It was not thought that there would be some major flaws in the design of widely used steel moment frames until the Northridge Earthquake hit the California on January 17, 1994. Until then, steel moment frames were practiced as the most ductile system and were used in buildings from few stories to skyscrapers. The heavy devastation from Northridge Earthquake was an alarm for all the people related to the design and construction of such structures and pushed everybody to act fast to find some possible solutions to such never-expected-problems. Following the earthquake, FEMA entered into a cooperative agreement with the SAC joint venture in order to get a transparent picture of the problems in the seismic performance of steel moment frames and to come up with suitable recommendations. The research was specifically done to address the following things: to inspect the earthquake-affected buildings in order to determine the damage incurred in the buildings, to find out ways to repair the damaged buildings and upgrade the performance of existing buildings, and to modify the design of new buildings in order to make them more reliable for seismic performance. Among the various new design suggestions, the Reduced Beam Section (RBS) connection has been one of the most efficient and reliable option for high ductility demands. The purpose of this research was to study the behavior of concrete slabs in the performance of steel moment frames with reduced beam sections based on ductility, strength and stiffness. The slab is an integral part of a building. It is always wiser to consider the slab in order to assess accurately the seismic behavior of a building under the earthquake loading. In this research, two sets of finite element models were analyzed. Each set had one bare steel moment frame and one concrete slab frame which acted as a composite section. The connections were designed using the AISC Seismic Design manual (AISC 2012). The finite element modeling was done using NISA DISPLAY-IV (NISA 2010). All the models, with and without the slab were analyzed under the same boundary conditions and loads. Both non-linear and linear analyses were performed. The results from non-linear analysis were used to compare the ductility and strength whereas linear analysis results were used to compare the stiffness between bare steel and composite frame models.

214 pages / The Fock-Tani (unitary) transformation of the second- quantized Hamiltonian gives a representation which treats reactants and products symmetrically, and composites exactly. Each term in the Fock-Tani potential corresponds to a specific physical process and contains terms orthogonalizing continuum states to the bound states. The difficulty in carrying out this transformation can be lessened by working in a center of mass system, giving (n-1) reduced mass particles. After a general analysis of such systems, the Fock- Tani transformations in the 3→2-body case are carried out for the reactions a⁺+(b⁺c⁻)→(a⁺c⁻)+b⁺ and a⁻+(b⁺c⁻)→(a⁻b⁺)+c⁻. It is found that for (2) the transformation in the symmetrical reduced mass system can easily be carried out, but the Jacobi reduced mass system requires the more complicated d-matrix approach. This transformation has not yet been attempted in the full 3-body system but is likely to be as difficult as that for (1). First order differential and total cross sections are computed for resonant charge transfer in (1) for a proton- hydrogen initial state. The Fock-Tani T-matrix for the initial-state Jacobi system is found to be identical to that for the full 3-body system. That for the symmetrical reduced mass system gives an error of order l/mprot in the incident wave vector. A comparison of the Jacobi version and a previous special case Fock-Tani transformation, where the proton mass is taken as infinite, is also made. Cross sections for (ls→ls) positronium formation in positron-hydrogen collisions, calculated using the same program as for the proton-hydrogen case, are found to disagree with the previous Fock-Tani result, probably due to lack of convergence of the previous result. Cross sections for reactions (1) involving muons in hydrogenic isotopes (of interest in quantum electrodynamics and catalyzed fusion) are also calculated. Finally, extension of the results to higher order is considered. Polarized Schrodinger wave functions for a system containing a hydrogenic atom and a fully kinetic external charge are found to first order. These would be used in the Fock-Tani matrix elements to account for some initial- and final-state effects. Calculations of distorted second-quantized states and second and third order T-matrix elements are also outlined.

