The prototypes vibration test carried out for obtaining reliable information concerning machine’s dynamic properties in development process. Analysis results should be able to correlate with FE model to determine if some underlying assumptions (material properties & boundary conditions) were correct. EMA used for extracting structure modal parameter under laboratory condition. However, EMA can generally not provide all required information concerning machine dynamic property. To simulate vibration in operating, it commonly requires the model based on dynamic properties of the machine under operating. Thus, vibration tests need carried out under operational condition. OMA is a useful tool for extracting information concerning dynamic properties of operating machine. This report concerns vibration test of part of mining machine under operating condition. Modal parameters extracted by two kinds of OMA methods. Results from OMA was compared with corresponding EMA results, illustrates reader the advantages of OMA.

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Digital models are essential to quantifying the behavior of structural systems. In many cases, the creation of these models involves manual measurements taken in the field, followed by a manual creation of this model using these measurements. Both of these steps are time consuming and prohibitively expensive, leading to a lack of utilization of accurate models. We propose a framework built on the processing of 3D laser scanning data to partially automate the creation of these models. We focus on steel structures, as they represent a gap in current research into this field. Previous research has focused on segmentation of the point cloud data in order to extract relevant geometries. These approaches cannot easily be extended to steel structures, so we propose a novel method of processing this data with the goal of creating a full finite element model from the information extracted. Our approach sidesteps the need for segmentation by directly extracting the centerlines of structural elements. We begin by taking "slices" of the point cloud in the three principal directions. Each of these slices is flattened into an image, which allows us to take advantage of powerful image processing techniques. Within these images we use 2d convolution as a template match to isolate structural cross sections. This gives us the centroids of cross sections in the image space, which we can map back to the point cloud space as points along the centerline of the element. By fitting lines in 3d space to these points, we can determine the equations for the centerline of each element. This information could be easily passed into a finite element modeling software where the cross sections are manually defined for each line element. / Modern buildings require a digital counterpart to the physical structure for accurate analysis. Historically, these digital counterparts would be created by hand using the measurements that the building was intended to be built to. Often this is not accurate enough and the as-built system must be measured on site to capture deviations from the original plans. In these cases, a large amount of time must be invested to send personnel out into the field and take large amounts of measurements of the structure. Additionally, these "hand measurements" are prone to user error. We propose a novel method of gathering these field measurements quickly and accurately by using a technique called "laser scanning". These laser scans essentially take a 3D snapshot of the site, which contains all the geometric information of visible elements. While it is difficult to locate items such as steel beams in the 3D data, the cross sections of these structural elements are easily defined in 2D. Our method involves taking 2D slices of this 3D scan which allows us to locate the cross sections of the structural members by searching for template cross-sectional shapes. Once the cross sections have been isolated, their centers can be mapped back from the 2D slice to the 3D space as points along the centerlines of the structural elements. These centerlines represent one of the most time consuming requirements to building digital models of modern buildings, so this method could drastically reduce the total modeling time required by automating this particular step.

Metal buildings account for over 40% of low-rise construction in the US. Despite this, predictive fundamental period equations that were obtained empirically for mid-rise construction are used in seismic design. Analytical modeling of metal building frames implied that these equations significantly underpredict the period, which led to the development of a new predictive equation. However, experimental tests showed that these models may overestimate the measured period. In this work, further tests were carried out in order to single out possible causes. Buildings were tested during different stages of construction to evaluate how non-structural elements could affect the behavior. Both planar and three-dimensional models were developed to determine if design assumptions are accurate for the purpose of estimating the period. The results from tests showed that, unlike other single-story buildings, non-structural components seem to have negligible effect on the structural behavior. However, several buildings seemed to exhibit signs of fixed conditions at the column base. This assertion was corroborated by updating the analytical models. The two modeling approaches showed good agreement with each other as well, validating the use of planar models to predict the period. Finally, new predictive equations are proposed that take into account the type of cladding, as it was found to be an important variable not previously considered. However, low mass participation ratios coupled with the stiffness provided by the secondary framing put the use of the equivalent lateral force procedure into question. / Master of Science / When designing buildings for earthquake loads it is necessary to know their dynamic properties in order to define the equivalent forces that must be applied. Building codes provide predictive equations that were obtained empirically for typical mid-rise construction. Metal buildings do not fall within the range of buildings tested for their development, and so a new equation was proposed for them based on a database of planar models. However, previous tests implied that this equation was predicting larger periods than those obtained experimentally. In this work, further tests were carried out during different stages of construction to evaluate how non-structural elements could affect the behavior. Models were also created for each building in order to determine if the approach used to develop the metal building database was adequate for estimating the period. The results from tests showed that, unlike other single-story buildings, non-structural components seem to have negligible effect on the structural behavior, and the modeling assumptions within the database were validated. Further analysis showed that the type of cladding (concrete or metal sheeting) had a large influence on the properties of metal buildings. In consequence, a new set of predictive equations is proposed that takes this into account.

