This thesis deals with asset management of structures through Building Information Modelling (BIM) and Digital Twins. Background: Current inspection and management processes for civil structures are time-consuming and can even be inaccurate. There is an increasingly high potential to improve these processes through recent advances in technology. Digital Twins offer a common platform to these technologies, so they can interact and be used to their optimal performance. Other industries have significantly advanced in the development of Digital Twins, however, in the construction industry there are still many gaps and room for improvement. Aim and objectives: The main aim of this project was to investigate the status of Digital Twins in the construction industry and propose a methodology for a Digital Twin for asset management of structures. The three immediate objectives sought are (i) Perform a literature review to establish the current practice with digital twins, in both construction and other industries, and what are the gaps for asset management of structures; (ii) Participate in a pilot experimental program that yields data to a potential digital twin prototype; and (iii) Define a methodology for a digital twin for asset management of structures which fills the identified gaps. Methods of investigation: A literature review was performed and served as basis for the development of a methodology for a digital twin. A pilot experimental program was defined and performed, and its results were used for BIM and Finite Element (FE) models. A webapp was also created using Autodesk Forge and Java programming language, andthe BIM model was uploaded into it. Results: The literature review provided insight into the maturity level of digital twins, as well as on bridge inspection, maintenance and monitoring, BIM, facility and asset management, and Bridge Management Systems (BMS). A methodology to achieve a digital twin for asset management was proposed, and the conducted experimental program yielded data results to be used in future research. Conclusion: There has been significant progress in technology to improve structural assessment and analysis, however, their full potential is still under-explored. A digital twin created in a common data environment can provide a platform for these technologies to improve efficiency of current practices. Nonetheless, the construction industry is still significantly behind other industries such as aerospace and automotive.

Bending deformation characteristics of monolithic, bi-layer and tri-layer laminate sheet materials are studied using Analytical and FE models in this work. The analytical model, based on advanced theory of pure bending considers von Mises yielding, Ludwik hardening law and Bauschinger effect for various laminate constituent thickness ratios. The principal stresses and strains through the thickness and, change in relative thickness at specified bend curvatures are obtained as a function of increasing curvature during bending. Additionally, 2D and 3D finite element (FE) based models for bending are developed to overcome simplifications of the analytical models such as the effect of specimen width on strain distribution. Further, to experimentally assess and validate bending characteristics from the analytical models, a new experimental bend test-jig that is closer to pure bending is developed. The experimental set-up is an open concept design that allows access to the tensile surface as well as through-thickness region for recording and analyzing strains using an online strain mapping system based on digital image correction (DIC) method. Experimental bending is carried out on annealed AA2024 monolithic aluminum alloy sheet and Steel/Aluminum (SS400/AA1050) bi-layer laminate sheet at different thickness ratios. The model and experiments are studied in terms of stress and strain distribution as a function of relative thickness for different clad to matrix thickness ratios. Further the case of simultaneous bending and stretching over small radius bending is analyzed for limit strain prediction using an existing limit strain criterion based on major strain acceleration. An angular stretch bend test is used to subject an hour-glass shaped AA20240-O aluminum sheet specimen to simultaneous stretching and bending deformation while continuously imaging the critical tensile surface region using an optical camera. The strain development in the critical region is subsequently analyzed using digital image correlation (DIC) method. The effect of DIC parameters such as facet size, facet step, and effect of curve fitting procedures on limit strain are studied. An average limit strain of 0.2 is obtained for AA2024 for a facet size of 9x9 pixels, a facet step of 5 pixels and by applying a 5th order polynomial curve fit to the strain data. The results obtained are comparable with a limit strain of the material. The results are compared with a commercially available tri-layer laminate sheet material Alclad 2024 that has 80 μm thin layer of soft AA1100 on both surfaces of harder AA2024 core material. An improved stretch bendability limit strain of 0.24 for Alclad 2024 tri-layer specimen was predicted by utilizing the major strain acceleration criterion. The thin AA1100 protective layer produced a positive effect on the stretch bendability of Alclad 2024 when compared with monolithic AA2024 specimen. / Thesis / Doctor of Philosophy (PhD)

