Two elastic supporting models to simulate the submerged floating tunnel and their equivalence on the free/forced vibrations

Abstract

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.