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Driver Behavior in Mixed Connected-Automated and Conventional Vehicle Traffic at a Freeway MergeUnknown Date (has links)
Wireless communication through automated and connected vehicles is an evolving technology. This ameliorates the driving conditions, reduces time spent in traffic and curtails the crash occurrences. One of the most challenging areas, where these interactions can be most useful, are freeway merge ramps. Both the drivers on mainline and the drivers merging would be skeptical about their decisions at this location. The drivers who want to merge to the freeway mainline would seek to find an appropriate gap to enter the mainline of the freeway. While the technology of connected and automated vehicles is being promoted, the reality now is that for the foreseeable future, the traffic would not comprise 100% of such connected and automated vehicles. In other words, there will be a mixed traffic of manually-driven and connected/automated vehicles, with various levels of automation in the latter types of vehicles. Capturing the driver behavior at the merge locations into a freeway with such mixed traffic, will be useful in learning and improving safety on the roadways. The Driving Simulator is a useful device in capturing driver behaviors. In this study scenarios are developed in the Driving Simulator which allows mixed traffic on mainline and also observe the driver behaviors from the ramp onto the merge. Overall there were three variations in the mixed traffic flow for the mainline freeway: 0%, 50% and 75% penetration rates. The freeway traffic was generated for the mixed traffic by first developing a mixed probability distribution which assumes exponential distributions for the inter-arrival times of manually-driven vehicles and a constant headway (uniform distribution) is assumed between connected vehicles. The mixed distribution was then used to randomly generate vehicles through Monte Carlo simulation, with assigned headways in the Driving Simulator for the various connected vehicle penetration rates. The subject driver’s speed along the ramp is monitored, as well as the speeds of those vehicles on the freeway. The gaps between freeway vehicles, which were accepted by the subject driver, were recorded for the various situations and scenarios. There were a total of 41 participants, with 29 young drivers (younger than 65 years) and 12 elderly drivers (65 years and older, amongst which 2 were between 55 and 65 years old). Three scenarios were presented to the drivers. The first driving task was to determine headway gap acceptance for the three penetration rates, based on the perception of the subject drivers (without driving). The second test involved the subjects actually driving on the ramp and implementing a suitable gap to merge on the freeway traffic at each ramp. From the data collected, the critical gaps were estimated based on perception. The gaps accepted while driving were also tabulated analyzed. It was observed that the critical gap for the young drivers in 0%, 50%, 75% penetrations rate are 2.9 sec, 1.8 sec, and 1.7 sec respectively. The critical gaps observed for elderly drivers aged over 65 are 3.5 sec, 2.0 sec, and 1.9 sec respectively. Based on an Analysis of Variance (ANOVA), there is no evidence to prove the equality of means for different groups classified by age, gender and driving experience in both perception and actual driving conditions for 0% and 50% penetration rates. It was observed that the headway gaps accepted by young and drivers, both by perception and driving in 0% penetration rate were 2.39 sec and 2.35 sec respectively. The headway gaps accepted by elderly drivers both by perception and driving in 0% penetration rate were 2.4 sec and 2.72 sec respectively. When the ANOVA was performed between the 0% and 50% penetration rates of driving conditions, it was observed that there is a lot of variation in the mean headway gaps accepted. The values of average headway gaps accepted for young drivers were estimated as 2.36 sec and 1.53 sec respectively, in the 0% and 50% penetration rates. For the elderly drivers the average headway gap values observed were 2.72 sec and 1.55 sec respectively, in the 0% and 50% penetration rates traffic. The results also indicated the subject driver acceleration and deceleration behavior at the merge ramp. The results also showed that when the (aggressive) drivers accelerated to match the velocity of mainline traffic and merged in between connected-automated vehicles with the shortest gap, effects were noticed on the mainline traffic, where the main line traffic had to decelerate rapidly. Overall, it was observed that the subject drivers accepted shorter headway gaps as the penetration rates increases. / A Thesis submitted to the Department of Civil Engineering in partial fulfillment of the Master of Science. / Summer Semester 2017. / July 18, 2017. / Includes bibliographical references. / John O. Sobanjo, Professor Directing Thesis; Eren Erman Ozguven, Committee Member; Lisa Spainhour, Committee Member.
