Abstract
Dynamic cable-tension is an important bridge-health indicator. However, it is difficult to be measured precisely and efficiently. A remote bridge dynamic cable-tension measurement method is proposed. It uses an interferometric radar sensor, a time-frequency analysis technique, and a tension estimation approach based on a string-vibration-equation. One radar can measure the displacements of multiple cables aligned on one side of a bridge, at the same time. By solving the string vibration equation, each cable-tension is calculated from its fundamental frequency, which is obtained by time-frequency analyzing a short section of the cable’s whole displacement vector in an overlapped-piecewise manner. An adaptive amplitude and phase estimation (APES) algorithm is used to solve the frequency resolution deterioration problem due to the short duration. Simulations and field experiments with a K band interferometric radar validate that the proposed method is superior to traditional cable-tension measurements in terms of precision, robustness, and efficiency. The proposed method is of great application value in measuring and monitoring large cable-stayed bridges and cable-suspended bridges.
Highlights
Cable-stayed bridges and suspension bridges are the first choices to build long-span bridges to cross rivers and seas [1]
This paper aims to get the precise fundamental frequency and the resulting cable-tension in a short duration
ResInultthsis section, the proposed method is evaluated by simulation and real interferometrIinc rthadisasredctaitoana, nthaelypsrios.posed method is evaluated by simulation and real interferometric radar data analysis. 4.1
Summary
Cable-stayed bridges and suspension bridges are the first choices to build long-span bridges to cross rivers and seas [1]. The vibration-frequency based cable-tension measurement is the most widely used method due to its simple applicability and good adaptability. The APES method is of great interest in a wide range of applications, including time-frequency signal analysis, speech processing, radar signals analysis, etc It can provide bias-free spectra estimation, which is the premier pursuit of cable-tension measurement. An APES-based time-frequency analysis method is proposed to estimate the dynamic cable-tension for dynamic load tests. When compared with other cable-tension estimation methods, it can achieve more accurate fundamental frequency, especially when there are nearby frequency interferences It can provide improved spectra resolution constrained by the duration of the measured displacement. As ∆ts is small in cable tension measuring radars, the interferometric phase lays in the principal value section, and no phase unwrapping is required. Vibration frequency can be calculated by using spectrum estimation methods, e.g., the FFT-based methods
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