Navegando por Assunto "Vibration"

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Acesso aberto (Open Access)
Análise de parâmetros globais de projeto em edifícios com estrutura de concreto armado
(Universidade Federal do Pará, 2015-12-22) VIEIRA, Vitor Vinicius dos Santos; VELOSO, Luís Augusto Conte Mendes; http://lattes.cnpq.br/9476653308517248
The verification of reinforced concrete buildings is carried out by local analysis and by global analysis. In the local analysis are evaluated the effects of deformations in the isolated elements. Already in the overall analysis of the behavior is evaluated considered the structure as a whole. Normally, this overall verification is done through design parameters, which allow to maintain control of problems that can affect the safety or performance of buildings of reinforced concrete. By means of computer systems, it’s possible to obtain, fairly quickly, a series of parameters that offer virtually complete diagnostic of the answers that the structures will present when external actions submitted, like the wind or the vertical loads. Howeverit is not enough process structural models and get results, it is necessary to interpret what these mean and verify its validity. Therefore, this study was done with the intention to contribute with the referring studies the overall analysis of the structures, based on the design parameters to know: 𝛾𝑧 and 𝑅𝑀2𝑀1 coefficients, overall critical load factor of buckling, horizontal displacements, fundamental frequency and acceleration. Are studied several cases of idealized structures, with the objective to evaluate the relation between these parameters and propose simplified equations for calculating the overall critical load factor and the fundamental frequency from the 𝛾𝑧 coefficient. Furthermore, are analyze some real building structures aiming to evaluate the proposed equations and draw comparisons with the limits recommended by Brazilian standards. For the processing of structures were used two analysis programs, the TQS and the SAP2000. Generally speaking, the equations that relate the 𝛾𝑧 coefficient with the critical load factor and with the fundamental frequency showed satisfactory results. For displacement and acceleration, could not establish equations due to inexistence of relation of these as the 𝛾𝑧. As for the normative limits, found to be that even structures that fulfill the safety criteria for the overall instability, nevertheless these may present problems related to excessive horizontal displacements and vibrations perceptible to the human being.
Acesso aberto (Open Access)
Análise dos efeitos da detonação na estabilidade de talude em mina de ferro no Quadrilátero Ferrífero em Minas Gerais
(Universidade Federal do Pará, 2022-08-03) AZEVEDO, Daniel Prado; MARQUES, Eduardo Antonio Gomes; http://lattes.cnpq.br/6725413897416818; ALENCAR JÚNIOR, Júlio Augusto de; http://lattes.cnpq.br/3663658632717465
The vibrations induced by blasting in mining are finite waves that can disrupt geotechnical structures. For the present research, seismographs were installed in various positions along a slope with approximately two hundred meters of difference in height from the bottom of the pit to the top, in order to analyze the speed and acceleration of the particles at the moment of the wave transmission and their consequences to the stability of rocky mass. It is known that the course of these vibratory oscillations causes the particles to move and then return to the equilibrium state. Therefore, it is important to study which waves were generated in the detonation and their behavior in the lithology covered. A slope in the selected mine, Vale S.A. property, was analyzed, which is composed mostly of phyllite and quartzite, sometimes continuous, sometimes discontinuous, as there is a fractured zone of N / S orientation that extends from the top of the slope to its base. In this context, there are at least 3 fracture directions that act as an escape zone for groundwater, constituting a geotechnical problem of material disaggregation, resulting in great erosion. The vibrations induced by the detonations of explosives in the mine can increase the erosion condition when they propagate through the fractured area. The highest seismographic reading obtained among the seismographs was used in this study and the evaluation of the reduction in the safety factor of selected sections was carried out. Later, the maximum value for vibration in which the slope remains stable is also calculated, on Slide2 software. The evaluation of the results on the slope Allowed the interpretation of the effects of vibrations on the slopes reduced between 4.1% and 4.8% the values of the safety factors and shows that the lower the slope safety factor, the greater this interference from the vibration in the stability of the structure. A difference equal to 8% was observed when comparing the section with the highest Safety Factor and the one with the lowest Safety Factor.
Acesso aberto (Open Access)
Análise estática e dinâmica de uma ponte ferroviária em concreto armado localizada na Estrada de Ferro Carajás
(Instituto Brasileiro do Concreto, 2010-09) TEIXEIRA, Ritermayer Monteiro; AMADOR, Sandro Diord Rescinho; OLIVEIRA, Dênio Ramam Carvalho de
This work presents results of static and dynamic analysis carried out on 593 m length bridge along Carajás railroad in Maranhão state. The bridge's behavior became important due to some changes over the static and dynamic loads once the future train will be heavier. Thus, a mathematic model was developed using the finite element method basis to evaluate its behavior and "in loco" structural moni- toring to get data as strains and vibrations when the trains go through. Several high precision accelerometers and strains gauges were placed along the slab, beams and columns. Numerical and experimental results are shown and the main conclusions validating the applied methodology are presented as well.
