To determine the loading conditions considering the action of both bending and torque moment for a passenger catamaran moving among waves, a method for calculating equivalent design waves under multiple load control parameters was derived based on wave load prediction results using three-dimensional potential flow theory. The method was developed by defining the wave amplitude discrepancy factors between the primary and second load of the combined bending and torquing equivalent design wave. The primary goal was to find a reasonable design wave. Finally, the design waves of a target passenger catamaran ship were calculated using the proposed method, and each load component of every design wave for the target hull was recalculated. The average error compared with the object load component was less than 1%, which verifies the effectiveness of the method and offers an effective engineering evaluation method for a catamaran.

This paper presents a novel dynamic modeling framework for gantry crane systems based on the cart double pendulum with dual cables (CDPD) model. The CDPD model systematically incorporates the effects of dual suspension cables, equalizer beams, and closed-chain kinematic constraints, enabling an accurate simulation of both symmetric and asymmetric lifting scenarios. Utilizing Kane’s method, the model efficiently handles redundant coordinates and holonomic constraints, resulting in a compact and numerically robust formulation. Validation results demonstrate strict energy conservation and consistency with traditional models in limiting cases. The proposed approach provides a unified and extensible foundation for the advanced analysis, control, and optimization of large-scale gantry crane operations.

For a cruise ship in heavy sea conditions, self-propulsion performance prediction is important for ensuring its safety. In this study, a numerical simulation approach that models the free running of a ship is presented, and a full-scale small cruise ship is verified using a ship model experiment. Based on this method, a free-running cruise ship encountering six kinds of wave conditions was simulated, and the characteristics of the ship’s motion, added resistance, and propeller loading were analyzed. The results demonstrated that the free-running approach can simulate the self-propelled motion of a full-scale ship, and that it converges more quickly than the traditional self-propulsion simulation method. The ship’s speed, heave, pitch, and thrust fluctuated when it moved through the waves, and λ/L_wl had a greater influence on the amplitude of these fluctuations than did H/L_wl. Furthermore, the propeller loading exhibited a sharp increase, and the maximum loading coefficient exceeded 500%, which may pose a safety risk.