Cam-type Femoro-Acetabular Impingement (FAI) is a common cause of hip osteoarthritis (OA). In this condition a bony abnormality at the head-neck junction of the femoral head, called the “cam”, abuts against the acetabulum causing labral damage and articular cartilage delamination, which in turn may lead to progressive degeneration and OA. The understanding of the damage mechanism is currently at a conceptual level. The aim of the thesis is to develop a more detailed understanding of the underlying mechanism so as to improve methods of detection and treatment of cam-type FAI and thus to help prevent hip OA. A geometric-kinematic model combining hip joint motion and hip joint geometry was cre- ated to determine what motions, activities or cam shapes give rise to cam-type impingement, which was quantified by the proximity of the acetabular and femoral bony surfaces. Five normal subjects and five symptomatic cam-type FAI patients were modelled. The FAI patients experienced early impingement during the impingement test but did not have impingement during common functional activities. The early impingement was possibly due to the larger coverage and protrusion of their cams and the smaller overall proximity in their hip joints. A 2D finite element (FE) model was created to simulate cam-type FAI. As idealised 2D rectangular and circular geometries did not reproduce the damage seen clinically, subject- specific geometry, loads, and motions were introduced. Under some circumstances, as the cam entered the hip joint, large shear strains developed near the cartilage-bone interface of the acetabulum which would result in cartilage delamination. In vitro experiments were undertaken to validate the FE model and verify the damage mech- anism by which cam-type FAI leads to cartilage delamination. Porcine cartilage-bone samples were loaded under conditions similar to those generated by a cam (shear and compression). A validation FE model was created that used the same material and contact representations and analysis framework as the impingement FE model but mimicked the experimental setup. The cartilage shear strains assessed with a video-based method were similar to predicted FE results. In vitro damage experiments demonstrated that delamination can be caused by repetitive shear and compressive loading that lead to large shear strains near the cartilage-bone interface. The impingement FE model was used to further explore the effect of cam anatomy. In hips with low clearance, cams with large protrusions (75% hip joint clearance) would not enter into the hip joint, but caused high shear strains in the labrum, which would result in labral tears. A narrower cam caused damage to the labral tip, whereas a wider cam caused damage to the labral-bone junction. In contrast, cams with small protrusion (25% hip joint clearance) were able to enter the joint and caused damage at the articular cartilage-bone interface, which would result in cartilage delamination. The wider the cam, the further into the hip joint the damage was initiated. The FE model was used to explore the effect of different labral anatomy and of reshaping surgery. A labrum connected to the articular cartilage resulted in shear strains of up to five times greater in the articular cartilage and labrum compared to an unconnected labrum and was more likely to cause articular cartilage delamination. For a cam that damages the articular cartilage, surgical removal of the cam reduced shear strains. For a cam that abuts the labrum, surgical removal of the cam eliminated labral abutment and increased the range of motion of the hip, but resulted in greater shear strains in the articular cartilage. It is not known whether these shear strains are normal or could possibly be damaging. Also, reshaping the head to be spherical resulted in slightly reduced shear strains in the articular cartilage compared to the current surgical practice of cutting deeper into the femoral head when removing the cam. This study has, for the first time, using a validated FE model demonstrated the mechanism by which a cam can cause articular cartilage delamination and labral tearing. Further analysis using the geometric and FE model should help identify cam deformities that would be likely to cause OA and the best way to treat them surgically so as to prevent OA.

