Advanced structural health monitoring of concrete structures with the aid of acoustic emission

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Introduction To Continuum Damage Mechanics

The purpose of this study is to identify the crack initiation and damage stress thresholds of granite from the Korea atomic energy research institute’s Underground Research Tunnel (KURT). From this, a quantitative damage evolution was inferred using various methods, including the crack volumetric strain, b value, the damage parameter from the moment tensor, and the acoustic emission (AE) energy. Uniaxial compression tests were conducted, during which both the stress–strain and AE activity were recorded simultaneously. The crack initiation threshold was found at a stress level of 0.42–0.53 σc, and the crack damage threshold was identified at 0.62–0.84 σc. The normalized integrity of KURT granite was inferred at each stress level from the damage parameter by assuming that the damage is accumulated beyond the crack initiation stress threshold. The maximum deviation between the crack volumetric strain and the AE method was 16.0 %, which was noted at a stress level of 0.84 σc. The damage parameters of KURT granite derived from a mechanically measured stress–strain relationship (crack volumetric strain) were successfully related and compared to those derived from physically detected acoustic emission waves. From a comprehensive comparison of damage identification and quantification methods, it was finally suggested that damage estimations using the AE energy method are preferred from the perspectives of practical field applicability and the reliability of the obtained damage values.

A Comparative Evaluation of Stress–Strain and Acoustic Emission Methods for Quantitative Damage Assessments of Brittle Rock

Corrosion of reinforced concrete (RC) structures has been one of the major causes of structural failure. Early detection of the corrosion process could help limit the location and the extent of necessary repairs or replacement, as well as reduce the cost associated with rehabilitation work. Non-destructive testing (NDT) methods have been found to be useful for in-situ evaluation of steel corrosion in RC, where the effect of steel corrosion and the integrity of the concrete structure can be assessed effectively. A complementary study of NDT methods for the investigation of corrosion is presented here. In this paper, acoustic emission (AE) effectively detects the corrosion of concrete structures at an early stage. The capability of the AE technique to detect corrosion occurring in real-time makes it a strong candidate for serving as an efficient NDT method, giving it an advantage over other NDT methods.

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Non-Destructive Evaluation for Corrosion Monitoring in Concrete: A Review and Capability of Acoustic Emission Technique

Extensive research and studies on concrete fracture and failure by means of the acoustic emission (AE) technique have shown that fracture and damage growth can be characterized through a single synthetic parameter, namely the b-value, which changes systematically during the different stages of the failure process, as shown by several AE tests carried out from the specimen to the structural scale [Sammonds PR, Meredith PG, Murrel SAF, Main IG. Modelling the damage evolution in rock containing porefluid by acoustic emission. In: Proceedings of the Eurock’94; 1994; Colombo S, Main IG, Forde MC. Assessing damage of reinforced concrete beam using “b-value” analysis of acoustic emission signals. J Mater Civil Eng ASCE 2003;15:280–6; Carpinteri A, Lacidogna G, Niccolini G. Critical behaviour in concrete structures and damage localisation by Acoustic Emission. Key Eng Mater 2006;312:305–10]. This parameter can be linked to the value of the exponent α of the power-law distribution of the crack size in a damaged structure. In this paper, we propose a statistical interpretation for the variation of the b-value during the evolution of damage, based on a treatment originally proposed by [Carpinteri A. Mechanical damage and crack growth in concrete: plastic collapse to brittle fracture. Dordrecht: Martinus Nijhoff Publishers; 1986; Carpinteri A. Decrease of apparent tensile and bending strength with specimen size: two different explanations based on fracture mechanics. Int J Solid Struct 1989;25:407–29; Carpinteri A. Scaling laws and renormalization groups for strength and toughness of disordered materials. Int J Solid Struct 1994;31:291–302]. The proposed model captures the transition from the condition of criticality, in which α = 3, to that of imminent failure, characterized by α = 2, in terms of damage localisation.

