Thèses sur le sujet « Load and structure nonlinearities »
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1
Guo, Jianping. « Sliding Mode Based Load Frequency Control for an Interconnected Power System with Nonlinearities ». Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1435857616.
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Archontakis, Theofanis. « Essays on term structure modeling : estimation, nonlinearities and immunization / ». [S.l. : s.n.], 2007. http://www.gbv.de/dms/zbw/558853412.pdf.
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Kumar, Avishek. « Multivariable control of wind turbines for fatigue load reduction in the presence of nonlinearities ». Thesis, University of Auckland, 2011. http://hdl.handle.net/2292/17839.
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In an effort to reduce cost of energy from wind, wind turbines have grown to immense sizes. This has led to large, flexible, lightly damped towers and rotors that can be excited by the wind. Reducing the resulting fatigue loading and maintaining power capture are primary objectives for advanced controllers. In this thesis, a synthesis procedure for creating a multivariable linear parameter varying (LPV) controller suitable for the wind turbine control problem is created. The LPV controller uses the current wind speed estimate from an Extended Kalman Filter (EKF) for gain scheduling in order to accommodate system nonlinearities. The synthesis procedure allows the use of a parameter dependance Lyapunov function without having to choose the form of the parameter dependence. Additionally, the synthesis procedure is designed for discrete time systems, allowing digital implementation of the controller. While the LPV controller is suitable for the wind turbine problem, its performance is limited by constrained actuators, as well as persistent disturbances to the system. Therefore a model predictive controller (MPC controller) that builds on the advantages of the LPV controller is created. The MPC controller utilises future wind speed information to increase controller performance and can maintain stability in the presence of constrained actuators. The ability of both controllers to reduce fatigue loading in the drivetrain, tower and blades whilst maintaining power capture relative to a baseline is tested in simulation. The testing includes six hours of simulations using a high order, nonlinear aeroelastic model of a three-bladed, 600kW wind turbine in full-field turbulent winds. The simulation conditions include above rated, below rated, and transitional winds. The LPV controller shows overall reductions in tower, drivetrain and blade loads relative to the baseline. The MPC controller shows poor performance in below rated winds due to high errors in the prediction model. In above rated winds, the MPC controller shows the ability to reduce loads in the blades, drivetrain and tower relative to the LPV controller. Furthermore, the MPC controller shows less pitch actuator usage and maintains performance in situations that cause the LPV controller to saturate the pitch actuators and lose performance.
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Terasima, Kentaro. « Studies on structure and optical nonlinearities of B_2O_3-Based glasses ». Kyoto University, 1997. http://hdl.handle.net/2433/202295.
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Kapila, Vikram. « Robust fixed-structure control of uncertain systems with input-ouput nonlinearities ». Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12069.
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Hatipoglu, Cem. « Variable Structure Control of Continuous Time Systems Involving Non-Smooth Nonlinearities ». The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1391691862.
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Hatipo?lu, Cem. « Variable structure control of continuous time systems involving non-smooth nonlinearities / ». The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487950153600937.
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Bingham, Christopher Malcolm. « Application of variable structure control methods to actuator nonlinearities in aerospace systems ». Thesis, Cranfield University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358823.
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Choi, Hyeongrak. « Photonic crystal cavity with self-similar structure and single-photon Kerr nonlinearities ». Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108985.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 31-34).
We propose a design of photonic crystal cavity with self-similar electromagnetic boundary conditions, that achieve ultrasmall mode volume (Vff). The electric energy density of a cavity mode can be maximized in the air or dielectric region, depending on the choice of boundary conditions. We illustrate the design concept with a silicon-air ID photon crystal cavity that reaches an ultrasmall mode volume of Vff ~ 7.01 x 10- 5 [lambda]3 at [lambda] ~ 1550 nm. We show that the extreme light concentration in our design can enable ultra-strong Kerr nonlinearities, even at the single photon level. These features open new directions in cavity quantum electrodynamics, spectroscopy, and quantum nonlinear optics.
by Hyeongrak Choi.
S.M.
10
Marathe, Anup Ramesh. « Buckling of dome structure with opening, under wind load ». To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Olofsson, Erik. « Chassis calculations for Frame design ». Thesis, Linköpings universitet, Mekanik och hållfasthetslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-121848.
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This is a Masters Thesis report of a project carried out at Scania AB in Södertälje. The project concerns rationalizing Chassis calculations for use in truck Frame design. The subject for analysis is a six-wheeled articulated truck, and the load cases under study is Lateral Loading, Frame Torsion and Vertical Load on Kingpin. Making robust deformation and stress models with a calculation time sufficiently short and accuracy consistently high for efficient design work is an arduous task. This report presents several approaches to tackle this type of problem. By means of simplifying contemporary modeling approaches and methods and automating the setup process, a method that enables short calculation iterations on a chassis frame of a truck is achieved. This is done using the Catia GAS framework in conjunction with several other licences commonly used by designers.
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PENEDO, ERIC ARTHUR DE FREITAS. « INSTRUMENTED LOAD TEST CARRIED OUT IN A PILED QUAY STRUCTURE ». PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2012. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=34995@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Esta dissertação apresenta os dados de um teste de carga instrumentado em um cais, enfatizando a importância da instrumentação de campo para melhor compreender o comportamento da estrutura durante o teste. Dentro desta abordagem, foi realizada uma revisão sobre o comportamento de grupo de estacas, direcionada à influência do espaçamento entre estacas na interação entre as mesmas, e da rigidez do bloco na distribuição de carga entre as estacas, no fator de segurança das mesmas e das distorções angulares do bloco. Em seguida, foram descritas as características geométricas e geotécnicas do cais testado, e foram apresentadas as características da instrumentação utilizada, composta por extensômetros elétricos, eletroníveis e nível topográfico, desde sua montagem e calibração, até a sua instalação em campo. Foi destacada a utilização dos eletroníveis, que apesar de pouco utilizados na prática da engenharia geotécnica, são instrumentos versáteis, precisos e podem ser reutilizados. O procedimento do teste de carga foi realizado de modo a simular a situação real da maneira mais próxima da realidade, onde foram monitoradas as deformações em quatro estacas, a rotação e o recalque da laje do cais. A estrutura apresentou bom desempenho durante o teste, com baixo nível de deformação nas estacas, distorção angular desprezível e baixos valores de recalque total e residual.
This dissertation presents the data of an instrumented load test in a wharf, emphasizing the importance of field instrumentation to analyze the behavior of the structure during the load test. First, a review was carried out on the behavior of pile groups, focusing on the influence of pile spacing in the interaction factors. It also considered the influence of the raft stiffness on the load distribution and factor of safety of the piles. The main characteristics of the wharf were presented, such as, geometry, dimensions, deformability and strength properties of the concrete. The geological and geotechnical subsoil profile have been presented, indicating a soft clay layer resting on a very compact residual soil. The particularities of the instrumentation used on the test, composed by strain gauges, electrolevels and a topographic level, were presented since the assembly and calibration, to the installation on field. Despite its underutilization in geotechnical engineering practice, the use of electrolevels was emphasized, due to its versatility, accuracy and the fact that they can be reutilized. The load test procedure was made to simulate the real situation as close as possible, where strain in four piles, rotation and settlement of the deck were monitored. The structure performanced well during the test, presenting low level of strain in piles, negligible angular distortion of the deck and low values of total and residual settlements.
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Foster, Anthony. « A Scalable, Load-Balancing Data Structure for Highly Dynamic Environments ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1212682598.
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Olivier, Jacques-Philippe 1969. « Design evaluation of naval combatant secondary structure under hydrostatic lateral load ». Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/91805.
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Thesis (S.M. in Naval Architecture and Marine Engineering)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.Includes bibliographical references (leaves 59-60).
by Jacques-Philippe Olivier.
S.M.in Naval Architecture and Marine Engineering
S.M.
15
Su, Isabelle. « Behavior of a silkworm silk fiber web structure under wind load ». Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99633.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 57-59).
