A simplified substructure model and dynamic response analysis of the submerged floating tunnel

A simplified substructure model of the submerged floating tunnel (SFT) was established by using the substructures' isolating/assembling technique. The effects of the intermediate supporting cables' stiffness and their non-uniformities of the SFT on the free vibrations and the responses by the moving loads were studied. The tube was divided into multiple beam-segments in span-range, and the supporting cables were considered as elastic supports with different stiffnesses. The global vibratory equation of multiple tube segments was built. The responses were ascertained by using the Galerkin truncation with multiple modes. The hydrodynamic load was simulated by the Morison equation, and the responses of moving loads were considered. The results show that the frequency distribution is related to the supporting cables' number and stiffness, and there is an aggregation phenomenon in the frequencies spectrum. The peak displacement occurs when the moving train passes the position, and the displacement and internal forces are closely related to the supporting cables' number, the buoyancy-weight ratio (BWR) and the non-uniformity of supporting stiffness. When the supporting cables' number decreases, the BWR increases and the supporting stiffness increases, the upper/lower limits of bending moment and shear force all increase. The proposed method of establishing the dynamic model of SFT by using substructures' isolating/assembling technique is feasible. And its correctness is verified based on the natural vibration characteristics, the responses by moving loads and the comparison with the results from the finite element method. It provides reference for further determining the reasonable stiffness of the supporting cables for the SFT. © 2022 Central South University of Technology. All rights reserved.