Acoustic emission monitoring of reinforced concrete beams subjected to four-point-bending

The aim of this study is to apply acoustic emission (AE) technique and study the damage mechanism of the reinforced concrete (RC) beams under four-point bending. Laboratory experiments are performed on three types of RC beams of grade M30 with 42, 64 and 93% of longitudinal steel against balanced section. The damage in the beams are classified into four zones symbolizing formation of micro cracks, visible cracks, steel yielding and concrete crushing. The AE parameters such as amplitude, rise time, count, duration and average frequency are quantified in each damage levels and a parametric analysis is performed between average frequency and RA value. The results showed that as the level of damage increased, the values of AE parameters such as count, hits, rise time, acoustic emission energy and duration increased except for average frequency. This results coincided with the visual observation results according to crack modes. The adequacy of the crack classification is also evaluated by Gaussian mixture modelling (GMM), a probabilistic based approach. GMM is used as a parametric model to overcome the randomness found in the data set generated by AE testing. The results of the present investigation can be utilized in health monitoring of concrete structures subjected to flexural load.