Dissertations / Theses on the topic 'Displacement-based analysis'

Phase-based methods are commonly applied in image registration. When working with phase-difference methods only a single is employed, although the algorithms are normally iterated over multiple scales, whereas phase-congruency methods utilize the phase from multiple scales simultaneously. This paper presents an extension to phase-difference methods employing parallel scales to achieve more accurate displacements. Results are also presented clearly favouring the use of parallel scales over single scale in more than 95% of the 120 tested cases.

Although performance based assessment procedures are mainly developed for reinforced concrete and steel buildings, URM buildings occupy significant portion of building stock in earthquake prone areas of the world as well as in Turkey. Variability of material properties, non-engineered nature of the construction and difficulties in structural analysis of perforated walls make analysis of URM buildings challenging. Despite sophisticated finite element models satisfy the modeling requirements, extensive experimental data for definition of material behavior and high computational resources are needed. Recently, nonlinear equivalent frame models which are developed assigning lumped plastic hinges to isotropic and homogenous equivalent frame elements are used for nonlinear modeling of URM buildings. The work presented in this thesis is about performance assessment of unreinforced brick masonry buildings in Turkey through nonlinear equivalent frame modeling technique. Reliability of the proposed model is tested with a reversed cyclic experiment conducted on a full scale, two-story URM building at the University of Pavia and a dynamic shake table test on a half scale, two story URM building at the Ismes Laboratory at Bergamo. Good agreement between numerical and experimental results is found. Finally, pushover and nonlinear time history analyses of three unreinforced brick masonry buildings which are damaged in 1995 earthquake of Dinar is conducted using the proposed three dimensional nonlinear equivalent model. After displacement demands of the buildings are determined utilizing Turkish Earthquake Code 2007, performance based assessment of the buildings are done.

Composite laminates are being more employed as fundamental structures due to its low weight and high stiffness. An example of this innovation is the primary structures of modern aircraft, which are lighter than the material formerly used. To predict the material response as load gradually increases can be quite demanding due to composite\'s complex failure mechanism. Hence superior computational models should be further investigated to precisely predict the mechanical behavior of composite media. This dissertation addresses an extended finite element procedure based on the layerwise displacement theory to simulate purely mode I delamination failure in composite laminates. The present model has the potential to perform structural analyzes in a pre-delaminated structure and also considering progressive failure. The type of element to be employed at the discretion of the model is the rectangular 4-node iso-parametric homogeneous element whose displacement field is approximated based in the layerwise theory. There are four types of degrees of freedom, one displacement in each direction, and one degree of freedom associated to the strong discontinuity. Numerical examples already solved in the bibliography are suggested in this dissertation, which demonstrate the potential of the model developed to accurately simulate pure mode I delamination in case of the investigation here is further elaborated. In addition, one possibility of future development of this dissertation is the modeling of fracture mode I without the need to discretize the cohesive planes as realized in traditional Cohesive Zone Methods.
Compósitos laminados estão sendo mais empregados como estruturas fundamentais devido ao seu baixo peso e alta rigidez. Um exemplo dessa inovação são as estruturas primárias das aeronaves modernas, que são mais leves do que as os materiais empregados antigamente. Prever a resposta do material à medida que a carga aumenta gradualmente pode ser difícil devido ao complexo mecanismo de falha dos compósitos. Portanto, modelos computacionais mais refinados devem ser investigados a fim de se prever um comportamento mecânico mais preciso. Esta dissertação aborda um procedimento de elementos finitos estendido baseado na teoria de deslocamento layerwise para simular falhas de delaminação modo I em laminados compósitos. O modelo abordado tem potencial para realizar análises em uma estrutura prédelaminada além de falha progressiva. O tipo de elemento a ser empregado na discrição do modelo é o isoparamétrico, homogêneo de 4 nós, retangular, e o campo de deslocamento é baseado na teoria layerwise. Existem quatro tipos de graus de liberdade, um deslocamento em cada direção, e um grau de liberdade associado à forte. Sugere-se nesse trabalho, exemplos, que são comparados com a bibliografia, e que apontam que o modelo desenvolvido nesta dissertação tem o potencial de simular o fenômeno de delaminação em modo I com acurácia, caso o estudo nessa dissertação seja estendido. Além disso, uma possibilidade de desenvolvimento futuro desse trabalho é a modelagem da fratura modo I sem a necessidade de discretizar os planos coesivos entre as lâminas, como realizado em métodos coesivos tradicionais.

