Dissertations / Theses on the topic 'Nonlinear static'
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Friesecke, Gero. "Static and dynamic problems in nonlinear mechanics." Thesis, Heriot-Watt University, 1993. http://hdl.handle.net/10399/1458.
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Seywald, Klaus. "Wingbox Mass Prediction considering Quasi-Static Nonlinear Aeroelasticity." Thesis, KTH, Flygdynamik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-59014.
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Nonplanar wing configurations promise a significant improvement of aerodynamic efficiency and are therefore currently investigated for future aircraft configurations. A reliable mass prediction for a new wing configuration is of great importance in preliminary aircraft design in order to enable a holistic assessment of potential benefits and drawbacks. In this thesis a generic numerical modeling approach for arbitrary unconventional wing configurations is developed and a simulation tool for their evaluation and mass prediction is implemented. The wingbox is modeled with a nonlinear finite element beam which is coupled to different low-fidelity aerodynamic methods obtaining a quasi-static aeroelastic model that considers the redistribution of aerodynamic forces due to deformation. For the preliminary design of the wingbox various critical loading conditions according to the Federal Aviation Regulations are taken into account. The simulation tool is validated for a range of existing aircraft types. Additionally, two unconventional configurations, the C-wing and the box-wing, are analyzed. The outlook provides suggestions for extensions and further development of the simulation tool as well as possible model refinements.
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Obst, Andreas W. "Nonlinear static and transient analysis of generally laminated beams." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-10102009-020113/.
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Atik, Malik. "Seismic evaluation of tall building structures using nonlinear static procedures." Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10116/document.
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L’analyse dynamique non linéaire constitue la méthode la plus efficace pour l'évaluation de la réponse non linéaire des structures soumises à de fortes sollicitations sismiques. Compte tenu de la complexité associée à l'analyse non linéaire temporelle, l'utilisation de l'analyse statique équivalente «Push-over » constitue une alternative simple et efficace à l'analyse dynamique temporelle. Cette thèse développe une méthode statique non linéaire innovante pour évaluer le comportement sismique des immeubles de grande hauteur.Dans la première partie, le modèle "continuum" qui est un outil simple et efficace de l'analyse des immeubles de grande hauteur à contreventement mixte est revisité. L'influence de la précision de calcul dans la détermination de la hauteur optimale d'interruption des voiles est examinée tout en analysant la relation entre la hauteur optimale et les sollicitations induites. La deuxième partie propose une nouvelle procédure Push-over adaptative à exécution unique pour l'évaluation sismique des structures. Cette méthode possède deux avantages principaux : elle représente un outil pratique intégrant l’effet des modes supérieurs avec une interaction complète entre eux. D'un autre côté, elle permet d'éviter les critiques relatives aux analyses adaptatives à exécution unique. La troisième partie présente une méthode innovante permettant la détermination du point de fonctionnement des immeubles de grande hauteur. Le principe des méthodes adaptatives Push-over à exécution unique est intégré à la méthode du spectre de capacité proposé par le règlement ATC -40 dont l'application est limitée aux structures oscillant au mode fondamentalNon linear dynamic analysis constitutes the most powerful method for the assessment of the non linear seismic response of structures subjected to strong earthquake motions. Considering the complexity associated to time history analysis, the use of nonlinear static techniques, or pushover analysis constitutes an efficient and easy to use alternative to dynamic analysis. This thesis develops innovative static nonlinear method to assess the seismic behavior of high-rise buildings. It is composed of three parts:In the first part, the continuum model which constitutes a simple and efficient tool to analyze high-rise wall-frame buildings is revisited. The influence of calculation precision in specifying the optimum level of wall curtailment is discussed. The relationship between the curtailment level and the resulting internal forces is investigated. The second part proposes a new single-run adaptive pushover method for the seismic assessment of shear wall structures. This method has two main advantages: It is practical tool to integrate the effect of higher modes with full interaction between them and it overcomes the criticisms forwarded against the previous single-run adaptive pushover analyses. The proposed method is presented as well as its numerical implementation. The third part presents an innovative method to specifying the seismic peak response quantities of the tall structures. The principle of the single-run adaptive pushover procedures is integrated with the capacity spectrum method proposed by ATC-40 (1996). Where, this latter is limited for structures that vibrate primarily in the fundamental mode
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Shafiei-Tehrany, Reza. "Nonlinear dynamic and static analysis of I-5 Ravenna Bridge." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/R_Shafiei-Tehrany_112608.pdf.
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Thesis (M.S. in civil engineering)--Washington State University, December 2008.Title from PDF title page (viewed on Apr. 10, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 127-133).
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Shi, Guangyu. "Nonlinear static and dynamic analyses of large-scale lattice-type structures and nonlinear active control by piezo actuators." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/19176.
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Sotoudeh, Zahra. "Nonlinear static and dynamic analysis of beam structures using fully intrinsic equations." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41179.
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Beams are structural members with one dimension much larger than the other two. Examples of beams include propeller blades, helicopter rotor blades, and high aspect-ratio aircraft wings in aerospace engineering; shafts and wind turbine blades in mechanical engineering; towers, highways and bridges in civil engineering; and DNA modeling in biomedical engineering. Beam analysis includes two sets of equations: a generally linear two-dimensional problem over the cross-sectional plane and a nonlinear, global one-dimensional analysis.
This research work deals with a relatively new set of equations for one-dimensional beam analysis, namely the so-called fully intrinsic equations. Fully intrinsic equations comprise a set of geometrically exact, nonlinear, first-order partial differential equations that is suitable for analyzing initially curved and twisted anisotropic beams. A fully intrinsic formulation is devoid of displacement and rotation variables, making it especially attractive because of the absence of singularities, infinite-degree nonlinearities, and other undesirable features associated with finite rotation variables.
In spite of the advantages of these equations, using them with certain boundary conditions presents significant challenges. This research work will take a broad look at these challenges of modeling various boundary conditions when using the fully intrinsic equations. Hopefully it will clear the path for wider and easier use of the fully intrinsic equations in future research.
This work also includes application of fully intrinsic equations in structural analysis of joined-wing aircraft, different rotor blade configuration and LCO analysis of HALE aircraft.
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Sakamoto, Takashi. "Nonlinear static and dynamic analysis of flexible risers subjected to vortex excitation." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309379.
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Vorfolomeyeva, Yuliya. "Nonlinear static analysis of rubble-stone masonry buildings performed with equivalent frame method." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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Nonlinear static analysis is an efficient tool for performance assessment of masonry structures. In particular, it facilitates the accurate prediction of seismic response of a structure to earthquakes. Numerical models based on Equivalent Frame Method allow to predict realistic failure modes observed after preceding seismic events with reasonable computational effort, a characteristic which is suitable for engineering practice. This thesis deals with nonlinear incremental static (pushover) analysis of masonry buildings and the subsequent discussion of the obtained results. TreMuri software is used for developing the numerical models, which are then analysed on the basis of elastic acceleration response spectra obtained according to the Nepal National Building Code. Different structural improvement techniques are implemented in the models and compared in order to determine their impact on seismic performance. Elastic stiffness obtained with the nonlinear analysis is examined in contrast to analytical estimation of the same, made with various mathematical models.
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Koko, Tamunoiyala Stanley. "Super finite elements for nonlinear static and dynamic analysis of stiffened plate structures." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30723.
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The analysis of stiffened plate structures subject to complex loads such as air-blast pressure waves from external or internal explosions, water waves, collisions or simply large static loads is still considered a difficult task. The associated response is highly nonlinear and although it can be solved with currently available commercial finite element programs, the modelling requires many elements with a huge amount of input data and very expensive computer runs. Hence this type of analysis is impractical at the preliminary design stage. The present work is aimed at improving this situation by introducing a new philosophy. That is, a new formulation is developed which is capable of representing the overall response of the complete structure with reasonable accuracy but with a sacrifice in local detailed accuracy. The resulting modelling is relatively simple thereby requiring much reduced data input and run times. It now becomes feasible to carry out design oriented response analyses.
Based on the above philosophy, new plate and stiffener beam finite elements are developed for the nonlinear static and dynamic analysis of stiffened plate structures. The elements are specially designed to contain all the basic modes of deformation response which occur in stiffened plates and are called super finite elements since only one plate element per bay or one beam element per span is needed to achieve engineering design level accuracy at minimum cost. Rectangular plate elements are used so that orthogonally stiffened plates can be modelled.
