Dissertations / Theses on the topic 'Linear load'

This thesis reviews the parameters required to perform linear response history analysis according to Chapter 16 of the American Standard ASCE 7-10. A careful analysis is presented about the selection of ground motions using real records and using artificial records generated such that their response spectrum matches with a defined target spectrum; three different techniques are studied for the generation of these artificial records. Also, this document revises the scaling of ground motion techniques in the American Standard ASCE-7 as well as in other seismic codes. It presents a detailed analysis of the variables influencing the scaling of ground motions, and it suggests a new scaling technique for linear response history analysis. The assumptions made establishing the flexibility of the diaphragms are also analyzed as well as dynamic methods to include accidental torsion when doing a linear response history analysis. Other modeling issues such as the orientation of the ground motion axis, scaling of element forces and displacements, orthogonal loading, solution techniques, P-Delta effects, modeling of the basement, and calculation of drifts are also studied in the context of linear response history analysis. The thesis concludes with suggested code language for linear response history analysis intended to be considered in future editions of the American Standard ASCE 7.<br>Master of Science

The main result is a new original algorithm: CONDOR ("COnstrained, Non-linear, Direct, parallel Optimization using trust Region method for high-computing load, noisy functions"). The aim of this algorithm is to find the minimum x* of an objective function F(x) (x is a vector whose dimension is between 1 and 150) using the least number of function evaluations of F(x). It is assumed that the dominant computing cost of the optimization process is the time needed to evaluate the objective function F(x) (One evaluation can range from 2 minutes to 2 days). The algorithm will try to minimize the number of evaluations of F(x), at the cost of a huge amount of routine work. CONDOR is a derivate-free optimization tool (i.e. the derivatives of F(x) are not required. The only information needed about the objective function is a simple method (written in Fortran, C++,) or a program (a Unix, Windows, Solaris, executable) which can evaluate the objective function F(x) at a given point x. The algorithm has been specially developed to be very robust against noise inside the evaluation of the objective function F(x). This hypotheses are very general, the algorithm can thus be applied on a vast number of situations. CONDOR is able to use several CPU's in a cluster of computers. Different computer architectures can be mixed together and used simultaneously to deliver a huge computing power. The optimizer will make simultaneous evaluations of the objective function F(x) on the available CPU's to speed up the optimization process. The experimental results are very encouraging and validate the quality of the approach: CONDOR outperforms many commercial, high-end optimizer and it might be the fastest optimizer in its category (fastest in terms of number of function evaluations). When several CPU's are used, the performances of CONDOR are currently unmatched (may 2004). CONDOR has been used during the METHOD project to optimize the shape of the blades inside a Centrifugal Compressor (METHOD stands for Achievement Of Maximum Efficiency For Process Centrifugal Compressors THrough New Techniques Of Design). In this project, the objective function is based on a 3D-CFD (computation fluid dynamic) code which simulates the flow of the gas inside the compressor.<br>Doctorat en sciences appliquées<br>info:eu-repo/semantics/nonPublished

ABSTRACT (italiano) Con crescente attenzione riguardo al problema della sicurezza di ponti e viadotti esistenti nei Paesi Bassi, lo scopo della presente tesi è quello di studiare, mediante la modellazione con Elementi Finiti ed il continuo confronto con risultati sperimentali, la risposta in esercizio di elementi che compongono infrastrutture del genere, ovvero lastre in calcestruzzo armato sollecitate da carichi concentrati. Tali elementi sono caratterizzati da un comportamento ed una crisi per taglio, la cui modellazione è, da un punto di vista computazionale, una sfida piuttosto ardua, a causa del loro comportamento fragile combinato a vari effetti tridimensionali. La tesi è incentrata sull'utilizzo della Sequentially Linear Analysis (SLA), un metodo di soluzione agli Elementi Finiti alternativo rispetto ai classici approcci incrementali e iterativi. Il vantaggio della SLA è quello di evitare i ben noti problemi di convergenza tipici delle analisi non lineari, specificando direttamente l'incremento di danno sull'elemento finito, attraverso la riduzione di rigidezze e resistenze nel particolare elemento finito, invece dell'incremento di carico o di spostamento. Il confronto tra i risultati di due prove di laboratorio su lastre in calcestruzzo armato e quelli della SLA ha dimostrato in entrambi i casi la robustezza del metodo, in termini di accuratezza dei diagrammi carico-spostamento, di distribuzione di tensioni e deformazioni e di rappresentazione del quadro fessurativo e dei meccanismi di crisi per taglio. Diverse variazioni dei più importanti parametri del modello sono state eseguite, evidenziando la forte incidenza sulle soluzioni dell'energia di frattura e del modello scelto per la riduzione del modulo elastico trasversale. Infine è stato effettuato un paragone tra la SLA ed il metodo non lineare di Newton-Raphson, il quale mostra la maggiore affidabilità della SLA nella valutazione di carichi e spostamenti ultimi insieme ad una significativa riduzione dei tempi computazionali. ABSTRACT (english) With increasing attention to the assessment of safety in existing dutch bridges and viaducts, the aim of the present thesis is to study, through the Finite Element modeling method and the continuous comparison with experimental results, the real response of elements that compose these infrastructures, i.e. reinforced concrete slabs subjected to concentrated loads. These elements are characterized by shear behavior and crisis, whose modeling is, from a computational point of view, a hard challenge, due to their brittle behavior combined with various 3D effects. The thesis is focused on the use of Sequentially Linear Analysis (SLA), an alternative solution technique to classical non linear Finite Element analyses that are based on incremental and iterative approaches. The advantage of SLA is to avoid the well-known convergence problems of non linear analyses by directly specifying a damage increment, in terms of a reduction of stiffness and strength in the particular finite element, instead of a load or displacement increment. The comparison between the results of two laboratory tests on reinforced concrete slabs and those obtained by SLA has shown in both the cases the robustness of the method, in terms of accuracy of load-displacements diagrams, of the distribution of stress and strain and of the representation of the cracking pattern and of the shear failure mechanisms. Different variations of the most important parameters have been performed, pointing out the strong incidence on the solutions of the fracture energy and of the chosen shear retention model. At last a confrontation between SLA and the non linear Newton-Raphson method has been executed, showing the better reliability of the SLA in the evaluation of the ultimate loads and displacements, together with a significant reduction of computational times.

Neste trabalho desenvolvemos o estudo da álgebra linear, secções cônicas e aplicações. Apresentamos os conceitos mais importantes da álgebra linear, estudando os espaços vetorias, subespaços vetoriais, matriz de mudança de base, transformações lineares e produto interno. O principal resultado do trabalho é o teorema espectral que fornece ferramentas para se estudar as secções cônicas não elementares, ou seja, aquelas nas quais uma parábola, elipse ou hipérbole são apresentadas com seus eixos não paralelos aos eixos coordenados do plano cartesiano. Uma vez de posse deste teorema é mostrado um processo prático no qual transformamos uma equação ax2 +bxy +cy2 +dx +ey + g = 0 na equação k1 (x\')2 + k2 (y\')2 + (dx1 + ey1) x\' + (dx2 + ey2) y\' + g = 0 sem o termo misto xy, onde após a eliminação deste, podemos deduzir a equação da cônica identificando assim esta curva. Apresentamos exemplos de cônicas com eixos paralelos e não paralelos aos coordenados do plano cartesiano e utilizamos o software geogebra para visualização. Também discutimos algumas aplicações das cônicas como trajetória de corpos celestes (planeta Terra e um cometa), princípio de reflexão da parábola mostrando o porquê das antenas e dos captadores de ondas sonoras serem parabólicos. Demonstramos um teorema que denominei de identificador de uma curva cônica pois com ele é possível classificar a cônica sem realizar o processo prático, apenas para isso identificamos através da equação ax2 +bxy + cy2 +dx + ey +g = 0, quais os valores de a;b e c e feito isto calculamos o discriminante b2 - 4ac, analisamos os sinais e a nulidade, ou seja, se é maior que zero, menor que zero ou igual a zero, assim é possível classificar a cônica.<br>The paper develops the study of linear algebra, conic sections and applications. I present the most important concepts of linear algebra, studying vector spaces, vector subspaces, base change matrix, linear transformations, internal product. The main result of the work is the spectral theorem, which provides tools to study the non-elementary conic sections, that is, those in which a parabola, ellipse or hyperbola are presented with their axes not parallel to the cartesian planes coordinate axes. Using this theorem we show a practical process in which we transform an equation ax2 +bxy + cy2 +dx +ey +g = 0 into the equation k1 (x\')2 +k2 (y\')2 + (dx1 +ey1) x\' (dx2 + ey2) y\' +g = 0 without the mixed term xy, where after its elimination we can deduce the conic equation thus identifying the curve we are looking for. I present examples of conic with parallel and non-parallel axes to the coordinates of the Cartesian plane and use the geogebra software for visualization. I discuss some applications of the conic as a trajectory of celestial bodies (planet Earth and a comet), principle of reflection of parabola showing why the antennas and sound wave pickups are parabolics. I demonstrate a theorem that I named the identifier of a conic curve, with it it is possible to classify the conic without realizing the practical process only for this. I identify through the equation ax2 +bxy + cy2 +dx + ey + g = 0, what are the values of a;b, and c and, with this done, I compute the discriminant b2 - 4ac and analyze the signs and the nullity, that is, if it is greater than zero, less than zero or equal to zero, therefore is possible to classify the conic.