Optimized by Nature for millions of years, silk is one of the strongest biomaterials with outstanding mechanical properties, it is both extensible and tough in order to ensure specific functions. In particular, protein-based Bombyx mori silkworm silk's stiffness is originated from the crystalline region of the semi-crystalline fibroin and the extensibility from the length hidden within the amorphous region. The silk fiber is coated with sericin which acts as a glue connecting fibers together and as a matrix in the three-dimensional nonwoven multi-layer composite structure of the cocoon. These properties can be engineered and enhanced with forced reeling silk: fast spun silks are stiffer and less extensible than slow reeled silk. For this study, two-dimensional single cocoon layer webs are created by silkworms and tested under an increasing wind load until failure, the deflections are recorded. To complement the experimental results, the web's structure is generated in two different models: straight fiber web and wavy fiber web models. Both models are studied under constant wind load for four type of fibers with different reeling speeds thus different mechanical properties. These tests indicate that the deflection increases with wind load for both the experiments and the simulations, but also that webs composed of fibers with different mechanical properties are not necessary stiffer and less extensible as the material they are composed of are stiffer and less extensible because of the high redundancy and randomness of the web structure. The divergence in results between the experiments and the simulations suggests the need to improve the models to be more in accordance with the real webs.
by Isabelle Su.
M. Eng.
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Nichols, Jonathan Tyler. « Application of Load Updating to a Complex Three Dimensional Frame Structure ». Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78274.
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This thesis presents a novel method for the correlation of FEM results to experimental test results known as the "Load updating method." Specifically, the load updating method uses the math model from the FEM and the strains measured from experimental or flight test data as inputs and then predicts the loads in the FEM which would result in strains that would correlate best to the measured strains in the least squared sense. In this research, the load updating method is applied to the analysis of a complex frame structure whose validation is challenging due to the complex nature of its structural behavior, load distributions, and error derived from residual strains. A FEM created for this structure is used to generate strain data for thirty-two different load cases. These same thirty-two load cases are replicated in an experimental setup consisting of the frame, supporting structure, and thirty actuators which are used to load the frame according to the specifications for each of the thirty-two load conditions. A force-strain matrix is created from the math model in NASTRAN using unit loads which are separately applied to each load point in order to extract strain results for each of the locations of the seventy-four strain gages. The strain data from the structural test and the force-strain matrix is then input into a Matlab code which is created to perform the load updating method. This algorithm delivers a set of coefficients which in turn gives the updated loads. These loads are applied to the FEM and the strain values extracted for correlation to the strains from test data. It is found that the load updating method applied to this structure produces strains which correlate well to the experimental strain data. Although the loads found using the load updating method do not perfectly match those which are applied during the test, this error is primarily attributed to residual strains within the structure. In summary, the load updating method provides a way to predict loads which, when applied to the FEM, would result in strains that correlate best to the experimental strains. Ultimately, this method could prove especially useful for predicting loads in experimental and flight test structures and could aid greatly in the Federal Aviation Administration (FAA) certification process.Master of Science
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Sharkas, M. Y. « The initial load-extension of 2/2 twill woven fabrics ». Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379562.
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Gehb, Christopher Maximilian [Verfasser], Tobias [Akademischer Betreuer] Melz et Eckhard [Akademischer Betreuer] Kirchner. « Uncertainty evaluation of semi-active load redistribution in a mechanical load-bearing structure / Christopher Maximilian Gehb ; Tobias Melz, Eckhard Kirchner ». Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1202112374/34.
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Ibrahim, Michael. « Mechanical load regulates transverse-tubule structure and function in left ventricular cardiomyocytes ». Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/10486.
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Chronic mechanical load variation triggers a wide range of responses in the heart, a part of which includes cellular remodelling. Over the past 15 years, evidence has amassed that a part of this remodelling process involves changes to a sophisticated structure in the cell membrane, called the transverse (t)-tubule system. The t-tubules are a series of regular membrane invaginations, which contain a high density of ion channels responsible for local Ca2+ induced Ca2+ release (CICR). This thesis addresses the question of whether the t-tubule system can be said to be specifically load sensitive, the nature of that load sensitivity and its molecular regulators. Using surgical models, the influence of mechanical load variation of different durations, degrees and settings are studied. Local CICR and t-tubule structure are investigated. First, it was found that prolonged mechanical unloading induces subtle changes to the t-tubule system, which functionally uncouples the Ryanodine receptors (RyR) and L-type Ca2+ channels (LTCC) and induces a loss of whole cell Ca2+ release synchrony. Second, heart failure was found to be associated with loss of t-tubule structure and Ca2+ handling abnormalities. Following mechanical unloading, the t-tubule system recovered with enhanced LTCC-RyR uncoupling, resulting in improved Ca2+ handling. Third, the t-tubules were found to be unchanged initially during graded mechanical load variation. Prolonged myocardial unloading or overloading impaired t-tubule structure, with loss of normal CICR. Telethonin (Tcap), a member of the cardiomyocyte stretch sensing complex, is a candidate regulator of the t-tubules. In a Tcap knock-out (KO), cardiomyocytes show a primary t-tubule defect, which becomes more pronounced following mechanical overload. These results support the notion that the t-tubule system is dynamically regulated by mechanical overload and unloading, via a molecular pathway including Tcap.
20
D'Elia, Samuel C. « The spray/load and dative alternations : aligning VP structure and contextual effects ». Thesis, University of Kent, 2016. https://kar.kent.ac.uk/54773/.
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The theoretical and experimental work presented in this thesis investigates the spray/load and dative alternations. The purpose is to provide a comprehensive analysis of the alternations in terms of their syntactic structures and to account for how contextual information drives differences in the linear order of their VP arguments. This analysis shows that the syntactic structures of the spray/load and dative alternations are identical; each variant in an alternation is characterised by one of two available structures proposed in Janke and Neeleman (2012). Each structure is shown to respect a novel thematic hierarchy that is based on the value of binary feature clusters (Reinhart, 2000) rather than by direct reference to semantic labels. The choice of a particular structure is demonstrated to be affected by the non-semantic context in which the spray/load or dative sentence is generated. This is a consequence of the limited processing capacity of Working Memory and the allocation of attentional resources to a stimulus. Experimental data from an as yet untested variable of the visual context – the egocentric perception of distance – is found to interact with word order preferences of the alternations. I conclude that non-semantic contextual information interacts with the encoding of an event which ultimately has consequences for syntactic choices.
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Wang, Ryan Po Chao. « Evaluation of wind load on large telescope structure based on performance-based design ». Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43515.
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Wind loads have been the governing factor that influences structural stability in overwhelmingly large structures. This is particularly of major concern when the analyzed structure in this study is merely a conceptual design. Previous studies have shown reduced pressure on structures due to application of windscreens, and a proposal had been made with preliminary structural analysis performed and proven to be feasible. Therefore, this research aims to analyze the extent of the functionality of the proposed windscreen by utilizing computational fluid dynamics and taking a performance-based design approach with performance objectives determined based on historical environmental data. In addition, different scenarios and boundary conditions are applied to provide a pressure envelope that generalizes the range of pressure experienced by the telescope.
Simulation of air flow is performed with CFDesign, and the results obtained supported the previously-made hypothesis suggesting that implementation of windscreen enables pressure reduction. Although in some cases pressure increase is observed, the general trend of decrease dominates the trend of increase. Pressure envelopes for all structural elements are also provided for engineers as a performance-based design guideline based on different impact levels of wind loading. However, further analyses are needed to investigate the possibility of a windscreen of greater height, to emphasize on the simulation of finer details, and to validate the results from this analysis in an actual scaled-model wind tunnel testing if possible.
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Harry, Ofonime Akpan. « Behaviour of reinforced concrete frame structure against progressive collapse ». Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/29623.
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A structure subjected to extreme load due to explosion or human error may lead to progressive collapse. One of the direct methods specified by design guidelines for assessing progressive collapse is the Alternate Load Path method which involves removal of a structural member and analysing the structure to assess its potential of bridging over the removed member without collapse. The use of this method in assessing progressive collapse therefore requires that the vertical load resistance function of the bridging beam assembly, which for a typical laterally restrained reinforced concrete (RC) beams include flexural, compressive arching action and catenary action, be accurately predicted. In this thesis, a comprehensive study on a reliable prediction of the resistance function for the bridging RC beam assemblies is conducted, with a particular focus on a) the arching effect, and b) the catenary effect considering strength degradations. A critical analysis of the effect of axial restraint, flexural reinforcement ratio and span-depth ratio on compressive arching action are evaluated in quantitative terms. A more detailed theoretical model for the prediction of load-displacement behaviour of RC beam assemblies within the compressive arching response regime is presented. The proposed model takes into account the compounding effect of bending and arching from both the deformation and force points of view. Comparisons with experimental results show good agreement. Following the compressive arching action, catenary action can develop at a much larger displacement regime, and this action could help address collapse. A complete resistance function should adequately account for the catenary action as well as the arching effect. To this end, a generic catenary model which takes into consideration the strength degradation due to local failure events (e.g. rupture of bottom rebar or fracture of a steel weld) and the eventual failure limit is proposed. The application of the model in predicting the resistance function in beam assemblies with strength degradations is discussed. The validity of the proposed model is checked against predictions from finite element model and experimental tests. The result indicate that strength degradation can be accurately captured by the model. Finally, the above developed model framework is employed in investigative studies to demonstrate the application of the resistance functions in a dynamic analysis procedure, as well as the significance of the compressive arching effect and the catenary action in the progressive collapse resistance in different designs. The importance of an accurate prediction of the arching effect and the limiting displacement for the catenary action is highlighted.
