This thesis work deals with the development of three different categories of interrogation techniques for Fiber Bragg Grating based sensor networks. Such networks are used for structural health monitoring and other applications. A bulk grating based interrogation system is described first, which includes an optical source, switch, circulator, embedded controller, and software. The center wavelength determination technique employed is detailed and is shown to be highly accurate from test data. The comparison with resistance strain gauges is presented which shows that the system developed provides an accurate strain reconstruction. The system is also compared with a commercial optical spectrum analyzer and is found to exhibit good accuracy and fidelity. The system has been field tested on an aircraft structure with 14 sensors spread over 4 channels. Strain data reconstruction from these tests is shown to accurately reproduce the loading conditions. A second system developed is based on the matched filter technique using a mechanical fiber stretcher; the details of this system are presented with a mathematical treatment of the technique. The design of the fiber stretcher is also described. This design is regarded to be novel since it tries to provide large interrogation bandwidths using a parallel topology. The results of tests have shown good resolution and comparative tests with resistance strain gauges have shown accurate reproduction of strain. Finally, an interrogation system based on a wavelength tunable source is presented. This system is a precursor to a time division multiplexed interrogation system, which has also been described. Three laser configurations have been set up and characterized. The laser sweep tests have been performed on two configurations and a sensor grating reconstruction test has also been carried out.

Bolted cores made of coated silicon steel sheets constitute a vital part of heavy electrical equipment for transformers, motors and turbogenerators. Bolted laminates are eminently suitable for facilitating smooth magnetic flux paths, but, unfortunately, they are unable to suppress interlaminate shearing caused by flexural vibration generating noise levels often exceeding 100 dB during operation. The resulting din and cacophony in the surrounding has become a major environmental concern. This thesis makes an attempt to develop theoretical, experimental and numerical models for evolving an effective stiffness approach enhancing the design and analysis underlying nonlinear flexure of bolted laminates. While large machine cores contain thousands of thin sheets bolted together along with end plates, this thesis reports the results obtained on two different assemblies. Two 375 mm long 60 mm wide and 10 mm thick plates assembled with 3, 4 or 5 bolts constitute the first configuration. The second one which is much more realistic comprises 80 coated 270 micron silicon steel sheets with end plates of 2 or 4 mm thickness held together by 3 or 5 bolts. Static 3 point bend tests on these bolted assemblies are followed by instrumented impact tests. Static bending tests highlight the role of frictional nonlinearity inducing a drop in the stiffness due to sliding between the plates. An experimentally determined effective modulus in the initial linear range is utilized for static and dynamic finite element simulations. Nonlinear response of bolted plates is simulated using contact elements in between the sliding plates, plates and the bolts heads. Since the first fundamental mode of vibration dominates the tribomechanical vibration induced noise, the primary focus is on the fundamental frequency in bending. There is generally a good overall agreement in all the results obtained through theory, experiment and FE simulation. Experiments, however, unveil quite complex nonlinear effects induced by friction and plasticity outside the scope of this thesis. However, the low amplitude response of bolted laminates which is reasonably well captured in this thesis represents the starting point for initiating a more elaborate effort for addressing large amplitude nonlinear flexure in bolted laminates. These findings shed light on estimating and controlling noise and vibration levels in heavy electric machines.

No description available.

