. Thus, TA can be used to complex or cross-link hydration products of cement at multi-binding sites so that the strength and durability of concrete can be significantly improved. A comprehensive research plan has been carried out to evaluate the potential of TA on performance enhancement of OPC-based concrete, understand how TA modifies the hydration of cement, mitigate the retardation of TA on cement’s hydration, and evaluate application potentials in concretes with SCMs. Experimental studies show that TA can strongly retard the hydration of cement and alite due to its ability to bind to various particles and chelate with calcium ions, causing less calcium hydroxide produced by the hydration. The strong interaction between the TA and hydration products leads to morphology change of the hydration products and generates nanoparticles at early age. Furthermore, addition of TA can significantly densify the nanostructure of cement pastes. Particularly, capillary pores smaller than 70nm are drastically reduced by TA. This finding is not only explaining why TA can enhance the micromechanical properties of concrete, but also opening a new approach to tune the nanoscale pores in concrete. Besides, a pre-hydration method is proposed and verified to mitigate the retarding effect of TA for widely adopted in practical application. Significant strength improvement at late age can be achieved by pre-hydration with TA without losing of strength at early age. TA is also successfully used in mortars with silica fume to achieve over 30% strength improvement, suggesting its huge potential to reduce the carbon footprint of concrete.
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    Synthesis and characterization of fly ash based self-dispersing, self-sensing geopolymer
    (University of Alabama Libraries, 2020-12) Pan, Wei; Wang, Jialai; University of Alabama Tuscaloosa
    Extensive studies have been carried out to use carbon nanotubes (CNTs) to reinforce cementitious materials because of the extraordinary strength of CNTs. More importantly, new functions such as self-sensing ability can be introduced to the materials due to the excellent electrical conductivity of CNTs. However, the application of CNTs in reinforcing materials is hampered by three major challenges: proper dispersion of the nanoscale additives, scale-up of laboratory results and implementation on larger scale, and a lowering of the cost benefit ratio. It is not easy to disperse CNTs into cementitious materials. Aiming to address all these three challenges simultaneously, this study proposes to produce CNTs reinforced cementitious materials through directly growing CNTs on fly ash particles using a novel Poptube method. Unlike any other exiting methods, Poptube method uses microwave irradiation as heating source, and a single chemical (e.g., ferrocene) to provide both the carbon source and the catalyst for CNTs’ growth. Compared with existing methods, the Poptube method is much more cost-effective and can be easily scaled-up for mass production. CNT reinforced geopolymer can be produced by mixing these CNTs grown fly ash particles with other ingredients. In this way, the time-consuming and difficult task of dispersion of CNTs is eliminated since CNTs are self-dispersed into the matrix by the fly ash particles on which CNTs were grown. To evaluate the effect of growing CNTs on the reactivity of fly ash particles, a series of tests were carried out, including dissolution testing, electric conductivity testing, and imaging with scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM). Results show that growing CNTs on the surface of fly ash does not reduce the reactivity of the fly ash because of the seeding effect provided by the CNTs. The composite effect induced by the CNTs was confirmed by Raman Spectrometer, which shows that the D-band of the CNTs varies with the applied thermal stress, suggesting effectively stress transfer from the geopolymer matrix to CNTs. This finding suggests that stress in CNTs reinforced geopolymer can be sensed by a Roman Spectrometer in a non-contact fashion. The self-sensing function of the nanocomposite mortar is evaluated using a four-electrode-DC method. At early age, geopolymer mortar is piezoresistive because of its high electric conductivity. However, DC induced polarization effect is very serious at this age. This polarization effect reduces with reaction time and becomes negligible at 35d. Similar piezoresitivity was achieved by the geopolymeric nanocomposite produced by using fly ash grown with CNTs using Poptube method, which is three orders magnitude more sensitive than the geopolymer one without any CNTs.
