Keywords: acoustic emission, severity assessment, b-value, Ib-value, history index, severity index.

As civil infrastructure such as bridges age, there is a concern for safety and a need for cost-effective and reliable monitoring tool. Different diagnostic techniques are available nowadays for structural health monitoring (SHM) of bridges. Acoustic emission is one such technique with the potential to predict failure. The phenomenon of rapid release of energy within a material by crack initiation or growth in the form of stress waves is known as acoustic emission (AE). An AE technique involves recording the stress waves by means of sensors and subsequent analysis of the recorded signals, which then conveys information about the nature of the source. AE can be used as a local SHM technique to monitor specific regions with visible presence of cracks or crack prone areas such as welded regions and joints with bolted connections or as a global technique to monitor the whole structure. The strength of an AE technique lies in its ability to detect active crack activity, thus helping in prioritising maintenance work by helping focus on active cracks rather than dormant cracks. In spite of being a promising tool, some challenges do still exist behind the successful application of the AE technique. One is the generation of large amounts of data during the testing; hence effective data analysis and management is necessary, especially for long term monitoring uses. Another major challenge is the quantification of damage level using appropriate analysis of data. Intensity analysis using severity and historic indices as well as b-value analysis are some important methods and will be discussed and applied for analysis of laboratory experimental data in this paper.

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