The flexural performance of composite systems made of reinforced concrete, Fibre Reinforced Polymers (FRPs) and adhesives was studied during the current research. The experimental investigation was principally concentrated on the potential use of Kevlar® 49 (aramid fibre) for RC beam strengthening. The main aims of research have been; (a) to investigate the relative merits of using Aramids in comparison to other FRPs, (b) strength optimisation of systems to prevent excessive losses of ductility, (c) to examine the failure mode and crack patterns, together with salient strength factors at ultimate limit state and (d) to carry out analytical modelling using a commercial FE package. The experimental investigation comprised of testing 55 simply supported RC beams of either 1.5m or 2.6m length. In addition to the parametric studies included in points (a)-(d) above (to assess the section characteristics), further experimentation was conducted to investigate the beam performance by varying the factors of; (e) beam shear span, (f) FRP anchorage length, (g) concrete surface preparation, (h) FRP end-anchoring, (i) beam precracking, (j) introduction of air-voids within the bond line of FRP/concrete, (k) influence of cyclic loading and, (1) exposure to aggressive environment. The results from current tests confirm elements of reports from other researchers (by thorough review of literature) that all FRPs have great potential for flexural strengthening of RC members. This is valid even in cases where additional environmental degradation and/or cracking (due to serviceability loads), had taken place. Aramid fibres were found to result in favourable outcomes concerning both strength and ductility enhancements. It was determined, both from experiments and non-linear modelling, that the amount of FRP fibre content is an important factor in every strengthening application. Experimentation showed that depending on the existing condition of the structure (concrete strength, internal reinforcement ratio, section dimensions, degradation level and load configuration), there seems to be a unique level of optimum fibre content. The FRP levels in excess of the optimum were seen to lead to premature brittle tearing-off failure modes. It was also found that to prevent premature beam failure (due to incompatibility of stress at concrete and FRP interface), a maximum possible anchorage length should be considered in order to deliver an optimum section performance. The results from the analytical modelling indicated a most satisfactory agreement with the experimental data after the initial mechanical properties were calibrated. It was found that actual representation of material properties (e.g. steel constitutive law) are of great significance, for an accurate modelling of RC element loaded behaviour. The bond developed between the FRP and concrete is one of the key parameters for achieving good performance of the systems. It was determined that concrete surface preparation and priming is beneficial, while the introduction of air-voids due to poor workmanship can reduce the section load bearing capabilities. Cyclic loading on FRP strengthened sections was found to curtail the full rotational capacity utilisation of the beam. However, even the above mentioned curtailed behaviour was more advantageous than cyclically loaded beam performance without FRP strengthening.

Este trabalho apresenta uma metodologia, baseada no método de Galerkin, para quantificar a incerteza no problema de flexão estocástica da viga de Euler-Bernoulli repousando em fundação de Pasternak. A incerteza nos coeficientes de rigidez da viga e da fundação é representada por meio de processos estocásticos parametrizados. A limitação em probabilidade dos parâmetros randômicos e a escolha adequada do espaço de soluções aproximadas, necessárias à posterior demonstração de unicidade e existência do problema, são consideradas por meio de hipóteses teóricas. O espaço de soluções aproximadas de dimensão finita é construído pelo produto tensorial entre espaços (determinístico e randômico), obtendo-se um espaço denso no espaço das soluções teóricas. O esquema de Wiener-Askey dos polinômios do caos generalizados é utilizado na representação do processo estocástico de deslocamento da viga. O método dos elementos finitos estocásticos é apresentado e empregado na solução numérica de exemplos selecionados. Os resultados, em termos de momentos estatísticos, são comparados aos obtidos por meio de simulações de Monte Carlo. / This study presents a methodology, based on the Galerkin method, to quantify the uncertainty in the stochastic bending problem of an Euler-Bernoulli beam resting on a Pasternak foundation. The uncertainty in the stiffness coefficients of the beam and foundation is represented by parametrized stochastic processes. The probability limitation on the random parameters and the choice of an appropriated approximate solution space, necessary for the subsequent demonstration of uniqueness and existence of the problem, are considered by means of theoretical hypothesis. The finite dimensional space of approximate solutions is built by tensor product between spaces (deterministic and randomic), obtaining a dense space in the theoretical solution space. The Wiener-Askey scheme of generalizes chaos polynomials is used to represent the stochastic process of the beam deflection. The stochastic finite element method is presented and employed in the numerical solution of selected examples. The results, in terms of statistical moments, are compared to results obtained through Monte Carlo simulations.