Load distribution problems in distributed computing networks have attracted much attention in the literature. A major objective in these studies is to distribute the processing load so as to minimize the time of processing of the entire load. In general, the processing load can be indivisible or divisible. An indivisible load has to be processed in its entirety on a single processor. On the other hand, a divisible load can be partitioned and processed on more than one processor. Divisible loads are either modularly divisible or arbitrarily divisible. Modularly divisible loads can be divided into pre-defined modules and cannot be further sub-divided. Further, precedence relations between modules may exist. Arbitrarily divisible loads can be divided into several fractions of arbitrary lengths which usually do not have any precedence relations. Such type of loads are characterized by their large volume and the property that each data element requires an identical and independent processing. One of the important problems here is to obtain an optimal load distribution, which minimizes the processing time when the distribution is subject to communication delays in the interconnecting links. A specific application in which such loads are encountered is in edge-detection of images. Here the given image frame can be arbitrarily divided into many sub-frames and each of these can be independently processed. Other applications include processing of massive experimental data. The problems associated with the distribution of such arbitrarily divisible loads are usually analysed in the framework of what is known as divisible job theory. The research work reported in this thesis is a contribution in the area of distributing arbitrarily divisible loads in distributed computing systems subject to communication delays. The main objective in this work is to design and analyseload distribution strategies to minimize the processing time of the entire load in a given network. Two types of networks are considered, namely (i) single-level tree (or star) network and (ii) linear network. In both the networks we assume that there is a non-zero delay associated with load transfer. Further, the processors in the network may or may not be equipped with front-ends (Le., communication co-processors). The main contributions in this thesis are summarized below. First, a mathematical formulation of the load distribution problem in single-level tree and linear networks is presented. In both the networks, it is assumed that there are (m +1) processors and m communication links. In the case of single-level tree networks, the load to be processed is assumed to originate at the root processor, which divides the load into (m +1) fractions, keeps its own share of the load for processing, and distributes the rest to the child processors one at a time and in a fixed sequence. In all the earlier studies in the literature, it had been assumed that for a load distribution to be optimal, it should be such that all the processors must stop computing at the same time. In this thesis, it is shown that this assumption is in general not true, and holds only for a restricted class of single-level tree networks which satisfy a certain condition. The concept of an equivalent network is introduced to obtain a precise formulation of this condition in terms of the processor and link speed parameters. It is shown that this condition can be used to identify processor-link pairs which can be eliminated from a given network (i.e., these processors need not be given any computational load) without degrading its time performance. It is proved that the resultant reduced network (a network from which these inefficient processor-link pairs have been removed) gives the optimal time performance if and only if the load distribution is such that all the processors stop computing at the same time instant. These results are first proved for the case when the root processor is equipped with a front-end and then extended to the case when it is not. In the latter case, an additional condition, between the speed of the root processor and the speed of each of the links, to be satisfied by the network is specified. An optimal sequence for applying these conditions is also obtained. In the case of linear networks the processing load is assumed to originate at the processor situated at one end of the network. Each processor in the network keeps its own load fraction for computing and transmits the rest to its successor. Here too, in all the earlier studies in the literature, it has been assumed that for the processing time to be a minimum, the load distribution must be such that all the processors must stop computing at the same instant in time. Though this condition has been proved by others to be both necessary and sufficient, a different and more rigorous proof, similar to the case of single-level tree network, is presented here. Finally, the effect of inaccurate modelling on the processing time and on the above conditions are discussed through an illustrative example and it is shown that the model adopted in this thesis gives reasonably accurate results. In the case of single-level tree networks, so far it has been assumed that the root processor distributes the processing load in a fixed sequence. However, since there are m child processors, a total of m! different sequences of load distribution are possible. Using the closed-form derived for the processing time, it is proved here that the optimal sequence of load distribution follows the decreasing order of link speeds. Further, if physical rearrangement of processors and links is allowed, then it is shown that the optimal arrangement follows a decreasing order of link and processor speeds with the fastest processor at the root. The entire analysis is first done for the case when the root processor is equipped with a front-end, and then extended to the case when it is not. In the without front-end case, it is shown that the same optimal sequencing result holds. However, in an optimal arrangement, the root processor need not be the fastest. In this case an algorithm has been proposed for obtaining optimal arrangement. Illustrative examples are given for all the cases considered. Next, a new strategy of load distribution is proposed by which the processing time obtained in earlier studies can be further minimized. Here the load is distributed by the root processor to a child processor in more than one installment (instead of in a single installment) such that the processing time is further minimized. First; the case in which all the processors are equipped :tn front-ends is considered. Recursive equations are obtained for a heterogeneous network and these are solved for the special case of a homogeneous network (having identical processors and identical links). Using this closed-form solution, the ultimate limits of performance are explored through an asymptotic analysis with respect to the number of installments and number of processors in the network. Trade-off relationships between the number of installments and the number of processors in the network are also presented. These results are then extended to the case when the processors are not equipped with front-ends. Finally, the efficiency of this new strategy of load distribution is demonstrated by comparing it with the existing single-installment strategy in the literature. The multi-installment strategy explained above is then applied to linear net-As. Here, .the processing load is assumed to originate at one extreme end of the network, First the case when all the processors are equipped with front-ends is considered. Recursive equations for a heterogeneous network are obtained and these are solved for the special case of a homogeneous network. Using this closed form solution, an asymptotic analysis is performed with respect to the number of installments. However, the asymptotic results with respect to the number of processors was obtained computationally since analytical results could not be obtained. It is found that for a given network, once the number of installments is fixed, there is an optimum number of processors to be used in the network, beyond which the time performance degrades. Trade-off relationships between the number of installments and the number of processors is obtained. These results are then extended to the case when the processors are not equipped with front-ends. Comparisions with the existing single-installment strategy is also done. The single-installment strategy discussed in the literature has the disadvantage that the front-ends of the processors are not utilized efficiently in a linear network. This is due to the fact that a processor starts computing its own load fraction only after the entire load to be communicated through its front-end has been received. In this thesis, a new strategy is proposed in which a processor starts computing as soon as it receives its load fraction, simultaneously allowing its front-end to receive and transmit load to its successors. Recursive equations are developed and solved for the special case of a heterogeneous network in which the processors and links are arranged in the decreasing order of speeds. Further, it is shown that in this strategy, if the processing load originates in the interior of the network, the sequence of load distribution should- be such that the load should be first distributed to the side with a lesser number of processors. An expression for the optimal load origination point in the network is derived. A comparative study of this strategy with an earlier strategy is also presented. Finally, it is shown that even though the analysis is carried out for a special case of a heterogeneous network, this load distribution strategy can also be applied to a linear network in which the processors and links are arbitrarily arranged and still obtain a significant improvement in the time performance.

