Estabilidade primária adequada em densidades ósseas de resistências variadas é um dos fatores importantes para o sucesso da osseointegração. O objetivo deste estudo foi avaliar comparativamente a estabilidade inicial de diferentes tipos de implantes, utilizando cilindros ósseos padronizados de origem suína, de alta e baixa densidades, em modelo in vitro, por meio de Análises Tri-dimensionais (microtomografia computadorizada); Torque de Inserção e Ensaio de Arrancamento. Os cilindros ósseos foram preparados a partir de osso suíno, retirados do côndilo mandibular ou da cabeça do fêmur, e separados em 2 grupos: Grupo A: cilindros removidos da cabeça do fêmur (alta densidade óssea), e Grupo B: cilindros removidos do côndilo mandibular (baixa densidade óssea). Previamente aos procedimentos experimentais os cilindros ósseos foram certificados por meio de análises de imagens 2D e 3D, para garantir a uniformidade intra-grupos e distinção entre-grupos dos espécimes. Após a certificação, foram feitas microtomografias computadorizadas dos cilindros ósseos, para análise tridimensional de imagens prévia à instalação dos implantes, avaliando os seguintes parâmetros: Densidade Óssea Tridimensional (DOT); Separação Trabecular (STB); Porcentagem de Poros Abertos (PPA); Porcentagem de Poros Fechados (PPF) e Porcentagem de Porosidade Total (PPT). Esses parâmetros foram avaliados em três níveis ósseos (N1 interno às roscas do implante a ser instalado; N2 adjacente ao final das roscas até 0,5 mm destas; N distante 0,5 mm a 1,5 mm do final das roscas). Depois disso, foram selecionados 20 implantes (Titaniumfix®) de dois modelos, divididos em 4 grupos, cada um com 05 implantes: Grupo 1 (G1): Implante e-Fix HE instalado em cilindro ósseo de alta densidade; Grupo 2 (G2): Implante e-Fix HE instalado em cilindro ósseo de baixa densidade; Grupo 3 (G3): Implante e-Fix HE Silver instalado em cilindro ósseo de alta densidade; Grupo 4 (G4) : Implante e-Fix HE Silver instalado em cilindro ósseo de baixa densidade. A instalação dos implantes seguiu o protocolo recomendado pelo fabricante, e durante o procedimento foi feita a medida do torque de inserção. Após a instalação dos implantes, todos os cilindros ósseos foram submetidos a nova análise tridimensional com os mesmos parâmetros e níveis ósseos previamente descritos, e ao ensaio de arrancamento. Os resultados das análises tridimensionais mostraram diferenças estatisticamente significantes intra grupos nas situações pré- e pós-implantes para G3 e G4, em todos os níveis e para todos os parâmetros tomográficos. Observou-se também no Nível 2 diferenças estatisticamente significantes intra grupos para todos os grupos e todos os parâmetros. No nível 3, foi observado um comprometimento nos valores dos parâmetros DOT e PPA, eststisticamente significante para G1, G3 e G4, e numericamente pronunciado no G2 (Teste de Friedman, p<0,05). Os ensaios biomecânicos mostraram que os implantes instalados no G3 (e-Fix HE Silver) tiveram maior torque de inserção e maior resistência ao arrancamento quando comparados ao mesmo tipo de implante instalado no G4 e aos implantes do modelo e-fix HE instalados no G2 (teste de Friedman, p<0,05). Concluiu-se que a metodologia apresentada gera cilindros ósseos padronizados de alta e baixa densidades, o formato dos implantes e-Fix Silver mostrou melhores resultados nos testes biomecânicos e a densidade óssea radiográfica e tomográfica correlacionou-se à estabilidade primária. / This study comparatively evaluated the primary stability of two different implants, placed in standardized porcine bone cylinders of high and low density, analyzing 3D images (computerized micro tomography - micro-CT), insertion torque and pullout strength test. Bone cylinders were prepared from porcine bone and separated into 2 groups: cylinders removed from femur head (high density bone - HDB), and