Дисертації з теми "Pavements, Composite"

Roadway systems in the United States have become huge assets that need massive resources to maintain and operate. To meet the long-term performance goal, government agencies developed pavement management systems (PMSs) to help them manage roadway assets effectively with limited resources. Currently, some PMSs in the United States have been designed for two types of pavements: asphalt and concrete. The composite pavement, another pavement type, which is the result of concrete pavement rehabilitations and constructed with an asphalt surface layer over a concrete base, was treated as asphalt. However, the literature review indicates that compared to asphalt pavements, composite pavements perform differently and have different dominant distresses. In addition, as the amount of composite pavements increases, it is necessary to investigate them independently to incorporate more accurate information into the PMS. Therefore, the goal of this research is to improve and to expand the PMS with an additional pavement type: composite pavements. To achieve this goal, the PMS managed by the North Carolina Department of Transportation (NCDOT) was used as a case study, and several objectives were accomplished in this research: 1) to identify composite pavements and generate the raw data based on the construction history; 2) to clean the raw data and mitigate errors using statistical methods and engineers’ experiences; 3) to develop nonlinear models to describe dominant distresses and pavement performances; 4) to propose quantile regression (QR) models to predict pavement performances; and 5) to investigate the pavement treatment effectiveness by exploring performance index jumps.

Based on findings of this research, it was concluded that the automated data were more consistent with engineers’ experience and revealed more information than the windshield data; longitudinal cracking and transverse cracking were found to be the dominant distresses in composite pavements, followed by alligator cracking and raveling; Interstate composite pavements deteriorated faster than both US and NC composite pavements, and NC composite pavements had the slowest deterioration rate; QR models can be used as a new prediction method of pavement performances at both the project and the network levels; in general the “Resurfacing” treatment was more effective than the “Chip Seal” treatment; and The average service life of asphalt and composite pavements were similar, but composite pavements have a smaller variation of service lives than that of asphalt pavements.

It was recommended that the automated data should be used in future PMS related research projects, due to its better data quality, and because of the robust performance of QR models at both network and project levels, QR models should be incorporated in the future PMS.

In summary, this research expanded the existing NCDOT PMS with composite pavements, proposed systematic methods to improve the quality of performance data, enriched the diversity of prediction models by exploring potentials of QR models, and investigated the effectiveness of pavement treatments. Essentially, transportation agencies can use the findings of this research to make informative investment decisions.

In most road infrastructure networks, the two prevalent types of pavements considered during the pavement type selection (PTS) process are flexible and rigid. Thus, these two structures are the most commonly constructed in the road industry. A consideration of a different pavement alternative is proposed in this study. Composite pavements, which are in essence a combination of a rigid base overlaid with a hot-mix asphalt (HMA) surface course, have the potential to meet the technical and economic requirements that are sought in the PTS process. For that reason, technical and economic evaluations were performed to justify the consideration of composite pavement systems in the PTS process.

At the technical level, composite pavement design guidelines from various transportation agencies were obtained and followed to design their respective composite pavement structures. A mechanistic analysis based on the multi-layer linear elastic theory was performed on different composite structures to understand the behavior they present when compared to traditional pavements. In addition, distresses affecting composite pavements such as fatigue (bottom-up and top-down) cracking, rutting, and reflective cracking were modeled and investigated using sensitivity analyses. At the economic level, a deterministic life cycle cost analysis (LCCA) based on Virginia Department of Transportation (VDOT) guidelines was performed. This LCCA compared two proposed composite pavements (one with a cement-treated base [CTB] and the other with a continuously reinforced concrete pavement [CRCP] base) to traditional flexible and rigid pavement structures. Furthermore, sensitivity analyses involving discount rates and traffic volumes were performed to investigate their effect on the present worth (PW) computation of the four pavement alternatives. Results from this study suggest that composite pavements have both the technical and economic potential to be considered during the PTS process.
Master of Science

Pavement foundations for major roads in the UK were historically designed on an empirical basis, related to a single design chart, restricting the incorporation of superior performing materials or materials for which the empirical data sets were not available. The adoption of performance based specifications was promoted as they are perceived to 'open up' the use of alternative materials (including 'local' sources of primary materials) or techniques, and allow for the incorporation of superior performance into the overall pavement design. Parallel developments to the performance based design of pavement foundations (allowing for superior performance) and in situ testing required the support of laboratory based performance tests. These laboratory based tests were required to determine material performance parameters (elastic modulus and resistance to permanent deformation) for both unbound and hydraulically bound pavement foundation materials. A review of the available laboratory apparatus indicated that they were either; unrealistic (and hence unable to provide the required material performance parameters), or overly complex and more suited to fundamental research. Therefore, the requirement for developmental research work was identified. The research reported herein details the development, manufacture and initial evaluation of simplified laboratory apparatus (the Springbox for unbound materials and static stiffness test for hydraulically bound mixtures) designed to produce the performance parameters of elastic modulus and relative resistance to permanent deformation for pavement foundation materials. The equipment and test procedure evaluation was undertaken across a range of materials, giving initial guidance on likely in situ performance. The innovative laboratory apparatus and materials guidance (including the potential to use recycled and secondary aggregates) was incorporated into key Highways Agency specification and guidance documents, which in turn influence construction practice outside of motorways and major trunk roads. This research concludes by outlining a number of recommendations for continued development and evaluation, including feeding back data sets from long term in situ performance testing for subsequent refinement of assumptions.

