This article presents the results and analysis of Acoustic Emission (AE) as recorded in a reinforced concrete (RC) slab supported by four steel columns and subjected to earthquake-type dynamic loading on a shake table. Fifteen seismic simulations were conducted using an accelerogram registered during the Campano-Lucano earthquake (Italy, 1980). The peak acceleration applied to the shake table was increased until the slab reinforcement was on the brink of yielding and slippage of the bars within the concrete occurred. This limit state is commonly associated with low-to-moderate intensity earthquakes in earthquake-prone regions. The evolution of damage to the slab was monitored in terms of AE energy and the history of plastic strain energy was calculated from the acceleration and displacement measurements. A good correlation was found between the energy dissipated by the concrete through plastic deformations and the AE energy associated with concrete cracking and friction. On this basis, a tentative formula is proposed for predicting the level of damage to RC slabs, based on the AE energy recorded by sensors located near the region of expected damage concentration under lateral loads.

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This paper presents a comparison of the acoustic emission (AE) energy and the plastic strain energy released by some reinforced concrete (RC) specimens subjected to cyclic or seismic loadings. AE energy is calculated, after proper filtering procedures, using the signals recorded by several AE low frequency sensors (25-100 kHz) attached on the specimens. Plastic strain energy is obtained by integrating the load displacement curves drawn from the measurements recorded during the test. Presented are the results obtained for: (i) two beams (with and without an artificial notch) and a beam-column connection subjected to several cycles of imposed flexural deformations; (ii) a reinforced concrete slab supported by four steel columns, and a reinforced concrete frame structure, both of the latter are subjected to seismic simulations with a uniaxial shaking table. The main contribution of this paper, which is a review of some papers previously published by the authors, is to highlight that, in all cases, a very good correlation is found between AE energy and plastic strain energy, until the onset of yielding in the reinforcing steel. After yielding, the AE energy is consistently lower than the plastic strain energy. The reason is that the plastic strain energy is the sum of the contribution of concrete and steel, while the AE energy acquired with thresholds higher than 35 dB AE captures only the contribution of the concrete cracking, not the steel plastic deformation. This good correlation between the two energies before the yielding point also lends credibility to the use of AE energy as a parameter for concrete damage evaluation in the context of structural health monitoring.