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Optimization of Alternative Wind Turbine Towers in Low Wind Resource RegionsUnknown Date (has links)
Taller wind turbines with big wheel area have been proposed for low wind speed sites, where conventional 80m tower cannot produce enough electricity. Hub height of 140m gives the potential to all 50 states to produce power from wind. However, it is not clear which tower (steel, concrete or hybrid) is economically attractive beyond 80m, or which design parameter is most critical in enabling tall yet economic tower. The aim of this paper is to come up with optimum designs for steel, concrete and hybrid towers while minimizing wind turbine cost and maximizing power production and then study the influence of changing one design variable on optimum designs. Also, it was of interest to study the effect of defining rotor dimeter of turbine as an independent design variable or as function of height. Multiple optimal solutions were obtained, which are called Pareto-optimal solutions. The design variables were chosen to be diameter, thickness, height of tower and blade radius. Design constraints were buckling, yielding, shear stresses for steel tower and ultimate and service limit states for the concrete tower. Those constraints have been used to control the stability of the tower. Different linear constraints have been applied for each tower, e.g. radius of the rotor should be less than the height of the tower. The design problem is conceptual design so detailed design is beyond scope of this research, such as the flange for the steel tower, connection between the concrete parts, and connection between the steel and concrete for the hybrid tower. Nonetheless, the cost of these parts was added to the design problem. Due to the highly constrained, non-convex and non-linear nature of the design problem, Genetic algorithm has been chosen as a solver for the problem. The towers were analyzed for operational and nonoperational aerodynamic conditions according to IEC 61400-1. A comparison of steel, concrete and hybrid towers was analyzed for heights ranging (80m-150m). Results showed that up to 95m, the cost difference was negligible between all towers options. Beyond 95m hybrid towers were dominating the solutions. For 150m hub height, concrete tower saved 12% when it is compared to its steel counterpart. Concrete base diameter decreases to less than 10m, industry preferred, when average concrete wall thickness was equal or greater than 0.4m or compressive strength of concrete increases. Increasing compressive strength of concrete by 10% also resulted in cost reduction of 2.18% for 150m hub height. Results showed that defining rotor diameter as a design variable was better than defining it as a function of height because the optimization problem had fewer constraints. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the Master of Science. / Summer Semester 2017. / June 19, 2017. / Genetic algorithm, Optimization, power, wind turbine tower / Includes bibliographical references. / Sungmoon Jung, Professor Directing Thesis; Michelle Rambo-Roddenberry, Committee Member; Lisa Spainhour, Committee Member.