This study set out to examine the effectiveness and reliability of six modifications to the Zhang et al. (2004) CPT-based lateral spread model. A regression analysis, distribution charts, and a discriminant analysis are performed to determine how effective the modifications are on the model. From the comparisons and statistical analysis performed in this study, application of these modifications reduces over-predictions from strain-based prediction methods. Unfortunately, the tendency to under-predict displacements on average is also increased.

One of the great challenges of microbial analysis in natural environments derives from the fact that a large proportion of microorganisms present is not culturable in standard conditions. To overcome this, various molecular approaches are widely used. Multiple Displacement Amplification (MDA) is especially useful as it can be applied in conjunction with other techniques to identify genes derived from individual microbial cells. The aim of this project was to study freshwater samples obtained from various environments in Ireland in order to identify dominant bacterial species and key genes associated with them that were likely to be involved in biodegradation of contaminating compounds. In order to do this, various molecular approaches were applied, with the most important being MDA assisted PCR. The tlree fresh water environments studied were: commercial bottled water, agriculturally contaminated ground water obtained from Co. Kilkenny, Ireland and ground water samples obtained from a diesel-contaminated site in Northern Ireland. In these environments, dominant bacterial strains were identified using MDA assisted PCR. Strains related to Rhodoferax ferrireducens were identified in commercial bottled water; Pseudomonas fluorescens and Polaromonas sp. in agriculturally-contaminated ground water samples; Dechloromonas aromatica and Pseudomonas putida in diesel-contaminated ground water samples. Functional genes (nitrate reductase and naphthalene dioxygenase) which are known to be involved in biodegradation were shown to be present in some of the strains. It was shown that the narG gene (nitrate reductase) was associated with strains related to Pseudomonas fluorescens, Alicycliphilus denitrificans and Polaromonas naphthalenivorans detected in agricultural-contaminated ground water. Naphthalene dioxygenase gene (nahAc) was associated with strains related to Pseudomonas fluorescens, Pseudomonas putida and nagAc (another naphthalene dioxygenase gene) with Ralstonia pickettii detected III ground water samples obtained from a diesel-contaminated site in Northern Ireland. To achieve a more comprehensive characterization of the studied environments corresponding 16S rRNA gene libraries were obtained and analysed. Sequences found in these libraries were affiliated with Proteobacteria, Bacteroidetes, Firmicutes, Chloroflexi, Actinobacteria and Cyanobacteria