Drivers for sustainability have made it necessary for the construction industry to adapt its traditional processes to become both more efficient and produce less waste. Performance based design and specification in the UK for motorways and trunk roads permits a very flexible approach to pavement design, material selection and performance related testing aimed at utilising materials to their maximum potential. However, it is clear that within the emerging philosophy of using materials that are 'fit for purpose' there are many technical challenges for design and specification. There is a need to develop suitable methods of evaluating materials prior to their being used on site. This project was born out of this requirement, with a particular emphasis on coarse granular materials due to their common role in capping construction and also their unique difficulty for measurement under laboratory conditions due to their large range of particle size. A novel assessment test for coarse capping materials for roads that can be used to indicate their likely short-term in situ performance, under controlled laboratory conditions before construction on site, has been developed during this research programme. Key findings relating to the behaviour of coarse capping materials, the use of stiffness measuring devices and variables that influence the measurement of composite stiffness are discussed in detail. The research highlights the necessity for adequate drainage and protection of foundation materials against increase in water content. When adopting a performance specification the timing of the pavement assessment is critical, both on site and in the laboratory. The performance measured on site should perhaps only be considered as a 'snapshot' relating to the stress state in the material at the time of testing.

A series of large-scale pavement model tests were conducted in a laboratory environment to investigate the effect of geosynthetics in improving the modulus of weak subgrades. Then, a series of supplement design charts that could be useful for industry practitioners to design geosynthetic reinforced flexible pavements were developed. The outcomes of this study promote the use of geosynthetics in road construction to make economical, environmentally friendly, climate resilient, and sustainable road infrastructure.

This PhD thesis is devoted in developing new multi-layer composite and concrete runway pavements to increase the resistance to impact load and heavy moving load and hence to extend the service life of runway pavement. A new series of laboratory tests results along with computer based structural analyses are presented to understand the effectiveness of new multi-layer composite and concrete runway pavements. The outcome of this research will be beneficial for the runway pavement designer to introduce and design such impact and moving load resistant multi-layer composite and concrete runway pavement and thereby to reduce the damage of runway pavement due to the hard landing of exceptionally large and heavy weighted aircrafts, high velocity and heavy weighted falling objects during accidents, terrorist attacks etc.

Motivado pela alteração do sistema construtivo de pavimentos de concreto de cimento Portland, na qual foi abolida a utilização da manta plástica entre placas e bases cimentadas, com conseqüente emprego de imprimação da base com emulsão asfáltica, este trabalho buscou responder algumas indagações surgidas durante este processo. Em laboratório, através de uma metodologia de ensaio especialmente adaptada para o estudo da resistência ao cisalhamento entre concreto de cimento Portland (CCP) e concreto compactado com rolo (CCR), inferiu-se, para diferentes tratamentos de interface, elevados níveis de resistência ao cisalhamento em interfaces sem emulsão asfáltica que potencializam o emprego de estruturas monolíticas de pavimentos. Quanto àquelas que continham material asfáltico, foram obtidos resultados muito inferiores aos anteriores, com caracterização de ruptura dúctil, por efeito de fluência do material betuminoso. Duas pistas experimentais instrumentadas, uma em whitetopping ultradelgado e outra em pavimento simples de concreto executado segundo a nova prática construtiva, capazes de mensurar as deformações específicas do CCP durante a execução de provas de carga dinâmica, associadas às modelagens por elementos finitos (MEF), realizadas com auxílio do programa ISLAB2000, propiciaram importantes inferências sobre o comportamento mecânico destes dois tipos de pavimentos de concreto. Verificou-se o trabalho mecânico composto (monolítico) das estruturas de whitetopping ultradelgado, com boas correlações entre as tensões medidas e numericamente calculadas; e entre os rebaixamentos da linha neutra (LN) determinados analítica, numérica e experimentalmente. No tocante ao pavimento simples de concreto sobreposto à base cimentada imprimada, apesar das ótimas correlações entre tensões medidas e determinadas numericamente, não se pode obter conclusões definitivas a despeito do trabalho mecânico desta estrutura, apesar da existência de indícios de comportamento não-monolítico.
This thesis intended to answer some inquiries, which arose during the alteration of the concrete pavement constructive process. This process substituted the plastic blanket by the asphalt emulsion, between the concrete slabs and the cemented bases. A laboratorial test methodology, specially adapted for the study of shear strength between the Portland cement concrete and the rolled concrete, inferred, for different types of interlayer treatments, high levels of shear strength, at the interfaces without asphalt emulsion. These shear strength levels enable the monolithic behavior of the pavement structure. When the asphalt emulsion was presented at the interlayer, the shear strength was much smaller than the former, with ductile rupture due to creep of the bituminous material. Two instrumented road tests, the first section in ultra-thin whitetopping pavement and de second one, in jointed plain concrete pavement (built according to new constructive process), and the finite element analyses led to important conclusions about the mechanical behavior of these pavement structures. This was possible because the strain-gages measured the specific concrete deformations during the dynamic load tests. The monolithic behavior of the ultra-thin whitetopping pavement was verified. There were good correlations between the measured stresses and theoretical stresses, which were calculated by the finite element method; and between the neutral axle displacements, estimated by analytical, numerical and experimental methods. With regard to the jointed plain concrete pavement, which was built over the cemented base (covered by the asphalt emulsion), great correlations between measured and simulated stresses were found, as well as it was found for ultra-thin whitetopping. However, it was not possible to conclude, definitively, concerning the mechanical behavior of this pavement structure, although there are clues that ndicated a non-monolithic behavior, that is, concrete slabs are unbounded up with the cemented base.

