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Open AccessArticle

A New TDR-Based Sensing Cable for Improving Performance of Bridge Scour Monitoring

1
Department of Civil Engineering, National Chiao Tung University, No. 1001 Ta-Hsueh Rd., Hsinchu City 300, Taiwan
2
Yijhu Township Office, No. 389, Renli Village, Yijhu Town, Chiayi County 624, Taiwan
*
Author to whom correspondence should be addressed.
Sensors 2020, 20(22), 6665; https://doi.org/10.3390/s20226665
Received: 15 October 2020 / Revised: 15 November 2020 / Accepted: 19 November 2020 / Published: 21 November 2020
(This article belongs to the Special Issue Innovative Sensors for Civil Infrastructure Condition Assessment)
The use of time domain reflectometry (TDR) for real-time monitoring of bridge scour process has gone through several stages of development. The recently-proposed concept of bundled TDR sensing cable, in which two sets of insulated steel strands are twisted around and connected to a central coaxial cable to form a compact sensing cable, is a major change that has several advantages including the bottom-up sensing mechanism. Nevertheless, there is big room for improving its measurement sensitivity and signal to noise ratio (SNR). Changes in waveguide configuration also need to be made to avoid the adverse effect of insulation abrasion observed in field implementation. This study evaluated three new conductor and insulator configurations for constructing the sensing waveguide, including a balanced two-conductor waveguide (Type I), an unbalanced three-conductor waveguide with insulation coating on the middle conductor (Type II) and an unbalanced three-conductor with insulation coating on the two outer conductors (Type III). In all cases, the spacing between the two sets of steel strands (i.e., the waveguide conductors) was especially enlarged by replacing some steel strands with non-conductor wires to increases measurement sensitivity and avoid shorted conditions due to insulation abrasion. Experimental results show that Type III has the best performance on all counts. A new improved TDR sensing cable was hence proposed based on Type III configuration. Its performance was further evaluated by a full-scale experiment to take into consideration the long range of measurement in most field conditions. Detailed discussions on improvements of measurement sensitivity and SNR, limitation of sensing range, and mitigating the adverse effect of insulation abrasion are presented. View Full-Text
Keywords: bridge scour; scour monitoring; time-domain reflectometry (TDR), TDR sensing waveguide bridge scour; scour monitoring; time-domain reflectometry (TDR), TDR sensing waveguide
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Wang, K.; Lin, C.-P.; Jheng, W.-H. A New TDR-Based Sensing Cable for Improving Performance of Bridge Scour Monitoring. Sensors 2020, 20, 6665.

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