Wire Breaking Acoustic Signal Experimental Detection and Analysis for Non-Destructive Testing and Structural Health Monitoring in Prestressed Reinforced Concrete Beams

The Acoustic Emissions (AE) technique is increasingly significant in the field of non-destructive testing and structural health monitoring research, particularly for prestressed reinforced concrete elements. Ultrasonic signals generated by damage to the concrete or the wires can be detected by appropriate piezoelectric sensors, whether resonant or broadband and can be further processed using specialized software to calculate individual event parameters as well as collective variables. The analysis of these parameters, both online and offline, enables the detection of defects and monitoring of the integrity of elements without damaging the specimen, which is crucial for structural health assessment. In this paper, the authors present the results obtained during a wire-breaking lab test on a prestressed reinforced concrete beam conducted at the STRENGTH Laboratory of the Department of Civil Engineering at the University of Salerno. During the test, wire breakings were produced manually and the resulting impulsive acoustic signals were detected and analysed by using an AE acquisition system. By comparison with literature data recorded on prestressed reinforced concrete bridges, the results obtained during this test demonstrate how the AE technique is effective in the early detection of wire breakings since the features of these signals are largely different from the standard background noise produced by road traffic and other loads on the bridges. Aside from some saturation issues in fact, (signals with more than 100 dB of amplitude were all classified in the same way), interesting correlations were found between the investigated parameters. The Root Mean Square of the signals, as, exhibits a linear correlation with the Energy of the signals. These findings reveal that, when combined with an on-site alarm system, the AE monitoring system can provide an early warning about potential failures in the bridge and, thus, can be used for fostering further inspections.