Predictive maintenance based on condition monitoring uses sensor and system data to prevent damage, in advance to a failure occurring, allowing for a service to be performed at an optimal position in time. Condition based predictive maintenance estimates time of system failure based on a priori information, which has shown to be much more cost effective than traditional maintenance methods. Typically, there are applications where either of the maintenance methods, reactive, preventative or predictive maintenance, prove most sufficient. The expensive downtime in industrial processes and systems has come to focus development of predictive maintenance which often is found to be the optimal solution in these settings. In order for a predictive maintenance algorithm to be developed, there has to be in depth knowledge about the system and big data to base the algorithm on. This project is aimed at analysis and condition monitoring of the AkzoNobel - intelliCURE separate spreader used in the lamella and beam industry. Specifically targeted at the detection of cavitation in the transportation pumps, which is a common destructive phenomenon occurring in pumps. Cavitation which is the formation and implosion of cavities in the liquid, produces excessive shock waves resulting in vibrations. Depending on severity, cavitation can, in time, lead to internal damage and cause leakage. The type and amount of cavitation in a system is dependent on the rotational operating speed, which results in lower amount of vibrations for slow speeds. Where low amount of vibrations presents challenges of measurability. In order to detect the low amount of vibrations before severe cavitation development the optimal solution of measurability must be applied. Therefore, the research investigates the optimal solution for cavitation detection in terms of accelerometer configuration based on sensor position and sensor type in relation to reliability. The results of the study found that the fault mode vibrations caused by cavitation were detectable at lower rotational speeds than what industry recommended as the limit for an implementation. Additionally, the position and sensor type results in different performance to detect cavitation at slow pump speeds. An optimal configuration was found for the specific use case of the rotary bi-winged positive displacement pump.
Prediktivt underhåll baserat på tillståndsövervakning använder sensorer och systemdata för att förhindra skador, innan fel uppstår, vilket möjliggör att schemalägga en service vid en optimal tidpunkt. Tillståndsbaserat prediktivt underhåll estimerar tidpunkten för när fel uppstår i system baserat på a-priori information, som har visats vara mycket mer kostnadseffektiv än traditionella underhållningsmetoder. Typiskt finns tillämpningar där vardera av underhållsmetoderna, reaktivt-, förebyggande- eller prediktivt underhåll kan vara bäst lämpade. De dyra driftstoppen inom industri har lett till fokus på utveckling av prediktiva underhållsmetoder som ofta är ansett som den optimala lösningen i dessa förhållanden. För att en prediktiv algoritm ska kunna utvecklas krävs djup kunskap om systemet och stor mängd data att basera en algoritm på. Projektet fokuserar på vibrationsanalys och tillståndsövervakning av maskinen AkzoNobel - intelliCURE strängspridare som används i lamell- och balkindustrin. Forskningen är specifikt inriktad mot att upptäcka kavitation i transportpumparna som används i applikationen, där kavitation är ett relativt vanligt förekommande destruktivt fenomen som uppstår i pumpar. Kavitation, som är formandet och implosion av håligheter i vätska, leder till chockvågor som resulterar i vibrationer. Beroende på intensitet av förekommande kavitation, så kan det i tid leda till interna skador och resultera i läckage. Typen och intensiteten av förekommande kavitation i systemet är beroende av rotationshastigheten, som leder till lägre vibrationsgrad för lägre hastigheter. Där låg vibrationsintensitet presenterar utmaningar i mätbarhet. För att detektera den låga graden av vibrationer innan allvarlig kavitation utvecklas måste en optimal lösning för mätbarhet användas. Därav undersöker denna forskning en optimal lösning för att upptäcka kavitation med hjälp av accelerometerkonfiguration baserat på sensorplacering och sensortyp samt hur det relaterar till pålitlighet. Resultatet från studien visar att mätbarheten av vibrationerna som uppstår vid lägre hastigheter är bättre än vad som rekommenderas som gräns för användandet av vibrationsanalys på industriella applikationer. Samt att positionen och typen av sensor resulterar i olika möjligheter att detektera kavitation vid låga pumphastigheter. En optimal lösning hittades för det specifika användningsområdet av en dubbelvingad vingrotorpump som studien applicerades på.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2006.
Littles, Jerrol W. Jr., Committee Member ; Johnson, W. Steven, Committee Member ; Kurfess, Thomas R., Committee Chair ; Melkote, Shreyes N., Committee Member.

Structural Health Monitoring (SHM) is a means of identifying damage from the structural response to environmental loads. Real-time SHM offers rapid assessment of structural safety by owners and civil defense authorities enabling more optimal response to major events. This research presents an real-time, convex, integral-based SHM methods for seismic events that use only acceleration measurements and infrequently measured displacements, and a non-linear baseline model including hysteretic dynamics and permanent deformation. The method thus identifies time-varying pre-yield and post-yield stiffness, elastic and plastic components of displacement and final residual displacement. For a linear baseline model it identifies only timevarying stiffness. Thus, the algorithm identifies all key measures of structural damage affecting the immediate safety or use of the structure, and the long-term cost of repair and retrofit. The algorithm is tested with simulated and measured El Centro earthquake response data from a four storey non-linear steel frame structure and simulated data from a two storey non-linear hybrid rocking structure. The steel frame and rocking structures exhibit contrasting dynamic response and are thus used to highlight the impact of baseline model selection in SHM. In simulation, the algorithm identifies stiffness to within 3.5% with 90% confidence, and permanent displacement to within 7.5% with 90% confidence. Using measured data for the frame structure, the algorithm identifies final residual deformation to within 1.5% and identifies realistic stiffness values in comparison to values predicted from pushover analysis. For the rocking structure, the algorithm accurately identifies the different regimes of motion and linear stiffness comparable to estimates from previous research. Overall, the method is seen to be accurate, effective and realtime capable, with the non-linear baseline model more accurately identifying damage in both of the disparate structures examined.

