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1
Shrestha, Santosh. "A COMPARATIVE STUDY OF EQUIVALENT LATERAL FORCE METHOD AND RESPONSE SPECTRUM ANALYSIS IN SEISMIC DESIGN OF STRUCTURAL FRAMES". OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2561.
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Equivalent Lateral Force Method (ELF) and Response Spectrum Analysis (RSA) are the two most popular methods of seismic design of structures. This study aims to present a comparative study of the two methods using hand-calculated approach as well as computer analysis according to ASCE 7-10 Standards. The two methods have been compared in terms of base shear and story forces by analyzing various models for different number of stories and different support conditions. It was found that ELF gives conservative results in comparison to RSA. This result was more obvious in case of four-story frames. Hence, for structures of increased elevation, the analysis from ELF may not be sufficient.
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Yang, Yan. "Nonstructural component field testing method for the evaluation of seismic demand incorporating floor response spectrum". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46567.
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Nonstructural component (NSC) failures due to earthquake events can cause significant economic losses and even life-threatening hazards to occupants. In order to mitigate nonstructural seismic damages, it is critical to assess the seismic force demand which can be utilized to optimize the design of the NSC, and/or to assess methods of rehabilitation on anchorages to enhance seismic strength.
The existing design codes and standards provide guidelines to calculate the minimum lateral earthquake force for designing a new NSC. However, they do not reflect the in-service condition of an existing NSC, which can vary significantly from when it was first installed. This study is intended to develop an easy-to-implement methodology to assess the seismic force demand of an existing NSC under normal operation.
The procedure of the proposed methodology includes two principle phases: 1) field modal identification testing and 2) floor response spectrum analyses using a 3D finite element model (FEM). The practicality of this methodology was assessed through a case study on the U.B.C Hospital Koerner Pavilion building. In this study, the focus is on the machinery and equipment that are critical for the operation of a hospital. During the experimental stage, the fundamental frequencies and damping ratios of eight NSCs were identified. In the second phase, the horizontal floor response spectra (FRS) were constructed from the linear time history analysis results performed on a FEM. Finally, the FRS is used to obtain the lateral seismic force of each NSC corresponding to its dynamic properties. These forces were then compared with those obtained using the NBCC 2010 code equation to demonstrate the effectiveness of this method.
Results from the case study provided evidence that the proposed method is overall a simple and effective tool for diagnosing the in-service modal properties of a NSC. The testing results can be easily applied in FRS analysis to obtain a more realistic nonstructural seismic force than that from the NBCC 2010 approach. The potential applications and limitations of the proposed methodology are also discussed in this dissertation to facilitate engineers to determine the suitability of this method to their specific projects.
3
Kinali, Kursat. "Seismic Fragility Assessment of Steel Frames in the Central and Eastern United States". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14528.
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The Central and Eastern United States (CEUS) is a region that is characterized by low frequency-high consequence seismic events such as the New Madrid sequence of 18111812. The infrequent nature of earthquakes in the region has led to a perception that the seismic risk in the area is low, and the current building stock reflects this perception. The majority of steel-framed buildings in the CEUS were designed without regard to seismic loads. Such frames possess limited seismic resistance, and may pose an unacceptable risk if a large earthquake were to occur in the region. A key ingredient of building performance and seismic risk assessment is the fragility, a term that describes the probability of failure to meet a performance objective as a function of demand on the system. The effects of uncertainties on building seismic performance can be displayed by a seismic fragility relationship. This fragility can be used in a conditional scenario-based seismic risk assessment or can be integrated with seismic hazard to obtain an estimate of annual or lifetime risk. The seismic fragility analyses in this study focus on steel frames that are typical of building construction in regions of infrequent seismicity; such frames have received little attention to date in building seismic risk assessment. Current steel building stock in Shelby Co., TN has been represented by five code-compliant model frames with different lateral force-resisting systems, i.e., braced-frames, partially-restrained moment frames and a rigid moment frame. The performance of model frames under certain hazard levels was assessed using fragility curves. Different rehabilitation methods were discussed and applied. Results indicate that PR frames behave better than expected and rehabilitated frames perform quite well even under severe earthquakes.
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Badaoui, M'Hammed. "Influence de l'hétérogénéité géologique et mécanique sur la réponse des sols multicouches". Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00462182.
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Dans cette thèse nous nous sommes intéressés à établir une formulation probabiliste pour l'analyse du comportement d'un sol multicouche avec des caractéristiques aléatoires. Deux grands axes sont traités : ?la consolidation primaire et ?la réponse sismique des sols multicouches ayant des caractéristiques aléatoires. Nous utilisons les simulations de Monte Carlo associées à des méthodes semi-analytiques adaptées aux sols multicouches avec une stratification horizontale. Nous avons aussi comparés les résultats obtenus à partir de cette formulation à ceux fournis par les règlements parasismiques suivants : RPA 99 (version 2003), UBC 97 et l'EC8. Cette étude a montré que les valeurs maximales des forces de cisaillement à la base des bâtiments variaient substantiellement en fonction de la variation de la hauteur du profil de sol ainsi que de son hétérogénéité pouvant atteindre un rapport relatif de l'ordre de 3 dans les cas les plus défavorables. Ce rapport peut également être inférieur à 1 conduisant à des structures moins économiques
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Dahl, Jason F. "Time Aliasing Methods of Spectrum Estimation". Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd157.pdf.
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Navrátilová, Martina. "Nelineární dynamická analýza konstrukce zatížena seismickými účinky". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227701.
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Diploma thesis compares the methods for the calculation of the response of structures with seismic loads. Linear and nonlinear analyses are used for the calculations. In the case of linear analysis response spectrum method is applied. For nonlinear analysis pushover method is used. These two methods are compared in programs AxisVM and RFEM on the examples of high-rise building and space frame.
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Čapičík, Martin. "Seismická analýza čerpadla 200-QHD". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231287.
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The main goal of this thesis is dynamic analysis of shaft of booster pump QHD-200. In the beginning we offer basic equations generally used in dynamics and common/possible methods for their solution. Then we focus on specific problems connected with rotor dynamics and using simple Laval rotor we show their mathematical interpretation. Based on given load as accelerogram we create response spectrum in different ways (using different methods) and compare their CPU time demand. In the next part we make three finite element models of different physical level. We perform modal analysis and comparison of eigen frequencies, mode shapes. In following chapter transient analysis was performed on all models. As load we use accelerogram. We evaluate translations in particular positions of model. After that, we decide whether or not gap between impeller and stator case will be erased. Finally we make assessment of force acting upon bearings.
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DITOLLA, ROBERT JOHN. "RANDOM VIBRATION ANALYSIS BY THE POWER SPECTRUM AND RESPONSE SPECTRUM METHODS (WHITE NOISE, FINITE-ELEMENT, VANMARCKE, DENSITY, NASTRAN)". Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183836.