The von Karman large deflection theory is used to model the nonlinear geometric behaviour. Material nonlinearities are modelled by von Mises yield criterion and associated flow rule using a bi-linear stress-strain law. The finite element equations are derived using the virtual work principle and the matrix quantities are evaluated by
Gauss quadrature. Temporal integration is carried out using the Newmark-β method with Newton-Raphson iteration for the nonlinear equations at each time step.
A computer code has been written to implement the theory and this has been applied to the static, vibration and transient analysis of unstiffened plates, beams and plates stiffened in one or two orthogonal directions. Good approximations have been obtained for both linear and nonlinear problems with only one element representations for each plate bay or beam span with significant savings in computing time and costs. The displacement and stress responses obtained from the present analysis compare well with experimental, analytical or other numerical results.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Shyu, In-Ming Kevin. "Forced, nonlinear, planar and nonplanar oscillations of a cantilvered beam including static deflection." Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-06062008-171257/.
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Ozmun, Phillip M. "Nonlinear control and design methodologies for electrostatic MEMS devices." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Theses/OZMUN__16.pdf.
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Gaheen, Mohammed El-Nabawey A. "Static and dynamic finite element analysis of pneumatic tyres including anisotropic and nonlinear effects." Thesis, Cranfield University, 1987. http://hdl.handle.net/1826/3406.
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This thesis introduces a versatile finite element package, which
is tailored for the static and dynamic analysis of radial tyres. A
new axisymmetric solid-of-revolution element which takes into
consideration, large deformation, the influence of composite
orthotropic material and the viscoelasticity and the nonlinearity of
the material properties, has been developed for a general loaded tyre.
The finite element package has been verified by comparing its results
with available analytical, numerical and experimental results. A full
static and dynamic investigation has been carried out for a commercial
tyre 175 HR 14 and results obtained by using the package have been
compared with available experimental results developed by DUNLOP or
carried out at Cranfieid.
The package has proved to be reliable, flexible, efficient,
economic and accurate. The numerical instability problems which are
prevalent in this type of analysis have been overcome by the
derivation of a developed Newton-Raphson iterative scheme.
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朱達善 and Dashan Zhu. "Nonlinear static and dynamic analysis of plates & shells by spline finite strip method." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1988. http://hub.hku.hk/bib/B31231743.
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Pacitti, Arnaud. "Nonlinear modeling of elastic cables : experimental data-based tension identification via static inverse problem." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1142/document.
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La connaissance de la tension dans les câbles de pont est un élément de diagnostic important, tant à l'échelle du câble qu'à celle de l'ouvrage dont il fait partie.Le présent travail de thèse propose une méthode d'évaluation de la tension parméthode inverse à partir d'une formulation variationnelle mixte de câble géométriquement exact permettant de coupler simplement et à bas coût un modèle universel de câble et des capteurs d'utilisation courante tels que des jauges de déformation et des capteurs de déplacement. Contrairement à de nombreuses méthodes existantes, la méthode pésentée ne nécessite pas une connaissance fine des paramètres du câble pour évaluer sa tension.Les choix de modélisation faits sont motivés par une étude approfondie des différentes typologies des câbles présents sur ouvrage et par une étude bibliographique qui tente de synthétiser l'immense littérature disponible dans le domaine des câbles. La modélisation retenue est issue de la théorie des lignes déformables des frères Cosserat, dont nous présentons les variantes avec et sans rigidité de flexion.Les moyens d'essai utilisés pour la validation expérimentale de la méthode mise au point ont été conçus et réalisés au cours du présent travail. Le montage expérimental imaginé permet d'appliquer la méthode inverse sur un câble montoron multicouches de 21 m de long et 22 mm de diamètre. Les essais sont réalisés à 6 différents niveaux de tension échelonnés par paliers de 30 kN de 55 kN à 205 kN. Ils montrent l'efficacité de la méthode sur le câble testé et la pertinence de son déploiement à venir sur d'autres typologies de câblesKnowledge of the tension in bridge cables is important not only to diagnostic the cable itself but also the construction it belongs to.The work presented in this thesis proposes to evaluate the tension of a geometrically exact cable using a static inverse method from a mixed variational formulation, by coupling simply and cheaply a universal cable model with usual sensors, such as displacement sensors and strain gauges. Contrarily to existing methods, a good knowledge of the cable's parameters, such as it length or weight per unit length, is not required.Combining a thorough study of various cable typologies encountered on bridges and the vast amounts of material available in the bibliography covering cables, lead to the modeling following the elastic theory of rods developed by the Cosserat brothers, François and Eugène, elaborating on their theory of rods with and without flexural stiffness.The experimental apparatus, designed and built in the course of this study, allowed to successfully validate the developed inverse method on a multilayered strand cable 21 m long and 22 mm in diameter at several tension levels. The universal aspect of the model introduced and its successful validation encourages its implementation to other cable typologies
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Zhu, Dashan. "Nonlinear static and dynamic analysis of plates & shells by spline finite strip method /." [Hong Kong] : University of Hong Kong, 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12427020.
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Jiang, Yaqun 1955. "Development of a new pipe element for static and dynamic analysis of nonlinear problems." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282325.
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This study presents a new straight pipe element that enables the efficient computation of large, three-dimensional deformations in pipes with circular cross-sections. Existing pipe elements have difficulties in applications including three-dimensional large deformations. To overcome these diffculties, the new element (called RC pipe element in this work), which supports rigid-body and constant-strain modes, is modeled using curvilinear shell coordinates and sinusoidal interpolation functions. This new element captures all stresses except the normal stress across the shell thickness (i.e. small thickness is assumed). Euler parameters are used to describe rotational rigid-body modes and are incorporated into the element's vector of degrees of freedom. Under general loading (axial, transverse, bending and torsion), the element allows large ovalization of its cross section and large, three-dimensional angular changes in the orientation of its reference axis. The formulation used to derive the element incorporates the nonlinear coupling between torsional and bending deformations. Results of the static analysis are presented for the stresses and deformations produced by combined bending and torsional loads. A comparison of these results to corresponding quantities generated by ABAQUS using a large number of 24 degree-of-freedom shell elements indicates excellent agreement and significant gains in computational efficiency because of a reduction in number of degrees of freedom. Results are also presented for the behaviour of the element in the presence of large rotational motion with internal pressure.
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Razzaq, Raja Javed. "Nonlinear static and dynamic analysis of composite layered plates and shells using finite strip methods." Thesis, Cranfield University, 2003. http://hdl.handle.net/1826/4049.
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In this thesis, a new concept of finite strip elements is introduced.
Lagrangian, Hermitian and spline-type interpolations have been
used independently along the two axes of the plate mid-plane.
Different plate-bending theories; Mindlin, Reissner and Kirchhoff
theories have been applied in the derivations of the new finitestrip
elements, for isotropic and composite materials. The new
elements have also been extended to work as faceted shell
elements for the analysis of cylindrical shells, folded plates and
stiffened plates.
An efficient modular programming package based on those
elements was designed, and it is capable of performing linear and
non-linear stress analysis, buckling analysis and natural frequency
analysis. The modular package, which was coded in FORTRAN
has different solvers and a built-in mesh generator for different
types of plate structures.
A number of case studies have been employed for the validation
of the package and testing its different capabilities. The package
has proved to be an efficient tool for numerical modelling of
plates, cylindrical shells, folded plates and stiffened plates made
of isotropic and composite layered materials.
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Kim, Taehyoun 1959. "Nonlinear large amplitude structural and aeroelastic behavior of composite rotor blades at large static deflection." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/43251.
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Pezeshky, Payam. "Distortional Static and Buckling Analysis of Wide Flange Steel Beams." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36074.
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Existing design provisions in design standards and conventional analysis methods for structural steel members are based on the simplifying kinematic Vlasov assumption that neglects cross-sectional distortional effects. While the non-distortional assumption can lead to reasonable predictions of beam static response and buckling strength in common situations, past work has shown the inadequacy of such assumption in a number of situations where it may lead to over-predicting the strength of the members. The present study thus develops a series of generalized theories/solutions for the static analysis and buckling analysis of steel members with wide flange cross-sections that capture distortional effects of the web. Rather than adopting the classical Vlasov assumption that postulates the cross-section to move and rotate in its own plane as a rigid disk, the present theories assume the web to be flexible in the plane of the cross-section and thus able to bend laterally, while both flanges to move as rigid plates within the plane of the cross-section to be treated as Euler-Bernouilli beams. The theories capture shear deformation effects in the web, as well as local and global warping effects.
