Abstract
In the maintenance of cable structures, such as cable-stayed bridges, it is necessary to estimate the tension acting on the cables. In current Japanese practice, the cable tension is estimated from the cable’s natural frequency using vibration-based methods. However, in recent years, dampers have been installed onto the cables to suppress aerodynamic vibrations. Because the damper changes the cable’s natural frequencies, the methods used for cables without dampers are not appropriate for cables with dampers. With this background, the authors previously proposed a method (Method 0F) for estimating the tension of a cable with a damper from the natural frequencies and their modal order. Method 0F partially ignores the imaginary part of the complex natural frequencies to simplify the problem. This study proposes a new method (Method 1F) that does not ignore the imaginary part of a complex natural frequency. Method 1F still needs both the natural frequencies and their modal order to be input. If the modal order is not correctly specified, the accuracy deteriorates. Therefore, a new method (Method 2F) that only requires the natural frequencies is also proposed. The validity of the proposed methods was confirmed by numerical simulations and experiments. The numerical and experimental verifications confirmed that the new methods were superior compared with previous methods, and that Method 2F has the highest effectiveness.
Highlights
In the maintenance of cable structures, such as cable-stayed bridges and extra-dosed bridges, the estimation of the tension acting on the cables plays an important role
4.3.1 Results of Tension Estimation Previous studies have reported that the tension estimation error of the higher-order vibration method is 5% for a cable without a damper (Shinko Wire Company, Ltd, 2020)
The accuracy deteriorates as the cable length increases because the effect of the damper decreases as the cable length increases
Summary
In the maintenance of cable structures, such as cable-stayed bridges and extra-dosed bridges, the estimation of the tension acting on the cables plays an important role. The correct bending stiffness is difficult to determine because bridge cables are typically prestressed steel strands rather than single-steel wires To address this problem, Yamagiwa et al (2000) proposed a higher-order vibration method based on the tensioned Bernoulli–Euler beam theory. Using the concept of the higher-order vibration method (Yamagiwa et al, 2000), a theoretical equation for estimating the natural frequencies of a cable with a damper has been derived (Furukawa et al, 2021a). In the authors’ previous method, the theoretical equation for estimating the complex natural frequencies from the tension and bending stiffness of the cable and the damper parameters was derived. The modal order has to be correctly assigned to each natural frequency, which is occasionally difficult With this background, this study proposes new tension estimation methods to improve the above-mentioned points. The estimated tension is compared with the tension measured by the load cell, and the accuracy and validity of the proposed methods are discussed
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