This research project presents a study of the fixation of screws in augmented and non-augmented cancellous bone at a microscopic scale. It is estimated that somewhere close to one million screws are failing each year. Therefore, the aim is to identify the key parameters affecting screw pull-out in order to improve screw fixation in cancellous bone, and hence screw design. The background for this study comes from work by Stryker, comparing screw pull-out from augmented and non-augmented cancellous bone, where a few cases of screw pull-out gave better results without bone augmentation. This is contrary to most evidence and the hypothesis to explain these results is that the screw pull-out from cancellous bone could be strongly affected by the cancellous bone micro architecture. The effect of the influence of the screw’s initial position was first verified with 2D finite element (FE) models of screw pull-out from simplified cancellous bone models. The results showed a force reaction variation up to 28% with small change in position. The hypothesis was then tested with 3D FE models of screw pull-out from more complex cancellous bone models with different volume fractions. Three volume fractions were tested and again the effects were confirmed, but only in models with the lower volume fraction. A variation up to 30% of the force reaction was observed. The 3D simplified cancellous bone models with 5.3% volume fraction were also used to study the influence of augmentation using calcium phosphate cement. A significant improvement of the screw holding power (almost 2 times) as well as an important diminution of the variability of the pull-out force due to the screw initial position was found. Other augmentation geometries were used to model cement. They all showed an increase of the screw pull-out force reaction with an increase of the cement volume. Validation of FE results was achieved by comparing screw pull-out from a cadaver cancellous bone and the FE model constructed from the same bone sample. New studies were then carried out from the cadaver cancellous bone model. The first study examined the screw initial position influence with cancellous and cortical screws and again showed that there is a strong correlation between screw pull-out stiffness and bone volume fraction. The cortical screw showed improved performance over the cancellous screw. Augmentation cases were explored using three bone samples with a range of volume fractions obtained from different sites within the cadaver bone sample. The cancellous screw was tested with 3 types of augmentation and the cortical screw was tested with one augmentation in these 3 samples. The results showed each time a significant improvement of stiffness with augmentation but when compared with the effect of volume variation inside the bone sample, it appeared that the improvement of stiffness from augmentation might not cover the loss in stiffness from a small change in bone structure. Finally, screw design parameters were investigated, as cortical screws seemed to give as good or better stiffness results than cancellous screw. The thread pitch, the thread angle and the core diameter were analysed independently and it appeared that the most important parameter was the thread pitch with an improvement of the stiffness of +46% for cancellous screws with a smaller thread pitch. The two other factors studied (core diameter and thread angle) showed somewhat stiffer results but with a relatively small influence (less than 10%). From this study, the best screw for use in cancellous bone could be a cortical screw (diameter and pitch) with thread angles similar to a cancellous screw.

Les composites tissés 3D, à l'aide de leurs grandes libertés de conception, peuvent fournir des propriétés mécaniques adaptées aux besoins spécifiques d'une structure. La complexité architecturale de ces matériaux induit néanmoins des propriétés, des comportements ainsi que des endommagements très difficiles à prédire. Les travaux présentés dans ce manuscrit s'inscrivent directement dans cette problématique et cherchent à développer des outils permettant, par simulation numérique, de prévoir les caractéristiques mécaniques de ce type de matériaux. Afin de répondre à cet objectif, une approche multiéchelle, alliant essais expérimentaux et simulations numériques, a été adoptée. Cette démarche permet, en appliquant des sollicitations réelles, de considérer la géométrie des renforts et les hétérogénéités du matériau, observables à l'échelle mésoscopique, qui sont responsables du comportement macroscopique du composite tissé. Le travail d'investigation expérimentale s'est attaché à caractériser le comportement d'un composite interlock 2,5D et des ses constituants ainsi que les mécanismes et cinétiques de rupture, pour des sollicitations de traction/flexion, grâce à des observations tomographiques aux rayons X et au concept d'interzone. En ce qui concerne la modélisation numérique, un critère de rupture permettant de simuler la dégradation ultime du composite, en coupant les fils de renforts, a été présenté et testé sur une cellule représentative du composite expérimentale. Les résultats en termes de localisations, d'orientations et de cinétiques de l'endommagement sont en accord avec les observations expérimentales. Ensuite, après avoir estimé l'influence des différents paramètres architecturaux sur le critère de rupture avec une campagne de calcul éléments finis, des architectures optimisées, pour les sollicitations considérées, ont pu être proposées et comparées à l'interlock 2,5D. Toujours dans l'optique d'une meilleure prédiction du comportement des composites tissés, les travaux se sont également intéressés à une modélisation plus fine des mécanismes d'endommagement. Une approche fiabiliste a donc été introduite sur le critère de rupture à l'aide d'une distribution statistique de Weibull. De plus, un autre mécanisme d'endommagement a aussi pu être pris en compte dans la modélisation en simulant, avec le modèle GTN (Gurson-Tvergaard-Needleman), la cavitation de la