Orientadores: Katia Lucchesi Cavalca Dedini, Euclides de Mesquita Neto / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-17T09:33:08Z (GMT). No. of bitstreams: 1 Ramalho_DeniseAlves_D.pdf: 3277236 bytes, checksum: d90e15781524b19a49afda1e9c94e31d (MD5) Previous issue date: 2010 / Resumo: Nas últimas três décadas houve um desenvolvimento notável em métodos e tópicos de pesquisa a respeito da análise da dinâmica de máquinas rotativas. Um dos tópicos que têm atraído a atenção de pesquisadores é a interação de máquinas rotativas com suas estruturas de suporte. Sabe-se que a dinâmica da estrutura pode exercer um importante papel na resposta do rotor. Mas há um tópico que ainda não recebeu a atenção que deveria. As estruturas de suporte do rotor estão colocadas sobre uma fundação e esta fundação interage com suas vizinhanças e com o solo. A questão da influência da fundação e do solo na resposta do rotor ainda não foi completamente estudada. Tentativas anteriores de descrever o comportamento do sistema rotor-fundação-solo são limitadas a modelos muito simples de solo. O objetivo deste trabalho é estudar a influência do solo no comportamento de máquinas rotativas. Isto foi feito através de um modelo rotor-mancais-fundação-solo. Obtém-se a resposta desbalanceada de um rotor Laval bidimensional, desprezando-se o efeito giroscópico. Variou-se o tipo de solo, considerando um semi-espaço e um solo do tipo camada sobre base rígida, sendo este último um solo com um aumento repentino de rigidez a uma determinada profundidade. Em cada um destes solos, houve uma variação do amortecimento interno. Além disso, para o solo do tipo camada sobre base rígida, houve uma variação da espessura dessa camada. Estes solos são caracterizados pela densidade, coeficiente de Poisson e módulo de cisalhamento, e são considerados viscoelásticos. Os modelos destes solos, utilizados neste trabalho, são modelos numéricos e foram obtidos utilizando o método dos elementos de contorno / Abstract: In the last three decades there has been a notable development of methods and research topics regarding the analysis of the dynamics of rotating machines. One topic that has attracted researcher's attention is the interaction of rotor - foundation interaction. It is well known that the dynamics of the structure play an important hole in the rotor response. However, one topic has still not received the attention it should have. The rotor support structure was placed on a foundation, and the foundation interacted with its neighbourwood and with the soil. The issue of the influence of both the foundation and the soil on the rotor response has not yet been completely studied. Previous attempts to describe the behaviour of the system rotor-foundationsoil were limited to very simple models of the soil. The objective of this work is to study the influence of the soil on the behaviour of rotating machines. This study was carried out by using a rotor-bearing-foundation-soil model. An unbalanced response of a bidimentional Laval rotor isobtained. The gyroscopic effect was neglected. The type of soil was varied, considering a halfspace and a stratified soil. The last soil had a sadden increase in the stiffness at a certain depth. In each one of these soils there has been a variation in the internal damping. Moreover, the thickness of the stratified soil has varied. These soils are caracterized by the density, Poisson's cofficient and shear modulus, and they are considered visco-elastic. In this work, the soil models are numerical and they were obtained by using the boundary element method / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica

Orientador: Euclides de Mesquita Neto / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-22T16:25:35Z (GMT). No. of bitstreams: 1 Damasceno_DanielaAndrade_M.pdf: 2682018 bytes, checksum: 7ce33af8b9732384f2d62dd3b6553c3f (MD5) Previous issue date: 2013 / Resumo: Neste trabalho procurou-se desenvolver uma metodologia para análise transiente de sistemas dinâmicos que apresentem acoplamento solo-estrutura. O sistema dinâmico inicialmente é um sistema acoplado, o qual será desacoplado em dois subsistemas. A metodologia desenvolvida é baseada em um método de acoplamento iterativo entre subsistemas, podendo os subsistemas apresentar domínios limitado e ilimitado. Os subsistemas são tratados de forma independente, podendo ser formulados de acordo com as características e necessidades do sistema, seja solo ou estrutura. O sistema dinâmico em analise é um sistema representado por uma fundação com massa, apoiada em um solo modelado como um semi-espaço tridimensional transversalmente isotrópico e viscoelástico. Desacoplando-se o sistema na interface solo-fundação têm-se dois subsistemas, um representado pela fundação com massa, apresentando um domínio limitado, e o outro representando o semi-espaço, apresentando um domínio ilimitado. O subsistema representado pela fundação com massa será formulado pelo Método numérico de Newmark, e o subsistema representado pelo semi-espaço será formulado pela Integral de Convolução, pois a solução em deslocamento está disponível no domínio da frequência, podendo assim utilizar a Transformada Rápida de Fourier para a obtenção da resposta transiente ao impulso do semi-espaço tridimensional / Abstract: The aim of this work is to present a methodology for transient analysis of coupled soil-structure systems. The initially coupled system is uncoupled into two subsystems. The methodology is based on a method of iterative coupling between subsystems, in which each subsystem may be a bounded or an unbounded domain. The subsystems are treated independently and may be formulated according to the characteristics and requirements of the system, soil or structure. The system that is studied in the present work comprises a foundation with mass, resting on the surface of a soil, which is modeled as a three-dimensional, viscoelastic, transversely isotropic half-space. The system is divided at the interface between the soil and the foundation. The first subsystem is the bounded domain comprising the foundation with mass, which is solved by Newmark numerical method. The second subsystem consists of the half-space, for which there is a classical solution in the frequency domain. This solution is used together with a convolution integral scheme to obtain the transient solution that is necessary to the present iterative method / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestra em Engenharia Mecânica

