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Title: LIVE LOAD FACTORS FOR CONTINUOUS GIRDER BRIDGES
Creator: Wang, Qing
Date: 2016, 2016-07
Description: Live load factors of Strength I limit state for continuous girder highway bridges are calibrated based on reliability concept adopted by...
Show moreLive load factors of Strength I limit state for continuous girder highway bridges are calibrated based on reliability concept adopted by AASHTO LRFD and LRFR specifications. A uniform reliability is maintained for multi-girder highway bridges with various span lengths. WIM data, gathered by California, Michigan, New York, Oregon, and Illinois State Department of Transportation are analyzed. Live load effects produced by WIM data are calculated using influence lines. Expected maximum live load effects in given periods are modeled and extrapolated by Gumbel distribution. A relativecalibration formula is developed in order to derive live load correction factors for designing/evaluating continuous highway bridges at a reliability level that is in consistent with simply supported highway bridges. Computer programming is conducted for data sorting and traffic statistical analysis.
Ph.D. in Civil Engineering, July 2016
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Title: SEISMIC DESIGN STUDY OF STEEL PLATE SHEAR WALL
Creator: Moshiri, Ali
Date: 2012-04-20, 2012-05
Description: plate shear walls are an innovative lateral load-resisting system capable of effectively and economically bracing a building against both wind...
Show moreplate shear walls are an innovative lateral load-resisting system capable of effectively and economically bracing a building against both wind and earthquake forces. The system consists of infill steel plates connected to boundary beams and columns over the full height of the framed bay. Beam-to-column connections can be rigid or shear connections and the infill plates can be either stiffened or unstiffened, depending on the design philosophy of the infill plates. The view of some structural designers is to use heavy stiffeners to reinforce and increase the buckling capacity of shear walls, whereas, if the walls are left unstiffened and allowed to buckle, their energy absorption will increase significantly due to the post-buckling capacity. Performance of 9-story SPSW with moment resisting beam to column connections was studied under quasi-static loading condition and 10 earthquake records recorded in Los Angeles by developing a nonlinear dynamic explicit finite element models in ABAQUS. All the models were validated with experimental results. Effect of stiffness of boundary elements (VBE and HBE) and plate thickness on general behavior of the structure were also investigated. In design of SPSWs, vertical boundary elements play a major role in increasing the capacity of the system. In high seismic zones there is always a chance of plastic hinge formation in the boundary elements specially columns in any intermediate floor. It is recommended that SPSWs not be used for medium to high rise buildings in high seismic regions until the lack of capacity design requirements for this type of SPSW is rectified.
Ph.D. in Structural Engineering, May 2012
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Title: INFLUENCE OF OWNER-ORGANIZATION IMPRESSION AND CONTRACT FRAMING ON CONSTRUCTION CONTRACTORS' RISK PERCEPTIONS
Creator: Hanioglu, Mehmet Nihat
Date: 2014, 2014-12
Description: In a construction project, it is generally accepted that the contractor's perceived risk is the main factor in determining what is to be...
Show moreIn a construction project, it is generally accepted that the contractor's perceived risk is the main factor in determining what is to be proposed as the project cost and duration. Both the owner-organization and the contractor are aware of the existing risks and the owner-organizations tend to mitigate the existing risks by using the construction contract. It is hypothesized that the contractor’s initial impression of the owner-organization is a factor in the contractor’s perception of risk. It is further hypothesized that the initial impression is influenced by the content and context of the construction bid documents, which further influences the perceived risk and the bid strategy. The goal is to investigate the factors that influence contractors' impression of the owner-organization and to study the effects of contract document language and content in the impression formation process and subsequent development of a bid strategy. By better understanding the factors and relationships that influence impression formation and risk perceptions, it is expected that substantial time, money and unnecessary contention between these parties can be eliminated.
Ph.D. in Civil Engineering, December 2014
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Title: NETWORK-LEVEL VEHICLE CRASH PREDICTIONS INCORPORATING TIME-DEPENDENT EFFECTS INTO CONSIDERATIONS
Creator: Dao, Hoang
Date: 2016, 2016-07
Description: Maintaining highway safety is viewed as the over-arching goal of mananging transportation systems at all levels. According to the National...
Show moreMaintaining highway safety is viewed as the over-arching goal of mananging transportation systems at all levels. According to the National Highway Traffic Safety Administration (NHTSA), over 37,000 people got killed and 2.35 million are injured in road crashes annually. The equivalent economic and societal losses are on the order of over $231 billion, or an average of $820 per person. Thus, developing vehicle crash models that can accurately predict crash occurrences becomes essential. The study begins with literature review of models for predicting vehicle crash frequencies and crash severity levels on highway segments and at highway intersections. The findings of literature review indicate that some models lack prediction accuracy owing to exclusion of many crashing contributing factors. Consequently, a new methodology for improved vehicle crash predictability is proposed to include as many crash contributing factors as possible. In addition, the proposed methodology aims to conduct crash predictions targeting a highway network. Two computational experiments are performed for methodology application, including one on highway segment-related crash predictions using data on Highway Safety Information System for Illinois from 2001 to 2010, and another one on intersection-related crash predictions using crash data on more than one thousand intersections for period 2004 to 2010 provided by city of Chicago. Cross comparisons are made on the results obtained by applying the proposed methodology, method documented in Highway Safety Manual (AASHTO, 2010), and Empirical Bayesian (EB) before-after method for validation. The proposed methodology is found to have out-performed the other two methods. Future research directions are provided for continuing refinements of the proposed methodology.