Based on the principle of minimum potential energy, a distortional theory is developed for the static analysis of wide flange steel beams with mono-symmetric cross-sections. The theory leads to two systems of differential equations of equilibrium. The first system consists of three coupled equilibrium differential equations that characterize the longitudinal-transverse response of the beam and the second system involves four coupled equilibrium differential equations of equilibrium and characterizes the lateral-torsional response of the beam. Closed form solutions are developed for both systems for general loading. Based on the kinematics of the new theory, two distortional finite elements are then developed. In the first element, linear and cubic Hermitian polynomials are employed to interpolate displacement fields while in the second element, the closed-form solutions developed are adopted to formulate special shape functions. For longitudinal-transverse response the elements consist of two nodes with four degree of freedom per node for longitudinal-transverse response and for lateral-torsional response, the elements consist of two nodes with eight degrees of freedom per node. The solution is able to predict the distortional deformation and stresses in a manner similar to shell solutions while keeping the modeling and computational effort to a minimum.
Applications of the new beam theory include (1) providing new insights on the response of steel beams under torsion whereby the top and bottom flanges may exhibit different angles of twist, (2) capturing the response of steel beams with a single restrained flange as may be the case when a concrete slab provides lateral and/or torsional restraint to the top flange of a steel beam, and (3) modelling the beneficial effect of transverse stiffeners in reducing distortional effects in the web.
The second part of the study develops a unified lateral torsional buckling finite element formulation for the analysis of beams with wide flange doubly symmetric cross-sections. The solution captures several non-conventional features. These include the softening effect due to web distortion, the stiffening effect induced by pre-buckling deformations, the pre-buckling nonlinear interaction between strong axis moments and axial forces, the contribution of pre-buckling shear deformation effects within the plane of the web, the destabilizing effects due to transverse loads being offset from the shear centre, and the presence of transverse stiffeners on web distortion. Within the framework of the present theory, it is possible to evoke or suppress any combination of the features and thus isolate the individual contribution of each effect or quantify the combined contributions of multiple effects on the member lateral torsional capacity. The new solution is then applied to investigate the influence of the ratios of beam span-to-depth, flange width-to-thickness, web height-to-thickness, and flange width-to-web height on the lateral torsional buckling strength of simply supported beams and cantilevers. Comparisons with conventional lateral torsional buckling solutions that omit distortional and pre-buckling effects quantify the influence of distortional and/or pre-buckling deformation effects. The theory is also used to investigate the influence of P-delta effects of beam-columns subjected to transverse and axial forces on their lateral torsional buckling resistance. The theory is used to investigate the load height effect relative to the shear centre. Comparisons are made with load height effects as predicted by non-distortional buckling theories. The solution is adopted to quantify the beneficial effect of transverse stiffeners in controlling/suppressing web distortion in beams and increasing their buckling resistance.
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Beauregard, Matthew Alan. "Nonlinear Dynamics of Elastic Filaments Conveying a Fluid and Numerical Applications to the Static Kirchhoff Equations." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194164.
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Two problems in the study of elastic filaments are considered.First, a reliable numerical algorithm is developed that candetermine the shape of a static elastic rod under a variety ofconditions. In this algorithm the governing equations are writtenentirely in terms of local coordinates and are discretized usingfinite differences. The algorithm has two significant advantages:firstly, it can be implemented for a wide variety of the boundaryconditions and, secondly, it enables the user to work with generalconstitutive relationships with only minor changes to thealgorithm. In the second problem a model is presented describingthe dynamics of an elastic tube conveying a fluid. First weanalyze instabilities that are present in a straight rod or tubeunder tension subject to increasing twist in the absence of afluid. As the twist is increased beyond a critical value, thefilament undergoes a twist-to-writhe bifurcation. A multiplescales expansion is used to derive nonlinear amplitude equationsto examine the dynamics of the elastic rod beyond the bifurcationthreshold. This problem is then reinvestigated for an elastic tubeconveying a fluid to study the effect of fluid flow on thetwist-to-writhe instability. A linear stability analysisdemonstrates that for an infinite rod the twist-to-writhethreshold is lowered by the presence of a fluid flow. Amplitudeequations are then derived from which the delay of bifurcation dueto finite tube length is determined. It is shown that the delayedbifurcation threshold depends delicately on the length of the tubeand that it can be either raised or lowered relative to thefluid-free case. The amplitude equations derived for the case of aconstant average fluid flux are compared to the case where theflux depends on the curvature. In this latter case it is shownthat inclusion of curvature results in small changes in some ofthe coefficients in the amplitude equations and has only a smalleffect on the post-bifurcation dynamics.
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Boberg, Frida. "Simulation of dynamic and static behavior of an electrically powered lift gate." Thesis, Linköping University, Department of Electrical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11627.
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Continental Automotive Systems is a German company that develops control systems for different applications in cars. A control system for electrically powered lift gates that are opened or closed on the driver’s command is one of the products developed. The drive system itself is composed of a spindle that is driven by a DC-motor over a gear and a spring. When developing the control system it is convenient to use a simulation model instead of having to implement it on the system every time. The simulation analytically describes how the system is behaving.
In this thesis a simulation model of a drive system and a lift gate is developed and evaluated. The model parameters are estimated using System Identification Toolbox in Matlab.
Continental Automotive Systems är ett tyskt företag som utvecklar styrsystem för olika tillämpningar i bilar. Bland annat utvecklas ett styrsystem till eldrivna bakluckor som öppnas och stängs av föraren per knapptryck. Själva drivanordningen består av en skruv som drivs av en likströmsmotor över en utväxling och en fjäder. Då man vill utveckla styrsystemet utan att behöva implementera det på systemet varje gång är en simuleringsmodell av drivanordningen och luckan ett bra hjälpmedel. Denna simuleringsmodell kan då analytiskt beräkna hur systemet uppför sig.
I detta examensarbete har en simuleringsmodell av en drivanordning med tillhörande lucka utvecklats och utvärderats. Modellparametrarna estimerades med hjälp av System Identification Toolbox i Matlab.
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Nguyen, Huy The [Verfasser], and Utz von [Akademischer Betreuer] Wagner. "Nonlinear Quasi-static and Dynamic Behavior of Piezoceramics at Moderate Strains / Huy The Nguyen. Betreuer: Utz von Wagner." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2011. http://d-nb.info/1017355398/34.
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Nguyen, Huy The Verfasser], and Utz von [Akademischer Betreuer] [Wagner. "Nonlinear Quasi-static and Dynamic Behavior of Piezoceramics at Moderate Strains / Huy The Nguyen. Betreuer: Utz von Wagner." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2011. http://nbn-resolving.de/urn:nbn:de:kobv:83-opus-33025.
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Alamri, Amro Abdullah. "DEVELOPING A FULL THREE-DIMENSIONAL MODEL OF SELF-CENTERING CONCENTRICALLY BRACED FRAME SYSTEMS USING NONLINEAR STATIC PUSHOVER ANALYSIS." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1627680240922479.
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RAIMUNDO, JULIANA DE MATOS PONTE. "INFLUENCE OF THE NONLINEAR FLEXURAL AND SWAY INTERACTION ON THE STATIC AND DYNAMIC INSTABILITY OF A CONCEPTUAL MODEL OF COLUMN." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=35769@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
A estabilidade das colunas de um pórtico plano depende da importância relativa da rigidez à flexão e rigidez lateral de cada coluna e elementos adjacentes. Um exemplo típico é a maior capacidade de carga de pórticos planos com restrição lateral em comparação com pórticos semelhantes, sem restrição lateral. Também esta restrição tem uma influência importante na resposta pós-crítica e na sensibilidade à imperfeição da estrutura. A carga de flambagem pode ser dominada pela rigidez à flexão da coluna ou pela rigidez das restrições laterais. Dependendo dos valores relativos desses parâmetros, pode ocorrer interação modal. Nesse caso, podem surgir vários caminhos pós-críticos, acoplados e desacoplados, levando a uma topologia complexa da energia potencial total com vários pontos críticos (máximos, mínimos e selas). Os caminhos pós-críticos instáveis influenciam na sua capacidade de carga e na sensibilidade da estrutura a imperfeições. Isso leva a um complexo comportamento dinâmico não linear da estrutura carregada axialmente. No presente trabalho, um modelo conceitual de dois graus de liberdade de um elemento de pórtico plano sob compressão é estudado. Uma análise detalhada é realizada a fim de estudar como a rigidez lateral influencia: os comportamentos pré- e pós-crítico, a instabilidade paramétrica do modelo sob uma excitação harmônica axial e o comportamento ressonante do sistema estrutural carregado axialmente sob uma excitação de base; contribuindo para uma melhor compreensão da resposta não linear desta classe de estruturas. A análise das bifurcações mostra que a estrutura pode exibir várias soluções estáveis e instáveis coexistentes, levando a bacias de atração entrelaçadas, cuja topologia controla a integridade dinâmica da estrutura em um ambiente dinâmico. Para estudar o comportamento não linear do modelo, foram utilizadas várias estratégias numéricas para obter os caminhos de equilíbrio não lineares, pontos fixos estáveis e instáveis, diagramas de bifurcação e bacias de atração.