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    Utilizing tree ring chronologies to reconstruct paleo streamflow: a case study at the alabama-florida state border
    (University of Alabama Libraries, 2020-12) Vines, Melanie; Terry, Leigh; University of Alabama Tuscaloosa
    This study examined the results from a statistical screening of tree-ring width records to evaluatethe strength of the hydrological signal in dendrochronological records from the Southeastern region of the United States. We used United States Geological Survey (USGS) streamflow data from five gages near the Alabama-Florida border and 74 regional tree-ring chronologies to create and analyze seasonal flow reconstructions. Prescreening methods included correlation and temporal stability analysis of predictors to ensure practical and reliable reconstructions. Seasonal correlation analysis revealed that several regional tree-ring chronologies were significantly correlated (p≤0.05) with March–October streamflow, and stepwise linear regression was used to create the reconstructions. Reconstructions for all five rivers were considered statistically skillful (R2≥0.50), with lengths ranging from 144 to 782 years. The reconstructions were statistically validated using the following parameters: R2 predicted validation, the sign test, the variance inflation factor (VIF), and the Durbin-Watson (D-W) statistic. The long-term streamflow variability was analyzed for the Choctawhatchee, Conecuh, Escambia, and Perdido Rivers and the recent (2000s) drought was identified as being the most severe in the instrumental record. The 2000s drought was also identified as being one of the most severe droughts when compared to the paleo-records developed for all five rivers.
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    The water purification robustness of metal-organic framework-polyamide nanocomposite thin films toward long term organic, inorganic, and bacterial contamination
    (University of Alabama Libraries, 2020-12) Dadashi Firouzjaei, Mostafa; Elliott, Mark; University of Alabama Tuscaloosa
    Forward osmosis (FO) is an osmotically driven process widely studied for water desalination, wastewater treatment, and water reuse, as well as dilution and concentration of aqueous streams. However, its application is still hampered by the lack of ideal draw solutes, high-performance membranes, and fouling/biofouling. Biofouling is particularly challenging when FO is applied for seawater desalination and wastewater treatment. Over the last decade, many attempts have been made to exploit advances in materials science to obtain membranes with anti-biofouling properties to prevent or to reduce the detrimental effects of this phenomenon. In this study, a polyamide FO membrane was functionalized with silver-based metal organic frameworks (Ag-MOFs) to improve its antibacterial and antifouling properties. The project has been carried out in three different phases using different types of Ag-MOFs with and without additives, with various fabrication methods for modification of the polyamide layer. All the membranes were fully characterized to confirm the successful functionalization of membranes. The results demonstrate that Ag-MOFs are robust antibacterial nanoparticles that can reduce membrane biofouling and organic fouling and stabilize long term water flux.
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    Crack identification through computer vision: from non-learning-based to learning-based methodologies, and from patch-level to pixel-level detections
    (University of Alabama Libraries, 2020-12) Zhou, Shanglian; Song, Wei; University of Alabama Tuscaloosa
    Modern society requires a sustainable, robust, and serviceable infrastructure to promote social welfare and boost economy. To support such infrastructure systems, an efficient health monitoring framework is needed which can promptly detect the presence of defects and perform associated rehabilitation and maintenance. In civil infrastructure, one of the most common types of defects is cracking, which evolves rapidly under the impacts of heavy traffic, aging of materials, and drastic environmental changes. In recent decades, image-based automated crack detection methodologies have been developed and extensively applied by professionals and researchers. Nevertheless, a few issues and challenges existing in this type of methodology are yet to be systematically investigated and properly addressed. In this study, an image-based condition assessment framework for roadway crack detection is developed. It consists of four topics: i) proposing a filter-based methodology that can address image disturbances to promote a robust image-based roadway crack detection; ii) performing a systematic study to investigate the impact from hyperparameter selection on the performance of deep convolutional neural network (DCNN) on roadway crack classification; iii) achieving pixel-level crack detection resolution on image data of real-world complexities through DCNN-based roadway crack segmentation; and iv) investigating the impact from heterogeneous image data on DCNN-based roadway crack detection and proposing heterogeneous image fusion strategies to address data uncertainties. Overall, experimental results and discussions show that the proposed crack detection framework is capable to properly address the issues under investigation and leads to improved and more robust crack detection performance than current image-based methodologies.
