Exploration And Analysis On Methodologies For Cable Force Identification

Cable as a stained component has been widely used in bridges in recent years. The stress state of cable is the main basis for assessing this type of bridge health condition, which is very important to ensure the safety of the bridges as well as to increase their lifespan in usage. This paper targets at the cable, especially the short cable. The identification method of the cable in vibration frequencies is investigated under the premise of unknown parameters in the bending stiffness and boundary conditions.This paper briefly introduces several existing methods for cable force identification, and analyzes the advantages and disadvantages of each method; followed by the relevant works about the vibration frequency method and their qualifications. This paper then describes the free vibration theory of cable, and gives the solution of the free vibration equation in different boundary conditions. In this paper, the theory of the finite element method is applied to calculate the cable force, then the effects of the bending stiffness and the boundary conditions for the cable force identification is analyzed through the numerical simulation.Three methods for cable force identification are discussed in this paper, all of which base on the vibration frequency theory.. In the first method, which is called equivalent length method, effective length is used to transform the other boundary conditions to the boundary conditions of the hinged at both ends. Solving of transcendental equation can be avoided in this method. Additionally, this method uses the first two orders of the measured frequency, so the bending rigidity can be identified. The second method uses BP neural network system. The training parameter data is calculated by the finite element algorithm. Then the trained system can be used to identify the cable parameters. The third method uses the search and optimization capabilities of genetic algorithms to transform the identification of the cable force into the solving of the minimum error function, so as to achieve the identification of cable parameters. All these three methods are analyzed regarding their simulated convergence and errors using the numerical simulation. And, each method is also verified through the analysis of experimental data. Therefore, the three methods can all be applied in engineering for effective cable force identification.