Muchas ciudades del Perú se encuentran ubicadas en el cinturón de fuego del Pacífico, en consecuencia, existe una mayor probabilidad de ocurrencias de sismos que generen cuantiosas pérdidas de vida y grandes perjuicios económicos. Debido a este problema, la ingeniería civil está en la obligación de investigar nuevos diseños sísmicos más precisos, los cuales originaron diversos métodos que usan a los desplazamientos de la estructura como parámetro principal, ya que a través de los desplazamientos se pueden obtener los momentos y cortantes de la estructura. A este método se le conoce como Diseño Basado en Desplazamientos. El autor que le dio los lineamientos teóricos más amplios y consistentes es Priestley, con su propuesta llamada Diseño Directo Basado en Desplazamientos. Por otro lado, en la realidad peruana, las edificaciones con sistema estructura del pórtico de acero son atípicos en comparación con las de sistema dual de concreto armado. En consecuencia, se desaprovecha las propiedades de este material y de este sistema estructural, el cual se sumerge más en el rango inelástico que el concreto. La tesis analizará los resultados obtenidos del análisis sísmico de una estructura de sistema dual y otra de pórticos de acero, ambas con una misma configuración arquitectónica, bajo las metodologías de Diseño Directo Basado en Desplazamientos y de Diseño Basado en Fuerzas. Esto generará la comparación entre los sistemas estructurales bajo las metodologías mencionadas.
Many cities in Peru are located in the Pacific ring of fire, consequently, there is a greater probability of earthquakes that generate large losses of life and great economic damage. Due to this problem, civil engineering is obliged to investigate new more accurate seismic designs, which originated several methods that use the displacements of the structure as the main parameter, since through the displacements the moments and shear of the structure can be obtained. This method is known as Displacement Based Design. The author who gave the broadest and most consistent theoretical guidelines is Priestley, with his proposal called Direct Displacement Based Design. On the other hand, in the Peruvian reality, steel frames buildings system are atypical compared to those of the dual wall-frame with reinforced concrete system. Consequently, the properties of this material and this structural system are wasted, which is more immersed in the inelastic range than concrete. The thesis will analyze the results obtained from the seismic analysis of a dual wall-frame building and another of steel frames, both with the same architectural configuration, under the Direct Displacement Based Design method and the Design Based Force method, which is the method used in most standards. The thesis will generate the comparison between the structural systems under the mentioned methodologies.
Tesis

The main objective of the work presented herein was to develop new semi-empirical design procedures for determination of bearing capacity and load-displacement response of axially loaded piles in clay. Hereunder also prediction of how the capacity will build up with time following the pile installation, primarily as a result of consolidation. A main basis for developing new procedures was the collection, detailed review and assessment of results from a series test programs carried out over the past 30 years on well instrumented piles. The data collected and reviewed include the pile installation, re-consolidation, and loading phases. The pile instrumentation includes measurement of the distribution of loads or shaft friction, pore pressure and earth pressure along the pile shafts. The soil conditions range from soft NC clays with undrained shear strength down to about 15 kPa, to very stiff and high OCR clays with undrained shear strength up to about 500 kPa. The plasticity index of the clays mostly lies in range 10 to 60 %. The test piles range from small scale model piles with diameter down to 36 mm and length down to 1- 2 m, to large scale piles with diameter up to 800 mm and length up 71 m. In addition to these fully instrumented pile tests, some recent large scale tests on non-instrumented piles are also reviewed and included as basis for developing the new proposed design procedures. Two new procedures for predicting ultimate shaft friction are proposed, respectively a so-called α- and β approach. They tie the local ultimate shaft friction along a pile to the “true” undisturbed in-situ undrained strength of the clay as determined from Direct Simple Shear Tests, the in-situ vertical effective stress, the overconsolidation ratio, and the plasticity index of the clay. No clear evidence is found of effects of pile diameter, length or stiffness on the local ultimate shaft friction, or whether the pile is open-or closed- ended. A moderate effect of pile length or flexibility on the total ultimate pile capacity will still come out of the proposed t-z curves, which include some postpeak reduction. A brief review and summary is also given of measured effects of cyclic loads on the axial capacity and pile head displacements of piles. It is concluded that this issue can be well accounted for by analytical or numerical procedures already in existence. A semi – empirical analytical procedure, based on linear radial consolidation theory, is proposed for predicting the time required for re-consolidation and “set-up” of the ultimate shaft friction. The main input parameters are the in-situ permeability and virgin modulus number (or virgin compression index) of the undisturbed clay. The same basic formula and correlations were found applicable to both open- and closed- ended or partially plugging piles. For design purposes it is very important to recognise that the time for full set-up can easily be a factor of 10 longer for a closed– ended pile than for an ideal nonplugging open- ended pile. It was also an objective to study how well the measured pile response during installation, re-consolidation and pile loading could be predicted from analytical and numerical models. Although such procedures can give very valuable insight, there is still a way to go before they can correctly capture all relevant elements of the pile response. The greatest need for improvement is to establish a better understanding of how the severe disturbance and strains induced by the pile installation affects the basic stress-strain, strength-, and volumetric compressibility- characteristics of the clay, depending on the level of induced shear strains as function of radial distance from the pile wall.