The stability of columns in a portal frame depends on the relative importance of the flexural and lateral stiffness of the column and connected elements. A typical example is the higher load capacity of non-sway frames as compared with that of similar frames with no lateral restrain. Also this restrain has an important influence on the post-critical response and imperfection sensitivity of the structure. The buckling load may be either dominated by the flexural stiffness of the columns or by the stiffness of the lateral restrains. Depending on the relative values of these parameters, interactive buckling may occur. In such case, several coupled and uncoupled post-buckling paths may arise, leading to a complex topology of the energy landscape with several critical points (maxima, minima and saddles). The resulting unstable post-buckling paths influence the structure s imperfection sensitivity and load carrying capacity of the structure. This leads to an involved nonlinear dynamic behaviour of the axially loaded structure. In the present work, a conceptual two-degree-of-freedom model of a plane-frame column is studied. A detailed analysis is conducted to study how the lateral stiffness influences the static buckling and post-buckling behavior, the parametric instability of the model under under axial harmonic excitation and the resonant behavior of the axially loaded structural system under base excitation, contributing to a better understanding of the nonlinear response of this class of structures. The bifurcation analysis shows that the structure may display several coexisting stable and unstable solutions, leading to intertwining basins of attraction, whose topology controls the dynamic integrity of the structure in a dynamic environment. To study the non-linear behavior of the model, several numerical strategies were used to obtain the nonlinear equilibrium paths, stable and unstable fixed points, bifurcation diagrams and basins of attraction.
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Kapoor, Hitesh. "Nonlinear Dynamic Response of Flexible Membrane Structures to Blast Loads." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/41238.
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The present work describes the finite element (FE) modeling and dynamic response of lightweight, deployable shelters (tent) to large external blast loads. Flexible shelters have been used as temporary storage places for housing equipments, vehicles etc. TEMPER Tents, Small Shelter System have been widely used by Air Force and Army, for various field applications. These shelters have pressurized Collective Protection System (CPS), liner, fitted to the frame structure, which can provide protection against explosives and other harmful agents. Presently, these shelter systems are being tested for the force protection standards against the explosions like air-blast. In the field tests carried out by Air Force Research Laboratory, it was revealed that the liner fitted inside the tent was damaged due to the air blast explosion at some distant from the structure, with major damage being on the back side of the tent. The damage comprised of tearing of liner and separation of zip seals. To investigate the failure, a computational approach, due to its simplicity and ability to solve the complex problems, is used.
The response of any structural form to dynamic loading condition is very difficult to predict due to its dependence on multiple factors like the duration of the loading, peak load, shape of the pulse, the impulse energy, boundary conditions and material properties etc. And dynamic analysis of shell structures pose even much greater challenge. Obtaining solution analytically presents a very difficult preposition when nonlinearity is considered. Therefore, the numerical approach is sought which provide simplicity and comparable accuracy.
A 3D finite element model has been developed, consisting of fabric skin supported over the frames based on two approaches. ANSYS has been used for obtaining the dynamic response of shelter against the blast loads. In the first approach, the shell is considered as a membrane away from its boundaries, in which the stress couple is neglected in its interior region. In the second approach, stress coupling is neglected over the whole region. Three models were developed using Shell 63, Shell 181 and Shell 41. Shell 63 element supports both the membrane only and membrane-bending combined options and include stress stiffening and large deflection capabilities. Shell 181 include all these options as Shell 63 does and also, accounts for the follower loads. Shell 41 is a membrane element and does not include any bending stiffness. This element also include stress stiffening and large deflection capabilities.
A nonlinear static analysis is performed for a simple plate model using the elements, Shell 41 and Shell 63. The membrane dominated behavior is observed for the shell model as the pressure load is increased. It is also observed that the higher value of Young's modulus (E) increases the stresses significantly.
Transient analysis is a method of determining the structural response due to time dependent loading conditions. The full method has been used for performing the nonlinear transient analysis. Its more expensive in terms of computation involved but it takes into account all types of nonlinearities such as plasticity, large deflection and large strain etc. Implicit approach has been used where Newmark method along with the Newton-Raphson method has been used for the nonlinear analysis. Dynamic response comprising of displacement-time history and dynamic stresses has been obtained. From the displacement response, it is observed that the first movement of the back wall is out of the tent in contrast to the other sides whose first movement is into the tent. Dynamic stresses showed fluctuations in the region when the blast is acting on the structure and in the initial free vibration zone.
A parametric study is performed to provide insight into the design criteria. It is observed that the mass could be an effective means of reducing the peak responses. As the value of the Young's Modulus (E) is increased, the peak displacements are reduced resulting from the increase in stiffness. The increased stiffness lead to reduced transmitted peak pressure and reduced value of maximum strain. But a disproportionate increase lead to higher stresses which could result in failure. Therefore, a high modulus value should be avoided.Master of Science
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Navarro, D., R. Valero, and J. Orihuela. "Evaluation of the Influence of Different Grades of Reinforcing Steel on the Seismic Performance of Concrete reinforced Frame Structures with Nonlinear Static Analysis." IOP Publishing Ltd, 2021. http://hdl.handle.net/10757/655954.
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In this investigation, the elasto-plastic behavior and the seismic performance of concrete reinforced frame structures reinforced are evaluated by applying the Pushover method. This evaluation is done on several cases: with high ductility steel (Grade 40), conventional steel (Grade 60) and high strength steel (Grade 75). For the previous, the capacity curve graph obtained from the displacement coefficient method was used to measure the capacity of the structure. In addition, the performance of the structure for different levels of seismic design are evaluated with the resulting values of ductility and rigidity of each case. The results showed that reinforcing a structure with a Grade 40 reinforcing steel increases the energy dissipation capacity, and if reinforced with a Grade 75 reinforcing steel increases the strength capacity in the structure. Finally, the comparative result of the various cases are presented to demonstrate the influence of reinforcing steel on the plastic behavior of concrete reinforced frame structures.
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Leung, Colin. "SENSITIVITY OF SEISMIC RESPONSE OF A 12 STORY REINFORCED CONCRETE BUILDING TO VARYING MATERIAL PROPERTIES." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/681.
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The main objective of this investigation is to examine how various material properties, governed by code specification, affect the seismic response of a twelve- story reinforced concrete building. This study incorporates the pushover and response history analysis to examine how varying steel yield strength (Fy), 28 day nominal compressive concrete strength (f’c), modes, and ground motions may affect the base shear capacity and displacements of a reinforced concrete structure.
Different steel and concrete strengths were found to have minimal impact on the initial stiffness of the structure. However, during the post-yielding phase, higher steel and concrete compressive strengths resulted in larger base shear capacities of up to 22%. The base shear capacity geometric median increased as f’c or Fy increased, and the base shear capacity dispersion measure decreased as f’c or Fy increased. Higher mode results were neglected in this study due to non-convergent pushover analyses results.
According to the response history analysis, larger yield and concrete compressive strengths result in lower roof displacement. The difference in roof displacement was less than 12% throughout. This displays the robustness of both analysis methods because material properties have insignificant impact on seismic response. Therefore, acceptable yield and compressive strengths governed by seismic code will result in acceptable building performance.
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Crabtree, Owen I. "A numerical study of nonlinear static and dynamic behavior of a square thin plate-membrane structure for application to a MEMS micro-generator." Online access for everyone, 2004. http://www.dissertations.wsu.edu/Thesis/Fall2004/o%5Fcrabtree%5F101304.pdf.
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Baylis, Charles Passant II. "Improved Techniques for Nonlinear Electrothermal FET Modeling and Measurement Validation." Scholar Commons, 2007. https://scholarcommons.usf.edu/etd/620.
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Accurate transistor models are important in wireless and microwave circuit design. Large-signal field-effect transistor (FET) models are generally extracted from current-voltage (IV) characteristics, small-signal S-parameters, and large-signal measurements. This dissertation describes improved characterization and measurement validation techniques for FET models that correctly account for thermal and trapping effects.
Demonstration of a customized pulsed-bias, pulsed-RF S-parameter system constructed by the author using a traditional vector network analyzer is presented, along with the design of special bias tees to allow pulsing of the bias voltages. Pulsed IV and pulsed-bias S-parameter measurements can provide results that are electrodynamically accurate; that is, thermal and trapping effects in the measurements are similar to those of radio-frequency or microwave operation at a desired quiescent bias point. The custom pulsed S-parameter system is benchmarked using passive devices and advantages and tradeoffs of pulsed S-parameter measurements are explored. Pulsed- and continuous-bias measurement results for a high-power transistor are used to validate thermal S-parameter correction procedures.