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Determination of the stresses and displacements which occur in response to random excitations cannot be accomplished by traditional deterministic analysis methods. As the specification of the excitation and the response of the structure become more complex, solutions by direct, closed-form methods require extensive computations. Two methods are presented which can be used in the analysis of structures which are subjected to random excitations. The Power Spectrum Method is a procedure which determines the random vibration response of the structure based upon a frequency response analysis of a structural model. The Response Spectrum Method is a method which is based upon specified forces or displacements as a function of time. A derivation of each of the methods is presented and followed by comparisons of the results which were obtained for single and multiple-degree-of-freedom systems. Assumptions and limitations of the methods are discussed as well as their accuracy over ranges of frequency, damping and loading specification. As a direct application and comparison of the two methods, an analysis of the support system for the primary mirror of the Space Infrared Telescope Facility (SIRTF) has been performed. In addition, a method for the evaluation of the critical damping in a single-degree-of-freedom structure is demonstrated.
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Wormell, Caroline Leslie. "Statistical properties of chaotic systems: from 1D maps to high dimensions". Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/22296.
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Many important physical systems, such as the Earth's climate, are chaotic: as such we would like (probabilistic) predictions of these systems into the far future. These systems' long-term statistical behaviour is mathematically encoded by various objects, which can be studied functional-analytically using the so-called transfer operator. While rigorous study of many simple, usually one-dimensional, chaotic systems is theoretically tractable, for more complex, high-dimensional systems it is not: as a result the statistical properties of simple chaotic systems are often used as models for those of more complex systems, an idea that has been partially formalised as the Gallavotti-Cohen chaotic hypothesis. To study these simple dynamical systems better, we will in the first part of this thesis rigorously develop efficient, powerful numerics for two classes of one-dimensional maps: uniformly expanding Markov maps, and intermittent maps. To do this, we harness the smooth structure of these problems, in particular by discretising transfer operators using spectral basis functions. We obtain highly accurate numerical estimates of statistical properties of these maps: later, we apply the methods profitably to a numerical continuation problem associated with more complex systems. In the second part of the thesis we investigate high-dimensional systems, focusing on the differentiability of the response of statistical properties to dynamical perturbations (linear response theory). Although there are rigorous examples of one-dimensional maps that do not have differentiable responses, it is commonly believed that complex, high-dimensional chaotic systems generally do. We examine this belief through a study of model classes of ``high-dimensional systems''. We provide a comprehensive picture of the response properties of these systems and give broadly-applicable criteria governing the response's differentiability. In particular, we find classes of maps that, despite being composed of microscopic subsystems with non-differentiable responses, obey linear response theory, and vice versa.
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Jakel, Roland. "Linear Dynamic System Analyses with Creo Simulate – Theory & Application Examples, Capabilities, Limitations –". Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-225992.
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1. Einführung in die Theorie dynamischer Analysen mit Creo Simulate 2. Modalanalysen (Standard und mit Vorspannung) 3. Dynamische Analysen einschließlich Klassifizierung der Analysen; einige einfache Beispiele für eigene Studien (eine Welle unter Unwuchtanregung und ein Ein-Massen-Schwinger) sowie etliche Beispiele größerer dynamischer Systemmodelle aus unterschiedlichsten Anwendungsbereichen 4. Feedback an den Softwareentwickler PTC (Verbesserungsvorschläge und Softwarefehler) 5. Referenzen1. Introduction to dynamic analysis theory in Creo Simulate 2. Modal analysis (standard and with prestress) 3. Dynamic analysis, including analysis classification, some simple examples for own self-studies (shaft under unbalance excitation and a one-mass-oscillator) and several real-world examples of bigger dynamic systems 4. Feedback to the software developer PTC (enhancement requests and code issues) 5. References
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Olsen, Peter A. "Shear Modulus Degradation of Liquefying Sand: Quantification and Modeling". BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1214.
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A major concern for geotechnical engineers is the ability to predict how a soil will react to large ground motions produced by earthquakes. Of all the different types of soil, liquefiable soils present some of the greatest challenges. The ability to quantify the degradation of a soil's shear modulus as it undergoes liquefaction would help engineers design more reliably and economically. This thesis uses ground motions recorded by an array of downhole accelerometers on Port Island, Japan, during the 1995 Kobe Earthquake, to quantify the shear modulus of sand as it liquefies. It has been shown that the shear modulus of sand decreases significantly as it liquefies, apparently decreasing in proportion to the increasing excess pore water pressure ratio (Ru). When completely liquefied, the shear modulus of sand (Ru = 1.0) for a relative density of 40 to 50% is approximately 15% of the high-strain modulus of the sand in its non-liquefied state, or 1% of its initial low-strain value. Presented in this thesis is an approach to modeling the shear modulus degradation of sand as it liquefies. This approach, called the "degrading shear modulus backbone curve method" reasonably predicts the hysteretic shear stress behavior of the liquefied sand. The shear stresses and ground accelerations computed using this method reasonably matches those recorded at the Port Island Downhole Array (PIDA) site. The degrading shear modulus backbone method is recommended as a possible method for conducting ground response analyses at sites with potentially liquefiable soils.
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Parent, Laure. "The use of Monte Carlo methods to study the effect of X-Ray spectral variations on the response of an Amorphous Silicon Electronic Portal Imaging Device". Thesis, Institute of Cancer Research (University Of London), 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444169.
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Plášil, Pavel. "Interakce konstrukce ocelové nádrže a kapaliny při seizmické události". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226475.
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Construction of structural computational model of the tank with fluid using program package ANSYS based on the Finite Element Method. Solve eigen-vibration of the tank with or without effects of fluid. Application of Euler and Lagrange method for modeling fluid. Solve seismic response using response spectra. Verify of the tank in accordance to EC 3 and EC8.
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Hipolito, Fabio Camilo. "Avaliação das metodologias de análise de sistemas de tubulações de vapor sujeitas a carregamentos do tipo Steam Hammer". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/85/85133/tde-11112016-151816/.