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Risk-Benefit Analysis and Optimization of LEED-Certified School Buildings Design and Construction: Statisitical and Machine Learning Approaches / Risk-Benefit Analysis and Optimization of LEED-Certified School Buildings Design and Construction: Statistical and Machine Learning ApproachesUnknown Date (has links)
As the strategy of green building becomes more and more popular due to a combination of environmental and economic concerns, there develops a need for clearly being able to understand the potential implications for choosing green strategies over conventional building practices. Some of the regions of interest consist of the additional upfront costs associated with green practices, potential life-cycle benefits associated with green building components, potential energy savings, and the ability to reduce emissions. Many of these areas can potentially be forecasted with a fair degree of certainty (e.g. energy consumption, additional upfront costs); however, some elements of green building are less well defined. One such area consists of the ability of green buildings to improve the productivity and well-being of its inhabitants through an improved indoor environmental quality (IEQ). It is difficult to grasp just how much a healthier and cleaner environmental can impact a person’s cognitive functions, mental state, and physical health. Several studies shown in the literature review of this paper lead show a positive correlation between green buildings and reductions in asthma symptoms, depression symptoms, improved well-being due to reductions in contaminants, a reduction in sick building syndrome (SBS) and building related illness (BRI). This paper aims to do what many have done before in attempting to quantify the potential impact that sustainable buildings can have on its occupants; however, the scope and methods to determine these potential correlations will differ. Perhaps the most noticeable difference will be in the paper’s focus on attempting to measure the potential impact that LEED (Leadership in Energy and Environmental Design) accredited schools have on their student occupants by measuring their productivity via the use of standardized test scores and attendance rates compared to those students in conventional (non-LEED) schools. To develop a balanced analysis, the paper will control for various school-related and socio-economic factors (e.g. economic status, race, percent of teachers with a Master’s degree or higher). To make a judgement on the effect that sustainability has on academic achievement and student wellbeing, 2 sample t-tests, regression analysis, and M5P decision trees will be implemented to determine if there are significant differences between LEED and conventional schools and to determine the relationship between LEED and non-LEED parameters on student achievement and wellbeing metrics. To ensure that a large population of students from across the nation are accounted for, the study intends on investigating at least three states-worth of student data. These states (Florida, New York and Virginia) are in different climates, thus allowing for an examination of the potential differences between the various climate zones and building codes. Lastly, a case study building information model (BIM) of College Park Elementary School (located in Virginia) will be run through the energy modeling (EM) software, Ecotect, to provide information related to the school’s annual energy consumption, acoustics, and daylight and lighting values. An optimization equation, developed using previous literature and findings from this study, will use information from the case study in an attempt to optimize its academic performance. The equation will attempt to minimize construction and operational costs while maximizing student performance metrics. The optimization equation will be run through NEOS server’s Nonlinearly Constrained Optimization, Knitro. The purpose of this study is to inform those decision-makers involved in the construction of schools, and who may be interested in obtaining LEED certification for the school, to what extent the LEED schools benefit the school’s student academic achievement levels. Accounting for soft benefits (e.g. productivity, morale, general wellbeing) in a cost-benefit analysis invites an element of risk due to the difficulties in soliciting, obtaining, and accurately measuring these performance metrics. When considering fields involving knowledge work, accurately measuring productivity is an inexact science that normally requires building occupants to perform self-examinations. The results from these examinations are reliant on the occupant’s perceptions and could be open to bias. This study avoids self-assessments through its use of standardized testing as a measure for productivity. The proposed outcome of this paper is that the impacts of LEED schools on their occupants’ academic achievement, health, and wellbeing will be better understood and easier to quantify. The authors hypothesize that LEED schools will outperform conventional schools, which can be attributed to improved IEQ due to tighter building envelopes, increased ventilation rates, better filtration, a reduction in building or cleaning products containing volatile organic compounds, etc. An absence of this data could point to the inability of LEED schools to directly impact their students in a meaningful way, particularly its Indoor Environmental Quality credits, which means that LEED could have to rethink its standards if it wishes to truly improve the productivity and wellbeing of its occupants. / A Dissertation submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2018. / May 29, 2018. / Indoor Environmental Quality, LEED, Machine Learning, Optimization, Sustainable Design / Includes bibliographical references. / Walter Boot, University Representative; John O. Sobanjo, Committee Member; Lisa Spainhour, Committee Member.