Ph.D. in Civil Engineering, July 2016
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Title: COORDINATED DRIVING IN CONNECTED AND AUTONOMOUS VEHICLE SYSTEM -- OPTIMAL ADVANCE LANE CHANGE ZONES AND COORDINATED PLATOON CAR FOLLOWING CONTROL
Creator: Gong, Siyuan
Date: 2017, 2017-07
Description: The connected and autonomous vehicle (CAV) system enables countless innovative coordinated driving approaches, such as coordinated lane change...
Show moreThe connected and autonomous vehicle (CAV) system enables countless innovative coordinated driving approaches, such as coordinated lane change and car-following in microscopic CAV control, and coordinated rounding and parking in macroscopic traffic flow guidance, which will improve the performance of our transportation system by enhancing traffic mobility, providing safe driving environment and reducing fuel consumption. Since the lane change and car-following behavior are indicated as crucial factors of traffic safety and efficiency, this dissertation focuses on developing the coordinated driving schemes in microscopic control and operation of lane change and car-following maneuvers. In particular, I develop an lane change zone optimization strategy and the coordinated platoon car-following control for a pure CAV platoon and a mixed platoon (i.e. mixed with human-drive vehicles and CAVs) respectively. This dissertation first explore the management strategy of the mandatory lane change near a two-lane highway off-ramp by optimizing the location of advance warning. The proposed approach considers that the area downstream of the advance warning includes two zones: the green and yellow zones corresponding to their respective most like lane change maneuvers. An optimization model is proposed to search for the optimal green and yellow zones. Traffic flow theory such as Greenshield model and shock wave analysis are used to analyze the impacts of the S-MLC and D-MLC maneuvers on the traffic delay. Numerical experiments indicate that the proposed optimization model can identify the optimal location to set the advance MLC warning nearby an off-ramp so that the traffic delay resulting from lane change maneuvers is minimized, and the corresponding capacity drop and traffic oscillation can be efficiently mitigated. Then, this research develops a novel car-following control scheme for a platoon of connected and autonomous vehicles on a straight highway. The platoon is modeled as an interconnected multi-agent dynamical system subject to physical and safety constraints. A constrained optimization based control scheme is proposed to ensure an entire platoon’s transient traffic smoothness and asymptotic dynamic performance. This dissertation develops dual based distributed algorithms to compute optimal solutions with proven convergence. Furthermore, the asymptotic stability of the unconstrained linear closed-loop system is established. These stability analysis results provide a principle to select penalty weights in the underlying optimization problem to achieve the desired closed-loop performance for both the transient and the asymptotic dynamics. By the motivation that CAVs and human-drive vehicles will co-exist on the road for a long period in the near future, the third part of this dissertation extends the pure CAV coordinated platooning control to the mixed flow environment. By integrating the Newell car-following model, a real-time curve matching algorithm is implemented to calibrate the ca-following model and anticipate the movement of human-drive vehicle by the real-time trajectory data. The constrained MPC are developed for each CAV platoon, considering their movement interaction through the human-drive vehicle platoon. Furthermore, this study provide a modified dual based distributed algorithm to improve convergence speed of the primal problem for the dual based distributed algorithm in Chapter 4. Several requirements of the penalty weights selection are provided by stability analysis under the unconstrained conditions. The numerical experiments based on field data will be conducted to illustrate the effectiveness and efficiency of the proposed the solution approach and the platoon control schemes.
Ph.D. in Civil Engineering, July 2017
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Title: DYNAMIC ANALYSIS OF UNCERTAIN STRUCTURES USING IMPRECISE PROBABILIY
Creator: Bergerson, Joshua D.
Date: 2014, 2014-05
Description: A new method for dynamic response spectrum analysis of structures with uncertainty in their mechanical properties utilizing the notion of...
Show moreA new method for dynamic response spectrum analysis of structures with uncertainty in their mechanical properties utilizing the notion of imprecise probability is developed. This finite-element-based method is capable of obtaining probabilistic bounds of the dynamic response of the structure with uncertainty defined by enveloping p-boxes. The developed method obtains probabilistic bounds on 1) the mode shapes, 2) modal coordinates, and 3) modal participation factor, leading to the p-boxes of modal responses. Finally maximum modal responses are combined to obtain the structure’s maximum total response with consideration of uncertainty. Numerical examples demonstrating the developed method are included. Keywords: Structural Dynamics, Uncertainty, Imprecise Probability, P-Box.
