No / Concrete filled steel tube (CFST) columns are becoming increasingly popular due to the advantages they offered. They are not only considered aesthetically pleasing but can also offer significant improvement in axial capacity without increases in crosssectional area being required. Elliptical steel hollow sections represent a recent and rare addition to the range of cross-sections available to structural engineers, however, despite widespread interest in their application, a lack of verified design guidance is inhibiting uptake. The use of elliptical steel hollow section with concrete infill is new and innovative, not only provides the advantage mentioned above, but also on the basis of both architectural appeal and structural efficiency. The aim of this paper is to investigate the behaviour of the elliptical CFSTs under axial loading. A total of 12 specimens were tested with wall thicknesses of 4 mm, 5 mm, 6.3 mm and concrete core strength of 30 MPa. This paper reported on the behaviour of concrete filled elliptical hollow sections under axial load. The effect of the wall thickness of the steel section, the bond between steel and concrete and the concrete confinement are presented.

In the assumptions, it was indicated that a modification in the method of analysis would allow taking into account the variation in pressure. This could be done by assuming that the internal pressure P used in the analysis was the pressure after deformation. During deformation, the mass of the enclosed gas remains constant. Thus, knowing the initial and final volumes and the final pressure, the initial internal pressure could be determined using the appropriate gas law. / Master of Science

Three models are presented which predict frequencies and mode shapes of transverse vibration for a continuous prismatic Bernoulli-Euler beam on elastic supports, subjected to a compressive axial load. The first model, which approximates support stiffnesses by an equivalent elastic foundation, is found to be inaccurate for wave lengths close to the support spacing. A discrete mass model is formulated which accounts for axial load by stability functions which modify the element stiffness matrices. A continuous model is formulated which yields an exact solution for Bernoulli-Euler beam theory. The frequencies predicted by the discrete mass model and continuous model are in excellent agreement. A method of predicting axial compressive load and support stiffness based on measured frequency and phase data is presented which can be used for either the discrete mass model or the continuous model. A frequency reduction factor is derived which accounts for the effects of shear deformation and rotatory inertia. Tests are performed on an eight span beam with compressive axial load. Test results show that the models accurately predict frequencies and mode shapes of vibration. Results indicate that the method formulated can be used to determine compressive axial load and support stiffness. / Master of Science

Inflated fabric is being considered as new structural material at the present time. It can be used in certain applications with the advantage of reducing the weight of structures, it is adaptable as an architectural element of construction; moreover, it may be developed to be one of the most economical, and simple structural materials in the future. A number of experimental investigations of these inflated fabric structures has been studied by research units of airship and fabric companies. However, due to the difficulties of solving such problems by analysis, there is still lack of theoretical methods, even approximate solutions. The purpose of this thesis is to investigate theoretical analysis for finding the relation between the applied load and the deflections, stresses, and also the end shortening of an inflated cylindrical fabric envelope subjected to axial compression, by the energy method. A cylindrical shape is selected because sphere and cylinder are considered more general in use and more easily to be treated than any other geometrical shapes. Also, for the sake of simplicity, a constant internal pressure is assumed in the analysis. The use or large deflection theory for finding the critical buckling loading of thin shells was first advanced by Von Karman and Tsien (reference 6 and 7). Based on their conception; numerous studies concerning the buckling strength under various loadings have been investigated by others subsequently. The strain-displacement relation in their papers is expressed in the following form including terms up to second order: ε_x= ∂u/∂x+(½)(∂w/∂x)² ε_x= ∂v/∂y+(½)(∂w/∂y)²-(w/R) In this thesis, although the idea is applied to develop an analysis by the energy method, the strain-displacement relation is expressed in a different way which will be shown in the following sections. Generally, in avoiding the mathematical difficulty of solving the differential equations obtained from the energy expression, most boundary-value problems in the theory of elasticity may be solved by assuming a solution in the form of a series which satisfies the boundary conditions, then minimizing the energy expression to determine the values of unknown parameters in the assumed solution. In this thesis, instead of using the variational method mentioned above, a graphical method for solving the differential equations is presented. However, owing to the fact that not all of the boundary conditions are specified at one point, the final results have to be obtained. by trial and error. / Master of Science