La méthode des éléments finis est couramment utilisée depuis les années 1970 pour prédire le comportement de structures telles que des automobiles, des avions, des machines, des ponts ou des bâtiments. Les choix de modélisation sont essentiels afin de construire un modèle représentatif, tout en maîtrisant le nombre de degrés de liberté. De nombreux travaux ont cherché à optimiser le modèle d’un point de vue du maillage en proposant notamment des techniques de maillage adaptatif. En revanche, concernant le choix de théorie, peu de travaux ont été menés pour obtenir un modèle éléments finis optimal. Dans le contexte de l’analyse linéaire statique et vibratoire, cette thèse a pour objectif de proposer une méthodologie de modélisation adaptative afin d’obtenir un modèle éléments finis optimal d’un point de vue du choix de théorie. Le maillage, composé uniquement d’éléments volumiques, est raffiné à chaque itération de la méthodologie. Un choix approprié entre les théories de poutre, de coque et d’élasticité 3D est effectué sur chaque élément fini à l’issue de chaque analyse. Dans les zones où les théories de poutre ou de coque sont pertinentes, des champs de déplacements spécifiques sont appliqués. De nouvelles approches volume-coque et volume-poutre, basées respectivement sur la théorie des coques et la théorie des poutres, sont développées à cet effet. Pour chacune de ces approches, des théories de premier ordre et d’ordre supérieur sont proposées. Dans ces zones l’application de relations cinématiques aux noeuds du maillage volumique, se traduisant par des équations linéaires, mène à une réduction du nombre de degrés de liberté. Dans le cadre de l’analyse statique et vibratoire, plusieurs exemples sont traités pour évaluer la méthodologie de modélisation adaptative. Les résultats numériques obtenus sont toujours très proches de ceux d’un modèle volumique de référence et la modélisation adaptative mène à une réduction significative de la taille du modèle
The finite element method has been widely used since the 1970s to predict the behavior of structures such as automobiles, airplanes, machines, bridges or buildings. The modeling choices are essential to build a representative model and control the number of degrees of freedom. Many works have sought to optimize the model from a mesh point of view, namely by proposing adaptive meshing techniques. On the other hand, concerning the theory choice, seldom work has been carried out to obtain an optimal finite element model. In the context of static and vibratory linear analysis, this thesis aims to propose an adaptive modeling methodology in order to obtain an optimal finite element model from the theory choice point of view. The mesh, composed only of solid elements, is refined at each iteration of the methodology. An appropriate choice between beam, shell and 3D elasticity theories is made on each finite element of the model at each analysis. In areas where beam or shell theories are relevant, specific displacement fields are applied. New solid-shell and solid-beam approaches, based respectively on shell theory and beam theory, have been developed for this purpose. For each of these two approaches, first-order and higher-order theories are proposed. In these areas, the application of kinematic relations at nodes of the solid mesh, by using linear equations, leads to a reduction of the number of degrees of freedom. In the context of static and vibratory analysis, several examples are treated to evaluate the methodology of adaptive modeling. The numerical results obtained are always very close to those of a reference solid model and the adaptive modeling method leads to a significant reduction in the model size

