Corrosion begins as moisture penetrates the protective barrier of a surface, starting an electrochemical process which over time leads to surface pitting. The combined action of mechanical stresses and corrosion induced pitting reduces structural integrity as the pits enlarge to form nucleation sites for surface cracks, which propagate into through-thickness cracks. In most cases, the total mass loss due to corrosion within the structure is small; however, significant reductions in mechanical strength and fatigue life can occur in the corroded material leading to advanced crack growth rates or fast fracture. Since the structural damage due to localized corrosion pitting is small and the crack growth rates may be large, traditional inspections methods and "find it and fix it" maintenance approaches may lead to catastrophic mechanical failures. Therefore, precise structural health monitoring of pre-crack surface corrosion is paramount to understanding and predicting the effect corrosion has on the fatigue life and integrity of a structure. In this first third of this study, the impedance method was experimentally tested to detect and the onset and growth of the earliest stages of pre-crack surface corrosion in beam and plate like structures. Experimental results indicate the impedance method is an effective detection tool for corrosion induced structural damage in plates and beams. For corrosion surface coverages less than 1.5% and pit depths of less than 25 microns (light corrosion), the impedance method could successfully detect corrosion on plates and beams at distances up to 150 cm from the sensor location. Since the impedance method is a proven tool for corrosion detection, it makes sense to determine how well the method can quantify and track key corrosion variables like location, pit depth, and surface coverage. In order to make fatigue life adjustments for corroded structures it is necessary to quantify those variables. Thus, the second portion of this study uses the impedance method to quantify corrosion location, pit depth, and location. Three separate tests are conducted on beam-like structures to determine how well the damage metrics from the impedance method correlate to the key corrosion variables. From the three tests, it is found that the impedance method correlates best with the changes in corrosion pit depth, so if combined with data from routine maintenance it would be possible to use the impedance method data in a predictive or tracking manner. The impedance method can be correlated to location and surface coverage changes, but the relationship is not as strong. Other NDE techniques like Lamb Waves could use the same sensors to quantify corrosion location, and perhaps surface coverage. The impedance method can detect and quantify pre-crack surface corrosion which leads to shortened fatigue life in structures; however, the sensors must be robust enough to withstand corrosive environments. The last portion of this study tests the following: corrosive effect on Lead Zirconate Titnate (PZT) and Macro Fiber Composites (MFC) sensors, Kapton protected MFC actuators for corrosion detection, and determines if corrosion damage can be sensed on the side of the structure opposite the damage. Sensor recommendations regarding the use of piezoelectric sensors in corrosive environments are made. / Master of Science

Les systèmes SHM (Structural Health Monitoring) basés sur la propagation d’ondes ultrasonores guidées sont utilisés pour des structures de grandes dimensions, par exemple dans les secteurs de l’aéronautique ou du génie civil. Les ondes de Lamb ou SH sont généralement employées car elles se propagent sur de longues distances dans des structures planes tout en sondant l’épaisseur des pièces. Cependant, des modes moins conventionnels se propagent dans les guides d’ondes de section droite finie, tels que les barreaux, les rails ou les tuyaux. Le nombre de modes peut être très élevé dans ce type de guide, et il est important de bien sélectionner un mode particulier.Les méthodes actuelles de sélectivité modale, basées sur l’emploi de plusieurs émetteurs,considèrent habituellement des éléments PZT identiques (même sensibilité, même réponse en fréquence...) et ne prennent pas en compte les conditions réelles de montage et leurs éventuelles imperfections (couplage variable entre traducteurs, mauvais alignement, différence de réponse de l’électronique...). Ce travail présente une méthodologie générale pour la sélectivité modale dans des guides à section droite finie, à l’aide de plusieurs éléments piézoélectriques disposés à leur surface. Cette sélectivité est basée sur la mesure expérimentale préalable, à l’aide d’un vibromètre laser 3D, des amplitudes des modes générés par chaque élément excité individuellement.Une procédure d’optimisation permet d’inverser le problème afin de maximiser l’amplitude du mode désiré, alors obtenue en excitant simultanément tous les émetteurs. Le problème à inverser requiert la connaissance des courbes de dispersion ainsi que des déformées modales des modes,obtenues en utilisant la méthode SAFE 2D. La méthodologie est testée à travers des simulations numériques et des mesures expérimentales sur un barreau d’aluminium de section rectangulaire instrumenté avec huit éléments PZT à sa surface. L’efficacité de la méthode pour générer différents modes purs, mais aussi pour détecter et localiser des défauts calibrés, est démontrée sur le barreau d’aluminium. Son fort potentiel pour des applications de SHM de structures plus complexes est étudié, tels qu’un rail ou un assemblage collé de matériaux composites. / SHM systems (Structural Health Monitoring) based on ultrasonic guided waves propagation are used for large structures, e.g. in Aerospace or Civil Engineering. Lamb or SH waves are usually employed as they propagate over long distances in plate-like structures while probing the entire thickness. However less conventional modes propagate in wave guides with finite crosssection,such as bars, rails or pipes. The number of modes can be very high even at low frequencyin this type of guide, and it is important to carefully select a specific mode. Current methods for modal selectivity, based on the use of several emitters, usually consider identical PZT elements(same sensitivity, same frequency response, etc.) and do not account for real experimental conditions and possible differences (variable coupling between transducers, flawed alignment,variable electronic response, etc.). This work presents a global methodology for modal selectivity in waveguides with finite cross-section, using several piezoelectric elements attached to their surface. This selectivity is based on experimental measurements, with a 3D laser vibrometer,of the amplitudes of the modes generated by each emitter. An optimization process allows to inverse the problem in order to maximize the amplitude of the desired mode, then generated by exciting all the emitters at once. This process requires knowing dispersion curves as well as the displacements of the various modes, calculated with SAFE 2D method. The methodology is tested through numerical simulations and experiments on an aluminium rectangular bar instrumented with 8 PZT elements on top. The method efficiency to generate different pure modes,and to detect and locate calibrated defects, is demonstrated for the aluminium bar. Its potential for SHM application of more complex structures is studied, like a rail or an adhesively bonded composite structure.

