Elastic waves have been long used for structural integrity evaluation of concrete materials and structures. Ultrasonic parameters are well related to crack density, deterioration of the elastic modulus, even empirical characterization of the strength. Recently, several ultrasonic studies have emerged also in the field of repair monitoring. Manual repair actions or self-healing strongly contribute to the sealing of the crack, and the regain of the mechanical properties. However, the restoration cannot be evaluated in a non-destructive manner, especially in-situ. Ultrasonic parameters exhibit strong sensitivity to the degree of filling of a single crack or of a distributed system of cracks, while they also have the capacity to monitor the self-healing process, due to the increase of elastic modulus of the healing compounds in the crack volume. The present abstract intends to give an overview of the recent developments in the field of ultrasound as a means of fracture and repair characterization. Through-the-thickness wave transmission, ultrasonic mapping, surface waves as well as air-coupled applications are reviewed as standalone methods or in conjunction with simulations in the framework of an optimal material assessment after fracture and consequent repair.
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The AE technique is highly adopted for the structural integrity assessment of materials as well as large-sized structures (buildings, bridges, etc.) due to its ability to offer information on their stability conditions. This paper presents a loading test on a prestressed concrete (PC) full-scale beam. It was taken from a bridge built in Turin (Italy) in 1970 and dismantled in 2018 for urban redevelopment works. The efficacy of the AE technique for determining the progression of damage is confirmed by the observed relations between the measured strain and the recorded AE activity.
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Extensive experimental investigations were conducted on Gypsum and Quartz compression specimens of different sizes. They were brought to complete failure, showing two different failure modalities: (1) Very brittle loading drop for micro-crystalline Gypsum and Quartz; (2) Strain-softening behaviour for macro-crystalline Gypsum. All the tested specimens emitted acoustic and electromagnetic waves and the single events cumulated up to the peak load (Figs.1,2). On the other hand, neutron emissions were evident only for the largest specimens, which are more brittle than the smaller ones [1-4]. The significant chemical composition changes occurred on the fracture surfaces are consistently explainable by the assumption of Low-energy Nuclear Reactions (LENR), both fusion and fission reactions [5-7]. It is the first time that fusion reactions emerge, whereas fission reactions have already explained the results related to other materials like the iron-rich natural rocks [5]. Let us observe that, in the case of macro-crystalline Gypsum, an original correlation seems to appear between mechanical behaviour (strain-softening) and LENR modalities (multi-body fusion reactions).
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As for building information modeling (BIM), digital twin of point-clouds of spillway of a rock fill dam is demonstrated. Reproduction of existing structures with point-clouds from still or movie images are shown. Necessary information in addition to the point-clouds such as surface and internal condition of the structure are depicted. Information such as surface deterioration condition as well as internal condition composed of elastic wave velocities, which will be crucially important to realize life-cycle-oriented design, construction, and maintenance, is incorporated into the digital twin. Through the suggested model, overall damage of the spillway is discussed in combination with the pin-point excavations for verification. Through the life cycle of the civil engineering structures roles of elastic wave approaches will be suggestively indicated.
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