Load distribution problems in distributed computing networks have attracted much attention in the literature. A major objective in these studies is to distribute the processing load so as to minimize the time of processing of the entire load. In general, the processing load can be indivisible or divisible. An indivisible load has to be processed in its entirety on a single processor. On the other hand, a divisible load can be partitioned and processed on more than one processor. Divisible loads are either modularly divisible or arbitrarily divisible. Modularly divisible loads can be divided into pre-defined modules and cannot be further sub-divided. Further, precedence relations between modules may exist. Arbitrarily divisible loads can be divided into several fractions of arbitrary lengths which usually do not have any precedence relations. Such type of loads are characterized by their large volume and the property that each data element requires an identical and independent processing. One of the important problems here is to obtain an optimal load distribution, which minimizes the processing time when the distribution is subject to communication delays in the interconnecting links. A specific application in which such loads are encountered is in edge-detection of images. Here the given image frame can be arbitrarily divided into many sub-frames and each of these can be independently processed. Other applications include processing of massive experimental data. The problems associated with the distribution of such arbitrarily divisible loads are usually analysed in the framework of what is known as divisible job theory. The research work reported in this thesis is a contribution in the area of distributing arbitrarily divisible loads in distributed computing systems subject to communication delays. The main objective in this work is to design and analyseload distribution strategies to minimize the processing time of the entire load in a given network. Two types of networks are considered, namely (i) single-level tree (or star) network and (ii) linear network. In both the networks we assume that there is a non-zero delay associated with load transfer. Further, the processors in the network may or may not be equipped with front-ends (Le., communication co-processors). The main contributions in this thesis are summarized below. First, a mathematical formulation of the load distribution problem in single-level tree and linear networks is presented. In both the networks, it is assumed that there are (m +1) processors and m communication links. In the case of single-level tree networks, the load to be processed is assumed to originate at the root processor, which divides the load into (m +1) fractions, keeps its own share of the load for processing, and distributes the rest to the child processors one at a time and in a fixed sequence. In all the earlier studies in the literature, it had been assumed that for a load distribution to be optimal, it should be such that all the processors must stop computing at the same time. In this thesis, it is shown that this assumption is in general not true, and holds only for a restricted class of single-level tree networks which satisfy a certain condition. The concept of an equivalent network is introduced to obtain a precise formulation of this condition in terms of the processor and link speed parameters. It is shown that this condition can be used to identify processor-link pairs which can be eliminated from a given network (i.e., these processors need not be given any computational load) without degrading its time performance. It is proved that the resultant reduced network (a network from which these inefficient processor-link pairs have been removed) gives the optimal time performance if and only if the load distribution is such that all the processors stop computing at the same time instant. These results are first proved for the case when the root processor is equipped with a front-end and then extended to the case when it is not. In the latter case, an additional condition, between the speed of the root processor and the speed of each of the links, to be satisfied by the network is specified. An optimal sequence for applying these conditions is also obtained. In the case of linear networks the processing load is assumed to originate at the processor situated at one end of the network. Each processor in the network keeps its own load fraction for computing and transmits the rest to its successor. Here too, in all the earlier studies in the literature, it has been assumed that for the processing time to be a minimum, the load distribution must be such that all the processors must stop computing at the same instant in time. Though this condition has been proved by others to be both necessary and sufficient, a different and more rigorous proof, similar to the case of single-level tree network, is presented here. Finally, the effect of inaccurate modelling on the processing time and on the above conditions are discussed through an illustrative example and it is shown that the model adopted in this thesis gives reasonably accurate results. In the case of single-level tree networks, so far it has been assumed that the root processor distributes the processing load in a fixed sequence. However, since there are m child processors, a total of m! different sequences of load distribution are possible. Using the closed-form derived for the processing time, it is proved here that the optimal sequence of load distribution follows the decreasing order of link speeds. Further, if physical rearrangement of processors and links is allowed, then it is shown that the optimal arrangement follows a decreasing order of link and processor speeds with the fastest processor at the root. The entire analysis is first done for the case when the root processor is equipped with a front-end, and then extended to the case when it is not. In the without front-end case, it is shown that the same optimal sequencing result holds. However, in an optimal arrangement, the root processor need not be the fastest. In this case an algorithm has been proposed for obtaining optimal arrangement. Illustrative examples are given for all the cases considered. Next, a new strategy of load distribution is proposed by which the processing time obtained in earlier studies can be further minimized. Here the load is distributed by the root processor to a child processor in more than one installment (instead of in a single installment) such that the processing time is further minimized. First; the case in which all the processors are equipped :tn front-ends is considered. Recursive equations are obtained for a heterogeneous network and these are solved for the special case of a homogeneous network (having identical processors and identical links). Using this closed-form solution, the ultimate limits of performance are explored through an asymptotic analysis with respect to the number of installments and number of processors in the network. Trade-off relationships between the number of installments and the number of processors in the network are also presented. These results are then extended to the case when the processors are not equipped with front-ends. Finally, the efficiency of this new strategy of load distribution is demonstrated by comparing it with the existing single-installment strategy in the literature. The multi-installment strategy explained above is then applied to linear net-As. Here, .the processing load is assumed to originate at one extreme end of the network, First the case when all the processors are equipped with front-ends is considered. Recursive equations for a heterogeneous network are obtained and these are solved for the special case of a homogeneous network. Using this closed form solution, an asymptotic analysis is performed with respect to the number of installments. However, the asymptotic results with respect to the number of processors was obtained computationally since analytical results could not be obtained. It is found that for a given network, once the number of installments is fixed, there is an optimum number of processors to be used in the network, beyond which the time performance degrades. Trade-off relationships between the number of installments and the number of processors is obtained. These results are then extended to the case when the processors are not equipped with front-ends. Comparisions with the existing single-installment strategy is also done. The single-installment strategy discussed in the literature has the disadvantage that the front-ends of the processors are not utilized efficiently in a linear network. This is due to the fact that a processor starts computing its own load fraction only after the entire load to be communicated through its front-end has been received. In this thesis, a new strategy is proposed in which a processor starts computing as soon as it receives its load fraction, simultaneously allowing its front-end to receive and transmit load to its successors. Recursive equations are developed and solved for the special case of a heterogeneous network in which the processors and links are arranged in the decreasing order of speeds. Further, it is shown that in this strategy, if the processing load originates in the interior of the network, the sequence of load distribution should- be such that the load should be first distributed to the side with a lesser number of processors. An expression for the optimal load origination point in the network is derived. A comparative study of this strategy with an earlier strategy is also presented. Finally, it is shown that even though the analysis is carried out for a special case of a heterogeneous network, this load distribution strategy can also be applied to a linear network in which the processors and links are arbitrarily arranged and still obtain a significant improvement in the time performance.

A Quadrotor (QR) is a type of unmanned aerial vehicles which has been absorbed lots of attention recently with many institutes have investigated on many application with this tools include search and rescue, surveillance, supply of food and medicine in emergency sub-problem of load transportation by the control of the cable suspended load or directly control of the QR robustly. The goal of this thesis is to present a nonlinear control approach and investigate on novel approach. The focus is lies on the quadrotor-load subsystem where the cable tension is not zero, which analogous to modeling a rigid link between the quadrotor and load. After introducing the basic concept, an introduction is given on geometric mechanics. This differential geometric based approach is used to model and control the system, based on the geometric properties of the system dynamics. It is shown how the configuration spaces and analyzed with the principles of differential geometry. Also the common approach for second approach will be hired for illustrate the configuration of the Quadrotor-load, while both approach avoiding the problem of singularities would occur on local charts. Next, the geometric properties are utilized to define tracking error functions on these same space. A back-stepping approach is applied to generate a cascade structure with multiple nonlinear geometric controllers, allowing control of several flight modes that are responsible for the control of a) quadrotor attitude b) load attitude c) load position. Finally, simulation illustrate the stability and ability of the geometric controller. Also Zero-dynamics is derived to compare both performances. The tracking performances of both controllers are discussed for many different experiences.

The load forecasting has become an important role in the operation of power system, and several models by using different techniques have been applied to solve these problems. In the literature, the linear regression models are considered as a traditional approach to predict power consumption, and more recently, the artificial neural network (ANN) models have received more attention for a great number of successful and practical applications. This report introduces both linear regression and ANN models to predict the power consumption for Fortum in Ekerö. The characteristics of power consumption of different kinds of consumers are analyzed, together with the effects of weather parameters to power consumption. Further, based on the gained information, the numerical models of load forecasting are built and tested by the historical data. The predictions of power consumption are focus on three cases separately: total power consumption in one year, daily peak power consumption during winter and hourly power consumption. The processes of development of the models will be described, such as the choice of the variables, the transformations of the variables, the structure of the models and the training cases of ANN model. In addition, two linear regression models will be built according to the number of input variables. They are simple linear regression with one input variable and multiple linear regression with several input variables. Comparison between the linear regression and ANN models will be carried out. In the end, it finds out that the linear regression obtains better results for all the cases in Ekerö. Especially, the simple linear regression outperforms in prediction of total power consumption in one year, and the multiple linear regression is better in prediction of daily peak load during the winter.

In recent decades there has been a rapidly growing demand for high quality, uninterrupted power. In light of this fact, this study has addressed some of the causes of poor power quality and control strategies to ensure a high performance level in inverter-fed power systems. In particular, specific loading conditions present interesting challenges to inverter-fed, high power systems. No-load, unbalanced loading, and non-linear loading each have unique characteristics that negatively influence the performance of the Voltage Source Inverter (VSI). Ideal, infinitely stiff power systems are uninfluenced by loading conditions; however, realistic systems, with finite output impedances, encounter stability issues, unbalanced phase voltage, and harmonic distortion. Each of the loading conditions is presented in detail with a proposed control strategy in order to ensure superior inverter performance. Simulation results are presented for a 90 kVA, 400 Hz VSI under challenging loading conditions to demonstrate the merits of the proposed control strategies. Unloaded or lightly loaded conditions can cause instabilities in inverter-fed power systems, because of the lightly damped characteristic of the output filter. An inner current loop is demonstrated to damp the filter poles at light load and therefore enable an increase in the control bandwidth by an order of magnitude. Unbalanced loading causes unequal phase currents, and consequently negative sequence and zero sequence (in four-wire systems) distortion. A proposed control strategy based on synchronous and stationary frame controllers is shown to reduce the phase voltage unbalance from 4.2% to 0.23% for a 100%-100%-85% load imbalance over fundamental positive sequence control alone. Non-linear loads draw harmonic currents, and likewise cause harmonic distortion in power systems. A proposed harmonic control scheme is demonstrated to achieve near steady state errors for the low order harmonics due to non-linear loads. In particular, the THD is reduced from 22.3% to 5.2% for full three-phase diode rectifier loading, and from 11.3% to 1.5% for full balanced single-phase diode rectifier loading, over fundamental control alone.<br>Master of Science

The present research develops a numerical fluid-structure interaction (FSI) code based on CFDShip-Iowa version 4, a general-purpose URANS/DES overset fluid solver. Linear and nonlinear FSI methods are developed to compute structural responses on surface ships or marine structures. The modal superposition transient analysis and the nonlinear FEM structure solver are used for small and large deformation FSI problems, respectively. The gluing method is applied to transfer the forces and displacements on non-matching grids for fluid and structure domains. The linear FEM solver is applied to deform the boundary layer grid with large deformation in the fluid domain, while the deformation is ignored in small deformation problems. Deformation of an interior point in the boundary layer grid is obtained using linear interpolation in both linear and nonlinear deformation problems. The S175 containership is studied in regular waves as an application example for the linear problem. Heave and pitch responses are compared with the experiments, showing good agreement. Time histories of vertical bending moment (VBM) are calculated using rigid model, one-way coupling, and two-way coupling approaches. The elastic models are able to capture the ringing of the VBM induced by slamming, while the rigid model shows a peak at the moment of slamming without further fluctuations. The two-way coupling method shows the effects of hull deformation on the amplitude and phase of VBM as well as the accelerations of heave and pitch. For the nonlinear deformation problem three sloshing tanks with an elastic bar clamped to its bottom or top are simulated and compared with the experiments and other numerical simulation results. The present simulation results show reasonable agreement with the experiments for bar deformation and free surface elevation. A secondary wave on the free surface is creadted by the vorticity generated from the free surface. The effect of the bar on the sloshing impact is studied comparing dynamic pressure acting on the tank wall without bar, with an elatic bar, and with a rigid bar.