Orientador: Vicente Lopes Junior / Resumo: Este trabalho analisa um método de Monitoramento da Integridade de Estruturas (SHM, do inglês Structural Health Monitoring) usando funções erro calculadas a partir de ondas guiadas que são refletidas nos danos. Este método foi primeiro testado por Gorgin et al em 2014, que apresentou o método aplicado para materiais isotrópicos. A abordagem é testada experimentalmente em materiais anisotrópicos e isotrópicos. O sinal da estrutura intacta, que será referido como baseline e o sinal atual para cada caminho de propagação (entre dois transdutores PZT) são medidos e a energia do sinal de dispersão para cada caminho é calculada em um dado intervalo. Assumindo que existe dano no ponto avaliado, a onda irá refletir neste ponto e se propagar até o sensor. A técnica é baseada no tempo de propagação (time-of-flight) entre o atuador (primeiro transdutor PZT) até o ponto avaliado mais o tempo de propagação do ponto avaliado até o sensor (segundo transdutor PZT, em uma configuração pitch-catch) para cada ponto da estrutura. A velocidade de propagação em materiais anisotrópicos é dependente da direção de propagação. Isto não acontece em materiais isotrópicos, onde a velocidade de propagação é constante e não é dependente da direção de propagação. No caso de materiais anisotrópicos as velocidades de propagação para diferentes direções foram calculadas experimentalmente e incorporadas ao algoritmo para calcular o time-of-flight corretamente para todos os pontos da estrutura. A energia do sina... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work highlights a method for Structural Health Monitoring using error functions computed from guided waves reflected from damage. This method was first tested by Gorgin et al in 2014, who presented the method for isotropic plates. The approach is experimentally tested on anisotropic and isotropic specimens such as composite and aluminum plates, respectively. The baseline and test signals of each sensing path (between two PZT transducers) are measured and the energy of the scatter signal for each path is calculated in a given range. The structure is meshed and the middle point of each component is considered in the calculations. Assuming that there is damage in the evaluated position, the wave will reflect at this point and propagate to the next transducer. The technique is based in the time-of-flight between the actuator (first PZT transducer) and the evaluated point plus the time-of-flight of the evaluated point to the sensor (second PZT transducer, for a pitch-catch configuration) for each mesh component of the structure. The wave speeds in anisotropic specimens are propagation direction dependent. It does not happen in isotropic materials, which have the wave speed constant and non-dependent of the propagation direction. In the case of anisotropic materials, the wave speed for different angles were experimentally computed and incorporated in the algorithm in order to calculate the proper time-of-flight. The energy of the scatter signal is computed in a time range base... (Complete abstract click electronic access below) / Mestre

Submitted by Vinicius Augusto Matheus Rosa null (vinicius91027@aluno.feis.unesp.br) on 2016-09-25T14:21:09Z No. of bitstreams: 1 Vinicius Rosa-PDF_FINAL.pdf: 3807538 bytes, checksum: d62638a8fa9c1ae27ad1e162a2d1d068 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-09-27T14:30:43Z (GMT) No. of bitstreams: 1 rosa_vam_me_ilha.pdf: 3807538 bytes, checksum: d62638a8fa9c1ae27ad1e162a2d1d068 (MD5) / Made available in DSpace on 2016-09-27T14:30:43Z (GMT). No. of bitstreams: 1 rosa_vam_me_ilha.pdf: 3807538 bytes, checksum: d62638a8fa9c1ae27ad1e162a2d1d068 (MD5) Previous issue date: 2016-07-25 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este trabalho analisa um método de Monitoramento da Integridade de Estruturas (SHM, do inglês Structural Health Monitoring) usando funções erro calculadas a partir de ondas guiadas que são refletidas nos danos. Este método foi primeiro testado por Gorgin et al em 2014, que apresentou o método aplicado para materiais isotrópicos. A abordagem é testada experimentalmente em materiais anisotrópicos e isotrópicos. O sinal da estrutura intacta, que será referido como baseline e o sinal atual para cada caminho de propagação (entre dois transdutores PZT) são medidos e a energia do sinal de dispersão para cada caminho é calculada em um dado intervalo. Assumindo que existe dano no ponto avaliado, a onda irá refletir neste ponto e se propagar até o sensor. A técnica é baseada no tempo de propagação (time-of-flight) entre o atuador (primeiro transdutor PZT) até o ponto avaliado mais o tempo de propagação do ponto avaliado até o sensor (segundo transdutor PZT, em uma configuração pitch-catch) para cada ponto da estrutura. A velocidade de propagação em materiais anisotrópicos é dependente da direção de propagação. Isto não acontece em materiais isotrópicos, onde a velocidade de propagação é constante e não é dependente da direção de propagação. No caso de materiais anisotrópicos as velocidades de propagação para diferentes direções foram calculadas experimentalmente e incorporadas ao algoritmo para calcular o time-of-flight corretamente para todos os pontos da estrutura. A energia do sinal de dispersão é calculada em um intervalo baseado no time-of-flight de cada posição analisada. A estimativa da localização do dano é definida através de uma função