Publicação
Dynamic structural identification using Wireless Sensor Networks
| Resumo: | Structural dynamic monitoring is currently used in several areas of engineering such as the mechanical, aeronautical, and civil communities. While in the most of these areas, dynamic monitoring tests started to be used in the 1970s, in the civil engineering field these tools have been used mostly since the 1980s for studying high flexible structures such as bridges and tall buildings. The use of these tools for monitoring cultural heritage buildings started to be studied at the University of Minho only in the last decade due to the interest in using non destructive methodologies for assessing the global response of these structures. The present work explores the possible inclusion of Wireless Sensor Networks (WSN) in the Operational Modal Analysis (OMA) schemes of existent structures. Since a complete solution of dynamic monitoring would also contemplate the improvement of feature extraction algorithms, the development of a new methodology for performing automatic and remote processes is addressed in this work. With this purpose, the possibilities of the commercial off-the-shelf solutions on WSN platforms were first explored. Laboratory and field OMA tests were carried out using these platforms and the results showed that this technology, as it is provided, has no direct application in this type of studies. The main reasons are the low resolution of the accelerometers and the ADCs embedded and the lack of communication protocols that assure not only a proper synchronization among nodes but also reliability in the communication processes. Once the limitations of the ready to use WSN solutions were identified a joint team involving electronic and communication engineers developed a prototype WSN system aiming at fulfilling the demanding requirements of OMA tests in existent structures. Despite the need of some improvements in this prototype system, the results of several rounds of validation tests demonstrated their excellent performance, which is comparable to conventional wired based systems, in scenarios with vibrations amplitudes higher than 0.1 mg. The last part of this work was dedicated to the improvement of the data processing stage of the dynamic monitoring processes. Due to the huge amount of collected data, the feasibility of continuous monitoring studies relies on the use of automatic feature extraction techniques. With this respect, a new algorithm was proposed for performing remote and automatic processes based on the interpretation of the information resulting from the parametric modal identification methods using a combination of the clustering techniques and the rule-based approach. The results of numerical and laboratory validation tests demonstrated the reliability of this algorithm since highly accurate estimations were obtained, with a high success rate. When the algorithm was tested in a field test using a 19th century church, the results demonstrated not only the efficacy of the algorithm but also the difficulties on using OMA tests in these structures, due to the fact that the environmental noise was, particularly during critical night hours, not enough to excite such heavy buildings. |
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| Autores principais: | Aguilar Velez, Rafael |
| Ano: | 2010 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso restrito |
| Instituição associada: | Universidade do Minho |
| Idioma: | português |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Structural dynamic monitoring is currently used in several areas of engineering such as the mechanical, aeronautical, and civil communities. While in the most of these areas, dynamic monitoring tests started to be used in the 1970s, in the civil engineering field these tools have been used mostly since the 1980s for studying high flexible structures such as bridges and tall buildings. The use of these tools for monitoring cultural heritage buildings started to be studied at the University of Minho only in the last decade due to the interest in using non destructive methodologies for assessing the global response of these structures. The present work explores the possible inclusion of Wireless Sensor Networks (WSN) in the Operational Modal Analysis (OMA) schemes of existent structures. Since a complete solution of dynamic monitoring would also contemplate the improvement of feature extraction algorithms, the development of a new methodology for performing automatic and remote processes is addressed in this work. With this purpose, the possibilities of the commercial off-the-shelf solutions on WSN platforms were first explored. Laboratory and field OMA tests were carried out using these platforms and the results showed that this technology, as it is provided, has no direct application in this type of studies. The main reasons are the low resolution of the accelerometers and the ADCs embedded and the lack of communication protocols that assure not only a proper synchronization among nodes but also reliability in the communication processes. Once the limitations of the ready to use WSN solutions were identified a joint team involving electronic and communication engineers developed a prototype WSN system aiming at fulfilling the demanding requirements of OMA tests in existent structures. Despite the need of some improvements in this prototype system, the results of several rounds of validation tests demonstrated their excellent performance, which is comparable to conventional wired based systems, in scenarios with vibrations amplitudes higher than 0.1 mg. The last part of this work was dedicated to the improvement of the data processing stage of the dynamic monitoring processes. Due to the huge amount of collected data, the feasibility of continuous monitoring studies relies on the use of automatic feature extraction techniques. With this respect, a new algorithm was proposed for performing remote and automatic processes based on the interpretation of the information resulting from the parametric modal identification methods using a combination of the clustering techniques and the rule-based approach. The results of numerical and laboratory validation tests demonstrated the reliability of this algorithm since highly accurate estimations were obtained, with a high success rate. When the algorithm was tested in a field test using a 19th century church, the results demonstrated not only the efficacy of the algorithm but also the difficulties on using OMA tests in these structures, due to the fact that the environmental noise was, particularly during critical night hours, not enough to excite such heavy buildings. |
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