A new implementation of the steepest-ascent search algorithm for load-pull is presented. This algorithm provides for high-resolution determination of the maximum power and associated load impedance using a small number of measured or simulated reflection-coefficient states. To perform a more thorough nonlinear model validation, it is often desired to find the impedance providing maximum output power or efficiency over variations of a parameter such as drain voltage, input power, or process variation. The new algorithm enables this type of validation that is otherwise extremely tedious or impractical with traditional load-pull.
A modified nonlinear FET model is presented in this work that allows characterization of both thermal and trapping effects. New parameters and equation terms providing a trapping-related quiescent-bias dependence have been added to a popular nonlinear ("Angelov") model. A systematic method for fitting the quiescent-dependence parameters, temperature coefficients, and thermal resistance is presented, using a GaN high electron-mobility transistor as an example. The thermal resistance providing a good fit in the modeling procedure is shown to correspond well with infrared measurement results.
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Bolander, Julie Christine. "Investigation of Torsional Effects on Thirteen-Story Reinforced Concrete Frame-Wall Structure Modeled in ETABS and SAP2000 Using Linear and Nonlinear Static and Dynamic Analyses." Thesis, University of California, San Diego, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1557303.
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The primary objective of this thesis is to evaluate the effects of torsion on the nonlinear seismic response of a thirteen-story reinforced concrete frame-wall structure with an asymmetric stiffness in plan. The NEHRP building structure, located in Berkeley, CA and previously designed by André Barbosa, was modeled in ETABS and SAP2000 to perform several analyses. The models accounted for realistic cracked concrete section stiffnesses, expected material properties, and nonlinear plastic hinges. Due to limitations of ETABS in performing nonlinear dynamic time history analysis, the model was exported to SAP2000. An asymmetric lateral stiffness model was created by moving one of the shear walls from the center of the building toward the outside of the building. OpenSees was used to find the nonlinear hinge moment-rotation relationships.
Using a suite of seven ground motion record pairs, an essentially linear dynamic time history analysis was performed on the symmetric and asymmetric ETABS models. The SAP2000 models were used to perform a series of nonlinear static (pushover) analyses. Fully nonlinear, including material and geometric nonlinearity, time history analyses were performed on the SAP2000 models using the seven ground motion pairs, appropriately cut to shorter lengths to reduce the analysis run-time. In each analysis case, the results of the symmetric and asymmetric models were compared. Overall, the asymmetric model typically experienced torsional effects and larger displacement responses than the symmetric model. The more nonlinear the structure behaved, the more influence torsion had on the response of the model with asymmetrically-placed shear walls.
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Heim, Eugene Henry DeWendt. "Development of Methods for Improved Data Integrity and Efficient Testing of Wind Tunnel Models for Dynamic Test Conditions in Unsteady and Nonlinear Flight Regimes." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31050.
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Todayâ s high performance aircraft are operating in expanded flight envelopes, often maneuvering at high angular rates at high angles-of-attack, even above maximum lift. Current aerodynamic models are inadequate in predicting flight characteristics in the expanded envelope, such as rapid aircraft departures and other unusual motions. Unsteady flows of aircraft are of real concern. The ability to accurately measure aerodynamic loads directly impacts the ability to accurately model and predict flight. Current wind tunnel testing techniques do not adequately address the data fidelity of a test point under the influence of fluctuating loads and moments. Additionally, forced oscillation test techniques, one of the primary tools used to develop dynamic models, do not currently provide estimates of the uncertainty of the results during an oscillation cycle. Further, in testing models across a range of flight conditions, there are frequently parts of the envelope which are well behaved and require few data points to arrive at a sound answer, and other parts of the envelope where the responses are much more active and require a large sample of data to arrive at an answer with statistical significance. Currently, test methods do not factor changes of flow physics into data acquisition schemes, so in many cases data are obtained over more iterations than required, or insufficient data may be obtained to determine a valid estimate. Methods of providing a measure of data integrity for static and forced oscillation test techniques are presented with examples. A method for optimizing required forced oscillation cycles based on decay of uncertainty gradients and balance tolerances is also presented.Master of Science
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Sapkota, Suman. "Seismic Capacity Evaluation of Reinforced Concrete Buildings Using Pushover Analysis." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1544707728674621.
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Cevik, Deniz. "Determination Of The Change In Building Capacity During Earthquakes." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607085/index.pdf.
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There is a great amount of building stock built in earthquake regions where earthquakes frequently occur. It is very probable that such buildings experience earthquakes more than once throughout their economic life. The motivation of this thesis arose from the lack of procedures to determine the change in building capacity as a result of prior earthquake damage. This study focuses on establishing a method that can be employed to determine the loss in the building capacity after experiencing an earthquake.
In order to achieve this goal a number of frames were analyzed under several randomly selected earthquakes. Nonlinear time-history analyses and nonlinear static analyses were conducted to assess the prior and subsequent capacities of the frames under consideration. The structural analysis programs DRAIN-2DX and SAP2000 were employed for this purpose. The capacity curves obtained by these methods were investigated to propose a procedure by which the capacity of previously damaged structures can be determined.
For time-history analyses the prior earthquake damage can be taken into account by applying the ground motion histories successively to the structure under consideration. In the case of nonlinear static analyses this was achieved by modifying the elements of the damaged structure in relation to the plastic deformation they experience.
Finally a simple approximate procedure was developed using the regression analysis of the results. This procedure relies on the modification of the structure stiffness in proportion to the ductility demand the former earthquake imposes.
The proposed procedures were applied to an existing 3D building to validate their applicability.
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Carloni, Federico. "A 3D model based on the SAM Method for seismic studies of masonry buildings." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/17151/.
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L'elaborato propone un metodo per la modellazione tridimensionale di interi edifici in muratura, con lo scopo di valutare le performance sismiche, mediante il programma di calcolo SAP2000. La metodologia proposta consente la modellazione di pareti in muratura simulandone il comportamento non lineare sotto azioni agenti nel piano ed allo stesso tempo permette di considerare la ripartizione delle azioni verticali e soprattutto orizzontali che avviene tra le pareti, dovuta alle zone di connessione, ai solai ed alla loro rigidezza a taglio nel piano. Per lo sviluppo del metodo di modellazione è stato utilizzato un edificio molto semplice. Successivamente la metodologia è stata applicata ad un caso più realistico sul quale si sono fatte anche considerazioni riguardo i diversi comportamenti della struttura in funzione della rigidezza dei solai.
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Kaymak, Yalcin. "A Composite Frame/joint Super Element For Structures Strengthened By Externally Bonded Steel/frp Plates." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1052547/index.pdf.
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A materially non-linear layered beam super element is developed for the analysis of RC beams and columns strengthened by externally bonded steel/FRP plates. The elasto-plastic behavior of RC member is incorporated by its internally generated or externally supplied moment-curvature diagram. The steel plate is assumed to be
elasto-plastic and the FRP laminate is assumed to behave linearly elastic up to
rupture. The thin epoxy layer between the RC member and the externally bonded lamina is simulated by a special interface element which allows for the changing failure modes from steel plate yielding/FRP plate rupture to separation of the bonded plates as a result of bond failure in the epoxy layer. An empirical failure criterion based on test results is used for the epoxy material of the interface.
The most critical aspect of such applications in real life frame structures is the anchorage conditions at the member ends and junctions. This has direct influence on the success and the effectiveness of the application. Therefore, a special corner piece anchorage element is also considered in the formulation of the joint super
element, which establishes the fixity and continuity conditions at the member ends
and the joints.
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Pathak, Rakesh. "The Effects of Diaphragm Flexibility on the Seismic Performance of Light Frame Wood Structures." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/27947.
