Estruturas como torres e chaminés industriais são bastante vulneráveis ao fenômeno de desprendimento de vórtices, devido à sua esbeltez e forma rombuda. Além disso, devido ao baixo amortecimento estrutural que possuem, essas estruturas também têm maiores chances de atingir grandes amplitudes de deslocamento, o que é causado pelo efeito de captura. Apesar de esse tipo de estrutura ser considerado simples dos pontos de vista estrutural e aerodinâmico, o estudo das vibrações transversais nessas estruturas é bastante complicado, pois envolve a interação entre tópicos complexos da mecânica dos fluidos e estrutural, tornando a determinação confiável da resposta estrutural um dos problemas mais difíceis da Engenharia do Vento. Ao longo das últimas cinco décadas, diversos pesquisadores vêm estudando esse fenômeno, buscando uma abordagem que consiga considerar todos os tópicos que envolvem o mecanismo de vibração por desprendimento de vórtices. Entretanto, apesar dos esforços, os modelos existentes para a verificação da resposta da estrutura são de caráter empírico, sendo os dois mais aceitos pela comunidade científica o modelo de comprimento de correlação de Ruscheweyh e o modelo matemático espectral de Vickery e Clark, o qual foi posteriormente aprimorado por Vickery e Basu. Primeiramente, são estudados em detalhe esses dois modelos e seus métodos derivados, os quais são apresentados em normas e códigos. Após isso, é feita uma proposta de cálculo de dimensionamento do deslocamento do topo de tais estruturas baseada no modelo de Vickery e Basu e adaptada às necessidades da NBR- 6123. E finalmente, são apresentados dados de 42 estruturas, as quais atingiram grandes amplitudes de vibração em seu topo. Essas estruturas foram dimensionadas segundo as diretrizes de cada um dos métodos estudados neste trabalho, o que demonstrou o bom desempenho do Método II do Eurocódigo, do Método do CICIND e da Proposta III-B para a NBR-6123. / Structures like towers and industrial chimneys are quite vulnerable to the vortex shedding phenomenon, due to their slenderness and non-aerodynamic form. Furthermore, due to their low structural damping, these structures are also more likely to reach large displacement amplitudes, which is caused by the lock-in effect. Although these structures are considered as simple from structural and aerodynamic points of view, the study of cross-wind vibrations in these structures is quite complicated, as it involves the interaction of complex topics of fluid and structural mechanics, turning a reliable determination of the structural response into one of the most complicated problems in Wind Engineering. Over the past five decades, several researchers have been studying this phenomenon, seeking an approach that could consider all topics involving the vibrating mechanism by vortex shedding. However, despite the efforts, the existing models for predicting the response of the structure are empirical, with the two most accepted by the scientific community being the Ruscheweyh’s correlation length model and the Vickery & Clark’s spectral mathematical model, which was further enhanced by Vickery & Basu. Firstly, these two models and their derivative methods, which are reported in standards and codes, are studied in detail. After, a calculation proposal for predicting the top displacement of such structures is presented, which is based on the Vickery & Basu model and adapted to the needs of NBR-6123. Finally, data for 42 real structures which have reached large vibration amplitudes at their tops is presented. These structures were designed according to the guidelines for each of the methods studied in this work, which demonstrated the good performance of the Eurocode II Method, of the CICIND Method and of the NBR-6123 III-B Proposal.

