Die Dimensionierung einer Betonfahrbahn zielt darauf ab, den Anteil der im Nutzungszeitraum versagenden Platten auf ein akzeptables Maß zu begrenzen. Der Anteil ausgefallener Platten entspricht der Versagenswahrscheinlichkeit der einzelnen Platte. Damit ergibt sich die Notwendigkeit, die Versagenswahrscheinlichkeit zu berechnen. Innerhalb der vorliegenden Arbeit werden grundlegende Methoden und Verfahrensweisen zur Lösung dieser Aufgabe entwickelt. Es wird gezeigt, wie die für die Quantifizierung der Versagenswahrscheinlichkeit entscheidenden Streuungen der Einflussgrößen mathematisch beschrieben und im Dimensionierungsverfahren berücksichtigt werden können. Dabei wird regelmäßig Bezug genommen auf das in Deutschland eingeführte Dimensionierungsmodell der RDO Beton [2]. Die Grundlage für die Berechnung der Versagenswahrscheinlichkeit liefern die Methoden der Statistik und Wahrscheinlichkeitsrechnung, sowie der Zuverlässigkeitstheorie. Es wird gezeigt, dass sowohl die mathematisch exakte Lösung, wie auch verschiedene Näherungsverfahren für die Problematik der Betonfahrbahnen anwendbar sind. Näher untersucht werden die Zuverlässigkeitstheorie 1. Ordnung (FORM) sowie die Monte-Carlo-Methode. Die jeweiligen Vor- und Nachteile werden analysiert. Es zeigt sich, dass für die Anwendung des FORM-Algorithmus das Berechnungsmodell der RDO Beton modifiziert werden muss. Der zeitliche Bezug der Berechnung kann über die Benutzung von Extremwertverteilungen, die Modellierung stochastischer Prozesse oder die Einführung einer Schadensakkumulationshypothese hergestellt werden. Besondere praktische Bedeutung hat die Berechnung der Versagenswahrscheinlichkeit für den Nutzungszeitraum mit zeitlich varianten Bedingungen. Für diesen Fall werden vier verschiedene Lösungsansätze aufgezeigt. Um die teilweise sehr hohen Rechenzeiten zu minimieren, werden Näherungslösungen entwickelt. Die praktische Eignung wird mit beispielhaften Berechnungen demonstriert. Es zeigt sich, dass die Berechnungsergebnisse stark davon abhängen, wie sich die Werte einzelner Parameter über den Nutzungszeitraum entwickeln. Die betreffenden zeitlichen Verlaufsfunktionen sind gegenwärtig nur unzureichend bekannt. Um eine hinreichend verlässliche Prognose zu berechnen, sind alle Berechnungsverfahren möglichst objektbezogen zu kalibrieren. / The dimensioning of a concrete pavements aims to limit the percentage of failing slabs to an acceptable level. The proportion of failed slabs corresponds to the probability of failure of each slab. This results in the need to calculate the probability of failure. Within the present work, basic methods and procedures for solving this problem are being developed. It is shown how the variations of parameters can be mathematically described and considered in the dimensioning process. Reference is frequently made to the model of RDO Beton [2]. The methods of statistics and probability theory, and reliability theory provide the basis for calculating the probability of failure. It is shown that both the mathematically exact solution and various approximation methods as well are applicable to the problem of concrete pavements. Be examined more closely the reliability theory 1st order (FORM) and Monte Carlo method. The respective advantages and disadvantages are analyzed. It turns out that the calculation model of the RDO concrete has to be modified for the use of FORM algorithm. The temporal relation of the calculation can be made on the use of extreme value distributions, modeling of a stochastic process or the introduction of a damage accumulation hypothesis. Particular practical significance has to calculate the probability of failure for the period of use with time-variant conditions. In this case, four different approaches are discussed. Approximate solutions to minimize the sometimes very high computation times has been developed. The practical suitability is demonstrated by exemplary calculations. It turns out that the calculation results depend strongly on how to develop the values of individual parameters over the period of use. These time course functions are insufficiently known at present. To calculate a sufficiently reliable forecast, all calculation methods are possible to calibrate object-related.

