Structural health monitoring – What is the prescription?

Structural health monitoring (SHM) systems can prevent structural failure of safety-critical structures such as aircraft, bridges, nuclear reactors and dams, which cannot be allowed to fail. An SHM system uses the techniques of non-destructive inspection (NDI) to provide continuous (or on-demand) information about the state of a structure, so that an assessment of the structural integrity can be made at any time, and timely remedial actions may be taken as necessary. A large number of sensors forms the front end of an SHM system to provide information on the condition of the structure. The information from the sensors is incorporated into structural analyses and failure models to assess the state of the structure and to predict the remaining lifetime. Thus, the underlying concept is based on detecting and characterizing damage and assessing it in terms of failure mechanics and damage growth laws. Materials engineering and applied mechanics play dominant roles in both the diagnostic and prognostic components of SHM. A probabilistic approach is essential, as will be shown by an example of the growth and detection, or lack thereof, of surface-breaking cracks. The probabilistic approach also plays a key role in the determination of inspection schedules.