Experimental Study on the Identification of Impact-Induced Secondary Damage Inside Concrete Based on Multi-Domain Vibration Signal Indicators

A large number of in-service concrete components in infrastructure are prone to internal secondary damage, which seriously threatens the long-term safety of structures. To effectively identify internal secondary damage in concrete structures and reveal the influence of cracks on structural dynamic characteristics, this study conducts comparative experiments on intact specimens and specimens with artificial cracks, performing repeated vibration tests under the same controlled conditions. Based on the collected vibration and acoustic signals, features are extracted from multiple dimensions, including energy, statistics, attenuation, frequency domain, and time-varying responses. Comprehensive analysis is carried out in combination with Fast Fourier Transform, Hilbert Transform, and Principal Component Analysis (PCA). The results indicate that internal secondary damage cannot be identified solely from raw time-domain waveforms; cracks simultaneously reduce the overall vibration energy of the structure, enhance signal nonlinearity, and accelerate energy dissipation, leading to differences in the overall stiffness and damping characteristics of the components and causing global dynamic deterioration. After multi-domain vibration-signal analysis, it is possible to distinguish between healthy and damaged specimens. The results of this study only verify that this multi-domain vibration-signal indicator analysis approach has potential feasibility for identifying concrete crack damage, and can offer experimental insights and preliminary references for follow-up research on concrete non-destructive testing. Obtained under laboratory conditions with fixed specimen size and single concealed-crack configuration, the findings require further validation with diverse crack geometries and boundary conditions before practical structural-health-monitoring deployment.