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Impact of Connected and Autonomous Vehicles on Freeway Traffic OperationsUnknown Date (has links)
This project evaluates using traffic simulation, the performance of a mixed traffic composition of Connected and Autonomous Vehicles (CAV) and conventional or human-driven vehicles, in comparison with the performance of the existing traffic composition of only conventional vehicles on a freeway segment. The introduction of CAVs into the existing transportation system is a phase in the evolution of automobile traffic currently generating a lot of concerns and questions that needs to be answered before the full deployment of these vehicles. Traffic simulation presents a safer and cost-effective approach to evaluating this innovative technology when compared with real world testing. Connected and autonomous vehicles (CAV) are designed to improve traffic operations, as the difference in their driving behavior from regular vehicles suggests a reasonable tendency to change the traffic flow pattern. However the issue being examined in this project is whether there would be a significant change in traffic operations resulting from their deployment, and also to verify whether the change is an improvement of the existing traffic condition in terms of performance measures used for the evaluation. Data was collected from the I-95 Freeway in South Florida, and used in the development of a traffic microsimulation model, in VISSIM. The model was calibrated using minimum error algorithm implemented in MATLAB to determine the optimal value of the two model parameters considered -- stand still distance (CC0), and headway time (CC1). The calibrated model was used as the base model and CAVs are incorporated into the base model in 10% increment, to examine their effect on the base model. The performance measures are average hourly speed, hourly traffic volume, travel time, delay, and safety. Findings show that for every increment in CAV market penetration, there is a change of 6.52% - 48% in the capacity of the freeway, 40% reduction in travel time, more than 30% reduction in delay per vehicle, more than 26% increase in average speed of the traffic at high demand volumes. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2018. / July 9, 2018. / Connected technology, Freeway, VISSIM / Includes bibliographical references. / John O. Sobanjo, Professor Directing Thesis; Eren Erman Ozguven, Committee Member; Maxim Dulebenets, Committee Member.
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Accelerated Slab Replacement Using Temporary Precast Panels and Self Consolidating ConcreteUnknown Date (has links)
As it stands, many of Florida’s roads have already reached their designed service life and are now in the process of being renewed. The current method in rehabilitation of concrete pavement requires the expired piece of pavement to be cut and removed, place new dowel bars, and then epoxied into the surrounding slabs. Once the slab area has been prepared, fresh concrete is poured, and finished. The concrete is then cured and monitored to achieve a strength requirement of 2,200 psi in the shortest possible time before the lanes can be opened for traffic. This event has been known to take a long time and on major highways lane where lane closure may not exceed 8 hours. This restriction limits the number of slabs that can be replaced. The types of concrete used on these projects are also problematic. In the past, high amounts of cementitious material was used and this can lead to premature cracking. To improve production levels, accelerate construction time at a reduced cost, and provide long lasting pavement, the current research study presents an alternative method of using precast slab panels and self-consolidating concrete. This was accomplished by testing several SCC mixes in the laboratory to achieve concrete with high workability without, high early strength and without segregation. Then, precast panels were designed and built for quick installation and removal. This study also necessitated full scaled field tests where precast slab panels with the proper SCC mix were used. The slabs were tested by a loaded truck moving over it repeatedly and the slab was monitored for any movement and displacements caused by driving and braking on it. After the data was collected from the precast panels, the slabs were then removed and fresh SCC was then poured into the empty pit. The SSC slab was left to cure and the maturity of the concrete was monitored to achieve the required strength for lane opining. In this study, three techniques were used to monitor the concrete maturity. These techniques involved the use of the conventional thermocouples, thermal camera, and laser gun. The traffic load was then applied by driving a dump truck loaded to 25000 pounds over the track for 100 laps. The SCC mix behaved as designed and presented in this study. It achieved a high workability and retained a high slump for nearly an hour. It also exceeded the required FDOT strength requirement of 2200 psi for lane opening. The precast panels proved to be highly durable during the installation, testing, removal and can be reused for other similar applications. Results from this study proved proved that using this method has several benefits including greater productivity, reduced maintenance of traffic, shorter project completion time. Further, it may reduce the case of premature cracking due to the increase amount of curing time. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2018. / July 23, 2018. / Includes bibliographical references. / Kamal Tawfiq, Professor Directing Thesis; Michelle Rambo-Roddenberry, Committee Member; Lisa Spainhour, Committee Member; Raphael Kampmann, Committee Member.