matrice. Enfin, des techniques de réduction de modèle ont été employées pour diminuer le coût calcul de la modélisation multiéchelle afin d'identifier, par exemple, des propriétés matériaux par méthode inverse ou de simuler des essais de fatigue. / With their large flexibility of design , 3D woven composites can provide mechanical properties tailored specificially to structural needs. However, the architectural complexity of woven reinforcements presents serious challenges when predicting properties, behaviours and damage processes. The present work deals with these challenges and seeks to develop numerical tools which are able to foresee the mechanical characteristics of this kind of materials. For this purpose, a multiscale approach, which combines experimental tests and numerical simulations, has been adopted. This approach allows, simultaneously, to take into account the loads and composite behavior, at the macroscopic scale, also the reinforcement geometry and the material heterogeneities which are only visible at the mesoscopic scale. The experimental investigation has been carried out to characterize the behaviour of an 2.5D interlock composite and its constituents. Examinations of the damage mechanisms have also been performed, using tomography and the interzone concept, for this woven composite under loadings in tension and combined tension and bending. With regards to the numerical modeling part, the ultimate degradation of the composite was simulated by cutting the reinforcement yarns with a failure criterion, previously reported, on a 3D representative cell of the experimental composite. For the two kinds of macroscopic loadings, the locations, orientations and kinetics of the damage were found to be fully in agreement with the experimental results. The influence of the architectural parameters on the failure criterion was then evaluated by finite element calculation. Consequently, it has been possible to proposed optimized architectures and make a camparison, for the two macroscopic loadings, with the 2.5D interlock woven composite. Still motivated to improve the prediction of the behaviour of woven composites, this work has also been on developing a finer modeling approach to the understanding of damage mechanisms. A stochastic approach was therefore introduced to the failure criterion using a Weibull statistical distribution. In addition, matrix cavitation has also been taken into account in the modelling. This damage mechanism was simulated using the GTN (Gurson-Tvergaard-Needleman) model. Finally, model reduction techniques have been applied to lower the cost of computing multiscale modeling in order to identify, for example, material properties by an inverse method or to simulate fatigue tests.

L’intégration hétérogène de circuits électroniques sur un interposeur silicium offre de nouvelles perspectives dans l’élaboration de systèmes complexes pour les applications nécessitant de grandes bande-passantes. L’assemblage vertical de puces à très haute densité sur cette plate-forme silicium de grande taille pose néanmoins d’importants défis technologiques. Le cœur de cette étude se concentre plus particulièrement sur les problématiques thermo-mécaniques qui affectent le processus de fabrication de l’interposeur à de multiples échelles. À l’échelle macroscopique, la courbure importante découlant des contraintes dans les couches diélectriques minces complexifie l’assemblage. La caractérisation de ces déformations par une technique de "shadow moiré" sert à définir et valider une solution de compensation de la courbure via le dépôt de diélectriques en face arrière. Une stratégie de mesure des contraintes mésoscopiques par des capteurs de contraintes en rosette est ensuite déployée. L’étude montre l’adéquation des capteurs piézorésistifs pour la mesure des interactions puces-puces dans les assemblages de circuits tridimensionnels. Enfin, les contraintes thermomécaniques microscopiques induites par les vias de cuivre traversant l’interposeur sont cartographiées à grande échelle par nano-diffraction d’un rayonnement synchrotron. Ces mesures débouchent sur l’élaboration d’un modèle numérique prédictif et l’estimation des variations de mobilité des porteurs de charge autour des vias. Les principales barrières à l’adoption de l’interposeur ont été finalement identifiées et un panel d’outils a été développé afin de garantir une faisabilité de réalisation de futurs prototypes. / The heterogeneous integration of microelectronic chips on a silicon interposer offers new perspectives in the manufacturing of complex systems for high bandwidths applications. However, the high density vertical assembly of several chips on this silicon platform has proven to be technologically challenging. This study is especially focused on the thermo-mechanical issues which affect the manufacturing of the interposer at multiple scales. At macroscopic scale, the high curvature of the die, induced by stress in thin films, has a negative impact on various assembly processes. By using a thermal shadow moiré technique, the characterization of the thermo-mechanical deformations aims to define and validate a strategy of curvature compensation through the deposition of thin dielectric layers on the back-side of the die. The integration of stress sensors to depict the mesoscopic local stress in 3D assemblies is then investigated. The study demonstrates the ability of piezoresistive based sensors to measure chip/package interactions in a typical interposer assembly flow. Eventually, the thermo-mechanical stress at microscopic scale induced by the copper through silicon vias in a silicon interposer are mapped thanks to a nanodiffraction technique using synchrotron radiation. Corresponding experimental investigations allow to validate a predictive numerical model and estimate the mobility variations of charge carriers in silicon around the vias. Eventually, the main barriers to silicon interposer adoption have been identified and several tools were developed to ensure the feasibility of future prototypes.

