## 5 Results  
### Dynamic Response Characteristics of the Salvage Operation  
At the start of the salvage operation, the shipw recreates a significant gravitational load owing to its net weight exceeding 10,000 tons. During this phase, the lifting barges encounter reactive forces from the lifting cables, causing the barges to move from their initial positions. As a result, the tension in the lifting cables increases drastically. As the lifting barges descend, the mooring cables slightly relax, leading to a minor reduction in cable tension. Subsequently, influenced by waves, the lifting barges rise again. These occurrences lead to complex variations in the movement of the three vessels and the cable tension during the shipw salvage process. The representative operational condition of the shipw in the P2 stage, subjected to waves in the 135\({}^{\circ}\) direction, has been chosen to clarify these phenomena. The schematic diagram illustrating the salvage operation under waves in the 135\({}^{\circ}\) direction is shown in Figure 7.  
Figure 8 illustrates the MA of the 6 DOFs in the P2 stage under wave action in the 135\({}^{\circ}\) direction. The MA vividly demonstrates the distinct characteristics of the three vessels. A and B denote the lifting barges, while C represents the shipw. Before the commencement of the salvage operation, engineers inflate the shipw's interior with airbags to increase buoyancy and adjust the ship's attitude and center of gravity. To better simulate the actual scenario, in our numerical simulation, the center of gravity of  
Figure 6: Increments in the maximum tension value of the lifting cables. Figure 7: Schematic diagram of the salvage of a sunken ship under the action of waves in the direction of 135\({}^{\circ}\). shipwreck C is not at the midpoint and is close to barge A. In general, lifting-barge A exhibits greater MA than lifting-barge B. Because shipwreck C is submerged, it is less influenced by waves, resulting in a relatively lower MA than lifting-barges A and B. In addition, the distance between the two lifting barges is small owing to the shipwck's substantial weight. Wave action in the 135\({}^{\circ}\) direction leads to a shadowing effect on the roll, sway, and heave responses. Notably, the roll amplitude of lifting-barge A is 1.58 times higher than that of lifting-barge B. This phenomenon is attributable to the fact that the wave first passes to A and then to B and to the unstable transmission of the shipwck's gravitational load in the transverse and vertical directions. The pitch, surge, and other response amplitudes fall within the permissible engineering range. Based on the analysis above, it becomes evident that the movements of the three vessels are not synchronized during the shipwck salvage process. This lack of synchronization results in varying tensions among the 30 lifting and 16 mooring cables, resulting in localized peaks. Figure 9 shows the maximum tension of the 16 mooring cables under wave action in the 135\({}^{\circ}\) direction. Lifting-barge A faces the impact of the wave, and lifting-barge B faces away from the impact of the wave. A1-A8 represent the maximum tension of the eight mooring cables of lifting-barge A, while B1-B8 denote the maximum tension of the eight mooring cables of lifting-barge B. Owing to the waves' influence, lifting-barges A and B move in opposite directions to the wave motion, causing the cable facing the wave to become taut and the cable facing away from the wave to become slack. The elongation of the cables leads to changes in tension. From Figure 6, it is evident that the five mooring cables (B1, A1, A2, A3, and A4), corresponding to areas that are the most affected by waves, exhibit peak values ranging from 368.8 to 424.8 kN, surpassing the tensions of the other cables. Based on the parameters of the mooring cables provided in Table 2, it can be ascertained that all mooring cables comfortably meet the safety factor requirements with significant safety margins.