Do you need to test the integrity of a structure over time?

ARTeMIS Modal Pro has a series of plugin modules designed for Structural Health Monitoring purposes. All modules are designed to analyse and present the health of a monitored structure in various manners, and they all rely on the same common data manager base module. This module administrates the recorded measurement files as well as the results obtained during a periodic monitoring.

Data Manager Base Module

Each recorded measurement file is uploaded into an Analysis Session that is the container for the particular measurements and the results obtained from it. The Data Manager Base Module is responsible for the administration of the Analysis Sessions. It stores and retrieves the different Analysis Sessions when requested by the analysis modules. The Data Manager extends the ARTeMIS Modal Pro platform that basically only handles a single Analysis Session. The features are summarized below:

• Support for Multiple Analysis Sessions.
• External storage with saving and loading of measurements and results for each Analysis Session.
• Historical measurement statistics (Maximum, Minimum, RMS, Median, Mean, Variance, Skewness, Kurtosis).
• 3D display of all measurements in frequency domain using the Singular Value Decomposition.
• Master Session definition, allowing automatic processing across all Analysis Sessions using settings of the Master Session. Includes automatic SSI modal estimation.
• Notification (Alert) services. Visual, sound, email, web service.

Damage Detection Module

The Damage Detection module consists of two different damage detection algorithms that have been developed for long-term monitoring of structures. The algorithms are robust to the natural change of a structure's dynamic behavior due to the changes of ambient conditions and can be set up to not reacting on such changes. The plugin also includes a Control Chart that, as input, can take a user-definable set of damage indicators and unify them to a single control value with corresponding statistical based threshold. This control chart can automatically notify (alert) when the threshold is being passed after an analysis. The notification can be sounds, emails or web service calls to third party systems.

The features are summarized below:

• Classic and Robust Damage Detection.
• Automatic damage indicator updates when new measurements are uploaded.
• Reference State Validation for visual validation of the null space estimation of the reference state model.
• Hotelling Control Chart unifying damage indicators into a single indicator with a single statistical based threshold.

In the figure below, the damage detection is demonstrated using data from a bridge in Italy, that was measured for a period before damaging it. There are eight reference measurements that are presented by the first eight green vertical bars in the diagram. The level of these bars shows the level of the damage indicators under normal conditions. From the first six measurements, a baseline (reference) model is determined by the module, and a threshold is automatically estimated based on the statistical evaluation of the damage indices of the six reference measurements. As seen, the last two reference measurements stay under the threshold which indicates that the bridge is still undamaged. The remaining 14 measurements are all acquired after the bridge experienced damage, and the associated damage indicators all pass the threshold significantly and indicate a permanent damage. For more information please watch this YouTube video

Modal Parameter History Module

Similar to the Damage Detection Module, the modes of the structure can be presented in a historical view. The Modal Parameter History Module has been designed for this. It presents the modal parameters as a function of the Analysis Sessions. In addition, it can automatically track modes determined in a reference state. Even though they change slightly in subsequent Analysis Sessions, the Mode Tracking is capable of keeping track of them. The tracked modes are presented as modal indicators that are inter-connected.Pointing at the line with the mouse allows further information of the particular tracked mode.

The features are summarized below:

• Historical presentation of natural frequencies and damping ratios.
• Historical export of modal parameters to SVS and UFF file formats.
• Automatic mode tracking based on the estimation of a set of reference modes obtained from a specified set of reference Analysis Sessions.
• Historical presentation of the tracked modes (Drawn interconnected). Natural frequencies and damping ratios - absolute and relative to their reference mode. Modal Assurance Criterion of the mode shapes relative to the mode shape of their reference mode.
• Historical export of tracked modes to SVS and UFF file formats.

For more information please watch this YouTube video.

In the figure below, the natural frequency of three tracked modes is presented. The two first modes are reasonable unaffected by the damage whereas the third mode is heavily influenced and even disappears for a while when damage occurs.