Made available in DSpace on 2014-06-11T19:25:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-04-11Bitstream added on 2014-06-13T18:53:17Z : No. of bitstreams: 1 moraes_vm_me_ilha_prot.pdf: 4456756 bytes, checksum: 70a028ea28db2cfaed1abecec234c525 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As pontes mistas com vigas de madeira e tabuleiro de concreto, que constituem uma técnica já bastante estudada pelo meio acadêmico brasileiro, vêm ganhando cada vez mais espaço entre os projetistas e construtores de pontes em estradas vicinais do interior do Brasil. Entretanto, o vão dessas pontes é limitado pelo comprimento das peças de madeira, cujos valores máximos, em geral, ficam em torno de 6 metros para vigas serradas e 12 metros para vigas roliças. Neste contexto, a presente pesquisa propõe um novo sistema estrutural de pontes mistas para vencer vãos da ordem de 15 a 20 metros, constituído por vigas treliçadas de madeira que suportam a laje de concreto armado. O tabuleiro do sistema proposto pode ser executado utilizando, como pré-laje, painéis treliçados pré-moldados auto-portantes, evitando-se escoramentos e, conseqüentemente, reduzindo o tempo e os custos de construção. A laje final é solidarizada às treliças de madeira por intermédio de pinos metálicos de cisalhamento, que fazem com que ambos os materiais trabalhem solidariamente na resistência aos esforços solicitantes, buscando, portanto, a otimização do uso estrutural desses materiais. A principal abordagem desta pesquisa é experimental, com a construção e análise de um modelo físico reduzido na escala 1:4... / Timber-concrete composite structures - TCCS - constitute a technique well studied by the Brazilian academy and have been each time more present among the designers and constructors of bridges in secondary roads in the interior of Brazil. However, the span of these bridges is limited by the length of the timber beams, whose maximum values, in general, are around 6 meters for sawed beams and 12 meters for round beams. In this context, the present research suggests a new structural system of composite bridges, to overcome spans from 15 to 20 meters, built by trussed timber beams that support a reinforced concrete deck. The deck of the system can be executed using precast self-supported trussed panels, preventing props and, consequently, reducing time and costs of construction. The final slab is connected to the trussed beams by metallic shear bolts, which make that both the materials (timber and concrete) work together in the resistance to the requesting efforts, aiming the optimization of the structural use of these materials. This research was based on an experimental approach, with the construction and analysis of a reduced physical model in the scale 1:4, based on a bridge design classified as 30t with a free span of 16 meters. The model was instrumented with strain gauges and... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:31:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-06-01Bitstream added on 2014-06-13T19:41:52Z : No. of bitstreams: 1 bertolini_ev_dr_botfca.pdf: 976816 bytes, checksum: 33d964ee6a502afaba9948bd767da98f (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Cada sistema de manejo do solo é trabalhado de maneira própria, alterando de forma diferenciada as propriedades químicas, físicas e biológicas do solo, podendo requerer modificações nas recomendações e no manejo da adubação. Com o objetivo de avaliar o efeito da antecipação da adubação de semeadura, de dois sistemas de manejo do solo e dois espaçamentos entrelinhas no desempenho da cultura do milho, foi realizado este estudo. O experimento foi instalado e conduzido na Fazenda Experimental Lageado, pertencente à Faculdade de Ciências Agronômicas (FCA) da Universidade Estadual Paulista (UNESP), Campus de Botucatu, nos anos agrícolas de 2005/2006 e 2006/2007, em Nitossolo Vermelho Distroférrico. O delineamento experimental utilizado foi de blocos ao acaso com parcelas subsubdivididas e quatro repetições. As parcelas foram constituídas pelos sistemas de manejo do solo (plantio direto e preparo reduzido, caracterizado pela escarificação do solo por meio de equipamento provido de disco de corte da palhada e rolo nivelador/destorroador, trabalhando na profundidade entre 25 e 30 cm), as subparcelas pelas formas de adubação (adubação de pré-semeadura realizada na superfície do solo em área total antes da semeadura do milho e adubação convencional) e as subsubparcelas pelos espaçamentos entrelinhas (90 e 45 cm), totalizando 8 tratamentos. Os resultados obtidos foram submetidos ao teste de Tukey a 5% de probabilidade para comparar as médias entre os sistemas de manejo do solo, as formas de adubação, os espaçamentos entrelinhas e os desdobramentos das interações entre esses três fatores. As análises estatísticas demonstraram que o sistema plantio