Structural Health Monitoring of Bridges: Source Localisation in Acoustic Emission Technique

Structural Health Monitoring of Bridges: Source Localisation in Acoustic Emission Technique

Manindra Kaphle (Queensland University of Technology, Australia), Andy Tan (Queensland University of Technology, Australia), David Thambiratnam (Queensland University of Technology, Australia) and Tommy Chan (Queensland University of Technology, Australia)
DOI: 10.4018/978-1-61692-022-7.ch017
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Abstract

Managing the sustainability of urban infrastructure requires regular health monitoring of key infrastructure such as bridges. The process of structural health monitoring involves monitoring a structure over a period of time using appropriate sensors, extracting damage sensitive features from the measurements made by the sensors, and analysing these features to determine the current state of the structure. Various techniques are available for structural health monitoring of structures, and acoustic emission is one technique that is finding an increasing use in the monitoring of civil infrastructures such as bridges. Acoustic emission technique is based on the recording of stress waves generated by rapid release of energy inside a material, followed by analysis of recorded signals to locate and identify the source of emission and assess its severity. This chapter first provides a brief background of the acoustic emission technique and the process of source localization. Results from laboratory experiments conducted to explore several aspects of the source localization process are also presented. The findings from the study can be expected to enhance knowledge of the acoustic emission process, and to aid the development of effective bridge structure diagnostics systems.
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Acoustic Emission Technique

Acoustic emission (AE) technique is based on the use of mechanical stress waves generated by rapid release of energy inside a material. Some common sources of AE waves in engineering structures include initiation/growth of cracks, yielding, material dislocations, and impacts and rubbing of contacting surfaces. AE waves produced inside a structure can be detected by means of sensors attached on the surface. These sensors are generally piezoelectric in nature and convert mechanical vibrations into electric signals. Analysis of the recorded signals can locate and identify the source of emission and assess the extent of damage. A diagrammatic representation of AE technique is shown in Figure 1, where a crack initiates in a specimen under the application of stress. The crack acts as a source of AE waves which propagate in all directions. A sensor attached on the surface records the waves and the signals are sent to the AE acquisition system for further analysis.

Figure 1.

Acoustic emission technique

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