Damage Identification in Concrete Using Instantaneous Dominant Frequency of Acoustic Emission Signals

The real-time assessment of structural damage in concrete structures using the acoustic emission (AE) technique presents substantial challenges. Traditional AE parameters often fail to effectively quantify the extent of concrete damage in real time. To address this limitation, an Instantaneous Dominant Frequency (IDF) method is proposed for identifying critical damage in concrete. This method leverages empirical mode decomposition (EMD), a self-adaptive time-frequency analysis approach, to process AE signals. By identifying the primary intrinsic mode function (IMF) and extracting the instantaneous frequency with the largest amplitude—termed the IDF—this method captures the dominant frequency characteristics of complex damage sources. The variation in IDF values provides insights into the progression of structural damage. In this study, AE signals obtained from uniaxial compression and four-point bending tests were analyzed using the IDF method. The results show that when the IDF value exceeds 300 kHz, significant damage, such as critical damage, occurs. These findings suggest that the IDF method offers an effective and reliable approach for identifying critical damage and determining the structural damage state during the failure process.