A avaliação numérica das cargas limites (de colapso) de estruturas é obtida geralmente ou pela aplicação direta dos teoremas de análise limite junto com processos de otimização ou mediante análises incrementais, que levam em consideração o comportamento elasto-plástico do material. Entretanto, ambas as estratégias conduzem eventualmente a dificuldades numéricas, particularmente para cargas próximas à de colapso. Neste trabalho, emprega-se uma alternativa que consiste em simular assintoticamente o comportamento elasto-plástico mediante uma relação elástica não-linear. As vantagens deste tipo de formulação são a possibilidade de se lidar com leis de fluxo não-associadas e um custo computacional reduzido. A relação elástica não-linear é implementada no programa comercial de elementos finitos ABAQUS, através de uma sub-rotina externa ao programa escrita em linguagem FORTRAN. Diversos exemplos de estruturas cujos materiais são regidos pelos critérios de resistência de von Mises e Drucker-Prager são modelados, verificando-se que os resultados das cargas limites obtidas com essa formulação são muito próximos daqueles encontrados na literatura. Por fim, a relação elástica não-linear é empregada para a determinação do domínio de resistência de meios porosos, com diferentes níveis de porosidade.<br>The numerical assessment of limit loads of structures is generally achieved through the direct implementation of limit analysis theorems together with optimization processes, or through incremental analyses, which account for the elastic-plastic behavior of the material. However, both the strategies may lead to numerical difficulties, particularly when the load is close to its limit value. In this context, the alternative approach presented in this work consists in simulating asymptotically the regime of free plastic flow by means of a fictitious non-linear elastic material. One of the main advantages of this kind of formulation lies in its ability to deal with non-associated flow rules and a reduced computational cost. The non-linear elastic behavior is implemented into the finite element computational software ABAQUS, making use of an external subroutine written in FORTRAN language. Several examples of geotechnical and structural problems with materials ruled by von Mises and Drucker-Prager failure criteria are analyzed. The results obtained with this formulation prove to be very close to those obtained through analytical solutions. At last, the non-linear elastic relation is used in the determination of the resistance domain of porous media with different levels of porosity.

Load frequency control (LFC) in interconnected multiarea power systems has become increasingly challenging due to the integration of renewable energy sources, random load variations, and system uncertainties. These factors contribute to frequency deviations, reduced system inertia, and compromised stability, necessitating robust control mechanisms. This research proposes an advanced sliding mode control (SMC)-based LFC framework, incorporating disturbance observer-based SMC, memory-based adaptive SMC, and event-triggered SMC to enhance system resilience, transient performance, and computational efficiency. A disturbance observer estimates lumped disturbances from tie-line power deviations, load variations, and renewable fluctuations, while a memory-based sliding mode strategy improves frequency stability by leveraging past system states. Additionally, an event-triggered SMC approach with output feedback reduces computational overhead while ensuring robust performance. The proposed framework guarantees globally stable and adaptive frequency regulation through linear matrix inequalities (LMIs) and H∞ robust performance criteria. Integrating an energy storage system (ESS) further enhances disturbance rejection and frequency response. Compared to conventional robust SMC-based LFC methods, the proposed strategy achieves superior disturbance rejection, reducing frequency overshoot, control effort, and response time. Numerical simulations and comparative studies validate the effectiveness of the framework in improving transient stability and decentralized scalability, making it a viable solution for real-world power systems. This research contributes to advancing resilient LFC strategies in renewable-integrated grids, paving the way for more adaptive and efficient grid management approaches.

Orientador: Renato Sussumu Nishioka<br>Banca: Renato Sussumu Nishioka<br>Banca: José Claudio Martins Segalla<br>Banca: Eduardo Shigueyuki Uemura<br>Resumo: O objetivo desse estudo foi avaliar a aplicação de carga e distribuição das microdeformações ao redor de implantes com conexão protética cone morse. Três implantes foram inseridos num bloco de poliuretano e pilares microunit foram instalados nos implantes com torque de 20 Ncm. Três coifas usinadas foram adaptadas nos pilares para configurar a supraestrutura protética (n=5) e comparar com as supra-estruturas obtidas com coifas plásticas. Quatro extensômetros foram colados na superfície superior do bloco. Uma carga vertical estática de 30 Kg foi aplicada em cinco pontos das supra-estruturas. Os registros obtidos dos extensômetros foram submetidos ao teste estatístico ANOVA e Tukey (α=5%). As medidas derivadas dessa simulação revelaram que durante a aplicação de carga: (1) existiu uma relação direta do local de aplicação e na distribuição da microdeformação ao redor dos implantes; (2) não existiu diferença na microdeformação entre coifas plásticas e usinadas.<br>Abstract: The aim of this study was to evaluate the load transfer and strain distribution by an implant-supported fixed partial prosthesis. Three implants Morse Taper were inserted in a polyurethane block and abutments microunit were installed on the implants with a torque of 20 Ncm. Plastic cylinders and prefabricated cylinders were adapted on abutments to fabricate the framework (n=5). Four strain gauges were attached on the superior surface of the block and then each framework was tight on the abutments with a torque of 10 Ncm and vertical load of 30Kg was applied to five points on the framework. The data obtained in the strain gauge analysis were submitted to the statistical tests ANOVA and Tukey (α=5%). The measurements derived from this simulation revealed that: (1) there was a direct proportion between the strain distribution in the metal framework and stresses created in the supporting structure around the implants; (2) there was not a strain difference between plastic and prefabricated cylinders during the load transfer<br>Mestre

Well-designed demand response is expected to play a vital role in operatingpower systems by reducing economic and environmental costs. However,the current system is operated without much information on the benefits ofend-users, especially the small ones, who use electricity. This thesis proposes aframework of operating power systems with demand models including the diversityof end-users’ benefits, namely adaptive load management (ALM). Sincethere are a large number of end-users having different preferences and conditionsin energy consumption, the information on the end-users’ benefits needsto be aggregated at the system level. This leads us to model the system ina multi-layered way, including end-users, load serving entities, and a systemoperator. On the other hand, the information of the end-users’ benefits can beuncertain even to the end-users themselves ahead of time. This information isdiscovered incrementally as the actual consumption approaches and occurs. Forthis reason ALM requires a multi-temporal model of a system operation andend-users’ benefits within. Due to the different levels of uncertainty along thedecision-making time horizons, the risks from the uncertainty of informationon both the system and the end-users need to be managed. The methodologyof ALM is based on Lagrange dual decomposition that utilizes interactive communicationbetween the system, load serving entities, and end-users. We showthat under certain conditions, a power system with a large number of end-userscan balance at its optimum efficiently over the horizon of a day ahead of operationto near real time. Numerical examples include designing ALM for theright types of loads over different time horizons, and balancing a system with a large number of different loads on a congested network. We conclude thatwith the right information exchange by each entity in the system over differenttime horizons, a power system can reach its optimum including a variety ofend-users’ preferences and their values of consuming electricity.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2017-10-11T18:37:37Z No. of bitstreams: 2 Dissertação - Danielly Luz Araújo de Morais - 2017.pdf: 12095443 bytes, checksum: a4733104fefc2df73c05b1bbb83c7895 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Approved for entry into archive by Erika Demachki (erikademachki@gmail.com) on 2017-10-11T21:27:00Z (GMT) No. of bitstreams: 2 Dissertação - Danielly Luz Araújo de Morais - 2017.pdf: 12095443 bytes, checksum: a4733104fefc2df73c05b1bbb83c7895 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Made available in DSpace on 2017-10-11T21:27:00Z (GMT). No. of bitstreams: 2 Dissertação - Danielly Luz Araújo de Morais - 2017.pdf: 12095443 bytes, checksum: a4733104fefc2df73c05b1bbb83c7895 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-06-27<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES<br>In the analytical study of conoidal shallow shells, one has the difficulty in analytically representing their displacement fields. In this way a numerical analysis, such as the Finite Element Method (MEF), has been used in the study of this type of structure. In this work, a static analysis of conoidal shallow shells from curved parabolic or cylindrical edges of linear, homogeneous and isotropic elastic material is performed, subjected to a transversal uniformly load distributed along the surface. With the thin-plate formulation derived from Kirchhoff's hypotheses and the theory developed by Marguerre for thin shells, the non-linear equilibrium equations that govern the behavior of the conoidal shell were determined, considering that this is a plate with an initial displacement. A linear parametric analysis of the critical loads and of buckling modes through the MEF is performed using ABAQUS 6.11® program, varying the contour and height conditions of the curved edges. Analytically, a complexity of the components of the buckling mode displacement fields of a given geometry is evaluated by its decomposition into double Fourier series. With the non-linear analysis via MEF, the non-linear equilibrium trajectories of the displacements are obtained and the first non-linear loading limit points are obtained. Nonlinear parabolic or cylindrical geometric parabolic geometry trajectories with describable supports at their four edges are also compared, evaluating how the geometric non-linearities influence the modes of the displacement fields during loading. Finally, a non-linear parametric analysis of the influence of the variation of the curved edge heights on the equilibrium trajectories of the membrane stresses and resulting from internal moments of the conoidal shell is carried out. It is verified, with this work, that linear analyzes can underestimate, or overestimate, the nonlinear behavior of the conoid. As the parametric analysis influences the behavior of the conoid in front of the load, either in the linear analysis, resulting in different critical loads and modes of buckling, or in the nonlinear analysis, resulting in differentiated limits loads and nonlinear equilibrium trajectories of the displacements and membrane stresses and moments.<br>No estudo analítico de cascas conoidais abatidas, tem-se a dificuldade de representar analiticamente os seus campos de deslocamentos. Dessa forma a análise numérica, como por exemplo, via Método dos Elementos Finitos (MEF), vem sendo utilizada no estudo desse tipo de estrutura. Neste trabalho, elabora-se uma análise estática de cascas conoidais abatidas de bordas curvas parabólicas, ou cilíndricas, de material elástico linear, homogêneo e isotrópico, submetidas a um carregamento transversal uniformemente distribuído ao longo da superfície. Com a formulação para placas finas derivada das hipóteses de Kirchhoff e a teoria desenvolvida por Marguerre para cascas finas, determinam-se as equações não-lineares de equilíbrio que regem o comportamento da casca conoidal, considerando que esta seja uma placa com um deslocamento inicial. Faz-se uma análise paramétrica linear das cargas críticas e modos de flambagem através do MEF utilizando o programa ABAQUS 6.11®, variando-se as condições de contorno e altura das bordas curvas. Avalia-se, analiticamente, a complexidade das componentes dos campos de deslocamentos do modo de flambagem de uma dada geometria através de sua decomposição em séries duplas de Fourier. Com a análise não-linear via MEF, obtêm-se as trajetórias não-lineares de equilíbrio dos deslocamentos da casca e obtêm-se os primeiros pontos limites de carregamento não-lineares. Comparam-se também as trajetórias não-lineares de equilíbrio de conóides de geometrias parabólicas, ou cilíndricas, com apoios indeslocáveis em suas quatro bordas, avaliando como as não-linearidades geométricas influenciam nos modos dos campos de deslocamentos durante o carregamento. Por fim, efetua-se uma análise paramétrica não-linear da influência da variação das alturas das bordas curvas nas trajetórias de equilíbrio dos esforços de membrana e resultantes de momentos internos dos conóides. Verifica-se, com este trabalho, que análises lineares podem subestimar, ou superestimar, o comportamento não-linear do conóide. Sendo que a análise paramétrica influencia o comportamento do conóide frente ao carregamento, seja no âmbito da análise linear, resultando em diferentes cargas críticas e modos de flambagem, seja na análise não-linear, resultando em cargas limites e trajetórias não-lineares de equilíbrio dos deslocamentos e dos esforços de membrana e momentos, diferenciados.

