Predicting the ultimate bending capacity of concrete beams from the “relaxation ratio” analysis of AE signals

This paper presents an alternative approach to the problem, based on “testing” the real structure rather than trying to model it. Experiments on reinforced concrete (RC) beams, representative of bridge beams, are described. The beams were loaded in cycles up to failure whilst recording the acoustic emissions (AE) generated. The analysis of the AE signals was then undertaken based on a proposed new parameter, named the “relaxation ratio”. This quantifies the AE energy recorded during the unloading and loading phases of a cycle test and it showed a clear correlation with the bending failure load of the RC beams. A change in trend was noted when the load reached approximately the 45% of the ultimate bending load. The results appeared to be influenced by factors such as the concrete strength and loading rate and further work is needed to extend the results to full scale testing of bridge beams.