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Kenchington, Christopher James. « The shock response of submerged masts ». Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/847588/.
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A study of the response of submerged mast-like structures to shock loads has been carried out. An analytical model has been developed which uses a lumped parameter system whose equations of motion are solved by the use of finite difference time integration techniques. The effects of the stiffness and damping inherent in the supporting restraints are successfully included into the analysis by assuming that they provide linear rotational stiffness and a viscous type of damping. An analysis of hydrodynamic interaction effects has been developed in order to investigate how the frequency response of the structure is affected by submergence. Changes in both the frequency and the damping characteristics are predicted as a function of the depth of submergence. Methods of incorporation of these hydrodynamic forces into the time domain solution of the lumped mass system are investigated and are found to be most accurate for slender structures. In order to develop a fuller understanding of the hydrodynamic response, two experimental investigations have been carried out. The first is laboratory based and uses carefully controlled free vibration tests to excite a number of modal frequencies of a rigidly clamped vertical mast in both submerged and partially submerged conditions. Results show that the frequency changes are closely predicted by the hydrodynamic analysis developed in this thesis and also show that hydrodynamic damping is a linear function of amplitude of deflection for the first natural response mode over the mast's elastic range of response. To investigate the shock response of submerged structures, a second test rig is used to subject a slender mast to a shock load radiating from an underwater explosion. The structural significance of the higher modal frequencies is evaluated through the use of Fourier Analysis and digital filtering techniques. The instrumentation performance including both damped and undamped transducers is assessed in order to make recommendations for future shock trials. The experimental investigation has shown that both the direct pressure loading and the movement of the supports are important factors in the mast response and that their combination produces important high frequency response modes.
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Sanders, Richard. « Some effects of nutrient load on the structure and functioning of pelagic coastal ecosystems ». Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327411.
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Keyhan, Hooman. « Fluid structure interaction (FSI) based wind load modeling for dynamic analysis of overhead transmission lines ». Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114457.
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Electricity is a crucial form of energy in our societies, and transmission lines are key elements to ensure the reliability of electric power grids. Continuity of service is the main preoccupation of electric utilities, and this continuity may be disrupted by a large variety of sources and accidents. Transmission lines, by their intrinsic topology, remain the grid components that are the most exposed to climatic sources of disruption.The most common and important source of dynamic loads on transmission lines results from wind effects on the towers and conductors. Conductors are particularly sensitive to wind effects as they are long and relatively flexible (compared to their supports) and are literally wind-catching structures in the power grid infrastructure. In cold climates, wind and ice have compounding effects on lines and give rise to the most severe design loading conditions. Therefore, accurate prediction of the wind pressure on overhead conductors is essential to conduct a reliable assessment of the line response, in terms of both electrical clearances and conductor loads transferred to supports. Spatial randomness of wind loads on overhead lines has already been addressed by stochastic analysis methods and is now taken into account in design with the use of so-called span factors. Further gains in wind load accuracy can be obtained by examining the physics of wind effects on conductors, in both non-iced and iced conditions, with improved predictions of lift and drag forces determined from fluid-structure interaction (FSI) analysis.The traditional design method to apply wind load on transmission lines is to convert the design wind speed to a static pressure through Bernoulli's equation where the pressure is proportional to the air density and the squared wind speed. In this approach the fluid-structure interaction of wind and line components is ignored: wind is considered as a quasi-static load on conductors and supports, while special instability effects due to particular wind conditions such as vortex shedding (Aeolian vibrations) and flutter (cable galloping) are accounted for separately with specific mitigation solutions if necessary.In gusty wind conditions with high turbulence intensity, conductors may experience large horizontal displacements that affect their surrounding wind flow. A physically accurate wind load evaluation on conductors is possible by computational wind-structure interaction analysis. To date, largely due to its high computational cost and the lack of experimental data to validate computational models, an advanced fluid-structure analysis framework for wind-cable interaction has not been developed. In this study a new approach based on FSI analysis to evaluate equivalent wind loads on conductors is developed. The first step in such an approach is accurate evaluation of wind pressure on conductor. For this purpose the FSI analysis is carried out in two dimensions where the detailed bare and iced conductor section geometry and surrounding air flow are modeled, considering a given incident wind speed. The conductor cross section is assumed to be supported on flexible supports to study the interaction between the conductor motion and the air flow. FSI analysis yields both the fluid and structure response. Of particular interest is the wind pressure field on the conductor section, which allows the computation of the resultant drag and lift forces. This process is repeated for several cross sections along the span and the resulting forces provide the effective span wise wind load distribution on the conductor. This wind loading is then used as input in a separate 3-D computational nonlinear dynamic analysis model to predict the line response. This dynamic analysis of the line section can be detailed to represent very realistic line sections including conductors, suspension links and supporting towers.Nos sociétés sont fortement dépendantes de l'électricité, et il ne fait pas de doute que la fonctionnalité des lignes de transport est déterminante pour assurer la fiabilité des réseaux électriques modernes. En effet, la continuité de l'approvisionnement en électricité reste la préoccupation majeure de toutes les compagnies d'électricité, et cette continuité du service peut être compromise par une multitude d'incidents ou d'accidents sur l'ensemble du réseau. Parmi toutes les sources possibles de charges dynamiques sollicitant les lignes de transport, celles provenant des effets du vent sur les pylônes et les conducteurs restent les plus fréquentes. Les conducteurs de lignes sont particulièrement vulnérables aux effets du vent car les portées sont longues et flexibles (comparé aux pylônes) et leur présence physique dans le réseau en font des structures exposées à toutes les intempéries qui peuvent survenir sur le territoire couvert. Cette vulnérabilité est encore plus grande dans les climats nordiques où les effets combinés du givrage atmosphérique et du vent créent des scénarios de charges de conception parmi les plus critiques et donc susceptibles de contrôler la conception finale des lignes. Il nous apparaît donc essentiel de comprendre la dynamique des fluides des effets du vent pour prédire avec réalisme et un degré de précision raisonnable la pression du vent exercée sur les conducteurs. Une meilleure évaluation des charges dues au vent permettrait par le fait même des prédictions plus réalistes de la réponse des lignes aux charges de vent, non seulement en terme de déplacements et dégagements électriques mais aussi en terme des charges nettes transférées aux pylônes par les conducteurs. La nature aléatoire des effets du vent sur les conducteurs a déjà fait l'objet de nombreuses études scientifiques et les méthodes d'analyse stochastique modernes permettent de cerner la question : les méthodes de conception simplifiées qui sont suggérées dans les normes et guides tiennent compte de ces effets en utilisant un coefficient de portée global qui ajuste à la baisse les efforts calculés au pylône sous des charges supposées synchrones et uniformes le long des conducteurs. Cette recherche ne concerne pas cet aspect de la question. Nous croyons que des gains de précision appréciables dans la prédiction des charges de vent sur les lignes sont possibles par une meilleure modélisation de la physique des effets du vent sur les conducteurs, dans les conditions givrées ou non, en utilisant les techniques d'analyse qui tiennent compte des interactions dynamiques fluide-structure. Ces interactions sont ignorées dans les méthodes d'analyse conventionnelles qui consistent simplement à calculer une pression statique proportionnelle à la vitesse carrée du fluide selon l'équation classique de Bernoulli. Bien sûr, les concepteurs ne négligent pas la considération des vibrations éoliennes ou du galop des conducteurs, mais ces phénomènes sont traités séparément et n'influencent pas le calcul des charges sur les pylônes. Dans cette recherche, nous nous intéressons aux conditions de vent de rafale avec grande turbulence qui caractérisent les tempêtes de vent. Ces vents forts et turbulents créent de grands déplacements des conducteurs qui modifient les conditions d'écoulement d'air. Une évaluation plus précise de ces conditions est possible par analyse computationnelle des interactions vent-conducteur.Les bases théoriques de la physique des phénomènes en présence sont connues mais aucun cadre d'application numérique n'a été proposé jusqu'à maintenant, en partie à cause des coûts numériques élevés mais aussi dû au manque de données expérimentales pouvant valider ces modèles computationnels.Nous avons développé un tel cadre d'analyse computationnelle dans cette recherche et l'avons illustré dans un cycle complet, du calcul des charges au calcul de la réponse d'une section de ligne, avec plusieurs exemples pratiques à chacune des étapes de développement
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Becker, Ralf. « Testing for nonlinear structure in time-series data ». Thesis, Queensland University of Technology, 2001.