erro resultante para cada ponto da área monitorada. Como a função erro é baseada na interferência do dano na propagação de ondas guiadas, o maior valor da função erro mostra uma menor probabilidade de dano naquela posição. Uma imagem é gerada com um valor da função erro para cada ponto avaliado da estrutura. A função erro compara valores de energia nos devidos intervalos para cada par de transdutores PZT. O método foi aplicado para várias frequências de excitação, afim de obter-se um resultado melhor. / This work highlights a method for Structural Health Monitoring using error functions computed from guided waves reflected from damage. This method was first tested by Gorgin et al in 2014, who presented the method for isotropic plates. The approach is experimentally tested on anisotropic and isotropic specimens such as composite and aluminum plates, respectively. The baseline and test signals of each sensing path (between two PZT transducers) are measured and the energy of the scatter signal for each path is calculated in a given range. The structure is meshed and the middle point of each component is considered in the calculations. Assuming that there is damage in the evaluated position, the wave will reflect at this point and propagate to the next transducer. The technique is based in the time-of-flight between the actuator (first PZT transducer) and the evaluated point plus the time-of-flight of the evaluated point to the sensor (second PZT transducer, for a pitch-catch configuration) for each mesh component of the structure. The wave speeds in anisotropic specimens are propagation direction dependent. It does not happen in isotropic materials, which have the wave speed constant and non-dependent of the propagation direction. In the case of anisotropic materials, the wave speed for different angles were experimentally computed and incorporated in the algorithm in order to calculate the proper time-of-flight. The energy of the scatter signal is computed in a time range based on the time of flight of each analyzed position. The estimated damage location is defined through a resultant error function for each evaluated point in the monitored area. As the error function is based on the interference of the damage in the propagation of guided waves, the higher value of the error implies the less likelihood of damage in that position. An image is generated with an error value for each mesh position in the plate. This error function compares the energy in the given ranges for each pair of transducers. In addition, several frequencies were tested and the results for each one were combined in order to get a better result. / CNPq: 160328/2014-4

Submitted by Danilo Ecidir Budoya (dbudoya.eng@gmail.com) on 2018-04-25T21:17:47Z No. of bitstreams: 1 Dissertação - Danilo Budoya.pdf: 3474646 bytes, checksum: 301f48ae4a6c065e915f91fe3d764dd8 (MD5) / Approved for entry into archive by Minervina Teixeira Lopes null (vina_lopes@bauru.unesp.br) on 2018-04-26T12:29:49Z (GMT) No. of bitstreams: 1 budoya_de_me_bauru.pdf: 3415870 bytes, checksum: 35422f7801e20a052d2c9a303aa7e2dd (MD5) / Made available in DSpace on 2018-04-26T12:29:49Z (GMT). No. of bitstreams: 1 budoya_de_me_bauru.pdf: 3415870 bytes, checksum: 35422f7801e20a052d2c9a303aa7e2dd (MD5) Previous issue date: 2018-04-20 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Sistemas de monitoramento de integridade estrutural (SHM – Structural Health Monitoring) são científica e economicamente relevantes como métodos de detecção de danos estruturais em diversos tipos de estruturas, aumentando assim a segurança e reduzindo os custos de manutenção. Entre os vários princípios de detecção de danos, o método da impedância eletromecânica (E/M) baseia-se na medição da impedância elétrica do transdutor piezelétrico fixado à estrutura monitorada. Aqui, a exatidão e precisão do sistema de medição são fundamentais para o diagnóstico correto da estrutura. Portanto, essa dissertação apresenta uma análise comparativa de duas técnicas de medição de impedância para detecção de danos que são tipicamente utilizadas em analisadores de impedância comerciais e em outros sistemas de medição alternativos: medições em estado transitório utilizando um sinal de excitação de varredura e medições em estado estacionário utilizando um sinal senoidal puro para cada frequência de excitação. Os testes foram realizados com cargas resistivas e capacitivas de valores nominais 100 Ω e 10 nF, respectivamente, e com um transdutor piezelétrico fixado em uma barra de alumínio que representa uma estrutura monitorada. As duas técnicas foram comparadas com base na exatidão, precisão, sensibilidade à danos e tempo necessário para as medições. Os resultados destacam as características importantes de cada técnica, as quais devem ser consideradas para o desenvolvimento de sistemas de SHM baseados na impedância e o diagnóstico correto das estruturas monitoradas. / Structural health monitoring (SHM) systems are scientifically and economically relevant as methods of detecting structural damage to various types of structures, thus increasing safety and reducing maintenance costs. Among the various principles of damage detection, the electromechanical impedance (EMI) method is based on the electrical impedance measurement of piezoelectric transducers attached to the monitored structure. Here, the accuracy and precision of the measurement system are fundamental for the correct diagnosis of