This thesis is part of a major research project to analyse vibro-acoustic characteristics from variable speed inverter driven induction motors (VSIDIM). The overall projects??? aimed at providing a better understanding of the mechanisms of sound generation from electromagnetic origins and developing a numerical model to predict the sound power emitted from a VSIDIM. The scope of this thesis is to assess experimentally the effect of various controller strategies on the radiated sound power and to develop a finite element method for calculating the electromagnetic force distribution over the stator. Various sources of noise in induction motors and their behaviour with speed and load have been reviewed. Models of the electromagnetic field and vibro-acoustic character have been discussed. An outline of various techniques of reducing noise in induction motors through design of inverters and modifications to the motor structure has been given. Experiments were conducted to assess the effect of controller strategies on the radiated sound power. Three different supplies were tested: a dynamotor which produces an almost sinusoidal supply with very low harmonic content, an inverter with a low switching frequency (less than 1kHz) and an inverter with a high switching frequency (8kHz) and various levels of random modulation. Results indicate that the sound power level of the MSC drive is a lot higher than that of the VSC 2000 drive and the dynamotor drive. The sound power level of the VSC 2000 drive and the dynamotor drive increases almost linearly with motor speed, that for the MSC drive is almost independent of speed. The sound power level of the MSC drive is almost 28dB higher than that of the dynamotor drive at 450rpm and the difference is reduced to 14dB at 1500rpm where the aerodynamic noise becomes more dominant. It has been found that at the rated speed (1500rpm), the sound power level varies by less than 3dB from no load to full load for all three sources. Although increasing the switching frequency increases the cost of the inverters and switching losses, results from the MSC and VSC 2000 drives clearly show that it reduces the radiated sound power by shifting the harmonics into higher and inaudible frequency range. The tonal nature around the switching frequency has been reduced by increasing the levels of random modulation to spread the energy over a wider range of frequencies, although the sound power level has not varied by more than 0.2dB. A finite element model has been developed to calculate the electromagnetic force distribution. The quasi-static solution method has been implemented by stepping the rotor through the time domain using a fine regular mesh in the air gap. The stator currents were experimentally obtained while the rotor currents were obtained using a 4 parameter state space model of the motor. Results of the simulation indicate the influence of stator and rotor slots, saturation and time harmonics in the current. The calculated electromagnetic force distribution has been used in a FEM/BEM acoustic model and SEA acoustic model to predict the radiated sound power which agrees reasonably well with the measured sound, thus validating indirectly the electromagnetic force simulations.

This study presents the investigation and the verification of the modal parameters of a plate-like structure by using different modal analysis methods. A fin-like structure which is generally used in aircraft is selected as a subcategory of a plate-like test structure. In the first part of the thesis, the natural frequencies and the corresponding mode shapes of the fin are extracted by Finite Element Analysis method. Classical Modal Analysis and Testing methods comprising both impact hammer and modal shaker applications are then applied in order to obtain the modal parameters such as / resonance frequencies, mode shapes and damping ratios. In the second part, a recent modal analysis technique, Operational Modal Analysis, is also applied in the laboratory environment. Since Operational Modal Analysis method does not require any information of input forcing, the fin structure is tested under both mechanical and acoustical types of excitations without measuring the given input forces. Finally, Operational Modal Analysis and Testing is also performed under various flow conditions generated in the wind tunnel which may simulate the real operating environment for the fin structure. The modal parameters extracted under these flow conditions are then compared with the previously obtained Finite Element, Classical and Operational Modal Analyses results.

