PSI - Issue 64

Victor Procópio de Oliveira et al. / Procedia Structural Integrity 64 (2024) 653–660 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Vibrating wire sensors, as described by Peng (2020), measure the opening of a joint or crack by detecting the elongation of an elastic metal wire induced to vibrate at an acoustic frequency, as illustrated in Figure 2c. These sensors can measure tensile forces within a specific range. When an external force is applied, it alters the wire's tension, which changes the vibration frequency. This measured frequency indicates the force acting on the sensor. The sensors contain built-in electronics to initiate the wire's vibration and record the frequency, like how guitar strings produce different frequencies when vibrating under varying tensions.

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Fig. 2. (a) Exemplification of the use of accelerometers in Structural Health Monitoring (FPRIMEC, 2020); (b) Representation of the position of the tiltmeter in the structure of the Fengman dam and recording of the apparatus (ZHUANG, 2020); (c) Vibrating wire sensor (HUI-LING & XIN-YIN, 2014); Piezoelectric sensors, as described by Ju et al. (2023), utilize the piezoelectric effect to convert mechanical stresses, such as pressure, force, vibrations, or strains, into electrical signals. According to Yuan (2021), this effect occurs in certain crystalline or ceramic materials, which generate an electric charge when subjected to mechanical stress or produce an electric voltage when a charge is applied. These sensors consist of piezoelectric crystals or ceramics and electrodes, generating an electrical charge proportional to the applied mechanical stress, which is then converted into an electrical signal for electronic equipment. In Structural Health Monitoring (SHM) of reinforced or prestressed concrete bridges, piezoelectric sensors can be applied to the concrete surface to monitor vibrations from loads, wind, traffic, or other excitations, helping assess dynamic responses and detect issues like unwanted resonance. They also measure pressure in structural components to identify excessive stress or irregular load distributions. When cracks or damage occur, these sensors measure resulting stresses and vibrations, aiding in identifying structural integrity changes and the need for inspection or repair. Ju (2023) emphasizes their suitability for continuous, long-term SHM. 4 Comparative analysis To review the information and data obtained during the review presented in this work, we conducted a comparative study between conventional and “smart” methods used in monitoring the structural health of bridges and viaducts in reinforced or prestressed concrete. This comparison, shown in Figure 3, included the measurements performed by each device and their similarities, where applicable.