cylinders removed from mandibular condyle (low density bone - LDB). The bone cylinders were previously certificated to guarantee intra-groups standardization and between groups discrimination. Then, 3D analysis evaluated the following tomographic parameters of bone cylinders: Tridimensional bone density (BV/TV), Trabecular Separation (Tb.Sp); Percentage of closed pores (POcl); Percentage of open pores (POop); Percentage of total porosity (POtot). These parameters were evaluated in 3 bone levels (L1 - bone volume internal to the threads; L2 - immediately adjacent to the end of threads until 0.5 mm; L3 - 0.5 mm to 1.5 mm distant to the end of threads). Twenty implants (TitaniumFix®) from two different models were divided in 4 groups (5 implants each): Group 1 (G1) - e-Fix HE implant placed in HDB cylinder; Group 2 (G2) - e-Fix HE implant placed in LDB cylinder; Group 3 (G3) - e-Fix HE Silver implant placed in HDB cylinder; Group 4 (G4) - e-Fix HE Silver implant placed in LDB cylinder. During implant placement the insertion torque was recorded. Following implant installation, bone cylinders were evaluated by micro-CT, as previously described. After that, pullout strength test was performed. The results of 3D analysis showed pre- and post-implants intra-groups statistically significant differences for G3 and G4, in all evaluation levels and for all tomographic parameters. The analysis of L3 showed a significant decrease from pre to post-implant situation in BV/TV and PO.op for G1, G3 and G4. Group 3 showed the higher values for insertion torque and pullout strength test (for all analysis, Friedman Test, p<0.05). It was concluded that this methodology can produce standardized bone cylinders of high and low bone density, e-Fix Silver implants showed better results in biomechanical assays, and different implant designs can promote diverse effects, modifying the bone structure .

When subjected to a combination of moment and shear force, a reinforced concrete (RC) beam with either little or no transverse reinforcement can fail in shear before reaching its full flexural strength. This type of failure is sudden in nature and usually disastrous because it does not give sufficient warning prior to collapse. To prevent this type of shear failure, reinforced concrete beams are traditionally reinforced with stirrups. However, the use of stirrups is not always cost effective since it increases labor costs, and can make casting concrete difficult in situations where closely-spaced stirrups are required. The use of steel fiber reinforced concrete (SFRC) could be considered as a potential alternative to the use of traditional shear reinforcement. Concrete is very weak and brittle in tension, SFRC transforms this behaviour and improves the diagonal tension capacity of concrete and thus can result in significant enhancements in shear capacity. However, one of the drawbacks associated with SFRC is that the addition of fibers to a regular concrete mix can cause problems in workability. The use of self-consolidating concrete (SCC) is an innovative solution to this problem and can result in improved workability when fibers are added to the mix. The thesis presents the experimental results from tests on twelve slender self-consolidating fiber reinforced concrete (SCFRC) beams tested under four-point loading. The results demonstrate the combined use of SCC and steel fibers can improve the shear resistance of reinforced concrete beams, enhance crack control and can promote flexural ductility. Despite extensive research, there is a lack of accurate and reliable design guidelines for the use of SFRC in beams. This study presents a rational model which can accurately predict the shear resistance of steel fiber reinforced concrete beams. The thesis also proposes a safe and reliable equation which can be used for the shear design of SFRC beams.