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Kolhatkar, Tanmay. « Nonlinear dynamic interactions between a rigid attachment bolted to a thin-walled sheet metal structure ». The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587124580918153.
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Lundgren, Eric Charles. « Durable Sandwich Structure Joining Technology for NASA's Ares V Launch Vehicle ». Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/79693.
Texte intégralRésumé :
Joining of uniformly-curved composite sandwich panel segments, typical in state of the art aerospace launch vehicles, should be mass-efficient. Adhesively bonded joints can provide increased mass-efficiency over mechanically-fastened joints. But, due to manufacturing sensitivities and certification requirements, conventional bonded joints can be improved upon by introducing structural redundancy. A longitudinal, durable redundant joint (DRJ) architecture featuring multiple adhesive load-paths, via a novel composite preform insert, was proposed to join composite sandwich panel segments of the interstage element for NASA's Ares V launch vehicle. A series of twenty-five static linear-elastic finite element models with plane strain solutions were developed to assess certain characteristics of a joint's structural response when subjected to a simplified circumferential hoop loading convention.
Shear and normal stress distributions at the adherend-adhesive interface along the splice plate bondline of the DRJ are compared with those from a conventional splice joint (CSJ) configuration for a series of linearly increasing bondlines thicknesses and joint overlap lengths. The parameter studies indicate the DRJ configuration's adhesive peak stresses are independent of the joint overlap length at the joint edges. Also, simulated bonding defects, in the form of local adhesive gaps, due to manufacturing processes are investigated to determine the load path redistribution for the DRJ and CSJ configurations. Results for pristine versions of both configurations are included. The defective CSJ joint exhibits severe overloading of certain laminates, while the defective DRJ load redistributions are relatively mild. Between the two primary types of bondline gaps considered for the DRJ configuration, the gap corresponding to the splice plate, a more mature manufacturing operation and also a more easily inspected location than the insert-to-face sheet interface, is noted to be more severe.
A direct joint-to-joint mass-comparison reveals a 164% increase in mass, per unit thickness, between the CSJ and DRJ. To put this in perspective, a second comparison is made using a four-segment sandwich panel barrel. A 3.51% increase in mass is observed between the CSJ and DRJ-based cylinders. Also, for a simplified sizing philosophy, based solely on the peak stresses in the adhesive domain, a CSJ may require a 1.5-inch longer joint overlap than a DRJ. The mass-estimate is recomputed, and the mass percent-increase of the segmented cylinder is reduced to 2.61% over a CSJ configuration.Master of Science
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Zale, Steven A. « Teaching Data Structure Using a Programming by Example System : Effects on Students Achievement and Cognitive Load ». NSUWorks, 2005. http://nsuworks.nova.edu/gscis_etd/946.
Texte intégralRésumé :
In an attempt to help alleviate the complexity of programming, the technique called Programming by Example (PBE) has been developed. Although businesses and educational institutions have embraced PBE systems, it has not been demonstrated that these systems can equally facilitate program learning and achievement by programmers in lieu of the traditional programming courses. The goal of this research was to determine the effects of the use of a PBE system with students who had experience in programming and design. This investigation examined the effects of teaching students a Data Structures course using a PBE system and analyzed their achievements and measured cognitive load. Data from this study were collected at Middlesex County College from four sections of Data Structures using C++ Programming. Data were gathered from the participants during the experimental semester by using a student programming self-efficacy survey and four programming achievement tests. The researcher made use of a C++ and Java programming expert panel to help develop and determine the validity of the content of the student self-efficacy survey and the four Data Structures achievement tests. In addition, students were asked on each test to subjectively evaluate their cognitive load pertaining to the material covered by each question. The data were examined for significant interactions among the students' prior programming languages experiences, exposure to using the PBE system, cognitive load, and achievement. However, due to violations of the MANOY A assumptions, only a descriptive analysis for the results was possible. The descriptive analysis indicated only minimal differences in the participants' levels of student achievement and cognitive load using PBE. The results of the MANOY A tests showed that student achievement and cognitive load were not correlated. The researcher made the following observations based upon the descriptive statistics regarding the combined quiz average scores and cognitive load z scores for all four quizzes. When taught using Agent Sheets, those students possessing high prior experience scored higher combined quiz averages and z scores than those students possessing low prior experience. In addition, those students, who were presented with Agent Sheets, possessing high prior experience scored lower combined quiz averages but higher z scores than those students classified with the same experience level and did not have exposure to the PBE course content.
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Wu, Xiong-Jian. « Motion and wave load analyses of large offshore structures and special vessels in waves ». Thesis, Brunel University, 1990. http://bura.brunel.ac.uk/handle/2438/7865.
Texte intégralRésumé :
Predictions of the environmental loading and induced motional and structural responses are among the most important aspects in the overall design process of offshore structures and ships. In this thesis, attention is focused on the wave loads and excited bodily motion responses of large offshore structures and special vessels. With the aim of improving the existing theoretical methods to provide techniques of theoretical effectiveness, computational efficiency, and engineering practicality in marine and offshore applications, the thesis concentrates upon describing fundamental and essential aspects in the physical phenomenon associated with wave-structure interactions and deriving new methods and techniques to analyse offshore structures and unconventional ships of practical interest. The total wave force arising from such a wave-structural interaction is assumed to be a simple superposition of the potential and the viscous flow force components. The linear potential forces are solved by the Green function integral equation whilst the viscous forces are estimated based on the Morison's damping formula. Forms of the Green function integral equation and the associated Green function are given systematically for various practical cases. The relevant two-dimensional versions are then derived by a transformation procedure. Techniques are developed to solve the integral equation numerically including the interior integral formulation and, in particular, to tackle the mathematical difficulties at irregular frequencies. In applying the integral equations to solve problems with various offshore structures and special vessels, some modified, improved or simplified methods are proposed. At first, simplified method is derived for predictions of the surge, sway and yaw motions of elongated bodies of full sectional geometry or structures with shallow draft. Then, a new shallow draft theory is described for both three- and two-dimensional cases with inclusion of the finite draft effect. Furthermore, a three-dimensional strip method is formulated where the end effects of the body are fully taken into account. Finally, an approximation to the horizontal mean drift forces of multi-column offshore structures are presented. Some new findings are also discussed including the multiple resonances occurring in the motions of multi-hulled marine structures due to the wave-body interaction, the mutual cancellation effect of the diffraction and the radiation forces arising from a full shaped slender body, and so on. Further to those verification studies for individual methods developed, more comprehensive example investigations are given related to two industrial applications. One is a derrick barge semi-submersible with zero forward speed; and the other, a SWATH ship with considerable speed. By correlation of all the proposed approaches with available analytical, numerical and experimental data, the thesis tries to demonstrate a principle that as long as principal physical aspects in the wave-structure interaction problem are properly treated, an appropriately modified or simplified method works, performs well and, sometimes, even better.
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Costa, d'Aguiar Sofia. « Numerical modelling of soil-pile axial load transfer mechanisms in granular soils ». Châtenay-Malabry, Ecole centrale de Paris, 2008. http://www.theses.fr/2008ECAP1075.