Objective- To compare the biomechanical properties of 3.5 locking compression plate (LCP) fixation to 3.5 limited contact dynamic compression plate (LC-DCP) fixation in a canine cadaveric, distal humeral metaphyseal gap model in static axial compression and cyclic axial compression and torsion. Study Design- Biomechanical in vitro study. Sample Population- 30 paired humeri from adult, medium to large breed dogs. Methods- Testing was performed monotonically to failure in axial compression on ten pairs of humeri, cyclically in axial compression for 10,000 cycles on ten pairs and cyclically in torsion for 500 cycles on the last ten pairs. Results- Humeral constructs stabilized with LCPs were significantly stiffer than those plated with LC-DCPs when loaded in axial compression (P=0.0004). When cyclically loaded in axial compression over 10,000 cycles, the LC-DCP constructs were significantly stiffer than those constructs stabilized with LCPs (P=0.0029). Constructs plated with LC-DCPs were significantly more resistant to torsion over 500 cycles than those plated with LCPs (P<0.0001), though no difference was detected during the first 280 cycles. Conclusions- The increased stiffness of LCP constructs in monotonic loading compared to constructs stabilized with non-locking plates may be attributed to the stability afforded by the plate-screw interface of locking plates. The LCP constructs demonstrated less stiffness in dynamic testing in this model, likely due to plate-bone offset secondary to non-anatomic contouring and occasional incomplete seating of the locking screws when using the torque-limiting screw driver. Clinical Relevance- LCPs yield less stiff fixation under dynamic loading than conventional LC-DCPs when applied to severely comminuted, metaphyseal fractures. Improving anatomical contouring of the plate and insuring complete screw insertion into the locking plate hole may improve stiffness when using LCPs in comminuted fractures. / Master of Science

An analytical and experimental investigation of the response of composite cylinders of elliptical cross-section to axial compression and internal pressure loadings is discussed. Nine eight-ply graphite-epoxy elliptical cylinders, three layups for each of three cross sectional aspect ratios, are specifically examined. The lay-ups studied are a quasi-isotropic (±45/0/90)_g, an axially-stiff (±45/0₂)_g, and a circumferentially-stiff (±45/90₂)_g. The elliptical cross sections studied are characterized by semi-minor axis (b) to semi-major axis (a) ratios of b/a = 0.70, 0.85, and 1.00 (circular). The cross sections are obtained by holding the semi-major axis constant for all cross sections, and only varying the semi-minor axis. The nominal semi-major axis for all specimens was 5.00 in. (127 mm), and all specimens were cut to the same length, which provided a length-to-radius ratio of 2.9 for the circular cylinders. For the elliptical cross section cylinders, the length to- radius ratios, L/R(s), ranged from two to slightly greater than six, where R(s) is the function describing the circumferential variation of the radius. A geometrically nonlinear special-purpose analysis, based on Donnell’s nonlinear shell equations, is developed to study the prebuckling responses of geometrically perfect cylinders. In this analysis the circumferentially-varying radius of curvature of the cylinder is expanded in a cosine series. While elliptical sections are studied here, it should be noted that such an expansion will accommodate any cross section with at least two axes of symmetry. The displacements are likewise expanded in a harmonic series using the Kantorovich method. The total potential energy, written in terms of the displacements, is then integrated over the circumferential coordinate. The variational process then yields the governing Euler-Lagrange equations and boundary conditions. This process has been automated using the symbolic manipulation package Mathematica ©. The resulting nonlinear ordinary differential equations are then integrated via the finite difference method. A geometrically nonlinear finite element analysis is also utilized to compare with the prebuckling solutions of the special-purpose analysis and to study the prebuckling and buckling responses of geometrically imperfect cylinders. The imperfect cylinder geometries are represented by an analytical approximation of the measured shape imperfections. An accompanying experimental program is carried out to provide a means for comparison between the real and theoretical systems using a test fixture specifically designed for the present investigation to allow for both axial compression and internal pressurization. A description