PSI - Issue 48

G. Gusev et al. / Procedia Structural Integrity 48 (2023) 176–182 Gusev et al / StructuralIntegrity Procedia 00 (2019) 000 – 000

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1. Introduction The main approach to ensure the safe operation of unique engineering and construction structures is the development and use of automated systems for monitoring deformation processes, as shown by Glot et al. (2021). At present, engineering science has sufficiently well formed the basic principles of building such systems. Research to improve various aspects of these systems covers a huge amount of work, both experimental and theoretical, as can be seen in works by Costa et al. (2012), Jia et al. (2021) and Yang et al. (2023). Most of these systems evaluate the criticality of the achieved level of SSS (stress-strain state) formed by the action of external factors and operational loads. This approach in conditions of instability and unpredictability of external factors and uncertainty of modes of operational loads does not allow timely and effective prediction, for example, of appearance of an irreversible defect in a structure, in the form of a localized crack of any scale. Therefore, one of the promising directions of development of monitoring systems is the use of "active systems". These systems contain devices that carry out diagnostic quasi-static or dynamic impact on the structure in a given mode. It is believed that such external influence has a "gentle" nature and does not lead to the appearance of irreversible defects and inelastic deformation in the structure. Such devices can be based on electromechanical actuators, namely ceramic piezoelectric elements. There are relatively few articles in scientific publications that reflect the results of using active diagnostic elements in automated deformation monitoring systems (ADMS). The work by Wang et al. (2021) presents a variant of power line base settlement diagnostics containing an active diagnostic element in the form of an electromechanical striker. The current state of the issue of using piezoelectric elements for registration, control and suppression (damping) of dynamic deformation phenomena in structures and devices is presented in a review article by Aabid et al. (2021). But it should be noted that in this article there is no information on the use of piezo elements as an active diagnostic element. Ideally, monitoring variants that use the electrical impedance of piezoelectric elements are close to active systems. This can be seen in the work by Neto et al. (2011). The purpose of this work is to establish the possibility of using ceramic piezoelectric actuators in monitoring systems for reinforced concrete structures to register the appearance of a defect in the form of a crack in any element. In this paper, this possibility is evaluated based on the results of numerical simulations. In the numerical experiment, the structure was represented as a fragment of a four-story reinforced concrete building. It is assumed that a physical experiment with the material image of this object will be carried out further. 2. Problem statement and solution methods In the first stage of the research, numerical simulation of the interaction between the device based on the piezoelectric element and the reinforced concrete structure was performed within the framework of electro-elasticity (Figure 1a). It made it possible to determine the structure and geometric image of the piezoelectric device generating a diagnostic signal with the required parameters of impulse impact (Figure 1b). Further, this signal was used as a diagnostic impact in the numerical simulation of the deformation response of the reinforced concrete structure. As a result of modeling, the spatial and temporal distribution of accelerations over the elements of the structure was obtained. The responses for a structure with defects in the form of cracks of various sizes have been considered in a sequential manner, and compared with the response of a defect-free structure. The model structure involved in the numerical experiment is a four-story fragment of a monolithic concrete structure. Other experiments with this structure can be seen in an article by Shardakov et al. (2020). Its length, width, and height are 6.4 m, 4.4 m, and 6.57 m, respectively. The floor height is 1.5 m. Step along the axes of columns - 2.0 m. The cross-section of the columns - 0.2 x 0.2 m. Thickness of floor disc - 0.15 m. The width of the crossbar - 0.2 m. The height of the protruding part of the transom - 0.1 m. Figure 1a shows the external view of the structure and marks the point of actuator impact on the outer face of the second-floor column. The geometric image of the actuator is shown in Figure 1b. In the calculations, the following mechanical characteristics of the model structure have been assumed: concrete strength class B15; reinforced concrete modulus of elasticity 32 GPa. As a result of the numerical solution of the problem of the interaction of the actuator with the characteristic elements of the structure, the energy characteristics of the diagnostic signal generated by the actuator were calculated. The