A SHM system is defined as both “the observation” and “the analysis” of a built asset over time using periodically sampled response measurements to monitor changes to the material and geometric properties of engineering structures such as bridges and buildings.
The fundamental objective of SHM is to manage the risks and to take the appropriate decisions associated with an asset, including information for the assessment of the risks and for understanding how they might develop with time. In this sense, measuring and monitoring are just the initial parts of the full concept of SHM: the one related to data-collection. SHM comprises also the post-processing and analysis of the data to evaluate the performance of the asset as well as to provide the prognosis of the performance.
According to the main objective of SHM systems, three aspects are worth pointing out:
- Design validation: to check whether the built asset behaves as planned at design stages. In bridges, this is usually carried out just after the completion of the structure via load tests.
- Assessment of the structural performance. This is carried out along the service-life and operation of the asset. In this case, the development of SHM techniques is oriented to:
- The identification of sensitive characteristics (damage features) to small levels of damage
- the ability to distinguish the effects in the correct performance due to damage, from those due to changes in the ambient and operating conditions (e.g. temperature, humidity, traffic in bridges, floor occupancy in buildings)
- the development of statistical models that foster a better comprehension of damaged vs. undamaged configurations.
- the development of methods concerning the definition of the optimal number and position of the sensors for accurately capturing the behaviour of the asset and its potential damage detection.
- Improving asset management. SHM can provide more information about how an asset or its elements are behaving, leading to a better understanding and interpretation of the trends of how their physical state may change in time, so the optimum interventions and maintenance strategies can be developed to avoid future malfunctions and reduce costs due to the loss of structural performance (preventive maintenance).
In this deliverable, the term SHM is understood from a wide point of view covering both, the gathering of the structural response of the built asset (e.g. strains, strength, vibration), and the performance aspects of the asset (e.g. air quality, temperature comfort, energy consumption, structural safety)