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This dissertation presents work targeted to study the effects of diaphragm flexibility on the seismic performance of light frame wood structures (LFWS). The finite element approach is considered for modeling LFWS as it is more detailed and provides a way to explicitly incorporate individual structural elements and corresponding material properties. It is also suitable for capturing the detailed response of LFWS components and the structure as a whole. The finite element modeling methodology developed herein is in general based on the work done by the other finite element researchers in this area. However, no submodeling or substructuring of subassemblages is performed and instead a detailed model considering almost every connection in the shear walls and diaphragms is developed. The studs, plates, sills, blockings and joists are modeled using linear isotropic three dimensional frame elements. A linear orthotropic shell element incorporating both membrane and plate behavior is used for the sheathings. The connections are modeled using oriented springs with modified Stewart hysteresis spring stiffnesses. The oriented spring pair has been found to give a more accurate representation of the sheathing to framing connections in shear walls and diaphragms when compared to non-oriented or single springs typically used by most researchers in the past. Fifty six finite element models of LFWS are created using the developed methodology and eighty eight nonlinear response history analyses are performed using the Imperial Valley and Northridge ground motions. These eighty eight analyses encompass the parametric study on the house models with varying aspect ratios, diaphragm flexibility and lateral force resisting system. Torsionally irregular house models showed the largest range of variation in peak base shear of individual shear walls, when corresponding flexible and rigid diaphragm models are compared. It is also found that presence of an interior shear wall helps in reducing peak base shears in the boundary walls of torsionally irregular models. The interior walls presence was also found to reduce the flexibility of diaphragm. A few analyses also showed that the nail connections are the major source of in-plane flexibility compared to sheathings within a diaphragm, irrespective of the aspect ratio of the diaphragm.
A major part of the dissertation focuses on the development of a new high performance nonlinear dynamic finite element analysis program which is also used to analyze all the LFWS finite element models presented in this study. The program is named WoodFrameSolver and is written on a mixed language platform Microsoft Visual Studio .NET using object-oriented C++, C and FORTRAN. This tool set is capable of performing basic structural analysis chores like static and dynamic analysis of 3D structures. It has a wide collection of linear, nonlinear and hysteretic elements commonly used in LFWS analysis. The advanced analysis features include static, nonlinear dynamic and incremental dynamic analysis. A unique aspect of the program lies in its capability of capturing elastic displacement participation (sensitivity) of spring, link, frame and solid elements in static analysis. The programâ s performance and accuracy are similar to that of SAP 2000 which is chosen as a benchmark for validating the results. The use of fast and efficient serial and parallel solver libraries obtained from INTEL has reduced the solution time for repetitive dynamic analysis. The utilization of the standard C++ template library for iterations, storage and access has further optimized the analysis process, especially when problems with a large number of degrees of freedom are encountered.Ph. D.
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Fernández, López Rodrigo Miguel, and Velásquez Ricardo Timoteo Zapata. "Análisis y diseño estructural de una torre de 40 pisos y 4 sótanos siguiendo normas peruanas incluyendo su desempeño sísmico en el distrito de Santiago de Surco, Lima." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/652425.
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En la presente investigación se realizará el análisis y diseño estructural de una torre de 40 pisos y 4 sótanos de concreto armado siguiendo normas peruanas y el cálculo de desempeño sísmico en el distrito de Santiago de Surco, Lima. Para esto, la hipótesis plantea sí las normas peruanas cumplen con el desempeño sismorresistente deseado para una torre alta como esta.
Para un entendimiento progresivo, primero se hará una descripción de la torre alta a estudiar, su arquitectura, estructura, suelo y otros. En la segunda parte se darán los conceptos necesarios para comprender los tipos de análisis lineal estático, lineal dinámico y no lineal estático. Se definirán los materiales, los diagramas momento – rotación también se explicará la obtención de la curva de capacidad del edificio. Se tocarán conceptos de viento y nivel de desempeño. En la tercera parte, se procederá con en análisis sísmico cumpliendo las exigencias de sismorresistencia, también se hará el análisis por viento para comparar ambos efectos. En el capítulo cuarto se procederá a hacer el diseño estructural usando las normas de concreto armado. En el capítulo cinco se hará el análisis por desempeño usando el método pushover para finalmente conseguir los resultados de este proyecto y a las conclusiones de este desarrollo.In the present investigation, the analysis and structural design of a 40-storey tower and 4 reinforced concrete basements will be carried out following Peruvian regulations and the calculation of seismic performance in the Santiago de Surco district, Lima. For this, the hypothesis states whether the Peruvian standards meet the desired seismic resistance performance for a tall tower like this one. For a progressive understanding, first a description will be made of the tall tower to study, its architecture, structure, soil and others. In the second part, the concepts necessary to understand the types of static linear analysis, dynamic linear analysis and static non-linear analysis will be given. The materials will be defined, the moment - rotation diagrams will also explain the obtaining of the building capacity curve. Wind and performance level concepts will be discussed. In the third part, we will proceed with seismic analysis complying with the seismic resistance requirements, we will also do the wind analysis to compare both effects. In the fourth chapter, the structural design will be carried out using the reinforced concrete standards. In chapter five the performance analysis will be done using the pushover method to finally get the results of this project and the conclusions of this development.
Tesis
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Cott, Andrew. "An examination of analysis and optimization procedures within a PBSD framework." Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/2318.
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Baylis, Charles Passant II. "Improved Current-Voltage Methods for RF Transistor Characterization." Scholar Commons, 2004. https://scholarcommons.usf.edu/etd/950.
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In the development of a nonlinear transistor model, several measurements are used to extract equivalent circuit parameters. The current-voltage (IV) characteristic of a transistor is one of the measurement data sets that allows the nonlinear model parameters to be extracted. The accuracy of the IV measurement greatly influences the accuracy of the large-signal model.
Numerous works have reported the inadequacy of traditional static DC IV measurements to accurately predict radio-frequency (RF) behavior for many devices. This inaccuracy results from slow processes in the device that do not have time to completely respond to the quick changes in terminal conditions when the device is operating at high frequencies; however, these slow processes respond fully to reach a new steady-state condition in the DC sweep measurement. The two dominant processes are self-heating of the device and changes in trap occupancy. One method of allowing the thermal and trap conditions to remain in a state comparable to that of RF operation is to perform pulsed IV measurements to obtain the IV curves. In addition, thermal correction can be used to adjust the IV curves to compensate for self-heating in the case that the predominant effect in the device is thermal.
To gain a better understanding of pulsed IV measurement techniques, measurement waveforms of a commercially available pulsed IV analyzer are examined in the time domain. In addition, the use of bias tees with pulsed IV measurement is explored; such a setup may be desired to maintain stability or to enable simultaneous pulsed S-parameter and pulsed IV measurement. In measurements with bias tees, the pulse length setting must be long enough to allow the voltage across the inductor to change before the measurement is made.
In many circumstances, it is beneficial to compare different sets of IV curves for a device. The comparison of pulsed and static IV measurements, measured and modeled IV measurements, as well as two measurements with identical settings on the same instrument (to ascertain instrument repeatability) can be performed using the proposed normalized difference unit (NDU). This unit provides a comparison that equally weights the two sets of data to be compared. Due to the normalization factor used, the value of the NDU is independent of the size of the device for which the IV curves are compared. The variety of comparisons for which this unit can be used and its ability to present differences quantitatively allow it to be used as a robust metric for comparing IV curves. Examples of the use of the NDU shown include determination of measurement repeatability, comparison of pulsed and static IV data, and a comparison of model fits.
The NDU can also be used to isolate thermal and trapping processes and to give the maximum pulse length that can be used for pulsed IV measurement without contamination by each of these processes. Plotting the NDU comparing static and pulsed IV data versus pulse length shows this maximum pulse length that can be used for each effect, while a plot of the NDU comparing pulsed IV data for two quiescent bias points of equal power dissipation reveals only differences due to trapping effects. In this way, trapping effects can be distinguished from thermal effects.
Electrothermal modeling has arisen as a method of correcting for self-heating processes in a device with predominantly thermal effects. A parallel RC circuit is used to model channel temperature as a function of ambient temperature and power dissipated in the channel or junction. A technique is proposed for thermal resistance measurement and compared with a technique found in the literature. It is demonstrated that the thermal time constant can be measured from a plot of the NDU versus pulse length, and the thermal capacitance is then obtained using the thermal resistance and time constant.
Finally, the results obtained through the thermal resistance measurement procedures are used to thermally correct static IV curves. Because trapping effects are negligible, it is shown that IV curves corresponding to different quiescent bias points for a Si LDMOSFET can be synthesized from three sets of static IV data taken at different ambient temperatures. The results obtained from this correction process for two quiescent bias points are compared to the pulsed IV results for these quiescent bias points and found to be quite accurate.
Use of the methods presented in this work for obtaining more accurate transistor IV data data should assist in allowing more accurate nonlinear models to be obtained.
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Yu, Xiaoyang. "Dynamic acoustic emission for the characterization of the nonlinear behavior of complex materials." Thesis, Le Mans, 2020. http://www.theses.fr/2020LEMA1019.
