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Analyzing Decision Making in Alternative Contracting for Highway Pavement Rehabilitation ProjectsIbrahim, Mohamed 10 June 2016 (has links)
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.
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Um estudo paramétrico sobre tensões, deformações e resistência à fadiga de pavimentos asfálticos / A Parametric study about stress, strains and fatigue resistance of asphalt pavementsTeodozio, Theonelly Nascimento 28 November 2012 (has links)
In Brazil, the investment in infrastructure of transports has increased for both maintenance and foundation of highways. Although, the traffic growth rates, in volume and weight, in addition to the weather conditions, has produce dearly degradation of the pavements. In this context, the numeric analysis of pavement structures became more and more relevant to predict the behavior of the pavements. This work evaluates numerically the stress and strain in pavements, according the traffic loading, using Finite Element Method. Thereby, the estimation of that effect in the life cycle of the wearing course is done. Several numerical analyses are fulfilled considering changes in the physical features of pavement layers. The adopted values for the layers features are acquired from the literature considering the interval of values obtained from each material in use. Each analysis includes the calculation of the deflection and the strain, respectively, in the top and in the base of wearing course. The estimation of the necessary number of cycles for the fatigue in the wearing course is done by three models from the literature. The analysis indicates the subbase course as relevant to reduce the stress in the top of subgrade, while the base and wearing course influence more significantly in the deflections in the top of pavement and the fatigue in wearing course. / No Brasil, o aumento nos investimentos em infraestrutura de transportes contempla tanto a manutenção quanto a implantação de novas rodovias. Contudo, o aumento do tráfego, em volume e peso, associado às condições de intempéries, tem resultado na degradação precoce do pavimento. Nesse contexto, a análise numérica da estrutura do pavimento torna-se cada vez mais relevante para prever o comportamento dos pavimentos. Este trabalho tem o objetivo de estudar numericamente as tensões e deformações em estruturas de pavimentos, submetidas a cargas de tráfego, através do Método dos Elementos Finitos, e avaliar seus efeitos sobre a vida útil da camada de revestimento. Diversas análises numéricas serão realizadas modificando as características físicas das camadas do pavimento. Os valores adotados para as características das camadas são obtidos através de pesquisa bibliográfica da faixa de valores encontrada para cada material utilizado. A cada análise é avaliado o valor da deflexão e da deformação, respectivamente, no topo e na base do revestimento. O número de ciclos necessários para a fadiga do revestimento é calculado através de três modelos disponíveis na literatura. As análises indicam que a camada de sub-base é relevante para reduzir as tensões no topo do subleito, enquanto que a base e o revestimento influenciam mais significativamente na deflexão no topo do pavimento e na fadiga do revestimento.
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