Magnetic force induced vibration evaluation (M5) method for frequency analysis of rebar-debonding in reinforced concrete

This paper aims to introduce a new nondestructive method dedicated to rebar concrete debonding detection (which may be caused by corrosion). The Magnetic Force Induced Vibration Evaluation (M5) method is designed to reduce damping (one of the biggest problems of currently known modal analysis methods) and enables evaluating elements inaccessible to traditional methods. The method's concept is to directly induce rebars' vibrations (not a whole structure), measure them, and analyze the frequency spectrum changes. Past studies have already proved that vibrational characteristics are susceptible to a structure debonding. The novelty of the method is related to excitation and detection of vibrations in the tested elements. The M5 method is presented against the background of other nondestructive methods used currently in building diagnostics. The comparison contains the classification and review of these methods. Two versions of the excitation subsystems were proposed and tested. In both cases, the excited vibrations, which are the reaction of reinforcing bars to an alternating magnetic field, are measured using a magnetically coupled accelerometer. With such solutions, the proposed method is fully non-contact and allows for achieving high sensitivity and repeatability. The usefulness of the method was demonstrated by measuring several concrete test specimens with simulated debonding and real samples collected from the dismantled element of the bridge slab.

Automated summary

The M5 method introduces a new nondestructive approach for detecting rebar concrete debonding by inducing vibrations directly to the rebars, allowing for evaluation of elements inaccessible to traditional methods. Compared to other nondestructive methods, it demonstrates high sensitivity and repeatability, proving its utility in building diagnostics.