En structure, le bois est soumis à des sollicitations différentes dont les principales sont physiques, mécaniques et environnementales. Lorsque ces sollicitations sont couplées, le comportement mécanique du bois devient difficile à appréhender. L’objectif de cette thèse est de mettre en évidence, via un protocole de suivi de l’évolution de la flèche, l’impact des variations des conditions climatiques sur la durée de vie en structure des poutres de bois. Le travail s’articule essentiellement autour de deux grands axes principaux, un protocole expérimental spécial et une approche analytique basée sur la résistance des matériaux (RDM) de l’évolution de la flèche d’une poutre entaillée en ambiance non contrôlée. Le dispositif prend en compte : les processus de fissuration du bois, notamment de l’ouverture et de la propagation de la pointe d’une fissure se propageant linéairement depuis le droit de l’entaille, jusqu’à la rupture totale de la poutre ; le suivi des paramètres climatiques que sont la température, l’humidité relative du milieu et les variations de l’humidité interne des poutres testées. Les résultats obtenus montrent qu’une humidification entraine une augmentation de la flèche relative et un séchage génère un départ de fissures pouvant conduire à une rupture de la poutre. Le modèle analytique de l’évolution de la flèche d’une poutre entaillée en ambiance non contrôlée, est tiré des hypothèses classiques de la théorie des poutres de Timoshenko et de l’ensemble des résultats expérimentaux obtenus. Il prend en compte les processus de fissuration, les variations de son humidité interne et l’intensité du chargement qui lui est appliqué. Le modèle représente assez bien les comportements instantané et différé de la poutre induits par les chargements mécanique et environnementaux. / In structure, wood is subjected to different loadings, where the principals are physical, mechanical and environmental. The coupling of these different loadings, make the understand of the mechanical behaviour of wood difficult. The aim of this thesis is to highlight, through a protocol for monitoring the evolution of the deflection, the impact of the conditions of climatic variations on the lifetime of timber of the notched beams. The work is essentially based around two major axes highlighting, respectively, a new experimental devices and a new analytical approach of the following of the evolution of the beam deflection, in outdoor conditions. The experimental device takes into account: the monitoring of the evolution of the notched-beam deflection; the cracking processes of wood, in particular the following of its initiation, the opening and the propagation of the tip of crack which appeared, on the notched-beam until its collapse; the monitoring of the climatic parameters such as temperature, the environmental relative humidity and the variations of the moisture content of the beams during the test. The results show that the variations of these climatic parameters favour the acceleration of the wood aging process in the structure. The analytical model of the evolution of the deflection of a notched beam, shown in this work, is based on the classical hypotheses of Timoshenko’s beam theory and all the experimental results obtained. It takes into account the cracking processes of notched-beam, the variations of its moisture content and the intensity of the loading applied on the beam.

Os materiais cerâmicos são utilizados pelo homem há milhares de anos e podem ser considerados os primeiros materiais utilizados na fabricação de ferramentas. Argamassas são materiais cerâmicos formados pela mistura de cimento, areia e água, são fluidos nas primeiras horas e endurecem com o tempo, ganhando resistência mecânica, já os refratários são materiais constituídos basicamente por duas partes, uma de granulometria fina denominada matriz e a outra de granulometria grosseira, chamada agregado, trabalham em altas temperaturas e muitas vezes sofrem choques térmicos. Devido a sua fragilidade, são susceptíveis a fratura catastrófica, por isso o conhecimento de seu comportamento mecânico é tão importante. Uma importante propriedade dos materiais cerâmicos é a energia de fratura e o método mais conhecido para a sua determinação é o da barra entalhada flexionada em três ou quatro pontos, porém o grande problema deste método é a relação de tamanho de agregado/área de fratura, pois como a barra apresenta, em geral, pequenas dimensões, o material pode apresentar um agregado de dimensões próximas à dimensão da área de fraturada e o resultado final pode ser fortemente afetado. Então, em 1986, Tschegg patenteou o método da cunha (wedge splitting test) que minimiza este efeito, devido à utilização de amostras com grande área de fratura. Desde então, este método vem sendo utilizado com freqüência por diversos pesquisadores no mundo. Porém não há estudos publicados que definam a posição ideal dos roletes do dispositivo de teste, levando ao uso de diferentes posições, sem que se saiba como isso pode influenciar o ensaio. Além de não existir uma definição de, a partir de que tamanho de agregado o método da barra entalhada passa a ser desaconselhável sendo necessário o uso do método da cunha. Neste trabalho analisou-se a influência da posição dos roletes e do tamanho de agregados nas medidas de energia de fratura e na carga máxima atingida no ensaio. / The ceramic materials are used by humans for thousands of years and can be considerate the first materials used in the manufacture of tools. Mortar are ceramic materials made by the mixture of cement, sand and water, it is fluid in the first hours and stiffen over time, gaining mechanical strength, the refractories in turn are made basically of two phases, one of fine granulometry called matrix and another of coarse called aggregate. It works over high temperature and many times suffer thermal shock. Due to its fragility, it is susceptible to catastrophic fracture; therefore the knowledge of its mechanical behavior is so important. One of the mainly properties of ceramic materials is the fracture energy and o most knew method for its determination is of three-point bending test on notched beams, but the biggest problem of this method is the relation between aggregate size and fracture area, because as the beam has small dimensions the aggregate can have a dimension so closed of the fracture area dimension and the final result can be tightly affect. Then in 1986, Tschegg patented the wedge splitting test, which minimizes this effect, because of the use of samples with a big fracture area. Since then, this method has been used for scientists around the world. But there are no studies that define the roll position of the test device, leading to the use of different positions, without know how it can influence the test. Besides not having a definition of from what aggregate size the wedge splitting test is advisable in despite of the bending test on notched beams. In this work was analyzed the influence of the rolls positions in the wedge splitting test and of the aggregate size in the measures of fracture energy and maximum load of test.