direto apresentou maior densidade do solo e resistência mecânica do solo à penetração, quando comparado ao preparo reduzido. Na operação de adubação de pré-semeadura os sistemas de manejo do solo... / Each soil tillage system is worked in proper way, modifying of differentiated form the chemical, physical and biological soil properties, and may require adaptations of fertilization recommendations and management. This study was conducted to evaluate the effect of sowing fertilization anticipation, two soil tillage systems and two row spacing on performance of the corn crop. The experiment was carried out at the “Faculdade de Ciências Agronômicas” (FCA), “Universidade Estadual Paulista” (UNESP), Botucatu-SP campus, from October 2005 to May 2007, in a Dystric Nitosol (FAO, 1974). The experimental design was in randomized blocks with split-split-plots and four repetitions. The main plots consisted of two soil tillage systems (no-tillage and reduced tillage with chisel plow with cut disk and planning roll, working at 25 to 30 cm deep), the split-plots of fertilizer application methods (surface fertilizer application before corn sowing and fertilizer application conventional) and split-split-plots of row spacings (0.90 m and 0.45 m), totalizing 8 treatments. Obtained results were analyzed by Tukey test at 5% of probability for comparing averages. Statistical analysis showed that no-tillage system had higher density as well as mechanical soil resistance to penetration, when compared to reduced tillage. For fertilizer application before corn sowing the soil tillage systems did not influence the traction force, bar power demanded, effective field capacity, demanded time, energy specific consumption and hourly fuel consumption; the reduced tillage showed higher area fuel consumption. For corn sowing it was observed that no-tillage system showed lower traction force, bar power demanded, energy specific consumption, hourly and area consumption of fuel. The 0.45 m row spacing showed higher traction force, bar power demanded, energy specific consumption... (Complete abstract click electronic access below)

A ventilação nas edificações tem por objetivo principal criar um ambiente interno confortável e saudável, preservando a qualidade do ar interior. Um dos principais sistemas de renovação do ar, e praticamente a única opção economicamente viável, utilizado no projeto de ambientes industriais é a ventilação natural. Esta pode ser promovida por dois mecanismos: o denominado efeito chaminé e o efeito dos ventos, porém também podem ocorrer pelos dois simultaneamente. O objetivo deste trabalho é pesquisar a viabilidade do emprego de modelos reduzidos no projeto da ventilação natural em pavilhões industriais, considerando unicamente o efeito chaminé. Para atingir esse objetivo foi ensaiado um modelo, com escala geométrica 1/100, de um pavilhão industrial real situado na cidade de Passo Fundo – RS, que será utilizado como uma fábrica para injeção de alumínio em carcaças e rotores elétricos. Nos ensaios foram medidas velocidades na abertura de saída, com anemômetro de fio quente, e temperaturas com termopares, tanto dentro como fora do modelo. Os resultados alcançados permitem avaliar quais são as leis de semelhança relevantes neste tipo de ensaio com modelo reduzido, as limitações do procedimento experimental e, ainda, determinar valores de vazões de ar nas aberturas de saída e compará-los com vazões obtidas através da utilização de alguns modelos teóricos. / The ventilation in the constructions has for main objective to create a comfortable and healthful internal environment, preserving the quality of the interior air. One of the main systems of renewal of air, and practically the only economically viable option, used in the industrial environment project is the natural ventilation. This can be promoted by two mechanisms: the called buoyancy and the effect of the winds, however also can occur for the two simultaneously. The objective of this work is to search the viability of the job of models reduced in the project of the natural ventilation in industrial pavilions, considering solely the buoyancy. To reach this objective a model was assayed, with geometric scale 1/100, of a situated real industrial pavilion in the city of Passo Fundo – RS, that will be used as a plant for injection of aluminum in carcasses and electric rotors. In the assays speeds in the exit opening had been measured, with anemometer of hot wire, and temperatures with thermocouples, in such a way inside as it are of the model. The reached results allow to evaluate which are the excellent laws of similarity in this type of assay with reduced model, the limitations of the experimental procedure and still to determine values of air outflows in the exit openings and to compare them with outflows gotten through the use of some theoretical models.