O tema está relacionado com o constante crescimento da necessidade em implantarnovas torres de telecomunicações devido ao crescimento acelerado da infraestrutura de telecomunicações no Brasil. Todos os dias, novos sistemas de transmissão e recepção de ondas eletromagnéticas estão sendo implantados no território brasileiro. O objetivo deste trabalho é propor um procedimento seguro e eficaz para a análise estrutural de torres de telecomunicações em concreto armado de grande esbeltez, com base em um modelo dinâmico não linear, submetendo à carga de vento. Estas cargas são simuladas pelo método do vento sintético proposto por Franco (1993). A análise do concreto armado será realizada de acordo com a NBR-6118 (ABNT, 2007). A fim de determinar com precisão os deslocamentos da estrutura submetida ao carregamento de vento, um método iterativo computacional será utilizado obter as respostas não lineares. Realiza-se uma análise linear e, a partir dos resultados de esforços solicitantes, as tensões e a porção fissurada de cada seção transversal é obtida e parte-se para a determinação dos deslocamentos de 2ª ordem da torre. Em cada iteração, um procedimento do tipo P-Delta será utilizado para levar em conta a não linearidade geométrica da estrutura. As condições de contorno do problema estão relacionadas com a restrição do nível de tensões, deslocamentos e frequências de vibração da estrutura. Ao fim, uma análise dinâmica em torno da configuração não linear será realizada, e o deslocamento total da torre será dado pela somatória da componente estática com a componente flutuante do vento.<br>The theme is related to the constant growth in the need to deploy new telecommunications towers due to the accelerated growth of telecommunications infrastructure in Brazil. Every day, new systems of transmission and reception of electromagnetic waves are being implanted in the Brazilian territory. The objective of this work is to propose a safe and efficient procedure for the structural analysis of telecommunication towers with high slenderness constructed in reinforced concrete, based on a dynamic nonlinear model, submitting it to the wind load. These loads are simulated by the synthetic wind method proposed by Franco (1993). The analysis of the reinforced concrete will be held according to NBR-6118 (ABNT, 2007). In order to determine accurately the displacements of the structure subjected to wind loading, an iterative computational method will be held to obtain non-linear responses. A linear analysis is carried out and, with the results of the forces, the tensions and the fissured portion of each cross section are obtained and then 2nd order displacements of the tower. In each iteration, a P-Delta type procedure will be held to take into account the geometric non-linearity of the structure. The boundary conditions of the problem are related to the restriction of the stress level, displacements and vibration frequencies of the structure. At the end, a dynamic analysis around the nonlinear configuration will be performed, and the total displacement of the tower will be given by the sum of the static component with the floating component of the wind.

This study presented a substructure based parallel linear solution framework for the static analysis of linear structural engineering problems having multiple loading conditions. The framework was composed of two separate programs designed to work on PC Clusters having the Windows operating system. The first program was responsible for creating the optimum substructures for the parallel solution and first partitioned the structure in such a way that the number of substructures was equal to the number of processors. Then, the estimated condensation time imbalance of the initial substructures was adjusted by iteratively transferring nodes from the substructures with slower estimated condensation times to the substructures with faster estimated condensation times. Once the final substructures were created, the second program started the solution. Each processor assembled its substructures stiffness matrix and condensed it to the interface with other substructures. The interface problem was solved by a parallel variable band solver. After computing the interface unknowns, each processor calculated the internal displacements and element stresses or forces. Examples which illustrate the applicability and efficiency of this approach were also presented. In these examples, the number of processors was varied from one to twelve to demonstrate the performance of the overall solution framework.

Made available in DSpace on 2014-06-11T19:28:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-03Bitstream added on 2014-06-13T18:58:12Z : No. of bitstreams: 1 abreu_cw_me_sjc.pdf: 508442 bytes, checksum: 720d525ea366cc2fd0575e67a37ba04e (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)<br>O objetivo desse estudo foi avaliar a aplicação de carga e distribuição das microdeformações ao redor de implantes com conexão protética cone morse. Três implantes foram inseridos num bloco de poliuretano e pilares microunit foram instalados nos implantes com torque de 20 Ncm. Três coifas usinadas foram adaptadas nos pilares para configurar a supraestrutura protética (n=5) e comparar com as supra-estruturas obtidas com coifas plásticas. Quatro extensômetros foram colados na superfície superior do bloco. Uma carga vertical estática de 30 Kg foi aplicada em cinco pontos das supra-estruturas. Os registros obtidos dos extensômetros foram submetidos ao teste estatístico ANOVA e Tukey (α=5%). As medidas derivadas dessa simulação revelaram que durante a aplicação de carga: (1) existiu uma relação direta do local de aplicação e na distribuição da microdeformação ao redor dos implantes; (2) não existiu diferença na microdeformação entre coifas plásticas e usinadas.<br>The aim of this study was to evaluate the load transfer and strain distribution by an implant-supported fixed partial prosthesis. Three implants Morse Taper were inserted in a polyurethane block and abutments microunit were installed on the implants with a torque of 20 Ncm. Plastic cylinders and prefabricated cylinders were adapted on abutments to fabricate the framework (n=5). Four strain gauges were attached on the superior surface of the block and then each framework was tight on the abutments with a torque of 10 Ncm and vertical load of 30Kg was applied to five points on the framework. The data obtained in the strain gauge analysis were submitted to the statistical tests ANOVA and Tukey (α=5%). The measurements derived from this simulation revealed that: (1) there was a direct proportion between the strain distribution in the metal framework and stresses created in the supporting structure around the implants; (2) there was not a strain difference between plastic and prefabricated cylinders during the load transfer

