Para realizar ensaios de fadiga, é preciso que a máquina ou equipamento de testes tenha uma durabilidade muito maior que as estruturas ou componentes a serem ensaiados. O presente trabalho propõe-se a investigar a estrutura de uma máquina de ensaio de fadiga de cadeira de rodas, com o objetivo de determinar sua vida em fadiga. Para isto, uma análise da interação entre cadeira de rodas e máquina de ensaio é feita, do ponto de vista dinâmico, através de dados experimentais e modelagem em elementos finitos. A máquina de ensaio é constituída por uma estrutura com dois tambores rotativos, que possuem ressaltos, e suportam as rodas da cadeira de rodas. Estimada a força no tempo que a cadeira exerce sobre os tambores, calculam-se as tensões na estrutura, identificam-se as regiões de maiores tensões e estima-se a vida em fadiga da estrutura. / Fatigue analysis of full-scale structures and components is possible by using appropriated devices and machines which has to be much more durable than the structures or components being tested. The present work is proposed to investigate the structure of a wheelchair fatigue testing machine and predict its fatigue life. To reach this goal a dynamic analysis based on experimental data combined with the finite element method of the testing machine and wheelchair interaction is done. The machine is made of a structure and two turning drums that have slats and support the wheelchairs. With the timedependent force that wheelchair applies to the drums, the stresses are calculated to the whole structure, the sites with higher stresses are identified and the fatigue life of the structure is predicted.

As forças devidas ao vento variam espacial e temporalmente e consequentemente provocam esforços de torção em edifícios. A magnitude desses esforços depende basicamente da forma do edifício, de sua altura e estrutura, da influência da vizinhança e da direção do vento. As normas técnicas geralmente negligenciam a importância da torção. A versão atual da norma brasileira de forças devidas ao vento (NBR 6123) não possui uma abordagem aplicável para modos de vibração torcionais. Verificando a falta de recomendações da norma brasileira a respeito dos efeitos dinâmicos da torção em edifícios, este trabalho apresenta uma metodologia para a estimativa do momento torçor devido ao vento, a qual contempla tanto a parcela média quanto a parcela flutuante da solicitação. Para sua calibração utilizaram-se dados de 19 edifícios altos ensaiados no túnel de vento do Laboratório de Aerodinâmica das Construções com o método High Frequency Pressure Integration (HFPI), bem como dados da literatura técnica. A análise dos resultados mostrou que as excentricidades das forças de arrasto para cálculo do momento torçor apresentadas na NBR 6123 são adequadas na estimativa dos efeitos estáticos para edificações com efeitos de vizinhança mas tendem a subestimar a solicitação nos casos sem efeito de vizinhança. Assim, propuseram-se novos valores de excentricidades baseadas na análise da base de dados. Finalmente, apresentou-se uma metodologia para estimativa dos momentos torçores estáticos equivalentes, a qual foi comparada com os valores fornecidos pelo HFPI e constatou-se que a proposta fornece valores adequados. / Wind loads change spatially and temporally consequently they induce torsional moments on buildings. These moments are affected by building shape and structure, by interfering effects of nearby buildings and wind direction. The importance of torsional loads is usually neglected by most codes. Indeed, dynamic torsional response is not presented on current Brazilian Wind Loads Code (NBR 6123). Therefore, a procedure to determine torsional dynamic response of buildings subjected to turbulent wind action is proposed. Experimental data of 19 buildings are used to improve the reliability of proposed procedure. These experimental tests were performed in boundary layer wind tunnel of Aerodynamic Laboratory using the High Frequency Pressure Integration (HFPI) technique. About torsional loads, results have shown that drag forces eccentricities present on the NBR 6123 are reliable when neighboring effects are considered, but they underestimate torsion when neighboring effects are not considered. New eccentricities values are proposed. Finally, a procedure to estimate the torsional static equivalent moment is presented and it agrees well with HFPI results. The average relative error between the results determined by the proposed formulae and the experimental data obtained by the HFPI shows the reliability and applicability of the proposed formulation to the design of isolated and nonisolated buildings.