of the test fixture is included. Three types of tests were run on each specimen: (1) low internal pressure with no axial end displacement, (2) low internal pressure with a low level compressive axial displacement and, (3) compressive axial displacement to failure, with no internal pressure. The experimental data from these tests are compared to predictions for both perfect and imperfect cylinder geometries. Prebuckling results are presented in the form of displacement and strain profiles for each of the three sets of load conditions. Buckling loads are also compared to predicted values based upon classical estimates as well as linear and nonlinear finite element results which include initial shape imperfections. Lastly, the postbuckling and failure characteristics observed during the tests are described. / Ph. D.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The purpose of this project is to investigate the method and accuracy of simulating axial ow fans with three-dimensional axisymmetric CFD models. Two models are evaluated and compared with experimental fan data. Veri cation data is obtained from a prototype fan tested in a facility conforming to the BS 848 standards. The ow eld over the blade surfaces is investigated further with a visualization experiment comprising of a stroboscope and wool tufts. Good correlation is found at medium to high ow rates and recommendations are made for simulation at lower ow rates as well as test guidelines at the fan test facility. The results and knowledge gained will be used to amend currently used actuator disc theory for axial ow fan simulation. / AFRIKAANSE OPSOMMING: Die doel van hierdie projek is om die metode en akkuraatheid om aksiaalvloeiwaaiers met drie-dimensionele BVM modelle te simuleer, te ondersoek. Twee modelle word geëvalueer en met eksperimentele waaiertoetse vergelyk. Veri- kasie data is verkry vanaf 'n prototipe waaier wat in 'n fasiliteit getoets is en wat aan die BS 848 standaarde voldoen. Die vloeiveld oor die lemoppervlaktes word ondersoek met 'n visualisering eksperiment wat uit 'n stroboskoop en wolletjies bestaan. Goeie korrelasie word gevind vir medium tot hoë massavloeie en aanbevelings word gemaak vir die simulasie by laer massavloeie met riglyne vir toetswerk in die toets-fasiliteit. Die resultate en kennis opgedoen sal gebruik word in die verbetering van huidige aksieskyfteorie vir numeriese aksiaalvloeiwaaier simulasies.

Les structures offshores sont conçues pour résister à des chargements environnementaux sévères. Des études expérimentales et numériques de la fondation d’une éolienne offshore soumise à des chargements statiques monotones/cycliques sont présentées dans ce manuscrit. Des pieux isolés (diamètre de 1,8 m et 40 m de longueur) et une structure en treillis fondée sur 4 pieux ont été testés à 100×g en centrifuge dans un massif de sable de Fontainebleau dense. Le comportement du pieu isolé a été identifié à travers des essais de chargement axial monotone. Différentes méthodes de mise en place de pieu ont été adoptées (installation à 1×g et à 100×g) et leur influence sur la capacité portante a été mesurée. Le diagramme de stabilité du pieu a été construit à partir des résultats des essais cycliques, des essais CPT ont été réalisés et l’influence des contraintes initiales a été étudiée. Des résultats expérimentaux de la fondation jacket soumise à des chargements latéraux cycliques sont enfin présentés. La méthode des éléments finis et un macro-élément pour des pieux ont été utilisés pour reproduire numériquement les résultats expérimentaux. Les lois de comportement adoptées sont basées sur la théorie d’hypo-plasticité et les contraintes initiales dans le sol sont issues de la méthode ICP-05. Les résultats numériques sont confrontés aux résultats expérimentaux et aux résultats analytiques obtenus à partir de la norme API. / Offshore structures are designed to resist to severe environmental loads. This manuscript presents experimental and numerical studies on offshore wind turbine pile foundations submitted to static monotonic/cyclic loads. Isolated piles (diameter of 1.8 m and embedded length of 40m) and a four-legged truss structure installed in dense Fontainebleau sand have been tested at 100×g in a geotechnical centrifuge. The behavior of the isolated piles has been characterized under monotonic axial load. The piles have been jacketed at 1×g and 100×g and the influence of the setup method on the bearing capacity has been measured. The stability diagram of a pile has been constructed using cyclic tests, CPT experiments have been performed and the influence of the initial stresses has been studied. Finally, experimental results of the jacket foundation submitted to lateral cyclic loadings are presented. The finite element method and a macro-element for piles have been used to numerically reproduce the experimental results. Constitutive laws are based on the hypoplasticity theory and the initial stresses in the soil have been calculated using the IC-05 method. The numerical results are compared with the experimental and the analytical results from the API standards.