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Analysis of Composite Timber Studs: An Optimization of Tall Wall StructuresUnknown Date (has links)
The National Design Specification for Wood Construction (NDS) outlines different factors and equations necessary for designing structures
exploiting timber. While analyzing a timber shear wall there are several specific equations and restraints that the design must satisfy. These
limitations come from not only the NDS, but also the Minimum Design Loads for Buildings and Other Structures (ASCE7), the Florida Building Code
(FBC), and the International Residential Code (IRC). ASCE7, paired with the NDS, provide a standard design methodology. The FBC and IRC focus
their framework around the minimum requirements. These manuals focus on the design strength of the individual components, rather than how they
react once affixed to one another. The sheathing is the foremost structural component which combats against the wind loads. Several different
types of sheathing, as well as nail sizes and patterns were analyzed as a connected structure. The methodology used was similar to that of
reinforced concrete, in that the properties of the nails and sheathing were transformed into that of the sawn lumber stud. This facilitated an
analytical comparison between the standard design method and that of a "composite I-beam". Increases and decreases in strength were found, due
to the complexity of the design equations, the addition of the sheathing component did not always enable a higher wall capacity. Deflection as
the ultimate failure of the member still rang true for the new method of design. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the
requirements for the degree of Master of Science. / Fall Semester 2018. / November 6, 2018. / Includes bibliographical references. / Michelle Rambo-Roddenberry, Professor Directing Thesis; Sungmoon Jung, Committee Member; Raphael Kampmann,
Committee Member; Lisa Spainhour, Committee Member.
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Biomechanics of Older Drivers in Vehicular CrashesUnknown Date (has links)
The aging population is expected to increase substantially in the future. The fatal crash rates (per mile traveled) involving older
drivers (65+) are considerably higher than those of younger drivers. This research involved conducting computational experiments involving
dummy models to investigate the biomechanics of older drivers in vehicular crashes. Before conducting these experiments, the concepts of
biological changes in older populations needed to be addressed. This allowed us to first find out what makes the older drivers different from
younger drivers. It was found that driving posture is one of the two key differences between the two age groups. The Hybrid III computational
dummy model was used to investigate the effect of driving posture. The other key finding shows that older drivers are affected by aging
factors such as material properties decrease and thickness decrease of bones. The Total Human Model for Safety (THUMS) was used because it
can be modified to represent an aged driver to be used in the crash simulations. For the posture investigation, the idea is that driving
posture for older drivers tend to be closer to the steering wheel whereas younger drivers are more laid back was incorporated. All
computational work was completed in LS-DYNA; a finite element code used for non-linear impact analysis. The Finite Element (FE) simulation
was validated by comparing the FE results with physical crash test results. These results were found in the Federal Motor Vehicle Safety
Standards and Regulations (FMVSS) Report 208 for Frontal Crash Test. For subsequent simulations, posture changes based on the idea of aging
according to literature review were implemented. For the Head Injury Criteria, the extended shoulders of an older driver yielded percent
differences as high as 16%. The arms acted like braces to restrain the torso while the head continued forward. The extended knees also
yielded a 16% increase in head injury. As for the chest acceleration, the extended hip and torso joints showed increased values. It was
concluded that sitting closer was beneficial for the Head Injury Criteria but the opposite was true for the chest acceleration. The posture
changes did not affect the pelvis acceleration. This investigation gave us a better understanding of what occurs in automobile accidents
specific to older occupants. This knowledge can be useful in designing engineering approaches to mitigate injuries. Using the aged model, the
material properties decrease yielded the highest chest deflection of 13.3%. For the bone thickness decrease, the chest acceleration showed
the highest increase of 12.5%. The head acceleration and chest deflection showed noticeable increases. Overall with all three aging factors
in place, the head and chest accelerations yielded high increases. Whereas for the deflection, it remains the same. The thoracic rotation
increased the head resultant acceleration. The rotation decreased the deflection of the thorax because the ribs were more in line with the
force imposed by the crash. It can withstand more force when the ribs are more parallel with the force. As for the chest acceleration, no
significant change was present. It can be concluded that the older drivers in rear impacts experienced higher (Neck Injury Criterion) NICmax
than younger drivers as much as 6.9% percent for the material property decrease and bone thickness decrease. The thorax rotation yielded a
4.7% decrease in NICmax. It is possible that this aging factor caused the thorax to conform more into the seatback thus reducing the injury.
