1. The biggest feature of a container ship is that it is equipped with standard containers, so its structure is very different from that of ordinary cargo ships. It adopts a vertical straight wall structure, and the width of its cargo hatch is almost as wide as the width of the cargo hold, leaving only a very small width of deck side plate on the side. Such openings are obviously detrimental to the bending, torsion and transverse strength of the ship. In order to make up for these shortcomings, container ships usually adopt the following structural strengthening measures:
(1)
Use double sides with watertight side tanks;
< p>(2)Increase the thickness of deck plating and side plating;
(3)
Enlarge the hatch between the two cargo hatches Dimensions of end beams and deck beams.
Due to the large opening of the cargo hold, corresponding strengthening measures must be taken to ensure strength. For the convenience of loading and unloading, from the perspective of torsional strength, the most convenient thing is to set up the inner longitudinal wall and torsion box on the side; from the perspective of stability, the most convenient thing is to set up the ballast water tank on the side.
2. The sides of the container ship's cargo hold area have double-layer shells, and the effective width of the cargo hold is similar to the width of the cargo hold. The inboard side longitudinal walls compensate for the weakening of the overall longitudinal strength caused by the large deck opening. In addition, side tanks can also improve the hull's sinking resistance and serve as ballast water tanks. A platform deck is generally installed in the side tank, which is helpful to increase the overall longitudinal strength and stiffness. At the same time, the platform deck can also be used as a personnel passage. The sides of container ships mostly adopt the longitudinal frame type. Some ships adopt the transverse frame type below the upper platform deck, and use a box-shaped structure between the upper platform and the deck as a torsion box to improve the torsional strength and overall longitudinal strength of the ship.
3. Because the deck of the container ship floats outward and the speed is high, the impact force of the waves on the hull is relatively large, and the resulting turbulence stress is also relatively large. In addition, the total longitudinal stress is also relatively large, so the bending moment value of the structure inside the hull is also Large, the size of the selected components should also be larger. Compared with ordinary cargo ships, it is subject to greater stress and more serious fatigue problems, which puts forward higher requirements for the design and construction of the upper deck and the design and construction of the hatch coaming.
4. In order to carry more containers, container ships are usually designed as large cargo hold openings and narrow deck strips. This causes the hull's horizontal bending, torsional effects, and transverse strength to significantly increase the proportion of its overall longitudinal strength. The hatch angle There will also be obvious stress concentration at the corners. As the width of the cargo hold opening increases, the stress concentration becomes more and more obvious. The stress concentration reaches the maximum at the intersection of the longitudinal and transverse members on the front wall of the cabin. Generally, the upper deck corners of ship cargo holds adopt parabolic, elliptical, or arc shapes. The stress concentration is greatest at the corners of the deck near the engine room. If it is designed in a conventional form such as a parabola, a large arc radius is required. This requires a larger gap between the container and the longitudinal and transverse bulkheads, which will also affect the The layout is rational, so it is usually designed with a negative radius structure at the corners. The size of the hatch corners will also affect the layout of the containers and the layout of the components.
5. In order to obtain more space and load more containers, the bow line of container ships often has a serious flare, and the angle between the side ribs and the outer plate is also very small (much less than 900). Moreover, the speed of container ships is very high, usually greater than 20kn, and accompanied by high ice levels, which also puts forward high requirements for strengthening the outer plating of the bow. For ice-strengthened container ships, the outer plating thickness of the bow has increased significantly, and the rib size has also increased significantly. In addition, a large number of anti-roll brackets have been installed in the ice-strengthened area. The forecastle of container ships is usually equipped with wave deflectors or wave shields.