Conventional methods used in the structural analysis are usually insufficient for the analysis of historical structures because of the complex geometry and heterogeneous material properties of the structure. Today&rsquo<br>s computing facilities and methods make FEM the most suitable analysis method for complex structural geometry and heterogeneous material properties. Even the shrinkage, creep of the material can be considered in the analysis. Because of this reason Finite Element Method (FEM) is used to analyze such structures. FEM converts the structure into finite number of elements with specific degree of freedoms and analyses the structure by using matrix algebra. However, advanced FEM methods considering the inelastic and time dependent behavior of material is a very complex and difficult task and consumes considerable time. Because of this reason, to analyze every historical structure is not feasible by applying advanced inelastic FEM, whereas elastic FEM analysis at low load levels is very helpful in understanding the behavior of the structure.The analysis of a masonry gate in the historical city, Hasankeyf is the case study of this thesis. Different common software are used in FEM to compare the stresses, deformations, modal shapes etc. of the same structure. Besides the inelastic behavior of the structure is investigated and compared with the elastic behavior of the structure. The study is intended to show that at the low load levels elastic FEM analysis is sufficient to understand the response of the structure and is preferable to the inelastic FEM analysis unless a very complex analysis is required

This paper investigates correlation between energy consumption 24 hours ahead and features used for predicting energy consumption. The features originate from three categories: weather, time and previous energy. The correlations are calculated using Pearson correlation and mutual information. This resulted in the highest correlated features being those representing previous energy consumption, followed by temperature and month. Two identical feature sets containing all attributes1 were obtained by ranking the features according to correlation. Three feature sets were created manually. The first set contained seven attributes representing previous energy consumption over the course of seven days prior to the day of prediction. The second set consisted of weather and time attributes. The third set consisted of all attributes from the first and second set. These sets were then compared on different machine learning models. It was found the set containing all attributes and the set containing previous energy attributes yielded the best performance for each machine learning model. 1In this report, the words ”attribute” and ”feature” are used interchangeably.<br>I denna rapport undersöks korrelation och betydelsen av olika attribut för att förutspå energiförbrukning 24 timmar framåt. Attributen härstammar från tre kategorier: väder, tid och tidigare energiförbrukning. Korrelationerna tas fram genom att utföra Pearson Correlation och Mutual Information. Detta resulterade i att de högst korrelerade attributen var de som representerar tidigare energiförbrukning, följt av temperatur och månad. Två identiska attributmängder erhölls genom att ranka attributen över korrelation. Tre attributmängder skapades manuellt. Den första mängden innehåll sju attribut som representerade tidigare energiförbrukning, en för varje dag, sju dagar innan datumet för prognosen av energiförbrukning. Den andra mängden bestod av väderoch tidsattribut. Den tredje mängden bestod av alla attribut från den första och andra mängden. Dessa mängder jämfördes sedan med hjälp av olika maskininlärningsmodeller. Resultaten visade att mängden med alla attribut och den med tidigare energiförbrukning gav bäst resultat för samtliga modeller.

The aim of this thesis was to study the load bearing capacity of anchor plates, used for anchorage to concrete located at nuclear facilities. Two different type of anchor plates were examined, which together constitute the majority of the anchor plates used at Forsmark nuclear facility in Sweden. The first is a cast-in-place anchor plate with headed studs and the second is a post-installed anchor plate which uses sleevetype expansion anchors. Hence, anchors with both a mechanical or a frictional interlock to the concrete were examined. The main analysis tool was the finite element method, through the use of the two commercially available software packages ABAQUS and ADINA and their non-linear material models for concrete and steel. As a first step, the numerical methods were verified against experimental results from the literature. However, these only concern single anchors. The results from the verifications were then used to build the finite element models of the anchor plates. These were then subjected to different load combinations with the purpose to find the ultimate load capacity. Failure loads from the finite element analyses were then compared to the corresponding loads calculated according to the new European technical specification SIS-CEN/TS 1992-4 (2009). Most of the failure loads from the numerical analyses were higher than the loads obtained from the technical specification, although in some cases the numerical results were lower than the technical specification value. However, many conservative assumptions regarding the finite element models were made, hence there might still be an overcapacity present. All analyses that underestimate the failure load were limited to large and slender anchor plates, which exhibit an extensive bending of the steel plate. The bending of the steel plate induce shear forces on the anchors, which leads to a lower tensile capacity. In design codes, which assume rigid steel plates, this phenomenon is neglected. The failure loads from all different load combinations analysed were then used to develop failure envelopes as a demonstration of a useful technique, which can be utilised in the design process of complex load cases.

The experimental studies performed on the behaviour of very thick concrete beams subjected to static loads have revealed that the shear mechanisms play an important role in the overall response and failure behaviour. The aim of this thesis is to recommend suitable design methods for thick concrete beams subjected to off-centre static concentrated load according Eurocode 2 by using non-linear finite element analysis (NLFEA). To achieve this task, Abaqus/Explicit has been used by employing constitutive material models to capture the material non-linearity and stiffness degradation of concrete. Concrete damaged plasticity model and perfect plasticity model has been used for concrete and steel respectively. Three dilation angles (30º, 38º and 45º) and fracture energy from FIB 1990 (76 N/m) and FIB 2010 (142 N/m) has been used to investigate their influence on the finite element model. The dilation angle of 38º and FIB 2010 fracture energy was adopted as the suitable choice that reasonably matched with the experimental results. In verifying and calibrating the finite element model, the experimental results of the thick reinforced concrete beam conducted by the American Concrete Institute have been used. Three design approaches in the ultimate and serviceability limit state according to Eurocode 2 recommendations have been used namely; the beam method, strut and tie method and shell element method. Using the reinforcement detailing of the hand calculations of beam method and strut and tie method and linear finite element analysis of shell element method, non-linear finite element models have been pre-processed and analysed in Abaqus/Explicit. During the post-processing, the results have been interpreted and compared between the three design methods. The results under consideration are hand-calculated load at 0.3 mm crack width, FE-load at 0.3 mm crack width, amount of reinforcement and FE-failure load. The comparison of the results between the three design approaches (beam method, strut and tie method and shell element method) indicates that strut and tie method is better design approach, because it is relatively economic with regards to the quantity of reinforcement bars, has the higher load capacity and has a higher load at crack width of 0.3 mm crack width.<br>De experimentella studier som utförts på tjocka betongbalkar som utsätts för statisk last har visat att skjuvning spelar en viktig roll i brottmekanismen. Syftet med detta examensarbete är att rekommendera lämpliga dimensioneringsmetoder för tjock betongbalkar utsatt for statisk koncentrerad last enligt Eurokod 2 med hjälp av ickelinjära finita element metod. Abaqus/Explicit användes genom att utnyttja konstitutiva materialmodeller för att fånga materialens icke-linjäritet och minskad styvhet. Tre dilatationsvinklar (30°, 38° och 45°) och två brottenergi från FIB 1990 (76 N/m) och FIB 2010 (142 N/m) tillämpas för att kontrollera deras inverkan på FE-modellerna. Dilatationsvinkel med 38° och FIB 2010 med högre brottenergi valdes i de icke-linjära finita elementanalyserna. Kontroll av FE-modellerna är baserad på ”American Concret Institutes” experimentella resultat på de tjocka betongbalkarna. Handberäkningar av tjocka betongbalkar har utförts i brott- och bruksgränstillstånd med tre dimensioneringsmetoder i Eurokod 2 nämligen balk metoden, fackverksmetoden och linjära-FE skalelementmetoden. Jämförelse har gjorts för de olika dimensioneringsmetoderna, genom att använda de armeringsdetaljer av handberäkningar i de verifierade och kalibrerade icke linjära FE-modellerna i Abaqus/Explicit. Resultaten i fråga är last för 0.3 mm handberäknad sprikvidd, FE-last för 0.3 mm sprikvidd, armeringsmängd och FE-brottlast. Jämförelse av resultaten mellan de tre dimensioneringsmetoder (balkmetod, fackverksmetod och skalelementmetod) visar att fackverksmetod är bättre design metod, eftersom det är relativt ekonomiskt med avseende på armeringsmängd, har högre lastkapacitet och last på 0.3 mm sprickvidd.

The rapidly expanding wireless market requires low cost, high integration and high performance of wireless communication systems. CMOS technology provides benefits of cost effectiveness and higher levels of integration. However, the design of highly efficient linear CMOS power amplifier that meets the requirement of advanced communication standards is a challenging task because of the inherent difficulties in CMOS technology. The objective of this research is to realize PAs for wireless communication systems that overcoming the drawbacks of CMOS process, and to develop design approaches that satisfying the demands of the industry. In this dissertation, a cascode bias technique is proposed for improving linearity and reliability of the multi-stage cascode CMOS PA. In addition, to achieve load variation immunity characteristic and to enhance matching and stability, a fully-integrated balanced PA is implemented in a 0.18-m CMOS process. A triple-mode balanced PA using switched quadrature coupler is also proposed, and this work saved a large amount of quiescent current and further improved the efficiency in the back-off power. For the low losses and a high quality factor of passive output combining, a transformer-based quadrature coupler was implemented using integrated passive device (IPD) process. Various practical approaches for linear CMOS PA are suggested with the verified results, and they demonstrate the potential PA design approach for WCDMA applications using a standard CMOS technology.