Texte intégralRésumé :
L’objectif du travail présenté dans cette thèse est l'analyse et modélisation numérique des mécanismes de transfert de charge axiale entre sol-pieu, dans les sols granulaires. En utilisant un modèle élastoplastique tridimensionnel d'élément finis, une attention particulière est prêtée à la modélisation du comportement de l’interface sol-structure. Ainsi, les outils numériques nécessaires ont été mis en place et les outils existants ont été améliorés afin que, l'analyse de l'interaction sol-pieu soit faisable. Deux nouveaux modèles de comportement 3D sont implémentés dans le code d'éléments finis GEFDYN: un modèle d'interface et, pour le sol, une formulation axisymétrique du modèle multimécanismes de l’ECP, déjà existant et également connus sous le nom de Hujeux. La performance des deux modèles de comportement est comparée avec des résultats expérimentaux: d'abord, en utilisant des essais directs de cisaillement sol-structure et ensuite des essais de charge statiques de pieux en modèle physiques de centrifugeuse. La formulation théorique et l'exécution numérique des modèles constitutifs se sont donc avérées adéquats pour l'analyse des mécanismes de transfert de charge de sol-pieux, pour différents états initiaux du sol, différentes rugosités de la surface sol-pieux et différentes géométries. Finalement, l'applicabilité des modèles proposés est également étudiée pour un cas d’étude réel d’essais de charge statique de pieux forés et à tarière continus, menés dans le site expérimental ISC2 à l’occasion de la 2nd International Conference on the Site Characterization. L’identification des paramètres du sol et la simulation des essais de charge in-situ a été réalisé avec succésThe purpose of the work presented in this thesis, which has a theoretical and numerical character, is the analysis and numerical modelling of soil-pile load transfer mechanisms, in granular soils, when the pile is subjected to axial vertical loads. In the three dimensional elastoplastic finite element model used, particular attention is paid to modelling soil-structure interface behavior. The necessary numerical tools were implemented and the existing ones enhanced so that, the analysis of the soil-pile interaction problem is feasible. Two newly implemented 3D constitutive laws, in the GEFDYN finite element code, are proposed: an interface model and, for soil, an axisymmetric formulation of the existing ECP multimechanism model, also known as Hujeux model. The performance of both constitutive models is compared with experimental results. First, using soil-structure direct shear tests and then, using results of static pile load tests of centrifuge physical models. The theoretical formulation and numerical implementation of the constitutive models proved to be adequate for the analysis of the soil-pile load transfer mechanisms for different soil initial states, soil-pile surface roughness conditions, and different geometries. Finally, the applicability of the proposed models, is also studied for a real case study of pile static load tests carried out in the ISC'2 experimental site, at the occasion of the 2nd International Conference on the Site Characterization. Soil’s laboratory characterization tests and in-situ pile static load tests on bored and CFA piles are simulated, and results successfully compared
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Hanáčík, Jan. « Rozhledna Vršek nad Zlínem ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227754.
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This thesis deals with the design and assessment of the load-bearing structure of the lookout tower. The tower is 37.45 m high with the layout in the shape of a regular octagon. The object is located within the city of Zlín. The project is provisionally drawn in two variants. Hand-static calculation, drawings and engineering report is processed only for one variant. The variants differ in the structure of staircase. The thesis is drawn up pursuant to the standards of ČSN EN.
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Kilgour, Alastair Scott. « Tribometer with programmable motion and load to investigate the influence of molecular structure on wear of orthopaedic polyethylene ». Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4628.
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Total hip arthroplasty commonly involves a hard metallic/ceramic femoral ball component articulating against an acetabular ultra-high molecular weight polyethylene (UHMWPE) counter-bearing. A novel six-station, wear tribometer, featuring programmable load and motion, was designed to further the investigation into wear, sub-surface plasticity and debris generation of UHMWPE. This thesis describes the pin-on-plate device, its validation and subsequent use to assess unirradiated (-PE) and gamma-irradiated highly crosslinked (+PE) UHMWPE wear behaviour. With the emphasis on dynamic loading and a closer gait matched open wear path, the tribometer improves on the clinical relevance of pin-on-plate testing. There is a requirement for this type of machine in order to investigate the directional dependence of wear and debris generation of UHMWPE more accurately, where “simplified” tribometers (adequate for constant load/constant velocity and constant load/sinusoidal velocity work) are not capable or suitable. For the first time in orthopaedic pin-on-plate studies, tests were conducted using an advanced dynamic load synchronised to a more physiologically accurate elliptical motion path. To validate the machine, three orthopaedic polymers of clinical relevance; Polytetrafluroethylene, Polyacetal, and UHMWPE were subjected to linear-reciprocating (LR) and novel elliptical motion paths under a Paul-type load profile. All three polymers showed higher wear factors under elliptical motion, by up to 2 orders of magnitude, agreeing well with explanted values. The UHMWPE elliptical wear factor was comparable to that reported for clinical, where kelliptical = 1.56 x 10-6 mm3/Nm. In the crosslinked study, the mean steady state wear of -PE and +PE groups under linear reciprocating motion was not significantly different. However, under elliptical motion, crosslinking reduced UHMWPE wear by up to 92% when compared to the unirradiated group. In –PE pins worn under LR motion and in +PE pins subjected to both motion paths a sub-surface damage zone with reduced crystallinity and increased strain was measured using Raman spectroscopy. This was attributed to large strain accumulation in the slower wearing surfaces providing a mechanism for de-crystallisation. The discovery of such a near-surface layer is in good agreement with critical strain wear models. In disagreement, however, we found the sliding induced layer to extend to greater depths than previous reported.
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Návarová, Michaela. « Nosná konstrukce montovaného bytového domu ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227700.
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The subject of this thesis is the static design of load bearing structure of a flat-building. The flat-building is designed as a two-floors building with cock-loft. The ground plan of the house is 15,04 x 16,74 m, the height is 9,25 m. The house is considered as II. snow area and II. wind area. The load bearing structure is designed in two variations. In first variation is designed load baering structure of the house by steel thin-walled sections, in second variation is designed by timber sections. In both variations load bearing structures is made of columns, garlands, ceiling beams and roof truss.
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Paik, Kwang Jun. « Simulation of fluid-structure interaction for surface ships with linear/nonlinear deformations ». Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/569.
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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.
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Otten, Zachary David. « Seismic Retrofitting of a Historic Structure with Limited Construction Documentation ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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Many buildings constructed during the middle of the 20th century were constructed with criteria that fall short of current requirements. Although shortcomings are possible in all aspects of the design, the inadequacies in terms of seismic design present a more pressing issue to human life. This risk has been seen in various earthquakes that have struck Italy recently, and subsequently, the codes have been altered to account for this underestimated danger. Structures built after these changes remain at risk and must be retrofitted depending on their use. This report centers around the Giovanni Michelucci Institute of Mathematics at the University of Bologna and the work required to modify the building so that it can withstand 60% of the current design requirements.
The goal of this particular report is to verify the previous reports written in Italian and present an accurate analysis along with intervention suggestions for this particular building. The work began with an investigation into the previous sources and work to find out how the structure had been interpreted. After understanding the building, corrections were made where required, and the failing elements were organized graphically to more easily show where the building needed the most work. Once the critical zones were mapped, remediation techniques were tested on the top floor, and the modeling techniques and effects of the interventions were presented to assist in further work on the structure.
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Cantoni, Lorenzo. « Load Control Aerodynamics in Offshore Wind Turbines ». Thesis, KTH, Kraft- och värmeteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291417.
Texte intégralRésumé :
Due to the increase of rotor size in horizontal axis wind turbine (HAWT) during the past 25 years in order to achieve higher power output, all wind turbine components and blades in particular, have to withstand higher structural loads. This upscalingproblem could be solved by applying technologies capable of reducing aerodynamic loads the rotor has to withstand, either with passive or active control solutions. These control devices and techniques can reduce the fatigue load upon the blades up to 40% and therefore less maintenance is needed, resulting in an important money savings for the wind farm manager. This project consists in a study of load control techniques for offshore wind turbines from an aerodynamic and aeroelastic point ofview, with the aim to assess a cost effective, robust and reliable solution which could operate maintenance free in quite hostile environments. The first part of this study involves 2D and 3D aerodynamic and aeroelastic simulations to validate the computational model with experimental data and to analyze the interaction between the fluid and the structure. The second part of this study is an assessment of the unsteady aerodynamic loads produced by a wind gust over the blades and to verify how a trailing edge flap would influence the aerodynamic control parameters for the selected wind turbine blade.På grund av ökningen av rotorstorleken hos horisontella vindturbiner (HAWT) under de senaste 25 åren, en design som har uppstod för att uppnå högre effekt, måste alla vindkraftkomponenter och blad stå emot högre strukturella belastningar. Detta uppskalningsproblem kan lösas genom att använda metoder som kan minska aerodynamiska belastningar som rotorn måste tåla, antingen med passiva eller aktiva styrlösningar. Dessa kontrollanordningar och tekniker kan minska utmattningsbelastningen på bladen med upp till 40 % och därför behövs mindre underhåll, vilket resulterar i viktiga besparingar för vindkraftsägaren. Detta projekt består av en studie av lastkontrolltekniker för havsbaserade vindkraftverk ur en aerodynamisk och aeroelastisk synvinkel, i syfte att bedöma en kostnadseffektiv, robust och pålitlig lösning som kan fungera underhållsfri i tuffa miljöer. Den första delen av denna studie involverar 2D- och 3D-aerodynamiska och aeroelastiska simuleringar för att validera beräkningsmodellen med experimentella data och för att analysera interaktionen mellan fluiden och strukturen. Den andra delen av denna studie är en bedömning av de ojämna aerodynamiska belastningarna som produceras av ett vindkast över bladen och för att verifiera hur en bakkantklaff skulle påverka de aerodynamiska styrparametrarna för det valda vindturbinbladet.
