AE Monitoring of Real Structures: Applications, Strengths, and Limitations

Abstract

The acoustic emission (AE) technique has been successfully used for decades to monitor fracture processes during laboratory testing. This final chapter discusses deliberations necessary when the technique is employed under the often harsh practical conditions that exist on real structures and the application of AE techniques is thus more challenging. As a result, many statements are on the more cautious side and less enthusiastic than what they might be coming from an optimistic perspective of a basic researcher or a system developer. Nevertheless, the authors believe that testing and monitoring approaches based on the AE technique provide significant benefits for both condition assessment and structural health monitoring (SHM) of structures not only in the laboratory but also on real structures, if employed appropriately. One main aspect of AE monitoring is the choice of the analysis technique to be utilized. Some approaches may work with data from only a few sensors and are thus computationally efficient and simple to apply. However, those typically allow only for qualitative assessments. In contrast, approaches that might provide detailed quantitative information regarding the physics of AE events require extensive sensor networks, involve sophisticated computations, and might fail under harsh real-world conditions. To illustrate these points, select examples of AE monitoring studies on real structures are provided. These help to understand the value and limitations of various signal- and parameter-based AE techniques and serve as a basis for decisions about appropriate monitoring strategies. Site conditions, cost, safety, and other aspects are discussed as well, in an attempt to provide a potential user with practical advice on AE monitoring of large-scale and real structures with high noise levels and limited access. While most statements and recommendations are transferable, the focus of this chapter is on concrete structures.