碩士
國立高雄應用科技大學
機械工程系
106
In this thesis, Taguchi quality design is applied and the gray relational method is used to explore the optimal design of the hinge of flexible mechanism applied in the displacement magnification mechanism. In the study, three models of flexible hinges and displacement amplifying mechanisms with different geometric shapes were established by using SolidWorks drawing software, and an appropriate force was applied as a force to simulate the finite element analysis software ANSYS Workbench and find out through Taguchi quality design. The best combination of the parameters of the displacement amplification mechanism and the influencing factors on the quality characteristics are used as the best solution to predict the combination of the various factors. Then the analysis of variance and the interaction check are carried out to ensure the correctness of the prediction. The gray correlation method was used to integrate multiple optimal target to maximize efficiency, so, in the multi-quality design features to determine the best combination of conflict problems encountered will be resolved in order to get the best solution. The results show that the optimization method of this study can obviously integrate the overall quality of the displacement and look at the characteristics of low-stress and low-quality. The best combination of parameters for the aluminum alloy material, the hinge length of 5 mm opening, the geometry S-type, the hinge thickness of 0.3 mm, the material thickness of 5 mm, and the hinge opening 10 mm, is conformed with the verification results. Also meet the expected goals and can successfully solve the conflict between multi-objective quality characteristics to achieve the best combination of both displacement and contingency.

碩士
國立彰化師範大學
機電工程學系
96
In this thesis, a method for measuring small displacements is presented based on the phenomenon of multiple total-internal reflections and heterodyne interferometric technique. The optical system of our method consists of a heterodyne light source, piezoelectric translator (PZT), a semi-sphere glass, a parallelogram prism, and some optical components. A heterodyne light beam reflected from the PZT passes through the center of the semi-sphere glass and impinges on the parallelogram prism. The beam is guided within the prism due to total-internal reflection. When the PZT generates a small displacement, the output beam from a semi-sphere glass is deflected. Therefore, the phase difference between the p- and s- polarization of the beam coming from the parallelogram prism is apparently changed. The variation of the phase difference can be measured accurately with heterodyne interferometry. The result, then, is fed into the derived equation, and the displacement can be estimated. This study also discusses the relations among the small displacement and the operated conditions of some optical components of the apparatus with numerical analysis software (Matlab). According to the simulation results, the measurable range of this method is up to ± 0.96 μ m, and its sensitivity up to 0.045 degree / nm. Because of its common-path configuration, this method possesses high stability and high precision.

碩士
國立臺灣科技大學
機械工程系
106
Continuum robot becomes more and more popular in recent years. Displacement analysis is necessary to find the position of continuum robots. In robot control, there are a lot of researches on path planning and how to bypass the obstacle. There are also many methods can be used to analyze the displacement of continuum robots like geometry models and beam theory models. These methods can also solve the kinematics problem about continuum robot with end loads. However, there is no research about what will happen when a continuum robot contacts an obstacle and keep going. Therefore, the purpose of this thesis is analyzing displacement of a continuum robot with a contacted obstacle. The geometry models are too simple, some of the beam theory models are too complicated, and some cannot solve this problem. Afterward, the neural network model is chosen to analyze displacement of continuum robot with contacted obstacle although there is no research about displacement analysis using a neural network model. By using the neural network model, the user only needs to decide what are the input data, the target data, and then do some experiments to get data. These data would be used to train the neural network model. After that, a trained model would be produced. The trained neural network model will output the position and orientation of the end-effector of the robot in a short time.

During a seismic event, the walls within an unreinforced masonry (URM) building must possess sufficient capacity to withstand out-of-plane collapse. Traditionally, design against this type of failure has been performed using a force-based (FB) approach, in which the engineer must ensure that the force capacity of the wall is not exceeded during a design earthquake. In recent years, however, seismic design philosophy for ductile systems has experienced a move away from FB methods and toward displacement-based (DB) methods, where the aim is to ensure that structural deformations are kept within acceptable displacement limits. URM walls subjected to out-of-plane actions make a prime candidate for the development of such methodology. This is particularly true for two-way spanning walls, which have significant displacement capacity as well as good energy dissipation capability during cyclic response—both highly favourable characteristics with respect to seismic performance. This thesis documents research undertaken at the University of Adelaide into the seismic response of two-way URM walls subjected to out-of-plane actions. The aims of this work were to facilitate improvements to the presently-used FB design methods and to provide a basis for the development of a reliable DB design approach. The following outcomes have been achieved: • Characterisation of the load-displacement behaviour of two-way walls through quasistatic cyclic testing using airbags; • Verification of this behaviour under true seismic loading conditions by means of dynamic shaketable tests; • Improvements to the current state-of-the-art design approach for predicting the ultimate load capacity of walls possessing tensile bond strength; • A probabilistic approach to deal with the different modes of possible failure in horizontal bending; • Development of analytical methodology for predicting the load capacity of walls using the assumption of zero tensile bond strength; • A proposed model for representing the nonlinear inelastic load-displacement behaviour of two-way walls; and finally, • Implementation of the load-displacement model into a simple DB seismic assessment procedure. It is anticipated that this research will eventually culminate in a multi-tiered seismic design procedure incorporating both the FB and DB components, with applicability toward the design of new buildings and assessment of existing buildings alike.
Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2012