ABSTRACT NON-LINEAR MATHEMATICAL MODELING OF GEAR-ROTOR-BEARING SYSTEMS INCLUDING BEARING CLEARANCE G&Uuml<br>RKAN, Niyazi Ersan M.S. Department of Mechanical Engineering Supervisor: Prof. Dr. H. Nevzat &Ouml<br>ZG&Uuml<br>VEN November 2005, 130 pages In this study, a non-linear mathematical model of gear-rotor systems which consists of elastic shafts on elastic bearings with clearance and coupled by a non-linear gear mesh interface is developed. The mathematical model and the software (NLGRD 2.0) developed in a previous study is extended to include the non-linear effects due to bearing clearances by using non-linear bearing models. The model developed combines the versatility of using finite element method and the rigorous treatment of non-linear effect of backlash and bearing clearances on the dynamics of the system. The software uses the output of Load Distribution Program (LDP), which computes loaded static transmission error and mesh compliance for the contact points of a typical mesh cycle, as input. Although non-varying mesh compliance is assumed in the model, the excitation effect of time varying mesh stiffness is indirectly included through the loaded static transmission error, which is taken as a displacement input into the system. Previous computer program which was written in Fortran 77 is rewritten by using MatLAB 7.0 and named as NLGRD (Non-Linear Geared Rotor Dynamics) Version 3.0. The program is highly flexible and open to further developments. The program calculates dynamic to static load ratio, dynamic transmission error, forces and displacements at bearings. The mathematical model suggested and the code (NLGRD version 3.0) are validated by comparing the numerical results obtained from the model suggested with experimental data available in literature. The results are also compared with those of previously developed non-linear models. The effects of different system parameters such as bearing stiffness, bearing clearance and backlash on the gears are investigated. The emphasis is placed on the interaction of clearances in bearings with other system parameters.

For positioning of linear stages in absolute coordinates, there is a general need to find a reference position since the initial one is unknown. This is commonly called homing. To reduce costs and facilitate assembly, homing can be performed without additional sensors, known as sensorless homing. This thesis delves into sensorless homing, specifically with respect to stepper motors, and develops a graphical application for control of them. The commercial technology StallGuard is applied inconjunction with exploration into how it – and sensorless load detectionin general – functions. The resulting graphical application can be used to configure the stepper motors, perform homing using StallGuard, and automatically tune StallGuard to work despite varying conditions. In addition, rudimentary sensorless load detection independent from StallGuard is developed, demonstrating how it could work in practice. Testing shows homing with StallGuard resulting in a position within a ±5μm window in 94% of cases, less than 1/7 the width of an average strand of human hair. Additionally, homing is easily performed with a single button press from the graphical interface, with optional additional configuration available.

Approved for public release; distribution is unlimited<br>To ensure sufficient capacity to handle unexpected demands for electric power, decision makers often over-estimate expeditionary power requirements. Therefore, we often use limited resources inefficiently by purchasing more generators and investing in more renewable energy sources than needed to run power systems on the battlefield. Improvement of the efficiency of expeditionary power units requires better managing of load requirements on the power grids and, where possible, shifting those loads to a more economical time of day. We analyze the performance of a previously developed optimization model for scheduling time-shiftable electrical loads in an expeditionary power grids model in two experiments. One experiment uses model data similar to the original baseline data, in which expected demand and expected renewable production remain constant throughout the day. The second experiment introduces unscheduled demand and realistic fluctuations in the power production and the demand distributions data that more closely reflect actual data. Our major findings show energy grid power production composition affects which uncertain factor(s) influence fuel con-sumption, and uncertainty in the energy grid system does not always increase fuel consumption by a large amount. We also discover that the generators running the most do not always have the best load factor on the grid, even when optimally scheduled.<br>Lieutenant Commander, United States Navy

Shallow foundations can provide the most economical solution for supporting small-scale structures. The design approach is quite simple considering the ultimate bearing capacity and working-load settlement. Research has shown that settlement calculations, determined using a linear-elastic approach, usually govern the design but this approach is inappropriate because soil is highly non-linear, even at small strains. The result is that signifi cant discrepancies are observed between predicted and actual settlements. This uncertainty has seen the development of settlement-based approaches such as Mobilisable Strength Design (MSD). MSD uses an assumed undrained mechanism and accounts for soil non-linearity by scaling a triaxial stress-strain curve to make direct predictions of footing load-settlement behaviour. Centrifuge experiments were conducted to investigate the mechanisms governing the settlement of shallow circular foundations on clay and saturated sand models. Clay model tests were performed on soft or rm kaolin beds, depending on its pre-consolidation. Sand model tests were performed on relatively loose Hostun sand saturated with methyl-cellulose to slow consolidation. One-dimensional actuators were developed to apply footing loads through dead-weight or pneumatic loading. A Perspex window in the centrifuge package allowed digital images to be captured of a central cross-section, during and after footing loading. These were used to deduce soil displacements by Particle Image Velocimetry which were consistent with footing settlements measured directly. Deformation mechanisms are presented for undrained penetration, consolidation due to transient flow, as measured by pore pressure transducers, and creep. A technique was developed for discriminating consolidation settlements from the varying rates of short and long-term creep of clay models. Using MSD, a method for predicting the undrained penetration of a spread foundation on clay was proposed, using database results alone, which then provided estimates of creep and consolidation settlements that follow. The importance of the undrained penetration necessitated further investigation by using the observed undrained mechanism as the basis of an ellipsoidal cavity expansion model. An upper-bound energy approach was used to determine the load-settlement behaviour of circular shallow foundations on linear-elastic and non-linear clays, with yield defined using the von Mises' yield criterion. Linear-elastic soil results were consistent with those obtained from nite element analyses. The non-linear model, as described by a power-law, showed good agreement with both centrifuge experiment results and some real case histories. The single design curve developed through this model for normalised footing pressure and settlement could be used by practising engineers based on existing soil correlations or site investigations.

Datahallar behöver reservkraft av god kvalitet för att garantera upprätthållandet av dess funktion. Laster i en datahall kommer att generera ström och spänningsövertoner som kan skapa problematik med elkvaliteten. Coromatic är intresserade av att veta mer hur dessa laster påverkar reservkraftsgeneratorn. En mätning utfördes på en datahall under ett funktionsprov. Resultatet blev att halten av THD ökade, främst är det 3:e övertonen som är framträdande. Mätvärdena för THDV ligger under gränsvärdena för SS-EN 50160 och 61000-2-2, men gränsvärdena för 3:e ton ligger långt över. Ingen åtgärd föreslås i nuläget för att hantera problemet. Denna avhandling har gett värdefull information till Coromatic att ta i beaktande vid utförande av nya reservkraftsanläggningar.<br>A facility full with computers needs backup-power to guarantee the function. Loads in this facility will produce current and voltage harmonics that can pollute and cause trouble with the quality of electricity. Coromatic are interested in knowing more about how these loads can affect the generator. A measurement was performed on a facility when they ran a functional test. The results indicated that THD increased, the third harmonic turned out to be the single harmonic with the highest value. The value is within the boundaries for THDV according to SS-EN 50160 and 61000-2-2, except for the third harmonic. Its value was far too high. No action is propsed to deal with the problem at the moment. This thesis has provided Coromatic with valuable information too consider when they building new systems.

Nesta tese, apresenta-se a análise numérica e experimental do comportamento dinâmico não linear de um pórtico excitado por uma fonte não ideal - um motor elétrico de corrente contínua desbalanceado - como exemplo dessa classe de problemas. Elabora-se um modelo matemático com quatro graus de liberdade: dois relacionados com o deslocamento horizontal e vertical do ponto de apoio da máquina e dois com os parâmetros de funcionamento do motor elétrico. Adota-se a formulação Lagrangeana para gerar as equações de movimento contendo termos não lineares até ordem cúbica. A solução numérica é obtida através do método de Runge-Kutta com passo adaptativo. Ensaios dinâmicos e estáticos foram realizados com o motor e com o sistema completo, com vistas a validar o modelo matemático. Um sistema de medição digital armazenou todos os dados obtidos em arquivos de fácil leitura pelos programas atualmente disponíveis. Filmagens de alta velocidade e fotografia estroboscópica registraram movimentos típicos relacionados com comportamentos não lineares. Os resultados numéricos e experimentais mostram boa correlação entre si, além de apresentarem alguns dos fenômenos associados ao se forçar uma estrutura a passar por uma de suas ressonâncias excitando-a com um dispositivo com potência limitada, como o efeito Sommerfeld. Outros fenômenos, devido ao comportamento geometricamente não linear da estrutura, são também detectados, tais como saturação modal e transferência de energia.<br>Numerical and experimental analysis of the nonlinear dynamics of a portal frame excited by a non-ideal source - an unbalanced direct current motor - is presented in this thesis as an example of this class of problems. A four degree of freedom model is elaborated: two of them related to the horizontal and vertical structural displacements and two others to the functioning parameters of the motor. A Lagrangian approach for deducing the equations of motion, up to cubic non-linear terms is followed. The numerical solution is obtained through Runge-Kutta algorithm with adaptive step. Static and dynamic tests were performed with the motor and with the complete system, in order to validate the mathematical model. A digital acquisition system recorded all data in computer files, ready to be read by available commercial programs. High speed filming and stroboscopic photography were used to register typical movements related to nonlinear behavior. Numerical and mathematical results show good correlation, as well as present some phenomena related to passage through resonance with limited power excitation such as the Sommerfeld effect. Some other phenomena, related to the nonlinear behavior of the structure are also detected, as modal saturation and energy transference.

