The determination of the non-loading condition of the rail cable shifting (RCS) system, which consists of the main cables, hangers, and rail cables, is the premise of girder erection for long-span suspension bridges. An analytical form-finding analysis model of the shifting system is established according to the basic assumptions of flexible cable structures. Herein, the rail cable is discretized into segmental linear cable elements and the main cable is discretized into segmental catenary elements. Moreover, the calculation and analysis equations of each member and their iterative solutions are derived by taking the elastic elongation of the sling into account. In addition, by taking the girder construction of the Aizhai suspension bridge as the engineering background, a global scale model of the RCS system is designed and manufactured. The test system and working conditions are also established. The comparison between the test results and analytical results shows the presented analytical method is correct and effective. The process is simplified in the analytical method, and the computational results and precision satisfy practical engineering requirements. In addition, the proposed method is suitable for application in the computation analysis of similar structures.
By applying two elastically supporting styles, the elastic supports beam (ESB) and elastic foundation beam (EFB) are proposed to simulate the underwater submerged floating tunnel (SFT) under hinged boundaries. Their equivalence is investigated through the frequencies/modes and forced responses caused by equidistant moving loads. The ESB model is built by regarding each tether as an elastic support and using the novel isolating/assembling technique between beam-segments and global tube, and the order of characteristic matrix for any number of intermediate elastic supports is reduced to 4 × 4. Then, the stiffness of all elastic supports and the uniformity/non-uniformity are well considered in the ESB model. The governing equations of the EFB model with a uniform linear elastic support are also given. The newly discovered results, which are verified by the finite element method (FEM), indicate the merging phenomena appear in the frequency spectrum in the ESB model. The equivalence holds for some uniform cases in the ESB model based on the peak values of responses by using the stiffness relationship and a correction coefficient, whereas the equivalence does not exist for the uneven case of elastic supports.
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