Damage detection on the joint of steel frame through high-frequency admittance signals

Abstract

ABSTRACT The basic idea of a piezoelectric admittance (reciprocal of impedance) technique for structural health monitoring is presented in this paper. An experimental study on damage detection of a steel frame structure is operated by the use of the high-frequency piezoelectric admittance signals. In this experiment, three PZT active sensors are bonded to three different components around a joint of the steel frame separately, and the looseness of bolts is identified by monitoring the variations of piezoelectric admittance measurements. From the experimental results it is found that the PZT active sensors hold the ability to detect structural local damage, i.e. they are insensitive to the damage in far fields. Subsequently, two damage indexes, the covariance and the cr oss correlation coefficient between two real admittance data sets are defined respectively, by which the extent of damage of the frame structure is evaluated. It is found that the cross correlation coefficient index can correctly reflect the damage extent of the frame structure qualitatively in different frequency ranges, but the covariance index can not.. Keywords: Piezoelectric impedance, damage detection, PZT, steel Frame