[pt] Em um maciço rochoso, as fraturas apresentam-se de forma irregular e descontínua. A complexidade na distribuição espacial destas descontinuidades faz com que o mecanismo de ruptura por tombamento ocorra mais frequentemente por uma combinação de dois tipos de fenômenos: Tombamento de blocos e flexural. Assim, a ruptura por tombamento do tipo bloco-flexural pode ser considerada a forma mais comum presente neste tipo de mecanismo. Trabalhos utilizando o método de equilíbrio limite ou modelos físicos estudam a influência desta combinação, mas a literatura relata poucos trabalhos numéricos que possam ajudar na compreensão dos fenômenos envolvidos neste processo de ruptura. O presente trabalho procura modelar o mecanismo de ruptura por tombamento bloco-flexural através do método dos elementos discretos (DEM), utilizando o software PFC (Particle Flow Code). Em particular, procura-se avaliar as potencialidades do método para estudos deste tipo, utilizando um novo modelo de contato entre partículas e a calibração das propriedades elásticas do material sintético. Apresentam-se também detalhes da metodologia utilizada e exemplos de validação, incluindo comparações com soluções analíticas e semi-analíticas disponíveis na literatura. / [en] Joints exhibit an irregular and discontinuous behavior inside the rock mass. The spatial distribution complexity of these discontinuities causes the toppling failure occurs more often by a combination of two types of toppling phenomena: toppling of rock blocks and flexural toppling. Thus, the block-flexural toppling can be considered the most common when a toppling process is being developed in rock slopes. Analytical and physical models approach, were presented in order to study each process individually, but the literature reports few works that may help to understand the influence of the two processes together. The present work aims to represents the mechanism of block-flexural toppling through the discrete elements method (DEM) using the PFC (Particle Flow Code) software. In particular, the objective is to assess the potential of the method for studies of this type, using a new model of contact between particles and the elastic properties calibration of the synthetic material. In order to do that, the work shows the methodology details and validation examples, including comparisons with analytical and semi-analytical solutions that are available in the literature.

ABSTRACT The repair and strengthening of concrete bridge members with CFRP has become increasingly popular over recent years. However, significant research is still needed in order to develop more robust guidelines and specifications. The research project aims to assist with improving design prosedures for damaged concrete members with the use of CFRP. This document summarizes the analysis and testing of full-scale 40’ foot long prestressed concrete (PSC) bridge girders exposed to simulated impact damage and repaired with carbon fiber reinforced polymers (CFRP) materials. A total of five AASHTO type II bridge girders fabricated in the 1960’s were taken from an existing bridge, and tested at the Florida Department of Transportation FDOT structures lab in Tallahassee, Florida. The test specimens were tested under static loading to failure under 4-point bending. Different CFRP configurations were applied to each of the girders. Each of the test girders performed very well as each of them held a higher capacity than the control girder. The repaired girders 5, 6 and 7 surpassed the control girder’s capacity by 10.88%, 15.9% and 11.39%. These results indicate that repairing laterally damaged prestressed concrete bridge girders with CFRP is an effective way to restore the girders flexural capacity.

The diploma thesis presents design of construction with FRP reinforcement. Including design process of cross-section with FRP reinforcement exposed to bending moment and shear force at ultimate limite state according to given standards and guidelines. Long term physical and mechanical properties of FRPs are taking into account. There are also compared load capacities of cross-section exposed to combination of bending moment and axial force, which were designed according to mentioned standards. In another part of diploma thesis there is a design of construction (precast gatehouse) with FRP reinforcement and steel reinforcement with ordinary and lightweight concerete.

