Health monitoring of reinforced concrete structures under impact using multiple piezo-based configurations

Abstract

With new advancements in construction technologies, the researchers and engineers have started taking a greater interest in structural health monitoring (SHM). Some of these techniques involve monitoring of structures using piezo sensors, made of smart materials such as Lead Zirconate Titanate (PZT) in form of thin patches. One of such techniques which has shown promising results in detecting damage at incipient stages is the electro-mechanical impedance (EMI) technique. In this study, damages incurred due to impact loading on reinforced concrete (RC) slabs were studied using four types of piezo-based configurations, namely concrete vibration sensor (CVS) with circular PZT patch (CVS-C), CVS with square PZT patch (CVS-S), resin jacketed piezo (RJP) sensor with a single layer of epoxy (RJP-I) and RJP with double layer of epoxy (RJP-II). The tests showed a successful detection of damage due to impacts by all the four types of piezo-based configurations. The CVS-C and RJP-I proved to be more sensitive in quantifying damage via root mean square deviation (RMSD) variation, i.e. increasing RMSD values with an increase in the number of impacts. In addition, CVS-C, CVS-S, and RJP-II, specifically detected an imminent failure in one of the RC slabs. The equivalent structural parameters computed from the admittance signatures showed a reduction in the equivalent stiffness with the incremental damage. An empirical model was successfully developed for each of the sensors to determine the remaining life of the structure based on a non-dimensional stiffness loss factor. The equivalent stiffness-based model was found to be an improvement over the previous damping-based models which can be reliably used in the field.