Insitu cementitious stabilisation is an economical, environmentally sustainable and socially advantageous means of rehabilitating pavements. With the recent availability of a wide range of binders and advanced construction equipment, the characterisation of cementitiously stabilised pavement materials has become the focus of further advancement of this technology. Australian practice has moved towards the use of Indirect Diametric Tensile (IDT) methods for the characterisation of these materials. A draft protocol for the IDT test has been prepared and specifies samples to be compacted by gyratory compactor. This procedure provides for both monotonic and repeated load testing, which aims to measure the material???s strength, modulus and fatigue life. A range of host materials, including a new crushed rock and a reclaimed existing pavement base course, were assessed when stabilised with a General Purpose cement binder as well as with a slag-lime blended binder. Materials were assess for their inherent material properties, Unconfined Compression Strength (UCS), Unconfined Compression modulus, IDT strength and modulus under both monotonic and repeated load. A number of amendments and refinements to the testing protocol were recommended. These included the use of minimum binder contents to ensure the binder was uniformly distributed and to promote heavy binding of the materials to ensure they behaved elastically. It was also recommended that samples be gyratory compacted to a pre-determined sample height to allow a constant density to be achieved. The variability of the test results was examined. UCS results were found to be comparatively as variable as other researchers had reported. IDT strength results contained a similar level of variability, which was considered to be acceptable. Modulus results, both monotonic and repeated load, were found to be five to ten times more variable than strength results, which is a generally accepted trend for modulus testing. Under repeated loading, some challenges with the test protocol were encountered. The primary challenge was obtaining reliable and repeatable diametrical displacement data for modulus calculation. This was partially overcome by the insertion of smooth spacers to prevent the Linear Voltage Displacement Transformer (LVDTs) becoming caught on the sample sides. The achievement of reliable and repeatable IDT modulus results through improved displacement measurements should be the focus of future research efforts in this area.

This research programme is an in-depth study regarding the sub-base layer of pavements made by a polymer composite using crumb recycled tyres, recycled plastic and fly ash as fillers with jute-fabric as a reinforcement. Emphasis is placed mostly on the mix proportions, mechanical properties and durability of the purposed composite as precast lightweight product.