The negative impacts associated with highway pavement rehabilitation projects drove state highway agencies (SHAs) towards increased adoption of alternative contracting methods (ACMs) to accelerate the construction of such projects; hence, reducing these impacts on the travelling public. However, the application of such methods showed mixed results due to the lack of specific guidelines addressing the adoption of such methods and the selection of the best ACM for each project. This lack of guidelines stems from the lack of research studies examining the impact of each of these methods on the time/cost trade-off relationship in highway rehabilitation projects. Existing literature includes several studies aimed at developing generic and subjective guidelines based on past experiences that do not take into consideration the unique nature of each of these methods. Hence, this research study aimed at analyzing the SHAs’ decision making process regarding two of the most-widely used ACMs: Incentive/Disincentive (I/D) and Cost + Time (A+B) contracting methods, in order to support decision makers in choosing the most-suitable method for their projects. To this end, two models were developed in this dissertation to examine the time/cost trade-off for each method using simulation and regression analysis. Each model was validated against real-life projects and used to assign appropriate ID and “B” values based on the SHA’s desired duration reduction and available budget. Furthermore, a risk analysis module was developed to determine the most-likely duration reduction that the contractor can achieve for each project under each method. The developed models should help improve the decision making process regarding the selection and implementation of these methods in highway rehabilitation projects. For example, the models can help SHAs identify the minimum ID level that can be offered for each project and the expected duration that the contractors can bid on under the A+B contracting method. Finally, the models were contrasted and applied to real-life projects with different characteristics to verify existing guidelines and establish the candidate ACM for each project category. The findings of this study will benefit the society, SHAs, and the economy in general by optimizing the use of available time and money resources.

Despite the widespread recycling of Reclaimed Asphalt Pavement (RAP), a large portion of it is still wasted. One of the main reasons is the concern with the performance of high RAP mixtures. Asphalt binder aging and subsequent rejuvenation is one source of uncertainty. Rejuvenators are frequently added to high RAP mixes to enhance the properties of the binder. This enhancement is often perceived as simply lowering the viscosity. Two important parameters that are not adequately addressed by existing methods are durability and homogeneity of the recycled binder. This research investigated these two concerns and provided quantitative indicators to measure them. The durability of rejuvenated binders was investigated through studying their long-term aging. Superpave PG tests and aging procedures were used for this purpose. Results indicated that the type and dosage of the rejuvenator has a significant impact on the aging of a rejuvenated binder. While using a proper rejuvenator can prolong the life of the binder, choosing a wrong product causes the binder to age significantly faster. The asphalt film that coats aggregates is not necessarily homogeneous. Different layers of the film are affected differently by aging and rejuvenation processes. A staged extraction method was implemented to provide representative samples from the different layers of asphalt. The stiffness of each sample was measured by Dynamic Shear Rheometer testing. Results indicated that most of the rejuvenator is absorbed by outer layers immediately after blending. As the mixture ages, the rejuvenator continues diffusing into the inner layers. Outer layers are also affected more intensely by the aging. The coupled effects of aging and rejuvenation make the recycled binder more homogeneous than virgin asphalt. This property can facilitate the use of higher target PG values for recycled binders without compromising the long-term performance. This research introduces two quantitative measures, critical PAV time and Durability Index, for evaluating the durability of recycled binders and two other parameters, Stiffness Gradient Factor and Homogeneity Index for describing the binder film homogeneity. These indicators and the knowledge obtained from this research make it possible to design and evaluate the binder rejuvenation process in a more effective manner.