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Carregamentos transientes termo hidráulicos do tipo Steam Hammer são eventos comuns em sistemas de tubulações de vapor com grandes potenciais de catástrofes em plantas de geração de energia. Uma vez iniciado o evento, ondas de pressões são geradas com amplitudes, geralmente, de grande magnitude ocasionando altas pressões no sistema, ruídos, deformações, fadiga, com possibilidade de danos materiais e econômicos e em casos extremos fatalidades. Os procedimentos da indústria para análise deste tipo de sistema consistem realização de análises estáticas equivalentes ou análise de espectro de resposta com carregamentos caracterizados por meio de métodos analíticos baseados em hipóteses simplificadoras do fluido e fluxo. Neste trabalho é proposta a analise de sistema de tubulações por meio do método de integração numérica com superposição modal e carregamento caracterizado por método numérico com base no método das características. Comparações foram efetuadas entre os resultados obtidos pela metodologia proposta e os procedimentos da indústria, demonstrando que, dado ao alto grau de conservadorismo, os procedimentos da indústria acarretam em superdimensionamento de estruturas e tubulações ocasionando custos adicionais de projeto, sendo a otimização do projeto obtida aplicando-se a metodologia proposta no trabalho.Steam Hammer is a common transient thermo hydraulic event in steam piping systems with potential to cause serious damages in power generation plants. It generates pressure waves, generally of great amplitude and magnitude, causing high pressures in the system, associated with noise, with possible material and economic damages and, in extreme case, even fatalities. Industry procedures for analysis of these events consists of performing equivalent static analysis, or response spectrum analysis, with transient loadings calculated by analytical methods based on assumptions of fluid and flow. This paper proposes a new methodology for the piping system analysis by the numerical integration method with modal superposition and transient loadings calculated by a numerical method based on the method of characteristics. Comparisons were made between the results obtained by the proposed methodology and the stablished industry procedures, confirming that, due to the high degree of conservatism, industry procedures can lead to additional cost to the design, with the optimization of the design being obtained by applying the methodology proposed in this paper.
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Petrusa, Douglas C. "Evaluation and analysis of DDG-81 simulated athwartship shock response". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FPetrusa.pdf.
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Kunicka, Beata Iwona. "Spacecraft dynamic analysis and correlation with test results : Shock environment analysis of LISA Pathfinder at VESTA test bed". Thesis, Luleå tekniska universitet, Rymdteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62910.
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The particular study case in this thesis is the shock test performed on the LISA Pathfinder satellite conducted in a laboratory environment on a dedicated test bed: Vega Shock Test Apparatus (VESTA). This test is considered fully representative to study shock levels produced by fairing jettisoning event at Vega Launcher Vehicle, which induces high shock loads towards the satellite. In the frame of this thesis, some transient response analyses have been conducted in MSC Nastran, and a shock simulation tool for the VESTA test configuration has been developed. The simulation tool is based on Nastran Direct Transient Response Analysis solver (SOL 109), and is representative of the upper composite of Vega with the LISA Pathfinder coupled to it. Post-processing routines of transient response signals were conducted in Dynaworks which served to calculate Shock Response Spectra (SRS). The simulation tool is a model of forcing function parameters for transient analysis which adequately correlates with the shock real test data, in order to understand how the effect of shock generated by the launcher is seen in the satellite and its sub-systems. Since available computation resources are limited the parameters for analysis were optimised for computation time, file size, memory capacity, and model complexity. The forcing function represents a release of the HSS clamp band which is responsible for fairing jettisoning, thus the parameters which were studied are mostly concerning the modelling of this event. Among many investigated, those which visibly improved SRS correlation are radial forcing function shape, implementation of axial impulse, clamp band loading geometry and refined loading scheme. Integration time step duration and analysis duration were also studied and found to improve correlation. From each analysis, the qualifying shock environment was then derived by linear scaling in proportion of the applied preload, and considering a qualification margin of 3dB. Consecutive tracking of structural responses along shock propagation path exposed gradual changes in responses pattern and revealed an important property that a breathing mode (n = 0) at the base of a conical Adapter translates into an axial input to the spacecraft. The parametrisation itself was based on responses registered at interfaces located in near-field (where the clamp band is located and forcing function is applied) and medium-field with respect to the shock event location. Following shock propagation path, the final step was the analysis of shock responses inside the satellite located in a far-field region, which still revealed a very good correlation of results. Thus, it can be said that parametrisation process was adequate, and the developed shock simulation tool can be qualified. However, due to the nature of shock, the tool cannot fully replace VESTA laboratory test, but can support shock assessment process and preparation to such test. In the last part of the thesis, the implementation of some finite element model improvements is investigated. Majority of the panels in spacecraft interior exhibited shock over-prediction due to finite element model limitation. Equipment units modelled as lump masses rigidly attached with RBE2 elements to the panel surface are a source of such local over-predictions. Thus, some of the units were remodelled and transient responses were reinvestigated. It was found that remodelling with either solid elements, or lump mass connected to RBE3 element and reinforced by RBE2 element, can significantly improve local transient responses. This conclusion is in line with conclusions found in ECSS Shock Handbook.
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Čada, Zdeněk. "Vliv technické a přírodní seizmicity na stavební konstrukce se zaměřením na konstrukce ze zdicích materiálů". Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-233808.
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The dissertation deals with selected issues in the field of the calculation of the response of building structures which are excited with dynamic non-stationary displacement loading of its ground. Seismic load has been assumed. Procedures, how to work with seismic records with respect to the accuracy of dynamic calculations, how to modify the response spectrum to ensure the reliability, how to generate synthetic accelerogram requiring more accurate response, are recommended. Synthetic akcelerogram has been generated by own approaching, which has been used as the excitation function in the experimental seismic testing of autoclaved concrete brick building in model scale. Response values of motion in the measured points of the experiment were compared with the linear and nonlinear dynamic calculations by using the finite element method models. Different levels of detail of the numerical models have been used. The shear wall behaviour has been modelled by using constitutive models with brittle failure as well as using of non-linear interaction interface with possible delamination between the masonry bricks. The behaviour of the mathematical model of wall systems has been calibrated with respect to the measured data at shear wall experiments in real and model scale of walls.
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Oudich, Hamza. "Analytical Investigation of Planetary Gears Instabilities and the Impact of Micro-Macro Geometry Modifications". Thesis, KTH, Farkostteknik och Solidmekanik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276775.
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Due to their large torque-speed ratio and transmission efficiency, planetary gears are widely used in the automotive industry. However, high amplitude vibrations remain their critical weakness, which limits their usage especially when new strict noise legislations come into action. A new approach to handle the instability problems of planetary gears encountered in real industrial context is presented in this work. First, the dynamic response of a planetary gear failing to pass the noise regulations is theoretically investigated through an analytical model. The equations of motion were solved using the Spectral Iterative Method. The observed experimental results correlated well with those from the developed model. In order to limit the resonance phenomena, impacts of different macro and micro-geometry modifications were analytically investigated: quadratic teeth profile, different planets positioning, different number of teeth and number of planets. Optimum modifications were retrieved and are expected to be tested experimentally on a test bench and on the truck. Finally, the analytical model’s limits and sensitivity to different parameters were investigated in order to certify its reliability, and suggestions for improvements were presented.