Η πλειονότητα των ερευνητών/ειδικών του αντισεισμικού σχεδιασμού συμφωνεί πως μια υπολογιστική διαδικασία που θα έχει ως βασική παράμετρο της απόκρισης τις σεισμικές μετακινήσεις θα είναι πιο ορθολογική και πιθανότατα πιο οικονομική απ’ τη συμβατική μεθοδολογία σχεδιασμού βάσει δυνάμεων. Η έλλειψη μιας μεθοδολογίας αντισεισμικού σχεδιασμού γεφυρών βάσει μετακινήσεων που να είναι απλή, εφικτή και συμβατή με την εφαρμοζόμενη πρακτική και η απουσία πρότασης σχεδιασμού των περιοχών του φορέα βάσει μετακινήσεων, αποδεικνύει το γνωστικό κενό που υπάρχει σ’ αυτή την περιοχή του αντισεισμικού σχεδιασμού. Η παρούσα εργασία επιχειρεί να συμβάλλει στην πλήρωση αυτού του κενού και προς τούτο προτείνει μια νέα μεθοδολογία. Αναφέρεται σε (μή-μονωμένες) γέφυρες σκυροδέματος και περιλαμβάνει μια απλή διαδικασία για την εκτίμηση των απαιτούμενων ανελαστικών παραμορφώσεων, τόσο των βάθρων, όσο και των περιοχών του φορέα - κάνοντας χρήση ελαστικής φασματικής ανάλυσης και επεκτείνοντας τον κανόνα των "Ίσων Μετακινήσεων" στο τοπικό επίπεδο. Η διαδικασία αναπτύσσεται και βαθμονομείται βάσει (σχεδόν δύο χιλιάδων) μή-γραμμικών δυναμικών αναλύσεων (με εν χρόνω ολοκλήρωση) αντιπροσωπευτικών γεφυρών, τριών έως πέντε ανοιγμάτων. Όμως για την εφαρμογή της απαιτούνται μόνο ελαστικά εργαλεία. Σε αντίθεση με τις έως τώρα ερευνητικές προσπάθειες, όπου γίνεται η απλουστευτική παραδοχή γραμμικής συμπεριφοράς του φορέα, στην παρούσα έρευνα δίνεται έμφαση στην προσομοίωση των περιοχών του φορέα και λαμβάνονται υπ’ όψιν οι μή-γραμμικότητές του. Από την εφαρμογή του διαπιστώνεται ότι ο προτεινόμενος σχεδιασμός βάσει μετακινήσεων προσφέρει πολύ οικονομικότερα ποσοστά όπλισης (από 1/2 έως 1/7 στο διαμήκη οπλισμό και από 1/1 έως 1/3 στον εγκάρσιο οπλισμό), χωρίς να επιβαρύνει ουσιαστικά την επιτελεστικότητα της γέφυρας - η υπεραντοχή των γεφυρών που σχεδιάζονται με την προτεινόμενη μεθοδολογία είναι πρακτικά ισοδύναμη με την υπεραντοχή των συμβατικά σχεδιασμένων γεφυρών. Η παρουσίαση της μεθοδολογίας περιλαμβάνει την περιγραφή της διαδικασίας σχεδιασμού υπό μορφή αλγόριθμου (Κεφ. 2), του τρόπου εφαρμογής της στην πράξη (διαδικασία προσομοίωσης, παραδείγματα σχεδιασμού: Κεφ. 3), του θεωρητικού υποβάθρου βάσει του οποίου αναπτύχθηκε (Κεφ. 4), των προβλημάτων της συμβατικής μεθοδολογίας (παραδείγματα σχεδιασμού βάσει δυνάμεων: Κεφ. 3) και των κενών που διαπιστώνονται στην τεκμηρίωση της συμβατικής μεθοδολογίας (Κεφ. 4). Η αποτίμηση του σχεδιασμού (Κεφ. 3) δεκαέξι αντιπροσωπευτικών γεφυρών (οκτώ σχεδιασμένων βάσει μετακινήσεων και οκτώ συμβατικά σχεδιασμένων), παρουσιάζεται υπό μορφή παράλληλης σύγκρισης της επιτελεστικότητας και συνηγορεί υπέρ των πλεονεκτημάτων της νέας μεθοδολογίας. Στα Παραρτήματα δίνονται πληροφορίες για τα υπολογιστικά εργαλεία που αναπτύχθηκαν για την προσομοίωση και την ανάλυση των γεφυρών (επέκταση προγράμματος ANSRuop).
The majority of seismic design researchers/specialists concludes that displacement-based design methodologies reduce the uncertainty of the design process and probably lead to less expensive structures. The absence of a simple displacement-based seismic design procedure for bridges that will be feasible and compatible with the current design practice and the nonexistence of a proposal for the displacement-based design of the deck indicate the gap of knowledge in this field of earthquake engineering. This thesis attempts to contribute to the reduction of this gap and for this scope proposes a new methodology. The procedure focuses on bridges with concrete piers monolithically connected to a prestressed concrete continuous deck and comprises simple steps for the estimation of the inelastic/nonlinear deformations of both the piers and the deck - through elastic modal response spectrum analysis, extending the applicability of the "equal displacement" rule to the level of member deformations. About two thousands nonlinear dynamic (time-history) analyses of several representative bridges (with deck of three or five spans) are used for the development and the calibration of the procedure. However, for the application of the methodology only elastic modal response spectrum analysis is needed. Contrary to other current researches, which adopt the hypothesis of deck elastic response, the nonlinearities of the deck are modeled. The proposed displacement-based procedure offers lower reinforcement ratios (from 1/2 to 1/7 for the longitudinal reinforcement and from 1/1 to 1/3 for the transverse reinforcement) at no detriment to the expected seismic performance - the global overstrength of the bridges which are designed with the proposed procedure is practically equivalent to the global overstrength of the conventionally designed bridges (current force-based design). The step by step description of the design algorithm (Chap. 2) is followed by the practical application of the methodology (modeling aspects, design examples: Chap. 3), the conceptual justification (Chap. 4), the deficiencies of the conventional design procedure (force-based design examples: Chap. 3) and the fallacies in the justification of the conventional design methodology (Chap. 4). Comparative performance-based design evaluation (Chap. 3) of sixteen representative bridges (eight bridges subjected to alternative seismic design) indicates the benefits of the proposed procedure. The computational capabilities which were developed for the modeling and the analysis of the bridges are described in the appendices (upgrade of program ANSRuop).