PH.D in Civil Engineering, May 2014
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Title: MATERIAL INVENTORY CONTROL AND MANAGEMENT SYSTEM IN CONSTRUCTION USING GIS APPLICATIONS AND A "HYBRID" TRACKING SYSTEM
Creator: Le, Kiet Tuan
Date: 2017, 2017-05
Description: Material inventory control and management is simply the process by which an organization is supplied with the goods and services that it needs...
Show moreMaterial inventory control and management is simply the process by which an organization is supplied with the goods and services that it needs to achieve its objectives of buying, storing and moving materials. There are usually plenty of materials in a construction site. A large amount of stored materials can meet unexpected demands, and can prevent future purchases that can be affected by an escalation of material prices. However, a large amount of stored materials can also cause negative impacts such as increased costs for storing redundant inventory, and decreased construction productivity. Therefore, a proper material inventory control and management system is critical for economy and efficiency in construction projects. A material inventory control and management system consists of two main elements: inventory control and inventory management. Inventory control is the process of monitoring the flow of materials on the construction site beginning when materials are received from manufacturers and ending when those materials are used in production. Inventory management is the practice overseeing and managing the ordering, storage and use of materials on the construction site. In this study, an automated material inventory control and management system is developed using Geographical Information System (GIS) applications and a “hybrid” tracking system to identify the need for materials, order, track, transport, store, control the inventory, circulate on site, and incorporate into production. The proposed system allows users to have access to real-time information about the materials on the construction such as: the arrival of materials, the amount of materials received, the status of materials (either in storage area or in-production), and the up-to-date information about site stocks. Furthermore, the system provides users the ability to make correct and timely decisions regarding materials on the construction site.
Ph.D. in Civil Engineering, May 2017
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Title: METHODOLOGY FOR VEHICLE EMISSION IMPACTS ANALYSIS FROM SIGNAL TIMING OPTIMIZATION OF AN URBAN STREET NETWORK
Creator: Lu, Pu
Date: 2017, 2017-05
Description: The pace of urban street capacity expansion is much slower than the growth of vehicle travel, leading to several traffic congestions. To...
Show moreThe pace of urban street capacity expansion is much slower than the growth of vehicle travel, leading to several traffic congestions. To mitigate traffic congestion expanding capacity is not feasible for many cases due to the high cost and space restriction. Improving the efficient use of the available capacity becomes the solution. Traffic signal optimization is one of the most widely used ways of efficient capacity utilization. Concurrent to traffic signal optimization, more smooth traffic operations in term of reasonably higher speed and a reduced traffic delay will in turn change vehicle emissions. This research aims to quantify changes in vehicle emissions resulted from traffic signal optimization by introducing a new methodology for quantifying network wide vehicle emissions and real world application in of the Chicago urban network for validation. The proposed methodology considers undersaturation and oversaturation of traffic conditions and urban street segments with varying speeds for different types of vehicles and pollutants by hour of the day and location within the network. It begins with information collection and research through a review of existing methods for urban street network vehicle emission estimation, intersection vehicle emission evaluation, and the running vehicle emission modeling. The proposed methodology focuses on three elements: estimation of emissions from vehicles stopped at intersections and for vehicles cruising along segments, as well as analysis of network wide vehicle emissions and changes in overall network vehicle emissions by time of the day and by areas. Major steps of methodology application included the use of Chicago TRANSIMS model implementing optimized signal timing plans to obtain refined traffic volumes at intersections and on segments, increased vehicle operating speeds, changed green splits, and vehicle compositions for all intersections and segments in the urban street network, the application of an intersection vehicle emission model for stopped vehicles and a segment vehicle emission model for vehicles cruising on segments, and the network wide analysis of vehicle emission changes by vehicle type and pollutant type in a 24-hour period within an urban street network, respectively. The proposed methodology for intersection vehicle emission estimation was successfully applied to a dense urban street network in Chicago for each approach per cycle and then extended for intersections in hours of the day to analyze the impacts of traffic changes at intersections on exhaust changes. In order to develop the network vehicle emission analysis method, it is essential to evaluate the segment vehicle emissions. This is achieved by using the concept of vehicle specific power which is used to estimate emissions of cruising vehicles considered along with vehicle speeds and speed changes and hence analyzing changes in segment vehicle emissions affected by traffic volume changes derived from signal timing optimization. The decreased number of vehicles stopped at intersections by applying signal timing optimization will reduce intersection emissions, hence reducing overall network vehicle emissions. In addition to have vehicle emissions got reduced at intersections, the increasing vehicle speed for vehicles on segments could further reduce vehicle emissions on segments.
Ph.D. in Civil Engineering, May 2017
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Title: INVESTIGATING THE SIGNIFICANCE OF HALF-SATURATION COEFFICIENTS ON WASTEWATER TREATMENT PROCESSES
Creator: Shaw, Andrew Robert
Date: 2015, 2015-05
Description: This research is focused on the half-saturation coefficient (KS), which is an important, but often overlooked, parameter in the Monod equation...
