PSI - Issue 37

Francisco Barros et al. / Procedia Structural Integrity 37 (2022) 880–887 Barros et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction The use of digital image correlation (DIC) for structural monitoring in urban settings should be able to provide an effective and integrated approach to the detection of st ructural anomalies in parts of a city’s infrastructure . DIC has been established as a structural monitoring technique used to assess the behaviour of bridges (Winkler & Hendy, 2017; Acikgoz, et al., 2018), as well as other structures which may experience changes in displacement behaviour under loads or permanent displacements over time (Tung, et al., 2013; Verstrynge, et al., 2018). Being a non-contact technique, its operation can be carried out with no physical interference with the structure; furthermore, since it is a field measurement technique, it can be used to monitor a moderately large area, covering a region with several zones where different anomalies could occur. The work presented in this document is intended as a step towards the development of a long term vision system setup able to detect permanent displacements and changes in behaviour under loads, with minimal disruption to the operation of the monitored structure. This means trying to avoid interfering with the structure by using targets or speckle patterns, as well as using existing infrastructure whenever possible for installing the cameras and other equipment, rather than construct a supporting structure for the hardware.

2. Test setup 2.1. Overview

This test had the goal of using DIC to measure the displacement of a pedestrian bridge located in the campus of the Faculty of Engineering of the University of Porto (FEUP), by applying a static load and comparing the loaded state with the unloaded state. The vision systems were assembled next to windows inside the FEUP library building, which is adjacent to the bridge. 2.2. Layout and equipment The test setup can be seen in Fig. 1. Two vision systems for DIC were installed inside the building: a 3D system capturing the bridge from above and a 2D system capturing the bridge from the side.

Fig. 1. Schematic of the 3D and 2D DIC test setups (locations are approximate).