Innovative technologies for structural health monitoring of SFTs: proposal of combination of infrared thermography with mixed reality

The paper focuses on a review of augmented reality/mixed reality (AR/MR) technologies in the perspective of the application to structural health monitoring (SHM) for submerged floating tunnels (SFT). In particular, Microsoft HoloLens Devices (MHD) are precious tools for survey purposes, since they allow the superimposition of information about the surrounding environment, leading to its complete control with a reduction of errors. Preliminary, the most common SHM techniques in traditional waterway crossings are examined, for identifying those best fitting with SFTs. The infrared (IR) thermography for damage detection is deepen. The possibility of connecting IR Camera and MHD, with the aim at facilitating the acquisition of thermal data and enabling stereoscopic thermal overlays in the worker's augmented view, is examined through three different experiments, namely steel fatigue crack detection on a steel plate, CFRP delamination detection and coating thickness detection on a steel members. To this purpose, a simulation of the combination of thermal image with HoloLens is performed showing the potentiality of how the view of the thermal camera in front of the user can enhance the perception of possible problems on the target structure earlier with respect to analyzing the data afterwards.