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Horský, Vojtěch. « Přístřešek restaurace s tanečním parketem ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265308.
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In my diploma thesis I designed 2 options for an arch roofing of place for dancing next to the restaurant in Dolní Jablonná. The first solution was designed as a timber structure with internal supporting arch from glue laminated timber. The second solution was designed as a two pin-supported steel beam. These variants were predesigned and as the final solution was chosen the timber structure. I designed a rafter, a glue laminated arch, a purlin, an anchorage and field joints. The thesis is including drawings of the layout design, details and anchorage plans.
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Šandor, Peter. « Víceúčelová sportovní hala ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409834.
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The goal of my thesis is the design of a multipurpose sport hall in Litoměřice locality made in two separate variants. Objects ground plan dimensions are 38x38 meters and the height of the object is 16 meters. Used material is S235 steel and C20/25 concrete. The periphery and roof casing of the object is realized from sandwich panels. The carrying construction of the object is made from cross truss, oblong truss and from pillars. Thesis consists of assessing the carrying elements of the construction, selected details and drawing documentation.
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Huang, Yiqun. « The effects of fuel volatility, structure, speed and load on HC emissions from piston wetting in direct injection spark ignition engines ». Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035951.
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Duport, Chloé. « Modeling with consideration of the fluid-structure interaction of the behavior under load of a kite for auxiliary traction of ships ». Thesis, Brest, École nationale supérieure de techniques avancées Bretagne, 2018. http://www.theses.fr/2018ENTA0011/document.
Texte intégralRésumé :
Cette thèse fait partie du projet beyond the sea® qui a pour but de développer la traction par cerf-volant à boudins gonflés (kite) comme système de propulsion auxiliaire des navires. Comme le kite est une structure souple, il est nécessaire de mettre en place une boucle d’interaction fluide-structure pour calculer la géométrie du kite en vol et ses performances aérodynamiques. Un modèle de Ligne Portante 3D Non-Linéaire a été développé pour pouvoir gérer ces ailes non planes, avec des angles de dièdre et de flèche qui varient le long de l’envergure, et également pour pouvoir prendre en compte la non-linéarité du coefficient de portance de la section aérodynamique. Le modèle a été vérifié par des simulations RANSE sur différentes géométries et donne des résultats satisfaisants pour des angles d’incidence et de dérapage variant jusqu’à 15°, avec des différences relatives de quelques pour cent pour l’estimation de la portance globale de l’aile. Les résultats locaux sont aussi correctement estimés, le modèle est capable d’estimer la position du minimum et du maximum de chargement local, selon l’envergure de l’aile, et cela même pour une aile en dérapage. En parallèle, un modèle structure a été développé. L’idée principale du modèle Kite as a Beam est de réduire le kite à un ensemble d’éléments poutre, chacun équivalent à une partie du kite composé d’une section du boudin d’attaque, de deux lattes gonflées et de la canopée correspondante. Le modèle Kite as a Beam a été comparé à un modèle éléments finis complet du kite sur des cas de déplacements élémentaires. Les résultats montrent certaines différences de comportement entre les deux modèles, avec notamment une surestimation de la raideur en torsion pour le modèle Kite as a Beam. Finalement, le modèle Kite as a Beam a été couplé avec la Ligne Portante 3D Non-Linéaire, puis comparé au modèle éléments finis, couplé également avec la Ligne Portante. La réduction du temps de calcul est réellement importante mais les résultats de la comparaison montrent la nécessité de calibrer le modèle Kite as a Beam pour pouvoir retrouver correctement les résultats du modèle éléments finisThe present thesis is part of the beyond the sea® project which aims to develop tethered kite systems as auxiliary devices for ship propulsion. As a kite is a flexible structure, fluid-structure interaction has to be taken into account to calculate the flying shape and aerodynamic performances of the wing. A 3D Non-Linear Lifting Line model has been developed to deal with non-straight kite wings, with dihedral and sweep angles variable along the span and take into account the non-linearity of the section lift coefficient. The model has been checked with 3D RANSE simulations over various geometries and produces satisfactory results for range of incidence and sideslip up to 15°, with typical relative differences of few percent for the overall lift. The local results are also correctly estimated, the model is able to predict the position of the minimum and maximum loading along the span, even for a wing in sideslip. Simultaneously, a structure model has been developed. The core idea of the Kite as a Beam model is to approximate a Leading Edge Inflatable kite by an assembly of beam elements, equivalent each to a part of the kite composed of a portion of the inflatable leading edge, two inflatable battens and the corresponding canopy. The Kite as a Beam model has been compared to a complete kite Finite Element model over elementary comparison cases. The results show the behaviour differences of the two models, for example the torsion stiffness is globally overestimated by the Kite as a Beam model. Eventually, the Kite as a Beam model coupled with the 3D Non-Linear Lifting Line model is compared to the complete finite element model coupled with the 3D Non-Linear Lifting Line model. The gain in computation time is really significant but the results show the necessity of model calibration if the Kite as a Beam model should be used to predict the results of the complete finite element model
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Ananthasubramanian, Srikanth, et Priyank Gupta. « Early assessment of composite structures : Framework to analyse the potential of fibre reinforced composites in a structure subjected to multiple load case ». Thesis, KTH, Lättkonstruktioner, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235309.
Texte intégralRésumé :
To meet the need of lightweight chassis in the near future, a technological step of introducing anisotropic materials like Carbon Fibre Reinforced Plastics (CFRP) in structural parts of cars is a possible way ahead. Though there are commercially available tools to find suitability of Fibre Reinforced Plastics (FRPs) and their orientations, they depend on numerical optimization and complexity increases with the size of the model. Nevertheless, the user has a very limited control of intermediate steps. To understand the type of material system that can be used in different regions for a lightweight chassis, especially during the initial concept phase, a more simplified, yet reliable tool is desirable.The thesis aims to provide a framework for determining fibre orientations according to the most-ideal loading path to achieve maximum advantage from FRP-materials. This has been achieved by developing algorithms to find best-fit material orientations analytically, which uses principal stresses and their orientations in a finite element originating from multiple load cases. This thesis takes inspiration from the Durst criteria (2008) which upon implementation provides information on how individual elements must be modelled in a component subjected to multiple load cases. This analysis pre-evaluates the potential of FRP-suitable parts. Few modifications have been made to the existing formulations by the authors which have been explained in relevant sections.The study has been extended to develop additional MATLAB subroutines which finds the type of laminate design (uni-directional, bi-axial or quasi-isotropic) that is suitable for individual elements.Several test cases have been run to check the validity of the developed algorithm. Finally, the algorithm has been implemented on a Body-In-White subjected to two load cases. The thesis gives an idea of how to divide the structure into sub-components along with the local fibre directions based on the fibre orientations and an appropriate laminate design based on classical laminate theory.
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Hansson, Henrik, et Martin Ludvigsson. « Praktisk Lastnedräkning och Stomstabilitet enligt Eurokoder ». Thesis, KTH, Byggvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-174067.