the structure. Therefore, this dissertation presents a comparative analysis of two impedance measurement techniques for damage detection that are typically used in commercial impedance analyzers and other alternative measurement systems: transient-state measurements using a sweep excitation signal and steady-state measurements using a pure sinusoidal signal for each excitation frequency. Tests were performed with resistive and capacitive loads with nominal values of 100 Ω e 10 nF, respectively, and a piezoelectric transducer fixed to an aluminum bar representing a monitored structure. The two techniques were compared based on the accuracy, precision, sensibility to damage and time required for the measurements. The results highlight the important features of each technique, which should be considered for the development of impedance-based SHM systems and the correct diagnosis of monitored structures. / 2015/23272-1

<p>U postupku praćenja stanja građevinskih struktura vr&scaron;i se nadzor nad fizičkim (mehaničkim), meteorolo&scaron;kim i hemijskim parametrima. U praksi se za merenje navedenih parametara koristi veliki broj instrumenata-senzora. Na osnovu uvida u aktuelno stanje iz oblasti istraživanja, zatim evidentne potrebe za istraživanjima o potencijalu postojećih i novih instrumenata i senzora za merenje geometrijskih deformacija i ekspanziji kori&scaron;ćenja fiber optičke senzorske tehnologije definisana je oblast istraživanja ove doktorske disertacije. U doktorskoj disertaciji izvr&scaron;eno je teorijsko i eksperimentalno istraživanje postojećih metoda za praćenje geometrijskih deformacija i razvoj sistema baziranog na fiber optičkom senzoru zakrivljenosti (eng. Fiber Optic Curvature Sensor &ndash; FOCS).</p> / <p>In the process of structural health monitoring (SHM) inspection of physical (mechanical), meteorological and chemical parameters is performed. In practice, a large number of instruments-sensors are used to measure these parameters. The field of research of this doctoral dissertation is based on the insight into the current state in the field of research, then the evident need for research on the potential of existing and new instruments and sensors for measuring geometric deformations and the usage expansion of fiber optic sensor technology. In the doctoral dissertation, theoretical and experimental study of the existing methods for monitoring geometric deformations and the development of a fiber optic curvature sensor (FOCS) system is performed.</p>

Les activités scientifiques que nous présentons dans ce manuscrit de thèse s’inscrivent dans la thématique de l’intelligence ambiante, axe stratégique ADREAM au sein du LAAS-CNRS. Depuis plusieurs années notre équipe de recherche N2IS fédère l’approche technologique de la SHM avec pour objectif la surveillance de santé structurelle. En effet, la maturité des matériaux innovants tels que les composites suscitent un intérêt certain auprès des constructeurs aéronautiques, ou bien encore l’utilisation des matériaux de type béton pour des ouvrages d’art, sont autant de structures hétérogènes qui nécessitent une surveillance périodique et/ou continue. Ceci, afin de détecter des cracks, des fissures, des corrosions surfaciques ou bien encore des délaminages. Pour ce faire, les solutions existantes s’appuient usuellement sur des technologies de contrôle non destructif (CND) qui intègrent le plus souvent des réseaux de capteurs à faible consommation interfacés avec des systèmes d’analyses des signaux. Ces approches CND présentent des limitations fonctionnelles majeures : elles ne sont pas versatiles et ne permettent pas d’assurer une continuité de service dans un mode « dégradé » lors d’un fonctionnement sur batterie avec un niveau d’énergie minimal. Notre travail de recherche se situe dans une perspective liée à la quantification d’un niveau de robustesse de structure hétérogène. Il a pour ambition le développement et l’intégration de systèmes matériels mixtes (analogiques/numériques) reconfigurables. Au terme d’une investigation sur les principales solutions technologiques matérielles reprogrammables et compte tenu de la problématique liée aux développements d’algorithmes d’analyse embarqués et de la minimisation de la consommation énergétique des capteurs, le choix s’est porté sur des technologies complémentaires FPAA et FPGA. Initialement nos études de recherche se sont focalisées sur l'étude de fonction analogique matérielle reconfigurable analogique. L'objectif est de démontrer une faisabilité conceptuelle en intégrant un système de conditionnement complexe (implémentation d'une technique de détection synchrone), ceci en considérant le compromis entre la prise de décision d’une reconfiguration à la volée vis-à-vis d’une gestion rationnelle de l'énergie du système. Dès lors, se pose la question de comment intégrer et stocker des données nécessaires au développement d’un traitement numérique performant ? Une solution repose sur une approche hybride avec une puce de type Zynq produite par Xilinx et embarquée sur une Zedboard. Cette solution, plus performante qu’une approche PSoC a permis le développement et l’implémentation de techniques de traitement de signal grâce à des outils d'optimisation et de génération de code de haut niveau. Au terme de ce travail de recherche, les résultats obtenus démontrent la validité des concepts mis en œuvre et permettent d'engager dès à présent le développement d’architectures