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OLIVEIRA, ICIMONE B. de. "Desenvolvimento do cristal semicondutor de brometo de tálio para aplicações como detector de radiação e fotodetector". reponame:Repositório Institucional do IPEN, 2006. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11385.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:01/09049-5
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MURA, LUIS F. L. "Medidas de taxas de reacao nuclear e de indices espectrais ao longo do raio das pastilhas combustiveis do reator IPEN/MB-01". reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9617.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Jakel, Roland. "Berechnung von Schockspektren und praktische Anwendung der dynamischen Stoßanalyse in Creo Elements / Pro Mechanica". Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-68407.
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Der Vortrag stellt Idee und Grundlagen der Berechnung von Schockantwortspektren dar. Er zeigt, wie man exemplarisch für einen Halbsinusstoß das Schockantwortspektrum in der PTC FEM-Software Creo Elements / Pro Mechanica berechnen kann. Die Schockantworten eines Ein- und Zweimassenschwingers werden sowohl zeitaufgelöst als auch über die dynamische Stoßanalyse berechnet. Die modalen Superpositionsmethoden "Absolute Summe" und "SRSS" (Square Root of the Sum of the Squares - geometrischer Mittelwert) werden vorgestellt. Als reales Beispiel werden Schockanalysen für verschiedene Halbsinusimpulse mit einem Wärmebildgerät der Firma Carl Zeiss Optronics GmbH durchgeführt und mit einer zeitaufgelösten Analyse verglichen. Abschließend wird auf die Erzeugung von Antwortspektren für die Substrukturauslegung eingegangenThe presentation explains idea and fundamentals of shock response spectra analysis. With help of the PTC FEM-software Creo Elements / Pro Mechanica the shock response spectra (SRS) for an exemplary half sine shock is calculated. The shock response of a one-mass and a two-mass oscillator are analyzed per dynamic time as well as per dynamic shock analysis. The modal superposition methods "absolute sum" and "SRSS" (Square Root of the Sum of the Squares) are explained. The method is applied for different half sine shocks on a realistic example: A thermal imaging system of the company Carl Zeiss Optronics GmbH. Finally, the creation of response spectra for global-local analysis is explained
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Chaouki, Saïd. "Logiciel de traitement du signal". Rouen, 1987. http://www.theses.fr/1987ROUES024.
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Etude d'un algorithme pour le traitement d'un signal. Cet algorithme est composé de différents programmes indépendants permettant le calcul des polynômes orthonormaux, le calcul récursif, le calcul de la transformée de Fourier, de densité spectrale, réponse impulsionnelle d'un filtre numérique. Application à la reconnaissance des formes et simulation du processus de Lévy
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Muscolino, G., i Alessandro Palmeri. "An earthquake response spectrum method for linear light secondary substructures". 2007. http://hdl.handle.net/10454/611.
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YesEarthquake response spectrum is the most popular tool in the seismic analysis and design of structures. In the case of combined primary-secondary (P-S) systems, the response of the supporting P substructure is generally evaluated without considering the S substructure, which in turn is only required to bear displacements and/or forces imposed by the P substructure (¿cascade¿ approach). In doing so, however, dynamic interaction between the P and S components is neglected, and the seismic-induced response of the S substructure may be heavily underestimated or overestimated. In this paper, a novel CQC (Complete Quadratic Combination) rule is proposed for the seismic response of linear light S substructures attached to linear P substructures. The proposed technique overcomes the drawbacks of the cascade approach by including the effects of dynamic interaction and different damping in the substructures directly in the cross-correlation coefficients. The computational effort is reduced by using the eigenproperties of the decoupled substructures and only one earthquake response spectrum for a reference value of the damping ratio.
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Dash, Sweta Swagatika. "Seismic Analysis of High- Rise Building by Response Spectrum Method". Thesis, 2015. http://ethesis.nitrkl.ac.in/7023/2/Seismic_Dash_2015.pdf.
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Reinforced Concrete Frames are the most commonly adopted buildings construction practices in India. With growing economy, urbanisation and unavailability of horizontal space increasing cost of land and need for agricultural land, high-rise sprawling structures have become highly preferable in Indian buildings scenario, especially in urban. With high-rise structures, not only the building has to take up gravity loads, but as well as lateral forces. Many important Indian cities fall under high risk seismic zones, hence strengthening of buildings for lateral forces is a prerequisite. In this study the aim is to analyze the response of a high-rise structure to ground motion using Response Spectrum Analysis. Different models, that is, bare frame, brace frame and shear wall frame are considered in Staad Pro. and change in the time period, stiffness, base shear, storey drifts and top-storey deflection of the building is observed and compared.
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RAZA, AAMIR. "SEISMIC ANALYSIS OF CONFINED MASONRY STRUCTURE USING ETABS". Thesis, 2022. http://dspace.dtu.ac.in:8080/jspui/handle/repository/19390.
Pełny tekst źródłaStreszczenie:
Buildings are our basic needs. It protect us from rain, sun, theif e.t.c. We spend most of
our time in a building whether it is residential, commercial, institutional, industrial. In
Damage or collapsing of such types of vital structures leads to a lot of risk for human
lives & results in monetary loss. So, the building should be earthquake resistant. One
of the reasons of failure of structure is earthquake. It is found that the reasons behind
these collapses are mostly due to the poor construction practices and substandard
practices involved in the construction of building. As a structural engineer our duty
should be to improve the seismic performance of structure with keeping economy in
mind.
Confined masonry structure is a construction technology/typology in which first wall
are constructed, followed by column and beam. It is similar to RCC and masonry
structure in appearance but different in resisting the earthquake load. Due to the lack of
relevant design and construction standards, confined masonry construction is currently
not practiced in India. However, several initiatives have been launched to promote
confined masonry construction over the last ten years.
This paper presents the seismic analysis of confined masonry structure using ETABS.
Response spectrum method is used for analysis to study the in plane and out of plane
behaviour under earthquake loading in seismic zone v. Effect of wall density and shape
of column on the seismic performance of confined masonry structure has been also
studied. To study the effect of wall density, analysis is done for 110 mm wall, 150mm
wall and 230mm wall. To study the effect of shape of column, rectangular and square
column is used. Performance of confined masonry and RC frame structure has been
also studied. Results are compared on the basis of maximum storey displacement, max
storey drift, base shear, overturning moment, modal mass participation ratio.
With the study it has been observed that by increasing the wall density seismic
performance of confined masonry structure has been increased. In CMS, it has been
observed that max storey displacement and drift was less but overturning moment &
base shear was more as compare to RC frame structure.
26
Lu, Shao-Tai, i 呂紹台. "Analysis and Verification of Micro-satellite Structure Subjected to Shock Environmental Loading Using Vibration Response Spectrum Method". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/13045472952742676316.