Uma parcela substancial das rodovias do país apresenta processos de deterioração graves de seus pavimentos, fato que acarreta sérios impactos econômicos, sociais e ambientais, resultando em aumento do consumo de combustível, dos gastos com manutenção dos veículos, da frequência de engarrafamentos e do tempo gasto em deslocamentos. A utilização de recapeamentos ou overlays de concreto tem demonstrado ser uma alternativa sustentável e econômica para a reabilitação de pavimentos. No entanto, em muitos casos, os overlays de concreto não tem conseguido prevenir a ocorrência de fissuração por reflexão. Os Engineered Cementitious Composite (ECCs) são um tipo especial de compósitos cimentícios de alto desempenho reforçados com fibras, cuja principal característica é a altíssima ductilidade. Esta propriedade faz com que os mesmos sejam capazes de superar muitas das limitações dos overlays de concreto tradicionais. Fibras de PVA com uma camada superficial modificada foram especialmente desenvolvidas para serem empregadas no reforço de ECCs (ou PVAECC). O custo de tais fibras é o principal responsável pelo elevado custo dos ECCs, o que pode inviabilizar seu emprego em alguns casos. Buscando alternativas, este estudo se focou na investigação da possibilidade de uso de fibras de polipropileno (PP) de alto desempenho. Estas fibras, com custo mais atraente, já são produzidas comercialmente no Brasil, e usadas na produção de fibrocimento. As mesmas se demonstraram adequadas para uso como reforço em ECCs (ou PPECC), sendo capazes de garantir que se atinja um comportamento dúctil através do desenvolvimento de um processo de múltipla fissuração. Um resultado importante foi que a dimensão média da abertura das fissuras nos PPECC foi de 10 m, enquanto nos PVAECC a mesma era 60 m. Este resultado pode resultar em incrementos na durabilidade de estruturas. Além disto, o trabalho investigou o comportamento à flexão e fadiga dos ECCs reforçados com fibras de polipropileno. Os resultados demonstraram que os compósitos produzidos com cimento Portland tipo V-ARI não se comportam adequadamente à fadiga, uma vez que ocorre a deterioração das fibras. Por outro lado, os compósitos produzidos com cimento tipo I, já usualmente empregado em ECCs, apresentaram resultados satisfatórios. Um modelo de previsão de vida útil foi gerado para recapeamentos de PPECC, PVAECC e concreto, em função das espessuras dos revestimentos. O mesmo indicou que os ECCs requerem camadas 1,5 a 2,5 vezes mais finas que as usuais de concreto. O material foi, então, testado especificamente quanto à resistência à fissuração por reflexão. Os resultados demonstraram que o PPECC pode modificar o modo de ruptura frágil dos recapeamentos através do processo de múltipla fissuração. Na última etapa do trabalho foi realizada uma análise do ciclo de vida e dos custos do ciclo de vida de quatro diferentes sistemas de recapeamento – concreto, asfalto, PVAECC e PPECC. Os resultados mostram que os overlays de ECCs são bastante atrativos, pois diminuem tanto o consumo de energia associado aos processos de projeto, construção e manutenção do recapeamento, bem como reduzem a liberação de emissões gasosas à atmosfera, constituindo uma alternativa mais sustentável que as demais. Os sistemas de recapeamento com ECC também resultaram em vantagens econômicas. Apesar do alto custo inicial, a menor frequência de atividades de manutenção resulta em uma redução do custo total ao longo do período de 40 anos considerado. Isto representa uma importante economia em termos de custos diretos para os responsáveis pelas rodovias. De forma geral, o trabalho evidenciou a viabilidade de uso dos PPECCs para reabilitação de pavimentos.
Many old pavements in service today are approaching the end of their design service lives. Others are in dire need of major repair to continue serving, resulting in economical, environmental and social impacts by increasing vehicle fuel consumption and maintenance costs, traffic jam and delays. For pavements subject to moderate and heavy traffic, concrete overlays are increasingly being used as a cost effective and sustainable rehabilitation technique. However, concrete overlays have some physical limitations that contribute to durability concerns, which increase the probability of pavement overlay failure and maintenance frequency. Consequently, alternative materials are being developed to improve overlay performance. Engineered Cementitious Composites (ECC) are a special type of high performance fiber reinforced cementitious composites, designed for high ductility and damage tolerance which may overcome concrete overlay limitations. Polyvinylalcohol (PVA) fibers with special coating are typically used as reinforcement of ECC. Although some successful field application of PVAECC, the use of ECC is restrained by the high cost of the material, consequence of high PVA fibers cost. This research is focused on the investigation of using high tenacity polypropylene fibers as reinforcement of engineered cementitious composites (PPECC). Those fibers are produced and available in Brazil for fibrocement industry by less than half price of PVA fibers. PP fibers have demonstrated good performance in reinforcing ECC, assuring composite strain-hardening behavior through the development of multiple cracking processes. An important finding was the tinier crack opening of PPECC – 10 m average- comparing to PVAECC – 60 m average. This result may result in higher material durability. Furthermore, flexural and fatigue behavior or ECCs reinforced with PP fibers were investigated. Results have shown that Portland cement type V (high early strength) is not adequate for PPECCs subject to fatigue loading, resulting in fiber deterioration and premature rupture. By the other hand, promising results were found with cement ordinary type I, usually used in ECC production. A model of service life prediction was developed for PPECC, PVAECC and concrete overlays correlated to overlay thickness. Results have shown that ECCs may reduce overlay thickness in 1.5 to 2.5 times the usual thickness of overlay concrete. Reflective cracking resistance of PPECC was also testes. From the results it is possible to deduce that PPECC may modify typical rupture mode of concrete overlays through the development of multiple cracking. In the last stage of this work, life cycle analyses and life cycle cost analyses of four different overlays systems – concrete, hot mix asphalt, PVAECC and PPECC – were carried out. The results of this study have shown that an ECC overlay system have lower environmental burdens, reducing the energy consumption related to design, construction and maintenance activities, reducing green house effect as well. Life cycle costs analyses over a 40 years service life revealed that PPECC is the most economical overlay system compared to concrete, hot mix asphalt and PVAECC overlay systems. Agency costs are significantly reduced by adopting PPECC overlays. PPECC is a feasible alternative for pavement rehabilitation.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
As pontes rodoviárias mistas (aço-concreto) estão sujeitadas às ações dinâmicas variáveis, por exemplo, devido ao tráfego de veículos sobre a superfície irregular do pavimento. Estas ações dinâmicas podem gerar a nucleação de fraturas ou mesmo a sua propagação sobre a estrutura. A correta consideração desses aspectos objetivou o desenvolvimento de uma metodologia de análise, com a finalidade de avaliar os níveis dos esforços e tensões oriundos do tráfego dos veículos sobre a superfície irregular do pavimento e, bem como, proceder uma verificação à fadiga de obras de arte rodoviárias em aço e mistas (aço-concreto). Para tal, as técnicas para a contagem de ciclos de tensão e a aplicação das regras de dano acumulado foram analisadas através de curvas do tipo S-N, associadas a diversas normas de projeto. A ponte rodoviária mista (aço-concreto) investigada neste estudo é constituída por quatro vigas de aço longitudinais e por um tabuleiro de concreto armado. O modelo numérico-computacional, desenvolvido para a análise dinâmica da ponte, foi concebido com base em técnicas usuais de discretização através do método dos elementos finitos. Simulam-se as almas das vigas de aço e as lajes de concreto do tabuleiro através de elementos finitos de casca. As mesas dessas vigas, transversinas e os enrijecedores são modelados por elementos de viga tridimensionais. Os veículos são representados a partir de sistemas "massa-mola-amortecedor". O tráfego dessas viaturas é considerado mediante a simulação de comboios semi-infinitos, deslocando-se com velocidade constante sobre a ponte. As conclusões da presente investigação versam acerca da vida útil de serviço dos elementos estruturais de pontes mistas (aço-concreto).
Steel and composite highway bridges (steel-concrete) are currently subjected to dynamic actions, for example, variable magnitude due to vehicles traffic on the deck rough pavement. These dynamic actions can generate the fractures nucleation or even their propagation on the structure. The correct consideration of these aspects pointed out to an analysis methodology developed, in order to evaluate the stresses through a dynamical analysis on highway bridge decks, due to vehicles crossing on the irregular pavement surfaces and to proceed a fatigue verification from Steel and composite highway bridges (steel-concrete). The stress cycles counting techniques and the cumulative damage rules application had been analyzed through S-N curves associated with diverse projects norms. The steel and composite highway bridge (steel-concrete), investigated in this study, is constituted by four longitudinal steel beams and a composite deck. The computational model, developed for the bridge dynamic analysis , adopted the usual mesh refinement techniques present in finite element method simulations. The beam web thickness was represented by shell finite elements. The beam top and bottom flange and the longitudinal and vertical stiffeners were simulated by three-dimensional beam elements, where flexural and torsion effects were considered. The bridge concrete slab was simulated by shell finite elements. The vehicles are represented from "mass-spring-damper" systems. The traffic of these vehicles is considered as a simulation of half-infinite convoys dislocating with constant speed on the bridge. The present study conclusions concerning steel and composite highway bridges (steel-concrete) structural elements service life.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
As pontes rodoviárias metálicas e mistas (aço-concreto) são submetidas a um grande número de carregamentos repetitivos de diferentes magnitudes, ao longo do tempo. Estas ações dinâmicas podem causar a nucleação de fraturas ou mesmo a propagação destas sobre o sistema estrutural. A depender da magnitude, estes efeitos podem comprometer o sistema estrutural e a sua confiabilidade, além de reduzir a vida útil das pontes. Assim sendo, neste trabalho de pesquisa foi investigada a resposta dinâmica de uma ponte mista (aço-concreto), simplesmente apoiada, com vão de 40,0 m, submetida ao tráfego de veículos sobre a superfície irregular do pavimento. Para tal um modelo numérico representativo do sistema estrutural foi desenvolvido com base no emprego do programa ANSYS, por meio do uso de técnicas usuais de discretização, via método dos elementos finitos. Um estudo paramétrico foi desenvolvido para identificar, de forma qualitativa e quantitativa, o efeito das irregularidades do pavimento sobre o comportamento dinâmico da ponte mista investigada. Em seguida, a verificação do projeto à fadiga do sistema misto foi realizada, com base no emprego do algoritmo de contagem de ciclos Rainflow e em curvas S-N associadas às principais normas de projeto sobre o tema. As conclusões deste trabalho de pesquisa alertam aos engenheiros estruturais para a possibilidade concreta acerca do aumento do dano por fadiga, relacionado às ações dinâmicas de veículos trafegando sobre o tabuleiro de pontes em aço e mistas (aço-concreto).
Steel and steel-concrete composite highway bridges are currently subjected to dynamic actions with variable magnitudes due to the action of vehicles crossing on the deck. These dynamic actions can generate the nucleation of fractures or even their propagation in the structures. Depending on the magnitude, these effects can compromise the structural system response and the reliability, which may also lead to a reduction of the expected bridge service life. This way, the dynamic response of a steel-concrete composite bridge spanning 40 m was investigated in this work. The computational model, developed for the composite bridge dynamic analysis, adopted the usual mesh refinement techniques present in finite element method simulations, and was implemented in the ANSYS program. A parametric study was performed to identify the effect of vehicle speed and roughness pavement on the investigated bridge dynamic behaviour. The proposed methodology for evaluate the bridge service life to fatigue was based on a linear cumulative damage rule, Rainflow-counting algorithm and S-N curves from main design codes. Results of a parametric analysis are presented to verify the extension of the dynamical effects on highway bridges due to vehicles crossing on the irregular pavement surface. The main conclusions of this work focuses on alerting structural engineers to the possibility of increase of fatigue damage, related to steel and composite highway bridges when subjected to vehicle dynamic actions.