https://staff.polito.it/alberto.carpinteri/papers/CARPINTERI_2009_N.521_CSF.pdf

From criticality to final collapse: Evolution of the ''b-value" from 1.5 to 1.0

Extensive research and studies on con- crete fracture and failure have shown that concrete should be viewed as a quasi-brittle material having a size-dependent behavior. Numerous experimental techniques have been employed to evaluate fracture processes, and a number of modeling approaches have been developed to predict fracture behavior. A non- destructive method based on the Acoustic Emission (AE) technique has proved to be highly effective, es- pecially to assess and measure the damage phenomena taking place inside a structure subjected to mechani- cal loading. In this paper, comparing AE frequency- magnitude statistics in solids subjected to damage processes with defect size distributions for disordered materials, critical parameters defining instability con- ditions for monitored structures are found. In addition, an experimental investigation conducted on concrete and RC structures by means of the AE technique is described. Experimental results confirm the described theories.

https://staff.polito.it/alberto.carpinteri/papers/CARPINTERI_2008_N.496_Meccanica.pdf

Critical defect size distributions in concrete structures detected by the acoustic emission technique

Extensive research and studies on concrete fracture and failure have shown that concrete should be viewed as a quasi-brittle material having a size-dependent behaviour. Numerous experimental techniques have been employed to evaluate fracture processes, and a number of modelling approaches have been developed to predict fracture behaviour. The non-destructive method based on the Acoustic Emission (AE) technique has proved highly effective, especially to check and measure the damage phenomena that take place inside a structure subjected to mechanical loading. In this paper an experimental investigation conducted on concrete and RC structures by means of the AE technique is described. The AE signals reflecting the release of energy taking place during the damage process were recorded and micro-cracking sources were localised by measuring time delays by means of spatially distributed AE sensors.

https://staff.polito.it/alberto.carpinteri/papers/CARPINTERI_2006_N.415_KEM.pdf

Critical behaviour in concrete structures and damage localization by acoustic emission

In this work we measured the electromagnetic field, given by the moving charges, during laboratory fracture experiments on specimens made of different heterogeneous materials. We investigated the mechanical behaviour of concrete and rocks samples loaded up to their failure by the analysis of Acoustic Emission (AE) and Electromagnetic Emission (EME). All specimens were tested in compression at a constant displacement rate and monitored by piezoelectric (PZT) transducers for AE data acquisition. Simultaneous investigation of magnetic activity was performed by a measuring device calibrated according to metrological requirements. In all the considered cases, the presence of AE events has been always observed during the damage process, whereas it is very interesting to note that the magnetic signals were generally observed only in correspondence of the final collapse or sharp stress drops.

https://staff.polito.it/alberto.carpinteri/papers/CARPINTERI_2011_N.640_STRAIN.pdf

Acoustic and Electromagnetic Emissions as Precursor Phenomena in Failure Processes

Acoustic and electromagnetic emissions as precursor phenomena in failure processes.

This paper presents a research work in which the stability of a multi-storeyed building in reinforced concrete, with two visible macrocracks periodically subjected to visual inspection, is assessed by the acoustic emission (AE) technique. The observed proportionality between the rates of recorded AE activity from the cracks and the measured crack growth rates confirms significantly the effectiveness of the AE technique for damage evolution assessment in structural elements. The AE activity has been correlated with the size of the source crack advancements by some fitting relationships established using models from Damage Mechanics, Fracture Mechanics and Geophysics. Copyright © 2010 John Wiley & Sons, Ltd.

Gianni Niccolini

Papers

Critical defect size distributions in concrete structures detected by the acoustic emission technique

Critical behaviour in concrete structures and damage localization by acoustic emission

Acoustic and Electromagnetic Emissions as Precursor Phenomena in Failure Processes

Acoustic and electromagnetic emissions as precursor phenomena in failure processes.

Damage analysis of reinforced concrete buildings by the acoustic emission technique