Des modèles géométriques ont été proposés pour reconstruire la géométrie de plis associés aux rampes (par exemple pli sur flexure de faille), en identifiant en particulier la profondeur de niveau de décollement et le déplacement total sur la rampe. Ces méthodes de reconstruction géométrique sont appliquées pour des plis partiellement érodés. Au cours de l'érosion, le cut-off de la rampe peut être érodé et, par conséquent, le déplacement sur la rampe est difficile à quantifier. Dans cette thèse, nous développons onze modèles thermo-géométriques. Les modèles combinent les données géométriques et les données d’enfouissement pour proposer une évolution cinématique d’un pli avec cut-off érodé. Nous supposons que la mise en place d'une unité tectonique produit une anomalie thermique dans le mur de la faille, et que cette anomalie thermique pourrait indiquer une épaisseur de bloc chevauchant. Les modèles fournissent une estimation de la profondeur de décollement et le déplacement total sur une rampe érodée, qui ne dépend pas de taux d’érosion. Dans le cas de chevauchements actifs, les modèles proposent un taux de déplacement et un âge de l'initiation de la faille en fonction de taux d'érosion. Ces données sont utilisées pour proposer un développement cinématique de coupes érodées. Nous appliquons les modèles sur les plis érodés et actif à Taiwan dans les zones de Choshui et Miaoli. On propose des coupes régionales équilibrées en utilisant la technique de modélisation directe. Dans la section Choshui, nous proposons un niveau de détachement de ~5 km à ~14 km, marquée par deux sauts successifs de rampes de ~5 km and ~4 km. En supposant un taux d'érosion à 4 mm/an, l'âge de l’initiation de chevauchement active est entre 3,3 Ma dans la partie intérieure de prisme (Chevauchement de Tili) à 0,9 Ma dans la partie extérieur (Chevauchement de Chelungpu). Le raccourcissement totale sur la coupe de Choshui est ~100 km et le taux de déplacement calculé est ~1 cm/an. Pour tester nos modèles thermo-géométriques dans une chaîne plissée inactive, on applique nos modèles sur les plis érodés associés aux failles de Pine Mountain et Jones Valley dans la chaîne plissée des Appalaches. L'application des modèles thermo-géométriques nous permet d’estimer une quantité de déplacement sur les deux failles et expliquer de manière satisfaisante l'anomalie thermique dans le mur des failles de Pine Mountain et Jones Valley. Afin d'améliorer la description de l’anomalie thermique qui se développe dans le soubassement des failles, on a étudié l'évolution des minéraux magnétiques des roches argileuses le long de quatre sections dans la chaîne plissée à Taiwan. On a remarqué que la greigite (Fe3S4) domine l'assemblage magnétique dans les roches enfouies à moins à moins de de 70°C. La magnétite (Fe3O4) se développe pour des températures d’enfouissement de ~50°C et domine l’assemblage magnétique jusqu'à ~350° C. A partir ~300°C, la pyrrhotite monoclinique (Fe7S8) se développe aux dépens de la magnétite, et à ~350°C, la magnétite n'est plus détecté. Ces résultats peuvent être utilisés en complément d'autres géothermomètres pour identifier les anomalies thermiques dans une gamme de de 50-70°C et de 300-350°C où les caractéristiques des minéraux magnétiques sont identifiées / Geometric models have been proposed to account satisfactorily for ramp-related folds (e.g. fault-bend fold), identifying in particular detachment depth and total shortening. These methods of geometric reconstruction are applied on partially eroded folds. During erosion, the fault cut-off may be removed and as a result, the displacement is difficult to quantify. In this thesis, we develop 11 thermo-geometric models combining geometric description of folds and burial data to propose kinematic evolution of folds with eroded cut-offs. We assume that the emplacement of a tectonic unit will result in a thermal anomaly in the footwall, and that this thermal anomaly might indicate a thickness of the overriding unit. The models provide an estimation of the detachment depth and the total shortening on an eroded ramp, independent of the erosion rate. In the case of active thrusts, the models provide an estimation of the slip rate and the age of the initiation of the thrust as a function of the erosion rate. These data are used to unravel the kinematic development of eroded cross-sections. We apply the models on eroded folds from Taiwan underlined by active thrusts in the Choshui and Miaoli sections. We propose regional balanced cross-sections using forward modeling technique. In the Choshui section, we propose a detachment profile with a depth between ~ 5 km and ~ 14 km, marked by two steps of ~ 5 km. Assuming erosion rate at 4 mm/a, the age of initiation of the active thrusts is ranging from 3.3 Ma inward (Tili thrust) to 0.9 Ma outward (Chelungpu thrust). The total shortening from the whole section is ~100 km and the calculated slip rate is about 1 cm/a. To test our models in a non-active fold-and-thrust belt, we study eroded folds associated to the Pine Mountain thrust and Jones Valley thrust from the Appalachian belt. The application of the thermo-geometric models provides a value of the total shortening and explains satisfactorily the thermal anomaly in the footwall of the Jones Valley thrust. In order to improve the description of the thermal anomaly, we have studied the evolution of magnetic minerals of argillaceous rocks in four sections from the Taiwan thrust belt. We found that the iron sulfide greigite (Fe3S4) is dominating the magnetic assemblage in the less buried rocks (<70°C). The magnetite (Fe3O4) develops at burial temperature of ~50°C and is dominating the magnetic assemblage up to ~350°C. By ~300°C, the monoclinic pyrrhotite (Fe7S8) develops at the expense of magnetite, and at ~350°C, the magnetite is no longer detected. These results can be used complementary to other geothermometers to identify thermal anomalies in the range 50-70°C and 300-350°C where characteristic magnetic minerals are identified

