Hydroelastic response and nonlinear wave load characteristics of a river–sea-going ship via a two-way coupled approach

River–sea-going ships are highly susceptible to springing and whipping due to their large breadth-to-depth ratio and shallow draft, which lead to pronounced hydroelastic effects under complex wave excitations. In this study, the nonlinear wave load responses of a scaled model of the “Han Hai 5” river–sea-going ship were systematically investigated using a two-way coupled approach integrating computational fluid dynamics and the finite element method. A comprehensive series of simulations covering various wavelengths, wave heights, ship speeds, and loading conditions was conducted to quantify the influence of key parameters on nonlinear responses. The results indicate that springing is the dominant source of high-frequency (HF) loads, with the vertical bending moment (VBM) at the midship amplified by up to 1.91 times under typical ballast conditions. The amplification factor exhibits a linear dependence on wave height and a nonlinear increase with ship speed, while full load conditions reduce it by approximately 30% owing to enhanced hydrodynamic damping and added mass effects. Furthermore, bow slamming is observed under ballast conditions. Although its contribution to the total VBM is limited, it plays a non-negligible role in fatigue-sensitive HF load components. Taken together, these findings provide additional physical insights into springing-driven HF load amplification and its distribution along the hull, and quantify bow slamming pressures together with the associated whipping-induced structural effects, thereby supporting structural safety assessment and design optimization of river–sea-going ships.