Acoustoelastic response in rebars of reinforced concrete structures

• Ano de defesa: 2025
• Autor(a) principal: Vasconcelos, Thiago Delfino Lima
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: acoustoelasticity; acustoelasticidade; concreto armado; guided wave; ondas guiadas; reinforced concrete; ultrasound; ultrassom
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/18/18134/tde-22042025-092310/

The monitoring of reinforced concrete structures is essential to ensure that the normative lifetime is reached, which can be achieved through both destructive and non-destructive methods. Non-destructive testing is an effective solution, as it can be applied without causing damage to the structure while providing a wealth of data in a short period. Among the non-destructive methods, ultrasound testing stands out, providing information through the analysis of wave profiles and velocities. One of the most recent research lines with ultrasound is the study of acoustoelasticity in concrete structures, related to the correlation of wave velocity variation with stress state variation in the structure, where most of the research is focused on plain concrete structures. Due to the inherent heterogeneity of concrete, results often exhibit significant variability. In this context, the reinforcement can be considered homogeneous when compared to concrete and may provide more consistent data through ultrasound waves, potentially reducing result variability. There are no studies about acoustoelasticity with guided waves in rebars of reinforced concrete structures. Therefore, the present work aims to evaluate the acoustoelastic effect in reinforced concrete structures with the application of the transducers directly on the rebars. For this, ultrasonic indirect measurements were carried out during mechanical tests on reinforced concrete prisms, in which access to the reinforcement was ensured during casting. In addition to experiments in isolated rebars under tension, compression and bending tests in prisms were conducted. Different bar diameters, from 8 to 20 mm, were used, and a central frequency of 250 kHz was chosen. Finally, the wave interferometry method was applied to obtain the velocity variation. Thus, in isolated bars under tension, the relative velocity variation was negative, and there was a linear behavior in most of them. In compression, a tendency was observed in the prisms with 8 and 10 mm rebars, whose trendline had an initial non-linear part. In prisms under bending, a tendency was observed among the negative curves, whose trendline was entirely non-linear. Therefore, the waves captured on the rebar surface of reinforced concrete presented a good sensitivity to acoustoelastic effect.