Les matériaux de construction par excellence que sont les matériaux à base cimentaire offrent une faible résistance à la traction ainsi qu’une faible capacité de déformation. Ils sont fragiles et particulièrement sensible à la fissuration, notamment la fissuration due au retrait dans le cas d’éléments à grande surface. Des joints de retrait judicieusement espacés permettent de localiser la fissuration et d’éviter le désordre apparent. Malheureusement, ils constituent aussi le point de départ de futurs désordres (pénétration d’agents agressifs, tuilage, etc.). Cette thèse est une contribution au développement d’un nouveau composite cimentaire présentant une capacité de déformation améliorée. Dans cet objectif, des granulats en caoutchouc (G.C.) issus du broyage de pneus usagés ont été utilisés en remplacement partiel du sable. Les résultats obtenus montrent que la présence de ces granulats est préjudiciable vis-à-vis de la rhéologie du matériau à l’état frais mais que l’utilisation d’un superplastifiant et d’un agent de viscosité permet de réaliser les corrections nécessaires. A l’état durci, une chute de la résistance mécanique et du module d’élasticité est observée, en contrepartie la capacité de déformation au stade de la localisation de la macrofissuration est significativement augmentée. Des essais dédiés permettent de démontrer que cette incorporation de G.C. permet de réduire la sensibilité à la fissuration de retrait avec un intérêt évident pour les applications à grande surface comme les chaussées et dallages sur terre-plein. L’influence de la présence de ces G.C. sur la cinétique de la fissuration a été analysée et confirmée par le biais d’une variable d’endommagement et par l’activité (émission) acoustique accompagnant le processus de fissuration.Le potentiel du composite dans les applications à grande surface comme les chaussées en béton a aussi été abordé par le biais de l’indice de qualité élastique qui a confirmé les promesses attendues. Compte tenu du rôle joué par le module d’élasticité du composite sur ces nouvelles propriétés et les applications potentielles, les outils prédictifs de ce module en fonction du dosage en G.C. présentent un intérêt pratique évident. Dans ce sens, cette thèse a permis de tester la pertinence de quelques modèles analytiques. Dans ce cadre, la borne inférieure de Hashin-Shtrikman qui reste perfectible s’est avérée la mieux indiquée.A côté de l’intérêt en termes d’application matériau Génie Civil, l’incorporation de G.C. constitue une voie de valorisation de pneus usagés non réutilisables et une contribution à la protection de l’environnement
Cement-based materials exhibit low tensile strength and poor strain capacity. They are brittle and are very sensitive to cracking particularly to shrinkage cracking in large area applications. Sawn joints allow shrinkage cracking to be localised a way to avoid unsightly cracking. Unfortunately they are also the starting point of future distress (ingress of aggressive agent, curling, etc.).This work is a contribution to the design of a cement-based material exhibiting an enhanced strain capacity. For a such objective rubber aggregates (RAs) obtained from grinding end of life tyres partly replacing natural sand have been used.Results showed that RAs are detrimental to the properties of the fresh materials (workability and segregation). However the use of optimized content of a superplasticiser and of a viscosity agent allows the required behaviour to be achieved.With regard to harden state, RAs reduce the strength and the modulus of elasticity of the composite but the strain capacity corresponding to the macrocracking formation is significantly improved. Specific tests showed that RAs reduced the propensity of the material for shrinkage cracking, offering an interest for large surface area such as pavements.Analysis by a scalar damage variable and by acoustic emission is in a good agreement with expected effect of RAs on the cracking kinetics and on the mechanical behaviour of the composite.The interest of the rubberized concrete in large area application such as concrete pavements has been studied and confirmed through the Elastic Quality Index. Given the major role of the modulus of elasticity of the composite on the new properties and expected applications, tools aimed to predict this modulus of elasticity as a function of RAs content are of practical benefit. With this purpose, the work allowed the relevance of some analytical models to be tested. In this context, the lower Hashin-Shtrikman bound which remains perfectible proved to be the most appropriate.Finally, apart from application of civil engineering material, the use of RAs from grinding end of life tyres is a solution of recovery of an industrial by-product and a contribution to a clean environment

