京都大学 / 新制・課程博士 / 博士(工学) / 甲第24900号 / 工博第5180号 / 新制||工||1989(附属図書館) / 京都大学大学院工学研究科建築学専攻 / (主査)教授 西山 峰広, 教授 池田 芳樹, 教授 山本 貴士 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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[pt] O Peru se localiza na região denominada cinturão de fogo do Pacífico, onde se registra aproximadamente 85 porcento da atividade sísmica mundial. Como grande produtor de minérios, importantes estruturas são construídas no país para desenvolvimento de projetos de mineração, incluindo barragens de rejeitos. Nesta dissertação é investigado o potencial de liquefação dinâmica de uma barragem de rejeitos localizada na região central do Peru, que atualmente passa por uma etapa de alteamento pelo método construtivo da linha de centro. A liquefação dos solos é um fenômeno caracterizado pela perda de rigidez e resistência durante curto intervalo de tempo, mas suficiente para causar instabilidades e, em casos extremos, o colapso da estrutura. Análises numéricas foram realizadas para verificar o potencial de liquefação dinâmica da barragem, representando o comportamento cíclico dos materiais suscetíveis à liquefação pelo modelo constitutivo UBCSand e de Byrne, considerando terremotos de magnitude 8,2, 7,8 e 8,1. Resultados numéricos obtidos foram comparados com formulações simplificadas, utilizadas na prática de engenharia para determinação do fator de segurança contra liquefação dinâmica. As análises indicaram que rejeitos finos, abaixo do nível de lençol freático, apresentam potencial de liquefação, conforme valores do parâmetro de razão de poropressão (ru) computados, porém sem provocar risco à estabilidade geral da estrutura. São também apresentados resultados de deslocamentos permanentes em alguns pontos da barragem e dos rejeitos. / [en] Peru is located in the region called the Pacific fire belt, where approximately 85 percent of the world seismic activity is recorded. As a major ore producer, important structures are built in the country to develop mining projects, including tailings dam. The dissertation investigates the potential for dynamic liquefaction of a tailings dam located in the central region of Peru, whose height is currently being raised by the center line construction method. Liquefaction of soils is a phenomenon characterized by loss of stiffness and resistance over a short period of time, but sufficient to cause instability and, in extreme cases, the collapse of the structure. Numerical analyses were carried out to verify the dynamic liquefaction potential of the dam, representing the cyclical behavior of the materials susceptible to liquefaction by the constitutive model UBCSand and Byrne, considering an earthquakes of magnitude 8,2, 7,8 and 8,1. Numerical results obtained were compared with simplified formulations used in the practice of engineering in order to determine the safety factor against dynamic liquefaction. The analyses indicated that fine tailings, below the water table level, have potential for liquefaction, according to the values of the poropression parameter (ru) computed, but without risk to the general stability of the structure. Results are also presented in terms of permanent displacements at some points of the dam and tailings.

[pt] Os efeitos catastróficos de terremotos que frequentemente acontecem na costa ocidental da América do Sul motivaram a realização desta pesquisa. O Equador, em particular, encontra-se localizado em uma zona de alta atividade sísmica devido a processos de subducção de placas tectônicas que originam sismos de grande magnitude, como o terremoto de magnitude Mw igual 7.8 acontecido em 16 de abril de 2016 na cidade costeira de Pedernales, que produziu grandes danos à infraestrutura e perdas de vidas humanas. A presente pesquisa tem como objetivo estudar o comportamento dinâmico de dois tipos de estruturas de terra: um talude de encosta composto de solo coluvial de altura aproximada de 70 m e a barragem de enrocamento de Mazar construída com altura de 166 m para fins de aproveitamento hidrelétrico. A barragem de Mazar, em função da sua altura, é classificada como barragem de grande tamanho pela International Commission on Large Dams (ICOLD) e qualificada pela Norma Equatoriana da Construção (NEC, 2014) como estrutura de importância essencial, com obrigatoriedade de verificação do seu desempenho sísmico para dois terremotos de projeto: o terremoto operacional base (OBE) e o máximo terremoto provável (MCE) com períodos de retorno de 475 anos e 2500 anos, respectivamente. As análises efetuadas neste trabalho incluíram a geração de sismos de projeto, investigação da estabilidade estática e pseudoestática de taludes, determinação de deslocamentos permanentes mediante métodos analíticos simplificados e simulações numéricas. Diferenças significativas nos deslocamentos permanentes máximos foram observadas empregando as abordagens analítica e numérica. / [en] The catastrophic effects of earthquakes that frequently occur on the West coast of South America motivated this research. Ecuador, in particular, is located in a zone of high seismic activity due to processes of tectonic plate subduction that give rise to earthquakes of great magnitude, such as the seismic motion of magnitude Mw equal 7.8 that struck the coastal city of Pedernales on April 16 2016, producing great damages to the infrastructure and losses of human lives. The present research aims to study the dynamic behavior of two types of earth structures: a slope composed of colluvial soil of approximately 70 m height and the Mazar rockfill dam constructed for hydroelectric generation. The Mazar dam, according to its height (166 m), is classified as a large dam by the International Commission on Large Dams (ICOLD) and qualified by the Ecuadorian Construction Standard (NEC, 2014) as a structure of essential importance, with mandatory analysis of seismic performance under two seismic design ground motions: the operating basis earthquake (OBE) and the maximum credible earthquake (MCE) with return periods of 475 years and 2500 years, respectively. The analyses carried out in this work included the generation of the OBE and MCE earthquakes, investigation of static and pseudo static stability of slopes, determination of permanent displacements using simplified analytical methods and numerical simulations. Significant differences in the maximum permanent displacements were observed using analytical and numerical approaches.

