The Research On Bridge Cable Force-Testing Ring Based On Fiber-Optic White Light Interferometry

The construction of large bridges is often costly. Under normal operation, their designed service life is more than 100 years. In the whole process of bridges, the external factors and their own material aging will bring down the structure’s ability to fight outside effect. Bridge accidents not only lead to huge economic losses to the society, but also threaten people’s personal safety. As main bearing component of bridge, the real-time monitoring and the evaluation of cable force are of great significance to the safety of the whole bridge operation.In this paper, the force-testing ring sensors are designed based on fiber-optic white light interferometry. This paper mainly focuses on works as follows:1. The existing main problems about structural health monitoring of large-span bridges were analyzed and put forward. The principle and application of measuring technologies for bridge cable force were stated and contrasted.2. The principle of fiber-optical white light interferometry and white light interference deformation measuring instrument was stated.3. According to the real application conditions of fiber optic white light interference force-testing ring, the influence of temperature on fiber-optic white light interference force-testing ring sensors in a free state and a restrained state was analyzed. Two calculation formulas of cable force were derived under the schemes of two kinds of temperature compensation.4. The early experiments of fiber-optic white light interference force-testing ring sensors for measuring cable force were carried out, which proved the feasibility of white light interference force-testing ring sensors for cable force monitoring. White light interference force-testing ring sensors were designed. Firstly, Calibration experiment of the sensors was carried out regardless of the temperature compensation, from which we found the necessity of temperature compensation when white light interference force-testing ring sensors are monitoring cable force. Secondly, the temperature calibration experiment was carried out, from which the temperature calibration coefficient was gained. Besides, the calibration experiment of the sensors was carried out considering the temperature compensation and another calibration coefficient was gained. Finally, Two formulas of fiber optic white light interference force-testing ring sensors for cable force evaluation were established, and the source of experiment error and sensor performance were analyzed.5. For an example of Dalian Xinghaiwan Bridge, the practical application of white light interference force-testing ring sensors when monitoring cable force were stated.