Application of the acoustic emission (AE) method to bridge testing and diagnostics comparison of procedures

Abstract

On the basis of experimental results, the paper presents and analyses three procedures using acoustic emission in non-destructive tests of reinforced concrete elements and structures. Two of those procedures, namely one published by The Ferguson Structural Engineering Laboratory - The University of Texas at Austin and the other covered by the Japanese standard JCMS-III B5706, describe measurements with the AE method taken on prestressed or reinforced concrete beams. In both cases the same AE signal sources are analysed: crack initiation, crack formation and propagation, crack closure (friction at the concrete-concrete interface), friction at the reinforcement-concrete interface, reinforcement yield and fracture. The procedures were developed on the basis of the analysis of destructive processes in reinforced concrete elements (beams) subjected to loading under laboratory conditions. The procedures are based on AE signal measurements when loading is performed in accordance with a strictly defined scheme. As regards bridges, especially those in service, it is almost impossible to obtain accurate loading values, so it is extremely difficult to achieve real results, which arises from the conditions of taking in-situ measurements. The results of laboratory tests also show substantial discrepancies in the evaluation of elements when both procedures are applied. The third, termed the IADP procedure, provides a diagnostic method for pre-stressed structures that remain in service. The procedure is based on the identification and location of destructive processes with AE testing. The method is applicable to all pre-stressed elements independent of their structure. It accounts for the interaction of different elements and damages, and also for ambient conditions (load, humidity, temperature, etc.). The usability of the procedure is confirmed by the results of both laboratory tests and those performed on real structures.