intelligentes de nouvelle génération / Scientific activities described in this PhD thesis are part of the theme of smart environment, strategy axes of ADREAM with the LAAS-CNRS. Since several years, our research team (N2IS) had a field of interest in SHM (Structural Health Monitoring) with the objective of doing a smart diagnostic on different heterogeneous structures. Indeed, the maturity of innovative materials such as composites triggering interest among aircraft manufacturers, or even the use of materials like concrete structures of civil engineering, all those heterogeneous structures that require periodic monitoring and / or continuous one. This is to detect cracks, disbond, surface corrosion or even delamination. To do this, existing solutions usually rely on technologies of nondestructive testing (NDT) that incorporate mostly sensor networks low-power systems interfaced with analysis of signals. These approaches have significant functional limitations: they are not versatile and do not allow for continuity of service in a "degraded" when operating on battery power with a minimum level of energy mode. Our research is a view related to the quantization level of robustness of a heterogeneous structure. Its aim is the development and integration of hardware reconfigurable mixed (A / D ) systems. After an investigation of the main technological solutions reprogrammable hardware and given the problems associated with developments in analytical embedded and minimizing the energy consumption of sensor algorithms. The choice was based on technologies like FPAA and FPGA. Initially our research studies have focused on the study of reconfigurable analog hardware analog. The objective was to show a conceptual feasibility of integrating a complex conditioning system (implementation of a synchronous detection technique), considering the tradeoff between a decision on the fly reconfiguration and a rational energy management system. Therefore, the question of how to integrate and store data necessary for the development of an efficient digital processing. A solution based on a hybrid approach with a chip produced by Xilinx called Zynq and embedded on a Zedboard. This solution is more efficient than a PSoC approach and allowed the development and implementation of signal processing techniques with tools for optimization and provided a solution of self-generation code trough a graphic interface. Following this research, the results obtained demonstrate the validity of the concepts implemented and allow us to imagine the next smart generation architectures

Bridges are vital components of the U.S. transportation network. However, every year, the transportation agencies report a large number of aging bridges that are structurally damaged. Also, evolving traffic and particularly the overloaded traversing traffic can threaten the bridges' integrity and safety further. Bridge weight-in-motion (BWIM) is a system that takes the instrumented bridges as a scale and uses the structure response to compute the trucks' weights with no interruption in the traffic. In a particular type of BWIM, called nothing-on-road BWIM (NOR-BWIM), only a few weighing sensors should be installed under the bridge top slab. Since nothing will be installed on the road surface, NOR-BWIM addresses some of the main challenges of pavement-based WIM and traditional BWIM systems. These include lane closure, interruption to the traveling traffic, and sensitivity to daily tire impacts and harsh weather conditions. It also provides a portable solution with a less labor-intense installation process. Additionally, previous studies have shown that BWIM systems are versatile candidates for overcoming the critical challenges of structural health monitoring (SHM) across various types of bridges. The integration of the two systems is more cost-effective with improved performance; thus, it is more attractive to practitioners. However, the current BWIMs have serious shortcomings that make the integrated SHM-BWIM systems impractical in real-world long-span bridges. In the first two phases of this study, these shortcomings are addressed and a novel BWIM system is proposed. Then, the novel BWIM system is used for SHM in the third phase of the study. These shortcomings are explained as follows. Most studies are performed on short/medium-span T-beam and slab-on-girder bridges. However, longer span lengths, construction methods, different slab properties (e.g., stiffness), etc., can affect the efficacy of the NOR-BWIM. Thus, there is a need to further evaluate this technique on other bridges, such as concrete-box-girder bridges with longer spans, in an effort to ascertain whether or not NOR-BWIM systems would still work effectively on such bridges. Thus, the first phase presents an experimental investigation conducted for a long-span concrete-box-girder bridge (144 m span) called the Smart Road bridge. A total of 18 experimental tests were performed on the bridge. Moreover, a cost-effective sensor placement was developed. It was found that the number of axles is detectable with an accuracy of 100%. Moreover, the estimated mean-absolute-error for axle spacing, vehicle speed, and gross vehicle weight were 4.6%, 2.6%, and 4.6%, respectively. Lastly, it was also demonstrated that the developed cost-effective NOR-BWIM system is capable of lane identification and truck position detection. The second main issue with the existing BWIM approaches