O objetivo desta pesquisa foi avaliar e comparar a atividade eletromiográfica de sete músculos da cintura escapular e braço durante a realização dos exercícios wall-press, bench-press e push-up sobre uma superfície estável e com carga axial controlada em dois níveis de esforço isométrico, um máximo (100%) e outro submáximo (80%). Os exercícios foram realizados com o braço em 90° de flexão no plano sagital, 0° de extensão do cotovelo e 90° de flexão da mão. Vinte voluntários do sexo masculino, saudáveis, destros e sem história de trauma no membro superior participaram da pesquisa. Os registros eletromiográficos e de força foram adquiridos, respectivamente, por sete canais para eletromiograma e por um canal auxiliar de um sistema de aquisição simultânea, ganho total de 50 vezes, 12 bits de faixa de resolução dinâmica e freqüência de amostragem por canal de 4 KHZ. Os sinais mioelétricos foram captados por eletrodos ativos simples diferencial, ganho de 20 vezes, impedância de entrada de 10G? e CMRR mínimo de 130 dB, colocados nos músculos serrátil anterior, porção anterior e posterior do músculo deltóide, porção clavicular do peitoral maior, fibras superiores do trapézio, cabeça longa do bíceps e tríceps braquial. Os exercícios foram realizados aleatoriamente, nos dois níveis de esforço isométrico, com intervalados entre si por 5 minutos. Os voluntários realizaram três repetições de cada exercício, com duração de 6 segundos cada, intervaladas entre si por 1,5 minutos e manutenção da força dentro dos valores previamente definidos, orientadas por um feedback sonoro. Os sinais brutos foram filtrados por um passa faixa de 20-500Hz, derivando os valores de amplitude eletromiográfica pelo cálculo da Root Mean Square (RMS). Os valores de RMS foram normalizados pelo valor máximo obtido de três contrações isométricas voluntárias máximas obtidas em prova de função muscular. A comparação dos valores normalizados entre os três exercícios nos dois níveis de esforço isométrico e entre o mesmo exercício nos dois níveis de esforço isométrico foi realizada através do Modelo Linear de Efeitos Mistos, com nível de significância de 5%. Os valores normalizados de RMS dos músculos estudados, em valores percentuais, foram usados para graduar o nível de atividade elétrica obtido em cada exercício. Os resultados demonstraram que houve uma diferença nos valores de RMS normalizados dos músculos avaliados nas comparações feitas entre os três exercícios, não confirmando a hipótese inicial deste trabalho, pois os dois níveis de esforços isométricos não foram capazes de influenciar a resposta eletromiográfica. Diferenças entre amplitudes de ativação normalizadas foram constatadas, variando entre os níveis mínimo e alto. O bench-press gerou maiores níveis de atividade eletromiográfica para a maioria dos músculos, possivelmente pelo maior esforço isométrico realizado. O wall-press gerou maior atividade eletromiográfica para a maioria dos músculos quando comparado ao push-up, apesar do esforço isométrico gerado ser menor. Este trabalho concluiu que, apesar de exercícios com carga axial, mesmo com esforço isométrico controlado, causaram diferentes níveis de atividade eletromiográfica nos músculos avaliados. / The purpose of this research was to investigate if biomechanically similar exercises produce similar myoelectric activation when the same level of maximal isometric effort is produced. Twenty volunteers participated in the study. All volunteers were right-handed, healthy men with no history of previous upper limb trauma. Electromyographic (EMG) recordings were obtained using a seven-channel simultaneous acquisition system, with gain of 50, 12 bit A/D converter board with a 4 KHz frequency. To monitor produced force, a load cell was attached through an auxiliary channel and force recording was accomplished simultaneously with the acquisition of EMG signal. Myoelectric signals were obtained using simple differential electrodes, with gain of 20, input impedance of 10 G? and minimum CMRR of 130 dB, placed on the serratus anterior, posterior and anterior deltoid, clavicular portion of the pectoralis major, upper trapezius, and biceps and triceps brachii muscles, following the European Recommendations for Surface Electromyography by SENIAM project, and instructions by Hintermeinster et al. (1998). EMG signals were recorded while performing push-up, bench-press, and wall-press exercises at different force levels (100% and 80% maximum isometric effort) with the dominant upper limb supported on a stable surface. Exercises were randomly performed with five-minute intervals between each exercise. Volunteers performed three repetitions of each exercise, each lasting six seconds, with 1.5-minute intervals, and maintaining the force within previously determined values, guided by audio feedback. Raw EMG signals were filtered by a 20-500 Hz pass-band in order to derivate EMG amplitude values by intervals calculating the Root Mean Square (RMS). RMS values were normalized by the maximum value obtained in three maximal voluntary isometric contractions during muscle testing. Normalized values were compared between the three exercises at both torque levels and between the same exercise at both isometric effort levels through the mixed-effects linear model, with a 5% level of significance. Normalized RMS values of the studied muscles (%) were used to rank the level of electric activity obtained during each exercise. Results indicate that maximal isometric effort levels had no influence on results from the comparison of EMG activity in any of the proposed exercises. Differences between normalized activation amplitudes were observed. However, the values reached levels between minimal and high, that is, under 60% of the activity generated during maximal voluntary isometric contraction. This study concludes that biomechanically comparable exercises did not necessarily produce similar EMG activity, in spite of controlling isometric effort. Moreover, exercises were capable of generating different EMG activity levels in the evaluated muscles. Therefore, such exercises are indicated for different rehabilitation program phases.