Atualmente, o cenário econômico mundial compreende a exploração cada vez mais intensa dos espaços urbanos, através de edificações que buscam maximizar a relação entre área construída e área disponível. Estas edificações, mais flexíveis e mais altas, dependem de avanços no uso de sistemas estruturais inovadores e materiais de elevada resistência com massa reduzida. Como consequência, a sensibilidade à ação dinâmica do vento aumentou. Estruturas esbeltas e flexíveis possuem frequências naturais de vibração livre mais baixas, o que as faz mais suscetíveis a vibrações induzidas pela turbulência atmosférica e pelo desprendimento de vórtices alternados. Essas vibrações têm o potencial de reduzir a segurança estrutural e causar desconforto aos usuários da edificação. A previsão da resposta induzida pela ação dinâmica do vento por métodos analíticos é complexa e de difícil resolução, principalmente para os efeitos transversais no sentido da velocidade média do vento. Em contrapartida, o uso de técnicas experimentais, através de ensaios em túnel de vento com modelos reduzidos, tem se mostrado bastante eficiente em termos de previsão de resultados. Neste contexto, este trabalho apresenta uma investigação numérica e experimental das parcelas estática e flutuante, da resposta nas direções longitudinal e transversal, dos efeitos da ação do vento sobre edifícios altos. O estudo experimental apresenta uma comparação de duas técnicas utilizadas no Túnel de Vento Professor Joaquim Blessmann, da Universidade Federal do Rio Grande do Sul, com um modelo em escala reduzida do CAARC Standard Tall Building. O método experimental de Integração de Pressões em Alta Frequência (HFPI – High Frequency Pressure Integration), está baseado na medição simultânea de pressões dinâmicas no edifício, através de transdutores eletrônicos, e posteriormente na integração dessas pressões para chegar-se a forças dinâmicas que são utilizadas em conjunto com um modelo numérico. A outra técnica consiste no uso de uma base flexível para modelagem aeroelástica de edifícios, através da qual se medem deslocamentos no topo ou momentos fletores na base. Os resultados experimentais são comparados com os resultados teóricos provenientes de formulações analíticas. Utiliza-se a NBR-6123 (1988), Capítulo 9, para a estimativa da resposta dinâmica na direção longitudinal ao vento. Já para a estimativa da resposta na direção transversal ao vento, utilizam-se a metodologia desenvolvida por Liang et al. (2002, pp. 1757-1770), que apresenta um completo modelo analítico para cargas dinâmicas transversais ao vento, e o processo da norma brasileira NBR-6123 Capítulo 10, que considera no cálculo da amplitude à máxima resposta. Demonstra-se que as duas técnicas conduzem a resultados compatíveis para o modelo testado, ao mesmo tempo em que se discutem as respectivas vantagens ou limitações em outras aplicações. / The world economic scenario is presently motivating intense urban land exploration, by means of building technologies that pursue maximizing the relation of built to available area. The buildings are far taller and more flexible than ever, relying on innovative structural systems and materials of improved resistance and reduced weight. As a predictable consequence, the sensitivity of such constructions to the dynamic wind loading has been increased. Such slender and more flexible structures present lower natural vibration frequencies, which makes them more prone to oscillate under atmospheric turbulence and alternate vortex shedding. These vibrations may have the capacity of reducing structural safety or causing discomfort to building users. The estimation of structural response induced by dynamic wind loading through analytical methods is quite complex and unreliable, mainly in respect to across-wind effects. On the other hand, the use of experimental techniques with reduced models tested in wind tunnels has proved to be very accurate and efficient. Within this context, this work presents numerical and experimental investigations of both static (mean) and dynamic (fluctuating) responses for wind loading on tall buildings for both along- and across-wind directions. It is an experimental study consisting of a comparison of two techniques presently used at the Boundary Layer Wind Tunnel "Professor Joaquim Blessmann" at the Federal University of Rio Grande do Sul with the benchmark model CAARC Standard Tall Building. The HFPI (High Frequency Pressure Integration) technique consists in simultaneously measuring the wind induced dynamic pressures at a stiff model surface, with electronic transducers, and integrating these pressures to yield the dynamic wind forces to be used along with a numerical model. The another technique makes use of a flexible base that along with a stiff model compose an aeroelastic model for the building allowing displacements and accelerations of the top and moments of the base to be measured. Experimental results are also compared with theoretical results of analytical procedure. Along-wind response is estimated according to the Brazilian Code NBR-6123 (1988), Chapter 9. The cross-wind response is estimated with the Liang et al. (2002, pp. 1757-1770) model, that it presents a complete analytical model for cross-wind dynamic loads, and the procedure of the Brazilian Code NBR-6123, Chapter 10, which considers to the calculation of the amplitude of the maximum response. It is finally shown that the two experimental techniques conduce to compatible results for the model tested, while advantages and limitations in other applications are also discussed.