The bone thickness decreased affected the NICmax greatly whereas the material property decreased did show signs of minimal positive
influence. The material property decreased yielded 0.8% increase while the thickness decreased yielded a 3.0% increase. / A Dissertation submitted to the Department of Civil and Environmental Engineering in partial fulfillment of
the requirements for the degree of Doctor of Philosophy. / Fall Semester 2017. / November 8, 2017. / Includes bibliographical references. / Sungmoon Jung, Professor Directing Dissertation; Changchun Zeng, University Representative; John
Sobanjo, Committee Member; Kamal Tawfiq, Committee Member.
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Effect of Friction on Vehicle Crashworthiness during RolloverUnknown Date (has links)
The State of Florida acquires over 300 cutaway buses every year. The increasing popularity of such buses raised concerns about passenger safety and overall crashworthiness of this
transportation mode. Dimensions of the cutaway buses and their two-stage manufacturing process made them exempted from safety standards which were developed for smaller passenger cars as
well as for large coaches. To fill this gap, cutaway bus manufacturers try to demonstrate the strength of their bus roof structures by using FMVSS 220 standard, which follows conservative
quasi-static load tests for school buses in the US. However, more advanced, dynamic based safety standard - Regulation 66, was developed in Europe. It is based on a dynamic rollover test
which more closely resembles an actual rollover accident. A cutaway bus is placed on a tilt table 800 mm above a concrete slab. The bus is tilted until it falls and impacts the concrete
deck and the deformation of the sidewalls is measured in order to check if there is any intrusion into a so called 'survival space'. This standard was endorsed by 44 countries through the
United Nation resolution. However, the Regulation 66 standard does not specify all the parameters regarding the rollover test. From multiple tests it can be observed that the friction
between the vehicle and the concrete slab which is being impacted by the bus has an influence on the outcomes of the experiment and has great contribution to either a positive or negative
assessment of the crashworthiness of a tested vehicle. This Master thesis focuses on the friction parameters between the impacting cutaway bus and a concrete slab used in the Regulation 66
standard. Due to dynamic nature of the experiment, the impact of the bus exerts a high normal force on the concrete slab. Together with an uneven and non-standard geometry of the elements
in contact with the concrete deck the standard coefficient of friction found in the literature or obtained using standard tests may not hold. The proper assessment of this coefficient is
important since many rollover tests are carried out numerically using Finite Element Methods. The use of numerical analysis reduces the cost of an expensive full scale rollover test.
However, it requires verified and validated parameters in order to consider the results trustworthy. The experimental part of this thesis consists of designing and carrying out experiments
to evaluate the coefficient of friction for an impacting cutaway bus and a concrete slab. The results from the experiments are incorporated into an explicit computer code LS-DYNA, which is
used for numerical analysis of the cutaway buses. The final outcome of this thesis will be validating the coefficient of friction used in the Finite Element Analysis which will lead to
improvement of the Finite Element models and will be used to check the influence of the coefficient of friction on vehicle structure deformation (Deformation Index) during rollover
accidents. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the Master of Science. / Fall Semester 2015. / November 5, 2015. / coefficient of friction, crashworthiness, structure deformation, vehicle rollover / Includes bibliographical references. / Sungmoon Jung, Professor Directing Thesis; Michelle Rambo-Roddenberry, Committee Member; Lisa Spainhour, Committee Member; Jerry W. Wekezer, Committee
Member.
