Response validation of a submerged floating tunnel segment

Abstract

Tube segments are the main structural components of submerged floating tunnels (SFTs). Accurately estimating the hydrodynamic properties of these components is of critical importance for the optimization and safe design of SFTs. Therefore, it is essential to understand the uncertainty associated with the frequently used assumptions inherent in the state-of-the-art calculation models for SFTs. In this paper, experimental data provided by the Norwegian Public Roads Administration (NPRA) were used to validate the hydrodynamic responses of a truncated tube segment of a SFT. The excitation force and motion response of the tube segment under different loading and constraint conditions were verified. The effects of different wave headings, submerged depths, and restoring spring stiffnesses on the hydrodynamic features of the SFT's tube segment were further investigated. The numerical results generally coincide well with the experimental results. Some interesting properties of the tube segment are presented, and the uncertainty level related to the state-of-the-art models is made clear. These are for instance regarding the main tube as a Morison element and neglecting the slow-drift force effects. The aspects that need to be given more attention to achieve more trustworthy estimations of the hydrodynamic responses are summarized. The results presented should be of value in relation to verification of analysis methods for SFTs, which represents an important step towards enhancing trustworthy design models.