Texte intégralRésumé :
Eurokoderna som utgör svenska normer för verifiering av bärförmåga, stadga och beständighet är i en fortgående utvecklingsfas och är ibland svåra och tidsödande att tillämpa i konstruktionsarbetet. Normerna anpassas kontinuerligt efter att frågor debatteras i branschen och det är viktigt att användarna av Eurokoderna håller sig uppdaterade. Svårtolkade begrepp och definitioner tillsammans med en omständig struktur i Eurokoderna skapar merarbete för användarna. Detta examensarbete sammanställer nödvändig information samt undersöker och utvecklar tillhörande begrepp för två ämnen, lastnedräkning och stomstabilitet. Examensarbetet kommer likt en handbok kunna användas i vardagligt konstruktörsarbete för att snabbt hitta rätt i Eurokoderna och bidra till att reda ut oklarheter kring de två berörda ämnena. Beräkningsexempel är upprättade som praktisk vägledning för respektive ämne där Eurokoderna tillämpas och hänvisas till. Examensarbetet är inriktat på handberäkningar. Dessa handberäkningar kan ligga till grund för initiala bedömningar av ett bärverks dimensioner och övergripande stabilitet men även vara ett stöd i beräkningar i bygghandlingsskeden.The Eurocodes, which serve as the Swedish standards for verification of mechanical resistance and stability, are in an ongoing development phase and are sometimes difficult and time consuming to apply in the design process. The standards are continuously adapted to issues debated in the industry and it is important that users of the Eurocodes keep themselves up to date. Indistinct terms and definitions in the Eurocodes create, together with an inconvenient structure, extra work for users. This thesis compiles the necessary information and examines and elaborates terms related to two topics, load distribution and structure stability. Similar to a handbook, this thesis can be used in designer’s everyday work to quickly find the right Eurocodes and help sort out the confusion related to the topics in this thesis. Calculation examples are given as a practical guide where Eurocodes are applied and referred to. The thesis is focused on hand calculations. These hand calculations could act as a base for initial assessments concerning structure dimensions and overall stability as well as a guide during final calculations for construction drawings.
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Sridi, Marwa. « Un modèle de structure de données Cache-aware pour un parallélisme et un équilibrage dynamique de la charge ». Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAM095.
Texte intégralRésumé :
Les architectures parallèles actuelles intègrent des processeurs avec un nombre de cœurs à mémoire partagée de plus en plus important et répondant à des contraintes d'utilisation spécifiques, notamment en matière de gestion de la mémoire cache. Pour tirer parti de cette puissance, un parallélisme unique à mémoire distribuée, nécessaire pour gérer les communications inter-nœuds, présente le désavantage de ne pas s'adapter directement aux particularités des architectures multi-cœurs. De plus, les environnements de calcul à mémoire partagée proposent des techniques pour l'équilibrage de la charge entre les cœurs disponibles, qui se présentent de manière plus délicate dans un contexte de mémoire distribuée. Ainsi, des modèles de programmation tels qu’OpenMP et XKAAPI sont une réponse bien adaptée aux spécificités de ces architectures.Au regard de ces problématiques, nous nous sommes intéressés, à développer une approche Hardware-aware prenant en considération l'organisation hiérarchique des architectures parallèles à mémoire partagée. Notre approche offre un modèle d'optimisation de l'utilisation des espaces de stockage dans ce contexte de parallélisme. Pour démontrer la pertinence de cette approche, nous l'avons implémentée dans le logiciel de simulation en dynamique rapide des fluides et des structures EUROPLEXUS, en se concentrant sur le parallélisme à mémoire partagée, complémentaire d'une approche à mémoire distribuée développée par ailleurs. De par son large panel d'applications, EUR0PLEXUS est caractérisé par une structure de données très riche et des dépendances très complexes entre ses routines. Nous nous sommes concentrés sur l'accélération de la boucle principale itérant sur les éléments du maillage. L'hétérogénéité des formulations et des matériaux des éléments pouvant co-exister dans un même modèle simulé engendre une grande variabilité entre les coûts des itérations de cette boucle. Une première parallélisation de cette boucle avec la bibliothèque XKAAPI basée sur un ordonnancement dynamique par vol de tâches a été implémentée. Cependant, malgré l'accélération atteinte par cette implémentation parallèle, les performances ont été freinées par les coûts des accès fréquents et dispersés à une structure de données complexe rendant l'exécution du code délicate à optimiser. A cause de cette structuration, une grande partie du temps d'exécution est écoulée dans des défauts de cache.Ces travaux reposent sur l’implémentation d'un modèle de structure de données assurant une meilleure localité des accès. Il consiste majoritairement à passer de la structure de données globale dans laquelle les champs physiques sont stockés dans des tableaux séparés à une structure basée sur le stockage des données dans des structures indépendantes appelées groupes. Ces groupes contiennent les données relatives à un certain nombre d'éléments dans des tableaux locaux. Ce nombre est un paramètre réglable selon la taille des niveaux du cache. Concrètement, cette méthode revient à imbriquer la boucle élémentaire dans une boucle itérant sur les groupes. Les itérations sur les groupes sont distribuées sur les cœurs de l'architecture. L'exécution de la boucle interne est séquentielle par cœur. Les meilleurs résultats sont obtenus pour des groupes de la taille du cache L2 privé par cœur. Pour cette taille particulière, l'utilisation d'un équilibrage dynamique de charge sous XKAAPI nous a permis de doubler l'accélération de la boucle élémentaire par rapport à une parallélisation avec XKAAPI de la version de référence du code.La deuxième partie de cette thèse repose sur la parallélisation de la boucle élémentaire à l'intérieur de la boucle déjà parallélisée. Nous avons démontré que ce second niveau de parallélisme est moins performant que celui à un seul niveau. Cependant, ce parallélisme imbriqué pourrait être intéressant sur les architectures Xeon Phi de Intel intégrant des cœurs hyper-threadés au niveau de leurs unités de calculThe current parallel architectures integrate processors with many cores to shared memory growing and responding to specific usage constraints, particularly in the cache management. To take advantage of this power, a unique distributed memory parallelism, to manage the inter-node communications is not directly adapted to the characteristics of multi-core architectures. In addition, the shared memory computing environments offer techniques for balancing the load among available cores more appropriate than those in a distributed memory context.Thus, programming models like OpenMP and KAAPI is a tailored response to the specific characteristics of these architectures.Given these issues, we are interested in developing a hardware-aware approach taking into consideration the hierarchical organization of parallel architectures with shared memory. Our approach provides an optimization model for the use of storage space in this context of parallelism.To prove the pertinence of this approach, we have implemented it in the fast dynamic simulation software EUROPLEXUS of fluids and structures, focusing on the shared memory parallelism complementary to the distributed memory approach developed elsewhere. Because of its wide range of applications, EUROPLEXUS is characterized by a very rich data structure and very complex dependencies among its routines. We focused on accelerating the main loop iterating over the mesh elements. The heterogeneity of the formulations and the materials of the elements that can co-exist in the same simulated model generates a large variability between the costs of the iterations of this loop. A first parallelization of the loop with the XKAAPI library based on a dynamic workstealing scheduling has been implemented. However, despite the acceleration achieved by the parallel implementation, performance has been restrained by frequent and dispersed access costs to a complex data structure. This makes the implementation of the code difficult to optimize. Because of this structure, much of the execution time has elapsed in cache misses. The work is based on the implementation of a model approximating the data structure that ensures a better access locality. It mainly consists in moving from the global data structure in which the physical fields are stored in separate tables to a structure based on the storage of data in independent structures called groups. These groups contain the data relating to a number of elements in the local tables. This number is an adjustable parameter depending on the size of the cache levels. Specifically, this method returns to the nest of the elementary loop in a loop iterating on groups. The iterations among the groups are distributed over the cores of the architecture.The execution of the inner loop is sequentially by core. The best results are obtained for groups of the L2 cache size. For this particular size, the use of a dynamic load balancing in XKAAPI allowed us to double the acceleration of the elementary loop compared to the reference version of the code. The second part of this thesis is based on the parallelization of elementary loop inside the already parallelized loop. We demonstrated that this second level of parallelism is less efficient than the single. However, this nested parallelism might be interesting on Intel Xeon Phi architectures incorporating hyper-threaded cores at their calculation units
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Škatula, Václav. « Hangár ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265485.
Texte intégralRésumé :
The final thesis is focused on a project of a load bearing structure of a aircraft maintenance hangar that has a rectangular ground plan 60,0x120,0 m and includes suspended mobile hoist of loading capacity 5,0t. The object is situated in the airport area of Ostrava Mošnov. The task provides two versions of design. The first version consists of eleven traverse joining beams witch are distanced twelve meters from each other. The second version consists of thirteen traverse joining beams witch are distanced ten meters from each other. The thesis focuses on the load pressure of the steel construction, the main emphasis being placed on the single structural components and assembling components. The calculation meet the standards of ČSN EN.
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Ford, Rebecca Jane. « The effect of shading and crop load on flavour and aroma compounds in Sauvignon blanc grapes and wine ». Master's thesis, Lincoln University. Agriculture and Life Sciences Division, 2007. http://theses.lincoln.ac.nz/public/adt-NZLIU20080523.100013/.