Dowel bars are provided at the transverse joints of the Jointed Plain Concrete Pavement (JPCP) to transfer the load between adjoining slabs and to allow for expansion and contraction of the pavement due to temperature and moisture changes. The current study involved evaluation of the performance of Glass Fibre Reinforced Polymer (GFRP) dowels in JPCP as an alternative to the conventional epoxy-coated steel dowel bars, especially in the presence of dowel misalignment. This research involved two main sets of experimental tests. The first set focused on the evaluation of load-deflection response of GFRP dowels using a scaled model of pavement slabs. The second set investigated the combined effect of dowel misalignment and cyclic wheel load on the performance of steel and GFRP dowels. The tested slabs (in the second set) were supported on a steel-beam base with stiffness such that the effects of the underlying layers of real pavements are incorporated. In both of these sets of experiment the GFRP dowels were compared with the steel dowels of similar flexural rigidity. The research also involved detailed numerical investigations using ABAQUS for all experimental tests in the current study. The validated numerical model was used to conduct three sets of parametric studies: to propose design considerations for the GFRP dowels; to simulate all important cases of dowel misalignment (111 cases) for steel and GFRP dowels and to give an insight into the damaged volume in the surrounding concrete pavement; and to investigate the effects of diameter, length and type of dowel bar, concrete grade, pavement thickness, and slab-base friction on the joint-opening behaviour. The results from the first set of experiments showed that the 38 mm GFRP dowels perform better in terms of deflection response compared to the 25 mm steel dowels. Also, it was observed that the relative deflection (RD) is more sensitive to the changes in the joint width rather than the concrete strength. The numerical results from the first set showed a good agreement with the experimental results and showed lower magnitude and better distribution of stress in the concrete underneath the GFRP dowels as compared with the steel dowels. Finally, on the basis of a detailed parametric study (70 different cases), design considerations for GFRP dowels in JPCP were suggested. The second set of experimental results showed that the GFRP dowels can withstand a cyclic traffic load and significantly reduce joint lockup and dowel looseness (DL) and can provide sufficient load transfer efficiency (LTE). It was also observed that the dowel misalignment affects DL significantly more than the repeated traffic load. Slab-base separation and the orientation of misaligned dowels have significant effects on the pull-out load required to open the joint. The numerical results from the second set indicated that the pull-out load was small for the vertical misalignment cases compared to the horizontal and combined misalignment cases. The results also indicated the occurrence of concrete spalling and deterioration at smaller joint openings for combined misalignment when compared to other misalignment types. The use of GFRP dowels significantly reduced the pull-out load and joint lockup when dowel misalignment exists. Consequently, the deterioration of the surrounding pavement substantially decreased. The long term performance of the JPCP fitted with GFRP dowels improves because of a reduction in the DL and the RD, and by maintaining a good LTE even for misaligned dowels. The numerical results also showed that the pull-out load increases significantly for an increase in the concrete compressive strength and the dowel bar diameter. Small increase in pull-out load was observed for higher embedded length of the dowel bar, whereas the increase was insignificant for an increase in the pavement thickness and slab-base friction. In general, the study showed the GFRP dowel can be a potential alternative for the conventional steel dowel bars in JPCP.

Orientador: Cassio Eduardo Lima de Paiva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-24T08:58:58Z (GMT). No. of bitstreams: 1 Watanabe_JulianaSilva_M.pdf: 2195811 bytes, checksum: 47a972a34bbdd51a602e9d71d473ff40 (MD5) Previous issue date: 2013 / Resumo: As ferrovias de carga pesada (heavy haul) têm como objetivo, trabalhar com grandes volumes de carga, mantendo uma velocidade que possibilite um tempo de percurso cada vez menor, mas esse deslocamento deve ser feito com segurança e para isso é necessário que a via permanente esteja sempre em condições aceitáveis de circulação. No Brasil, a estrutura atual desse tipo de via férrea atualmente está dimensionada para suportar aproximadamente até 32 toneladas por eixo, mas para favorecer o maior escoamento e tornar a ferrovia mais eficiente intenciona-se chegar a 40 toneladas por eixo. Baseado nessas informações, o objetivo deste trabalho foi analisar uma solução técnica de via férrea adequada para uma carga de 40 toneladas por eixo. Foram avaliadas duas situações: na primeira utilizou-se uma camada de lastro apoiada diretamente sobre a plataforma; e na segunda foi adotada uma placa de concreto de cimento Portland entre a camada de lastro e a plataforma da via. Para a primeira situação foram calculadas as tensões no trilho e na plataforma através dos modelos numéricos propostos por Eisenmann e Zimmermann, e na situação da placa de concreto, dimensionou-se uma estrutura baseada no método de dimensionamento de pisos industriais da Associação Brasileira de Cimento Portland. Para os dois casos, as tensões atuantes na via permanente foram verificadas através do programa computacional FERROVIA. As conclusões foram obtidas através de comparações entre os valores das tensões calculados pelos métodos teóricos e pelo método computacional / Abstract: