In this paper, a shear connection bolt loosening damage detection technique for a steel-concrete composite girder based on the electromechanical impedance (EMI) measurement of piezoceramic sensors was proposed. A number of piezoelectric Lead Zirconate Titanate (PZT) patches were surface-bonded on the upper flange of the steel girder and the concrete slab and the corresponding EMI was measured by an impedance analyzer before and after the loosening of the connection bolts. Based on the impedance measurement, several overall statistics damage metrics including the root mean square deviation (RMSD), the mean absolute percentage deviation (MAPD) and the correlation coefficients deviation (CCD) were employed to compare the impedance spectra and to assess the presence of connection bolts. Results showed the impedance based damage metrics can be employed to detect the existence of bolt loosening of the concrete-steel composite girder. The proposed approaches have great potential to be applied in practice for the inaccessible interface performance monitoring of composite structures.
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