Detection of gap in concrete-metal structures using piezoelectric sensor technique

![CDATA[A piezoelectric sensor technique has been proposed for non-invasive detection of gap between metal and concrete in concrete-metal composite structures such as concrete-filled steel tubes. This technique includes piezoelectric transducers attached to the external surface of the metal. The sine burst signal is generated by an actuator using a signal generation unit which propagates along the metal and is received by a sensor. The signal received by the sensor without gap is taken as a reference and compared with the signal at different gaps. Two different specimens based on concrete block are measured, one with a steel plate and another with an aluminium plate. Statistical indexes including correlation coefficient, peak-to-peak amplitude of resultant signal and root mean square deviation are used for comparison and quantitative analysis of gap. The proposed technique is able to detect gap value as low as 0.1 mm and it demonstrates the applicability of this technique for gap detection in concrete-filled steel tubes.]]