The heavy haul lines objective is to carry elevated freight, maintaining speeds that assure a shorter travel time. It must be done safely and, for this, it is required good conditions for the track. This Brazilian railway structure is designed to support 32 tonnes per axle, however to promote a better flow and to become more efficient there is an intention of change this freight to 40 tonnes per axle. Based on that, the aim of this study was to analyze a suitable technical solution t for 40 t/ axle load. Two situations have been evaluated: in one of them it was used a ballast layer over the formation; and in the other one it was adopted a concrete slab between the ballast layer and the formation. For the first situation stresses on rail and formation were calculated based on the theoretical models (Zimmermann and Eisenmann methods), and for the second one, a structure similar to a concrete pavement has been designed (ABCP industrial floor method). For both cases, the tresses on the track have been verified by the computational program FERROVIA. The conclusions were based on comparisons between the stresses values calculated by the theoretical and computational methods / Mestrado / Transportes / Mestra em Engenharia Civil

Performance-based maintenance contracts differ significantly from material and method-based contracts that have been traditionally used to maintain roads. Road agencies around the world have moved towards a performance-based contract approach because it offers several advantages like cost saving, better budgeting certainty, better customer satisfaction with better road services and conditions. Payments for the maintenance of road are explicitly linked to the contractor successfully meeting certain clearly defined minimum performance indicators in these contracts. Quantitative evaluation of the cost of performance-based contracts has several difficulties due to the complexity of the pavement deterioration process. Based on a probabilistic analysis of failures of achieving multiple performance criteria over the length of the contract period, an effort has been made to develop a model that is capable of estimating the cost of these performance-based contracts. One of the essential functions of such model is to predict performance of the pavement as accurately as possible. Prediction of future degradation of pavement is done using Markov Chain Process, which requires estimating transition probabilities from previous deterioration rate for similar pavements. Transition probabilities were derived using historical pavement condition rating data, both for predicting pavement deterioration when there is no maintenance, and for predicting pavement improvement when maintenance activities are performed. A methodological framework has been developed to estimate the cost of maintaining road based on multiple performance criteria such as crack, rut and, roughness. The application of the developed model has been demonstrated via a real case study of Miami Dade Expressways (MDX) using pavement condition rating data from Florida Department of Transportation (FDOT) for a typical performance-based asphalt pavement maintenance contract. Results indicated that the pavement performance model developed could predict the pavement deterioration quite accurately. Sensitivity analysis performed shows that the model is very responsive to even slight changes in pavement deterioration rate and performance constraints. It is expected that the use of this model will assist the highway agencies and contractors in arriving at a fair contract value for executing long term performance-based pavement maintenance works.

abstract: Several ways exist to improve pavement performance over time. One suggestion is to tailor the asphalt pavement mix design according to certain specified specifications, set up by each state agency. Another option suggests the addition of modifiers that are known to improve pavement performance, such as crumb rubber and fibers. Nowadays, improving asphalt pavement structures to meet specific climate conditions is a must. In addition, time and cost are two crucial settings and are very important to consider; these factors sometimes play a huge role in modifying the asphalt mix design needed to be set into place, and therefore alter the desired pavement performance over the expected life span of the structure. In recent studies, some methods refer to predicting pavement performance based on the asphalt mixtures volumetric properties. In this research, an effort was undertaken to gather and collect most recent asphalt mixtures’ design data and compare it to historical data such as those available in the Long-Term Pavement Performance (LTPP), maintained by the Federal Highway Administration (FHWA). The new asphalt mixture design data was collected from 25 states within the United States and separated according to the four suggested climatic regions. The previously designed asphalt mixture designs in the 1960’s present in the LTPP Database implemented for the test sections were compared with the recently designed pavement mixtures gathered, and pavement performance was assessed using predictive models. Three predictive models were studied in this research. The models were related to three major asphalt pavement distresses: Rutting, Fatigue Cracking and Thermal Cracking. Once the performance of the asphalt mixtures was assessed, four ranking criteria were developed to support the assessment of the mix designs quality at hand; namely, Low, Satisfactory, Good or Excellent. The evaluation results were reasonable and deemed acceptable. Out of the 48 asphalt mixtures design evaluated, the majority were between Satisfactory and Good. The evaluation methodology and criteria developed are helpful tools in determining the quality of asphalt mixtures produced by the different agencies. They provide a quick insight on the needed improvement/modification against the potential development of distress during the lifespan of the pavement structure. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2020