Soit G un groupe de Lie résoluble connexe et H un de ses sous-groupes fermés connexes d'algèbres de Lie g et h respectivement. On note g* (resp. h*) le dual linéaire de g (resp. h) ). Le sujet de ma thèse consiste à étudier la restriction d'une série discrète π de G, associée à une orbite coadjointe Ω C g*, à H. Si la restriction de π à H se décompose en somme directe de représentations de H avec multiplicités finies, on dit que π est H-admissible. Notons Pg,n : Ω → h* l'application restriction. Il s'agit de démontrer la conjecture suivante due à Michel Duflo : 1. La représentation π est H-admissible si et seulement si l'application moment Pg,n est propre sur l'image. 2. Si π est H-admissible, et si T est une série discrète de H alors sa multiplicité dans la restriction de π à H doit pouvoir se calculer en « quantifiant » l'espace réduit correspondant (qui est compact dans ce cas). Dans cette thèse, nous apportons une réponse positive à cette conjecture dans deux situations, à savoir :(i) Le groupe G est résoluble exponentiel. (ii) Le groupe G est le produit semi direct d'un tore compact par le groupe de Heisenberg et H est un sous-groupe algébrique connexe. / Let G be a connected solvable Lie group and H a closed connected subgroup with Lie algebra g and h respectively. We denote g* (resp. h*) the dual of g (resp. h). The aim of my thesis is to study the restriction of a discrete series π of G, associated with a coadjoint orbit Ω C g* to H. If the restriction of π to H can be decomposed in to a direct sum of representations of H with finite multiplicities, we say that π is H-admissible. Let Pg,n : Ω → h* denote the restriction map. My objective is to show the following conjecture due to Michel Duflo : 1. The representation π i s H-admissible if and only if the moment application Pg,n is proper on the image. 2. If π is H-admissible, and if T is a discrete series of H then it s multiplicity in the restriction of π to H must be calculated by « quantifying » the corresponding reduced space (that is compact in this case). In this thesis, we provide a positive response to this conjecture in two situations, namely when: (i) G is exponential solvable Lie group. (ii) G is the semi direct product of a compact torus and the Heisenberg group and H is a connected algebraic subgroup.

abstract: Recent studies of the occurrence of post-flutter limit cycle oscillations (LCO) of the F-16 have provided good support to the long-standing hypothesis that this phenomenon involves a nonlinear structural damping. A potential mechanism for the appearance of nonlinearity in the damping are the nonlinear geometric effects that arise when the deformations become large enough to exceed the linear regime. In this light, the focus of this investigation is first on extending nonlinear reduced order modeling (ROM) methods to include viscoelasticity which is introduced here through a linear Kelvin-Voigt model in the undeformed configuration. Proceeding with a Galerkin approach, the ROM governing equations of motion are obtained and are found to be of a generalized van der Pol-Duffing form with parameters depending on the structure and the chosen basis functions. An identification approach of the nonlinear damping parameters is next proposed which is applicable to structures modeled within commercial finite element software. The effects of this nonlinear damping mechanism on the post-flutter response is next analyzed on the Goland wing through time-marching of the aeroelastic equations comprising a rational fraction approximation of the linear aerodynamic forces. It is indeed found that the nonlinearity in the damping can stabilize the unstable aerodynamics and lead to finite amplitude limit cycle oscillations even when the stiffness related nonlinear geometric effects are neglected. The incorporation of these latter effects in the model is found to further decrease the amplitude of LCO even though the dominant bending motions do not seem to stiffen as the level of displacements is increased in static analyses. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2015

abstract: This investigation develops small-size reduced order models (ROMs) that provide an accurate prediction of the response of only part of a structure, referred to as component-centric ROMs. Four strategies to construct such ROMs are presented, the first two of which are based on the Craig-Bampton Method and start with a set of modes for the component of interest (the β component). The response in the rest of the structure (the α component) induced by these modes is then determined and optimally represented by applying a Proper Orthogonal Decomposition strategy using Singular Value Decomposition. These first two methods are effectively basis reductions techniques of the CB basis. An approach based on the “Global - Local” Method generates the “global” modes by “averaging” the mass property over α and β comp., respectively (to extract a “coarse” model of α and β) and the “local” modes orthogonal to the “global” modes to add back necessary “information” for β. The last approach adopts as basis for the entire structure its linear modes which are dominant in the β component response. Then, the contributions of other modes in this part of the structure are approximated in terms of those of the dominant modes with close natural frequencies and similar mode shapes in the β component. In this manner, the non-dominant modal contributions are “lumped” onto the dominant ones, to reduce the number of modes for a prescribed accuracy. The four approaches are critically assessed on the structural finite element model of a 9-bay panel with the modal lumping-based method leading to the smallest sized ROMs. Therefore, it is extended to the nonlinear geometric situation and first recast as a rotation of the modal basis to achieve unobservable modes. In the linear case, these modes completely disappear from the formulation owing to orthogonality. In the nonlinear case, however, the generalized coordinates of these modes are still present in the nonlinear terms of the observable modes. A closure-type algorithm is then proposed to eliminate the unobserved generalized coordinates. This approach, its accuracy and computational savings, was demonstrated on a simple beam model and the 9-bay panel model. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2017