Temporal variations of Earth\'s magnetic field provide a great range of geophysical information about the dynamics at different layers of the Earth. Since it is a planetary field, regional and global aspects can be explored, depending on the timescale of variations. In this thesis, the geomagnetic field variations for the last two millennia were investigated. For that, some improvement on the methods to recover the ancient magnetic field intensity from archeological material were done, new data was acquired and a critical assessment of the global archaeomagnetic database was performed. Two methodological advances are reported, comprising: i) the correction for microwave method of the cooling rate effect, which is associated to the difference between the cooling times during the manufactory of the material and that of the heating steps during the archaeointensity experiment; (ii) a test for thermoremanent anisotropy correction from the arithmetic mean of six orthogonal samples. The temporal variation of the magnetic intensity for South America was investigated from nine new data, three from ruins of the Guaraní Jesuit Missions and six from archaeological sites associated with jerky beef farms, both located in Rio Grande do Sul, Brazil, with ages covering the last 400 years. These data combined with the regional archaeointensity database, demonstrates that the influence of significant non-dipole components in South America started at ~1800 CE. Finally, from a reassessment of the global archaeointensity database, a new interpretation was proposed about the geomagnetic axial dipole evolution, where this component falls constantly since ~700 CE associated to the breaking of the symmetry of the advective sources operating in the outer core. / Variações temporais do campo magnético da Terra fornecem uma grande diversidade de informações geofísicas sobre a dinâmica das diferentes camadas da Terra. Por ser um campo planetário, aspectos regionais e globais podem ser explorados, dependendo da escala de tempo das variações. Nesta tese, foram investigadas as variações do campo geomagnético para os dois últimos milênios. Para isso, aprimoramentos nos métodos de aquisição da intensidade geomagnética registrada em materiais arqueológicos foram realizados, bem como a aquisição de novos dados e uma avaliação crítica da base de dados arqueomagnética global. Dois novos avanços metodológicos são aqui propostos, sendo eles: i) correção para o método de micro-ondas do efeito da taxa de resfriamento, que está associada à diferença entre os tempos de resfriamento durante a manufatura do material e o das etapas de aquecimento durante o experimento de arqueointensidade; (ii) teste para correção da anisotropia termorremanente a partir da média aritmética de seis amostras posicionadas ortogonalmente umas às outras durante o experimento de arqueointensidade. A variação temporal da intensidade magnética para a América do Sul foi investigada a partir de nove dados inéditos, sendo três provenientes das ruínas das Missões Jesuíticas Guaraníticas e seis de sítios arqueológicos associados a fazendas de charque, ambos localizados no Rio Grande do Sul, Brasil, com idades que cobrem os últimos 400 anos. Esses dados, combinados com o banco de dados regionais de arqueointensidade, demonstram que a influência significativa de componentes não-dipolares do campo magnético na América do Sul começou em ~1800 CE. Finalmente, a partir de uma reavaliação do banco de dados globais de arqueointensidade uma nova interpretação foi proposta a respeito da evolução do dipolo axial geomagnético, sugerindo que essa componente está decrescendo constantemente desde ~700 CE devido à quebra da simetria das fontes advectivas que operam no núcleo externo.