An acoustic emission energy index for damage evaluation of reinforced concrete slabs under seismic loads

Abstract

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.

Correlation of Plastic Strain Energy and Acoustic Emission Energy in Reinforced Concrete Structures

“…It is also worth noting that, in a real experiment or in a real structure, calculating the damage index in terms of AE MARSE energy requires an estimation of the final value of the AE MARSE energy (i.e., the value associated with failure). Past research [15,32] ascertained that this estimation can be made on the basis of the information collected from previous experiments and the volume of concrete of the specimen or of the real structure. A change in specimen size does not have appreciable effects on damage patterns, but the volume V of damaged concrete affects the number of AE events as well as the AE MARSE energy; simple relationships that relate AE MARSE energy with V have been proposed [33][34][35][36].…”

“…Sci. 2016, 6, 84 10 of 15 channels [15]. As an example, Figure 17 shows E AE with dashed lines for simulations D1 (before the sliding point of the reinforcement steel inside the concrete) and D2 (after sliding point).…”

“…An AE signal discrimination procedure was applied to prevent spurious and friction sources using guard sensors and an RMS filter [18]. The accumulated AE MARSE energy, E AE , was calculated for the first-hit of the events constructed with the eight channels [15]. As an example, Figure 17 shows E AE with dashed lines for simulations D1 (before the sliding point of the reinforcement steel inside the concrete) and D2 (after sliding point).…”

“…Based on this correlation, the level of damage in an RC structure can be assessed from the AE records. The correlation is demonstrated under relatively simple loading conditions, i.e., static and monotonic loadings [12,13], yet also under extremely cumbersome loads such as random dynamic cyclic loading caused by earthquakes [13][14][15][16][17][18][19]. The AE signals recorded during a seismic event are extraordinarily complex; and unveiling their relation with the damage accumulated on the structure requires considerable post-processing work [13,16,[18][19][20].…”

“…From this prototype structure, the corresponding test model was derived by applying the similarity laws described in [15]. The depth of the slab was 125 mm.…”