Monitoramento de integridade estrutural utilizando a técnica da Impedância Eletromecânica Aplicada em Estruturas de Concreto

Abstract

The malfunctioning of a civilian structure can lead to considerable economic loss, as well as a great inconvenience in the everyday life of the population that uses it. In this sense, studies and experiments should be conducted in order to provide a mean for a reliable evaluation of their condition, thus allowing establishing criteria to guarantee their use within safety standards. In this context, it is interesting and necessary to carry out a continuous monitoring of the structural health and, eventually, to study how to increase its useful life. Non-destructive methods facilitate such analyzes as they are not invasive, and they do not interfere on the functioning of the structure. This PhD thesis intends to evaluate the application of the method of monitoring the structural integrity of the structure as based on the electromechanical impedance technique for the detection of damage in concrete structures. This approach is a non-destructive technique. For this aim, the electromechanical impedance technique was explored and tested for this type of composite structure taking into account parameters that can influence the diagnostics, such as temperature and humidity. Applications of the electromechanical impedance technique were performed on different concrete structural elements, such as prismatic and cylindrical concrete specimens, and a concrete slab, in order to adequately understand the monitoring process, as well as to refine the proposed methodology. This technique uses piezoelectric transducers (intelligent) acting simultaneously as sensor and actuator coupled to the host structure. Since these smart materials are brittle, a so-called Smart Capsule was developed to incorporate the sensor to the host structure. This capsule consists of a piezoelectric transducer coated with epoxy resin, aiming at protecting the integrity of the transducer during the monitoring process. Temperature compensation techniques were implemented in order to avoid false diagnoses. Furthermore, a statistical model to establish threshold indices according to a defined level of confidence was utilized. When analyzing the obtained results, one can verify that this research reached a satisfactory evaluation of the electromechanical impedance technique in the detection of damage in concrete structures. Finally, this PhD thesis offers important contributions with emphasis on the expertise and improvement of the proposed methodology, making it promissory regarding its application in large civil engineering structures, together with conventional techniques.