Show moreThis research is focused on the half-saturation coefficient (KS), which is an important, but often overlooked, parameter in the Monod equation commonly used to describe biological wastewater treatment processes. Following an initial literature review, the research uses data for a denitrifying activated sludge process to show that KS is a function of the maximum rate and, further, that the relationship can be described either using a simple linear regression or by modeling diffusion explicitly. Building on this initial investigation of a particular treatment system, the research introduces and uses a “porter-diffusion” model that approximates diffusion to a linear equation for KS in the Monod equation. This is used to describe the linear relationship between KS and maximum rate for four different biological wastewater treatment systems. Finally, a sensitivity analysis is carried out on the parameters in the porter-diffusion model to show that r0 – a measure of cell size or diffusion distance – is the most sensitive parameter for a simple activated sludge process model based on a modified version of the International Water Association (IWA) activated sludge model #1 (ASM1). Overall this research has shown that in all of the biological wastewater treatment systems investigated in this thesis: (1) KS is not a constant but is a function of the maximum rate; (2) diffusion is a dominant mechanism that influences KS; (3) that a suitable expression for KS can be estimated using the porter-diffusion model, a linear data fit, or by modeling diffusion explicitly; and (4) measurements of KS in the laboratory must be carried out at the same food-to-microorganism (F/M) ratio as the full-scale system under investigation.
Ph.D. in Civil Engineering, May 2015
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Title: SEISMIC STUDY OF DUCTILE AND NON-DUCTILE CONCENTRICALL1 BRACED FRAMES
Creator: Sutchiewcharn, Narathip
Date: 2013, 2013-07
Description: Braced Frames, both ductile and non-ductile systems, are in high demand due to their considerable strength and attractiveness. Therefore, the...
Show moreBraced Frames, both ductile and non-ductile systems, are in high demand due to their considerable strength and attractiveness. Therefore, the better understanding of their behaviors will be beneficial, in which, is the focus in this study. With different failure modes expected based on design methodology, the study of non-ductile system is focused on connections and their contributions toward performance of frame systems, while the ductile system is concentrated on the behavior of braces itself. For non-ductile system with the model-based simulation approach, local brace connection models were developed extending from the validation with the existing specimens. Then, the extensive seismic global performances including local joints, from both local brace and gravity frame connections, are evaluated with the adaptation of collapse methodology outlined in FEMA-P695. For ductile system, with the expectation of hinges formed in braces causing by buckling, the global performances under reversal loadings, e.g. ground motions, are in jeopardy due to the strength degradation. Taking advantage of FEM simulations in addition to testing, the proposed tube-in-tube brace configuration is introduced as buckling-controlled brace (BCB). The effects of parameters are studied using analytical models. The performances observed from proposed tube-in-tube configuration are satisfied under both monotonic and cyclic loadings.
PH.D in Civil Engineering, July 2013
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Title: HEURISTIC DECISION-MAKING MODEL FOR ELECTRICAL FOREMEN WHEN WORKFLOW IS DISRUPTED
Creator: Pandey, Arjun R.
Date: 2016, 2016-05
Description: The decision-making process used by construction foremen at a job site when the workflow is disrupted was investigated in this study. The...
Show moreThe decision-making process used by construction foremen at a job site when the workflow is disrupted was investigated in this study. The foremen’s decision-making process was mapped and then modeled to a heuristic model. This study focuses on cognitive decision or psychological heuristic models. The study shows that construction foremen use a heuristic decision model in their decision-making. The capability of heuristic to yield fast decision is very useful in construction because it is common for a construction foreman to experience several disruptions during the course of a single workday. With heuristic decision-making, a work-around decision can be rapidly and effectively made following a construction site disruption. Understanding the ability of heuristics to facilitate rapid and effective decision-making will help the construction industry to save time and increase productivity. Research was conducted in order to map a decision process that foremen were using in their decision-making and to develop a model for a heuristic decision-making process. Interviews were conducted with 22 construction foremen in the electrical trade in 88 real disruption cases in order to understand how decisions were made after disruptions occurred. Interviews were subsequently conducted with 10 additional industry foremen in 10 real disruption cases to validate the data. Using this data, a heuristic decision-making model was developed. To validate this model, a survey was conducted with another 11 industry foremen. The findings indicate that construction foremen currently use a heuristic decision-making model known as “determinant decision attribute” (referred to as DDA) heuristics model. This DDA heuristic model was compared to the similar model with equal weighing and elimination by aspects (referred to as EW/EBA) to assess the performance of the heuristic. The DDA heuristic model correctly predicted, on average, 91% of the time what foremen’s decisions were as to which decision task to choose to assign or re-assign to crew members. Whereas, the EW/EBA model correctly predicted, on average, 82% of the time, the foremen’s decisions. A computer program was also developed for DDA heuristic model to help foremen expedite the process of their decision-making.
Ph.D. in Civil Engineering, May 2016
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Title: LAND USE EFFECTS ON WATER QUALITY: BUILDING A FRAMEWORK FOR CHICAGO RIVER WATERSHED
Creator: Mahdi, Naila Ghidey Ismail
Date: 2012-05-09, 2012-05
Description: The purpose of this study is to introduce a framework that enables a holistic watershed approach that models the dynamics of water quality and...