Pełny tekst źródłaStreszczenie:
碩士國立成功大學
航空太空工程學系碩博士班
96
The main goal of this thesis is using vibration response spectrum method to predict the resonance response of a single-degree-of-freedom structural system under the base vibration excitation that is induced by external shock environment. Also, with using FEM simulation software “ANSYS”, we could simulate the dynamic response of a PCB structure under vibration load. Then, discussed the diverseness of projection between response spectrum of multi-degree-of-freedom system and vibration response spectrum method of a single-degree-of-freedom system. Moreover, with using free-falling impact tester to generate the same shock environment on PCB structure. We can verify the accuracy of vibration response spectrum method under the shock vibration environment. Subsequently, with the application of the aforesaid method, the structural analysis of LEAP satellite which made by NCKU can show the acceleration response of main payload in satellite system under launch shock vibration environment. For the sake of reference of future analysis, design and improvement of satellite, the survey of cumulation between the natural frequency and peak value of vibration response method prediction is important. Herewith the survival rate of satellite and payload can be raised during the launching. Besides, the subsystem and payload damage caused by the improper design of structure can be reduced accordingly.
27
VISHWAKARMA, ADITYA. "ANALYSIS OF SEISMIC SUSCEPTIBILITY OF AN IRREGULARLY PLANNED SETBACK STRUCTURE WITH A SOFT STOREY ON SLOPING TERRAIN AND PLAIN TERRAIN". Thesis, 2023. http://dspace.dtu.ac.in:8080/jspui/handle/repository/19972.
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The construction of multi-story setback buildings with soft storey, or open ground floor,
is in high demand and becoming more and more popular. This effort decreases the
setback configuration's vertical stability and the lateral load resisting system's rigidity.
When a building is supported on sloping land, there are several possibilities for short
and long columns inside the same structure. During earthquake shaking, all columns
and floor slabs at every level move horizontally by the same amount, which may result
in structural damage. In this study, an attempt is made to examine the seismic
performance of setback buildings standing on flat ground as well as on a slope, with
soft storey layout. ETABS, a widely used software programme, was used to analyse
simple 3-D frames of SETBACK structures. Using the study findings several graphs
were drawn for like base shear, storey drift, storey stiffness, displacement, rotation
about z axis are developed for both terrains i.e. plain and sloping. To create a technical
expertise two identical structure were examined on both terrains. All the modelled
structures with open ground storey have been analysed using two distinct methods:
equivalent static force technique, response spectrum method. To counteract this soft
storey impact and the severe reactions, mitigation approaches have been implemented,
and the most effective of these mitigation techniques is provided.
28
YanHuang, Jiun, i 黃俊諺. "Numerical Analysis and Experiment study of Reduced Mockup Micro-satellite Structure Model Subjected to impulsive Loading Using the Shock Response Spectrum Method". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/63831159990298339804.
Pełny tekst źródłaStreszczenie:
碩士國立成功大學
航空太空工程學系碩博士班
98
The main goal of this thesis is using shock response spectrum method that is expanded from the single-degree-of-freedom structural system to predict the response under the base shock excitation induced by external shock environment. The closed-form solutions for the transient structural response of an undamped structural system with SDOF sustain the impact acceleration pulse from five types of waveform(half sine, rectangular, decay triangular, sawtooth, symmetrical triangular) are derived. The largest response describes the shock response spectrum. After that, confer the effect of different drop impact test conditions on the transient structural response of the printed circuit board. And then with using FEM simulation software “ANSYS” and “Ls-Dyna” to simulate the dynamic response of a PCB structure under shock load, and then the response will compared with the transient analysis and the spectrum analysis. Moreover, use free-falling impact tester to generate the same shock environment on PCB structure. We can verify the accuracy of shock response spectrum method under the shock vibration environment. The transient analysis was using Input-G-method which the acceleration can be directly input to the support screw of PCB assembly as boundary condition and requires building the model of the test vehicle only whereas does not have to consider friction of the guide rod for the drop table and the strike material. The spectrum analysis combine the shock response spectrum to predict the largest response of structure, and the analysis method can be used in Pyroshock, Seismic Shock and launcher flying. Subsequently, with the application of the aforesaid method, the structural analysis of CKUTEX satellite which made by NCKU can show the effect of main payload and control PCB in satellite system under launcher shock vibration environment. For the sake of reference of future analysis, design and improvement of satellite, Herewith the survival rate of satellite and payload can be raised during the launching. Besides, the subsystem and payload damage caused by the improper design of structure can be reduced accordingly.
29
余建鴻. "Comparisons of Various Response-Spectrum Methods". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/03766777793199336892.
Pełny tekst źródłaStreszczenie:
碩士國立成功大學
土木工程研究所
88
The purpose of this study is to determine the optimal reponse - spectrum method by comparing with the time - history method. The time - history analysis can be considered as the most accurate method of dynamic analyses that can analyze the structural deflections and the member inner force of each time step. However, the data are too huge to design. Therefore, it is reasonable to use the response - spectrum methods in this study to calculate the maximum member forces and moments. There are twelve kinds of earthquakes consist of six kinds of X - direction and six kinds of Y - direction under the assumptions of the rigidity and flexibility of the building diagram. All buildings have different sizes and stories. From these data, we discovered that CQC rule is the optimal response - spectrum method.
30
B, Mallikarjun. "Response of extended eulerbernoulli beam under impulse load using wavelet spectral finite element method". Thesis, 2012. http://ethesis.nitrkl.ac.in/3909/1/RESPONSE_OF_EXTENDED_EULER-BERNOULLI_BEAM_UNDER_IMPULSE_LOAD_USING_WAVELET_SPECTRAL_FINITE_ELEMENT_METHOD.pdf.
Pełny tekst źródłaStreszczenie:
Transform methods are some of those methods which are able to solve certain difficult ordinary and partial differential equation. The most commonly used transform for these solutions are Laplace and Fourier transforms. Wavelet transforms are new entrants in to this area, although
they are quite popular with electrical and communication engineers in characterizing and synthesizing the time signals. The utility of wavelet transforms is shown in structural engineering by addressing problems involving solutions of ordinary and partial differential equations
encountered in dynamical related problems.
Dynamical problems in structural engineering fall under two categories, one involving low frequencies, which is called structural dynamics problems, and the other involving very high frequencies, which is called the wave propagation problems. The most problems in structural engineering fall under the former category, wherein the response of the entire structural system is characterized using only the first few vibrational modes. The wave propagation is a multi-modal phenomenon involving vibrational modes of very high frequencies. Conventional analysis tools
such as finite element cannot handle these problems due to modeling limitations and extensive computational cost. The only alternative to such problems is the method based on transforms.Spectral finite element (SFE) method is one such transform method, which can be a viable alternative to solving problems involving high frequency excitations. SFE based on Fourier transform is quite well known and established. However, it has severe limitations in handling
finite structures and specifying non-zero boundary/initial conditions, and thus its utility in solving real world problems involving high frequency excitation is limited.