is their limited suitability for simultaneous multiple-vehicle cases on multiple-lane bridges. To address this limitation, in the second phase of this study, a novel BWIM approach is proposed. The approach is built around the removal of the non-localized portion of the strain response. Keeping the localized portion of the strain response, which is not sensitive to nearby loads, allowing for enhanced detection. The superiority of this approach stems from its capability to handle multiple-vehicle cases. These may present with an arbitrary number of trucks and light-weight vehicles, simultaneously passing the bridge in any arbitrary pattern or configuration. To show the applicability of the approach, a finite element (FE) model of a long-span concrete-box-girder bridge was simulated. The model was validated against the experimental data collected under known large events. The FE model was then used to consider single-truck events (for proof-of-concept) as well as complex multiple-truck traffic cases. These included in-one-row trucks, zigzag patterns, side-by-side trucks, and a combination of several trucks with several light-weight vehicles present. The results demonstrated that the proposed BWIM approach is capable of detecting the axle weights and gross vehicle weight (GVW) of the traversing trucks. Based on all complex multiple-truck cases, the overall mean absolute errors for GVW and axle weight estimations were 4.5% and 11.3%, respectively. In the last phase, a multiple-presence dual-purpose (MPDP) SHM approach was proposed to monitor the integrity of bridges using the BWIM system existing sensors. This approach centers on the influence line (IL) change and uses a developed multiple-presence IL (MP-IL) technique (in the second phase) for SHM application. This can effectively handle the multiple presence issue of the current integrated SHM-BWIM systems to make them more practical. Also, unlike many SHM-BWIM studies, noise and transverse position change (defined as false damage indicators) were included in the proposed procedure to provide a more realistic bridge health monitoring approach. To show the applicability of the approach, a similar FE model simulated in the second phase was used. The model was then used to evaluate the MPDP approach under single and multiple truck events. Eleven damage scenarios were simulated, and three SHM trucks (a 3-axle, a 4-axle, and a 5-axle) were used to improve the SHM accuracy. Also, an updated sensor placement was proposed to effectively work for both BWIM and SHM applications in both single and multiple-truck events. According to the results, the MPDP SHM procedure coupled with the novel MP-IL and the proposed sensor placement could effectively detect the damage scenarios in both single and multiple-truck events. Also, it was shown that using several independent SHM trucks can make the monitoring process more effective. / Doctor of Philosophy / Every year, the transportation agencies report a large number of aging bridges that are structurally damaged. Also, evolving traffic and particularly overloaded traffic can threaten the bridges' integrity and safety further. Bridge weight-in-motion (BWIM) is a traffic system that takes the instrumented bridges as a scale and uses the structure response to compute the trucks' weights with no interruption in the traffic. In a particular type of BWIM, called nothing-on-road BWIM (NOR-BWIM), only a few weighing sensors should be installed under the road surface. Since nothing will be installed on the road surface, NOR-BWIM addresses some of the main challenges of pavement-based WIM and traditional BWIM systems. These include lane closure, interruption to the traveling traffic, and sensitivity to daily tire impacts and harsh weather conditions. It also provides a portable solution with a less labor-intense installation process. Additionally, previous studies have shown that BWIM systems are versatile candidates for overcoming the critical challenges of structural health monitoring (SHM) across various types of bridges. The integration of the two systems is more attractive to practitioners because it brings improved performance at a lower cost. However, the current BWIMs have serious shortcomings that make the integrated SHM-BWIM systems impractical in real-world long-span bridges. In the first two phases of this study, these shortcomings are addressed and a novel BWIM system is proposed. Then, the novel BWIM system is used for SHM in the third phase of the study. These shortcomings are explained as follows. Most studies are performed on short/medium-span bridges with particular types of structures. However, longer span lengths, construction methods, different bridge components' properties, etc., can affect the efficacy of the NOR-BWIM. Thus, there is a need to further evaluate this technique on other bridges with longer spans and different structural systems to ascertain whether or not NOR-BWIM systems would still work effectively on such bridges. Thus, the first phase presents an experimental investigation conducted for a long-span concrete-box-girder bridge (a different structural system than the literature) with 144-m spans. A total of 18 experimental tests were performed on the bridge. Moreover, a cost-effective sensor placement was developed. It was found that the number of axles is detectable with no error. Moreover, the estimated error for axle spacing, vehicle speed, and gross vehicle