Show moreThe purpose of this study is to introduce a framework that enables a holistic watershed approach that models the dynamics of water quality and landuse in a highly urbanized watershed. The landuse-water quality relationship is a complex relationship and has not been adequately addressed for highly urbanized watersheds. Factors such as inadequate urban planning, increase of impervious areas and dynamics of population growth are some of the reasons for the complex relationship. Also point sources are always easy to be identified and controlled unlike nonpoint sources such as urban storm runoff. Both quantities and transport pathways of pollutant inputs are impacted by land use in the watershed. So, examining the factors that govern the relationship between different land uses and water quality within a watershed can give insights and important information about existing and potential sources of contamination. The two backbone concepts in this study are the holistic watershed perspective and the role of historical data records as part of assessment, modeling and integration tools of the watershed framework. Analysis of the records will explain watershed conditions identifying the major problem areas and justify the modeling and post analysis procedures. Data sources are often important but data availability, heterogeneity and conformity are the main challenges in integrating these sources. This research presents an approach to integrate the watershed data in a single repository and methodologies for analyzing and assessing the watershed using data warehouse and data mining technologies. A multi-dimensional model that supports complex querying of watershed data and discovery of trends and patterns in data by incorporating 40 years worth of watershed data from different source agencies in a central repository is introduced. Also, the discipline of data driven modeling was introduced in this thesis using the developed central repository. Several regression and classification algorithms were presented and assessed for their appropriateness for predicting total nitrates using few watershed attributes. The results show acceptable prediction accuracy. Five years of water quality simulation using the multi-purpose environmental analysis system BASINS coupled with the comprehensive, conceptual, and continuous simulation watershed scale model HSPF resulted in export coefficients for level (III), detailed land use for the Chicago River watershed. The water quality simulation approach utilized in this research to generate the coefficients constitutes a new contribution to the Chicago River watershed and other highly urbanized watersheds. The continuous calibrated and validated model can be used in the investigation and analysis of different scenarios and possible future conditions, thus providing a planning tool for regulatory environmental agencies. The data driven models developed can be used as operation tool to maintain the water quality parameters especially if TMDL and WQS are developed for Chicago River Watershed. So the framework proposed for this study can be considered robust with the proposed integration, planning and operating techniques and tools. Furthermore, an optimization tool is introduced in the future work section.
Ph.D. in Environmental Engineering, May 2012
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Title: METHODOLOGY FOR PERFORMANCE BASED TRANSPORTATION SYSTEMS MANAGEMENT SIMULTANEOUSLY CONSIDERING DEMAND AND SUPPLY, WITH PRICING CONSIDERAnON
Creator: Patel, Harshingar
Date: 2015, 2015-05
Description: The ever growing demands for the use of transportation infrastructure and its maintenance and repairs at an acceptable level of service are...
Show moreThe ever growing demands for the use of transportation infrastructure and its maintenance and repairs at an acceptable level of service are the prime concern for transportation agencies today. The available financial resources can never be sufficient to match the exorbitantly high requirements for construction, maintenance and rehabilitation of transportation systems. With the advent of the technological revolution, the intelligence transfer amongst various engineering fields has made it possible to reduce transportation costs. However, the slow growing budget caused by economic recession and revenue decrease over time puts transportation agencies under enormous pressure to effectively restore the deteriorated transportation facility and system operation conditions under the budget constraint. The proposed research aims to utilize the concept of roadway pricing coupled with a holistic framework of asset management to support performance-based management of transportation systems and help transportation agencies achieve the future vision of the nation's strategic planning requirements to enable sustainable management of the system. A computational study for the City of Chicago’s central district is conducted by using the proposed roadway pricing framework. The proposed roadway pricing framework can be utilized for urban as well as rural regions, by public as well as private agencies, to manage the system in a sustainable manner, by means of fair pricing to the users of the system, for their facility condition and usage impacts.
Ph.D. in Civil Engineering, May 2015
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Title: INVESTIGATING THE MEDIATION OF HEMOGLOBIN PROTEINS IN NITRIFICATION AT LOW DISSOLVED OXYGEN CONDITIONS
Creator: Arnaldos, Marina Orts
Date: 2012-10-30, 2012-12
Description: Due to the high aeration and energy requirements of nitrifying activated sludge processes, there is great interest in developing biological...