Ao contrário de edificações baixas, nas quais os carregamentos verticais são predominantes, nos edifícios altos os carregamentos horizontais devidos à ação do vento possuem grande importância, muitas vezes se tornando as principais solicitações da edificação. Este trabalho aborda o tema de efeitos dinâmicos em edifícios altos devidos à ação do vento, que provocam, principalmente, oscilações devidas ao desprendimento de vórtices, tanto na direção transversal ao escoamento do vento, quanto oscilações torcionais. Estas oscilações, muitas vezes se tornam ressonantes, provocando grandes deslocamentos à estrutura. Um dos edifícios estudados é um modelo criado a fim de permitir a comparação entre diversos estudos realizados em túneis de vento diferentes, possuindo ampla bibliografia, denominado CAARC Standard Tall Building. O outro modelo é de um edifício real (RCA), construído no Brasil, que apresenta arquitetura diferenciada. Busca-se determinar a resposta em termos de suas componentes médias e flutuantes, para deslocamentos longitudinais e transversais à direção do vento e a torção, através do uso de uma balança dinâmica de três graus de liberdade (BD3GDL), dois em flexão, admitindo que são ortogonais entre si e aproximados de forma linear, e um em torção, aproximado de forma constante, e através do método de integração de pressões em alta freqüência, utilizando modelos em escala reduzida em ensaios em túnel de vento. O primeiro apresentou, para ventos perpendiculares às fachadas, boa concordância entre as respostas encontradas através dos métodos experimentais, além de concordarem também com as respostas encontradas por outros autores. O segundo modelo apresentou no geral, também, boa concordância entre as curvas de resposta obtidas nos ensaios experimentais, para ventos perpendiculares às quatro fachadas, e os métodos teórico-numéricos considerados neste estudo. A BD3GDL simulou satisfatoriamente bem o comportamento dos edifícios altos frente à ação do vento, até mesmo efeitos dinâmicos como o desprendimento cadenciado de vórtices, e mostrou-se uma ferramenta útil em ensaios em túnel de vento, pela facilidade em ajustar os parâmetros dinâmicos dos edifícios testados e pelos resultados coerentes com o esperado e com outros autores e métodos analíticos. / Opposite to low buildings, where vertical loads are predominant, in tall buildings horizontal loads due to wind action have great importance, often becoming the main loading of the building. This research approaches the issue of dynamic wind effects in tall buildings, which cause mainly cross-wind and torsional excitations due to vortex shedding. These oscillations often become resonant, causing large displacements of the structure. One of the buildings studied is a model created in order to allow comparison among various studies in different wind tunnels, having wide bibliography, called CAARC Standard Tall Builging. The other model is a real building (RCA), built in Brazil, with distinct architecture. The aim is to determine along-wind, cross-wind and torsional response in terms of their mean and fluctuating components, using a dynamic balance with three degrees of freedom (BD3GDL), two bending, assuming they are orthogonal and linear, and one torsional, which is assumed constant along the height, and through the high frequency pressure integration (HFPI) method, using reduced scale models in wind tunnel tests. The obtained experimental results for CAARC for normal wind acting on the facade were compared with other researchers’ values and they were in good agreement. The obtained experimental results for the Brazilian building for normal wind to the four facades, were compared with values obtained from theoretical-numerical methods considered in this study and they were, generally, also in good agreement. The BD3GDL simulated satisfactorily well the dynamic behavior of tall buildings under wind loading, even for an aeroelastic phenomena such as the resonance due to vortex shedding. The dynamic balance with three degrees of freedom has proved a useful tool in wind tunnel tests, for the facility to adjust the dynamic parameters of buildings tested and the results consistent with expectations as well as with other authors and analytical methods.

