Study on the applicability of the single cable model in cable force identification of in-service beam string structures

At present, the frequency-based cable force identification method based on single cable model assumption is still one of the most popular methods for its efficiency and convenience. However, the applicability of the single cable model assumption in the cable force identification of complex structures such as beam string structures (BSS) is worth of studying for the cables in BSS are usually short and thick, and the joints connection are complex, the cable force-frequency relationship will be possibly affected by the boundary assumption. Therefore, this paper studies the applicability of the single-cable model hinged at both ends in the cable force identification of BSS from the perspective of overall structure. Firstly, the finite element method (FEM) models for the overall BSS are established to describe the true parameters and boundary conditions of each cable within the BSS. Secondly, a “Three-criteria method” is conducted for extracting the local modes of each cable element from the global modes of the overall structure under pre-designated cable forces; and then the cable force-frequency correlation considering the influence of overall structure can be established. On this basis, the error magnitude of the single-cable model hinged at both ends for frequency-based cable force identification is analyzed corresponding to the changes of different sensitive factors. Some meaningful conclusions are obtained. Finally, the effectiveness of the method and the conclusions in this paper is verified by the testing data of an actual truss string project. The research in this paper provides a foundation for further research on improving the identification precision.