Modal parameter identification of a structure is done through modal testing and modal analysis using various system identification methods. These methods employ linear input-output relationships to extract the modes of a structure. There are cases where laboratory testing of a structure is not possible or information about the structure under operating conditions is seeked. A set of techniques called Operational Modal Analysis have been developed for modal parameter identification in operating conditions of a structure. These techniques use only response measurements to extract the modes. The aim of this study is to investigate the applicability and use of three selected time-domain methods adapted to operational modal analysis. The algorithms are programmed in Matlab&copy / environment, and various cases are evaluated using computer simulations for each method. Two of the selected methods are evaluated on a laboratory scale test setup.

Detecção de dano em estruturas de engenharia de grandes dimensões através da análise de suas características dinâmicas envolve diversos campos de estudo. O primeiro deles trata da identificação dos parâmetros modais da estrutura, uma vez que executar testes de vibração livre em tais estruturas não é uma tarefa simples, necessita-se de um método robusto que seja capaz de identificar os parâmetros modais dessa estrutura a ações ambientais, campo esse chamado de análise modal operacional. Este trabalho trata do problema de detecção de dano em estruturas que possam ser representadas através de modelos em pórticos planos e vigas e que estejam submetidos à ação de vibrações ambientais. A localização do dano é determinada através de um algoritmo de otimização conhecido como Backtracking Search Algorithm (BSA) fazendo uso de uma função objetivo que utiliza as frequências naturais e modos de vibração identificados da estrutura. Simulações e testes são feitos a fim de verificar a concordância da metodologia para ambos os casos. Para as simulações, são utilizados casos mais gerais de carregamentos dinâmicos, e dois níveis de ruído (3% e 5%) são adicionados ao sinal de respostas para que esses ensaios se assemelhem aos ensaios experimentais, onde o ruído é inerente do processo. Já nos ensaios experimentais, apenas testes de vibração livre são executados. Diversos cenários de dano são propostos para as estruturas analisadas a fim de se verificar a robustez da rotina de detecção de dano. Os resultados mostram que a etapa de identificação modal estocástica através do método de identificação estocástica de subespaço (SSI) teve ótimos resultados, possibilitando, assim, a localização da região danificada da estrutura em todos os casos analisados. / Damage detection in large dimensions engineering structures through the analysis of their dynamic characteristics involves several fields. The first one deals with the structure modal identification parameter, since running free vibration tests in such structures is not a simple task, robust methods are needed in order to identify the modal parameters of this structure under ambient vibrations, this field is known as operational modal analysis. This work deals with the problem of damage detection in structures under ambient vibrations that can be represented by FEM using frame and beam elements. The damage location is determined through an optimization algorithm know as Backtracking Search Algorithm (BSA). It uses as objective function the identified natural frequencies and modes of vibration of the structure. Numerical and experimental tests are performed to assess the agreement of the methodology for both cases. For the numerical tests, more general cases of dynamic loads are used, and two noise levels (3% and 5%) are added to the response signal to assessing the robustness of the methodology close to the field conditions, in which noise is inherent of the process. In the experimental tests, only free vibration tests are performed. Several damage scenarios are proposed for the analyzed structures to check the robustness of the damage detection routine. The results show that the stochastic modal identification using the stochastic subspace identification (SSI) method had excellent results, thus allowing the location of the damaged region of the structure in all analyzed cases.