weight were all low. Lastly, it was also demonstrated that the developed cost-effective NOR-BWIM system is capable of lane identification and truck position detection. The second main issue with the existing BWIM approaches is their limited suitability for simultaneous multiple vehicles on multiple-lane bridges. To address this limitation, in the second phase of this study, a novel BWIM approach is proposed. The superiority of this approach stems from its capability to handle multiple-vehicle cases. These may present with an arbitrary number of trucks and light-weight vehicles, simultaneously passing the bridge in any arbitrary pattern or configuration. To show the applicability of the approach, a model of the long-span bridge was simulated. The model was validated against the experimental data collected under known traffic events. The model was then used to consider single-truck events and complex multiple-truck traffic cases. The results demonstrated that the proposed BWIM approach can detect the axle weights and gross vehicle weight (GVW) of the traversing trucks. Based on all complex multiple-truck cases, the overall errors for GVW and axle weight estimations were 4.5% and 11.3%, respectively. In the last phase, a novel SHM approach was proposed to monitor the integrity of bridges using the existing sensors for BWIM. This approach uses the proposed BWIM system for SHM application. This can effectively handle the multiple presence issue of the current integrated SHM-BWIM systems to make them more practical. Also, unlike many SHM-BWIM studies, noise and transverse position change were included in the proposed procedure to provide a more realistic bridge health monitoring approach. A similar model simulated in the second phase was used to show the applicability of the approach. The model was then used to evaluate the MPDP approach under single and multiple truck events. Eleven damage scenarios were simulated. Also, an updated sensor placement was proposed to work effectively for both BWIM and SHM applications in single and multiple-truck events. According to the results, the proposed SHM procedure coupled with the novel BWIM and the proposed sensor placement could effectively detect the damage scenarios in both single and multiple-truck events.

Ce travail s’inscrit dans le cadre de la mise en place d’une stratégie de SHM (Structural Health Monitoring) dédiée à la surveillance des structures en génie civil. Il a porté, d’une part, sur l’étude des méthodes de détection et de localisation de l’endommagement du bâti existant et, d’autre part, sur l’élaboration du cahier des charges d’un capteur « intégré » capable de délivrer des informations par transmission compacte des données pour les communiquer à une chaîne SHM. Des études numériques et expérimentales ont été réalisées dans cet objectif. L’état de l’art a clairement mis en évidence plusieurs points faibles des méthodes de détection et de localisation d’endommagements usuelles comme, par exemple, le manque de précision et/ou la complexité de mise en place. On observe aussi que la sensibilité de ces méthodes par rapport à plusieurs paramètres, essentiellement la direction de mesure, le positionnement des capteurs et la sévérité des endommagements, ne permet pas à ce jour de dresser un diagnostic précis de l’état de santé des structures. Pour répondre au cahier des charges d’une chaîne SHM, un Algorithme de Détection et de Localisation (ADL) a été élaboré. Cet algorithme fait appel à des méthodes utilisant les paramètres modaux, essentiellement les fréquences propres et les déformées modales. Leurs mises en œuvre séquentielles et itératives, judicieusement structurées et pilotées,a permis de répondre aux objectifs fixés. Les paramètres modaux requis sont identifiés à l’aide des techniques d’Analyse Modale Opérationnelle (AMO) et à partir de la réponse en accélérations des structures. Deux algorithmes d’AMO ont été utilisés pour leur efficacité et pour leur aptitude à l’automatisation: la méthode stochastique par sous ensemble (SSI), et la méthode de décomposition dans le domaine fréquentiel (FDD). En fusionnant les algorithmes d’AMO avec l’ADL, une chaîne complète de surveillance a été créée. La validation des algorithmes et de la chaîne de surveillance s’est faite à plusieurs niveaux. Tout d’abord, basés sur la théorie des éléments finis, des modèles numériques de la tour de l'Ophite et du pont canadien de la Rivière aux-Mulets ont permis d'évaluer l'ADL. Ces modèles sont endommagés par des signaux sismiques et fournissent les données accélérométriques, données d’entrée du logiciel que nous avons développé. Les résultats obtenus sont tout à fait satisfaisants voire meilleurs que ceux issus des méthodes usuelles. Dans un second temps, nous avons traité des données expérimentales «réelles », issues des mesures accélérométriques sur la tour de l’Ophite. La confrontation entre les résultats d’identification des fréquences propres et des déformées modales issus des algorithmes d’AMO et ceux reportés par la bibliographie, a révélé l’efficacité des algorithmes développés.Enfin, une maquette d’un bâtiment à échelle réduite a également été élaborée et instrumentée.L’application de la chaine de surveillance a permis, d’une part, de détecter et localiser l’endommagement introduit dans la structure et, d’autre part, de mettre en évidence l’intérêt de la surveillance automatique. Finalement, une étude a été menée dans le but de réduire