Cable Force Identification Method Based On Additional Virtual Constructions

Cables of cable-stayed bridge, suspenders of suspension bridge and arch are the most crucial elements, that stress state plays a vital role in the construction of the structure and normal work period of the bridge.Therefore, cable and suspender belong to the key monitoring objects, cable force is the main monitoring physical quantities.In recent years, a lot of damage identification methods appeared, but the damage identification method based on frequency is an more economic method. The frequency of the Cable and suspender is related to many factors, such as cable force, boundary conditions, stiffness, length and sag and so on, especially for a short length of the suspender, the bending stiffness is bigger, the boundary often cannot be directly simplified as fixed or hinged. Aiming at these problems, this article is based on the virtual distortion method and the substructure isolation method, research the influence of cable dynamic characteristics via additional virtual construct and cable-force identification method through additional virtual construct.The following is the research contents of this paper.Firstly, the single cable structure model is established in ANSYS and MATLAB, and numerical solutions of the basic frequency is calculated, compared with using the analytical solution obtained from the formula, that indicated the model meet the accuracy requirement. Aim at engineering structure of a suspension bridge, ANSYS and MATLAB was used to establish model jointly. First of all, cable boundary position degrees of freedom as the main degrees of freedom polycondensation stiffness and mass matrix, and use MATLAB to establish accurate cable model of stiffness and mass matrix, and uses the finite element method to obtain the whole model.Secondly, the main ideas of the additional virtual construct are introduced as well as the basic formula is deduced, through additional virtual construct on cables to achieve the index of high sensitivity for cable-force identification. The changes of cable modal after additional virtual mass and stiffness on cable were compared, and according to additional parameters sensitivity analysis. Further researching additional virtual support on cable, virtual support can separate a length of cable, reduce the effect of boundary conditions, so according to the corresponding relationship of cable-force and frequency of cable-force identification.Finally, by using the method of additional virtual support to cable-force identification of suspension bridge cables. In order to avoid to measure rotational response, a certain length stiffness strengthening segment is set on cable, in strengthening border layout two sensors that are used to simulate the virtual fixed support.Secondly, sensors of boundary can be converted to virtual supports through the combination of convolution response is zero, thus the isolation substructure response is obtained. In the end, the ERA method is using to identify the frequency of the substructure, according to the change rule of frequency and cable-force to identify the cable force.