Bone drilling is a major part of orthopaedic surgery performed during the internal fixation of fractured bones. At present, information related to drilling force, drilling torque, rate of drill bit penetration and drill bit rotational speed is not available to orthopaedic surgeons, clinicians and researchers as bone drilling is performed manually. This research demonstrates that bone drilling force data if recorded in-vivo, during the repair of bone fractures, can provide information about the strength/quality of the bone. Drilling force does not give a direct measure of bone strength; therefore it has been correlated with the shear strength and screw pullout strength to determine the efficacy in estimating the bone strength. Various synthetic bone material densities and animal bones have been tested to demonstrate the use of drilling force data. A novel automated experimental test rig, which enables drilling tests, screw insertion and screw pullout tests to be carried out in a controlled environment, has been developed. Both drilling and screw pullout tests have been carried out in a single setting of the specimen to reduce the experimental errors and increase repeatability of the results. A significantly high value of correlation (r² > 0.99) between drilling force & shear strength and also between drilling force & normalised screw pullout strength in synthetic bone material was found. Furthermore, a high value of correlation (r² = 0.958 for pig bones and r² = 0.901 for lamb bones) between maximum drilling force & normalised screw pullout strength was also found. The result shows that drilling data can be used to predict material strength. Bone screws are extensively used during the internal fixation of fractured bones. The amount of screw been tightened is one of the main factor which affects the bone-screw fixation quality. Over tightening of screw can result into the loss of bone-screw fixation strength, whereas under tightening can result in the screw loosening. Therefore, optimum tightening of the screw is important to achieve the maximum bone-screw fixation strength. At present, optimum tightening of the screw is entirely dependent upon the skill and judgment of the surgeon, which is predominantly based on the feel of the screw tightening torque. Various studies have been reported in the literature to develop an algorithm to set an optimum tightening torque value to be used in surgery. A method which is based on the use of rotation angle of the screw while tightening, rather than using screw insertion/tightening torque, to optimise the bone-screw fixation strength is proposed in this research. The effectiveness of the proposed method has been successfully demonstrated on the synthetic bone material using the designed test rig. The optimum angle for the tested screw was found to be 120° which is equivalent to 33% of the screw pitch.

When subjected to a combination of moment and shear force, a reinforced concrete (RC) beam with either little or no transverse reinforcement can fail in shear before reaching its full flexural strength. This type of failure is sudden in nature and usually disastrous because it does not give sufficient warning prior to collapse. To prevent this type of shear failure, reinforced concrete beams are traditionally reinforced with stirrups. However, the use of stirrups is not always cost effective since it increases labor costs, and can make casting concrete difficult in situations where closely-spaced stirrups are required. The use of steel fiber reinforced concrete (SFRC) could be considered as a potential alternative to the use of traditional shear reinforcement. Concrete is very weak and brittle in tension, SFRC transforms this behaviour and improves the diagonal tension capacity of concrete and thus can result in significant enhancements in shear capacity. However, one of the drawbacks associated with SFRC is that the addition of fibers to a regular concrete mix can cause problems in workability. The use of self-consolidating concrete (SCC) is an innovative solution to this problem and can result in improved workability when fibers are added to the mix. The thesis presents the experimental results from tests on twelve slender self-consolidating fiber reinforced concrete (SCFRC) beams tested under four-point loading. The results demonstrate the combined use of SCC and steel fibers can improve the shear resistance of reinforced concrete beams, enhance crack control and can promote flexural ductility. Despite extensive research, there is a lack of accurate and reliable design guidelines for the use of SFRC in beams. This study presents a rational model which can accurately predict the shear resistance of steel fiber reinforced concrete beams. The thesis also proposes a safe and reliable equation which can be used for the shear design of SFRC beams.

When subjected to a combination of moment and shear force, a reinforced concrete (RC) beam with either little or no transverse reinforcement can fail in shear before reaching its full flexural strength. This type of failure is sudden in nature and usually disastrous because it does not give sufficient warning prior to collapse. To prevent this type of shear failure, reinforced concrete beams are traditionally reinforced with stirrups. However, the use of stirrups is not always cost effective since it increases labor costs, and can make casting concrete difficult in situations where closely-spaced stirrups are required. The use of steel fiber reinforced concrete (SFRC) could be considered as a potential alternative to the use of traditional shear reinforcement. Concrete is very weak and brittle in tension, SFRC transforms this behaviour and improves the diagonal tension capacity of concrete and thus can result in significant enhancements in shear capacity. However, one of the drawbacks associated with SFRC is that the addition of fibers to a regular concrete mix can cause problems in workability. The use of self-consolidating concrete (SCC) is an innovative solution to this problem and can result in improved workability when fibers are added to the mix. The thesis presents the experimental results from tests on twelve slender self-consolidating fiber reinforced concrete (SCFRC) beams tested under four-point loading. The results demonstrate the combined use of SCC and steel fibers can improve the shear resistance of reinforced concrete beams, enhance crack control and can promote flexural ductility. Despite extensive research, there is a lack of accurate and reliable design guidelines for the use of SFRC in beams. This study presents a rational model which can accurately predict the shear resistance of steel fiber reinforced concrete beams. The thesis also proposes a safe and reliable equation which can be used for the shear design of SFRC beams.