Detecção de dano em estruturas de engenharia de grandes dimensões através da análise de suas características dinâmicas envolve diversos campos de estudo. O primeiro deles trata da identificação dos parâmetros modais da estrutura, uma vez que executar testes de vibração livre em tais estruturas não é uma tarefa simples, necessita-se de um método robusto que seja capaz de identificar os parâmetros modais dessa estrutura a ações ambientais, campo esse chamado de análise modal operacional. Este trabalho trata do problema de detecção de dano em estruturas que possam ser representadas através de modelos em pórticos planos e vigas e que estejam submetidos à ação de vibrações ambientais. A localização do dano é determinada através de um algoritmo de otimização conhecido como Backtracking Search Algorithm (BSA) fazendo uso de uma função objetivo que utiliza as frequências naturais e modos de vibração identificados da estrutura. Simulações e testes são feitos a fim de verificar a concordância da metodologia para ambos os casos. Para as simulações, são utilizados casos mais gerais de carregamentos dinâmicos, e dois níveis de ruído (3% e 5%) são adicionados ao sinal de respostas para que esses ensaios se assemelhem aos ensaios experimentais, onde o ruído é inerente do processo. Já nos ensaios experimentais, apenas testes de vibração livre são executados. Diversos cenários de dano são propostos para as estruturas analisadas a fim de se verificar a robustez da rotina de detecção de dano. Os resultados mostram que a etapa de identificação modal estocástica através do método de identificação estocástica de subespaço (SSI) teve ótimos resultados, possibilitando, assim, a localização da região danificada da estrutura em todos os casos analisados. / Damage detection in large dimensions engineering structures through the analysis of their dynamic characteristics involves several fields. The first one deals with the structure modal identification parameter, since running free vibration tests in such structures is not a simple task, robust methods are needed in order to identify the modal parameters of this structure under ambient vibrations, this field is known as operational modal analysis. This work deals with the problem of damage detection in structures under ambient vibrations that can be represented by FEM using frame and beam elements. The damage location is determined through an optimization algorithm know as Backtracking Search Algorithm (BSA). It uses as objective function the identified natural frequencies and modes of vibration of the structure. Numerical and experimental tests are performed to assess the agreement of the methodology for both cases. For the numerical tests, more general cases of dynamic loads are used, and two noise levels (3% and 5%) are added to the response signal to assessing the robustness of the methodology close to the field conditions, in which noise is inherent of the process. In the experimental tests, only free vibration tests are performed. Several damage scenarios are proposed for the analyzed structures to check the robustness of the damage detection routine. The results show that the stochastic modal identification using the stochastic subspace identification (SSI) method had excellent results, thus allowing the location of the damaged region of the structure in all analyzed cases.

Detecção de dano em estruturas de engenharia de grandes dimensões através da análise de suas características dinâmicas envolve diversos campos de estudo. O primeiro deles trata da identificação dos parâmetros modais da estrutura, uma vez que executar testes de vibração livre em tais estruturas não é uma tarefa simples, necessita-se de um método robusto que seja capaz de identificar os parâmetros modais dessa estrutura a ações ambientais, campo esse chamado de análise modal operacional. Este trabalho trata do problema de detecção de dano em estruturas que possam ser representadas através de modelos em pórticos planos e vigas e que estejam submetidos à ação de vibrações ambientais. A localização do dano é determinada através de um algoritmo de otimização conhecido como Backtracking Search Algorithm (BSA) fazendo uso de uma função objetivo que utiliza as frequências naturais e modos de vibração identificados da estrutura. Simulações e testes são feitos a fim de verificar a concordância da metodologia para ambos os casos. Para as simulações, são utilizados casos mais gerais de carregamentos dinâmicos, e dois níveis de ruído (3% e 5%) são adicionados ao sinal de respostas para que esses ensaios se assemelhem aos ensaios experimentais, onde o ruído é inerente do processo. Já nos ensaios experimentais, apenas testes de vibração livre são executados. Diversos cenários de dano são propostos para as estruturas analisadas a fim de se verificar a robustez da rotina de detecção de dano. Os resultados mostram que a etapa de identificação modal estocástica através do método de identificação estocástica de subespaço (SSI) teve ótimos resultados, possibilitando, assim, a localização da região danificada da estrutura em todos os casos analisados. / Damage detection in large dimensions engineering structures through the analysis of their dynamic characteristics involves several fields. The first one deals with the structure modal identification parameter, since running free vibration tests in such structures is not a simple task, robust methods are needed in order to identify the modal parameters of this structure under ambient vibrations, this field is known as operational modal analysis. This work deals with the problem of damage detection in structures under ambient vibrations that can be represented by FEM using frame and beam elements. The damage location is determined through an optimization algorithm know as Backtracking Search Algorithm (BSA). It uses as objective function the identified natural frequencies and modes of vibration of the structure. Numerical and experimental tests are performed to assess the agreement of the methodology for both cases. For the numerical tests, more general cases of dynamic loads are used, and two noise levels (3% and 5%) are added to the response signal to assessing the robustness of the methodology close to the field conditions, in which noise is inherent of the process. In the experimental tests, only free vibration tests are performed. Several damage scenarios are proposed for the analyzed structures to check the robustness of the damage detection routine. The results show that the stochastic modal identification using the stochastic subspace identification (SSI) method had excellent results, thus allowing the location of the damaged region of the structure in all analyzed cases.

The aim of this work is to determine the influence of noise on determination of own frequen-cies for machine tool by operational modal analysis. For the assigned machine tool operation-al analysis is performed using Data-Driven and Covariance-Driven method for multiple exci-tation variants. Based on the results are created stabilization diagrams used to determine ma-chine tool own frequencies. The results for each excitation variant are compared to each oth-er and the effect of noise influence on the results is determined.

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