Acoustic Emission Measurements During a Four-Point Bending Test on a Reinforced Concrete Specimen

Acoustic emission (AE) measurements were carried out during a four-point bending test to in-vestigate the influence of the shear load-bearing capacity of reinforced concrete beams (so-called Leonhardt beam) with shear reinforcement. The results of AE measurements show that the AE activity begins immediately after starting loading. During the test approximately 3.500 AE events could be automatically located using longitudinal and transverse wave arrival times. Most AE events are in the central region of the specimen within the sensor network. Therefore, only the flexural tensile cracks are represented through AE locations. The transverse shear crack that occurred during the ultimate failure of the specimen is outside the sensor arrangement and has not been detected. Due to the localization error, the AE events are distributed in a cloud-like manner, and as a result, they do not sharply depict the macroscopic flexural tensile cracks. Ra-ther, acoustic emission indicates that a crack network of many small microscopic cracks formed in the tensile area, resulting in a very rough and fragmented crack morphology. Additional to the conventional source location, we applied the so-called collapsing method to highlight structures already inherent within the unfocused AE events clouds.