Full textAbstract:
L’émission acoustique (EA) est reconnue pour être une technique efficace de surveillance de la santé des structures permettant de détecter la création et la propagation de microfissures dans les matériaux structuraux tels que le béton ou les composites lorsqu'ils sont soumis à des contraintes quasi-statiques. Sur la base de méthodes de traitement de signaux adéquates, différentes études ont établi des liens entre les salves d’EA et les micro-dommages créés. D'autres travaux ont montré qu'il est possible de corréler le temps de relaxation des composites et l'énergie des mécanismes d'endommagement mesurée durant la charge quasi-statique en utilisant les salves d’EA enregistrées. Cette thèse propose d'utiliser un protocole expérimental original pour détecter la relaxation non-linéaire d'échantillons de bétons à l'état intact et endommagés. Ce protocole est basé sur l'utilisation de l’EA pour capter passivement la relaxation non-linéaire d'échantillons de bétons au lieu du signal de faible amplitude habituellement utilisé dans les expériences de dynamique lente. Les résultats montrent que les méthodes de détection passives et actives conduisent à des temps de relaxation équivalents. De plus, le capteur d’EA révèle l’existence d’une ‘période de silence’ pendant les premières minutes de la relaxation non-linéaire après laquelle les salves d’EA commencent à être détectées. De plus, les caractéristiques des salves d’EA enregistrées pendant la relaxation passive ont montré une nette ressemblance avec celles obtenues lors de l'endommagement des mêmes échantillons, où des mécanismes de cisaillement et de compression sont impliqués. Enfin, nous notons qu’en plus de l'utilisation d'une approche de reconnaissance des formes non- supervisée pour la classification des salves d’EA, ce travail propose une nouvelle approche de classification des signaux d’EA basé sur l’image de la représentation en ondelettes continue (CWT) et le réseau de neurones convolutifs (CNN). Les résultats liés aux données d’EA dynamiques non-linéaires et quasi-statiques montrent que les deux approches de traitement du signal ont une grande précision de classification, ce qui représente un intérêt certain pour le développement de méthodes d’EA dynamiques en présence de microfissuresAcoustic emission (AE) is well known to be an efficient structural health monitoring technique to detect the creation and propagation of micro-cracks within structural materials such as concrete or composites when submitted to quasi-static stresses. Based on adequate signal processing methods, different research studies have established links between the detected AE hits and the created micro-damages. Other works have shown that it is possible to correlate the relaxation time in composites and the energy of the damage mechanisms measured during the quasi-static loading using the recorded AE hits. This thesis proposes to use an original experimental protocol to probe the nonlinear relaxation of concrete samples at the intact and damaged states. This protocol is based on the use of AE to passively probe the nonlinear relaxation of concrete samples instead of the weak amplitude signal usually used in slow dynamics experiments. Results show that passive and active probing methods lead to equivalent relaxation times. Furthermore, AE probing reveals the existence of a ‘silence period’ during the first minutes of the nonlinear relaxation after which AE hits start to be detected. In addition, the characteristics of AE hits recorded during the passive relaxation showed a clear resemblance to those obtained during the damaging of the same samples, where shear and compression mechanisms are involved. For the clustering of the AE hits, in addition to use of an unsupervised pattern recognition approach to cluster the detected AE hits, this work proposes a novel ‘image- based AE classification’ approach based on continuous wavelet transform (CWT) and convolutional neural network (CNN). Results related to the nonlinear dynamic and quasi-static AE data show that both signal processing approaches have high classification accuracy, which represents a great interest in the development of dynamic AE methods in the presence of micro-cracks
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Okur, Abdullah. "Comparison Of Seismic Assessment Procedures In The Current Turkish Code." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12609197/index.pdf.
Full textAbstract:
In Turkey, most of the existing buildings are vulnerable to earthquakes due to their poor material quality and inaccurate design. Besides, so many destructive earthquakes occurred in the past, because Turkey is located on a seismically active region. Therefore, existing buildings should be assessed and necessary precautions should be taken before a probable earthquake. To assess seismic performance of the existing buildings, the 2007 Turkish Earthquake Code offers two methods which are linear and nonlinear. For linear assessment, members are controlled by comparing the force demands and capacities where for nonlinear assessment, strains corresponding to the plastic rotations of the members are compared with the limits given in the code.
In this study, the building, which stands in Bakirköy district of istanbul, was assessed according the linear elastic and nonlinear static procedures given in the 2007 Turkish Earthquake Code. In addition, it was retrofitted by adding shear walls to the structural system and same assessment procedures were performed. In the last case study, building is re-designed according to the code and re-assessed. Comparative results and conclusions were summarized in the last chapter.
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Ozcelik, Ramazan. "Seismic Upgrading Of Reinforced Concrete Frames With Structural Steel Elements." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613450/index.pdf.
Full textAbstract:
This thesis examines the seismic internal retrofitting of existing deficient reinforced concrete
(RC) structures by using structural steel members. Both experimental and numerical studies
were performed. The strengthening methods utilized with the scope of this work are chevron
braces, internal steel frames (ISFs), X-braces and column with shear plate. For this purpose,
thirteen strengthened and two as built reference one bay one story portal frame specimens
having 1/3 scales were tested under constant gravity load and increasing cyclic lateral
displacement excursions. In addition, two ½scaled three bay-two story frame specimens strengthened with chevron brace and ISF were tested by employing continuous pseudo dynamic testing methods. The test results indicated that the cyclic performance of the Xbrace and column with shear plate assemblage technique were unsatisfactory. On the other hand, both chevron brace and ISF had acceptable cyclic performance and these two techniques were found to be candidate solutions for seismic retrofitting of deficient RC structures. The numerical simulations by conducting nonlinear static and dynamic analysis were used to estimate performance limits of the RC frame and steel members. Suggested strengthening approaches, chevron brace and ISF, were also employed to an existing five story case study RC building to demonstrate the performance efficiency. Finally, design approaches by using existing strengthening guidelines in Turkish Earthquake Code and ASCE/SEI 41 (2007) documents were suggested.
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Gilbert, Gregory S. Jr. "Scaling a Prismatic Revolute Joint (Pr) Manipulator Using Similitude and Buckingham Pi Techniques." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36599.
Full textAbstract:
This thesis presents scaling methods for sizing a prototype micro prismatic revolute (PR) manipulator actuated by permanent magnet (PM) direct current (d.c.) gearmotors. Dimensional analysis was the principle tool used in this investigation, and addressed the problems of scaling a trajectory planner, control law, and gearmotors that exhibit internal nonlinear friction. Similitude methods were used to develop a scaleable two degree-of-freedom trajectory planner from a third order polynomial. Scaling laws were developed from Buckingham's Pi theorem to facilitate the selection process of gearmotors. Nondimensional, nonlinear, differential equations were developed to describe viscous, Coulomb and static friction in comparative PM d.c. motors. From the insights gained through dimensional analysis, a scaleable controller based on the computed torque method was developed and implemented with a cubic trajectory planner. Model and prototype PR manipulator systems were simulated using a hybrid Matlab/Simulink simulation scheme. Experimental systems were constructed with dissimilar model and prototype motors. Control was provided by an AT class PC equipped with 12-bit A/D, D/A cards operating at a sample rate of 100 Hz. The control algorithm was written in Borland 3.1 C for DOS. Results from the experimental testing showed excellent agreement between the test and simulated data and verified the viability of the scaling laws. The techniques presented in this thesis are expected to be applicable to any application that involves scaling PM d.c. micro gearmotors that have significant internal friction terms. These simple, practical tools should be especially beneficial to designers of micro robotic systems.Master of Science
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Weis, Lukáš. "Materiálově nelineární řešení konstrukcí z plastů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-234540.
Full textAbstract:
The presented thesis focuses on static analysis of plastic structures, taking into account nonlinear behaviour of the material depending on the stress. The static analysis is performed using the finite element method. The difference between material linear and material nonlinear approach is illustratively described in the introduction. A shell finite element, which is enhanced by the possibility of further delamination into layers and integration points along its thickness, is suitable to be used for a numerical analysis of a plastic structures. Separate chapters are devoted to the integration of the resulting values over the height of the cross-section. The integration of the material stiffness matrix correctly reflects the emergence of eccentricity. A part of the attention is devoted to the numerical quadrature rules. Next chapter is devoted to material nonlinear models. Two approaches are described: a simpler one, using the isotropic nonlinear elastic model, and more general one, using the orthotropic plastic model. The theoretical description is complemented by the graphic interpretation of the criteria according to the individual authors. A significant portion of this work is devoted to the algorithmization of calculation procedures described in the theoretical chapters. The algorithmization itself is implemented in Fortran language into a dynamic-link library which is part of the software program RFEM 5 which is widely used in engineering practice. A part of the work is a study comparing the performance of the different technologies applicable for the algorithmization of the described issues. The agreement of the theoretical analysis of the material models and subsequent implementation within the RFEM 5 is demonstrated on the example of the bent cantilever. The thermoplastic aboveground tank structure is subject of detailed material linear, and nonlinear analysis respectively. The various approaches are compared on the results of stress, deformation an
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Isoldi, Liércio André. "Análise estática e dinâmica de estruturas delgadas de materiais compostos laminados incluindo materiais piezelétricos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/14378.
