Assessing damage of reinforced concrete beam using "b-value" analysis of acoustic emission signals

Concrete bridges in the United Kingdom represent a major legacy that is starting to show signs of distress. Therefore, the need for monitoring them is an urgent task. The acoustic emission (AE) technique was proposed as a valid method for monitoring these bridges but more study is needed to develop methods of analyzing the data recorded during the monitoring. The writers would like to propose a b-value analysis as a possible way to process AE data obtained during a local monitoring. The b-value is defined as the log-linear slope of the frequency-magnitude distribution of acoustic emissions. This paper presents the results of a b-value analysis carried out on data recorded during a laboratory test on a reinforced concrete beam designed as representative of a bridge beam. During the experiment, the specimen was loaded cyclically and it was continuously monitored with an AE system. The data obtained were processed and a b-value analysis was carried out. The b-value was compared with the applied load, with a damage parameter, and with the cracks appearing on the beam. The damage parameter represents the cumulative damage in terms of total sum of acoustic emissions. The results showed a good agreement with the development of the fracture process of the concrete. From a study of the b-value calculated for a whole loading cycle and for each channel, some quantitative conclusions were also drawn. Further development work is needed to make the b-value technique suitable for practical use on a real bridge.