Research on Non-Contact and Non-Fixed Cable Force Measurement Based on Smartphone

Abstract

Stay cable is the major load-carrying element in cable-stayed bridges. The process of monitoring cable forces would be beneficial to ensure the safety of bridges. The conventional sensor-based approaches to measure stay cable forces is complicated in operation, time-consuming and relatively expensive. In order to confront these disadvantages, a lightweight measurement method using smartphone imagery was proposed in this paper. The video data acquisition process was first standardized by using a pre-designed target. Then, a novel algorithm to extract the vibration displacement of stay cables under complex condition was developed. An automatic correction algorithm was provided to further improve the displacement results. On top of that, a smartphone-based software for determining cable forces was developed and tested on a real-life bridge. The results showed a maximum error of 1.99% compared with the cable force obtained by using a dynamic tester. The developed software is proven to be feasible in real-life projects and can achieve high accuracy in cable force determination. At the same time, the proposed method does not require a fixed camera for measurement and is not limited by personnel experience and measurement time, facilitating real-time monitoring of multiple projects, multiple cable surfaces and multiple personnel in a visual vibration environment.

Nondestructive Testing and Health Monitoring Techniques for Structural Effective Prestress

“…For example, based on digital image processing and digital image correlation technique, Du et al [96] achieved cable force identifcation with capturing single and multiple points images by the camera, and the relative deviation between the cable force measuring values based on the above two methods and the results based on the accelerometer is within 5%. In addition, Wang et al [103] proposed a method for capturing vibration images using a smartphone. Tian et al [102] and Zhang et al [105] developed computer vision-based cable vibration measuring approaches using unmanned aerial vehicles.…”

Dynamic Measurement of Cable Force Using Vibration Frequency Detection Method

“…The jack pressure gauge detection method to test the cable force will become very difficult and inconvenient if the cable installation is completed [1]. For the detection method, the grating pressure sensor its performance and measurement accuracy are also constantly changing, so it needs to be calibrated regularly [2]. The disadvantages of the resistance strain gauge detection method are that the strain gauge is not easy to protect, the survival rate of the patch is low, and because of the large elongation of the cable after the tension, the zero point should be selected very carefully.…”

A Phase Correlation Anti-Noise Displacement Estimation Method Based on PSD Phase Screening

“…In addition, this technology is rapidly developing, as more scholars have invested in the research of visual monitoring technology during recent years. For example, Barkhordari et al [11] used visual-based methods for automatic structural damage identification; Wang et al [12] proposed a lightweight measurement method based on smartphone images and developed corresponding mobile phone software for this method; Alessandro Galdelli et al [13] designed a new remote visual inspection system for bridge predictive maintenance based on a visual-based monitoring method.…”