Study on vibration response of submerged floating tunnel considering vehicle eccentric load

Abstract

The submerged floating tunnel (SFT) is a novel traffic structure for crossing long channels and deep waterways. The moving vehicles within the SFT have a remarkable influence on structural vibration response. To analyze the eccentric load effect of vehicles in the SFT, the structure is simplified as a spatial beam on elastic foundation, while the vehicle is simulated as a seven-DOF model with three dimensions. Using the Morison equation to express the effect of nonlinear fluid resistance, the vehicle-tunnel coupling vibration equations under the action of a motorcade running on one lane of the roadway are derived using the Hamilton Principle. Then, with the help of the mode superposition method and the fourth-order Runge–Kutta method, the solution for the equation is obtained. The accuracy of the proposed theoretical derivation and corresponding programming are verified by the finite element method. Based on the analysis, the SFT with a total span of 1000 m is selected as the research object to explore the spatial behavior of the SFT under vehicle-tunnel coupling vibration. The results show that the vertical displacement peak appears at the quarter-span of the tube, whereas the peaks of horizontal displacement and torsional angle appear at the mid-span under the eccentric load of a motorcade. The contribution of high order modes on the structural displacement should be considered. Moreover, the form of the motorcade affects the vertical displacement and torsional angle of the tube, and with the change of motorcade layout and vehicle speed, the resonance effect and vibration elimination effect will appear in the vehicle-tunnel coupling vibration system. Furthermore, the design parameters of the cable have a significant effect on the deformation resistance of the tube, therefore the selection and layout of the cable should take both the anchoring stiffness and material cost into account. For controlling the eccentric load effect, the inclined angle and installation angle of the cable are recommended to be 60° and 75°, respectively.