CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / VÃrios fatores podem influenciar no comportamento resiliente de materiais granulares, dentre eles vale citar a umidade que pode variar de acordo com as condiÃÃes ambientais a que os pavimentos estarÃo sujeitos no campo (infiltraÃÃo de Ãgua de chuva pelas trincas do pavimento ou pelos acostamentos, variaÃÃo do nÃvel do lenÃol freÃtico, transferÃncia de umidade entre as camadas devido Ãs variaÃÃes de temperatura, etc). As variaÃÃes climÃticas sazonais podem acarretar alteraÃÃes que comprometam o desempenho do pavimento, sendo importante verificar quais os materiais locais que melhor resistem a tais variaÃÃes. Na tentativa de analisar um pavimento mais adequado Ãs caracterÃsticas regionais, o presente trabalho teve o objetivo de avaliar os efeitos da variaÃÃo da umidade dos solos na anÃlise dos pavimentos à luz de mÃtodos empÃricos e mecanÃsticos-empÃricos. Para tanto, foram realizadas anÃlises numÃricas (atravÃs do programa de anÃlise CAP3D e do programa de dimensionamento SisPav) para determinar tensÃes e deslocamentos atuantes nos pavimentos asfÃlticos, considerando-se o efeito da variaÃÃo da umidade nos solos. Para execuÃÃo do programa experimental foram coletados solos no municÃpio de Caucaia, localizado na RegiÃo Metropolitana de Fortaleza, estado do CearÃ, que foram submetidos aos ensaios de caracterizaÃÃo, compactaÃÃo, CBR (Ãndice de Suporte CalifÃrnia) e MR (MÃdulo de ResiliÃncia). O ensaio de CBR foi realizado em diferentes condiÃÃes de imersÃo. Jà o MR dos solos foi avaliado nas umidades de compactaÃÃo e pÃs-compactaÃÃo. A partir dos resultados de laboratÃrio foram realizadas anÃlises numÃricas para determinar tensÃes e deslocamentos atuantes nos pavimentos asfÃlticos. Os resultados mostram que os valores de MR sÃo mais sensÃveis à variaÃÃo do teor de umidade para o caso de solos pertencentes ao subleito do que para os provenientes de jazidas. Os estudos mostram, ainda, que a variaÃÃo da umidade influencia nos resultados dos deslocamentos verticais, das tensÃes horizontais e verticais dos pavimentos. Verificou-se que a alteraÃÃo de  2% em termos absolutos em torno da umidade Ãtima, normalmente aceito para a compactaÃÃo do solo em campo, pode representar variaÃÃes significativas nos dimensionamentos dos pavimentos. Percebeu-se que estruturas mais esbeltas sÃo obtidas quando se considera os materiais 2% abaixo da umidade Ãtima, tanto de compactaÃÃo quanto de pÃs-compactaÃÃo. Mas esta prÃtica nÃo deve ser incentivada, pois se a umidade vier a aumentar a tendÃncia à que o pavimento seja prejudicado. / Several factors may influence the resilient behavior of granular materials, among which it is worth mentioning the moisture content. The moisture variation depends on the environmental conditions to which the pavements will be subjected in the field (infiltration of rainwater through the cracks of the pavement or shoulders, groundwater level variation, moisture transfer between layers due to temperature variations, etc.). It is well known that seasonal climatic changes can affect the performance of the pavement. Thus, it is important to choose local materials that better resist such changes. In an attempt to analyze a pavement that best suits regional characteristics, this study aims to evaluate the effects of soil moisture variation in the analysis of pavements in the light of empirical and mechanistic-empirical design methods. Numerical analyses were performed (through the programs CAP3D and SisPav) to determine stresses and displacements on asphalt pavements with different soil layers moisture contents. For the experimental program, different soils were collected in the city of Caucaia, located in the Metropolitan Region of Fortaleza, state of CearÃ, which were subjected to the following laboratory tests: compaction, CBR (California Bearing Ratio) and MR (Resilient Modulus). CBR was conducted in different conditions of saturation. On the other hand, resilient moduli were evaluated in the compaction and post-compaction humidities. Using the results of laboratory tests, numerical analyses were performed to obtain stresses and displacements on asphalt pavements. The results show that MR values are more sensitive to variation of the moisture content in the case of subgrade soils than for those soils of deposits. The studies also show that the variation of moisture affects the results of vertical displacements, as well as horizontal and vertical stresses. It was found that the variation of  2%, in absolute terms around the optimum moisture normally accepted for soil compaction in the field, may represent significant variations in the design of flexible pavements. It was also observed that slender structures are obtained when considering materials 2% below the optimum moisture content in compaction and in post-compaction cases. But this practice should not be encouraged, because if moisture increases the pavement will probably be damaged.

In this thesis, the focus has been on micro-mechanical mechanisms in polymer-based materials and structures. The first part of the thesis treats length-scale effects on polymer materials. Experiments have showed that the smaller the specimen, the stronger is the material. The length-scale effect was examined experimentally in two different polymers materials, polystyrene and epoxy. First micro-indentations to various depths were made on polystyrene. The experiments showed that length-scale effects in inelastic deformations exist in polystyrene. It was also possible to show a connection between the experimental findings and the molecular length. The second experimental study was performed on glass-sphere filled epoxy, where the damage development for tensile loading was investigated. It could be showed that the debond stresses increased with decreasing sphere diameter. The debonding grew along the interface and eventually these cracks kinked out into the matrix. It was found that the length to diameter ratio of the matrix cracks increased with increasing diameter. The experimental findings may be explained by a length-scale effect in the yield process which depends on the strain gradients. The second part of the thesis treats mechano-sorptive creep in paper, i.e. the acceleration of creep by moisture content changes. Paper can be seen as a polymer based composite that consists of a network of wood fibres, which in its turn are natural polymer composites. A simplified network model for mechano-sorptive creep has been developed. It is assumed that the anisotropic hygroexpansion of the fibres leads to large stresses at the fibre-fibre bonds when the moisture content changes. The resulting stress state will accelerate creep if the fibre material obeys a constitutive law that is non-linear in stress. Fibre kinks are included in order to capture experimental observations of larger mechano-sorptive creep effects in compression than in tension. Furthermore, moisture dependent material parameters and anisotropy are taken into account. Theoretical predictions based on the developed model are compared to experimental results for anisotropic paper both under tensile and compressive loading at varying moisture content. The important features in the experiments are captured by the model. Different kinds of drying conditions have also been examined. / QC 20100910