Application of vibrating string strain gauges in reinforced concrete structures: from vibration theory to engineering solutions

Introduction. String strain sensors, or string-type strain gauges, are high-precision devices designed to measure deformations in various structures, including concrete. These devices are widely used in the monitoring of constructions. The operation of these sensors is based on measuring changes in the resonant frequency of a taut string depending on the applied forces, which allows for precise determination of deformations in structures. This article presents the theoretical justification for determining the natural vibrations of a string depending on the tension force and applied forces.

Aim. The objective of this work is not only to analyze the theoretical behavior of the string sensor and describe the vibrations of the string, but also to evaluate the stress-strain state of the device under the influence of forces. Another goal of the work is to verify the consistency of the theoretical results with the actual data obtained from string sensors, compared with numerical experiments conducted using a finite element model of the sensor. Despite the long-standing use of string sensors, such studies in similar conditions, taking into account the specific nature of the problem and types of structures, have not yet been conducted.

Materials and methods. Analytical calculation methods and the finite element method were used to assess the stress-strain state of string sensors. To verify the theoretical solutions, calculations were performed using the ANSYS software package.

Results. As a result of the conducted analysis, a mathematical model was developed to determine the resonance frequency of the string, and its vibrational characteristics were also investigated. Additionally, the calculations were verified using the ANSYS software package, and the theoretical data were compared with actual measurements, which confirmed the high accuracy of the calculations. The results presented demonstrate good agreement between the theoretical models and real data, confirming the reliability of the method and its applicability in monitoring stresses in the reinforcement of reinforced concrete structures.

Conclusions. Thus, the use of string strain sensors for monitoring stresses in the reinforcement of reinforced concrete structures represents a promising and effective method. This work, including the verification of theoretical calculations against actual data and the validation through finite element modeling, confirms the reliability of the developed method for calculating the stress-strain state of the sensors. These sensors provide accurate data on stresses in the reinforcement and can be used for longterm monitoring in various structures, enhancing the safety and durability of the objects.

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