An Investigation into the Acquisition Parameters for GB-SAR Assessment of Bridge Structural Components

Abstract

<p>Structural health monitoring (SHM) is a necessary measure to maintain bridge infrastructure safe. To this purpose, remote sensing has proven effective in acquiring data with high accuracy in relatively short time. Amongst the available methods, the ground-based synthetic aperture radar (GB-SAR) can detect sub-zero deflections up to 0.01 mm generated by moving vehicles or the environmental excitation of the bridges [1]. Interferometric radars are also capable of data collection regardless of weather, day, and night conditions (Alba et al., 2008). However, from the available literature - there is lack of studies and methods focusing on the actual capabilities of the GB-SAR to target specific structural elements and components of the bridge - which makes it difficult to associate the measured deflection with the actual bridge section. According to the antenna type, the footprint of the radar signal gets wider in distance which encompasses more elements and the presence of multiple targets in the same resolution cell adds uncertainty to the acquired data (Michel & Keller, 2021). To this effect, the purpose of the present research is to introduce a methodology for pinpointing targets using GB-SAR and aid the data interpretation. An experimental procedure is devised to control acquisition parameters and targets, and being able to analyse the returned outputs in a more clinical condition. The outcome of this research will add to the existing literature in terms of collecting data with enhanced precision and certainty.</p> <p><strong> </strong></p> <p><strong>Keywords</strong></p> <p>Structural Health Monitoring (SHM), GB-SAR, Remote Sensing, Interferometric Radar</p> <p> </p> <p><strong>Acknowledgements</strong></p> <p>This research was funded by the Vice-Chancellor’s PhD Scholarship at the University of West London.</p> <p> </p> <p><strong>References</strong></p> <p>[1] Benedettini, F., & Gentile, C. (2011). Operational modal testing and FE model tuning of a cable-stayed bridge.<em> </em><em>Engineering Structures, 33</em>(6), 2063-2073.</p> <p>[2] Alba, M., Bernardini, G., Giussani, A., Ricci, P. P., Roncoroni, F., Scaioni, M., Valgoi, P., & Zhang, K. (2008). Measurement of dam deformations by terrestrial interferometric techniques.<em> Int.Arch.Photogramm.Remote Sens.Spat.Inf.Sci, 37</em>(B1), 133-139.</p> <p>[3] Michel, C., & Keller, S. (2021). Advancing ground-based radar processing for bridge infrastructure monitoring.<em> Sensors, 21</em>(6), 2172.</p>

Detection of structural targets using ground-based interferometric synthetic aperture radar and augmented reality

“…This is important to calibrate the measurement and, hence, to realistically project the signal on the investigated target area (Figure 4-b). The AR-aided setting up process was capable of producing signal outputs consistent with the empirically estimated boundaries of the beam of radiation [16]. Relying on this evidence, areas of interest in each range and the targets within them could be easily defined.…”

“…For the purpose of this study, a horn antenna with a 19 dBi gain was deployed on the IBIS-FS Plus. The boundaries of the beam of radiation were empirically determined within a distance to a reference vertical plane ranging from 0.7 to 1.7 m [16]. This surface was employed to define the boundaries of the footprint.…”

A study into the integration of AR-based data collection and multi-dimensional signal processing methods for GB-SAR target detection

“…This can contribute to enhance visualisation and raise knowledge on detecting multiple targets in the same bin range. This topic has been recently investigated in the literature [12,13]. Augmented reality (AR) has proven to be a lucrative technology in the inspection and monitoring of civil structures [14,15].…”

“…Three experimental scenarios were devised to represent different conditions of target location within the radar footprint on the reference board, i.e., no target (test 1), single target at the footprint's centre (test 2) and multiple targets (i.e., one target at the centre of the footprint and one target 250 mm distant along the x axis -test 3), as illustrated in Figure3. The targets' positions in relation to the radar footprint were designed based on the empirically estimated boundaries of the beam of radiation at a radar-board distance under consideration in this study[12].…”