la quantité d’informations enregistrées sur les structures et de faciliter le transfert des données servant comme entrées de la chaîne de surveillance. Les résultats de ces études ont contribué à la spécification d’un nouveau système de surveillance / The work presented in this thesis is part of the development of a Structural Health Monitoring(SHM) system dedicated to civil engineering applications. First, it studies the methods of damagedetection and localization. Furthermore, it helps elaborate the specifications of an integratedsensor capable of delivering information by compact transmission of data to an SHM chain.Numerical and experimental studies have been carried out for this purpose. The study of theliterature clearly highlighted several weak points of the traditional damage detection andlocalization methods, such as the lack of precision and the complexity of implementation. Thesensitivity of these methods with respect to several parameters, essentially the measurementdirection, the positioning of the sensors and the severity of the damage, makes it impossible todraw up an accurate diagnosis of the structures. In order to overcome these limitations, a damageDetection and Localization Algorithm (DLA) was developed. By applying Vibration-Based Damage Detection Methods, following a precise order and taking into account the sensitivity, the simplicityand the SHM level of each method, this algorithm made it possible to meet the objectives set at the beginning of this work. The required modal parameters, namely eigen-frequencies and modeshapes, were identified from the structure’s output-only response using Operational ModalAnalysis techniques (OMA). Two OMA algorithms were used for their efficiency and automationability: the Stochastic Subspace Identification method (SSI) and the Frequency DomainDecomposition method (FDD). By merging the OMA algorithms with the DLA, a complete SHMchain was created. The algorithms validation was made at several levels. First, the DLA wasevaluated using a Finite Element Model (FEM) of the Ophite tower and the Rivière aux Muletsbridge. The results obtained were quite satisfactory. Secondly, experimental data were processed,from accelerometric measurements on the Ophite tower. The confrontation between the results ofeigen-frequencies and mode shapes identification using OMA algorithms and those reported in theliterature revealed the efficiency of the developed algorithms. Finally, a scale model of a buildingwas developed, instrumented and damaged. The use of the surveillance chain allowed thedetection and localization of the damage. Moreover, it showed all the interest of using automatic surveillance. The last step of this work dealt with a study carried out to reduce the amount of datarecorded on structures in order to facilitate their transfer to the SHM chain. As a conclusion, the results of these studies contributed to the specification of a new monitoring system

Ce travail de recherche consiste en la proposition d’une nouvelle approche de caractérisation non destructive de l’endommagement des matériaux composites (carbone/époxy) sollicités en fatigue par des essais d’auto-échauffement (blocs de chargements croissants). Cette approche est basée sur l’utilisation de plusieurs techniques non destructives appliquées in-situ, en temps réel ou différé, dont l’analyse est, soit redondante soit complémentaire. Au total, six techniques ont été utilisées (émission acoustique, thermographie infrarouge, corrélation d’images numériques, acousto-ultrasons, ultrasons C-scan et ondes de Lamb) et leurs résultats post-traités puis fusionnés à l’aide d’algorithmes basés sur les réseaux de neurones. Les résultats obtenus ont permis d’évaluer et de localiser l’endommagement du matériau et d’estimer sa durée de vie résiduelle. Ce faisant, plusieurs avancés scientifiques ont été obtenus en réalisant, par exemple, une localisation 2D des évènements acoustiques à l’aide seulement de deux capteurs avec une précision millimétrique, ou encore le développement d’une nouvelle technique imagée d’acousto-ultrasons permettant un contrôle hors contraintes de l’état d’endommagement du matériau, …et enfin, le pronostic de la durée de vie résiduelle du matériau basé sur une fusion de données par réseaux de neurones. / This research work consists in a new approach for non-destructive characterisation of damage in composite materials (carbon/epoxy) subjected to fatigue during self-heating tests (increasing load blocks). This approach is based on the use of several non-destructive techniques applied in-situ, in real time or delayed, whose analysis is either redundant or complementary. Six techniques were used (acoustic emission, infrared thermography, digital image correlation, acousto-ultrasound, C-scan ultrasound and lamb waves) and their post-processed results were merged using algorithms based on neural networks. The results obtained made it possible to assess and locate the damage of the material and to estimate its residual life. In doing so, several scientific advances have been obtained by, for example, carrying out a 2D localization of acoustic events using only two sensors with millimetric precision, or the development of a new pictorial acousto-ultrasonic technique allowing an control of the state of material damage at free stress conditions, ... and finally, the prognosis of the residual lifetime of the material based on a data fusion by neural networks.