The aim of the present work is to show that the wavelet transform is very useful in solving ordinary differential equations by modeling the structure as a discrete system involving structural dynamic problems and it is to use wavelet transform to solve those problems involving partial
differential equations. In this work, the response of an cantilever Extended Euler-Bernoulli aluminum beam under impulse load applied axial and transverse at the free end is shown. The response is being obtained by coding programs in MATLAB.
31
Venna, Venkateswarareddy. "Delamination effect on response of a composite beam by wavelet spectral finite element method". Thesis, 2012. http://ethesis.nitrkl.ac.in/3913/1/DELAMINATION_EFFECT_ON_RESPONSE_OF_A_COMPOSITE_BEAM_BY_WAVELET_SPECTRAL_FINITE_ELEMENT_METHOD.pdf.
Pełny tekst źródłaStreszczenie:
Transform methods are very useful to solve the ordinary and partial differential equations. Fourier and Laplace transforms are the most commonly used transforms. Wavelet transforms are most popular with electrical and communication engineers to analyse the signals. From last few years, Wavelet transforms are in use for structural engineering problems, like solution of ordinary and partial differential equations. Dynamical problems in structural engineering fall under two categories, one involving low frequencies (structural dynamics problems) and the other involving high frequencies (wave propagation problems).
Spectral Finite Element (SFE) method is a transform method to solve the high frequency excitation problems which are encountered in structural engineering. SFE based on Fourier transforms has high limitations in handling finite structures and boundary conditions. SFE based with wavelet transforms is a very good tool to analyse the dynamical problems and eliminate many limitations.
In this project, a model for embedded de-laminated composite beam is developed using the wavelet based spectral finite element (WSFE) method for the de-lamination effect on response using wave propagation analysis. The simulated responses are used as surrogate experimental results for the inverse problem of detection of damage using wavelet filtering. The technique used to model a structure that, through width de-lamination subdivides the beam into base-laminates and sub-laminates along the line of de-lamination. The base-laminates and sub-laminates are treated as structural waveguides and kinematics are enforced along the connecting line. These waveguides are modeled as Timoshenko beams with elastic and inertial coupling and the corresponding spectral elements have three degrees of freedom, namely axial, transverse and shear displacements at each node. The internal spectral elements in the region of de-lamination are assembled assuming constant cross sectional rotation and equilibrium at the interfaces between the base-laminates and sub-laminates. Finally, the redundant internal spectral element nodes are condensed out to form two-noded spectral elements with embedded de-lamination. The response is being obtained by coding programs in MATLAB.
32
Choi, Myoung. "THE MODAL DISTRIBUTION METHOD: A NEW STATISTICAL ALGORITHM FOR ANALYZING MEASURED RESPONSE". 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-580.
Pełny tekst źródłaStreszczenie:
A new statistical algorithm, the "modal distribution method", is proposed to
statistically quantify the significance of changes in mean frequencies of individual
modal vibrations of measured structural response data. In this new method, a power
spectrum of measured structural response is interpreted as being a series of independent modal responses, each of which is isolated over a frequency range and treated as
a statistical distribution. Pairs of corresponding individual modal distributions from
different segments are compared statistically.
The first version is the parametric MDM. This method is applicable to well-
separated modes having Gaussian shape. For application to situations in which the
signal is corrupted by noise, a new noise reduction methodology is developed and
implemented. Finally, a non-parametric version of the MDM based on the Central
Limit Theorem is proposed for application of MDM to general cases including closely
spaced peaks and high noise. Results from all three MDMs are compared through
application to simulated clean signals and the two extended MDMs are compared
through application to simulated noisy signals. As expected, the original parametric MDM is found to have the best performance if underlying requirements are met:
signals that are clean and have well-separated Gaussian mode shapes. In application
of nonparametric methods to Gaussian modes with high noise corruption, the noise reduction MDM is found to have lower probability of false alarms than the nonparametric MDM, though the nonparametric is more efficient at detecting changes.
In closely related work, the Hermite moment model is extended to highly skewed
data. The aim is to enable transformation from non-Gaussian modes to Gaussian
modes, which would provide the possibility of applying parametric MDM to well-
separated non-Gaussian modes. A new methodology to combine statistical moments
using a histogram is also developed for reliable continuous monitoring by means of
MDM.
The MDM is a general statistical method. Because of its general nature, it may
find a broad variety of applications, but it seems particularly well suited to structural
health monitoring applications because only very limited knowledge of the excitation
is required, and significant changes in computed power spectra may indicate changes,
such as structural damage.
33
(10702248), Hugo Esquivel. "Efficient Spectral-Chaos Methods for Uncertainty Quantification in Long-Time Response of Stochastic Dynamical Systems". Thesis, 2021.
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Uncertainty quantification techniques based on the spectral approach have been studied extensively in the literature to characterize and quantify, at low computational cost, the impact that uncertainties may have on large-scale engineering problems. One such technique is the generalized polynomial chaos (gPC) which utilizes a time-independent orthogonal basis to expand a stochastic process in the space of random functions. The method uses a specific Askey-chaos system that is concordant with the measure defined in the probability space in order to ensure exponential convergence to the solution. For nearly two decades, this technique has been used widely by several researchers in the area of uncertainty quantification to solve stochastic problems using the spectral approach. However, a major drawback of the gPC method is that it cannot be used in the resolution of problems that feature strong nonlinear dependencies over the probability space as time progresses. Such downside arises due to the time-independent nature of the random basis, which has the undesirable property to lose unavoidably its optimality as soon as the probability distribution of the system's state starts to evolve dynamically in time.
Another technique is the time-dependent generalized polynomial chaos (TD-gPC) which utilizes a time-dependent orthogonal basis to better represent the stochastic part of the solution space (aka random function space or RFS) in time. The development of this technique was motivated by the fact that the probability distribution of the solution changes with time, which in turn requires that the random basis is frequently updated during the simulation to ensure that the mean-square error is kept orthogonal to the discretized RFS. Though this technique works well for problems that feature strong nonlinear dependencies over the probability space, the TD-gPC method possesses a serious issue: it suffers from the curse of dimensionality at the RFS level. This is because in all gPC-based methods the RFS is constructed using a tensor product of vector spaces with each of these representing a single RFS over one of the dimensions of the probability space. As a result, the higher the dimensionality of the probability space, the more vector spaces needed in the construction of a suitable RFS. To reduce the dimensionality of the RFS (and thus, its associated computational cost), gPC-based methods require the use of versatile sparse tensor products within their numerical schemes to alleviate to some extent the curse of dimensionality at the RFS level. Therefore, this curse of dimensionality in the TD-gPC method alludes to the need of developing a more compelling spectral method that can quantify uncertainties in long-time response of dynamical systems at much lower computational cost.