Full textAbstract:
Sabe-se que materiais compostos laminados são, hoje em dia, geralmente usados nas indústrias aeronáutica, aeroespacial, naval e outras, principalmente por causa de suas atrativas propriedades se comparadas aos materiais isotrópicos, como alta rigidez/peso, alta resistência, alto amortecimento e boas propriedades relacionadas ao isolamento térmico e acústico, entre outras. Porém, o comportamento de estruturas feitas de materiais compostos pode ser aperfeiçoado através da utilização de materiais inteligentes. Dentre os diferentes tipos comercialmente disponíveis de materiais inteligentes, os materiais piezelétricos são amplamente usados como sensores e atuadores para o monitoramento e controle de estruturas. O efeito piezelétrico direto define que uma deformação mecânica aplicada ao material é convertida em uma carga elétrica. Por outro lado, o efeito piezelétrico inverso define que um potencial elétrico aplicado ao material é convertido em deformação mecânica. Estes efeitos governam a interação eletromecânica nos materiais piezelétricos. O Método dos Elementos Finitos, uma ferramenta amplamente reconhecida e poderosa para a análise de estruturas complexas, é capaz de realizar a integração dos componentes inteligentes e das partes estruturais clássicas. Sendo assim, o comportamento estático e dinâmico, linear e geometricamente não-linear, de estruturas compostas laminadas delgadas com lâminas piezelétricas incorporadas é analisado neste trabalho usando o Método dos Elementos Finitos (MEF). Elementos triangulares, chamados GPL-T9, com três nós e seis graus de liberdade por nó (três componentes de deslocamento e três de rotação) e um grau de liberdade por camada piezelétrica (potencial elétrico) são usados. Para a análise estática não-linear as equações de equilíbrio são solucionadas usando o Método do Controle de Deslocamentos Generalizados (MCDG) enquanto a solução dinâmica é obtida usando o Método de Newmark com Formulação Lagrangeana Atualizada (FLA). O sistema de equações é resolvido usando o Método dos Gradientes Conjugados (MGC) e nos casos não-lineares um esquema iterativo-incremental é empregado. Diversos exemplos numéricos são apresentados e comparados com resultados obtidos por outros autores com diferentes tipos de elementos e diferentes formulações. A concordância entre estes resultados demonstra a validade e a eficácia dos modelos desenvolvidos.It is well known that laminate composite materials are nowadays commonly used in the aeronautical, aerospace, naval and other industries mainly because their attractive properties as compared to isotropic materials, such as higher stiffness/weight, higher strength, higher damping and good properties related to thermal or acoustic isolation, among others. However, the behavior of structures made of composite materials can be improved using smart materials. Among several kinds of commercially available smart materials, the piezoelectric materials are widely used as sensors and actuators for the monitoring and control of structures. The direct piezoelectric effect states that a mechanical strain applied to the material is converted to an electric charge. On the other hand, the converse piezoelectric effect states that an electric potential applied to the material is converted to mechanical strain. These effects govern the electromechanical interaction in piezoelectric materials. The finite element method, a widely accepted and powerful tool for analyzing complex structures, is capable of dealing with the integration of smart components and classic structural parts. So, linear and geometrically nonlinear static and dynamic behavior of thin laminate composite structures embedded with piezoelectric layers are analyzed in this work using the Finite Element Method (FEM). Triangular elements, called GPL-T9, with three nodes and six degrees of freedom per node (three displacement and three rotation components) and one degree of freedom per piezoelectric layer (electrical potential) are used. For static analysis the nonlinear equilibrium equations are solved using the Generalized Displacement Control Method (GDCM) while the dynamic solution is performed using the classical Newmark Method with an Updated Lagrangean Formulation (ULF). The system of equations is solved using the Gradient Cojugate Method (GCM) and in nonlinear cases an iterative-incremental scheme is employed. Several numerical examples are presented and compared with results obtained by other authors with different kind of elements and different schemes. The agreement among these results demonstrates the validity and effectiveness of the developed models.
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Hakala, Tim. "Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse Control." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/1061.
Full textAbstract:
A new method of adaptive impulse control is developed to precisely and quickly control the position of machine components subject to friction. Friction dominates the forces affecting fine positioning dynamics. Friction can depend on payload, velocity, step size, path, initial position, temperature, and other variables. Control problems such as steady-state error and limit cycles often arise when applying conventional control techniques to the position control problem. Studies in the last few decades have shown that impulsive control can produce repeatable displacements as small as ten nanometers without limit cycles or steady-state error in machines subject to dry sliding friction. These displacements are achieved through the application of short duration, high intensity pulses. The relationship between pulse duration and displacement is seldom a simple function. The most dependable practical methods for control are self-tuning; they learn from online experience by adapting an internal control parameter until precise position control is achieved. To date, the best known adaptive pulse control methods adapt a single control parameter. While effective, the single parameter methods suffer from sub-optimal settling times and poor parameter convergence. To improve performance while maintaining the capacity for ultimate precision, a new control method referred to as Adaptive Impulse Control (AIC) has been developed. To better fit the nonlinear relationship between pulses and displacements, AIC adaptively tunes a set of parameters. Each parameter affects a different range of displacements. Online updates depend on the residual control error following each pulse, an estimate of pulse sensitivity, and a learning gain. After an update is calculated, it is distributed among the parameters that were used to calculate the most recent pulse. As the stored relationship converges to the actual relationship of the machine, pulses become more accurate and fewer pulses are needed to reach each desired destination. When fewer pulses are needed, settling time improves and efficiency increases. AIC is experimentally compared to conventional PID control and other adaptive pulse control methods on a rotary system with a position measurement resolution of 16000 encoder counts per revolution of the load wheel. The friction in the test system is nonlinear and irregular with a position dependent break-away torque that varies by a factor of more than 1.8 to 1. AIC is shown to improve settling times by as much as a factor of two when compared to other adaptive pulse control methods while maintaining precise control tolerances.
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Braun, Michael Rainer. "Characterization of nonlinearity parameters in an elastic material with quadratic nonlinearity with a complex wave field." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26566.
Full textAbstract:
Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.Committee Chair: Jacobs, Laurence; Committee Co-Chair: Qu, Jianmin; Committee Member: DesRoches, Reginald. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Duzce, Zeynep. "Performance Evaluation Of Existing Medium Rise Reinforced Concrete Buildings According To 2006 Turkish Seismic Rehabilitation Code." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607834/index.pdf.
Full textAbstract:
Linear elastic and nonlinear analysis procedures of 2006 Turkish Seismic Rehabilitation Code are applied to medium rise reinforced concrete buildings. In this study, four storey residential buildings are designed according to the 1998 and 1975 Turkish Seismic Design Codes, and the analysis procedures are verified on these case studies. In addition to these buildings, the analysis procedures are tested on an existing school building before and after retrofitting.
The assessment procedures employed in the 2006 Turkish Seismic Rehabilitation Code are based on linear elastic analysis (equivalent lateral load method, mode superposition method)non-linear analysis (pushover analysis with equivalent lateral load method and mode superposition method) and non-linear time history analysis. In this study, linear elastic analysis with equivalent lateral loads and non-linear static analysis (pushover analysis) with equivalent lateral loads are investigated comparatively. SAP2000 software is used for pushover analysis
however the plastic rotation values obtained from SAP2000 are not used directly but defined according to the code procedures. Post-elastic rotations at yielding sections are transferred to Excel and the corresponding strains are calculated from these rotations by Excel Macro. These strains are compared with strain limits described in the 2006 Turkish Seismic Rehabilitation Code to obtain the member performances. In the linear elastic procedure, structural analysis is performed also by SAP2000 to obtain the demand values, whereas the capacity values are calculated by another Excel Macro. With these demand and capacity values, corresponding demand to capacity ratios are calculated and compared with demand to capacity ratio limits described in 2006 Turkish Seismic Rehabilitation Code to obtain the member performances. Global performances of the buildings are estimated from the member performances and from the inter-storey drifts for both two methods. The results are compared to each other, and critically evaluated.