Steel Fibre Reinforced Concrete (SFRC) is defined as concrete containing randomly oriented discrete steel fibres. The main incentive of adding steel fibres to concrete is to control crack propagation and crack widening after the concrete matrix has cracked. Control of cracking automatically improves the mechanical properties of the composite material (SFRC). The most significant property of SFRC is its post-cracking strength that can impart the ability to absorb large amounts of energy before collapse. Ground slabs are structural applications that could benefit from these advantageous features of the SFRC. Many tests on SFRC ground slabs show that the material can offer distinct advantages compared to plain concrete. In concrete road pavements, SFRC is particularly suitable for increasing load-carrying capacity and fatigue resistance. Not surprisingly, recent years have witnessed acceleration in full-scale tests of SFRC and eventually acceptance of its use in concrete pavements. The use of SFRC in pavements has been slowed down by the absence of a reliable theoretical model to analyse and design these pavements. The analysis of ground slabs has traditionally been based on an elastic analysis assuming un-cracked concrete. Using such a method for SFRC would ignore the post-cracking contribution the SFRC can make to the flexural behaviour of the slab. Despite the growing trend of using methods of analysis based on yield-line theory, which can consider the post-cracking strength of SFRC, these methods were also found to underestimate the load-carrying capacity of SFRC ground slabs. To effectively account for the post-cracking strength of SFRC in the analysis of such slabs requires a method such as the finite element method. In the present work, non-linear methods are used to model the behaviour of SFRC ground slabs subjected to mechanical load. An analytical method is used to determine a tensile stress-strain response for SFRC. In this method, the post-cracking strength of SFRC is taken into account and hence the material model is sensitive to the element size used. The calculated stress-strain response is utilised in finite element analysis of SFRC beams and ground slabs. A smeared crack approach is used to simulate the behaviour of concrete cracking. The analytical method used to determine the tensile stress-strain response, as well as the finite element model, are evaluated using results from experiments on SFRC beams and ground slabs. The analytical results are found to compare well with the observations. The non-linear methods are further used to study the effect of the material model parameters as well as the support stiffness on load-displacement behaviour of SFRC ground slabs. The developed finite element model is shown to be more efficient compared to methods based on the yield-line theory. This is because it produces the load-displacement behaviour of the SFRC ground slab up to a reasonable limit and it provides the tensile stresses as well as the extent of cracking of the slab at every point on the load-displacement response. Using the developed finite element model will allow for considerable material saving since smaller slab thickness can be calculated compared to analytical models currently in use.
Thesis (PhD(Transportation Engineering))--University of Pretoria, 2008.
Civil Engineering
PhD
unrestricted