abstract: Functional or dynamic responses are prevalent in experiments in the fields of engineering, medicine, and the sciences, but proposals for optimal designs are still sparse for this type of response. Experiments with dynamic responses result in multiple responses taken over a spectrum variable, so the design matrix for a dynamic response have more complicated structures. In the literature, the optimal design problem for some functional responses has been solved using genetic algorithm (GA) and approximate design methods. The goal of this dissertation is to develop fast computer algorithms for calculating exact D-optimal designs. First, we demonstrated how the traditional exchange methods could be improved to generate a computationally efficient algorithm for finding G-optimal designs. The proposed two-stage algorithm, which is called the cCEA, uses a clustering-based approach to restrict the set of possible candidates for PEA, and then improves the G-efficiency using CEA. The second major contribution of this dissertation is the development of fast algorithms for constructing D-optimal designs that determine the optimal sequence of stimuli in fMRI studies. The update formula for the determinant of the information matrix was improved by exploiting the sparseness of the information matrix, leading to faster computation times. The proposed algorithm outperforms genetic algorithm with respect to computational efficiency and D-efficiency. The third contribution is a study of optimal experimental designs for more general functional response models. First, the B-spline system is proposed to be used as the non-parametric smoother of response function and an algorithm is developed to determine D-optimal sampling points of a spectrum variable. Second, we proposed a two-step algorithm for finding the optimal design for both sampling points and experimental settings. In the first step, the matrix of experimental settings is held fixed while the algorithm optimizes the determinant of the information matrix for a mixed effects model to find the optimal sampling times. In the second step, the optimal sampling times obtained from the first step is held fixed while the algorithm iterates on the information matrix to find the optimal experimental settings. The designs constructed by this approach yield superior performance over other designs found in literature. / Dissertation/Thesis / Doctoral Dissertation Industrial Engineering 2015

As forças devidas ao vento variam espacial e temporalmente e consequentemente provocam esforços de torção em edifícios. A magnitude desses esforços depende basicamente da forma do edifício, de sua altura e estrutura, da influência da vizinhança e da direção do vento. As normas técnicas geralmente negligenciam a importância da torção. A versão atual da norma brasileira de forças devidas ao vento (NBR 6123) não possui uma abordagem aplicável para modos de vibração torcionais. Verificando a falta de recomendações da norma brasileira a respeito dos efeitos dinâmicos da torção em edifícios, este trabalho apresenta uma metodologia para a estimativa do momento torçor devido ao vento, a qual contempla tanto a parcela média quanto a parcela flutuante da solicitação. Para sua calibração utilizaram-se dados de 19 edifícios altos ensaiados no túnel de vento do Laboratório de Aerodinâmica das Construções com o método High Frequency Pressure Integration (HFPI), bem como dados da literatura técnica. A análise dos resultados mostrou que as excentricidades das forças de arrasto para cálculo do momento torçor apresentadas na NBR 6123 são adequadas na estimativa dos efeitos estáticos para edificações com efeitos de vizinhança mas tendem a subestimar a solicitação nos casos sem efeito de vizinhança. Assim, propuseram-se novos valores de excentricidades baseadas na análise da base de dados. Finalmente, apresentou-se uma metodologia para estimativa dos momentos torçores estáticos equivalentes, a qual foi comparada com os valores fornecidos pelo HFPI e constatou-se que a proposta fornece valores adequados. / Wind loads change spatially and temporally consequently they induce torsional moments on buildings. These moments are affected by building shape and structure, by interfering effects of nearby buildings and wind direction. The importance of torsional loads is usually neglected by most codes. Indeed, dynamic torsional response is not presented on current Brazilian Wind Loads Code (NBR 6123). Therefore, a procedure to determine torsional dynamic response of buildings subjected to turbulent wind action is proposed. Experimental data of 19 buildings are used to improve the reliability of proposed procedure. These experimental tests were performed in boundary layer wind tunnel of Aerodynamic Laboratory using the High Frequency Pressure Integration (HFPI) technique. About torsional loads, results have shown that drag forces eccentricities present on the NBR 6123 are reliable when neighboring effects are considered, but they underestimate torsion when neighboring effects are not considered. New eccentricities values are proposed. Finally, a procedure to estimate the torsional static equivalent moment is presented and it agrees well with HFPI results. The average relative error between the results determined by the proposed formulae and the experimental data obtained by the HFPI shows the reliability and applicability of the proposed formulation to the design of isolated and nonisolated buildings.

Para realizar ensaios de fadiga, é preciso que a máquina ou equipamento de testes tenha uma durabilidade muito maior que as estruturas ou componentes a serem ensaiados. O presente trabalho propõe-se a investigar a estrutura de uma máquina de ensaio de fadiga de cadeira de rodas, com o objetivo de determinar sua vida em fadiga. Para isto, uma análise da interação entre cadeira de rodas e máquina de ensaio é feita, do ponto de vista dinâmico, através de dados experimentais e modelagem em elementos finitos. A máquina de ensaio é constituída por uma estrutura com dois tambores rotativos, que possuem ressaltos, e suportam as rodas da cadeira de rodas. Estimada a força no tempo que a cadeira exerce sobre os tambores, calculam-se as tensões na estrutura, identificam-se as regiões de maiores tensões e estima-se a vida em fadiga da estrutura. / Fatigue analysis of full-scale structures and components is possible by using appropriated devices and machines which has to be much more durable than the structures or components being tested. The present work is proposed to investigate the structure of a wheelchair fatigue testing machine and predict its fatigue life. To reach this goal a dynamic analysis based on experimental data combined with the finite element method of the testing machine and wheelchair interaction is done. The machine is made of a structure and two turning drums that have slats and support the wheelchairs. With the timedependent force that wheelchair applies to the drums, the stresses are calculated to the whole structure, the sites with higher stresses are identified and the fatigue life of the structure is predicted.