abstract: This research focused on the structure-property relationships of a rejuvenator to understand the comprehensive rejuvenation mechanism of aged asphalt binder. Aged asphalt such as recycled asphalt shingles (RAS) and reclaimed asphalt pavement (RAP) contain various amounts of asphalt binder. However, the asphalt binder in RAS and RAP is severely aged and inferior in properties compared to a virgin binder. To address this issue, liquid additives have been used under the general title of rejuvenators. That poses an additional challenge associated with the lack of clear metrics to differentiate between softeners and rejuvenators. Therefore, there is a need for a thorough study of rejuvenators. In this study, diverse-sourced rejuvenators have been used in RAS and RAP-modified binders as well as laboratory-prepared aged binders. The properties of the rejuvenated aged binder were characterized at a macro-level and molecular level. The study showed that the performance of the RAS-modified binder was significantly improved after bio-modification by a bio-rejuvenator. This study further evaluated laboratory-prepared aged asphalt rejuvenated with different rejuvenators. The results found that oxidized bitumen became soft after adding rejuvenators, regardless of their source. Molecular dynamics simulation showed that the effective rejuvenator restored the molecular conformation and reduced the size of asphaltene nanoaggregates. The study results showed that due to the specific chemical composition of certain rejuvenators, they may negatively impact the durability of the mixture, especially about its resistance to moisture damage and aging. Computational analysis showed that while the restoration capacity of rejuvenators is related to their penetration into and peptizing of asphaltene nanoaggregates, the durability of the restored aged asphalt is mainly related to the polarizability values of the rejuvenator. Rejuvenators with lower polarizability showed better resistance to aging and moisture damage. In summary, this study develops the rheology-based indicators which relate to the molecular level phenomenon in the rejuvenation mechanism. The rheology-based indicators, for instance, crossover modulus and crossover frequency differentiated the rejuvenators from recycling agents. Moreover, the study found that rejuvenation efficiency and durability are depended on the chemistry of rejuvenators. Finally, based on the learning of chemistry, a chemically balanced rejuvenator is synthesized with superior rejuvenation properties. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2020

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22414号 / 工博第4675号 / 新制||工||1729(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 杉浦 邦征, 教授 河野 広隆, 教授 八木 知己 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The objectives of this research were to 1) investigate the effects of lower concrete albedo on the thermal behavior of concrete pavement by directly comparing temperatures and moisture contents of typical and darkened concrete pavements and 2) investigate changes in roughness of both typical and darkened concrete pavements as a result of changes in temperature and moisture gradients. The scope of the research included instrumentation, testing, and analysis of typical and darkened concrete pavements constructed in northern Utah.Procedures related to field testing included infrared thermography, thermocouple readings, sensor data collection, and roughness surveys. Elevation surveys and albedo measurements were also performed to further characterize the site. Procedures related to laboratory testing included elastic modulus, compressive strength, rapid chloride permeability, thermal conductivity, and Schmidt rebound hammer testing of cylinders prepared from typical and darkened concrete.When considered over the entire monitoring period, the average surface temperatures of the darkened pavement were higher than those of the typical pavement by 3.3°F, and the average subsurface temperatures of the darkened pavement were higher than those of the typical pavement by 3.1°F. A strong positive correlation exists between the air temperature and both the surface and the subsurface pavement temperatures. The difference between both the surface and subsurface temperatures of the darkened and typical pavements decreases as the air temperature decreases. The results of a simple linear regression suggest that, when the air temperature is 32°F, the surface temperature of the darkened concrete is just 0.2°F higher than that of the typical concrete and the subsurface temperature of the darkened concrete is 1.1°F higher than that of the typical concrete. The difference in surface temperature is expected to be 0°F when the air temperature is 30.5°F, while the difference in subsurface temperature is expected to be 0°F when the air temperature is 17.9°F. Therefore, the darkened pavement is unlikely to melt snow and ice faster than the typical pavement or provide significantly greater frost protection to subsurface layers and buried utilities during winter for conditions similar to those in this research. The roughness measurements for the typical pavement exhibit much more daily variability than seasonal variability. The roughness measurements for the darkened pavement also exhibit more daily variability than seasonal variability but less overall variability than that of the typical pavement. Neither pavement temperature gradient nor moisture gradient appears to be correlated to roughness for either the typical pavement or the darkened pavement.