O melhor comportamento de uma estrutura de solo reforçado com geossintéticos não depende só da elevada resistência à tração da inclusão, mas também da sua rigidez e do nível de carregamento sob o qual a estrutura está submetida. Dessa maneira, a interação entre o reforço e as respectivas camadas de solo ao seu redor torna-se de grande importância, pois a mobilização cisalhante combina a deformação da interface solo-reforço e o alongamento do geossintético. Sendo que a melhor forma de avaliar a interação entre o solo e a geogrelha é por meio de ensaios de arrancamento, pensa-se na realização de ensaios de arrancamento cíclico para analisar a interação dinâmica entre o solo e a inclusão quando certas estruturas são submetidas a esse tipo de solicitação. Por causa disso, o objetivo principal deste trabalho é analisar o efeito produzido por carregamentos monotônicos e cíclicos de interface numa geogrelha biaxial de polipropileno, quando inserida na interface de um solo argiloso e um solo arenoso sob diferentes tensões de confinamento. Para isso, são utilizados os equipamentos de pequenas e grandes dimensões do Laboratório de Geossintéticos da EESC-USP, visando avaliar a sua relação e a viabilidade de uso do equipamento de pequenas dimensões. Inicialmente foram realizados ensaios de arrancamento monotônico em ambos os equipamentos sob tensões de confinamento de 25, 50 e 100 kPa, sendo que as resistências obtidas com as tensões de 25 e 100 kPa permitiram definir as amplitudes do carregamento cíclico correspondentes ao 20% de tais valores. Adicionalmente, após a aplicação dos 10.000 ciclos de carga correspondentes à capacidade do equipamento, foi aplicado novamente um carregamento monotônico com o intuito de determinar o efeito do carregamento dinâmico na resistência ao arrancamento e assim poder realizar as respectivas comparações com os valores iniciais. Com base nos resultados obtidos, foi possível observar a diferença no grau de confinamento entre ambos os equipamentos, sendo maior no de grandes dimensões por causa da melhor distribuição das tensões sobre a área ocupada pela geogrelha. Adicionalmente, o grau de confinamento em ambos os equipamentos também influenciou a diferença no efeito do carregamento dinâmico, sendo de desconfinamento no de grandes dimensões e de densificação no de pequenas dimensões. / The best behavior of a reinforced soil structure with geosynthetics not only depends on the high tensile strength of the inclusion, but also on its rigidity and the loading level in which the structure is subjected. Thus, the interaction between the reinforcement and the respective layers of soil around, becomes very important because the shear mobilization combines the deformation of the soil-reinforcement interface and the lengthening of the geosynthetic. Since the best way to assess the soil-geogrid interaction is through pullout tests, it is thought in performing cyclic pullout tests to examine the dynamic soil-inclusion interaction when some structures are submitted to that kind of loads. Because of that, the main objective of this work is to analize the effect that is produced by monotonic and cyclic interface loading on a biaxial polypropylene geogrid, when it is inserted into the interface of a clayey soil and a sandy soil under different confinement stresses. For that, the small and large dimensions equipments of the Geosynthetics Laboratory at EESC-USP are used, looking to evaluate their relationship and the feasibility of using a small dimensions equipment. Initially, they were performed monotonic pullout tests in both equipments under confinement stresses of 25, 50 and 100 kPa, wherein the pullout strengths obtained with 25 and 100 kPa allowed the definition of the load cyclic amplitudes, which corresponded to 20% of such values. Additionally, after applying 10.000 load cycles, corresponding to the capacity of the equipment, it was applied a monotonic loading in order to determine the dynamic loading effect on pullout strength, being useful to compare such values with the initial response. Based on the obtained results, it was possible to observe the difference in the confinement degree between both equipments, being higher in the large one because of the better stress distribution on the geogrid area. Aditionally, the confinement degree in both equipments also influenced the difference in the dynamic loading effect, being deconfinement in the soil-geogrid interface of the large one and densification in the other one.