Acesso aberto (Open Access)
Implementação e análise do desempenho de técnicas de monitoramento através de medição de vibração e correlação com corrente estatórica
(Universidade Federal do Pará, 2010-06-16) JESUS, Keliene Maria Sousa de; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
The growing demand for electricity coupled with the great importance of this sector to the national economic system has led the government and private companies to invest in studies for improving the performance of the systems involved in this process, given the important gains that this initiative can produce. In this context, this work is a contribution to the study of the development of a methodology for diagnosis of defects to the machine number three hydro Hydropower Plant Coaracy Nunes, located in Amapa State. In many situations the methods of vibration analysis is used to detect the presence of faults in this type of machine, this work will also be used to analyze the current signals to provide similar indications. This work aims to present a methodology for fault diagnosis in electrical machines using the vibration signals and correlation with the analysis of the stator current. Throughout this work presents a review of techniques for monitoring and diagnosis of the condition of electrical machinery, through vibration tests correlated with the characteristics of the stator current. The result of the correlation of vibration measurement with the current measurement is based on a methodology implemented by a system of acquisition and data processing platform developed in LabView. The experimental results were obtained from mechanical defects (unbalance and mechanical defects on the slopes, and internal bearings) induced in an experimental device designed with the intention to represent a generation system. Finally, the vibration and current signals were analyzed and compared to verify that the defects that were detected by the conventional vibration altered the behavior of current signals. The good results of this study demonstrate the feasibility of future studies in this area.
Acesso aberto (Open Access)
Proposta de metodologia para diagnóstico de falha em rolamentos de baixa velocidade
(Universidade Federal do Pará, 2024-04-19) COSTA, Thiago Barroso; MESQUITA, Alexandre Luiz Amarante; http://lattes.cnpq.br/3605920981600245; https://orcid.org/0000-0001-5605-8381
Monitoring low-speed bearings with vibration analysis is more challenging due to the low energy level of the vibration signal that carries the failure data, making it more susceptible to interference from other sources, impairing the interpretation of information. Thus, an alternative is to calculate signal predictors that may be sensitive to pattern changes relative to failure onset and progression. Hence, the present work extracted different types of features, among them two nonlinear features and eleven extracted from the signal in the time domain. Those features were ranked and selected based on their sensibility to class differentiation, which was estimated using the t-Welch statistic value. Among them is the Largest Lyapunov Exponent, which, in this work, had a modification in one of its calculation steps, improving its sensitivity in some cases. In addition, the influence of the vibration signal window size on the class separability of the indicators was evaluated (which is a scarce content in low-speed bearing monitoring literature). After feature selection, the data were subjected to a linear transformation through PCA (Principal Component Analysis), aiming to reduce the data dimensionality to three dimensions and to minimize the redundancy effects of highly correlated features. In sequence, the data represented in the space of principal components were projected on a Hotelling T2 statistic control chart. The chart allowed the detection and rejection of potential outliers, which consisted of points above a limit line estimated based on F statistic distribution. Finally, binary and multiclass Support Vector Machine classification models were trained with experimental data acquired from normal conditions and three levels of incipient fault in bearing. The models performed well, mainly the binary model with test data obtained from belt conveyor pulley bearings in industrial operation.
Acesso aberto (Open Access)
Redes neurais de múltiplas camadas para redução do tempo de aquisição de dados para testes modais em estruturas flexíveis
(Universidade Federal do Pará, 2007-05-14) MACHADO, José Aristides dos Santos; MELLO, Hiran de; http://lattes.cnpq.br/2127559774805521; VIEIRA JÚNIOR, Petrônio; http://lattes.cnpq.br/1958791286192330
This work presents techniques to improve the dynamics parameters estimation of Single Degree of Freedom (SDOF) and Multiple Degree of Freedom (MDOF) models characteristic from flexible structures. The analyses are referred to the method that uses the Frequency Response Function (FRF) obtained from the impulse response of the flexible structure. We use for assumption that the considered models are convenient for a suitable description of the system. Thus, an experimental good method of obtaining the FRF should produce a significant accordance between the theoretical and the experimental FRF. The improvement in increasing the acquisition time artificially (forecasting) is analyzed by using a Multilayer Neural Network (MNN) model. The performance of neural forecaster is compared with results obtained using ARX and ARMAX models. The obtained results in this research, suggest the viability to use the MNN.