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A new precast-prestressed cross section was recently developed by a consortium of engineers from the six New England states, New York and members of the northeast region of PCI. The northeast extreme Tee (NEXT) beam is efficient for medium Bridge spans (50 to 80 ft long). Field formwork savings are introduced by having a flange cast integrally during fabrication of the beams at the precasting plant. Job safety is increased because a working platform is created. The flange width of the NEXT Beams can be adjusted during fabrication to accommodate roadways of different widths and skew angles. Because the section is new with complexity in its shape, the present design guidance cannot be used to evaluate LLDFs for NEXT beams within the context of the AASHTO LRFD. In particular, the use of live-load distribution factors (LLDFs) equations in LRFD for NEXT beams is not straightforward. The distance between the beam webs is variable depending on whether it is measured within a beam module or between adjacent modules. In absence of detailed information a PCI technical committee evaluated LLDFs (through AASHTO 2010 Bridge specification) for the NEXT beams used in the Brimfield Bridge by two different approaches and found one of them conservative. The conservative approach was single stem which uses the average spacing (between webs ([S1+S3]/2)) for use in the LLDF equations.. The committee expressed concerns about whether trends of LLDFs would be similar for other parametric sets, and would like to standardize the methodology for the Bridge projects in Massachusetts with NEXT beam as the girder. To verify the conservativeness of single stem methodology (for the evaluation of LLDFs) for other parameters this research project was initiated. LLDFs are evaluated based on the two approaches and compared with the LLDFs obtained through finite element modeling. The results of 40-3D finite element models have been used to compare the LLDFs obtained from AASHTO 2010 Bridge design specification. The results were also used to compare different parameters that affect LLDFs of NEXT beams including span, skew angle, and beam end fixity. The finite element models were created using a Bridge prototype that is being instrumented for future field verification of the analyses. The models were created using frame elements for the beams and shell elements for the cast in place deck. The integral abutment and foundation of the Bridges was included in the models in which piles are created using frame elements and abutments are created using shell elements. The results indicate that the approach taken for the design of NEXT beams is in general conservative for interior girders of the Bridge. On the contrary such the adopted approach was not yielding the higher value of LLDFs. The variation in strains due to losses are compared by two methods (strains variation obtained from field data and strain variation obtained based on AASHTO equation of losses) to verify the AASHTO equation of losses.

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Seismic pressures on displacing or rigid retaining or basement walls have been derived based on the original work of Mononobe and Okabe, who used a shake table to calculate dynamic pressures of displacing retaining walls existing in cohesionless soils. Since this original work was done over eighty years ago, the results of Mononobe and Okabe, colloquially known as M-O theory, have been applied to different conditions, including non-displacing basement walls, as well as changes in soil properties. Since the original work of M-O, there have been numerous studies completed to verify the accuracy of the original calculation, most notably the work of Seed and Whitman (1970), Wood (1973), Sitar (Various), and Ostadan (2005). This has resulted in varying opinions for the accuracy of M-O theory, whether it is grossly unconservative or conservative, as well as its effectiveness for situations where the wall does not displace enough to engage active soil conditions. This study examines (3) different wall cases, a cantilever retaining wall, gravity retaining wall, and rigid basement wall, through an implcit finite element analysis, under simple sinusoidal boundary accelerations. The soil is modeled using the Drucker-Prager model for elastic-plastic properties. The dynamic pressure increment is observed for different driving frequencies, with the anticipation that an in-phase and out of phase response between the soil and structure will be achieved, resulting in both lower and higher than M-O pressure values.

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