Non-Destructive testing to detect multiple cracks in reinforced concrete beam using electromechanical impedance technique

Abstract

One of the most common engineering constructions is the Reinforced Concrete (RC) structure. As a result, it's critical to monitor the structure's health constantly. Significant causes of damage in RC structures are overloading, deficient design, fatigue; these factors induce cracks. These induced cracks severely impact the capacity of RC structures. It's critical to surveil the existence and progression of cracks early on in the damage cycle to prevent catastrophic structural failure. Electromechanical Impedance (EMI) is an effective non-destructive testing technique that uses smart materials-based Lead Zirconate Titanate (PZT) to detect cracks. The EMI technique generates admittance ((Y)) ̅ comprising of conductance, G and susceptance, B. The structure's diagnosis of damage signature is a plot of G over a frequency range. Any variation in the plot of G indicates damage in the structure. The proposed method is experimentally validated using surface-bonded PZTs on the lab-sized RC beam of grade M25. Two PZTs are bonded near each support, with one in the RC beam's centre. The RC beam is put through a four-point bending test in the experiment. Shear and flexural cracks in the beam have been monitored continuously by extracting admittance signatures from the surface bonded PZTs using an LCR meter. The admittance signatures measured at the pristine and damaged stage are compared to locate the damages. The lateral and vertical shifts in conductance signatures indicated cracks in the beam. RMSD and MAPD are used as pattern recognition techniques to quantify the variations of damaged signatures with undamaged signatures of the host structure. It demonstrates that EMI method based on PZT transducers have the ability to detect the shear and flexural cracks of the beam, and the pattern recognition techniques can effectively quantify the damage levels. The proposed method of damage detection is quite effective and sensitive to concrete.