Spatial dynamic response of submerged floating tunnel under impact load

Abstract

AbstractIn order to analyze the global spatial dynamic response of a submerged floating tunnel (SFT) under the impact load, the tube is treated as a beam on elastic foundation (BOEF) with three degrees of freedom (horizontal displacement, vertical displacement, and torsion angle). The governing differential equations of the tube are derived based on the Hamilton principle considering the non-linear hydraulic resistance. The spatial displacement responses of the SFT are presented by the modal superposition method and Runge-Kutta method. The coupling motion of the horizontal displacement and torsion angle is also investigated. A finite element model of the SFT is established in ABAQUS to verify the results of the BOEF model, and the UAMP subroutine is used to simulate the effect of hydraulic resistance. Finally, the effects of the parameters, such as the anchorage stiffness, inclined angle of the cable, buoyancy-weight ratio, and hydraulic resistance on the impact response are studied. The results show the BOEF model is validated to be a suitable simplified method for the global impact response analysis. The coupling motion between the horizontal displacement and torsion angle has a significant influence on the torsion. The change of buoyancy-weight ratio has effect on displacement results and the natural frequency of the tube. It suggests the reasonable inclined angle of cable is between 45° and 60°. The hydraulic resistance considered in this paper had an effect of more than 20% on the maximum displacement, so it should not be ignored in analyses.