Folkhem is a Swedish company exclusively building timber residential buildings in the Stockholm area. The company is currently in the planning stages of what would be the world’s tallest timber building, a 22-storey timber residential buiding in Hallonbergen, Sundbyberg. In this master thesis, this proposed building has been analyzed with regards to its wind-induced dynamic response. The work includes studies of stabilization of tall structures, case studies of existing buildings and developed systems for tall timber construction and analyzed options for structural design of the Hallonbergen project. Eleven different structural systems have been investigated with regards to their displacement at the top and their peak acceleration when subject to wind loading. The peak acceleration has been calculated using both Eurocode and ISO 4354. The values have been assessed against ISO 6897 and ISO 10137. The results indicate that it is possible to construct the Hallonbergen project without risk of unacceptable dynamic response, using any of the following options; The Martinson’s system with 259 mm CLT plates The Kauffmann system The structural system presented in “The Case for Tall Wood Buildings” The structural system presented in “The Timber Tower Research Project”

The limitations lying behind the applications of EN-1991-1-4, Eurocode1, actions on structures-general actions-wind load-part 1-4, lead the structural designers to a great confusion. This may be due to the fact that EC1 only provides the guidance for bridges whose fundamental modes of vibration have a constant sign (e.g. simply supported structures) or a simple linear sign (e.g. cantilever structures) and these modes are the governing modes of vibration of the structure. EC1 analyzes only the along-wind response of the structure and does not deal with the cross wind response. The simplified methods that are recommended in this code can be used to analyze structures with simple geometrical configurations. In this report, the analytical methods which are used to describe the fluctuating wind behavior and predict the relative static and dynamic response of the structure are studied and presented. The criteria used to judge the acceptability of the wind load and the corresponding structural responses along with the serviceability considerations are also presented. Then based on the given methods the wind forces acting on a continuous bridge whose main span is larger than the 50 meters (i.e. > 50 meter requires dynamic assessment) is studied and compared with the results which could be obtained from the simplified methods recommended in the EC1.

No description available.

A damage detection approach based on Artificial Neural Network (ANN), using the statistics of structural dynamic responses as the damage index, is proposed in this study for Structural Health Monitoring (SHM). Based on the sensitivity analysis, the feasibility of using the changes of variances and covariance of dynamic responses of railway bridges under moving trains as the indices for damage detection is evaluated.   A FE Model of a one-span simply supported beam bridge is built, considering both single damage case and multi-damage case. A Back-Propagation Neural Network (BPNN) is designed and trained to simulate the detection process. A series of numerical tests on the FE model with different train properties prove the validity and efficiency of the proposed approach. The results show not only that the trained ANN together with the statistics can correctly estimate the location and severity of damage in the structure, but also that the identification of the damage location is more difficult than that of the damage severity. In summary, it is concluded that the use of statistical property of structural dynamic response as damage index with the Artificial Neural Network as detection tool for damage detection is reliable and effective.

The application of polymers in robust engineering designs is on the rise due to their excellent mechanical properties such as high fracture toughness, specific strength, durability, as well as, thermal and chemical resistances. Implementation of some advanced polymeric solids is limited due to the lack of available mechanical properties. In order for these materials to endure strenuous engineering designs it is vital to investigate their response in multiple loading rates and conditions. In this thesis, the mechanical response of polyethermide (PEI) is characterized under quasi-static, high strain rate, and multiple impact conditions. Standard tension, torsion, and compression experiments are performed in order to distinguish the multi-regime response of PEI. The effects of physical ageing and rejuvenation on the quasi-static mechanical response are investigated. The strain softening regime resulting from strain localization is eliminated by thermal and mechanical rejuvenation, and the advantages of these processes are discussed. The dynamic fracture toughness of the material in response to notched impact via Charpy impact test is evaluated. The high strain-rate response of PEI to uniaxial compression is evaluated at rates exceeding 104/s via miniaturized Split Hopkinson Pressure Bar (MSHPB), and compared to the quasi-static case to determine strain-rate sensitivity. The elastic response of the aged material to multiple loading conditions are correlated using the Ramberg-Osgood equation, while the elastoplastic response of rejuvenated PEI is correlated using a both the Ramberg-Osgood equation and a novel model. The strain-rate sensitivity of the strength is found to be nominally bilinear and transition strains are modeled using the Ree-Erying formulation. Finally, multiple impact experiments are performed on PEI using the MSHPB and a model is proposed to quantify damage as a result of collision.