碩士
淡江大學
土木工程學系
90
Due to the rapid expansion of our domestic highway networks, the demands for pavement maintenance and rehabilitation (M & R) activities are increasing dramatically. Proper selections of M & R activities can extend pavement service life to assure the best use of our limited resources. The major objective of this study is to conduct an in-depth investigation on the application of composite index in pavement engineering. The current practices of domestic pavement M & R activities are first reviewed. The fundamental concepts and evolutions of several structural and functional evaluation indices including Present Serviceability Index (PSI), Maysmeter Output (MO), International Roughness Index (IRI), Pavement Condition Index (PCI), and Pavement Surface Distress Index (PSDI) are investigated. It was found that our domestic practices did not quite follow the global trends of objectivity, simplification, automation, and standardization in using composite indices. Consequently, the relationships, advantages, and deficiencies of both PCI and PSDI are compared in this study. The results indicate that PCI is more preferred due to its measuring ability, replicability, objectivity, and consistency. Toward standardization is also one of the major concerns for using the PCI. Together with the utilization of “uniform sections” and “sampling” concepts, an automated project-level PCI prototype program with well-organized Windows-based graphical user interfaces was developed using Microsoft Visual Basic 6.0 program. Several case studies are conducted to validate the correctness of this prototype program through comparisons of manual calculations and the results of the well-known MicroPaver program. To illustrate the application of the PCI, this program is also implemented in the existing prototype Intelligent Consultant System for Pavement Maintenance And Rehabilitation Technologies for Rigid Pavements (ICSMART-R) and for Flexible Pavements (ICSMART-F), and NETwork Dynamic Segmentation Database (NETDSD) programs for both project level and network level pavement management, respectively. Due to the large amount of data required to determine the PCI, it is not recommended for use in the current domestic network pavement management activities. Several recommendations for carrying out domestic pavement evaluation activities including ascertaining management levels, data requirements, selection of composite indices, personnel and training, automated distress survey and devices, selection of M & R criteria, and pavement performance models are discussed.