Edifícios altos têm pouca rigidez lateral devido a suas dimensões. Os principais carregamentos laterais nestas estruturas são de sismos e vento. Portanto, suas propriedades dinâmicas e a correta estimativa das mesmas são fundamentais. Todavia, mesmo havendo muita pesquisa nesta área, a predição de frequências naturais de vibração livre de edifícios altos com precisão não é trivial. Métodos computacionais e fórmulas de normas ao redor do mundo divergem, ao passo que cidades brasileiras estão crescendo com a construção de maiores estruturas com frequências naturais estimadas abaixo de valores esperados. Neste trabalho, as incertezas acerca da estimativa de frequências naturais são investigadas através da comparação de resultados de diferentes metodologias. Primeiramente, frequências naturais estimadas ainda na fase de projeto de 8 prédios altos construídos ou em construção no Brasil são comparadas com formulações típicas baseadas em dados experimentais. Em um segundo momento, 3 edifícios altos têm suas primeiras frequências naturais estimadas através de: um método simplificado proposto neste trabalho; 2 programas de MEF diferentes; um modelo em MEF incluindo diagonais de compressão a fim de replicar o comportamento da alvenaria de fechamento e, finalmente, através da aplicação de um fator para calibrar a frequência natural obtida via programação em MEF. Tal fator é oriundo de uma formulação elaborada neste estudo para corrigir a frequência natural estimada sem a consideração do acréscimo de rigidez causado pela alvenaria de fechamento. Os resultados evidenciam que as baixas frequências naturais são semelhantes a medições de resposta sísmica. Também é relatada uma boa convergência para diferentes métodos computacionais enquanto os resultados das análises com alvenaria não estrutural revelam uma ótima convergência. Este estudo apresenta um melhor entendimento das razões para as baixas frequências naturais dos arranha-céus brasileiros enquanto expõe avanços na estimativa de frequências naturais com alta precisão. / Tall buildings have low lateral stiffness due to their dimensions and the main lateral forces on these structures are wind and seismic loads. Therefore, an accurate estimation of their dynamic properties is essential. Nevertheless, even with plenty of studies in this area, predicting natural frequencies of tall buildings is not trivial. Numeric computational methods and simplified procedures around the world diverge, whereas Brazilian cities are growing with the construction of higher buildings with lower estimated values for natural frequencies than the expected. In this work, the uncertainties are investigated through the comparison of different methods of estimating natural frequencies. Firstly, the natural frequencies estimated during project phase of 8 buildings, recently constructed or under construction in Brazil, are compared with formulas based on experimental measurements. Secondly, the natural frequencies of 3 buildings are estimated with different methods: two FEM models made with two computer programs commercially available, a simplified method proposed in this work, a FEM model with diagonal elements representing the masonry infill and a method based on applying a correction factor on the natural frequency obtained with another method. This last method is proposed here in order to consider the effect of infill masonry on the stiffness. The results evince that the low frequencies are similar to the ones measured on seismic response. The different computational methods have a good convergence while the analysis including the infill masonry has an outstanding convergence. This study reveals a better understanding of the reasons for low natural frequencies of the Brazilian tall buildings while presents improvements on estimating natural frequencies with high precision.

Head injuries are a major health concern for sport participants as 90% of emergency department visits for sport-related brain injuries are concussion related (Canadian Institute for Health Information, 2016). Recently, reports have shown a higher incidence of sport-related concussion in female athletes compared to males (Agel et al., 2007). Few studies have described the events by which concussions occur in women’s hockey (Delaney et al., 2014, Brainard et al., 2012; Wilcox et al., 2014), however a biomechanical analysis of the risk of concussion has not yet been conducted. Therefore, the purpose of this study was to identify the riskiest concussive events in elite women’s hockey and characterize these events through reconstructions to identify the associated levels of peak linear and angular acceleration and strain from finite element analysis. 44 head impact events were gathered from elite women’s hockey game video and analyzed for impact event, location and velocity. In total, 27 distinct events based on impact event, location and velocity were reconstructed using a hybrid III headform and various testing setups to obtain dynamic response and brain tissue response. A three-way Multivariate Analysis of Variance (MANOVA) was conducted to determine the influence of event, location and velocity. The results of this study show that head-to-ice impacts resulted in significantly higher responses compared to shoulder-to-head collisions and head-to boards impacts however, shoulder and boards impacts were more frequent. All events produced responses comparable to proposed concussion threshold values (Zhang et al., 2004). This research demonstrates the importance of considering the event, the impact characteristics, the magnitude of response, and the frequency of these impacts when attempting to capture the short and long term risks of brain trauma in women’s hockey.

