Abstract: To investigate the hydrodynamic response and mechanical behavior of the connection structures of an adjustable-draft modular submerged barge during floating transportation, a combined physical model testing and numerical simulation approach was adopted. A case study was conducted using the construction equipment developed for the Lungui Road inland immersed-tunnel project in Shunde, China. Considering the segmented transportation and on-site assembly characteristics of the modular barge, the structural loads and motion responses under representative wave-current conditions and different draft levels were systematically analyzed, with particular emphasis on the critical connection components. A numerical model was subsequently established in AQWA and validated against the physical model test results. Frequency-domain analyses were then performed to obtain the response amplitude operators under different wave periods and to characterize the motion responses of the structure. The results show that: (1) The adjustable-draft barge exhibits pronounced directional hydrodynamic responses. Beam waves are more likely to induce roll and sway resonance, and produce substantially greater peak tensions and structural loads than head waves, making them the critical design condition. (2) Wave height is the primary factor governing peak tension, whereas abrupt load variations are more likely under irregular waves. During immersion, the increase in buoyancy effectively reduces sling-force levels. (3) The numerical results agree well with the physical model test data. The response amplitude operator analysis indicates that the dominant resonance period is approximately 5 s for roll and 7 s for pitch, thereby identifying the principal resonance ranges of system’s motion degrees of freedom.

Key words: combined submerged barge, immersed tunnel, numerical simulation, physical model testing, adjustable draft, hydrodynamic response