[pt] O Peru está localizado em uma área de alta atividade sísmica conhecida como cinturão de fogo. Os terremotos registrados com diferentes mecanismos de falha resultam da interação entre as placas tectônicas de Nazca e Sul-americana. É nesta região onde acontecem atividades de mineração no país, juntamente com a construção de grandes estruturas civis, como barragens de rejeitos, projetadas para armazenar grande quantidade de material na menor área possível. Neste trabalho, foi avaliado o comportamento sísmico de uma barragem de rejeitos localizada em Arequipa, Peru, construída com o método a montante. Em evento sísmico ocorrido em 2013, a barragem sofreu trincas no seu corpo, recalques na crista e pequenos vulcões de areia, indicando a redução dos parâmetros de resistência no rejeito devido a possível fenômeno de liquefação. Nesta pesquisa, a estimativa da ameaça sísmica foi feita por métodos probabilísticos, com o terremoto artificial de projeto obtido por método de ajuste espectral. Foram feitas análises pseudo-estáticas de estabilidade dos taludes, bem como estimados deslocamentos permanentes e o potencial de liquefação dinâmica por métodos simplificados. A análise global da barragem de rejeitos foi executada pelo método dos elementos finitos, considerando o modelo constituivo UBC3D-PLM para simular o comportamento mecânico dos rejeitos sob carregamento cíclico. / [en] Peru is located in an area of high seismic activity known as the fire belt. Earthquakes recorded with different failure mechanisms result from the interaction between the Nazca and South-American tectonic plates. It is in this region where mining activities take place in the country, along with the construction of large civil structures, such as tailings dams, designed to store large amounts of material in the smallest possible area. In this work, the seismic behavior of a tailings dam located in Arequipa, Peru, built with the upstream method, was evaluated. In a seismic event that occurred in 2013, the dam suffered cracks in its body, settlement in the crest and small sand boils, indicating the reduction of the tailings resistance parameters due to possible dynamic liquefaction. In this research, the seismic hazard assessment was made by probabilistic methods, with the artificial design earthquake obtained by the spectral adjustment method. Pseudo-static analyzes of slope stability were performed, as well as the estimated permanent displacements and the potential of dynamic liquefaction were obtainded by simplified methods. The global seismic analysis of the tailings dam was carried out through the finite element method, considering the UBC3D-PLM constitutive model to simulate the mechanical behavior of tailings under cyclic loading.

The presented research investigated the viability of a double-braided synthetic fiber rope for providing improved performance of steel moment frames subjected to earthquake-induced ground motions. A series of experimental tests, including a 1:3-scale dynamic test and 1:6-scale shaking table tests, was conducted using Northridge ground-motion input. A series of nonlinear dynamic analytical studies, using DRAIN-2DX, was conducted to develop the experimental tests. Throughout experimental testing, the ropes exhibited a hyper-elastic loading response and a reduced-stiffness unloading response. A conditioning cycle was defined as a loading cycle induced in the rope above the highest load expected to be experienced by the rope, and was determined to be requisite for ropes intended to be used for the stated objectives of the research program. After experiencing a conditioning cycle, the rope response returned to initial conditions without permanent deformation, demonstrating repeatability of response through several loading cycles below the conditioning load. In the 1:6-scale shaking-table experiments, the ropes drastically improved the performance of the steel moment frames. Maximum and residual drift were reduced significantly, with a corresponding minimal increase to the maximum base shear. Base shear was reduced at several peaks subsequent to the initial pulse of the Northridge ground-motion input. The analytical model developed was excellent for predicting elastic response of the 1:6-scale shaking table experiments and adequate for the purpose of planning shaking table studies. Correlation of peak rope forces between the analytical model and experimental results was poor, and was attributed to limitations of the pre-defined elements used to represent the rope devices in the software program. The inability of the elements to capture the complex unloading response of the rope was specifically noted. / Ph. D.

In this dissertation, I conduct a reflection on the effects of disaster on time perceptions and their consequences on architecture as a vessel of social and individual values, through a study of two major paradigmatic disasters spaces – Post World War II Japan and Post-earthquake Haiti. While on the surface these two cases do not have many points in common, both are instrumental to establishing the manifestation of disasters' impacts on the culture of construction and on the architectural theories that ensue from them. The first case, Japan after the Second World War, establishes the long term influences and changes in social and architectural thought that occur after a disaster, while Haiti, examines the role of the architect in the reconstruction phases and attempts to register the immediate impressions of local architects on the disaster's impact on their practice. I show that both cases exhibit manifestations of the importance of the architect's role of not only building back, but moving forward while capitalizing on the events and social changes that happened. / Ph. D.

Concrete filled steel tubes are regarded as ideal frame members in seismic resisting systems, as they combine large axial and flexural capacity with ductility. The combination of the two materials increases the strength of the confined concrete and avoids premature local buckling of the steel tube. These benefits are more prominent for circular than for rectangular concrete filled steel tubes. However, most common connection configurations for circular concrete filled tubes are not economic in the US market due to (a) the desire of designers to use only fully restrained connections and its associated (b) high cost of fabrication and field welding. Research indicates that well designed partially restrained connections can supply equal or even better cyclic behavior. Partially restrained connections also possess potential capability to develop self-centering system, which has many merits in seismic design. The goal of this research is to develop a new connection configuration between circular concrete filled steel columns and conventional W steel beams. The new connection configuration is intended to provide another option for rapid assembling on site with low erection costs. The proposed connection is based on an extended stiffened end plate that utilizes through rods. The rods are a combination of conventional steel and shape memory alloy that provide both energy dissipation and self-centering capacity. The new connection configuration should be workable for large beam sizes and can be easily expanded to a biaxial bending moment connection. / Ph. D.