Show moreDue to the high aeration and energy requirements of nitrifying activated sludge processes, there is great interest in developing biological nitrifying processes that operate efficiently under low dissolved oxygen (DO) conditions. In this framework, the present study has investigated the acclimation of ammonia-oxidizing communities (AOC) to low DO concentrations. Under controlled laboratory conditions, two sequencing batch reactors seeded with activated sludge from the same source were operated at high DO (near saturation) and low DO (0.1 mg O2/L) concentrations for a period of 385 days. Stable and complete nitrification at low DO after an acclimation period of approximately 140 days was demonstrated. Modeling of oxygen transfer and uptake behavior demonstrated the low DO reactor to achieve equal performance to the high DO reactor, when the latter is operated at design DO concentration (2 mg O2/L), with approximately 20 % improvement in aeration requirements and oxygen mass transfer efficiency. The effect of DO on AOC dynamics was evaluated using the 16S rRNA gene as the basis for phylogenetic comparisons and organism quantification. Ammonium consumption by ammonia-oxidizing archaea and anaerobic ammonia-oxidizing bacteria was ruled out in both reactors. Even though N. europaea was the dominant AOB lineage in both SBRs at the end of operation, this enrichment could not be linked to acclimation to oxygen-limited conditions. This finding challenges the hypothesis that low DO conditions select for ammonia-oxidizing lineages characterized by high oxygen affinities, and points to the alternative mechanism of a physiological change of a generalist nitrifying community. Acclimation brought about increased specific oxygen uptake rates and enhanced expression of a particular heme protein in the soluble fraction of the biomass in the low DO reactor as compared to the high DO reactor. The heme protein induced was determined not to be any of the enzymes playing a role in ammonia metabolism of ammonia oxidizing bacteria, including a soluble oxidase and soluble peroxidase of unknown function. Further molecular studies are required to verify the hypothesis put forward in this study that the heme protein detected is a hemoglobin.
PH.D in Environmental Engineering, December 2012
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Title: WIND TURBINE FARMS IMPACT ON POLLEN TRANSPORT DISPERSION PATTER S
Creator: Hsu, Chin Yu
Date: 2012-11-28, 2012-12
Description: Wind energy has become more and more popular because electricity generation by wind power brings much less environmental impacts than...
Show moreWind energy has become more and more popular because electricity generation by wind power brings much less environmental impacts than conventional energy generation using coal. Also, energy generated by wind power does not require expensive fuel imported from overseas. Since the land in between turbines is still cultivated for crops and grazing, it is important to know the potential interference of wind turbines with pollen transport and dispersion, or the possible change of patterns established for thousands of years. However, these issues have not been studied in the literature. The co-existence of conventional crops with genetically modified (GM) crops has become a subject of debate. In particular, pollen transfer from GM crops to non-GM crops might result in the introgression of transgenes into natural populations as maize is mainly wind-pollinated. This study thus reports and assesses a comprehensive method that estimates maize pollen transport in the presence of turbines to ascertain the potential for maize pollen transport. The study on the concentrations of maize pollen transport affected by the wind turbines considers different dispersion parameters given the additional mechanical turbulence introduced by the presence of operating wind turbines. For instance, the wind turbines can increase surface roughness which subsequently causes increased mechanical turbulence. A high mechanical turbulence subsequently reduces downwind concentrations because of the mixing higher and wider into the atmosphere, which dilutes the maize pollen plume with more clean air. This study compares maize hourly concentrations and ground level flux levels inside and outside a virtual maize flux in the presence and absence of operating wind turbines. Results from a 14-day simulation of maize transport xii with and without operating wind turbines indicate that each difference of corresponding concentration and flux levels is statistically significant. Likewise, patterns of maize pollen transport inside the farm with turbine effects are significantly different from those without turbine effects. Overall, the average maize pollen concentration inside the farm in the absence of turbine effects is about 5 times greater than the corresponding maize pollen concentration with turbine effects. The total mass of maize pollen released into the air is the same whether the wind turbines are present or not. The portion of maize pollen staying inside the farm, on the other hand, is influenced by turbulence. For instance, the increased surface roughness caused by the turbine effects will increase the mechanical turbulence. Because the high mechanical turbulence carries a large portion of maize pollen away from the farm, only a small portion of maize pollen stays inside the farm due to the high turbulence that lifts maize pollen into higher levels of flow where the wind speed is stronger. In contrast, without turbine effects, a small portion of maize pollen leaves the farm while most of it deposits on the ground much sooner than it would with turbine effects. Therefore, maize pollen concentration and ground level flux in the presence of turbine effects will be greater than they are without turbine effects at a relatively far distance from the farm.
PH.D in Environmental Engineering, December 2012
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Title: DEVELOPMENT OF PERMEABLE REACTIVE FILTER SYSTEMS (PRFS) FOR TREATMENT OF URBAN STORMWATER RUNOFF
Creator: Prabhukumar, Giridhar
Date: 2013, 2013-05
Description: Urban stormwater runoff is a major contributor of pollutants to nearshore beach water of Lake Michigan and other water bodies. Reduction of...