In this work, a novel numerical method based on the spectral approach is proposed to resolve the curse-of-dimensionality issue mentioned above. The method has been called the flow-driven spectral chaos (FSC) because it uses a novel concept called enriched stochastic flow maps to track the evolution of a finite-dimensional RFS efficiently in time. The enriched stochastic flow map does not only push the system's state forward in time (as would a traditional stochastic flow map) but also its first few time derivatives. The push is performed this way to allow the random basis to be constructed using the system's enriched state as a germ during the simulation and so as to guarantee exponential convergence to the solution. It is worth noting that this exponential convergence is achieved in the FSC method by using only a few number of random basis vectors, even when the dimensionality of the probability space is considerably high. This is for two reasons: (1) the cardinality of the random basis does not depend upon the dimensionality of the probability space, and (2) the cardinality is bounded from above by M+n+1, where M is the order of the stochastic flow map and n is the order of the governing stochastic ODE. The boundedness of the random basis from above is what makes the FSC method be curse-of-dimensionality free at the RFS level. For instance, for a dynamical system that is governed by a second-order stochastic ODE (n=2) and driven by a stochastic flow map of fourth-order (M=4), the maximum number of random basis vectors to consider within the FSC scheme is just 7, independent whether the dimensionality of the probability space is as low as 1 or as high as 10,000.
With the aim of reducing the complexity of the presentation, this dissertation includes three levels of abstraction for the FSC method, namely: a specialized version of the FSC method for dealing with structural dynamical systems subjected to uncertainties (Chapter 2), a generalized version of the FSC method for dealing with dynamical systems governed by (nonlinear) stochastic ODEs of arbitrary order (Chapter 3), and a multi-element version of the FSC method for dealing with dynamical systems that exhibit discontinuities over the probability space (Chapter 4). This dissertation also includes an implementation of the FSC method to address the dynamics of large-scale stochastic structural systems more effectively (Chapter 5). The implementation is done via a modal decomposition of the spatial function space as a means to reduce the number of degrees of freedom in the system substantially, and thus, save computational runtime.
34
ALDERUCCI, TIZIANA. "Methods for the analysis of structural systems subjected to seismic acceleration modelled as stochastic processes". Doctoral thesis, 2017. http://hdl.handle.net/11570/3105309.
Pełny tekst źródłaStreszczenie:
In the framework of the design and of the reliability assessment of fixed structures, among the static and dynamic loads that have to be considered, certainly the most important one is the seismic load, due to its terrible and disastrous consequences, not only in terms of the breakdown of the structure but also for the preservation of life. In fact during the past decades Italy has been the scene of terrible earthquakes, that destroyed whole cities and with a lot of human victims. First of all, in terms of magnitude and, unfortunately, a large number of deaths, Messina earthquake, in 1908, caused about 120000 victims, between Messina and Reggio Calabria, with an estimated magnitude of 7.1 (Richter scale). Then Irpinia earthquake, in 1980 (2914 victims, 6.5 Ricther), L’Aquila earthquake, in 2009 (309 victims, 5.9 Ricther) and the last events in 2016 in the centre of Italy, see Amatrice (299 victims, 6 Richter), Ussita (5.9 Richter), and Norcia (2 victims, 6.1 Ricther).
Due to the difficulty in the prevision of the seismic event, one of the most important and hard problem in seismic engineering is the correct characterization of the ground motion acceleration; in fact it has been demonstrated that it is possible to increase the reliability level of the structures defining in a suitable way the seismic input and shaping realistically the structure.
Nowadays, from the analysis of the large amount of data of recorded events, it is possible to study the main characteristics of real earthquakes and reproduce them with analytical models. In particular, because of the randomness of the seismic event, in terms of energy distribution and intensity, propagation path of the seismic waves through any specified location from the earthquake focus to the epicenter, etc…, it has been shown that it should be modelled as a stochastic process.
On the other hand, once the input has been defined, the second problem in the seismic engineering is the reliability assessment of the structures subjected to the ground motion acceleration. It is obvious that, if the excitations are modelled as random processes, the dynamic responses are random processes too, and the structural safety needs to be evaluated in a probabilistic sense. Among the models of failure, the simplest one, which is also the most widely used in practical analyses, is based on the assumption that a structure fails as soon as the response at a critical location exits a prescribed safe domain for the first time. In random vibration theory, the problem of probabilistically predicting this event is termed first passage problem. Unfortunately, this is one of the most complicated problem in computational stochastic mechanics. Therefore, several approximate procedures have been proposed. These procedures lead to the probabilistic assessment of structural failure as a function of barrier crossing rates, distribution of peaks and extreme values. The latter quantities can be evaluated, for non-stationary input process, as a function of the well-known Non-Geometric Spectral Moments (NGSMs).
Aim of this thesis is to propose a novel procedure to obtain closed form solutions of the spectral characteristics of the response of linear structural systems subjected to seismic acceleration modelled as stochastic processes. The proposed method is a powerful tool in the analysis of both classically and non-classically damped systems, in reliability assessment problems and takes into account also the case of multi-correlated forcing input.
In Chapter 1 the preliminary definitions of probability theory are outlined, starting from the concept of random variable and stochastic process, analysing the stationary Gaussian random process with its statistics, with a short discussion on the probability distribution for maxima.
Chapter 2 focuses on the characterization of the ground motion acceleration, thanks’ to a statistical analysis of a set of real earthquakes; the different strategies to model the ground motion acceleration stochastic process will be investigated. Furthermore, in order to follow the prescriptions of the building codes, a procedure to generate artificial fully non-stationary spectrum-compatible accelerograms will be proposed.
The spectral characteristics of the response of linear structural systems, subjected to non-stationary excitation, will be obtained in Chapter 3 and, in Chapter 4, closed form solutions of the Time-Frequency varying Response (TFR) vector function will be proposed. In particular the main steps of the proposed approach are: i) the use of modal analysis, or the complex modal analysis, to decouple the equation of motion; ii) the introduction of the modal state variable in order to evaluate the NGSMs, in the time domain, as element of the Pre-Envelope Covariance (PEC) matrix; iii) the determination, in state variable, by very handy explicit closed-form solutions, of the TFR vector functions and of the Evolutionary Power Spectral Density (EPSD) matrix function of the structural response for the most common adopted models of the seismic input in the framework of stochastic analysis; iv) the evaluation of the spectral characteristics of the stochastic response by adopting the closed-form expression of the EPSD matrix function.
Finally, in Chapter 5 the reliability assessment of structural systems will be performed; in particular two different approaches for the first passage probability problem will be used: the method requiring the evaluation of the mean up-crossing rate of given thresholds, considered independent or occurring in clumps, and the method requiring censored closures of the non-stationary extreme value random response process.
