Concrete substructures are often subjected to environmental deterioration, such as sulfate and acid attack, which leads to severe damage and causes structure degradation or even failure. In order to improve the durability of concrete, the High Performance Concrete (HPC) has become widely used by partially replacing cement with pozzolanic materials. However, HPC degradation mechanisms in sulfate and acidic environments are not completely understood. It is therefore important to evaluate the performance of the HPC in such conditions and predict concrete service life by establishing degradation models. This study began with a review of available environmental data in the State of Florida. A total of seven bridges have been inspected. Concrete cores were taken from these bridge piles and were subjected for microstructural analysis using Scanning Electron Microscope (SEM). Ettringite is found to be the products of sulfate attack in sulfate and acidic condition. In order to quantitatively analyze concrete deterioration level, an image processing program is designed using Matlab to obtain quantitative data. Crack percentage (Acrack/Asurface) is used to evaluate concrete deterioration. Thereafter, correlation analysis was performed to find the correlation between five related variables and concrete deterioration. Environmental sulfate concentration and bridge age were found to be positively correlated, while environmental pH level was found to be negatively correlated. Besides environmental conditions, concrete property factor was also included in the equation. It was derived from laboratory testing data. Experimental tests were carried out implementing accelerated expansion test under controlled environment. Specimens of eight different mix designs were prepared. The effect of pozzolanic replacement rate was taken into consideration in the empirical equation. And the empirical equation was validated with existing bridges. Results show that the proposed equations compared well with field test results with a maximum deviation of ± 20%. Two examples showing how to use the proposed equations are provided to guide the practical implementation. In conclusion, the proposed approach of relating microcracks to deterioration is a better method than existing diffusion and sorption models since sulfate attack cause cracking in concrete. Imaging technique provided in this study can also be used to quantitatively analyze concrete samples.

Variable Speed Limit (VSL) strategies identify and disseminate dynamic speed limits that are determined to be appropriate based on prevailing traffic conditions, road surface conditions, and weather conditions. This dissertation develops and evaluates a shockwave-based VSL system that uses a heuristic switching logic-based controller with specified thresholds of prevailing traffic flow conditions. The system aims to improve operations and mobility at critical bottlenecks. Before traffic breakdown occurrence, the proposed VSL’s goal is to prevent or postpone breakdown by decreasing the inflow and achieving uniform distribution in speed and flow. After breakdown occurrence, the VSL system aims to dampen traffic congestion by reducing the inflow traffic to the congested area and increasing the bottleneck capacity by deactivating the VSL at the head of the congested area. The shockwave-based VSL system pushes the VSL location upstream as the congested area propagates upstream. In addition to testing the system using infrastructure detector-based data, this dissertation investigates the use of Connected Vehicle trajectory data as input to the shockwave-based VSL system performance. Since the field Connected Vehicle data are not available, as part of this research, Vehicle-to-Infrastructure communication is modeled in the microscopic simulation to obtain individual vehicle trajectories. In this system, wavelet transform is used to analyze aggregated individual vehicles’ speed data to determine the locations of congestion. The currently recommended calibration procedures of simulation models are generally based on the capacity, volume and system-performance values and do not specifically examine traffic breakdown characteristics. However, since the proposed VSL strategies are countermeasures to the impacts of breakdown conditions, considering breakdown characteristics in the calibration procedure is important to have a reliable assessment. Several enhancements were proposed in this study to account for the breakdown characteristics at bottleneck locations in the calibration process. In this dissertation, performance of shockwave-based VSL is compared to VSL systems with different fixed VSL message sign locations utilizing the calibrated microscopic model. The results show that shockwave-based VSL outperforms fixed-location VSL systems, and it can considerably decrease the maximum back of queue and duration of breakdown while increasing the average speed during breakdown.