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Judicial discretion and contempt power : two elements of equity that would benefit the EAPO and future EU-wide provisional and protective measuresKyriakides, Nicolas January 2016 (has links)
A person filing a civil claim faces the risk of being unable to enforce a favourable judgment. This is because their opponent may dissipate his assets and consequently be unable to satisfy a judgment given against him. Several mechanisms seek to alleviate this risk by preserving the defendant's assets pending judgment. These are predominantly the civilian in rem order and the common law freezing order. Fundamental differences between the common and civil law traditions may be observed in the freezing order and its civilian counterpart. Primarily, these are to be found in the margin of discretion given to the judge and the sanctions against non-compliance. The latter issue is closely related to the entity against which an order is directed: in the common law it is directed against the person, while in the civil law, against the asset. The significantly diverse approaches in these areas show the different course each of the legal families has taken in the administration of justice. The problem of preserving assets pending judgment becomes more complicated when the assets are not located in the same country as the courts with jurisdiction on the merits. The recently introduced European Account Preservation Order (âEAPO') regulation is a pre-judgment instrument which enables a litigant to obtain an order preventing the transfer of funds held by the respondent in a bank account within the EU. It is the first of what may become several EU-wide provisional and protective measures. At first glance, the EAPO resembles the continental model rather than its common law counterpart, and, thus, brings into the open the differences between the two traditions in the area of provisional and protective measures. This work examines whether the features of the common law tradition - which in fact derive from the law of equity - ie judicial discretion in granting or refusing relief and contempt of court sanctions, could improve the EAPO as well as other EU-wide provisional and protective measures that may follow. It is argued that greater judicial discretion and a contempt sanction, provided that they are kept within certain limits, would improve the EAPO and similar measures in terms of efficiency and fairness.
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Accelerated Slab Replacement Using Temporary Precast Panels and Self Consolidating ConcreteUnknown Date (has links)
As it stands, many of Florida’s roads have already reached their designed service life and are now in the process of being renewed. The current method in rehabilitation of concrete pavement requires the expired piece of pavement to be cut and removed, place new dowel bars, and then epoxied into the surrounding slabs. Once the slab area has been prepared, fresh concrete is poured, and finished. The concrete is then cured and monitored to achieve a strength requirement of 2,200 psi in the shortest possible time before the lanes can be opened for traffic. This event has been known to take a long time and on major highways lane where lane closure may not exceed 8 hours. This restriction limits the number of slabs that can be replaced. The types of concrete used on these projects are also problematic. In the past, high amounts of cementitious material was used and this can lead to premature cracking. To improve production levels, accelerate construction time at a reduced cost, and provide long lasting pavement, the current research study presents an alternative method of using precast slab panels and self-consolidating concrete. This was accomplished by testing several SCC mixes in the laboratory to achieve concrete with high workability without, high early strength and without segregation. Then, precast panels were designed and built for quick installation and removal. This study also necessitated full scaled field tests where precast slab panels with the proper SCC mix were used. The slabs were tested by a loaded truck moving over it repeatedly and the slab was monitored for any movement and displacements caused by driving and braking on it. After the data was collected from the precast panels, the slabs were then removed and fresh SCC was then poured into the empty pit. The SSC slab was left to cure and the maturity of the concrete was monitored to achieve the required strength for lane opining. In this study, three techniques were used to monitor the concrete maturity. These techniques involved the use of the conventional thermocouples, thermal camera, and laser gun. The traffic load was then applied by driving a dump truck loaded to 25000 pounds over the track for 100 laps. The SCC mix behaved as designed and presented in this study. It achieved a high workability and retained a high slump for nearly an hour. It also exceeded the required FDOT strength requirement of 2200 psi for lane opening. The precast panels proved to be highly durable during the installation, testing, removal and can be reused for other similar applications. Results from this study proved proved that using this method has several benefits including greater productivity, reduced maintenance of traffic, shorter project completion time. Further, it may reduce the case of premature cracking due to the increase amount of curing time. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2018. / July 23, 2018. / Includes bibliographical references. / Kamal Tawfiq, Professor Directing Thesis; Michelle Rambo-Roddenberry, Committee Member; Lisa Spainhour, Committee Member; Raphael Kampmann, Committee Member.
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