The long-term consequences of repetitive mild traumatic brain injuries (mTBIs), or concussions, as well as the immediate acute dangers of head collisions in sport have become of growing concern in the field of medicine, research and athletics. An estimated 3.8 million sports-related concussions occur in the United States annually, with the highest incidence having been documented in football, hockey, soccer, basketball and rugby (Harmon et al., 2013). The incidence of concussion in the National Rugby League (NRL) corresponds to approximately 8.0-17.5 injuries per 1000 playing hours, with tackling having been identified as the most common cause (Gardner et al., 2014; King et al., 2014). The highest incidence of rugby concussive impacts is a result of shoulder-to-head collisions (35%) during tackles and game play (Gardner et al., 2014). Shoulder-to-head concussive events occur primarily on the ball carrier and secondarily on the tacklers (Hendricks et al., 2014; Quarrie & Hopkins, 2008). While some studies report that the ball carrier is at a greater risk of sustaining a concussion (Gardner et al., 2015; King et al., 2010, 2014), others have demonstrated a greater incidence of tacklers being removed from play for sideline concussion evaluation (Gardner et al., 2014). Given this discrepancy, the purpose of this study was to compare dynamic response and brain tissue deformation metrics for ball carriers and defensive tacklers in professional rugby during shoulder-to-head concussive impacts using in-laboratory reconstructions. Ten cases with an injured defensive tackler and ten cases with an injured ball carrier were reconstructed using a pneumatic linear impactor striking a 50th percentile Hybrid III headform to calculate dynamic response and maximum principal strain values. There was no significant difference between the two impact conditions for peak resultant linear and rotational accelerations, as well as brain tissue deformation. Differences between metrics in this research and past research where the impacting system was not reported were discussed. These differences reflect the importance of accounting for impact compliance when describing the risk associated with collisions in professional rugby.

The dynamic response of the demand is defined as the time-domain real and reactive power response to a voltage disturbance, and it represents the dynamic load characteristics. This thesis develops a methodology for probabilistic estimation and prediction of dynamic responses of the demand at bulk supply points. The main outcome of the research is being able to predict the contribution of different categories of loads to the total demand mix and their controllability without conducting detailed customer surveys or collecting smart meter data, and to predict the dynamic response of the demand without performing field tests. The prediction of the contributions of different load categories and their controllability and load characteristics in the near future (e.g., day ahead) plays an important role in system analysis and planning, especially in the short-term dispatch and control. However, the research related to this topic is missing in the publically available literature, and an approach needs to be developed to enable the prediction of the participation of different loads in total load mix, their controllability and the dynamic response of the demand. This research contributes to a number of areas, such as load forecasting, load disaggregation and load modelling. First, two load forecasting methodologies which have not been compared before are compared; and based on the results of comparison and considering the actual requirements in this research, a methodology is selected and used to predict both the real and reactive power. Second, a unique methodology for load disaggregation is developed. This methodology enables the estimation of the contributions of different load categories to the total demand mix and their controllability based on RMS measured voltage and real and reactive power. The confidence level of the estimation is also assessed. The methodology for disaggregation is integrated with the load forecasting tool to enable prediction of load compositions and dynamic responses of the demand. The prediction is validated with data collected from real UK power network. Finally, based on the prediction, an example of load shifting is used to demonstrate that different dynamic responses can be obtained based on the availability and redistribution of controllable devices and that load shifting decisions, i.e., demand side management actions, should be made based not only on the amount of demand to be shifted, but also on predicted responses before and after load shifting.

In this work, a pioneering application of the Solution Structure Method (SSM) for structural dynamics problems is presented. Vibration analysis is an important aspect of any design-analysis cycle for which reliable computational methods are required. Unlike many meshfree methods, SSM is capable of {\it exact treatment of all prescribed boundary conditions}. In addition, the method is capable of using basis functions which do not conform to the shape of the geometric model. Together, this defines an unprecedented geometric flexibility of the SSM. This work focused on the development of numerical algorithms for 2D in-plane and 3D natural vibration analysis and 2D in-plane dynamic response. The convergence and numerical properties of the method were evaluated by comparing meshfree results with those obtained using traditional Finite Element Analysis implemented in Solidworks and ANSYS. The numerical experiments presented in this work illustrate that the Solution Structure Method possesses good convergence and in some cases, such as geometries with partially fixed boundaries, this method converges much more rapidly than traditional FEA. Finally, in addition to complex boundary conditions, this method can easily handle complex geometries without losing favorable convergence properties.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22759号 / 工博第4758号 / 新制||工||1744(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 三村 衛, 教授 渦岡 良介, 准教授 肥後 陽介 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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