El aumento de la flota, debido al desarrollo económico del país en la última década, ha generado problemas y dificultades que presentan los usuarios al momento de conducir en las calles de ciudades de todo el territorio nacional. Este conflicto no es ajeno al distrito de Lince, uno de los principales objetivos de este proyecto es llevar a cabo un análisis del problema existente en una de las intersecciones más concurridas de Lince con la ayuda de modelos de microsimulación y mesosimulación adecuados. Por otro lado, las instituciones y / o las empresas de construcción o consultoras que realizan proyectos de viales deben crear modelos computacionales o analíticos como parte fundamental de la etapa de diseño. Sin embargo, con el objetivo de ahorrar o por desconocimiento, realizan simulaciones mesoscópicas o macroscópicas, sin considerar que sus parámetros y ecuaciones son menos exactos que un modelo microscópico. Consistentemente, los resultados obtenidos no han sido correctos, debido a las características observadas en nuestra intersección, como presencia de vehículos pesados, estilo de manejo de conductores, numerosas paradas de transporte público, etc., para evaluar hasta qué punto es eficiente usar un modelo mesoscópico y evitar los tiempos computacionales de un modelo microscópico, se realizará un análisis comparativo de los resultados del Vissim, bajo la metodología de HCM 2010, en una intersección del distrito de Lince y así, optar por un rediseño semafórico coordinado para el cruce de la intersección que mejore el nivel de servicio como para las demoras, en la intersección estudiada. / The increase in the fleet, due to the economic development of the country in the last decade, has generated problems and difficulties that users present when driving on the streets of cities throughout the national territory. This conflict is not alien to the Lince district, one of the main objectives of this project is to carry out an analysis of the existing problem in one of the busiest intersections of Lince with the help of suitable microsimulation and mesosimulation models. On the other hand, institutions and / or construction or consulting companies that carry out road projects must create computational or analytical models as a fundamental part of the design stage. However, with the aim of saving or due to ignorance, they carry out mesoscopic or macroscopic simulations, without considering that their parameters and equations are less exact than a microscopic model. Consistently, the results obtained have not been correct, due to the characteristics observed in our intersection, such as the presence of heavy vehicles, driving style of drivers, numerous public transport stops, etc., to evaluate to what extent it is efficient to use a model In order to avoid the computational times of a microscopic model, a comparative analysis of the Vissim results will be carried out, under the HCM 2010 methodology, at an intersection of the Lince district and thus, opt for a coordinated traffic light redesign for the intersection of the intersection that improves the level of service as well as for delays, in the studied intersection. / Tesis

This Master thesis was created as research for project GA 102/09/1897 Security in car traffic - BAD, which is i.a. considers testing of continuousness of traffic with dynamically updated navigation. Main goal of project is simulator of traffic infrastructure creation. Simulators are two. One of them evaluate trafiic flow on bigger network of roads and crossroads. Second one simulate behaviour of cars during passage of crossroads. In this project is as well parsed theory of traffic activity and mentioned theoretical principles on which are built both simulators.

The aim of this thesis is to observe behavior of traffic flow and to verify or refute traditional so called fundamental relationships. It analyze data based on older measurements, personal measurements executed on the I/43 road, and mathematical models.There were three tools used provided by "VUT" in Brno as well as own developed tool based on cellular automat..