Show moreUrban stormwater runoff is a major contributor of pollutants to nearshore beach water of Lake Michigan and other water bodies. Reduction of pollutants levels to within safe limits in urban runoff from near shore areas by means of filtration using low-impact reactive multi-media systems is the subject of research in this dissertation. The key research issues addressed are the identification of effective filter materials and laboratory-scale testing of the selected materials for permeable reactive filter systems (PRFS) that are feasible for installation in urban environment. The focus was to evaluate different media materials for removal of total suspended solids (TSS), nutrients (nitrate and phosphate), heavy metals (Cd, Cr, Cu, Pb, Ni and Zn), polycyclic aromatic hydrocarbons (naphthalene and phenanthrene) and microbial (E. coli.) contaminants from stormwater runoff to levels below standard discharge criteria. Eight different media materials were initially selected, including calcite, anthracite coal, zeolite, sand, iron-oxide coated sand (IOCS), iron filings, perlite and biochar. Of these, calcite (C), zeolite (Z), sand (S) and iron filings (Fe0) were screened based on preliminary column experiment results and used for further studies. Physical and chemical characterization studies were carried out to understand the material properties. Contaminant attenuation studies with lab-scale column experiments for the four individual media materials (C, Z, S and Fe0) were conducted with synthetic stormwater solution containing all the aforementioned pollutants. Results showed that calcite and sand were efficient in TSS, nutrients and polycyclic aromatic hydrocarbons (PAHs) removal, zeolite was efficient for metals removal and the only material that was able to lower E. coli level to below its safe xv limit of 126 most probable number (MPN) per 100ml, and iron filings was efficient in nutrients and metals removal. Column experiments were also conducted with three mixed media compositions, C-Z-S, C-Z-Fe0 and C-Z-S-Fe0. The results indicated that a multi-media based filtration system can perform efficiently to treat a wide range of pollutants and runoff flow conditions. Finally, several conceptual designs for PRFS were proposed that are suitable for application at various urban locations.
PH.D in Environmental Engineering, May 2013
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Title: FATIGUE AND BARKHAUSEN EFFECT
Creator: Tong, Wei
Date: 2013, 2013-05
Description: Piezomagnetism designates a change in the magnetization of materials induced by mechanical actions such as tension or compression. The type of...
Show morePiezomagnetism designates a change in the magnetization of materials induced by mechanical actions such as tension or compression. The type of Barkhausen effect that occurs in this work consists of sudden, discontinuous jumps in a material’s magnetization that appear in response to smooth (continuous) stress variations. A series of strain controlled fatigue tests with an alternating sinusoidal waveform were carried out to study the relationship between the endurance limit and the Barkhausen effect. Results of fatigue tests on steel specimens exhibiting Barkhausen pulses at various stages are reported and a threshold-crossing analysis is applied to the test results. These studies show that when the fatigue limit is approached, the Barkhausen pulses become, in general, more intense in amplitude and quantity than at other stress levels. A hypothetical mechanism is proposed that relates the intensity of the Barkhausen response to the inception of micro-cracking and rearrangements of the mechanical lattice at the microscopic level.
PH.D in Civil Engineering, May 2013
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Title: SEISMIC STUDY OF HYBRID SHEAR WALL SYSTEM
Creator: Xu, Lifeng
Date: 2013, 2013-07
Description: This thesis represents the seismic behavior of new hybrid shear wall system, which consists of two exterior precast wall layers and one...
Show moreThis thesis represents the seismic behavior of new hybrid shear wall system, which consists of two exterior precast wall layers and one interior cast-in-place concrete layer. The “sandwich” shaped shear walls were already tested as a full scale specimen subjecting to vertical pressure and cyclic horizontal load in Anhui University of Architecture, China (2010). A series of 3D non-linear finite element models which include all significant details and specifications were then created in ABAQUS to simulate the experiments. The pushover analyses method was employed to reproduce the test procedures. The response of the structure was computed both at macro and micro level at the result in order to validate the correctness of the analytical model. After verifying the good agreement between the experimental observations and simulation results, an extended parametric study was conducted towards this hybrid shear wall system to explore its damage mechanism and design optimization. Based on hybrid shear wall's specific seismic resisting capacity which derived from the previous simulation, a series of 2D models were created in SAP2000 to evaluate the seismic performance of hybrid shear wall structure. What's more, in order to precisely represent the 3D model effect into 2D model in SAP2000,3D model was created in ABAQUS to account for the influence of semi-rigid connection between the concrete diaphragm and hybrid shear wall. After applying the ability of semi-rigid connection and hybrid shear wall, pushover method and time history analysis were conducted towards this 18 story structure model. The global seismic performance factor is finally evaluated according to the FEMA-P695.
PH.D in Civil Engineering, July 2013
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Title: MANAGING THE BIDDING PROCESS FOR THE CONSTRUCTION OWNER – DETECTION AND PREVENTION OF UNBALANCED BIDS AND COLLUSIVE BIDS
Creator: Chotibhongs, Ranon
Date: 2011-09, 2011-12
Description: There are two major problems that affect bidding efficiency: unbalanced bidding and collusive bidding. Unbalanced bidding is a serious...