碩士
國立中央大學
土木工程研究所
98
"Road" is the major channel to connect places, the most important national infrastructure, and one of the most frequently contacted public facilities. In order to effectively maintain the road quality, the authority of road management must trace and investigate the pavement performance index, by comparing quantitative data, evaluating the quality and effectiveness of road, the pavement’s essential function is maintained and its service span is extended. With such enormous road network, intelligent pavement survey vehicles are needed to quickly and completely build up. Necessary information pavement survey vehicles used in detecting procedures not only reduce the detecting time and avoid a waste of human resources, but also improve the detection efficiency. In order to use pavement survey vehicle to replace conventional human testing procedures, many countries are interested in investing in its research and development. The purpose of this study is to develop a pavement detecting system for the intelligent pavement survey vehicle. Through the modular design, the detective system of detect vehicle is dismantled into different functional modules, and detective equipment of functional module is selected to integrate composite testing module. The composite detective module we have developed can be used to detect the pavement roughness and pavement conditions. It will make the multi-function detection of road network more rapidly and more accurately. It can also provide authority of road management real-time road pavement information, and thus improves road network management.

Support systems including base and subgrade layers play a pivotal role in manifesting and maintaining acceptable behavior and performance of continuously reinforced concrete pavement (CRCP). In Texas, especially, use of non-erodible stabilized base layers have been recommended to prevent failures of the CRCP related with pumping and erosion of the support materials. The non-erodible base materials, however, have given high initial construction cost of the rigid pavements. For this reason, it has been desired to decrease the construction cost with acceptable long-term performance of the pavement system. The primary objective of this study is to determine acceptable combination of support properties and concrete slab thickness satisfying not only adequate structural ability but also construction expense. For this purpose, field support conditions were investigated using Falling Weight Deflectometer (FWD), Dynamic Cone Penetrometer (DCP), and static plate load test in phase one. Previously developed support analysis models for rigid pavement design were examined using finite element analysis method, which model could more accurately express field support behavior. Also, effects of each support properties including base thickness, elastic modulus of base material, and subgrade k-value were mechanistically identified on composite k-value, and a method selecting optimum combinations of the support properties completing desired composite k-value was developed in phase two. Also, CRCP behavior were examined under not only diverse structural and material conditions of the support system but also the CRCP slab thickness and transverse crack spacing due to temperature and vehicle wheel loading conditions in phase three. In phase four, maximum critical stress induced in the CRCP slab was evaluated under various combinations of support conditions and slab thickness. Effects of the support properties and the slab thickness on the critical stress in the CRCP slab were mechanistically identified, and the factor with the greatest effect was verified. Moreover, regression equations were developed to estimate the maximum critical stresses for various support properties and the CRCP slab thickness under temperature and wheel loadings. In phase five, a guideline determining optimum combination of support properties and slab thickness were proposed as aspect of initial construction cost of the CRCP.
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Most engineering as well as pavement materials are composites composed of two or more components to obtain a variety of solid properties to support internal and external loading. The composite materials rely on physical or chemical properties and volume fraction of each component. While the properties can be identified easily, the volume fraction is hard to be estimated due to the volumetric variation during the performance in the field. Various test procedures have been developed to measure the volume fractions; however, they depend on subjective determination and judgment. As an alternative, electromagnetic technique using dielectric constant was developed to estimate the volume fraction. Empirical and mechanistic approaches were used to relate the dielectric constant and volume fraction. While the empirical models are not very accurate in all cases, the mechanistic models require assumptions of constituent dielectric constants. For those reasons, the existing approaches might produce less accurate estimate of volume fraction. In this study, a mechanistic-based approach using the self consistent scheme was developed to be applied to multiphase materials. The new approach was based on calibrated dielectric constant of components to improve results without any assumptions. Also, the system identification was used iteratively to solve for dielectric parameters and volume fraction at each step. As the validation performed to verify the viability of the new approach using soil mixture and portland cement concrete, it was found that the approach has produced a significant improvement in the accuracy of the estimated volume fraction.