abstract: This investigation is focused on the consideration of structural uncertainties in nearly-straight pipes conveying fluid and on the effects of these uncertainties on the dynamic response and stability of those pipes. Of interest more specifically are the structural uncertainties which affect directly the fluid flow and its feedback on the structural response, e.g., uncertainties on/variations of the inner cross-section and curvature of the pipe. Owing to the complexity of introducing such uncertainties directly in finite element models, it is desired to proceed directly at the level of modal models by randomizing simultaneously the appropriate mass, stiffness, and damping matrices. The maximum entropy framework is adopted to carry out the stochastic modeling of these matrices with appropriate symmetry constraints guaranteeing that the nature, e.g., divergence or flutter, of the bifurcation is preserved when introducing uncertainty. To support the formulation of this stochastic ROM, a series of finite element computations are first carried out for pipes with straight centerline but inner radius varying randomly along the pipe. The results of this numerical discovery effort demonstrate that the dominant effects originate from the variations of the exit flow speed, induced by the change in inner cross-section at the pipe end, with the uncertainty on the cross-section at other locations playing a secondary role. Relying on these observations, the stochastic reduced order model is constructed to model separately the uncertainty in inner cross-section at the pipe end and at other locations. Then, the fluid related mass, damping, and stiffness matrices of this stochastic reduced order model (ROM) are all determined from a single random matrix and a random variable. The predictions from this stochastic ROM are found to closely match the corresponding results obtained with the randomized finite element model. It is finally demonstrated that this stochastic ROM can easily be extended to account for the small effects due to uncertainty in pipe curvature. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2017

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Mingjun Wei / In this study, a global Proper Orthogonal Decomposition (POD)-Galerkin based Reduced Order model (ROM) is proposed. It is extended from usual fixed-domain problems to more general fluid-solid systems with moving boundaries/interfaces. The idea of the extension is similar to the immersed boundary method in numerical simulations which uses embedded forcing terms to represent boundary motions and domain changes. This immersed boundary method allows a globally defined fixed domain including both fluid and solid, where POD-Galerkin projection can be directly applied. However, such a modified approach cannot get away with the unsteadiness of boundary terms which appear as time-dependent coefficients in the new Galerkin model. These coefficients need to be pre-computed for prescribed periodic motion, or worse, to be computed at each time step for non-prescribed (e.g. with fluid-structure interaction) or non-periodic situations. Though computational time for each unsteady coefficient is smaller than the coefficients in a typical Galerkin model, because the associated integration is only in the close neighborhood of moving boundaries. The time cost is still much higher than a typical Galerkin model with constant coefficients. This extra expense for moving-boundary treatment eventually undermines the value of using ROMs. An aggressive approach is to decompose the moving boundary/domain to orthogonal modes and derive another low-order model with fixed coefficients for boundary motion. With this domain decomposition, an approach including two coupled low-order models both with fixed coefficients is proposed. Therefore, the new global ROM with decomposed approach is more efficient. Though the model with the domain decomposition is less accurate at the boundary, it is a fair trade-off for the benefit on saving computational cost. The study further shows, however, that the most time-consuming integration in both approaches, which come from the unsteady motion, has almost negligible impact on the overall dynamics. Dropping these time-consuming terms reduces the computation cost by at least one order while having no obvious effect on model accuracy. Based on this global POD-Galerkin based ROM with forcing term, an improved ROM which can handle the parametric variation of body motions in a certain range is also presented. This study shows that these forcing terms not only represent the moving of the boundary, but also decouple the moving parameters from the computation of model coefficients. The decoupling of control parameters provides the convenience to adapt the model for the prediction on states under variation of control parameters. An improved ROM including a shit mode seems promising in model adaptation for typical problems in a fixed domain. However, the benefit from adding a shit mode to model diminishes when the method is applied to moving-boundary problems. Instead, a combined model, which integrates data from a different set of parameters to generate the POD modes, provides a stable and accurate ROM in a certain range of parametric space for moving-boundary problems. By introducing more data from a different set of parameters, the error of the new model can be further reduced. This shows that the combined model can be trained by introducing more and more information. With the idea of the combined model, the improved global ROM with forcing terms shows impressive capability to predict problems with different unknown moving parameters, and can be used in future parametric control and optimization problems.