Os materiais cerâmicos são utilizados pelo homem há milhares de anos e podem ser considerados os primeiros materiais utilizados na fabricação de ferramentas. Argamassas são materiais cerâmicos formados pela mistura de cimento, areia e água, são fluidos nas primeiras horas e endurecem com o tempo, ganhando resistência mecânica, já os refratários são materiais constituídos basicamente por duas partes, uma de granulometria fina denominada matriz e a outra de granulometria grosseira, chamada agregado, trabalham em altas temperaturas e muitas vezes sofrem choques térmicos. Devido a sua fragilidade, são susceptíveis a fratura catastrófica, por isso o conhecimento de seu comportamento mecânico é tão importante. Uma importante propriedade dos materiais cerâmicos é a energia de fratura e o método mais conhecido para a sua determinação é o da barra entalhada flexionada em três ou quatro pontos, porém o grande problema deste método é a relação de tamanho de agregado/área de fratura, pois como a barra apresenta, em geral, pequenas dimensões, o material pode apresentar um agregado de dimensões próximas à dimensão da área de fraturada e o resultado final pode ser fortemente afetado. Então, em 1986, Tschegg patenteou o método da cunha (wedge splitting test) que minimiza este efeito, devido à utilização de amostras com grande área de fratura. Desde então, este método vem sendo utilizado com freqüência por diversos pesquisadores no mundo. Porém não há estudos publicados que definam a posição ideal dos roletes do dispositivo de teste, levando ao uso de diferentes posições, sem que se saiba como isso pode influenciar o ensaio. Além de não existir uma definição de, a partir de que tamanho de agregado o método da barra entalhada passa a ser desaconselhável sendo necessário o uso do método da cunha. Neste trabalho analisou-se a influência da posição dos roletes e do tamanho de agregados nas medidas de energia de fratura e na carga máxima atingida no ensaio. / The ceramic materials are used by humans for thousands of years and can be considerate the first materials used in the manufacture of tools. Mortar are ceramic materials made by the mixture of cement, sand and water, it is fluid in the first hours and stiffen over time, gaining mechanical strength, the refractories in turn are made basically of two phases, one of fine granulometry called matrix and another of coarse called aggregate. It works over high temperature and many times suffer thermal shock. Due to its fragility, it is susceptible to catastrophic fracture; therefore the knowledge of its mechanical behavior is so important. One of the mainly properties of ceramic materials is the fracture energy and o most knew method for its determination is of three-point bending test on notched beams, but the biggest problem of this method is the relation between aggregate size and fracture area, because as the beam has small dimensions the aggregate can have a dimension so closed of the fracture area dimension and the final result can be tightly affect. Then in 1986, Tschegg patented the wedge splitting test, which minimizes this effect, because of the use of samples with a big fracture area. Since then, this method has been used for scientists around the world. But there are no studies that define the roll position of the test device, leading to the use of different positions, without know how it can influence the test. Besides not having a definition of from what aggregate size the wedge splitting test is advisable in despite of the bending test on notched beams. In this work was analyzed the influence of the rolls positions in the wedge splitting test and of the aggregate size in the measures of fracture energy and maximum load of test.

Self-consolidating concrete (SCC) has wide use for placement in congested reinforced concrete structures in recent years. SCC represents one of the most outstanding advances in concrete technology during the last two decades. In the current work a great deal of cognizance pertaining to mechanical properties of SCC and comparison of fracture characteristics of notched and unnotched beams of plain concrete as well as using acoustic emission to understand the localization of crack patterns at different stages has been done. An artificial neural network (ANN) is proposed to predict the 28day compressive strength of a normal and high strength of SCC and HPC with high volume fly ash. The ANN is trained by the data available in literature on normal volume fly ash because data on SCC with high volume fly ash is not available in sufficient quantity. Fracture characteristics of notched and unnotched beams of plain self consolidating concrete using acoustic emission to understand the localization of crack patterns at different stages has been done. Considering this as a platform, further analysis has been done using moment tensor analysis as a new notion to evaluate fracture characteristics in terms of crack orientation, direction of crack propagation at nano and micro levels. Analysis of B-value (b-value based on energy) is also carried out, and this has introduced to a new idea of carrying out the analysis on the basis of energy which gives a clear picture of results when compared with the analysis carried out using amplitudes. Further a new concept is introduced to analyze crack smaller than micro (could be hepto cracks) in solid materials. Each crack formation corresponds to an AE event and is processed and analyzed for crack orientation, crack volume at hepto and micro levels using moment tensor analysis based on energy. Cracks which are tinier than microcracks (could be hepto), are formed in large numbers at very early stages of loading prior to peak load. The volume of hepto and micro cracks is difficult to measure physically, but could be characterized using AE data in moment tensor analysis based on energy. It is conjectured that the ratio of the volume of hepto to that of micro could reach a critical value which could be an indicator of onset of microcracks after the formation of hepto cracks.