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    A decision analysis tool for building renovations regarding adaptive reuse
    (University of Alabama Libraries, 2020-12) Harbin, Kristopher Belton; Moynihan, Gary P.; University of Alabama Tuscaloosa
    Renovation projects are an important part of a building’s life cycle and are performed for a variety of reasons, including adaptive reuse which can vary in scope and size. They are also prone to unexpected issues which can lead to costly changes. This can be exacerbated by arbitrarily choosing the renovation space. The renovation project may waste time, money, and effort and lead to a space that does not meet the needs of the user.A better understanding of a project’s scope earlier in the development process helps to identify renovation spaces that meets users’ needs with less need for renovation. This leads to the selection of a renovation space that reduces construction by minimizing the impact to existing systems. This benefits everyone involved in the renovation process. This dissertation presents an improved approach to minimize the impact of adaptive reuse by providing a decision analysis tool to help select the space for renovation. The tool provides information to help reduce the arbitrary nature of selection. The decision analysis tool allows users to select a space that minimizes the impact yet fits the renovation needs. The tool provides an exhaustive search of room combinations with room areas and shape, and impacts to building system and current room usages. The information is provided to users in a format that is easy to filter and sort. The tool addresses some of the deficiencies of earlier methods such as providing misaligned room selections. By providing the fit of the room shape users can choose the space that best fits the needs of the renovation. The tool also minimizes the need for user input, which has been an issue for previous approaches. User inputs do not require an extensive knowledge of the tool or general building information. The tool uses building information and renovation standards from The University of Alabama in the decision analysis. The research incorporates existing buildings on The University of Alabama campus to help ensure adequate historical information is available for validation. In the future, any building could be analyzed by the tool as long as the necessary information is available.
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    Enhancing the management proficiencies in developing countries: the impact of project risk management within a project management maturity model on project performance
    (University of Alabama Libraries, 2020-12) Hatamleh, Muhammad Tyseer Marzoq; Moynihan, Gary P.; Batson, Robert G.; University of Alabama Tuscaloosa
    In developing countries, construction activities account for about 80% of the total capital assets, 10 % of their Gross Domestic Product (GDP), and more than 50% of the wealth invested in fixed assets. The success of construction projects in developing countries is often uncertain due to planning in an unpredictable and poorly resourced environment. The economy of Jordan is growing rapidly due to changes in the region, and several large construction projects are being proposed and implemented. However, there is a lack of modern tools, methods, and techniques necessary to achieve the desired goals within time, cost, and standards. In addition, previous research in the project risk management discipline suggests that practitioners, especially in developing countries, are not fully aware of its importance. This research offers an in-depth understanding of the project management maturity concept, which allows construction organizations to improve their management practices, overcome past management malpractices, and achieve better project performance. Hence, several project management maturity models (e.g., Project Management Maturity Model (PM3)) have been utilized to generate a new maturity model that enables a Jordanian organization to evaluate its capabilities in project management, while focusing on the risk management process. The Project Management Body of Knowledge (PMBOK) offers a project management process consisting of ten knowledge areas. This research investigates the main role that risk management plays within the proposed model by exploring its impact on project performance and its relationship with the other knowledge areas.
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    Preparing small urban areas for shared mobility with autonomous vehicles: a case study of college town
    (University of Alabama Libraries, 2020-12) Nie, Qifan; Liu, Jun JL; University of Alabama Tuscaloosa
    The emergence of autonomous vehicles (AVs) presents people with new possibilities for daily travel. Since the first completion of Google’s self-driving car on-road test in 2009, a variety of automobile manufacturers, high-tech companies, and transportation network companies have joined the autonomous vehicle competition in order to have a leading role in the future transportation industry. Given their self-driving capabilities, AVs are expected to further promote the current shared mobility programs, including both car-sharing and ride-hailing services. Shared autonomous vehicles (SAVs) appear to be a promising future travel mode. This dissertation envisions an AV-supported shared mobility system in the Tuscaloosa, Alabama region. Tuscaloosa is a college town (UA) with a large group of young and high-educated individuals who could be among the first SAV user groups. This dissertation investigates the public perceptions towards shared mobility services powered by AVs. Twitter data were used to capture the perceptions among the general public and a student-centered survey was conducted among UA students to understand how this demographic perceives SAVs. Next, this dissertation exploits open-source social-economic data to construct high-resolution daily travel patterns to simulate a fleet of SAVs serving Tuscaloosa residents. An agent-based activity-based simulation was developed to envision the operations of an SAV system serving travelers in Tuscaloosa. This dissertation makes significant contributions in three aspects. First, the dissertation presents general impressions from social media alongside college students’ specific perceptions toward AV-supported shared mobility services, revealing public beliefs and concerns about SAV concepts and the characteristics of potential SAV users in future implementation. Second, this dissertation provides one of the first studies into development of data-intensive high-resolution travel behavior and mobility service simulations for small cities where data are often limited. A framework for preparing data for such simulations is presented in this dissertation. Third, the findings show the potential operational characteristics (e.g., demand) and consequences (e.g., empty vehicle miles) of implementing a college town SAV system. Decision-makers may utilize these findings to determine the feasibility of introducing SAVs in their cities, and operators or investors can gain insights regarding the operations of SAVs (e.g., fare rates, fleet size) in a region.