Several numerical applications will be done in order to test the effectiveness of the proposed procedure; in particular the presented results will be compared with the Monte Carlo simulation method, that will confirm the validity and the generality of the proposed method.
35
Sarkar, Soumyadipta. "Methods on Probabilistic Structural Vibration using Stochastic Finite Element Framework". Thesis, 2016. http://etd.iisc.ac.in/handle/2005/3071.
Pełny tekst źródłaStreszczenie:
Analysis of vibration of systems with uncertainty in material properties under the influence of a random forcing function is an active area of research. Especially the characterization based on mode shapes and frequencies of linear vibrating systems leads to much discussed random eigenvalue problem, which repeatedly appears while analyzing a number of engineering systems. Such analyses with conventional schemes for significant variation of system parameters for large systems are often not viable because of the high computational costs involved. Appropriate tools to reduce the size of stochastic vibrating systems and efficient response calculation are yet to mature. Among the mathematical tools used in this case, polynomial chaos formulation of uncertainties shows promise. But this comes with the implementation issue of solving large systems of nonlinear equations arising from Bubnov-Galerking projection in the formulation. This dissertation reports the study of such dynamic systems with uncertainties characterized by the probability distribution of eigen solutions under a stochastic finite element framework.
In the context of structural vibration, the determination of appropriate modes to be considered in a stochastic framework is not straightforward. In this dissertation, at first the choice of dominant modes in stochastic framework is studied for vibration problems. A relative measure, based on the average energy contribution of each mode to the system, is developed. Further the interdependence of modes and the effect of the shape of the load on the choice of dominant modes are studied. Using these considerations, a hybrid algorithm is developed based on polynomial chaos framework for the response analysis of a structure with random mass and sickness and under the influence of random force. This is done by using modal truncation for response analysis with in a Monte Carlo loop. The algorithm is observed to be more efficient and achieves a high degree of accuracy compared to conventional techniques.
Considering the fact that the Monte Carlo loops within the above mentioned hybrid algorithm is easily parallelizable, the efficient implementation of it depends on the SFE solution. The set of nonlinear equations arising from polynomial chaos formulation is solved using matrix-free Newton’s iteration using GMRES as linear solver. Solution of a large system using a iterative method like GMRES necessitates the use of a good preconditioner. Keeping focus on the par-allelizability of the algorithm, a number of efficient but cheap-to-construct preconditioners are developed and the most effective among them is chosen. The solution process is parallelized for large systems. The scalability of solution process in conjunction with the preconditioner is studied in details.
36
Sarkar, Soumyadipta. "Methods on Probabilistic Structural Vibration using Stochastic Finite Element Framework". Thesis, 2016. http://hdl.handle.net/2005/3071.
Pełny tekst źródłaStreszczenie:
Analysis of vibration of systems with uncertainty in material properties under the influence of a random forcing function is an active area of research. Especially the characterization based on mode shapes and frequencies of linear vibrating systems leads to much discussed random eigenvalue problem, which repeatedly appears while analyzing a number of engineering systems. Such analyses with conventional schemes for significant variation of system parameters for large systems are often not viable because of the high computational costs involved. Appropriate tools to reduce the size of stochastic vibrating systems and efficient response calculation are yet to mature. Among the mathematical tools used in this case, polynomial chaos formulation of uncertainties shows promise. But this comes with the implementation issue of solving large systems of nonlinear equations arising from Bubnov-Galerking projection in the formulation. This dissertation reports the study of such dynamic systems with uncertainties characterized by the probability distribution of eigen solutions under a stochastic finite element framework.
In the context of structural vibration, the determination of appropriate modes to be considered in a stochastic framework is not straightforward. In this dissertation, at first the choice of dominant modes in stochastic framework is studied for vibration problems. A relative measure, based on the average energy contribution of each mode to the system, is developed. Further the interdependence of modes and the effect of the shape of the load on the choice of dominant modes are studied. Using these considerations, a hybrid algorithm is developed based on polynomial chaos framework for the response analysis of a structure with random mass and sickness and under the influence of random force. This is done by using modal truncation for response analysis with in a Monte Carlo loop. The algorithm is observed to be more efficient and achieves a high degree of accuracy compared to conventional techniques.
Considering the fact that the Monte Carlo loops within the above mentioned hybrid algorithm is easily parallelizable, the efficient implementation of it depends on the SFE solution. The set of nonlinear equations arising from polynomial chaos formulation is solved using matrix-free Newton’s iteration using GMRES as linear solver. Solution of a large system using a iterative method like GMRES necessitates the use of a good preconditioner. Keeping focus on the par-allelizability of the algorithm, a number of efficient but cheap-to-construct preconditioners are developed and the most effective among them is chosen. The solution process is parallelized for large systems. The scalability of solution process in conjunction with the preconditioner is studied in details.
37
(9708611), Zackery Ray Roberson. "Advances in Gas Chromatography and Vacuum UV Spectroscopy: Applications to Fire Debris Analysis & Drugs of Abuse". Thesis, 2021.
Znajdź pełny tekst źródłaStreszczenie:
In forensic chemistry, a quicker and more accurate analysis of a sample is always being pursued. Speedy analyses allow the analyst to provide quick turn-around times and potentially decrease back-logs that are known to be a problem in the field. Accurate analyses are paramount with the futures and lives of the accused potentially on the line. One of the most common methods of analysis in forensic chemistry laboratories is gas chromatography, chosen for the relative speed and efficiency afforded by this method. Two major routes were attempted to further improve on gas chromatography applications in forensic chemistry.The first route was to decrease separation times for analysis of ignitable liquid residues by using micro-bore wall coated open-tubular columns. Micro-bore columns are much shorter and have higher separation efficiencies than the standard columns used in forensic chemistry, allowing for faster analysis times while maintaining the expected peak separation. Typical separation times for fire debris samples are between thirty minutes and one hour, the micro-bore columns were able to achieve equivalent performance in three minutes. The reduction in analysis time was demonstrated by analysis of ignitable liquid residues from simulated fire debris exemplars.
The second route looked at a relatively new detector for gas chromatography known as a vacuum ultraviolet (VUV) spectrophotometer. The VUV detector uses traditional UV and far-ultraviolet light to probe the pi and sigma bonds of the gas phase analytes as well as Rydberg traditions to produce spectra that are nearly unique to a compound. Thus far, the only spectra that were not discernable were from enantiomers, otherwise even diastereomers have been differentiated. The specificity attained with the VUV detector has achieved differentiation of compounds that mass spectrometry, the most common detection method for chromatography in forensic chemistry labs, has difficulty distinguishing. This specificity has been demonstrated herein by analyzing various classes of drugs of abuse and applicability to “real world” samples has been demonstrated by analysis of de-identified seized samples.