Study of fracture evolution in FRP-strengthened reinforced concrete beam under cyclic load by acoustic emission technique: An integrated mechanical-acoustic energy approach

• An RC specimen strengthened with CFRP was tested in the laboratory.
• Sentry function that combines both mechanical and acoustic energy information was employed.
• Fracture mechanisms were identified by applying sentry function.

Acoustic emission (AE) is an effective tool to evaluate the damage progression qualitatively and it can be used to assess important damage mechanism points of a structural element during loading. These assessments are made either by signal-based analyses or parameter-based analyses. In order to investigate the behavior of a reinforced concrete element strengthened with carbon fiber reinforced polymers (CFRP), both mechanical and acoustic information have been considered independently in several studies. However, it is important to combine both the mechanical and acoustic energy information to make a more comprehensive damage characterization. In order to perform a deeper analysis of FRP-strengthened reinforced concrete structure’s damage evolution, a unitless function so called “sentry” that combines both the mechanical and acoustic energy information is employed in this study. This function is expressed in the terms of the logarithmic ratio of the strain energy (ES) and the acoustic energy (EAC).According to the results obtained in this study, sentry function is proved to be successful and efficient method in CFRP-strengthened reinforced concrete elements that can be used in observing their structural failure mechanism for realistic assessments.