This thesis presents an investigation of the modelling and optimal design of a particular 3-degree-of-freedom (DOF) XYθz micro-motion stage. This stage provides micron-scale motion in X and Y directions and a rotation about the Z-axis. Such a stage can be used for applications where positioning of components with micrometre, or even nanometre positioning accuracy is required. Some applications are; the positioning of samples in a scanning-electron-microscope; the positioning of masks in lithography; aligning fibre-optics and lasers; and manipulation of micro-scale objects in micro-biology or micro-systems assembly. The XYθz micro-motion stage investigated in this study uses a particular topology of monolithic compliant mechanism and three stack piezoelectric actuators. The compliant mechanism used is a 3RRR (three revolute-revolute-revolute) parallel compliant mechanism using flexure hinges. This parallel mechanism uses three RRR linkages. Each of the three RRR linkages uses three circular profile flexure hinges. Each flexure hinge provides predominantly rotational motion about one axis. This topology of mechanism has a symmetrical structure and provides numerous advantages that make it appropriate for use in a micro-motion stage. However, as yet this topology of compliant mechanism has only been investigated by a handful of researchers and it has not been used in any commercially developed systems. The design methodology of a stage using the 3RRR compliant mechanism has not been investigated in detail. In this thesis a study is presented that investigates different approaches to model the 3RRR compliant mechanism and also considers the piezo-actuator modelling, to give the complete XYθz micro-motion stage. Three models are presented and compared; the Pseudo-Rigid-Body Model (PRBM); a two-dimensional Finite-Element-Model (2-D FEM); and a third model is developed that is similar to the PRBM, but uses analytical equations to model the multiple degree-of-freedom compliance of the flexure hinges. The models developed are then used in parametric study so that the relationship between design parameters and output behaviour can be understood. An optimal design approach is then presented to develop an XYθz micro-motion stage for a particular application in a Scanning-Electron-Microscope (SEM). Finally experimental validation of the models is presented. The results of this study indicate which modelling approaches are accurate enough to prove useful for design, while also considering which models are computationally simple enough to be efficient and easy to use. The kinematic and dynamic behaviour of the 3RRR compliant mechanism and XYθz micro-motion stage is discussed in detail. This includes; a comprehensive description of the stage workspace, defining reachable and constant-rotation workspace areas; a discussion of actuator coupling; and in depth investigation of the modes of vibration. The results of the parametric study provide useful insight to aid the design of the XYz micro-motion stage and help simplify optimal design. The parametric study also highlights the difference in trends predicted by different modelling methods, which demonstrates the importance of using an appropriate model in design. The experimental validation demonstrates the accuracy of some modelling approaches while highlighting the limited accuracy of others. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1272186 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2007