Vibration-based cable tension estimation using two iterative algorithms: Methodology and experimental validation

Subject Areas : Structural Mechanics

Latif Doosti ¹ , Omid Bahar ² , Mohsen Ghafory-Ashtiany ³ , Mohsen Elmi ⁴

1 - Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES)
2 - International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran.
3 - International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran.
4 - Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES)

Received: 2023-11-29 Accepted : 2024-01-24 Published : 2024-02-12

Keywords: System Identification, Post-tensioning, Cable Structures, Tension estimation, Vibration-based methods,

Abstract :

In this paper, a reliable method based on two iterative algorithms is proposed for the estimation of cable tension forces. In this method, a Finite Element model, considering the cable's geometric and mechanical characteristics, is used in order to obtain mass and stiffness matrices. The initial geometric stiffness matrix of the structure is calculated according to the taut string theory, assuming an initial value for the tension force. Furthermore, the natural frequency of the MDOF system is calculated using Ritz Method, and then compared to measured vibration frequencies, which can be obtained by output-only system identification methods. In this method, the difference between the computational and measured frequencies should not exceed the pre-defined threshold, otherwise the iteration process would be repeated after modifying the initial assumption of the cable force. To evaluate the accuracy and the effectiveness of the proposed method, an experimental study was performed on an external cable in the IIEES structural laboratory. Also, existing cable forces of the Hwamyeong cable-stayed bridge in South Korea have been employed. In both cases, the iterative method is compared with common theoretical and empirical equations in the literature. The results have shown that the iterative method is of high accuracy and great applicability, reducing the difference to even less than 2%.