Show moreThere are two major problems that affect bidding efficiency: unbalanced bidding and collusive bidding. Unbalanced bidding is a serious unethical problem in the construction industry. The owner may end up paying more money if the bid is unbalanced by the contractor. A bid can be rejected by the owner if it is unbalanced. A bidder unbalances a bid by inflating the unit price of some line items and reducing the unit price of other line items. Frontloading is the most common practice where a bidder can mathematically unbalance a bid by overstating the unit price of line items scheduled to be performed early in the project and understating the unit price of line items performed later. A bidder can also overstate the unit price of a line item whose quantity was somehow underrated by the engineer. If the owner proves that a mathematically unbalanced bid costs more to perform, the bid is said to be materially unbalanced, in which case the owner can reject the bid. A model is presented that formalizes and automates the process of detecting mathematically and materially unbalanced bids by comparing line item prices with the engineer’s estimates or the average prices offered by the bidders. This model allows owners to detect and reject unbalanced bids, and deters bidders from unbalancing their bid. Another matter that inflates bids and reduces bidding efficiency is collusion. Collusion is an insidious issue in the construction industry. Even though, it is widely acknowledged as unethical and illegal, there are not many research studies conducted to detect collusive bidding. This study proposes a two-step method to detect collusive bidding by analyzing historical bidding data provided by a construction owner. The construction owner in this study was a public agency that commissioned 108 construction projects that was worth $1.3 billion during a 10-year study period (2001-2010). The first step involves indentifying the potential cartel bidders using the residual test and the cost structure stability test developed in earlier work. The second involves comparing the behavior of the potential cartel bidders and non-cartel bidders by analyzing bid distributions, their cost dispersion, and the differences in their cost structures. After conducting the tests, it was found that the suspected cartel bidders identified in Step 1 behaved in ways to confirm collusion. Also, in an unrelated search, it was found that two of the six potential cartel bidders who were identified in this study had been audited by the public agency for bid fraud, and that another potential cartel bidder had been found guilty by the courts and forbidden from doing business with the public agency.
Ph.D. in Civil Engineering, December 2011
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Title: METHODOLOGY FOR URBAN AREA SNOW REMOVAL USING NEW MACHINE AND PERFORMANCE-BASED ANALYSIS
Creator: Neishapouri, Mohammad
Date: 2015, 2015-12
Description: The need for alternative methods that facilitate removal of snow on urban streets with minimal pavement and bridge damages, vehicles...
Show moreThe need for alternative methods that facilitate removal of snow on urban streets with minimal pavement and bridge damages, vehicles corrosions, and environmental impacts due to use of chemicals and salts has been growing over time. Conversely, this issue has not been thoroughly investigated. This is particularly true for large urban areas where the snow removal machine and background traffic share already congested streets. In this research, a new methodology is introduced for effectively managing snow removal that involves new machine and performance-based analysis. The new machine aims to melt snow and ice using technically adequate mechanical system including special engine, heat pumps and very fast ventilation pumps in order to suck and discharge water from pavement surface to road sides. The performance-based analysis employs a life cycle cost analysis approach to estimate reductions in expenditures to pavements and bridges, and vehicle corrosions of background traffic as a result of using new machine for snow melting instead of using chemicals and salts; and an optimization model for effective dispatching of new machine across a large area, leading to a significant level of travel timing savings to the background traffic owning to shorter duration oftravel way closures. The proposed methodology is implemented in a computational study to examine the current snow removal programs in the city of Chicago for a typical winter day involving moderate and severe snowfalls that correspond to its 50 percent and 100 percent programs for filed dispatching one-half and all snow plow trucks. Compared with the use of snow removal trucks coupled with chemicals and salts, the use of new machine could result in better equivalent annualized savings as benefits component and less amount of cost components which cause the project implementation has benefit to cost ratio Xl11The need for alternative methods that facilitate removal of snow on urban streets with minimal pavement and bridge damages, vehicles corrosions, and environmental impacts due to use of chemicals and salts has been growing over time. Conversely, this issue has not been thoroughly investigated. This is particularly true for large urban areas where the snow removal machine and background traffic share already congested streets. In this research, a new methodology is introduced for effectively managing snow removal that involves new machine and performance-based analysis. The new machine aims to melt snow and ice using technically adequate mechanical system including special engine, heat pumps and very fast ventilation pumps in order to suck and discharge water from pavement surface to road sides. The performance-based analysis employs a life cycle cost analysis approach to estimate reductions in expenditures to pavements and bridges, and vehicle corrosions of background traffic as a result of using new machine for snow melting instead of using chemicals and salts; and an optimization model for effective dispatching of new machine across a large area, leading to a significant level of travel timing savings to the background traffic owning to shorter duration oftravel way closures. The proposed methodology is implemented in a computational study to examine the current snow removal programs in the city of Chicago for a typical winter day involving moderate and severe snowfalls that correspond to its 50 percent and 100 percent programs for filed dispatching one-half and all snow plow trucks. Compared with the use of snow removal trucks coupled with chemicals and salts, the use of new machine could result in better equivalent annualized savings as benefits component and less amount of cost components which cause the project implementation has benefit to cost ratio respectively 2.15 and 2 by CPI analysis and 3 and 3.04 by CCI analysis. Compared with the current practice of filed dispatching of snow plow trucks or new machine for snow removal, the optimization model for vehicle dispatching could further improve the snow removal productivity by 2-4 percent for the 100 percent program and 3-8 percent for the 50 percent program, respectively.
Ph.D. in Civil Engineering, December 2015
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