O melhor comportamento de uma estrutura de solo reforçado com geossintéticos não depende só da elevada resistência à tração da inclusão, mas também da sua rigidez e do nível de carregamento sob o qual a estrutura está submetida. Dessa maneira, a interação entre o reforço e as respectivas camadas de solo ao seu redor torna-se de grande importância, pois a mobilização cisalhante combina a deformação da interface solo-reforço e o alongamento do geossintético. Sendo que a melhor forma de avaliar a interação entre o solo e a geogrelha é por meio de ensaios de arrancamento, pensa-se na realização de ensaios de arrancamento cíclico para analisar a interação dinâmica entre o solo e a inclusão quando certas estruturas são submetidas a esse tipo de solicitação. Por causa disso, o objetivo principal deste trabalho é analisar o efeito produzido por carregamentos monotônicos e cíclicos de interface numa geogrelha biaxial de polipropileno, quando inserida na interface de um solo argiloso e um solo arenoso sob diferentes tensões de confinamento. Para isso, são utilizados os equipamentos de pequenas e grandes dimensões do Laboratório de Geossintéticos da EESC-USP, visando avaliar a sua relação e a viabilidade de uso do equipamento de pequenas dimensões. Inicialmente foram realizados ensaios de arrancamento monotônico em ambos os equipamentos sob tensões de confinamento de 25, 50 e 100 kPa, sendo que as resistências obtidas com as tensões de 25 e 100 kPa permitiram definir as amplitudes do carregamento cíclico correspondentes ao 20% de tais valores. Adicionalmente, após a aplicação dos 10.000 ciclos de carga correspondentes à capacidade do equipamento, foi aplicado novamente um carregamento monotônico com o intuito de determinar o efeito do carregamento dinâmico na resistência ao arrancamento e assim poder realizar as respectivas comparações com os valores iniciais. Com base nos resultados obtidos, foi possível observar a diferença no grau de confinamento entre ambos os equipamentos, sendo maior no de grandes dimensões por causa da melhor distribuição das tensões sobre a área ocupada pela geogrelha. Adicionalmente, o grau de confinamento em ambos os equipamentos também influenciou a diferença no efeito do carregamento dinâmico, sendo de desconfinamento no de grandes dimensões e de densificação no de pequenas dimensões. / The best behavior of a reinforced soil structure with geosynthetics not only depends on the high tensile strength of the inclusion, but also on its rigidity and the loading level in which the structure is subjected. Thus, the interaction between the reinforcement and the respective layers of soil around, becomes very important because the shear mobilization combines the deformation of the soil-reinforcement interface and the lengthening of the geosynthetic. Since the best way to assess the soil-geogrid interaction is through pullout tests, it is thought in performing cyclic pullout tests to examine the dynamic soil-inclusion interaction when some structures are submitted to that kind of loads. Because of that, the main objective of this work is to analize the effect that is produced by monotonic and cyclic interface loading on a biaxial polypropylene geogrid, when it is inserted into the interface of a clayey soil and a sandy soil under different confinement stresses. For that, the small and large dimensions equipments of the Geosynthetics Laboratory at EESC-USP are used, looking to evaluate their relationship and the feasibility of using a small dimensions equipment. Initially, they were performed monotonic pullout tests in both equipments under confinement stresses of 25, 50 and 100 kPa, wherein the pullout strengths obtained with 25 and 100 kPa allowed the definition of the load cyclic amplitudes, which corresponded to 20% of such values. Additionally, after applying 10.000 load cycles, corresponding to the capacity of the equipment, it was applied a monotonic loading in order to determine the dynamic loading effect on pullout strength, being useful to compare such values with the initial response. Based on the obtained results, it was possible to observe the difference in the confinement degree between both equipments, being higher in the large one because of the better stress distribution on the geogrid area. Aditionally, the confinement degree in both equipments also influenced the difference in the dynamic loading effect, being deconfinement in the soil-geogrid interface of the large one and densification in the other one.