The backdrop for this research paper is the tunnelling that is currently nearing completion in the Epirus region of Northern Greece, as part of the Egnatia Odos Highway construction. Highly deformed and altered sediments and low grade rock masses dominate the near surface environment creating a variety of technical challenges for tunnelling. Accurate equivalent rock mass performance reductions for tunnels in these materials is complicated by geomorphologic peculiarities such as those found in Flysch materials. The mechanisms of rock-support interaction related to face or near-face reinforcement systems are poorly understood at this time. As well, the mechanics of weak rock materials in the complex deformation regime in advance of a tunnel face are not robustly integrated into current 2D design models. Design decisions are currently possible using empirical techniques and simplified models, but a true optimized and mechanicsbased design process for the various support technologies are not fully developed. This research addresses elements of such issues, such as: use of the Longitudinal Displacement Profile (LDP) of the Convergence-Confinement method of tunnel design, relating 2D numerical models to their distance from the face using the size of the plastic zone as an indicator, near face tunnel support analysis in weak rock masses, boundary condition assessment for numerical modelling of such weak rock masses, the influence of plasticity zones surrounding tunnel excavations, and modelling optimization techniques for weak rock tunnelling in order to optimize the design of such underground structures and better predict near-face deformation and yield development. This work involved the use of 2D and 3D numerical models of tunnel sequencing for numerical simulation of composite material behaviour and sequential tunnel deformation response.
Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2009-09-01 08:46:30.537