Cette thèse porte sur l’analyse et l’homogénéisation d’équations aux dérivées partielles (EDP) posées sur des réseaux avec des applications en trafic routier. Deux types de travaux ont été réalisés : le premier axe de travail consiste à considérer des modèles microscopiques de trafic routier et d’établir une connexion entre ces modèles et des modèles macroscopiques du genre de ceux introduit par Imbert et Monneau [1]. Une telle connexion va permettre de justifier rigoureusement les modèles macroscopiques du trafic routier. En effet, les modèles microscopiques décrivent la dynamique de chaque véhicule individuellement et sont donc plus faciles à justifier du point de vue modélisation. Par contre, ces modèles ne sont pas utilisables pour décrire le trafic à grande échelle (des villes par exemple). Les modèles macroscopiques font le jeu inverse : ils sont fort pour décrire le trafic à grande échelle mais du point de vue modélisation, ils sont compliqués à mettre en œuvre pour prédire toutes les situations du trafic (par exemple trafic libre ou congestionné). Le passage du microscopique au macroscopique est fait en s’appuyant sur la théorie des solutions de viscosité et en particulier les techniques d’homogénéisation. Le second axe consiste à considérer une équation d’Hamilton-Jacobi avec une jonction qui bouge en temps. Cette équation peut décrire la circulation des voitures sur une route avec la présence d’un véhicule particulier (plus lent que les voitures par exemple). On prouve l’existence et l’unicité (par un principe de comparaison) d’une solution de viscosité pour cette EDP. [1] Cyril Imbert and Régis Monneau. Flux-limited solutions for quasi-convex hamilton-jacobi equations on networks. Annales Scientifiques de l’ENS, 50(2) :357–448, 2013. / This thesis deals with the analysis and homogenization of partial differential equations (PDE) posed on networks with application to traffic. Two types of work are done : the first line of work consists to consider microscopic traffic models in order to establish a connection between these models and macroscopic models like the one introduced by Imbert and Monneau [1]. Such connection allows to justify rigorously the macroscopic models of traffic. In fact, microscopic models describe the dynamic of each vehicle individually and so they are easy to justify from the modelization point of view. On the other hand, these models are complicated to implement in order to describe the traffic at large scales (cities for example). Macroscopic models do the opposite : they are effective for describing the traffic at large scales but from the modelization point of view, they are incapable to predict all traffic situations (for example free or congested flow). The passage from microscopic to macroscopic is done using the viscosity solutions theory and in particular homogenization technics. The second line of work consists to consider a Hamilton-Jacobi equation coupled by a junction condition which moves in time. This equation can describe the circulation of cars on a road with the presence of a particular vehicle (slower than the cars for example). We prove existence and uniqueness (by a comparison principle) of viscosity solution of this PDE. [1] Cyril Imbert and Régis Monneau. Flux-limited solutions for quasi-convex hamilton-jacobi equations on networks. Annales Scientifiques de l’ENS, 50(2) :357–448, 2013.

Magneto-sensitive elastomers (MSEs) establish a special class of smart materials, which are able to change their shape and mechanical behavior under external magnetic field. Nowadays, MSEs are one of the most perspective smart materials, since they can be used for design of functionally integrated lightweight structures in sensors, robotics, actuators and damper applications. MSEs typically consist of micron-sized magnetizable particles (e.g. carbonyl iron) dispersed within a non-magnetic elastomeric matrix. The spatial distribution of magnetic particles in MSEs can be either isotropic or anisotropic, depending on whether they have been aligned by an applied magnetic field before the cross-linking of the polymer. Depending on the magnetic properties of the particles, their shape, size and spatial distribution, the MSEs can exhibit different mechanical behavior. Most experimental studies show that MSEs with isotropic distribution of magnetic particles demonstrate a uniaxial expansion along the magnetic field. On the other side, it was shown experimentally that MSEs with anisotropic particle distributions demonstrate a uniaxial contraction along the magnetic field. Also, the experimental works show that the shear moduli of MSEs increase with increasing strength of the magnetic field and depend on the magnetic properties, volume fraction and spatial distribution of particles. Different analytical approaches were used in theoretical studies of the mechanical behavior of MSEs. They can be roughly classified as phenomenological, continuum-mechanics and microscopic approaches. In the phenomenological approaches, the expansion into a series of the shear modulus as a function of the strength of the magnetic field has been proposed, the coefficients of the expansion being considered as phenomenological fitting parameters. In the continuum-mechanics approach, an MSE is considered as continuous magnetic media. It allows us to determine the shape and the change in volume of a spherical MSE sample, placed in a uniform magnetic field. However, this approach is restricted to homogeneous particle distributions. The microscopic approach has a clear advantage, while a discrete particle distribution and pair-wise interactions between induced magnetic dipoles can be considered explicitly. The aim of the present work is to develop a microscopic theory, which properly describes the mechanical behavior of MSEs in the external magnetic field. The theory takes a microscopic structure, finite shape of the samples and magneto-mechanical coupling between particle positions and sample deformation explicitly into account.