Texte intégralRésumé :
The effects of crop load and berry exposure on the composition of Marlborough Sauvignon blanc grapes and wine from the Brancott vineyard, Blenheim, were explored.
Commercially grown, 2-cane and 4-cane Sauvignon blanc vines were used with a row orientation of north-south. Two exposure treatments were imposed in the following manner: complete leaf removal was undertaken in the fruit zone and 50% shade cloth was erected to give a uniform shading treatment to half the trial vines. Weekly thirty-berry and whole bunch samples were taken from each of the 32 plots with the exception of the veraison period when two samples per week were taken. Vine vigour was assessed using pruning and leaf area per vine data. Harvest occurred on different dates for 2-cane and 4-cane pruned vines so that fruit attained from both treatments had similar °Brix. Fruit was processed at the Lincoln University winery. Must analysis and wine analysis were
undertaken. As expected, 4-cane vines had almost double the yield of 2-cane vines. Higher crop load
significantly reduced leaf area per shoot and shoot thickness. Lower leaf area to fruit ratio
for 4-cane berries resulted in delayed onset of veraison and slowed the rate of sugar accumulation. Crop load, which limited leaf area to fruit ratio, appeared to be the dominant
factor in determining timing of grape physiological ripeness as expressed by °Brix over
other factors such as fruit exposure. Malic acid, tartaric acid, IPMP (iso-propylmethoxypyrazine)
and IBMP (iso-butyl-methoxypyrazine) were lower at equivalent °Brix in 4-cane compared with 2-cane berries. Significantly higher concentrations of quercetin were found in exposed compared to shaded berries. Must analysis showed a significant influence of crop load on berry titratable acidity and pH, reflecting berry ripening results. Exposure significantly increased the concentrations of nitrogenous compounds in 4-cane must yet showed no influence on 2-cane must.
After wine processing lower malic acid concentrations in wines made from 100% exposed
fruit became evident in lower wine titratable acidity but showed no influence on wine pH.
Bentonite addition to wines had a small but statistically significant influence on wine by
reducing pH, titratable acidity and alcohol. Bound sulphur concentrations were significantly
higher in 4-cane versus 2-cane wines. At harvest, methoxypyrazine levels in grapes and wines were very low; IBMP concentrations where significantly lower than those normally found in Sauvignon blanc wines from Marlborough. This was attributed to the absence of basal leaves from the shoots of ripening berries.
The results suggest that leaf area to fruit ratio is a powerful determinant of grape and wine
quality.
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Abboud, Youssef. « Développement d’un macroélément pour l’étude des fondations superficielles sous charge sismique ». Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1010/document.
Texte intégralRésumé :
Cette thèse vise à développer une méthode pour la justification des fondations superficielles sous charge sismique dans le cadre du nouveau zonage sismique de la France, entré en vigueur en 2011 et des justifications post Fukushima. Elle s’inscrit dans le cadre d’un contrat de recherche entre l’IFSTTAR et EDF CEIDRE.Un modèle basé sur le concept de macroélément est développé pour étudier l’interaction sol-structure (ISS) en prenant en compte les différentes non linéarités. Sa formulation se base sur la théorie de l’élastoplasticité et s’inspire des normes en vigueur (Eurocodes 7 et 8) et. Les différents paramètres sont définis à partir d’essais au laboratoire ou in situ, ou à partir de simulations numériques en conditions statiques. Les coûts de calcul sont réduits du fait que les non linéarités liées à l’interaction sol-structure sont concentrés en des points particuliers du modèle de calcul. L’avantage du macroélément réside dans une formulation en efforts et déplacements, ce qui facilite son utilisation pour la justification des fondations (capacité portante, glissement, décollement, tassements, translations, distorsions et rotations).Le macroélément est implémenté dans le code par éléments finis CESAR LCPC et permet de simuler le comportement statique et sismique d’une fondation superficielle. Trois approches pour la modélisation de la radiation des ondes sismiques dans le sol sont comparées en considérant des chargements statiques et sismiques.Ensuite, des études paramétriques sont réalisées sur une structure en mettant en jeu plusieurs signaux réels. L’influence des différents paramètres de nocivité sur le comportement de la structure est étudiée.Le comportement statique et sismique d’un ouvrage réel est aussi analysé. Il s’agit d’un bâtiment fondé sur un radier reposant sur un sol stratifié. L’aléa sismique est défini par 5 accélérogrames d’accélération maximale égale à 0.4g. Des justifications normatives sont menées en se basant sur les résultats des différentes simulations réaliséesThis PhD work concerns the elaboration of a method to verify the seismic sustainability of shallow foundations considering 2011 seismic zoning of France. It is a part of a research contract between EDF CEIDRE and IFSTTAR.To this end, a macroelement based model is developed in order to assess nonlinear soil structure interaction. The elastoplastic formulation of the macroelement constitutive model is compliant with the classical plasticity theory. The formulations for the plastic mechanisms are inspired from the applied standard (Eurocodes 7 & 8). The rate dependent response and the effects of the embedment and the soil inertia efforts are taken into account. The parameters for the constitutive model are defined from laboratory or field tests, or calibrated from static finite element method simulations. The calculation cost is significantly reduced due to the simplified modelling of the soil and its non linearities. Another advantage is that the macroelement based tool is formulated in terms of generalized variables (forces and displacements): this promotes its application in the verification of the sustainability of shallow foundations (bearing capacity, sliding, overturning, settlements, translations, rotations and distortions).The macroelement is implemented in the Finite Element software CESAR LCPC. It allows to simulate the static and the seismic behaviour of a shallow foundation. Three alternative approaches to assess SSI through this model are possible. These alternative approaches are explained and tested under static and seismic load.Then, it is used to perform parametric studies involving various input motions derived from earthquake recordings. The seismic response of a simple structure is studied with respect to the input motion key parameters.Finally, the static and seismic behaviour of a real structure is analysed. The structure is founded on a large raft foundation laying on a multi-layered soil. The seismic hazard is defined by five 0.4 g-PGA accelerograms. Verification to the applied standards is performed on the base of the simulation results, considering many features of the seismic behaviour
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Chytil, Jan. « Statická zatěžovací zkouška nosné konstrukce ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227811.
Texte intégralRésumé :
Subject of the thesis is experimental verification of load capacity of construction for storage coal by using load test. In the first part, the analysis of sorts of load tests is made and its execution in causality with standard regulations. Further possible options of bringing test load are described and also the method of evaluation of static load test. Second part looks into the analysis of means of measurement which can be used to determine required quantity. Final part is dedicated to realization and evaluation of the load test on material construction followed by comparison of experimental values with values established on a model of construction created by using computing program.
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Kopal, Marek. « Autosalon ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372263.
Texte intégralRésumé :
By submitting my thesis I designed three variants of the steel construction of the motor show. The ground dimensions of the entire structure are 56 x 40 m. The building eaches a height of 21 m above the surrounding terrain. The object is the administrative part of the rectangular ground plan and the exhibition space of the perimeter ground plan. The circular part is a covered dome. Variants differ in design of the radial arc cross section in the dome cover. Part of the main structural elements. The winning variant includes a solution of selected details elaboration of detailed drawings of solved connections and creation of workshop documentation of the selected work.
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Andersson, Maria, et Hanna Kristofferson. « Structural Optimization of Product Families : With Application to Vehicle Body Structures ». Thesis, Linköping University, Department of Mechanical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6078.
Texte intégralRésumé :
Some products share one or two modules and while developing these products, structural optimization with stiffness as the objective function can be a useful tool. There might be no or very little CAD-data available in the pre-development phase and it is not certain that existing designs can be, or is desirable to use as a reference. The main objective of this thesis is to establish an accurate and fast-to-use methodology which can be utilized while developing new cars.
In this thesis, the Volvo products S40, V50 and C70 serve as a basis for this case study. All the models are beam structures and the masses of components are added as point and line masses. Several optimization analyses are performed on one or three products exposed to seven load cases. Additional analyses with shell elements, more simplified models and changed load case balance achieved by normalization of the different load case compliances are also studied to investigate how these factors influence the results.
Analyses show that front crash to a great extent dominates the results while normalization increases the influence of the remaining load cases. Since front crash is dominating and the front area is shared in all products, the performance is remarkably similar when three products are optimized compared to separate analyses of one product. Analysis of models without added point or line masses gives a result which greatly differs from previous results and therefore shows that added masses are required. The methodology is applicable to develop products and detect new load paths through the car.