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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Lin, Chih-PingSubject: search.filters.subject.time domain reflectometry (TDR)

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Now showing 1 - 4 of 4
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    Applicability and limitations of time domain reflectometry bridge scour monitoring system in general field conditions
    (1970-01-01)
    Wang, Kai
    ;
    Lin, Chih-Ping
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    土木工程學系
    ;
    Department of Civil Engineering
    A real-time and durable system for scour process monitoring with sufficient spatial precision is in pressing need for bridge safety management. In light of this, an innovative bundled time domain reflectometry sensing cable was recently proposed to enhance the time domain reflectometry technique for scour monitoring. However, current development only dealt with the construction of bundled sensing cable and the corresponding new data reduction method. Before it can be put into practical use, issues related to the effect of hydrological conditions, long-distance measurement, and actual field implementation are yet to be investigated. This study used both numerical simulations and laboratory experiments to examine the time domain reflectometry signals in response to both scour and deposition in different water-level conditions. As a result, the first guideline of waveform classification and interpretation is newly proposed to validly determine scour depth under various field conditions. Since field measurements often come with significant signal attenuation from resistance loss of long cable and dielectric and conductive loss in the sensing section, numerical simulations and a series of full-scale experiments were also conducted to assess the time domain reflectometry scour measurement range. The maximum measurement range of the latest time domain reflectometry scour sensing cable was found to be about 6 m. Within this range, the maximum error of scour estimation is within 0.2 m. Considering the new findings, a field time domain reflectometry scour monitoring system using the bundled time domain reflectometry sensing cable was designed accordingly and implemented at a bridge for the first time. The monitoring system successfully captured the scour process during a storm event and revealed some practical issues for future improvement as well.
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    A bundled time domain reflectometry-based sensing cable for monitoring of bridge scour
    (2019-05-01)
    Wang, Kai
    ;
    Lin, Chih-Ping
    ;
    Chung, Chih-Chung
    ;
    土木工程學系
    ;
    Department of Civil Engineering
    Scour monitoring is crucial for providing early warning of bridge safety and extending the knowledge of scour process. Traditional methods that rely on underwater instruments encounter difficulties in installation and operation in harsh fluvial environment. Time domain reflectometry (TDR)-based scour sensing wire was recently introduced as a promising technique to improve field deployment and durability. This study focused on further improving the concept of TDR sensing wire for better sensor package and performance. An innovative bundled bottom-up sensing cable was proposed to improve sensor durability and avoid the adverse effect of sensor fouling. The sensor durability is enhanced by twisting two sets of steel strands (as two opposing electrodes for the waveguide) around a coaxial cable into a composite sensing cable. The inner coaxial cable is introduced and armored by the sensing steel strands to direct TDR pulse to the bottom end before connecting to the sensing waveguide formed by steel strands for bottom-up sensing. Furthermore, taking advantage of a new data reduction method by using time-lapse differential waveform, robustness of system calibration and scour estimation is further enhanced. Experimental results revealed the optimal design of bundled TDR sensing cable, effectiveness of the bottom-up sensing approach, and better performance of the differential waveform method.
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    New types of time domain reflectometry sensing waveguides for bridge scour monitoring
    (2017-07-01)
    Lin, Chih-Ping
    ;
    Wang, Kai
    ;
    Chung, Chih-Chung
    ;
    Weng, Yu-Wen
    ;
    土木工程學系
    Scour is a major threat to bridge safety, especially in harsh fluvial environments. Real-time monitoring of bridge scour is still very limited due to the lack of robust and economic scour monitoring device. Time domain reflectometry (TDR) is an emerging waveguide-based technique holding great promise to develop more durable scour monitoring devices. This study presents new types of TDR sensing waveguides in forms of either sensing rod or sensing wire, taking into account of the measurement range, durability, and ease of field installation. The sensing rod is composed of a hollow grooved steel rod paired up with a metal strip on the insulating groove, while the sensing wire consists of two steel strands with one of them coated with an insulating jacket. The measurement sensitivity is inevitably sacrificed when other properties such as the measurement range, field durability, and installation easiness are enhanced. Factors affecting the measurement sensitivity were identified and experimentally evaluated for better arranging the waveguide conductors. A data reduction method for scour-depth estimation without the need for identifying the sediment/water reflection and a two-step calibration procedure for rating propagation velocities were proposed to work with the new types of TDR sensing waveguides. Both the calibration procedure and the data reduction method were experimentally validated. The test results indicated that the new TDR sensing waveguide provides accurate scour depth measurements regardless of the sacrificed sensitivity. The insulating coating of the new TDR sensing waveguide was also demonstrated to be effective in extending the measurement range up to at least 15 m.
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    TDR Method for Compaction Quality Control: Multi Evaluation and Sources of Error
    (2012-09-01)
    Lin, Chun-Hung
    ;
    Lin, Chih-Ping
    ;
    Drnevich, Vincent
    ;
    交大名義發表
    ;
    National Chiao Tung University
    The use of the time domain reflectometry (TDR) method, designated ASTM D6780 (ASTM D6780, 2005, "Standard Test Method for Water Content and Density of Soil in Place by Time Domain Reflectometry (TDR)," Annual Book of ASTM Standards, Vol. 04.09 ASTM International, West Conshohocken, PA), to measure water content and soil density is relatively new with both successful and unsatisfactory results being reported. This paper reexamines the TDR method from various aspects, including laboratory investigation of the relation between TDR-measured electrical properties and soil phase parameters, full scale laboratory evaluation of the standardized methods, real world performance evaluation at construction sites of earth dams, and theoretical reexamination. Laboratory calibration reveals the effect of soil type on soil electrical properties, and its implication on the TDR method is discussed. The full scale laboratory evaluation supports the validity of both the one-step and two-step TDR methods. But the field evaluation at construction sites of earth dams indicates otherwise, particularly in the measurement of soil density. The errors in the two-step method are attributed to the penetration disturbance of the field multipole resonance probe (MRP). An additional source of error in the One-Step method is found to be a theoretical flaw in the current empirical adjustment process for correcting the variation of pore-fluid conductivity from the calibration test to field measurements. Remediation for the two-step method and updating of the ASTM D6780 to overcome the shortcomings of the one-step testing are in progress.