Identification of Acoustic Emission Signatures and Their Capability to Assess the Damage of Reinforced Concrete Beam under Incremental Cyclic Loading.

Acoustic emission (AE) has been widely used for damage detection and characterization in reinforced concrete (RC) structures. However, there is little work focusing on correlation of AE signatures and physical phenomena involved within the failure process of RC beams. In this paper, AE monitoring was performed on five small-scale RC beams that were subjected to an incremental cyclic loading regimen. Correlation of AE activity with in situ crack progression was performed by comparing AE signatures with a series of real-time images of crack development. Based on the combination of AE response and development of flexural and shear crack patterns, four phases named microcrack formation, macrocrack initiation, crack opening/closing, and near failure were recognizable. Meanwhile, AE cumulative energy (CE) analysis during loading and unloading demonstrated its potential for damage detection and qualification. The test results show crack initiation and propagation are accompanied with significantly greater AE activity in comparison to existing crack reopening or closing; and during the unloading step when the RC beams are near failure, the calculated CE is greater than that for initial crack appearance. In addition, AE event localization method and waveform analysis were performed to aid in identifying the source mechanisms of meaningful events. Crack propagation events were associated with burst type signals. During unloading step near failure, signals of high amplitude and long rise time are located along the reinforcement indicating a potential loss of bond as the reinforcement interacts with its surrounding concrete. The results showed that the combination of each analysis type aided in determining whether AE generated during loading/unloading of RC can be a meaningful parameter in monitoring damage of RC structures. [ABSTRACT FROM AUTHOR]