A non-linear finite element program to simulate the behaviour of infilled frames and plane stress reinforced concrete members under the action of monotonic and cyclic loading has been developed. Steel is modelled as a strain hardening plastic material, and in the concrete model cracking, yielding and crushing are considered. The separation, sliding, and opening and closing of initial gaps at the interfaces between the frame and the infill panels are accounted for by adjusting the properties of interface elements. The non-linear equations of equilibrium are solved using an incremental-iterative technique performed under load or displacement control. The iterative techniques use the standard and modified Newton-Raphson method or the secant Newton method. An automatic load incrementation scheme, line searches, and restart facilities are included. The capabilities of the program have been examined and demonstrated by analysing five reinforced concrete panels, a deep beam, a shear wall, and eight infilled frames. The accuracy of the analytical results was assessed by comparing them with the experimental results and those obtained analytically by other workers and shown to be good. A study of the effects of some material and numerical parameters on the results of analyses of reinforced concrete deep beam has been carried out. Two techniques have been proposed and used to overcome numerical problems associated with local strain concentrations which occur with the displacement control, when path dependent incremental iterative procedures are used for inelastic materials. The displacement control provided with these modifications has been shown to be more efficient than the load control.

The goal of this thesis is to develop nontraditional strategies to provide motion control for different engineering applications. We focus our attention on three topics: 1) roll reduction of ships in a seaway; 2) response reduction of buildings under seismic excitations; 3) new training strategies and neural-network configurations. The first topic of this research is based on a multidisciplinary simulation, which includes ship-motion simulation by means of a numerical model called LAMP, the modeling of fins and computation of the hydrodynamic forces produced by them, and a neural-network/fuzzy-logic controller. LAMP is based on a source-panel method to model the flowfield around the ship, whereas the fins are modeled by a general unsteady vortex-lattice method. The ship is considered to be a rigid body and the complete equations of motion are integrated numerically in the time domain. The motion of the ship and the complete flowfield are calculated simultaneously and interactively. The neural-network/fuzzy-logic controller can be progressively trained. The second topic is the development of a neural-network-based approach for the control of seismic structural response. To this end, a two-dimensional linear model and a hysteretic model of a multistory building are used. To control the response of the structure a tuned mass damper is located on the roof of the building. Such devices provide a good passive reduction. Once the mass damper is properly tuned, active control is added to improve the already efficient passive controller. This is achieved by means of a neural network. As part of the last topic, two new flexible and expeditious training strategies are developed to train the neural-network and fuzzy-logic controllers for both naval and civil engineering applications. The first strategy is based on a load-matching procedure, which seeks to adjust the controller in order to counteract the loads (forces and moments) which generate the motion that is to be reduced. A second training strategy provides training by means of an adaptive gradient search. This technique provides a wide flexibility in defining the parameters to be optimized. Also a novel neural-network approach called modal neural network is designed as a suitable controller for multiple-input multiple output control systems (MIMO).<br>Ph. D.

To meet the future traffic demands there is a constant need of making the infrastructure moreeffective. This can be achieved by increasing the capacity and/or life length of traffic lines. Apart of the efforts to do this is increasing the load carrying capacity of the railway bridges sothat it is possible to allow heavier freight trains to pass the bridges.In this thesis the assessment of the load carrying capacity of a strengthened concrete troughrailway bridge, The Övik Bridge, with two spans in Örnsköldsvik, in northern Sweden, istreated. To investigate the ultimate behavior of the bridge a full scale load test up to failure wasperformed in 2006.At the loading test in Örnsköldsvik a steel beam was placed in the mid of one of the spans ofthe bridge. The failure was caused by pulling the steel beam downwards with cables whichwere anchored with injection into the drilled holes in the bedrock beneath the bridge.While the mechanism of a bending failure is commonly considered to be well investigated, thestructural models for the shear failure are still the object of intense research. The bottom sidesof the edge beams of the Örnsköldsvik Bridge were strengthened with Near Surface Mountedreinforcement (NSM) consisting of Carbon Fibre Reinforced Polymers (CFRP) to increase thebending capacity and in that way steer the bridge to failure in shear instead of bending.The material properties of the reinforcement were determined in tension tests. Concreteproperties were determined by testing drilled core samples. Displacements and deflections ofthe bridge, strains in concrete, steel and carbon fibre reinforcement were measured during thetest as a function of the increasing load.In this thesis the analysis of the failure of the bridge, structural models describing the behaviorand load carrying capacity are evaluated according to different design codes. Advanced finiteelement analysis is applied with both geometrical and material non-linearities included. Toverify the models used in codes and computer calculations the response of the bridge duringthe test is compared with the calculation results.The refined and calibrated FEM model is used to predict how high axle loads of a train theÖvik Bridge could have sustained. The Övik Bridge was designed in 1950’s for axle loads of20 ton. The calculations methods developed in this thesis show that the axle loads in the failurestate could have been increased at least up to 154 tons without strengthening and to 215 tonwith strengthening of the bridge slab with carbon fibre reinforcement bars with Af = 100 mm2c 150 mm using statistical mean values of loads and material properties in the calculations.<br>Bärförmågan hos en förstärkt betongbroIcke-linjär finit elementmodellering av en brottbelastningTillståndsbedömning av en järnvägstrågbro med två spann i Örnsköldsvik förstärkt med stänger av kolfiberarmerade polymerer (CFRP)För att möta de framtida krav som trafiksektorn står inför måste infrastrukturen effektiviseras. Detta kan bland annat uppnås genom att öka trafikledernas kapacitet och livslängd. En del av denna ambition består av att öka lastkapaciteten på järnvägsbroar så att man kan tillåta tyngre godståg att passera.I denna avhandling behandlas tillståndsbedömning av en förstärkt trågbro av armerad betong. Bron hade två spann och var belägen i Örnsköldsvik i Sverige. Ett fullskaleförsök utfördes år 2006 för att studera brons beteende under ökande last tills brott uppstod.Under testet i Örnsköldsvik placerades en stålbalk i mitten av brons ena spann. Brottet frambringades genom att stålbalken drogs neråt med kablar, som hade förankrats i berget med injektion under bron, så att lasten på bron ökade. Medan mekanismen för böjmoment allmänt anses vara väl utredd är olika modeller för bärförmågan för tvärkraft fortfarande föremål för intensiv forskning. För att undvika det icke-intressanta böjbrottet förstärktes kantbalkarna i underkanten med kolfiberarmering (CFRP) i form av stavar som limmades fast i utsågade slitsar (Near Surface Mounted reinforcement, NSM). På det viset styrdes bron till att få skjuvbrott istället för böjbrott.Materialegenskaper för betongen bestämdes med hjälp av utborrade cylindrar och för armeringen med dragprov. Förskjutningar och utböjningar av bron samt töjningar i betong, stål- och kolfiberarmering mättes under pågående test som funktion av den ökande lasten.Bron analyserades på flera sätt för att jämföra verklig bärförmåga med olika normer. Ickelinjära finita element har härvid använts för att utvärdera hur avancerade beräkningsverktyg kan beskriva det verkliga skeendet. Olinjäriteter har beaktats i såväl material som geometri. Den förfinade och kalibrerade FEM -modellen användes för att bedöma den maximala axellasten för tåg som Öviksbron skulle ha kunnat bära. Öviksbron dimensionerades på 1950- talet för axellaster på 20 ton. Beräkningsmodellerna utvecklade i avhandlingen visar att bron i brottstadiet hade kunnat klara axellaster på minst 154 ton utan den utförda förstärkningen och på 215 ton med förstärkningen av broplattan med kolfiberstänger med Af = 100 mm2 c 150 mm. Statistiska medelvärden av laster och materialparametrar har härvid använts i beräkningarna.<br>Godkänd; 2012; 20120425 (ysko); DISPUTATION Ämnesområde: Konstruktionsteknik/Structural Engineering Opponent: Docent Mario Plos, Institutionen för bygg- och miljöteknik, Chalmers Tekniska Högskola, Göteborg Ordförande: Professor Mats Emborg, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Onsdag den 30 maj 2012, kl 10.15 Plats: F1031, Luleå tekniska universitet

The number of horizontal wells is increasing rapidly in all over the world with the growth of new technological developments. During horizontal well drilling, much more complex problems occur when compared with vertical well drilling, such as decrease in load transfer to the bit, tubular failure, tubular fatigue and tubular lock-up. This makes selection of appropriate tubular and making the right drill string design more important. As the total compression load on the horizontal section increases, the behavior of the tubular changes from straight to sinusoidal buckling, and if the total compression load continues to increase the behavior of the tubular changes to helical buckling. Determination of critical buckling loads with finite element method (FEM) in horizontal wells is the main objective of this study. Initially, a computer program (ANSYS) that uses FEM is employed to simulate different tubular and well conditions. Four different pipe sizes, four different wellbore sizes and three different torque values are used to model the cases. Critical buckling load values corresponding to significant variables are collected from these simulated cases. The results are classified into different buckling modes according to the applied weight on bit values and the main properties of the simulated model, such as modulus of elasticity, moment of inertia of tubular cross section, weight per unit length of tubular and radial clearance between the wellbore and the tubular. Then, the boundary equations between the buckling modes are obtained. The equations developed in this thesis by simulating the cases for the specific tubular sizes are used to make a comparison between the critical buckling load values from the models in the literature and this work. It is observed that the results of this work fit with literature models as the tubular size increases. The influence of torque on critical buckling load values is investigated. It is observed that torque has a slight effect on critical buckling load values. Also the applicability of ANSYS for buckling problems was revealed by comparing the ANSYS results with the literature models&amp<br>#8217<br>results and the experimental study in the literature.