Assessment of Crack Activity by Acoustic Emission in Concrete Structures

Concrete and steel are the most widely used major materials for constructing civil structures such as bridges, dam, and buildings. From the acoustic emission (AE) point of view, contrary to steel itself, a lot of AE signals are acquired in concrete itself under service loads whether the crack is active or not. This paper aims to identify the differences of AE event patterns caused by developing cracks from those of a normal or safe state, and also to suggest a new algorithm for assessing the integrity of concrete structures using acoustic emission method. AE event patterns under various loading conditions were investigated experimentally for two types of reinforced concrete beams. Significant differences of AE event patterns between normal and damage developing states were observed in acoustic emission parameters like total number of hit, hit rate, differences of primary and secondary AE peak, and relative AE hit rates from sensors at different locations. Finally, based on the key parameter analysis, a new algorithm for practical AE diagnosis was suggested for assessing the conditions of damage and distress in concrete structures. From this study, it is revealed that AE monitoring can be applied to estimate whether the damage is active or not and can announce the signs of failure of concrete structures earlier.