Investigation on Acoustic Emission Parameters due to Fatigue Damage of Concrete Beams with Variable Notched Depth

Acoustic Emission (AE) application for Structural Health Monitoring (SHM) has undergone a swift advance through research and innovation in recent times. The AE monitoring is widely exploited as a tool for damage detection in materials research and structure monitoring. Various advantages of the AE, such as the potential use in large and complex structures, high-sensitivity, real-time monitoring capability, and potential application across a wide range of field study, has given the technique an edge over other approaches. Nevertheless, most of the reported studies had focused on the interpretation of the results in both quantitative and qualitative perspectives to extend the capabilities and application of AE for damage detection strategy. Eventually, the quantification of the damage level of the concrete structure relative to fatigue loading remained unanswered. Therefore, this study presented the experimental investigation of four types of plain concrete beams with a fixed dimension of 100 × 200 × 600 mm in the different notch-to-depth ratios under cyclic loading. A setup of the instrument consisting of four AE sensors type R6I was employed on each concrete beam sample to ensure a precise measurement for the three-point bending test. The b-value, improved b-value (Ib-value), severity, and intensity analysis methods were applied to quantify the damage level of the concrete structure under fatigue loading. Based on the results, the AE analysis successfully classified the damage levels following the observation made during the increasing cyclic loading on the notched concrete beams, the initiation of cracks, the steady growth of cracks, and beam failure. Valuable insights were recorded throughout the observation, including the progression of the fatigue failure mechanism from the Ib-value results, the intensity chart patterns from the intensity analysis, and the increased severity due to the increased loading cycles from the severity analysis. Conclusively, this study would enable researchers to understand the trend in monitoring the damage level under fatigue loading using the AE technique as well as providing fresh insights for further research.