A Primary objective of the present research is the development of robust CAE (Computer-Aided Engineering)-based approaches for designing armour plates subjected to ballistic impact by small-calibre hardened peojectiles with or without a protective sheath. Amongst the challenges in simulation is the capturing of target plate material behaviour at high strain rates with possibilities of adiabatic heating. A comprehensive numerical study carried out has resulted in the identification of simulation guidelines using a commercially available explicit finite element anlaysis solver (viz. LS_DYNA). The interferences thus drawn in terms of modeling approach 9I.e. shell, solid or axisymmetric or a mixed representation). Mesh density and element type, contact condition, and constitutive model 9I.e. discrete strain-rate based, Cowper-Symonds, or Johnson-Cook) with failure criteria are verifiable and greatly beneficial for armour plate design. Confidence in the suggested procedures has been obtained through extensive correlation of numerical results with experimental residual velocities and ballistic limits as well as projectile and target plate failure modes. A wide range of impact velocities has been considered (from a low velocity of about 5m/s to an ordnance range velocity of 800+ m/s). Target plates made of variants of mild steel and aluminium alloys have been studied. The simulation approaches have been applied to single-layered as well as multi-layered target plates. Although a majority of the comparisons has been made against published test results, a new ballistic impact testing facility has been set up in course of the current research and excellent correlation of numerically predicted residual velocities and failure modes has been obtained against the tests carried out for aluminium plate using the latter facility. A unique feature of the current experimental effort is the capturing of the complete trajectory of projectile beginning with oblique impact through subsequent perforation/ricochet. Furthermore, projectiles of various nose-shapes such as ogival, conical, hemispherical and blunt have been employed. The power of simulation has been demonstrated with the help of a number of parametric studies with variables such as plate thickness and material properties, as well as projectile mass and diameter, and obtaining physically consistent results. Additionally, existing semi empirical models for residual velocity and ballistic limit prediction have been reviewed, and new user-friendly models have been proposed based on energy conservation and predominant shear plugging failure mode of target plate. Finally, the goal of applying the present research work as a design tool can be well-served by packaging the knowledge gathered here in the form of a user-friendly guide with a graphical user interface(GUI). To this end, an application using MS windows VC++ utilities has been created with the functionalities of: (a) viewing reference LS-DYNA input data files for selecting typical problems of impact on steel and aluminium plates; (b) computing complete lists of strain rate-based material quantities required in LS-DYNA material models like discrete strain rate-based, Cowper-Symonds and Johnson-Cook by specifying the minimum number of easily available quasi-static properties (such as elastic modulus, yield and ultimate strengths, etc.), and (c) estimating residual velocities using the semi-empirical relations for steel and aluminium plates derived in the current work.

Steel-deck composite floor systems are being increasingly used in high-rise building construction, especially in Australia, as they are economical and easy to construct. These composite floor systems use high strength materials to achieve longer spans and are thus slender. As a result, they are vulnerable to vibration induced under service loads. These floors are normally designed using static methods which will not reveal the true behaviour and miss the dynamic amplifications resulting in inappropriate designs, which ultimately cause vibration and discomfort to occupants. At present there is no adequate design guidance to address the vibration in these composite floors, due to a lack of research information, resulting in wasteful post event retrofits. To address this gap in knowledge, a comprehensive research project is presented in this thesis, which investigated the dynamic performance of composite floors under various human induced loads. A popular type of composite floor system was selected for this investigation and subjected to load models representing different human activities. These load models have variable parameters such as load intensity, activity type (contact ratio), activity frequency and damping and are applied as pattern loads to capture the maximum responses in terms of deflections and accelerations. Computer models calibrated against experimental results are used in the analysis to generate the required information. The dynamic responses of deflections and accelerations are compared with the serviceability deflection limits and human comfort levels (of accelerations) to assess these floor types. This thesis also treats the use of visco-elastic (VE) dampers to mitigate excessive vibrations in steel-deck composite floors. VE damper properties have been presented and their performances in reducing the excessive vibrations have been assessed this thesis. The results identified possible occupancies under different loading conditions that can be used in planning, design and evaluation. The findings can also be used to plan retrofitting measures in problematic floor systems.