2-D statistical damage detection of concrete structures combining smart piezoelectric materials and scanning laser doppler vibrometry

Abstract

In the present study a new structural health monitoring (SHM) technique is proposed as well as a new damage index based on 2-D error statistics. The proposed technique combines the electromechanical impedance technique (EMI) which is based on the use of piezoelectric Lead Zirconate Titanate (PZT) patches and Scanning Laser Doppler Vibrometry (SLDV) for damage detection purposes of concrete structures and early age monitoring. Typically the EMI technique utilizes the direct and inverse piezoelectric effect of a PZT patch attached to a host structure via an impedance analyzer that is used for both the actuation and sensing the response of the PZT-Host structure system. In the proposed technique the attached PZTs are actuated via a function generator and the PZT-Host structure response is obtained by a Scanning Laser Doppler Vibrometer. Spectrums of oscillation velocity of the surface of the attached PZTs vertical to the laser beam versus frequency are obtained and are evaluated for SHM purposes. This damage detection approach also includes the use of a damage index denoted as ECAR (Ellipse to Circle Area Ratio) based on 2-D error statistics and is compared to the Root Mean Square Deviation (RMSD) damage index commonly used in SHM applications. Experimental results include ascending uniaxial compressive load of concrete cubic specimens, ascending three point bending of reinforced concrete beam specimens and early age monitoring of concrete. Results illustrate the efficiency of the proposed technique in damage detection as well as early age monitoring as, in the first case, both severity and location of damage can be determined by examining the values of damage indices for each damaged state and in the early age monitoring case damage indices follow the strength gain curve.