Many car-following models predict a stable car-following behavior with a very small fluctuation around an equilibrium value g* of the net headway g with zero speed-difference Δv between the following and the lead vehicle. However, it is well-known and additionally demonstrated by data in this paper, that the fluctuations are much larger than these models predict. Typically, the fluctuation in speed difference is around ±2m/s, while the fluctuation in the net time headway T=g/v can be as big as one or even two seconds, which is as large as the mean time headway itself. By analyzing data from loop detectors as well as data from vehicle trajectories, evidence is provided that this randomness is not due to driver heterogeneity, but can be attributed to an internal stochasticity of the driver itself. A final model-based analysis supports the hypothesis, that the preferred headway of the driver is the parameter that is not kept constant but fluctuates strongly, thus causing the even macroscopically observable randomness in traffic flow.

The Macroscopic Fundamental Diagram (MFD) describes the relation of average network flow, density and speed in urban networks. It can be estimated based on empirical or simulation data, or approximated analytically. Two main analytical approximation methods to derive the MFD for arterial roads and urban networks exist at the moment. These are the method of cuts (MoC) and related approaches, as well as the stochastic approximation (SA). This paper systematically evaluates these methods including their most recent advancements for the case of an urban arterial MFD. Both approaches are evaluated based on a traffic data set for a segment of an arterial in the city of Munich, Germany. This data set includes loop detector and signal data for a typical working day. It is found that the deterministic MoC finds a more accurate upper bound for the MFD for the studied case. The estimation error of the stochastic method is about three times higher than the one of the deterministic method. However, the SA outperforms the MoC in approximating the free-flow branch of the MFD. The analysis of the discrepancies between the empirical and the analytical MFDs includes an investigation of the measurement bias and an in-depth sensitivity study of signal control and public transport operation related input parameters. This study is conducted as a Monte-Carlo-Simulation based on a Latin Hypercube sampling. Interestingly, it is found that applying the MoC for a high number of feasible green-to-cycle ratios predicts the empirical MFD well. Overall, it is concluded that the availability of signal data can improve the analytical approximation of the MFD even for a highly inhomogeneous arterial.

This research is concerned with the modeling and development of algorithmic approaches for solving airport operational problems that arise in Air Traffic Control (ATC) systems within the terminal area at hub airports. Specifically, the problems addressed include the Aircraft Sequencing Problem (ASP) for runway operations, the Network Assignment Problem (NAP) for taxiway operations, and a simulation model for the evaluation of current or proposed ATC system in detail. For the ASP, we develop a mathematical model and apply the Reformulation-Linearization-Technique (RLT) of Sherali and Adams to construct an enhanced tightened version of the proposed model. Since ASP is NP-Hard and in fact, it is a variation of the well-known Traveling Salesman Problem with time-windows, sub-optimal solutions are usually derived to accommodate the real-time constraints of ATC systems. Nevertheless, we exhibit a significant advancement in this challenging class of problem. Also for the purpose of solving relatively large sized problems in practice, we develop and test suitable heuristic procedures. For the NAP, we propose a quasi-dynamic assignment scheme which is based on the incremental assignment technique. This quasi-dynamic assignment method assumes that the current aircraft route is influenced only by the previous aircraft assigned to the network. This simplified assumption obviates the need for iterative rerouting procedures to reach a pure equilibrium state which might not be achievable in practical taxiway operations. To evaluate the overall system, we develop a microscopic simulation model. The simulation model is designed to have the capability for reproducing not only the dynamic behavior of aircraft, but also incorporates communication activities between controllers and pilots. These activities are critical in ATC operations, and in some instances, might limit the capacity of the facility. Finally, using the developed simulation model named Virginia Tech Airport Simulation Model (VTASM) in concert with ASP and NAP, we compare the overall efficiencies of several control strategies, including that of the existing control system as well as of the proposed advanced control system. / Ph. D.